Science.gov

Sample records for closed loop aocs

  1. Closing the Loop Sampler.

    ERIC Educational Resources Information Center

    California Integrated Waste Management Board, Sacramento.

    Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

  2. Closing the Loop Sampler.

    ERIC Educational Resources Information Center

    California Integrated Waste Management Board, Sacramento.

    Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

  3. Closing the Assessment Loop

    ERIC Educational Resources Information Center

    Banta, Trudy W.; Blaich, Charles

    2011-01-01

    Accreditors, speakers at assessment conferences, and campus leaders all decry the fact that too few faculty are closing the loop--that is, studying assessment findings to see what improvements might be suggested and taking the appropriate steps to make them. This is difficult enough with locally developed measures; adding the need to interpret…

  4. Closing the loop.

    PubMed

    Dassau, E; Atlas, E; Phillip, M

    2011-02-01

    Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging

  5. Closed loop spray cooling apparatus

    NASA Technical Reports Server (NTRS)

    Alger, D. L.; Schwab, W. B.; Furman, E. R. (Inventor)

    1979-01-01

    A closed loop apparatus for jet spraying coolant against the back of a radiation target is described. The coolant is circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material is disposed between the bubble and the surface of the liquid coolant which is below the bubble at a predetermined level. In a second arrangement no inert gas is used, the bubble consists of vapor produced when the coolant is sprayed against the target.

  6. Closed-Loop Neuromorphic Benchmarks

    PubMed Central

    Stewart, Terrence C.; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris

    2015-01-01

    Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of “minimal” simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820

  7. Microgyroscope with closed loop output

    NASA Technical Reports Server (NTRS)

    Challoner, A. Dorian (Inventor); Gutierrez, Roman C. (Inventor); Tang, Tony K. (Inventor); Cargille, Donald R. (Inventor)

    2002-01-01

    A micro-gyroscope (10) having closed loop operation by a control voltage (V.sub.TY), that is demodulated by an output signal of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis). The present invention provides wide-band, closed-loop operation for a micro-gyroscope (10) and allows the drive frequency to be closely tuned to a high Q sense axis resonance. A differential sense signal (S1-S2) is compensated and fed back by differentially changing the voltage on the drive electrodes to rebalance Coriolis torque. The feedback signal is demodulated in phase with the drive axis signal (K.sub..omega..crclbar..sub.x) to produce a measure of the Coriolis force.

  8. Closed loop steam cooled airfoil

    DOEpatents

    Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

    2006-04-18

    An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

  9. Closing the loop with blur

    NASA Astrophysics Data System (ADS)

    Tani, Jacopo

    A great variety of systems use image sensors to provide measurements for closed loop operation. A drawback of using image sensors in real-time feedback is that they provide measurements at slower sampling rates as compared to the actuators, typically around 30 Hz for CCD cameras, hence acting as the bottleneck for closed loop control bandwidths. While high speed cameras exist, higher frame rates imply an upper bound on exposures which lowers the signal-to-noise-ratio (SNR), reducing measurements accuracy. The integrative nature of image sensors though offers the opportunity to prolong the exposure window and collect motion blurred measurements. This research describes how to exploit the dynamic information of observed system outputs, encoded in motion blur, to control fast systems at the fast rate through slow rate image sensors. In order to achieve this objective it is necessary to (a) design a controller providing fast rate input to the system based on the slow image measurements. Ideally such a controller would require a fast rate estimate of the system's state variables in order to provide the necessary control action, therefore an (b) image blur based estimator is to be developed. State estimators typically need a model of the system in order to provide their estimates, so (c) a system identification problem has to be addressed, where a reliable model describing the frequency content of the system, up to frequencies corresponding to the fast rate, has to be determined through slow rate image sensor measurements. Alternatively when such a procedure is not possible for lack, e.g., of knowledge of the input to the system, then (d) a method to reconstruct the output signal frequency content up to frequencies above those set by the limitations of the sampling theorem is to be devised. Therefore in order to "close the loop with blur", this work describes how to pose and solve the problems of, namely: system identification , state estimation, closed loop control and

  10. External Tank CIL Closed Loop Verification System

    NASA Technical Reports Server (NTRS)

    Hartley, Eugene A., Jr.

    2005-01-01

    Lockheed Martin was requested to develop a closed loop CIL system following the Challenger accident. The system that was developed has proven to be very robust with minimal problems since implementation, having zero escapes in the last 7 years (27 External Tanks). We are currently investigating expansion of the CIL Closed Loop system to include "MI" CILs.

  11. Closed-loop neurostimulation: the clinical experience.

    PubMed

    Sun, Felice T; Morrell, Martha J

    2014-07-01

    Neurostimulation is now an established therapy for the treatment of movement disorders, pain, and epilepsy. While most neurostimulation systems available today provide stimulation in an open-loop manner (i.e., therapy is delivered according to preprogrammed settings and is unaffected by changes in the patient's clinical symptoms or in the underlying disease), closed-loop neurostimulation systems, which modulate or adapt therapy in response to physiological changes, may provide more effective and efficient therapy. At present, few such systems exist owing to the complexities of designing and implementing implantable closed-loop systems. This review focuses on the clinical experience of four implantable closed-loop neurostimulation systems: positional-adaptive spinal cord stimulation for treatment of pain, responsive cortical stimulation for treatment of epilepsy, closed-loop vagus nerve stimulation for treatment of epilepsy, and concurrent sensing and stimulation for treatment of Parkinson disease. The history that led to the development of the closed-loop systems, the sensing, detection, and stimulation technology that closes the loop, and the clinical experiences are presented.

  12. Closed Loop Fire Control System

    DTIC Science & Technology

    1976-11-01

    bD 0 C 0 0 0 r- C0 - 1 u 0 z 2-5 F-t WI > zI C 0 t V). /- 0 LLI I 2-56 in the case of Vu . The estimation of V is...2-57 1! F𔃻 5 ’E-4 LMOSOW - - - 4 c- 44- <L V) L 0: 0 < ~ * ~ L., 0 I I I2-5 2.5 OPEN LOOP FIREl CONTROL COMIPUTATIION The objetctivye of tilt opel ...ELECTRONICS ASSY ITEM QTY FrQ N i N FAMILY 7Qx N 1 6 Connector Sets - 70 Pin PW BD , Solder Cup 1.0 1. 7 10.2 Airborne 2 7 Double Sided Printed

  13. The cut-closed-reconnected Roux loop.

    PubMed

    Kummer, E W; Gerritsen, J J; Brummelkamp, W H

    2000-02-01

    Motility disturbances in the Roux loop can negatively influence the outcome of reflux gastritis; the uncut Roux loop does not have these disadvantages, but is less suitable for clinical application because of staple dehiscence. The reported "cut-closed-reconnected" Roux loop has the same physiological starting points as the uncut Roux loop, but a difference is an extra closure at the site of the seromuscular level. The technique of the cut-closed-reconnected Roux loop is described. After 1 year, the clinical findings in 8 patients were as follows: 1 patient free of symptoms, 4 with gastric pain, 2 patients vomited (1 bilious), and 1 felt fullness. Dehiscence of the closure could not be demonstrated by endoscopy, barium contrast roentgenography, and HIDA scan.

  14. Closed loop electrostatic levitation system

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Saffren, M. M.; Elleman, D. D. (Inventor)

    1985-01-01

    An electrostatic levitation system is described, which can closely control the position of objects of appreciable size. A plurality of electrodes surround the desired position of an electrostatically charged object, the position of the objects is monitored, and the voltages applied to the electrodes are varied to hold the object at a desired position. In one system, the object is suspended above a plate-like electrode which has a concave upper face to urge the object toward the vertical axis of the curved plate. An upper electrode that is also curved can be positioned above the object, to assure curvature of the field at any height above the lower plate. In another system, four spherical electrodes are positioned at the points of a tetrahedron, and the voltages applied to the electrodes are varied in accordance with the object position as detected by two sensors.

  15. Study of the Open Loop and Closed Loop Oscillator Techniques

    SciTech Connect

    Imel, George R.; Baker, Benjamin; Riley, Tony; Langbehn, Adam; Aryal, Harishchandra; Benzerga, M. Lamine

    2015-04-11

    This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.

  16. Study of the open loop and closed loop oscillator techniques

    SciTech Connect

    Baker, Benjamin; Riley, Tony; Langbehn, Adam; Imel, George R.; Benzerga, M. Lamine; Aryal, Harishchandra

    2015-07-01

    This paper presents some aspects of a five year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques. The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this paper we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems. (authors)

  17. Bringing closed-loop home: recent advances in closed-loop insulin delivery.

    PubMed

    Thabit, Hood; Hovorka, Roman

    2014-04-01

    To highlight the recent advances in closed-loop research, the development and progress towards utilizing closed loop outside of the clinical research setting and at patients' homes. In spite of the modern insulin therapy in type 1 diabetes, hypoglycaemia is still a major limiting factor. This often leads to suboptimal glycaemic control and risk of diabetes complications. Closed loop has been shown to improve glycaemic control whilst avoiding hypoglycaemia. Incremental progress has been made in this field, from the use of automated systems and bihormonal closed-loop systems in clinical research facility settings under close supervision to the use of ambulatory closed-loop prototype at patients' homes in free-living conditions. Different population of patients with type 1 diabetes and control algorithm approaches have been studied, assessing the efficacy and safety. Transitional and home studies present different challenges at achieving better glycaemic outcome with closed loop. Improved glucose sensor reliability may accelerate the clinical use and faster insulin analogues increase the clinical utility. Results and experience with closed-loop insulin delivery have been encouraging, leading the way for future improvements and development in the field, to make closed loop suitable for use in clinical practice.

  18. Development and Closed-Loop Experimental Results of a Reaction Sphere Elegant Breadboard

    NASA Astrophysics Data System (ADS)

    Rossini, L.; Onillon, E.; Boletis, A.; Mingard, S.; Wawrzaszek, R.; Serin, J.; Ortega, C.

    2015-09-01

    Attitude and orbit control systems (AOCS) are responsible for the orbital behavior and pointing precision of stabilized satellites. As an alternative to a traditional reaction wheels (RW) assembly, the use of a single reaction sphere (RS) was proposed. This article presents the design and closed-loop experimental results of a novel elegant breadboard (EBB) of a RS actuator. The proposed RS consists of a spherical rotor with permanent magnets (PM) that can be accelerated about any axis thanks to a multi-coil stator that also fulfils the function of magnetic bearing. The design of the EBB is based on Proba-3 requirements. Functional closed-loop experimental results are presented showing the ability of simultaneously levitating the rotor while rotating it about any desired axis up to 300 rpm.

  19. Similarity Metrics for Closed Loop Dynamic Systems

    NASA Technical Reports Server (NTRS)

    Whorton, Mark S.; Yang, Lee C.; Bedrossian, Naz; Hall, Robert A.

    2008-01-01

    To what extent and in what ways can two closed-loop dynamic systems be said to be "similar?" This question arises in a wide range of dynamic systems modeling and control system design applications. For example, bounds on error models are fundamental to the controller optimization with modern control design methods. Metrics such as the structured singular value are direct measures of the degree to which properties such as stability or performance are maintained in the presence of specified uncertainties or variations in the plant model. Similarly, controls-related areas such as system identification, model reduction, and experimental model validation employ measures of similarity between multiple realizations of a dynamic system. Each area has its tools and approaches, with each tool more or less suited for one application or the other. Similarity in the context of closed-loop model validation via flight test is subtly different from error measures in the typical controls oriented application. Whereas similarity in a robust control context relates to plant variation and the attendant affect on stability and performance, in this context similarity metrics are sought that assess the relevance of a dynamic system test for the purpose of validating the stability and performance of a "similar" dynamic system. Similarity in the context of system identification is much more relevant than are robust control analogies in that errors between one dynamic system (the test article) and another (the nominal "design" model) are sought for the purpose of bounding the validity of a model for control design and analysis. Yet system identification typically involves open-loop plant models which are independent of the control system (with the exception of limited developments in closed-loop system identification which is nonetheless focused on obtaining open-loop plant models from closed-loop data). Moreover the objectives of system identification are not the same as a flight test and

  20. Closed Loop System Identification with Genetic Algorithms

    NASA Technical Reports Server (NTRS)

    Whorton, Mark S.

    2004-01-01

    High performance control design for a flexible space structure is challenging since high fidelity plant models are di.cult to obtain a priori. Uncertainty in the control design models typically require a very robust, low performance control design which must be tuned on-orbit to achieve the required performance. Closed loop system identi.cation is often required to obtain a multivariable open loop plant model based on closed-loop response data. In order to provide an accurate initial plant model to guarantee convergence for standard local optimization methods, this paper presents a global parameter optimization method using genetic algorithms. A minimal representation of the state space dynamics is employed to mitigate the non-uniqueness and over-parameterization of general state space realizations. This control-relevant system identi.cation procedure stresses the joint nature of the system identi.cation and control design problem by seeking to obtain a model that minimizes the di.erence between the predicted and actual closed-loop performance.

  1. Closed-loop approach to thermodynamics

    NASA Astrophysics Data System (ADS)

    Goupil, C.; Ouerdane, H.; Herbert, E.; Benenti, G.; D'Angelo, Y.; Lecoeur, Ph.

    2016-09-01

    We present the closed-loop approach to linear nonequilibrium thermodynamics considering a generic heat engine dissipatively connected to two temperature baths. The system is usually quite generally characterized by two parameters: the output power P and the conversion efficiency η , to which we add a third one, the working frequency ω . We establish that a detailed understanding of the effects of the dissipative coupling on the energy conversion process requires only knowing two quantities: the system's feedback factor β and its open-loop gain A0, which product A0β characterizes the interplay between the efficiency, the output power, and the operating rate of the system. By raising the abstract hermodynamic analysis to a higher level, the feedback loop approach provides a versatile and economical, hence fairly efficient, tool for the study of any conversion engine operation for which a feedback factor can be defined.

  2. Closed-loop pulsed helium ionization detector

    DOEpatents

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

    A helium ionization detector for gas chromatography is operated in a constant current, pulse-modulated mode by configuring the detector, electrometer and a high voltage pulser in a closed-loop control system. The detector current is maintained at a fixed level by varying the frequency of fixed-width, high-voltage bias pulses applied to the detector. An output signal proportional to the pulse frequency is produced which is indicative of the charge collected for a detected species.

  3. Closed-Loop Endoatmospheric Ascent Guidance

    NASA Technical Reports Server (NTRS)

    Lu, Ping; Sun, Hongsheng; Jackson, Scott (Technical Monitor)

    2002-01-01

    This paper will present a complete formulation of the optimal control problem for atmospheric ascent of rocket powered launch vehicles subject to usual load constraints and final condition constraints. We shall demonstrate that the classical finite difference method for two-point-boundary-value-problems (TPBVP) is suited for solving the ascent trajectory optimization problem in real time, therefore closed-loop optimal endoatmospheric ascent guidance becomes feasible. Numerical simulations with a the vehicle data of a reusable launch vehicle will be provided.

  4. Closed-Loop Resuscitation of Hemorrhagic Shock

    DTIC Science & Technology

    2011-02-21

    thank ONR for the last 9 years of basic and applied research on titrated fluid therapy of hypovolemic shock . This grant was instrumental in not only the...Phone: 409-772-3969 Fax: 409-772-8895 Project Title: Closed-Loop Resuscitation of Hemorrhagic Shock ONR Award No: N000140610300 Organization...Resuscitation Of Hemorrhagic Shock 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK

  5. Closed loop orbit trim using GPS

    NASA Technical Reports Server (NTRS)

    Parkinson, B. W.; Axelrad, P.

    1989-01-01

    This paper describes an onboard closed-loop navigation and control system capable of executing extremely precise orbit maneuvers. It uses information from the Global Positioning System (GPS) and an onboard controller to perform orbit adjustments. As a result, the system circumvents the need for extensive ground support. The particular application considered is an orbit injection system for NASA's Gravity Probe B (GP-B) spacecraft. Eccentricity adjustments of 0.0004 to 0.005, and inclination and node changes of 0.001 to 0.01 deg are demonstrated. The same technique can be adapted to other satellite missions.

  6. Closing the loop of deep brain stimulation

    PubMed Central

    Carron, Romain; Chaillet, Antoine; Filipchuk, Anton; Pasillas-Lépine, William; Hammond, Constance

    2013-01-01

    High-frequency deep brain stimulation is used to treat a wide range of brain disorders, like Parkinson's disease. The stimulated networks usually share common electrophysiological signatures, including hyperactivity and/or dysrhythmia. From a clinical perspective, HFS is expected to alleviate clinical signs without generating adverse effects. Here, we consider whether the classical open-loop HFS fulfills these criteria and outline current experimental or theoretical research on the different types of closed-loop DBS that could provide better clinical outcomes. In the first part of the review, the two routes followed by HFS-evoked axonal spikes are explored. In one direction, orthodromic spikes functionally de-afferent the stimulated nucleus from its downstream target networks. In the opposite direction, antidromic spikes prevent this nucleus from being influenced by its afferent networks. As a result, the pathological synchronized activity no longer propagates from the cortical networks to the stimulated nucleus. The overall result can be described as a reversible functional de-afferentation of the stimulated nucleus from its upstream and downstream nuclei. In the second part of the review, the latest advances in closed-loop DBS are considered. Some of the proposed approaches are based on mathematical models, which emphasize different aspects of the parkinsonian basal ganglia: excessive synchronization, abnormal firing-rate rhythms, and a deficient thalamo-cortical relay. The stimulation strategies are classified depending on the control-theory techniques on which they are based: adaptive and on-demand stimulation schemes, delayed and multi-site approaches, stimulations based on proportional and/or derivative control actions, optimal control strategies. Some of these strategies have been validated experimentally, but there is still a large reservoir of theoretical work that may point to ways of improving practical treatment. PMID:24391555

  7. CLOSED-LOOP STRIPPING ANALYSIS (CLSA) OF ...

    EPA Pesticide Factsheets

    Synthetic musk compounds have been found in surface water, fish tissues, and human breast milk. Current techniques for separating these compounds from fish tissues require tedious sample clean-upprocedures A simple method for the deterrnination of these compounds in fish tissues has been developed. Closed-loop stripping of saponified fish tissues in a I -L Wheaton purge-and-trap vessel is used to strip compounds with high vapor pressures such as synthetic musks from the matrix onto a solid sorbent (Abselut Nexus). This technique is useful for screening biological tissues that contain lipids for musk compounds. Analytes are desorbed from the sorbent trap sequentially with polar and nonpolar solvents, concentrated, and directly analyzed by high resolution gas chromatography coupled to a mass spectrometer operating in the selected ion monitoring mode. In this paper, we analyzed two homogenized samples of whole fish tissues with spiked synthetic musk compounds using closed-loop stripping analysis (CLSA) and pressurized liquid extraction (PLE). The analytes were not recovered quantitatively but the extraction yield was sufficiently reproducible for at least semi-quantitative purposes (screening). The method was less expensive to implement and required significantly less sample preparation than the PLE technique. The research focused on in the subtasks is the development and application of state-of the-art technologies to meet the needs of the public, Office of Water,

  8. Monitoring Digital Closed-Loop Feedback Systems

    NASA Technical Reports Server (NTRS)

    Katz, Richard; Kleyner, Igor

    2011-01-01

    A technique of monitoring digital closed-loop feedback systems has been conceived. The basic idea is to obtain information on the performances of closed-loop feedback circuits in such systems to aid in the determination of the functionality and integrity of the circuits and of performance margins. The need for this technique arises as follows: Some modern digital systems include feedback circuits that enable other circuits to perform with precision and are tolerant of changes in environment and the device s parameters. For example, in a precision timing circuit, it is desirable to make the circuit insensitive to variability as a result of the manufacture of circuit components and to the effects of temperature, voltage, radiation, and aging. However, such a design can also result in masking the indications of damaged and/or deteriorating components. The present technique incorporates test circuitry and associated engineering-telemetry circuitry into an embedded system to monitor the closed-loop feedback circuits, using spare gates that are often available in field programmable gate arrays (FPGAs). This technique enables a test engineer to determine the amount of performance margin in the system, detect out of family circuit performance, and determine one or more trend(s) in the performance of the system. In one system to which the technique has been applied, an ultra-stable oscillator is used as a reference for internal adjustment of 12 time-to-digital converters (TDCs). The feedback circuit produces a pulse-width-modulated signal that is fed as a control input into an amplifier, which controls the circuit s operating voltage. If the circuit s gates are determined to be operating too slowly or rapidly when their timing is compared with that of the reference signal, then the pulse width increases or decreases, respectively, thereby commanding the amplifier to increase or reduce, respectively, its output level, and "adjust" the speed of the circuits. The nominal

  9. Closed-loop active optical system control

    NASA Astrophysics Data System (ADS)

    Sparks, T. E.

    1980-01-01

    A control system, based on a real-time lateral shear interferometer has been developed for use in control during thermal tests and static error compensation experiments. The minicomputer which controls the interferometer and provides its service functions also controls the active system, thereby giving flexibility to the algorithm. The minicomputer system contains 288 K bytes of memory and 15 M bytes of disk storage. The interferometer system employed is composed of the measuring head and its support electronics, a video display on which wavefront contour maps are generated, and a DECwriter operator console. The versatility provided by the use of a general purpose interferometer system allows for interactive control of the closed-loop process. Various arithmetic capabilities such as the addition of wavefronts, division by a constant, and fitting of wavefront data with Zernike polynomials, allow for measurements to be averaged and for removal of alignment errors before correction is performed.

  10. Closed Loop Requirements and Analysis Management

    NASA Technical Reports Server (NTRS)

    Lamoreaux, Michael; Verhoef, Brett

    2015-01-01

    Effective systems engineering involves the use of analysis in the derivation of requirements and verification of designs against those requirements. The initial development of requirements often depends on analysis for the technical definition of specific aspects of a product. Following the allocation of system-level requirements to a product's components, the closure of those requirements often involves analytical approaches to verify that the requirement criteria have been satisfied. Meanwhile, changes that occur in between these two processes need to be managed in order to achieve a closed-loop requirement derivation/verification process. Herein are presented concepts for employing emerging Team center capabilities to jointly manage requirements and analysis data such that analytical techniques are utilized to effectively derive and allocate requirements, analyses are consulted and updated during the change evaluation processes, and analyses are leveraged during the design verification process. Recommendations on concept validation case studies are also discussed.

  11. CLOSED-LOOP STRIPPING ANALYSIS (CLSA) OF ...

    EPA Pesticide Factsheets

    Synthetic musk compounds are used as inexpensive fragrance materials for the production of perfumes and as additives to soap, detergent, and shampoo. They have been found in surface water, fish tissues, and human breast milk. The ubiquity of this class of compounds in the environment is attributable to high use and release into the environment. Current techniques for separating these compounds from fish tissues require tedious sample clean-up procedures. To obtain fat-free extracts, gel permeation chromatography (GPC), column chromatography using alumina, and silica gel, and thin layer chromatography (TLC clean-up procedures are frequently employed. Despite the considerable effort and resources devoted to these processes, a fraction of the lipids and lipid-like compounds frequently remains in the extracts. These low-level lipids foul injection liners, contaminate columns, and yield elevated baselines during gas chromatographic analysis of synthetic musk compounds. In this study, a simple method for the determination of synthetic musk compounds in fish tissues has been developed. Closed-loop stripping of saponified fish tissues in a I -L Wheaton purge- and-trap vessel, is used to strip compounds with high vapor pressures such as synthetic musks from the matrix onto a solid sorbent (Abselut Nexus). This technique is useful for screening biological tissues that contain lipids for musk compounds. Analytes are desorbed from the sorbent trap sequentially with polar an

  12. Closed Loop Control of Oxygen Delivery and Oxygen Generation

    DTIC Science & Technology

    2017-08-01

    AFRL-SA-WP-SR-2017-0024 Closed Loop Control of Oxygen Delivery and Oxygen Generation Dr. Jay Johannigman1, Richard Branson1...TITLE AND SUBTITLE Closed Loop Control of Oxygen Delivery and Oxygen Generation 5a. CONTRACT NUMBER FA8650-10-2-6140 5b. GRANT NUMBER...humans would be the next step in validating this system. 15. SUBJECT TERMS Closed loop control, oxygen generation , oxygen concentration

  13. Advances in closed-loop deep brain stimulation devices.

    PubMed

    Parastarfeizabadi, Mahboubeh; Kouzani, Abbas Z

    2017-08-11

    Millions of patients around the world are affected by neurological and psychiatric disorders. Deep brain stimulation (DBS) is a device-based therapy that could have fewer side-effects and higher efficiencies in drug-resistant patients compared to other therapeutic options such as pharmacological approaches. Thus far, several efforts have been made to incorporate a feedback loop into DBS devices to make them operate in a closed-loop manner. This paper presents a comprehensive investigation into the existing research-based and commercial closed-loop DBS devices. It describes a brief history of closed-loop DBS techniques, biomarkers and algorithms used for closing the feedback loop, components of the current research-based and commercial closed-loop DBS devices, and advancements and challenges in this field of research. This review also includes a comparison of the closed-loop DBS devices and provides the future directions of this area of research. Although we are in the early stages of the closed-loop DBS approach, there have been fruitful efforts in design and development of closed-loop DBS devices. To date, only one commercial closed-loop DBS device has been manufactured. However, this system does not have an intelligent and patient dependent control algorithm. A closed-loop DBS device requires a control algorithm to learn and optimize the stimulation parameters according to the brain clinical state. The promising clinical effects of open-loop DBS have been demonstrated, indicating DBS as a pioneer technology and treatment option to serve neurological patients. However, like other commercial devices, DBS needs to be automated and modernized.

  14. DC servomechanism parameter identification: a Closed Loop Input Error approach.

    PubMed

    Garrido, Ruben; Miranda, Roger

    2012-01-01

    This paper presents a Closed Loop Input Error (CLIE) approach for on-line parametric estimation of a continuous-time model of a DC servomechanism functioning in closed loop. A standard Proportional Derivative (PD) position controller stabilizes the loop without requiring knowledge on the servomechanism parameters. The analysis of the identification algorithm takes into account the control law employed for closing the loop. The model contains four parameters that depend on the servo inertia, viscous, and Coulomb friction as well as on a constant disturbance. Lyapunov stability theory permits assessing boundedness of the signals associated to the identification algorithm. Experiments on a laboratory prototype allows evaluating the performance of the approach.

  15. Direct-contact closed-loop heat exchanger

    DOEpatents

    Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

    1984-01-01

    A high temperature heat exchanger with a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

  16. Closing the Feedback Loop Is Not Enough: The Assessment Spiral

    ERIC Educational Resources Information Center

    Wehlburg, Catherine M.

    2007-01-01

    For quite some time, the call to close the feedback loop has been heard throughout higher education. Faculty and administrators have paid attention, and now they can more easily than ever point to the fact that at their institution, the feedback loop is almost always closed. As reviewers from accreditation teams visit campuses, they often hear…

  17. Closing the Feedback Loop Is Not Enough: The Assessment Spiral

    ERIC Educational Resources Information Center

    Wehlburg, Catherine M.

    2007-01-01

    For quite some time, the call to close the feedback loop has been heard throughout higher education. Faculty and administrators have paid attention, and now they can more easily than ever point to the fact that at their institution, the feedback loop is almost always closed. As reviewers from accreditation teams visit campuses, they often hear…

  18. Multiday Fully Closed Loop Insulin Delivery in Monitored Outpatient Conditions

    ClinicalTrials.gov

    2014-04-29

    To Demonstrate That the Closed Loop System Can be Used Safely Over a Few Consecutive Days.; To Assess Effectiveness in Maintaining Patients' Glucose Levels in the Target Range of 70 to 180 mg/dl, Measured by Blood Glucose Sensor.; To Evaluate the User Experience With a Closed Loop System

  19. Closed-Loop Neuroscience and Non-Invasive Brain Stimulation: A Tale of Two Loops

    PubMed Central

    Zrenner, Christoph; Belardinelli, Paolo; Müller-Dahlhaus, Florian; Ziemann, Ulf

    2016-01-01

    Closed-loop neuroscience is receiving increasing attention with recent technological advances that enable complex feedback loops to be implemented with millisecond resolution on commodity hardware. We summarize emerging conceptual and methodological frameworks that are available to experimenters investigating a “brain in the loop” using non-invasive brain stimulation and briefly review the experimental and therapeutic implications. We take the view that closed-loop neuroscience in fact deals with two conceptually quite different loops: a “brain-state dynamics” loop, used to couple with and modulate the trajectory of neuronal activity patterns, and a “task dynamics” loop, that is the bidirectional motor-sensory interaction between brain and (simulated) environment, and which enables goal-directed behavioral tasks to be incorporated. Both loops need to be considered and combined to realize the full experimental and therapeutic potential of closed-loop neuroscience. PMID:27092055

  20. Iterative LQG Controller Design Through Closed-Loop Identification

    NASA Technical Reports Server (NTRS)

    Hsiao, Min-Hung; Huang, Jen-Kuang; Cox, David E.

    1996-01-01

    This paper presents an iterative Linear Quadratic Gaussian (LQG) controller design approach for a linear stochastic system with an uncertain open-loop model and unknown noise statistics. This approach consists of closed-loop identification and controller redesign cycles. In each cycle, the closed-loop identification method is used to identify an open-loop model and a steady-state Kalman filter gain from closed-loop input/output test data obtained by using a feedback LQG controller designed from the previous cycle. Then the identified open-loop model is used to redesign the state feedback. The state feedback and the identified Kalman filter gain are used to form an updated LQC controller for the next cycle. This iterative process continues until the updated controller converges. The proposed controller design is demonstrated by numerical simulations and experiments on a highly unstable large-gap magnetic suspension system.

  1. Dynamics of closed-loop systems containing flexible bodies

    NASA Technical Reports Server (NTRS)

    Tadikonda, Sivakumar S. K.; Singh, Ramendra P.

    1991-01-01

    An important characteristic of flexible multibody systems containing closed-loop topologies is that the component modes used to describe individual bodies will no longer be independent because of loop closure constraints. Thus, the issue of component modal selection becomes even more complicated. In addition, the foreshortening effect that has been studied extensively in the literature in the context of open-loop topologies will also be present in these constraint equations. Simulation results presented demonstrate the effects of modal selection and foreshortening on the dynamic response of closed-loop flexible systems.

  2. Dynamics of closed-loop systems containing flexible bodies

    NASA Technical Reports Server (NTRS)

    Tadikonda, Sivakumar S. K.; Singh, Ramendra P.

    1991-01-01

    An important characteristic of flexible multibody systems containing closed-loop topologies is that the component modes used to describe individual bodies will no longer be independent because of loop closure constraints. Thus, the issue of component modal selection becomes even more complicated. In addition, the foreshortening effect that has been studied extensively in the literature in the context of open-loop topologies will also be present in these constraint equations. Simulation results presented demonstrate the effects of modal selection and foreshortening on the dynamic response of closed-loop flexible systems.

  3. Spacecraft Closed Loop Three-Axis Momentum Unloading System.

    DTIC Science & Technology

    reaction wheel speed information, wheel speed threshold and geomagnetic latitude information and controls magnetic dipoles that will create a spacecraft torque and desaturate reaction wheels in a closed loop system. (Author)

  4. Tight Loops Close-Up [video

    NASA Image and Video Library

    2017-09-27

    NASA's Solar Dynamics Observatory (SDO) zoomed in almost to its maximum level to watch tight, bright loops and much longer, softer loops shift and sway above an active region on the sun, while a darker blob of plasma in their midst was pulled about every which way (May 13-14, 2014). The video clip covers just over a day beginning at 14:19 UT on May 13. The frames were taken in the 171-angstroms wavelength of extreme ultraviolet light, but colorized red, instead of its usual bronze tone. This type of dynamic activity continues almost non-stop on the sun as opposing magnetic forces tangle with each other. Credit: NASA/Solar Dynamics Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  5. Closed loop spray cooling apparatus. [for particle accelerator targets

    NASA Technical Reports Server (NTRS)

    Alger, D. L.; Schwab, W. B.; Furman, E. R. (Inventor)

    1978-01-01

    A closed loop apparatus for spraying coolant against the back of a radiation target is described. The coolant was circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material was disposed between the bubble and the surface of the liquid coolant which was below the bubble at a predetermined level. In a second embodiment, no inert gas was used, the bubble consisting of a vapor produced when the coolant was sprayed against the target.

  6. Virtual Grasping: Closed-Loop Force Control Using Electrotactile Feedback

    PubMed Central

    Jorgovanovic, Nikola; Dosen, Strahinja; Djozic, Damir J.; Krajoski, Goran; Farina, Dario

    2014-01-01

    Closing the control loop by providing somatosensory feedback to the user of a prosthesis is a well-known, long standing challenge in the field of prosthetics. Various approaches have been investigated for feedback restoration, ranging from direct neural stimulation to noninvasive sensory substitution methods. Although there are many studies presenting closed-loop systems, only a few of them objectively evaluated the closed-loop performance, mostly using vibrotactile stimulation. Importantly, the conclusions about the utility of the feedback were partly contradictory. The goal of the current study was to systematically investigate the capability of human subjects to control grasping force in closed loop using electrotactile feedback. We have developed a realistic experimental setup for virtual grasping, which operated in real time, included a set of real life objects, as well as a graphical and dynamical model of the prosthesis. We have used the setup to test 10 healthy, able bodied subjects to investigate the role of training, feedback and feedforward control, robustness of the closed loop, and the ability of the human subjects to generalize the control to previously “unseen” objects. Overall, the outcomes of this study are very optimistic with regard to the benefits of feedback and reveal various, practically relevant, aspects of closed-loop control. PMID:24516504

  7. Virtual grasping: closed-loop force control using electrotactile feedback.

    PubMed

    Jorgovanovic, Nikola; Dosen, Strahinja; Djozic, Damir J; Krajoski, Goran; Farina, Dario

    2014-01-01

    Closing the control loop by providing somatosensory feedback to the user of a prosthesis is a well-known, long standing challenge in the field of prosthetics. Various approaches have been investigated for feedback restoration, ranging from direct neural stimulation to noninvasive sensory substitution methods. Although there are many studies presenting closed-loop systems, only a few of them objectively evaluated the closed-loop performance, mostly using vibrotactile stimulation. Importantly, the conclusions about the utility of the feedback were partly contradictory. The goal of the current study was to systematically investigate the capability of human subjects to control grasping force in closed loop using electrotactile feedback. We have developed a realistic experimental setup for virtual grasping, which operated in real time, included a set of real life objects, as well as a graphical and dynamical model of the prosthesis. We have used the setup to test 10 healthy, able bodied subjects to investigate the role of training, feedback and feedforward control, robustness of the closed loop, and the ability of the human subjects to generalize the control to previously "unseen" objects. Overall, the outcomes of this study are very optimistic with regard to the benefits of feedback and reveal various, practically relevant, aspects of closed-loop control.

  8. Xerox's closed recycling loop still contains kinks

    SciTech Connect

    Not Available

    1995-02-01

    Xerox Corp. has established a recycling loop for plastics screw-top toner bottles and dry-ink containers used in most of the company's high-volume copiers. However, a severe shortage of post-consumer recycled plastic has been short-circuiting Xerox's good intentions. Last year, the Stamford, Conn.-based company stopped manufacturing toner containers from virgin plastics and instead began using recycled raw materials, such as discarded milk and water jugs collected from municipal curbside recycling programs. The bottles are ground and remolded into such products as air filters for vacuum cleaners, plastic lumber, compost bins, landscape ties, benches and fence posts. However, what sounds like a win-win situation actually is costing too much money. Contrary to popular belief, post-consumer recycled plastic costs more than virgin plastic. Despite the added expense, Xerox will continue to use recycled plastics when possible.

  9. Direct-contact closed-loop heat exchanger

    DOEpatents

    Berry, G.F.; Minkov, V.; Petrick, M.

    1981-11-02

    A high temperature heat exchanger is disclosed which has a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

  10. Closing the Loop on Classroom Interventions

    ERIC Educational Resources Information Center

    McCue, Patrick

    2010-01-01

    No Child Left Behind's mandate to close the achievement gap for students with disabilities and the emergence of response to intervention (RTI) as a means to address students' learning needs have led many schools to use more preventive academic supports within the general education classroom. The use of a diagnostic, intervention-based approach to…

  11. The effect of insulin feedback on closed loop glucose control.

    PubMed

    Steil, Garry M; Palerm, Cesar C; Kurtz, Natalie; Voskanyan, Gayane; Roy, Anirban; Paz, Sachiko; Kandeel, Fouad R

    2011-05-01

    Initial studies of closed-loop proportional integral derivative control in individuals with type 1 diabetes showed good overnight performance, but with breakfast meal being the hardest to control and requiring supplemental carbohydrate to prevent hypoglycemia. The aim of this study was to assess the ability of insulin feedback to improve the breakfast-meal profile. We performed a single center study with closed-loop control over approximately 30 h at an inpatient clinical research facility. Eight adult subjects with previously diagnosed type 1 diabetes participated. Subjects received closed-loop insulin delivery with supplemental carbohydrate as needed. Outcome measures were plasma insulin concentration, model-predicted plasma insulin concentration, 2-h postprandial and 3- to 4-h glucose rate-of-change following breakfast after 1 d of closed-loop control, and the need for supplemental carbohydrate in response to nadir hypoglycemia. Plasma insulin levels during closed loop were well correlated with model predictions (R = 0.86). Fasting glucose after 1 d of closed loop was not different from nighttime target (118 ± 9 vs. 110 mg/dl; P = 0.38). Two-hour postbreakfast glucose was 132 ± 16 mg/dl with stable values 3-4 h after the meal (0.03792 ± 0.0884 mg/dl · min, not different from 0; P = 0.68) and at target (97 ± 6 mg/dl, not different from 90; P = 0.28). Three subjects required supplemental carbohydrates after breakfast on d 2 of closed loop. Insulin feedback can be implemented using a model estimate of concentration. Proportional integral derivative control with insulin feedback can achieve a desired breakfast response but still requires supplemental carbohydrate to be delivered in some instances. Studies assessing more optimal control configurations and safeguards need to be conducted.

  12. Open-loop versus closed-loop control of MEMS devices: choices and issues

    NASA Astrophysics Data System (ADS)

    Borovic, B.; Liu, A. Q.; Popa, D.; Cai, H.; Lewis, F. L.

    2005-10-01

    From a controls point of view, micro electromechanical systems (MEMS) can be driven in an open-loop and closed-loop fashion. Commonly, these devices are driven open-loop by applying simple input signals. If these input signals become more complex by being derived from the system dynamics, we call such control techniques pre-shaped open-loop driving. The ultimate step for improving precision and speed of response is the introduction of feedback, e.g. closed-loop control. Unlike macro mechanical systems, where the implementation of the feedback is relatively simple, in the MEMS case the feedback design is quite problematic, due to the limited availability of sensor data, the presence of sensor dynamics and noise, and the typically fast actuator dynamics. Furthermore, a performance comparison between open-loop and closed-loop control strategies has not been properly explored for MEMS devices. The purpose of this paper is to present experimental results obtained using both open- and closed-loop strategies and to address the comparative issues of driving and control for MEMS devices. An optical MEMS switching device is used for this study. Based on these experimental results, as well as computer simulations, we point out advantages and disadvantages of the different control strategies, address the problems that distinguish MEMS driving systems from their macro counterparts, and discuss criteria to choose a suitable control driving strategy.

  13. Closed-loop performance of pyramid wavefront sensor

    NASA Astrophysics Data System (ADS)

    Esposito, Simone; Riccardi, Armando; Feeney, Orla

    2000-07-01

    We consider the performance of the wavefront reconstruction process when a Pyramid wavefront Sensor is used in a closed loop Adaptive Optics System. The Pyramid Sensor sensitivity in closed loop operations has been the subject of a first heuristic analysis showing that the sensor sensitivity is higher than that of a Shack-Hartmann sensor, at least when low order modes are considered. In this paper we evaluate the sensor accuracy by determining the closed loop reconstruction matrix. This is done using a diffractive analysis of the sensor behavior. Furthermore, knowledge of this matrix enables us to quantify the effect of error sources like sensor non linearity and photon noise on the reconstructed wavefront accuracy. Finally, a comparison of the performance of the Shack-Hartmann and Pyramid wavefront sensors is given.

  14. Closed-Loop and Activity-Guided Optogenetic Control

    PubMed Central

    Grosenick, Logan; Marshel, James H.; Deisseroth, Karl

    2016-01-01

    Advances in optical manipulation and observation of neural activity have set the stage for widespread implementation of closed-loop and activity-guided optical control of neural circuit dynamics. Closing the loop optogenetically (i.e., basing optogenetic stimulation on simultaneously observed dynamics in a principled way) is a powerful strategy for causal investigation of neural circuitry. In particular, observing and feeding back the effects of circuit interventions on physiologically relevant timescales is valuable for directly testing whether inferred models of dynamics, connectivity, and causation are accurate in vivo. Here we highlight technical and theoretical foundations as well as recent advances and opportunities in this area, and we review in detail the known caveats and limitations of optogenetic experimentation in the context of addressing these challenges with closed-loop optogenetic control in behaving animals. PMID:25856490

  15. Closing the loop In Practice to Assure the Desired Performance

    PubMed Central

    Stead, William W.; Patel, Neal R.; Starmer, John M.

    2008-01-01

    A closed loop control process assures that a system performs within control limits. In closed loop control, the system's output feeds back directly to change the system's inputs. We describe an approach to planning and monitoring care that uses closed loop control to assure the desired performance using examples from Vanderbilt University Medical Center's ventilator management initiative. The approach has three components: an explicit end-to-end plan; a record of what is done as it is done; and an instant display of the status of each patient against their plan. The status display provides process control by showing the clinical team where correction is needed while they have time to act prospectively. Plans, displays and performance evolve together iteratively until the desired performance is achieved. PMID:18596845

  16. Neuroelectronics and Biooptics: Closed-Loop Technologies in Neurological Disorders.

    PubMed

    Krook-Magnuson, Esther; Gelinas, Jennifer N; Soltesz, Ivan; Buzsáki, György

    2015-07-01

    Brain-implanted devices are no longer a futuristic idea. Traditionally, therapies for most neurological disorders are adjusted based on changes in clinical symptoms and diagnostic measures observed over time. These therapies are commonly pharmacological or surgical, requiring continuous or irreversible treatment regimens that cannot respond rapidly to fluctuations of symptoms or isolated episodes of dysfunction. In contrast, closed-loop systems provide intervention only when needed by detecting abnormal neurological signals and modulating them with instantaneous feedback. Closed-loop systems have been applied to several neurological conditions (most notably epilepsy and movement disorders), but widespread use is limited by conceptual and technical challenges. Herein, we discuss how advances in experimental closed-loop systems hold promise for improved clinical benefit in patients with neurological disorders.

  17. Closed-loop phase behaviour in block copolymers.

    PubMed

    Ryu, Du Yeol; Jeong, Unyong; Kim, Jin Kon; Russell, Thomas P

    2002-10-01

    Closed-loop phase diagrams are known in systems with specific intermolecular interactions. In weakly interacting systems, however, such behaviour has never been observed. Here, diblock copolymers formed from polystyrene covalently linked to poly (n-pentylmethacrylate), P(S-b-nPMA), which have only weak segmental interactions, are shown to exhibit a closed-loop phase behaviour over a narrow range of molecular weight. The endothermic transitions from the disordered to ordered and back to the disordered state, as a function of increasing temperature, are dominantly entropic in origin. The morphology and rheological properties of P(S-b-nPMA) undergo characteristic changes at the transitions. Whereas the disorder-to-order transition temperature increases with decreasing molecular weight, the order-to-disorder transition temperature decreases. At a limiting molecular weight, the closed-loop vanishes and no ordering occurs. These findings provide quantitative insight into an elusive transition in weakly interacting multicomponent systems.

  18. System identification from closed-loop data with known output feedback dynamics

    NASA Technical Reports Server (NTRS)

    Phan, Minh; Juang, Jer-Nan; Horta, Lucas G.; Longman, Richard W.

    1992-01-01

    This paper presents a procedure to identify the open loop systems when it is operating under closed loop conditions. First, closed loop excitation data are used to compute the system open loop and closed loop Markov parameters. The Markov parameters, which are the pulse response samples, are then used to compute a state space representation of the open loop system. Two closed loop configurations are considered in this paper. The closed loop system can have either a linear output feedback controller or a dynamic output feedback controller. Numerical examples are provided to illustrate the proposed closed loop identification method.

  19. Closed loop control of inspired oxygen concentration in trauma patients.

    PubMed

    Johannigman, Jay A; Branson, Richard D; Edwards, Michael G

    2009-05-01

    Transport of mechanically ventilated patients in a combat zone presents challenges, including conservation of resources. In the battlefield setting, provision of oxygen supplies remains an important issue. Autonomous control of oxygen concentration can allow a reduction in oxygen usage and reduced mission weight. Trauma patients requiring ventilation and inspired oxygen concentration (FIO(2)) > 0.40 were evaluated for study. Patients were randomized to consecutive 4-hour periods of closed loop control or standard care. The system for autonomous control consisted of a ventilator, oximeter, and a portable computer. The computer housed the control algorithm and collected data every 5 seconds. The controller goal was to maintain pulse oximetry (SpO(2)) at 94 +/- 2% through discrete changes of 1% to 5% every 30 seconds. Ventilator settings and SpO(2) were recorded every 5 seconds for analysis. Forty-five patients were enrolled in this study. Oxygen saturation was maintained in the 92% to 96% saturation range 33 +/- 36% of the time during clinician control versus 83 +/- 21% during closed loop control. Time spent at the target SpO(2) 92% to 96% was 193.3 +/- 59.18 minutes during closed loop control and 87.08 +/- 87.95 minutes during clinician control (p < 0.001). Hyperoxemia was more frequent during clinician control (144.29 +/- 90.09 minutes) than during closed loop control (38.91 +/- 55.86 minutes; p < 0.001). There were no differences in the number of episodes of SpO(2) < 88%. Oxygen usage was reduced by 32% during closed loop control. Closed loop control of FIO(2) offers the opportunity for maximizing oxygen resources, reducing mission weight, and providing targeted normoxemia without increasing risk of hypoxemia in ventilated trauma patients.

  20. Crystal structures of Physcomitrella patens AOC1 and AOC2: insights into the enzyme mechanism and differences in substrate specificity.

    PubMed

    Neumann, Piotr; Brodhun, Florian; Sauer, Kristin; Herrfurth, Cornelia; Hamberg, Mats; Brinkmann, Jens; Scholz, Julia; Dickmanns, Achim; Feussner, Ivo; Ficner, Ralf

    2012-11-01

    In plants, oxylipins regulate developmental processes and defense responses. The first specific step in the biosynthesis of the cyclopentanone class of oxylipins is catalyzed by allene oxide cyclase (AOC) that forms cis(+)-12-oxo-phytodienoic acid. The moss Physcomitrella patens has two AOCs (PpAOC1 and PpAOC2) with different substrate specificities for C₁₈- and C₂₀-derived substrates, respectively. To better understand AOC's catalytic mechanism and to elucidate the structural properties that explain the differences in substrate specificity, we solved and analyzed the crystal structures of 36 monomers of both apo and ligand complexes of PpAOC1 and PpAOC2. From these data, we propose the following intermediates in AOC catalysis: (1) a resting state of the apo enzyme with a closed conformation, (2) a first shallow binding mode, followed by (3) a tight binding of the substrate accompanied by conformational changes in the binding pocket, and (4) initiation of the catalytic cycle by opening of the epoxide ring. As expected, the substrate dihydro analog cis-12,13S-epoxy-9Z,15Z-octadecadienoic acid did not cyclize in the presence of PpAOC1; however, when bound to the enzyme, it underwent isomerization into the corresponding trans-epoxide. By comparing complex structures of the C₁₈ substrate analog with in silico modeling of the C₂₀ substrate analog bound to the enzyme allowed us to identify three major molecular determinants responsible for the different substrate specificities (i.e. larger active site diameter, an elongated cavity of PpAOC2, and two nonidentical residues at the entrance of the active site).

  1. Closed-Loop System Removes Contaminants From Inert Gas

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.

    1995-01-01

    Concentration of oxygen in this closed-loop system kept low by use of heated catalytic sorbent bed in cartridge. Proposed to keep concentration of water vapor low by use of predried zeolite sorbent bed in another cartridge, and to remove particles smaller than 0.1 micrometer by use of porous metal filters. In specific application, chamber is one in which semiconducting materials processed. By virtue of closed-loop operation, limited supply of inert gas adequate to provide atmosphere for industrial processing of semiconductors.

  2. [Closed-loop blood transfusion management system based on PDA].

    PubMed

    Chen, Yiyi; Chen, Canda; Luo, Luo; Yin, Zhou; Zhou, Min; Xie, Qiong; Xu, Min; Zhang, Qiutao

    2013-09-01

    A closed-loop transfusion management system is constructed that covers blood preservation, transportation, transfer, distribution of blood, distribution, clinical blood specimen collection and blood transfusion process, which can monitor the implementation of doctor's advice, view the transport process of blood and blood samples, and record blood transfusion and adverse reaction information. These measurements can play a good effect in reduction of manual records and handover links in blood transfusion management, enhance the blood bank management, guarantee safely using blood, and realize the goal of real-time monitoring and closed-loop management.

  3. Development of closed loop roll control for magnetic balance systems

    NASA Technical Reports Server (NTRS)

    Covert, E. E.; Haldeman, C. W.; Ramohalli, G.; Way, P.

    1982-01-01

    This research was undertaken with the goal of demonstrating closed loop control of the roll degree of freedom on the NASA prototype magnetic suspension and balance system at the MIT Aerophysics Laboratory, thus, showing feasibility for a roll control system for any large magnetic balance system which might be built in the future. During the research under this grant, study was directed toward the several areas of torque generation, position sensing, model construction and control system design. These effects were then integrated to produce successful closed loop operation of the analogue roll control system. This experience indicated the desirability of microprocessor control for the angular degrees of freedom.

  4. Operational results of a Closed Brayton Cycle test-loop.

    SciTech Connect

    Fuller, Robert; Wright, Steven Alan; Nichols, Kenneth Graham.; Brown, Nicholas; Lipinski, Ronald J.

    2004-11-01

    A number of space and terrestrial power system designs plan to use nuclear reactors that are coupled to Closed-loop Brayton Cycle (CBC) systems to generate electrical power. Because very little experience exists regarding the operational behavior of these systems, Sandia National Laboratories (through its Laboratory Directed Research and Development program) is developing a closed-loop test bed that can be used to determine the operational behavior of these systems and to validate models for these systems. Sandia has contracted Barber-Nichols Corporation to design, fabricate, and assemble a Closed-loop Brayton Cycle (CBC) system. This system was developed by modifying commercially available hardware. It uses a 30 kWe Capstone C-30 gas-turbine unit (www.capstoneturbine.com) with a modified housing that permits the attachment of an electrical heater and a water cooled chiller that are connected to the turbo-machinery in a closed loop. The test-loop reuses the Capstone turbine, compressor, and alternator. The Capstone system's nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system are also reused. The rotational speed of the turbo-machinery is controlled either by adjusting the alternator load by either using the electrical grid or a separate load bank. This report describes the test-loop hardware SBL-30 (Sandia Brayton Loop-30kWe). Also presented are results of early testing and modeling of the unit. The SBL-30 hardware is currently configured with a heater that is limited to 80 kW{sub th} with a maximum outlet temperature of {approx}1000 K.

  5. Operational Results of a Closed Brayton Cycle Test-Loop

    NASA Astrophysics Data System (ADS)

    Wright, Steven A.; Fuller, Robert; Lipinski, Ronald J.; Nichols, Kenneth; Brown, Nicholas

    2005-02-01

    A number of space and terrestrial power system designs plan to use nuclear reactors that are coupled to Closed-loop Brayton Cycle (CBC) systems to generate electrical power. Because very little experience exists regarding the operational behavior of these systems, Sandia National Laboratories (through its Laboratory Directed Research and Development program) is developing a closed-loop test bed that can be used to determine the operational behavior of these systems and to validate models for these systems. Sandia has contracted Barber-Nichols Corporation to design, fabricate, and assemble a Closed-loop Brayton Cycle (CBC) system. This system was developed by modifying commercially available hardware. It uses a 30 kWe Capstone C-30 gas-turbine unit (www.capstoneturbine.com) with a modified housing that permits the attachment of an electrical heater and a water cooled chiller that are connected to the turbo-machinery in a closed loop. The test-loop reuses the Capstone turbine, compressor, and alternator. The Capstone system's nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system are also reused. The rotational speed of the turbo-machinery is controlled either by adjusting the alternator load by either using the electrical grid or a separate load bank. This report describes the test-loop hardware SBL-30 (Sandia Brayton Loop-30kWe). Also presented are results of early testing and modeling of the unit. The SBL-30 hardware is currently configured with a heater that is limited to 80 kWth with a maximum outlet temperature of ˜1000 K.

  6. Closed loop identification using a modified Hansen scheme

    NASA Astrophysics Data System (ADS)

    Sekunda, A.; Niemann, H.; Kjølstad Poulsen, N.; Santos, I.

    2015-11-01

    It is often not feasible or even impossible to identify a plant in open loop. This might be because the plant contains unstable poles, or it is simply too expensive to remove the plant from its intended operation, among other possibilities. There are several methods for identifying a plant in closed loop [4], and one such method is the Hansen scheme [1]. Standard identification using Hansen scheme demands generating the identification signals indirectly. In this paper it is instead proposed to use the relationship between the Youla factorization of a plant and its stabilizing controller to directly measure the signals used for identification. A simulation example and identification of a gas bearing is given to show the method in action. Rotors supported by controllable gas bearings are open loop stable systems. However as the rotational speed is increased feedback control is necessary in order to keep the system stable. Furthermore because the dynamics of such a system depends on the rotational speed it is needed to conduct an identification while the system is part of a closed loop scheme. The authors believe the paper able to contribute towards a simpler and more direct way of identifying closed loop plants using Hansen scheme.

  7. Perception as a closed-loop convergence process

    PubMed Central

    Ahissar, Ehud; Assa, Eldad

    2016-01-01

    Perception of external objects involves sensory acquisition via the relevant sensory organs. A widely-accepted assumption is that the sensory organ is the first station in a serial chain of processing circuits leading to an internal circuit in which a percept emerges. This open-loop scheme, in which the interaction between the sensory organ and the environment is not affected by its concurrent downstream neuronal processing, is strongly challenged by behavioral and anatomical data. We present here a hypothesis in which the perception of external objects is a closed-loop dynamical process encompassing loops that integrate the organism and its environment and converging towards organism-environment steady-states. We discuss the consistency of closed-loop perception (CLP) with empirical data and show that it can be synthesized in a robotic setup. Testable predictions are proposed for empirical distinction between open and closed loop schemes of perception. DOI: http://dx.doi.org/10.7554/eLife.12830.001 PMID:27159238

  8. Integrated closed-loop cavity of a tunable laser

    NASA Astrophysics Data System (ADS)

    Ren, M.; Cai, H.; Gu, Y. D.; Chin, L. K.; Radhakrishnan, K.; Ser, W.; Sun, H. D.; Liang, Q. X.; Kwong, D.-L.; Liu, A. Q.

    2016-10-01

    In this paper, a closed-loop cavity of a tunable laser integrated onto a silicon chip is demonstrated. The closed-loop cavity consists of a semiconductor optical amplifier chip, two separated micro-ring resonators, and a U-shaped waveguide sub-loop, enabling dominating lasing in the counterclockwise direction. The lasing wavelength is tuned by varying the effective refractive index of the thermal ring-resonators. It has achieved wide tuning range (55.4 nm), high spectral purity (50-dB side mode suppression ratio), ˜1-mW output power, and 36-dB counter-propagation power suppression ratio. The integrated tunable laser has high potential in applications such as optical network, optical sensing, and integrated optoelectronic systems.

  9. Closed-loop real-time infrared scene generator

    NASA Astrophysics Data System (ADS)

    Crow, Dennis R.; Coker, Charles F.; Garbo, Dennis L.; Olson, Eric M.

    1998-07-01

    A computer program has been developed to provide closed-loop infrared imagery of composite targets and backgrounds in real- time. This program operates on parametric databases generated off-line by computationally intensive first principle physics codes such as the Composite Hardbody and Missile Plume (CHAMP) program, Synthetic Scene Generation Model (SSGM), and Multi- Spectral Modeling and Analysis (MSMA/Irma program. The parametric databases allow dynamic variations in flight and engagement scenarios to be modeled as closed-loop guidance and control algorithms modify the operational dynamics. The program is tightly coupled with the parametric databases to produce infrared radiation results in real-time and OpenGL graphic libraries to interface with high performance graphic hardware. The program is being sponsored for development by the Kinetic Kill Vehicle Hardware-in-the-Loop Simulator facility of the Air Force Research Laboratory Munitions Directorate located at Eglin AFB, Florida.

  10. Feasibility of Outpatient Fully Integrated Closed-Loop Control

    PubMed Central

    Kovatchev, Boris P.; Renard, Eric; Cobelli, Claudio; Zisser, Howard C.; Keith-Hynes, Patrick; Anderson, Stacey M.; Brown, Sue A.; Chernavvsky, Daniel R.; Breton, Marc D.; Farret, Anne; Pelletier, Marie-Josée; Place, Jérôme; Bruttomesso, Daniela; Del Favero, Simone; Visentin, Roberto; Filippi, Alessio; Scotton, Rachele; Avogaro, Angelo; Doyle, Francis J.

    2013-01-01

    OBJECTIVE To evaluate the feasibility of a wearable artificial pancreas system, the Diabetes Assistant (DiAs), which uses a smart phone as a closed-loop control platform. RESEARCH DESIGN AND METHODS Twenty patients with type 1 diabetes were enrolled at the Universities of Padova, Montpellier, and Virginia and at Sansum Diabetes Research Institute. Each trial continued for 42 h. The United States studies were conducted entirely in outpatient setting (e.g., hotel or guest house); studies in Italy and France were hybrid hospital–hotel admissions. A continuous glucose monitoring/pump system (Dexcom Seven Plus/Omnipod) was placed on the subject and was connected to DiAs. The patient operated the system via the DiAs user interface in open-loop mode (first 14 h of study), switching to closed-loop for the remaining 28 h. Study personnel monitored remotely via 3G or WiFi connection to DiAs and were available on site for assistance. RESULTS The total duration of proper system communication functioning was 807.5 h (274 h in open-loop and 533.5 h in closed-loop), which represented 97.7% of the total possible time from admission to discharge. This exceeded the predetermined primary end point of 80% system functionality. CONCLUSIONS This study demonstrated that a contemporary smart phone is capable of running outpatient closed-loop control and introduced a prototype system (DiAs) for further investigation. Following this proof of concept, future steps should include equipping insulin pumps and sensors with wireless capabilities, as well as studies focusing on control efficacy and patient-oriented clinical outcomes. PMID:23801798

  11. A new closed loop control method for HVDC transmission

    SciTech Connect

    Karlecik-Maier, F.

    1996-10-01

    The paper presents a new closed loop control method which uses information locally available at each converter station and combines and coordinates control possibilities with the objective of improving the dynamic behavior during fault recoveries and disturbances around the operating points.

  12. Closing the Loop on a Continuous Program Improvement Process

    ERIC Educational Resources Information Center

    Booth, Vickie; Booth, Larry

    2010-01-01

    The WebBSIT, a Bachelor of Science in Information Technology, is a fully online degree offered through a consortium of five University System of Georgia institutions. This paper begins by summarizing the change management system developed for continuous program improvement. Analysis of data should drive improvement, closing the loop. The balance…

  13. Closing the Loop on a Continuous Program Improvement Process

    ERIC Educational Resources Information Center

    Booth, Vickie; Booth, Larry

    2010-01-01

    The WebBSIT, a Bachelor of Science in Information Technology, is a fully online degree offered through a consortium of five University System of Georgia institutions. This paper begins by summarizing the change management system developed for continuous program improvement. Analysis of data should drive improvement, closing the loop. The balance…

  14. Novel imaging closed loop control strategy for heliostats

    NASA Astrophysics Data System (ADS)

    Bern, Gregor; Schöttl, Peter; Heimsath, Anna; Nitz, Peter

    2017-06-01

    Central Receiver Systems use up to thousands of heliostats to concentrate solar radiation. The precise control of heliostat aiming points is crucial not only for efficiency but also for reliable plant operation. Besides the calibration of open loop control systems, closed loop tracking strategies are developed to address a precise and efficient aiming strategy. The need for cost reductions in the heliostat field intensifies the motivation for economic closed loop control systems. This work introduces an approach for a closed loop heliostat tracking strategy using image analysis and signal modulation. The approach aims at the extraction of heliostat focal spot position within the receiver domain by means of a centralized remote vision system decoupled from the rough conditions close to the focal area. Taking an image sequence of the receiver while modulating a signal on different heliostats, their aiming points are retrieved. The work describes the methodology and shows first results from simulations and practical tests performed in small scale, motivating further investigation and deployment.

  15. Part-Time Instructors: Closing the Quality Loop

    ERIC Educational Resources Information Center

    Glaskin-Clay, Bruce

    2007-01-01

    This article looks at ways to ensure client quality in continuing education part-time programs. It identifies the stakeholders involved in these programs as the instructor, the student, the college, and the employer. It then addresses methods of feedback to close the quality loop thus ensuring alignment of outcomes for all stakeholders. It was…

  16. [Influencing Factors of Assimilable Organic Carbon (AOC) Formation in Drinking Water During Ozonation Process].

    PubMed

    Dong, Bing-zhi; Zhang, Jia-li; He, Chang

    2016-05-15

    The influences of ozone dosage, pH and ionic strength on the formation of Assimilable Organic Carbon (AOC) during ozonation were investigated. The result demonstrated that within the range of 1-5 mg · L⁻¹ O₃, the formation of AOC increased with increasing ozone dosage, but higher ozone dosage (9 mg · L⁻¹) resulted in reduction of AOC formation. AOC formation increased with higher pH but decreased with increasing ionic strength. The result also showed that AOC formation with hydrophobic fraction (HPO) was the most, followed by transphilic fraction (TPI), and charged hydrophilic fraction (CHPI), while neutral hydrophilic fraction (NHPI) was the least. It was found that AOC formation related closely with SUVA of small molecular weight organics, and the lower SUVA produced more AOC.

  17. Design validation and performance of closed loop gas recirculation system

    NASA Astrophysics Data System (ADS)

    Kalmani, S. D.; Joshi, A. V.; Majumder, G.; Mondal, N. K.; Shinde, R. R.

    2016-11-01

    A pilot experimental set up of the India Based Neutrino Observatory's ICAL detector has been operational for the last 4 years at TIFR, Mumbai. Twelve glass RPC detectors of size 2 × 2 m2, with a gas gap of 2 mm are under test in a closed loop gas recirculation system. These RPCs are continuously purged individually, with a gas mixture of R134a (C2H2F4), isobutane (iC4H10) and sulphur hexafluoride (SF6) at a steady rate of 360 ml/h to maintain about one volume change a day. To economize gas mixture consumption and to reduce the effluents from being released into the atmosphere, a closed loop system has been designed, fabricated and installed at TIFR. The pressure and flow rate in the loop is controlled by mass flow controllers and pressure transmitters. The performance and integrity of RPCs in the pilot experimental set up is being monitored to assess the effect of periodic fluctuation and transients in atmospheric pressure and temperature, room pressure variation, flow pulsations, uniformity of gas distribution and power failures. The capability of closed loop gas recirculation system to respond to these changes is also studied. The conclusions from the above experiment are presented. The validations of the first design considerations and subsequent modifications have provided improved guidelines for the future design of the engineering module gas system.

  18. Utility Plastic Recycling, Inc.: Closing the loop in-house

    SciTech Connect

    Harrison, S.

    1995-07-01

    Despite current favorable markets, ``closing the loop`` in recycling can remain a vexing problem. New York City`s Utility Plastic Recycling, Inc., has eliminated some of the guesswork by manufacturing recycled products on the premises of its materials recovery facility (MRF). Utility Plastic is a member of the Waste Management of New York (WMNY) family of companies that also includes JLJ Recycling, Commercial Recycling Technology, and Evergreen Recycling. The company is a third-generation firm that began commercially recycling glass and cardboard collected from the Knickerbocker Brewery in 1928. WMNY`s service in every aspect of recycling -- including program planning and implementation, collection, processing, manufacturing, and marketing -- makes them one of the first true close-loop recyclers. Processing almost half of the recyclables in New York City`s residential program, in addition to materials collected from several suburban communities and thousands of commercial contracts, also makes them one of the largest.

  19. Closed-Loop Analysis of Soft Decisions for Serial Links

    NASA Technical Reports Server (NTRS)

    Lansdowne, Chatwin A.; Steele, Glen F.; Zucha, Joan P.; Schlesinger, Adam M.

    2013-01-01

    We describe the benefit of using closed-loop measurements for a radio receiver paired with a counterpart transmitter. We show that real-time analysis of the soft decision output of a receiver can provide rich and relevant insight far beyond the traditional hard-decision bit error rate (BER) test statistic. We describe a Soft Decision Analyzer (SDA) implementation for closed-loop measurements on single- or dual- (orthogonal) channel serial data communication links. The analyzer has been used to identify, quantify, and prioritize contributors to implementation loss in live-time during the development of software defined radios. This test technique gains importance as modern receivers are providing soft decision symbol synchronization as radio links are challenged to push more data and more protocol overhead through noisier channels, and software-defined radios (SDRs) use error-correction codes that approach Shannon's theoretical limit of performance.

  20. Closed-Loop Analysis of Soft Decisions for Serial Links

    NASA Technical Reports Server (NTRS)

    Lansdowne, Chatwin A.; Steele, Glen F.; Zucha, Joan P.; Schlensinger, Adam M.

    2012-01-01

    Modern receivers are providing soft decision symbol synchronization as radio links are challenged to push more data and more overhead through noisier channels, and software-defined radios use error-correction techniques that approach Shannon s theoretical limit of performance. The authors describe the benefit of closed-loop measurements for a receiver when paired with a counterpart transmitter and representative channel conditions. We also describe a real-time Soft Decision Analyzer (SDA) implementation for closed-loop measurements on single- or dual- (orthogonal) channel serial data communication links. The analyzer has been used to identify, quantify, and prioritize contributors to implementation loss in real-time during the development of software defined radios.

  1. [The Way to Closed Loop - Dream and Reality].

    PubMed

    Biester, Torben; Danne, Thomas; Kordonouri, Olga

    2017-05-01

    An old dream of patients with type 1 diabetes and medical teams alike is a fully automated insulin therapy. Available sensor-augmented insulin-pumps are able to intervene in insulin therapy by reducing the dose. Aim of several studies is to add an algorithm to the interaction of pump and sensor, so that insulin doses can be regulated fully automatically. Totally closed loop systems are currently not yet available for outpatient use. Hybrid closed loop systems have been approved in the US. They can improve the metabolic status of patients with type 1 diabetes. Risks are similar to sensor-augmented insulin-pump therapy. Patients' detailed education will continue to be essential for success. © Georg Thieme Verlag KG Stuttgart · New York.

  2. Multi-Nozzle Spray Cooling in a Closed Loop (POSTPRINT)

    DTIC Science & Technology

    2011-03-01

    facing upward, (b) vertical, and (c) horizontal facing downward. The thermal performance of the horizontal facing downward surface was the best. A...transfer, closed loop, CHF 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT: SAR 18. NUMBER OF PAGES 12 19a. NAME OF...the spray target surface, namely (a) horizontal facing upward, (b) vertical, and (c) horizontal facing downward. The thermal performance of the

  3. Closed-loop air cooling system for a turbine engine

    DOEpatents

    North, William Edward

    2000-01-01

    Method and apparatus are disclosed for providing a closed-loop air cooling system for a turbine engine. The method and apparatus provide for bleeding pressurized air from a gas turbine engine compressor for use in cooling the turbine components. The compressed air is cascaded through the various stages of the turbine. At each stage a portion of the compressed air is returned to the compressor where useful work is recovered.

  4. Assisted closed-loop optimization of SSVEP-BCI efficiency

    PubMed Central

    Fernandez-Vargas, Jacobo; Pfaff, Hanns U.; Rodríguez, Francisco B.; Varona, Pablo

    2012-01-01

    We designed a novel assisted closed-loop optimization protocol to improve the efficiency of brain-computer interfaces (BCI) based on steady state visually evoked potentials (SSVEP). In traditional paradigms, the control over the BCI-performance completely depends on the subjects' ability to learn from the given feedback cues. By contrast, in the proposed protocol both the subject and the machine share information and control over the BCI goal. Generally, the innovative assistance consists in the delivery of online information together with the online adaptation of BCI stimuli properties. In our case, this adaptive optimization process is realized by (1) a closed-loop search for the best set of SSVEP flicker frequencies and (2) feedback of actual SSVEP magnitudes to both the subject and the machine. These closed-loop interactions between subject and machine are evaluated in real-time by continuous measurement of their efficiencies, which are used as online criteria to adapt the BCI control parameters. The proposed protocol aims to compensate for variability in possibly unknown subjects' state and trait dimensions. In a study with N = 18 subjects, we found significant evidence that our protocol outperformed classic SSVEP-BCI control paradigms. Evidence is presented that it takes indeed into account interindividual variabilities: e.g., under the new protocol, baseline resting state EEG measures predict subjects' BCI performances. This paper illustrates the promising potential of assisted closed-loop protocols in BCI systems. Probably their applicability might be expanded to innovative uses, e.g., as possible new diagnostic/therapeutic tools for clinical contexts and as new paradigms for basic research. PMID:23443214

  5. Closed-Loop Optimal Control Implementations for Space Applications

    DTIC Science & Technology

    2016-12-01

    OPTIMAL CONTROL IMPLEMENTATIONS FOR SPACE APPLICATIONS by Colin S. Monk December 2016 Thesis Advisor: Mark Karpenko Second Reader: I. M...COVERED Master’s thesis, Jan-Dec 2016 4. TITLE AND SUBTITLE CLOSED-LOOP OPTIMAL CONTROL IMPLEMENTATIONS FOR SPACE APPLICATIONS 5. FUNDING NUMBERS...IMPLEMENTATIONS FOR SPACE APPLICATIONS Colin S. Monk Lieutenant Commander, United States Navy B.S., Tulane University, 2003 Submitted in partial

  6. Joint angle sensors for closed-loop control

    NASA Astrophysics Data System (ADS)

    Ko, Wen H.; Miao, Chih-Lei

    In order to substitute braces that have built-in goniometers and to provide feedback signals for closed loop control of lower extremity Functional Neuromuscular System in paraplegics, a stretchable capacitive sensor was developed to accurately detect angular movement in joints. Promising clinical evaluations on the knee joints of a paraplegic and a volunteer were done. The evaluations show great promise for the possibility of implantation applications.

  7. Interplanetary travel: Is gravity needed to close the loop

    NASA Technical Reports Server (NTRS)

    Vernikos-Danellis, Joan

    1988-01-01

    Evidence has been accumulating from spaceflight and ground simulation studies suggesting that the normal relationship between neuroendocrine driving mechanisms and their respective target organs may become uncoupled; and that the sensitivity of the various components of the closed-loop systems may be altered. Changes in the regulation of the pituitary-adrenal system and the angioten-sinaldosterone system is discussed in support of this thesis.

  8. Interplanetary travel: Is gravity needed to close the loop

    NASA Technical Reports Server (NTRS)

    Vernikos-Danellis, Joan

    1988-01-01

    Evidence has been accumulating from spaceflight and ground simulation studies suggesting that the normal relationship between neuroendocrine driving mechanisms and their respective target organs may become uncoupled; and that the sensitivity of the various components of the closed-loop systems may be altered. Changes in the regulation of the pituitary-adrenal system and the angioten-sinaldosterone system is discussed in support of this thesis.

  9. Hypnosis closed loop TCI systems in outpatient surgery.

    PubMed

    Ramos-Luengo, A; Asensio-Merino, F

    Determine the influence of general anaesthesia with closed-loop systems in the results of outpatient varicose vein surgery. Retrospective observational study including data from 270 outpatients between 2014 and 2015. The patients were divided into 2 groups according to the type of general anaesthesia used. The CL Group included patients who received propofol in closed-loop guided by BIS and remifentanil using TCI, and the C Group received non-closed-loop anaesthesia. Age, sex, surgical time, discharge time and failure of outpatient surgery were recorded. Quantitative data were checked for normal distribution by the method of Kolmogorov-Smirnov-Lilliefors. Differences between groups were analysed by a Student-t-test or Mann-Whitney-Wilcoxon test, depending on their distribution. Categorical data were analysed by a Chi-squared test. We used Kaplan-Meier estimator and the effect size (calculated by Cohen's d) to study the discharge time. Statistical analysis was performed using R 3.2.3 binary for Mac OS X 10.9. There were no significant differences in age, sex and surgical time and failure of outpatient surgery. Discharge time was different in both groups: 200 (100) vs. 180 (82.5) minutes, C Group and CL Group, respectively (data are median and interquartile rank); P=.005. The use of closed-loop devices for the hypnotic component of anaesthesia hastens discharge time. However, for this effect to be clinically significant, some improvements still need to be made in our outpatient surgery units. Copyright © 2016 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Publicado por Elsevier España, S.L.U. All rights reserved.

  10. Closed loop models for analyzing engineering requirements for simulators

    NASA Technical Reports Server (NTRS)

    Baron, S.; Muralidharan, R.; Kleinman, D.

    1980-01-01

    A closed loop analytic model, incorporating a model for the human pilot, (namely, the optimal control model) that would allow certain simulation design tradeoffs to be evaluated quantitatively was developed. This model was applied to a realistic flight control problem. The resulting model is used to analyze both overall simulation effects and the effects of individual elements. The results show that, as compared to an ideal continuous simulation, the discrete simulation can result in significant performance and/or workload penalties.

  11. High resolution interface circuit for closed-loop accelerometer

    NASA Astrophysics Data System (ADS)

    Liang, Yin; Xiaowei, Liu; Weiping, Chen; Zhiping, Zhou

    2011-04-01

    This paper reports a low noise switched-capacitor CMOS interface circuit for the closed-loop operation of a capacitive accelerometer. The time division multiplexing of the same electrode is adopted to avoid the strong feedthrough between capacitance sensing and electrostatic force feedback. A PID controller is designed to ensure the stability and dynamic response of a high Q closed-loop accelerometer with a vacuum package. The architecture only requires single ended operational amplifiers, transmission gates and capacitors. Test results show that a full scale acceleration of ±3 g, non-linearity of 0.05% and signal bandwidth of 1000 Hz are achieved. The complete module operates from a ±5 V supply and has a measured sensitivity of 1.2 V/g with a noise of floor of in closed-loop. The chip is fabricated in the 2 μm two-metal and two-poly n-well CMOS process with an area of 15.2 mm2. These results prove that this circuit is suitable for high performance micro-accelerometer applications like seismic detection and oil exploration.

  12. Closed-Loop and Robust Control of Quantum Systems

    PubMed Central

    Wang, Lin-Cheng

    2013-01-01

    For most practical quantum control systems, it is important and difficult to attain robustness and reliability due to unavoidable uncertainties in the system dynamics or models. Three kinds of typical approaches (e.g., closed-loop learning control, feedback control, and robust control) have been proved to be effective to solve these problems. This work presents a self-contained survey on the closed-loop and robust control of quantum systems, as well as a brief introduction to a selection of basic theories and methods in this research area, to provide interested readers with a general idea for further studies. In the area of closed-loop learning control of quantum systems, we survey and introduce such learning control methods as gradient-based methods, genetic algorithms (GA), and reinforcement learning (RL) methods from a unified point of view of exploring the quantum control landscapes. For the feedback control approach, the paper surveys three control strategies including Lyapunov control, measurement-based control, and coherent-feedback control. Then such topics in the field of quantum robust control as H∞ control, sliding mode control, quantum risk-sensitive control, and quantum ensemble control are reviewed. The paper concludes with a perspective of future research directions that are likely to attract more attention. PMID:23997680

  13. Closed-loop snowplow applicator control using road condition measurements

    NASA Astrophysics Data System (ADS)

    Erdogan, Gurkan; Alexander, Lee; Rajamani, Rajesh

    2011-04-01

    Closed-loop control of a snowplow applicator, based on direct measurement of the road surface condition, is a valuable technology for the optimisation of winter road maintenance costs and for the protection of the environment from the negative impacts of excessive usage of de-icing chemicals. To this end, a novel friction measurement wheel is designed to provide a continuous measurement of road friction coefficient, which is, in turn, utilised to control the applicator automatically on a snowplow. It is desired that the automated snowplow applicator deploy de-icing materials right from the beginning of any slippery surface detected by the friction wheel, meaning that no portion of the slippery road surface should be left untreated behind, as the snowplow travels over it at a reasonably high speed. This paper describes the developed wheel-based measurement system, the friction estimation algorithm and the expected performance of the closed-loop applicator system. Conventional and zero velocity applicators are introduced and their hardware time delays are measured in addition to the time delay of the friction estimation algorithm. The overall performance of the closed-loop applicator control system is shown to be reliable at typical snowplowing speeds if the zero velocity applicator is used.

  14. Integrated otpical monitoring of MEMS for closed-loop control

    NASA Astrophysics Data System (ADS)

    Dawson, Jeremy M.; Wang, Limin; McCormick, W. B.; Rittenhouse, S. A.; Famouri, Parviz F.; Hornak, Lawrence A.

    2003-01-01

    Robust control and failure assessment of MEMS employed in physically demanding, mission critical applications will allow for higher degrees of quality assurance in MEMS operation. Device fault detection and closed-loop control require detailed knowledge of the operational states of MEMS over the lifetime of the device, obtained by a means decoupled from the system. Preliminary through-wafer optical monitoring research efforts have shown that through-wafer optical probing is suitable for characterizing and monitoring the behavior of MEMS, and can be implemented in an integrated optical monitoring package for continuous in-situ device monitoring. This presentation will discuss research undertaken to establish integrated optical device metrology for closed-loop control of a MUMPS fabricated lateral harmonic oscillator. Successful linear closed-loop control results using a through-wafer optical microprobe position feedback signal will be presented. A theoretical optical output field intensity study of grating structures, fabricated on the shuttle of the resonator, was performed to improve the position resolution of the optical microprobe position signal. Through-wafer microprobe signals providing a positional resolution of 2 μm using grating structures will be shown, along with initial binary Fresnel diffractive optical microelement design layout, process development, and testing results. Progress in the design, fabrication, and test of integrated optical elements for multiple microprobe signal delivery and recovery will be discussed, as well as simulation of device system model parameter changes for failure assessment.

  15. Efficient dynamic modeling of manipulators containing closed kinematic loops

    NASA Astrophysics Data System (ADS)

    Ferretti, Gianni; Rocco, Paolo

    An approach to efficiently solve the forward dynamics problem for manipulators containing closed chains is proposed. The two main distinctive features of this approach are: the dynamics of the equivalent open loop tree structures (any closed loop can be in general modeled by imposing some additional kinematic constraints to a suitable tree structure) is computed through an efficient Newton Euler formulation; the constraint equations relative to the most commonly adopted closed chains in industrial manipulators are explicitly solved, thus, overcoming the redundancy of Lagrange's multipliers method while avoiding the inefficiency due to a numerical solution of the implicit constraint equations. The constraint equations considered for an explicit solution are those imposed by articulated gear mechanisms and planar closed chains (pantograph type structures). Articulated gear mechanisms are actually used in all industrial robots to transmit motion from actuators to links, while planar closed chains are usefully employed to increase the stiffness of the manipulators and their load capacity, as well to reduce the kinematic coupling of joint axes. The accuracy and the efficiency of the proposed approach are shown through a simulation test.

  16. Is a closing "GA pair" a rule for stable loop-loop RNA complexes?

    PubMed

    Ducongé, F; Di Primo, C; Toulme, J J

    2000-07-14

    RNA hairpin aptamers specific for the trans-activation-responsive (TAR) RNA element of human immunodeficiency virus type 1 were identified by in vitro selection (Ducongé, F., and Toulmé, J. J. (1999) RNA 5, 1605-1614). The high affinity sequences selected at physiological magnesium concentration (3 mm) were shown to form a loop-loop complex with the targeted TAR RNA. The stability of this complex depends on the aptamer loop closing "GA pair" as characterized by preliminary electrophoretic mobility shift assays. Thermal denaturation monitored by UV-absorption spectroscopy and binding kinetics determined by surface plasmon resonance show that the GA pair is crucial for the formation of the TAR-RNA aptamer complex. Both thermal denaturation and surface plasmon resonance experiments show that any other "pairs" leads to complexes whose stability decreases in the order AG > GG > GU > AA > GC > UA > CA, CU. The binding kinetics indicate that stability is controlled by the off-rate rather than by the on-rate. Comparison with the complex formed with the TAR* hairpin, a rationally designed TAR RNA ligand (Chang, K. Y., and Tinoco, I. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 8705-8709), demonstrates that the GA pair is a key determinant which accounts for the 50-fold increased stability of the TAR-aptamer complex (K(d) = 2.0 nm) over the TAR-TAR* one (K(d) = 92. 5 nm) at physiological concentration of magnesium. Replacement of the wild-type GC pair next to the loop of RNA I' by a GA pair stabilizes the RNA I'-RNA II' loop-loop complex derived from the one involved in the control of the ColE1 plasmid replication. Thus, the GA pair might be the preferred one for stable loop-loop interactions.

  17. Closed-loop conductance scanning tunneling spectroscopy: demonstrating the equivalence to the open-loop alternative.

    PubMed

    Hellenthal, Chris; Sotthewes, Kai; Siekman, Martin H; Kooij, E Stefan; Zandvliet, Harold J W

    2015-01-01

    We demonstrate the validity of using closed-loop z(V) conductance scanning tunneling spectroscopy (STS) measurements for the determination of the effective tunneling barrier by comparing them to more conventional open-loop I(z) measurements. Through the development of a numerical model, the individual contributions to the effective tunneling barrier present in these experiments, such as the work function and the presence of an image charge, are determined quantitatively. This opens up the possibility of determining tunneling barriers of both vacuum and molecular systems in an alternative and more detailed manner.

  18. Closed-loop suppression of chaos in nonlinear driven oscillators

    NASA Astrophysics Data System (ADS)

    Aguirre, L. A.; Billings, S. A.

    1995-05-01

    This paper discusses the suppression of chaos in nonlinear driven oscillators via the addition of a periodic perturbation. Given a system originally undergoing chaotic motions, it is desired that such a system be driven to some periodic orbit. This can be achieved by the addition of a weak periodic signal to the oscillator input. This is usually accomplished in open loop, but this procedure presents some difficulties which are discussed in the paper. To ensure that this is attained despite uncertainties and possible disturbances on the system, a procedure is suggested to perform control in closed loop. In addition, it is illustrated how a model, estimated from input/output data, can be used in the design. Numerical examples which use the Duffing-Ueda and modified van der Pol oscillators are included to illustrate some of the properties of the new approach.

  19. Closed-loop control of flow-induced cavity oscillations

    NASA Astrophysics Data System (ADS)

    Song, Qi

    Flow-induced cavity oscillations are a coupled flow-acoustic problem in which the inherent closed-loop system dynamics can lead to large unsteady pressure levels in and around the cavity, resulting in both broadband noise and discrete tones. This problem exists in many practical environments, such as landing gear bays and weapon delivery systems on aircraft, and automobile sunroofs and windows. Researchers in both fluid dynamics and controls have been working on this problem for more than fifty years. This is because not only is the physical nature of this problem rich and complex, but also it has become a standard test bed for controller deign and implementation in flow control. The ultimate goal of this research is to minimize the cavity acoustic tones and the broadband noise level over a range of freestream Mach numbers. Although open-loop and closed-loop control methodologies have been explored extensively in recent years, there are still some issues that need to be studied further. For example, a low-order theoretical model suitable for controller design does not exist. Most recent flow-induced cavity models are based either on Rossiter's semi-expirical formula or a proper orthogonal decomposition (POD) based models. These models cannot be implemented in adaptive controller design directly. In addition, closed-loop control of high subsonic and supersonic flows remains an unexplored area. In order to achieve these objectives, an analytical system model is first developed in this research. This analytical model is a transfer function based model and it can be used as a potential model for controller design. Then, a MIMO system identification algorithm is derived and combined with the generalized prediction control (GPC) algorithm. The resultant integration of adaptive system ID and GPC algorithms can potentially track nonstationary cavity dynamics and reduce the flow-induced oscillations. A novel piezoelectric-driven synthetic jet actuator array is designed for

  20. Closing the tau loop: the missing tau mutation.

    PubMed

    McCarthy, Allan; Lonergan, Roisin; Olszewska, Diana A; O'Dowd, Sean; Cummins, Gemma; Magennis, Brian; Fallon, Emer M; Pender, Niall; Huey, Edward D; Cosentino, Stephanie; O'Rourke, Killian; Kelly, Brendan D; O'Connell, Martin; Delon, Isabelle; Farrell, Michael; Spillantini, Maria Grazia; Rowland, Lewis P; Fahn, Stanley; Craig, Peter; Hutton, Michael; Lynch, Tim

    2015-10-01

    model was first proposed and no mutations have been found within the 'loop' region as expected. Therefore we 'close the tau loop' having 'opened the loop' 21 years ago.

  1. Online Learning ARMA Controllers With Guaranteed Closed-Loop Stability.

    PubMed

    Sahin, Savas; Guzelis, Cuneyt

    2016-11-01

    This paper presents a novel online block adaptive learning algorithm for autoregressive moving average (ARMA) controller design based on the real data measured from the plant. The method employs ARMA input-output models both for the plant and the resulting closed-loop system. In a sliding window, the plant model parameters are identified first offline using a supervised learning algorithm minimizing an ε -insensitive and regularized identification error, which is the window average of the distances between the measured plant output and the model output for the input provided by the controller. The optimal controller parameters are then determined again offline for another sliding window as the solution to a constrained optimization problem, where the cost is the ε -insensitive and regularized output tracking error and the constraints that are linear inequalities of the controller parameters are imposed for ensuring the closed-loop system to be Schur stable. Not only the identification phase but also the controller design phase uses the input-output samples measured from the plant during online learning. In the developed online controller design method, the controller parameters can always be kept in a parameter region providing Schur stability for the closed-loop system. The ε -insensitiveness provides robustness against disturbances, so does the regularization better generalization performance in the identification and the control. The method is tested on benchmark plants, including the inverted pendulum and dc motor models. The method is also tested on an emulated and also a real dc motor by online block adaptive learning ARMA controllers, in particular, Proportional-Integral-Derivative controllers.

  2. Closed-Loop Control for Sonic Fatigue Testing Systems

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Bossaert, Guido

    2001-01-01

    This article documents recent improvements to the acoustic control system of the Thermal Acoustic Fatigue Apparatus (TAFA), a progressive wave tube test facility at the NASA Langley Research Center, Hampton, VA. A brief summary of past acoustic performance is first given to serve as a basis of comparison with the new performance data using a multiple-input, closed-loop, narrow-band controller. Performance data in the form of test section acoustic power spectral densities and coherence are presented for a variety of input spectra including uniform, band-limited random and an expendable launch vehicle payload bay environment.

  3. Integrated Evaluation of Closed Loop Air Revitalization System Components

    NASA Technical Reports Server (NTRS)

    Murdock, K.

    2010-01-01

    NASA s vision and mission statements include an emphasis on human exploration of space, which requires environmental control and life support technologies. This Contractor Report (CR) describes the development and evaluation of an Air Revitalization System, modeling and simulation of the components, and integrated hardware testing with the goal of better understanding the inherent capabilities and limitations of this closed loop system. Major components integrated and tested included a 4-Bed Modular Sieve, Mechanical Compressor Engineering Development Unit, Temperature Swing Adsorption Compressor, and a Sabatier Engineering and Development Unit. The requisite methodolgy and technical results are contained in this CR.

  4. The Future of Seizure Prediction and Intervention: Closing the loop

    PubMed Central

    Nagaraj, Vivek; Lee, Steven; Krook-Magnuson, Esther; Soltesz, Ivan; Benquet, Pascal; Irazoqui, Pedro; Netoff, Theoden

    2014-01-01

    The ultimate goal of epilepsy therapies is to provide seizure control for all patients while eliminating side effects. Improved specificity of intervention through on-demand approaches may overcome many of the limitations of current intervention strategies. This article reviews progress in seizure prediction and detection, potential new therapies to provide improved specificity, and devices to achieve these ends. Specifically, we discuss 1) potential signal modalities and algorithms for seizure detection and prediction, 2) closed-loop intervention approaches, and 3) hardware for implementing these algorithms and interventions. Seizure prediction and therapies maximize efficacy while minimizing side-effects through improved specificity may represent the future of epilepsy treatments. PMID:26035672

  5. Aharonov-Bohm effect without closing a loop

    SciTech Connect

    Retzker, A.; Nussinov, S.; Reznik, B.; Aharonov, Y.; Botero, A.

    2006-03-15

    We discuss the consequences of the Aharonov-Bohm (AB) effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bipartite or multipartite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron-hole pairs. We discuss the relevance of such effects in 'vacuum birefringence' in QED, and comment on their connection to other known effects.

  6. Closed loop air cooling system for combustion turbines

    DOEpatents

    Huber, David John; Briesch, Michael Scot

    1998-01-01

    Convective cooling of turbine hot parts using a closed loop system is disclosed. Preferably, the present invention is applied to cooling the hot parts of combustion turbine power plants, and the cooling provided permits an increase in the inlet temperature and the concomitant benefits of increased efficiency and output. In preferred embodiments, methods and apparatus are disclosed wherein air is removed from the combustion turbine compressor and delivered to passages internal to one or more of a combustor and turbine hot parts. The air cools the combustor and turbine hot parts via convection and heat is transferred through the surfaces of the combustor and turbine hot parts.

  7. Closed loop air cooling system for combustion turbines

    DOEpatents

    Huber, D.J.; Briesch, M.S.

    1998-07-21

    Convective cooling of turbine hot parts using a closed loop system is disclosed. Preferably, the present invention is applied to cooling the hot parts of combustion turbine power plants, and the cooling provided permits an increase in the inlet temperature and the concomitant benefits of increased efficiency and output. In preferred embodiments, methods and apparatus are disclosed wherein air is removed from the combustion turbine compressor and delivered to passages internal to one or more of a combustor and turbine hot parts. The air cools the combustor and turbine hot parts via convection and heat is transferred through the surfaces of the combustor and turbine hot parts. 1 fig.

  8. Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development

    DTIC Science & Technology

    2016-09-01

    ARL-TN-0779 ● SEP 2016 US Army Research Laboratory Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and...Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development by Neal Tesny Sensors and Electron Devices Directorate...TITLE AND SUBTITLE Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development 5a. CONTRACT NUMBER 5b

  9. A translational platform for prototyping closed-loop neuromodulation systems.

    PubMed

    Afshar, Pedram; Khambhati, Ankit; Stanslaski, Scott; Carlson, David; Jensen, Randy; Linde, Dave; Dani, Siddharth; Lazarewicz, Maciej; Cong, Peng; Giftakis, Jon; Stypulkowski, Paul; Denison, Tim

    2012-01-01

    While modulating neural activity through stimulation is an effective treatment for neurological diseases such as Parkinson's disease and essential tremor, an opportunity for improving neuromodulation therapy remains in automatically adjusting therapy to continuously optimize patient outcomes. Practical issues associated with achieving this include the paucity of human data related to disease states, poorly validated estimators of patient state, and unknown dynamic mappings of optimal stimulation parameters based on estimated states. To overcome these challenges, we present an investigational platform including: an implanted sensing and stimulation device to collect data and run automated closed-loop algorithms; an external tool to prototype classifier and control-policy algorithms; and real-time telemetry to update the implanted device firmware and monitor its state. The prototyping system was demonstrated in a chronic large animal model studying hippocampal dynamics. We used the platform to find biomarkers of the observed states and transfer functions of different stimulation amplitudes. Data showed that moderate levels of stimulation suppress hippocampal beta activity, while high levels of stimulation produce seizure-like after-discharge activity. The biomarker and transfer function observations were mapped into classifier and control-policy algorithms, which were downloaded to the implanted device to continuously titrate stimulation amplitude for the desired network effect. The platform is designed to be a flexible prototyping tool and could be used to develop improved mechanistic models and automated closed-loop systems for a variety of neurological disorders.

  10. Optical Closed-Loop Propulsion Control System Development

    NASA Technical Reports Server (NTRS)

    Poppel, Gary L.

    1998-01-01

    The overall objective of this program was to design and fabricate the components required for optical closed-loop control of a F404-400 turbofan engine, by building on the experience of the NASA Fiber Optic Control System Integration (FOCSI) program. Evaluating the performance of fiber optic technology at the component and system levels will result in helping to validate its use on aircraft engines. This report includes descriptions of three test plans. The EOI Acceptance Test is designed to demonstrate satisfactory functionality of the EOI, primarily fail-safe throughput of the F404 sensor signals in the normal mode, and validation, switching, and output of the five analog sensor signals as generated from validated optical sensor inputs, in the optical mode. The EOI System Test is designed to demonstrate acceptable F404 ECU functionality as interfaced with the EOI, making use of a production ECU test stand. The Optical Control Engine Test Request describes planned hardware installation, optical signal calibrations, data system coordination, test procedures, and data signal comparisons for an engine test demonstration of the optical closed-loop control.

  11. Closed-loop quantum control utilizing time domain maps

    NASA Astrophysics Data System (ADS)

    Biteen, Julie S.; Geremia, J. M.; Rabitz, Herschel

    2003-05-01

    Closed-loop laser control of quantum dynamics phenomena may be accomplished through frequency domain manipulations in the laboratory guided by a learning algorithm. This paper presents an alternative method based on the use of nonlinear input→output maps generated in the time domain, although the actual experiments and control optimization are carried out in the frequency domain. The procedure first involves the construction of input→output maps relating the field structure to the observed control performance. These maps are utilized as a substitute for actual experiments in the subsequent optimization stage in order to find the field that drives the system to a specified target. This closed-loop learning process is repeated with a sufficient number of maps until a control field is found that yields the target observable as best as possible. The overall algorithm is simulated with two model quantum systems. It is shown that excellent quality control can be achieved through this sequential learning procedure, even with individual maps that have only modest global accuracy.

  12. Closed-loop control of magnetic fluid deformable mirrors.

    PubMed

    Iqbal, Azhar; Wu, Zhizheng; Ben Amara, Foued

    2009-10-12

    This paper presents the first-ever experimental evaluation of a closed-loop adaptive optics system based on a magnetic fluid deformable mirror (MFDM). MFDMs are a new type of wavefront correctors used in adaptive optics systems to compensate for complex optical aberrations. They have been found particularly suitable for ophthalmic imaging systems where they can be used to compensate for the aberrations in the eye that lead to blurry retinal images. However, their practical implementation in clinical devices requires effective methods to control the shape of their deformable surface. This paper presents one such control method which is based on an innovative technique used to linearize the response of the MFDM surface shape. The design of the controller is based on a DC-decoupled model of the multi-input multi-output system and on considering a decentralized PI controller. Experimental results showing the performance of the closed-loop system comprising the developed controller and a 19-channel prototype MFDM are presented.

  13. Closed-Loop Rehabilitation of Age-Related Cognitive Disorders

    PubMed Central

    Mishra, Jyoti; Gazzaley, Adam

    2015-01-01

    Cognitive deficits are common in older adults, as a result of both the natural aging process and neurodegenerative disease. Although medical advancements have successfully prolonged the human lifespan, the challenge of remediating cognitive aging remains. The authors discuss the current state of cognitive therapeutic interventions and then present the need for development and validation of more powerful neurocognitive therapeutics. They propose that the next generation of interventions be implemented as closed-loop systems that target specific neural processing deficits, incorporate quantitative feedback to the individual and clinician, and are personalized to the individual’s neurocognitive capacities using real-time performance-adaptive algorithms. This approach should be multimodal and seamlessly integrate other treatment approaches, including neurofeedback and transcranial electrical stimulation. This novel approach will involve the generation of software that engages the individual in an immersive and enjoyable game-based interface, integrated with advanced biosensing hardware, to maximally harness plasticity and assure adherence. Introducing such next-generation closed-loop neurocognitive therapeutics into the mainstream of our mental health care system will require the combined efforts of clinicians, neuroscientists, bioengineers, software game developers, and industry and policy makers working together to meet the challenges and opportunities of translational neuroscience in the 21st century. PMID:25520029

  14. A closed-loop air revitalization process technology demonstrator

    NASA Astrophysics Data System (ADS)

    Mulloth, Lila; Perry, Jay; Luna, Bernadette; Kliss, Mark

    Demonstrating a sustainable, reliable life support system process design that possesses the capability to close the oxygen cycle to the greatest extent possible is required for extensive surface exploration of the Moon and Mars by humans. A conceptual closed-loop air revitalization system process technology demonstrator that combines the CO2 removal, recovery, and reduction and oxygen generation operations in a single compact envelope is described. NASA has developed, and in some cases flown, process technologies for capturing metabolic CO2 from air, reducing CO2 to H2O and CH4, electrolyzing H2O to O2, and electrolyzing CO2 to O2 and CO among a number of candidates. Traditionally, these processes either operate in parallel with one another or have not taken full benefit of a unit operation-based design approach to take complete advantage of the synergy between individual technologies. The appropriate combination of process technologies must capitalize on the advantageous aspects of individual technologies while eliminating or transforming the features that limit their feasibility when considered alone. Such a process technology integration approach also provides advantages of optimized mass, power and volume characteristics for the hardware embodiment. The conceptual air revitalization system process design is an ideal technology demonstrator for the critically needed closed-loop life support capabilities for long duration human exploration of the lunar surface and extending crewed space exploration toward Mars. The conceptual process design incorporates low power CO2 removal, process gas drying, and advanced engineered adsorbents being developed by NASA and industry.

  15. Transcranial brain stimulation: closing the loop between brain and stimulation

    PubMed Central

    Karabanov, Anke; Thielscher, Axel; Siebner, Hartwig Roman

    2016-01-01

    Purpose of review To discuss recent strategies for boosting the efficacy of noninvasive transcranial brain stimulation to improve human brain function. Recent findings Recent research exposed substantial intra- and inter-individual variability in response to plasticity-inducing transcranial brain stimulation. Trait-related and state-related determinants contribute to this variability, challenging the standard approach to apply stimulation in a rigid, one-size-fits-all fashion. Several strategies have been identified to reduce variability and maximize the plasticity-inducing effects of noninvasive transcranial brain stimulation. Priming interventions or paired associative stimulation can be used to ‘standardize’ the brain-state and hereby, homogenize the group response to stimulation. Neuroanatomical and neurochemical profiling based on magnetic resonance imaging and spectroscopy can capture trait-related and state-related variability. Fluctuations in brain-states can be traced online with functional brain imaging and inform the timing or other settings of transcranial brain stimulation. State-informed open-loop stimulation is aligned to the expression of a predefined brain state, according to prespecified rules. In contrast, adaptive closed-loop stimulation dynamically adjusts stimulation settings based on the occurrence of stimulation-induced state changes. Summary Approaches that take into account trait-related and state-related determinants of stimulation-induced plasticity bear considerable potential to establish noninvasive transcranial brain stimulation as interventional therapeutic tool. PMID:27224087

  16. Closed-loop Separation Control Using Oscillatory Flow Excitation

    NASA Technical Reports Server (NTRS)

    Allan, Brian G.; Juang, Jer-Nan; Raney, David L.; Seifert, Avi; Pack, latunia G.; Brown, Donald E.

    2000-01-01

    Design and implementation of a digital feedback controller for a flow control experiment was performed. The experiment was conducted in a cryogenic pressurized wind tunnel on a generic separated configuration at a chord Reynolds number of 16 million and a Mach number of 0.25. The model simulates the upper surface of a 20% thick airfoil at zero angle-of-attack. A moderate favorable pressure gradient, up to 55% of the chord, is followed by a severe adverse pressure gradient which is relaxed towards the trailing edge. The turbulent separation bubble, behind the adverse pressure gradient, is then reduced by introducing oscillatory flow excitation just upstream of the point of flow separation. The degree of reduction in the separation region can be controlled by the amplitude of the oscillatory excitation. A feedback controller was designed to track a given trajectory for the desired degree of flow reattachment and to improve the transient behavior of the flow system. Closed-loop experiments demonstrated that the feedback controller was able to track step input commands and improve the transient behavior of the open-loop response.

  17. Closed loop deep brain stimulation: an evolving technology.

    PubMed

    Hosain, Md Kamal; Kouzani, Abbas; Tye, Susannah

    2014-12-01

    Deep brain stimulation is an effective and safe medical treatment for a variety of neurological and psychiatric disorders including Parkinson's disease, essential tremor, dystonia, and treatment resistant obsessive compulsive disorder. A closed loop deep brain stimulation (CLDBS) system automatically adjusts stimulation parameters by the brain response in real time. The CLDBS continues to evolve due to the advancement in the brain stimulation technologies. This paper provides a study on the existing systems developed for CLDBS. It highlights the issues associated with CLDBS systems including feedback signal recording and processing, stimulation parameters setting, control algorithm, wireless telemetry, size, and power consumption. The benefits and limitations of the existing CLDBS systems are also presented. Whilst robust clinical proof of the benefits of the technology remains to be achieved, it has the potential to offer several advantages over open loop DBS. The CLDBS can improve efficiency and efficacy of therapy, eliminate lengthy start-up period for programming and adjustment, provide a personalized treatment, and make parameters setting automatic and adaptive.

  18. Reciprocal Feedback: Closing the Loop on Postactivity Surveys.

    PubMed

    Watson, Richard A

    2015-01-01

    Those who conduct feedback surveys, which follow almost every CME presentation and medical-school lecture, would do well to offer participants' reciprocal feedback. That is, the course director should provide each survey respondent, on request, a brief summary of the comments received from this survey and the extent to which the recommendations will lead to objective improvements in the future. Surveyors who provide respondents with reciprocal feedback can expect heightened credibility, more reliable feedback in the future, and an added incentive to effect significant change for the better. Feedback has not circled all the way back until we have provided a succinct summary of results to those who have offered us their comments and suggestions. Let us close the loop; let reciprocal feedback become the last word in CME surveys.

  19. Safety-preserving closed-loop control of anesthesia.

    PubMed

    Yousefi, Mahdi; van Heusden, Klaske; Dumont, Guy A; Ansermino, J Mark

    2015-08-01

    In safety-critical control systems, such as closed-loop control of anesthesia, it is of utmost importance to guarantee the ability of a control approach to maintain states of the systems within a safe region. In this paper, we address the problem by applying a safety-preserving control technique to anesthesia control. The approach relies on a conservative approximation of the viability set. The set specifies initial states for which there exists an input that keeps the trajectory emanating from those states within the safe region. This approach can be applied to any type of controller which satisfies the performance criteria. Furthermore, it prevents the performance controller from taking the states out of the safe region.

  20. Nonlinear adaptive filter for closed-loop fire control

    NASA Astrophysics Data System (ADS)

    Marshall, William C.

    1990-09-01

    This paper presents an adaptive or self-learning filter design intended for use in real-time closed loop pointing control systems engaging multiple targets. The design approach is based upon use of a performance index (based upon the Mahalanobis generalized distance function) and multiple filters processed in parallel using the same nonlinear measurements as input. Application of performance index criteria to the statistics of individual filter residuals allows the selection of the optimum filter set without the time delays typically encountered and thereby allows the composite filter structure to adapt (or self-learn) to uncertainties in modeling target acceleration capabilities. An advantage of this approach is that it also provides to an operator (or a robotic controller) the confidence level of tracking system performance against a maneuvering target. This information is of interest for deployment of counter-measures (e.g., fire control eventing, alarms, engagement priority, etc) or simply for laboratory system tests of design adequacy.

  1. Closing the loop of the soil water retention curve

    USGS Publications Warehouse

    Lu, Ning; Alsherif, N; Wayllace, Alexandra; Godt, Jonathan W.

    2015-01-01

    The authors, to their knowledge for the first time, produced two complete principal soil water retention curves (SWRCs) under both positive and negative matric suction regimes. An innovative testing technique combining the transient water release and imbibition method (TRIM) and constant flow method (CFM) was used to identify the principal paths of SWRC in the positive pore-water pressure regime under unsaturated conditions. A negative matric suction of 9.8 kPa is needed to reach full saturation or close the loop of the SWRC for a silty soil. This work pushes the understanding of the interaction of soil and water into new territory by quantifying the boundaries of the SWRC over the entire suction domain, including both wetting and drying conditions that are relevant to field conditions such as slope wetting under heavy rainfall or rapid groundwater table rise in earthen dams or levees.

  2. Closed loop computer control for an automatic transmission

    DOEpatents

    Patil, Prabhakar B.

    1989-01-01

    In an automotive vehicle having an automatic transmission that driveably connects a power source to the driving wheels, a method to control the application of hydraulic pressure to a clutch, whose engagement produces an upshift and whose disengagement produces a downshift, the speed of the power source, and the output torque of the transmission. The transmission output shaft torque and the power source speed are the controlled variables. The commanded power source torque and commanded hydraulic pressure supplied to the clutch are the control variables. A mathematical model is formulated that describes the kinematics and dynamics of the powertrain before, during and after a gear shift. The model represents the operating characteristics of each component and the structural arrangement of the components within the transmission being controlled. Next, a close loop feedback control is developed to determine the proper control law or compensation strategy to achieve an acceptably smooth gear ratio change, one in which the output torque disturbance is kept to a minimum and the duration of the shift is minimized. Then a computer algorithm simulating the shift dynamics employing the mathematical model is used to study the effects of changes in the values of the parameters established from a closed loop control of the clutch hydraulic and the power source torque on the shift quality. This computer simulation is used also to establish possible shift control strategies. The shift strategies determined from the prior step are reduced to an algorithm executed by a computer to control the operation of the power source and the transmission.

  3. Lunar base extension program and closed loop life support systems.

    PubMed

    Nitta, K; Ohya, H

    1991-01-01

    Much of papers describing the Lunar Base Construction have been already published. Lunar Base has been considered to be one of the very useful facilities to conduct the excellent scientific program in near future and also to develop the lunar resources such as 3He and oxygen in order to expand the human activities in space. The scale of lunar base and the construction methods to be adopted should be determined based upon the utilization program to be conducted after the initiation of outpost habitation. In order to construct lunar base, it needs to transport lunar base elements such as habitat modules, experiment modules and so on having 20-30 tons weight and to install, connect and activate on lunar surface. The development of transportation system such as OTV enabling to transport over 30 ton payload weight from earth to moon seems to be very difficult in near future, and it seems reasonable to transport three elements per year as described in many papers already published. Therefore, the initial habitat outpost would not have enough volume to produce foods and has to have ECLS system similar to that of space station already going to be developed. After 2-3 years from the initiation of habitation, the addition of food production facilities could be started to expand the habitability of lunar base and finally the complete closed loop life support system could be installed after spending 6-7 years. This paper describes ECLS technologies to be used in the initial habitat outpost and design philosophy of the closed loop technologies to be utilized in the final stage.

  4. Lunar base extension program and closed loop life support systems

    NASA Astrophysics Data System (ADS)

    Nitta, Keiji; Ohya, Haruhiko

    Much of papers describing the Lunar Base Construction have been already published. Lunar Base has been considered to be one of the very useful facilities to conduct the excellent scientific program in near future and also to develop the lunar resources such as 3He and oxygen in order to expand the human activities in space. The scale of lunar base and the construction methods to be adopted should be determined based upon the utilization program to be conducted after the initiation of outpost habitation. In order to construct lunar base, it needs to transport lunar base elements such as habitat modules, experiment modules and so on having 20-30 tons weight and to install, connect and activate on lunar surface. The development of transportation system such as OTV enabling to transport over 30 ton payload weight from earth to moon seems to be very difficult in near future, and it seems reasonable to transport three elements per year as described in many papers already published. /1/. Therefore, the initial habitat outpost would not have enough volume to produce foods and has to have ECLS system similar to that of space station already going to be developed. After 2-3 years from the initiation of habitation, the addition of food production facilities could be started to expand the habitability of lunar base and finally the complete closed loop life support system could be installed after spending 6-7 years. This paper describes ECLS technologies to be used in the initial habitat outpost and design philosophy of the closed loop technologies to be utilized in the final stage.

  5. Closed Loop Short Rotation Woody Biomass Energy Crops

    SciTech Connect

    Brower, Michael

    2012-09-30

    CRC Development LLC is pursuing commercialization of shrub willow crops to evaluate and confirm estimates of yield, harvesting, transportation and renewable energy conversion costs and to provide a diverse resource in its supply portfolio.The goal of Closed Loop Short Rotation Woody Biomass Energy Crops is supply expansion in Central New York to facilitate the commercialization of willow biomass crops as part of the mix of woody biomass feedstocks for bioenergy and bioproducts. CRC Development LLC established the first commercial willow biomass plantation acreage in North America was established on the Tug Hill in the spring of 2006 and expanded in 2007. This was the first 230- acres toward the goal of 10,000 regional acres. This project replaces some 2007-drought damaged acreage and installs a total of 630-acre new planting acres in order to demonstrate to regional agricultural producers and rural land-owners the economic vitality of closed loop short rotation woody biomass energy crops when deployed commercially in order to motivate new grower entry into the market-place. The willow biomass will directly help stabilize the fuel supply for the Lyonsdale Biomass facility, which produces 19 MWe of power and exports 15,000 pph of process steam to Burrows Paper. This project will also provide feedstock to The Biorefinery in New York for the manufacture of renewable, CO2-neutral liquid transportation fuels, chemicals and polymers. This project helps end dependency on imported fossil fuels, adds to region economic and environmental vitality and contributes to national security through improved energy independence.

  6. Impaired standing balance: the clinical need for closing the loop.

    PubMed

    Pasma, J H; Engelhart, D; Schouten, A C; van der Kooij, H; Maier, A B; Meskers, C G M

    2014-05-16

    Impaired balance may limit mobility and daily activities, and plays a key role in the elderly falling. Maintaining balance requires a concerted action of the sensory, nervous and motor systems, whereby cause and effect mutually affect each other within a closed loop. Aforementioned systems and their connecting pathways are prone to chronological age and disease-related deterioration. System redundancy allows for compensation strategies, e.g. sensory reweighting, to maintain standing balance in spite of the deterioration of underlying systems. Once those strategies fail, impaired balance and possible falls may occur. Targeted interventions to prevent falling require knowledge of the quality of the underlying systems and the compensation strategies used. As current clinical balance tests only measure the ability to maintain standing balance and cannot distinguish between cause and effect in a closed loop, there is a clear clinical need for new techniques to assess standing balance. A way to disentangle cause-and-effect relations to identify primary defects and compensation strategies is based on the application of external disturbances and system identification techniques, applicable in clinical practice. This paper outlines the multiple deteriorations of the underlying systems that may be involved in standing balance, which have to be detected early to prevent impaired standing balance. An overview of clinically used balance tests shows that early detection of impaired standing balance and identification of causal mechanisms is difficult with current tests, thereby hindering the development of well-timed and target-oriented interventions as described next. Finally, a new approach to assess standing balance and to detect the underlying deteriorations is proposed. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

  7. Closing the tau loop: the missing tau mutation

    PubMed Central

    McCarthy, Allan; Lonergan, Roisin; Olszewska, Diana A.; O’Dowd, Sean; Cummins, Gemma; Magennis, Brian; Fallon, Emer M.; Pender, Niall; Huey, Edward D.; Cosentino, Stephanie; O’Rourke, Killian; Kelly, Brendan D.; O’Connell, Martin; Delon, Isabelle; Farrell, Michael; Spillantini, Maria Grazia; Rowland, Lewis P.; Fahn, Stanley; Craig, Peter; Hutton, Michael

    2015-01-01

    stem-loop model was first proposed and no mutations have been found within the ‘loop’ region as expected. Therefore we ‘close the tau loop’ having ‘opened the loop’ 21 years ago. PMID:26297556

  8. Numerical Analysis of Combined Well and Open-Closed Loops Geothermal (CWG) Systems

    NASA Astrophysics Data System (ADS)

    Park, Yu-Chul

    2016-04-01

    Open-loop geothermal heat pump (GHP) system and closed-loop heat pump systems have been used in Korea to reduce emission of greenhouse gases such as carbon dioxide (CO2). The GHP systems have the pros and cons, for example, the open-loop GHP system is good energy-efficient and the closed-loop GHP system requires minimum maintenance costs. The open-loop GHP system can be used practically only with large amount of groundwater supply. The closed-loop GHP system can be used with high costs of initial installation. The performance and efficiency of the GHP system depend on the characteristics of the GHP system itself in addition to the geologic conditions. To overcome the cons of open-loop or closed-loop GHP system, the combined well and open-closed loops geothermal (CWG) system was designed. The open-loop GHP system is surrounded with closed-loop GHP systems in the CWG system. The geothermal energy in closed-loop GHP systems is supplied by the groundwater pumped by the open-loop GHP system. In this study, 2 different types of the CWG systems (small aperture hybrid CWG system and large aperture CWG system) are estimated using numerical simulation models in the aspect of energy efficiency. This work was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No.20153030111120).

  9. Designing optimized industrial process analysers for closed loop control

    PubMed Central

    Grevesmuehl, Bernard; Kradjel, Cynthia; Kellner, Hanno

    1991-01-01

    Manufacturers are now looking closely at ways of optimizing ‘quality’ and increasing process efficiency while reducing manufacturing costs. Near infra-red (NIR) technology is a popular solution to this challenge: it provides manufacturers with rapid and reliable in-process analysis and thousands of systems have already been installed in the food, chemical, pharmaceutical and agricultural markets. For over 10 years, NIR has been successfully applied to at-line process analysis. Rugged and easy-to-operate filter analysers are traditionally located in the control room–process operators can then ‘grab samples’ and obtain results in less than a minute. There are many practical advantages to using at-line filter systems. Products from many lines can be run on one system, and, since there is no direct process interface, installation, operation and maintenance are quite simple. Many manufacturers, however, are now striving to achieve on-line closed loop control, in these cases the benefit of obtaining continuous measurement is well worth the effort required to automate the analysis. PMID:18924898

  10. An ultrasonic horn atomizer with closed loop driving circuit

    NASA Astrophysics Data System (ADS)

    Chou, Yuan-Fang; Chen, Kai-Jhong; Hsu, Jui-Mei; Chou, Pei-En

    2016-04-01

    A novel ultrasonic horn atomizer is developed for the purpose of obtaining small size droplets at a large flow rate. The ultrasonic horn has a non-monotonically decreasing cross sectional area to provide a large atomizing surface. Consisting of two horns and one actuator section, the 301 kHz atomizer nozzle is made of {100} silicon wafer with its axis aligned in the <100> direction to minimize the length. Two PZT plates are adhered to each side of the actuator section to provide driving power. This device atomizes the liquid film on its nozzle tip to generate droplets. It is capable of atomizing more than 350 μl/min water into droplet. The mean diameter of droplet is 9.61 μm and the size distribution is quite narrow. The atomizing mechanism is based on the capillary wave on liquid surface. Once the wave amplitude exceeds the critical value, the motion of surface liquid becomes unstable and releases droplets. Therefore, driving at resonant frequency is the most effective way for atomizing. Dimension deviation combined with different kind of liquid to be atomized causes resonant frequencies of nozzles changed from time to time. Due to the high Q nature of nozzles, atomizing performance will drop drastically once the driving frequency is different from its resonant frequency by very little amount. Therefore, a feedback circuit is designed to tracking resonant frequency automatically instead of adjusting driving frequency manually. Comparing the atomizing performance between the open loop system and the closed loop system, significant improvement is obtained.

  11. Albumin dialysis in artificial liver support systems: open-loop or closed-loop dialysis mode?

    PubMed

    Pei, Yingying; Sun, Yize; Sun, Sijie; Gao, Dayong; Ding, Weiping

    2015-01-01

    In artificial liver support systems, the open-loop albumin dialysis mode (OLM) is usually used to remove protein-bound toxins from the blood of patients with liver failure. However, there is still interest in the closed-loop albumin dialysis mode (CLM) because this mode may enable not only the regeneration and reuse of albumin but also the miniaturization of artificial liver systems. In this article, we compared the two modes under a fixed amount of albumin in dialysate experimentally and theoretically. The results show that according to the detoxification efficiency in the 3 hour dialysis for removing albumin-bound bilirubin, CLM is better than OLM. The usage efficiency of albumin in CLM is also higher. Moreover, the advantage of CLM is more significant when the concentration of bilirubin in blood is lower. Under a given amount of albumin in dialysate, if the concentration of bilirubin in blood is high, one may further increase the performance of CLM by means of increasing the flow rate of the albumin dialysate or using the highly concentrated albumin dialysate.

  12. Closed loop supply chain network design with fuzzy tactical decisions

    NASA Astrophysics Data System (ADS)

    Sherafati, Mahtab; Bashiri, Mahdi

    2016-01-01

    One of the most strategic and the most significant decisions in supply chain management is reconfiguration of the structure and design of the supply chain network. In this paper, a closed loop supply chain network design model is presented to select the best tactical and strategic decision levels simultaneously considering the appropriate transportation mode in activated links. The strategic decisions are made for a long term; thus, it is more satisfactory and more appropriate when the decision variables are considered uncertain and fuzzy, because it is more flexible and near to the real world. This paper is the first research which considers fuzzy decision variables in the supply chain network design model. Moreover, in this study a new fuzzy optimization approach is proposed to solve a supply chain network design problem with fuzzy tactical decision variables. Finally, the proposed approach and model are verified using several numerical examples. The comparison of the results with other existing approaches confirms efficiency of the proposed approach. Moreover the results confirms that by considering the vagueness of tactical decisions some properties of the supply chain network will be improved.

  13. Closed-loop control for power tower heliostats

    NASA Astrophysics Data System (ADS)

    Convery, Mark R.

    2011-10-01

    In a Power Tower solar thermal power plant, alignment and control of the heliostats constitutes one of the largest costs of both time and money. This is especially the case in systems where individual heliostats are small (~1m2). I describe a closed-loop control system that generates the required feedback by inducing small mechanical vibrations in the heliostat reflector surface using piezoelectric actuators. These vibrations induce time-dependent changes in the reflected wavefront that can be detected by photosensors surrounding the thermal receiver target. Time and frequency encoding of the vibrations allows identification of a misaligned heliostat from among the thousands in the system. Corrections can then be applied to bring the reflected beam onto the receiver target. This technique can, in principle, control thousands of heliostats simultaneously.Outdoor testing of a small-scale model of this system has confirmed that such a system is effective and can achieve milliradian tracking accuracy. If such a system were implemented in a commercial plant, it could relax the accuracy specification required of the heliostats as well as provide an automated alignment and calibration system. This could significantly reduce the installed cost of the heliostat field.

  14. Closed Loop Control of a Tethered Magnetic Capsule Endoscope

    PubMed Central

    Taddese, Addisu Z.; Slawinski, Piotr R.; Obstein, Keith L.; Valdastri, Pietro

    2017-01-01

    Magnetic field gradients have repeatedly been shown to be the most feasible mechanism for gastrointestinal capsule endoscope actuation. An inverse quartic magnetic force variation with distance results in large force gradients induced by small movements of a driving magnet; this necessitates robotic actuation of magnets to implement stable control of the device. A typical system consists of a serial robot with a permanent magnet at its end effector that actuates a capsule with an embedded permanent magnet. We present a tethered capsule system where a capsule with an embedded magnet is closed loop controlled in 2 degree-of-freedom in position and 2 degree-of-freedom in orientation. Capitalizing on the magnetic field of the external driving permanent magnet, the capsule is localized in 6-D allowing for both position and orientation feedback to be used in a control scheme. We developed a relationship between the serial robot's joint parameters and the magnetic force and torque that is exerted onto the capsule. Our methodology was validated both in a dynamic simulation environment where a custom plug-in for magnetic interaction was written, as well as on an experimental platform. The tethered capsule was demonstrated to follow desired trajectories in both position and orientation with accuracy that is acceptable for colonoscopy. PMID:28286886

  15. A closed-loop neurobotic system for fine touch sensing

    NASA Astrophysics Data System (ADS)

    Bologna, L. L.; Pinoteau, J.; Passot, J.-B.; Garrido, J. A.; Vogel, J.; Ros Vidal, E.; Arleo, A.

    2013-08-01

    Objective. Fine touch sensing relies on peripheral-to-central neurotransmission of somesthetic percepts, as well as on active motion policies shaping tactile exploration. This paper presents a novel neuroengineering framework for robotic applications based on the multistage processing of fine tactile information in the closed action-perception loop. Approach. The integrated system modules focus on (i) neural coding principles of spatiotemporal spiking patterns at the periphery of the somatosensory pathway, (ii) probabilistic decoding mechanisms mediating cortical-like tactile recognition and (iii) decision-making and low-level motor adaptation underlying active touch sensing. We probed the resulting neural architecture through a Braille reading task. Main results. Our results on the peripheral encoding of primary contact features are consistent with experimental data on human slow-adapting type I mechanoreceptors. They also suggest second-order processing by cuneate neurons may resolve perceptual ambiguities, contributing to a fast and highly performing online discrimination of Braille inputs by a downstream probabilistic decoder. The implemented multilevel adaptive control provides robustness to motion inaccuracy, while making the number of finger accelerations covariate with Braille character complexity. The resulting modulation of fingertip kinematics is coherent with that observed in human Braille readers. Significance. This work provides a basis for the design and implementation of modular neuromimetic systems for fine touch discrimination in robotics.

  16. Automated closed loop control of inspired oxygen concentration.

    PubMed

    Claure, Nelson; Bancalari, Eduardo

    2013-01-01

    Oxygen therapy is extensively used in premature infants and adults with respiratory insufficiency. In the premature infant the goal during manual control of the F(IO(2)) is to maintain adequate oxygenation and to minimize the exposure to hypoxemia, hyperoxemia, and oxygen. However, this is frequently not achieved during routine care, which increases the risks of associated side effects affecting the eye, lungs, and central nervous system. In the adult the primary goal is to avoid hypoxemia, but conventional methods of oxygen supplementation may fall short during periods of increased demand. On the other hand, there are growing concerns related to unnecessarily high F(IO(2)) levels that increase the exposure to hyperoxemia and excessive oxygen use in settings where resources are limited. Systems for automated closed loop control of F(IO(2)) have been developed for use in neonates and adults. This paper will give an overview of the rationale for the development of these systems, present the evidence, and discuss important advantages and limitations.

  17. Closed-loop color calibration for the home user

    NASA Astrophysics Data System (ADS)

    Bhattacharjya, Anoop K.

    1997-04-01

    The proliferation of cheap color peripherals such as printers, scanners and digital cameras, has rendered them accessible to home users who can connect them to capture color images, and print these out on a color hard-copy device such as an ink-jet printer. Color consistency between the scanned original and the printed image is a well-known problem that has been approached by various techniques. Industry standards for color-management systems attempt to provide a device-independent framework for the consistent transfer of color images between devices in a manner that is transparent to the user. These systems require the specification of device characteristics that are often unavailable for older and/or inexpensive peripherals. In this paper, a closed-loop color-matching system to achieve consistent color reproduction between an original color image and a printed copy of the scanned original, is presented. The technique is designed for home users of scanners and printers who may not have access to expensive equipment for conducting photometric measurements. The algorithm requires minimal user intervention and is computationally efficient. To perform a calibration run, a small set of reference color patches printed by the printer are scanned using the scanner. A computer program analyzes the correspondence between the printed and scanned values to generate the necessary mappings.

  18. Automating the weaning process with advanced closed-loop systems.

    PubMed

    Burns, Karen E A; Lellouche, Francois; Lessard, Martin R

    2008-10-01

    Limiting the duration of invasive ventilation is an important goal in caring for critically ill patients. Several clinical trials have shown that compared to traditional care, protocols can reduce the total duration of mechanical ventilation. Computerized or automated weaning has the potential to improve weaning, while decreasing associated workload, and to transfer best evidence into clinical practice by integrating closed-loop technology into protocols that can be operationalized continuously. In this article, we review the principles of automated systems, discuss automated systems that can be used during weaning, and examine the best-current evidence from randomized trials and observational studies supporting their use. We highlight three commercially available systems (Mandatory Minute Ventilation, Adaptive Support Ventilation and SmartCare) that can be used to automate the weaning process. We note advantages and disadvantages associated with individual weaning systems and differences among them. We discuss the potential role for automation in complimenting clinical acumen, reducing practice pattern variation and facilitating knowledge translation into clinical practice, and underscore the need for additional high quality investigations to evaluate automated weaning systems in different practice settings and diverse patient populations.

  19. Intelligent closed-loop insulin delivery systems for ICU patients.

    PubMed

    Wang, Youqing; Xie, Hongzhi; Jiang, Xu; Liu, Bo

    2014-01-01

    Good glycemic control through insulin administration among intensive care unit (ICU) patients can reduce mortality significantly; however, it remains a big challenge because of scarcity of individualized models for ICU patients. To deal with this challenge, a new combination of particle swarm optimization (PSO) and model predictive control (MPC) has been proposed to identify the model online as well as to optimally design the input, i.e., the insulin delivery rate automatically. According to the population distribution, ten typical linear dynamic models were selected such that any patient's model could be approximated by a linear combination of these ten typical models. PSO was used to update the weight coefficients while MPC was used to design the insulin delivery rate based on the combination model identified by using PSO. The proposed strategy was compared with the Yale protocol on 30 virtual subjects. According to the control-variability grid analysis, the percentage values in A + B zone were, respectively, 100% under the proposed strategy and while 51% under the Yale protocol, which demonstrates the superior performance of the proposed strategy. As a good candidate for the full closed-loop insulin delivery method, this new combination can control the glucose level by bringing it to a safe range promptly thereby reducing the risk of death.

  20. The hydrodynamic model testing for closed loop DP assisted mooring

    SciTech Connect

    Aalbers, A.B.; Merchant, A.A.

    1996-12-31

    Far East Levingston Shipbuilding (FELS) is presently completing the construction of the Smedvig Production Unit SPU 380, which will be operated as FPSO for Esso Balder Field Offshore Norway. In good cooperation with FELS and ND and A Inc. of Houston an extensive model test program was carried out for approval and optimization of the DP assisted mooring system. The main aspects were: investigate the performance of the mooring in two water depths, i.e. 250 m and 70 m; optimization of DP control for the three azimuthing thrusters; measurement of motions and wave induced loads at e.g., the bilge keels, keel and deckhouse front; and determination of limit sea state for turning the vessel around against the weather. The tests were carried out in the Wave and Current Basin of MARIN, using a closed loop DP control system to steer the thrusters. The paper presents the findings with respect to the effect of DP control strategy on mooring loads and presents selected results of wave induced loads on bilge keels and deck house.

  1. Wireless technologies for closed-loop retinal prostheses.

    PubMed

    Ng, David C; Bai, Shun; Yang, Jiawei; Tran, Nhan; Skafidas, Efstratios

    2009-12-01

    In this paper, we discuss various technologies needed to develop retinal prostheses with wireless power and data telemetry operation. In addition to the need to communicate with the implanted device, supply of power to the retinal prosthesis is especially difficult. This is because, in the implanted state, the device is not fixed in position due to constant motion of the eye. Furthermore, a retinal prosthesis incorporating a high density electrode array of more than 1000 electrodes is expected to consume approximately 45 mW of power and require 300 kbps of image and stimulation data. The front end of the wireless power and data transmission, the antenna, needs to be small compared to the size of the eye. Also, the wireless module is expected to operate in the reactive near-field region due to small separation between the transmit and receive antennas compared to their size and corresponding operating wavelength. An inductive link is studied as a means to transfer power and for data telemetry between the implant and external unit. In this work, the use of integrated circuit and microfabrication technologies for implementing inductive links is discussed. A closed-loop approach is taken to improve performance and reach optimum operation condition. Design and simulation data are presented as the basis for development of viable wireless module prototypes.

  2. Passive Identification is Non Stationary Objects With Closed Loop Control

    NASA Astrophysics Data System (ADS)

    Dyadik, Valeriy F.; Nadezhdin, Igor S.; Goryunov, Alexey G.; Manenti, Flavio

    2016-08-01

    Typically chemical processes have significant nonlinear dynamics, but despite this, industry is conventionally still using PID-based regulatory control systems. Moreover, process units are interconnected, in terms of inlet and outlet material/energy flows, to other neighbouring units, thus their dynamic behaviour is strongly influenced by these connections and, as a consequence, conventional control systems performance often proves to be poor. However, there a hybrid fuzzy PID control logic, whose tuning parameters are provided in real time. The fuzzy controller tuning is made on the basis of Mamdani controller, also exploiting the results coming from an identification procedure that is carried on when an unmeasured step disturbance of any shape affects the process behaviour. This paper presents procedure for identifying technological object control in a closed loop, i. e. that operates the automated control system. The variation in the controlled variable, caused by the change of the nonmeasurable disturbance, is considered the initial signal for the identification procedure. The parameters of the control object are found by optimization method Levenberg-Marquardt.

  3. Real-Time Closed Loop Modulated Turbine Cooling

    NASA Technical Reports Server (NTRS)

    Shyam, Vikram; Culley, Dennis E.; Eldridge, Jeffrey; Jones, Scott; Woike, Mark; Cuy, Michael

    2014-01-01

    It has been noted by industry that in addition to dramatic variations of temperature over a given blade surface, blade-to-blade variations also exist despite identical design. These variations result from manufacturing variations, uneven wear and deposition over the life of the part as well as limitations in the uniformity of coolant distribution in the baseline cooling design. It is proposed to combine recent advances in optical sensing, actuation, and film cooling concepts to develop a workable active, closed-loop modulated turbine cooling system to improve by 10 to 20 the turbine thermal state over the flight mission, to improve engine life and to dramatically reduce turbine cooling air usage and aircraft fuel burn. A reduction in oxides of nitrogen (NOx) can also be achieved by using the excess coolant to improve mixing in the combustor especially for rotorcraft engines. Recent patents filed by industry and universities relate to modulating endwall cooling using valves. These schemes are complex, add weight and are limited to the endwalls. The novelty of the proposed approach is twofold 1) Fluidic diverters that have no moving parts are used to modulate cooling and can operate under a wide range of conditions and environments. 2) Real-time optical sensing to map the thermal state of the turbine has never been attempted in realistic engine conditions.

  4. Radiant Cooling for Closed-Loop Water Containment: Exploration of Possible Application in Dry Docks

    DTIC Science & Technology

    2015-08-20

    Radiant Cooling For Closed-Loop Water Containment: Exploration of Possible Application in Dry Docks by Trevor R. Murphy, Mechanical...Organization: SPAWAR Sponsoring Organization: NESDI Keywords: Dry Dock Cooling , Heat Transfer, Closed Loop, Pipe System, Cost, Pareto List of Programs...provide data for estimating the cost of implementing a closed-loop radiant cooling system for ships in dry docks. Depending on the material used, pipe

  5. Closed-Loop Control of Vortex Formation in Separated Flows

    NASA Technical Reports Server (NTRS)

    Colonius, Tim; Joe, Won Tae; MacMynowski, Doug; Rowley, Clancy; Taira, Sam; Ahuja, Sunil

    2010-01-01

    In order to phase lock the flow at the desired shedding cycle, particularly at Phi,best, We designed a feedback compensator. (Even though the open-loop forcing at Wf below Wn can lead to phase-locked limit cycles with a high average lift,) This feedback controller resulted in the phase-locked limit cycles that the open-loop control could not achieve for alpha=30 and 40 Particularly for alpha=40, the feedback was able to stabilize the limit cycle that was not stable with any of the open-loop periodic forcing. This results in stable phase-locked limit cycles for a larger range of forcing frequencies than the open-loop control. Also, it was shown that the feedback achieved the high-lift unsteady flow states that open-loop control could not sustain even after the states have been achieved for a long period of time.

  6. Influences of frailty syndrome on open-loop and closed-loop postural control strategy.

    PubMed

    Toosizadeh, Nima; Mohler, Jane; Wendel, Christopher; Najafi, Bijan

    2015-01-01

    As the population of older adults quickly increases, the incidence of frailty syndrome, a reduction in physiological reserve across multiple physiological systems, likewise increases. To date, impaired balance has been associated with frailty; however, the underlying frailty-related postural balance mechanisms remain unclear. The aim of the current study was to use open-loop (OL; postural muscles) and closed-loop (CL; postural muscles plus sensory feedback) mechanisms to explore differences in postural balance mechanisms between nonfrail (n = 44), prefrail (n = 59) and frail individuals (n = 19). One hundred and twenty-two older adults (age ≥65 years) without major mobility disorders were recruited, and frailty was measured using Fried's criteria. Each participant performed two 15-second trials of Romberg balance assessment, once with their eyes open and once with their eyes closed. Body-worn sensors were used to estimate center of gravity (COG) plots. Body-sway (traditional stabilogram analysis) and OLCL (stabilogram diffusion analysis) parameters were derived using COG plots and compared between groups using ANOVA. Frailty and prefrailty were estimated using a multiple variable logistic regression while controlling for age, body mass index, body-sway and OLCL parameters. Between-group differences in the parameters of interest were more pronounced during the eyes-closed condition, for which OL duration was approximately 33 and 22% shorter, respectively, in the frail and prefrail groups when compared to nonfrail controls (mean = 1.9 ± 1.1 s, p = 0.01). The average rate of sway during the OL was 164 and 66% higher, respectively, in frail and prefrail when compared to nonfrail subjects (0.03 ± 0.02 cm(2)/s, p < 0.001). RESULTS also suggest that OLCL parameters can predict frail and prefrail categories when compared to nonfrail controls. Using this method, frailty was identified with a sensitivity and specificity of 97 and 88% (as compared to nonfrail), and

  7. Crystal Structures of Physcomitrella patens AOC1 and AOC2: Insights into the Enzyme Mechanism and Differences in Substrate Specificity1[W][OA

    PubMed Central

    Neumann, Piotr; Brodhun, Florian; Sauer, Kristin; Herrfurth, Cornelia; Hamberg, Mats; Brinkmann, Jens; Scholz, Julia; Dickmanns, Achim; Feussner, Ivo; Ficner, Ralf

    2012-01-01

    In plants, oxylipins regulate developmental processes and defense responses. The first specific step in the biosynthesis of the cyclopentanone class of oxylipins is catalyzed by allene oxide cyclase (AOC) that forms cis(+)-12-oxo-phytodienoic acid. The moss Physcomitrella patens has two AOCs (PpAOC1 and PpAOC2) with different substrate specificities for C18- and C20-derived substrates, respectively. To better understand AOC’s catalytic mechanism and to elucidate the structural properties that explain the differences in substrate specificity, we solved and analyzed the crystal structures of 36 monomers of both apo and ligand complexes of PpAOC1 and PpAOC2. From these data, we propose the following intermediates in AOC catalysis: (1) a resting state of the apo enzyme with a closed conformation, (2) a first shallow binding mode, followed by (3) a tight binding of the substrate accompanied by conformational changes in the binding pocket, and (4) initiation of the catalytic cycle by opening of the epoxide ring. As expected, the substrate dihydro analog cis-12,13S-epoxy-9Z,15Z-octadecadienoic acid did not cyclize in the presence of PpAOC1; however, when bound to the enzyme, it underwent isomerization into the corresponding trans-epoxide. By comparing complex structures of the C18 substrate analog with in silico modeling of the C20 substrate analog bound to the enzyme allowed us to identify three major molecular determinants responsible for the different substrate specificities (i.e. larger active site diameter, an elongated cavity of PpAOC2, and two nonidentical residues at the entrance of the active site). PMID:22987885

  8. Closing The Fromm Control Loop On The Infrared Thermal Imager

    NASA Astrophysics Data System (ADS)

    Kaplan, Herbert

    1988-11-01

    Substituting infrared thermal sensors for conventional thermocouples to measure the temperature of a product, or a point in a process, often provides the industrial user with distinct advantages such as freedom from contact with the product and better speed of response. The major disadvantage has always been higher sensor cost. Now that costs of ir sensors have come down, the non-contact approach is becoming more of a valid alternative, and the instrument or process control engineer often weighs the relative advantages of the two approaches before making a decision. With the advent of "smart" thermal scanning systems, however, it is becoming possible to rapidly measure and control several, many or all points on a product surface remotely and without contact, a capability without precedent, and not feasible with conventional contact sensors. This paper will trace the evolution of infrared noncontact temperature measurement, its development as a process control tool and the introduction of IR line scanners and imagers as industrial control sensors. Several applications of modern closed-loop control systems based on infrared sensors, scanners and imagers will be reviewed. 1. INTRODUCTION Temperature and thermal behavior of materials and fabricated parts in process are most critical factors in the manufacturing process. For this reason temperature is by far the most measured quantity in industrial process monitoring and control. Conventional methods of temperature measurement using thermometers and thermocouples are commonly used for the majority of monitoring and control applications. Non-contact temperature measurement using infrared sensors has become an increasingly desirable alternative over conventional methods as ir sensors have become less expensive, more reliable and electrically interchangeable with conventional thermistors and thermocouples. Now, with the introduction of innovative computer hardware and software, full image thermal control of products and

  9. Clinical requirements for closed-loop control systems.

    PubMed

    Clarke, William L; Renard, Eric

    2012-03-01

    Closed-loop (CL) therapy systems should be safe, efficacious, and easily manageable for type 1 diabetes mellitus patient use. For the first two clinical requirements, noninferiority and superiority criteria must be determined based on current conventional and intensive therapy outcomes. Current frequencies of hypoglycemia and diabetic ketoacidosis are reviewed and safety expectations for CL therapy systems are proposed. Glycosylated hemoglobin levels lower than current American Diabetes Association recommendations for different age groups are proposed as superiority criteria. Measures of glycemic variability are described and the recording of blood glucose levels as percentages within, above, and below a target range are suggested as reasonable alternatives to sophisticated statistical analyses. It is also suggested that Diabetes Quality of Life and Fear of Hypoglycemia surveys should be used to track psychobehavioral outcomes. Manageability requirements for safe and effective clinical management of CL systems are worth being underscored. The weakest part of the infusion system remains the catheter, which is exposed to variable and under-delivery incidents. Detection methods are needed to warn both the system and the patient about altered insulin delivery, including internal pressure and flow alarms. Glucose monitor sensor accuracy is another requirement; it includes the definition of conditions that lead to capillary glucose measurement, eventually followed by sensor recalibration or replacement. The crucial clinical requirement will be a thorough definition of the situations when the patient needs to move from CL to manual management of insulin delivery, or inversely can switch back to CL after a requested interruption. Instructions about these actions will constitute a major part of the education process of the patients before using CL systems and contribute to the manageability of these systems. © 2012 Diabetes Technology Society.

  10. A study of closed-loop application for logic patterning

    NASA Astrophysics Data System (ADS)

    Imai, Hidemichi; Yoshikawa, Shingo; Takamizawa, Hideyoshi; Le-Gratiet, Bertrand; Pelletier, Alice; Sundermann, Frank; Buttgereit, Ute; Trautzsch, Thomas; Thaler, Thomas; Graitzer, Erez

    2012-06-01

    Optical lithography stays at 193nm with a numerical aperture of 1.35 for several more years before moving to EUV lithography. Utilization of 193nm lithography for 45nm and beyond forces the mask shop to produce complex mask designs and tighter lithography specifications which in turn make process control more important than ever. High yield with regards to chip production requires accurate process control. Critical Dimension Uniformity (CDU) is one of the key parameters necessary to assure good performance and reliable functionality of any integrated circuit. There are different contributors which impact the total wafer CDU, mask CD uniformity, resist process, scanner and lens fingerprint, wafer topography, etc. In this paper, the wafer level CD metrology tool WLCD of Carl Zeiss SMS is utilized for CDU measurements in conjunction with the CDC tool from Carl Zeiss SMS which provides CD uniformity correction. The WLCD measures CD based on proven aerial imaging technology. The CDC utilizes an ultrafast femto-second laser to write intra-volume shading elements (Shade-In ElementsTM) inside the bulk material of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in a manner that improves wafer CDU when the corrected mask is printed. The objective of this study is to evaluate the usage of these two tools in a closed loop process to optimize CDU of the mask before leaving the mask shop and to ensure improved intra-field CDU at wafer level. Mainly we present the method of operation and results for logic pattering by using these two tools.

  11. Clinical performance of automatic closed-loop stimulation systems.

    PubMed

    Griesbach, Lothar; Gestrich, Brigitta; Wojciechowski, Dariusz; Weyers, Georg; Tönges, Jürgen; Schier, Matthias; Danilovic, Dejan

    2003-07-01

    Inos pacemakers use contraction dynamics to regulate the pacing rate according to the Closed-Loop Stimulation (CLS) principle. The physician can program only the lower and upper rate limits, while the internal rate responsive parameters are continually adjusted to changing patient conditions. Seventy-two patients with sinus node disease were enrolled in the multicenter Rate Behavior of the Pacing System Inos (2) CLS during Daily Life (RAPID) study to evaluate the appropriateness of CLS rates during daily activities and the long-term stability of the system. The pacemakers clearly differentiated between climbing stairs, descending stairs, and slow walking, with the corresponding peak rates of 104 +/- 18, 95 +/- 15, and 88 +/- 11 beats/min, respectively (P < 0.001 for any pair of activities). The peak CLS rate during the color-word test was significantly higher than that at rest (80 +/- 8 vs 67 +/- 7 beats/min, P = 0.002). The 24-hour heart rate trends retrieved from the pacemaker memory at 3, 6, and 12 months after implantation appeared appropriate in all patients except for two whose pacing rates were occasionally too fast during the night. Mean diurnal and nocturnal rates determined at 3-month, 6-month, and 12-month examinations fluctuated only slightly, from 74.6-75.3 beats/min (diurnal,P = NS) and from 67.0-68.1 beats/min (nocturnal,P = NS), indicating a satisfactory long-term stability of the system. The incidence of atrial pacing events during the entire follow-up was 82 +/- 18%. A 6.5-8.3 beats/min difference, on average, between day and night (P < 0.001)and distinction between different daily activities seem to evidence sensitivity of the automatic CLS-driven pacemakers to physiological demands despite minimum programming requirements.

  12. Sensor Life and Overnight Closed Loop: A Randomized Clinical Trial.

    PubMed

    Tauschmann, Martin; Allen, Janet M; Wilinska, Malgorzata E; Ruan, Yue; Thabit, Hood; Acerini, Carlo L; Dunger, David B; Hovorka, Roman

    2017-05-01

    Closed-loop (CL) systems direct insulin delivery based on continuous glucose monitor (CGM) sensor values. CGM accuracy varies with sensor life, being least accurate on day 1 of sensor insertion. We evaluated the effect of sensor life (enhanced Enlite, Medtronic MiniMed, Northridge, CA) on overnight CL. In an open-label, randomized, 2-period, inpatient crossover pilot study, 12 adolescents on insulin pump (age 16.7 ± 1.9 years; HbA1c 66 ± 10 mmol/mol) attended a clinical research facility on 2 overnight occasions. In random order, participants received CL on day 1 or on day 3-4 after sensor insertion. During both periods, glucose was automatically controlled by a model predictive control algorithm informed by sensor glucose. Plasma glucose was measured every 30 to 60 min. During overnight CL (22:30 to 07:30), the proportion of time with plasma glucose readings in the target range (3.9-8.0 mmol/l, primary endpoint) when initiated on day 1 of sensor insertion vs day 3-4 were comparable (58 ± 32% day 1 vs 56 ± 36% day 3-4; P = .34), and there were no significant differences between interventions in terms of mean plasma glucose ( P = .26), percentage time above 8.0 mmol/l ( P = .49), and time spent below 3.9 mmol/l ( P = .93). Sensor accuracy varied with sensor life (mean absolute relative difference 19.8 ± 15.0% on day 1 and 13.7 ± 10.2% on day 3 to 4). Sensor glucose tended to under-read plasma glucose inflating benefits of CL on glucose control. In spite of differences in sensor accuracy, overnight CL glucose control informed by sensor glucose on day 1 or day 3-4 after sensor insertion was comparable. The model predictive controller appears to mitigate against sensor inaccuracies.

  13. Closed-loop carrier phase synchronization techniques motivated by likelihood functions

    NASA Technical Reports Server (NTRS)

    Tsou, H.; Hinedi, S.; Simon, M.

    1994-01-01

    This article reexamines the notion of closed-loop carrier phase synchronization motivated by the theory of maximum a posteriori phase estimation with emphasis on the development of new structures based on both maximum-likelihood and average-likelihood functions. The criterion of performance used for comparison of all the closed-loop structures discussed is the mean-squared phase error for a fixed-loop bandwidth.

  14. Comparison of open loop and closed loop reactivity measurement techniques on the ISU-AGN-201 reactor

    NASA Astrophysics Data System (ADS)

    Baker, Benjamin Allen

    For some time now at Idaho State University, a project to compare techniques that are capable of obtaining reactivity values with uncertainties limited by the inherent reactor noise has been under study. This dissertation compares open loop techniques (pile oscillator method analyzed with harmonic analysis and inverse kinetics) with a closed loop technique (reactivity oscillator method). Open and closed loop techniques are defined in the classic control sense -- closed loop utilizes feedback while open loop has no imposed feedback. In order to analyze the data appropriately, a set of optimized reactor parameters were determined experimentally for the AGN-201 reactor by the use of a perturbation technique followed by a non-linear regression of the data to fit the zero power transfer function model. After an optimized set of parameters were obtained, the reactivity value for a sample of cadmium was obtained using both open and closed loop techniques at various frequencies to show the differences in the results and application of the two techniques. In the last portion of the dissertation, experiments were performed to determine the reactivity worth of a small sample on the order of 0.05 cents. All techniques were shown to produce results that were limited only by reactor noise.

  15. Closed-Loop Attention Management: Using Augmented Cognition to Sustain Vigilance

    DTIC Science & Technology

    2008-12-01

    CLOSED-LOOP ATTENTION MANAGEMENT: USING AUGMENTED COGNITION TO SUSTAIN VIGILANCE Mark St. John* & Matthew R. Risser Pacific Science...sustained vigilance via a closed-loop attention management system (CLAM). A CLAM system monitors operators’ psychophysiology for signs of inattention and...successful real- time detection of inattention and an effective countermeasure for rousing participants and sustaining vigilance and task performance. The

  16. An optimal open/closed-loop control method with application to a pre-stressed thin duralumin plate

    NASA Astrophysics Data System (ADS)

    Nadimpalli, Sruthi Raju

    The excessive vibrations of a pre-stressed duralumin plate, suppressed by a combination of open-loop and closed-loop controls, also known as open/closed-loop control, is studied in this thesis. The two primary steps involved in this process are: Step (I) with an assumption that the closed-loop control law is proportional, obtain the optimal open-loop control by direct minimization of the performance measure consisting of energy at terminal time and a penalty on open-loop control force via calculus of variations. If the performance measure also involves a penalty on closed-loop control effort then a Fourier based method is utilized. Step (II) the energy at terminal time is minimized numerically to obtain optimal values of feedback gains. The optimal closed-loop control gains obtained are used to describe the displacement and the velocity of open-loop, closed-loop and open/closed-loop controlled duralumin plate.

  17. Closed-loop control better than open-loop control of profofol TCI guided by BIS: a randomized, controlled, multicenter clinical trial to evaluate the CONCERT-CL closed-loop system.

    PubMed

    Liu, Yu; Li, Min; Yang, Dong; Zhang, Xuena; Wu, Anshi; Yao, Shanglong; Xue, Zhanggang; Yue, Yun

    2015-01-01

    The CONCERT-CL closed-loop infusion system designed by VERYARK Technology Co., Ltd. (Guangxi, China) is an innovation using TCI combined with closed-loop controlled intravenous anesthesia under the guide of BIS. In this study we performed a randomized, controlled, multicenter study to compare closed-loop control and open-loop control of propofol by using the CONCERT-CL closed-loop infusion system. 180 surgical patients from three medical centers undergone TCI intravenous anesthesia with propofol and remifentanil were randomly assigned to propofol closed-loop group and propofol opened-loop groups. Primary outcome was global score (GS, GS = (MDAPE+Wobble)/% of time of bispectral index (BIS) 40-60). Secondary outcomes were doses of the anesthetics and emergence time from anesthesia, such as, time to tracheal extubation. There were 89 and 86 patients in the closed-loop and opened-loop groups, respectively. GS in the closed-loop groups (22.21±8.50) were lower than that in the opened-loop group (27.19±15.26) (p=0.009). The higher proportion of time of BIS between 40 and 60 was also observed in the closed-loop group (84.11±9.50%), while that was 79.92±13.17% in the opened-loop group, (p=0.016). No significant differences in propofol dose and time of tracheal extubation were observed. The frequency of propofol regulation in the closed-loop group (31.55±9.46 times/hr) was obverse higher than that in the opened-loop group (6.84±6.21 times/hr) (p=0.000). The CONCERT-CL closed-loop infusion system can automatically regulate the TCI of propofol, maintain the BIS value in an adequate range and reduce the workload of anesthesiologists better than open-loop system. ChiCTR ChiCTR-OOR-14005551.

  18. Seizure Suppression Efficacy of Closed-Loop Versus Open-Loop Deep Brain Stimulation in a Rodent Model of Epilepsy.

    PubMed

    Salam, M Tariqus; Perez Velazquez, Jose Luis; Genov, Roman

    2016-06-01

    We assess and compare the effects of both closed-loop and open-loop neurostimulation of the rat hippocampus by means of a custom low-power programmable therapeutic neurostimulation device on the suppression of spontaneous seizures in a rodent model of epilepsy. Chronic seizures were induced by intraperitoneal kainic acid injection. Two bipolar electrodes were implanted into the CA1 regions of both hippocampi. The electrodes were connected to the custom-built programmable therapeutic neurostimulation device that can trigger an electrical stimulation either in a periodic manner or upon detection of the intracerebral electroencephalographic (icEEE) seizure onset. This device includes a microchip consisting of a 256-channel icEEG recording system and a 64-channel stimulator, and a programmable seizure detector implemented in a field-programmable gate array (FPGA). The neurostimulator was used to evaluate seizure suppression efficacy in ten epileptic rats for a total of 240 subject-days (5760 subject-hours). For this purpose, all rats were randomly divided into two groups: the no-stimulation group and the stimulation group. The no-stimulation group did not receive stimulation. The stimulation group received, first, closed-loop stimulation and, next, open-loop stimulation. The no-stimulation and stimulation groups had a similar seizure frequency baseline, averaging five seizures per day. Closed-loop stimulation reduced seizure frequency by 90% and open-loop stimulation reduced seizure frequency by 17%, both in the stimulation group as compared to the no-stimulation group.

  19. Closed-form decomposition of one-loop massive amplitudes

    SciTech Connect

    Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo

    2008-07-15

    We present formulas for the coefficients of 2-, 3-, 4-, and 5-point master integrals for one-loop massive amplitudes. The coefficients are derived from unitarity cuts in D dimensions. The input parameters can be read off from any unitarity-cut integrand, as assembled from tree-level expressions, after simple algebraic manipulations. The formulas presented here are suitable for analytical as well as numerical evaluation. Their validity is confirmed in two known cases of helicity amplitudes contributing to gg{yields}gg and gg{yields}gH, where the masses of the Higgs and the fermion circulating in the loop are kept as free parameters.

  20. Improved Closed-Loop Carrier-Phase Synchronization In BPSK

    NASA Technical Reports Server (NTRS)

    Simon, Marvin K.; Tsou, Haiping; Hinedi, Sami M.

    1996-01-01

    Scheme motivated by maximum-likelihood approach offers advantages over other well-known schemes. Proposed signal-processing system generates error signal proportional to derivative of conditional probability density function with respect to estimated carrier phase. Signal serves as feedback signal in carrier-phase-tracking loop.

  1. Advanced Hybrid Spacesuit Concept Featuring Integrated Open Loop and Closed Loop Ventilation Systems

    NASA Technical Reports Server (NTRS)

    Daniel, Brian A.; Fitzpatrick, Garret R.; Gohmert, Dustin M.; Ybarra, Rick M.; Dub, Mark O.

    2013-01-01

    A document discusses the design and prototype of an advanced spacesuit concept that integrates the capability to function seamlessly with multiple ventilation system approaches. Traditionally, spacesuits are designed to operate both dependently and independently of a host vehicle environment control and life support system (ECLSS). Spacesuits that operate independent of vehicle-provided ECLSS services must do so with equipment selfcontained within or on the spacesuit. Suits that are dependent on vehicle-provided consumables must remain physically connected to and integrated with the vehicle to operate properly. This innovation is the design and prototype of a hybrid spacesuit approach that configures the spacesuit to seamlessly interface and integrate with either type of vehicular systems, while still maintaining the ability to function completely independent of the vehicle. An existing Advanced Crew Escape Suit (ACES) was utilized as the platform from which to develop the innovation. The ACES was retrofitted with selected components and one-off items to achieve the objective. The ventilation system concept was developed and prototyped/retrofitted to an existing ACES. Components were selected to provide suit connectors, hoses/umbilicals, internal breathing system ducting/ conduits, etc. The concept utilizes a lowpressure- drop, high-flow ventilation system that serves as a conduit from the vehicle supply into the suit, up through a neck seal, into the breathing helmet cavity, back down through the neck seal, out of the suit, and returned to the vehicle. The concept also utilizes a modified demand-based breathing system configured to function seamlessly with the low-pressure-drop closed-loop ventilation system.

  2. Time scale analysis of a closed-loop discrete optimal control system

    NASA Technical Reports Server (NTRS)

    Naidu, D. S.; Price, D. B.

    1986-01-01

    A two-time scale discrete control system is considered. The closed-loop optimal linear quadratic (LQ) regulator for the system requires the solution of a full-order algebraic matrix Riccati equation. Alternatively, the original system is decomposed into reduced-order slow and fast subsystems. The closed-loop optimal control of the subsystems requires the solution of two algebraic matrix Riccati equations of order lower than that required for the full-order system. A composite, closed-loop suboptimal control is created from the sum of the slow and fast feedback optimal controls. Numerical results obtained for an aircraft model show a very close agreement between the exact (optimal) solutions and computationally simpler composite (suboptimal) solutions. The main advantage of the method is the considerable reduction in the overall computational requirements for the closed-loop optimal control of digital flight systems.

  3. A LabVIEW model incorporating an open-loop arterial impedance and a closed-loop circulatory system.

    PubMed

    Cole, R T; Lucas, C L; Cascio, W E; Johnson, T A

    2005-11-01

    While numerous computer models exist for the circulatory system, many are limited in scope, contain unwanted features or incorporate complex components specific to unique experimental situations. Our purpose was to develop a basic, yet multifaceted, computer model of the left heart and systemic circulation in LabVIEW having universal appeal without sacrificing crucial physiologic features. The program we developed employs Windkessel-type impedance models in several open-loop configurations and a closed-loop model coupling a lumped impedance and ventricular pressure source. The open-loop impedance models demonstrate afterload effects on arbitrary aortic pressure/flow inputs. The closed-loop model catalogs the major circulatory waveforms with changes in afterload, preload, and left heart properties. Our model provides an avenue for expanding the use of the ventricular equations through closed-loop coupling that includes a basic coronary circuit. Tested values used for the afterload components and the effects of afterload parameter changes on various waveforms are consistent with published data. We conclude that this model offers the ability to alter several circulatory factors and digitally catalog the most salient features of the pressure/flow waveforms employing a user-friendly platform. These features make the model a useful instructional tool for students as well as a simple experimental tool for cardiovascular research.

  4. Open- and Closed-Loop Dynamics of the High-Efficiency Antenna Subreflector

    NASA Astrophysics Data System (ADS)

    Kuczenski, M. B.; Gawronski, W.

    2000-07-01

    The subreflector of the high-efficiency (HEF) antenna moves in three axes, while the subreflector controller supervises these movements. The precision of subreflector response to the controller commands is essential to maintaining the antenna-pointing precision. This article presents the development of the control system model of the HEF antenna subreflector. It includes the dynamics of the open-loop (or rate-loop) system, the development of the controller, and the simulations of the closed-loop performance. The analysis shows that the closed-loop dynamics, such as settling time, overshoot, and bandwidth, are comparable to the antenna closed-loop dynamics; thus, they are able to meet the pointing requirements.

  5. A comparison of open and closed loop applications of the minimum distance guidance technique

    NASA Technical Reports Server (NTRS)

    Lattimore, J. P., Jr.

    1972-01-01

    A comparison is made of open and closed loop applications of a second order guidance algorithm, using the minimum distance strategy. A nonlinear reoptimization procedure is used as the ideal guidance history. The system model used for the comparison is a low-thrust vehicle performing a minimum time, three-dimensional, heliocentric Earth-Mars transfer. For the example problem considered, closed loop guidance proves to be much more accurate on satisfaction of the final state than the open loop procedure. On the other hand, closed loop guidance proves to be much more vulnerable to perturbation by highly nonlinear regions in the trajectory. Finally, the results indicate that for this problem the best loop closure interval is at each integration step, about one day, or more often, if possible.

  6. Psychosocial aspects of closed- and open-loop insulin delivery: closing the loop in adults with Type 1 diabetes in the home setting.

    PubMed

    Barnard, K D; Wysocki, T; Thabit, H; Evans, M L; Amiel, S; Heller, S; Young, A; Hovorka, R

    2015-05-01

    To explore the psychosocial experiences of closed-loop technology and to compare ratings of closed- and open-loop technology for adults with Type 1 diabetes taking part in a randomized crossover study. Adults (aged > 18 years) on insulin pump therapy were recruited to receive a first phase of either real-time continuous glucose monitoring with overnight closed-loop or real-time continuous glucose monitoring alone (open-loop) followed by a second phase of the alternative treatment in random order, at home for 4 weeks, unsupervised. Participants were invited to share their views in semi-structured interviews. The impact of the closed-loop technology, positive and negative aspects of living with the device overnight, along with the hopes and anxieties of the participants, were explored. The participants in the trial were 24 adults with a mean (sd) age of 43 (12) years, of whom 54% were men. The mean (range) interview duration was 26 (12-46) min. Content and thematic analysis showed the following key positive themes: improved blood glucose control (n = 16); reassurance/reduced worry (n = 16); improved overnight control leading to improved daily functioning and diabetes control (n = 16); and improved sleep (n = 8). The key negative themes were: technical difficulties (n = 24); intrusiveness of alarms (n = 13); and size of equipment (n = 7). Of the 24 participant, 20 would recommend the closed-loop technology. Closed-loop therapy has positive effects when it works in freeing participants from the demands of self-management. The downside was technical difficulties, particularly concerning the pump and 'connectivity', which it is hoped will improve. Future research should continue to explore the acceptability of the closed-loop system as a realistic therapy option, taking account of user concerns as new systems are designed. Failure to do this may reduce the eventual utility of new systems. © 2015 The Authors. Diabetic Medicine © 2015 Diabetes UK.

  7. Closed-loop liquid-vapor equilibrium in a one-component system.

    PubMed

    Almarza, N G

    2012-09-01

    We report Monte Carlo simulations that show a closed-loop liquid-vapor equilibrium in a pure substance. This finding has been achieved on a two-dimensional lattice model for patchy particles that can form network fluids. We have considered related models with a slightly different patch distribution in order to understand the features of the distribution of patches on the surface of the particles that make possible the presence of the closed-loop liquid-vapor equilibrium, and its relation to the phase diagram containing so-called empty liquids. Finally we discuss the likelihood of finding the closed-loop liquid-vapor equilibria on related models for three-dimensional models of patchy particles in the continuum, and speculate on the possible relationship between the mechanism behind the closed-loop liquid-vapor equilibrium of our simple lattice model and the salt-induced reentrant condensation found in complex systems.

  8. Bidirectional neural interface: Closed-loop feedback control for hybrid neural systems.

    PubMed

    Chou, Zane; Lim, Jeffrey; Brown, Sophie; Keller, Melissa; Bugbee, Joseph; Broccard, Frédéric D; Khraiche, Massoud L; Silva, Gabriel A; Cauwenberghs, Gert

    2015-01-01

    Closed-loop neural prostheses enable bidirectional communication between the biological and artificial components of a hybrid system. However, a major challenge in this field is the limited understanding of how these components, the two separate neural networks, interact with each other. In this paper, we propose an in vitro model of a closed-loop system that allows for easy experimental testing and modification of both biological and artificial network parameters. The interface closes the system loop in real time by stimulating each network based on recorded activity of the other network, within preset parameters. As a proof of concept we demonstrate that the bidirectional interface is able to establish and control network properties, such as synchrony, in a hybrid system of two neural networks more significantly more effectively than the same system without the interface or with unidirectional alternatives. This success holds promise for the application of closed-loop systems in neural prostheses, brain-machine interfaces, and drug testing.

  9. Closed Loop Software Control of the MIDEX Power System

    NASA Technical Reports Server (NTRS)

    Castell, Karen; Hernandez-Pellerano, Amri; Wismer, Margaret

    1998-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The design and analysis of the MAP attitude control system (ACS) have been refined since work previously reported. The full spacecraft and instrument flexible model was developed in NASTRAN, and the resulting flexible modes were plotted and reduced with the Modal Significance Analysis Package (MSAP). The reduced-order model was used to perform the linear stability analysis for each control mode, the results of which are presented in this paper. Although MAP is going to a relatively disturbance-free Lissajous orbit around the Earth-Sun L2 Lagrange point, a detailed disturbance-torque analysis is required because there are only a small number of opportunities for momentum unloading each year. Environmental torques, including solar pressure at L2, and aerodynamic and gravity gradient during phasing-loop orbits, were calculated and simulated. A simple model of fuel slosh was derived to model its effect on the motion of the spacecraft. In addition, a thruster mode linear impulse controller was developed to meet the accuracy requirements of the phasing loop burns. A dynamic attitude error limiter was added to improve the performance of the ACS during large attitude slews. The result of this analysis is a stable ACS subsystem that meets all of the mission's requirements.

  10. White Lake AOC Habitat Restoration Project

    EPA Pesticide Factsheets

    The Muskegon Conservation District and the White Lake Public Advisory Council in 2012 completed the White Lake AOC Shoreline Habitat Restoration Project to address the loss of shoreline and nearshore habitat.

  11. Leveraging ITIL to Govern AOC Information Technology

    DTIC Science & Technology

    2005-12-01

    III, BS Major, USAF Approved: _____//Signed//_______________________ 5 Dec 05 Dr. Robert F. Mills (Chairman) Date...Signed//_______________________ 5 Dec 05 Maj Scott R. Graham (Member) Date _____//Signed//_______________________ 5 Dec 05 Dr. Michael R... 5 1.5 AOC IT Governance

  12. Closed-Loop Insulin Delivery during Pregnancy in Women with Type 1 Diabetes.

    PubMed

    Stewart, Zoe A; Wilinska, Malgorzata E; Hartnell, Sara; Temple, Rosemary C; Rayman, Gerry; Stanley, Katharine P; Simmons, David; Law, Graham R; Scott, Eleanor M; Hovorka, Roman; Murphy, Helen R

    2016-08-18

    In patients with type 1 diabetes who are not pregnant, closed-loop (automated) insulin delivery can provide better glycemic control than sensor-augmented pump therapy, but data are lacking on the efficacy, safety, and feasibility of closed-loop therapy during pregnancy. We performed an open-label, randomized, crossover study comparing overnight closed-loop therapy with sensor-augmented pump therapy, followed by a continuation phase in which the closed-loop system was used day and night. Sixteen pregnant women with type 1 diabetes completed 4 weeks of closed-loop pump therapy (intervention) and sensor-augmented pump therapy (control) in random order. During the continuation phase, 14 of the participants used the closed-loop system day and night until delivery. The primary outcome was the percentage of time that overnight glucose levels were within the target range (63 to 140 mg per deciliter [3.5 to 7.8 mmol per liter]). The percentage of time that overnight glucose levels were in the target range was higher during closed-loop therapy than during control therapy (74.7% vs. 59.5%; absolute difference, 15.2 percentage points; 95% confidence interval, 6.1 to 24.2; P=0.002). The overnight mean glucose level was lower during closed-loop therapy than during control therapy (119 vs. 133 mg per deciliter [6.6 vs. 7.4 mmol per liter], P=0.009). There were no significant differences between closed-loop and control therapy in the percentage of time in which glucose levels were below the target range (1.3% and 1.9%, respectively; P=0.28), in insulin doses, or in adverse-event rates. During the continuation phase (up to 14.6 additional weeks, including antenatal hospitalizations, labor, and delivery), glucose levels were in the target range 68.7% of the time; the mean glucose level was 126 mg per deciliter (7.0 mmol per liter). No episodes of severe hypoglycemia requiring third-party assistance occurred during either phase. Overnight closed-loop therapy resulted in better

  13. Feasibility of closed-loop insulin delivery in type 2 diabetes: a randomized controlled study.

    PubMed

    Kumareswaran, Kavita; Thabit, Hood; Leelarathna, Lalantha; Caldwell, Karen; Elleri, Daniela; Allen, Janet M; Nodale, Marianna; Wilinska, Malgorzata E; Evans, Mark L; Hovorka, Roman

    2014-01-01

    Closed-loop insulin delivery offers a promising treatment option, but to date, it has only been evaluated in type 1 diabetes. Our aim was to evaluate the feasibility of fully closed-loop subcutaneous insulin delivery in insulin-naïve patients with type 2 diabetes. Twelve subjects (seven males, age 57.2 years, BMI 30.5 kg/m2) with noninsulin-treated type 2 diabetes (HbA1c 8.4% [68 mmol/mol], diabetes duration 7.6 years) underwent two 24-h visits (closed-loop and control) in a randomized crossover design. During closed-loop visits, the subjects' routine diabetes therapy was replaced with model predictive control algorithm-driven subcutaneous insulin pump delivery based on real-time continuous glucose monitoring. Meals were unannounced, and no additional insulin was administered for carbohydrates consumed. During control visits, the usual diabetes regimen was continued (metformin 92%, sulfonylureas 58%, dipeptidyl peptidase-4 inhibitors 33%). On both visits, subjects consumed matched 50- to 80-g carbohydrate meals and optional 15-g carbohydrate snacks and remained largely sedentary. Plasma glucose measurements evaluated closed-loop performance. Compared with conventional therapy, 24 h of closed-loop insulin delivery increased overall the median time in target plasma glucose (3.9-8.0 mmol/L) from 24 to 40% (P = 0.016), despite sensor under-reading by a median of 1.2 mmol/L. The benefit of the closed-loop system was more prominent overnight, with greater time in target glucose (median 78 vs. 35%; P = 0.041) and less time in hyperglycemia (22 vs. 65%; P = 0.041). There was no hypoglycemia during either intervention. A closed-loop system without meal announcement and using subcutaneous insulin delivery in insulin-naïve patients with type 2 diabetes appears feasible and safe. Improvement in postprandial glucose control may require further optimization of system performance.

  14. Adjustment of Open-Loop Settings to Improve Closed-Loop Results in Type 1 Diabetes: A Multicenter Randomized Trial

    PubMed Central

    Dassau, Eyal; Brown, Sue A.; Basu, Ananda; Pinsker, Jordan E.; Kudva, Yogish C.; Gondhalekar, Ravi; Patek, Steve; Lv, Dayu; Schiavon, Michele; Lee, Joon Bok; Dalla Man, Chiara; Hinshaw, Ling; Castorino, Kristin; Mallad, Ashwini; Dadlani, Vikash; McCrady-Spitzer, Shelly K.; McElwee-Malloy, Molly; Wakeman, Christian A.; Bevier, Wendy C.; Bradley, Paige K.; Kovatchev, Boris; Cobelli, Claudio; Zisser, Howard C.

    2015-01-01

    Context: Closed-loop control (CLC) relies on an individual's open-loop insulin pump settings to initialize the system. Optimizing open-loop settings before using CLC usually requires significant time and effort. Objective: The objective was to investigate the effects of a one-time algorithmic adjustment of basal rate and insulin to carbohydrate ratio open-loop settings on the performance of CLC. Design: This study reports a multicenter, outpatient, randomized, crossover clinical trial. Patients: Thirty-seven adults with type 1 diabetes were enrolled at three clinical sites. Interventions: Each subject's insulin pump settings were subject to a one-time algorithmic adjustment based on 1 week of open-loop (i.e., home care) data collection. Subjects then underwent two 27-hour periods of CLC in random order with either unchanged (control) or algorithmic adjusted basal rate and carbohydrate ratio settings (adjusted) used to initialize the zone-model predictive control artificial pancreas controller. Subject's followed their usual meal-plan and had an unannounced exercise session. Main Outcomes and Measures: Time in the glucose range was 80–140 mg/dL, compared between both arms. Results: Thirty-two subjects completed the protocol. Median time in CLC was 25.3 hours. The median time in the 80–140 mg/dl range was similar in both groups (39.7% control, 44.2% adjusted). Subjects in both arms of CLC showed minimal time spent less than 70 mg/dl (median 1.34% and 1.37%, respectively). There were no significant differences more than 140 mg/dL. Conclusions: A one-time algorithmic adjustment of open-loop settings did not alter glucose control in a relatively short duration outpatient closed-loop study. The CLC system proved very robust and adaptable, with minimal (<2%) time spent in the hypoglycemic range in either arm. PMID:26204135

  15. A Design Method of a Full Closed Loop Sampled Servo Control for Hard Disk Drive

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Takashi; Atsumi, Takenori

    This paper presents a design methodology for fast and precise positioning using a full closed loop sampled servo control system. A servo control of hard disk drive (HDD) achieves 3-4 ms fast access and nanoscale positioning accuracy. To achieve the nanoscale precise positioning, a full closed loop feedback control is a key structure. From control theory viewpoint, the full closed loop is an ideal method, but it is difficult to take this method in industries due to sensor allocation. In HDD, this full closed loop feedback control has been applied for last 20 years. The full closed loop sometimes brings drawbacks to the servo control design. In HDD case, that is a limited sampling rate selection. In this paper, based on these two features which are the full closed loop and a sampled servo, uniquely developed servo design methods for HDD are presented, which include two-degrees-of-freedom (TDOF) controller with multi-rate sampling, reference trajectory design not to excite higher order mechanical resonances, settling servo to compensate for tracking error near the target, phase stabilized design of feedback control to have better sensitivity, and multi-rate filter design to suppress disturbances above the Nyquist frequency.

  16. Enhanced open-loop but not closed-loop cardiac baroreflex sensitivity during orthostatic stress in humans.

    PubMed

    Akimoto, Toshinari; Sugawara, Jun; Ichikawa, Daisuke; Terada, Nobuyuki; Fadel, Paul J; Ogoh, Shigehiko

    2011-11-01

    The neural interaction between the cardiopulmonary and arterial baroreflex may be critical for the regulation of blood pressure during orthostatic stress. However, studies have reported conflicting results: some indicate increases and others decreases in cardiac baroreflex sensitivity (i.e., gain) with cardiopulmonary unloading. Thus the effect of orthostatic stress-induced central hypovolemia on regulation of heart rate via the arterial baroreflex remains unclear. We sought to comprehensively assess baroreflex function during orthostatic stress by identifying and comparing open- and closed-loop dynamic cardiac baroreflex gains at supine rest and during 60° head-up tilt (HUT) in 10 healthy men. Closed-loop dynamic "spontaneous" cardiac baroreflex sensitivities were calculated by the sequence technique and transfer function and compared with two open-loop carotid-cardiac baroreflex measures using the neck chamber system: 1) a binary white-noise method and 2) a rapid-pulse neck pressure-neck suction technique. The gain from the sequence technique was decreased from -1.19 ± 0.14 beats·min(-1)·mmHg(-1) at rest to -0.78 ± 0.10 beats·min(-1)·mmHg(-1) during HUT (P = 0.005). Similarly, closed-loop low-frequency baroreflex transfer function gain was reduced during HUT (P = 0.033). In contrast, open-loop low-frequency transfer function gain between estimated carotid sinus pressure and heart rate during white-noise stimulation was augmented during HUT (P = 0.01). This result was consistent with the maximal gain of the carotid-cardiac baroreflex stimulus-response curve (from 0.47 ± 0.15 beats·min(-1)·mmHg(-1) at rest to 0.60 ± 0.20 beats·min(-1)·mmHg(-1) at HUT, P = 0.037). These findings suggest that open-loop cardiac baroreflex gain was enhanced during HUT. Moreover, under closed-loop conditions, spontaneous baroreflex analyses without external stimulation may not represent open-loop cardiac baroreflex characteristics during orthostatic stress.

  17. Bifurcations of limit cycles in open and closed loop reverse flow reactors

    NASA Astrophysics Data System (ADS)

    Russo, Lucia; Crescitelli, Silvestro; Brasiello, Antonio

    2013-10-01

    The present work analyses the bifurcations of limit cycles in open and loop reverse flow reactors. The open loop system consists of a reactor where the flow direction is periodically forced whereas in the closed loop system, the flow inversion is dictated by a control law which activates when the temperature at the edge of catalytic bed falls below the set-point value. We performed the bifurcation analysis of the open loop system as the switch time is varied and we constructed the solution diagram through the application of continuation technique. Many Naimark-Sacker bifurcations leading to quasi-periodic regimes have been found on the limit cycles branches. Finally, we compared these limit cycles with those of the closed loop system where the flow inversion is dictated by a control system which acts if the temperature measured at the edge of reactor falls below a set-point value.

  18. Closed-loop analysis and control of a non-inverting buck-boost converter

    NASA Astrophysics Data System (ADS)

    Chen, Zengshi; Hu, Jiangang; Gao, Wenzhong

    2010-11-01

    In this article, a cascade controller is designed and analysed for a non-inverting buck-boost converter. The fast inner current loop uses sliding mode control. The slow outer voltage loop uses the proportional-integral (PI) control. Stability analysis and selection of PI gains are based on the nonlinear closed-loop error dynamics incorporating both the inner and outer loop controllers. The closed-loop system is proven to have a nonminimum phase structure. The voltage transient due to step changes of input voltage or resistance is predictable. The operating range of the reference voltage is discussed. The controller is validated by a simulation circuit. The simulation results show that the reference output voltage is well-tracked under system uncertainties or disturbances, confirming the validity of the proposed controller.

  19. Assessing the effect of dynamics on the closed-loop protein-folding hypothesis

    PubMed Central

    Chintapalli, Sree V.; Illingworth, Christopher J. R.; Upton, Graham J. G.; Sacquin-Mora, Sophie; Reeves, Philip J.; Mohammedali, Hani S.; Reynolds, Christopher A.

    2014-01-01

    The closed-loop (loop-n-lock) hypothesis of protein folding suggests that loops of about 25 residues, closed through interactions between the loop ends (locks), play an important role in protein structure. Coarse-grain elastic network simulations, and examination of loop lengths in a diverse set of proteins, each supports a bias towards loops of close to 25 residues in length between residues of high stability. Previous studies have established a correlation between total contact distance (TCD), a metric of sequence distances between contacting residues (cf. contact order), and the log-folding rate of a protein. In a set of 43 proteins, we identify an improved correlation (r2 = 0.76), when the metric is restricted to residues contacting the locks, compared to the equivalent result when all residues are considered (r2 = 0.65). This provides qualified support for the hypothesis, albeit with an increased emphasis upon the importance of a much larger set of residues surrounding the locks. Evidence of a similar-sized protein core/extended nucleus (with significant overlap) was obtained from TCD calculations in which residues were successively eliminated according to their hydrophobicity and connectivity, and from molecular dynamics simulations. Our results suggest that while folding is determined by a subset of residues that can be predicted by application of the closed-loop hypothesis, the original hypothesis is too simplistic; efficient protein folding is dependent on a considerably larger subset of residues than those involved in lock formation. PMID:24258160

  20. Downlink Training Techniques for FDD Massive MIMO Systems: Open-Loop and Closed-Loop Training With Memory

    NASA Astrophysics Data System (ADS)

    Choi, Junil; Love, David J.; Bidigare, Patrick

    2014-10-01

    The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD massive MIMO be used for training signal transmissions and channel state information (CSI) feedback. To reduce the overhead of the downlink training phase, we propose practical open-loop and closed-loop training frameworks in this paper. We assume the base station and the user share a common set of training signals in advance. In open-loop training, the base station transmits training signals in a round-robin manner, and the user successively estimates the current channel using long-term channel statistics such as temporal and spatial correlations and previous channel estimates. In closed-loop training, the user feeds back the best training signal to be sent in the future based on channel prediction and the previously received training signals. With a small amount of feedback from the user to the base station, closed-loop training offers better performance in the data communication phase, especially when the signal-to-noise ratio is low, the number of transmit antennas is large, or prior channel estimates are not accurate at the beginning of the communication setup, all of which would be mostly beneficial for massive MIMO systems.

  1. Continuous Glucose Monitoring Considerations for the Development of a Closed-Loop Artificial Pancreas System

    PubMed Central

    Keenan, D Barry; Grosman, Benyamin; Clark, Harry W; Roy, Anirban; Weinzimer, Stuart A; Shah, Rajiv V; Mastrototaro, John J

    2011-01-01

    Background Commercialization of a closed-loop artificial pancreas system that employs continuous subcutaneous insulin infusion and interstitial fluid glucose sensing has been encumbered by state-of-the-art technology. Continuous glucose monitoring (CGM) devices with improved accuracy could significantly advance development efforts. However, the current accuracy of CGM devices might be adequate for closed-loop control. Methods The influence that known CGM limitations have on closed-loop control was investigated by integrating sources of sensor inaccuracy with the University of Virginia Padova Diabetes simulator. Non-glucose interference, physiological time lag and sensor error measurements, selected from 83 Enlite™ glucose sensor recordings with the Guardian® REAL-Time system, were used to modulate simulated plasma glucose signals. The effect of sensor accuracy on closed-loop controller performance was evaluated in silico, and contrasted with closed-loop clinical studies during the nocturnal control period. Results Based on n = 2472 reference points, a mean sensor error of 14% with physiological time lags of 3.28 ± 4.62 min (max 13.2 min) was calculated for simulation. Sensor bias reduced time in target for both simulation and clinical experiments. In simulation, additive error increased time <70 mg/dl and >180 mg/dl by 0.2% and 5.6%, respectively. In-clinic, the greatest low blood glucose index values (max = 5.9) corresponded to sensor performance. Conclusion Sensors have sufficient accuracy for closed-loop control, however, algorithms are necessary to effectively calibrate and detect erroneous calibrations and failing sensors. Clinical closed-loop data suggest that control with a higher target of 140 mg/dl during the nocturnal period could significantly reduce the risk for hypoglycemia. PMID:22226249

  2. First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

    NASA Technical Reports Server (NTRS)

    Gill, E.; Naasz, Bo; Ebinuma, T.

    2003-01-01

    A closed-loop system for the demonstration of autonomous satellite formation flying technologies using hardware-in-the-loop has been developed. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. The autonomous closed-loop formation acquisition and keeping strategy is based on Lyapunov's direct control method as applied to the standard set of Keplerian elements. This approach not only assures global and asymptotic stability of the control but also maintains valuable physical insight into the applied control vectors. Furthermore, the approach can account for system uncertainties and effectively avoids a computationally expensive solution of the two point boundary problem, which renders the concept particularly attractive for implementation in onboard processors. A guidance law has been developed which strictly separates the relative from the absolute motion, thus avoiding the numerical integration of a target trajectory in the onboard processor. Moreover, upon using precise kinematic relative GPS solutions, a dynamical modeling or filtering is avoided which provides for an efficient implementation of the process on an onboard processor. A sample formation flying scenario has been created aiming at the autonomous transition of a Low Earth Orbit satellite formation from an initial along-track separation of 800 m to a target distance of 100 m. Assuming a low-thrust actuator which may be accommodated on a small satellite, a typical control accuracy of less than 5 m has been achieved which proves the applicability of autonomous formation flying techniques to

  3. Quantitative Evaluation of Closed-Loop-Shaped Cardiomyocyte Network by Using Ring-Shaped Electrode

    NASA Astrophysics Data System (ADS)

    Nomura, Fumimasa; Kaneko, Tomoyuki; Hamada, Tomoyo; Hattori, Akihiro; Yasuda, Kenji

    2012-06-01

    Re-entry of excitation in the heart is one of the abnormal phenomena that causes lethal arrhythmia and is thought to be induced by the looped structure of the excitation conduction pathway. To evaluate the geometrical pattern dependence of electrophysiological results, we fabricated three models of cardiomyocyte networks and compared their beating frequencies (BFs), amplitudes of a depolarization peak, and field potential durations (FPDs). The set of different closed-loop-shaped network models from 3 to 8 mm in length showed the same BFs, amplitudes, and FPDs independent of their loop lengths, whereas the BFs and FPDs of 60 µm small clusters, and the FPDs of the 2 mm open-line-shaped network model were different from those of a closed-loop-shaped network model. These results indicate that the mm order larger size of clusters might create lower BFs, and the closed-loop-shaped model may generate longer FPDs. They also suggest the importance of spatial arrangement control of the cardoimyocyte community for reproducible measurement of electrophysiological properties of cardiomyocytes, especially control of the closed-loop formation, which might change the waveforms of FPDs depending on the difference in the geometry and conduction pathway of the cell network.

  4. Open-loop, closed-loop and compensatory control: performance improvement under pressure in a rhythmic task

    PubMed Central

    Wei, Kunlin; Sternad, Dagmar

    2012-01-01

    According to explicit monitoring theories, the phenomenon of choking under pressure is due to actors focusing their attention on the execution of the skill. This step-by-step perceptually guided control may then interfere with automatic execution. In order to examine the changes in control at the sensorimotor level, we examined the rhythmic task of ball bouncing which affords detailed quantification of indicators of control based on previous research. The hypothesis was that under psychological pressure perceptually guided control should lead to decreased performance due to over-emphasis on closed-loop control and decreased compensatory control. In two experiments of different difficulty psychological stress was induced via setting up a fake competition. Results showed that, contrary to the hypothesis, performance accuracy and consistency improved together with an increase in compensatory control. Indicators for open- and closed-loop processes did not change. Only under more challenging conditions in Experiment 2, enhanced performance under pressure was accompanied by more active, closed-loop and less passive control. The results are discussed in light of task demands and the continuous rhythmic nature of the task: in more challenging tasks, control appears to be more prone to disturbance due to psychological stress. The different control demands in continuous rhythmic tasks may be less prone to interference due to psychological stress than in discrete tasks. PMID:19943039

  5. Closed-loop control of anesthesia: a primer for anesthesiologists.

    PubMed

    Dumont, Guy A; Ansermino, J Mark

    2013-11-01

    Feedback control is ubiquitous in nature and engineering and has revolutionized safety in fields from space travel to the automobile. In anesthesia, automated feedback control holds the promise of limiting the effects on performance of individual patient variability, optimizing the workload of the anesthesiologist, increasing the time spent in a more desirable clinical state, and ultimately improving the safety and quality of anesthesia care. The benefits of control systems will not be realized without widespread support from the health care team in close collaboration with industrial partners. In this review, we provide an introduction to the established field of control systems research for the everyday anesthesiologist. We introduce important concepts such as feedback and modeling specific to control problems and provide insight into design requirements for guaranteeing the safety and performance of feedback control systems. We focus our discussion on the optimization of anesthetic drug administration.

  6. Irradiation Testing Vehicles for Fast Reactors from Open Test Assemblies to Closed Loops

    SciTech Connect

    Sienicki, James J.; Grandy, Christopher

    2016-12-15

    A review of irradiation testing vehicle approaches and designs that have been incorporated into past Sodium-Cooled Fast Reactors (SFRs) or envisioned for incorporation has been carried out. The objective is to understand the essential features of the approaches and designs so that they can inform test vehicle designs for a future U.S. Fast Test Reactor. Fast test reactor designs examined include EBR-II, FFTF, JOYO, BOR-60, PHÉNIX, JHR, and MBIR. Previous designers exhibited great ingenuity in overcoming design and operational challenges especially when the original reactor plant’s mission changed to an irradiation testing mission as in the EBRII reactor plant. The various irradiation testing vehicles can be categorized as: Uninstrumented open assemblies that fit into core locations; Instrumented open test assemblies that fit into special core locations; Self-contained closed loops; and External closed loops. A special emphasis is devoted to closed loops as they are regarded as a very desirable feature of a future U.S. Fast Test Reactor. Closed loops are an important technology for irradiation of fuels and materials in separate controlled environments. The impact of closed loops on the design of fast reactors is also discussed in this report.

  7. Closed-loop for type 1 diabetes - an introduction and appraisal for the generalist.

    PubMed

    Bally, Lia; Thabit, Hood; Hovorka, Roman

    2017-01-23

    Rapid progress over the past decade has been made with the development of the 'Artificial Pancreas', also known as the closed-loop system, which emulates the feedback glucose-responsive functionality of the pancreatic beta cell. The recent FDA approval of the first hybrid closed-loop system makes the Artificial Pancreas a realistic therapeutic option for people with type 1 diabetes. In anticipation of its advent into clinical care, we provide a primer and appraisal of this novel therapeutic approach in type 1 diabetes for healthcare professionals and non-specialists in the field. Randomised clinical studies in outpatient and home settings have shown improved glycaemic outcomes, reduced risk of hypoglycaemia and positive user attitudes. User input and interaction with existing closed-loop systems, however, are still required. Therefore, management of user expectations, as well as training and support by healthcare providers are key to ensure optimal uptake, satisfaction and acceptance of the technology. An overview of closed-loop technology and its clinical implications are discussed, complemented by our extensive hands-on experience with closed-loop system use during free daily living. The introduction of the artificial pancreas into clinical practice represents a milestone towards the goal of improving the care of people with type 1 diabetes. There remains a need to understand the impact of user interaction with the technology, and its implication on current diabetes management and care.

  8. A monolithic MEMS position sensor for closed-loop high-speed atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Hosseini, N.; Nievergelt, A. P.; Adams, J. D.; Stavrov, V. T.; Fantner, G. E.

    2016-04-01

    The accuracy and repeatability of atomic force microscopy (AFM) imaging significantly depend on the accuracy of the piezoactuator. However, nonlinear properties of piezoactuators can distort the image, necessitating sensor-based closed-loop actuators to achieve high accuracy AFM imaging. The advent of high-speed AFM has made the requirements on the position sensors in such a system even more stringent, requiring higher bandwidths and lower sensor mass than traditional sensors can provide. In this paper, we demonstrate a way for high-speed, high-precision closed-loop AFM nanopositioning using a novel, miniaturized micro-electro-mechanical system position sensor in conjunction with a simple PID controller. The sensor was developed to respond to the need for small, lightweight, high-bandwidth, long-range and sub-nm-resolution position measurements in high-speed AFM applications. We demonstrate the use of this sensor for closed-loop operation of conventional as well as high-speed AFM operation to provide distortion-free images. The presented implementation of this closed-loop approach allows for positioning precision down to 2.1 Å, reduces the integral nonlinearity to below 0.2%, and allows for accurate closed loop imaging at line rates up to 300 Hz.

  9. Insulin pump therapy in youth with type 1 diabetes: toward closed-loop systems.

    PubMed

    Tauschmann, Martin; Hovorka, Roman

    2014-06-01

    Insulin pump technology has advanced considerably over the past three decades, leading to more favorable metabolic control and less hypoglycemic events when compared with multiple daily injection therapy. The use of insulin pumps is increasing, particularly in children and adolescents with type 1 diabetes. This review outlines recent developments in insulin pump therapy from a pediatric perspective. 'Smart' pumps, sensor-augmented pump therapy and threshold-suspend feature of insulin pumps are reviewed in terms of efficacy, safety and psychosocial impact. The current status of closed-loop systems focusing on clinical outcomes is highlighted. Closed-loop insulin delivery is gradually progressing from bench to the clinical practice. Longer and larger studies in home settings are needed to expand on short- to medium-term outpatient evaluations. Predictive low glucose management and overnight closed-loop delivery may be the next applications to be implemented in daily routine. Further challenges include improvements of control algorithms, sensor accuracy, duration of insulin action, integration and size of devices and connectivity and usability. Gradual improvements and increasing sophistication of closed-loop components lie on the path toward unsupervised hands-off fully closed-loop system.

  10. Film cooling air pocket in a closed loop cooled airfoil

    DOEpatents

    Yu, Yufeng Phillip; Itzel, Gary Michael; Osgood, Sarah Jane; Bagepalli, Radhakrishna; Webbon, Waylon Willard; Burdgick, Steven Sebastian

    2002-01-01

    Turbine stator vane segments have radially inner and outer walls with vanes extending between them. The inner and outer walls are compartmentalized and have impingement plates. Steam flowing into the outer wall plenum passes through the impingement plate for impingement cooling of the outer wall upper surface. The spent impingement steam flows into cavities of the vane having inserts for impingement cooling the walls of the vane. The steam passes into the inner wall and through the impingement plate for impingement cooling of the inner wall surface and for return through return cavities having inserts for impingement cooling of the vane surfaces. To provide for air film cooing of select portions of the airfoil outer surface, at least one air pocket is defined on a wall of at least one of the cavities. Each air pocket is substantially closed with respect to the cooling medium in the cavity and cooling air pumped to the air pocket flows through outlet apertures in the wall of the airfoil to cool the same.

  11. Closed-loop fiber-optic gyroscope with a sawtooth phase-modulated feedback.

    PubMed

    Ebberg, A; Schiffner, G

    1985-06-01

    Theoretical and experimental investigations of a closed-loop fiber-optic gyroscope are reported. Phase nulling is accomplished by applying a sawtooth modulation to an integrated-optic phase modulator located at one side of the sensing loop. The frequency of the phase modulation is proportional to the rotation rate, thus permitting a digital readout. The influence of a finite flyback period on the scale factor is investigated.

  12. Double closed-loop cascade control for lower limb exoskeleton with elastic actuation.

    PubMed

    Zhu, Yanhe; Zheng, Tianjiao; Jin, Hongzhe; Yang, Jixing; Zhao, Jie

    2015-01-01

    Unlike traditional rigid actuators, the significant features of Series Elastic Actuator (SEA) are stable torque control, lower output impedance, impact resistance and energy storage. Recently, SEA has been applied in many exoskeletons. In such applications, a key issue is how to realize the human-exoskeleton movement coordination. In this paper, double closed-loop cascade control for lower limb exoskeleton with SEA is proposed. This control method consists of inner SEA torque loop and outer contact force loop. Utilizing the SEA torque control with a motor velocity loop, actuation performances of SEA are analyzed. An integrated exoskeleton control system is designed, in which joint angles are calculated by internal encoders and resolvers and contact forces are gathered by external pressure sensors. The double closed-loop cascade control model is established based on the feedback signals of internal and external sensor. Movement experiments are accomplished in our prototype of lower limb exoskeleton. Preliminary results indicate the exoskeleton movements with pilot can be realized stably by utilizing this double closed-loop cascade control method. Feasibility of the SEA in our exoskeleton robot and effectiveness of the control method are verified.

  13. The MROI fringe tracker: closing the loop on ICoNN

    NASA Astrophysics Data System (ADS)

    McCracken, T. M.; Jurgenson, C. A.; Santoro, F.; Shtromberg, A. V.; Alvidrez, V.; Torres, N.; Dahl, C.; Farris, A.; Buscher, D. F.; Haniff, C. A.; Young, J. S.; Seneta, E. B.; Creech-Eakman, M. J.

    2012-07-01

    The characterization of ICoNN, the Magdalena Ridge Observatory Interferometer's fringe tracker, through labor­ tory simulations is presented. The performance limits of an interferometer are set by its ability to keep the optical path difference between combination partners minimized. This is the job of the fringe tracker. Understanding the behavior and limits of the fringe tracker in a controlled environment is key to maximize the science output. This is being done with laboratory simulations of on-sky fringe tracking, termed the closed-loop fringe experi­ ment. The closed-loop fringe experiment includes synthesizing a white light source and atmospheric piston with estimation of the tracking error being fed back to mock delay lines in real-time. We report here on the progress of the closed-loop fringe experiment detailing its design, layout, controls and software.

  14. A design method for closed loop solar energy systems with concentrating collectors

    NASA Astrophysics Data System (ADS)

    Ryan, W. A.

    1982-01-01

    A method of performance prediction and design for closed loop concentrating solar collector systems is presented, along with a comparison of prediction with results using a compound parabolic concentrating collector. The numerical model is an extension of Collares-Pereira and Rabl (1978) model for concentrating collectors to a closed-loop scenario, using a monthly average utilizability factor and the f-chart technique. The predictions were compared with simulations using the TRNSYS program, considering 1.5, 3.0, and 5.0 concentration factors, and a sensible heat storage system. Performance predictions were found to depart from the simulations by an average of 14.04% for all cases, with the predictions giving consistently lower results. The method is concluded to be useful for optimizing collector areas and concentration ratios in closed-loop systems.

  15. A closed-loop brain computer interface for real-time seizure detection and control.

    PubMed

    Liang, Sheng-Fu; Shaw, Fu-Zen; Young, Chung-Ping; Chang, Da-Wei; Liao, Yi-Cheng

    2010-01-01

    The worldwide prevalence of epilepsy is approximately 1%, and 25% of epilepsy patients cannot be treated sufficiently by available therapies. Brain stimulation with closed-loop seizure control has recently been proposed as an innovative and effective alternative. In this paper, a portable closed-loop brain computer interface for seizure control was developed and shown with several aspects of advantages, including high seizure detection rate (92-99% during wake-sleep states), low false detection rate (1.2-2.5%), and small size. The seizure detection and electrical stimulation latency was not greater than 0.6 s after seizure onset. A wireless communication feature also provided flexibility for subjects freeing from the hassle of wires. Experimental data from freely moving rats supported the functional possibility of a real-time closed-loop seizure controller.

  16. Lidar-based wake tracking for closed-loop wind farm control

    NASA Astrophysics Data System (ADS)

    Raach, Steffen; Schlipf, David; Cheng, Po Wen

    2016-09-01

    This work presents two advancements towards closed-loop wake redirecting of a wind turbine. First, a model-based estimation approach is presented which uses a nacelle-based lidar system facing downwind to obtain information about the wake. A reduced order wake model is described which is then used in the estimation to track the wake. The tracking is demonstrated with lidar measurement data from an offshore campaign and with simulated lidar data from a SOWFA simulation. Second, a controller for closed-loop wake steering is presented. It uses the wake tracking information to set the yaw actuator of the wind turbine to redirect the wake to a desired position. Altogether, this paper aims to present the concept of closed-loop wake redirecting and gives a possible solution to it.

  17. Toward Closing the Loop: An Update on Insulin Pumps and Continuous Glucose Monitoring Systems

    PubMed Central

    Aye, Tandy; Block, Jen; Buckingham, Bruce

    2010-01-01

    Synoposis In this paper we review current pump and continuous glucose monitoring therapy and what will be required to integrate these systems into closed-loop control. Issues with sensor accuracy, lag time and calibration are discussed as well as issues with insulin pharmacodynamics which result in a delayed onset of insulin action in a closed-loop system. A stepwise approach to closed-loop therapy is anticipated where the first systems will suspend insulin delivery based on actual or predicted hypoglycemia. Subsequent systems may “control-to-range” limiting the time spent in hyperglycemia by mitigating the effects of a missed food bolus or underestimate of consumed carbohydrates while minimizing the risk of hypoglycemia. PMID:20723823

  18. Linear state feedback, quadratic weights, and closed loop eigenstructures. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Thompson, P. M.

    1979-01-01

    Results are given on the relationships between closed loop eigenstructures, state feedback gain matrices of the linear state feedback problem, and quadratic weights of the linear quadratic regulator. Equations are derived for the angles of general multivariable root loci and linear quadratic optimal root loci, including angles of departure and approach. The generalized eigenvalue problem is used for the first time to compute angles of approach. Equations are also derived to find the sensitivity of closed loop eigenvalues and the directional derivatives of closed loop eigenvectors (with respect to a scalar multiplying the feedback gain matrix or the quadratic control weight). An equivalence class of quadratic weights that produce the same asymptotic eigenstructure is defined, sufficient conditions to be in it are given, a canonical element is defined, and an algorithm to find it is given. The behavior of the optimal root locus in the nonasymptotic region is shown to be different for quadratic weights with the same asymptotic properties.

  19. A digital wireless system for closed-loop inhibition of nociceptive signals

    NASA Astrophysics Data System (ADS)

    Zuo, Chao; Yang, Xiaofei; Wang, Yang; Hagains, Christopher E.; Li, Ai-Ling; Peng, Yuan B.; Chiao, J.-C.

    2012-10-01

    Neurostimulation of the spinal cord or brain has been used to inhibit nociceptive signals in pain management applications. Nevertheless, most of the current neurostimulation models are based on open-loop system designs. There is a lack of closed-loop systems for neurostimulation in research with small freely-moving animals and in future clinical applications. Based on our previously developed analog wireless system for closed-loop neurostimulation, a digital wireless system with real-time feedback between recorder and stimulator modules has been developed to achieve multi-channel communication. The wireless system includes a wearable recording module, a wearable stimulation module and a transceiver connected to a computer for real-time and off-line data processing, display and storage. To validate our system, wide dynamic range neurons in the spinal cord dorsal horn have been recorded from anesthetized rats in response to graded mechanical stimuli (brush, pressure and pinch) applied in the hind paw. The identified nociceptive signals were used to automatically trigger electrical stimulation at the periaqueductal gray in real time to inhibit their own activities by the closed-loop design. Our digital wireless closed-loop system has provided a simplified and efficient method for further study of pain processing in freely-moving animals and potential clinical application in patients. Groups 1, 2 and 3 contributed equally to this project.

  20. A digital wireless system for closed-loop inhibition of nociceptive signals.

    PubMed

    Zuo, Chao; Yang, Xiaofei; Wang, Yang; Hagains, Christopher E; Li, Ai-Ling; Peng, Yuan B; Chiao, J-C

    2012-10-01

    Neurostimulation of the spinal cord or brain has been used to inhibit nociceptive signals in pain management applications. Nevertheless, most of the current neurostimulation models are based on open-loop system designs. There is a lack of closed-loop systems for neurostimulation in research with small freely-moving animals and in future clinical applications. Based on our previously developed analog wireless system for closed-loop neurostimulation, a digital wireless system with real-time feedback between recorder and stimulator modules has been developed to achieve multi-channel communication. The wireless system includes a wearable recording module, a wearable stimulation module and a transceiver connected to a computer for real-time and off-line data processing, display and storage. To validate our system, wide dynamic range neurons in the spinal cord dorsal horn have been recorded from anesthetized rats in response to graded mechanical stimuli (brush, pressure and pinch) applied in the hind paw. The identified nociceptive signals were used to automatically trigger electrical stimulation at the periaqueductal gray in real time to inhibit their own activities by the closed-loop design. Our digital wireless closed-loop system has provided a simplified and efficient method for further study of pain processing in freely-moving animals and potential clinical application in patients.

  1. Sensory feedback in prosthetics: a standardized test bench for closed-loop control.

    PubMed

    Dosen, Strahinja; Markovic, Marko; Hartmann, Cornelia; Farina, Dario

    2015-03-01

    Closing the control loop by providing sensory feedback to the user of a prosthesis is an important challenge, with major impact on the future of prosthetics. Developing and comparing closed-loop systems is a difficult task, since there are many different methods and technologies that can be used to implement each component of the system. Here, we present a test bench developed in Matlab Simulink for configuring and testing the closed-loop human control system in standardized settings. The framework comprises a set of connected generic blocks with normalized inputs and outputs, which can be customized by selecting specific implementations from a library of predefined components. The framework is modular and extensible and it can be used to configure, compare and test different closed-loop system prototypes, thereby guiding the development towards an optimal system configuration. The use of the test bench was demonstrated by investigating two important aspects of closed-loop control: performance of different electrotactile feedback interfaces (spatial versus intensity coding) during a pendulum stabilization task and feedforward methods (joystick versus myocontrol) for force control. The first experiment demonstrated that in the case of trained subjects the intensity coding might be superior to spatial coding. In the second experiment, the control of force was rather poor even with a stable and precise control interface (joystick), demonstrating that inherent characteristics of the prosthesis can be an important limiting factor when considering the overall effectiveness of the closed-loop control. The presented test bench is an important instrument for investigating different aspects of human manual control with sensory feedback.

  2. Experiences of closed-loop insulin delivery among pregnant women with Type 1 diabetes.

    PubMed

    Farrington, C; Stewart, Z A; Barnard, K; Hovorka, R; Murphy, H R

    2017-06-20

    To explore the experiences of pregnant women with Type 1 diabetes, and the relationships between perceptions of glucose control, attitudes to technology and glycaemic responses with regard to closed-loop insulin delivery. We recruited 16 pregnant women with Type 1 diabetes [mean ± sd age 34.1 ± 4.6 years, duration of diabetes 23.6 ± 7.2 years, baseline HbA1c 51±5 mmol/mol (6.8 ± 0.6%)] to a randomized crossover trial of sensor-augmented pump therapy vs automated closed-loop therapy. Questionnaires (Diabetes Technology Questionnaire, Hypoglycaemia Fear Survey) were completed before and after each intervention, with qualitative interviews at baseline and follow-up. Women described the benefits and burdens of closed-loop systems during pregnancy. Feelings of improved glucose control, excitement and empowerment were counterbalanced by concerns about device visibility, obsessive data checking and diminished attentiveness to hyper- and hypoglycaemia symptoms. Responding to questionnaires, eight participants felt less worry about overnight hypoglycaemia and that diabetes 'did not run their lives'; however, five reported that closed-loop increased time thinking about diabetes, and three felt it made sleep and preventing hyperglycaemia more problematic. Women slightly overestimated their glycaemic response to closed-loop therapy. Most became more positive in their technology attitudes throughout pregnancy. Women with more positive technology attitudes had higher degrees of overestimation, and poorer levels of glycaemic control. Women displayed complex psychosocial responses to closed-loop therapy in pregnancy. Perceptions of glycaemic response may diverge from biomedical data. © 2017 Diabetes UK.

  3. An experimental study of heat transfer around turbine airfoils with closed-loop cooling

    NASA Astrophysics Data System (ADS)

    Yen, Chih-Hung (Erik)

    Closed-Loop cooling has been identified as one of the promising cooling schemes for the next generation gas turbine systems. The closed-loop cooling design collects the spent coolants and directs them to be recovered to do useful work in engine cycle. Due to the requirement of the closed-loop cooling and adoption of innovative cooling methods, the geometric configuration of a closed-loop cooling design is usually complicated. The complexity induces the heat transfer and flow uncertainties and necessitates the detailed heat transfer study for the cooling design. The present research was designed to examine heat transfer of innovative closed-loop cooling designs of an advanced gas turbine system. A heat transfer measurement system employing the Thermochromic Liquid Crystal (TLC) has been developed in order to study detailed heat transfer of the complicated cooling designs. A hybrid technique has been proposed to combine two models: lumped heat capacity model and one-dimension model. The technique has been successfully demonstrated to be a reliable means by studying heat transfer phenomenon on pin fin arrays. Pin fin arrays, sometimes termed pedestals, are widely used in modern gas turbines to provide heat transfer enhancement. In addition, the study on pin fins array revealed effects of heat transfer by two increasingly important, yet not much being explored geometric parameters: shape of pin fin element and gap atop pin fin array. Heat transfer study using the measurement system has revealed detailed heat transfer distribution and eliminated heat transfer uncertainties for five scaled Perplex models of the most crucial designs in the closed-loop cooling system. This study has also demonstrated the improvement in design practice with assistance of the developed system. For a design that relies on the unverified data sets and correlation, the system provides a means to eliminate the uncertainties and provide prompt feedback to designers for modification of the design.

  4. Hardware platforms for MEMS gyroscope tuning based on evolutionary computation using open-loop and closed -loop frequency response

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Ferguson, Michael I.; Fink, Wolfgang; Oks, Boris; Peay, Chris; Terrile, Richard; Cheng, Yen; Kim, Dennis; MacDonald, Eric; Foor, David

    2005-01-01

    We propose a tuning method for MEMS gyroscopes based on evolutionary computation to efficiently increase the sensitivity of MEMS gyroscopes through tuning. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation. We also report on the development of a hardware platform for integrated tuning and closed loop operation of MEMS gyroscopes. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). The hardware platform easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

  5. Phase III integrated water recovery testing at MSFC - Partially closed hygiene loop and open potable loop results and lessons learned

    NASA Technical Reports Server (NTRS)

    Bagdigian, R. M.; Traweek, M. S.; Griffith, G. K.; Griffin, M. R.

    1991-01-01

    A series of tests has been conducted at the NASA Marshall Space Flight Center (MSFC) to evaluate the performance of a predevelopment water recovery system. Potable, hygiene, and urine reclamation subsystems were integrated with end-use equipment items and successfully operated in open and partially closed-loop modes, with man-in-the-loop, for a total of 28 days. Several significant subsystem physical anomalies were encountered during testing. Reclaimed potable and hygiene water generally met the current Space Station Freedom (SSF) water quality specifications for inorganic and microbiological constituents, but exceeded the maximum allowable concentrations for Total Organic Carbon (TOC). This paper summarizes the test objectives, system design, test activities/protocols, significant results/anomalies, and major lessons learned.

  6. Hardware platforms for MEMS gyroscope tuning based on evolutionary computation using open-loop and closed -loop frequency response

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Ferguson, Michael I.; Fink, Wolfgang; Oks, Boris; Peay, Chris; Terrile, Richard; Cheng, Yen; Kim, Dennis; MacDonald, Eric; Foor, David

    2005-01-01

    We propose a tuning method for MEMS gyroscopes based on evolutionary computation to efficiently increase the sensitivity of MEMS gyroscopes through tuning. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation. We also report on the development of a hardware platform for integrated tuning and closed loop operation of MEMS gyroscopes. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). The hardware platform easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

  7. Simulation of open-loop plasma vertical movement response in the Damavand tokamak using closed-loop subspace system identification

    NASA Astrophysics Data System (ADS)

    Darestani Farahani, N.; Abbasi Davani, F.

    2016-02-01

    The formulation of a multi-input single-output closed-loop subspace method for system identification has been employed for the purpose of obtaining control-relevant model of the open loop response for plasma vertical movement in the Damavand tokamak. Such a model is particularly well suited for the robust controller design. The method described in this paper is a kind of worst-case identification technique, aiming to minimize the error between the identified model and the true plant. The accuracy of the estimation of the plant dynamics has been tested by different experiments. The fitness of the identified model around the defined operating point has been more than 90%, and compared to the physical-based model, it has better root mean squared error (RMSE) measure of the goodness of fitting.

  8. Disk oxygen generator with closed flow loop for long-term COIL operation

    NASA Astrophysics Data System (ADS)

    Schreiber, Christian J. M.; Gruenewald, Karin; Handke, Juergen; Duschek, Frank; Schall, Wolfgang O.

    2003-11-01

    A test facility was designed to operate a disk type singlet delta oxygen generator in a closed loop for the flow of basic hydrogen peroxide (BHP). The facility allows the investigations of the influence of operating conditions like BHP flow, gas flow, disk rotation speed, and system components like disk package parameters and type of liquid separator on the generator performance and the ascertainment of the facilities capability for long term COIL operation. The dimension of the generator in the closed flow loop is chosen in accordance with the 10 kW-DLR-COIL.

  9. CFD and experimental data of closed-loop wind tunnel flow.

    PubMed

    Calautit, John Kaiser; Hughes, Ben Richard

    2016-06-01

    The data presented in this article were the basis for the study reported in the research articles entitled 'A validated design methodology for a closed loop subsonic wind tunnel' (Calautit et al., 2014) [1], which presented a systematic investigation into the design, simulation and analysis of flow parameters in a wind tunnel using Computational Fluid Dynamics (CFD). The authors evaluated the accuracy of replicating the flow characteristics for which the wind tunnel was designed using numerical simulation. Here, we detail the numerical and experimental set-up for the analysis of the closed-loop subsonic wind tunnel with an empty test section.

  10. A novel Cs-(129)Xe atomic spin gyroscope with closed-loop Faraday modulation.

    PubMed

    Fang, Jiancheng; Wan, Shuangai; Qin, Jie; Zhang, Chen; Quan, Wei; Yuan, Heng; Dong, Haifeng

    2013-08-01

    We report a novel Cs-(129)Xe atomic spin gyroscope (ASG) with closed-loop Faraday modulation method. This ASG requires approximately 30 min to start-up and 110 °C to operate. A closed-loop Faraday modulation method for measurement of the optical rotation was used in this ASG. This method uses an additional Faraday modulator to suppress the laser intensity fluctuation and Faraday modulator thermal induced fluctuation. We theoretically and experimentally validate this method in the Cs-(129)Xe ASG and achieved a bias stability of approximately 3.25 °∕h.

  11. Towards closed-loop neuromodulation: a wireless miniaturized neural implant SoC

    NASA Astrophysics Data System (ADS)

    Liu, Wentai; Wang, Po-Min; Lo, Yi-Kai

    2017-05-01

    This work reports a platform technology toward the development of closed-loop neuromodulation. A neural implant based on the SoC developed in our laboratory is used as an example to illustrate the necessary functionalities for the efficacious implantable system. We also present an example of using the system to investigate the epidural stimulation for partial motor function recovery after spinal cord injury in a rat model. This hardware-software co-design tool demonstrate its promising potential towards an effective closed-loop neuromodulation for various biomedical applications.

  12. Deployable space manipulator closed-loop control, ideas and possibilities of using GPS as a sensor

    NASA Astrophysics Data System (ADS)

    Romero, I.; Vignjevic, R.

    2002-07-01

    In the area of study of the dynamics and control of large flexible spacecraft one of the most challenging areas is that of large space-based robotic manipulators. The Deployable Space Manipulator is a large manipulator concept for Low Earth Orbit operation with one rotational joint and one prismatic joint. In this paper the dynamics of the manipulator undergoing large rotational motion while carrying a payload and extending its length are developed and the need for closed loop control is discussed. An output feedback closed loop control approach is presented and a concept for using GPS antennas mounted on the structure as feedback sensor for the control law is presented and discussed.

  13. Closed-Loop Basal Insulin Delivery Over 36 Hours in Adolescents With Type 1 Diabetes

    PubMed Central

    Elleri, Daniela; Allen, Janet M.; Kumareswaran, Kavita; Leelarathna, Lalantha; Nodale, Marianna; Caldwell, Karen; Cheng, Peiyao; Kollman, Craig; Haidar, Ahmad; Murphy, Helen R.; Wilinska, Malgorzata E.; Acerini, Carlo L.; Dunger, David B.; Hovorka, Roman

    2013-01-01

    OBJECTIVE We evaluated the safety and efficacy of closed-loop basal insulin delivery during sleep and after regular meals and unannounced periods of exercise. RESEARCH DESIGN AND METHODS Twelve adolescents with type 1 diabetes (five males; mean age 15.0 [SD 1.4] years; HbA1c 7.9 [0.7]%; BMI 21.4 [2.6] kg/m2) were studied at a clinical research facility on two occasions and received, in random order, either closed-loop basal insulin delivery or conventional pump therapy for 36 h. During closed-loop insulin delivery, pump basal rates were adjusted every 15 min according to a model predictive control algorithm informed by subcutaneous sensor glucose levels. During control visits, subjects’ standard infusion rates were applied. Prandial insulin boluses were given before main meals (50–80 g carbohydrates) but not before snacks (15–30 g carbohydrates). Subjects undertook moderate-intensity exercise, not announced to the algorithm, on a stationary bicycle at a 140 bpm heart rate in the morning (40 min) and afternoon (20 min). Primary outcome was time when plasma glucose was in the target range (71–180 mg/dL). RESULTS Closed-loop basal insulin delivery increased percentage time when glucose was in the target range (median 84% [interquartile range 78–88%] vs. 49% [26–79%], P = 0.02) and reduced mean plasma glucose levels (128 [19] vs. 165 [55] mg/dL, P = 0.02). Plasma glucose levels were in the target range 100% of the time on 17 of 24 nights during closed-loop insulin delivery. Hypoglycemia occurred on 10 occasions during control visits and 9 occasions during closed-loop delivery (5 episodes were exercise related, and 4 occurred within 2.5 h of prandial bolus). CONCLUSIONS Day-and-night closed-loop basal insulin delivery can improve glucose control in adolescents. However, unannounced moderate-intensity exercise and excessive prandial boluses pose challenges to hypoglycemia-free closed-loop basal insulin delivery. PMID:23193217

  14. Closed loop models for analyzing the effects of simulator characteristics. [digital simulation of human operators

    NASA Technical Reports Server (NTRS)

    Baron, S.; Muralidharan, R.; Kleinman, D. L.

    1978-01-01

    The optimal control model of the human operator is used to develop closed loop models for analyzing the effects of (digital) simulator characteristics on predicted performance and/or workload. Two approaches are considered: the first utilizes a continuous approximation to the discrete simulation in conjunction with the standard optimal control model; the second involves a more exact discrete description of the simulator in a closed loop multirate simulation in which the optimal control model simulates the pilot. Both models predict that simulator characteristics can have significant effects on performance and workload.

  15. CFD and experimental data of closed-loop wind tunnel flow

    PubMed Central

    Calautit, John Kaiser; Hughes, Ben Richard

    2016-01-01

    The data presented in this article were the basis for the study reported in the research articles entitled ‘A validated design methodology for a closed loop subsonic wind tunnel’ (Calautit et al., 2014) [1], which presented a systematic investigation into the design, simulation and analysis of flow parameters in a wind tunnel using Computational Fluid Dynamics (CFD). The authors evaluated the accuracy of replicating the flow characteristics for which the wind tunnel was designed using numerical simulation. Here, we detail the numerical and experimental set-up for the analysis of the closed-loop subsonic wind tunnel with an empty test section. PMID:26958641

  16. A closed-loop dual-modulation multi-spectral polarimeter for glucose monitoring

    NASA Astrophysics Data System (ADS)

    Yu, Zhen fang; Pirnstill, Casey W.; Coté, Gerard L.

    2016-03-01

    Optical polarimetry is a promising noninvasive means of assessing glucose concentration in the aqueous humor of the eye. One the major limiting factors is time-varying cornea birefringence due to motion artifact, which prevents the realization of this device. In this study, we simultaneously utilize laser intensity modulation and Faraday polarization rotation modulation for a real-time closed-loop multi-spectral polarimeter for glucose monitoring in vitro. In this report, a real-time closed-loop dual-modulation dual-spectral polarimeter was presented and in vitro glucose measurements were performed demonstrating the accuracy and repeatability of this polarimeter.

  17. First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

    NASA Technical Reports Server (NTRS)

    Gill, E.; Naasz, Bo; Ebinuma, T.

    2003-01-01

    A closed-loop system for the demonstration of formation flying technologies has been developed at NASA s Goddard Space Flight Center. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. A sample scenario has been set up where the autonomous transition of a satellite formation from an initial along-track separation of 800 m to a final distance of 100 m has been demonstrated. As a result, a typical control accuracy of about 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

  18. Pulsatile desynchronizing delayed feedback for closed-loop deep brain stimulation

    PubMed Central

    Lysyansky, Borys; Rosenblum, Michael; Pikovsky, Arkady; Tass, Peter A.

    2017-01-01

    High-frequency (HF) deep brain stimulation (DBS) is the gold standard for the treatment of medically refractory movement disorders like Parkinson’s disease, essential tremor, and dystonia, with a significant potential for application to other neurological diseases. The standard setup of HF DBS utilizes an open-loop stimulation protocol, where a permanent HF electrical pulse train is administered to the brain target areas irrespectively of the ongoing neuronal dynamics. Recent experimental and clinical studies demonstrate that a closed-loop, adaptive DBS might be superior to the open-loop setup. We here combine the notion of the adaptive high-frequency stimulation approach, that aims at delivering stimulation adapted to the extent of appropriately detected biomarkers, with specifically desynchronizing stimulation protocols. To this end, we extend the delayed feedback stimulation methods, which are intrinsically closed-loop techniques and specifically designed to desynchronize abnormal neuronal synchronization, to pulsatile electrical brain stimulation. We show that permanent pulsatile high-frequency stimulation subjected to an amplitude modulation by linear or nonlinear delayed feedback methods can effectively and robustly desynchronize a STN-GPe network of model neurons and suggest this approach for desynchronizing closed-loop DBS. PMID:28273176

  19. A Method for Precision Closed-Loop Irrigation Using a Modified PID Control Algorithm

    NASA Astrophysics Data System (ADS)

    Goodchild, Martin; Kühn, Karl; Jenkins, Malcolm; Burek, Kazimierz; Dutton, Andrew

    2016-04-01

    The benefits of closed-loop irrigation control have been demonstrated in grower trials which show the potential for improved crop yields and resource usage. Managing water use by controlling irrigation in response to soil moisture changes to meet crop water demands is a popular approach but requires knowledge of closed-loop control practice. In theory, to obtain precise closed-loop control of a system it is necessary to characterise every component in the control loop to derive the appropriate controller parameters, i.e. proportional, integral & derivative (PID) parameters in a classic PID controller. In practice this is often difficult to achieve. Empirical methods are employed to estimate the PID parameters by observing how the system performs under open-loop conditions. In this paper we present a modified PID controller, with a constrained integral function, that delivers excellent regulation of soil moisture by supplying the appropriate amount of water to meet the needs of the plant during the diurnal cycle. Furthermore, the modified PID controller responds quickly to changes in environmental conditions, including rainfall events which can result in: controller windup, under-watering and plant stress conditions. The experimental work successfully demonstrates the functionality of a constrained integral PID controller that delivers robust and precise irrigation control. Coir substrate strawberry growing trial data is also presented illustrating soil moisture control and the ability to match water deliver to solar radiation.

  20. Close-loop simulation of the medial olivocochlear anti-masking effects

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Wen; Yu, Lu-Ming; Wu, Po-Jui

    2015-12-01

    The medial olivocochlear reflex (MOCR) is known to affect cochlear signal processing via the electromechanical changes it induces in outer hair cells (OHCs). Experiments showed that electrically stimulating the MOC efferents (i.e., open-loop stimulation) suppresses cochlear responses to acoustic noise while enhancing the response to tone bursts if the signal-to-noise ratio is sufficiently high [5]. However, such experiments did not reveal precisely how MOCR affects cochlear signal processing in a close loop. Presently we have built an integrated computer model for the MOCR pathway; the constituting sub-models include a model for cochlear mechanics with electromotile OHCs [11], a neurotransmitter release model for the synapse between inner hair cells (IHCs) and spiral ganglion cells [16], an electrical model for the T-multipolar (TM) cells in the cochlear nucleus [6], a relay from TM cells to the MOC interneurons, and a convolution kernel describing the change of OHC potassium conductance triggered by the MOC inhibitory post synaptic potentials. Thus, close-loop responses of the entire system can be simulated for arbitrary acoustic stimuli. Both open-loop and close-loop simulations demonstrate a decrease in the auditory nerve fiber (ANF) response to noise but an increase in the response to high-level tone bursts. The present integrated computer model can potentially be used for testing hypotheses regarding the physiological mechanisms for MOC anti-masking effects.

  1. The AOCS publications: a 100 year history

    USDA-ARS?s Scientific Manuscript database

    The growth of societies and its associated publications is an indicator of how chemistry, a society such as AOCS, and the fats and oils industry have grown over time. During the late 18th century a shift from monographs to chemical periodicals occurred. Since then journals have been the preferred ...

  2. Model-Driven Safety Analysis of Closed-Loop Medical Systems.

    PubMed

    Pajic, Miroslav; Mangharam, Rahul; Sokolsky, Oleg; Arney, David; Goldman, Julian; Lee, Insup

    2012-10-26

    In modern hospitals, patients are treated using a wide array of medical devices that are increasingly interacting with each other over the network, thus offering a perfect example of a cyber-physical system. We study the safety of a medical device system for the physiologic closed-loop control of drug infusion. The main contribution of the paper is the verification approach for the safety properties of closed-loop medical device systems. We demonstrate, using a case study, that the approach can be applied to a system of clinical importance. Our method combines simulation-based analysis of a detailed model of the system that contains continuous patient dynamics with model checking of a more abstract timed automata model. We show that the relationship between the two models preserves the crucial aspect of the timing behavior that ensures the conservativeness of the safety analysis. We also describe system design that can provide open-loop safety under network failure.

  3. Model-Driven Safety Analysis of Closed-Loop Medical Systems

    PubMed Central

    Pajic, Miroslav; Mangharam, Rahul; Sokolsky, Oleg; Arney, David; Goldman, Julian; Lee, Insup

    2013-01-01

    In modern hospitals, patients are treated using a wide array of medical devices that are increasingly interacting with each other over the network, thus offering a perfect example of a cyber-physical system. We study the safety of a medical device system for the physiologic closed-loop control of drug infusion. The main contribution of the paper is the verification approach for the safety properties of closed-loop medical device systems. We demonstrate, using a case study, that the approach can be applied to a system of clinical importance. Our method combines simulation-based analysis of a detailed model of the system that contains continuous patient dynamics with model checking of a more abstract timed automata model. We show that the relationship between the two models preserves the crucial aspect of the timing behavior that ensures the conservativeness of the safety analysis. We also describe system design that can provide open-loop safety under network failure. PMID:24177176

  4. A Review of Control Strategies in Closed-Loop Neuroprosthetic Systems

    PubMed Central

    Wright, James; Macefield, Vaughan G.; van Schaik, André; Tapson, Jonathan C.

    2016-01-01

    It has been widely recognized that closed-loop neuroprosthetic systems achieve more favorable outcomes for users then equivalent open-loop devices. Improved performance of tasks, better usability, and greater embodiment have all been reported in systems utilizing some form of feedback. However, the interdisciplinary work on neuroprosthetic systems can lead to miscommunication due to similarities in well-established nomenclature in different fields. Here we present a review of control strategies in existing experimental, investigational and clinical neuroprosthetic systems in order to establish a baseline and promote a common understanding of different feedback modes and closed-loop controllers. The first section provides a brief discussion of feedback control and control theory. The second section reviews the control strategies of recent Brain Machine Interfaces, neuromodulatory implants, neuroprosthetic systems, and assistive neurorobotic devices. The final section examines the different approaches to feedback in current neuroprosthetic and neurorobotic systems. PMID:27462202

  5. Design and simulation of a sensor for heliostat field closed loop control

    NASA Astrophysics Data System (ADS)

    Collins, Mike; Potter, Daniel; Burton, Alex

    2017-06-01

    Significant research has been completed in pursuit of capital cost reductions for heliostats [1],[2]. The camera array closed loop control concept has potential to radically alter the way heliostats are controlled and installed by replacing high quality open loop targeting systems with low quality targeting devices that rely on measurement of image position to remove tracking errors during operation. Although the system could be used for any heliostat size, the system significantly benefits small heliostats by reducing actuation costs, enabling large numbers of heliostats to be calibrated simultaneously, and enabling calibration of heliostats that produce low irradiance (similar or less than ambient light images) on Lambertian calibration targets, such as small heliostats that are far from the tower. A simulation method for the camera array has been designed and verified experimentally. The simulation tool demonstrates that closed loop calibration or control is possible using this device.

  6. A component-level failure detection and identification algorithm based on open-loop and closed-loop state estimators

    NASA Astrophysics Data System (ADS)

    You, Seung-Han; Cho, Young Man; Hahn, Jin-Oh

    2013-04-01

    This study presents a component-level failure detection and identification (FDI) algorithm for a cascade mechanical system subsuming a plant driven by an actuator unit. The novelty of the FDI algorithm presented in this study is that it is able to discriminate failure occurring in the actuator unit, the sensor measuring the output of the actuator unit, and the plant driven by the actuator unit. The proposed FDI algorithm exploits the measurement of the actuator unit output together with its estimates generated by open-loop (OL) and closed-loop (CL) estimators to enable FDI at the component's level. In this study, the OL estimator is designed based on the system identification of the actuator unit. The CL estimator, which is guaranteed to be stable against variations in the plant, is synthesized based on the dynamics of the entire cascade system. The viability of the proposed algorithm is demonstrated using a hardware-in-the-loop simulation (HILS), which shows that it can detect and identify target failures reliably in the presence of plant uncertainties.

  7. Closed-loop response properties of a visual interneuron involved in fly optomotor control.

    PubMed

    Ejaz, Naveed; Krapp, Holger G; Tanaka, Reiko J

    2013-01-01

    Due to methodological limitations neural function is mostly studied under open-loop conditions. Normally, however, nervous systems operate in closed-loop where sensory input is processed to generate behavioral outputs, which again change the sensory input. Here, we investigate the closed-loop responses of an identified visual interneuron, the blowfly H1-cell, that is part of a neural circuit involved in optomotor flight and gaze control. Those behaviors may be triggered by attitude changes during flight in turbulent air. The fly analyses the resulting retinal image shifts and performs compensatory body and head rotations to regain its default attitude. We developed a fly robot interface to study H1-cell responses in a 1 degree-of-freedom image stabilization task. Image shifts, induced by externally forced rotations, modulate the cell's spike rate that controls counter rotations of a mobile robot to minimize relative motion between the robot and its visual surroundings. A feedback controller closed the loop between neural activity and the rotation of the robot. Under these conditions we found the following H1-cell response properties: (i) the peak spike rate decreases when the mean image velocity is increased, (ii) the relationship between spike rate and image velocity depends on the standard deviation of the image velocities suggesting adaptive scaling of the cell's signaling range, and (iii) the cell's gain decreases linearly with increasing image accelerations. Our results reveal a remarkable qualitative similarity between the response dynamics of the H1-cell under closed-loop conditions with those obtained in previous open-loop experiments. Finally, we show that the adaptive scaling of the H1-cell's responses, while maximizing information on image velocity, decreases the cell's sensitivity to image accelerations. Understanding such trade-offs in biological vision systems may advance the design of smart vision sensors for autonomous robots.

  8. Feasibility of outpatient fully integrated closed-loop control: first studies of wearable artificial pancreas.

    PubMed

    Kovatchev, Boris P; Renard, Eric; Cobelli, Claudio; Zisser, Howard C; Keith-Hynes, Patrick; Anderson, Stacey M; Brown, Sue A; Chernavvsky, Daniel R; Breton, Marc D; Farret, Anne; Pelletier, Marie-Josée; Place, Jérôme; Bruttomesso, Daniela; Del Favero, Simone; Visentin, Roberto; Filippi, Alessio; Scotton, Rachele; Avogaro, Angelo; Doyle, Francis J

    2013-07-01

    To evaluate the feasibility of a wearable artificial pancreas system, the Diabetes Assistant (DiAs), which uses a smart phone as a closed-loop control platform. Twenty patients with type 1 diabetes were enrolled at the Universities of Padova, Montpellier, and Virginia and at Sansum Diabetes Research Institute. Each trial continued for 42 h. The United States studies were conducted entirely in outpatient setting (e.g., hotel or guest house); studies in Italy and France were hybrid hospital-hotel admissions. A continuous glucose monitoring/pump system (Dexcom Seven Plus/Omnipod) was placed on the subject and was connected to DiAs. The patient operated the system via the DiAs user interface in open-loop mode (first 14 h of study), switching to closed-loop for the remaining 28 h. Study personnel monitored remotely via 3G or WiFi connection to DiAs and were available on site for assistance. The total duration of proper system communication functioning was 807.5 h (274 h in open-loop and 533.5 h in closed-loop), which represented 97.7% of the total possible time from admission to discharge. This exceeded the predetermined primary end point of 80% system functionality. This study demonstrated that a contemporary smart phone is capable of running outpatient closed-loop control and introduced a prototype system (DiAs) for further investigation. Following this proof of concept, future steps should include equipping insulin pumps and sensors with wireless capabilities, as well as studies focusing on control efficacy and patient-oriented clinical outcomes.

  9. Closed-loop response properties of a visual interneuron involved in fly optomotor control

    PubMed Central

    Ejaz, Naveed; Krapp, Holger G.; Tanaka, Reiko J.

    2013-01-01

    Due to methodological limitations neural function is mostly studied under open-loop conditions. Normally, however, nervous systems operate in closed-loop where sensory input is processed to generate behavioral outputs, which again change the sensory input. Here, we investigate the closed-loop responses of an identified visual interneuron, the blowfly H1-cell, that is part of a neural circuit involved in optomotor flight and gaze control. Those behaviors may be triggered by attitude changes during flight in turbulent air. The fly analyses the resulting retinal image shifts and performs compensatory body and head rotations to regain its default attitude. We developed a fly robot interface to study H1-cell responses in a 1 degree-of-freedom image stabilization task. Image shifts, induced by externally forced rotations, modulate the cell’s spike rate that controls counter rotations of a mobile robot to minimize relative motion between the robot and its visual surroundings. A feedback controller closed the loop between neural activity and the rotation of the robot. Under these conditions we found the following H1-cell response properties: (i) the peak spike rate decreases when the mean image velocity is increased, (ii) the relationship between spike rate and image velocity depends on the standard deviation of the image velocities suggesting adaptive scaling of the cell’s signaling range, and (iii) the cell’s gain decreases linearly with increasing image accelerations. Our results reveal a remarkable qualitative similarity between the response dynamics of the H1-cell under closed-loop conditions with those obtained in previous open-loop experiments. Finally, we show that the adaptive scaling of the H1-cell’s responses, while maximizing information on image velocity, decreases the cell’s sensitivity to image accelerations. Understanding such trade-offs in biological vision systems may advance the design of smart vision sensors for autonomous robots. PMID

  10. Assurance of Learning and the MFT: Closing the Loops with an Online Review

    ERIC Educational Resources Information Center

    Middleton, Karen L.; Loveland, Karen A.

    2014-01-01

    The authors describe the four stages of the closing the loop process undertaken by a college of business (COB) over a 6-year period. The COB developed and offered an online, noncredit review course to help students prepare for the Major Field Test in Business (MFT). Early results demonstrated the efficacy of the course as student scores rose from…

  11. Closed loop operation eliminates need for auxiliary gas in high pressure pumping station

    NASA Technical Reports Server (NTRS)

    Landy, D. G.

    1966-01-01

    Closed loop system for a liquid nitrogen high pressure pump feeds back gaseous nitrogen generated by heat leak into the reservoir to maintain the pressure in the storage tank. This safer, more efficient system eliminates the need for auxiliary gas to maintain the tank pressure and can be used on relatively high cryogenic pumping systems.

  12. Assurance of Learning and the MFT: Closing the Loops with an Online Review

    ERIC Educational Resources Information Center

    Middleton, Karen L.; Loveland, Karen A.

    2014-01-01

    The authors describe the four stages of the closing the loop process undertaken by a college of business (COB) over a 6-year period. The COB developed and offered an online, noncredit review course to help students prepare for the Major Field Test in Business (MFT). Early results demonstrated the efficacy of the course as student scores rose from…

  13. Closing the Loop: Engaging Community College Faculty and Staff Leaders through Professional Development

    ERIC Educational Resources Information Center

    Gambino, Laura M.

    2013-01-01

    In higher education, and in community colleges in particular, there is a need to engage faculty and staff in closing the loop--using evidence for assessment, planning, and decision-making. Connect to Learning, a Fund for the Improvement of Post-Secondary Education (FIPSE) funded grant project brings together 26 colleges and universities to work as…

  14. Challenges and Recent Progress in the Development of a Closed-loop Artificial Pancreas

    PubMed Central

    Bequette, B. Wayne

    2012-01-01

    Pursuit of a closed-loop artificial pancreas that automatically controls the blood glucose of individuals with type 1 diabetes has intensified during the past six years. Here we discuss the recent progress and challenges in the major steps towards a closed-loop system. Continuous insulin infusion pumps have been widely available for over two decades, but “smart pump” technology has made the devices easier to use and more powerful. Continuous glucose monitoring (CGM) technology has improved and the devices are more widely available. A number of approaches are currently under study for fully closed-loop systems; most manipulate only insulin, while others manipulate insulin and glucagon. Algorithms include on-off (for prevention of overnight hypoglycemia), proportional-integral-derivative (PID), model predictive control (MPC) and fuzzy logic based learning control. Meals cause a major “disturbance” to blood glucose, and we discuss techniques that our group has developed to predict when a meal is likely to be consumed and its effect. We further examine both physiology and device-related challenges, including insulin infusion set failure and sensor signal attenuation. Finally, we discuss the next steps required to make a closed-loop artificial pancreas a commercial reality. PMID:23175620

  15. Closing the Loop: Engaging Community College Faculty and Staff Leaders through Professional Development

    ERIC Educational Resources Information Center

    Gambino, Laura M.

    2013-01-01

    In higher education, and in community colleges in particular, there is a need to engage faculty and staff in closing the loop--using evidence for assessment, planning, and decision-making. Connect to Learning, a Fund for the Improvement of Post-Secondary Education (FIPSE) funded grant project brings together 26 colleges and universities to work as…

  16. Flight Engineer Donald R. Pettit looks closely at Sodium Chloride within a 50-millimeter metal loop

    NASA Image and Video Library

    2003-03-12

    ISS006-E-39142 (12 March 2003) --- Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, looks closely at a water bubble within a 50-millimeter metal loop. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

  17. AACSB Learning Goals: One-Minute Guest Speakers Help to "Close-the-Loop"

    ERIC Educational Resources Information Center

    Ryker, Randy

    2011-01-01

    A key activity in any assurance of learning process is to identify learning deficiencies and then to develop and implement tools and strategies to correct the deficiencies. The activity is often referred to as "closing-the-loop." This paper describes a process whereby the College of Business's Board of Advisors is engaged in a series of…

  18. Maximized Gust Loads of a Closed-Loop, Nonlinear Aeroelastic System Using Nonlinear Systems Theory

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.

    1999-01-01

    The problem of computing the maximized gust load for a nonlinear, closed-loop aeroelastic aircraft is discusses. The Volterra theory of nonlinear systems is applied in order to define a linearized system that provides a bounds on the response of the nonlinear system of interest. The method is applied to a simplified model of an Airbus A310.

  19. Closing the loop in legged neuromechanics: an open-source computer vision controlled treadmill.

    PubMed

    Spence, Andrew J; Nicholson-Thomas, Georgia; Lampe, Rachel

    2013-05-15

    The neural circuitry that controls legged locomotion is exquisitely state dependent. The response to a perturbation at one phase of the locomotor cycle is very different from another. As such, tools that enable closed loop experiments in which freely moving animals can be precisely perturbed, either neurally or mechanically, will improve our ability to probe the locomotor control architecture. Because locomotion emerges from the coupled interaction of the nervous system, musculoskeletal system, and physics of the moving body, ideally an experimenter could simultaneously perturb the nervous system, mechanics of the moving animal, or both, at precise moments during well defined locomotor behaviour. Combining the new technique of optogenetics with closed loop tracking of state and fast mechanical perturbations would make this possible. Here we present a computer vision feedback controlled treadmill designed to enable such perturbations. We show that insects (cockroaches Blaberus discoidalis) and mice (Mus mus; C57BL/6) run freely, with preferred speeds in agreement with the literature, over many strides, on the system. We demonstrate the utility of the closed loop system by automatically gathering high speed video (HSV) data when the running animal meets specific operational criteria; here, running within a restricted range of speeds near the midline of the treadmill for a minimum of 2s. We quantify the mouse's gait from HSV data with a phase-based approach, confirming a normal trotting gait. These results demonstrate the system's potential for dissecting the neuromechanical basis of legged locomotion through closed-loop experimental design.

  20. Evaluation of closed-loop site-specific irrigation with wireless sensor network

    USDA-ARS?s Scientific Manuscript database

    Automated site-specific sprinkler irrigation system can save water and maximize productivity, but implementing automated irrigation is challenging in system integration and decision making. A controllable irrigation system was integrated into a closed-loop control with a distributed wireless in-fiel...

  1. Hippocampal Closed-Loop Modeling and Implications for Seizure Stimulation Design

    PubMed Central

    Sandler, Roman A.; Song, Dong; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.; Marmarelis, Vasilis Z.

    2016-01-01

    Objective Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the Entorhinal Cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. Approach Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3→CA1, via the Schaffer-Collateral synapse, and CA1→CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (Principal Dynamic Modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. Main Results Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. Significance DBS is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy. PMID:26355815

  2. A closed-loop controller for mechanical ventilation of patients with ARDS.

    PubMed

    Anderson, Jeffrey R; East, Thomas D

    2002-01-01

    Mechanical ventilators are routinely used to care for patients who cannot adequately breath on their own. Management of mechanical ventilation often involves a careful watch of the patient's arterial blood-oxygen tension and requires frequent adjustment of ventilation parameters to optimize the therapy. This situation lends itself as a candidate for closed-loop control. This report describes a closed-loop control system based on well-established protocols to systematically maintain appropriate levels of positive end-expiratory pressure (PEEP) and inspired oxygen (FiO2) in patients with Adult Respiratory Distress Syndrome (ARDS). The closed-loop control system consists of an in-dwelling arterial oxygenation (PaO2) sensor (Pfizer Continucath), coupled to a Macintosh computer that continuously controls FiO2 and PEEP settings on a Hamilton Amadeus ventilator. The implemented protocols provide continuous closed-loop control of oxygenation and a balance between patient need and minimal therapy. The controller is based on a traditional proportional-integral-derivative (PID) approach. The idea is to control, or maintain, the patient's PaO2 level at a target value determined, or set, by the patient's physician. The controller also features non-linear and adaptive characteristics that allow the system to respond more aggressively to "threatening" levels of PaO2. Another benefit of the control system is the ability to display, monitor, record and store all system parameters, settings, and control variables for future analysis and study. The system was extensively tested in the laboratory and in animal trials prior to use on human subjects. The results of a small clinical trial indicated that the system maintained control of the patient's therapy nearly 84% of the time. During the remainder of this time, the controller was interrupted primarily for suctioning, PaO2 sensor calibration or replacement. The response of the closed-loop controller was found to be appropriate

  3. Hippocampal closed-loop modeling and implications for seizure stimulation design.

    PubMed

    Sandler, Roman A; Song, Dong; Hampson, Robert E; Deadwyler, Sam A; Berger, Theodore W; Marmarelis, Vasilis Z

    2015-10-01

    Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.

  4. An enriched simulation environment for evaluation of closed-loop anesthesia.

    PubMed

    Fang, Mengqi; Tao, Yuan; Wang, Youqing

    2014-02-01

    To simulate and evaluate the administration of anesthetic agents in the clinical setting, many pharmacology models have been proposed and validated, which play important roles for in silico testing of closed-loop control methods. However, to the authors' best knowledge, there is no anesthesia simulator incorporating closed-loop feedback control of anesthetic agent administration freely available and accessible to the public. Consequently, many necessary but time consuming procedures, such as selecting models from the available literatures and establishing new simulator algorithms, will be repeated by different researchers who intend to explore a novel control algorithm for closed-loop anesthesia. To address this issue, an enriched anesthesia simulator was devised in our laboratory and made freely available to the anesthesia community. This simulator was built by using MATLAB(®) (The MathWorks, Natick, MA). The GUI technology embedded in MATLAB was chosen as the tool to develop a human-machine interface. This simulator includes four types of anesthetic models, and all have been wildly used in closed-loop anesthesia studies. For each type of model, 24 virtual patients were created with significant diversity. In addition, the platform also provides a model identification module and a control method library. For the model identification module, the least square method and particle swarm optimization were presented. In the control method library, a proportional-integral-derivative control and a model predictive control were provided. Both the model identification module and the control method library are extensive and readily accessible for users to add user-defined functions. This simulator could be a benchmark-testing platform for closed-loop control of anesthesia, which is of great value and has significant development potential. For convenience, this simulator is termed as Wang's Simulator, which can be downloaded from http://www.AutomMed.org .

  5. Applying Computer Models to Realize Closed-Loop Neonatal Oxygen Therapy.

    PubMed

    Morozoff, Edmund; Smyth, John A; Saif, Mehrdad

    2017-01-01

    Within the context of automating neonatal oxygen therapy, this article describes the transformation of an idea verified by a computer model into a device actuated by a computer model. Computer modeling of an entire neonatal oxygen therapy system can facilitate the development of closed-loop control algorithms by providing a verification platform and speeding up algorithm development. In this article, we present a method of mathematically modeling the system's components: the oxygen transport within the patient, the oxygen blender, the controller, and the pulse oximeter. Furthermore, within the constraints of engineering a product, an idealized model of the neonatal oxygen transport component may be integrated effectively into the control algorithm of a device, referred to as the adaptive model. Manual and closed-loop oxygen therapy performance were defined in this article by 3 criteria in the following order of importance: percent duration of SpO2 spent in normoxemia (target SpO2 ± 2.5%), hypoxemia (less than normoxemia), and hyperoxemia (more than normoxemia); number of 60-second periods <85% SpO2 and >95% SpO2; and number of manual adjustments. Results from a clinical evaluation that compared the performance of 3 closed-loop control algorithms (state machine, proportional-integral-differential, and adaptive model) with manual oxygen therapy on 7 low-birth-weight ventilated preterm babies, are presented. Compared with manual therapy, all closed-loop control algorithms significantly increased the patients' duration in normoxemia and reduced hyperoxemia (P < 0.05). The number of manual adjustments was also significantly reduced by all of the closed-loop control algorithms (P < 0.05). Although the performance of the 3 control algorithms was equivalent, it is suggested that the adaptive model, with its ease of use, may have the best utility.

  6. Hippocampal closed-loop modeling and implications for seizure stimulation design

    NASA Astrophysics Data System (ADS)

    Sandler, Roman A.; Song, Dong; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.; Marmarelis, Vasilis Z.

    2015-10-01

    Objective. Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. Approach. Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. Main results. Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. Significance. Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.

  7. Robust closed-loop control of induction and maintenance of propofol anesthesia in children.

    PubMed

    West, Nicholas; Dumont, Guy A; van Heusden, Klaske; Petersen, Christian L; Khosravi, Sara; Soltesz, Kristian; Umedaly, Aryannah; Reimer, Eleanor; Ansermino, J Mark

    2013-08-01

    During closed-loop control, a drug infusion is continually adjusted according to a measure of clinical effect (e.g., an electroencephalographic depth of hypnosis (DoH) index). Inconsistency in population-derived pediatric pharmacokinetic/pharmacodynamic models and the large interpatient variability observed in children suggest a role for closed-loop control in optimizing the administration of intravenous anesthesia. To clinically evaluate a robustly tuned system for closed-loop control of the induction and maintenance of propofol anesthesia in children undergoing gastrointestinal endoscopy. One hundred and eight children, aged 6-17, ASA I-II, were enrolled. Prior to induction of anesthesia, NeuroSENSE™ sensors were applied to obtain the WAVCNS DoH index. An intravenous cannula was inserted and lidocaine (0.5 mg·kg(-1) ) administered. Remifentanil was administered as a bolus (0.5 μg·kg(-1) ), followed by continuous infusion (0.03 μg·kg(-1) ·min(-1) ). The propofol infusion was closed-loop controlled throughout induction and maintenance of anesthesia, using WAVCNS as feedback. Anesthesia was closed-loop controlled in 102 cases. The system achieved and maintained an adequate DoH without manual adjustment in 87/102 (85%) cases. Induction of anesthesia (to WAVCNS  ≤ 60) was completed in median 3.8 min (interquartile range (IQR) 3.1-5.0), culminating in a propofol effect-site concentration (Ce ) of median 3.5 μg·ml(-1) (IQR 2.7-4.5). During maintenance of anesthesia, WAVCNS was measured within 10 units of the target for median 89% (IQR 79-96) of the time. Spontaneous breathing required no manual intervention in 91/102 (89%) cases. A robust closed-loop system can provide effective propofol administration during induction and maintenance of anesthesia in children. Wide variation in the calculated Ce highlights the limitation of open-loop regimes based on pharmacokinetic/pharmacodynamic models. © 2013 John Wiley & Sons Ltd.

  8. Closed-Loop Communication Improves Task Completion in Pediatric Trauma Resuscitation.

    PubMed

    El-Shafy, Ibrahim Abd; Delgado, Jennifer; Akerman, Meredith; Bullaro, Francesca; Christopherson, Nathan A M; Prince, Jose M

    2017-08-02

    Pediatric trauma care requires effective and clear communication in a time-sensitive manner amongst a variety of disciplines. Programs such as Crew Resource Management in aviation have been developed to systematically prevent errors. Similarly, teamSTEPPS has been promoted in healthcare with a strong focus on communication. We aim to evaluate the ability of closed-loop communication to improve time-to-task completion in pediatric trauma activations. All pediatric trauma activations from January to September, 2016 at an American College of Surgeons verified level I pediatric trauma center were video recorded and included in the study. Two independent reviewers identified and classified all verbal orders issued by the trauma team leader for order audibility, directed responsibility, check-back, and time-to-task-completion. The impact of pre-notification and level of activation on time-to-task-completion was also evaluated. All analyses were performed using SAS® version 9.4(SAS Institute Inc., Cary, NC). In total, 89 trauma activation videos were reviewed, with 387 verbal orders identified. Of those, 126(32.6%) were directed, 372(96.1%) audible, and 101(26.1%) closed-loop. On average each order required 3.85 minutes to be completed. There was a significant reduction in time-to-task-completion when closed-loop communication was utilized (p < 0.0001). Orders with closed-loop communication were completed 3.6 times sooner as compared to orders with an open-loop [HR = 3.6 (95% CI: 2.5, 5.3)]. There was not a significant difference in time-to-task-completion with respect to pre-notification by emergency service providers (p < 0.6100). [HR = 1.1 (95% CI: 0.9, 1.3)]. There was also not a significant difference in time-to-task-completion with respect to level of trauma team activation (p < 0.2229). [HR = 1.3 (95% CI: 0.8, 2.1)]. While closed-loop communication prevents medical errors, our study highlights the potential to increase the speed and efficiency with which tasks are

  9. Real-time closed-loop control for micro mirrors with quasistatic comb drives

    NASA Astrophysics Data System (ADS)

    Schroedter, Richard; Sandner, Thilo; Janschek, Klaus; Roth, Matthias; Hruschka, Clemens

    2016-03-01

    This paper presents the application of a real-time closed-loop control for the quasistatic axis of electrostatic micro scanning mirrors. In comparison to resonantly driven mirrors, the quasistatic comb drive allows arbitrary motion profiles with frequencies up to its eigenfrequency. A current mirror setup at Fraunhofer IPMS is manufactured with a staggered vertical comb (SVC) drive and equipped with an integrated piezo-resistive deflection sensor, which can potentially be used as position feedback sensor. The control design is accomplished based on a nonlinear mechatronic system model and the preliminary parameter characterization. In previous papers [1, 2] we have shown that jerk-limited trajectories, calculated offline, provide a suitable method for parametric trajectory design, taking into account physical limitations given by the electrostatic comb and thus decreasing the dynamic requirements. The open-loop control shows in general unfavorable residual eigenfrequency oscillations leading to considerable tracking errors for desired triangle trajectories [3]. With real-time closed-loop control, implemented on a dSPACE system using an optical feedback, we can significantly reduce these errors and stabilize the mirror motion against external disturbances. In this paper we compare linear and different nonlinear closed-loop control strategies as well as two observer variants for state estimation. Finally, we evaluate the simulation and experimental results in terms of steady state accuracy and the concept feasibility for a low-cost realization.

  10. Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.; Rosen, I. G.

    1987-01-01

    In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

  11. Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.; Rosen, I. G.

    1985-01-01

    In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

  12. Real-time, closed-loop dual-wavelength optical polarimetry for glucose monitoring

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Coté, Gerard L.

    2010-01-01

    The development of a real-time, dual-wavelength optical polarimetric system to ultimately probe the aqueous humor glucose concentrations as a means of noninvasive diabetic glucose monitoring is the long-term goal of this research. The key impact of the work is the development of an approach for the reduction of the time-variant corneal birefringence due to motion artifact, which is still a limiting factor preventing the realization of such a device. Our dual-wavelength approach utilizes real-time, closed-loop feedback that employs a classical three-term feedback controller and efficiently reduces the effect of motion artifact that appears as a common noise source for both wavelengths. In vitro results are shown for the open-loop system, and although the dual-wavelength system helps to reduce the noise, it is shown that closed-loop control is necessary to bring the noise down to a sufficient level for physiological monitoring. Specifically, in vitro measurement results with the closed-loop dual-wavelength approach demonstrate a sensitivity of 12.8 mg/dl across the physiologic glucose range in the presence of time-variant test cell birefringence. Overall, it is shown that this polarimetric system has the potential to be used as a noninvasive measure of glucose for diabetes.

  13. A Closed Loop Wireless Power Transmission System Using a Commercial RFID Transceiver for Biomedical Applications

    PubMed Central

    Kiani, Mehdi

    2010-01-01

    This paper presents a standalone closed loop wireless power transmission system that is built around a commercial off-the-shelf (COTS) radio frequency identification (RFID) transceiver (MLX90121) operating at 13.56 MHz. It can be used for inductively powering implantable biomedical devices in a closed loop fashion. Any changes in the distance and misalignment between transmitter and receiver coils in near-field wireless power transmission can cause a significant change in the received power, which can cause either malfunction or excessive heat dissipation. RFID transceivers are often used open loop. However, their back telemetry capability can be utilized to stabilize the received voltage on the implant. Our measurements showed that the delivered power to the transponder was maintained at 1.48 mW over a range of 6 to 12 cm, while the transmitter power consumption changed from 0.3 W to 1.21 W. The closed loop system can also oppose voltage variations as a result of sudden changes in load current. PMID:19963595

  14. Real-time, closed-loop dual-wavelength optical polarimetry for glucose monitoring

    PubMed Central

    Malik, Bilal H.; Coté, Gerard L.

    2010-01-01

    The development of a real-time, dual-wavelength optical polarimetric system to ultimately probe the aqueous humor glucose concentrations as a means of noninvasive diabetic glucose monitoring is the long-term goal of this research. The key impact of the work is the development of an approach for the reduction of the time-variant corneal birefringence due to motion artifact, which is still a limiting factor preventing the realization of such a device. Our dual-wavelength approach utilizes real-time, closed-loop feedback that employs a classical three-term feedback controller and efficiently reduces the effect of motion artifact that appears as a common noise source for both wavelengths. In vitro results are shown for the open-loop system, and although the dual-wavelength system helps to reduce the noise, it is shown that closed-loop control is necessary to bring the noise down to a sufficient level for physiological monitoring. Specifically, in vitro measurement results with the closed-loop dual-wavelength approach demonstrate a sensitivity of 12.8 mg∕dl across the physiologic glucose range in the presence of time-variant test cell birefringence. Overall, it is shown that this polarimetric system has the potential to be used as a noninvasive measure of glucose for diabetes. PMID:20210476

  15. Closed-loop deep brain stimulation by pulsatile delayed feedback with increased gap between pulse phases.

    PubMed

    Popovych, Oleksandr V; Lysyansky, Borys; Tass, Peter A

    2017-04-21

    Computationally it was shown that desynchronizing delayed feedback stimulation methods are effective closed-loop techniques for the control of synchronization in ensembles of interacting oscillators. We here computationally design stimulation signals for electrical stimulation of neuronal tissue that preserve the desynchronizing delayed feedback characteristics and comply with mandatory charge deposit-related safety requirements. For this, the amplitude of the high-frequency (HF) train of biphasic charge-balanced pulses used by the standard HF deep brain stimulation (DBS) is modulated by the smooth feedback signals. In this way we combine the desynchronizing delayed feedback approach with the HF DBS technique. We show that such a pulsatile delayed feedback stimulation can effectively and robustly desynchronize a network of model neurons comprising subthalamic nucleus and globus pallidus external and suggest this approach for desynchronizing closed-loop DBS. Intriguingly, an interphase gap introduced between the recharging phases of the charge-balanced biphasic pulses can significantly improve the stimulation-induced desynchronization and reduce the amount of the administered stimulation. In view of the recent experimental and clinical studies indicating a superiority of the closed-loop DBS to open-loop HF DBS, our results may contribute to a further development of effective stimulation methods for the treatment of neurological disorders characterized by abnormal neuronal synchronization.

  16. A closed loop wireless power transmission system using a commercial RFID transceiver for biomedical applications.

    PubMed

    Kiani, Mehdi; Ghovanloo, Maysam

    2009-01-01

    This paper presents a standalone closed loop wireless power transmission system that is built around a commercial off-the-shelf (COTS) radio frequency identification (RFID) transceiver (MLX90121) operating at 13.56 MHz. It can be used for inductively powering implantable biomedical devices in a closed loop fashion. Any changes in the distance and misalignment between transmitter and receiver coils in near-field wireless power transmission can cause a significant change in the received power, which can cause either malfunction or excessive heat dissipation. RFID transceivers are often used open loop. However, their back telemetry capability can be utilized to stabilize the received voltage on the implant. Our measurements showed that the delivered power to the transponder was maintained at 1.48 mW over a range of 6 to 12 cm, while the transmitter power consumption changed from 0.3 W to 1.21 W. The closed loop system can also oppose voltage variations as a result of sudden changes in load current.

  17. Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.; Rosen, I. G.

    1987-01-01

    In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

  18. Simple PID parameter tuning method based on outputs of the closed loop system

    NASA Astrophysics Data System (ADS)

    Han, Jianda; Zhu, Zhiqiang; Jiang, Ziya; He, Yuqing

    2016-05-01

    Most of the existing PID parameters tuning methods are only effective with pre-known accurate system models, which often require some strict identification experiments and thus infeasible for many complicated systems. Actually, in most practical engineering applications, it is desirable for the PID tuning scheme to be directly based on the input-output response of the closed-loop system. Thus, a new parameter tuning scheme for PID controllers without explicit mathematical model is developed in this paper. The paper begins with a new frequency domain properties analysis of the PID controller. After that, the definition of characteristic frequency for the PID controller is given in order to study the mathematical relationship between the PID parameters and the open-loop frequency properties of the controlled system. Then, the concepts of M-field and θ-field are introduced, which are then used to explain how the PID control parameters influence the closed-loop frequency-magnitude property and its time responses. Subsequently, the new PID parameter tuning scheme, i.e., a group of tuning rules, is proposed based on the preceding analysis. Finally, both simulations and experiments are conducted, and the results verify the feasibility and validity of the proposed methods. This research proposes a PID parameter tuning method based on outputs of the closed loop system.

  19. An RFID-Based Closed-Loop Wireless Power Transmission System for Biomedical Applications.

    PubMed

    Kiani, Mehdi; Ghovanloo, Maysam

    2010-04-01

    This brief presents a standalone closed-loop wireless power transmission system that is built around a commercial off-the-shelf (COTS) radio-frequency identification (RFID) reader (TRF7960) operating at 13.56 MHz. It can be used for inductively powering implantable biomedical devices in a closed loop. Any changes in the distance and misalignment between transmitter and receiver coils in near-field wireless power transmission can cause a significant change in the received power, which can cause either a malfunction or excessive heat dissipation. RFID circuits are often used in an open loop. However, their back telemetry capability can be utilized to stabilize the received voltage on the implant. Our measurements showed that the delivered power to the transponder was maintained at 11.2 mW over a range of 0.5 to 2 cm, while the transmitter power consumption changed from 78 mW to 1.1 W. The closed-loop system can also oppose voltage variations as a result of sudden changes in the load current.

  20. Closed-loop, pilot/vehicle analysis of the approach and landing task

    NASA Technical Reports Server (NTRS)

    Schmidt, D. K.; Anderson, M. R.

    1985-01-01

    Optimal-control-theoretic modeling and frequency-domain analysis is the methodology proposed to evaluate analytically the handling qualities of higher-order manually controlled dynamic systems. Fundamental to the methodology is evaluating the interplay between pilot workload and closed-loop pilot/vehicle performance and stability robustness. The model-based metric for pilot workload is the required pilot phase compensation. Pilot/vehicle performance and loop stability is then evaluated using frequency-domain techniques. When these techniques were applied to the flight-test data for thirty-two highly-augmented fighter configurations, strong correlation was obtained between the analytical and experimental results.

  1. A closed-loop time-alignment system for baseband combining

    NASA Technical Reports Server (NTRS)

    Feria, Y.

    1994-01-01

    In baseband combining, the key element is the time alignment of the baseband signals. This article describes a closed-loop time-alignment system that estimates and adjusts the relative delay between two baseband signals received from two different antennas for the signals to be coherently combined. This system automatically determines which signal is advanced and delays it accordingly with a resolution of a sample period. The performance of the loop is analyzed, and the analysis is verified through simulation. The variance of the delay estimates and the signal-to-noise ratio degradation in the simulations agree with the theoretical calculations.

  2. Falcon: a highly flexible open-source software for closed-loop neuroscience

    NASA Astrophysics Data System (ADS)

    Ciliberti, Davide; Kloosterman, Fabian

    2017-08-01

    Objective. Closed-loop experiments provide unique insights into brain dynamics and function. To facilitate a wide range of closed-loop experiments, we created an open-source software platform that enables high-performance real-time processing of streaming experimental data. Approach. We wrote Falcon, a C++ multi-threaded software in which the user can load and execute an arbitrary processing graph. Each node of a Falcon graph is mapped to a single thread and nodes communicate with each other through thread-safe buffers. The framework allows for easy implementation of new processing nodes and data types. Falcon was tested both on a 32-core and a 4-core workstation. Streaming data was read from either a commercial acquisition system (Neuralynx) or the open-source Open Ephys hardware, while closed-loop TTL pulses were generated with a USB module for digital output. We characterized the round-trip latency of our Falcon-based closed-loop system, as well as the specific latency contribution of the software architecture, by testing processing graphs with up to 32 parallel pipelines and eight serial stages. We finally deployed Falcon in a task of real-time detection of population bursts recorded live from the hippocampus of a freely moving rat. Main results. On Neuralynx hardware, round-trip latency was well below 1 ms and stable for at least 1 h, while on Open Ephys hardware latencies were below 15 ms. The latency contribution of the software was below 0.5 ms. Round-trip and software latencies were similar on both 32- and 4-core workstations. Falcon was used successfully to detect population bursts online with ~40 ms average latency. Significance. Falcon is a novel open-source software for closed-loop neuroscience. It has sub-millisecond intrinsic latency and gives the experimenter direct control of CPU resources. We envisage Falcon to be a useful tool to the neuroscientific community for implementing a wide variety of closed-loop experiments, including those

  3. Evaluation of closed-loop anesthesia delivery for propofol anesthesia in pediatric cardiac surgery.

    PubMed

    Biswas, Indranil; Mathew, Preethy J; Singh, Rana S; Puri, Goverdhan D

    2013-12-01

    The objective of this study was to compare the feasibility of closed-loop anesthesia delivery with manual control of propofol in pediatric patients during cardiac surgery. Forty ASA II-III children, undergoing elective cardiac surgery under cardiopulmonary bypass (CPB) in a tertiary care hospital, were randomized to receive propofol either through a closed-loop anesthesia delivery system (CL group) or through traditional manual control (manual group) to achieve a target BIS of 50. Patients were induced and subsequently maintained with a propofol infusion. The propofol usage and the efficacy of closed-loop system in controlling BIS within ±10 of the target were compared with that of manual control. The maintenance of BIS within ±10 of target and intraoperative hemodynamic stability were similar between the two groups. However, induction dose of propofol was less in the CL group (2.06 ± 0.79 mg·kg(-1) ) than the manual group (2.95 ± 1.03 mg·kg(-1) ) (P = 0.006) with less overshoot of BIS during induction in the closed-loop group (P = 0.007). Total propofol used in the off-CPB period was less in the CL group (6.29 ± 2.48 mg·kg(-1) h(-1) vs 7.82 ± 2.1 mg·kg(-1) h(-1) ) (P = 0.037). Phenylephrine use in the pre-CPB period was more in the manual group (16.92 ± 10.92 μg·kg(-1) vs 5.79 ± 5.98 μg·kg(-1) ) (P = 0.014). Manual group required a median of 18 (range 8-29) dose adjustments per hour, while the CL group required none. This study demonstrated the feasibility of closed-loop controlled propofol anesthesia in children, even in challenging procedures such as cardiac surgery. Closed-loop system needs further and larger evaluation to establish its safety and efficacy. © 2013 John Wiley & Sons Ltd.

  4. Falcon: a highly flexible open-source software for closed-loop neuroscience.

    PubMed

    Ciliberti, Davide; Kloosterman, Fabian

    2017-05-26

    Closed-loop experiments provide unique insights into brain dynamics and function. To facilitate a wide range of closed-loop experiments, we created an open-source software platform that enables high-performance real-time processing of streaming experimental data. We wrote Falcon, a C++ multi-threaded software in which the user can load and execute an arbitrary processing graph. Each node of a Falcon graph is mapped to a single thread and nodes communicate with each other through thread-safe buffers. The framework allows for easy implementation of new processing nodes and data types. Falcon was tested both on a 32-core and a 4-core workstation. Streaming data was read from either a commercial acquisition system (Neuralynx) or the open-source Open Ephys hardware, while closed-loop TTL pulses were generated with a USB module for digital output. We characterized the round-trip latency of our Falcon-based closed-loop system, as well as the specific latency contribution of the software architecture, by testing processing graphs with up to 32 parallel pipelines and eight serial stages. We finally deployed Falcon in a task of real-time detection of population bursts recorded live from the hippocampus of a freely moving rat. On Neuralynx hardware, round-trip latency was well below 1 ms and stable for at least 1 h, while on Open Ephys hardware latencies were below 15 ms. The latency contribution of the software was below 0.5 ms. Round-trip and software latencies were similar on both 32- and 4-core workstations. Falcon was used successfully to detect population bursts online with ~40 ms average latency. Falcon is a novel open-source software for closed-loop neuroscience. It has sub-millisecond intrinsic latency and gives the experimenter direct control of CPU resources. We envisage Falcon to be a useful tool to the neuroscientific community for implementing a wide variety of closed-loop experiments, including those requiring use of complex data structures and real

  5. Relative stability of the open and closed conformations of the active site loop of streptavidin

    PubMed Central

    General, Ignacio J.; Meirovitch, Hagai

    2011-01-01

    The eight-residue surface loop, 45–52 (Ser, Ala, Val, Gly, Asn, Ala, Glu, Ser), of the homotetrameric protein streptavidin has a “closed” conformation in the streptavidin-biotin complex, where the corresponding binding affinity is one of the strongest found in nature (ΔG ∼ –18 kcal∕mol). However, in most of the crystal structures of apo (unbound) streptavidin, the loop conformation is “open” and typically exhibits partial disorder and high B-factors. Thus, it is plausible to assume that the loop structure is changed from open to closed upon binding of biotin, and the corresponding difference in free energy, ΔF = Fopen – Fclosedin the unbound protein, should therefore be considered in the total absolute free energy of binding. ΔF (which has generally been neglected) is calculated here using our “hypothetical scanning molecular-dynamics” (HSMD) method. We use a protein model in which only the atoms closest to the loop are considered (the “template”) and they are fixed in the x-ray coordinates of the free protein; the x-ray conformation of the closed loop is attached to the same (unbound) template and both systems are capped with the same sphere of TIP3P water. Using the force field of the assisted model building with energy refinement (AMBER), we carry out two separate MD simulations (at temperature T = 300 K), starting from the open and closed conformations, where only the atoms of the loop and water are allowed to move (the template-water and template-loop interactions are considered). The absolute Fopen and Fclosed (of loop + water) are calculated from these trajectories, where the loop and water contributions are obtained by HSMD and a thermodynamic integration (TI) process, respectively. The combined HSMD-TI procedure leads to total (loop + water) ΔF = −27.1 ± 2.0 kcal∕mol, where the entropy TΔS constitutes 34% of ΔF, meaning that the effect of S is significant and should not be ignored. Also, ΔS is positive, in accord with

  6. Potential and benefits of closed loop ECLS systems on the ISS.

    PubMed

    Raatschen, W; Preiss, H

    2001-01-01

    To close open loops for long manned missions in space is a big challenge for aeronautic engineers throughout the world. The paper's focus is on the oxygen reclamation from carbon dioxide within a space habitat. A brief description of the function principle of a fixed alkaline electrolyzer, a solid amine carbon dioxide concentrator and a Sabatier reactor is given. By combining these devices to an air revitalization system the technical and economical benefits are explained. Astrium's Air Revitalization System (ARES) as a potential future part of the International Space Station's Environmental Control and Life Support System would close the oxygen loop. The amount of oxygen, needed for an ISS crew of seven astronauts could be provided by ARES. The upload of almost 1500 kg of water annually for oxygen generation through the onboard electrolyzer would be reduced by more than 1000 kg, resulting in savings of more than 30M$ per year. Additionally, the payload capacity of supply flights would be increased by this amount of mass. Further possibilities are addressed to combine ECLS mass flows with those of the power, propulsion and attitude control systems. Such closed loop approaches will contribute to ease long time missions (e. g. Mars, Moon) from a cost and logistic point of view. The hardware realization of Astrium's space-sized operating ARES is shown and test results of continuous and intermittent closed chamber tests are presented. c2001 Astrium GmbH. Published by Elsevier Science Ltd.

  7. Modulation of critical brain dynamics using closed-loop neurofeedback stimulation.

    PubMed

    Zhigalov, Alexander; Kaplan, Alexander; Palva, J Matias

    2016-08-01

    EEG long-range temporal correlations (LRTCs) are a significant for both human cognition and brain disorders, but beyond suppression by sensory disruption, there are little means for influencing them non-invasively. We hypothesized that LRTCs could be controlled by engaging intrinsic neuroregulation through closed-loop neurofeedback stimulation. We used a closed-loop-stimulation paradigm where supra-threshold α-waves trigger visual flash stimuli while the subject performs the standard eyes-closed resting-state task. As a "sham" control condition, we applied similar stimulus sequences without the neurofeedback. Over three sessions, a significant difference in the LRTCs of α-band oscillations (U=89, p<0.028, Wilcoxon rank sum test) and their scalp topography (T=-2.92, p<0.010, T-test) emerged between the neurofeedback and sham conditions so that the LRTCs were stronger during neurofeedback than sham. No changes (F=0.16, p>0.69, ANOVA test) in the scalp topography of α-band power were observed in either condition. This study provides proof-of-concept for that EEG LRTCs, and hence critical brain dynamics, can be modulated with closed-loop stimulation in an automatic, involuntary fashion. We suggest that this modulation is mediated by an excitation-inhibition balance change achieved by the closed-loop neuroregulation. Automatic LRTC modulation opens novel avenues for both examining the functional roles of brain criticality in healthy subjects and for developing novel therapeutic approaches for brain disorders associated with abnormal LRTCs. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  8. Bio-Inspired Controller on an FPGA Applied to Closed-Loop Diaphragmatic Stimulation

    PubMed Central

    Zbrzeski, Adeline; Bornat, Yannick; Hillen, Brian; Siu, Ricardo; Abbas, James; Jung, Ranu; Renaud, Sylvie

    2016-01-01

    Cervical spinal cord injury can disrupt connections between the brain respiratory network and the respiratory muscles which can lead to partial or complete loss of ventilatory control and require ventilatory assistance. Unlike current open-loop technology, a closed-loop diaphragmatic pacing system could overcome the drawbacks of manual titration as well as respond to changing ventilation requirements. We present an original bio-inspired assistive technology for real-time ventilation assistance, implemented in a digital configurable Field Programmable Gate Array (FPGA). The bio-inspired controller, which is a spiking neural network (SNN) inspired by the medullary respiratory network, is as robust as a classic controller while having a flexible, low-power and low-cost hardware design. The system was simulated in MATLAB with FPGA-specific constraints and tested with a computational model of rat breathing; the model reproduced experimentally collected respiratory data in eupneic animals. The open-loop version of the bio-inspired controller was implemented on the FPGA. Electrical test bench characterizations confirmed the system functionality. Open and closed-loop paradigm simulations were simulated to test the FPGA system real-time behavior using the rat computational model. The closed-loop system monitors breathing and changes in respiratory demands to drive diaphragmatic stimulation. The simulated results inform future acute animal experiments and constitute the first step toward the development of a neuromorphic, adaptive, compact, low-power, implantable device. The bio-inspired hardware design optimizes the FPGA resource and time costs while harnessing the computational power of spike-based neuromorphic hardware. Its real-time feature makes it suitable for in vivo applications. PMID:27378844

  9. Bio-Inspired Controller on an FPGA Applied to Closed-Loop Diaphragmatic Stimulation.

    PubMed

    Zbrzeski, Adeline; Bornat, Yannick; Hillen, Brian; Siu, Ricardo; Abbas, James; Jung, Ranu; Renaud, Sylvie

    2016-01-01

    Cervical spinal cord injury can disrupt connections between the brain respiratory network and the respiratory muscles which can lead to partial or complete loss of ventilatory control and require ventilatory assistance. Unlike current open-loop technology, a closed-loop diaphragmatic pacing system could overcome the drawbacks of manual titration as well as respond to changing ventilation requirements. We present an original bio-inspired assistive technology for real-time ventilation assistance, implemented in a digital configurable Field Programmable Gate Array (FPGA). The bio-inspired controller, which is a spiking neural network (SNN) inspired by the medullary respiratory network, is as robust as a classic controller while having a flexible, low-power and low-cost hardware design. The system was simulated in MATLAB with FPGA-specific constraints and tested with a computational model of rat breathing; the model reproduced experimentally collected respiratory data in eupneic animals. The open-loop version of the bio-inspired controller was implemented on the FPGA. Electrical test bench characterizations confirmed the system functionality. Open and closed-loop paradigm simulations were simulated to test the FPGA system real-time behavior using the rat computational model. The closed-loop system monitors breathing and changes in respiratory demands to drive diaphragmatic stimulation. The simulated results inform future acute animal experiments and constitute the first step toward the development of a neuromorphic, adaptive, compact, low-power, implantable device. The bio-inspired hardware design optimizes the FPGA resource and time costs while harnessing the computational power of spike-based neuromorphic hardware. Its real-time feature makes it suitable for in vivo applications.

  10. Day and Night Closed-Loop Control Using the Integrated Medtronic Hybrid Closed-Loop System in Type 1 Diabetes at Diabetes Camp.

    PubMed

    Ly, Trang T; Roy, Anirban; Grosman, Benyamin; Shin, John; Campbell, Alex; Monirabbasi, Salman; Liang, Bradley; von Eyben, Rie; Shanmugham, Satya; Clinton, Paula; Buckingham, Bruce A

    2015-07-01

    To evaluate the feasibility and efficacy of a fully integrated hybrid closed-loop (HCL) system (Medtronic MiniMed Inc., Northridge, CA), in day and night closed-loop control in subjects with type 1 diabetes, both in an inpatient setting and during 6 days at diabetes camp. The Medtronic MiniMed HCL system consists of a fourth generation (4S) glucose sensor, a sensor transmitter, and an insulin pump using a modified proportional-integral-derivative (PID) insulin feedback algorithm with safety constraints. Eight subjects were studied over 48 h in an inpatient setting. This was followed by a study of 21 subjects for 6 days at diabetes camp, randomized to either the closed-loop control group using the HCL system or to the group using the Medtronic MiniMed 530G with threshold suspend (control group). The overall mean sensor glucose percent time in range 70-180 mg/dL was similar between the groups (73.1% vs. 69.9%, control vs. HCL, respectively) (P = 0.580). Meter glucose values between 70 and 180 mg/dL were also similar between the groups (73.6% vs. 63.2%, control vs. HCL, respectively) (P = 0.086). The mean absolute relative difference of the 4S sensor was 10.8 ± 10.2%, when compared with plasma glucose values in the inpatient setting, and 12.6 ± 11.0% compared with capillary Bayer CONTOUR NEXT LINK glucose meter values during 6 days at camp. In the first clinical study of this fully integrated system using an investigational PID algorithm, the system did not demonstrate improved glucose control compared with sensor-augmented pump therapy alone. The system demonstrated good connectivity and improved sensor performance. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

  11. Closed-loop enhancement of jet mixing with extremum-seeking and physics-based strategies

    NASA Astrophysics Data System (ADS)

    Wu, Z.; Zhou, Y.; Cao, H. L.; Li, W. J.

    2016-06-01

    The closed-loop control of a turbulent round air jet is experimentally investigated based on two unsteady minijets, with a view to enhancing jet mixing. The two minijets are placed at diametrically opposite locations upstream of the nozzle exit. The open-loop control experiments are first performed. Given the mass flow rate ratio C m of the minijets to that of the main jet, the decay rate overline{K} of jet centerline mean velocity exhibits a maximum at the frequency ratio f e/ f 0 ≈ 1.0, where f e and f 0 are the excitation frequency of minijets and the preferred mode frequency of the natural main jet, respectively. An extremum-seeking feedback control has been developed to achieve autonomously the optimal control performance. It has been found that, given C m, this closed-loop control technique may obtain automatically and rapidly the optimal value of f e and the desired or maximum overline{K}, as achieved in the open-loop control. This control technique is robust and adaptable when the Reynolds number and initial excitation frequency are changed separately. A flow-physics-based feedback control strategy has also been investigated, which could achieve the optimal control performance automatically with a shorter convergence time than the extremum-seeking control, not robust though.

  12. Unbiased identification of finite impulse response linear systems operating in closed-loop.

    PubMed

    Westwick, David T; Perreault, Eric J

    2006-01-01

    The force and position data issued to construct models of joint dynamics are often obtained from closed-loop experiments, where the joint position is perturbed using an actuator configured as a position servo. If the position servo is orders of magnitude staffer than the joint, as is often the case, it is possible to treat the data as if they were obtained in open loop. It may be more relevant to study joint dynamics in compliant environments. This can be accomplished by adding an admittance controller, programmed to simulate a compliant environment, into the servo. Under these conditions, the presence of feedback cannot be ignored. Unbiased estimates of a system can be directly obtained from closed-loop data using the prediction error method. However, this is not true, in general, when linear regression or correlation-based analysis is used to fit nonparametric time- or frequency domain models. We develop a prediction error minimization based identification method for a nonparametric time-domain model, augmented with a parametric noise model. Simulations suggest that the method produces unbiased estimates of the dynamics of a system operating inside a feedback loop, even though linear regression results in substantial biases.

  13. Closed-loop control of deep brain stimulation: a simulation study.

    PubMed

    Santaniello, Sabato; Fiengo, Giovanni; Glielmo, Luigi; Grill, Warren M

    2011-02-01

    Deep brain stimulation (DBS) is an effective therapy to treat movement disorders including essential tremor, dystonia, and Parkinson's disease. Despite over a decade of clinical experience the mechanisms of DBS are still unclear, and this lack of understanding makes the selection of stimulation parameters quite challenging. The objective of this work was to develop a closed-loop control system that automatically adjusted the stimulation amplitude to reduce oscillatory neuronal activity, based on feedback of electrical signals recorded from the brain using the same electrode as implanted for stimulation. We simulated a population of 100 intrinsically active model neurons in the Vim thalamus, and the local field potentials (LFPs) generated by the population were used as the feedback (control) variable for closed loop control of DBS amplitude. Based on the correlation between the spectral content of the thalamic activity and tremor (Hua , 1998), (Lenz , 1988), we implemented an adaptive minimum variance controller to regulate the power spectrum of the simulated LFPs and restore the LFP power spectrum present under tremor conditions to a reference profile derived under tremor free conditions. The controller was based on a recursively identified autoregressive model (ARX) of the relationship between stimulation input and LFP output, and showed excellent performances in tracking the reference spectral features through selective changes in the theta (2-7 Hz), alpha (7-13 Hz), and beta (13-35 Hz) frequency ranges. Such changes reflected modifications in the firing patterns of the model neuronal population, and, differently from open-loop DBS, replaced the tremor-related pathological patterns with patterns similar to those simulated in tremor-free conditions. The closed-loop controller generated a LFP spectrum that approximated more closely the spectrum present in the tremor-free condition than did open loop fixed intensity stimulation and adapted to match the spectrum

  14. The Future of Open and Closed-Loop Insulin Delivery for Diabetes Mellitus

    PubMed Central

    Farmer, Terry G.; Edgar, Thomas F.

    2011-01-01

    Several aspects of insulin-dependent diabetes mellitus are analyzed, including the glucose metabolic system, diabetes complications, and previous and ongoing research aimed at controlling glucose in diabetic patients. An expert review of various models and control algorithms developed for the glucose homeostasis system is presented, along with an analysis of research towards the development of a polymeric insulin infusion system. Recommendations for future directions in creating a true closed-loop glucose control system are presented, including the development of multivariable models and control systems to more accurately describe and control the multi-metabolite, multi-hormonal system, as well as in vivo assessments of implicit closed-loop control systems. PMID:18088499

  15. Closed loop control of dielectric elastomer actuators based on self-sensing displacement feedback

    NASA Astrophysics Data System (ADS)

    Rizzello, G.; Naso, D.; York, A.; Seelecke, S.

    2016-03-01

    This paper describes a sensorless control algorithm for a positioning system based on a dielectric elastomer actuator (DEA). The voltage applied to the membrane and the resulting current can be measured during the actuation and used to estimate its displacement, i.e., to perform self-sensing. The estimated displacement can be then used as a feedback signal for a position control algorithm, which results in a compact device capable of operating in closed loop control without the need for additional electromechanical or optical transducers. In this work, a circular DEA preloaded with a bi-stable spring is used as a case of study to validate the proposed control architecture. A comparison of the closed loop performance achieved using an accurate laser displacement sensor for feedback is also provided to better assess the performance limitations of the overall sensorless scheme.

  16. Fault Detection and Safety in Closed-Loop Artificial Pancreas Systems

    PubMed Central

    2014-01-01

    Continuous subcutaneous insulin infusion pumps and continuous glucose monitors enable individuals with type 1 diabetes to achieve tighter blood glucose control and are critical components in a closed-loop artificial pancreas. Insulin infusion sets can fail and continuous glucose monitor sensor signals can suffer from a variety of anomalies, including signal dropout and pressure-induced sensor attenuations. In addition to hardware-based failures, software and human-induced errors can cause safety-related problems. Techniques for fault detection, safety analyses, and remote monitoring techniques that have been applied in other industries and applications, such as chemical process plants and commercial aircraft, are discussed and placed in the context of a closed-loop artificial pancreas. PMID:25049365

  17. Closed Loop Control of Penetration Depth during CO2 Laser Lap Welding Processes

    PubMed Central

    Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P.; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis in 't; Ancona, Antonio

    2012-01-01

    In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth. PMID:23112646

  18. A closed-loop MEMS accelerometer with capacitive sensing interface ASIC

    NASA Astrophysics Data System (ADS)

    Liu, Minjie; Chi, Baoyong; Liu, Yunfeng; Dong, Jingxin

    2013-01-01

    A closed-loop MEMS accelerometer with capacitive sensing interface ASIC (application specific integrated circuit) is presented. The parasitic-insensitive switched-capacitor sample-charge architecture is used to implement the capacitive sensing, which is crucial to the case where sensor and interface ASIC are combined in a two-chip approach to implement the closed-loop MEMS accelerometer. Based on the 0.35 µm CMOS sensing interface ASIC, an accelerometer prototype has been implemented, in which force-rebalance with the lag-proportional-integral controller is applied to improve the system stability and frequency response performance, and the testing results indicate the sensitivity of the presented accelerometer is 650 mV/g, the full measurement range ±15 g, the non-linearity 0.098% and the noise floor 23.17 µg/rt-Hz.

  19. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump

    PubMed Central

    Chu, Yixing; Dong, Jingxin; Chi, Baoyong; Liu, Yunfeng

    2016-01-01

    This paper presents a novel digital closed loop microelectromechanical system (MEMS) accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS) process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg. PMID:26999157

  20. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump.

    PubMed

    Chu, Yixing; Dong, Jingxin; Chi, Baoyong; Liu, Yunfeng

    2016-03-18

    This paper presents a novel digital closed loop microelectromechanical system (MEMS) accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS) process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg.

  1. System dynamics research of remanufacturing closed-loop supply chain dominated by the third party.

    PubMed

    Miao, Shidi; Wang, Tengfei; Chen, Deyun

    2017-04-01

    With the rapid development of the electronic information industry in recent years, electronic products are being updated faster and faster, and e-waste recycling has become a common problem around the world. Firstly, this article contrasts recycling at home and abroad using the predicament of Midea Corp. Based on a closed-loop supply chain with the system dynamics method, a model is constructed and simulated. In this model, the collection point coverage rate is introduced to adjust the e-waste recycling rate dynamically. Aiming at a recycling mode dominated by the third party of the closed-loop supply chain, the article mainly discusses the impact on the sales rate and market share of the recycling model by third-party enterprises and compares the total revenue of all supply chains. Simulation results show that the model is more effective and optimal than the traditional recycling model.

  2. Learning in closed-loop brain-machine interfaces: modeling and experimental validation.

    PubMed

    Héliot, Rodolphe; Ganguly, Karunesh; Jimenez, Jessica; Carmena, Jose M

    2010-10-01

    Closed-loop operation of a brain-machine interface (BMI) relies on the subject's ability to learn an inverse transformation of the plant to be controlled. In this paper, we propose a model of the learning process that undergoes closed-loop BMI operation. We first explore the properties of the model and show that it is able to learn an inverse model of the controlled plant. Then, we compare the model predictions to actual experimental neural and behavioral data from nonhuman primates operating a BMI, which demonstrate high accordance of the model with the experimental data. Applying tools from control theory to this learning model will help in the design of a new generation of neural information decoders which will maximize learning speed for BMI users.

  3. Development of Closed-Loop Simulation Methods for a Next-Generation Terminal Area Automation System

    NASA Technical Reports Server (NTRS)

    Robinson, John E., III; Isaacson, Douglas R.

    2002-01-01

    A next-generation air traffic decision support tool, known as the Active Final Approach Spacing Tool (aFAST), will generate heading, speed and altitude commands to achieve more precise separation of aircraft in the terminal area. The techniques used to analyze the performance of earlier generation decision support tools are not adequate to analyze the performance of aFAST. This paper summarizes the development of a new and innovative fully closed-loop testing method for aFAST. This method, called trajectory feedback testing, closes each aircraft's control loop inside of the aFAST scheduling algorithm. Validation of trajectory feedback testing by examination of the variation of aircraft time-of-arrival predictions between schedule updates and the variation of aircraft excess separation distances between simulation runs is presented.

  4. Sub-mm functional decoupling of electrocortical signals through closed-loop BMI learning.

    PubMed

    Ledochowitsch, P; Koralek, A C; Moses, D; Carmena, J M; Maharbiz, M M

    2013-01-01

    Volitional control of neural activity lies at the heart of the Brain-Machine Interface (BMI) paradigm. In this work we investigated if subdural field potentials recorded by electrodes < 1mm apart can be decoupled through closed-loop BMI learning. To this end, we fabricated custom, flexible microelectrode arrays with 200 µm electrode pitch and increased the effective electrode area by electrodeposition of platinum black to reduce thermal noise. We have chronically implanted these arrays subdurally over primary motor cortex (M1) of 5 male Long-Evans Rats and monitored the electrochemical electrode impedance in vivo to assess the stability of these neural interfaces. We successfully trained the rodents to perform a one-dimensional center-out task using closed-loop brain control to adjust the pitch of an auditory cursor by differentially modulating high gamma (70-110 Hz) power on pairs of surface microelectrodes that were separated by less than 1 mm.

  5. IMC-PID design based on model matching approach and closed-loop shaping.

    PubMed

    Jin, Qi B; Liu, Q

    2014-03-01

    Motivated by the limitations of the conventional internal model control (IMC), this communication addresses the design of IMC-based PID in terms of the robust performance of the control system. The IMC controller form is obtained by solving an H-infinity problem based on the model matching approach, and the parameters are determined by closed-loop shaping. The shaping of the closed-loop transfer function is considered both for the set-point tracking and for the load disturbance rejection. The design procedure is formulated as a multi-objective optimization problem which is solved by a specific optimization algorithm. A nice feature of this design method is that it permits a clear tradeoff between robustness and performance. Simulation examples show that the proposed method is effective and has a wide applicability.

  6. Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation.

    PubMed

    Forlim, Caroline Garcia; Pinto, Reynaldo Daniel; Varona, Pablo; Rodríguez, Francisco B

    2015-01-01

    In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish's own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish.

  7. A closed-loop control scheme for steering steady states of glycolysis and glycogenolysis pathway.

    PubMed

    Panja, Surajit; Patra, Sourav; Mukherjee, Anirban; Basu, Madhumita; Sengupta, Sanghamitra; Dutta, Pranab K

    2013-01-01

    Biochemical networks normally operate in the neighborhood of one of its multiple steady states. It may reach from one steady state to other within a finite time span. In this paper, a closed-loop control scheme is proposed to steer states of the glycolysis and glycogenolysis (GG) pathway from one of its steady states to other. The GG pathway is modeled in the synergism and saturation system formalism, known as S-system. This S-system model is linearized into the controllable Brunovsky canonical form using a feedback linearization technique. For closed-loop control, the linear-quadratic regulator (LQR) and the linear-quadratic gaussian (LQG) regulator are invoked to design a controller for tracking prespecified steady states. In the feedback linearization technique, a global diffeomorphism function is proposed that facilitates in achieving the regulation requirement. The robustness of the regulated GG pathway is studied considering input perturbation and with measurement noise.

  8. Closed-loop experiment of resonator integrated optic gyro with triangular wave phase modulation

    NASA Astrophysics Data System (ADS)

    Tang, Yichuang; Liu, Huilan; Zhi, Yinzhou; Feng, Lishuang; Wang, Junjie

    2014-10-01

    A closed-loop resonator integrated optic gyro (RIOG) scheme based on triangular wave phase modulation is proposed. Only one integrated optic modulator (IOM) is employed. Triangular wave is applied on the IOM to modulate the passing light wave, and the feedback serrodyne wave is superimposed upon the triangular wave to compensate the resonant frequency-difference. The experimental setup is established and the related measurements are performed. The results show that the proposed scheme can realize the closed-loop RIOG employing an IOM, which has the advantage of miniature size. A bias stability of 0.39 deg/s (10 s integration time) over 1 hour is achieved. Moreover, good linearity and large dynamic range are also experimental demonstrated.

  9. A classical model for closed-loop diagrams of binary liquid mixtures

    SciTech Connect

    Schnitzler, J.v.; Prausnitz, J.M. |

    1994-03-01

    A classical lattice model for closed-loop temperature-composition phase diagrams has been developed. It considers the effect of specific interactions, such as hydrogen bonding, between dissimilar components. This van Laar-type model includes a Flory-Huggins term for the excess entropy of mixing. It is applied to several liquid-liquid equilibria of nonelectrolytes, where the molecules of the two components differ in size. The model is able to represent the observed data semi-quantitatively, but in most cases it is not flexible enough to predict all parts of the closed loop quantitatively. The ability of the model to represent different binary systems is discussed. Finally, attention is given to a correction term, concerning the effect of concentration fluctuations near the upper critical solution temperature.

  10. An error criterion for determining sampling rates in closed-loop control systems

    NASA Technical Reports Server (NTRS)

    Brecher, S. M.

    1972-01-01

    The determination of an error criterion which will give a sampling rate for adequate performance of linear, time-invariant closed-loop, discrete-data control systems was studied. The proper modelling of the closed-loop control system for characterization of the error behavior, and the determination of an absolute error definition for performance of the two commonly used holding devices are discussed. The definition of an adequate relative error criterion as a function of the sampling rate and the parameters characterizing the system is established along with the determination of sampling rates. The validity of the expressions for the sampling interval was confirmed by computer simulations. Their application solves the problem of making a first choice in the selection of sampling rates.

  11. Optimization and closed loop guidance of drag modulated aeroassisted orbital transfer

    NASA Technical Reports Server (NTRS)

    Kechichian, J. A.; Cruz, M. I.; Rinderle, E. A.; Vinh, N. X.

    1983-01-01

    An analysis of optimal and near optimal atmospheric flight trajectories for drag modulated aeroassisted orbital transfer is presented. An explicit and adaptive closed loop guidance approach for this mode of orbit transfer is also presented with performance near the optimal nominal trajectories. The orbital transfer of interest is for return from high earth orbit to low earth orbit. Most of what is discussed in this paper concerns the aeroassisted or atmospheric segment which lowers the apogee of the high earth orbit to the apogee of the low earth orbit. Minimization of the total impulsive delta-V at this low earth orbit apogee is the optimization criterion. Control about this impulse due to a number of potential error sources in atmospheric braking is the requirement imposed on closed loop guidance.

  12. Fault detection and safety in closed-loop artificial pancreas systems.

    PubMed

    Bequette, B Wayne

    2014-11-01

    Continuous subcutaneous insulin infusion pumps and continuous glucose monitors enable individuals with type 1 diabetes to achieve tighter blood glucose control and are critical components in a closed-loop artificial pancreas. Insulin infusion sets can fail and continuous glucose monitor sensor signals can suffer from a variety of anomalies, including signal dropout and pressure-induced sensor attenuations. In addition to hardware-based failures, software and human-induced errors can cause safety-related problems. Techniques for fault detection, safety analyses, and remote monitoring techniques that have been applied in other industries and applications, such as chemical process plants and commercial aircraft, are discussed and placed in the context of a closed-loop artificial pancreas.

  13. Development of Closed-Loop Simulation Methods for a Next-Generation Terminal Area Automation System

    NASA Technical Reports Server (NTRS)

    Robinson, John E., III; Isaacson, Douglas R.

    2002-01-01

    A next-generation air traffic decision support tool, known as the Active Final Approach Spacing Tool (aFAST), will generate heading, speed and altitude commands to achieve more precise separation of aircraft in the terminal area. The techniques used to analyze the performance of earlier generation decision support tools are not adequate to analyze the performance of aFAST. This paper summarizes the development of a new and innovative fully closed-loop testing method for aFAST. This method, called trajectory feedback testing, closes each aircraft's control loop inside of the aFAST scheduling algorithm. Validation of trajectory feedback testing by examination of the variation of aircraft time-of-arrival predictions between schedule updates and the variation of aircraft excess separation distances between simulation runs is presented.

  14. Production implementation of fully automated, closed loop cure control for advanced composite structures

    NASA Astrophysics Data System (ADS)

    Johnson, Sean A.; Roberts, Nancy K.

    Economic of advanced composite part production requires development and use of the most aggressive cure cycles possible without sacrificing quality. As cure cycles are shortened and heating rates increase, tolerance windows for process parameters become increasingly narrow. These factors are intensified by condensation curing systems which generate large amounts of volatiles. Management of the situation requires fully automated, closed loop process control and a fundamental understanding of the material system used for the application. No turnkey system for this application is currently available. General Dynamics Pomona Division (GD/PD) has developed an integrated closed loop control system which is now being proofed in production. Realization of this system will enable cure time reductions of nearly 50 percent, while increasing yield and maintaining quality.

  15. Closed-loop flow test Miravalles Geothermal Field well log results

    SciTech Connect

    Dennis, B.; Eden, G.; Lawton, R.

    1992-10-01

    The Instituto Costarricense de Electricidad (ICE) conducted a closed-loop flow test in the Miravalles Geothermal Field. The closed-loop test was started in May and ran through August of 1990. The effluent from the production well PG-11 was carried by a pipeline through a monitor station to the injection well PG-2. Before starting the long-term flow test in May, cold-water injection experiments were performed in each well to determine the pressure and temperature response. A series of downhole measurements were made in each well to obtain background information. The downhole measurements were repeated in August just before terminating the flow test to evaluate the results.

  16. Closed-loop flow test Miravalles Geothermal Field well log results

    SciTech Connect

    Dennis, B.; Eden, G.; Lawton, R.

    1992-01-01

    The Instituto Costarricense de Electricidad (ICE) conducted a closed-loop flow test in the Miravalles Geothermal Field. The closed-loop test was started in May and ran through August of 1990. The effluent from the production well PG-11 was carried by a pipeline through a monitor station to the injection well PG-2. Before starting the long-term flow test in May, cold-water injection experiments were performed in each well to determine the pressure and temperature response. A series of downhole measurements were made in each well to obtain background information. The downhole measurements were repeated in August just before terminating the flow test to evaluate the results.

  17. Closed-loop results of a compact high-speed adaptive optics system with H∞ control

    NASA Astrophysics Data System (ADS)

    Frazier, Benjamin W.; Tyson, Robert K.; Ackman, Jacqueline; Smith, Mark

    2003-12-01

    We report on the results of experiments that demonstrate a robust control system for a general-purpose adaptive optics system and provide robust stability analysis for such a system. Using a commercially available high-speed CCD camera in the Shack-Hartmann wavefront sensor and a 37-actuator Xinetics deformable mirror, we are able to achieve closed-loop performance sufficient for many astronomical, vision science, or laser communications applications. The control system must be robust for the various applications and the entire system must be easily set-up, calibrated, and run by a minimally-trained operator. An H-infinity controller, which optimizes the closed-loop stability of a system, is implemented and analyzed.

  18. Androgynous, Reconfigurable Closed Loop Feedback Controlled Low Impact Docking System With Load Sensing Electromagnetic Capture Ring

    NASA Technical Reports Server (NTRS)

    Lewis, James L. (Inventor); Carroll, Monty B. (Inventor); Morales, Ray H. (Inventor); Le, Thang D. (Inventor)

    2002-01-01

    The present invention relates to a fully androgynous, reconfigurable closed loop feedback controlled low impact docking system with load sensing electromagnetic capture ring. The docking system of the present invention preferably comprises two Docking- assemblies, each docking assembly comprising a load sensing ring having an outer face, one of more electromagnets, one or more load cells coupled to said load sensing ring. The docking assembly further comprises a plurality of actuator arms coupled to said load sensing ring and capable of dynamically adjusting the orientation of said load sensing ring and a reconfigurable closed loop control system capable of analyzing signals originating from said plurality of load cells and of outputting real time control for each of the actuators. The docking assembly of the present invention incorporates an active load sensing system to automatically dynamically adjust the load sensing ring during capture instead of requiring significant force to push and realign the ring.

  19. Improvements To Progressive Wave Tube Performance Through Closed-Loop Control

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.

    2000-01-01

    This report documents recent improvements to the acoustic and thermal control systems of the Thermal Acoustic Fatigue Apparatus (TAFA), a progressive wave tube test facility at the NASA Langley Research Center, Hampton, Virginia. A brief summary of past acoustic performance is given first to serve as a basis for comparison with the new performance data using a multiple-input, closed-loop, narrow-band controller. Performance data in the form of test section acoustic power spectral densities and coherence are presented in three of six facility configurations for a variety of input spectra. Tested spectra include uniform, two cases of pink noise, three cases of narrow-band random, a simulated launch payload bay environment for an expendable launch vehicle, and a simulated external acoustic load for the aft section of a reusable launch vehicle. In addition, a new closed-loop temperature controller and thermocouple data acquisition system are described.

  20. A Closed Loop Brain-machine Interface for Epilepsy Control Using Dorsal Column Electrical Stimulation

    PubMed Central

    Pais-Vieira, Miguel; Yadav, Amol P.; Moreira, Derek; Guggenmos, David; Santos, Amílcar; Lebedev, Mikhail; Nicolelis, Miguel A. L.

    2016-01-01

    Although electrical neurostimulation has been proposed as an alternative treatment for drug-resistant cases of epilepsy, current procedures such as deep brain stimulation, vagus, and trigeminal nerve stimulation are effective only in a fraction of the patients. Here we demonstrate a closed loop brain-machine interface that delivers electrical stimulation to the dorsal column (DCS) of the spinal cord to suppress epileptic seizures. Rats were implanted with cortical recording microelectrodes and spinal cord stimulating electrodes, and then injected with pentylenetetrazole to induce seizures. Seizures were detected in real time from cortical local field potentials, after which DCS was applied. This method decreased seizure episode frequency by 44% and seizure duration by 38%. We argue that the therapeutic effect of DCS is related to modulation of cortical theta waves, and propose that this closed-loop interface has the potential to become an effective and semi-invasive treatment for refractory epilepsy and other neurological disorders. PMID:27605389

  1. Direct observation of closed-loop ferrohydrodynamic pumping under traveling magnetic fields

    NASA Astrophysics Data System (ADS)

    Mao, Leidong; Elborai, Shihab; He, Xiaowei; Zahn, Markus; Koser, Hur

    2011-09-01

    Ferrofluid-based liquid manipulation schemes typically actuate an immiscible liquid via a ferrofluid plug, using high magnetic flux (˜1 T) densities and strong field gradients created with bulky permanent magnets. They rely on surface tension effects to maintain the cohesion of the ferrofluid plug, necessitating miniature channels and slow (˜1 μl/min) flow speeds. Here, we demonstrate direct ferrohydrodynamic pumping using traveling magnetic fields at controllable speeds in a simple, closed-loop geometry without any mechanically actuated components. The pumping approach is compact, scalable, and practical. Using moderate field amplitudes (˜10 mT), we obtained a maximum volumetric flow rate of 0.69 ml/s using a readily available commercial ferrofluid. Our closed-loop pumping approach could lead to integrated and efficient liquid manipulation and cooling schemes based on ferrofluids.

  2. Closed-loop controller for chest compressions based on coronary perfusion pressure: a computer simulation study.

    PubMed

    Wang, Chunfei; Zhang, Guang; Wu, Taihu; Zhan, Ningbo; Wang, Yaling

    2016-03-01

    High-quality cardiopulmonary resuscitation contributes to cardiac arrest survival. The traditional chest compression (CC) standard, which neglects individual differences, uses unified standards for compression depth and compression rate in practice. In this study, an effective and personalized CC method for automatic mechanical compression devices is provided. We rebuild Charles F. Babbs' human circulation model with a coronary perfusion pressure (CPP) simulation module and propose a closed-loop controller based on a fuzzy control algorithm for CCs, which adjusts the CC depth according to the CPP. Compared with a traditional proportion-integration-differentiation (PID) controller, the performance of the fuzzy controller is evaluated in computer simulation studies. The simulation results demonstrate that the fuzzy closed-loop controller results in shorter regulation time, fewer oscillations and smaller overshoot than traditional PID controllers and outperforms the traditional PID controller for CPP regulation and maintenance.

  3. A Survey on Security and Privacy in Emerging Sensor Networks: From Viewpoint of Close-Loop

    PubMed Central

    Zhang, Lifu; Zhang, Heng

    2016-01-01

    Nowadays, as the next generation sensor networks, Cyber-Physical Systems (CPSs) refer to the complex networked systems that have both physical subsystems and cyber components, and the information flow between different subsystems and components is across a communication network, which forms a closed-loop. New generation sensor networks are found in a growing number of applications and have received increasing attention from many inter-disciplines. Opportunities and challenges in the design, analysis, verification and validation of sensor networks co-exists, among which security and privacy are two important ingredients. This paper presents a survey on some recent results in the security and privacy aspects of emerging sensor networks from the viewpoint of the closed-loop. This paper also discusses several future research directions under these two umbrellas. PMID:27023559

  4. A Survey on Security and Privacy in Emerging Sensor Networks: From Viewpoint of Close-Loop.

    PubMed

    Zhang, Lifu; Zhang, Heng

    2016-03-26

    Nowadays, as the next generation sensor networks, Cyber-Physical Systems (CPSs) refer to the complex networked systems that have both physical subsystems and cyber components, and the information flow between different subsystems and components is across a communication network, which forms a closed-loop. New generation sensor networks are found in a growing number of applications and have received increasing attention from many inter-disciplines. Opportunities and challenges in the design, analysis, verification and validation of sensor networks co-exists, among which security and privacy are two important ingredients. This paper presents a survey on some recent results in the security and privacy aspects of emerging sensor networks from the viewpoint of the closed-loop. This paper also discusses several future research directions under these two umbrellas.

  5. Closing the Loop: Control and Robot Navigation in Wireless Sensor Networks

    DTIC Science & Technology

    2006-09-05

    Closing the Loop: Control and Robot Navigation in Wireless Sensor Networks Shawn Michael Schaffert Electrical Engineering and Computer Sciences...WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) University of California at Berkeley, Electrical Engineering and Computer Sciences...submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Electrical Engineering and Computer Science in the GRADUATE

  6. Low-temperature plasma technology as part of a closed-loop resource management system

    NASA Technical Reports Server (NTRS)

    Hetland, Melanie D.; Rindt, John R.; Jones, Frank A.; Sauer, Randal S.

    1990-01-01

    The results of this testing indicate that the agitated low-temperature plasma reactor system successfully converted carbon, hydrogen, and nitrogen into gaseous products at residence times that were about ten times shorter than those achieved by stationary processing. The inorganic matrix present was virtually unchanged by the processing technique. It was concluded that this processing technique is feasible for use as part of a close-looped processing resource management system.

  7. First closed-loop goal directed fluid therapy during surgery: a pilot study.

    PubMed

    Rinehart, J; Le Manach, Y; Douiri, H; Lee, C; Lilot, M; Le, K; Canales, C; Cannesson, M

    2014-03-01

    Intraoperative haemodynamic optimization based on fluid management and stroke volume optimization (Goal Directed Fluid Therapy [GDFT]) can improve patients' postoperative outcome. We have described a closed-loop fluid management system based on stroke volume variation and stroke volume monitoring. The goal of this system is to apply GDFT protocols automatically. After conducting simulation, engineering, and animal studies the present report describes the first use of this system in the clinical setting. Prospective pilot study. Patients undergoing major surgery. Twelve patients at two institutions had intraoperative GDFT delivered by closed-loop controller under the direction of an anaesthesiologist. Compliance with GDFT management was defined as acceptable when a patient spent more than 85% of the surgery time in a preload independent state (defined as stroke volume variation<13%), or when average cardiac index during the case was superior or equal to 2.5l/min/m(2). Closed-loop GDFT was completed in 12 patients. Median surgery time was 447 [309-483] min and blood loss was 200 [100-1000] ml. Average cardiac index was 3.2±0.8l/min/m(2) and on average patients spent 91% (76 to 100%) of the surgery time in a preload independent state. Twelve of 12 patients met the criteria for compliance with intraoperative GDFT management. Intraoperative GDFT delivered by closed-loop system under anaesthesiologist guidance allowed to obtain targeted objectives in 91% of surgery time. This approach may provide a way to ensure consistent high-quality delivery of fluid administration and compliance with perioperative goal directed therapy. Copyright © 2013 Société française d’anesthésie et de réanimation (Sfar). Published by Elsevier SAS. All rights reserved.

  8. Automated Droplet Manipulation Using Closed-Loop Axisymmetric Drop Shape Analysis.

    PubMed

    Yu, Kyle; Yang, Jinlong; Zuo, Yi Y

    2016-05-17

    Droplet manipulation plays an important role in a wide range of scientific and industrial applications, such as synthesis of thin-film materials, control of interfacial reactions, and operation of digital microfluidics. Compared to micron-sized droplets, which are commonly considered as spherical beads, millimeter-sized droplets are generally deformable by gravity, thus introducing nonlinearity into control of droplet properties. Such a nonlinear drop shape effect is especially crucial for droplet manipulation, even for small droplets, at the presence of surfactants. In this paper, we have developed a novel closed-loop axisymmetric drop shape analysis (ADSA), integrated into a constrained drop surfactometer (CDS), for manipulating millimeter-sized droplets. The closed-loop ADSA generalizes applications of the traditional drop shape analysis from a surface tension measurement methodology to a sophisticated tool for manipulating droplets in real time. We have demonstrated the feasibility and advantages of the closed-loop ADSA in three applications, including control of drop volume by automatically compensating natural evaporation, precise control of surface area variations for high-fidelity biophysical simulations of natural pulmonary surfactant, and steady control of surface pressure for in situ Langmuir-Blodgett transfer from droplets. All these applications have demonstrated the accuracy, versatility, applicability, and automation of this new ADSA-based droplet manipulation technique. Combining with CDS, the closed-loop ADSA holds great promise for advancing droplet manipulation in a variety of material and surface science applications, such as thin-film fabrication, self-assembly, and biophysical study of pulmonary surfactant.

  9. Closed-loop bluff-body wake stabilization via fluidic excitation

    NASA Astrophysics Data System (ADS)

    Stalnov, O.; Fono, I.; Seifert, A.

    2011-06-01

    This article describes an experimental study aimed at stabilizing the wake of a shedding bluff-body by means of closed-loop active flow control at low Reynolds numbers. A D-shaped (6.5 mm thick) cylinder was used to allow a direct wake interaction rather than mixed wake-boundary-layer separation control. The fluidic actuators, installed inside the thin body, were ideally located at the separation locations, i.e., the trailing edges' upper and lower corners. The wake unsteadiness was monitored by a pair of hot wires (HWs), while a single surface-mounted hot-film (HF) sensor was used as a frequency and phase reference for closed-loop control. The HF signal was contaminated by noise. Hence, a technique for real-time tracking of a low signal-to-noise ratio (SNR) signal was necessary. This was achieved by means of a Phase-Locked Loop (PLL), common in communications systems. The closed-loop scheme was based on real-time measurement of the wake-state, using the surface-mounted HF sensor, and control authority imposed by the fluidic actuators. By using opposition control at frequencies close to the natural vortex shedding frequency (VSF), it was possible to significantly reduce the wake unsteadiness. Applying the same approach, but sensing the wake HW signal, rather than the surface-mounted HF signal, as the controller input did not result in wake stabilization. On the contrary, the unsteadiness increased at all the tested conditions. It is expected that a similar approach would work at much higher Reynolds numbers as well, as long as a clearly identifiable and nominally 2D vortex shedding occurs, even when the background flow is fully turbulent.

  10. Closed-Loop and Decision-Assist Resuscitation of Burn Patients

    DTIC Science & Technology

    2008-04-01

    hemorrhagic shock. Artif Cells Blood Substit Immobil Biotechnol. 1997;25:61–73. 42. Lowell JA, Schifferdecker C, Driscoll DF, Benotti PN, Bistrian BR...unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 renal blood flow, and cardiac output are likely to be adequate. Target values are...clinical trials demon- strating effective closed-loop control of nitroprusside infusion for postoperative blood pressure regulation in cardiac patients.26

  11. Feasibility of Overnight Closed-Loop Control Based on Hourly Blood Glucose Measurements

    PubMed Central

    Patte, Caroline; Pleus, Stefan; Galley, Paul; Weinert, Stefan; Haug, Cornelia; Freckmann, Guido

    2012-01-01

    Introduction Safe and effective closed-loop control (artificial pancreas) is the ultimate goal of insulin delivery. In this study, we examined the performance of a closed-loop control algorithm used for the overnight time period to safely achieve a narrow target range of blood glucose (BG) concentrations prior to breakfast. The primary goal was to compare the quality of algorithm control during repeated overnight experiments. Materials and Methods Twenty-three subjects with type 1 diabetes performed 2 overnight experiments on each of three visits at the study site, resulting in 138 overnight experiments. On the first evening, the subject’s insulin therapy was applied; on the second, the insulin was delivered by an algorithm based on subcutaneous continuous glucose measurements (including meal control) until midnight. Overnight closed-loop control was applied between midnight and 6 a.m. based on hourly venous BG measurements during the first and second nights. Results The number of BG values within the target range (90–150 mg/dl) increased from 52.9% (219 out of 414 measure-ments) during the first nights to 72.2% (299 out of 414 measurements) during the second nights (p < .001, χ2-test). The occurrence of hypoglycemia interventions was reduced from 14 oral glucose interventions, the latest occurring at 2:36 a.m. during the first nights, to 1 intervention occurring at 1:02 a.m. during the second nights (p < .001, χ2-test). Conclusions Overnight controller performance improved when optimized initial control was given; this was suggested by the better metabolic control during the second night. Adequate controller run-in time seems to be important for achieving good overnight control. In addition, the findings demonstrate that hourly BG data are sufficient for the closed-loop control algorithm tested to achieve appropriate glycemic control. PMID:22920817

  12. Simulation Environment to Evaluate Closed-Loop Insulin Delivery Systems in Type 1 Diabetes

    PubMed Central

    Wilinska, Malgorzata E.; Chassin, Ludovic J.; Acerini, Carlo L.; Allen, Janet M.; Dunger, David B.; Hovorka, Roman

    2010-01-01

    Background Closed-loop insulin delivery systems linking subcutaneous insulin infusion to real-time continuous glucose monitoring need to be evaluated in humans, but progress can be accelerated with the use of in silico testing. We present a simulation environment designed to support the development and testing of closed-loop insulin delivery systems in type 1 diabetes mellitus (T1DM). Methods The principal components of the simulation environment include a mathematical model of glucose regulation representing a virtual population with T1DM, the glucose measurement model, and the insulin delivery model. The simulation environment is highly flexible. The user can specify an experimental protocol, define a population of virtual subjects, choose glucose measurement and insulin delivery models, and specify outcome measures. The environment provides graphical as well as numerical outputs to enable a comprehensive analysis of in silico study results. The simulation environment is validated by comparing its predictions against a clinical study evaluating overnight closed-loop insulin delivery in young people with T1DM using a model predictive controller. Results The simulation model of glucose regulation is described, and population values of 18 synthetic subjects are provided. The validation study demonstrated that the simulation environment was able to reproduce the population results of the clinical study conducted in young people with T1DM. Conclusions Closed-loop trials in humans should be preceded and concurrently guided by highly efficient and resource-saving computer-based simulations. We demonstrate validity of population-based predictions obtained with our simulation environment. PMID:20167177

  13. Osmotic Ballasts Enhance Faradaic Efficiency in Closed-Loop, Membrane-Based Energy Systems.

    PubMed

    Kingsbury, Ryan S; Coronell, Orlando

    2017-02-07

    Aqueous processes for energy storage and conversion based on reverse electrodialysis (RED) require a significant concentration difference across ion exchange membranes, creating both an electrochemical potential and an osmotic pressure difference. In closed-loop RED, which we recently demonstrated as a new means of energy storage, the transport of water by osmosis has a very significant negative impact on the faradaic efficiency of the system. In this work, we use neutral, nonpermeating solutes as "osmotic ballasts" in a closed-loop concentration battery based on RED. We present experimental results comparing two proof-of-concept ballast molecules, and show that the ballasts reduce, eliminate, or reverse the net transport of water through the membranes when cycling the battery. By mitigating osmosis, faradaic and round-trip energy efficiency are more than doubled, from 18% to 50%, and 7% to 15%, respectively in this nonoptimized system. However, the presence of the ballasts has a slightly negative impact on the open circuit voltage. Our results suggest that balancing osmotic pressure using noncharged solutes is a promising approach for significantly reducing faradaic energy losses in closed-loop RED systems.

  14. Artificial Pancreas Device Systems for the Closed-Loop Control of Type 1 Diabetes

    PubMed Central

    Trevitt, Sara; Simpson, Sue; Wood, Annette

    2015-01-01

    Background: Closed-loop artificial pancreas device (APD) systems are externally worn medical devices that are being developed to enable people with type 1 diabetes to regulate their blood glucose levels in a more automated way. The innovative concept of this emerging technology is that hands-free, continuous, glycemic control can be achieved by using digital communication technology and advanced computer algorithms. Methods: A horizon scanning review of this field was conducted using online sources of intelligence to identify systems in development. The systems were classified into subtypes according to their level of automation, the hormonal and glycemic control approaches used, and their research setting. Results: Eighteen closed-loop APD systems were identified. All were being tested in clinical trials prior to potential commercialization. Six were being studied in the home setting, 5 in outpatient settings, and 7 in inpatient settings. It is estimated that 2 systems may become commercially available in the EU by the end of 2016, 1 during 2017, and 2 more in 2018. Conclusions: There are around 18 closed-loop APD systems progressing through early stages of clinical development. Only a few of these are currently in phase 3 trials and in settings that replicate real life. PMID:26589628

  15. Closed-loop Brain-Machine-Body Interfaces for Noninvasive Rehabilitation of Movement Disorders

    PubMed Central

    Broccard, Frédéric D.; Mullen, Tim; Chi, Yu Mike; Peterson, David; Iversen, John R.; Arnold, Mike; Kreutz-Delgado, Kenneth; Jung, Tzyy-Ping; Makeig, Scott; Poizner, Howard; Sejnowski, Terrence; Cauwenberghs, Gert

    2014-01-01

    Traditional approaches for neurological rehabilitation of patients affected with movement disorders, such as Parkinson's disease (PD), dystonia, and essential tremor (ET) consist mainly of oral medication, physical therapy, and botulinum toxin injections. Recently, the more invasive method of deep brain stimulation (DBS) showed significant improvement of the physical symptoms associated with these disorders. In the past several years, the adoption of feedback control theory helped DBS protocols to take into account the progressive and dynamic nature of these neurological movement disorders that had largely been ignored so far. As a result, a more efficient and effective management of PD cardinal symptoms has emerged. In this paper, we review closed-loop systems for rehabilitation of movement disorders, focusing on PD, for which several invasive and noninvasive methods have been developed during the last decade, reducing the complications and side effects associated with traditional rehabilitation approaches and paving the way for tailored individual therapeutics. We then present a novel, transformative, noninvasive closed-loop framework based on force neurofeedback and discuss several future developments of closed-loop systems that might bring us closer to individualized solutions for neurological rehabilitation of movement disorders. PMID:24833254

  16. Depressor effect of closed-loop chip system in spontaneously hypertensive rats.

    PubMed

    Gao, Xing-Ya; Huang, Xing-Lin; Wang, Han-Jun; Zhou, Li-Min; Xu, Yao; Wang, Wei; Zhu, Guo-Qing

    2007-12-30

    We previously reported that a closed-loop chip system was designed to decrease arterial pressure in normal rabbits and rats. In the present study, the depressor effects of the chip system were investigated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The arterial pressure was recorded, sampled, operated and processed in the chip system. The chip system instantaneously controlled arterial pressure by stimulating the left aortic depressor nerve according to the feedback signals of arterial pressure. The closed-loop chip system effectively decreased mean arterial pressure (MAP) and heart rate (HR) in both SHR and WKY rats. It decreased the duration and the maximal MAP level of the pressor response evoked by either intravenous injection of phenylephrine or cutaneous nociceptive stimulation in SHR, but had no significant effect on the magnitude of the increase in MAP. Furthermore, the chip system significantly increased the baroreflex gain in SHR, but not in normal WKY rats. These results suggest that the closed-loop chip system effectively decreases the arterial pressure and increases baroreflex gain in SHR. The chip system does not abolish the arterial pressure responses to accidental pressor events, but decreases the duration and the maximal MAP level of the pressor responses.

  17. Translation factors promote formation of two states of the closed loop mRNP

    PubMed Central

    AMRANI, NADIA; GHOSH, SHUBHENDU; MANGUS, DAVID A.; JACOBSON, ALLAN

    2008-01-01

    Efficient translation initiation and optimal stability of most eukaryotic mRNAs depends on the formation of a closed loop structure and the resulting synergistic interplay between the 5′ m7G cap and the 3′ poly(A) tail1,2. Evidence of eIF4G and Pab1p interaction supports the notion of a closed loop mRNP3, but the mechanistic events that lead to its formation and maintenance are still unknown. Here we have used toeprinting and polysome profiling assays to delineate ribosome positioning at initiator AUG codons and ribosome:mRNA association, respectively, and find that two distinct stable (cap analog resistant) closed loop structures are formed during initiation in yeast cell-free extracts. The integrity of both forms requires the mRNA cap and poly(A) tail, as well as eIF4E, eIF4G, Pab1p, and eIF3, and is dependent on the length of both the mRNA and the poly(A) tail. Formation of the first structure requires the 48S ribosomal complex whereas the second requires an 80S ribosome and the termination factors eRF3/Sup35p and eRF1/Sup45p. Surprisingly, the involvement of the termination factors is independent of a termination event. PMID:18496529

  18. Closed-loop brain-machine-body interfaces for noninvasive rehabilitation of movement disorders.

    PubMed

    Broccard, Frédéric D; Mullen, Tim; Chi, Yu Mike; Peterson, David; Iversen, John R; Arnold, Mike; Kreutz-Delgado, Kenneth; Jung, Tzyy-Ping; Makeig, Scott; Poizner, Howard; Sejnowski, Terrence; Cauwenberghs, Gert

    2014-08-01

    Traditional approaches for neurological rehabilitation of patients affected with movement disorders, such as Parkinson's disease (PD), dystonia, and essential tremor (ET) consist mainly of oral medication, physical therapy, and botulinum toxin injections. Recently, the more invasive method of deep brain stimulation (DBS) showed significant improvement of the physical symptoms associated with these disorders. In the past several years, the adoption of feedback control theory helped DBS protocols to take into account the progressive and dynamic nature of these neurological movement disorders that had largely been ignored so far. As a result, a more efficient and effective management of PD cardinal symptoms has emerged. In this paper, we review closed-loop systems for rehabilitation of movement disorders, focusing on PD, for which several invasive and noninvasive methods have been developed during the last decade, reducing the complications and side effects associated with traditional rehabilitation approaches and paving the way for tailored individual therapeutics. We then present a novel, transformative, noninvasive closed-loop framework based on force neurofeedback and discuss several future developments of closed-loop systems that might bring us closer to individualized solutions for neurological rehabilitation of movement disorders.

  19. Likelihood Gradient Ascent (LGA): a closed-loop decoder adaptation algorithm for brain-machine interfaces.

    PubMed

    Dangi, Siddharth; Gowda, Suraj; Carmena, Jose M

    2013-01-01

    Closed-loop decoder adaptation (CLDA) is an emerging paradigm for improving or maintaining the online performance of brain-machine interfaces (BMIs). Here, we present Likelihood Gradient Ascent (LGA), a novel CLDA algorithm for a Kalman filter (KF) decoder that uses stochastic, gradient-based corrections to update KF parameters during closed-loop BMI operation. LGA's gradient-based paradigm presents a variety of potential advantages over other "batch" CLDA methods, including the ability to update decoder parameters on any time-scale, even on every decoder iteration. Using a closed-loop BMI simulator, we compare the LGA algorithm to the Adaptive Kalman Filter (AKF), a partially gradient-based CLDA algorithm that has been previously tested in non-human primate experiments. In contrast to the AKF's separate mean-squared error objective functions, LGA's update rules are derived directly from a single log likelihood objective, making it one step towards a potentially optimal continuously adaptive CLDA algorithm for BMIs.

  20. Closed-Loop Double Endobutton Technique for Repair of Unstable Distal Clavicle Fractures

    PubMed Central

    Struhl, Steven; Wolfson, Theodore S.

    2016-01-01

    Background: Displaced fractures of the distal clavicle are inherently unstable and lead to nonunion in a high percentage of cases. The optimal surgical management remains controversial. Hypothesis: Indirect osteosynthesis with a closed-loop double endobutton construct would result in reliable fracture union and obviate the need for additional surgery. Study Design: Case series; Level of evidence, 4. Methods: Eight patients with an acute unstable Neer type IIB distal clavicle fracture were treated with a closed-loop double endobutton implant. Mean follow-up averaged 3.4 years (range, 1-9 years). Two patients were lost to follow-up. The remaining 6 patients underwent a detailed functional and radiologic evaluation. Results: Definitive fracture healing was achieved in all patients. There were no complications, and no patients required additional surgery related to the index procedure. The mean Constant score was 97 at final follow-up. Conclusion: The closed-loop double endobutton technique was reliable and effective in achieving fracture union in all patients with unstable Neer type IIB fractures of the distal clavicle. This technique obviates the need for late hardware removal that is often necessary when direct osteosynthesis is used and avoids potential complications associated with coracoclavicular cerclage constructs that require knot fixation. PMID:27504466

  1. Closed-Loop Process Control for Electron Beam Freeform Fabrication and Deposition Processes

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M. (Inventor); Hafley, Robert A. (Inventor); Martin, Richard E. (Inventor); Hofmeister, William H. (Inventor)

    2013-01-01

    A closed-loop control method for an electron beam freeform fabrication (EBF(sup 3)) process includes detecting a feature of interest during the process using a sensor(s), continuously evaluating the feature of interest to determine, in real time, a change occurring therein, and automatically modifying control parameters to control the EBF(sup 3) process. An apparatus provides closed-loop control method of the process, and includes an electron gun for generating an electron beam, a wire feeder for feeding a wire toward a substrate, wherein the wire is melted and progressively deposited in layers onto the substrate, a sensor(s), and a host machine. The sensor(s) measure the feature of interest during the process, and the host machine continuously evaluates the feature of interest to determine, in real time, a change occurring therein. The host machine automatically modifies control parameters to the EBF(sup 3) apparatus to control the EBF(sup 3) process in a closed-loop manner.

  2. Closed-loop motor control using high-speed fiber optics

    NASA Technical Reports Server (NTRS)

    Dawson, Reginald (Inventor); Rodriquiz, Dagobert (Inventor)

    1991-01-01

    A closed-loop control system for controlling the operation of one or more servo motors or other controllable devices is described. The system employs a fiber optics link immune to electromagnetic interference, for transmission of control signals from a controller or controllers at a remote station to the power electronics located in proximity to the motors or other devices at the local station. At the remote station the electrical control signals are time-multiplexed, converted to a formatted serial bit stream, and converted to light signals for transmission over a single fiber of the fiber optics link. At the local station, the received optical signals are reconstructed as electrical control signals for the controlled motors or other devices. At the local station, an encoder sensor linked to the driven device generates encoded feedback signals which provide information as to a condition of the controlled device. The encoded signals are placed in a formatted serial bit stream, multiplexed, and transmitted as optical signals over a second fiber of the fiber optic link which closes the control loop of the closed-loop motor controller. The encoded optical signals received at the remote station are demultiplexed, reconstructed and coupled to the controller(s) as electrical feedback signals.

  3. Behavioral analysis of differential Hebbian learning in closed-loop systems.

    PubMed

    Kulvicius, Tomas; Kolodziejski, Christoph; Tamosiunaite, Minija; Porr, Bernd; Wörgötter, Florentin

    2010-10-01

    Understanding closed loop behavioral systems is a non-trivial problem, especially when they change during learning. Descriptions of closed loop systems in terms of information theory date back to the 1950s, however, there have been only a few attempts which take into account learning, mostly measuring information of inputs. In this study we analyze a specific type of closed loop system by looking at the input as well as the output space. For this, we investigate simulated agents that perform differential Hebbian learning (STDP). In the first part we show that analytical solutions can be found for the temporal development of such systems for relatively simple cases. In the second part of this study we try to answer the following question: How can we predict which system from a given class would be the best for a particular scenario? This question is addressed using energy, input/output ratio and entropy measures and investigating their development during learning. This way we can show that within well-specified scenarios there are indeed agents which are optimal with respect to their structure and adaptive properties.

  4. Angles-only relative navigation and closed-loop guidance for spacecraft proximity operations

    NASA Astrophysics Data System (ADS)

    Luo, Jianjun; Gong, Baichun; Yuan, Jianping; Zhang, Zhaofei

    2016-11-01

    This research investigates angles-only relative navigation and closed-loop guidance algorithm for spacecraft mid-range orbital proximity operations when the orbital maneuver allows for range observability. Emphasis and contribution are on developing angles-only relative navigation and guidance coupling algorithm in the context of Clohessy-Wiltshire and Tschauner-Hempel dynamics. Observability analysis of the relative state is done and the general mathematical expression of the observable condition is obtained. Coupling relationship between the angles-only relative navigation and the multi-pulse sliding guidance is discussed and its analytic expression is derived. A novel closed-loop guidance scheme is designed based on the coupling relationship and unscented kalman filter. Two-body Monte Carlo simulations are conducted to evaluate the validity and test the performance of the closed-loop system. The sensitivities of the navigation and guidance accuracy to the line-of-sight angles accuracy, initial separation and initial state uncertainties, number of pulses, and dynamics are presented and discussed.

  5. Closed-loop control of fluid therapy for treatment of hypovolemia.

    PubMed

    Kramer, George C; Kinsky, Michael P; Prough, Donald S; Salinas, Jose; Sondeen, Jill L; Hazel-Scerbo, Michelle L; Mitchell, Charles E

    2008-04-01

    Closed-loop algorithms and resuscitation systems are being developed to control IV infusion rate during early resuscitation of hypovolemia. Although several different physiologic variables have been suggested as an endpoint to guide fluid therapy, blood pressure remains the most used variable for the initial assessment of hemorrhagic shock and the treatment response to volume loading. Closed-loop algorithms use a controller function to alter infusion rate inversely to blood pressure. Studies in hemorrhaged conscious sheep suggest that: (1) a small reduction in target blood pressure can result in a significant reduction in volume requirement; (2) nonlinear algorithms may reduce the risk of increased internal bleeding during resuscitation; (3) algorithm control functions based on proportional-integral, fuzzy logic, or nonlinear decision tables were found to restore and maintain blood pressure equally well. Proportional-integral and fuzzy logic algorithms reduced mean fluid volume requirements compared with the nonlinear decision table; and (4) several algorithms have been constructed to the specific mechanism of injury and the volume expansion properties of different fluids. Closed-loop systems are undergoing translation from animal to patient studies. Future smart resuscitation systems will benefit from new noninvasive technologies for monitoring blood pressure and the development of computer controlled high flow intravenous pumps.

  6. Real-time Electrophysiology: Using Closed-loop Protocols to Probe Neuronal Dynamics and Beyond.

    PubMed

    Linaro, Daniele; Couto, João; Giugliano, Michele

    2015-06-24

    Experimental neuroscience is witnessing an increased interest in the development and application of novel and often complex, closed-loop protocols, where the stimulus applied depends in real-time on the response of the system. Recent applications range from the implementation of virtual reality systems for studying motor responses both in mice and in zebrafish, to control of seizures following cortical stroke using optogenetics. A key advantage of closed-loop techniques resides in the capability of probing higher dimensional properties that are not directly accessible or that depend on multiple variables, such as neuronal excitability and reliability, while at the same time maximizing the experimental throughput. In this contribution and in the context of cellular electrophysiology, we describe how to apply a variety of closed-loop protocols to the study of the response properties of pyramidal cortical neurons, recorded intracellularly with the patch clamp technique in acute brain slices from the somatosensory cortex of juvenile rats. As no commercially available or open source software provides all the features required for efficiently performing the experiments described here, a new software toolbox called LCG was developed, whose modular structure maximizes reuse of computer code and facilitates the implementation of novel experimental paradigms. Stimulation waveforms are specified using a compact meta-description and full experimental protocols are described in text-based configuration files. Additionally, LCG has a command-line interface that is suited for repetition of trials and automation of experimental protocols.

  7. A dimensionally-heterogeneous closed-loop model for the cardiovascular system and its applications.

    PubMed

    Blanco, P J; Feijóo, R A

    2013-05-01

    In the present work a computational model of the entire cardiovascular system is developed using heterogeneous mathematical representations. This model integrates different levels of detail for the blood circulation. The arterial tree is described by a one dimensional model in order to simulate the wave propagation phenomena that take place at the larger arterial vessels. The inflow and outflow locations of this 1D model are coupled with lumped parameter descriptions of the remainder part of the circulatory system, closing the loop. The four cardiac valves are considered using a valve model which allows for stenoses and regurgitation phenomena. In addition, full 3D geometrical models of arterial districts are embedded in this closed-loop circuit to model the local blood flow in specific vessels. This kind of detailed closed-loop network for the cardiovascular system allows hemodynamics analyses of patient-specific arterial district, delivering naturally the appropriate boundary conditions for different cardiovascular scenarios. An example of application involving the effect of aortic insufficiency on the local hemodynamics of a cerebral aneurism is provided as a motivation to reproduce, through numerical simulation, the hemodynamic environment in patients suffering from infective endocarditis and mycotic aneurisms. The need for incorporating homeostatic control mechanisms is also discussed in view of the large sensitivity observed in the results, noting that this kind of integrative modeling allows such incorporation. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

  8. Identification-Based Closed-Loop NMES Limb Tracking With Amplitude-Modulated Control Input.

    PubMed

    Cheng, Teng-Hu; Wang, Qiang; Kamalapurkar, Rushikesh; Dinh, Huyen T; Bellman, Matthew; Dixon, Warren E

    2016-07-01

    An upper motor neuron lesion (UMNL) can be caused by various neurological disorders or trauma and leads to disabilities. Neuromuscular electrical stimulation (NMES) is a technique that is widely used for rehabilitation and restoration of motor function for people suffering from UMNL. Typically, stability analysis for closed-loop NMES ignores the modulated implementation of NMES. However, electrical stimulation must be applied to muscle as a modulated series of pulses. In this paper, a muscle activation model with an amplitude modulated control input is developed to capture the discontinuous nature of muscle activation, and an identification-based closed-loop NMES controller is designed and analyzed for the uncertain amplitude modulated muscle activation model. Semi-global uniformly ultimately bounded tracking is guaranteed. The stability of the closed-loop system is analyzed with Lyapunov-based methods, and a pulse frequency related gain condition is obtained. Experiments are performed with five able-bodied subjects to demonstrate the interplay between the control gains and the pulse frequency, and results are provided which indicate that control gains should be increased to maintain stability if the stimulation pulse frequency is decreased to mitigate muscle fatigue. For the first time, this paper brings together an analysis of the controller and modulation scheme.

  9. Closed-Loop Control System for Friction Stir Welding Retractable Pin Tool

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Romine, Peter L.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    NASA invention disclosure, NASA Case No. MFS-31413, entitled "System for Controlling the Stirring Pin of a Friction Stir Welding Apparatus", (Patent Pending) authored by Jeff Ding, Dr Peter Romine and Pete Oelgoetz, addresses the precision control of the friction stir welding process. The closed-loop control system automatically adjusts the spinning welding pin, real-time, to maintain a precise penetration ligament (i.e., distance between pin-tip and weld panel backside surface). A specific pin length can be maintained while welding constant thickness or tapered material thickness weld panels. The closed-loop control system provides operator data and information relative to the exact position of the welding pin inside the weld joint. This paper presents the closed-loop RPT control system that operates using the auto-feedback of force signals sensed by the tip and shoulder of the welding pin. Significance: The FSW process can be successfully used in a production environment only if there is a method or technique that informs the FSW operator the precise location of the welding pin inside the weld joint. This is essential for applications in aerospace, automotive, pressure vessel, commercial aircraft and other industries.

  10. Closed-Loop Control System for Friction Stir Welding Retractable Pin Tool

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Romine, Peter L.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    NASA invention disclosure, NASA Case No. MFS-31413, entitled "System for Controlling the Stirring Pin of a Friction Stir Welding Apparatus", (Patent Pending) authored by Jeff Ding, Dr Peter Romine and Pete Oelgoetz, addresses the precision control of the friction stir welding process. The closed-loop control system automatically adjusts the spinning welding pin, real-time, to maintain a precise penetration ligament (i.e., distance between pin-tip and weld panel backside surface). A specific pin length can be maintained while welding constant thickness or tapered material thickness weld panels. The closed-loop control system provides operator data and information relative to the exact position of the welding pin inside the weld joint. This paper presents the closed-loop RPT control system that operates using the auto-feedback of force signals sensed by the tip and shoulder of the welding pin. Significance: The FSW process can be successfully used in a production environment only if there is a method or technique that informs the FSW operator the precise location of the welding pin inside the weld joint. This is essential for applications in aerospace, automotive, pressure vessel, commercial aircraft and other industries.

  11. Advancing the food-energy-water nexus: Closing nutrient loops in arid river corridors

    NASA Astrophysics Data System (ADS)

    Gonzalez-Pinzon, R.; Mortensen, J.; Dahm, C.; Wang, J.; Zeglin, L. H.; Van Horn, D. J.

    2016-12-01

    Closing nutrient loops in terrestrial and aquatic ecosystems is integral to achieve resource security in the food-energy-water (FEW) nexus. We performed multiyear (2005-08), monthly sampling of instream dissolved inorganic nutrient concentrations (NH4-N, NO3-N, soluble reactive phosphorus-SRP) along a 306-km arid-land river (Rio Grande, NM, USA) and generated nutrient budgets to investigate how the net source/sink behavior of wastewater and irrigated agriculture can be holistically managed to improve water quality and close nutrient loops. Treated wastewater on average contributed over 90% of the instream dissolved inorganic nutrients (101 kg/day NH4-N, 1097 kg/day NO3-N, 656 kg/day SRP). During growing seasons, the irrigation network downstream of wastewater outfalls retained on average 37% of NO3-N and 45% of SRP inputs, with maximum retention exceeding 60% and 80% of NO3-N and SRP inputs, respectively. Accurate quantification of NH4-N retention was hindered by low loading and high variability. Nutrient retention in the irrigation network and instream processes together limited downstream export during growing seasons, with total retention of 33-99% of NO3-N inputs and 45-99% of SRP inputs. From our synoptic analysis, we identify tradeoffs associated with wastewater reuse for agriculture within the scope of the FEW nexus and propose strategies for closing nutrient loops in arid-land rivers.

  12. Closed-Loop, Multichannel Experimentation Using the Open-Source NeuroRighter Electrophysiology Platform

    PubMed Central

    Newman, Jonathan P.; Zeller-Townson, Riley; Fong, Ming-Fai; Arcot Desai, Sharanya; Gross, Robert E.; Potter, Steve M.

    2013-01-01

    Single neuron feedback control techniques, such as voltage clamp and dynamic clamp, have enabled numerous advances in our understanding of ion channels, electrochemical signaling, and neural dynamics. Although commercially available multichannel recording and stimulation systems are commonly used for studying neural processing at the network level, they provide little native support for real-time feedback. We developed the open-source NeuroRighter multichannel electrophysiology hardware and software platform for closed-loop multichannel control with a focus on accessibility and low cost. NeuroRighter allows 64 channels of stimulation and recording for around US $10,000, along with the ability to integrate with other software and hardware. Here, we present substantial enhancements to the NeuroRighter platform, including a redesigned desktop application, a new stimulation subsystem allowing arbitrary stimulation patterns, low-latency data servers for accessing data streams, and a new application programming interface (API) for creating closed-loop protocols that can be inserted into NeuroRighter as plugin programs. This greatly simplifies the design of sophisticated real-time experiments without sacrificing the power and speed of a compiled programming language. Here we present a detailed description of NeuroRighter as a stand-alone application, its plugin API, and an extensive set of case studies that highlight the system’s abilities for conducting closed-loop, multichannel interfacing experiments. PMID:23346047

  13. Disturbance rejection performance analyses of closed loop control systems by reference to disturbance ratio.

    PubMed

    Alagoz, Baris Baykant; Deniz, Furkan Nur; Keles, Cemal; Tan, Nusret

    2015-03-01

    This study investigates disturbance rejection capacity of closed loop control systems by means of reference to disturbance ratio (RDR). The RDR analysis calculates the ratio of reference signal energy to disturbance signal energy at the system output and provides a quantitative evaluation of disturbance rejection performance of control systems on the bases of communication channel limitations. Essentially, RDR provides a straightforward analytical method for the comparison and improvement of implicit disturbance rejection capacity of closed loop control systems. Theoretical analyses demonstrate us that RDR of the negative feedback closed loop control systems are determined by energy spectral density of controller transfer function. In this manner, authors derived design criteria for specifications of disturbance rejection performances of PID and fractional order PID (FOPID) controller structures. RDR spectra are calculated for investigation of frequency dependence of disturbance rejection capacity and spectral RDR analyses are carried out for PID and FOPID controllers. For the validation of theoretical results, simulation examples are presented. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

  14. Surface EEG-Transcranial Direct Current Stimulation (tDCS) Closed-Loop System.

    PubMed

    Leite, Jorge; Morales-Quezada, Leon; Carvalho, Sandra; Thibaut, Aurore; Doruk, Deniz; Chen, Chiun-Fan; Schachter, Steven C; Rotenberg, Alexander; Fregni, Felipe

    2017-09-01

    Conventional transcranial direct current stimulation (tDCS) protocols rely on applying electrical current at a fixed intensity and duration without using surrogate markers to direct the interventions. This has led to some mixed results; especially because tDCS induced effects may vary depending on the ongoing level of brain activity. Therefore, the objective of this preliminary study was to assess the feasibility of an EEG-triggered tDCS system based on EEG online analysis of its frequency bands. Six healthy volunteers were randomized to participate in a double-blind sham-controlled crossover design to receive a single session of 10[Formula: see text]min 2[Formula: see text]mA cathodal and sham tDCS. tDCS trigger controller was based upon an algorithm designed to detect an increase in the relative beta power of more than 200%, accompanied by a decrease of 50% or more in the relative alpha power, based on baseline EEG recordings. EEG-tDCS closed-loop-system was able to detect the predefined EEG magnitude deviation and successfully triggered the stimulation in all participants. This preliminary study represents a proof-of-concept for the development of an EEG-tDCS closed-loop system in humans. We discuss and review here different methods of closed loop system that can be considered and potential clinical applications of such system.

  15. Synchronization of fractional-order colored dynamical networks via open-plus-closed-loop control

    NASA Astrophysics Data System (ADS)

    Yang, Lixin; Jiang, Jun; Liu, Xiaojun

    2016-02-01

    In this paper, the synchronization of a fractional-order colored complex dynamical network model is studied for the first time. In this network model, color edges imply that both the outer coupling topology and the inner interactions between any pair of nodes may be different, and color nodes mean that local dynamics may be different. Based on the stability theory of fractional-order systems, the scheme of synchronization for fractional-order colored complex dynamical networks is presented. To achieve the synchronization of a complex fractional-order edge-colored network, the open-plus-closed-loop (OPCL) strategy is adopted and effective controllers for synchronization are designed. The open-plus-closed-loop (OPCL) strategy avoids the need for computation of eigenvalues of a very large matrix. Then, a synchronization method for a class of fractional-order colored complex network, containing both colored edges and colored nodes, is developed and some effective synchronization conditions via close-loop control are presented. Two examples of numerical simulations are presented to show the effectiveness of the proposed control strategies.

  16. Closed-loop insulin therapy improves glycemic control in children aged <7 years: a randomized controlled trial.

    PubMed

    Dauber, Andrew; Corcia, Liat; Safer, Jason; Agus, Michael S D; Einis, Sara; Steil, Garry M

    2013-02-01

    To assess the possibility of improving nocturnal glycemic control as well as meal glycemic response using closed-loop therapy in children aged <7 years. This was a randomized controlled crossover trial comparing closed-loop with standard open-loop insulin pump therapy performed in an inpatient clinical research center. Ten subjects aged <7 years with type 1 diabetes for >6 months treated with insulin pump therapy were studied. Closed-loop therapy and standard open-loop therapy were compared from 10:00 p.m. to 12:00 p.m. on 2 consecutive days. The primary outcome was plasma glucose time in range (110-200 mg/dL) during the night (10:00 p.m.-8:00 a.m.). Secondary outcomes included peak postprandial glucose levels, incidence of hypoglycemia, degree of hyperglycemia, and prelunch glucose levels. A trend toward a higher mean nocturnal time within target range was noted for closed- versus open-loop therapy, although not reaching statistical significance (5.3 vs. 3.2 h, P = 0.12). There was no difference in peak postprandial glucose or number of episodes of hypoglycemia. There was significant improvement in time spent >300 mg/dL overnight with closed-loop therapy (0.18 vs. 1.3 h, P = 0.035) and the total area under the curve of glucose >200 mg/dL (P = 0.049). Closed-loop therapy returned prelunch blood glucose closer to target (189 vs. 273 mg/dL on open loop, P = 0.009). Closed-loop insulin delivery decreases the severity of overnight hyperglycemia without increasing the incidence of hypoglycemia. The therapy is better able to reestablish target glucose levels in advance of a subsequent meal. Younger children with type 1 diabetes may reap significant benefits from closed-loop therapy.

  17. The "Glucositter" overnight automated closed loop system for type 1 diabetes: a randomized crossover trial.

    PubMed

    Nimri, Revital; Danne, Thomas; Kordonouri, Olga; Atlas, Eran; Bratina, Natasa; Biester, Torban; Avbelj, Magdalena; Miller, Shahar; Muller, Ido; Phillip, Moshe; Battelino, Tadej

    2013-05-01

    Tight glucose control is needed to prevent long-term diabetes complications; this is hindered by the risk of hypoglycemia, especially at night. To assess the safety and efficacy of the closed-loop MD-Logic Artificial Pancreas (MDLAP), controlling nocturnal glucose levels in patients with type 1 diabetes mellitus (T1DM). This was a randomized, multicenter, multinational, crossover trial conducted in Slovenia, Germany, and Israel. Twelve patients with T1DM (age 23.8 ± 15.6 yr; duration of diabetes 13.5 ± 11.9 yr; A1c 8.1 ± 0.8%, mean ±  SD) were randomly assigned to participate in two sequential overnight sessions: one using continuous subcutaneous insulin infusion (CSII) and the other, closed-loop insulin delivery by MDLAP. The primary outcome was the number of hypoglycemic events below 63 mg/dL. Endpoints analyses were based on sensor glucose readings. Three events of nocturnal hypoglycemia occurred during CSII and none during the closed-loop control (p = 0.18). The percentage of time spent in the near normal range of 63-140 mg/dL was significantly higher in the overnight closed-loop sessions [76% (54-85)] than during CSII therapy [29% (11-44)] [p = 0.02, median (interquartile range)]. The mean overnight glucose level was reduced by 36 mg/dL with closed-loop insulin delivery (p = 0.02) with a significantly less glucose variability when compared with the CSII nights (p < 0.001). The results of this study demonstrate the ability of the MDLAP to safely improve overnight glucose control without increased risk of hypoglycemia in patients with T1DM at three different national, geographic, and clinical centers (ClinicalTrials.gov number, NCT 01238406). © 2013 John Wiley & Sons A/S.

  18. Evaluating the Performance of a Novel Embedded Closed-loop System

    PubMed Central

    Leelarathna, Lalantha; Thabit, Hood; Allen, Janet M.; Nodale, Marianna; Wilinska, Malgorzata E.; Powell, Kevin; Lane, Stephen; Evans, Mark L.

    2014-01-01

    The objective was to assess the reliability of a novel automated closed-loop glucose control system developed within the AP@home consortium in adults with type 1 diabetes. Eight adults with type 1 diabetes on insulin pump therapy (3 men; ages 40.5 ± 14.3 years; HbA1c 8.2 ± 0.8%) participated in an open-label, single-center, single-arm, 12-hour overnight study performed at the clinical research facility. A standardized evening meal (80 g CHO) accompanied by prandial insulin boluses were given at 19:00 followed by an optional snack of 15 g at 22:00 without insulin bolus. Automated closed-loop glucose control was started at 19:00 and continued until 07:00 the next day. Basal insulin delivery (Accu-Chek Spirit, Roche) was automatically adjusted by Cambridge model predictive control algorithm, running on a purpose-built embedded device, based on real-time continuous glucose monitor readings (Dexcom G4 Platinum). Closed-loop system was operational as intended over 99% of the time. Overnight plasma glucose levels (22:00 to 07:00) were within the target range (3.9 to 8.0 mmol/l) for 75.4% (37.5, 92.9) of the time without any time spent in hypoglycemia (<3.9 mmol/l). Mean overnight glucose was 7.8 ± 1.3 mmol/l. For the entire 12-hour closed-loop period (19:00 until 07:00) plasma glucose levels were within the target range (3.9 to 10.0 mmol/l) for 84.4% (63.3, 100) of time. There were no adverse events noted during the trial. We observed a high degree of reliability of the automated closed-loop system. The time spent in target glucose level overnight was comparable to results of previously published studies. Further developments to miniaturize the system for home studies are warranted. PMID:24876577

  19. A hybrid solution approach for a multi-objective closed-loop logistics network under uncertainty

    NASA Astrophysics Data System (ADS)

    Mehrbod, Mehrdad; Tu, Nan; Miao, Lixin

    2014-09-01

    The design of closed-loop logistics (forward and reverse logistics) has attracted growing attention with the stringent pressures of customer expectations, environmental concerns and economic factors. This paper considers a multi-product, multi-period and multi-objective closed-loop logistics network model with regard to facility expansion as a facility location-allocation problem, which more closely approximates real-world conditions. A multi-objective mixed integer nonlinear programming formulation is linearized by defining new variables and adding new constraints to the model. By considering the aforementioned model under uncertainty, this paper develops a hybrid solution approach by combining an interactive fuzzy goal programming approach and robust counterpart optimization based on three well-known robust counterpart optimization formulations. Finally, this paper compares the results of the three formulations using different test scenarios and parameter-sensitive analysis in terms of the quality of the final solution, CPU time, the level of conservatism, the degree of closeness to the ideal solution, the degree of balance involved in developing a compromise solution, and satisfaction degree.

  20. Closed-loop thrust and pressure profile throttling of a nitrous oxide/hydroxyl-terminated polybutadiene hybrid rocket motor

    NASA Astrophysics Data System (ADS)

    Peterson, Zachary W.

    Hybrid motors that employ non-toxic, non-explosive components with a liquid oxidizer and a solid hydrocarbon fuel grain have inherently safe operating characteristics. The inherent safety of hybrid rocket motors offers the potential to greatly reduce overall operating costs. Another key advantage of hybrid rocket motors is the potential for in-flight shutdown, restart, and throttle by controlling the pressure drop between the oxidizer tank and the injector. This research designed, developed, and ground tested a closed-loop throttle controller for a hybrid rocket motor using nitrous oxide and hydroxyl-terminated polybutadiene as propellants. The research simultaneously developed closed-loop throttle algorithms and lab scale motor hardware to evaluate the fidelity of the throttle simulations and algorithms. Initial open-loop motor tests were performed to better classify system parameters and to validate motor performance values. Deep-throttle open-loop tests evaluated limits of stable thrust that can be achieved on the test hardware. Open-loop tests demonstrated the ability to throttle the motor to less than 10% of maximum thrust with little reduction in effective specific impulse and acoustical stability. Following the open-loop development, closed-loop, hardware-in-the-loop tests were performed. The closed-loop controller successfully tracked prescribed step and ramp command profiles with a high degree of fidelity. Steady-state accuracy was greatly improved over uncontrolled thrust.

  1. Closed loop statistical performance analysis of N-K knock controllers

    NASA Astrophysics Data System (ADS)

    Peyton Jones, James C.; Shayestehmanesh, Saeed; Frey, Jesse

    2017-09-01

    The closed loop performance of engine knock controllers cannot be rigorously assessed from single experiments or simulations because knock behaves as a random process and therefore the response belongs to a random distribution also. In this work a new method is proposed for computing the distributions and expected values of the closed loop response, both in steady state and in response to disturbances. The method takes as its input the control law, and the knock propensity characteristic of the engine which is mapped from open loop steady state tests. The method is applicable to the 'n-k' class of knock controllers in which the control action is a function only of the number of cycles n since the last control move, and the number k of knock events that have occurred in this time. A Cumulative Summation (CumSum) based controller falls within this category, and the method is used to investigate the performance of the controller in a deeper and more rigorous way than has previously been possible. The results are validated using onerous Monte Carlo simulations, which confirm both the validity of the method and its high computational efficiency.

  2. Evaluation of a Closed Loop Inductive Power Transmission System on an Awake Behaving Animal Subject

    PubMed Central

    Kiani, Mehdi; Kwon, Ki Yong; Zhang, Fei; Oweiss, Karim; Ghovanloo, Maysam

    2011-01-01

    This paper presents in vivo experimental results for a closed loop wireless power transmission system to implantable devices on an awake behaving animal subject. In this system, wireless power transmission takes place across an inductive link, controlled by a commercial off-the-shelf (COTS) radio frequency identification (RFID) transceiver (TRF7960) operating at 13.56 MHz. Induced voltage on the implantable secondary coil is rectified, digitized by a 10-bit analog to digital converter, and transmitted back to the primary via back telemetry. Transmitter (Tx) and receiver (Rx) circuitry were mounted on the back of an adult rat with a nominal distance of ~7 mm between their coils. Our experiments showed that the closed loop system was able to maintain the Rx supply voltage at the designated 3.8 V despite changes in the coils’ relative distance and alignment due to animal movements. The Tx power consumption changed between 410 ~ 560 mW in order to deliver 27 mW to the receiver. The open loop system, on the other hand, showed undesired changes in the Rx supply voltage while the Tx power consumption was constant at 660 mW. PMID:22256112

  3. Analysis of dead zone sources in a closed-loop fiber optic gyroscope.

    PubMed

    Chong, Kyoung-Ho; Choi, Woo-Seok; Chong, Kil-To

    2016-01-01

    Analysis of the dead zone is among the intensive studies in a closed-loop fiber optic gyroscope. In a dead zone, a gyroscope cannot detect any rotation and produces a zero bias. In this study, an analysis of dead zone sources is performed in simulation and experiments. In general, the problem is mainly due to electrical cross coupling and phase modulation drift. Electrical cross coupling is caused by interference between modulation voltage and the photodetector. The cross-coupled signal produces spurious gyro bias and leads to a dead zone if it is larger than the input rate. Phase modulation drift as another dead zone source is due to the electrode contamination, the piezoelectric effect of the LiNbO3 substrate, or to organic fouling. This modulation drift lasts for a short or long period of time like a lead-lag filter response and produces gyro bias error, noise spikes, or dead zone. For a more detailed analysis, the cross-coupling effect and modulation phase drift are modeled as a filter and are simulated in both the open-loop and closed-loop modes. The sources of dead zone are more clearly analyzed in the simulation and experimental results.

  4. Evaluation of a closed loop inductive power transmission system on an awake behaving animal subject.

    PubMed

    Kiani, Mehdi; Kwon, Ki Yong; Zhang, Fei; Oweiss, Karim; Ghovanloo, Maysam

    2011-01-01

    This paper presents in vivo experimental results for a closed loop wireless power transmission system to implantable devices on an awake behaving animal subject. In this system, wireless power transmission takes place across an inductive link, controlled by a commercial off-the-shelf (COTS) radio frequency identification (RFID) transceiver (TRF7960) operating at 13.56 MHz. Induced voltage on the implantable secondary coil is rectified, digitized by a 10-bit analog to digital converter, and transmitted back to the primary via back telemetry. Transmitter (Tx) and receiver (Rx) circuitry were mounted on the back of an adult rat with a nominal distance of ~7 mm between their coils. Our experiments showed that the closed loop system was able to maintain the Rx supply voltage at the designated 3.8 V despite changes in the coils' relative distance and alignment due to animal movements. The Tx power consumption changed between 410 ~ 560 mW in order to deliver 27 mW to the receiver. The open loop system, on the other hand, showed undesired changes in the Rx supply voltage while the Tx power consumption was constant at 660 mW.

  5. A servo-control system for open- and closed-loop blood pressure regulation.

    PubMed

    Nafz, B; Persson, P B; Ehmke, H; Kirchheim, H R

    1992-02-01

    An electropneumatic servo-control system is described that can reduce and control arterial blood pressure in experimental animals. The device has been proved useful in the analysis of pressure-dependent physiological processes and allows the following two modes of operation: 1) a conventional open-loop setting that will reduce arterial pressure to a preselected set point and 2) a closed-loop mode that enables an adjustment to a dynamic pressure set point (i.e., the controlled pressure is reduced to a constant value below a reference pressure). A pneumatic servo-control mechanism was chosen to provide minimal control latency. The accuracy of the system under physiological conditions is well within +/- 1 mmHg. The device can be useful in a number of studies demanding a precise regulation of local arterial pressure, such as experiments on blood flow autoregulation, arterial baroreceptor reflexes, and all experiments involving the study of pressure-dependent excretory and incretory functions of the kidney. The closed-loop setting is useful for studying physiological feedback systems.

  6. The effects of spaceflight on open-loop and closed-loop postural control mechanisms: human neurovestibular studies on SLS-2

    NASA Technical Reports Server (NTRS)

    Collins, J. J.; De Luca, C. J.; Pavlik, A. E.; Roy, S. H.; Emley, M. S.; Young, L. R. (Principal Investigator)

    1995-01-01

    Stabilogram-diffusion analysis was used to examine how prolonged periods in microgravity affect the open-loop and closed-loop postural control mechanisms. It was hypothesized that following spaceflight: (1) the effective stochastic activity of the open-loop postural control schemes in astronauts is increased; (2) the effective stochastic activity and uncorrelated behavior, respectively, of the closed-loop postural control mechanisms in astronauts are increased; and (3) astronauts utilized open-loop postural controls schemes for shorter time intervals and smaller displacements. Four crew members and two alternates from the 14-day Spacelab Life Sciences 2 Mission were included in the study. Each subject was tested under eyes-open, quiet-standing conditions on multiple preflight and postflight days. The subjects' center-of-pressure trajectories were measured with a force platform and analyzed according to stabilogram-diffusion analysis. It was found that the effective stochastic activity of the open-loop postural control schemes in three of the four crew members was increased following spaceflight. This result is interpreted as an indication that there may be in-flight adaptations to higher-level descending postural control pathways, e.g., a postflight increase in the tonic activation of postural muscles. This change may also be the consequence of a compensatory (e.g., "stiffening") postural control strategy that is adopted by astronauts to account for general feeling of postflight unsteadiness. The crew members, as a group, did not exhibit any consistent preflight/postflight differences in the steady-state behavior of their closed-loop postural control mechanisms or in the functional interaction of their open-loop and closed-loop postural control mechanisms. These results are interpreted as indications that although there may be in-flight adaptations to the vestibular system and/or proprioceptive system, input from the visual system can compensate for such changes

  7. The effects of spaceflight on open-loop and closed-loop postural control mechanisms: human neurovestibular studies on SLS-2

    NASA Technical Reports Server (NTRS)

    Collins, J. J.; De Luca, C. J.; Pavlik, A. E.; Roy, S. H.; Emley, M. S.; Young, L. R. (Principal Investigator)

    1995-01-01

    Stabilogram-diffusion analysis was used to examine how prolonged periods in microgravity affect the open-loop and closed-loop postural control mechanisms. It was hypothesized that following spaceflight: (1) the effective stochastic activity of the open-loop postural control schemes in astronauts is increased; (2) the effective stochastic activity and uncorrelated behavior, respectively, of the closed-loop postural control mechanisms in astronauts are increased; and (3) astronauts utilized open-loop postural controls schemes for shorter time intervals and smaller displacements. Four crew members and two alternates from the 14-day Spacelab Life Sciences 2 Mission were included in the study. Each subject was tested under eyes-open, quiet-standing conditions on multiple preflight and postflight days. The subjects' center-of-pressure trajectories were measured with a force platform and analyzed according to stabilogram-diffusion analysis. It was found that the effective stochastic activity of the open-loop postural control schemes in three of the four crew members was increased following spaceflight. This result is interpreted as an indication that there may be in-flight adaptations to higher-level descending postural control pathways, e.g., a postflight increase in the tonic activation of postural muscles. This change may also be the consequence of a compensatory (e.g., "stiffening") postural control strategy that is adopted by astronauts to account for general feeling of postflight unsteadiness. The crew members, as a group, did not exhibit any consistent preflight/postflight differences in the steady-state behavior of their closed-loop postural control mechanisms or in the functional interaction of their open-loop and closed-loop postural control mechanisms. These results are interpreted as indications that although there may be in-flight adaptations to the vestibular system and/or proprioceptive system, input from the visual system can compensate for such changes

  8. The effects of spaceflight on open-loop and closed-loop postural control mechanisms: human neurovestibular studies on SLS-2.

    PubMed

    Collins, J J; De Luca, C J; Pavlik, A E; Roy, S H; Emley, M S

    1995-01-01

    Stabilogram-diffusion analysis was used to examine how prolonged periods in microgravity affect the open-loop and closed-loop postural control mechanisms. It was hypothesized that following spaceflight: (1) the effective stochastic activity of the open-loop postural control schemes in astronauts is increased; (2) the effective stochastic activity and uncorrelated behavior, respectively, of the closed-loop postural control mechanisms in astronauts are increased; and (3) astronauts utilized open-loop postural controls schemes for shorter time intervals and smaller displacements. Four crew members and two alternates from the 14-day Spacelab Life Sciences 2 Mission were included in the study. Each subject was tested under eyes-open, quiet-standing conditions on multiple preflight and postflight days. The subjects' center-of-pressure trajectories were measured with a force platform and analyzed according to stabilogram-diffusion analysis. It was found that the effective stochastic activity of the open-loop postural control schemes in three of the four crew members was increased following spaceflight. This result is interpreted as an indication that there may be in-flight adaptations to higher-level descending postural control pathways, e.g., a postflight increase in the tonic activation of postural muscles. This change may also be the consequence of a compensatory (e.g., "stiffening") postural control strategy that is adopted by astronauts to account for general feeling of postflight unsteadiness. The crew members, as a group, did not exhibit any consistent preflight/postflight differences in the steady-state behavior of their closed-loop postural control mechanisms or in the functional interaction of their open-loop and closed-loop postural control mechanisms. These results are interpreted as indications that although there may be in-flight adaptations to the vestibular system and/or proprioceptive system, input from the visual system can compensate for such changes

  9. Multinational study of subcutaneous model-predictive closed-loop control in type 1 diabetes mellitus: summary of the results.

    PubMed

    Kovatchev, Boris; Cobelli, Claudio; Renard, Eric; Anderson, Stacey; Breton, Marc; Patek, Stephen; Clarke, William; Bruttomesso, Daniela; Maran, Alberto; Costa, Silvana; Avogaro, Angelo; Dalla Man, Chiara; Facchinetti, Andrea; Magni, Lalo; De Nicolao, Giuseppe; Place, Jerome; Farret, Anne

    2010-11-01

    In 2008-2009, the first multinational study was completed comparing closed-loop control (artificial pancreas) to state-of-the-art open-loop therapy in adults with type 1 diabetes mellitus (T1DM). The design of the control algorithm was done entirely in silico, i.e., using computer simulation experiments with N=300 synthetic "subjects" with T1DM instead of traditional animal trials. The clinical experiments recruited 20 adults with T1DM at the Universities of Virginia (11); Padova, Italy (6); and Montpellier, France (3). Open-loop and closed-loop admission was scheduled 3-4 weeks apart, continued for 22 h (14.5 h of which were in closed loop), and used a continuous glucose monitor and an insulin pump. The only difference between the two sessions was that insulin dosing was performed by the patient under a physician's supervision during open loop, whereas insulin dosing was performed by a control algorithm during closed loop. In silico design resulted in rapid (less than 6 months compared to years of animal trials) and cost-effective system development, testing, and regulatory approvals in the United States, Italy, and France. In the clinic, compared to open-loop, closed-loop control reduced nocturnal hypoglycemia (blood glucose below 3.9 mmol/liter) from 23 to 5 episodes (p<.01) and increased the amount of time spent overnight within the target range (3.9 to 7.8 mmol/liter) from 64% to 78% (p=.03). In silico experiments can be used as viable alternatives to animal trials for the preclinical testing of insulin treatment strategies. Compared to open-loop treatment under identical conditions, closed-loop control improves the overnight regulation of diabetes. © 2010 Diabetes Technology Society.

  10. Identification of multivariable high performance turbofan engine dynamics from closed loop data

    NASA Technical Reports Server (NTRS)

    Merrill, W.

    1982-01-01

    The multivariable instrumental variable/approximate maximum likelihood (IV/AML) method or recursive time-series analysis is used to identify the multivariable (four inputs-three outputs) dynamics of the Pratt and Whitney F100 engine. A detailed nonlinear engine simulation is used to determine linear engine model structures and parameters at an operating point using open loop data. Also, the IV/AML method is used in a direct identification mode to identify models from actual closed loop engine test data. Models identified from simulated and test data are compared to determine a final model structure and parameterization that can predict engine response for a wide class of inputs. The ability of the IV/AML algorithm to identify useful dynamic models from engine test data is assessed.

  11. Open and closed loop manipulation of charged microchiplets in an electric field

    SciTech Connect

    Lu, J. P. Thompson, J. D.; Whiting, G. L.; Biegelsen, D. K.; Raychaudhuri, S.; Lujan, R.; Veres, J.; Lavery, L. L.; Völkel, A. R.; Chow, E. M.

    2014-08-04

    We demonstrate the ability to orient, position, and transport microchips (“chiplets”) with electric fields. In an open-loop approach, modified four phase traveling wave potential patterns manipulate chiplets in a dielectric solution using dynamic template agitation techniques. Repeatable parallel assembly of chiplets is demonstrated to a positional accuracy of 6.5 μm using electrodes of 200 μm pitch. Chiplets with dipole surface charge patterns are used to show that orientation can be controlled by adding unique charge patterns on the chiplets. Chip path routing is also demonstrated. With a closed-loop control system approach using video feedback, dielectric, and electrophoretic forces are used to achieve positioning accuracy of better than 1 μm with 1 mm pitch driving electrodes. These chip assembly techniques have the potential to enable future printer systems where inputs are electronic chiplets and the output is a functional electronic system.

  12. Recovery of Dynamics and Function in Spiking Neural Networks with Closed-Loop Control

    PubMed Central

    Vlachos, Ioannis; Deniz, Taşkin; Aertsen, Ad; Kumar, Arvind

    2016-01-01

    There is a growing interest in developing novel brain stimulation methods to control disease-related aberrant neural activity and to address basic neuroscience questions. Conventional methods for manipulating brain activity rely on open-loop approaches that usually lead to excessive stimulation and, crucially, do not restore the original computations performed by the network. Thus, they are often accompanied by undesired side-effects. Here, we introduce delayed feedback control (DFC), a conceptually simple but effective method, to control pathological oscillations in spiking neural networks (SNNs). Using mathematical analysis and numerical simulations we show that DFC can restore a wide range of aberrant network dynamics either by suppressing or enhancing synchronous irregular activity. Importantly, DFC, besides steering the system back to a healthy state, also recovers the computations performed by the underlying network. Finally, using our theory we identify the role of single neuron and synapse properties in determining the stability of the closed-loop system. PMID:26829673

  13. Recovery of Dynamics and Function in Spiking Neural Networks with Closed-Loop Control.

    PubMed

    Vlachos, Ioannis; Deniz, Taşkin; Aertsen, Ad; Kumar, Arvind

    2016-02-01

    There is a growing interest in developing novel brain stimulation methods to control disease-related aberrant neural activity and to address basic neuroscience questions. Conventional methods for manipulating brain activity rely on open-loop approaches that usually lead to excessive stimulation and, crucially, do not restore the original computations performed by the network. Thus, they are often accompanied by undesired side-effects. Here, we introduce delayed feedback control (DFC), a conceptually simple but effective method, to control pathological oscillations in spiking neural networks (SNNs). Using mathematical analysis and numerical simulations we show that DFC can restore a wide range of aberrant network dynamics either by suppressing or enhancing synchronous irregular activity. Importantly, DFC, besides steering the system back to a healthy state, also recovers the computations performed by the underlying network. Finally, using our theory we identify the role of single neuron and synapse properties in determining the stability of the closed-loop system.

  14. Identification of multivariable high performance turbofan engine dynamics from closed loop data

    NASA Technical Reports Server (NTRS)

    Merrill, W.

    1983-01-01

    The multivariable instrumental variable/approximate maximum likelihood (IV/AML) method of recursive time-series analysis is used to identify the multivariable (four inputs-three outputs) dynamics of the Pratt and Whitney F100 engine. A detailed nonlinear engine simulation is used to determine linear engine model structures and parameters at an operating point using open loop data. Also, the IV/AML method is used in a direct identification made to identify models from actual closed loop engine test data. Models identified from simulated and test data are compared to determine a final model structure and parameterization that can predict engine response for a wide class of inputs. The ability of the IV/AML algorithm to identify useful dynamic models from engine test data is assessed. Previously announced in STAR as N82-20339

  15. Closing the sensorimotor loop: haptic feedback facilitates decoding of motor imagery

    NASA Astrophysics Data System (ADS)

    Gomez-Rodriguez, M.; Peters, J.; Hill, J.; Schölkopf, B.; Gharabaghi, A.; Grosse-Wentrup, M.

    2011-06-01

    The combination of brain-computer interfaces (BCIs) with robot-assisted physical therapy constitutes a promising approach to neurorehabilitation of patients with severe hemiparetic syndromes caused by cerebrovascular brain damage (e.g. stroke) and other neurological conditions. In such a scenario, a key aspect is how to reestablish the disrupted sensorimotor feedback loop. However, to date it is an open question how artificially closing the sensorimotor feedback loop influences the decoding performance of a BCI. In this paper, we answer this issue by studying six healthy subjects and two stroke patients. We present empirical evidence that haptic feedback, provided by a seven degrees of freedom robotic arm, facilitates online decoding of arm movement intention. The results support the feasibility of future rehabilitative treatments based on the combination of robot-assisted physical therapy with BCIs.

  16. Investigation of assimilable organic carbon (AOC) in flemish drinking water.

    PubMed

    Polanska, Monika; Huysman, Koen; van Keer, Chris

    2005-06-01

    The aim of the study was to investigate the drinking water supplied to majority of residents of Flanders in Belgium. Over 500 water samples were collected from different locations, after particular and complete treatment procedure to evaluate the efficiency of each treatment step in production of biologically stable drinking water. In this study assimilable organic carbon (AOC) was of our interest and was assumed as a parameter responsible for water biostability. The influence of seasons and temperature changes on AOC content was also taken into account. The AOC in most of the non-chlorinated product water of the studied treatment plants could not meet the biostability criteria of 10 mug/l, resulting in the mean AOC concentration of 50 microg/l. However, majority of the examined chlorinated water samples were consistent with proposed criteria of 50--100 microg/l for systems maintaining disinfectant residual. Here, mean AOC concentration of 72 microg/l was obtained. Granular activated carbon filtration was helpful in diminishing AOC content of drinking water; however, the nutrient removal was enhanced by biological process incorporated into water treatment (biological activated carbon filtration). Disinfection by means of chlorination and ozonation increased the water AOC concentration while the ultraviolet irradiation showed no impact on the AOC content. Examination of seasonal AOC variations showed similar fluctuations in six units with the highest values in summer and lowest in winter.

  17. A Closed-Loop Hardware Simulation of Decentralized Satellite Formation Control

    NASA Technical Reports Server (NTRS)

    Ebimuma, Takuji; Lightsey, E. Glenn; Baur, Frank (Technical Monitor)

    2002-01-01

    In recent years, there has been significant interest in the use of formation flying spacecraft for a variety of earth and space science missions. Formation flying may provide smaller and cheaper satellites that, working together, have more capability than larger and more expensive satellites. Several decentralized architectures have been proposed for autonomous establishment and maintenance of satellite formations. In such architectures, each satellite cooperatively maintains the shape of the formation without a central supervisor, and processing only local measurement information. The Global Positioning System (GPS) sensors are ideally suited to provide such local position and velocity measurements to the individual satellites. An investigation of the feasibility of a decentralized approach to satellite formation flying was originally presented by Carpenter. He extended a decentralized linear-quadratic-Gaussian (LQG) framework proposed by Speyer in a fashion similar to an extended Kalman filter (EKE) which processed GPS position fix solutions. The new decentralized LQG architecture was demonstrated in a numerical simulation for a realistic scenario that is similar to missions that have been proposed by NASA and the U.S. Air Force. Another decentralized architecture was proposed by Park et al. using carrier differential-phase GPS (CDGPS). Recently, Busse et al demonstrated the decentralized CDGPS architecture in a hardware-in-the-loop simulation on the Formation Flying TestBed (FFTB) at Goddard Space Flight Center (GSFC), which features two Spirent Cox 16 channel GPS signal generator. Although representing a step forward by utilizing GPS signal simulators for a spacecraft formation flying simulation, only an open-loop performance, in which no maneuvers were executed based on the real-time state estimates, was considered. In this research, hardware experimentation has been extended to include closed-loop integrated guidance and navigation of multiple spacecraft

  18. Stereovision and augmented reality for closed-loop control of grasping in hand prostheses.

    PubMed

    Markovic, Marko; Dosen, Strahinja; Cipriani, Christian; Popovic, Dejan; Farina, Dario

    2014-08-01

    Technologically advanced assistive devices are nowadays available to restore grasping, but effective and effortless control integrating both feed-forward (commands) and feedback (sensory information) is still missing. The goal of this work was to develop a user friendly interface for the semi-automatic and closed-loop control of grasping and to test its feasibility. We developed a controller based on stereovision to automatically select grasp type and size and augmented reality (AR) to provide artificial proprioceptive feedback. The system was experimentally tested in healthy subjects using a dexterous hand prosthesis to grasp a set of daily objects. The subjects wore AR glasses with an integrated stereo-camera pair, and triggered the system via a simple myoelectric interface. The results demonstrated that the subjects got easily acquainted with the semi-autonomous control. The stereovision grasp decoder successfully estimated the grasp type and size in realistic, cluttered environments. When allowed (forced) to correct the automatic system decisions, the subjects successfully utilized the AR feedback and achieved close to ideal system performance. The new method implements a high level, low effort control of complex functions in addition to the low level closed-loop control. The latter is achieved by providing rich visual feedback, which is integrated into the real life environment. The proposed system is an effective interface applicable with small alterations for many advanced prosthetic and orthotic/therapeutic rehabilitation devices.

  19. Stereovision and augmented reality for closed-loop control of grasping in hand prostheses

    NASA Astrophysics Data System (ADS)

    Markovic, Marko; Dosen, Strahinja; Cipriani, Christian; Popovic, Dejan; Farina, Dario

    2014-08-01

    Objective. Technologically advanced assistive devices are nowadays available to restore grasping, but effective and effortless control integrating both feed-forward (commands) and feedback (sensory information) is still missing. The goal of this work was to develop a user friendly interface for the semi-automatic and closed-loop control of grasping and to test its feasibility. Approach. We developed a controller based on stereovision to automatically select grasp type and size and augmented reality (AR) to provide artificial proprioceptive feedback. The system was experimentally tested in healthy subjects using a dexterous hand prosthesis to grasp a set of daily objects. The subjects wore AR glasses with an integrated stereo-camera pair, and triggered the system via a simple myoelectric interface. Main results. The results demonstrated that the subjects got easily acquainted with the semi-autonomous control. The stereovision grasp decoder successfully estimated the grasp type and size in realistic, cluttered environments. When allowed (forced) to correct the automatic system decisions, the subjects successfully utilized the AR feedback and achieved close to ideal system performance. Significance. The new method implements a high level, low effort control of complex functions in addition to the low level closed-loop control. The latter is achieved by providing rich visual feedback, which is integrated into the real life environment. The proposed system is an effective interface applicable with small alterations for many advanced prosthetic and orthotic/therapeutic rehabilitation devices.

  20. Rendered and Characterized Closed-Loop Accuracy of Impedance-Type Haptic Displays.

    PubMed

    Colonnese, Nick; Siu, Alexa F; Abbott, Caroline M; Okamura, Allison M

    2015-01-01

    Impedance-type kinesthetic haptic displays aim to render arbitrary desired dynamics to a human operator using force feedback. To render realistic virtual environments, the difference between desired and rendered dynamics must be small. In this paper, we analyze the closed-loop dynamics of haptic displays for three common virtual environments: a spring, a damper, and a spring-damper, including the effects of time delay and low-pass filtering. Using a linear model, we identify important parameters for the rendered dynamics in terms of effective impedances, a conceptual tool that decomposes the displays closed-loop impedance into components with physical analogs. Our results establish bandwidth limits for rendering effective stiffness and damping. The effective stiffness bandwidth is limited by the virtual stiffness and device mass, and the effective damping bandwidth is limited by the cut-off frequency of the low-pass filter which filters the device velocity estimate. We show that a general system impedance can be characterized by a mass, damper, and spring optimally by the solution to a convex optimization problem, and we present a quantitative metric, the Average Distortion Error (ADE), to describe the fidelity of this model. Time delay has no significant effect on characterized stiffness, and reduces characterized damping by the product of virtual stiffness and total time delay. Reducing the low-pass filter cut-off frequency reduces the characterized damping. Experimental data gathered with a Phantom Premium 1.5 validates the theoretical analysis. We also conducted human user experiments to investigate the effects of time delay and low-pass filtering on perceived stiffness and damping. Similar to the characterized dynamics results, we observed no significant effect of time delay on perceived stiffness, and increasing time delay resulted in reduced perceived damping. Lower filter cut-off frequencies resulted in lower perceived damping. This work informs haptic

  1. Novel closed-loop approaches for precise relative navigation of widely separated GPS receivers in LEO

    NASA Astrophysics Data System (ADS)

    Tancredi, U.; Renga, A.; Grassi, M.

    2014-01-01

    This paper deals with the relative navigation of a formation of two spacecrafts separated by hundreds of kilometers based on processing dual-frequency differential carrier-phase GPS measurements. Specific requirements of the considered application are high relative positioning accuracy and real-time on board implementation. These can be conflicting requirements. Indeed, if on one hand high accuracy can be achieved by exploiting the integer nature of double-difference carrier-phase ambiguities, on the other hand the presence of large ephemeris errors and differential ionospheric delays makes the integer ambiguities determination challenging. Closed-loop schemes, which update the relative position estimates of a dynamic filter with feedback from integer ambiguities fixing algorithms, are customarily employed in these cases. This paper further elaborates such approaches, proposing novel closed loop techniques aimed at overcoming some of the limitations of traditional algorithms. They extend techniques developed for spaceborne long baseline relative positioning by making use of an on-the-fly ambiguity resolution technique especially developed for the applications of interest. Such techniques blend together ionospheric delay compensation techniques, nonlinear models of relative spacecraft dynamics, and partial integer validation techniques. The approaches are validated using flight data from the Gravity Recovery and Climate Experiment (GRACE) mission. Performance is compared to that of the traditional closed-loop scheme analyzing the capability of each scheme to maximize the percentage of correctly fixed integer ambiguities as well as the relative positioning accuracy. Results show that the proposed approach substantially improves performance of the traditional approaches. More specifically, centimeter-level root-mean square relative positioning is feasible for spacecraft separations of more than 260 km, and an integer ambiguity fixing performance as high as 98% is

  2. Effect of ambient pressure variation on closed loop gas system for India based Neutrino Observatory (INO)

    NASA Astrophysics Data System (ADS)

    Satyanarayana, B.; Majumder, G.; Mondal, N. K.; Kalmani, S. D.; Shinde, R. R.; Joshi, A.

    2014-10-01

    Pilot unit of a closed loop gas mixing and distribution system for the INO project was designed and is being operated with 1.8meters × 1.9meters RPCs for about two years. A number of studies on controlling the flow and optimisation of the gas mixture through the RPC stack were carried out during this period. The gas system essentially measures and attempts to maintain absolute pressure inside the RPC gas volume. During typical Mumbai monsoon seasons, the barometric pressure changes rather rapidly, due to which the gas system fails to maintain the set differential pressure between the ambience and the RPC gas volume. As the safety bubblers on the RPC gas input lines are set to work on fixed pressure differentials, the ambient pressure changes lead to either venting out and thus wasting gas through safety bubblers or over pressuring the RPCs gas volume and thus degrading its performance. The above problem also leads to gas mixture contamination through minute leaks in gas gap. The problem stated above was solved by including the ambient barometric pressure as an input parameter in the closed loop. Using this, it is now possible to maintain any set differential pressure between the ambience and RPC gas volumes between 0 to 20mm of water column, thus always ensuring a positive pressure inside the RPC gas volume with respect to the ambience. This has resulted in improved performance of the gas system by maintaining the constant gas flow and reducing the gas toping up frequency. In this paper, we will highlight the design features and improvements of the closed loop gas system. We will present some of the performance studies and considerations for scaling up the system to be used with the engineering module and then followed by Iron Calorimeter detector (ICAL), which is designed to deploy about 30,000 RPCs of 1.8meters × 1.9 meters in area.

  3. A closed-loop model of the respiratory system: focus on hypercapnia and active expiration.

    PubMed

    Molkov, Yaroslav I; Shevtsova, Natalia A; Park, Choongseok; Ben-Tal, Alona; Smith, Jeffrey C; Rubin, Jonathan E; Rybak, Ilya A

    2014-01-01

    Breathing is a vital process providing the exchange of gases between the lungs and atmosphere. During quiet breathing, pumping air from the lungs is mostly performed by contraction of the diaphragm during inspiration, and muscle contraction during expiration does not play a significant role in ventilation. In contrast, during intense exercise or severe hypercapnia forced or active expiration occurs in which the abdominal "expiratory" muscles become actively involved in breathing. The mechanisms of this transition remain unknown. To study these mechanisms, we developed a computational model of the closed-loop respiratory system that describes the brainstem respiratory network controlling the pulmonary subsystem representing lung biomechanics and gas (O2 and CO2) exchange and transport. The lung subsystem provides two types of feedback to the neural subsystem: a mechanical one from pulmonary stretch receptors and a chemical one from central chemoreceptors. The neural component of the model simulates the respiratory network that includes several interacting respiratory neuron types within the Bötzinger and pre-Bötzinger complexes, as well as the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG) representing the central chemoreception module targeted by chemical feedback. The RTN/pFRG compartment contains an independent neural generator that is activated at an increased CO2 level and controls the abdominal motor output. The lung volume is controlled by two pumps, a major one driven by the diaphragm and an additional one activated by abdominal muscles and involved in active expiration. The model represents the first attempt to model the transition from quiet breathing to breathing with active expiration. The model suggests that the closed-loop respiratory control system switches to active expiration via a quantal acceleration of expiratory activity, when increases in breathing rate and phrenic amplitude no longer provide sufficient ventilation. The model

  4. Performance recovery of a thick turbulent airfoil using a distributed closed-loop flow control system

    NASA Astrophysics Data System (ADS)

    Troshin, Victor; Seifert, Avraham

    2012-12-01

    This paper describes an experimental study aimed at controlling the performance of a thick airfoil, typical to the root section of a wind turbine blade. The main purpose is recovering decreased performance due to degraded surface quality, leading to decreased lift and increased drag. Since wind turbines are designed to operate for decades, the blades' surface quality degradation due to environmental effects is unavoidable. This process promotes early transition to turbulent flow, leading to premature boundary layer separation in the post-transitional regime. In addition, non-uniform and unsteady wind speeds cause dynamic loads on the blade and on the overall turbine structure. Controlling unsteady and non-uniform loads by changing the blades' (or its cross-section) performance will allow building larger, lighter and more durable to aging wind turbines. Active flow control (AFC) is a possible remedy to boundary layer separation, including rough surface effects. Currently, three arrays of synthetic jet actuators are controlled based on state estimation provided by feedback from hot-film and pressure sensors. The unsteady pressure sensors' data are used to estimate the lift while the unsteady and un-calibrated hot-films data are used to determine the flow separation location and define the relative magnitude of actuation imparted by each of the three actuator rows. The aerodynamic results demonstrate that the "clean" turbine blade performance, with lift-based controller, is recovered by the closed-loop active flow control system at Reynolds numbers around half a million and excitation at Strouhal numbers larger than 10. The total closed-loop AFC system energy efficiency was measured and shown to increase by up to 60 % compared to the airfoil with degraded surface quality. The current results indicate the potential of a closed-loop AFC system to provide significant increase in the net energy harvesting capability of a wind turbine blade with degraded surface quality

  5. Performance recovery of a thick turbulent airfoil using a distributed closed-loop flow control system

    NASA Astrophysics Data System (ADS)

    Troshin, Victor; Seifert, Avraham

    2013-01-01

    This paper describes an experimental study aimed at controlling the performance of a thick airfoil, typical to the root section of a wind turbine blade. The main purpose is recovering decreased performance due to degraded surface quality, leading to decreased lift and increased drag. Since wind turbines are designed to operate for decades, the blades' surface quality degradation due to environmental effects is unavoidable. This process promotes early transition to turbulent flow, leading to premature boundary layer separation in the post-transitional regime. In addition, non-uniform and unsteady wind speeds cause dynamic loads on the blade and on the overall turbine structure. Controlling unsteady and non-uniform loads by changing the blades' (or its cross-section) performance will allow building larger, lighter and more durable to aging wind turbines. Active flow control (AFC) is a possible remedy to boundary layer separation, including rough surface effects. Currently, three arrays of synthetic jet actuators are controlled based on state estimation provided by feedback from hot-film and pressure sensors. The unsteady pressure sensors' data are used to estimate the lift while the unsteady and un-calibrated hot-films data are used to determine the flow separation location and define the relative magnitude of actuation imparted by each of the three actuator rows. The aerodynamic results demonstrate that the "clean" turbine blade performance, with lift-based controller, is recovered by the closed-loop active flow control system at Reynolds numbers around half a million and excitation at Strouhal numbers larger than 10. The total closed-loop AFC system energy efficiency was measured and shown to increase by up to 60 % compared to the airfoil with degraded surface quality. The current results indicate the potential of a closed-loop AFC system to provide significant increase in the net energy harvesting capability of a wind turbine blade with degraded surface quality

  6. MAGNETIC RECONNECTION: FROM 'OPEN' EXTREME-ULTRAVIOLET LOOPS TO CLOSED POST-FLARE ONES OBSERVED BY SDO

    SciTech Connect

    Zhang, Jun; Yang, Shuhong; Li, Ting; Zhang, Yuzong; Li, Leping; Jiang, Chaowei E-mail: shuhongyang@nao.cas.cn E-mail: yuzong@nao.cas.cn E-mail: cwjiang@spaceweather.ac.cn

    2013-10-10

    We employ Solar Dynamics Observatory observations and select three well-observed events including two flares and one extreme-ultraviolet (EUV) brightening. During the three events, the EUV loops clearly changed. One event was related to a major solar flare that took place on 2012 July 12 in active region NOAA AR 11520. 'Open' EUV loops rooted in a facula of the AR deflected to the post-flare loops and then merged with them while the flare ribbon approached the facula. Meanwhile, 'open' EUV loops rooted in a pore disappeared from top to bottom as the flare ribbon swept over the pore. The loop evolution was similar in the low-temperature channels (e.g., 171 Å) and the high-temperature channels (e.g., 94 Å). The coronal magnetic fields extrapolated from the photospheric vector magnetograms also show that the fields apparently 'open' prior to the flare become closed after it. The other two events were associated with a B1.1 flare on 2010 May 24 and an EUV brightening on 2013 January 03, respectively. During both of these two events, some 'open' loops either disappeared or darkened before the formation of new closed loops. We suggest that the observations reproduce the picture predicted by the standard magnetic reconnection model: 'open' magnetic fields become closed due to reconnection, manifesting as a transformation from 'open' EUV loops to closed post-flare ones.

  7. Closed-Loop Performance Measures for Flight Controllers Subject to Neutron-Induced Upsets

    NASA Technical Reports Server (NTRS)

    Gray, W. Steven; Zhang, Hong; Gonzalex, Oscar R.

    2003-01-01

    It has been observed that atmospheric neutrons can produce single event upsets in digital flight control hardware. The phenomenon has been studied extensively at the chip level, and now system level experiments are underway. In this paper analytical closed-loop performance measures for the tracking error are developed for a plant that is stabilized by a recoverable computer system subject to neutron induced upsets. The underlying model is a Markov jump-linear system with process noise. The steady-state tracking error is expressed in terms of a generalized observability Gramian.

  8. A Hardware Platform for Tuning of MEMS Devices Using Closed-Loop Frequency Response

    NASA Technical Reports Server (NTRS)

    Ferguson, Michael I.; MacDonald, Eric; Foor, David

    2005-01-01

    We report on the development of a hardware platform for integrated tuning and closed-loop operation of MEMS gyroscopes. The platform was developed and tested for the second generation JPL/Boeing Post-Resonator MEMS gyroscope. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). A software interface allows the user to configure, calibrate, and tune the bias voltages on the micro-gyro. The interface easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

  9. Time Difference Amplifier with Robust Gain Using Closed-Loop Control

    NASA Astrophysics Data System (ADS)

    Nakura, Toru; Mandai, Shingo; Ikeda, Makoto; Asada, Kunihiro

    This paper presents a Time Difference Amplifier (TDA) that amplifies the input time difference into the output time difference. Cross coupled chains of variable delay cells with the same number of stages are applicable for TDA, and the gain is adjusted via the closed-loop control. The TDA was fabricated using 65nm CMOS and the measurement results show that the time difference gain is 4.78 at a nominal power supply while the designed gain is 4.0. The gain is stable enough to be less than 1.4% gain shift under ±10% power supply voltage fluctuation.

  10. Development of a Closed Loop Simulator for Poloidal Field Control in DIII-D

    SciTech Connect

    J.A. Leuer; M.L. Walker; D.A. Humphreys; J.R. Ferron; A. Nerem; B.G. Penaflor

    1999-11-01

    The design of a model-based simulator of the DIII-D poloidal field system is presented. The simulator is automatically configured to match a particular DIII-D discharge circuit. The simulator can be run in a data input mode, in which prior acquired DIII-D shot data is input to the simulator, or in a stand-alone predictive mode, in which the model operates in closed loop with the plasma control system. The simulator is used to design and validate a multi-input-multi-output controller which has been implemented on DIII-D to control plasma shape. Preliminary experimental controller results are presented.

  11. Model-Based, Closed-Loop Control of PZT Creep for Cavity Ring-Down Spectroscopy

    PubMed Central

    McCartt, A D; Ognibene, T J; Bench, G; Turteltaub, K W

    2014-01-01

    Cavity ring-down spectrometers typically employ a PZT stack to modulate the cavity transmission spectrum. While PZTs ease instrument complexity and aid measurement sensitivity, PZT hysteresis hinders the implementation of cavity-length-stabilized, data-acquisition routines. Once the cavity length is stabilized, the cavity’s free spectral range imparts extreme linearity and precision to the measured spectrum’s wavelength axis. Methods such as frequency-stabilized cavity ring-down spectroscopy have successfully mitigated PZT hysteresis, but their complexity limits commercial applications. Described herein is a single-laser, model-based, closed-loop method for cavity length control. PMID:25395738

  12. Wind tunnel testing of a closed-loop wake deflection controller for wind farm power maximization

    NASA Astrophysics Data System (ADS)

    Campagnolo, Filippo; Petrović, Vlaho; Schreiber, Johannes; Nanos, Emmanouil M.; Croce, Alessandro; Bottasso, Carlo L.

    2016-09-01

    This paper presents results from wind tunnel tests aimed at evaluating a closed- loop wind farm controller for wind farm power maximization by wake deflection. Experiments are conducted in a large boundary layer wind tunnel, using three servo-actuated and sensorized wind turbine scaled models. First, we characterize the impact on steady-state power output of wake deflection, achieved by yawing the upstream wind turbines. Next, we illustrate the capability of the proposed wind farm controller to dynamically driving the upstream wind turbines to the optimal yaw misalignment setting.

  13. Fuzzy PID controller combines with closed-loop optimal fuzzy reasoning for pitch control system

    NASA Astrophysics Data System (ADS)

    Li, Yezi; Xiao, Cheng; Sun, Jinhao

    2013-03-01

    PID and fuzzy PID controller are applied into the pitch control system. PID control has simple principle and its parameters setting are rather easy. Fuzzy control need not to establish the mathematical of the control system and has strong robustness. The advantages of fuzzy PID control are simple, easy in setting parameters and strong robustness. Fuzzy PID controller combines with closed-loop optimal fuzzy reasoning (COFR), which can effectively improve the robustness, when the robustness is special requirement. MATLAB software is used for simulations, results display that fuzzy PID controller which combines with COFR has better performances than PID controller when errors exist.

  14. Modified function projective synchronization of hyperchaotic systems through Open-Plus-Closed-Loop coupling

    NASA Astrophysics Data System (ADS)

    Sudheer, K. Sebastian; Sabir, M.

    2010-04-01

    Recently introduced modified function projective synchronization (MFPS) in which chaotic systems synchronize up to a scaling function matrix has important applications in secure communications. We design coupling function for unidirectional coupling in identical and mismatched hyperchaotic oscillators to realize MFPS through Open-Plus-Closed-Loop (OPCL) coupling method. The arbitrary scaling function matrix elements are properly chosen such that we can produce function projective synchronization, synchronization, anti-synchronization and amplitude death on desired states of the response system simultaneously. Numerical simulations on identical hyperchaotic Rossler and mismatched hyperchaotic Lu system are presented to verify the effectiveness of the proposed scheme. A secure communication scheme based on MFPS is also presented.

  15. New trends in diabetes management: mobile telemedicine closed-loop system.

    PubMed

    Hernando, M Elena; Gómez, Enrique J; Gili, Antonio; Gómez, Mónica; García, Gema; del Pozo, Francisco

    2004-01-01

    The rapid growth and development of information technologies over recent years, in the areas of mobile and wireless technologies is shaping a new technological scenario of telemedicine in diabetes. This telemedicine scenario can play an important role for further acceptance by diabetic patients of the existing continuous glucose monitoring systems and insulin pumps with the final goal of improving current therapeutic procedures. This paper describes a Personal Smart Assistant integrated in a multi-access telemedicine architecture for the implementation of a mobile telemedicine closed-loop system for diabetes management. The system is being evaluated within the European Union project named INCA ("Intelligent Control Assistant for Diabetes").

  16. Design of biomass management systems and components for closed loop life support systems

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The goal of the EGM 4000/1 Design class was to investigate a Biomass Management System (BMS) and design, fabricate, and test components for biomass management in a closed-loop life support system (CLLSS). The designs explored were to contribute to the development of NASA's Controlled Ecological Life Support System (CELSS) at Kennedy Space Center. Designs included a sectored plant growth unit, a container and transfer mechanism, and an air curtain system for fugitive particle control. The work performed by the class members is summarized.

  17. Fuzzy control for closed-loop, patient-specific hypnosis in intraoperative patients: a simulation study.

    PubMed

    Moore, Brett L; Pyeatt, Larry D; Doufas, Anthony G

    2009-01-01

    Research has demonstrated the efficacy of closed-loop control of anesthesia using bispectral index (BIS) as the controlled variable, and the recent development of model-based, patient-adaptive systems has considerably improved anesthetic control. To further explore the use of model-based control in anesthesia, we investigated the application of fuzzy control in the delivery of patient-specific propofol-induced hypnosis. In simulated intraoperative patients, the fuzzy controller demonstrated clinically acceptable performance, suggesting that further study is warranted.

  18. Bolusing frequency and amount impacts glucose control during hybrid closed-loop.

    PubMed

    Bally, L; Thabit, H; Ruan, Y; Mader, J K; Kojzar, H; Dellweg, S; Benesch, C; Hartnell, S; Leelarathna, L; Wilinska, M E; Evans, M L; Arnolds, S; Pieber, T R; Hovorka, R

    2017-07-29

    To compare bolus insulin delivery patterns during closed-loop home studies in adults with suboptimally [HbA1c 58-86 mmol/mol (7.5%-10%)] and well-controlled [58 mmol/mol (< 7.5%)] Type 1 diabetes. Retrospective analysis of daytime and night-time insulin delivery during home use of closed-loop over 4 weeks. Daytime and night-time controller effort, defined as amount of insulin delivered by closed-loop relative to usual basal insulin delivery, and daytime bolus effort, defined as total bolus insulin delivery relative to total daytime insulin delivery were compared between both cohorts. Correlation analysis was performed between individual bolus behaviour (bolus effort and frequency) and daytime controller efforts, and proportion of time spent within and below sensor glucose target range. Individuals with suboptimally controlled Type 1 diabetes had significantly lower bolus effort (P = 0.038) and daily bolus frequency (P < 0.001) compared with those with well-controlled diabetes. Controller effort during both daytime (P = 0.007) and night-time (P = 0.005) were significantly higher for those with suboptimally controlled Type 1 diabetes. Time when glucose was within the target range (3.9-10.0 mmol/L) during daytime correlated positively with bolus effort (r = 0.37, P = 0.016) and bolus frequency (r = 0.33, P = 0.037). Time when glucose was below the target range during daytime was comparable in both groups (P = 0.36), and did not correlate significantly with bolus effort (r = 0.28, P = 0.066) or bolus frequency (r = -0.21, P = 0.19). More frequent bolusing and higher proportion of insulin delivered as bolus during hybrid closed-loop use correlated positively with time glucose was in target range. This emphasises the need for user input and educational support to benefit from this novel therapeutic modality. © 2017 The Authors. Diabetic Medicine published by John Wiley & Sons Ltd on behalf of Diabetes UK.

  19. Closing the loop on nursing library instruction: using student performance to improve outcomes.

    PubMed

    Moreton, Elizabeth O; Conklin, Jamie L

    2015-01-01

    Two librarians analyzed nursing students' performance on an information literacy assignment to determine how they could change their instruction to better assist the students in comprehending the material. After identifying major areas of difficulty, including the use of search techniques, they revised both the instruction and the assignment, closing the loop by utilizing their assessment data. Next, they analyzed those results to evaluate the effectiveness of their changes and to make further improvements, thus demonstrating the iterative nature of instruction and assessment. The evidence-based instruction cycle of teaching, assessing, and revising should be repeated frequently to keep the assignment fresh and relevant.

  20. Gas powered, closed loop power system and process for using same

    SciTech Connect

    Cardone, J.T.; Dill, J.M.; Shatz, K.J.

    1982-06-08

    This invention relates to a gas powered, closed loop power generating system which generates power substantially as a result of the flow of gas through its power generating means. Gas flows through the power generating means because of a pressure drop caused by dissolving the gas in a solvent medium on the exit side of the power generating means. The solution is then separated into the solvent medium, and the gas. The gas pressure is raised and it is then fed back into the power generating means while the separated solvent medium is recycled to redissolve more exiting gas. A process for generating power is also disclosed.

  1. Closed-loop control for tip-tilt compensation on systems under vibration

    NASA Astrophysics Data System (ADS)

    Castro, Mario; Escárate, Pedro; Garcés, Javier; Zúñiga, Sebastián.; Rojas, Diego; Marchioni, José; Guesalaga, Andrés.

    2016-07-01

    Mechanical vibrations affect the performance in modern adaptive optics systems. These structural vibrations induce aberration mainly in tip-tilt modes that reduce the accuracy of the astronomical instrument. Therefore, control actions need to be taken. With this purpose we present a laboratory demonstration of vibration rejection of tip-tilt modes using closed-loop control, inducing vibration on the test bench via an eccentric motor with controllable frequency, in order to simulate the structural vibrations mentioned above. We measure the laser vibration and its tip-tilt aberration using a camera and a Shack Hartmann Wave Front Sensor. The control action is carried out by a Fast Steering Mirror (FSM).

  2. A Hardware Platform for Tuning of MEMS Devices Using Closed-Loop Frequency Response

    NASA Technical Reports Server (NTRS)

    Ferguson, Michael I.; MacDonald, Eric; Foor, David

    2005-01-01

    We report on the development of a hardware platform for integrated tuning and closed-loop operation of MEMS gyroscopes. The platform was developed and tested for the second generation JPL/Boeing Post-Resonator MEMS gyroscope. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). A software interface allows the user to configure, calibrate, and tune the bias voltages on the micro-gyro. The interface easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

  3. Pharmacokinetics of Insulin Aspart and Glucagon in Type 1 Diabetes during Closed-Loop Operation

    PubMed Central

    Haidar, Ahmad; Duval, Claire; Legault, Laurent; Rabasa-Lhoret, Rémi

    2013-01-01

    Background We assessed the pharmacokinetics of subcutaneous insulin aspart and glucagon during closed-loop operation and their relationship with body composition variables. Methods We retrospectively analyzed data collected from closed-loop experiments in 15 type 1 diabetes patients (age 47.1 ± 12.3 years, body mass index 25.9 ± 4.6 kg/m2, glycated hemoglobin 7.9% ± 0.7%). Patients received an evening meal accompanied with prandial insulin bolus and stayed in the clinical facility until the next morning. Glucose levels were regulated by dual-hormone closed-loop delivery. Insulin and glucagon were delivered using two subcutaneous infusion pumps installed on the abdominal wall. Plasma insulin and glucagon were measured every 10–30 min. Percentage of body fat, percentage of fat in the abdominal area, and mass of abdominal fat were measured by dual X-ray absorptiometry. Results A pharmacokinetic model estimated time-to-peak plasma concentrations [tmax insulin 51 (19) min, tmax glucagon 19 (4) min, mean (standard deviation)], metabolic clearance rate [MCR insulin 0.019 (0.015–0.026) liter/kg/min, MCR glucagon 0.012 (0.010–0.014) liter/kg/min, median (interquartile range)], and the background plasma concentrations [Ib insulin 10.2 (6.3–15.2) mU/liter, Ib glucagon 50 (45–56) pg/ml, median (interquartile range)]. tmax correlated positively between insulin and glucagon (r = 0.7; p = .007) while MCR correlated negatively (r = -0.7; p = .015). In this small sample size, tmax, MCR, and Ib of insulin and glucagon did not correlate with percentage of body fat, percentage of fat in the abdominal area, or total mass of abdominal fat. Conclusions Insulin and glucagon pharmacokinetics might be related during closed-loop operation. Our data suggest that slower absorption of insulin is associated with slower absorption of glucagon. Body composition does not seem to influence insulin and glucagon pharmacokinetics. PMID:24351176

  4. Pharmacokinetics of insulin aspart and glucagon in type 1 diabetes during closed-loop operation.

    PubMed

    Haidar, Ahmad; Duval, Claire; Legault, Laurent; Rabasa-Lhoret, Rémi

    2013-11-01

    We assessed the pharmacokinetics of subcutaneous insulin aspart and glucagon during closed-loop operation and their relationship with body composition variables. We retrospectively analyzed data collected from closed-loop experiments in 15 type 1 diabetes patients (age 47.1 ± 12.3 years, body mass index 25.9 ± 4.6 kg/m², glycated hemoglobin 7.9% ± 0.7%). Patients received an evening meal accompanied with prandial insulin bolus and stayed in the clinical facility until the next morning. Glucose levels were regulated by dual-hormone closed-loop delivery. Insulin and glucagon were delivered using two subcutaneous infusion pumps installed on the abdominal wall. Plasma insulin and glucagon were measured every 10-30 min. Percentage of body fat, percentage of fat in the abdominal area, and mass of abdominal fat were measured by dual X-ray absorptiometry. A pharmacokinetic model estimated time-to-peak plasma concentrations [t(max) insulin 51 (19) min, t(max) glucagon 19 (4) min, mean (standard deviation)], metabolic clearance rate [MCR insulin 0.019 (0.015-0.026) liter/kg/min, MCR glucagon 0.012 (0.010-0.014) liter/kg/min, median (interquartile range)], and the background plasma concentrations [I(b) insulin 10.2 (6.3-15.2) mU/liter, I(b) glucagon 50 (45-56) pg/ml, median (interquartile range)]. t(max) correlated positively between insulin and glucagon (r = 0.7; p = .007) while MCR correlated negatively (r = -0.7; p = .015). In this small sample size, t(max), MCR, and I(b) of insulin and glucagon did not correlate with percentage of body fat, percentage of fat in the abdominal area, or total mass of abdominal fat. Insulin and glucagon pharmacokinetics might be related during closed-loop operation. Our data suggest that slower absorption of insulin is associated with slower absorption of glucagon. Body composition does not seem to influence insulin and glucagon pharmacokinetics. © 2013 Diabetes Technology Society.

  5. Closed-loop phase diagrams, vaporization, and multicriticality in binary liquid mixtures

    NASA Astrophysics Data System (ADS)

    Caflisch, Robert G.; Walker, James S.

    1983-09-01

    The coupled Potts-Ising models of Walker and Vause, which successfully describe closed-loop phase diagrams in hydrogen-bonding mixtures, are generalized to encompass the vapor phase, and are studied using position-space renormalization-group techniques. Global phase diagrams are generated, exhibiting such features as miscibility-immiscibility criticality, liquid-vapor critical points, critical end points, and bicritical and tricritical points. In addition, new types of phase diagrams are found, involving upper and lower azeotropes, for example, which are expected to be physically realizable in experimental systems.

  6. Tool for Turbine Engine Closed-Loop Transient Analysis (TTECTrA) Users' Guide

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Zinnecker, Alicia M.

    2014-01-01

    The tool for turbine engine closed-loop transient analysis (TTECTrA) is a semi-automated control design tool for subsonic aircraft engine simulations. At a specific flight condition, TTECTrA produces a basic controller designed to meet user-defined goals and containing only the fundamental limiters that affect the transient performance of the engine. The purpose of this tool is to provide the user a preliminary estimate of the transient performance of an engine model without the need to design a full nonlinear controller.

  7. Domain Hierarchy and closed Loops (DHcL): a server for exploring hierarchy of protein domain structure

    PubMed Central

    Koczyk, Grzegorz; Berezovsky, Igor N.

    2008-01-01

    Domain hierarchy and closed loops (DHcL) (http://sitron.bccs.uib.no/dhcl/) is a web server that delineates energy hierarchy of protein domain structure and detects domains at different levels of this hierarchy. The server also identifies closed loops and van der Waals locks, which constitute a structural basis for the protein domain hierarchy. The DHcL can be a useful tool for an express analysis of protein structures and their alternative domain decompositions. The user submits a PDB identifier(s) or uploads a 3D protein structure in a PDB format. The results of the analysis are the location of domains at different levels of hierarchy, closed loops, van der Waals locks and their interactive visualization. The server maintains a regularly updated database of domains, closed loop and van der Waals locks for all X-ray structures in PDB. DHcL server is available at: http://sitron.bccs.uib.no/dhcl. PMID:18502776

  8. Closed-loop focal plane wavefront control with the SCExAO instrument

    NASA Astrophysics Data System (ADS)

    Martinache, Frantz; Jovanovic, Nemanja; Guyon, Olivier

    2016-09-01

    Aims: This article describes the implementation of a focal plane based wavefront control loop on the high-contrast imaging instrument SCExAO (Subaru Coronagraphic Extreme Adaptive Optics). The sensor relies on the Fourier analysis of conventional focal-plane images acquired after an asymmetric mask is introduced in the pupil of the instrument. Methods: This absolute sensor is used here in a closed-loop to compensate for the non-common path errors that normally affects any imaging system relying on an upstream adaptive optics system.This specific implementation was used to control low-order modes corresponding to eight zernike modes (from focus to spherical). Results: This loop was successfully run on-sky at the Subaru Telescope and is used to offset the SCExAO deformable mirror shape used as a zero-point by the high-order wavefront sensor. The paper details the range of errors this wavefront-sensing approach can operate within and explores the impact of saturation of the data and how it can be bypassed, at a cost in performance. Conclusions: Beyond this application, because of its low hardware impact, the asymmetric pupil Fourier wavefront sensor (APF-WFS) can easily be ported in a wide variety of wavefront sensing contexts, for ground- as well space-borne telescopes, and for telescope pupils that can be continuous, segmented or even sparse. The technique is powerful because it measures the wavefront where it really matters, at the level of the science detector.

  9. Molecular dynamics simulations of "loop closing" in the enzyme triose phosphate isomerase.

    PubMed

    Brown, F K; Kollman, P A

    1987-12-05

    We present molecular dynamics simulations on the active site region of dimeric triose phosphate isomerase (TIM) using the co-ordinates of native chicken muscle TIM as a starting point and performing simulations with no substrate, with dihydroxyacetone phosphate (DHAP), the natural substrate, and with dihydroxyacetone sulfate (DHAS), a substrate analog. Whereas most of the protein moves less than 1 A during the simulation, some residues in the active site loop move more than 8 A during the 10.5 picoseconds of dynamics for each of the simulations. Most interestingly, the nature of the loop motion depends on the substrate, with the largest motion found in the presence of DHAP, and only in the presence of DHAP does the loop move to "close off" the active site pocket. The final structure found for the DHAP-chicken TIM complex is qualitatively similar to that described by Alber et al. for DHAP-yeast TIM. Simulations on the monomeric protein gives insight into why the molecule is active only as a dimer.

  10. Overnight closed-loop insulin delivery in young people with type 1 diabetes: a free-living, randomized clinical trial.

    PubMed

    Hovorka, Roman; Elleri, Daniela; Thabit, Hood; Allen, Janet M; Leelarathna, Lalantha; El-Khairi, Ranna; Kumareswaran, Kavita; Caldwell, Karen; Calhoun, Peter; Kollman, Craig; Murphy, Helen R; Acerini, Carlo L; Wilinska, Malgorzata E; Nodale, Marianna; Dunger, David B

    2014-01-01

    To evaluate feasibility, safety, and efficacy of overnight closed-loop insulin delivery in free-living youth with type 1 diabetes. Overnight closed loop was evaluated at home by 16 pump-treated adolescents with type 1 diabetes aged 12-18 years. Over a 3-week period, overnight insulin delivery was directed by a closed-loop system, and on another 3-week period sensor-augmented therapy was applied. The order of interventions was random. The primary end point was time when adjusted sensor glucose was between 3.9 and 8.0 mmol/L from 2300 to 0700 h. Closed loop was constantly applied over at least 4 h on 269 nights (80%); sensor data were collected over at least 4 h on 282 control nights (84%). Closed loop increased time spent with glucose in target by a median 15% (interquartile range -9 to 43; P < 0.001). Mean overnight glucose was reduced by a mean 14 (SD 58) mg/dL (P < 0.001). Time when glucose was <70 mg/dL was low in both groups, but nights with glucose <63 mg/dL for at least 20 min were less frequent during closed loop (10 vs. 17%; P = 0.01). Despite lower total daily insulin doses by a median 2.3 (interquartile range -4.7 to 9.3) units (P = 0.009), overall 24-h glucose was reduced by a mean 9 (SD 41) mg/dL (P = 0.006) during closed loop. Unsupervised home use of overnight closed loop in adolescents with type 1 diabetes is safe and feasible. Glucose control was improved during the day and night with fewer episodes of nocturnal hypoglycemia.

  11. Overnight Closed-Loop Insulin Delivery in Young People With Type 1 Diabetes: A Free-Living, Randomized Clinical Trial

    PubMed Central

    Hovorka, Roman; Elleri, Daniela; Thabit, Hood; Allen, Janet M.; Leelarathna, Lalantha; El-Khairi, Ranna; Kumareswaran, Kavita; Caldwell, Karen; Calhoun, Peter; Kollman, Craig; Murphy, Helen R.; Acerini, Carlo L.; Wilinska, Malgorzata E.; Nodale, Marianna; Dunger, David B.

    2014-01-01

    OBJECTIVE To evaluate feasibility, safety, and efficacy of overnight closed-loop insulin delivery in free-living youth with type 1 diabetes. RESEARCH DESIGN AND METHODS Overnight closed loop was evaluated at home by 16 pump-treated adolescents with type 1 diabetes aged 12–18 years. Over a 3-week period, overnight insulin delivery was directed by a closed-loop system, and on another 3-week period sensor-augmented therapy was applied. The order of interventions was random. The primary end point was time when adjusted sensor glucose was between 3.9 and 8.0 mmol/L from 2300 to 0700 h. RESULTS Closed loop was constantly applied over at least 4 h on 269 nights (80%); sensor data were collected over at least 4 h on 282 control nights (84%). Closed loop increased time spent with glucose in target by a median 15% (interquartile range −9 to 43; P < 0.001). Mean overnight glucose was reduced by a mean 14 (SD 58) mg/dL (P < 0.001). Time when glucose was <70 mg/dL was low in both groups, but nights with glucose <63 mg/dL for at least 20 min were less frequent during closed loop (10 vs. 17%; P = 0.01). Despite lower total daily insulin doses by a median 2.3 (interquartile range −4.7 to 9.3) units (P = 0.009), overall 24-h glucose was reduced by a mean 9 (SD 41) mg/dL (P = 0.006) during closed loop. CONCLUSIONS Unsupervised home use of overnight closed loop in adolescents with type 1 diabetes is safe and feasible. Glucose control was improved during the day and night with fewer episodes of nocturnal hypoglycemia. PMID:24757227

  12. A Closed-loop Brain Computer Interface to a Virtual Reality Avatar: Gait Adaptation to Visual Kinematic Perturbations

    PubMed Central

    Luu, Trieu Phat; He, Yongtian; Brown, Samuel; Nakagome, Sho; Contreras-Vidal, Jose L.

    2016-01-01

    The control of human bipedal locomotion is of great interest to the field of lower-body brain computer interfaces (BCIs) for rehabilitation of gait. While the feasibility of a closed-loop BCI system for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a virtual reality (BCI-VR) environment has yet to be demonstrated. In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control the walking movements of a virtual avatar. Moreover, virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. These findings have implications for the development of BCI-VR systems for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI system. PMID:27713915

  13. Evolving Refractory Major Depressive Disorder Diagnostic and Treatment Paradigms: Toward Closed-Loop Therapeutics

    PubMed Central

    Ward, Matthew P.; Irazoqui, Pedro P.

    2010-01-01

    Current antidepressant therapies do not effectively control or cure depressive symptoms. Pharmaceutical therapies altogether fail to address an estimated 4 million Americans who suffer from a recurrent and severe treatment-resistant form of depression known as refractory major depressive disorder. Subjective diagnostic schemes, differing manifestations of the disorder, and antidepressant treatments with limited theoretical bases each contribute to the general lack of therapeutic efficacy and differing levels of treatment resistance in the refractory population. Stimulation-based therapies, such as vagus nerve stimulation, transcranial magnetic stimulation, and deep brain stimulation, are promising treatment alternatives for this treatment-resistant subset of patients, but are plagued with inconsistent reports of efficacy and variable side effects. Many of these problems stem from the unknown mechanisms of depressive disorder pathogenesis, which prevents the development of treatments that target the specific underlying causes of the disorder. Other problems likely arise due to the non-specific stimulation of various limbic and paralimbic structures in an open-loop configuration. This review critically assesses current literature on depressive disorder diagnostic methodologies, treatment schemes, and pathogenesis in order to emphasize the need for more stringent depressive disorder classifications, quantifiable biological markers that are suitable for objective diagnoses, and alternative closed-loop treatment options tailored to well-defined forms of the disorder. A closed-loop neurostimulation device design framework is proposed, utilizing symptom-linked biomarker abnormalities as control points for initiating and terminating a corrective electrical stimulus which is autonomously optimized for correcting the magnitude and direction of observed biomarker abnormality. PMID:20631824

  14. Evolving refractory major depressive disorder diagnostic and treatment paradigms: toward closed-loop therapeutics.

    PubMed

    Ward, Matthew P; Irazoqui, Pedro P

    2010-01-01

    Current antidepressant therapies do not effectively control or cure depressive symptoms. Pharmaceutical therapies altogether fail to address an estimated 4 million Americans who suffer from a recurrent and severe treatment-resistant form of depression known as refractory major depressive disorder. Subjective diagnostic schemes, differing manifestations of the disorder, and antidepressant treatments with limited theoretical bases each contribute to the general lack of therapeutic efficacy and differing levels of treatment resistance in the refractory population. Stimulation-based therapies, such as vagus nerve stimulation, transcranial magnetic stimulation, and deep brain stimulation, are promising treatment alternatives for this treatment-resistant subset of patients, but are plagued with inconsistent reports of efficacy and variable side effects. Many of these problems stem from the unknown mechanisms of depressive disorder pathogenesis, which prevents the development of treatments that target the specific underlying causes of the disorder. Other problems likely arise due to the non-specific stimulation of various limbic and paralimbic structures in an open-loop configuration. This review critically assesses current literature on depressive disorder diagnostic methodologies, treatment schemes, and pathogenesis in order to emphasize the need for more stringent depressive disorder classifications, quantifiable biological markers that are suitable for objective diagnoses, and alternative closed-loop treatment options tailored to well-defined forms of the disorder. A closed-loop neurostimulation device design framework is proposed, utilizing symptom-linked biomarker abnormalities as control points for initiating and terminating a corrective electrical stimulus which is autonomously optimized for correcting the magnitude and direction of observed biomarker abnormality.

  15. Physiological closed-loop control in intelligent oxygen therapy: A review.

    PubMed

    Sanchez-Morillo, Daniel; Olaby, Osama; Fernandez-Granero, Miguel Angel; Leon-Jimenez, Antonio

    2017-07-01

    Oxygen therapy has become a standard care for the treatment of patients with chronic obstructive pulmonary disease and other hypoxemic chronic lung diseases. In current systems, manually continuous adjustment of O2 flow rate is a time-consuming task, often unsuccessful, that requires experienced staff. The primary aim of this systematic review is to collate and report on the principles, algorithms and accuracy of autonomous physiological close-loop controlled oxygen devices as well to present recommendations for future research and studies in this area. A literature search was performed on medical database MEDLINE, engineering database IEEE-Xplore and wide-raging scientific databases Scopus and Web of Science. A narrative synthesis of the results was carried out. A summary of the findings of this review suggests that when compared to the conventional manual practice, the closed-loop controllers maintain higher saturation levels, spend less time below the target saturation, and save oxygen resources. Nonetheless, despite of their potential, autonomous oxygen therapy devices are scarce in real clinical applications. Robustness of control algorithms, fail-safe mechanisms, limited reliability of sensors, usability issues and the need for standardized evaluating methods of assessing risks can be among the reasons for this lack of matureness and need to be addressed before the wide spreading of a new generation of automatic oxygen devices. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Closed-loop control concept for kinematic 3D-profile bending

    NASA Astrophysics Data System (ADS)

    Staupendahl, Daniel; Chatti, Sami; Tekkaya, A. Erman

    2016-10-01

    Kinematic tube and profile bending processes produce bending contours by the relative movement of single process axes. Tools only need to be adapted to fit the cross-section of the tubular material. While offering a great flexibility in production, kinematic bending processes cause a high part springback and as a result, compensatory methods are needed to achieve target contours. These compensatory methods are generally embedded in bending tables or analytical calculations that in turn are embedded into the process control software. This procedure can cope with known material behavior, as for instance gained through a tensile test of the material batch prior to the bending process. Material variations inside a batch cannot be detected however and cause contour deviations. To counter this error, a closed-loop control system can be used, which can quickly adapt axes' movements to produce target shapes and thus reduce scrap. In this paper, two methods to apply closed-loop control to 3D profile bending will be presented. An indirect approach, using the bending force and torque, and a direct approach, by measuring the profile contour after bending.

  17. A wirelessly-powered homecage with animal behavior analysis and closed-loop power control.

    PubMed

    Yaoyao Jia; Zheyuan Wang; Canales, Daniel; Tinkler, Morgan; Chia-Chun Hsu; Madsen, Teresa E; Mirbozorgi, S Abdollah; Rainnie, Donald; Ghovanloo, Maysam

    2016-08-01

    This paper presents a new EnerCage-homecage system, EnerCage-HC2, for longitudinal electrophysiology data acquisition experiments on small freely moving animal subjects, such as rodents. EnerCage-HC2 is equipped with multi-coil wireless power transmission (WPT), closed-loop power control, bidirectional data communication via Bluetooth Low Energy (BLE), and Microsoft Kinect® based animal behavior tracking and analysis. The EnerCage-HC2 achieves a homogeneous power transfer efficiency (PTE) of 14% on average, with ~42 mW power delivered to the load (PDL) at a nominal height of 7 cm by the closed-loop power control mechanism. The Microsoft Kinect® behavioral analysis algorithm can not only track the animal position in real-time but also classify 5 different types of rodent behaviors: standstill, walking, grooming, rearing, and rotating. A proof-of-concept in vivo experiment was conducted on two awake freely behaving rats while successfully operating a one-channel stimulator and generating an ethogram.

  18. Inventory decision in a closed-loop supply chain with inspection, sorting, and waste disposal

    NASA Astrophysics Data System (ADS)

    Dwicahyani, A. R.; Jauhari, W. A.; Kurdhi, N. A.

    2016-02-01

    The study of returned item inventory management in a closed-loop supply chain system has become an important issue in recent years. So far, investigations about inventory decision making in a closed-loop supply chain system have been confined to traditional forward and reverse oriented material flow supply chain. In this study, we propose an integrated inventory model consisting a supplier, a manufacturer, and a retailer where the manufacturer inspects all of the returned items collected from the customers and classifies them as recoverable or waste. Returned items that recovered through the remanufacturing process and the newly manufactured products are then used to meet the demand of the retailer. However, some recovered items which are not comparable to the ones in quality, classified as refurbished items, are sold to a secondary market at a reduced price. This study also suggests that the flow of returned items is controlled by a decision variable, namely an acceptance quality level of recoverable item in the system. We apply multiple remanufacturing cycle and multiple production cycle policy to the proposed model and give the corresponding iterative procedure to determine the optimal solutions. Further, numerical examples are presented for illustrative purpose.

  19. Closed-Loop Control of Humidification for Artifact Reduction in Capacitive ECG Measurements.

    PubMed

    Leicht, Lennart; Eilebrecht, Benjamin; Weyer, Soren; Leonhardt, Steffen; Teichmann, Daniel

    2017-01-25

    Recording biosignals without the need for direct skin contact offers new opportunities for ubiquitous health monitoring. Electrodes with capacitive coupling have been shown to be suitable for the monitoring of electrical potentials on the body surface, in particular ECG. However, due to triboelectric charge generation and motion artifacts, signal and thus diagnostic quality is inferior to galvanic coupling. Active closed-loop humidification of capacitive electrodes is proposed in this work as a new concept to improve signal quality. A capacitive ECG recording system integrated into a common car seat is presented. It can regulate the micro climate at the interface of electrode and patient by actively dispensing water vapour and monitoring humidity in a closed-loop approach. As a regenerative water reservoir, silica gel is used. The system was evaluated with respect to subjective and objective ECG signal quality. Active humidification was found to have a significant positive effect in case of previously poor quality. Also, it had no diminishing effect in case of already good signal quality.

  20. Algorithms for a Closed-Loop Artificial Pancreas: The Case for Model Predictive Control

    PubMed Central

    Bequette, B. Wayne

    2013-01-01

    The relative merits of model predictive control (MPC) and proportional-integral-derivative (PID) control are discussed, with the end goal of a closed-loop artificial pancreas (AP). It is stressed that neither MPC nor PID are single algorithms, but rather are approaches or strategies that may be implemented very differently by different engineers. The primary advantages to MPC are that (i) constraints on the insulin delivery rate (and/or insulin on board) can be explicitly included in the control calculation; (ii) it is a general framework that makes it relatively easy to include the effect of meals, exercise, and other events that are a function of the time of day; and (iii) it is flexible enough to include many different objectives, from set-point tracking (target) to zone (control to range). In the end, however, it is recognized that the control algorithm, while important, represents only a portion of the effort required to develop a closed-loop AP. Thus, any number of algorithms/approaches can be successful—the engineers involved in the design must have experience with the particular technique, including the important experience of implementing the algorithm in human studies and not simply through simulation studies. PMID:24351190

  1. A reconfigurable visual-programming library for real-time closed-loop cellular electrophysiology.

    PubMed

    Biró, István; Giugliano, Michele

    2015-01-01

    Most of the software platforms for cellular electrophysiology are limited in terms of flexibility, hardware support, ease of use, or re-configuration and adaptation for non-expert users. Moreover, advanced experimental protocols requiring real-time closed-loop operation to investigate excitability, plasticity, dynamics, are largely inaccessible to users without moderate to substantial computer proficiency. Here we present an approach based on MATLAB/Simulink, exploiting the benefits of LEGO-like visual programming and configuration, combined to a small, but easily extendible library of functional software components. We provide and validate several examples, implementing conventional and more sophisticated experimental protocols such as dynamic-clamp or the combined use of intracellular and extracellular methods, involving closed-loop real-time control. The functionality of each of these examples is demonstrated with relevant experiments. These can be used as a starting point to create and support a larger variety of electrophysiological tools and methods, hopefully extending the range of default techniques and protocols currently employed in experimental labs across the world.

  2. Anti-hypertensive effects of a closed-loop chip system in renovascular hypertensive rats.

    PubMed

    Zhou, Li-Min; Zhu, Guo-Qing; Wang, Han-Jun; Zhao, Cong-Kan; Xu, Yao; Gao, Xing-Ya

    2008-08-01

    The authors' previous study showed a closed-loop chip system that was used to control arterial pressure in normal rabbits and rats. In the present study the anti-hypertensive effects of the chip system were investigated in anaesthetized two-kidney one-clip (2K1C) renovascular hypertensive rats and compared with sham-operated rats. The chip system recorded, sampled, and processed the signals of arterial pressure and instantaneously controlled arterial pressure by stimulating the left aortic depressor nerve. The frequency of stimulation was determined according to the feedback signals of arterial pressure. The chip system, running three different programs, successfully achieved a different degree of depressor effects. It effectively decreased not only mean arterial pressure (MAP), but also renal sympathetic nerve activity (RSNA) in both 2K1C rats and sham-operated rats. The chip system significantly increased the baroreflex gain in the 2K1C rats, but not in the sham-operated rats. It normalized the increased left ventricle developing pressure and maximal rise rate of the left ventricle pressure (dP/dtmax) in the 2K1C rats. These results indicate that the depressor effect can be controlled by changing the programs of the chip system. The closed-loop chip system effectively decreased arterial pressure and sympathetic outflow, increased baroreflex gain, and normalized the enhanced cardiac contractility in renovascular hypertensive rats.

  3. Closing the Loop for Memory Prostheses: Detecting the Role of Hippocampal Neural Ensembles Using Nonlinear Models

    PubMed Central

    Hampson, Robert E.; Song, Dong; Chan, Rosa H.M.; Sweatt, Andrew J.; Riley, Mitchell R.; Goonawardena, Anushka V.; Marmarelis, Vasilis Z.; Gerhardt, Greg A.; Berger, Theodore W.; Deadwyler, Sam A.

    2012-01-01

    A major factor involved in providing closed loop feedback for control of neural function is to understand how neural ensembles encode online information critical to the final behavioral endpoint. This issue was directly assessed in rats performing a short-term delay memory task in which successful encoding of task information is dependent upon specific spatiotemporal firing patterns recorded from ensembles of CA3 and CA1 hippocampal neurons. Such patterns, extracted by a specially designed nonlinear multi-input multi-output (MIMO) nonlinear mathematical model, were used to predict successful performance online via a closed loop paradigm which regulated trial difficulty (time of retention) as a function of the “strength” of stimulus encoding. The significance of the MIMO model as a neural prosthesis has been demonstrated by substituting trains of electrical stimulation pulses to mimic these same ensemble firing patterns. This feature was used repeatedly to vary “normal” encoding as a means of understanding how neural ensembles can be “tuned” to mimic the inherent process of selecting codes of different strength and functional specificity. The capacity to enhance and tune hippocampal encoding via MIMO model detection and insertion of critical ensemble firing patterns shown here provides the basis for possible extension to other disrupted brain circuitry. PMID:22498704

  4. Wireless Magnetic-Based Closed-Loop Control of Self-Propelled Microjets

    PubMed Central

    Khalil, Islam S. M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Misra, Sarthak

    2014-01-01

    In this study, we demonstrate closed-loop motion control of self-propelled microjets under the influence of external magnetic fields. We control the orientation of the microjets using external magnetic torque, whereas the linear motion towards a reference position is accomplished by the thrust and pulling magnetic forces generated by the ejecting oxygen bubbles and field gradients, respectively. The magnetic dipole moment of the microjets is characterized using the U-turn technique, and its average is calculated to be 1.310−10 A.m2 at magnetic field and linear velocity of 2 mT and 100 µm/s, respectively. The characterized magnetic dipole moment is used in the realization of the magnetic force-current map of the microjets. This map in turn is used for the design of a closed-loop control system that does not depend on the exact dynamical model of the microjets and the accurate knowledge of the parameters of the magnetic system. The motion control characteristics in the transient- and steady-states depend on the concentration of the surrounding fluid (hydrogen peroxide solution) and the strength of the applied magnetic field. Our control system allows us to position microjets at an average velocity of 115 m/s, and within an average region-of-convergence of 365 m. PMID:24505244

  5. Can macrophyte harvesting from eutrophic water close the loop on nutrient loss from agricultural land?

    PubMed

    Quilliam, Richard S; van Niekerk, Melanie A; Chadwick, David R; Cross, Paul; Hanley, Nick; Jones, Davey L; Vinten, Andy J A; Willby, Nigel; Oliver, David M

    2015-04-01

    Eutrophication is a major water pollution issue and can lead to excessive growth of aquatic plant biomass (APB). However, the assimilation of nutrients into APB provides a significant target for their recovery and reuse, and harvesting problematic APB in impacted freshwater bodies offers a complementary approach to aquatic restoration, which could potentially deliver multiple wider ecosystem benefits. This critical review provides an assessment of opportunities and risks linked to nutrient recovery from agriculturally impacted water-bodies through the harvesting of APB for recycling and reuse as fertilisers and soil amendments. By evaluating the economic, social, environmental and health-related dimensions of this resource recovery from 'waste' process we propose a research agenda for closing the loop on nutrient transfer from land to water. We identify that environmental benefits are rarely, if ever, prioritised as essential criteria for the exploitation of resources from waste and yet this is key for addressing the current imbalance that sees environmental managers routinely undervaluing the wider environmental benefits that may accrue beyond resource recovery. The approach we advocate for the recycling of 'waste' APB nutrients is to couple the remediation of eutrophic waters with the sustainable production of feed and fertiliser, whilst providing multiple downstream benefits and minimising environmental trade-offs. This integrated 'ecosystem services approach' has the potential to holistically close the loop on agricultural nutrient loss, and thus sustainably recover finite resources such as phosphorus from waste.

  6. A closed-loop controlled electrochemically actuated micro-dosing system

    NASA Astrophysics Data System (ADS)

    Böhm, Sebastian; Timmer, Björn; Olthuis, Wouter; Bergveld, Piet

    2000-12-01

    In this paper a closed-loop controlled micromachined dosing system is presented, for the accurate manipulation of liquids in microsystems down to the nanoliter range. The applied driving force to dispense liquids originates from the electrochemical generation of gas bubbles by the electrolysis of water. The proposed dosing system comprises a micromachined channel/reservoir structure in silicon, capped with a Pyrex® cover on which a set of platinum electrodes is patterned. By adopting an interdigitated electrode geometry, the electrodes can be used for electrochemical gas generation as well as for the simultaneous determination of the total gas bubble volume, via an impedance measurement of the gas/liquid mixture in the reservoir. As this measured gas bubble volume equals the dosed liquid volume, active control of dosed volumes can be obtained. It will be shown that the cell impedance can be applied to accurately determine the generated gas volume and that by using this parameter in a closed-loop control system, dosed volumes can be controlled in the nanoliter range.

  7. Self-sensing dielectric elastomer actuators in closed-loop operation

    NASA Astrophysics Data System (ADS)

    Rosset, Samuel; O'Brien, Benjamin M.; Gisby, Todd; Xu, Daniel; Shea, Herbert R.; Anderson, Iain A.

    2013-10-01

    Because of their large output strain, dielectric elastomer actuators (DEAs) have been proposed for tunable optics applications such as tunable gratings. However, the inherent viscoelastic drift of these actuators is an important drawback and closed-loop operation of DEAs is a prerequisite for any accurate real-world application. In this paper, we show how capacitive self-sensing can be used to drive a DEA in closed-loop without the need for any external sensor. The method has been demonstrated on a DEA tunable grating based on a VHB acrylic and silicone membrane. The results show that the widely used VHB presents a time-dependent drift between the capacitance of the electrodes and their strain. The silicone-based grating does not exhibit such a drift, and its strain can be stabilized by regulating the capacitance of the device to a constant value. We also report on an new fabrication method for thin deformable gratings based on replication on a water-soluble master and a 27% change in the grating period has been obtained on a VHB-based device.

  8. A reconfigurable visual-programming library for real-time closed-loop cellular electrophysiology

    PubMed Central

    Biró, István; Giugliano, Michele

    2015-01-01

    Most of the software platforms for cellular electrophysiology are limited in terms of flexibility, hardware support, ease of use, or re-configuration and adaptation for non-expert users. Moreover, advanced experimental protocols requiring real-time closed-loop operation to investigate excitability, plasticity, dynamics, are largely inaccessible to users without moderate to substantial computer proficiency. Here we present an approach based on MATLAB/Simulink, exploiting the benefits of LEGO-like visual programming and configuration, combined to a small, but easily extendible library of functional software components. We provide and validate several examples, implementing conventional and more sophisticated experimental protocols such as dynamic-clamp or the combined use of intracellular and extracellular methods, involving closed-loop real-time control. The functionality of each of these examples is demonstrated with relevant experiments. These can be used as a starting point to create and support a larger variety of electrophysiological tools and methods, hopefully extending the range of default techniques and protocols currently employed in experimental labs across the world. PMID:26157385

  9. Closed-loop Habitation Air Revitalization Model for Regenerative Life Support Systems

    NASA Technical Reports Server (NTRS)

    Hart, Maxwell M.

    1991-01-01

    The primary function of any life support system is to keep the crew alive by providing breathable air, potable water, edible food, and for disposal of waste. In a well-balanced or regenerative life support system, the various components are each using what is available and producing what is needed by other components so that there will always be enough chemicals in the form in which they are needed. Humans are not just users, but also one of the participating parts of the system. If a system could continuously recycle the original chemicals, this would make it virtually a Closed-loop Habitation (CH). Some difficulties in trying to create a miniature version of a CH are briefly discussed. In a miniature CH, a minimal structure must be provided and the difference must be made up by artificial parts such as physicochemical systems that perform the conversions that the Earth can achieve naturally. To study the interactions of these parts, a computer model was designed that simulates a miniature CH with emphasis on the air revitalization part. It is called the Closed-loop Habitation Air Revitalization Model (CHARM).

  10. Statistical mechanical model for a closed loop plectoneme with weak helix specific forces.

    PubMed

    Lee, Dominic J O'

    2017-04-12

    We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure of a plectoneme. Notably, due to their chiral nature, helix structure dependent forces break the symmetry between left and right handed supercoiling. The theoretical approach, presented here, also provides a systematic way of enforcing the topological constraint of closed loop supercoiling in the variational approximation. At large plectoneme lengths, by considering correlation functions in an expansion in terms of the spatial mean twist density about its thermally averaged value, it can be argued that topological constraint may be approximated by replacing twist and writhe by their thermal averages. A Lagrange multiplier, containing the sum of average twist and writhe, can be added to the free energy to conveniently inforce this result. The average writhe can be calculated through the thermal average of the Gauss' integral in the variational approximation. Furthermore, this approach allows for a possible way to calculate finite size corrections due to the topological constraint. Using interaction energy terms from the mean-field Kornyshev-Leikin theory, for parameter values that correspond to weak helix dependent forces, we calculate the free energy, fluctuation magnitudes and mean geometric parameters for the plectoneme. We see a slight asymmetry, where interestingly, left handed supercoils have a looser structure than right handed ones, although with a lower free energy, unlike what the previous ground state calculations would suggest.

  11. Closed-Loop Supply Chain Models with Considering the Environmental Impact

    PubMed Central

    Fallah, Mohammad

    2014-01-01

    Global warming and climate changes created by large scale emissions of greenhouse gases are a worldwide concern. Due to this, the issue of green supply chain management has received more attention in the last decade. In this study, a closed-loop logistic concept which serves the purposes of recycling, reuse, and recovery required in a green supply chain is applied to integrate the environmental issues into a traditional logistic system. Here, we formulate a comprehensive closed-loop model for the logistics planning considering profitability and ecological goals. In this way, we can achieve the ecological goal reducing the overall amount of CO2 emitted from journeys. Moreover, the profitability criterion can be supported in the cyclic network with the minimum costs and maximum service level. We apply three scenarios and develop problem formulations for each scenario corresponding to the specified regulations and investigate the effect of the regulation on the preferred transport mode and the emissions. To validate the models, some numerical experiments are worked out and a comparative analysis is investigated. PMID:25309960

  12. Closed-Loop Prevention of Hypotension in the Heartbeating Brain-Dead Porcine Model.

    PubMed

    Soltesz, Kristian; Sturk, Christopher; Paskevicius, Audrius; Liao, Qiuming; Qin, Guangqi; Sjoberg, Trygve; Steen, Stig

    2017-06-01

     Objective: The purpose of this paper is to demonstrate feasibility of a novel closed-loop controlled therapy for prevention of hypertension in the heartbeating brain-dead porcine model. Dynamic modeling and system identification were based on in vivo data. A robust controller design was obtained for the identified models. Disturbance attenuation properties and reliability of operation of the resulting control system were evaluated in vivo. The control system responded both predictably and consistently to external disturbances. It was possible to prevent mean arterial pressure to fall below a user-specified reference throughout 24 h of completely autonomous operation. Parameter variability in the identified models confirmed the benefit of closed-loop controlled administration of the proposed therapy. The evaluated robust controller was able to mitigate both process uncertainty and external disturbances. Prevention of hypertension is critical to the care of heartbeating brain-dead organ donors. Its automation would likely increase the fraction of organs suitable for transplantation from this patient group.

  13. Closed Loop Interactions between Spiking Neural Network and Robotic Simulators Based on MUSIC and ROS

    PubMed Central

    Weidel, Philipp; Djurfeldt, Mikael; Duarte, Renato C.; Morrison, Abigail

    2016-01-01

    In order to properly assess the function and computational properties of simulated neural systems, it is necessary to account for the nature of the stimuli that drive the system. However, providing stimuli that are rich and yet both reproducible and amenable to experimental manipulations is technically challenging, and even more so if a closed-loop scenario is required. In this work, we present a novel approach to solve this problem, connecting robotics and neural network simulators. We implement a middleware solution that bridges the Robotic Operating System (ROS) to the Multi-Simulator Coordinator (MUSIC). This enables any robotic and neural simulators that implement the corresponding interfaces to be efficiently coupled, allowing real-time performance for a wide range of configurations. This work extends the toolset available for researchers in both neurorobotics and computational neuroscience, and creates the opportunity to perform closed-loop experiments of arbitrary complexity to address questions in multiple areas, including embodiment, agency, and reinforcement learning. PMID:27536234

  14. Decision support for hemodynamic management: from graphical displays to closed loop systems.

    PubMed

    Michard, Frederic

    2013-10-01

    The way hemodynamic therapies are delivered today in anesthesia and critical care is suboptimal. Hemodynamic variables are not always understood correctly and used properly. The adoption of hemodynamic goal-directed strategies, known to be clinically useful, is poor. Ensuring therapies are delivered effectively is the goal of decision support tools and closed loop systems. Graphical displays (metaphor screens) may help clinicians to better capture and integrate the multivariable hemodynamic information. This may result in faster and more accurate diagnosis and therapeutic decisions. Graphical displays (target screens) have the potential to increase adherence to goal-directed strategies and ultimately improve patients' outcomes, but this remains to be confirmed by prospective studies. Closed loop systems are the ultimate solution to ensure therapies are delivered. However, most therapeutic decisions cannot be based on a limited number of output variables. Therefore, one should focus on the development of systems designed to relieve clinicians from very simple and repetitive tasks. Whether intraoperative goal-directed fluid therapy may be one of these tasks remains to be evaluated.

  15. Precision Closed-Loop Orbital Maneuvering System Design and Performance for the Magnetospheric Multiscale Formation

    NASA Technical Reports Server (NTRS)

    Chai, Dean J.; Queen, Steven Z.; Placanica, Samuel J.

    2015-01-01

    NASAs Magnetospheric Multiscale (MMS) mission successfully launched on March 13,2015 (UTC) consists of four identically instrumented spin-stabilized observatories that function as a constellation to study magnetic reconnection in space. The need to maintain sufficiently accurate spatial and temporal formation resolution of the observatories must be balanced against the logistical constraints of executing overly-frequent maneuvers on a small fleet of spacecraft. These two considerations make for an extremely challenging maneuver design problem. This paper focuses on the design elements of a 6-DOF spacecraft attitude control and maneuvering system capable of delivering the high-precision adjustments required by the constellation designers specifically, the design, implementation, and on-orbit performance of the closed-loop formation-class maneuvers that include initialization, maintenance, and re-sizing. The maneuvering control system flown on MMS utilizes a micro-gravity resolution accelerometer sampled at a high rate in order to achieve closed-loop velocity tracking of an inertial target with arc-minute directional and millimeter-per second magnitude accuracy. This paper summarizes the techniques used for correcting bias drift, sensor-head offsets, and centripetal aliasing in the acceleration measurements. It also discusses the on-board pre-maneuver calibration and compensation algorithms as well as the implementation of the post-maneuver attitude adjustments.

  16. Beating of Aharonov-Bohm oscillations in a closed-loop interferometer

    SciTech Connect

    Jo, Sanghyun; Chang, Dong-In; Lee, Hu-Jong; Khym, Gyong Luck; Kang, Kicheon; Chung, Yunchul; Mahalu, Diana; Umansky, Vladimir

    2007-07-15

    One of the points at issue with closed-loop-type interferometers is beating in the Aharonov-Bohm (AB) oscillations. Recent observations suggest the possibility that the beating results from the Berry-phase pickup by the conducting electrons in materials with the strong spin-orbit interaction (SOI). In this study, we also observed beats in the AB oscillations in a gate-defined closed-loop interferometer fabricated on a GaAs/Al{sub 0.3}Ga{sub 0.7}As two-dimensional electron-gas heterostructure. Since this heterostructure has very small SOI, the picture of the Berry-phase pickup is ruled out. The observation of beats in this study, with the controllability of forming a single transverse subband mode in both arms of our gate-defined interferometer, also rules out the often-claimed multiple transverse subband effect. It is observed that nodes of the beats with an h/2e period exhibit a parabolic distribution for varying the side gate. These results are shown to be well interpreted, without resorting to the SOI effect, by the existence of two-dimensional multiple longitudinal modes in a single transverse subband. The Fourier spectrum of measured conductance, despite showing multiple h/e peaks with the magnetic-field dependence that are very similar to that from strong-SOI materials, can also be interpreted as the two-dimensional multiple-longitudinal-modes effect.

  17. Closed-loop control of spinal cord stimulation to restore hand function after paralysis.

    PubMed

    Zimmermann, Jonas B; Jackson, Andrew

    2014-01-01

    As yet, no cure exists for upper-limb paralysis resulting from the damage to motor pathways after spinal cord injury or stroke. Recently, neural activity from the motor cortex of paralyzed individuals has been used to control the movements of a robot arm but restoring function to patients' actual limbs remains a considerable challenge. Previously we have shown that electrical stimulation of the cervical spinal cord in anesthetized monkeys can elicit functional upper-limb movements like reaching and grasping. Here we show that stimulation can be controlled using cortical activity in awake animals to bypass disruption of the corticospinal system, restoring their ability to perform a simple upper-limb task. Monkeys were trained to grasp and pull a spring-loaded handle. After temporary paralysis of the hand was induced by reversible inactivation of primary motor cortex using muscimol, grasp-related single-unit activity from the ventral premotor cortex was converted into stimulation patterns delivered in real-time to the cervical spinal gray matter. During periods of closed-loop stimulation, task-modulated electromyogram, movement amplitude, and task success rate were improved relative to interleaved control periods without stimulation. In some sessions, single motor unit activity from weakly active muscles was also used successfully to control stimulation. These results are the first use of a neural prosthesis to improve the hand function of primates after motor cortex disruption, and demonstrate the potential for closed-loop cortical control of spinal cord stimulation to reanimate paralyzed limbs.

  18. Closed-loop helium circulation system for actuation of a continuously operating heart catheter pump.

    PubMed

    Karabegovic, Alen; Hinteregger, Markus; Janeczek, Christoph; Mohl, Werner; Gföhler, Margit

    2017-06-09

    Currently available, pneumatic-based medical devices are operated using closed-loop pulsatile or open continuous systems. Medical devices utilizing gases with a low atomic number in a continuous closed loop stream have not been documented to date. This work presents the construction of a portable helium circulation addressing the need for actuating a novel, pneumatically operated catheter pump. The design of its control system puts emphasis on the performance, safety and low running cost of the catheter pump. Static and dynamic characteristics of individual elements in the circulation are analyzed to ensure a proper operation of the system. The pneumatic circulation maximizes the working range of the drive unit inside the catheter pump while reducing the total size and noise production.Separate flow and pressure controllers position the turbine's working point into the stable region of the pressure creation element. A subsystem for rapid gas evacuation significantly decreases the duration of helium removal after a leak, reaching subatmospheric pressure in the intracorporeal catheter within several milliseconds. The system presented in the study offers an easy control of helium mass flow while ensuring stable behavior of its internal components.

  19. Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation

    PubMed Central

    Forlim, Caroline Garcia; Pinto, Reynaldo Daniel; Varona, Pablo; Rodríguez, Francisco B.

    2015-01-01

    In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish’s own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish. PMID:26473597

  20. Distributed flow sensing for closed-loop speed control of a flexible fish robot.

    PubMed

    Zhang, Feitian; Lagor, Francis D; Yeo, Derrick; Washington, Patrick; Paley, Derek A

    2015-10-23

    Flexibility plays an important role in fish behavior by enabling high maneuverability for predator avoidance and swimming in turbulent flow. This paper presents a novel flexible fish robot equipped with distributed pressure sensors for flow sensing. The body of the robot is molded from soft, hyperelastic material, which provides flexibility. Its Joukowski-foil shape is conducive to modeling the fluid analytically. A quasi-steady potential-flow model is adopted for real-time flow estimation, whereas a discrete-time vortex-shedding flow model is used for higher-fidelity simulation. The dynamics for the flexible fish robot yield a reduced model for one-dimensional swimming. A recursive Bayesian filter assimilates pressure measurements to estimate flow speed, angle of attack, and foil camber. The closed-loop speed-control strategy combines an inverse-mapping feedforward controller based on an average model derived for periodic actuation of angle-of-attack and a proportional-integral feedback controller utilizing the estimated flow information. Simulation and experimental results are presented to show the effectiveness of the estimation and control strategy. The paper provides a systematic approach to distributed flow sensing for closed-loop speed control of a flexible fish robot by regulating the flapping amplitude.

  1. Radiology reporting: a closed-loop cycle from order entry to results communication.

    PubMed

    Weiss, David L; Kim, Woojin; Branstetter, Barton F; Prevedello, Luciano M

    2014-12-01

    With the increasing prevalence of PACS over the past decade, face-to-face image review among health care providers has become a rarity. This change has resulted in increasing dependence on fast and accurate communication in radiology. Turnaround time expectations are now conveyed in minutes rather than hours or even days. Ideal modern radiology communication is a closed-loop cycle with multiple interoperable applications contributing to the final product. The cycle starts with physician order entry, now often performed through the electronic medical record, with clinical decision support to ensure that the most effective imaging study is ordered. Radiology reports are now almost all in electronic format. The majority are produced using speech recognition systems. Optimization of this software use can alleviate some, if not all, of the inherent user inefficiencies in this type of reporting. Integrated third-party software applications that provide data mining capability are extremely helpful in both academic and clinical settings. The closed-loop ends with automated communication of imaging results. Software products for this purpose should facilitate use of levels of alert, automated escalation to providers, and recording of audit trails of reports received. The multiple components of reporting should be completely interoperable with each other, as well as with the PACS, the RIS, and the electronic medical record. This integration will maximize radiologist efficiency and minimize the possibility of communication error. Copyright © 2014. Published by Elsevier Inc.

  2. The Martian and extraterrestrial UV radiation environment--1. Biological and closed-loop ecosystem considerations.

    PubMed

    Cockell, C S; Andrady, A L

    1999-01-01

    The Martian surface is exposed to both UVC radiation (<280 nm) and higher doses of UVB (280-315 nm) compared to the surface of the Earth. Terrestrial organisms have not evolved to cope with such high levels of UVC and UVB and thus any attempts to introduce organisms to Mars, particularly in closed-loop life support systems that use ambient sunlight, must address this problem. Here we examine the UV radiation environment of Mars with respect to biological systems. Action spectra and UV surface fluxes are used to estimate the UV stress that both DNA and chloroplasts would experience. From this vantage point it is possible to consider appropriate measures to address the problem of the Martian UV environment for future long term human exploration and settlement strategies. Some prospects for improving the UV tolerance of organisms are also discussed. Existing artificial ecosystems such as Biosphere 2 can provide some insights into design strategies pertinent to high UV environments. Some prospects for improving the UV tolerance of organisms are also discussed. The data also have implications for the establishment of closed-loop ecosystems using natural sunlight on the lunar surface and elsewhere in the Solar System.

  3. Reverse engineering of free-form surface based on the closed-loop theory.

    PubMed

    He, Xue Ming; He, Jun Fei; Wu, Mei Ping; Zhang, Rong; Ji, Xiao Gang

    2015-01-01

    To seek better methods of measurement and more accurate model of reconstruction in the field of reverse engineering has been the focus of researchers. Based on this, a new method of adaptive measurement, real-time reconstruction, and online evaluation of free-form surface was presented in this paper. The coordinates and vectors of the prediction points are calculated according to a Bézier curve which is fitted by measured points. Final measured point cloud distribution is in agreement with the geometric characteristics of the free-form surfaces. Fitting the point cloud to a surface model by the nonuniform B-spline method, extracting some check points from the surface models based on grids and a feature on the surface, review the location of these check points on the surface with CMM and evaluate the model, and then update the surface model to meet the accuracy. Integrated measurement, reconstruction, and evaluation, with the closed-loop reverse process, established an accurate model. The results of example show that the measuring points are distributed over the surface according to curvature, and the reconstruction model can be completely expressed with micron level. Meanwhile, measurement, reconstruction and evaluation are integrated in forms of closed-loop reverse system.

  4. Insulin Patch Pumps: Their Development and Future in Closed-Loop Systems

    PubMed Central

    Bohannon, Nancy J.V.

    2010-01-01

    Abstract Steady progress is being made toward the development of a so-called “artificial pancreas,” which may ultimately be a fully automated, closed-loop, glucose control system comprising a continuous glucose monitor, an insulin pump, and a controller. The controller will use individualized algorithms to direct delivery of insulin without user input. A major factor propelling artificial pancreas development is the substantial incidence of—and attendant patient, parental, and physician concerns about—hypoglycemia and extreme hyperglycemia associated with current means of insulin delivery for type 1 diabetes mellitus (T1DM). A successful fully automated artificial pancreas would likely reduce the frequency of and anxiety about hypoglycemia and marked hyperglycemia. Patch-pump systems (“patch pumps”) are likely to be used increasingly in the control of T1DM and may be incorporated into the artificial pancreas systems of tomorrow. Patch pumps are free of tubing, small, lightweight, and unobtrusive. This article describes features of patch pumps that have been approved for U.S. marketing or are under development. Included in the review is an introduction to control algorithms driving insulin delivery, particularly the two major types: proportional integrative derivative and model predictive control. The use of advanced algorithms in the clinical development of closed-loop systems is reviewed along with projected next steps in artificial pancreas development. PMID:20515308

  5. Environmentally conscious closed-loop aqueous and semi-aqueous cleaning systems for defluxing and degreasing

    SciTech Connect

    Smith, M.D.; Christoff, G.W.

    1996-03-01

    The purpose of this project was to develop an environmentally conscious closed-loop cleaning process which would meet the cleaning needs of ATC, reduce worker exposure to hazardous chemicals, and eliminate or reduce their hazardous waste. In order to accomplish this, new cleaning materials needed to be tested for cleaning efficacy as compared to trichloroethylene. The project work plan was broken down into five phases including establishing a baseline cleaning level, evaluating alternative cleaners, specifying and purchasing closed-loop cleaning equipment, installing and evaluating the new equipment, and publicizing the results. In general, it was the responsibility of the KCP to perform cleaning efficacy measurements on sample panels and actual parts that were processed by ATC. The cleaners chosen were evaluated for their abilities to remove the potential contaminants using an ultrasonic cleaning process at the KCP. The cleaning abilities of 20 different cleaners were compared to that of trichloroethylene, the baseline cleaning material. At least nine alternative cleaners produced cleaning results which exceeded trichloroethylene for this application. After evaluating the alternative cleaners and as new cleaning equipment was being tested, ATC terminated the Cooperative Agreement. Further equipment evaluations were suspended.

  6. Closed-loop control of spinal cord stimulation to restore hand function after paralysis

    PubMed Central

    Zimmermann, Jonas B.; Jackson, Andrew

    2014-01-01

    As yet, no cure exists for upper-limb paralysis resulting from the damage to motor pathways after spinal cord injury or stroke. Recently, neural activity from the motor cortex of paralyzed individuals has been used to control the movements of a robot arm but restoring function to patients' actual limbs remains a considerable challenge. Previously we have shown that electrical stimulation of the cervical spinal cord in anesthetized monkeys can elicit functional upper-limb movements like reaching and grasping. Here we show that stimulation can be controlled using cortical activity in awake animals to bypass disruption of the corticospinal system, restoring their ability to perform a simple upper-limb task. Monkeys were trained to grasp and pull a spring-loaded handle. After temporary paralysis of the hand was induced by reversible inactivation of primary motor cortex using muscimol, grasp-related single-unit activity from the ventral premotor cortex was converted into stimulation patterns delivered in real-time to the cervical spinal gray matter. During periods of closed-loop stimulation, task-modulated electromyogram, movement amplitude, and task success rate were improved relative to interleaved control periods without stimulation. In some sessions, single motor unit activity from weakly active muscles was also used successfully to control stimulation. These results are the first use of a neural prosthesis to improve the hand function of primates after motor cortex disruption, and demonstrate the potential for closed-loop cortical control of spinal cord stimulation to reanimate paralyzed limbs. PMID:24904251

  7. Linear state feedback, quadratic weights, and closed loop eigenstructures. M.S. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Thompson, P. M.

    1980-01-01

    Equations are derived for the angles of general multivariable root loci and linear quadratic optimal root loci, including angles of departure and approach. The generalized eigenvalue problem is used to compute angles of approach. Equations are also derived to find the sensitivity of closed loop eigenvalue and the directional derivatives of closed loop eigenvectors. An equivalence class of quadratic weights that produce the same asymptotic eigenstructure is defined, a canonical element is defined, and an algorithm to find it is given. The behavior of the optimal root locus in the nonasymptotic region is shown to be different for quadratic weights with the same asymptotic properties. An algorithm is presented that can be used to select a feedback gain matrix for the linear state feedback problem which produces a specified asymptotic eigenstructure. Another algorithm is given to compute the asymptotic eigenstructure properties inherent in a given set of quadratic weights. Finally, it is shown that optimal root loci for nongeneric problems can be approximated by generic ones in the nonasymptotic region.

  8. Statistical mechanical model for a closed loop plectoneme with weak helix specific forces

    NASA Astrophysics Data System (ADS)

    (O’ Lee, Dominic J.

    2017-04-01

    We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure of a plectoneme. Notably, due to their chiral nature, helix structure dependent forces break the symmetry between left and right handed supercoiling. The theoretical approach, presented here, also provides a systematic way of enforcing the topological constraint of closed loop supercoiling in the variational approximation. At large plectoneme lengths, by considering correlation functions in an expansion in terms of the spatial mean twist density about its thermally averaged value, it can be argued that topological constraint may be approximated by replacing twist and writhe by their thermal averages. A Lagrange multiplier, containing the sum of average twist and writhe, can be added to the free energy to conveniently inforce this result. The average writhe can be calculated through the thermal average of the Gauss’ integral in the variational approximation. Furthermore, this approach allows for a possible way to calculate finite size corrections due to the topological constraint. Using interaction energy terms from the mean-field Kornyshev–Leikin theory, for parameter values that correspond to weak helix dependent forces, we calculate the free energy, fluctuation magnitudes and mean geometric parameters for the plectoneme. We see a slight asymmetry, where interestingly, left handed supercoils have a looser structure than right handed ones, although with a lower free energy, unlike what the previous ground state calculations would suggest.

  9. Closed-loop step response for tuning PID-fractional-order-filter controllers.

    PubMed

    Amoura, Karima; Mansouri, Rachid; Bettayeb, Maâmar; Al-Saggaf, Ubaid M

    2016-09-01

    Analytical methods are usually applied for tuning fractional controllers. The present paper proposes an empirical method for tuning a new type of fractional controller known as PID-Fractional-Order-Filter (FOF-PID). Indeed, the setpoint overshoot method, initially introduced by Shamsuzzoha and Skogestad, has been adapted for tuning FOF-PID controller. Based on simulations for a range of first order with time delay processes, correlations have been derived to obtain PID-FOF controller parameters similar to those obtained by the Internal Model Control (IMC) tuning rule. The setpoint overshoot method requires only one closed-loop step response experiment using a proportional controller (P-controller). To highlight the potential of this method, simulation results have been compared with those obtained with the IMC method as well as other pertinent techniques. Various case studies have also been considered. The comparison has revealed that the proposed tuning method performs as good as the IMC. Moreover, it might offer a number of advantages over the IMC tuning rule. For instance, the parameters of the fractional controller are directly obtained from the setpoint closed-loop response data without the need of any model of the plant to be controlled.

  10. Closed-loop supply chain models with considering the environmental impact.

    PubMed

    Mohajeri, Amir; Fallah, Mohammad

    2014-01-01

    Global warming and climate changes created by large scale emissions of greenhouse gases are a worldwide concern. Due to this, the issue of green supply chain management has received more attention in the last decade. In this study, a closed-loop logistic concept which serves the purposes of recycling, reuse, and recovery required in a green supply chain is applied to integrate the environmental issues into a traditional logistic system. Here, we formulate a comprehensive closed-loop model for the logistics planning considering profitability and ecological goals. In this way, we can achieve the ecological goal reducing the overall amount of CO2 emitted from journeys. Moreover, the profitability criterion can be supported in the cyclic network with the minimum costs and maximum service level. We apply three scenarios and develop problem formulations for each scenario corresponding to the specified regulations and investigate the effect of the regulation on the preferred transport mode and the emissions. To validate the models, some numerical experiments are worked out and a comparative analysis is investigated.

  11. Enhanced Performance Controller Design for Stochastic Systems by Adding Extra State Estimation onto the Existing Closed Loop Control

    SciTech Connect

    Zhou, Yuyang; Zhang, Qichun; Wang, Hong

    2016-08-30

    To enhance the performance of the tracking property , this paper presents a novel control algorithm for a class of linear dynamic stochastic systems with unmeasurable states, where the performance enhancement loop is established based on Kalman filter. Without changing the existing closed loop with the PI controller, the compensative controller is designed to minimize the variances of the tracking errors using the estimated states and the propagation of state variances. Moreover, the stability of the closed-loop systems has been analyzed in the mean-square sense. A simulated example is included to show the effectiveness of the presented control algorithm, where encouraging results have been obtained.

  12. Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat

    PubMed Central

    Wu, Hemmings; Ghekiere, Hartwin; Beeckmans, Dorien; Tambuyzer, Tim; van Kuyck, Kris; Aerts, Jean-Marie; Nuttin, Bart

    2015-01-01

    Conventional deep brain stimulation (DBS) applies constant electrical stimulation to specific brain regions to treat neurological disorders. Closed-loop DBS with real-time feedback is gaining attention in recent years, after proved more effective than conventional DBS in terms of pathological symptom control clinically. Here we demonstrate the conceptualization and validation of a closed-loop DBS system using open-source hardware. We used hippocampal theta oscillations as system input, and electrical stimulation in the mesencephalic reticular formation (mRt) as controller output. It is well documented that hippocampal theta oscillations are highly related to locomotion, while electrical stimulation in the mRt induces freezing. We used an Arduino open-source microcontroller between input and output sources. This allowed us to use hippocampal local field potentials (LFPs) to steer electrical stimulation in the mRt. Our results showed that closed-loop DBS significantly suppressed locomotion compared to no stimulation, and required on average only 56% of the stimulation used in open-loop DBS to reach similar effects. The main advantages of open-source hardware include wide selection and availability, high customizability, and affordability. Our open-source closed-loop DBS system is effective, and warrants further research using open-source hardware for closed-loop neuromodulation. PMID:25897892

  13. Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat.

    PubMed

    Wu, Hemmings; Ghekiere, Hartwin; Beeckmans, Dorien; Tambuyzer, Tim; van Kuyck, Kris; Aerts, Jean-Marie; Nuttin, Bart

    2015-04-21

    Conventional deep brain stimulation (DBS) applies constant electrical stimulation to specific brain regions to treat neurological disorders. Closed-loop DBS with real-time feedback is gaining attention in recent years, after proved more effective than conventional DBS in terms of pathological symptom control clinically. Here we demonstrate the conceptualization and validation of a closed-loop DBS system using open-source hardware. We used hippocampal theta oscillations as system input, and electrical stimulation in the mesencephalic reticular formation (mRt) as controller output. It is well documented that hippocampal theta oscillations are highly related to locomotion, while electrical stimulation in the mRt induces freezing. We used an Arduino open-source microcontroller between input and output sources. This allowed us to use hippocampal local field potentials (LFPs) to steer electrical stimulation in the mRt. Our results showed that closed-loop DBS significantly suppressed locomotion compared to no stimulation, and required on average only 56% of the stimulation used in open-loop DBS to reach similar effects. The main advantages of open-source hardware include wide selection and availability, high customizability, and affordability. Our open-source closed-loop DBS system is effective, and warrants further research using open-source hardware for closed-loop neuromodulation.

  14. Observations of Multiple Blobs in Homologous Solar Coronal Jets in Closed Loop

    NASA Astrophysics Data System (ADS)

    Zhang, Q. M.; Ji, H. S.; Su, Y. N.

    2016-03-01

    Coronal bright points (CBPs) and jets are ubiquitous small-scale brightenings that are often associated with each other. We here report our multiwavelength observations of two groups of homologous jets. The first group was observed by the Extreme-Ultraviolet Imager (EUVI) onboard the Solar TErrestrial RElations Observatory (STEREO) Behind spacecraft in 171 Å and 304 Å on 2014 September 10, from a location where no data from the Solar Dynamic Observatory (SDO) could be obtained. The jets (J1 - J6) recurred for six times with intervals of 5 - 15 minutes. They originated from the same primary CBP (BP1) and propagated in the northeast direction along large-scale, closed coronal loops. Two of the jets (J3 and J6) produced sympathetic CBPs (BP2 and BP3) after reaching the remote footpoints of the loops. The time delays between the peak times of BP1 and BP2 (BP3) are 240±75 s (300±75 s). The jets were not coherent. Instead, they were composed of bright and compact blobs. The sizes and apparent velocities of the blobs are 4.5 - 9 Mm and 140 - 380 km s-1. The arrival times of the multiple blobs in the jets at the far end of the loops indicate that the sympathetic CBPs are caused by jet flows and not by thermal conduction fronts. The second group was observed by the Atmospheric Imaging Assembly onboard SDO in various wavelengths on 2010 August 3. Similar to the first group, the jets originated from a short-lived BP at the boundary of Active Region 11092 and propagated along a small-scale, closed loop before flowing into the active region. Several tiny blobs with sizes of ˜1.7 Mm and an apparent velocity of ˜238 km s^{-1} were identified in the jets. We carried out differential emission measure (DEM) inversions to investigate the temperatures of the blobs, finding that the blobs were multithermal with an average temperature of 1.8 - 3.1 MK. The estimated number densities of the blobs were (1.7 - 2.8)×109 cm^{-3}.

  15. Closed-Loop Control of a Neuroprosthetic Hand by Magnetoencephalographic Signals

    PubMed Central

    Fukuma, Ryohei; Yanagisawa, Takufumi; Yorifuji, Shiro; Kato, Ryu; Yokoi, Hiroshi; Hirata, Masayuki; Saitoh, Youichi; Kishima, Haruhiko; Kamitani, Yukiyasu; Yoshimine, Toshiki

    2015-01-01

    Objective A neuroprosthesis using a brain–machine interface (BMI) is a promising therapeutic option for severely paralyzed patients, but the ability to control it may vary among individual patients and needs to be evaluated before any invasive procedure is undertaken. We have developed a neuroprosthetic hand that can be controlled by magnetoencephalographic (MEG) signals to noninvasively evaluate subjects’ ability to control a neuroprosthesis. Method Six nonparalyzed subjects performed grasping or opening movements of their right hand while the slow components of the MEG signals (SMFs) were recorded in an open-loop condition. The SMFs were used to train two decoders to infer the timing and types of movement by support vector machine and Gaussian process regression. The SMFs were also used to calculate estimated slow cortical potentials (eSCPs) to identify the origin of motor information. Finally, using the trained decoders, the subjects controlled a neuroprosthetic hand in a closed-loop condition. Results The SMFs in the open-loop condition revealed movement-related cortical field characteristics and successfully inferred the movement type with an accuracy of 75.0 ± 12.9% (mean ± SD). In particular, the eSCPs in the sensorimotor cortex contralateral to the moved hand varied significantly enough among the movement types to be decoded with an accuracy of 76.5 ± 10.6%, which was significantly higher than the accuracy associated with eSCPs in the ipsilateral sensorimotor cortex (58.1 ± 13.7%; p = 0.0072, paired two-tailed Student’s t-test). Moreover, another decoder using SMFs successfully inferred when the accuracy was the greatest. Combining these two decoders allowed the neuroprosthetic hand to be controlled in a closed-loop condition. Conclusions Use of real-time MEG signals was shown to successfully control the neuroprosthetic hand. The developed system may be useful for evaluating movement-related slow cortical potentials of severely paralyzed patients

  16. Non-Nuclear Validation Test Results of a Closed Brayton Cycle Test-Loop

    NASA Astrophysics Data System (ADS)

    Wright, Steven A.

    2007-01-01

    Both NASA and DOE have programs that are investigating advanced power conversion cycles for planetary surface power on the moon or Mars, or for next generation nuclear power plants on earth. Although open Brayton cycles are in use for many applications (combined cycle power plants, aircraft engines), only a few closed Brayton cycles have been tested. Experience with closed Brayton cycles coupled to nuclear reactors is even more limited and current projections of Brayton cycle performance are based on analytic models. This report describes and compares experimental results with model predictions from a series of non-nuclear tests using a small scale closed loop Brayton cycle available at Sandia National Laboratories. A substantial amount of testing has been performed, and the information is being used to help validate models. In this report we summarize the results from three kinds of tests. These tests include: 1) test results that are useful for validating the characteristic flow curves of the turbomachinery for various gases ranging from ideal gases (Ar or Ar/He) to non-ideal gases such as CO2, 2) test results that represent shut down transients and decay heat removal capability of Brayton loops after reactor shut down, and 3) tests that map a range of operating power versus shaft speed curve and turbine inlet temperature that are useful for predicting stable operating conditions during both normal and off-normal operating behavior. These tests reveal significant interactions between the reactor and balance of plant. Specifically these results predict limited speed up behavior of the turbomachinery caused by loss of load, the conditions for stable operation, and for direct cooled reactors, the tests reveal that the coast down behavior during loss of power events can extend for hours provided the ultimate heat sink remains available.

  17. Characterization of AOC2 gene encoding a copper-binding amine oxidase expressed specifically in retina.

    PubMed

    Zhang, Qiang; Mashima, Yukihiko; Noda, Setsuko; Imamura, Yutaka; Kudoh, Jun; Shimizu, Nobuyoshi; Nishiyama, Takatsune; Umeda, Shinsuke; Oguchi, Yoshihisa; Tanaka, Yasuhiko; Iwata, Takeshi

    2003-10-30

    We have previously cloned a human, retina-specific, amine oxidase gene (RAO, gene symbol: AOC2), a member of the copper-binding amine oxidase super family. AOC2 shares sequence identity with the human kidney amine oxidase gene (KAO, gene symbol: AOC1) and the vascular adhesion protein-1 gene (VAP-1, gene symbol: AOC3). For further analysis of AOC2, the sequences surrounding the human AOC2 and the complete mouse and partial rat homologue of AOC2 were cloned for characterization. Real-time quantitative PCR, in situ hybridization, and immunohistochemistry were performed to determine the specific expression of AOC2 in the mouse retina and especially in the retinal ganglion cells. Our results demonstrated that the copper-binding motif and the enzyme active site of AOC1 and AOC3 were both conserved in mouse AOC2. The human and mouse AOC2 was flanked by two genes, the Psme3 gene for PA-28 gamma subunit and, surprisingly, the AOC3 gene. Rat AOC2 contained a stop codon that terminated the peptide length to 127 amino acids. The presence of human and rat AOC pseudogene in this region, in addition to the tandemly positioned two AOC genes, indicates the possibility of successful AOC3 replication to retina-specific AOC2 for human and mouse but unsuccessful for rat.

  18. The Euclid AOCS science mode design

    NASA Astrophysics Data System (ADS)

    Bacchetta, A.; Saponara, M.; Torasso, A.; Saavedra Criado, G.; Girouart, B.

    2015-06-01

    Euclid is a Medium-Class mission of the ESA Cosmic Vision 2015-2025 plan. Thales Alenia Space Italy has been selected as prime contractor for the Euclid design and implementation. The spacecraft will be launched in 2020 on a Soyuz launch vehicle from Kourou, to a large-amplitude orbit around the sun-earth libration point L2. The objective of Euclid is to understand the origin of the Universe's accelerating expansion, by mapping large-scale structure over a cosmic time covering the last 10 billion years. The mission requires the ability to survey a large fraction of the extragalactic sky (i.e. portion of sky with latitude higher than 30 deg with respect to galactic plane) over its lifetime, with very high system stability (telescope, focal plane, spacecraft pointing) to minimize systematic effects. The AOCS is a key element to meet the scientific requirements. The AOCS design drivers are pointing performance and image quality (Relative Pointing Error over 700 s less than 25 m as, 68 % confidence level), and minimization of slew time between observation fields to meet the goal of completing the Wide Extragalactic Survey in 6 years. The first driver demands a Fine Guidance Sensor in the telescope focal plane for accurate attitude measurement and actuators with low noise and fine command resolution. The second driver requires high-torque actuators and an extended attitude control bandwidth. In the design, reaction wheels (RWL) and cold-gas micro-propulsion (MPS) are used in a synergetic and complementary way during different operational phases of the science mode. The RWL are used for performing the field slews, whereas during scientific observation they are stopped not to perturb the pointing by additional mechanical noise. The MPS is used for maintaining the reference attitude with high pointing accuracy during the scientific observation. This unconventional concept achieves the pointing performance with the shortest maneuver times, with significant mass savings with

  19. Analysis and design of a 3rd order velocity-controlled closed-loop for MEMS vibratory gyroscopes.

    PubMed

    Wu, Huan-ming; Yang, Hai-gang; Yin, Tao; Jiao, Ji-wei

    2013-09-18

    The time-average method currently available is limited to analyzing the specific performance of the automatic gain control-proportional and integral (AGC-PI) based velocity-controlled closed-loop in a micro-electro-mechanical systems (MEMS) vibratory gyroscope, since it is hard to solve nonlinear functions in the time domain when the control loop reaches to 3rd order. In this paper, we propose a linearization design approach to overcome this limitation by establishing a 3rd order linear model of the control loop and transferring the analysis to the frequency domain. Order reduction is applied on the built linear model's transfer function by constructing a zero-pole doublet, and therefore mathematical expression of each control loop's performance specification is obtained. Then an optimization methodology is summarized, which reveals that a robust, stable and swift control loop can be achieved by carefully selecting the system parameters following a priority order. Closed-loop drive circuits are designed and implemented using 0.35 μm complementary metal oxide semiconductor (CMOS) process, and experiments carried out on a gyroscope prototype verify the optimization methodology that an optimized stability of the control loop can be achieved by constructing the zero-pole doublet, and disturbance rejection capability (D.R.C) of the control loop can be improved by increasing the integral term.

  20. Automated overnight closed-loop glucose control in young children with type 1 diabetes.

    PubMed

    Elleri, Daniela; Allen, Janet M; Nodale, Marianna; Wilinska, Malgorzata E; Mangat, Jasdip S; Larsen, Anne Mette F; Acerini, Carlo L; Dunger, David B; Hovorka, Roman

    2011-04-01

    We evaluated the effectiveness of automated overnight closed-loop (AOCL) insulin delivery and the influence of timing of initiation on glucose control overnight in young children with type 1 diabetes (T1D). Eight children with T1D (four boys, four girls) (mean ± SD: 9.4 ± 2.7 years old; body mass index, 18.3 ± 2.3 kg/m(2); duration of diabetes, 3.9 ± 2.5 years; total daily insulin dose, 0.7 ± 0.1 U/kg/day; glycosylated hemoglobin, 7.9 ± 0.9%) were studied in a clinical research facility on two separate occasions. Subjects had a meal at 18:00 (77 ± 8 g of carbohydrate [CHO]) and snack at 21:00 (21 ± 6 g of CHO), both accompanied by a prandial insulin bolus. In random order, AOCL was started at 18:00 or 21:00 h and ran until 08:00 h the next day. Subcutaneous continuous glucose monitoring data were fed automatically into the model predictive control algorithm. Calculated subcutaneous insulin infusion rates were sent wirelessly to an insulin pump. Plasma glucose was measured to assess closed-loop performance. No rescue CHOs were administered. Time spent with plasma glucose in the target range from 3.9 to 8.0 mmol/L was 50.7% (29.0%, 72.2%), and it did not differ on the two occasions: median (interquartile range), 42% (18%, 64%) versus 58% (32%, 79%) (P = 0.161). Time when plasma glucose was above 8.0 mmol/L (42% [25%, 82%] vs. 29% [14%, 64%], P = 0.093), time below 3.9 mmol/L (0% [0%, 11%] vs. 8% [0%, 17%], P = 0.500), low blood glucose index (0.1 [0.0, 2.5] vs. 1.7 [0.4, 3.3], P = 0.380), plasma glucose at the start of AOCL (12.5 ± 2.7 vs. 11.6 ± 4.2 mmol/L, P = 0.562), and mean overnight plasma glucose (8.3 ± 2.1 vs. 7.5 ± 2.2 mmol/L, P = 0.246) were also similar. AOCL is feasible in young children with T1D. Comparable results were obtained when closed-loop was initiated at 18:00 or 21:00 h.

  1. Intraoperative stroke volume optimization using stroke volume, arterial pressure, and heart rate: closed-loop (learning intravenous resuscitator) versus anesthesiologists.

    PubMed

    Rinehart, Joseph; Chung, Elena; Canales, Cecilia; Cannesson, Maxime

    2012-10-01

    The authors compared the performance of a group of anesthesia providers to closed-loop (Learning Intravenous Resuscitator [LIR]) management in a simulated hemorrhage scenario using cardiac output monitoring. A prospective cohort study. In silico simulation. University hospital anesthesiologists and the LIR closed-loop fluid administration system. Using a patient simulator, a 90-minute simulated hemorrhage protocol was run, which included a 1,200-mL blood loss over 30 minutes. Twenty practicing anesthesiology providers were asked to manage this scenario by providing fluids and vasopressor medication at their discretion. The simulation program was also run 20 times with the LIR closed-loop algorithm managing fluids and an additional 20 times with no intervention. Simulated patient weight, height, heart rate, mean arterial pressure, and cardiac output (CO) were similar at baseline. The mean stroke volume, the mean arterial pressure, CO, and the final CO were higher in the closed-loop group than in the practitioners group, and the coefficient of variance was lower. The closed-loop group received slightly more fluid (2.1 v 1.9 L, p < 0.05) than the anesthesiologist group. Despite the roughly similar volumes of fluid given, the closed-loop maintained more stable hemodynamics than the practitioners primarily because the fluid was given earlier in the protocol and CO optimized before the hemorrhage began, whereas practitioners tended to resuscitate well but only after significant hemodynamic change indicated the need. Overall, these data support the potential usefulness of this closed-loop algorithm in clinical settings in which dynamic predictors are not available or applicable. Published by Elsevier Inc.

  2. Assessing performance of closed-loop insulin delivery systems by continuous glucose monitoring: drawbacks and way forward.

    PubMed

    Hovorka, Roman; Nodale, Marianna; Haidar, Ahmad; Wilinska, Malgorzata E

    2013-01-01

    We investigated whether continuous glucose monitoring (CGM) levels can accurately assess glycemic control while directing closed-loop insulin delivery. Data were analyzed retrospectively from 33 subjects with type 1 diabetes who underwent closed-loop and conventional pump therapy on two separate nights. Glycemic control was evaluated by reference plasma glucose and contrasted against three methods based on Navigator (Abbott Diabetes Care, Alameda, CA) CGM levels. Glucose mean and variability were estimated by unmodified CGM levels with acceptable clinical accuracy. Time when glucose was in target range was overestimated by CGM during closed-loop nights (CGM vs. plasma glucose median [interquartile range], 86% [65-97%] vs. 75% [59-91%]; P=0.04) but not during conventional pump therapy (57% [32-72%] vs. 51% [29-68%]; P=0.82) providing comparable treatment effect (mean [SD], 28% [29%] vs. 23% [21%]; P=0.11). Using the CGM measurement error of 15% derived from plasma glucose-CGM pairs (n=4,254), stochastic interpretation of CGM gave unbiased estimate of time in target during both closed-loop (79% [62-86%] vs. 75% [59-91%]; P=0.24) and conventional pump therapy (54% [33-66%] vs. 51% [29-68%]; P=0.44). Treatment effect (23% [24%] vs. 23% [21%]; P=0.96) and time below target were accurately estimated by stochastic CGM. Recalibrating CGM using reference plasma glucose values taken at the start and end of overnight closed-loop was not superior to stochastic CGM. CGM is acceptable to estimate glucose mean and variability, but without adjustment it may overestimate benefit of closed-loop. Stochastic CGM provided unbiased estimate of time when glucose is in target and below target and may be acceptable for assessment of closed-loop in the outpatient setting.

  3. Closing the loop overnight at home setting: psychosocial impact for adolescents with type 1 diabetes and their parents

    PubMed Central

    Barnard, Katharine D; Wysocki, Tim; Allen, Janet M; Elleri, Daniela; Thabit, Hood; Leelarathna, Lalantha; Gulati, Arti; Nodale, Marianna; Dunger, David B; Tinati, Tannaze; Hovorka, Roman

    2014-01-01

    Objective To explore the experiences of adolescents with type 1 diabetes mellitus (T1DM) and their parents taking part in an overnight closed loop study at home, using qualitative and quantitative research methods. Research design and methods Adolescents aged 12–18 years on insulin pump therapy were recruited to a pilot closed loop study in the home setting. Following training on the use of a study insulin pump and continuous glucose monitoring (CGM), participants were randomized to receive either real-time CGM combined with overnight closed loop or real-time CGM alone followed by the alternative treatment for an additional 21 days with a 2–3-week washout period in between study arms. Semistructured interviews were performed to explore participants’ perceptions of the impact of the closed loop technology. At study entry and again at the end of each 21-day crossover arm of the trial, participants completed the Diabetes Technology Questionnaire (DTQ) and Hypoglycemia Fear Survey (HFS; also completed by parents). Results 15 adolescents and 13 parents were interviewed. Key positive themes included reassurance/peace of mind, confidence, ‘time off’ from diabetes demands, safety, and improved diabetes control. Key negative themes included difficulties with calibration, alarms, and size of the devices. DTQ results reflected these findings. HFS scores were mixed. Conclusions Closed loop insulin delivery represents cutting-edge technology in the treatment of T1DM. Results indicate that the psychological and physical benefits of the closed loop system outweighed the practical challenges reported. Further research from longitudinal studies is required to determine the long-term psychosocial benefit of the closed loop technology. PMID:25452866

  4. Efficient Computation of Closed-loop Frequency Response for Large Order Flexible Systems

    NASA Technical Reports Server (NTRS)

    Maghami, Peiman G.; Giesy, Daniel P.

    1997-01-01

    An efficient and robust computational scheme is given for the calculation of the frequency response function of a large order, flexible system implemented with a linear, time invariant control system. Advantage is taken of the highly structured sparsity of the system matrix of the plant based on a model of the structure using normal mode coordinates. The computational time per frequency point of the new computational scheme is a linear function of system size, a significant improvement over traditional, full-matrix techniques whose computational times per frequency point range from quadratic to cubic functions of system size. This permits the practical frequency domain analysis of systems of much larger order than by traditional, full-matrix techniques. Formulations are given for both open and closed loop loop systems. Numerical examples are presented showing the advantages of the present formulation over traditional approaches, both in speed and in accuracy. Using a model with 703 structural modes, a speed-up of almost two orders of magnitude was observed while accuracy improved by up to 5 decimal places.

  5. Closed-loop separation control over a sharp edge ramp using genetic programming

    NASA Astrophysics Data System (ADS)

    Debien, Antoine; von Krbek, Kai A. F. F.; Mazellier, Nicolas; Duriez, Thomas; Cordier, Laurent; Noack, Bernd R.; Abel, Markus W.; Kourta, Azeddine

    2016-03-01

    We experimentally perform open and closed-loop control of a separating turbulent boundary layer downstream from a sharp edge ramp. The turbulent boundary layer just above the separation point has a Reynolds number Re_{θ }≈ 3500 based on momentum thickness. The goal of the control is to mitigate separation and early re-attachment. The forcing employs a spanwise array of active vortex generators. The flow state is monitored with skin-friction sensors downstream of the actuators. The feedback control law is obtained using model-free genetic programming control (GPC) (Gautier et al. in J Fluid Mech 770:442-457, 2015). The resulting flow is assessed using the momentum coefficient, pressure distribution and skin friction over the ramp and stereo PIV. The PIV yields vector field statistics, e.g. shear layer growth, the back-flow area and vortex region. GPC is benchmarked against the best periodic forcing. While open-loop control achieves separation reduction by locking-on the shedding mode, GPC gives rise to similar benefits by accelerating the shear layer growth. Moreover, GPC uses less actuation energy.

  6. ICFT: An initial closed-loop flow test of the Fenton Hill Phase II HDR reservoir

    SciTech Connect

    Dash, Z.V.; Aguilar, R.G.; Dennis, B.R.; Dreesen, D.S.; Fehler, M.C.; Hendron, R.H.; House, L.S.; Ito, H.; Kelkar, S.M.; Malzahn, M.V.

    1989-02-01

    A 30-day closed-loop circulation test of the Phase II Hot Dry Rock reservoir at Fenton Hill, New Mexico, was conducted to determine the thermal, hydraulic, chemical, and seismic characteristics of the reservoir in preparation for a long-term energy-extraction test. The Phase II heat-extraction loop was successfully tested with the injection of 37,000 m/sup 3/ of cold water and production of 23,300 m/sup 3/ of hot water. Up to 10 MW/sub t/ was extracted when the production flow rate reached 0.0139 m/sup 3//s at 192/degree/C. By the end of the test, the water-loss rate had decreased to 26% and a significant portion of the injected water was recovered; 66% during the test and an additional 20% during subsequent venting. Analysis of thermal, hydraulic, geochemical, tracer, and seismic data suggests the fractured volume of the reservoir was growing throughout the test. 19 refs., 64 figs., 19 tabs.

  7. Extending the Capabilities of Closed-loop Distributed Engine Control Simulations Using LAN Communication

    NASA Technical Reports Server (NTRS)

    Aretskin-Hariton, Eliot D.; Zinnecker, Alicia Mae; Culley, Dennis E.

    2014-01-01

    Distributed Engine Control (DEC) is an enabling technology that has the potential to advance the state-of-the-art in gas turbine engine control. To analyze the capabilities that DEC offers, a Hardware-In-the-Loop (HIL) test bed is being developed at NASA Glenn Research Center. This test bed will support a systems-level analysis of control capabilities in closed-loop engine simulations. The structure of the HIL emulates a virtual test cell by implementing the operator functions, control system, and engine on three separate computers. This implementation increases the flexibility and extensibility of the HIL. Here, a method is discussed for implementing these interfaces by connecting the three platforms over a dedicated Local Area Network (LAN). This approach is verified using the Commercial Modular Aero-Propulsion System Simulation 40k (C-MAPSS40k), which is typically implemented on one computer. There are marginal differences between the results from simulation of the typical and the three-computer implementation. Additional analysis of the LAN network, including characterization of network load, packet drop, and latency, is presented. The three-computer setup supports the incorporation of complex control models and proprietary engine models into the HIL framework.

  8. Improvement of mechanical performance for vibratory microgyroscope based on sense mode closed-loop control

    NASA Astrophysics Data System (ADS)

    Xiao, Dingbang; Su, Jianbin; Chen, Zhihua; Hou, Zhanqiang; Wang, Xinghua; Wu, Xuezhong

    2013-04-01

    In order to improve its structural sensitivity, a vibratory microgyroscope is commonly sealed in high vacuum to increase the drive mode quality factor. The sense mode quality factor of the microgyroscope will also increase simultaneously after vacuum sealing, which will lead to a long decay time of free response and even self-oscillation of the sense mode. As a result, the mechanical performance of the microgyroscope will be seriously degraded. In order to solve this problem, a closed-loop control technique is presented to adjust and optimize the sense mode quality factor. A velocity feedback loop was designed to increase the electric damping of the sense mode vibration. A circuit was fabricated based on this technique, and experimental results indicate that the sense mode quality factor of the microgyroscope was adjusted from 8052 to 428. The decay time of the sense mode free response was shortened from 3 to 0.5 s, and the vibration-rejecting ability of the microgyroscope was improved obviously without sensitivity degradation.

  9. Closing the Loop with Sensors in Commercial Building Systems: Applying Lessons from Automotive Vehicles

    NASA Astrophysics Data System (ADS)

    Mantese, Joseph

    2011-08-01

    Automotive systems have evolved extensively over the past 50 years, providing a fully integrated system of sub-systems that work in concert for optimal vehicle level closed loop control. In this talk we look at several automotive sub-systems: stability and control, safety and security, emissions and comfort, diagnostics and maintenance, infotainment and communications; with an eye toward understanding their technology drivers and associated value propositions. Conversely, we examine how commercial building systems currently are represented as a collection of sub-systems that often work independently of each other for local optimization, often relying upon open loop control systems developed and installed decades ago. Reasoning primarily by analogy we explore opportunities for energy and efficiency, comfort and environment, and safety/security; asking whether there is sufficient value associated with a new class of building sensors and how those technologies might be brought to bear in improving performance. Finally, we examine the fundamental architecture of detection systems built upon sensing elements, with the aim of understanding trade-offs between: detection, false alarm rate, power, and cost.

  10. Investigation of creep by use of closed loop servo-hydraulic test system

    NASA Technical Reports Server (NTRS)

    Wu, H. C.; Yao, J. C.

    1981-01-01

    Creep tests were conducted by means of a closed loop servo-controlled materials test system. These tests are different from the conventional creep tests in that the strain history prior to creep may be carefully monitored. Tests were performed for aluminum alloy 6061-0 at 150 C and monitored by a PDP 11/04 minicomputer at a preset constant plastic-strain rate prehistory. The results show that the plastic-strain rate prior to creep plays a significant role in creep behavior. The endochronic theory of viscoplasticity was applied to describe the observed creep curves. The concepts of intrinsic time and strain rate sensitivity function are employed and modified according to the present observation.

  11. Design of biomass management systems and components for closed loop life support systems

    NASA Technical Reports Server (NTRS)

    Nevill, Gale E., Jr.

    1991-01-01

    The design of a biomass management system (BMS) for use in a closed loop support system is presented by University of Florida students as the culmination of two design courses. The report is divided into two appendixes, each presenting the results of one of the design courses. The first appendix discusses the preliminary design of the biomass management system and is subdivided into five subsystems: (1) planting and harvesting, (2) food management, (3) resource recovery, (4) refurbishing, and (5) transport. Each subsystem is investigated for possible solutions to problems, and recommendations and conclusions for an integrated BMS are discussed. The second appendix discusses the specific design of components for the BMS and is divided into three sections: (1) a sectored plant growth unit with support systems, (2) a container and receiving mechanism, and (3) an air curtain system for fugitive particle control. In this section components are designed, fabricated, and tested.

  12. Measurement error robustness of a closed-loop minimal sampling method for HIV therapy switching.

    PubMed

    Cardozo, E Fabian; Zurakowski, Ryan

    2011-01-01

    We test the robustness of a closed-loop treatment scheduling method to realistic HIV viral load measurement error. The purpose of the algorithm is to allow the accurate detection of an induced viral load minimum with a reduced number of samples. Therapy must be switched at or near the viral-load minimum to achieve optimal therapeutic benefit; therapeutic benefit decreases logarithmically with increased viral load at the switching time. The performance of the algorithm is characterized using a number of metrics. These include the number of samples saved vs. fixed-rate sampling, the risk-reduction achieved vs. the risk-reduction possible with frequent sampling, and the difference between the switching time vs. the theoretical optimal switching time. The algorithm is applied to simulated patient data generated from a family of data-driven patient models and corrupted by experimentally confirmed levels of log-normal noise.

  13. A closed-loop life cycle assessment of recycled aggregate concrete utilization in China.

    PubMed

    Ding, Tao; Xiao, Jianzhuang; Tam, Vivian W Y

    2016-10-01

    This paper studies the potential environmental impact of recycled coarse aggregate (RCA) for concrete production in China. According to the cradle-to-cradle theory, a closed-loop life cycle assessment (LCA) on recycled aggregate concrete (RAC) utilization in China with entire local life cycle inventory (LCI) is performed, regarding the environmental influence of cement content, aggregate production, transportation and waste landfilling. Special attention is paid on the primary resource and energy conservation, as well as climate protection induced by RAC applications. Environmental impact between natural aggregate concrete (NAC) and RAC are also compared. It is shown that cement proportion and transportation are the top two contributors for carbon dioxide (CO2) emissions and energy consumption for both NAC and RAC. Sensitivity analysis also proves that long delivery distances for natural coarse aggregate (NCA) leave a possible opportunity for lowering environmental impact of RAC in China. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Optimal reconstruction for closed-loop ground-layer adaptive optics with elongated spots.

    PubMed

    Béchet, Clémentine; Tallon, Michel; Tallon-Bosc, Isabelle; Thiébaut, Éric; Le Louarn, Miska; Clare, Richard M

    2010-11-01

    The design of the laser-guide-star-based adaptive optics (AO) systems for the Extremely Large Telescopes requires careful study of the issue of elongated spots produced on Shack-Hartmann wavefront sensors. The importance of a correct modeling of the nonuniformity and correlations of the noise induced by this elongation has already been demonstrated for wavefront reconstruction. We report here on the first (to our knowledge) end-to-end simulations of closed-loop ground-layer AO with laser guide stars with such an improved noise model. The results are compared with the level of performance predicted by a classical noise model for the reconstruction. The performance is studied in terms of ensquared energy and confirms that, thanks to the improved noise model, central or side launching of the lasers does not affect the performance with respect to the laser guide stars' flux. These two launching schemes also perform similarly whatever the atmospheric turbulence strength.

  15. Process step response based fractional PIλDμ controller parameters tuning for desired closed loop response

    NASA Astrophysics Data System (ADS)

    Fergani, Nadir; Charef, Abdelfatah

    2016-02-01

    In this paper, a tuning method of the fractional PIλDμ controllers for classical feedback control systems is proposed. The PIλDμ controller design strategy is drawn up such that the closed loop system is equivalent to a desired fractional order model whose transfer function is Bode's ideal function ?, a widely used function in the fractional order control domain because of its iso-damping property which is an important robustness feature. In this tuning technique, the values of the five parameters of the fractional PIλDμ controller are derived analytically using only the step response of a stable process without requirement of its model. The derived formulations of the tuning technique are presented. Illustrative examples are given to test the effectiveness and the usefulness of the proposed PIλDμ controller tuning approach.

  16. Closed Loop, DM Diversity-based, Wavefront Correction Algorithm for High Contrast Imaging Systems

    NASA Technical Reports Server (NTRS)

    Give'on, Amir; Belikov, Ruslan; Shaklan, Stuart; Kasdin, Jeremy

    2007-01-01

    High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

  17. The Physical/Chemical Closed-Loop Life Support Research Project

    NASA Technical Reports Server (NTRS)

    Bilardo, Vincent J., Jr.

    1990-01-01

    The various elements of the Physical/Chemical Closed-Loop Life Support Research Project (P/C CLLS) are described including both those currently funded and those planned for implementation at ARC and other participating NASA field centers. The plan addresses the entire range of regenerative life support for Space Exploration Initiative mission needs, and focuses initially on achieving technology readiness for the Initial Lunar Outpost by 1995-97. Project elements include water reclamation, air revitalization, solid waste management, thermal and systems control, and systems integration. Current analysis estimates that each occupant of a space habitat will require a total of 32 kg/day of supplies to live and operate comfortably, while an ideal P/C CLLS system capable of 100 percent reclamation of air and water, but excluding recycling of solid wastes or foods, will reduce this requirement to 3.4 kg/day.

  18. Autonomous Closed-Loop Tasking, Acquisition, Processing, and Evaluation for Situational Awareness Feedback

    NASA Technical Reports Server (NTRS)

    Frye, Stuart; Mandl, Dan; Cappelaere, Pat

    2016-01-01

    This presentation describes the closed loop satellite autonomy methods used to connect users and the assets on Earth Orbiter- 1 (EO-1) and similar satellites. The base layer is a distributed architecture based on Goddard Mission Services Evolution Concept (GMSEC) thus each asset still under independent control. Situational awareness is provided by a middleware layer through common Application Programmer Interface (API) to GMSEC components developed at GSFC. Users setup their own tasking requests, receive views into immediate past acquisitions in their area of interest, and into future feasibilities for acquisition across all assets. Automated notifications via pubsub feeds are returned to users containing published links to image footprints, algorithm results, and full data sets. Theme-based algorithms are available on-demand for processing.

  19. Numerical simulation of a glucose sensitive composite membrane closed-loop insulin delivery system.

    PubMed

    Mukherjee, Shashi Bajaj; Datta, Debabrata; Raha, Soumyendu; Pal, Debnath

    2017-06-24

    Closed-loop insulin delivery system works on pH modulation by gluconic acid production from glucose, which in turn allows regulation of insulin release across membrane. Typically, the concentration variation of gluconic acid can be numerically modeled by a set of non-linear, non-steady state reaction diffusion equations. Here, we report a simpler numerical approach to time and position dependent diffusivity of species using finite difference and differential quadrature (DQ) method. The results are comparable to that obtained by analytical method. The membrane thickness directly determines the concentrations of the glucose and oxygen in the system, and inversely to the gluconic acid. The advantage with the DQ method is that its parameter values need not be altered throughout the analysis to obtain the concentration profiles of the glucose, oxygen and gluconic acid. Our work would be useful for modeling diabetes and other systems governed by such non-linear and non-steady state reaction diffusion equations.

  20. Experiments of Closed-Loop Flow Control for Laminar Boundary Layers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu

    The Tollmien-Schlichting (T-S) instability is important for the transition process of boundary layer flows. The cancellation of its unstable modes will help delay the occurrence of transition and then turbulence. In this article the T-S instability was attempted to attenuate through an active closed-loop control strategy. The frequency responses of unstable travelling T-S waves were obtained for the implementation of control strategy. Information such as velocity disturbances of both incoming unstable waves and cancelling waves were then fed into the control system. A controller was deliberately designed and tested for the active cancellation of instabilities which were excited by velocity disturbances normal to the wall. The cancellation performance of the control system was validated by experiments in a low turbulence wind tunnel, which proved the functionality of above control strategy upon the active cancellation of boundary layer instabilities.

  1. Towards a recycling society: ecological sanitation--closing the loop to food security.

    PubMed

    Esrey, S A

    2001-01-01

    A recycling society must switch from linear solutions to circular approaches, protecting ecosystems and harmonising with natural systems. Ecological sanitation, an alternative to conventional approaches, considers excreta a resource. Excreta are rendered safe at the source prior to reuse. The ecosystem approach helps restore soil fertility, and ultimately enhances food security. It is a system requiring little or no water; thus it conserves and protects fresh and marine water sources, enhances biodiversity, and it may confer multiple benefits in urban settings. It can generate jobs, be financially more affordable than conventional approaches, improve local ecology, create decentralised economies, and contribute toward improved health and nutrition of people. Ecological sanitation closes water and nutrient loops, reducing reliance on external inputs and reducing output of wastes from the system.

  2. Closed loop control of the induction heating process using miniature magnetic sensors

    DOEpatents

    Bentley, Anthony E.; Kelley, John Bruce; Zutavern, Fred J.

    2003-05-20

    A method and system for providing real-time, closed-loop control of the induction hardening process. A miniature magnetic sensor located near the outer surface of the workpiece measures changes in the surface magnetic field caused by changes in the magnetic properties of the workpiece as it heats up during induction heating (or cools down during quenching). A passive miniature magnetic sensor detects a distinct magnetic spike that appears when the saturation field, B.sub.sat, of the workpiece has been exceeded. This distinct magnetic spike disappears when the workpiece's surface temperature exceeds its Curie temperature, due to the sudden decrease in its magnetic permeability. Alternatively, an active magnetic sensor can measure changes in the resonance response of the monitor coil when the excitation coil is linearly swept over 0-10 MHz, due to changes in the magnetic permeability and electrical resistivity of the workpiece as its temperature increases (or decreases).

  3. Sub-millisecond closed-loop feedback stimulation between arbitrary sets of individual neurons

    PubMed Central

    Müller, Jan; Bakkum, Douglas J.; Hierlemann, Andreas

    2012-01-01

    We present a system to artificially correlate the spike timing between sets of arbitrary neurons that were interfaced to a complementary metal–oxide–semiconductor (CMOS) high-density microelectrode array (MEA). The system features a novel reprogrammable and flexible event engine unit to detect arbitrary spatio-temporal patterns of recorded action potentials and is capable of delivering sub-millisecond closed-loop feedback of electrical stimulation upon trigger events in real-time. The relative timing between action potentials of individual neurons as well as the temporal pattern among multiple neurons, or neuronal assemblies, is considered an important factor governing memory and learning in the brain. Artificially changing timings between arbitrary sets of spiking neurons with our system could provide a “knob” to tune information processing in the network. PMID:23335887

  4. Proportional Insulin Infusion in Closed-Loop Control of Blood Glucose

    PubMed Central

    Grasman, Johan

    2017-01-01

    A differential equation model is formulated that describes the dynamics of glucose concentration in blood circulation. The model accounts for the intake of food, expenditure of calories and the control of glucose levels by insulin and glucagon. These and other hormones affect the blood glucose level in various ways. In this study only main effects are taken into consideration. Moreover, by making a quasi-steady state approximation the model is reduced to a single nonlinear differential equation of which parameters are fit to data from healthy subjects. Feedback provided by insulin plays a key role in the control of the blood glucose level. Reduced β-cell function and insulin resistance may hamper this process. With the present model it is shown how by closed-loop control these defects, in an organic way, can be compensated with continuous infusion of exogenous insulin. PMID:28060898

  5. Closed-loop power and focus control of laser welding for full-penetration monitoring.

    PubMed

    Bardin, Fabrice; Cobo, Adolfo; Lopez-Higuera, Jose M; Collin, Olivier; Aubry, Pascal; Dubois, Thierry; Högström, Mats; Nylen, Per; Jonsson, Peter; Jones, Julian D C; Hand, Duncan P

    2005-01-01

    We describe a closed-loop control system ensuring full penetration in welding by controlling the focus position and power of a 4-kW Nd:YAG laser. A focus position monitoring system was developed based on the chromatic aberration of the focusing optics. With the laser power control system we can determine the degree of penetration by analyzing the keyhole image intensity profile. We demonstrate performance in bead-on-plate welding of Inconel 718 and titanium. The focus control system maintained a focal position on tilted and nonflat workpieces, and the penetration monitoring technique successfully controlled the laser power to maintain the full-penetration regime in the presence of linear and step changes of thickness. Finally we discuss the performances and the limits of the systems when applied to a realistic complex aerospace component.

  6. Closed loop regeneration system for generating mechanical energy and the method therefor

    SciTech Connect

    Hanrahan, R.J.; Gupta, A.K.

    1989-01-17

    A closed loop regeneration system is described for generating mechanical and thermal energy comprising: means for combining molecular chlorine and hydrogen to form hydrogen chloride at high temperatures and pressure; means receiving the hydrogen chloride from the combining means for generating mechanical power; means for extracting thermal energy from the hydrogen chloride; means for converting the hydrogen chloride to molecular hydrogen and chlorine; the converting means comprising a first reactor containing copper and cuprous chloride; means for passing the hydrogen chloride over the copper and cuprous chloride at a temperature of at least about 100/sup 0/C to thereby generate cuprous chloride, cupric chloride and molecular hydrogen; a second reactor containing cuprous chloride and cupric chloride; means for conveying the thermal energy from the extracting means to the second reactor to thereby generate copper, cuprous chloride and molecular chlorine; and means for conveying the generated molecular chlorine and hydrogen to the combining means.

  7. Cycle-averaged dynamics of a periodically driven, closed-loop circulation model

    NASA Technical Reports Server (NTRS)

    Heldt, T.; Chang, J. L.; Chen, J. J. S.; Verghese, G. C.; Mark, R. G.

    2005-01-01

    Time-varying elastance models have been used extensively in the past to simulate the pulsatile nature of cardiovascular waveforms. Frequently, however, one is interested in dynamics that occur over longer time scales, in which case a detailed simulation of each cardiac contraction becomes computationally burdensome. In this paper, we apply circuit-averaging techniques to a periodically driven, closed-loop, three-compartment recirculation model. The resultant cycle-averaged model is linear and time invariant, and greatly reduces the computational burden. It is also amenable to systematic order reduction methods that lead to further efficiencies. Despite its simplicity, the averaged model captures the dynamics relevant to the representation of a range of cardiovascular reflex mechanisms. c2004 Elsevier Ltd. All rights reserved.

  8. Closed Loop Active Flow Separation Detection and Control in a Multistage Compressor

    NASA Technical Reports Server (NTRS)

    Bright, Michelle M.; Culley, Dennis E.; Braunscheidel, Edward P.; Welch, Gerard E.

    2005-01-01

    Active closed loop flow control was successfully demonstrated on a full annulus of stator vanes in a low speed axial compressor. Two independent methods of detecting separated flow conditions on the vane suction surface were developed. The first technique detects changes in static pressure along the vane suction surface, while the second method monitors variation in the potential field of the downstream rotor. Both methods may feasibly be used in future engines employing embedded flow control technology. In response to the detection of separated conditions, injection along the suction surface of each vane was used. Injected mass flow on the suction surface of stator vanes is known to reduce separation and the resulting limitation on static pressure rise due to lowered diffusion in the vane passage. A control algorithm was developed which provided a proportional response of the injected mass flow to the degree of separation, thereby minimizing the performance penalty on the compressor system.

  9. Closed Loop Guidance with Multiple Constraints for Low Orbit Vehicle Trajectory Optimization

    NASA Astrophysics Data System (ADS)

    Zhang, Rufei; Zhao, Shifan

    Low orbit has features of strong invisibility and penetration, but needs more shutdown energy comparable to high orbit under the same range, which strongly requires studying the problem of delivery capacity optimization for multi-stage launch vehicles. Based on remnant apparent velocity and constraints models, multi-constraint closed-loop guidance with constraints of trajectory maximum height and azimuth was proposed, which adopted elliptical orbit theory and Newton iteration algorithm to optimize trajectory and thrust direction, reached to take full advantage of multi-stage launch vehicle propellant, and guided low orbit vehicle to enter maximum range trajectory. Theory deduction and numerical example demonstrate that the proposed guidance method could extend range and achieve precise control for orbit maximum height and azimuth.

  10. Cycle-averaged dynamics of a periodically driven, closed-loop circulation model

    NASA Technical Reports Server (NTRS)

    Heldt, T.; Chang, J. L.; Chen, J. J. S.; Verghese, G. C.; Mark, R. G.

    2005-01-01

    Time-varying elastance models have been used extensively in the past to simulate the pulsatile nature of cardiovascular waveforms. Frequently, however, one is interested in dynamics that occur over longer time scales, in which case a detailed simulation of each cardiac contraction becomes computationally burdensome. In this paper, we apply circuit-averaging techniques to a periodically driven, closed-loop, three-compartment recirculation model. The resultant cycle-averaged model is linear and time invariant, and greatly reduces the computational burden. It is also amenable to systematic order reduction methods that lead to further efficiencies. Despite its simplicity, the averaged model captures the dynamics relevant to the representation of a range of cardiovascular reflex mechanisms. c2004 Elsevier Ltd. All rights reserved.

  11. A micro flow-meter for closed-loop management of biological samples.

    PubMed

    Accoto, Dino; Damiani, Francesco; Campisi, Michele; Castrataro, Piero; Campolo, Domenico; Guglielmelli, Eugenio; Dario, Paolo

    2005-01-01

    The closed-loop management of biological samples in μTAS requires proper flow-sensors to be inserted in the hydraulic path. The optimal choice between hybrid mounting and monolithic fabrication depends on several design variables, one of which is the technological compatibility between the sensor and the pumping mechanism. Monolithic integration appears to be the eligible solution if both pumps and sensors can be fabricated with the same technological process. In this paper we show that it is actually possible to fabricate a flow-sensor, based on streaming potential detection, with the same soft-lithographic process used for the fabrication of electroosmotic pumps. The device has been fabricated in PDMS and experimentally tested, showing a good linearity. Finally, its time-varying response, related to the aging of the PDMS surface, is discussed.

  12. Capacitive sensing circuit for closed-loop control of wide tuning range microspectrometers

    NASA Astrophysics Data System (ADS)

    Susli, Mohamad; Silva, K. K. M. B. Dilusha; Boussaid, Farid; Faraone, Lorenzo; Dell, John M.

    2010-04-01

    We examine the problem of simultaneous drive and capacitance sensing, on a microelectromechanical systems (MEMS) device, where the drive is a bipolar AC waveform. The attention of this paper is particularly focused on wavelength calibration of the microspectrometer, a MEMS micromachined Fabry Perot filter monolithically integrated with a photodetector. However, this work is also very pertinent to other bipolar AC driven MEMS devices, which presently use separate measurement MEMS structures. To avoid charging effects, the microspectrometer must be driven by an AC waveform and, the only option for capacitance measurement is to do so simultaneously, on the same terminals, as the drive waveform is applied. We propose a novel differential capacitive sensing circuit to determine the centre wavelength of the MEMS-based micro-spectrometer, allowing closed-loop control of the microspectrometer's centre wavelength. Automatic calibration can be realized with the addition of a known light source.

  13. A statistical learning strategy for closed-loop control of fluid flows

    NASA Astrophysics Data System (ADS)

    Guéniat, Florimond; Mathelin, Lionel; Hussaini, M. Yousuff

    2016-12-01

    This work discusses a closed-loop control strategy for complex systems utilizing scarce and streaming data. A discrete embedding space is first built using hash functions applied to the sensor measurements from which a Markov process model is derived, approximating the complex system's dynamics. A control strategy is then learned using reinforcement learning once rewards relevant with respect to the control objective are identified. This method is designed for experimental configurations, requiring no computations nor prior knowledge of the system, and enjoys intrinsic robustness. It is illustrated on two systems: the control of the transitions of a Lorenz'63 dynamical system, and the control of the drag of a cylinder flow. The method is shown to perform well.

  14. Wide field adaptive optics laboratory demonstration with closed-loop tomographic control.

    PubMed

    Costille, Anne; Petit, Cyril; Conan, Jean-Marc; Kulcsár, Caroline; Raynaud, Henri-François; Fusco, Thierry

    2010-03-01

    HOMER, the new bench developed at ONERA devoted to wide field adaptive optics (WFAO) laboratory research, has allowed the first experimental validations of multi-conjugate adaptive optics (MCAO) and laser tomography adaptive optics (LTAO) concepts with a linear quadratic Gaussian (LQG) control approach. Results obtained in LTAO in closed loop show the significant gain in performance brought by LQG control, which allows tomographic reconstruction. We present a calibration and model identification strategy. Experimental results are shown to be consistent with end-to-end simulations. These results are very encouraging and demonstrate robustness of performance with respect to inevitable experimental uncertainties. They represent a first step for the study of very large telescope (VLT) and extremely large telescopes (ELT) instruments.

  15. Closed-loop control for global coverage and equatorial hovering about an asteroid

    NASA Astrophysics Data System (ADS)

    Guelman, Mauricio M.

    2017-08-01

    The purpose of this work is to develop a simple control law to implement stable orbits about a small rotating celestial body to achieve global coverage as well as fixed-body hovering on the equatorial plane. The celestial body is assumed to be rotating about a principal axis, with constant rotational velocity along the largest moment of inertia. A simple three dimensional closed-loop guidance law function of position and velocity is defined and analyzed, enabling the determination of the guidance constants to assure convergence to any desired circular orbit about the irregular celestial body, controlling independently five orbital parameters: inclination, right ascension of the ascending node, orbital radius, orbital rate and equatorial longitude. Representative numerical results are presented for an Eros type asteroid.

  16. Closed-loop training of attention with real-time brain imaging.

    PubMed

    deBettencourt, Megan T; Cohen, Jonathan D; Lee, Ray F; Norman, Kenneth A; Turk-Browne, Nicholas B

    2015-03-01

    Lapses of attention can have negative consequences, including accidents and lost productivity. Here we used closed-loop neurofeedback to improve sustained attention abilities and reduce the frequency of lapses. During a sustained attention task, the focus of attention was monitored in real time with multivariate pattern analysis of whole-brain neuroimaging data. When indicators of an attentional lapse were detected in the brain, we gave human participants feedback by making the task more difficult. Behavioral performance improved after one training session, relative to control participants who received feedback from other participants' brains. This improvement was largest when feedback carried information from a frontoparietal attention network. A neural consequence of training was that the basal ganglia and ventral temporal cortex came to represent attentional states more distinctively. These findings suggest that attentional failures do not reflect an upper limit on cognitive potential and that attention can be trained with appropriate feedback about neural signals.

  17. Closed Loop, DM Diversity-based, Wavefront Correction Algorithm for High Contrast Imaging Systems

    NASA Technical Reports Server (NTRS)

    Give'on, Amir; Belikov, Ruslan; Shaklan, Stuart; Kasdin, Jeremy

    2007-01-01

    High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

  18. Development of closed-loop supply chain network in terms of corporate social responsibility.

    PubMed

    Pedram, Ali; Pedram, Payam; Yusoff, Nukman Bin; Sorooshian, Shahryar

    2017-01-01

    Due to the rise in awareness of environmental issues and the depletion of virgin resources, many firms have attempted to increase the sustainability of their activities. One efficient way to elevate sustainability is the consideration of corporate social responsibility (CSR) by designing a closed loop supply chain (CLSC). This paper has developed a mathematical model to increase corporate social responsibility in terms of job creation. Moreover the model, in addition to increasing total CLSC profit, provides a range of strategic decision solutions for decision makers to select a best action plan for a CLSC. A proposed multi-objective mixed-integer linear programming (MILP) model was solved with non-dominated sorting genetic algorithm II (NSGA-II). Fuzzy set theory was employed to select the best compromise solution from the Pareto-optimal solutions. A numerical example was used to validate the potential application of the proposed model. The results highlight the effect of CSR in the design of CLSC.

  19. Plant Biomass Leaching for Nutrient Recovery in Closed Loop Systems Project

    NASA Technical Reports Server (NTRS)

    Zeitlin, Nancy P.; Wheeler, Raymond (Compiler); Lunn, Griffin

    2015-01-01

    Plants will be important for food and O2 production during long term human habitation in space. Recycling of nutrients (e.g., from waste materials) could reduce the resupply costs of fertilizers for growing these plants. Work at NASA's Kennedy Space Center has shown that ion exchange resins can extract fertilizer (plant essential nutrients) from human waste water, after which the residual brine could be treated with electrodialysis to recover more water and produce high value chemicals (e.g., acids and bases). In habitats with significant plant production, inedible biomass becomes a major source of solid waste. To "close the loop" we also need to recover useful nutrients and fertilizer from inedible biomass. We are investigating different approaches to retrieve nutrients from inedible plant biomass, including physical leaching with water, processing the biomass in bioreactors, changing the pH of leaching processing, and/or conducting multiple leaches of biomass residues.

  20. Safe and Ecological Refluxing with a Closed-Loop Air Cooling System.

    PubMed

    Böhmdorfer, Stefan; Eilenberger, Gottfried; Zweckmair, Thomas; Sumerskii, Ivan; Potthast, Antje; Rosenau, Thomas

    2017-01-20

    Off-the-shelf computer cooling hardware was used to construct a closed-loop air cooling system (CLACS) that is distinguished by scalability, low energy, and no tap water consumption. Constructed to be generally used with laboratory condensers, the system was tested with several common low and high boiling solvents and showed a condensation performance equivalent to conventional tap water cooling. Reaction yields were therefore unaffected. Also, long-lasting Soxhlet extractions showed no performance loss relative to conventional cooling. Optionally, the device can be assembled from low-voltage components and be powered from a battery, rendering it independent of the main power. Both investment and running costs are minimal, allowing a lab-wide adoption and elimination of the two major drawbacks of commonly employed tap water cooling: waste of drinking water and the risk of flooding. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. On-board closed-loop congestion control for satellite based packet switching networks

    NASA Technical Reports Server (NTRS)

    Chu, Pong P.; Ivancic, William D.; Kim, Heechul

    1993-01-01

    NASA LeRC is currently investigating a satellite architecture that incorporates on-board packet switching capability. Because of the statistical nature of packet switching, arrival traffic may fluctuate and thus it is necessary to integrate congestion control mechanism as part of the on-board processing unit. This study focuses on the closed-loop reactive control. We investigate the impact of the long propagation delay on the performance and propose a scheme to overcome the problem. The scheme uses a global feedback signal to regulate the packet arrival rate of ground stations. In this scheme, the satellite continuously broadcasts the status of its output buffer and the ground stations respond by selectively discarding packets or by tagging the excessive packets as low-priority. The two schemes are evaluated by theoretical queuing analysis and simulation. The former is used to analyze the simplified model and to determine the basic trends and bounds, and the later is used to assess the performance of a more realistic system and to evaluate the effectiveness of more sophisticated control schemes. The results show that the long propagation delay makes the closed-loop congestion control less responsive. The broadcasted information can only be used to extract statistical information. The discarding scheme needs carefully-chosen status information and reduction function, and normally requires a significant amount of ground discarding to reduce the on-board packet loss probability. The tagging scheme is more effective since it tolerates more uncertainties and allows a larger margin of error in status information. It can protect the high-priority packets from excessive loss and fully utilize the downlink bandwidth at the same time.

  2. A neurochemical closed-loop controller for deep brain stimulation: toward individualized smart neuromodulation therapies.

    PubMed

    Grahn, Peter J; Mallory, Grant W; Khurram, Obaid U; Berry, B Michael; Hachmann, Jan T; Bieber, Allan J; Bennet, Kevin E; Min, Hoon-Ki; Chang, Su-Youne; Lee, Kendall H; Lujan, J L

    2014-01-01

    Current strategies for optimizing deep brain stimulation (DBS) therapy involve multiple postoperative visits. During each visit, stimulation parameters are adjusted until desired therapeutic effects are achieved and adverse effects are minimized. However, the efficacy of these therapeutic parameters may decline with time due at least in part to disease progression, interactions between the host environment and the electrode, and lead migration. As such, development of closed-loop control systems that can respond to changing neurochemical environments, tailoring DBS therapy to individual patients, is paramount for improving the therapeutic efficacy of DBS. Evidence obtained using electrophysiology and imaging techniques in both animals and humans suggests that DBS works by modulating neural network activity. Recently, animal studies have shown that stimulation-evoked changes in neurotransmitter release that mirror normal physiology are associated with the therapeutic benefits of DBS. Therefore, to fully understand the neurophysiology of DBS and optimize its efficacy, it may be necessary to look beyond conventional electrophysiological analyses and characterize the neurochemical effects of therapeutic and non-therapeutic stimulation. By combining electrochemical monitoring and mathematical modeling techniques, we can potentially replace the trial-and-error process used in clinical programming with deterministic approaches that help attain optimal and stable neurochemical profiles. In this manuscript, we summarize the current understanding of electrophysiological and electrochemical processing for control of neuromodulation therapies. Additionally, we describe a proof-of-principle closed-loop controller that characterizes DBS-evoked dopamine changes to adjust stimulation parameters in a rodent model of DBS. The work described herein represents the initial steps toward achieving a "smart" neuroprosthetic system for treatment of neurologic and psychiatric disorders.

  3. Driving Sleep Slow Oscillations by Auditory Closed-Loop Stimulation—A Self-Limiting Process

    PubMed Central

    Ngo, Hong-Viet V.; Miedema, Arjan; Faude, Isabel; Martinetz, Thomas; Mölle, Matthias

    2015-01-01

    The <1 Hz EEG slow oscillation (SO) is a hallmark of slow-wave sleep (SWS) and is critically involved in sleep-associated memory formation. Previous studies showed that SOs and associated memory function can be effectively enhanced by closed-loop auditory stimulation, when clicks are presented in synchrony with upcoming SO up states. However, increasing SOs and synchronized excitability also bear the risk of emerging seizure activity, suggesting the presence of mechanisms in the healthy brain that counter developing hypersynchronicity during SOs. Here, we aimed to test the limits of driving SOs through closed-loop auditory stimulation in healthy humans. Study I tested a “Driving stimulation” protocol (vs “Sham”) in which trains of clicks were presented in synchrony with SO up states basically as long as an ongoing SO train was identified on-line. Study II compared Driving stimulation with a “2-Click” protocol where the maximum of stimuli delivered in a train was limited to two clicks. Stimulation was applied during SWS in the first 210 min of nocturnal sleep. Before and after sleep declarative word-pair memories were tested. Compared with the Sham control, Driving stimulation prolonged SO trains and enhanced SO amplitudes, phase-locked spindle activity, and overnight retention of word pairs (all ps < 0.05). Importantly, effects of Driving stimulation did not exceed those of 2-Click stimulation (p > 0.180), indicating the presence of a mechanism preventing the development of hypersynchronicity during SO activity. Assessment of temporal dynamics revealed a rapidly fading phase-locked spindle activity during repetitive click stimulation, suggesting that spindle refractoriness contributes to this protective mechanism. PMID:25926443

  4. Closed-loop control of renal perfusion pressure in physiological experiments.

    PubMed

    Campos-Delgado, D U; Bonilla, I; Rodríguez-Martínez, M; Sánchez-Briones, M E; Ruiz-Hernández, E

    2013-07-01

    This paper presents the design, experimental modeling, and control of a pump-driven renal perfusion pressure (RPP)-regulatory system to implement precise and relatively fast RPP regulation in rats. The mechatronic system is a simple, low-cost, and reliable device to automate the RPP regulation process based on flow-mediated occlusion. Hence, the regulated signal is the RPP measured in the left femoral artery of the rat, and the manipulated variable is the voltage applied to a dc motor that controls the occlusion of the aorta. The control system is implemented in a PC through the LabView software, and a data acquisition board NI USB-6210. A simple first-order linear system is proposed to approximate the dynamics in the experiment. The parameters of the model are chosen to minimize the error between the predicted and experimental output averaged from eight input/output datasets at different RPP operating conditions. A closed-loop servocontrol system based on a pole-placement PD controller plus dead-zone compensation was proposed for this purpose. First, the feedback structure was validated in simulation by considering parameter uncertainty, and constant and time-varying references. Several experimental tests were also conducted to validate in real time the closed-loop performance for stepwise and fast switching references, and the results show the effectiveness of the proposed automatic system to regulate the RPP in the rat, in a precise, accurate (mean error less than 2 mmHg) and relatively fast mode (10-15 s of response time).

  5. Closed-loop regulation of arterial pressure after acute brain death.

    PubMed

    Soltesz, Kristian; Sjöberg, Trygve; Jansson, Tomas; Johansson, Rolf; Robertsson, Anders; Paskevicius, Audrius; Liao, Quiming; Qin, Guangqi; Steen, Stig

    2017-06-10

    The purpose of this concept study was to investigate the possibility of automatic mean arterial pressure (MAP) regulation in a porcine heart-beating brain death (BD) model. Hemodynamic stability of BD donors is necessary for maintaining acceptable quality of donated organs for transplantation. Manual stabilization is challenging, due to the lack of vasomotor function in BD donors. Closed-loop stabilization therefore has the potential of increasing availability of acceptable donor organs, and serves to indicate feasibility within less demanding patient groups. A dynamic model of nitroglycerine pharmacology, suitable for controller synthesis, was identified from an experiment involving an anesthetized pig, using a gradient-based output error method. The model was used to synthesize a robust PID controller for hypertension prevention, evaluated in a second experiment, on a second, brain dead, pig. Hypotension was simultaneously prevented using closed-loop controlled infusion of noradrenaline, by means of a previously published controller. A linear model of low order, with variable (uncertain) gain, was sufficient to describe the dynamics to be controlled. The robustly tuned PID controller utilized in the second experiment kept the MAP within a user-defined range. The system was able to prevent hypertension, exceeding a reference of 100 mmHg by more than 10%, during 98% of a 12 h experiment. This early work demonstrates feasibility of the investigated modelling and control synthesis approach, for the purpose of maintaining normotension in a porcine BD model. There remains a need to characterize individual variability, in order to ensure robust performance over the expected population.

  6. Hybrid Closed-Loop Insulin Delivery in Type 1 Diabetes During Supervised Outpatient Conditions

    PubMed Central

    Grosman, Benyamin; Ilany, Jacob; Roy, Anirban; Kurtz, Natalie; Wu, Di; Parikh, Neha; Voskanyan, Gayane; Konvalina, Noa; Mylonas, Chrystaleni; Gottlieb, Rebecca; Kaufman, Francine; Cohen, Ohad

    2016-01-01

    Background: Efficacy and safety of the Medtronic Hybrid Closed-Loop (HCL) system were tested in subjects with type 1 diabetes in a supervised outpatient setting. Methods: The HCL system is a prototype research platform that includes a sensor-augmented insulin pump in communication with a control algorithm housed on an Android-based cellular device. Nine subjects with type 1 diabetes (5 female, mean age 53.3 years, mean A1C 7.2%) underwent 9 studies totaling 571 hours of closed-loop control using either default or personalized parameters. The system required meal announcements with estimates of carbohydrate (CHO) intake that were based on metabolic kitchen quantification (MK), dietician estimates (D), or subject estimates (Control). Postprandial glycemia was compared for MK, D, and Control meals. Results: The overall sensor glucose mean was 145 ± 43, the overall percentage time in the range 70-180 mg/dL was 80%, the overall percentage time <70 mg/dL was 0.79%. Compared to intervals of default parameter use (225 hours), intervals of personalized parameter use (346 hours), sensor glucose mean was 158 ± 49 and 137 ± 37 mg/dL (P < .001), respectively, and included more time in range (87% vs 68%) and less time below range (0.54% vs 1.18%). Most subjects underestimated the CHO content of meals, but postprandial glycemia was not significantly different between MK and matched Control meals (P = .16) or between D and matched Control meals (P = .76). There were no episodes of severe hypoglycemia. Conclusions: The HCL system was efficacious and safe during this study. Personally adapted HCL parameters were associated with more time in range and less time below range than default parameters. Accurate estimates of meal CHO did not contribute to improved postprandial glycemia. PMID:26880389

  7. Synthesis of high-complexity rhythmic signals for closed-loop electrical neuromodulation.

    PubMed

    Zalay, Osbert C; Bardakjian, Berj L

    2013-06-01

    We propose an approach to synthesizing high-complexity rhythmic signals for closed-loop electrical neuromodulation using cognitive rhythm generator (CRG) networks, wherein the CRG is a hybrid oscillator comprised of (1) a bank of neuronal modes, (2) a ring device (clock), and (3) a static output nonlinearity (mapper). Networks of coupled CRGs have been previously implemented to simulate the electrical activity of biological neural networks, including in silico models of epilepsy, producing outputs of similar waveform and complexity to the biological system. This has enabled CRG network models to be used as platforms for testing seizure control strategies. Presently, we take the application one step further, envisioning therapeutic CRG networks as rhythmic signal generators creating neuromimetic signals for stimulation purposes, motivated by recent research indicating that stimulus complexity and waveform characteristics influence neuromodulation efficacy. To demonstrate this concept, an epileptiform CRG network generating spontaneous seizure-like events (SLEs) was coupled to a therapeutic CRG network, forming a closed-loop neuromodulation system. SLEs are associated with low-complexity dynamics and high phase coherence in the network. The tuned therapeutic network generated a high-complexity, multi-banded rhythmic stimulation signal with prominent theta and gamma-frequency power that suppressed SLEs and increased dynamic complexity in the epileptiform network, as measured by a relative increase in the maximum Lyapunov exponent and decrease in phase coherence. CRG-based neuromodulation outperformed both low and high-frequency periodic pulse stimulation, suggesting that neuromodulation using complex, biomimetic signals may provide an improvement over conventional electrical stimulation techniques for treating neurological disorders such as epilepsy.

  8. Closed-Loop Control Without Meal Announcement in Type 1 Diabetes.

    PubMed

    Cameron, Faye M; Ly, Trang T; Buckingham, Bruce A; Maahs, David M; Forlenza, Gregory P; Levy, Carol J; Lam, David; Clinton, Paula; Messer, Laurel H; Westfall, Emily; Levister, Camilla; Xie, Yan Yan; Baysal, Nihat; Howsmon, Daniel; Patek, Stephen D; Bequette, B Wayne

    2017-08-02

    A fully closed-loop insulin-only system was developed to provide glucose control in patients with type 1 diabetes without requiring announcement of meals or activity. Our goal was to assess initial safety and efficacy of this system. The multiple model probabilistic controller (MMPPC) anticipates meals when the patient is awake. The controller used the subject's basal rates and total daily insulin dose for initialization. The system was tested at two sites on 10 patients in a 30-h inpatient study, followed by 15 subjects at three sites in a 54-h supervised hotel study, where the controller was challenged by exercise and unannounced meals. The system was implemented on the UVA DiAs system using a Roche Spirit Combo Insulin Pump and a Dexcom G4 Continuous Glucose Monitor. The mean overall (24-h basis) and nighttime (11 PM-7 AM) continuous glucose monitoring (CGM) values were 142 and 125 mg/dL during the inpatient study. The hotel study used a different daytime tuning and manual announcement, instead of automatic detection, of sleep and wake periods. This resulted in mean overall (24-h basis) and nighttime CGM values of 152 and 139 mg/dL for the hotel study and there was also a reduction in hypoglycemia events from 1.6 to 0.91 events/patient/day. The MMPPC system achieved a mean glucose that would be particularly helpful for people with an elevated A1c as a result of frequent missed meal boluses. Current full closed loop has a higher risk for hypoglycemia when compared with algorithms using meal announcement.

  9. Detecting a Cortical Fingerprint of Parkinson's Disease for Closed-Loop Neuromodulation

    PubMed Central

    Kern, Kevin; Naros, Georgios; Braun, Christoph; Weiss, Daniel; Gharabaghi, Alireza

    2016-01-01

    Recent evidence suggests that deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) mediates its clinical effects by modulating cortical oscillatory activity, presumably via a direct cortico-subthalamic connection. This observation might pave the way for novel closed-loop approaches comprising a cortical sensor. Enhanced beta oscillations (13-35 Hz) have been linked to the pathophysiology of PD and may serve as such a candidate marker to localize a cortical area reliably modulated by DBS. However, beta-oscillations are widely distributed over the cortical surface, necessitating an additional signal source for spotting the cortical area linked to the pathologically synchronized cortico-subcortical motor network. In this context, both cortico-subthalamic coherence and cortico-muscular coherence (CMC) have been studied in PD patients. Whereas, the former requires invasive recordings, the latter allows for non-invasive detection, but displays a rather distributed cortical synchronization pattern in motor tasks. This distributed cortical representation may conflict with the goal of detecting a cortical localization with robust biomarker properties which is detectable on a single subject basis. We propose that this limitation could be overcome when recording CMC at rest. We hypothesized that—unlike healthy subjects—PD would show CMC at rest owing to the enhanced beta oscillations observed in PD. By performing source space analysis of beta CMC recorded during resting-state magnetoencephalography, we provide preliminary evidence in one patient for a cortical hot spot that is modulated most strongly by subthalamic DBS. Such a spot would provide a prominent target region either for direct neuromodulation or for placing a potential sensor in closed-loop DBS approaches, a proposal that requires investigation in a larger cohort of PD patients. PMID:27065781

  10. Driving sleep slow oscillations by auditory closed-loop stimulation-a self-limiting process.

    PubMed

    Ngo, Hong-Viet V; Miedema, Arjan; Faude, Isabel; Martinetz, Thomas; Mölle, Matthias; Born, Jan

    2015-04-29

    The <1 Hz EEG slow oscillation (SO) is a hallmark of slow-wave sleep (SWS) and is critically involved in sleep-associated memory formation. Previous studies showed that SOs and associated memory function can be effectively enhanced by closed-loop auditory stimulation, when clicks are presented in synchrony with upcoming SO up states. However, increasing SOs and synchronized excitability also bear the risk of emerging seizure activity, suggesting the presence of mechanisms in the healthy brain that counter developing hypersynchronicity during SOs. Here, we aimed to test the limits of driving SOs through closed-loop auditory stimulation in healthy humans. Study I tested a "Driving stimulation" protocol (vs "Sham") in which trains of clicks were presented in synchrony with SO up states basically as long as an ongoing SO train was identified on-line. Study II compared Driving stimulation with a "2-Click" protocol where the maximum of stimuli delivered in a train was limited to two clicks. Stimulation was applied during SWS in the first 210 min of nocturnal sleep. Before and after sleep declarative word-pair memories were tested. Compared with the Sham control, Driving stimulation prolonged SO trains and enhanced SO amplitudes, phase-locked spindle activity, and overnight retention of word pairs (all ps < 0.05). Importantly, effects of Driving stimulation did not exceed those of 2-Click stimulation (p > 0.180), indicating the presence of a mechanism preventing the development of hypersynchronicity during SO activity. Assessment of temporal dynamics revealed a rapidly fading phase-locked spindle activity during repetitive click stimulation, suggesting that spindle refractoriness contributes to this protective mechanism.

  11. A neurochemical closed-loop controller for deep brain stimulation: toward individualized smart neuromodulation therapies

    PubMed Central

    Grahn, Peter J.; Mallory, Grant W.; Khurram, Obaid U.; Berry, B. Michael; Hachmann, Jan T.; Bieber, Allan J.; Bennet, Kevin E.; Min, Hoon-Ki; Chang, Su-Youne; Lee, Kendall H.; Lujan, J. L.

    2014-01-01

    Current strategies for optimizing deep brain stimulation (DBS) therapy involve multiple postoperative visits. During each visit, stimulation parameters are adjusted until desired therapeutic effects are achieved and adverse effects are minimized. However, the efficacy of these therapeutic parameters may decline with time due at least in part to disease progression, interactions between the host environment and the electrode, and lead migration. As such, development of closed-loop control systems that can respond to changing neurochemical environments, tailoring DBS therapy to individual patients, is paramount for improving the therapeutic efficacy of DBS. Evidence obtained using electrophysiology and imaging techniques in both animals and humans suggests that DBS works by modulating neural network activity. Recently, animal studies have shown that stimulation-evoked changes in neurotransmitter release that mirror normal physiology are associated with the therapeutic benefits of DBS. Therefore, to fully understand the neurophysiology of DBS and optimize its efficacy, it may be necessary to look beyond conventional electrophysiological analyses and characterize the neurochemical effects of therapeutic and non-therapeutic stimulation. By combining electrochemical monitoring and mathematical modeling techniques, we can potentially replace the trial-and-error process used in clinical programming with deterministic approaches that help attain optimal and stable neurochemical profiles. In this manuscript, we summarize the current understanding of electrophysiological and electrochemical processing for control of neuromodulation therapies. Additionally, we describe a proof-of-principle closed-loop controller that characterizes DBS-evoked dopamine changes to adjust stimulation parameters in a rodent model of DBS. The work described herein represents the initial steps toward achieving a “smart” neuroprosthetic system for treatment of neurologic and psychiatric disorders

  12. Partial hepatectomy hemodynamics changes: Experimental data explained by closed-loop lumped modeling.

    PubMed

    Audebert, Chloe; Bekheit, Mohamed; Bucur, Petru; Vibert, Eric; Vignon-Clementel, Irene E

    2017-01-04

    The liver function may be degraded after partial liver ablation surgery. Adverse liver hemodynamics have been shown to be associated to liver failure. The link between these hemodynamics changes and ablation size is however poorly understood. This article proposes to explain with a closed-loop lumped model the hemodynamics changes observed during twelve surgeries in pigs. The portal venous tree is modeled with a pressure-dependent variable resistor. The variables measured, before liver ablation, are used to tune the model parameters. Then, the liver partial ablation is simulated with the model and the simulated pressures and flows are compared with post-operative measurements. Fluid infusion and blood losses occur during the surgery. The closed-loop model presented accounts for these blood volume changes. Moreover, the impact of blood volume changes and the liver lobe mass estimations on the simulated variables is studied. The typical increase of portal pressure, increase of liver pressure loss, slight decrease of portal flow and major decrease in arterial flow are quantitatively captured by the model for a 75% hepatectomy. It appears that the 75% decrease in hepatic arterial flow can be explained by the resistance increase induced by the surgery, and that no hepatic arterial buffer response (HABR) mechanism is needed to account for this change. The different post-operative states, observed in experiments, are reproduced with the proposed model. Thus, an explanation for inter-subjects post-operative variability is proposed. The presented framework can easily be adapted to other species circulations and to different pathologies for clinical hepatic applications.

  13. Evaluation of a novel artificial pancreas: closed loop glycemic control system with continuous blood glucose monitoring.

    PubMed

    Tsukamoto, Yuuki; Kinoshita, Yoshihiko; Kitagawa, Hiroyuki; Munekage, Masaya; Munekage, Eri; Takezaki, Yuka; Yatabe, Tomoaki; Yamashita, Koichi; Yamazaki, Rie; Okabayashi, Takehiro; Tarumi, Masatoshi; Kobayashi, Masaki; Mishina, Suguru; Hanazaki, Kazuhiro

    2013-04-01

    A closed-loop glycemic control system using an artificial pancreas has been applied with many clinical benefits in Japan since 1987. To update this system incorporating user-friendly features, we developed a novel artificial pancreas (STG-55). The purpose of this study was to evaluate STG-55 for device usability, performance of blood glucose measurement, glycemic control characteristics in vivo in animal experiments, and evaluate its clinical feasibility. There are several features for usability improvement based on the design concepts, such as compactness, display monitor, batteries, guidance function, and reduction of the preparation time. All animal study data were compared with a clinically available artificial pancreas system in Japan (control device: STG-22). We examined correlations of both blood glucose levels between two groups (STG-55 vs. control) using Clarke's error grid analysis, and also compared mean glucose infusion rate (GIR) during glucose clamp. The results showed strong correlation in blood glucose concentrations (Pearson's product-moment correlation coefficient: 0.97; n = 1636). Clarke's error grid analysis showed that 98.4% of the data fell in Zones A and B, which represent clinically accurate or benign errors, respectively. The difference in mean GIRs was less than 0.2 mg/kg/min, which was considered not significant. Clinical feasibility study demonstrated sufficient glycemic control maintaining target glucose range between 80 and 110 (mg/dL), and between 140 and 160 without any hypoglycemia. In conclusion, STG-55 was a clinically acceptable artificial pancreas with improved interface and usability. A closed-loop glycemic control system with STG-55 would be a useful tool for surgical and critical patients in intensive care units, as well as diabetic patients. © 2013, Copyright the Authors. Artificial Organs © 2013, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  14. Detecting a Cortical Fingerprint of Parkinson's Disease for Closed-Loop Neuromodulation.

    PubMed

    Kern, Kevin; Naros, Georgios; Braun, Christoph; Weiss, Daniel; Gharabaghi, Alireza

    2016-01-01

    Recent evidence suggests that deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) mediates its clinical effects by modulating cortical oscillatory activity, presumably via a direct cortico-subthalamic connection. This observation might pave the way for novel closed-loop approaches comprising a cortical sensor. Enhanced beta oscillations (13-35 Hz) have been linked to the pathophysiology of PD and may serve as such a candidate marker to localize a cortical area reliably modulated by DBS. However, beta-oscillations are widely distributed over the cortical surface, necessitating an additional signal source for spotting the cortical area linked to the pathologically synchronized cortico-subcortical motor network. In this context, both cortico-subthalamic coherence and cortico-muscular coherence (CMC) have been studied in PD patients. Whereas, the former requires invasive recordings, the latter allows for non-invasive detection, but displays a rather distributed cortical synchronization pattern in motor tasks. This distributed cortical representation may conflict with the goal of detecting a cortical localization with robust biomarker properties which is detectable on a single subject basis. We propose that this limitation could be overcome when recording CMC at rest. We hypothesized that-unlike healthy subjects-PD would show CMC at rest owing to the enhanced beta oscillations observed in PD. By performing source space analysis of beta CMC recorded during resting-state magnetoencephalography, we provide preliminary evidence in one patient for a cortical hot spot that is modulated most strongly by subthalamic DBS. Such a spot would provide a prominent target region either for direct neuromodulation or for placing a potential sensor in closed-loop DBS approaches, a proposal that requires investigation in a larger cohort of PD patients.

  15. Pre-frontal control of closed-loop limbic neurostimulation by rodents using a brain-computer interface

    NASA Astrophysics Data System (ADS)

    Widge, Alik S.; Moritz, Chet T.

    2014-04-01

    Objective. There is great interest in closed-loop neurostimulators that sense and respond to a patient's brain state. Such systems may have value for neurological and psychiatric illnesses where symptoms have high intraday variability. Animal models of closed-loop stimulators would aid preclinical testing. We therefore sought to demonstrate that rodents can directly control a closed-loop limbic neurostimulator via a brain-computer interface (BCI). Approach. We trained rats to use an auditory BCI controlled by single units in prefrontal cortex (PFC). The BCI controlled electrical stimulation in the medial forebrain bundle, a limbic structure involved in reward-seeking. Rigorous offline analyses were performed to confirm volitional control of the neurostimulator. Main results. All animals successfully learned to use the BCI and neurostimulator, with closed-loop control of this challenging task demonstrated at 80% of PFC recording locations. Analysis across sessions and animals confirmed statistically robust BCI control and specific, rapid modulation of PFC activity. Significance. Our results provide a preliminary demonstration of a method for emotion-regulating closed-loop neurostimulation. They further suggest that activity in PFC can be used to control a BCI without pre-training on a predicate task. This offers the potential for BCI-based treatments in refractory neurological and mental illness.

  16. Pre-frontal control of closed-loop limbic neurostimulation by rodents using a brain-computer interface.

    PubMed

    Widge, Alik S; Moritz, Chet T

    2014-04-01

    There is great interest in closed-loop neurostimulators that sense and respond to a patient's brain state. Such systems may have value for neurological and psychiatric illnesses where symptoms have high intraday variability. Animal models of closed-loop stimulators would aid preclinical testing. We therefore sought to demonstrate that rodents can directly control a closed-loop limbic neurostimulator via a brain-computer interface (BCI). We trained rats to use an auditory BCI controlled by single units in prefrontal cortex (PFC). The BCI controlled electrical stimulation in the medial forebrain bundle, a limbic structure involved in reward-seeking. Rigorous offline analyses were performed to confirm volitional control of the neurostimulator. All animals successfully learned to use the BCI and neurostimulator, with closed-loop control of this challenging task demonstrated at 80% of PFC recording locations. Analysis across sessions and animals confirmed statistically robust BCI control and specific, rapid modulation of PFC activity. Our results provide a preliminary demonstration of a method for emotion-regulating closed-loop neurostimulation. They further suggest that activity in PFC can be used to control a BCI without pre-training on a predicate task. This offers the potential for BCI-based treatments in refractory neurological and mental illness.

  17. The Effects of Closed-Loop Medical Devices on the Autonomy and Accountability of Persons and Systems.

    PubMed

    Kellmeyer, Philipp; Cochrane, Thomas; Müller, Oliver; Mitchell, Christine; Ball, Tonio; Fins, Joseph J; Biller-Andorno, Nikola

    2016-10-01

    Closed-loop medical devices such as brain-computer interfaces are an emerging and rapidly advancing neurotechnology. The target patients for brain-computer interfaces (BCIs) are often severely paralyzed, and thus particularly vulnerable in terms of personal autonomy, decisionmaking capacity, and agency. Here we analyze the effects of closed-loop medical devices on the autonomy and accountability of both persons (as patients or research participants) and neurotechnological closed-loop medical systems. We show that although BCIs can strengthen patient autonomy by preserving or restoring communicative abilities and/or motor control, closed-loop devices may also create challenges for moral and legal accountability. We advocate the development of a comprehensive ethical and legal framework to address the challenges of emerging closed-loop neurotechnologies like BCIs and stress the centrality of informed consent and refusal as a means to foster accountability. We propose the creation of an international neuroethics task force with members from medical neuroscience, neuroengineering, computer science, medical law, and medical ethics, as well as representatives of patient advocacy groups and the public.

  18. Development of spin coater with close loop control system using ATMega8535 microcontroller

    NASA Astrophysics Data System (ADS)

    Pratama, Iqbal; Mindara, Jajat Yuda; Maulana, Dwindra W.; Panatarani, C.; Joni, I. Made

    2016-02-01

    Spin coater usually applied in preparation of a thin layer in industrial coatings and advanced material functionalization in various applications. This paper reports the development of spin coater with a closed loop control system using ATMega8535 microcontroller. The thickness of the thin film layer depend on the rotation of spin coater in which usually controlled by open-loop type. In long-term utilization of the spin coater, the performance of the motor usually degraded and caused the speed of the rotation is no longer accurate. Therefore to resolve the drawback, a close-loop system is applied in currently developed spin coater. The speed range of the spin coater was designed in between 450-6000 rpm, equipped with user interface through push button and LCD display. The rotary encoder transducer was applied to sense the speed of the dc motor. The pulse width modulation (PWM) method is applied to control the speed of the dc motor. The performance of the control system were evaluated based on the applied voltage to the PWM driver (L298) versus speed of the motor and also the rise time, overshoot, and settling time of the control system. The result shows that in the setting of low speed (450 rpm), the settling time is very fast about 12 seconds and very high overshoot about 225 rpm, contrary for the high speed (5550 rpm) the setting time is 71 seconds and very low overshot about 30 rpm. In addition, to evaluate the stability of the mechanical system, the spin coater was tested to prepare a ZnO thin film in various speed of rotations and at various concentrations of the solution, i.e. 10 wt.% and 15 wt.%. It is concluded that the spin coater can be utilized for thin film coating after pass the maximum of the settling time (71 seconds). The currently developed spin coater produce a film with common characteristics of the spin coater where thicker film was obtained when higher concentration was used and thinner the film was obtained when higher speed of the rotation

  19. A closed expression for the UV-divergent parts of one-loop tensor integrals in dimensional regularization

    NASA Astrophysics Data System (ADS)

    Sulyok, G.

    2017-07-01

    Starting from the general definition of a one-loop tensor N-point function, we use its Feynman parametrization to calculate the ultraviolet (UV-)divergent part of an arbitrary tensor coefficient in the framework of dimensional regularization. In contrast to existing recursion schemes, we are able to present a general analytic result in closed form that enables direct determination of the UV-divergent part of any one-loop tensor N-point coefficient independent from UV-divergent parts of other one-loop tensor N-point coefficients. Simplified formulas and explicit expressions are presented for A-, B-, C-, D-, E-, and F-functions.

  20. On the evaluation of ultra-high-precision frequency ratio measurements: examining closed loops in a graph theory framework

    NASA Astrophysics Data System (ADS)

    Robertsson, L.

    2016-12-01

    A simple method is proposed for the evaluation of comparative measurements when closed measurement loops are present in the data. Using a graph theory representation of the data a basis for the residual subspace is readily identified that together with loop closure values provide the input to a matrix equation of the same rank as the number of independent loops in the graph. As an example, ultra-high-precision frequency ratio measurements including optical standards are considered and small corrections to the experimental data are derived, yielding a list of consistent frequency ratios for work on precision frequency standards and discussions relating to a possible future redefinition of the SI second.