Science.gov

Sample records for multi-bunch feedback system

  1. A longitudinal multi-bunch feedback system using parallel digital signal processors

    SciTech Connect

    Sapozhnikov, L.; Fox, J.D.; Olsen, J.J.; Oxoby, G.; Linscott, I.; Drago, A.; Serio, M.

    1993-12-01

    A programmable longitudinal feedback system based on four AT&T 1610 digital signal processors has been developed as a component of the PEP-II R&D program. This longitudinal quick prototype is a proof of concept for the PEP-II system and implements full-speed bunch-by-bunch signal processing for storage rings with bunch spacing of 4 ns. The design incorporates a phase-detector-based front end that digitizes the oscillation phases of bunchies at the 250 MHz crossing rate, four programmable signal processors that compute correction signals, and a 250-MHz hold buffer/kicker driver stage that applies correction signals back on the beam. The design implements a general-purpose, table-driven downsampler that allows the system to be operated at several accelerator facilities. The hardware architecture of the signal processing is described, and the software algorithms used in the feedback signal computation are discussed. The system configuration used for tests at the LBL Advanced Light Source is presented.

  2. Programmable DSP-Based Multi-Bunch Feedback - Operating Experience from Six Installations

    SciTech Connect

    Fox, John D

    2000-05-15

    A longitudinal instability control system, originally developed for the PEP-II, DAPHNE and ALS machines has in the last two years been commissioned for use at the PLS and BESSY-II light sources. All of the installations are running identical hardware and use a common software distribution package. This common structure is beneficial in sharing expertise among the labs, and allows rapid commissioning of each new installation based on well-understood diagnostic and operational techniques. While the installations share the common instability control system, there are significant differences in machine dynamics between the various colliders and light sources. These differences require careful specification of the feedback algorithm and system configuration at each installation to achieve good instability control and useful operational margins. This paper highlights some of the operational experience at each installation, using measurements from each facility to illustrate the challenges unique to each machine. The authors experience on the opportunities and headaches of sharing development and operational expertise among labs on three continents is also offered.

  3. Multi-bunch energy compensation in the NLC bunch compressor

    SciTech Connect

    Zimmermann, F.; Raubenheimer, T.O.; Thomson, K.A.

    1996-06-01

    The task of the NLC bunch compressor is to reduce the length of each bunch in a train of 90 bunches from 4 mm, at extraction from the damping ring, to about 100 {mu}m, suitable for injection into the X-band main linac. This task is complicated by longitudinal long-range wake fields and the multi-bunch beam loading in the various accelerating sections of the compressor. One possible approach to compensate the multi-bunch beam loading is to add two RF systems with slightly different frequencies ({prime} {Delta}f{prime} scheme) to each accelerating section, as first proposed by Kikuchi. This paper summarizes the choice of parameters for three such compensating sections, and presents simulation results of combined single- and multi-bunch dynamics for four different NLC versions. The multi-bunch energy compensation is shown to be straightforward and its performance to be satisfactory.

  4. Multi-Bunch Simulations of the ILC for Luminosity Performance Studies

    SciTech Connect

    White, G.; Walker, N.; Schulte, D.; /CERN

    2005-07-11

    To study the luminosity performance of the International Linear Collider (ILC) with different design parameters, a simulation was constructed that tracks a multi-bunch representation of the beam from the Damping Ring extraction through to the Interaction Point. The simulation code PLACET is used to simulate the LINAC, MatMerlin is used to track through the Beam Delivery System and GUINEA-PIG for the beam-beam interaction. Included in the simulation are ground motion and wakefield effects, intra-train fast feedback and luminosity-based feedback systems. To efficiently study multiple parameters/multiple seeds, the simulation is deployed on the Queen Mary High-Throughput computing cluster at Queen Mary, University of London, where 100 simultaneous simulation seeds can be run.

  5. COMMISSIONING OF THE DIGITAL TRANSVERSE BUNCH-BY-BUNCH FEEDBACK SYSTEM FOR THE TLS.

    SciTech Connect

    HU, K.H.; KUO, C.H.; CHOU, P.J.; LEE, D.; HSU, S.Y.; CHEN, J.; WANG, C.J.; HSU, K.T.; KOBAYASHI, K.; NAKAMURA, T.; CHAO, A.W.; WENG, W.T.

    2006-06-26

    Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even beam loss. Feedback systems are used to suppress multi-bunch instabilities associated with the resistive wall of the beam ducts, cavity-like structures, and trapped ions. A new digital transverse bunch-by-bunch feedback system has recently been commissioned at the Taiwan Light Source, and has replaced the previous analog system. The new system has the advantages that it enlarges the tune acceptance and improves damping for transverse instability at high currents, such that top-up operation is achieved. After a coupled-bunch transverse instability was suppressed, more than 350 mA was successfully stored during preliminary commissioning. In this new system, a single feedback loop simultaneously suppresses both horizontal and vertical multi-bunch instabilities. Investigating the characteristics of the feedback loop and further improving the system performances are the next short-term goals. The feedback system employs the latest generation of field-programmable gate array (FPGA) processor to process bunch signals. Memory has been installed to capture up to 250 msec of bunch oscillation signal, considering system diagnostics suitable to support various beam physics studies.

  6. Laser pulse shaping for multi-bunches photoinjectors

    NASA Astrophysics Data System (ADS)

    Villa, F.; Cialdi, S.; Anania, M. P.; Gatti, G.; Giorgianni, F.; Pompili, R.

    2014-03-01

    Multi-bunch electron linac operation is required in many applications, like plasma wake field acceleration, narrow band THz generation and two color FEL. We present a short review of laser techniques employed in multi-bunch photoinjectors and propose a new scheme based on spectral phase manipulation of the laser pulse. In conclusion we show some application of multi-bunches electron beams done at SPARC_ LAB.

  7. Modeling Multi-Bunch X-band Photoinjector Challenges

    SciTech Connect

    Marsh, R A; Anderson, S G; Gibson, D J; Barty, C J

    2012-05-09

    An X-band test station is being developed at LLNL to investigate accelerator optimization for future upgrades to mono-energetic gamma-ray technology at LLNL. The test station will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. Of critical import to the functioning of the LLNL X-band system with multiple electron bunches is the performance of the photoinjector. In depth modeling of the Mark 1 LLNL/SLAC X-band rf photoinjector performance will be presented addressing important challenges that must be addressed in order to fabricate a multi-bunch Mark 2 photoinjector. Emittance performance is evaluated under different nominal electron bunch parameters using electrostatic codes such as PARMELA. Wake potential is analyzed using electromagnetic time domain simulations using the ACE3P code T3P. Plans for multi-bunch experiments and implementation of photoinjector advances for the Mark 2 design will also be discussed.

  8. Observation, control and modal analysis of longitudinal coupled-bunch instabilities in the ALS via a digital feedback system

    SciTech Connect

    Fox, J.D.; Claus, R.; Hindi, H.

    1996-09-01

    The operation of a longitudinal multi-bunch damping system using digital signal processing techniques is shown via measurements from the LBL Advanced Light Source. The feedback system (developed for use by PEP-II, ALS and DA{Phi}NE) uses a parallel array of signal processors to implement a bunch by bunch feedback system for sampling rates up to 500 MHz. The programmable DSP system allows feedback control as well as accelerator diagnostics. A diagnostic technique is illustrated which uses the DSP system to excite and then damp the beam. The resulting 12 ms time domain transient is Fourier analyzed to provide the simultaneous measurement of growth rates and damping rates of all unstable coupled-bunch beam modes.

  9. Ambulatory Feedback System

    NASA Technical Reports Server (NTRS)

    Finger, Herbert; Weeks, Bill

    1985-01-01

    This presentation discusses instrumentation that will be used for a specific event, which we hope will carry on to future events within the Space Shuttle program. The experiment is the Autogenic Feedback Training Experiment (AFTE) scheduled for Spacelab 3, currently scheduled to be launched in November, 1984. The objectives of the AFTE are to determine the effectiveness of autogenic feedback in preventing or reducing space adaptation syndrome (SAS), to monitor and record in-flight data from the crew, to determine if prediction criteria for SAS can be established, and, finally, to develop an ambulatory instrument package to mount the crew throughout the mission. The purpose of the Ambulatory Feedback System (AFS) is to record the responses of the subject during a provocative event in space and provide a real-time feedback display to reinforce the training.

  10. School Formative Feedback Systems

    ERIC Educational Resources Information Center

    Halverson, Richard

    2010-01-01

    Data-driven instructional improvement relies on developing coherent systems that allow school staff to generate, interpret, and act upon quality formative information on students and school programs. This article offers a formative feedback system model that captures how school leaders and teachers structure artifacts and practices to create…

  11. Controlling multi-bunches by a fast phase switching

    SciTech Connect

    Decker, F.J.; Jobe, R.K.; Merminga, N.; Thompson, K.A.

    1990-09-01

    In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a traveling wave-structure, so that each bunch receives a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e{sup +},e{sup {minus}}) for the high energy collisions and one (e{sup {minus}}-scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e{sup {minus}}-bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6{degree} in phase). This allows a low energy spread of this third bunch at the e{sup +}-production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented.

  12. Analyzing Feedback Control Systems

    NASA Technical Reports Server (NTRS)

    Bauer, Frank H.; Downing, John P.

    1987-01-01

    Interactive controls analysis (INCA) program developed to provide user-friendly environment for design and analysis of linear control systems, primarily feedback control. Designed for use with both small- and large-order systems. Using interactive-graphics capability, INCA user quickly plots root locus, frequency response, or time response of either continuous-time system or sampled-data system. Configuration and parameters easily changed, allowing user to design compensation networks and perform sensitivity analyses in very convenient manner. Written in Pascal and FORTRAN.

  13. Difference between BPM reading one bunch and the average of multi-bunch in Booster

    SciTech Connect

    Xi Yang

    2004-08-18

    Differences caused by BPM reading one bunch and multi-bunch average need to be well understood before the beam parameters, such as the synchrotron tune, betatron tune, and chromaticity, are extracted from those BPM data. It is easy to perform such a study using numerical simulation other than modifying the BPM electronics.

  14. Balanced bridge feedback control system

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J. (Inventor)

    1990-01-01

    In a system having a driver, a motor, and a mechanical plant, a multiloop feedback control apparatus for controlling the movement and/or positioning of a mechanical plant, the control apparatus has a first local bridge feedback loop for feeding back a signal representative of a selected ratio of voltage and current at the output driver, and a second bridge feedback loop for feeding back a signal representative of a selected ratio of force and velocity at the output of the motor. The control apparatus may further include an outer loop for feeding back a signal representing the angular velocity and/or position of the mechanical plant.

  15. A Drive Laser for Multi-Bunch Photoinjector Operation

    SciTech Connect

    Gibson, D J; Cormier, E; Messerly, M J; Prantil, M A; Barty, C J

    2012-05-11

    Numerous electron beam applications would benefit from increased average current without sacrificing beam brightness. Work is underway at LLNL to investigate the performance of X-band photoinjectors that would generate electron bunches at a rate matching the RF drive frequency, i.e. one bunch per RF cycle. A critical part of this effort involves development of photo-cathode drive laser technology. Here we present a new laser architecture that can generate pulse trains at repetition rates up to several GHz. This compact, fiber-based system is driven directly by the accelerator RF and so is inherently synchronized with the accelerating fields, and scales readily over a wide range of drive frequencies (L-band through X-band). The system will be required to produce 0.5 {mu}J, {approx}200 fs rise time, spatially and temporally shaped UV pulses designed to optimize the electron beam brightness. Presented is the current status of this system, producing 2 ps pulses from a continuous-wave source.

  16. Position feedback control system

    DOEpatents

    Bieg, Lothar F.; Jokiel, Jr., Bernhard; Ensz, Mark T.; Watson, Robert D.

    2003-01-01

    Disclosed is a system and method for independently evaluating the spatial positional performance of a machine having a movable member, comprising an articulated coordinate measuring machine comprising: a first revolute joint; a probe arm, having a proximal end rigidly attached to the first joint, and having a distal end with a probe tip attached thereto, wherein the probe tip is pivotally mounted to the movable machine member; a second revolute joint; a first support arm serially connecting the first joint to the second joint; and coordinate processing means, operatively connected to the first and second revolute joints, for calculating the spatial coordinates of the probe tip; means for kinematically constraining the articulated coordinate measuring machine to a working surface; and comparator means, in operative association with the coordinate processing means and with the movable machine, for comparing the true position of the movable machine member, as measured by the true position of the probe tip, with the desired position of the movable machine member.

  17. Probabilistic models for feedback systems.

    SciTech Connect

    Grace, Matthew D.; Boggs, Paul T.

    2011-02-01

    In previous work, we developed a Bayesian-based methodology to analyze the reliability of hierarchical systems. The output of the procedure is a statistical distribution of the reliability, thus allowing many questions to be answered. The principal advantage of the approach is that along with an estimate of the reliability, we also can provide statements of confidence in the results. The model is quite general in that it allows general representations of all of the distributions involved, it incorporates prior knowledge into the models, it allows errors in the 'engineered' nodes of a system to be determined by the data, and leads to the ability to determine optimal testing strategies. In this report, we provide the preliminary steps necessary to extend this approach to systems with feedback. Feedback is an essential component of 'complexity' and provides interesting challenges in modeling the time-dependent action of a feedback loop. We provide a mechanism for doing this and analyze a simple case. We then consider some extensions to more interesting examples with local control affecting the entire system. Finally, a discussion of the status of the research is also included.

  18. Physiological Feedback Method and System

    NASA Technical Reports Server (NTRS)

    Pope, Alan T. (Inventor); Severance, Kurt E. (Inventor)

    2002-01-01

    A method and system provide physiological feedback for a patient and/or physician. At least one physiological effect experienced by a body part of a patient is measured noninvasively. A three-dimensional graphics model serving as an analogous representation of the body part is altered in accordance with the measurements. A binocular image signal representative of the three-dimensional graphics model so-altered is displayed for the patient and/or physician in a virtual reality environment.

  19. Suppression of Beam-Ion Instability in Electron Rings with Multi-Bunch Train Beam Fillings

    SciTech Connect

    Wang, L.; Cai, Y.; Raubenheimer, T.O.; Fukuma, H.; /KEK, Tsukuba

    2011-08-18

    The ion-caused beam instability in the future light sources and electron damping rings can be serious due to the high beam current and ultra-small emittance of picometer level. One simple and effective mitigation of the instability is a multi-bunch train beam filling pattern which can significantly reduce the ion density near the beam, and therefore reduce the instability growth rate up to two orders of magnitude. The suppression is more effective for high intensity beams with low emittance. The distribution and the field of trapped ions are benchmarked to validate the model used in the paper. The wake field of ion-cloud and the beam-ion instability is investigated both analytically and numerically. We derived a simple formula for the build-up of ion-cloud and instability growth rate with the multi-bunch-train filling pattern. The ion instabilities in ILC damping ring, SuperKEKB and SPEAR3 are used to compare with our analyses. The analyses in this paper agree well with simulations.

  20. Feedback: Part of a System

    ERIC Educational Resources Information Center

    Wiliam, Dylan

    2012-01-01

    Just as a thermostat adjusts room temperature, effective feedback helps maintain a supportive environment for learning. Because of the many factors affecting how recipients respond to feedback, research offers no simple prescription for making feedback work effectively. What works in one classroom for one teacher will not work for another teacher.…

  1. Multimedia Feedback Systems for Engineering

    SciTech Connect

    Gladwell, S.; Gottlieb, E.J.; McDonald, M.J.; Slutter, C.L.

    1998-12-15

    The World Wide Web has become a key tool for information sharing. Engineers and scientists are finding that the web is especially suited to publishing the graphical, multi-layered information that is typical of their work. Web pages are easier to distribute than hardcopy. Web movies have become more accessible, in many offices, than videos. Good VRML viewing software, bundled with most new PCs, has sufficient power to support many engineering needs. In addition to publishing information science and engineering has an important tradition of peer and customer review. Reports, drawings and graphs are typically printed, distributed, reviewed, marked up, and returned to the author. Adding review comments to paper is easy. When, however, the information is in electronic form, this ease of review goes away. It's hard to write on videos. It's even harder to write comments on animated 3D models. These feedback limitations reduce the value of the information overall. Fortunately, the web can also be a useful tool for collecting peer and customer review information. When properly formed, web reports, movies, and 3D animations can be readily linked to review notes. This paper describes three multimedia feed-back systems that Sandia National Laboratories has developed to tap that potential. Each system allows people to make context-sensitive comments about specific web content and electronically ties the comments back to the web content being referenced. The fuel system ties comments to specific web pages, the second system ties the comments to specific frames of digital movies, and the third ties the comments to specific times and viewpoints within 3D animations. In addition to the technologies, this paper describes how they are being used to support intelligent machine systems design at Sandia.

  2. Feedbacks in Human-Landscape Systems

    NASA Astrophysics Data System (ADS)

    Chin, Anne; Florsheim, Joan L.; Wohl, Ellen; Collins, Brian D.

    2014-01-01

    This article identifies key questions and challenges for geomorphologists in investigating coupled feedbacks in human-landscape systems. While feedbacks occur in the absence of human influences, they are also altered by human activity. Feedbacks are a key element to understanding human-influenced geomorphic systems in ways that extend our traditional approach of considering humans as unidirectional drivers of change. Feedbacks have been increasingly identified in Earth-environmental systems, with studies of coupled human-natural systems emphasizing ecological phenomena in producing emerging concepts for social-ecological systems. Enormous gaps or uncertainties in knowledge remain with respect to understanding impact-feedback loops within geomorphic systems with significant human alterations, where the impacted geomorphic systems in turn affect humans. Geomorphology should play an important role in public policy by identifying the many diffuse and subtle feedbacks of both local- and global-scale processes. This role is urgent, while time may still be available to mitigate the impacts that limit the sustainability of human societies. Challenges for geomorphology include identification of the often weak feedbacks that occur over varied time and space scales ranging from geologic time to single isolated events and very short time periods, the lack of available data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, the varied tools and metrics needed to represent both physical and human processes, and the need to collaborate with social scientists with expertise in the human causes of geomorphic change, as well as the human responses to such change.

  3. Negative feedback system reduces pump oscillations

    NASA Technical Reports Server (NTRS)

    Rosenmann, W.

    1967-01-01

    External negative feedback system counteracts low frequency oscillations in rocket engine propellant pumps. The system uses a control piston to sense pump discharge fluid on one side and a gas pocket on the other.

  4. Migration towards periodicity in systems with feedback

    NASA Astrophysics Data System (ADS)

    Wotherspoon, Timothy David

    2009-12-01

    We study adaptation to the edge of chaos in dynamical systems as caused by feedback mechanisms between the state variables and the parameters. We begin by examining a system know for exhibiting chaotic dynamics and then move on to a spatially extended system. First, we study the effect of low-pass band filters on the dynamics of a non-isothermal autocatalator by selecting Fourier coefficients for the modes in the pass band according to a uniform distribution. Numerical simulations over many realizations of feedback are compared to theoretical predictions for the feedback size as a function of the parameter. We find that the variance in the feedback is non-zero only nearby to and within chaotic regimes in the parameter space. We numerically calculate the probability density for the parameter showing that the system adapts to the edge of chaos. We attempt to expand on this work to a spatially extended system. Although an analytical description of the natural dynamics for video feedback is beyond the scope of this work, we model video feedback in one-dimension and examine the effects of spatially averaging feedback mechanism onto a system parameter. While the unfiltered dynamics approach a fixed point for the entire parameter range, we also identify parameter ranges where the filtered system adapts to non-linear oscillations as well as fixed points.

  5. Choice of parameters for linear colliders in multi-bunch mode

    SciTech Connect

    Claus, J.

    1987-01-01

    The energy efficiency of a linear collider in multi-bunch mode is calculated for the case that the bunches in each of the two interacting beams are identical in all interaction points, a configuration which can be realized by taking advantage of the beam-beam effect between beams of opposite electric charge. The maximization of the efficiency is discussed, the maximum appears to increase nearly linearly with beam brightness and accelerating gradient, and about quadratically with the length of the ir. The optimum operating frequency for the linacs increases also, while the pulse repetition rate and the beam current needed for fixed luminosity, decrease. The increasing brightness and the decreasing current needed for higher efficiency lead to smaller transverse spotsizes in the crossing points; this imposes tighter tolerances on the relative transverse coordinates of the two beam-axes. Pillbox or similar resonators, excited in the TM01 mode, may be preferable to quadrupoles for transverse focusing, at the high frequencies and gradients that seem desirable, particularly in the final focus. 4 refs., 7 figs.

  6. RHIC 10 Hz global orbit feedback system

    SciTech Connect

    Michnoff, R.; Arnold, L.; Carboni, L.; Cerniglia, P; Curcio, A.; DeSanto, L.; Folz, C.; Ho, C.; Hoff, L.; Hulsart, R.; Karl, R.; Luo, Y.; Liu, C.; MacKay, W.; Mahler, G.; Meng, W.; Mernick, K.; Minty, M.; Montag, C.; Olsen, R.; Piacentino, J.; Popken, P.; Przybylinski, R.; Ptitsyn, V.; Ritter, J.; Schoenfeld, R.; Thieberger, P.; Tuozzolo, J.; Weston, A.; White, J.; Ziminski, P.; Zimmerman, P.

    2011-03-28

    Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the horizontal beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including a local beam feedback system at each of the two experimental areas, reinforcing the magnet base support assembly, and a mechanical servo feedback system. However, the local feedback system was insufficient because perturbation amplitudes outside the experimental areas were still problematic, and the mechanical solutions are very expensive. A global 10 Hz orbit feedback system consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two 3.8 km circumference counter-rotating rings has been developed and commissioned in February 2011. A description of the system architecture and results with beam will be discussed.

  7. Computer automation for feedback system design

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Mathematical techniques and explanations of various steps used by an automated computer program to design feedback systems are summarized. Special attention was given to refining the automatic evaluation suboptimal loop transmission and the translation of time to frequency domain specifications.

  8. Feedbacks in human-landscape systems

    NASA Astrophysics Data System (ADS)

    Chin, Anne

    2015-04-01

    As human interactions with Earth systems intensify in the "Anthropocene", understanding the complex relationships among human activity, landscape change, and societal responses to those changes is increasingly important. Interdisciplinary research centered on the theme of "feedbacks" in human-landscape systems serves as a promising focus for unraveling these interactions. Deciphering interacting human-landscape feedbacks extends our traditional approach of considering humans as unidirectional drivers of change. Enormous challenges exist, however, in quantifying impact-feedback loops in landscapes with significant human alterations. This paper illustrates an example of human-landscape interactions following a wildfire in Colorado (USA) that elicited feedback responses. After the 2012 Waldo Canyon Fire, concerns for heightened flood potential and debris flows associated with post-fire hydrologic changes prompted local landowners to construct tall fences at the base of a burned watershed. These actions changed the sediment transport regime and promoted further landscape change and human responses in a positive feedback cycle. The interactions ultimately increase flood and sediment hazards, rather than dampening the effects of fire. A simple agent-based model, capable of integrating social and hydro-geomorphological data, demonstrates how such interacting impacts and feedbacks could be simulated. Challenges for fully capturing human-landscape feedback interactions include the identification of diffuse and subtle feedbacks at a range of scales, the availability of data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, and the varied metrics and data needed to represent both the physical and human systems. By collaborating with social scientists with expertise in the human causes of landscape change, as well as the human responses to those changes, geoscientists could more fully recognize and anticipate the coupled

  9. Feedbacks in human-landscape systems.

    PubMed

    Chin, Anne; Florsheim, Joan L; Wohl, Ellen; Collins, Brian D

    2014-01-01

    This article identifies key questions and challenges for geomorphologists in investigating coupled feedbacks in human-landscape systems. While feedbacks occur in the absence of human influences, they are also altered by human activity. Feedbacks are a key element to understanding human-influenced geomorphic systems in ways that extend our traditional approach of considering humans as unidirectional drivers of change. Feedbacks have been increasingly identified in Earth-environmental systems, with studies of coupled human-natural systems emphasizing ecological phenomena in producing emerging concepts for social-ecological systems. Enormous gaps or uncertainties in knowledge remain with respect to understanding impact-feedback loops within geomorphic systems with significant human alterations, where the impacted geomorphic systems in turn affect humans. Geomorphology should play an important role in public policy by identifying the many diffuse and subtle feedbacks of both local- and global-scale processes. This role is urgent, while time may still be available to mitigate the impacts that limit the sustainability of human societies. Challenges for geomorphology include identification of the often weak feedbacks that occur over varied time and space scales ranging from geologic time to single isolated events and very short time periods, the lack of available data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, the varied tools and metrics needed to represent both physical and human processes, and the need to collaborate with social scientists with expertise in the human causes of geomorphic change, as well as the human responses to such change. PMID:23592016

  10. High-resolution pulsed-field ionization photoelectron spectroscopy using multi-bunch synchrotron radiation

    SciTech Connect

    Hsu, C.W.; Evans, M.; Ng, C.Y.; Heimann, P.

    1997-04-01

    BL9.0.2.2 is the newly constructed experimental End Station 2 at the Chemical Dynamics Beamline 9.0.2 of the Advanced Light Source (ALS). It is dedicated to the high resolution photoionization study of molecules of interest to atmospheric and combustion chemistry. This End Station is equipped with a high resolution scanning monochromator, which has been demonstrated to have a world record resolution of E/{delta}E=70,000. Taking the advantage of the high resolution ALS light, the authors have improved the energy resolution in threshold photoelectron spectroscopy (TPES) to 0.8 meV. The TPES is a popular technique for photoionization experiments at all synchrotron radiation facilities due to its high energy resolution as compared to that of traditional photoelectron spectroscopy (PES). TPES achieves higher energy resolution by preferentially detecting near zero kinetic energy photoelectrons resulting from threshold photoionization. However, the spectra obtained from the TPES technique generally are complicated by the simultaneous detection of electrons with nonzero kinetic energy, which are not fully discriminated against. On the other hand, the spectra obtained from pulsed field ionization photoelectron spectroscopy (PFI-PES) are completely free of the contamination from kinetic electrons. The PFI-PE technique basically involves the detection of the photoelectrons from field ionization of the very high-n Rydberg states, a few cm{sup {minus}1} below the ionization energy (IE), by applying a delayed pulsed electric field. Within a delay of a few microseconds, all the prompt electrons formed from direct ionization will escape from the photoionization region and will not be collected. The authors have recently overcome problems with energy resolution of an electron time-of-flight technique, and incorporated the PFI-PE technique with multi-bunch VUV synchrotron radiation.

  11. FEEDBACK SCORING SYSTEMS FOR REUSABLE KINDERGARTEN WORKBOOKS.

    ERIC Educational Resources Information Center

    GACH, PENELOPE J.; AND OTHERS

    THE DEVELOPMENT OF ECONOMICAL FEEDBACK SCORING SYSTEMS FOR REUSABLE KINDERGARTEN WORKBOOKS IS DESCRIBED. THREE PROTOTYPE SYSTEMS WERE DEVELOPED--(1) A METAL FOIL ACTIVATING AN ELECTRICAL PROBE, (2) A METAL FOIL REACTING WITH A MAGNETIC PROBE, AND (3) INVISIBLE FLUORESCENT INK REVEALED BY THE APPLICATION OF LONGWAVE ULTRAVIOLET LIGHT. (MS)

  12. Diversity in School Performance Feedback Systems

    ERIC Educational Resources Information Center

    Verhaeghe, Goedele; Schildkamp, Kim; Luyten, Hans; Valcke, Martin

    2015-01-01

    As data-based decision making is receiving increased attention in education, more and more school performance feedback systems (SPFSs) are being developed and used worldwide. These systems provide schools with data on their functioning. However, little research is available on the characteristics of the different SPFSs. Therefore, this study…

  13. Feedback linearization application for LLRF control system

    SciTech Connect

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, T.

    1999-06-01

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of the LLRF control system for LEDA. The authors propose a control law which is based on exact feedback linearization coupled with gain scheduling which reduces the effect of the deterministic klystron cathode voltage ripple that is due to harmonics of the high voltage power supply and achieves tracking of desired set points. Also, they propose an estimator of the ripple and its time derivative and the estimates based feedback linearization controller.

  14. Feedback linearization application for LLRF control system

    SciTech Connect

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, T.

    1998-12-31

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of the LLRF control system for LEDA. The authors propose a control law which is based on exact feedback linearization coupled with gain scheduling which reduces the effect of the deterministic klystron cathode voltage ripple that is due to harmonics of the high voltage power supply and achieves tracking of desired set points. Also, they propose an estimator of the ripple and its time derivative and the estimates based feedback linearization controller.

  15. Mining Feedback in Ranking and Recommendation Systems

    ERIC Educational Resources Information Center

    Zhuang, Ziming

    2009-01-01

    The amount of online information has grown exponentially over the past few decades, and users become more and more dependent on ranking and recommendation systems to address their information seeking needs. The advance in information technologies has enabled users to provide feedback on the utilities of the underlying ranking and recommendation…

  16. Kaleidoscopic light feedback for television systems

    NASA Technical Reports Server (NTRS)

    Davis, J. G.; Woods, J. M.

    1971-01-01

    Technique generates special effects for broadcast television to study effects of light feedback on television systems. Signals are produced for tape recording, broadcasting, or displaying on black-and-white or color monitors. The patterns have from three to eight sides and expand, contract, or rotate at various speeds.

  17. A Responsive High School Feedback System.

    ERIC Educational Resources Information Center

    Duby, Paul B.

    1991-01-01

    Few higher education institutions provide systematic information for high schools beyond what is involved in the application/admissions process. The Northern Michigan University (NMU) High School Feedback System was designed to meet the needs expressed by high school personnel in the Upper Peninsula of Michigan for increased frequency, quantity,…

  18. Wearable feedback systems for rehabilitation

    PubMed Central

    Sung, Michael; Marci, Carl; Pentland, Alex

    2005-01-01

    In this paper we describe LiveNet, a flexible wearable platform intended for long-term ambulatory health monitoring with real-time data streaming and context classification. Based on the MIT Wearable Computing Group's distributed mobile system architecture, LiveNet is a stable, accessible system that combines inexpensive, commodity hardware; a flexible sensor/peripheral interconnection bus; and a powerful, light-weight distributed sensing, classification, and inter-process communications software architecture to facilitate the development of distributed real-time multi-modal and context-aware applications. LiveNet is able to continuously monitor a wide range of physiological signals together with the user's activity and context, to develop a personalized, data-rich health profile of a user over time. We demonstrate the power and functionality of this platform by describing a number of health monitoring applications using the LiveNet system in a variety of clinical studies that are underway. Initial evaluations of these pilot experiments demonstrate the potential of using the LiveNet system for real-world applications in rehabilitation medicine. PMID:15987514

  19. FAST DIGITAL ORBIT FEEDBACK SYSTEMS AT NSLS.

    SciTech Connect

    PODOBEDOV,B.; KUSHNER,B.; RAMAMOORTHY,S.; TANG,Y.; ZITVOGEL,E.

    2001-06-18

    We are implementing digital orbit feedback systems to replace the analog ones in both the VUV and the X-ray rings. We developed an original VME-based design which is run by a powerful Motorola 2305 CPU and consists entirely of off-the-shelf VME boards. This makes the system inexpensive and easy to configure, and allows for high digitizing rates. The new 5 kHz digital global feedback system is currently operational in the VUV ring, and the X-ray system is in the commissioning phase. Some of the parameters achieved include vertical correction bandwidth of 200 Hz (at DC gain of 100) and typical orbit drift over a fill of <3% of the rms beam size. In this paper we discuss the system architecture, implementation and performance.

  20. Programmable DSP-based multi-bunch feedback—operational experience from six installations

    NASA Astrophysics Data System (ADS)

    Fox, J.; Prabhakar, S.; Teytelman, D.; Young, A.; Stover, G.; Drago, A.; Serio, M.; Khan, S.; Knuth, T.; Kim, Y.; Park, M.

    2000-11-01

    A longitudinal instability control system, originally developed for the PEP-II, DAΦNE and ALS machines has in the last two years been commissioned for use at the PLS and BESSY-II light sources. All of the installations are running identical hardware and use a common software distribution package. This common structure is beneficial in sharing expertise among the labs, and allows rapid commissioning of each new installation based on well-understood diagnostic and operational techniques. While the installations share the common instability control system, there are significant differences in machine dynamics between the various colliders and light sources. These differences require careful specification of the feedback algorithm and system configuration at each installation to achieve good instability control and useful operational margins. This paper highlights some of the operational experience at each installation, using measurements from each facility to illustrate the challenges unique to each machine. Our experience on the opportunities and headaches of sharing development and operational expertise among labs on three continents is also offered.

  1. Terrestrial biogeochemical feedbacks in the climate system

    NASA Astrophysics Data System (ADS)

    Arneth, A.; Harrison, S. P.; Zaehle, S.; Tsigaridis, K.; Menon, S.; Bartlein, P. J.; Feichter, J.; Korhola, A.; Kulmala, M.; O'Donnell, D.; Schurgers, G.; Sorvari, S.; Vesala, T.

    2010-08-01

    The terrestrial biosphere is a key regulator of atmospheric chemistry and climate. During past periods of climate change, vegetation cover and interactions between the terrestrial biosphere and atmosphere changed within decades. Modern observations show a similar responsiveness of terrestrial biogeochemistry to anthropogenically forced climate change and air pollution. Although interactions between the carbon cycle and climate have been a central focus, other biogeochemical feedbacks could be as important in modulating future climate change. Total positive radiative forcings resulting from feedbacks between the terrestrial biosphere and the atmosphere are estimated to reach up to 0.9 or 1.5 W m-2 K-1 towards the end of the twenty-first century, depending on the extent to which interactions with the nitrogen cycle stimulate or limit carbon sequestration. This substantially reduces and potentially even eliminates the cooling effect owing to carbon dioxide fertilization of the terrestrial biota. The overall magnitude of the biogeochemical feedbacks could potentially be similar to that of feedbacks in the physical climate system, but there are large uncertainties in the magnitude of individual estimates and in accounting for synergies between these effects.

  2. 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

  3. Assessing biosphere feedbacks on Earth System Processes

    NASA Astrophysics Data System (ADS)

    McElwain, Jennifer

    2016-04-01

    The evolution and ecology of plant life has been shaped by the direct and indirect influence of plate tectonics. Climatic change and environmental upheaval associated with the emplacement of large igneous provinces have triggered biosphere level ecological change, physiological modification and pulses of both extinction and origination. This talk will investigate the influence of large scale changes in atmospheric composition on plant ecophysiology at key intervals of the Phanerozoic. Furthermore, I will assess the extent to which plant ecophysiological response can in turn feedback on earth system processes such as the global hydrological cycle and biogeochemical cycling of nitrogen and carbon. Palaeo-atmosphere simulation experiments, palaeobotanical data and recent historical (last 50 years) data-model comparison will be used to address the extent to which plant physiological responses to atmospheric CO2 can modulate global climate change via biosphere level feedback.

  4. Feedback system design with an uncertain plant

    NASA Technical Reports Server (NTRS)

    Milich, D.; Valavani, L.; Athans, M.

    1986-01-01

    A method is developed to design a fixed-parameter compensator for a linear, time-invariant, SISO (single-input single-output) plant model characterized by significant structured, as well as unstructured, uncertainty. The controller minimizes the H(infinity) norm of the worst-case sensitivity function over the operating band and the resulting feedback system exhibits robust stability and robust performance. It is conjectured that such a robust nonadaptive control design technique can be used on-line in an adaptive control system.

  5. System analysis of force feedback microscopy

    NASA Astrophysics Data System (ADS)

    Rodrigues, Mario S.; Costa, Luca; Chevrier, Joël; Comin, Fabio

    2014-02-01

    It was shown recently that the Force Feedback Microscope (FFM) can avoid the jump-to-contact in Atomic force Microscopy even when the cantilevers used are very soft, thus increasing force resolution. In this letter, we explore theoretical aspects of the associated real time control of the tip position. We take into account lever parameters such as the lever characteristics in its environment, spring constant, mass, dissipation coefficient, and the operating conditions such as controller gains and interaction force. We show how the controller parameters are determined so that the FFM functions at its best and estimate the bandwidth of the system under these conditions.

  6. System analysis of force feedback microscopy

    SciTech Connect

    Rodrigues, Mario S.; Chevrier, Joël; Comin, Fabio

    2014-02-07

    It was shown recently that the Force Feedback Microscope (FFM) can avoid the jump-to-contact in Atomic force Microscopy even when the cantilevers used are very soft, thus increasing force resolution. In this letter, we explore theoretical aspects of the associated real time control of the tip position. We take into account lever parameters such as the lever characteristics in its environment, spring constant, mass, dissipation coefficient, and the operating conditions such as controller gains and interaction force. We show how the controller parameters are determined so that the FFM functions at its best and estimate the bandwidth of the system under these conditions.

  7. Synthesis of oscillating adaptive feedback systems

    NASA Technical Reports Server (NTRS)

    Smay, J. W.

    1973-01-01

    A synthesis theory is developed which allows system design to proceed from practical specifications on system command and/or disturbance response to a design which is very nearly optimal in terms of feedback sensor noise effects. The approach taken is to replace the nonlinear element by a mean square error minimizing approximation (dual-input describing function), and then use linear frequency domain synthesis techniques subject to additional constraints imposed by the limit cycle and the approximator. Synthesis techniques are also developed for a similar system using an externally excited oscillating signal with the above approach. The results remove the design of the systems considered from the realm of simulation and experimentation, permitting true synthesis and the optimization that accompanies it.

  8. Computing using delayed feedback systems: towards photonics

    NASA Astrophysics Data System (ADS)

    Appeltant, L.; Soriano, M. C.; Van der Sande, G.; Danckaert, J.; Massar, S.; Dambre, J.; Schrauwen, B.; Mirasso, C. R.; Fischer, I.

    2012-06-01

    Reservoir computing has recently been introduced as a new paradigm in the eld of machine learning. It is based on the dynamical properties of a network of randomly connected nodes or neurons and shows to be very promising to solve complex classication problems in a computationally ecient way. The key idea is that an input generates nonlinearly transient behavior rendering transient reservoir states suitable for linear classication. Our goal is to study up to which extent systems with delay, and especially photonic systems, can be used as reservoirs. Recently an new architecture has been proposed1 , based on a single nonlinear node with delayed feedback. An electronic1 and an opto-electronic implementation2, 3 have been demonstrated and both have proven to be very successful in terms of performance. This simple conguration, which replaces an entire network of randomly connected nonlinear nodes with one single hardware node and a delay line, is signicantly easier to implement experimentally. It is no longer necessary to construct an entire network of hundreds or even thousands of circuits, each one representing a node. With this approach one node and a delay line suce to construct a computational unit. In this manuscript, we present a further investigation of the properties of delayed feedback congurations used as a reservoir. Instead of quantifying the performance as an error obtained for a certain benchmark, we now investigate a task-independent property, the linear memory of the system.

  9. Adaptive output feedback control of flexible systems

    NASA Astrophysics Data System (ADS)

    Yang, Bong-Jun

    Neural network-based adaptive output feedback approaches that augment a linear control design are described in this thesis, and emphasis is placed on their real-time implementation with flexible systems. Two different control architectures that are robust to parametric uncertainties and unmodelled dynamics are presented. The unmodelled effects can consist of minimum phase internal dynamics of the system together with external disturbance process. Within this context, adaptive compensation for external disturbances is addressed. In the first approach, internal model-following control, adaptive elements are designed using feedback inversion. The effect of an actuator limit is treated using control hedging, and the effect of other actuation nonlinearities, such as dead zone and backlash, is mitigated by a disturbance observer-based control design. The effectiveness of the approach is illustrated through simulation and experimental testing with a three-disk torsional system, which is subjected to control voltage limit and stiction. While the internal model-following control is limited to minimum phase systems, the second approach, external model-following control, does not involve feedback linearization and can be applied to non-minimum phase systems. The unstable zero dynamics are assumed to have been modelled in the design of the existing linear controller. The laboratory tests for this method include a three-disk torsional pendulum, an inverted pendulum, and a flexible-base robot manipulator. The external model-following control architecture is further extended in three ways. The first extension is an approach for control of multivariable nonlinear systems. The second extension is a decentralized adaptive control approach for large-scale interconnected systems. The third extension is to make use of an adaptive observer to augment a linear observer-based controller. In this extension, augmenting terms for the adaptive observer can be used to achieve adaptation in

  10. Feedback Systems for Use with Paper-Based Instructional Products.

    ERIC Educational Resources Information Center

    Strandberg, Joel E.

    This survey describes 15 systems that provide feedback to students. Feedback is defined as information transfer from the instructional material to the student after a response is made by the student. The feedback is directed primarily to the student, but when a permanent record of the response occurs this information is also available to the…

  11. Utilizing feedback in adaptive SAR ATR systems

    NASA Astrophysics Data System (ADS)

    Horsfield, Owen; Blacknell, David

    2009-05-01

    Existing SAR ATR systems are usually trained off-line with samples of target imagery or CAD models, prior to conducting a mission. If the training data is not representative of mission conditions, then poor performance may result. In addition, it is difficult to acquire suitable training data for the many target types of interest. The Adaptive SAR ATR Problem Set (AdaptSAPS) program provides a MATLAB framework and image database for developing systems that adapt to mission conditions, meaning less reliance on accurate training data. A key function of an adaptive system is the ability to utilise truth feedback to improve performance, and it is this feature which AdaptSAPS is intended to exploit. This paper presents a new method for SAR ATR that does not use training data, based on supervised learning. This is achieved by using feature-based classification, and several new shadow features have been developed for this purpose. These features allow discrimination of vehicles from clutter, and classification of vehicles into two classes: targets, comprising military combat types, and non-targets, comprising bulldozers and trucks. The performance of the system is assessed using three baseline missions provided with AdaptSAPS, as well as three additional missions. All performance metrics indicate a distinct learning trend over the course of a mission, with most third and fourth quartile performance levels exceeding 85% correct classification. It has been demonstrated that these performance levels can be maintained even when truth feedback rates are reduced by up to 55% over the course of a mission.

  12. Programming and Systems Design for a Classroom Information Feedback System.

    ERIC Educational Resources Information Center

    Byers, Frances R.

    The primary outcome of any information feedback system must be data for the classroom teacher. For this reason, a system's value has to be measured in terms of its usefulness to the teacher in making instructional decisions. A report should contain only data that the teacher needs and should be produced in an understandable format. User feedback…

  13. Students' feedback: An effective tool in teachers' evaluation system

    PubMed Central

    Husain, Musharraf; Khan, Sabina

    2016-01-01

    Background: Evaluation is an integral part of medical education. Although there are various methods of teachers' evaluation, student’s feedback is considered as the most effective and reliable method albeit a controversial one. In this study, we have tried to evaluate the effectiveness of the students' feedback in teachers' evaluation in an upcoming medical college. Aim: The aim of this study was to improve the quality of teaching by introducing students' feedback as a teachers' evaluation system in a new medical college. Materials and Methods: A feedback of second professional teachers was obtained from the fourth-semester students. This feedback was obtained through a proforma which was validated through peer review. Based on the feedback, teachers were informed about their strengths and weaknesses in a confidential manner. A uniform opportunity was then provided to these teachers for 3 months to improve their teaching skills. At the end of the period, again a questionnaire was administered to both the students and the teachers to assess the effectiveness of the feedback system. Results: More than two-third of the students and teachers alike agreed that the student’s feedback is an effective tool for the faculty development. Majority of the teachers were satisfied with the present format of the feedback system and agreed that it sensitized them toward the students need. Conclusions: Student’s feedback is an effective tool for teachers' evaluation resulting in faculty development. However, other sources of feedback may also be utilized for the overall assessment of a teacher.

  14. Bat's auditory system: Corticofugal feedback and plasticity

    NASA Astrophysics Data System (ADS)

    Suga, Nobuo

    2001-05-01

    The auditory system of the mustached bat consists of physiologically distinct subdivisions for processing different types of biosonar information. It was found that the corticofugal (descending) auditory system plays an important role in improving and adjusting auditory signal processing. Repetitive acoustic stimulation, cortical electrical stimulation or auditory fear conditioning evokes plastic changes of the central auditory system. The changes are based upon egocentric selection evoked by focused positive feedback associated with lateral inhibition. Focal electric stimulation of the auditory cortex evokes short-term changes in the auditory cortex and subcortical auditory nuclei. An increase in a cortical acetylcholine level during the electric stimulation changes the cortical changes from short-term to long-term. There are two types of plastic changes (reorganizations): centripetal best frequency shifts for expanded reorganization of a neural frequency map and centrifugal best frequency shifts for compressed reorganization of the map. Which changes occur depends on the balance between inhibition and facilitation. Expanded reorganization has been found in different sensory systems and different species of mammals, whereas compressed reorganization has been thus far found only in the auditory subsystems highly specialized for echolocation. The two types of reorganizations occur in both the frequency and time domains. [Work supported by NIDCO DC00175.

  15. Educators' Perceptions of Automated Feedback Systems

    ERIC Educational Resources Information Center

    Debuse, Justin C. W.; Lawley, Meredith; Shibl, Rania

    2008-01-01

    Assessment of student learning is a core function of educators. Ideally students should be provided with timely, constructive feedback to facilitate learning. However, provision of high quality feedback becomes more complex as class sizes increase, modes of study expand and academic workloads increase. ICT solutions are being developed to…

  16. Direct laser additive fabrication system with image feedback control

    DOEpatents

    Griffith, Michelle L.; Hofmeister, William H.; Knorovsky, Gerald A.; MacCallum, Danny O.; Schlienger, M. Eric; Smugeresky, John E.

    2002-01-01

    A closed-loop, feedback-controlled direct laser fabrication system is disclosed. The feedback refers to the actual growth conditions obtained by real-time analysis of thermal radiation images. The resulting system can fabricate components with severalfold improvement in dimensional tolerances and surface finish.

  17. An Optimization Framework for Driver Feedback Systems

    SciTech Connect

    Malikopoulos, Andreas; Aguilar, Juan P.

    2013-01-01

    Modern vehicles have sophisticated electronic control units that can control engine operation with discretion to balance fuel economy, emissions, and power. These control units are designed for specific driving conditions (e.g., different speed profiles for highway and city driving). However, individual driving styles are different and rarely match the specific driving conditions for which the units were designed. In the research reported here, we investigate driving-style factors that have a major impact on fuel economy and construct an optimization framework to optimize individual driving styles with respect to these driving factors. In this context, we construct a set of polynomial metamodels to reflect the responses produced in fuel economy by changing the driving factors. Then, we compare the optimized driving styles to the original driving styles and evaluate the effectiveness of the optimization framework. Finally, we use this proposed framework to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving styles in response to actual driving conditions to improve fuel efficiency.

  18. Optical encoder feedback system for levitating rotor system

    NASA Astrophysics Data System (ADS)

    Khanna, Shrey; Ho, Joe N.; Irwen, Jonathan; Rakka, Gurjinder; Wang, Weichih

    2010-03-01

    This paper describes the design and fabrication of feedback control system for a three phase motor with a diamagnetically levitating rotor. The planar rotor described in this paper uses a triangular configuration of magnets that rotates due to nine electric coils evenly spaced around the rotor. An optical mechanical feedback system controls the frequency at which the rotor spins. The current input to the coil is controlled by a mechanical relay circuit which latches based on a DC pulse signal generated by a PID control algorithm. The mechanical relay circuit allows current to flow to each coils (the actuators of this system), which then produces a magnetic field strong enough to spin the rotor.

  19. Information feedback strategy for beltways in intelligent transportation systems

    NASA Astrophysics Data System (ADS)

    Li, Wen-Ting; Li, Jian-Qing; Chen, Bo-Kui; Huang, Xin; Wang, Zhen

    2016-03-01

    As an important part of the Intelligent Transportation System (ITS), the information feedback strategy has drawn more and more scholars' attention. A variety of feedback strategies are proposed to improve the traffic efficiency. These strategies are based on simple route scenarios, but most route scenarios are always complex in reality. In this letter, based on a complex beltway scenario, we propose a new traffic information feedback strategy called Beltway Feedback Strategy (BFS). The simulation results show that the BFS can effectively improve the transportation ability of beltways.

  20. An Automated Individual Feedback and Marking System: An Empirical Study

    ERIC Educational Resources Information Center

    Barker, Trevor

    2011-01-01

    The recent National Students Survey showed that feedback to students was an ongoing problem in Higher Education. This paper reports on the extension of our past research into the provision of automated feedback for objective testing. In the research presented here, the system has been further developed for marking practical and essay questions and…

  1. Digital Global Orbit Feedback System Developing In SRRC

    NASA Astrophysics Data System (ADS)

    Kuo, C. H.; Lin, K. K.; Chen, Jenny; Chen, J. S.; Wang, C. J.; Chen, C. S.; Hsu, K. T.

    1997-05-01

    The digital global orbit feedback system for the storage ring of SRRC has been upgraded in terms of its feedback bandwidth extension by increasing its data acquisition sampling rate and compensating eddy current effect of vacuum chamber with filter. This orbit feedback system has been applied incorporate with the insertion devices operation, such as W20 wiggler and APU undulator, in order to eliminate beam orbit disturbance. Applying this system to suppress orbit drift during energy ramping has also shown to be effective. Performance of this upgraded system will be presented in this report.

  2. Corresponding Angle Feedback in an innovative weighted transportation system

    NASA Astrophysics Data System (ADS)

    Dong, Chuanfei; Ma, Xu

    2010-05-01

    The optimal information feedback has a significant effect on many socioeconomic systems like stock market and traffic systems aiming to make full use of resources. In this Letter, we study dynamics of traffic flow with real-time information. The influence of a feedback strategy named Corresponding Angle Feedback Strategy (CAFS) is introduced, based on a two-route scenario in which dynamic information can be generated and displayed on the board to guide road users to make a choice. Our model incorporates the effects of adaptability into the cellular automaton models of traffic flow and simulation results adopting this optimal information feedback strategy have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the other three information feedback strategies, i.e., vehicle number and flux.

  3. Defining and Quantifying Feedbacks in Earth's Climate System

    NASA Astrophysics Data System (ADS)

    Schwartz, S. E.

    2008-12-01

    Feedbacks in Earth's climate system are increasingly being examined to identify processes controlling Earth's climate sensitivity, to quantify the effects of these processes, and to assess the ability of climate models to accurately represent the actual climate system and changes due to increases in greenhouse gases and other forcings. At present differing explicit or implicit choices of the measure of climate change, of definitions of feedbacks, and of the underlying non-feedback climate to which feedbacks must be referred have resulted in differing measures of feedbacks. The single variable that is most commonly taken as a measure of climate response to radiative perturbation is global (and annual) mean (near) surface (air) temperature GMST; climate models indicate that many other changes in Earth's climate scale with change in GMST. The choice of GMST as the index of climate change together with recognition that Earth's energy content H is controlled by shortwave absorption and by longwave emission at the top of the atmosphere as dH/dt = γJS/4 - ɛσTs4, where Ts is GMST, γ is the planetary coalbedo (complement of the Bond albedo, ~0.70), JS is the solar constant (~1368 W m-2), σ is the Stefan-Boltzmann constant, and ɛ defines an effective emissivity (~0.62) as the ratio of the longwave flux emitted at the top of the atmosphere to that emitted by a black body radiator at the global mean surface temperature, leads to the choice of reference no- feedback or "open loop" climate sensitivity S0 as the equilibrium change in GMST that would result from a small change the planetary energy budget, forcing ΔF, normalized to that forcing, for γ and ɛ held constant. This definition yields to first order a climate sensitivity in the absence of feedbacks S0 = (dTs/dΔF)0 = Ts/γ0JS, where the subscript 0 denotes absence of feedback. For Ts = 288 K, S0 = 0.30 K/(W m-2); for forcing from doubled CO2 taken as ΔF2X = 3.7 W m-2, the corresponding CO2 doubling temperature

  4. Sparse feedback structures for wireless control of civil systems

    NASA Astrophysics Data System (ADS)

    Verdoljak, Reuben D.; Linderman, Lauren E.

    2015-03-01

    Although originally popularized for structural health monitoring, wireless smart sensors are an attractive alternative to traditional tethered systems for structural control. Their onboard sensing, processing, and wireless communication offer all the components of a feedback control system. However, wireless smart sensors pose unique challenges for the application of centralized control, which is common in most modern control systems. Decentralized control offers several advantages to wireless structural control, including limiting the wireless communication required and the associated slow sampling rate and time delays in the control system. Previous decentralized structural control algorithms, both Ad-Hoc and Heuristic, enforce a spatial sparsity pattern during the design, which is assumed a priori. Therefore, the optimal feedback structure is not considered in the design. This work explores a decentralized optimal LQR design algorithm where the sparsity of the feedback gain is incorporated into the objective function. The control approach is compared to previous decentralized control techniques on the 20-Story control benchmark structure. Sparsity and control requirements are compared to centralized designs. The optimal sparse feedback design offers the best balance of performance, measurement feedback, and control effort. Additionally, the feedback structure identified is not easily identifiable a priori; thus, highlighting the significance of particular measurements in this feedback framework.

  5. Thermodynamics of Nonequilibrium Systems with Feedback Control

    NASA Astrophysics Data System (ADS)

    Sagawa, Takahiro

    2015-03-01

    In modern nonequilibrium physics, ``Maxwell's demon'' has attracted renewed attentions in both terms of theory and experiment. The demon plays a key role to unify thermodynamics and information theory, which can extract the useful work from a heat bath by using the obtained information via feedback control. In this talk, I will talk about the recent development of thermodynamics of information. In particular, I will focus on the generalizations of the second law of thermodynamics and the Jarzynski equality in the presence of feedback control, where information contents and thermodynamic quantities are treated on an equal footing. I will also discuss recent experimental results that realized Maxwell's demon by colloidal particles and single electrons.

  6. Indirect Identification of Linear Stochastic Systems with Known Feedback Dynamics

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    An algorithm is presented for identifying a state-space model of linear stochastic systems operating under known feedback controller. In this algorithm, only the reference input and output of closed-loop data are required. No feedback signal needs to be recorded. The overall closed-loop system dynamics is first identified. Then a recursive formulation is derived to compute the open-loop plant dynamics from the identified closed-loop system dynamics and known feedback controller dynamics. The controller can be a dynamic or constant-gain full-state feedback controller. Numerical simulations and test data of a highly unstable large-gap magnetic suspension system are presented to demonstrate the feasibility of this indirect identification method.

  7. Behavioral System Feedback Measurement Failure: Sweeping Quality under the Rug

    ERIC Educational Resources Information Center

    Mihalic, Maria T.; Ludwig, Timothy D.

    2009-01-01

    Behavioral Systems rely on valid measurement systems to manage processes and feedback and to deliver contingencies. An examination of measurement system components designed to track customer service quality of furniture delivery drivers revealed the measurement system failed to capture information it was designed to measure. A reason for this…

  8. Coherent versus Measurement Feedback: Linear Systems Theory for Quantum Information

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoki

    2014-10-01

    To control a quantum system via feedback, we generally have two options in choosing a control scheme. One is the coherent feedback, which feeds the output field of the system, through a fully quantum device, back to manipulate the system without involving any measurement process. The other one is measurement-based feedback, which measures the output field and performs a real-time manipulation on the system based on the measurement results. Both schemes have advantages and disadvantages, depending on the system and the control goal; hence, their comparison in several situations is important. This paper considers a general open linear quantum system with the following specific control goals: backaction evasion, generation of a quantum nondemolished variable, and generation of a decoherence-free subsystem, all of which have important roles in quantum information science. Some no-go theorems are proven, clarifying that those goals cannot be achieved by any measurement-based feedback control. On the other hand, it is shown that, for each control goal there exists a coherent feedback controller accomplishing the task. The key idea to obtain all the results is system theoretic characterizations of the above three notions in terms of controllability and observability properties or transfer functions of linear systems, which are consistent with their standard definitions.

  9. Output feedback for linear multivariable systems with parameter uncertainty.

    NASA Technical Reports Server (NTRS)

    Basuthakur, S.; Knapp, C. H.

    1973-01-01

    A minimax design method is applied to the problem of obtaining an acceptable output feedback matrix for linear multivariable systems with parameter uncertainty. The result is a set of nonlinear matrix equations (similar to those obtained by Levine and Athans (1970)), which must be solved for the feedback matrix. An example illustrates the technique and the fact that better results are achieved for large parameter variation than with a purely nominal design.

  10. Feedback Control of Two-Component Regulatory Systems.

    PubMed

    Groisman, Eduardo A

    2016-09-01

    Two-component systems are a dominant form of bacterial signal transduction. The prototypical two-component system consists of a sensor that responds to a specific input(s) by modifying the output of a cognate regulator. Because the output of a two-component system is the amount of phosphorylated regulator, feedback mechanisms may alter the amount of regulator, and/or modify the ability of a sensor or other proteins to alter the phosphorylation state of the regulator. Two-component systems may display intrinsic feedback whereby the amount of phosphorylated regulator changes under constant inducing conditions and without the participation of additional proteins. Feedback control allows a two-component system to achieve particular steady-state levels, to reach a given steady state with distinct dynamics, to express coregulated genes in a given order, and to activate a regulator to different extents, depending on the signal acting on the sensor. PMID:27607549

  11. Beam position feedback system for the Advanced Photon Source

    SciTech Connect

    Chung, Y.

    1993-12-31

    The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and X-ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back the global orbit data to the local feedback systems. The effect of the vacuum chamber eddy current induced by the AC corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the X-ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will be presented.

  12. User Feedback--Influence on Online System Operators.

    ERIC Educational Resources Information Center

    Williams, Martha E.

    The users of online retrieval systems can and should provide feedback to the system operators or vendors to influence them to make changes and further improvements, or to reinforce operator's decisions to make changes in the systems. All members of the database chain--database producers, processors, search service brokers, searchers, and end users…

  13. A force-feedback control system for micro-assembly

    NASA Astrophysics Data System (ADS)

    Lu, Zhe; Chen, Peter C. Y.; Ganapathy, Anand; Zhao, Guoyong; Nam, Joohoo; Yang, Guilin; Burdet, Etienne; Teo, Cheeleong; Meng, Qingnian; Lin, Wei

    2006-09-01

    In this paper, we report the development of an explicit force-feedback control system for micro-assembly, focusing on the key issues of force transmission and control. The force-feedback system is incorporated with a compound flexure stage, which is driven by a voice-coil actuator and designed to provide frictionless translation motion along one axis. A force sensor measures the interaction force between the micromanipulator and its environment, while an explicit force controller controls the interaction force to follow a desired force trajectory. The effectiveness of this prototype force-control system has been demonstrated in an experimental application, where parts (with dimensions in microns) were picked up and assembled under explicit force-feedback control.

  14. Introducing a feedback training system for guided home rehabilitation

    PubMed Central

    2010-01-01

    As the number of people requiring orthopaedic intervention is growing, individualized physiotherapeutic rehabilitation and adequate postoperative care becomes increasingly relevant. The chances of improvement in the patients condition is directly related to the performance and consistency of the physiotherapeutic exercises. In this paper a smart, cost-effective and easy to use Feedback Training System for home rehabilitation based on standard resistive elements is introduced. This ensures high accuracy of the exercises performed and offers guidance and control to the patient by offering direct feedback about the performance of the movements. 46 patients were recruited and performed standard physiotherapeutic training to evaluate the system. The results show a significant increase in the patient's ability to reproduce even simple physiotherapeutic exercises when being supported by the Feedback Training System. Thus physiotherapeutic training can be extended into the home environment whilst ensuring a high quality of training. PMID:20078852

  15. Feedback Control Systems Loop Shaping Design with Practical Considerations

    NASA Technical Reports Server (NTRS)

    Kopsakis, George

    2007-01-01

    This paper describes loop shaping control design in feedback control systems, primarily from a practical stand point that considers design specifications. Classical feedback control design theory, for linear systems where the plant transfer function is known, has been around for a long time. But it s still a challenge of how to translate the theory into practical and methodical design techniques that simultaneously satisfy a variety of performance requirements such as transient response, stability, and disturbance attenuation while taking into account the capabilities of the plant and its actuation system. This paper briefly addresses some relevant theory, first in layman s terms, so that it becomes easily understood and then it embarks into a practical and systematic design approach incorporating loop shaping design coupled with lead-lag control compensation design. The emphasis is in generating simple but rather powerful design techniques that will allow even designers with a layman s knowledge in controls to develop effective feedback control designs.

  16. Feedback-bounded stabilisation of certain discrete Volterra systems

    NASA Astrophysics Data System (ADS)

    Kotsios, Stelios

    2016-06-01

    Throughout this paper, we present a method for designing feedback-laws which stabilise nonlinear discrete Volterra systems. Our method is based on a factorisation algorithm which decomposes the original system as a composition of a δ-polynomial and a linear series.

  17. Multiple Learner Errors and Feedback: A Challenge for ICALL Systems.

    ERIC Educational Resources Information Center

    Heift, Trude

    2003-01-01

    Describes a web-based intelligent computer assisted language learning (ICALL) system for German that provides error-specific feedback suited to learner expertise. Focuses on the Domain Knowledge and Filtering Module. Concludes with a study that supports the need for a CALL system that addresses multiple errors by considering language teaching…

  18. Two improved coherent optical feedback systems for optical information processing

    NASA Technical Reports Server (NTRS)

    Lee, S. H.; Bartholomew, B.; Cederquist, J.

    1976-01-01

    Coherent optical feedback systems are Fabry-Perot interferometers modified to perform optical information processing. Two new systems based on plane parallel and confocal Fabry-Perot interferometers are introduced. The plane parallel system can be used for contrast control, intensity level selection, and image thresholding. The confocal system can be used for image restoration and solving partial differential equations. These devices are simpler and less expensive than previous systems. Experimental results are presented to demonstrate their potential for optical information processing.

  19. Dynamic output feedback H ∞ control for affine fuzzy systems

    NASA Astrophysics Data System (ADS)

    Wang, Huimin; Yang, Guang-Hong

    2013-06-01

    This article investigates the problem of designing H ∞ dynamic output feedback controllers for nonlinear systems, which are described by affine fuzzy models. The system outputs have been chosen as premise variables, which can guarantee that the plant and the controller always switch to the same region. By using a piecewise Lyapunov function and adding slack matrix variables, a piecewise-affine dynamic output feedback controller design method is obtained in the formulation of linear matrix inequalities (LMIs), which can be efficiently solved numerically. In contrast to the existing work, the proposed approach needs less LMI constraints and leads to less conservatism. Finally, numerical examples illustrate the effectiveness of the new result.

  20. Event-triggered output feedback control for distributed networked systems.

    PubMed

    Mahmoud, Magdi S; Sabih, Muhammad; Elshafei, Moustafa

    2016-01-01

    This paper addresses the problem of output-feedback communication and control with event-triggered framework in the context of distributed networked control systems. The design problem of the event-triggered output-feedback control is proposed as a linear matrix inequality (LMI) feasibility problem. The scheme is developed for the distributed system where only partial states are available. In this scheme, a subsystem uses local observers and share its information to its neighbors only when the subsystem's local error exceeds a specified threshold. The developed method is illustrated by using a coupled cart example from the literature. PMID:26708304

  1. Optimal feedback control infinite dimensional parabolic evolution systems: Approximation techniques

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Wang, C.

    1989-01-01

    A general approximation framework is discussed for computation of optimal feedback controls in linear quadratic regular problems for nonautonomous parabolic distributed parameter systems. This is done in the context of a theoretical framework using general evolution systems in infinite dimensional Hilbert spaces. Conditions are discussed for preservation under approximation of stabilizability and detectability hypotheses on the infinite dimensional system. The special case of periodic systems is also treated.

  2. Feedback Improvement in Automatic Program Evaluation Systems

    ERIC Educational Resources Information Center

    Skupas, Bronius

    2010-01-01

    Automatic program evaluation is a way to assess source program files. These techniques are used in learning management environments, programming exams and contest systems. However, use of automated program evaluation encounters problems: some evaluations are not clear for the students and the system messages do not show reasons for lost points.…

  3. An Introduction to Dynamic Systems and Feedback.

    ERIC Educational Resources Information Center

    Rabins, Michael J.

    This introduction to dynamic systems is intended for freshman and sophomore students in engineering, physical science, or social science. Material has been class tested and has led to increased student interest in further work in systems analysis and operations research. Notes are written for the student and are self-contained. Material can be…

  4. Topic: Catchment system dynamics: Processes and feedbacks

    NASA Astrophysics Data System (ADS)

    Keesstra, Saskia

    2015-04-01

    In this meeting we can talk about my main expertise: the focus of my research ocus revolves around understanding catchment system dynamics in a holistic way by incorporating both processes on hillslopes as well as in the river channel. Process knowledge enables explanation of the impact of natural and human drivers on the catchment systems and which consequences these drivers have for water and sediment connectivity. Improved understanding of the catchment sediment and water dynamics will empower sustainable land and river management and mitigate soil threats like erosion and off-side water and sediment accumulation with the help of nature's forces. To be able to understand the system dynamics of a catchment, you need to study the catchment system in a holistic way. In many studies only the hillslopes or even plots are studied; or only the channel. However, these systems are connected and should be evaluated together. When studying a catchment system any intervention to the system will create both on- as well as off sites effects, which should especially be taken into account when transferring science into policy regulations or management decisions.

  5. Output feedback regulator design for jet engine control systems

    NASA Technical Reports Server (NTRS)

    Merrill, W. C.

    1977-01-01

    A multivariable control design procedure based on the output feedback regulator formulation is described and applied to turbofan engine model. Full order model dynamics, were incorporated in the example design. The effect of actuator dynamics on closed loop performance was investigaged. Also, the importance of turbine inlet temperature as an element of the dynamic feedback was studied. Step responses were given to indicate the improvement in system performance with this control. Calculation times for all experiments are given in CPU seconds for comparison purposes.

  6. Output feedback regulator design for jet engine control systems

    NASA Technical Reports Server (NTRS)

    Merrill, W.

    1977-01-01

    A multivariable control design procedure based on the output feedback regulator formulation is described and applied to an F100 turbofan engine model. Full order model dynamics, are incorporated in the example design. The effect of actuator dynamics on closed loop performance is investigated. Also, the importance of turbine inlet temperature as an element of the dynamic feedback is studied. Step responses are given to indicate the improvement in system performance with this control. Calculation times for all experiments are given in CPU seconds for comparison purposes.

  7. Prelinguistic Infants' Communicative System: Role of Caregiver Social Feedback

    ERIC Educational Resources Information Center

    Miller, Jennifer L.; Lossia, Amanda K.

    2013-01-01

    Infants' prelinguistic vocalizations and gestures are rarely studied as a communicative system. As a result, there are few studies examining mechanisms of change concurrently in prelinguistic vocal and gesture behavior. Here we report the first evidence that contingent caregiver social feedback to infant gestures influences not only gesture…

  8. A Chinese Interactive Feedback System for a Virtual Campus

    ERIC Educational Resources Information Center

    Chen, Jui-Fa; Lin, Wei-Chuan; Jian, Chih-Yu; Hung, Ching-Chung

    2008-01-01

    Considering the popularity of the Internet, an automatic interactive feedback system for Elearning websites is becoming increasingly desirable. However, computers still have problems understanding natural languages, especially the Chinese language, firstly because the Chinese language has no space to segment lexical entries (its segmentation…

  9. Constructing a Multimedia Mobile Classroom Using a Novel Feedback System

    ERIC Educational Resources Information Center

    Huang, Wen-Chen; Chen, Ching-Wen; Weng, Richard

    2015-01-01

    In the conventional classroom, many obstacles hinder interaction between an instructor and students, such as limited class hours, fixed seating, and inadequate time for meetings after class. This work develops a novel multimedia mobile classroom feedback system (MMCFS) that instantly displays students' responses, such as class-related questions or…

  10. Design of multivariable feedback control systems via spectral assignment

    NASA Technical Reports Server (NTRS)

    Mielke, R. R.; Tung, L. J.; Marefat, M.

    1983-01-01

    The applicability of spectral assignment techniques to the design of multivariable feedback control systems was investigated. A fractional representation design procedure for unstable plants is presented and illustrated with an example. A computer aided design software package implementing eigenvalue/eigenvector design procedures is described. A design example which illustrates the use of the program is explained.

  11. Development of the orbit feedback system for the VSX ring

    NASA Astrophysics Data System (ADS)

    Satoh, M.; Harada, K.; Takaki, H.; Koseki, T.; Nakamura, N.; Kamiya, Y.; Hanawa, K.

    2001-07-01

    An orbit feedback system will be installed in the VSX ring to stabilize the photon beam. The new COD correction method, the eigenvector method with constraints, is adopted for calculation of the steering-magnet currents. A computer simulation shows that the new method can tightly fix the beam positions at insertion devices, correcting the whole closed orbit globally with almost the same performance as the ordinary eigenvector method. A test VME unit including DSP and shared memory boards is being developed for the fast feedback control and its performance test shows that the total feedback time is less than 1 ms (875 μs) except for the network and VME-bus transfer times related to the shared memory board.

  12. Position feedback system for volume holographic storage media

    DOEpatents

    Hays, Nathan J.; Henson, James A.; Carpenter, Christopher M.; Akin, Jr.. William R.; Ehrlich, Richard M.; Beazley, Lance D.

    1998-07-07

    A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g. voice coil motor) which respond to position feedback information and adjust the angular position of the reference angle of a reference beam to maximize SNR by reducing crosstalk, thereby improving storage capacity.

  13. Feedback instability in the magnetosphere-ionosphere coupling system: Revisited

    SciTech Connect

    Watanabe, T.-H.

    2010-02-15

    A coupled set of the reduced magnetohydrodynamic and the two-fluid equations is applied to the magnetosphere-ionosphere (M-I) feedback interactions in relation to growth of quite auroral arcs. A theoretical analysis revisiting the linear feedback instability reveals asymptotic behaviors of the dispersion relation and a non-Hermite property in the M-I coupling. A nonlinear simulation of the feedback instability in the M-I coupling system manifests growth of the Kelvin-Helmholtz-like mode in the magnetosphere as the secondary instability. The distorted vortex and field-aligned current profiles propagating as the shear Alfven waves lead to spontaneous deformation of ionospheric density and current structures associated with auroral arcs.

  14. Digital Cryptography and Feedback Synchronization of Chaotic Systems

    NASA Astrophysics Data System (ADS)

    Mitra, Mala; Banerjee, Santo

    Secure communications via chaotic synchronization is demonstrated in this literature. At first we have designed a feedback controller for chaotic synchronization utilizing the Lyapunov stability theory for cascade-connected systems.The method has been applied successfully to make two identical systems globally asymptotically synchronized. The result of numerical simulations are given to validate the effectiveness of this method. Then we have discussed a new method of cryptography for this coupled system which is very simple to implement and effective.

  15. Architecture of the APS real-time orbit feedback system.

    SciTech Connect

    Carwardine, J. A.; Lenkszus, F. R.

    1997-11-21

    The APS Real-Time Orbit Feedback System is designed to stabilize the orbit of the stored positron beam against low-frequency sources such as mechanical vibration and power supply ripple. A distributed array of digital signal processors is used to measure the orbit and compute corrections at a 1kHz rate. The system also provides extensive beam diagnostic tools. This paper describes the architectural aspects of the system and describes how the orbit correction algorithms are implemented.

  16. On stability theory. [of nonlinear feedback control systems

    NASA Technical Reports Server (NTRS)

    Safonov, M. G.; Athans, M.

    1979-01-01

    It is found that under mild assumptions, feedback system stability can be concluded if one can 'topologically separate' the infinite-dimensional function space containing the system's dynamical input-output relations into two regions, one region containing the dynamical input-output relation of the 'feedforward' element of the system and the other region containing the dynamical output-input relation of the 'feedback' element. Nonlinear system stability criteria of both the input-output type and the state-space (Liapunov) type are interpreted in this context. The abstract generality and conceptual simplicity afforded by the topological separation perspective clarifies some of the basic issues underlying stability theory and serves to suggest improvements in existing stability criteria. A generalization of Zames' (1966) conic-relation stability criterion is proved, laying the foundation for improved multivariable generalizations of the frequency-domain circle stability criterion for nonlinear systems.

  17. Feedbacks between conservation and social-ecological systems

    PubMed Central

    Miller, Brian W.; Caplow, Susan C.; Leslie, Paul W.

    2012-01-01

    Robust ways to meet objectives of environmental conservation and social and economic development remain elusive. This struggle may in part be related to insufficient understanding of the feedbacks between conservation initiatives and social-ecological systems, specifically, the ways in which conservation initiatives result in social changes that have secondary effects on the environments targeted by conservation. To explore this idea we sampled peer-reviewed articles addressing the social and environmental dimensions of conservation and coded each paper according to its research focus and characterization of these feedbacks. The majority of articles in our sample focused either on the effect of conservation initiatives on people (e.g., relocation, employment) or the effect of people on the environment (e.g., fragmentation, conservation efficacy of traditional management systems). Few studies in our sample empirically addressed both the social dynamics resulting from conservation initiatives and subsequent environmental effects. In many cases, one was measured and the other was discussed anecdotally. Among the studies that describe feedbacks between social and environmental variables, there was more evidence of positive (amplifying) feedbacks between social and environmental outcomes (i.e., undesirable social outcomes yielded undesirable environmental effects, and desirable social outcomes yielded desirable environmental effects). The major themes within the sampled literature include conflict between humans and wild animals, social movements, adaptive comanagement, loss of traditional management systems, traditional ecological knowledge, human displacement and risks to livelihoods, and conservation and development. The narratives associated with each theme can serve as hypotheses for facilitating further discussion about conservation issues and for catalyzing future studies of the feedbacks between conservation and social-ecological systems. PMID:22443128

  18. Modeling mutual feedback between users and recommender systems

    NASA Astrophysics Data System (ADS)

    Zeng, An; Yeung, Chi Ho; Medo, Matúš; Zhang, Yi-Cheng

    2015-07-01

    Recommender systems daily influence our decisions on the Internet. While considerable attention has been given to issues such as recommendation accuracy and user privacy, the long-term mutual feedback between a recommender system and the decisions of its users has been neglected so far. We propose here a model of network evolution which allows us to study the complex dynamics induced by this feedback, including the hysteresis effect which is typical for systems with non-linear dynamics. Despite the popular belief that recommendation helps users to discover new things, we find that the long-term use of recommendation can contribute to the rise of extremely popular items and thus ultimately narrow the user choice. These results are supported by measurements of the time evolution of item popularity inequality in real systems. We show that this adverse effect of recommendation can be tamed by sacrificing part of short-term recommendation accuracy.

  19. Autonomous learning by simple dynamical systems with delayed feedback

    NASA Astrophysics Data System (ADS)

    Kaluza, Pablo; Mikhailov, Alexander S.

    2014-09-01

    A general scheme for the construction of dynamical systems able to learn generation of the desired kinds of dynamics through adjustment of their internal structure is proposed. The scheme involves intrinsic time-delayed feedback to steer the dynamics towards the target performance. As an example, a system of coupled phase oscillators, which can, by changing the weights of connections between its elements, evolve to a dynamical state with the prescribed (low or high) synchronization level, is considered and investigated.

  20. Stability of constant gain systems with vector feedback

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.

    1978-01-01

    The state space, the controllability, and the observability concepts are discussed in connection with the proposed stability analysis which permits drastic dimensional reductions for a vector feedback problem. Any constant gain system's stability can thus be analyzed in the frequency domain with a single Nyquist plot. The analysis considers the total system with all loops closed, a disturbance vector as input, and the feedback vector as output. All constant gain systems are shown to be decomposable into stable subsystems where the degree of the decomposition determines the dimensions. The maximum decomposition results in the state-space approach which is the limit case. The method is demonstrated with the stability analysis of the pogo phenomenon, an oscillatory interaction between the propulsion and the structure of a space vehicle. This problem, with eigenvalues over a hundred, was drastically but rigorously reduced to a stability analysis of a 4x4 matrix.

  1. On reliable control system designs with and without feedback reconfigurations

    NASA Technical Reports Server (NTRS)

    Birdwell, J. D.; Castanon, D. A.; Athans, M.

    1979-01-01

    This paper contains an overview of a theoretical framework for the design of reliable multivariable control systems, with special emphasis on actuator failures and necessary actuator redundancy levels. Using a linear model of the system, with Markovian failure probabilities and quadratic performance index, an optimal stochastic control problem is posed and solved. The solution requires the iteration of a set of highly coupled Riccati-like matrix difference equations; if these converge one has a reliable design; if they diverge, the design is unreliable, and the system design cannot be stabilized. In addition, it is shown that the existence of a stabilizing constant feedback gain and the reliability of its implementation is equivalent to the convergence properties of a set of coupled Riccati-like matrix difference equations. In summary, these results can be used for offline studies relating the open loop dynamics, required performance, actuator mean time to failure, and functional or identical actuator redundancy, with and without feedback gain reconfiguration strategies.

  2. Predictive Feedback and Feedforward Control for Systems with Unknown Disturbances

    NASA Technical Reports Server (NTRS)

    Juang, Jer-Nan; Eure, Kenneth W.

    1998-01-01

    Predictive feedback control has been successfully used in the regulation of plate vibrations when no reference signal is available for feedforward control. However, if a reference signal is available it may be used to enhance regulation by incorporating a feedforward path in the feedback controller. Such a controller is known as a hybrid controller. This paper presents the theory and implementation of the hybrid controller for general linear systems, in particular for structural vibration induced by acoustic noise. The generalized predictive control is extended to include a feedforward path in the multi-input multi-output case and implemented on a single-input single-output test plant to achieve plate vibration regulation. There are cases in acoustic-induce vibration where the disturbance signal is not available to be used by the hybrid controller, but a disturbance model is available. In this case the disturbance model may be used in the feedback controller to enhance performance. In practice, however, neither the disturbance signal nor the disturbance model is available. This paper presents the theory of identifying and incorporating the noise model into the feedback controller. Implementations are performed on a test plant and regulation improvements over the case where no noise model is used are demonstrated.

  3. Commissioning of the IGp Feedback System at DAFNE

    SciTech Connect

    Drago, A.; Fox, J.D.; Teytelman, D.; Tobiyama, M.; /KEK, Tsukuba

    2011-11-01

    The iGp (Integrated Gigasample Processor) is an innovative digital bunch-by-bunch feedback system developed by a KEK / SLAC / INFN-LNF joint collaboration. The processing unit can sample at 500 MHz and compute the bunch-by-bunch output signal for up to {approx}5000 bunches. The feedback gateware code is implemented inside just one FPGA (Field Programmable Gate Array) chip, a Xilinx Virtex-II. The FPGA implements two banks of 16-tap FIR (Finite Impulse Response) filters. Each filter is realtime programmable through the operator interface. At DA{Phi}NE, the Frascati {Phi}-Factory, two iGp units have been commissioned in the April 2007. The iGp systems have substituted the previous betatron feedback systems. This insertion has been very fast and has shown no problems involving just a substitution of the old, less flexible, digital systems, letting unchanged the baseband analog frontend and backend. The commissioning has been very simple, due to the complete and powerful EPICS operator interface, working well in local and remote operations. The software includes also tools for analyzing post processor data. A description of the commissioning with the operations done is reported.

  4. Feedback loops from the Hubble Space Telescope data processing system

    NASA Astrophysics Data System (ADS)

    Fraquelli, Dorothy A.; Arquilla, Richard; Ellis, Tracy; Hamilton, Forrest C.; Holm, Albert; Kochte, Mark

    2002-12-01

    This paper presents an overview of the history and technology by which tools placed in the Hubble Space Telescope (HST) data processing pipeline were used to feedback information on observation execution to the scheduling system and observers. Because the HST is in a relatively low orbit, which imposes a number of constraints upon its observations, it operates in a carefully planned, fully automated mode. To substitute for direct observer involvement available at most ground-based observatories and to provide rapid feedback on failures that might affect future visits, the Space Telescope Science Institute (STScI) gradually evolved a system for screening science and engineering products during pipeline processing. The highly flexible HST data processing system (OPUS) allows tools to be introduced to use the content of FITS keywords to alert production staff to potential telescope and instrument performance failures. Staff members review the flagged data and, if appropriate, notify the observer and the scheduling staff so that they can resolve the problems and possibly repeat the failed observations. This kind of feedback loop represents a case study for other automated data collection systems where rapid response to certain quantifiable events in the data is required. Observatory operations staff can install processes to look for these events either in the production pipeline or in an associated pipeline into which the appropriate data are piped. That process can then be used to notify scientists to evaluate the data and decide upon a response or to automatically initiate a response.

  5. Integration of the Longitudinal Feedback System in NSRRC

    SciTech Connect

    Hu, K.H.; Kuo, C.H.; Yeh, M.S.; Lau, W.K.; Lee, Demi; Hsu, S.Y.; Yang Teno; Chou, P.J.; Chen, Jenny; Hsu, K.T.

    2004-11-10

    An operation version of longitudinal feedback baseband processing electronics was implemented. The system consists of a bunch phase detector, a 500-MS/s analog-to-digital converter and demultiplexer module (ADC/DEMUX), DSP modules, a digital-to-analog converter and multiplexer module (DAC/MUX), and an RF modulator. The ADC/DEMUX unit has a fast ADC that digitizes the bunch phase signal. The down-sampled phase error data of each bunch are then distributed to the DSP boards to perform filtering and applied control rule. In the DAC/MUX, bunch kick signals are converted into analog signals for bunch phase feedback. Design and implementation of the system will be summarized in this report.

  6. Time optimal feedback control of discrete systems with bounded inputs

    NASA Technical Reports Server (NTRS)

    Chen, Xin; Longman, Richard W.; Klein, George

    1990-01-01

    Deadbeat control theory gives a feedback solution to the time optimal control of discrete time systems. Experience has shown the results to be impractical because they ignore bounds on the actuator strength. This paper develops two algorithms for generating time optimal control in feedback form for discrete systems with bounded controls. The results are also applicable for generating recovery regions and the set of reachable states. For multiple control problems a method of generating sublayers is developed which decreases off-line and on-line computational effort. Two algorithms are presented with somewhat different computational and storage requirements. The algorithms are practical within certain dimension constraints, and are natural for implementation with parallel processing.

  7. Challenges in the Implementation of Measurement Feedback Systems.

    PubMed

    de Jong, Kim

    2016-05-01

    This commentary on the articles published in the special section on the development and implementation of measurement feedback systems (MFSs) discusses three challenging themes in the process of MFS implementation: design and planning, organizational context, and sustainability and unintended consequences. It is argued that the implementation of MFSs is complex, but is an important step in improving outcomes in routine care for children and young persons. PMID:26518779

  8. Design of the ALS transverse coupled-bunch feedback system

    SciTech Connect

    Barry, W.; Byrd, J.M.; Corlett, J.N.; Hinkson, J.; Johnson, J.; Lambertson, G.R.; Fox, J.D.

    1993-05-01

    Calculations of transverse coupled bunch growth rates in the Advanced Light Source (ALS), a 1.5 GeV electron storage ring for producing synchrotron radiation, indicate the need for damping via a transverse feedback (TFB) system. We present the design of such a system. The maximum bunch frequency is 500 MHz, requiring that the FB system have a broadband response of at least 250 MHz. We described, in detail, the choice of broadband components such as kickers, pickups, power amplifiers, and electronics.

  9. Global Orbit Feedback System Upgrade At The Canadian Light Source

    NASA Astrophysics Data System (ADS)

    Hu, Song; Payne, Chris; Chabot, Daron; Maxwell, Dylan; Dallin, Les

    2013-03-01

    The Canadian Light Source has been using a Matlab application called CLSORB to perform slow orbit correction in the storage ring. A fast global orbit feedback system is recently deployed to replace the old system. The correction rate is about 45 Hz and all the corrections are calculated and applied by an RTEMS IOC. This upgrade has resulted in increased beam stability and reduced perturbations caused by the ramping of superconducting wigglers. This paper will discuss the implementation and performance of the fast orbit correction system.

  10. Dissipative control for linear systems by static output feedback

    NASA Astrophysics Data System (ADS)

    Feng, Zhiguang; Lam, James; Shu, Zhan

    2013-08-01

    In this article, the problem of static output-feedback dissipative control is investigated for linear continuous-time system based on an augmented system approach. A necessary and sufficient condition for stability and strict (Q,S,R)-dissipativity of the closed-loop system is established in terms of a matrix inequality with free parametrisation matrix. An equivalent characterisation with some slack matrices for numerical solvability is then proposed. Based on this, a necessary and sufficient condition for the existence of a desired controller is given, and a corresponding iterative algorithm is developed to solve the condition. The effectiveness of results developed in this article is demonstrated by some numerical examples.

  11. Enhancing the Impact of Formative Feedback on Student Learning through an Online Feedback System

    ERIC Educational Resources Information Center

    Hatziapostolou, Thanos; Paraskakis, Iraklis

    2010-01-01

    Formative feedback is instrumental in the learning experience of a student. It can be effective in promoting learning if it is timely, personal, manageable, motivational, and in direct relation with assessment criteria. Despite its importance, however, research suggests that students are discouraged from engaging in the feedback process primarily…

  12. Transverse beam feedback system for PLS storage ring

    NASA Astrophysics Data System (ADS)

    Huang, J. Y.; Park, M. K.; Kim, D. T.; Kang, H. S.; Hwang, W. H.; Nam, S. H.

    2001-07-01

    As the stored beam current increases over 240 mA, transverse coupled-beam instability limits higher beam current in Pohang Light Source. A bunch by bunch transverse feedback system has been developed to cure these beam instabilities. It consists of beam oscillation detectors, betatron phase adjuster, power amplifiers and a stripline kicker. Design of each circuit and its functions are described with simple trigonometric equations. The result of the beam test has shown more than 30 dB damping of the beam oscillation in the full bandwidth of the system.

  13. Output feedback control of a mechanical system using magnetic levitation.

    PubMed

    Beltran-Carbajal, F; Valderrabano-Gonzalez, A; Rosas-Caro, J C; Favela-Contreras, A

    2015-07-01

    This paper presents an application of a nonlinear magnetic levitation system to the problem of efficient active control of mass-spring-damper mechanical systems. An output feedback control scheme is proposed for reference position trajectory tracking tasks on the flexible mechanical system. The electromagnetically actuated system is shown to be a differentially flat nonlinear system. An extended state estimation approach is also proposed to obtain estimates of velocity, acceleration and disturbance signals. The differential flatness structural property of the system is then employed for the synthesis of the controller and the signal estimation approach presented in this work. Some experimental and simulation results are included to show the efficient performance of the control approach and the effective estimation of the unknown signals. PMID:25707718

  14. Spectrometer for shot-to-shot photon energy characterization in the multi-bunch mode of the free electron laser at Hamburg

    SciTech Connect

    Palutke, S. Wurth, W.; Gerken, N. C.; Mertens, K.; Klumpp, S.; Martins, M.; Mozzanica, A.; Schmitt, B.; Wunderer, C.; Graafsma, H.; Meiwes-Broer, K.-H.

    2015-11-15

    The setup and first results from commissioning of a fast online photon energy spectrometer for the vacuum ultraviolet free electron laser at Hamburg (FLASH) at DESY are presented. With the use of the latest advances in detector development, the presented spectrometer reaches readout frequencies up to 1 MHz. In this paper, we demonstrate the ability to record online photon energy spectra on a shot-to-shot base in the multi-bunch mode of FLASH. Clearly resolved shifts in the mean wavelength over the pulse train as well as shot-to-shot wavelength fluctuations arising from the statistical nature of the photon generating self-amplified spontaneous emission process have been observed. In addition to an online tool for beam calibration and photon diagnostics, the spectrometer enables the determination and selection of spectral data taken with a transparent experiment up front over the photon energy of every shot. This leads to higher spectral resolutions without the loss of efficiency or photon flux by using single-bunch mode or monochromators.

  15. Spectrometer for shot-to-shot photon energy characterization in the multi-bunch mode of the free electron laser at Hamburg.

    PubMed

    Palutke, S; Gerken, N C; Mertens, K; Klumpp, S; Mozzanica, A; Schmitt, B; Wunderer, C; Graafsma, H; Meiwes-Broer, K-H; Wurth, W; Martins, M

    2015-11-01

    The setup and first results from commissioning of a fast online photon energy spectrometer for the vacuum ultraviolet free electron laser at Hamburg (FLASH) at DESY are presented. With the use of the latest advances in detector development, the presented spectrometer reaches readout frequencies up to 1 MHz. In this paper, we demonstrate the ability to record online photon energy spectra on a shot-to-shot base in the multi-bunch mode of FLASH. Clearly resolved shifts in the mean wavelength over the pulse train as well as shot-to-shot wavelength fluctuations arising from the statistical nature of the photon generating self-amplified spontaneous emission process have been observed. In addition to an online tool for beam calibration and photon diagnostics, the spectrometer enables the determination and selection of spectral data taken with a transparent experiment up front over the photon energy of every shot. This leads to higher spectral resolutions without the loss of efficiency or photon flux by using single-bunch mode or monochromators. PMID:26628121

  16. Practical Loop-Shaping Design of Feedback Control Systems

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    2010-01-01

    An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design. The conception of this improved methodology was motivated by challenges in designing control systems of the types needed for supersonic propulsion. But the methodology is generally applicable to any classical control-system design where the transfer function of the plant is known or can be evaluated. In the case of a supersonic aerospace vehicle, a major challenge is to design the system to attenuate anticipated external and internal disturbances, using such actuators as fuel injectors and valves, bypass doors, and ramps, all of which are subject to limitations in actuator response, rates, and ranges. Also, for supersonic vehicles, with long slim type of structures, coupling between the engine and the structural dynamics can produce undesirable effects that could adversely affect vehicle stability and ride quality. In order to design distributed controls that can suppress these potential adverse effects, within the full capabilities of the actuation system, it is important to employ a systematic control design methodology such as this that can maximize the

  17. Postural balance indicator and associated feedback compensation system.

    PubMed

    Ingerson, Paul; Druzgalski, Christopher

    2004-01-01

    Postural balance related disorders not only limit individual mobility but also often result in serious injuries or even death in particular in the elderly. Presented statistical data demonstrates the severity of this growing problem as the population at large is getting older. In addition, the disorders of the vesitibular system, often of idiopathic origin, and related abnormalities affect population across all age groups. Therefore, in order to provide an assessment of balance, awareness to patients, as well as continuous feedback to assist in maintaining equilibrium, a low cost unobtrusive system for postural balance management has been designed. The system is based on two designed and perpendicularly placed level sensors with optical detection, and a set of vibrators interfaced with the PIC based BS2 board by Parallax. The tilt identifiable vibrators provide a feedback. A programmable delay and curtailment of movement related superficial responses provides additional adaptability. The premise of this compact battery operated system is to assist patients in restoring mobility and gaining independence. PMID:17270776

  18. Feedback stabilization system for pulsed single longitudinal mode tunable lasers

    DOEpatents

    Esherick, Peter; Raymond, Thomas D.

    1991-10-01

    A feedback stabilization system for pulse single longitudinal mode tunable lasers having an excited laser medium contained within an adjustable length cavity and producing a laser beam through the use of an internal dispersive element, including detection of angular deviation in the output laser beam resulting from detuning between the cavity mode frequency and the passband of the internal dispersive element, and generating an error signal based thereon. The error signal can be integrated and amplified and then applied as a correcting signal to a piezoelectric transducer mounted on a mirror of the laser cavity for controlling the cavity length.

  19. Modelling human balance using switched systems with linear feedback control.

    PubMed

    Kowalczyk, Piotr; Glendinning, Paul; Brown, Martin; Medrano-Cerda, Gustavo; Dallali, Houman; Shapiro, Jonathan

    2012-02-01

    We are interested in understanding the mechanisms behind and the character of the sway motion of healthy human subjects during quiet standing. We assume that a human body can be modelled as a single-link inverted pendulum, and the balance is achieved using linear feedback control. Using these assumptions, we derive a switched model which we then investigate. Stable periodic motions (limit cycles) about an upright position are found. The existence of these limit cycles is studied as a function of system parameters. The exploration of the parameter space leads to the detection of multi-stability and homoclinic bifurcations. PMID:21697168

  20. Design study of a feedback control system for the Multicyclic Flap System rotor (MFS)

    NASA Technical Reports Server (NTRS)

    Weisbrich, R.; Perley, R.; Howes, H.

    1977-01-01

    The feasibility of automatically providing higher harmonic control to a deflectable control flap at the tip of a helicopter rotor blade through feedback of selected independent parameter was investigated. Control parameters were selected for input to the feedback system. A preliminary circuit was designed to condition the selected parameters, weigh limiting factors, and provide a proper output signal to the multi-cyclic control actuators. Results indicate that feedback control for the higher harmonic is feasible; however, design for a flight system requires an extension of the present analysis which was done for one flight condition - 120 kts, 11,500 lbs gross weight and level flight.

  1. A method for designing robust multivariable feedback systems

    NASA Technical Reports Server (NTRS)

    Milich, David Albert; Athans, Michael; Valavani, Lena; Stein, Gunter

    1988-01-01

    A new methodology is developed for the synthesis of linear, time-invariant (LTI) controllers for multivariable LTI systems. The aim is to achieve stability and performance robustness of the feedback system in the presence of multiple unstructured uncertainty blocks; i.e., to satisfy a frequency-domain inequality in terms of the structured singular value. The design technique is referred to as the Causality Recovery Methodology (CRM). Starting with an initial (nominally) stabilizing compensator, the CRM produces a closed-loop system whose performance-robustness is at least as good as, and hopefully superior to, that of the original design. The robustness improvement is obtained by solving an infinite-dimensional, convex optimization program. A finite-dimensional implementation of the CRM was developed, and it was applied to a multivariate design example.

  2. A method for designing robust multivariable feedback systems

    NASA Technical Reports Server (NTRS)

    Milich, David A.; Athans, Michael; Valavani, Lena; Stein, Gunter

    1988-01-01

    A new methodology is developed for the synthesis of linear, time-invariant (LTI) controllers for multivariable LTI systems. The aim is to achieve stability and performance robustness of the feedback system in the presence of multiple unstructured uncertainty blocks; i.e., to satisfy a frequency-domain inequality in terms of the structured singular value. The design technique is referred to as the causality recovery methodology (CRM). Starting with an initial (nominally) stabilizing compensator, the CRM produces a closed-loop system whose performance-robustness is at least as good as, and hopefully superior to, that of the original design. The robustness improvement is obtained by solving an infinite-dimensional, convex optimization program. A finite-dimensional implementation of the CRM was developed, and it was applied to a multivariate design example.

  3. Output feedback trajectory stabilization of the uncertainty DC servomechanism system.

    PubMed

    Aguilar-Ibañez, Carlos; Garrido-Moctezuma, Ruben; Davila, Jorge

    2012-11-01

    This work proposes a solution for the output feedback trajectory-tracking problem in the case of an uncertain DC servomechanism system. The system consists of a pendulum actuated by a DC motor and subject to a time-varying bounded disturbance. The control law consists of a Proportional Derivative controller and an uncertain estimator that allows compensating the effects of the unknown bounded perturbation. Because the motor velocity state is not available from measurements, a second-order sliding-mode observer permits the estimation of this variable in finite time. This last feature allows applying the Separation Principle. The convergence analysis is carried out by means of the Lyapunov method. Results obtained from numerical simulations and experiments in a laboratory prototype show the performance of the closed loop system. PMID:22884179

  4. Delayed feedback control method for dynamical systems with chaotic saddles

    NASA Astrophysics Data System (ADS)

    Kobayashi, Miki U.; Aihara, Kazuyuki

    2012-08-01

    We consider systems whose orbits diverge after chaotic transient for a finite time, and propose a controlmethod for preventing the divergence. These systems generally possess not chaotic attractors but some chaotic saddles. Our aim of control, i.e., the prevention of divergence, is achieved through the stabilization of unstable periodic orbits embedded in the chaotic saddle by making use of the delayed feedback controlmethod. The key concept of our control strategy is the application of the Proper Interior Maximum (PIM) triple method and the method to detect unstable periodic orbits from time series, originally developed by Lathrop and Kostelich, as initial steps before adding the delayed feedback control input. We show that our control method can be applied to the Hénon map and an intermittent androgen suppression (IAS) therapy model, which is a model for therapy of advanced prostate cancer. The fact that our method can be applied to the IAS therapy model indicates that our control strategy may be useful in the therapy of advanced prostate cancer.

  5. A Measurement Feedback System (MFS) Is Necessary to Improve Mental Health Outcomes

    ERIC Educational Resources Information Center

    Bickman, Leonard

    2008-01-01

    The importance of measurement feedback system (MFS) for the improvement of mental health services for youths is discussed. As feedback obtained from clients and families is subject to distortions, a standardized MFS including clinical processes, contexts, outcomes, and feedback to clinicians and supervisors is necessary for improvement in quality…

  6. Feedback Systems. Symposium 28. [Concurrent Symposium Session at AHRD Annual Conference, 2000.

    ERIC Educational Resources Information Center

    2000

    This packet contains three papers from a symposium on feedback systems held at a conference on human resource development (HRD). The first paper, "The Role of Feedback in Management Development Training" (K. Peter Kuchinke), reports on a survey-based study that investigated the role of feedback in nine management development training settings in a…

  7. Improving the security of optoelectronic delayed feedback system by parameter modulation and system coupling

    NASA Astrophysics Data System (ADS)

    Liu, Lingfeng; Miao, Suoxia; Cheng, Mengfan; Gao, Xiaojing

    2016-02-01

    A coupled system with varying parameters is proposed to improve the security of optoelectronic delayed feedback system. This system is coupled by two parameter-varied optoelectronic delayed feedback systems with chaotic modulation. Dynamics performance results show that this system has a higher complexity compared to the original one. Furthermore, this system can conceal the time delay effectively against the autocorrelation function and delayed mutual information method and can increase the dimension space of secure parameters to resist brute-force attack by introducing the digital chaotic systems.

  8. Quantifying and Reducing Climate-Carbon Cycle Feedback Uncertainties: Analysis of CMIP5 Earth System Model Feedbacks

    NASA Astrophysics Data System (ADS)

    Hoffman, F. M.; Randerson, J. T.

    2011-12-01

    Increasing atmospheric carbon dioxide (CO2) concentrations, resulting from anthropogenic perturbation of the global carbon cycle, are altering the Earth's climate. Climate change is expected to induce feedbacks on future CO2 concentrations and on the climate system itself. These feedbacks are highly uncertain, potentially large, and difficult to predict using Earth System Models (ESMs). In order to reduce the range of uncertainty in climate predictions, model representation of feedbacks must be improved through comparisons with contemporary observations. In this study, we quantify the terrestrial and ocean carbon storage sensitivity to climate and atmospheric CO2 concentration of ESMs participating in the Climate Model Intercomparison Project Phase 5 (CMIP5) following the methodology of Friedlingstein et al. (2006). In order to evaluate the models' abilities to capture the 21st century carbon cycle and to offer possible constraints on the modeled feedback strengths, comparisons with contemporary observations will be made over three different time scales: seasonal to annual, interannual to decadal, and decadal to centennial. A conceptual framework for evaluating climate-carbon cycle feedbacks in global models--employing best-available observational data--will be presented, along with results from application of this framework to CMIP5 model output. Included in the analysis will be prototype model evaluation benchmarks of the carbon cycle being designed for the International Land Model Benchmarking (ILAMB) Project.

  9. Thermal feedback in virtual reality and telerobotic systems

    NASA Technical Reports Server (NTRS)

    Zerkus, Mike; Becker, Bill; Ward, Jon; Halvorsen, Lars

    1994-01-01

    A new concept has been developed that allows temperature to be part of the virtual world. The Displaced Temperature Sensing System (DTSS) can 'display' temperature in a virtual reality system.The DTSS can also serve as a feedback device for telerobotics. For virtual reality applications the virtual world software would be required to have a temperature map of its world. By whatever means (magnetic tracker, ultrasound tracker, etc.) the hand and fingers, which have been instrumented with thermodes, would be tracked. The temperature associated with the current position would be transmitted to the DRSS via a serial data link. The DTSS would provide that temperature to the fingers. For telerobotic operation the function of the DTSS is to transmit a temperature from a remote location to the fingers where the temperature can be felt.

  10. A feedback control for the advanced launch system

    NASA Technical Reports Server (NTRS)

    Seywald, Hans; Cliff, Eugene M.

    1991-01-01

    A robust feedback algorithm is presented for a near-minimum-fuel ascent of a two-stage launch vehicle operating in the equatorial plane. The development of the algorithm is based on the ideas of neighboring optimal control and can be derived into three phases. In phase 1, the formalism of optimal control is employed to calculate fuel-optimal ascent trajectories for a simple point-mass model. In phase 2, these trajectories are used to numerically calculate gain functions of time for the control(s), the total flight time, and possibly, for other variables of interest. In phase 3, these gains are used to determine feedback expressions for the controls associated with a more realistic model of a launch vehicle. With the Advanced Launch System in mind, all calculations are performed on a two-stage vehicle with fixed thrust history, but this restriction is by no means important for the approach taken. Performance and robustness of the algorithm is found to be excellent.

  11. Ecohydrology Controls on Feedbacks Between Northern Wetlands and Climate Systems

    NASA Astrophysics Data System (ADS)

    Turetsky, M.; Harden, J.; McGuire, A.; Waddington, J.

    2007-12-01

    Boreal regions contain large stocks of soil carbon, mostly in poorly drained areas where peat accumulating wetlands have served as a long-term sink for atmospheric carbon. It is unknown whether northern wetlands globally will continue to represent a net sink for atmospheric carbon dioxide, or whether changes in the Earth's climate will cause these ecosystems to release stored carbon back to the atmosphere. Such feedbacks between northern wetlands and regional or global climate systems will depend on interactions between wetland vegetation, peat properties, and hydrology. Within many wetlands, hydrology is the dominant control on plant community structure and decomposition rates. In turn, both plant and microbial activity determine the quantity and quality of litter, which govern the nature of peat accumulation and soil properties critical to hydrology. Here, we will present research from our field and modeling studies investigating the effects of drought, permafrost degradation, and wildfire on vegetation, carbon cycling, and hydrological processes in northern wetlands at multiple spatial scales. At local scales, our findings show that interactions among vegetation, soil, and hydrology can lead to unexpected and often complex changes in soil environments, with potential 'carbon surprises'. For example, in a nonpermafrost peatland, we found that sustained drought led to peat subsidence that limited the development of oxic surface peat layers and inhibited ecosystem respiration. The decrease in porosity and water content with drought reduced seasonal ice thaw, which also likely limited microbial activity. In contrast, peatlands underlain by permafrost are increasingly experiencing thermokarst and soil flooding with increasing active layer depth. Changes in moss productivity post-thaw led to increased rates of organic matter accumulation, with very different hydrologic and soil properties than peat accumulated in permafrost settings. In addition to local

  12. Control of force through feedback in small driven systems.

    PubMed

    Dieterich, E; Camunas-Soler, J; Ribezzi-Crivellari, M; Seifert, U; Ritort, F

    2016-07-01

    Controlling a time-dependent force applied to single molecules or colloidal particles is crucial for many types of experiments. Since in optical tweezers the primary controlled variable is the position of the trap, imposing a target force requires an active feedback process. We analyze this feedback process for the paradigmatic case of a nonequilibrium steady state generated by a dichotomous force protocol, first theoretically for a colloidal particle in a harmonic trap and then with both simulations and experiments for a long DNA hairpin. For the first setup, we find there is an optimal feedback gain separating monotonic from oscillatory response, whereas a too strong feedback leads to an instability. For the DNA molecule, reaching the target force requires substantial feedback gain since weak feedback cannot overcome the tendency to relax towards the equilibrium force. PMID:27575077

  13. Control of force through feedback in small driven systems

    NASA Astrophysics Data System (ADS)

    Dieterich, E.; Camunas-Soler, J.; Ribezzi-Crivellari, M.; Seifert, U.; Ritort, F.

    2016-07-01

    Controlling a time-dependent force applied to single molecules or colloidal particles is crucial for many types of experiments. Since in optical tweezers the primary controlled variable is the position of the trap, imposing a target force requires an active feedback process. We analyze this feedback process for the paradigmatic case of a nonequilibrium steady state generated by a dichotomous force protocol, first theoretically for a colloidal particle in a harmonic trap and then with both simulations and experiments for a long DNA hairpin. For the first setup, we find there is an optimal feedback gain separating monotonic from oscillatory response, whereas a too strong feedback leads to an instability. For the DNA molecule, reaching the target force requires substantial feedback gain since weak feedback cannot overcome the tendency to relax towards the equilibrium force.

  14. Design of power system stabilizer through state variable feedback

    SciTech Connect

    Abe, S.; Takeda, S.

    1980-05-01

    When the transmission line is very long or the generator is operated at a power factor nearly equal to 1.0, the machine regulated by an automatic voltage regulator (AVR) cannot be operated stably due to poor dynamic stability. To overcome this difficulty, the so called power system stabilizer (PSS) is very useful, in that output power or rotor speed of the generator is used as a feedback signal. The primary obective of the PSS is to damp the swing of the generator as quickly as possible. A method is proposed for designing PSS which yields a given eigenvalue. In the second method, the use of a Heffron-Phillips model is discussed. Next, a detailed procedure for the proposed design method is presented. A generalized method of a PSS design based on Park's equation and matrix operation is proposed.

  15. Composite Adaptive Fuzzy Output Feedback Control Design for Uncertain Nonlinear Strict-Feedback Systems With Input Saturation.

    PubMed

    Li, Yongming; Tong, Shaocheng; Li, Tieshan

    2015-10-01

    In this paper, a composite adaptive fuzzy output-feedback control approach is proposed for a class of single-input and single-output strict-feedback nonlinear systems with unmeasured states and input saturation. Fuzzy logic systems are utilized to approximate the unknown nonlinear functions, and a fuzzy state observer is designed to estimate the unmeasured states. By utilizing the designed fuzzy state observer, a serial-parallel estimation model is established. Based on adaptive backstepping dynamic surface control technique and utilizing the prediction error between the system states observer model and the serial-parallel estimation model, a new fuzzy controller with the composite parameters adaptive laws are developed. It is proved that all the signals of the closed-loop system are bounded and the system output can follow the given bounded reference signal. A numerical example and simulation comparisons with previous control methods are provided to show the effectiveness of the proposed approach. PMID:25438335

  16. A hypertext system that learns from user feedback

    NASA Technical Reports Server (NTRS)

    Mathe, Nathalie

    1994-01-01

    Retrieving specific information from large amounts of documentation is not an easy task. It could be facilitated if information relevant in the current problem solving context could be automatically supplied to the user. As a first step towards this goal, we have developed an intelligent hypertext system called CID (Computer Integrated Documentation). Besides providing an hypertext interface for browsing large documents, the CID system automatically acquires and reuses the context in which previous searches were appropriate. This mechanism utilizes on-line user information requirements and relevance feedback either to reinforce current indexing in case of success or to generate new knowledge in case of failure. Thus, the user continually augments and refines the intelligence of the retrieval system. This allows the CID system to provide helpful responses, based on previous usage of the documentation, and to improve its performance over time. We successfully tested the CID system with users of the Space Station Freedom requirements documents. We are currently extending CID to other application domains (Space Shuttle operations documents, airplane maintenance manuals, and on-line training). We are also exploring the potential commercialization of this technique.

  17. A Prevalence Formula for Automatic Relevance Feedback in Boolean Systems.

    ERIC Educational Resources Information Center

    Dillon, Martin; And Others

    1983-01-01

    Implementation of relevance feedback explored here demonstrates feasibility of query reformulation for boolean retrievals from online databases. Improvements to a term prevalence formula used in earlier research are presented, along with experimental results that confirm crucial role of term weights in relevance feedback. Seven references are…

  18. Analysis of the feedback system in a nonintrusive dynamic flowmeter for measuring Pogo oscillations

    NASA Technical Reports Server (NTRS)

    Chapin, W. G.

    1974-01-01

    Equations were developed which describe the closed loop feedback system operation of a proposed ultrasonic, dynamic, nonintrusive flowmeter whose design is based on a constant phase, voltage controlled frequency feedback concept. These equations are based on linear feedback system theory. The time constant of a low pass filter is taken into account. The equations show that the larger the open loop gain, the smaller the error due to fluctuations in the speed of sound and the smaller the effective time constant.

  19. Design of the ILC Prototype FONT4 Digital Intra-Train Beam-Based Feedback System

    SciTech Connect

    Burrows, P.; Christian, G.B.; Hartin, A.F.; Dabiri Khah, H.; White, G.R.; Clarke, C.C.; Perry, C.; Kalinin, A.; McCormick, D.J.; Molloy, S.; Ross, M.C.; /SLAC

    2007-04-16

    We present the design of the FONT4 digital intra-train beam position feedback system prototype and preliminary results of initial beam tests at the Accelerator Test Facility (ATF) at KEK. The feedback system incorporates a fast analogue beam position monitor (BPM) front-end signal processor, a digital feedback board, and a kicker driver amplifier. The short bunchtrain, comprising 3 electron bunches separated by c. 150ns, in the ATF extraction line was used to test components of the prototype feedback system.

  20. Implementing Audio Digital Feedback Loop Using the National Instruments RIO System

    SciTech Connect

    Huang, G.; Byrd, J. M.

    2006-11-20

    Development of system for high precision RF distribution and laser synchronization at Berkeley Lab has been ongoing for several years. Successful operation of these systems requires multiple audio bandwidth feedback loops running at relatively high gains. Stable operation of the feedback loops requires careful design of the feedback transfer function. To allow for flexible and compact implementation, we have developed digital feedback loops on the National Instruments Reconfigurable Input/Output (RIO) platform. This platform uses an FPGA and multiple I/Os that can provide eight parallel channels running different filters. We present the design and preliminary experimental results of this system.

  1. Neural networks for feedback feedforward nonlinear control systems.

    PubMed

    Parisini, T; Zoppoli, R

    1994-01-01

    This paper deals with the problem of designing feedback feedforward control strategies to drive the state of a dynamic system (in general, nonlinear) so as to track any desired trajectory joining the points of given compact sets, while minimizing a certain cost function (in general, nonquadratic). Due to the generality of the problem, conventional methods are difficult to apply. Thus, an approximate solution is sought by constraining control strategies to take on the structure of multilayer feedforward neural networks. After discussing the approximation properties of neural control strategies, a particular neural architecture is presented, which is based on what has been called the "linear-structure preserving principle". The original functional problem is then reduced to a nonlinear programming one, and backpropagation is applied to derive the optimal values of the synaptic weights. Recursive equations to compute the gradient components are presented, which generalize the classical adjoint system equations of N-stage optimal control theory. Simulation results related to nonlinear nonquadratic problems show the effectiveness of the proposed method. PMID:18267810

  2. Global feedback control of Turing patterns in network-organized activator-inhibitor systems

    NASA Astrophysics Data System (ADS)

    Hata, S.; Nakao, H.; Mikhailov, A. S.

    2012-06-01

    Results of the first systematic study on feedback control of nonequilibrium pattern formation in networks are reported. Effects of global feedback control on Turing patterns in network-organized activator-inhibitor system have been investigated. The feedback signal was introduced into one of the parameters of the system and was proportional to the amplitude of the developing Turing pattern. Without the control, the Turing instability corresponded to a subcritical bifurcation and hysteresis effects were observed. Sufficiently strong feedback control rendered, however, the bifurcation supercritical and eliminated the hysteresis effects.

  3. Improving Lectures and Practical Classes in Using an Automatically Feedback System.

    ERIC Educational Resources Information Center

    Bollin, Andreas

    This paper presents a World Wide Web-based electronic feedback system for use in lectures and practical classes. The system is based on Java and provides a configurable feedback form, a managing tool for administrators, and a statistics viewer for presenting the generated statistical data in various ways. In addition, it generates a statistical…

  4. A Dynamic Social Feedback System to Support Learning and Social Interaction in Higher Education

    ERIC Educational Resources Information Center

    Thoms, Brian

    2011-01-01

    In this research, we examine the design, construction, and implementation of a dynamic, easy to use, feedback mechanism for social software. The tool was integrated into an existing university's online learning community (OLC). In line with constructivist learning models and practical information systems (IS) design, the feedback system provides…

  5. A Social Learning Management System Supporting Feedback for Incorrect Answers Based on Social Network Services

    ERIC Educational Resources Information Center

    Son, Jiseong; Kim, Jeong-Dong; Na, Hong-Seok; Baik, Doo-Kwon

    2016-01-01

    In this research, we propose a Social Learning Management System (SLMS) enabling real-time and reliable feedback for incorrect answers by learners using a social network service (SNS). The proposed system increases the accuracy of learners' assessment results by using a confidence scale and a variety of social feedback that is created and shared…

  6. Modeling Feedbacks Between Water and Vegetation in the Climate System

    NASA Technical Reports Server (NTRS)

    Miller, James R.; Russell, Gary L.; Hansen, James E. (Technical Monitor)

    2001-01-01

    Not only is water essential for life on earth, but life itself affects the global hydrologic cycle and consequently the climate of the planet. Whether the global feedbacks between life and the hydrologic cycle tend to stabilize the climate system about some equilibrium level is difficult to assess. We use a global climate model to examine how the presence of vegetation can affect the hydrologic cycle in a particular region. A control for the present climate is compared with a model experiment in which the Sahara Desert is replaced by vegetation in the form of trees and shrubs common to the Sahel region. A second model experiment is designed to identify the separate roles of two different effects of vegetation, namely the modified albedo and the presence of roots that can extract moisture from deeper soil layers. The results show that the presence of vegetation leads to increases in precipitation and soil moisture in western Sahara. In eastern Sahara, the changes are less clear. The increase in soil moisture is greater when the desert albedo is replaced by the vegetation albedo than when both the vegetation albedo and roots are added. The effect of roots is to withdraw water from deeper layers during the dry season. One implication of this study is that the insertion of vegetation into the Sahara modifies the hydrologic cycle so that the vegetation is more likely to persist than initially.

  7. Failsafe device for air/fuel ratio feedback control system

    SciTech Connect

    Otsuka, K.; Hasegawa, S.; Narasaka, S.

    1983-11-15

    A fail safe device is disclosed, comprising means for detecting a failure in an air/fuel ratio feedback control system and generating a fault signal when such failure is detected, and means responsive to the fault signal to drive an actuator for driving an air/fuel ratio control valve and also responsive to a reference position signal supplied thereto during the above driving, which is generated when the actuator passes its reference position, to stop the actuator at the reference position. The actuator driving/stopping means may comprise means for repeatedly driving the actuator over a predetermined operating range inclusive of the reference position a plurality of times when it is not supplied with the reference position signal upon the actuator passing the reference position, and means for driving the actuator from its extreme operating position to a predetermined position and holding the same there when it is not supplied with the reference position signal even after a predetermined number of times of the above repeated driving of the actuator.

  8. Multiscale Land surface feedbacks within agricultural and urban systems

    NASA Astrophysics Data System (ADS)

    Niyogi, D.

    2012-12-01

    This presentation will first discuss the interplay between agricultural landscapes and regional hydroclimatology with particular emphasis on the US Corn Belt. Results and experiences from studies underway as part of a multistate project (Making Climate Information Useful 2 Usable- U2U) will be summarized. The presentation will also highlight experiences regarding the different challenges in developing the regional assessment and guidance regarding sustainable futures. Study results will also be compared with findings from other geographical regions where agriculture - climate linkages are stretching the limits of sustainable water use. A vulnerability framework that can be considered for such agriculture - climate - water links will also be presented. The second issue the presentation will discuss relates to the urban land surface feedbacks and efforts underway to guide efforts related to greening as well as regional landuse planning. The complex links between city structures, urban layouts, and regional climate will be synthesized and the framework regarding a decision support system that is being developed will be presented. Salient points of the modeling efforts, data challenges, and the need for linking multiple disciplines will be presented with special focus on droughts and the need for considering complex multiscale coupled interactions within the analysis.

  9. Assessment of the Volunteered Geographic Information Feedback System for the Dutch Topographical Key Register

    NASA Astrophysics Data System (ADS)

    Grus, M.; te Winkel, D.

    2015-08-01

    Since Topographical Key Register has become an open data the amount of users increased enormously. The highest grow was in the private users group. The increasing number of users and their growing demand for high actuality of the topographic data sets motivates the Dutch Kadaster to innovate and improve the Topographical Key Register (BRT). One of the initiatives was to provide a voluntary geographical information project aiming at providing a user-friendly feedback system adjusted to all kinds of user groups. The feedback system is a compulsory element of the Topographical Key Register in the Netherlands. The Dutch Kadaster is obliged to deliver a feedback system and the key-users are obliged to use it. The aim of the feedback system is to improve the quality and stimulate the usage of the data. The results of the pilot shows that the user-friendly and open to everyone feedback system contributes enormously to improve the quality of the topographic dataset.

  10. Finite-time stabilisation of simple mechanical systems using continuous feedback

    NASA Astrophysics Data System (ADS)

    Sanyal, Amit K.; Bohn, Jan

    2015-04-01

    Stabilisation of simple mechanical systems in finite time with continuous state feedback is considered here. The dynamics are represented by generalised (local) coordinates. A general methodology to construct control Lyapunov functions that are Hölder continuous and that can be used to show finite-time stability of the feedback controlled system, is presented. This construction also gives the feedback control law, and results in the feedback system being Hölder continuous as well. Unlike Lipschitz continuous feedback control systems, the feedback control scheme given here converges to the desired equilibrium in finite time. Moreover, unlike discontinuous and hybrid control schemes, the feedback control law does not lead to chattering in the presence of measurement noise, does not excite unmodelled high-frequency dynamics, and can be implemented with actuators that can only deliver continuous control inputs. The advantages of continuous finite-time stabilisation over continuous asymptotic stabilisation of mechanical systems, has been described in some prior research on finite-time stabilisation of the double integrator. The finite-time stabilisation scheme given here generalises this prior research to multiple degree-of-freedom mechanical systems. A numerical comparison is carried out through numerical simulations on two example systems that are representative of a broad class of simple mechanical systems.

  11. A Moral Experience Feedback Loop: Modeling a System of Moral Self-Cultivation in Everyday Life

    ERIC Educational Resources Information Center

    Sherblom, Stephen A.

    2015-01-01

    This "systems thinking" model illustrates a common feedback loop by which people engage the moral world and continually reshape their moral sensibility. The model highlights seven processes that collectively form this feedback loop: beginning with (1) one's current moral sensibility which shapes processes of (2) perception, (3)…

  12. Using Instant Feedback System and Micro Exams to Enhance Active Learning

    ERIC Educational Resources Information Center

    Sabag, N.; Kosolapov, S.

    2012-01-01

    This paper presents the outcomes of the preliminary survey in which the method of IFS was used to integrate motivating questions into the lecture presentations in order to increase the students' involvement. Instant Feedback System (IFS) enables the educators to improve their own teaching by getting instant and real-time feedback about how clear…

  13. Efficient force feedback transmission system for tele surgery.

    PubMed

    Natarajan, Sriram; Ganz, Aura

    2008-01-01

    Remote surgery information requires quick and reliable transmission between the surgeon and the patient side. However, the interconnecting network is usually time varying and lossy which can cause packet loss and delay jitter. In this paper we introduce an adaptive packet prediction and buffer time adjustment algorithm which reduces the negative effects caused by the time varying networks on the transmission of force feedback data. To evaluate our scheme we run a virtual reality applet built in Matlab. Our results show, for severe packet loss and variable delay jitter, the integrated synchronization technique significantly improves the performance of the force feedback device. PMID:19163399

  14. Effect of biased feedback on motor imagery learning in BCI-teleoperation system

    PubMed Central

    Alimardani, Maryam; Nishio, Shuichi; Ishiguro, Hiroshi

    2014-01-01

    Feedback design is an important issue in motor imagery BCI systems. Regardless, to date it has not been reported how feedback presentation can optimize co-adaptation between a human brain and such systems. This paper assesses the effect of realistic visual feedback on users' BCI performance and motor imagery skills. We previously developed a tele-operation system for a pair of humanlike robotic hands and showed that BCI control of such hands along with first-person perspective visual feedback of movements can arouse a sense of embodiment in the operators. In the first stage of this study, we found that the intensity of this ownership illusion was associated with feedback presentation and subjects' performance during BCI motion control. In the second stage, we probed the effect of positive and negative feedback bias on subjects' BCI performance and motor imagery skills. Although the subject specific classifier, which was set up at the beginning of experiment, detected no significant change in the subjects' online performance, evaluation of brain activity patterns revealed that subjects' self-regulation of motor imagery features improved due to a positive bias of feedback and a possible occurrence of ownership illusion. Our findings suggest that in general training protocols for BCIs, manipulation of feedback can play an important role in the optimization of subjects' motor imagery skills. PMID:24782721

  15. Thoracic ROM measurement system with visual bio-feedback: system design and biofeedback evaluation.

    PubMed

    Ando, Takeshi; Kawamura, Kazuya; Fujitani, Junko; Koike, Tomokazu; Fujimoto, Masashi; Fujie, Masakatsu G

    2011-01-01

    Patients with diseases such as chronic obstructive pulmonary disease (COPD) need to improve their thorax mobility. Thoracic ROM is one of the simplest and most useful indexes to evaluate the respiratory function. In this paper, we have proposed the prototype of a simple thoracic ROM measurement system with real-time visual bio-feedback in the chest expansion test. In this system, the thoracic ROM is measured using a wire-type linear encoder whose wire is wrapped around the thorax. In this paper, firstly, the repeatability and reliability of measured thoracic ROM was confirmed as a first report of the developed prototype. Secondly, we analyzed the effect of the bio-feedback system on the respiratory function. The result of the experiment showed that it was easier to maintain a large and stable thoracic ROM during deep breathing by using the real-time visual biofeedback system of the thoracic ROM. PMID:22254548

  16. Ultrashort pulse laser microsurgery system with plasma luminescence feedback control

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchik, A.M.; Gold, D.M.; Darrow, C.B.; Da Silva, L.B.

    1997-11-10

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue during ultrashort pulse laser (USPL) micro-spinal surgery. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  17. Develop feedback system for intelligent dynamic resource allocation to improve application performance.

    SciTech Connect

    Gentile, Ann C.; Brandt, James M.; Tucker, Thomas; Thompson, David

    2011-09-01

    This report provides documentation for the completion of the Sandia Level II milestone 'Develop feedback system for intelligent dynamic resource allocation to improve application performance'. This milestone demonstrates the use of a scalable data collection analysis and feedback system that enables insight into how an application is utilizing the hardware resources of a high performance computing (HPC) platform in a lightweight fashion. Further we demonstrate utilizing the same mechanisms used for transporting data for remote analysis and visualization to provide low latency run-time feedback to applications. The ultimate goal of this body of work is performance optimization in the face of the ever increasing size and complexity of HPC systems.

  18. Implementation of an in-house visual feedback system for motion management during radiation therapy.

    PubMed

    Nguyen, Vi Nhan V; Ellerbusch, David C; Cetnar, Ashley J; James, Joshua A; Wang, Brian

    2016-01-01

    In this Technical Note, we describe an in-house video goggles feedback system assembled using several commercially available products. This goggle video feed-back system is currently being used at University of Louisville and Mayo Clinic for both CT simulation and linac treatment delivery. The setup details, including specific recommendations, are provided, along with an alternative option for using the video goggles system. PMID:26894353

  19. The FONT5 Bunch-by-Bunch Position and Angle Feedback System at ATF2

    NASA Astrophysics Data System (ADS)

    Apsimon, R. J.; Bett, D. R.; Burrows, P. N.; Christian, G. B.; Constance, B.; Davis, M. R.; Gerbershagen, A.; Perry, C.; Resta-Lopez, J.

    The FONT5 upstream beam-based feedback system at ATF2 is designed to correct the position and angle jitter at the entrance to the ATF2 final-focus system, and also to demonstrate a prototype intra-train feedback system for the International Linear Collider interaction point. We discuss the hardware, from stripline BPMs to kickers, and RF and digital signal processing, as well as presenting results from the latest beam tests at ATF2.

  20. Asymmetric interjoint feedback contributes to postural control of redundant multi-link systems

    NASA Astrophysics Data System (ADS)

    Bunderson, Nathan E.; Ting, Lena H.; Burkholder, Thomas J.

    2007-09-01

    Maintaining the postural configuration of a limb such as an arm or leg is a fundamental neural control task that involves the coordination of multiple linked body segments. Biological systems are known to use a complex network of inter- and intra-joint feedback mechanisms arising from muscles, spinal reflexes and higher neuronal structures to stabilize the limbs. While previous work has shown that a small amount of asymmetric heterogenic feedback contributes to the behavior of these systems, a satisfactory functional explanation for this non-conservative feedback structure has not been put forth. We hypothesized that an asymmetric multi-joint control strategy would confer both an energetic and stability advantage in maintaining endpoint position of a kinematically redundant system. We tested this hypothesis by using optimal control models incorporating symmetric versus asymmetric feedback with the goal of maintaining the endpoint location of a kinematically redundant, planar limb. Asymmetric feedback improved endpoint control performance of the limb by 16%, reduced energetic cost by 21% and increased interjoint coordination by 40% compared to the symmetric feedback system. The overall effect of the asymmetry was that proximal joint motion resulted in greater torque generation at distal joints than vice versa. The asymmetric organization is consistent with heterogenic stretch reflex gains measured experimentally. We conclude that asymmetric feedback has a functionally relevant role in coordinating redundant degrees of freedom to maintain the position of the hand or foot.

  1. Distinct noise-controlling roles of multiple negative feedback mechanisms in a prokaryotic operon system.

    PubMed

    Nguyen, L K; Kulasiri, D

    2011-03-01

    Molecular fluctuations are known to affect dynamics of cellular systems in important ways. Studies aimed at understanding how molecular systems of certain regulatory architectures control noise therefore become essential. The interplay between feedback regulation and noise has been previously explored for cellular networks governed by a single negative feedback loop. However, similar issues within networks consisting of more complex regulatory structures remain elusive. The authors investigate how negative feedback loops manage noise within a biochemical cascade concurrently governed by multiple negative feedback loops, using the prokaryotic tryptophan (trp) operon system in Escherechia coli as the model system. To the authors knowledge, this is the first study of noise in the trp operon system. They show that the loops in the trp operon system possess distinct, even opposing, noise-controlling effects despite their seemingly analogous feedback structures. The enzyme inhibition loop, although controlling the last reaction of the cascade, was found to suppress noise not only for the tryptophan output but also for other upstream components. In contrast, the Repression (Rep) loop enhances noise for all systems components. Attenuation (Att) poses intermediate effects by attenuating noise for the upstream components but promoting noise for components downstream of its target. Regarding noise at the output tryptophan, Rep and Att can be categorised as noise-enhancing loops whereas Enzyme Inhibition as a noise-reducing loop. These findings suggest novel implications in how cellular systems with multiple feedback mechanisms control noise. [Includes supplementary material]. PMID:21405203

  2. Issues on stability of ADP feedback controllers for dynamical systems.

    PubMed

    Balakrishnan, S N; Ding, Jie; Lewis, Frank L

    2008-08-01

    This paper traces the development of neural-network (NN)-based feedback controllers that are derived from the principle of adaptive/approximate dynamic programming (ADP) and discusses their closed-loop stability. Different versions of NN structures in the literature, which embed mathematical mappings related to solutions of the ADP-formulated problems called "adaptive critics" or "action-critic" networks, are discussed. Distinction between the two classes of ADP applications is pointed out. Furthermore, papers in "model-free" development and model-based neurocontrollers are reviewed in terms of their contributions to stability issues. Recent literature suggests that work in ADP-based feedback controllers with assured stability is growing in diverse forms. PMID:18632377

  3. System justification and electrophysiological responses to feedback: support for a positivity bias.

    PubMed

    Tritt, Shona M; Page-Gould, Elizabeth; Peterson, Jordan B; Inzlicht, Michael

    2014-06-01

    Conservatives, compared to liberals, are consistently found to exhibit physiological sensitivity to aversive stimuli. However, it remains unknown whether conservatives are also sensitive to salient positively valenced stimuli. We therefore used event-related potentials to determine the relationship between system justification (SJ), a fundamental component of conservative political ideology, and neural processing of negative and positive feedback. Participants (N = 29) filled out questionnaire assessments of SJ. Feedback-related negativity (FRN), an event-related potential component thought to index activity in neural regions associated with reward processing, was assessed in response to positive and negative feedback on a time estimation task. A significant interaction was noted between SJ and feedback type in predicting FRN. Simple effects tests suggested that SJ predicted greater FRN in response to positive but not to negative feedback. Conservatives may experience salient positive information with a heightened intensity. PMID:24274321

  4. Tests of the FONT3 Linear Collider Intra-Train Beam Feedback System at the ATF

    SciTech Connect

    Burrows, P.N.; Christian, G.; Clarke, C.; Hartin, A.; Dabiri Khah, H.; Molloy, S.; White, G.R.; Frisch, J.C.; Markiewicz, T.W.; McCormick, D.J.; Ross, M.C.; Smith, S.; Smith, T.J.; Kalinin, A.; Perry, C.; /Oxford Instruments

    2006-03-14

    We report preliminary results of beam tests of the FONT3 Linear Collider intra-train position feedback system prototype at the Accelerator Test Facility at KEK. The feedback system incorporates a novel beam position monitor (BPM) processor with a latency below 5 nanoseconds, and a kicker driver amplifier with similar low latency. The 56 nanosecond-long bunchtrain in the ATF extraction line was used to test the prototype BPM processor. The achieved latency will allow a demonstration of intra-train feedback on timescales relevant even for the CLIC Linear Collider design.

  5. A real-time auditory feedback system for retraining gait.

    PubMed

    Maulucci, Ruth A; Eckhouse, Richard H

    2011-01-01

    Stroke is the third leading cause of death in the United States and the principal cause of major long-term disability, incurring substantial distress as well as medical cost. Abnormal and inefficient gait patterns are widespread in survivors of stroke, yet gait is a major determinant of independent living. It is not surprising, therefore, that improvement of walking function is the most commonly stated priority of the survivors. Although many such individuals achieve the goal of walking, the caliber of their walking performance often limits endurance and quality of life. The ultimate goal of the research presented here is to use real-time auditory feedback to retrain gait in patients with chronic stroke. The strategy is to convert the motion of the foot into an auditory signal, and then use this auditory signal as feedback to inform the subject of the existence as well as the magnitude of error during walking. The initial stage of the project is described in this paper. The design and implementation of the new feedback method for lower limb training is explained. The question of whether the patient is physically capable of handling such training is explored. PMID:22255509

  6. Electronic systems for transverse coupled-bunch feedback in the Advanced Light Source (ALS)

    SciTech Connect

    Barry, W.; Lambertson, G.R.; Lo, C.C.

    1993-10-01

    In order to effectively control a large number of transverse coupled-bunch modes in the LBL Advanced Light Source (ALS) storage ring, a broad-band, bunch-by-bunch feedback system has been designed, and is beginning to undergo testing and commissioning. This paper addresses, in some detail, the major electronic components of the feedback system. In particular, the components described include: broad-band microwave position detection receivers, closed orbit offset signal rejection circuitry, and baseband quadrature processing circuitry.

  7. Finite-time state feedback stabilisation of stochastic high-order nonlinear feedforward systems

    NASA Astrophysics Data System (ADS)

    Xie, Xue-Jun; Zhang, Xing-Hui; Zhang, Kemei

    2016-07-01

    This paper studies the finite-time state feedback stabilisation of stochastic high-order nonlinear feedforward systems. Based on the stochastic Lyapunov theorem on finite-time stability, by using the homogeneous domination method, the adding one power integrator and sign function method, constructing a ? Lyapunov function and verifying the existence and uniqueness of solution, a continuous state feedback controller is designed to guarantee the closed-loop system finite-time stable in probability.

  8. Global exponential stability of recurrent neural networks for synthesizing linear feedback control systems via pole assignment.

    PubMed

    Zhang, Yunong; Wang, Jun

    2002-01-01

    Global exponential stability is the most desirable stability property of recurrent neural networks. The paper presents new results for recurrent neural networks applied to online computation of feedback gains of linear time-invariant multivariable systems via pole assignment. The theoretical analysis focuses on the global exponential stability, convergence rates, and selection of design parameters. The theoretical results are further substantiated by simulation results conducted for synthesizing linear feedback control systems with different specifications and design requirements. PMID:18244461

  9. Improving vision-based motor rehabilitation interactive systems for users with disabilities using mirror feedback.

    PubMed

    Jaume-i-Capó, Antoni; Martínez-Bueso, Pau; Moyà-Alcover, Biel; Varona, Javier

    2014-01-01

    Observation is recommended in motor rehabilitation. For this reason, the aim of this study was to experimentally test the feasibility and benefit of including mirror feedback in vision-based rehabilitation systems: we projected the user on the screen. We conducted a user study by using a previously evaluated system that improved the balance and postural control of adults with cerebral palsy. We used a within-subjects design with the two defined feedback conditions (mirror and no-mirror) with two different groups of users (8 with disabilities and 32 without disabilities) using usability measures (time-to-start (T(s)) and time-to-complete (T(c))). A two-tailed paired samples t-test confirmed that in case of disabilities the mirror feedback facilitated the interaction in vision-based systems for rehabilitation. The measured times were significantly worse in the absence of the user's own visual feedback (T(s) = 7.09 (P < 0.001) and T(c) = 4.48 (P < 0.005)). In vision-based interaction systems, the input device is the user's own body; therefore, it makes sense that feedback should be related to the body of the user. In case of disabilities the mirror feedback mechanisms facilitated the interaction in vision-based systems for rehabilitation. Results recommends developers and researchers use this improvement in vision-based motor rehabilitation interactive systems. PMID:25295310

  10. Improving Vision-Based Motor Rehabilitation Interactive Systems for Users with Disabilities Using Mirror Feedback

    PubMed Central

    Martínez-Bueso, Pau; Moyà-Alcover, Biel

    2014-01-01

    Observation is recommended in motor rehabilitation. For this reason, the aim of this study was to experimentally test the feasibility and benefit of including mirror feedback in vision-based rehabilitation systems: we projected the user on the screen. We conducted a user study by using a previously evaluated system that improved the balance and postural control of adults with cerebral palsy. We used a within-subjects design with the two defined feedback conditions (mirror and no-mirror) with two different groups of users (8 with disabilities and 32 without disabilities) using usability measures (time-to-start (Ts) and time-to-complete (Tc)). A two-tailed paired samples t-test confirmed that in case of disabilities the mirror feedback facilitated the interaction in vision-based systems for rehabilitation. The measured times were significantly worse in the absence of the user's own visual feedback (Ts = 7.09 (P < 0.001) and Tc = 4.48 (P < 0.005)). In vision-based interaction systems, the input device is the user's own body; therefore, it makes sense that feedback should be related to the body of the user. In case of disabilities the mirror feedback mechanisms facilitated the interaction in vision-based systems for rehabilitation. Results recommends developers and researchers use this improvement in vision-based motor rehabilitation interactive systems. PMID:25295310

  11. Load speed regulation in compliant mechanical transmission systems using feedback and feedforward control actions.

    PubMed

    Raul, P R; Dwivedula, R V; Pagilla, P R

    2016-07-01

    The problem of controlling the load speed of a mechanical transmission system consisting of a belt-pulley and gear-pair is considered. The system is modeled as two inertia (motor and load) connected by a compliant transmission. If the transmission is assumed to be rigid, then using either the motor or load speed feedback provides the same result. However, with transmission compliance, due to belts or long shafts, the stability characteristics and performance of the closed-loop system are quite different when either motor or load speed feedback is employed. We investigate motor and load speed feedback schemes by utilizing the singular perturbation method. We propose and discuss a control scheme that utilizes both motor and load speed feedback, and design an adaptive feedforward action to reject load torque disturbances. The control algorithms are implemented on an experimental platform that is typically used in roll-to-roll manufacturing and results are shown and discussed. PMID:27126600

  12. The Effectiveness of Clinician Feedback in the Treatment of Depression in the Community Mental Health System

    PubMed Central

    Connolly Gibbons, Mary Beth; Kurtz, John E.; Thompson, Donald L.; Mack, Rachel A.; Lee, Jacqueline K.; Rothbard, Aileen; Eisen, Susan V.; Gallop, Robert; Crits-Christoph, Paul

    2015-01-01

    Objective We describe the development and evaluation of a clinician feedback intervention for use in community mental health settings. The Community Clinician Feedback System (CCFS) was developed in collaboration with a community partner to meet the needs of providers working in such community settings. Method The CCFS consists of weekly performance feedback to clinicians as well as a clinical feedback report that assists clinicians with patients who are not progressing as expected. Patients in the randomized sample (N=100) were pre-dominantly female African-Americans, with a mean age of 39. Results Satisfaction ratings of the CCFS indicate that the system was widely accepted by clinicians and patients. An HLM analysis comparing rates of change across conditions controlling for baseline gender, age, and racial group indicated a moderate effect in favor of the feedback condition for symptom improvement (t(94) = 2.41, p = .017, d = .50). Thirty-six percent of feedback patients compared to only 13% of patients in the no feedback condition demonstrated clinically significant change across treatment (χ2(1) = 6.13, p = .013). Conclusions These results indicate that our CCFS is acceptable to providers and patients of mental health services, and has the potential to improve the effectiveness of services for clinically meaningful depression in the community mental health setting. PMID:26052874

  13. Computing Jet Screech: a Complex Aeroacoustic Feedback System

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Hultgren, Lennart S.

    2002-01-01

    The space-time conservation-element and solution-element method is employed to numerically study the near-field axisymmetric screech-tone noise of a typical underexpanded circular jet issuing from a sonic nozzle. For the computed case, corresponding to a fully expanded Mach number of 1.19, the self-sustained feedback loop is established without artificial means. The computed shock-cell structure, acoustic wave length, screech tone frequency, and sound pressure levels are in good agreement with existing experimental results

  14. PFC design via FRIT Approach for Adaptive Output Feedback Control of Discrete-time Systems

    NASA Astrophysics Data System (ADS)

    Mizumoto, Ikuro; Takagi, Taro; Fukui, Sota; Shah, Sirish L.

    This paper deals with a design problem of an adaptive output feedback control for discrete-time systems with a parallel feedforward compensator (PFC) which is designed for making the augmented controlled system ASPR. A PFC design scheme by a FRIT approach with only using an input/output experimental data set will be proposed for discrete-time systems in order to design an adaptive output feedback control system. Furthermore, the effectiveness of the proposed PFC design method will be confirmed through numerical simulations by designing adaptive control system with adaptive NN (Neural Network) for an uncertain discrete-time system.

  15. Investigation on the synchronized characteristics of the incoherent optical feedback chaotic system

    NASA Astrophysics Data System (ADS)

    Xu, Li; Wu, Zhengmao; Li, Linfu; Fan, Li; Fan, Yan; Xia, Guangqiong

    2007-11-01

    Based on the theoretical model of the synchronization system with incoherent optical feedback, the influence of the internal parameter mismatch on the synchronized characteristics of the chaotic system has been investigated. The result shows that the chaotic system with incoherent optical feedback can be realized more easily than the complete synchronized system, and has higher security than injection locking synchronization system. Using encoding of chaos shift keying, the message can be hidden efficiently during the transmission in the system and decoded easily in receiver.

  16. Numerical Simulation of the Oscillations in a Mixer: An Internal Aeroacoustic Feedback System

    NASA Technical Reports Server (NTRS)

    Jorgenson, Philip C. E.; Loh, Ching Y.

    2004-01-01

    The space-time conservation element and solution element method is employed to numerically study the acoustic feedback system in a high temperature, high speed wind tunnel mixer. The computation captures the self-sustained feedback loop between reflecting Mach waves and the shear layer. This feedback loop results in violent instabilities that are suspected of causing damage to some tunnel components. The computed frequency is in good agreement with the available experimental data. The physical phenomena are explained based on the numerical results.

  17. Optimal output feedback control of linear systems in presence of forcing and measurement noise

    NASA Technical Reports Server (NTRS)

    Joshi, S. M.

    1974-01-01

    The problem of obtaining an optimal control law, which is constrained to be a linear feedback of the available measurements, for both continuous and discrete time linear systems subjected to additive white process noise and measurement noise was Necessary conditions are obtained for minimizing a quadratic performance function for both finite and infinite terminal time cases. The feedback gains are constrained to be time invariant for the infinite terminal time cases. For all the cases considered, algorithms are derived for generating sequences of feedback gain matrices which successively improve the performance function. A continuous time numerical example is included for the purpose of demonstration.

  18. Adaptive Neural Control of MIMO Nonstrict-Feedback Nonlinear Systems With Time Delay.

    PubMed

    Zhao, Xudong; Yang, Haijiao; Karimi, Hamid Reza; Zhu, Yanzheng

    2016-06-01

    In this paper, an adaptive neural output-feedback tracking controller is designed for a class of multiple-input and multiple-output nonstrict-feedback nonlinear systems with time delay. The system coefficient and uncertain functions of our considered systems are both unknown. By employing neural networks to approximate the unknown function entries, and constructing a new input-driven filter, a backstepping design method of tracking controller is developed for the systems under consideration. The proposed controller can guarantee that all the signals in the closed-loop systems are ultimately bounded, and the time-varying target signal can be tracked within a small error as well. The main contributions of this paper lie in that the systems under consideration are more general, and an effective design procedure of output-feedback controller is developed for the considered systems, which is more applicable in practice. Simulation results demonstrate the efficiency of the proposed algorithm. PMID:26099151

  19. Sandia SCADA Program Real-Time Feedback Control of Power Systems

    SciTech Connect

    BENTLEY, ANTHONY E.; STAMP, JASON E.; CARLSON, ROLF E.

    2001-11-01

    This report documents work supporting the Sandia National Laboratories initiative in Distributed Energy Resources (DERs) and Supervisory Control and Data Acquisition (SCADA) systems. One approach for real-time control of power generation assets using feedback control, Quantitative feedback theory (QFT), has recently been applied to voltage, frequency, and phase-control of power systems at Sandia. QFT provided a simple yet powerful philosophy for designing the control systems--allowing the designer to optimize the system by making design tradeoffs without getting lost in complex mathematics. The feedback systems were effective in reducing sensitivity to large and sudden changes in the power grid system. Voltage, frequency, and phase were accurately controlled, even with large disturbances to the power grid system.

  20. Digital closed orbit feedback system for the Advanced Photon Source storage ring

    NASA Astrophysics Data System (ADS)

    Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A. J.

    1996-09-01

    Closed orbit feedback for the Advanced Photon Source (APS) storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing. Hardware and software aspects of the system will be described. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm, application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware, including the digital signal processor (DSPs), is distributed in 20 VME crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically networked reflective memories.

  1. RKH space approximations for the feedback operator in a linear hereditary control system

    NASA Technical Reports Server (NTRS)

    Reneke, J. A.; Fennell, R. E.

    1987-01-01

    Computational implementation of feedback control laws for linear hereditary systems requires the approximation of infinite dimensional feedback operators with finite dimensional operators. The dense subspaces of K-polygonal functions in reproducing kernel Hilbert spaces, RKH spaces, suggest finite dimensional approximations of the matrix representations of the control operators. A convergence theorem is developed for the approximations and the numerical implementation of the approximations is discussed.

  2. Homeostasis of Brain Dynamics in Epilepsy: A Feedback Control Systems Perspective of Seizures

    PubMed Central

    Chakravarthy, Niranjan; Tsakalis, Kostas; Sabesan, Shivkumar; Iasemidis, Leon

    2010-01-01

    In an effort to understand basic functional mechanisms that can produce epileptic seizures, some key features are introduced in coupled lumped-parameter neural population models that produce “seizure”-like events and dynamics similar to the ones during the route of the epileptic brain towards seizures. In these models, modified from existing ones in the literature, internal feedback mechanisms are incorporated to maintain the normal low level of synchronous behavior in the presence of coupling variations. While the internal feedback is developed using basic feedback systems principles, it is also functionally equivalent to actual neurophysiological mechanisms such as homeostasis that act to maintain normal activity in neural systems that are subject to extrinsic and intrinsic perturbations. Here it is hypothesized that a plausible cause of seizures is a pathology in the internal feedback action; normal internal feedback quickly regulates an abnormally high coupling between the neural populations, whereas pathological internal feedback can lead to “seizure”-like high amplitude oscillations. Several external seizure-control paradigms, that act to achieve the operational objective of maintaining normal levels of synchronous behavior, are also developed and tested in this paper. In particular, closed-loop “modulating” control with predefined stimuli, and closed-loop feedback decoupling control are considered. Among these, feedback decoupling control is the consistently successful and robust seizure-control strategy. The proposed model and remedies are consistent with a variety of recent observations in the human and animal epileptic brain, and with theories from nonlinear systems, adaptive systems, optimization, and neurophysiology. The results from the analysis of these models have two key implications, namely, developing a basic theory for epilepsy and other brain disorders, and the development of a robust seizure-control device through electrical

  3. Effects of changes in climate on landscape and regional processes, and feedbacks to the climate system.

    PubMed

    Callaghan, Terry V; Björn, Lars Olof; Chernov, Yuri; Chapin, Terry; Christensen, Torben R; Huntley, Brian; Ims, Rolf A; Johansson, Margareta; Jolly, Dyanna; Jonasson, Sven; Matveyeva, Nadya; Panikov, Nicolai; Oechel, Walter; Shaver, Gus; Schaphoff, Sibyll; Sitch, Stephen

    2004-11-01

    Biological and physical processes in the Arctic system operate at various temporal and spatial scales to impact large-scale feedbacks and interactions with the earth system. There are four main potential feedback mechanisms between the impacts of climate change on the Arctic and the global climate system: albedo, greenhouse gas emissions or uptake by ecosystems, greenhouse gas emissions from methane hydrates, and increased freshwater fluxes that could affect the thermohaline circulation. All these feedbacks are controlled to some extent by changes in ecosystem distribution and character and particularly by large-scale movement of vegetation zones. Indications from a few, full annual measurements of CO2 fluxes are that currently the source areas exceed sink areas in geographical distribution. The little available information on CH4 sources indicates that emissions at the landscape level are of great importance for the total greenhouse balance of the circumpolar North. Energy and water balances of Arctic landscapes are also important feedback mechanisms in a changing climate. Increasing density and spatial expansion of vegetation will cause a lowering of the albedo and more energy to be absorbed on the ground. This effect is likely to exceed the negative feedback of increased C sequestration in greater primary productivity resulting from the displacements of areas of polar desert by tundra, and areas of tundra by forest. The degradation of permafrost has complex consequences for trace gas dynamics. In areas of discontinuous permafrost, warming, will lead to a complete loss of the permafrost. Depending on local hydrological conditions this may in turn lead to a wetting or drying of the environment with subsequent implications for greenhouse gas fluxes. Overall, the complex interactions between processes contributing to feedbacks, variability over time and space in these processes, and insufficient data have generated considerable uncertainties in estimating the net

  4. Programmable immersive peripheral environmental system (PIPES): a prototype control system for environmental feedback devices

    NASA Astrophysics Data System (ADS)

    Frend, Chauncey; Boyles, Michael

    2015-03-01

    This paper describes an environmental feedback device (EFD) control system aimed at simplifying the VR development cycle. Programmable Immersive Peripheral Environmental System (PIPES) affords VR developers a custom approach to programming and controlling EFD behaviors while relaxing the required knowledge and expertise of electronic systems. PIPES has been implemented for the Unity engine and features EFD control using the Arduino integrated development environment. PIPES was installed and tested on two VR systems, a large format CAVE system and an Oculus Rift HMD system. A photocell based end-to-end latency experiment was conducted to measure latency within the system. This work extends previously unpublished prototypes of a similar design. Development and experiments described in this paper are part of the VR community goal to understand and apply environment effects to VEs that ultimately add to users' perceived presence.

  5. Robust design of feedback feed-forward iterative learning control based on 2D system theory for linear uncertain systems

    NASA Astrophysics Data System (ADS)

    Li, Zhifu; Hu, Yueming; Li, Di

    2016-08-01

    For a class of linear discrete-time uncertain systems, a feedback feed-forward iterative learning control (ILC) scheme is proposed, which is comprised of an iterative learning controller and two current iteration feedback controllers. The iterative learning controller is used to improve the performance along the iteration direction and the feedback controllers are used to improve the performance along the time direction. First of all, the uncertain feedback feed-forward ILC system is presented by an uncertain two-dimensional Roesser model system. Then, two robust control schemes are proposed. One can ensure that the feedback feed-forward ILC system is bounded-input bounded-output stable along time direction, and the other can ensure that the feedback feed-forward ILC system is asymptotically stable along time direction. Both schemes can guarantee the system is robust monotonically convergent along the iteration direction. Third, the robust convergent sufficient conditions are given, which contains a linear matrix inequality (LMI). Moreover, the LMI can be used to determine the gain matrix of the feedback feed-forward iterative learning controller. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed schemes.

  6. 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.

  7. At the Intersection of Health Information Technology and Decision Support: Measurement Feedback Systems... and Beyond.

    PubMed

    Chorpita, Bruce F; Daleiden, Eric L; Bernstein, Adam D

    2016-05-01

    We select and comment on concepts and examples from the target articles in this special issue on measurement feedback systems, placing them in the context of some of our own insights and ideas about measurement feedback systems, and where those systems lie at the intersection of technology and decision making. We contend that, connected to the many implementation challenges relevant to many new technologies, there are fundamental design challenges that await a more elaborate specification of the clinical information and decision models that underlie these systems. Candidate features of such models are discussed, which include referencing multiple evidence bases, facilitating observed and expected value comparisons, fostering collaboration, and allowing translation across multiple ontological systems. We call for a new metaphor for these technologies that goes beyond measurement feedback and encourages a deeper consideration of the increasingly complex clinical decision models needed to manage the uncertainty of delivering clinical care. PMID:26604202

  8. Finite-time stabilization of uncertain nonholonomic systems in feedforward-like form by output feedback.

    PubMed

    Gao, Fangzheng; Wu, Yuqiang; Zhang, Zhongcai

    2015-11-01

    This paper investigates the problem of finite-time stabilization by output feedback for a class of nonholonomic systems in chained form with uncertainties. Comparing with the existing relevant literature, a distinguishing feature of the systems under investigation is that the x-subsystem is a feedforward-like rather than feedback-like system. This renders the existing control methods inapplicable to the control problems of the systems. A constructive design procedure for output feedback control is given. The designed controller renders that the states of closed-loop system are regulated to zero in a finite time. Two simulation examples are provided to illustrate the effectiveness of the proposed approach. PMID:26434417

  9. Integrated regional changes in arctic climate feedbacks: Implications for the global climate system

    USGS Publications Warehouse

    McGuire, A.D.; Chapin, F. S., III; Walsh, J.E.; Wirth, C.

    2006-01-01

    The Arctic is a key part of the global climate system because the net positive energy input to the tropics must ultimately be resolved through substantial energy losses in high-latitude regions. The Arctic influences the global climate system through both positive and negative feedbacks that involve physical, ecological, and human systems of the Arctic. The balance of evidence suggests that positive feedbacks to global warming will likely dominate in the Arctic during the next 50 to 100 years. However, the negative feedbacks associated with changing the freshwater balance of the Arctic Ocean might abruptly launch the planet into another glacial period on longer timescales. In light of uncertainties and the vulnerabilities of the climate system to responses in the Arctic, it is important that we improve our understanding of how integrated regional changes in the Arctic will likely influence the evolution of the global climate system. Copyright ?? 2006 by Annual Reviews. All rights reserved.

  10. Design of an optimal output feedback control system with modal insensitivity

    NASA Technical Reports Server (NTRS)

    Raman, K. V.; Calise, A. J.

    1984-01-01

    This paper deals with the design of an output feedback controller which results in selected modal insensitivity, and at the same time optimizes a quadratic performance index representative of desired system performance for nominal plant parameter values. The approach taken here is to characterize the class of attainable eigenvectors for a given set of eigenvalues (distinct or non-distinct) which lie in a subspace called the 'Modal Insensitivity Subspace'. A constraint is established on the feedback matrix which results in modal insensitivity. Necessary conditions for optimality subject to the constraint on the feedback matrix are given. This forms the basis for a numerical algorithm to compute the optimal feedback gain which analyzed for convergence. To illustrate the procedure, a design is carried out using the lateral dynamics of an L-1011 aircraft.

  11. State derivative feedback in second-order linear systems: A comparative analysis of perturbed eigenvalues under coefficient variation

    NASA Astrophysics Data System (ADS)

    Araújo, José M.; Dórea, Carlos E. T.; Gonçalves, Luiz M. G.; Datta, Biswa N.

    2016-08-01

    This paper presents a comparative study of sensitivity to parameter variation in two feedback techniques applied in second-order linear systems: state feedback technique and the less conventional state derivative feedback technique. The former uses information on displacements and velocities whereas the latter uses velocities and accelerations. Several contributions on the problem of partial or full eigenvalue/eigenstructure assignment using the state feedback technique are presented in the literature. Recently, some interesting possibilities, such as solving the regularization problem in singular mass second-order systems, are approached using state derivative feedback. In this work, a general equivalence between state feedback and state derivative feedback is first established. Then, figures of merit on the resulting perturbed spectrum are proposed in order to assess the sensitivity of the closed-loop system to variations on the system matrices. Numerical examples are presented to support the obtained results.

  12. Decentralised memory static output feedback control for the nonlinear time-delay similar interconnected systems

    NASA Astrophysics Data System (ADS)

    Ma, Yuechao; Jin, Shujie; Gu, Nannan

    2016-07-01

    In this paper, the problem of decentralised memory static output feedback control for a class of nonlinear time-delayed interconnected systems with similar structure is investigated, where both the linear and nonlinear state vectors involve time delay. The contributions of the paper include the following: (1) a new similar structure is presented via memory static output feedback; (2) by exploiting the structure of interconnected systems, the new integral inequalities, constrained Lyapunov equations and LMI method, the decentralised memory static output derivative feedback controllers with similar structure are designed, which is dependent of time delays, to stabilise the interconnected systems uniformly asymptotically; and (3) the stability domain is estimated. The conservatism of the results obtained is reduced by full using the system output information. Finally, the numerical examples are given to demonstrate the effectiveness of the results obtained in this paper.

  13. Feedback-linearization-based neural adaptive control for unknown nonaffine nonlinear discrete-time systems.

    PubMed

    Deng, Hua; Li, Han-Xiong; Wu, Yi-Hu

    2008-09-01

    A new feedback-linearization-based neural network (NN) adaptive control is proposed for unknown nonaffine nonlinear discrete-time systems. An equivalent model in affine-like form is first derived for the original nonaffine discrete-time systems as feedback linearization methods cannot be implemented for such systems. Then, feedback linearization adaptive control is implemented based on the affine-like equivalent model identified with neural networks. Pretraining is not required and the weights of the neural networks used in adaptive control are directly updated online based on the input-output measurement. The dead-zone technique is used to remove the requirement of persistence excitation during the adaptation. With the proposed neural network adaptive control, stability and performance of the closed-loop system are rigorously established. Illustrated examples are provided to validate the theoretical findings. PMID:18779092

  14. Nonlinear analysis of a maglev system with time-delayed feedback control

    NASA Astrophysics Data System (ADS)

    Zhang, Lingling; Campbell, Sue Ann; Huang, Lihong

    2011-10-01

    This paper undertakes a nonlinear analysis of a model for a maglev system with time-delayed feedback. Using linear analysis, we determine constraints on the feedback control gains and the time delay which ensure stability of the maglev system. We then show that a Hopf bifurcation occurs at the linear stability boundary. To gain insight into the periodic motion which arises from the Hopf bifurcation, we use the method of multiple scales on the nonlinear model. This analysis shows that for practical operating ranges, the maglev system undergoes both subcritical and supercritical bifurcations, which give rise to unstable and stable limit cycles respectively. Numerical simulations confirm the theoretical results and indicate that unstable limit cycles may coexist with the stable equilibrium state. This means that large enough perturbations may cause instability in the system even if the feedback gains are such that the linear theory predicts that the equilibrium state is stable.

  15. Control of Multibunch Longitudinal Instabilities and Beam Diagnostics Using a DSP-based Feedback System

    SciTech Connect

    Teytelman, Dmitry

    2000-03-30

    A bunch-by-bunch longitudinal feedback system has been designed and built to control coupled-bunch instabilities in the PEP-II machine. A prototype system has been installed at the Advanced Light Source at LBNL. Programmable DSPs allow longitudinal feedback processing in conjunction with data acquisition or instrumentation algorithms. Here the authors describe techniques developed for different beam and system diagnostics, such as measurements of the modal growth and damping rates and measurements of the bunch-by-bunch currents. Results from the Advanced Light Source are presented to illustrate these techniques.

  16. An active feedback system to control synchrotron oscillations in the SLC Damping Rings

    SciTech Connect

    Corredoura, P.L.; Pellegrin, J.L.; Schwarz, H.D.; Sheppard, J.C.

    1989-03-01

    Initially the SLC Damping Rings accomplished Robinson instability damping by operating the RF accelerating cavities slightly detuned. In order to be able to run the cavities tuned and achieve damping for Robinson instability and synchrotron oscillations at injection an active feedback system has been developed. This paper describes the theoretical basis for the feedback system and the development of the hardware. Extensive measurements of the loop response including stored beam were performed. Overall performance of the system is also reported. 3 refs., 6 figs.

  17. The use of differential pressure feedback in an automatic flight control system

    NASA Technical Reports Server (NTRS)

    Levy, D. W.; Roskam, J.; Finn, P. D.

    1982-01-01

    A feasibility study has been performed to evaluate the performance of a system whereby a control surface is positioned with differential pressure as the feedback variable. Analogous to a position command system, the control surface is commanded to move until a certain differential pressure is achieved at a given point on the surface. Frequency response tests and theoretical considerations indicate that the pressure feedback transfer function is first order, with a break frequency up to 50 rad/sec. There exist applications to the outer loops of flight control systems as well. Stability augmentation, gust alleviation, and stall prevention appear to be possible by feeding back differential pressure across lifting and control surfaces.

  18. Autogenic-Feedback Training Exercise (AFTE) Method and System

    NASA Technical Reports Server (NTRS)

    Cowings, Patricia S. (Inventor)

    1997-01-01

    The Autogenic-Feedback Training Exercise (AFTE) method of the present invention is a combined application of physiologic and perceptual training techniques. such as autogenic therapy and biofeedback. This combined therapy approach produces a methodology that is appreciably more effective than either of the individual techniques used separately. The AFTE method enables sufficient magnitude of control necessary to significantly reduce the behavioral and physiologic reactions to severe environmental stressors. It produces learned effects that are persistent over time and are resistant to extinction and it can be administered in a short period of time. The AFTE method may be used efficiently in several applications, among which are the following: to improve pilot and crew performance during emergency flying conditions; to train people to prevent the occurrence of nausea and vomiting associated with motion and sea sickness, or morning sickness in early pregnancy; as a training method for preventing or counteracting air-sickness symptoms in high-performance military aircraft; for use as a method for cardiovascular training, as well as for multiple other autonomic responses, which may contribute to the alleviation of Space Motion Sickness (SMS) in astronauts and cosmonauts; training people suffering from migraine or tension headaches to control peripheral blood flow and reduce forehead and/or trapezius muscle tension; training elderly people suffering from fecal incontinence to control their sphincter muscles; training cancer patients to reduce the nauseagenic effects of chemotherapy; and training patients with Chronic Intestinal Pseudo-obstruction (CIP).

  19. Robust Nonlinear Feedback Control of Aircraft Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Garrard, William L.; Balas, Gary J.; Litt, Jonathan (Technical Monitor)

    2001-01-01

    This is the final report on the research performed under NASA Glen grant NASA/NAG-3-1975 concerning feedback control of the Pratt & Whitney (PW) STF 952, a twin spool, mixed flow, after burning turbofan engine. The research focussed on the design of linear and gain-scheduled, multivariable inner-loop controllers for the PW turbofan engine using H-infinity and linear, parameter-varying (LPV) control techniques. The nonlinear turbofan engine simulation was provided by PW within the NASA Rocket Engine Transient Simulator (ROCETS) simulation software environment. ROCETS was used to generate linearized models of the turbofan engine for control design and analysis as well as the simulation environment to evaluate the performance and robustness of the controllers. Comparison between the H-infinity, and LPV controllers are made with the baseline multivariable controller and developed by Pratt & Whitney engineers included in the ROCETS simulation. Simulation results indicate that H-infinity and LPV techniques effectively achieve desired response characteristics with minimal cross coupling between commanded values and are very robust to unmodeled dynamics and sensor noise.

  20. Biotic carbon feedbacks in a materially closed soil-vegetation-atmosphere system

    NASA Astrophysics Data System (ADS)

    Milcu, Alexandru; Lukac, Martin; Subke, Jens-Arne; Manning, Pete; Heinemeyer, Andreas; Wildman, Dennis; Anderson, Robert; Ineson, Phil

    2012-04-01

    The magnitude and direction of the coupled feedbacks between the biotic and abiotic components of the terrestrial carbon cycle is a major source of uncertainty in coupled climate-carbon-cycle models. Materially closed, energetically open biological systems continuously and simultaneously allow the two-way feedback loop between the biotic and abiotic components to take place, but so far have not been used to their full potential in ecological research, owing to the challenge of achieving sustainable model systems. We show that using materially closed soil-vegetation-atmosphere systems with pro rata carbon amounts for the main terrestrial carbon pools enables the establishment of conditions that balance plant carbon assimilation, and autotrophic and heterotrophic respiration fluxes over periods suitable to investigate short-term biotic carbon feedbacks. Using this approach, we tested an alternative way of assessing the impact of increased CO2 and temperature on biotic carbon feedbacks. The results show that without nutrient and water limitations, the short-term biotic responses could potentially buffer a temperature increase of 2.3°C without significant positive feedbacks to atmospheric CO2. We argue that such closed-system research represents an important test-bed platform for model validation and parameterization of plant and soil biotic responses to environmental changes.

  1. Terrestrial biogeochemical feedbacks in the climate system: from past to future

    SciTech Connect

    Arneth, A.; Harrison, S. P.; Zaehle, S.; Tsigaridis, K; Menon, S; Bartlein, P.J.; Feichter, J; Korhola, A; Kulmala, M; O'Donnell, D; Schurgers, G; Sorvari, S; Vesala, T

    2010-01-05

    The terrestrial biosphere plays a major role in the regulation of atmospheric composition, and hence climate, through multiple interlinked biogeochemical cycles (BGC). Ice-core and other palaeoenvironmental records show a fast response of vegetation cover and exchanges with the atmosphere to past climate change, although the phasing of these responses reflects spatial patterning and complex interactions between individual biospheric feedbacks. Modern observations show a similar responsiveness of terrestrial biogeochemical cycles to anthropogenically-forced climate changes and air pollution, with equally complex feedbacks. For future conditions, although carbon cycle-climate interactions have been a major focus, other BGC feedbacks could be as important in modulating climate changes. The additional radiative forcing from terrestrial BGC feedbacks other than those conventionally attributed to the carbon cycle is in the range of 0.6 to 1.6 Wm{sup -2}; all taken together we estimate a possible maximum of around 3 Wm{sup -2} towards the end of the 21st century. There are large uncertainties associated with these estimates but, given that the majority of BGC feedbacks result in a positive forcing because of the fundamental link between metabolic stimulation and increasing temperature, improved quantification of these feedbacks and their incorporation in earth system models is necessary in order to develop coherent plans to manage ecosystems for climate mitigation.

  2. The Construction of Plasma Density Feedback Control System on J-TEXT Tokamak

    NASA Astrophysics Data System (ADS)

    Ke, Xin; Chen, Zhipeng; Ba, Weigang; Shu, Shuangbao; Gao, Li; Zhang, Ming; Zhuang, Ge

    2016-02-01

    The plasma density feedback control system (PDFCS) has been established on the Joint Texas Experimental Tokamak (J-TEXT) for meeting the need for an accurate plasma density in physical experiments. It consists of a density measurement subsystem, a feedback control subsystem and a gas puffing subsystem. According to the characteristic of the gas puffing system, a voltage amplitude control mode has been applied in the feedback control strategy, which is accomplished by the proportion, integral and differential (PID) controller. In this system, the quantity calibration of gas injection, adjusted responding to the change of the density signal, has been carried out. Some experimental results are shown and discussed. supported by the National Magnetic Confinement Fusion Science Program (Nos. 2014GB103001 and 2013GB106001) and National Natural Science Foundation of China (Nos. 11305070 and 11105028)

  3. Down sampled signal processing for a B Factory bunch-by-bunch feedback system

    SciTech Connect

    Hindi, H.; Hosseini, W.; Briggs, D.; Fox, J.; Hutton, A.

    1992-03-01

    A bunch-by-bunch feedback scheme is studied for damping coupled bunch synchrotron oscillations in the proposed PEP II B Factory. The quasi-linear feedback systems design incorporates a phase detector to provide a quantized measure of bunch phase, digital signal processing to compute an error correction signal and a kicker system to correct the energy of the bunches. A farm of digital processors, operating in parallel, is proposed to compute correction signals for the 1658 bunches of the B Factory. This paper studies the use of down sampled processing to reduce the computational complexity of the feedback system. We present simulation results showing the effect of down sampling on beam dynamics. Results show that down sampled processing can reduce the scale of the processing task by a factor of 10.

  4. Benefits and Drawbacks of Computer-Based Assessment and Feedback Systems: Student and Educator Perspectives

    ERIC Educational Resources Information Center

    Debuse, Justin C. W.; Lawley, Meredith

    2016-01-01

    Providing students with high quality feedback is important and can be achieved using computer-based systems. While student and educator perspectives of such systems have been investigated, a comprehensive multidisciplinary study has not yet been undertaken. This study examines student and educator perspectives of a computer-based assessment and…

  5. A generalization of the Nyquist stability criterion. [extension to multivariable linear feedback systems

    NASA Technical Reports Server (NTRS)

    Stevens, P. K.

    1981-01-01

    This paper presents a generalization of the Nyquist stability criterion to include general multivariable linear stationary systems subject to linear static and dynamic feedback. At the same time, a unifying proof is given for all known versions of the Nyquist criterion for finite dimensional systems.

  6. Teacher Feedback and Student Academic Achievement: Teacher Use of Student Information Systems

    ERIC Educational Resources Information Center

    Bishop, Daniel J.

    2013-01-01

    In an era of professional standards for educators and teacher evaluations linked to measures of student achievement, researchers use data from student information systems to address research questions linking teacher feedback to student achievement. A quantitative study of teacher use of the Skyward student information system (SIS) was conducted…

  7. A System of Student Feedback: Considerations of Academic Staff Taken into Account

    ERIC Educational Resources Information Center

    Hulpiau, Veerle; Masschelein, Evelien; Van Der Stockt, Luc; Verhesschen, Piet; Waeytens, Kim

    2007-01-01

    As a consequence of the suspension of a system of yearly evaluations of individual courses with student questionnaires, the University of Leuven organised a broad consultation of the academic community focussing on what they expect from a system based on student feedback. The study revealed that this community attaches great importance to a clear…

  8. A New KE-Free Online ICALL System Featuring Error Contingent Feedback

    ERIC Educational Resources Information Center

    Tokuda, Naoyuki; Chen, Liang

    2004-01-01

    As a first step towards implementing a human language teacher, we have developed a new template-based on-line ICALL (intelligent computer assisted language learning) system capable of automatically diagnosing learners' free-format translated inputs and returning error contingent feedback. The system architecture we have adopted allows language…

  9. Design of multivariable feedback control systems via spectral assignment. [as applied to aircraft flight control

    NASA Technical Reports Server (NTRS)

    Liberty, S. R.; Mielke, R. R.; Tung, L. J.

    1981-01-01

    Applied research in the area of spectral assignment in multivariable systems is reported. A frequency domain technique for determining the set of all stabilizing controllers for a single feedback loop multivariable system is described. It is shown that decoupling and tracking are achievable using this procedure. The technique is illustrated with a simple example.

  10. Optimal control of nonlinear continuous-time systems in strict-feedback form.

    PubMed

    Zargarzadeh, Hassan; Dierks, Travis; Jagannathan, Sarangapani

    2015-10-01

    This paper proposes a novel optimal tracking control scheme for nonlinear continuous-time systems in strict-feedback form with uncertain dynamics. The optimal tracking problem is transformed into an equivalent optimal regulation problem through a feedforward adaptive control input that is generated by modifying the standard backstepping technique. Subsequently, a neural network-based optimal control scheme is introduced to estimate the cost, or value function, over an infinite horizon for the resulting nonlinear continuous-time systems in affine form when the internal dynamics are unknown. The estimated cost function is then used to obtain the optimal feedback control input; therefore, the overall optimal control input for the nonlinear continuous-time system in strict-feedback form includes the feedforward plus the optimal feedback terms. It is shown that the estimated cost function minimizes the Hamilton-Jacobi-Bellman estimation error in a forward-in-time manner without using any value or policy iterations. Finally, optimal output feedback control is introduced through the design of a suitable observer. Lyapunov theory is utilized to show the overall stability of the proposed schemes without requiring an initial admissible controller. Simulation examples are provided to validate the theoretical results. PMID:26111400

  11. Depression as a systemic syndrome: mapping the feedback loops of major depressive disorder

    PubMed Central

    Wittenborn, A. K.; Rahmandad, H.; Rick, J.; Hosseinichimeh, N.

    2016-01-01

    Background Depression is a complex public health problem with considerable variation in treatment response. The systemic complexity of depression, or the feedback processes among diverse drivers of the disorder, contribute to the persistence of depression. This paper extends prior attempts to understand the complex causal feedback mechanisms that underlie depression by presenting the first broad boundary causal loop diagram of depression dynamics. Method We applied qualitative system dynamics methods to map the broad feedback mechanisms of depression. We used a structured approach to identify candidate causal mechanisms of depression in the literature. We assessed the strength of empirical support for each mechanism and prioritized those with support from validation studies. Through an iterative process, we synthesized the empirical literature and created a conceptual model of major depressive disorder. Results The literature review and synthesis resulted in the development of the first causal loop diagram of reinforcing feedback processes of depression. It proposes candidate drivers of illness, or inertial factors, and their temporal functioning, as well as the interactions among drivers of depression. The final causal loop diagram defines 13 key reinforcing feedback loops that involve nine candidate drivers of depression. Conclusions Future research is needed to expand upon this initial model of depression dynamics. Quantitative extensions may result in a better understanding of the systemic syndrome of depression and contribute to personalized methods of evaluation, prevention and intervention. PMID:26621339

  12. Approaching system equilibrium with accurate or not accurate feedback information in a two-route system

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-mei; Xie, Dong-fan; Li, Qi

    2015-02-01

    With the development of intelligent transport system, advanced information feedback strategies have been developed to reduce traffic congestion and enhance the capacity. However, previous strategies provide accurate information to travelers and our simulation results show that accurate information brings negative effects, especially in delay case. Because travelers prefer to the best condition route with accurate information, and delayed information cannot reflect current traffic condition but past. Then travelers make wrong routing decisions, causing the decrease of the capacity and the increase of oscillations and the system deviating from the equilibrium. To avoid the negative effect, bounded rationality is taken into account by introducing a boundedly rational threshold BR. When difference between two routes is less than the BR, routes have equal probability to be chosen. The bounded rationality is helpful to improve the efficiency in terms of capacity, oscillation and the gap deviating from the system equilibrium.

  13. Factorization and the synthesis of optimal feedback gains for distributed parameter systems

    NASA Technical Reports Server (NTRS)

    Milman, Mark H.; Scheid, Robert E.

    1990-01-01

    An approach based on Volterra factorization leads to a new methodology for the analysis and synthesis of the optimal feedback gain in the finite-time linear quadratic control problem for distributed parameter systems. The approach circumvents the need for solving and analyzing Riccati equations and provides a more transparent connection between the system dynamics and the optimal gain. The general results are further extended and specialized for the case where the underlying state is characterized by autonomous differential-delay dynamics. Numerical examples are given to illustrate the second-order convergence rate that is derived for an approximation scheme for the optimal feedback gain in the differential-delay problem.

  14. R-parametrization and its role in classification of linear multivariable feedback systems

    NASA Technical Reports Server (NTRS)

    Chen, Robert T. N.

    1988-01-01

    A classification of all the compensators that stabilize a given general plant in a linear, time-invariant multi-input, multi-output feedback system is developed. This classification, along with the associated necessary and sufficient conditions for stability of the feedback system, is achieved through the introduction of a new parameterization, referred to as R-Parameterization, which is a dual of the familiar Q-Parameterization. The classification is made to the stability conditions of the compensators and the plant by themselves; and necessary and sufficient conditions are based on the stability of Q and R themselves.

  15. Stabilization and robustness of non-linear unity-feedback system - Factorization approach

    NASA Technical Reports Server (NTRS)

    Desoer, C. A.; Kabuli, M. G.

    1988-01-01

    The paper is a self-contained discussion of a right factorization approach in the stability analysis of the nonlinear continuous-time or discrete-time, time-invariant or time-varying, well-posed unity-feedback system S1(P, C). It is shown that a well-posed stable feedback system S1(P, C) implies that P and C have right factorizations. In the case where C is stable, P has a normalized right-coprime factorization. The factorization approach is used in stabilization and simultaneous stabilization results.

  16. DESIGN AND ANALYSIS OF AN FPGA-BASED ACTIVE FEEDBACK DAMPING SYSTEM

    SciTech Connect

    Xie, Zaipeng; Schulte, Mike; Deibele, Craig Edmond

    2010-01-01

    The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory is a high-intensity proton-based accelerator that produces neutron beams for neutronscattering research. As the most powerful pulsed neutron source in the world, the SNS accelerator has experienced an unprecedented beam instability that has a wide bandwidth (0 to 300MHz) and fast growth time (10 to100 s). In this paper, we propose and analyze several FPGA-based designs for an active feedback damping system. This signal processing system is the first FPGA-based design for active feedback damping of wideband instabilities in high intensity accelerators. It can effectively mitigate instabilities in highintensity protons beams, reduce radiation, and boost the accelerator s luminosity performance. Unlike existing systems, which are designed using analog components, our FPGA-based active feedback damping system offers programmability while maintaining high performance. To meet the system throughput and latency requirements, our proposed designs are guided by detailed analysis of resource and performance tradeoffs. These designs are mapped onto a reconfigurable platform that includes Xilinx Virtex-II Pro FPGAs and high-speed analog-to-digital and digital-toanalog converters. Our results show that our FPGA-based active feedback damping system can provide increased flexibility and improved signal processing performance that are not feasible with existing analog systems.

  17. Multivariable control of the Space Shuttle Remote Manipulator System using linearization by state feedback. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Gettman, Chang-Ching LO

    1993-01-01

    This thesis develops and demonstrates an approach to nonlinear control system design using linearization by state feedback. The design provides improved transient response behavior allowing faster maneuvering of payloads by the SRMS. Modeling uncertainty is accounted for by using a second feedback loop designed around the feedback linearized dynamics. A classical feedback loop is developed to provide the easy implementation required for the relatively small on board computers. Feedback linearization also allows the use of higher bandwidth model based compensation in the outer loop, since it helps maintain stability in the presence of the nonlinearities typically neglected in model based designs.

  18. Synthesis procedure for linear time-varying feedback systems with large parameter ignorance

    NASA Technical Reports Server (NTRS)

    Mcdonald, T. E., Jr.

    1972-01-01

    The development of synthesis procedures for linear time-varying feedback systems is considered. It is assumed that the plant can be described by linear differential equations with time-varying coefficients; however, ignorance is associated with the plant in that only the range of the time-variations are known instead of exact functional relationships. As a result of this plant ignorance the use of time-varying compensation is ineffective so that only time-invariant compensation is employed. In addition, there is a noise source at the plant output which feeds noise through the feedback elements to the plant input. Because of this noise source the gain of the feedback elements must be as small as possible. No attempt is made to develop a stability criterion for time-varying systems in this work.

  19. Delayed feedback control of the Lorenz system: An analytical treatment at a subcritical Hopf bifurcation

    NASA Astrophysics Data System (ADS)

    Pyragas, V.; Pyragas, K.

    2006-03-01

    We develop an analytical approach for the delayed feedback control of the Lorenz system close to a subcritical Hopf bifurcation. The periodic orbits arising at this bifurcation have no torsion and cannot be stabilized by a conventional delayed feedback control technique. We utilize a modification based on an unstable delayed feedback controller. The analytical approach employs the center manifold theory and the near identity transformation. We derive the characteristic equation for the Floquet exponents of the controlled orbit in an analytical form and obtain simple expressions for the threshold of stability as well as for an optimal value of the control gain. The analytical results are supported by numerical analysis of the original system of nonlinear differential-difference equations.

  20. Delayed feedback control of the Lorenz system: an analytical treatment at a subcritical Hopf bifurcation.

    PubMed

    Pyragas, V; Pyragas, K

    2006-03-01

    We develop an analytical approach for the delayed feedback control of the Lorenz system close to a subcritical Hopf bifurcation. The periodic orbits arising at this bifurcation have no torsion and cannot be stabilized by a conventional delayed feedback control technique. We utilize a modification based on an unstable delayed feedback controller. The analytical approach employs the center manifold theory and the near identity transformation. We derive the characteristic equation for the Floquet exponents of the controlled orbit in an analytical form and obtain simple expressions for the threshold of stability as well as for an optimal value of the control gain. The analytical results are supported by numerical analysis of the original system of nonlinear differential-difference equations. PMID:16605639

  1. A program to evaluate a control system based on feedback of aerodynamic pressure differentials

    NASA Technical Reports Server (NTRS)

    Levy, D. W.; Finn, P.; Roskam, J.

    1981-01-01

    The use of aerodynamic pressure differentials to position a control surface is evaluated. The system is a differential pressure command loop, analogous to a position command loop, where the surface is commanded to move until a desired differential pressure across the surface is achieved. This type of control is more direct and accurate because it is the differential pressure which causes the control forces and moments. A frequency response test was performed in a low speed wind tunnel to measure the performance of the system. Both pressure and position feedback were tested. The pressure feedback performed as well as position feedback implying that the actuator, with a break frequency on the order of 10 Rad/sec, was the limiting component. Theoretical considerations indicate that aerodynamic lags will not appear below frequencies of 50 Rad/sec, or higher.

  2. An adaptable image retrieval system with relevance feedback using kernel machines and selective sampling.

    PubMed

    Azimi-Sadjadi, Mahmood R; Salazar, Jaime; Srinivasan, Saravanakumar

    2009-07-01

    This paper presents an adaptable content-based image retrieval (CBIR) system developed using regularization theory, kernel-based machines, and Fisher information measure. The system consists of a retrieval subsystem that carries out similarity matching using image-dependant information, multiple mapping subsystems that adaptively modify the similarity measures, and a relevance feedback mechanism that incorporates user information. The adaptation process drives the retrieval error to zero in order to exactly meet either an existing multiclass classification model or the user high-level concepts using reference-model or relevance feedback learning, respectively. To facilitate the selection of the most informative query images during relevance feedback learning a new method based upon the Fisher information is introduced. Model-reference and relevance feedback learning mechanisms are thoroughly tested on a domain-specific image database that encompasses a wide range of underwater objects captured using an electro-optical sensor. Benchmarking results with two other relevance feedback learning methods are also provided. PMID:19447718

  3. Feedback Allocation for OFDMA Systems With Slow Frequency-Domain Scheduling

    NASA Astrophysics Data System (ADS)

    Ganapathy, Harish; Banerjee, Siddhartha; Dimitrov, Nedialko B.; Caramanis, Constantine

    2012-12-01

    We study the problem of allocating limited feedback resources across multiple users in an orthogonal-frequency-division-multiple-access downlink system with slow frequency-domain scheduling. Many flavors of slow frequency-domain scheduling (e.g., persistent scheduling, semi-persistent scheduling), that adapt user-sub-band assignments on a slower time-scale, are being considered in standards such as 3GPP Long-Term Evolution. In this paper, we develop a feedback allocation algorithm that operates in conjunction with any arbitrary slow frequency-domain scheduler with the goal of improving the throughput of the system. Given a user-sub-band assignment chosen by the scheduler, the feedback allocation algorithm involves solving a weighted sum-rate maximization at each (slow) scheduling instant. We first develop an optimal dynamic-programming-based algorithm to solve the feedback allocation problem with pseudo-polynomial complexity in the number of users and in the total feedback bit budget. We then propose two approximation algorithms with complexity further reduced, for scenarios where the problem exhibits additional structure.

  4. Instruction, Feedback and Biometrics: The User Interface for Fingerprint Authentication Systems

    NASA Astrophysics Data System (ADS)

    Riley, Chris; Johnson, Graham; McCracken, Heather; Al-Saffar, Ahmed

    Biometric authentication is the process of establishing an individual’s identity through measurable characteristics of their behaviour, anatomy or physiology. Biometric technologies, such as fingerprint systems, are increasingly being used in a diverse range of contexts from immigration control, to banking and personal computing. As is often the case with emerging technologies, the usability aspects of system design have received less attention than technical aspects. Fingerprint systems pose a number of challenges for users and past research has identified issues with correct finger placement, system feedback and instruction. This paper describes the development of an interface for fingerprint systems using an iterative, participative design approach. During this process, several different methods for the presentation of instruction and feedback were identified. The different types of instruction and feedback were tested in a study involving 82 participants. The results showed that feedback had a statistically significant effect on overall system performance, but instruction did not. The design recommendations emerging from this study, and the use of participatory design in this context, are discussed.

  5. Nonlinear feedback model attitude control using CCD in magnetic suspension system

    NASA Technical Reports Server (NTRS)

    Lin, CHIN-E.; Hou, Ann-San

    1994-01-01

    A model attitude control system for a CCD camera magnetic suspension system is studied in this paper. In a recent work, a position and attitude sensing method was proposed. From this result, model position and attitude of a magnetic suspension system can be detected by generating digital outputs. Based on this achievement, a control system design using nonlinear feedback techniques for magnetic suspended model attitude control is proposed.

  6. Pathology tickler: an HL7 monitoring system to provide clinical feedback

    NASA Astrophysics Data System (ADS)

    Mongkolwat, Pattanasak; Davis, Elizabeth; Bhalodia, Pankit; Singh, Harinder; Channin, David S.

    2003-05-01

    The purpose of this project is to develop a software system to provide feedback to radiologists and other clinicians from interventional procedures in which they participate. Using Health Level Seven (HL7) traffic between the anatomy/pathology information system and other major information systems, we were able to develop a semi-automatic 'tickler' system that can notify clinicians of pathology results as well as the absence of pathology results after a specified time interval. By using this system, radiologists can get more rapid feedback concerning their interpretations and thereby learn to distinguish false positive from true positive cases. Potentially, fewer patients would fall through the follow-up cracks when using our system versus a paper-based method. The system demonstrates, among other things, how HL7 information can be a powerful tool at an institution when used for purposes for which it was not intentionally designed.

  7. Feedback control and beam diagnostic algorithms for a multiprocessor DSP system

    SciTech Connect

    Teytelman, D.; Claus, R.; Fox, J.; Hindi, H.; Linscott, I.; Prabhakar, S.; Drago, A.; Stover, G.

    1996-09-01

    The multibunch longitudinal feedback system developed for use by PEP-II, ALS and DA{Phi}NE uses a parallel array of digital signal processors to calculate the feedback signals from measurements of beam motion. The system is designed with general-purpose programmable elements which allow many feedback operating modes as well as system diagnostics, calibrations and accelerator measurements. The overall signal processing architecture of the system is illustrated. The real-time DSP algorithms and off-line postprocessing tools are presented. The problems in managing 320 K samples of data collected in one beam transient measurement are discussed and the solutions are presented. Example software structures are presented showing the beam feedback process, techniques for modal analysis of beam motion(used to quantify growth and damping rates of instabilities) and diagnostic functions (such as timing adjustment of beam pick-up and kicker components). These operating techniques are illustrated with example results obtained from the system installed at the Advanced Light Source at LBL.

  8. Feedback control and beam diagnostic algorithms for a multiprocessor DSP system

    SciTech Connect

    Teytelman, D.; Claus, R.; Fox, J.; Hindi, H.; Linscott, I.; Prabhakar, S.; Drago, A.; Stover, G.

    1997-01-01

    The multibunch longitudinal feedback system developed for use by PEP-II, ALS, and DA{Phi}NE uses a parallel array of digital signal processors (DSPs) to calculate the feedback signals from measurements of beam motion. The system is designed with general-purpose programmable elements which allow many feedback operating modes as well as system diagnostics, calibrations, and accelerator measurements. The overall signal processing architecture of the system is illustrated. The real-time DSP algorithms and off-line postprocessing tools are presented. The problems in managing 320k samples of data collected in one beam transient measurement are discussed and our solutions are presented. Example software structures are presented showing the beam feedback process, techniques for modal analysis of beam motion (used to quantify growth and damping rates of instabilities), and diagnostic functions (such as timing adjustment of beam pick-up and kicker components). These operating techniques are illustrated with example results obtained from the system installed at the Advanced Light Source at LBL. {copyright} {ital 1997 American Institute of Physics.}

  9. Performance of the FONT3 Fast Analogue Intra-Train Beam-Based Feedback System at ATF

    SciTech Connect

    Burrows, P.; Christian, G.B.; Hartin, A.F.; Dabiri Khah, H.; White, G.R.; Clarke, C.C.; Perry, C.; Kalinin, A.; McCormick, D.J.; Molloy, S.; Ross, M.C.; /SLAC

    2007-04-16

    We report results of beam tests of the FONT3 intra-train position feedback system prototype at the Accelerator Test Facility (ATF) at KEK. The feedback system incorporates a novel beam position monitor (BPM) processor with latency below 5 nanoseconds, and a kicker driver amplifier with similar low latency. The 56 nanosecond-long bunchtrain in the ATF extraction line was used to test the prototype feedback system. The achieved latency of 23ns provides a demonstration of intra-train feedback on very short timescales relevant even for the CLIC Linear Collider design.

  10. Enhancement of mobility in an interacting colloidal system under feedback control

    NASA Astrophysics Data System (ADS)

    Gernert, Robert; Klapp, Sabine H. L.

    2015-08-01

    Feedback control schemes are a promising way to manipulate transport properties of driven colloidal suspensions. In the present article, we suggest a feedback scheme to enhance the collective transport of colloidal particles with repulsive interactions through a one-dimensional tilted washboard potential. The control is modeled by a harmonic confining potential, mimicking an optical "trap," with the center of this trap moving with the (instantaneous) mean particle position. Our theoretical analysis is based on the Smoluchowski equation combined with dynamical density functional theory for systems with hard-core or ultrasoft (Gaussian) interactions. For either type of interaction, we find that the feedback control can lead to an enhancement of the mobility by several orders of magnitude relative to the uncontrolled case. The largest effects occur for intermediate stiffness of the trap and large particle numbers. Moreover, in some regions of the parameter space the feedback control induces oscillations of the mean velocity. Finally, we show that the enhancement of mobility is robust against a small time delay in implementing the feedback control.

  11. Simulation of a Feedback System for the Attenuation of e-Cloud Driven Instability

    SciTech Connect

    Vay, J.-L.; Furman, M.A.; Fox, J.; Rivetta, C.; de Maria, R.; Rumolo, G.

    2009-05-04

    Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST and the code Headtail to study the growth rate and frequency patterns in space-time of the electron cloud driven beam breakup instability in the CERN SPS accelerator with, or without, an idealized feedback model for damping the instability.

  12. Multivariable output feedback robust adaptive tracking control design for a class of delayed systems

    NASA Astrophysics Data System (ADS)

    Mirkin, Boris; Gutman, Per-Olof

    2015-02-01

    In this paper, we develop a model reference adaptive control scheme for a class of multi-input multi-output nonlinearly perturbed dynamic systems with unknown time-varying state delays which is also robust with respect to an external disturbance with unknown bounds. The output feedback adaptive control scheme uses feedback actions only, and thus does not require a direct measurement of the command or disturbance signals. A suitable Lyapunov-Krasovskii type functional is introduced to design the adaptation algorithms and to prove stability.

  13. Development and Evaluation of a Feedback Support System with Audio and Playback Strokes

    ERIC Educational Resources Information Center

    Li, Kai; Akahori, Kanji

    2008-01-01

    This paper describes the development and evaluation of a handwritten correction support system with audio and playback strokes used to teach Japanese writing. The study examined whether audio and playback strokes have a positive effect on students using honorific expressions in Japanese writing. The results showed that error feedback with audio…

  14. Spatial-temporal optical oscillations in feedback system and eye-brain model

    NASA Astrophysics Data System (ADS)

    Akchurin, Garif G.

    1997-02-01

    We report on the experimental results concerning the regimes of transition to the spatial-temporal chaos in an optical system with the delayed feedback based on the CCD camera and TV display. The analogy between the observed optical instabilities and the complex oscillations in the human pupil light reflex are discussed.

  15. Strategic choices for global energy: constraints from feedbacks in the climate system.

    PubMed

    Anderson, James G

    2009-01-01

    The climate system itself provides feedback on the current state of pollution levels through several markers. With ever-rising population numbers and energy demand, what should guide us when transforming our society into one that develops in a sustainable manner? PMID:19418501

  16. Development of an Interactive Upper Extremity Gestural Robotic Feedback System: From Bench to Reality

    PubMed Central

    Wood, Krista A. Coleman; Lathan, Corinna E.; Kaufman, Kenton R.

    2010-01-01

    Development of an interactive system to treat patients with movement impairments of the upper extremity is described. Gestures and movement of patients as instructed by therapists are detected by accelerometers and feedback is provided directly to the patient via a robot. PMID:19964144

  17. Effectiveness of an Online Automated Evaluation and Feedback System in an Introductory Computer Literacy Course

    ERIC Educational Resources Information Center

    Varank, Ilhan; Erkoç, M. Fatih; Büyükimdat, Meryem Köskeroglu; Aktas, Mehmet; Yeni, Sabiha; Adigüzel, Tufan; Cömert, Zafer; Esgin, Esad

    2014-01-01

    The purpose of this study was to investigate the effectiveness of an online automated evaluation and feedback system that assessed students' word processing assignments prepared with Microsoft Office Word. The participants of the study were 119 undergraduate teacher education students, 86 of whom were female and 32 were male, enrolled in…

  18. Approaching Error-Free Customer Satisfaction through Process Change and Feedback Systems

    ERIC Educational Resources Information Center

    Berglund, Kristin M.; Ludwig, Timothy D.

    2009-01-01

    Employee-based errors result in quality defects that can often impact customer satisfaction. This study examined the effects of a process change and feedback system intervention on error rates of 3 teams of retail furniture distribution warehouse workers. Archival records of error codes were analyzed and aggregated as the measure of quality. The…

  19. Effectiveness of Feedback for Enhancing English Pronunciation in an ASR-Based CALL System

    ERIC Educational Resources Information Center

    Wang, Y.-H.; Young, S. S.-C.

    2015-01-01

    This paper presents a study on implementing the ASR-based CALL (computer-assisted language learning based upon automatic speech recognition) system embedded with both formative and summative feedback approaches and using implicit and explicit strategies to enhance adult and young learners' English pronunciation. Two groups of learners including 18…

  20. An Evaluation of the Effectiveness of an Automated Observation and Feedback System on Safe Sitting Postures

    ERIC Educational Resources Information Center

    Yu, Eunjeong; Moon, Kwangsu; Oah, Shezeen; Lee, Yohaeng

    2013-01-01

    This study evaluated the effectiveness of an automated observation and feedback system in improving safe sitting postures. Participants were four office workers. The dependent variables were the percentages of time participants spent in five safe body positions during experimental sessions. We used a multiple-baseline design counterbalanced across…

  1. Hardware design and implementation of the closed-orbit feedback system at APS

    SciTech Connect

    Barr, D.; Chung, Youngjoo

    1996-10-01

    The Advanced Photon Source (APS) storage ring will utilize a closed-orbit feedback system in order to produce a more stable beam. The specified orbit measurement resolution is 25 microns for global feedback and 1 micron for local feedback. The system will sample at 4 kHz and provide a correction bandwidth of 100 Hz. At this bandwidth, standard rf BPMs will provide a resolution of 0.7 micron, while specialized miniature BPMs positioned on either side of the insertion devices for local feedback will provide a resolution of 0.2 micron (1). The measured BPM noise floor for standard BPMs is 0.06 micron per root hertz mA. Such a system has been designed, simulated, and tested on a small scale (2). This paper covers the actual hardware design and layout of the entire closed-loop system. This includes commercial hardware components, in addition to many components designed and built in-house. The paper will investigate the large-scale workings of all these devices, as well as an overall view of each piece of hardware used.

  2. Efficacy of an ICALL Tutoring System and Process-Oriented Corrective Feedback

    ERIC Educational Resources Information Center

    Choi, Inn-Chull

    2016-01-01

    A Web-based form-focused intelligent computer-assisted language learning (ICALL) tutoring system equipped with a process-oriented corrective feedback function was developed to investigate the extent to which such a program may serve as a viable method of teaching grammar to Korean secondary and elementary students. The present study was also…

  3. Improving Students' Help-Seeking Skills Using Metacognitive Feedback in an Intelligent Tutoring System

    ERIC Educational Resources Information Center

    Roll, Ido; Aleven, Vincent; McLaren, Bruce M.; Koedinger, Kenneth R.

    2011-01-01

    The present research investigated whether immediate metacognitive feedback on students' help-seeking errors can help students acquire better help-seeking skills. The Help Tutor, an intelligent tutor agent for help seeking, was integrated into a commercial tutoring system for geometry, the Geometry Cognitive Tutor. Study 1, with 58 students, found…

  4. Robust adaptive dynamic programming and feedback stabilization of nonlinear systems.

    PubMed

    Jiang, Yu; Jiang, Zhong-Ping

    2014-05-01

    This paper studies the robust optimal control design for a class of uncertain nonlinear systems from a perspective of robust adaptive dynamic programming (RADP). The objective is to fill up a gap in the past literature of adaptive dynamic programming (ADP) where dynamic uncertainties or unmodeled dynamics are not addressed. A key strategy is to integrate tools from modern nonlinear control theory, such as the robust redesign and the backstepping techniques as well as the nonlinear small-gain theorem, with the theory of ADP. The proposed RADP methodology can be viewed as an extension of ADP to uncertain nonlinear systems. Practical learning algorithms are developed in this paper, and have been applied to the controller design problems for a jet engine and a one-machine power system. PMID:24808035

  5. Toward a Naval Aviation Training Quality Feedback System

    ERIC Educational Resources Information Center

    Phillips, Henry L., IV; Foster, T. Chris

    2008-01-01

    Naval aviation needs a unified standard for job-task analyses and data collection. Such a standard would facilitate consolidation of data across aviation platforms and permit evaluation of training content across phases of the training continuum. It would also make possible the construction of a training transfer evaluation system. The Navy cannot…

  6. A System for Real-Time Feedback to Improve Gait and Posture in Parkinson's Disease.

    PubMed

    Jellish, Jeremy; Abbas, James J; Ingalls, Todd M; Mahant, Padma; Samanta, Johan; Ospina, Maria Cristina; Krishnamurthi, Narayanan

    2015-11-01

    For people with Parkinson's disease (PD), gait and postural impairments can significantly affect their ability to perform activities of daily living. Presentation of appropriate cues has been shown to improve gait in PD. Based on this, a treadmill-based system and experimental paradigm were developed to determine if people with PD can utilize real-time feedback (RTFB) of step length or back angle (uprightness) to improve gait and posture. Eleven subjects (mean age 67 ± 8 years) with mild-to-moderate PD (Hoehn and Yahr stage I-III) were evaluated regarding their ability to successfully utilize RTFB of back angle or step length during quiet standing and treadmill walking tasks during a single session in their medication-on state. Changes in back angle and step length due to feedback were compared using Friedman nonparametric tests with Wilcoxon Signed-Rank tests for post-hoc comparisons. Improvements in uprightness were observed as an increase in back angle during quiet standing (p = 0.005) and during treadmill walking (p = 0.005) with back angle feedback when compared to corresponding tasks without feedback. Improvements in gait were also observed as an increase in step length (p = 0.005) during step length feedback compared to tasks without feedback. These results indicate that people with mild-to-moderate PD can utilize RTFB to improve upright posture and gait. Future work will investigate the long-term effects of this RTFB paradigm and the development of systems for clinical or home-based use. PMID:26316235

  7. Passive thermo-optic feedback for robust athermal photonic systems

    SciTech Connect

    Rakich, Peter T.; Watts, Michael R.; Nielson, Gregory N.

    2015-06-23

    Thermal control devices, photonic systems and methods of stabilizing a temperature of a photonic system are provided. A thermal control device thermally coupled to a substrate includes a waveguide for receiving light, an absorption element optically coupled to the waveguide for converting the received light to heat and an optical filter. The optical filter is optically coupled to the waveguide and thermally coupled to the absorption element. An operating point of the optical filter is tuned responsive to the heat from the absorption element. When the operating point is less than a predetermined temperature, the received light is passed to the absorption element via the optical filter. When the operating point is greater than or equal to the predetermined temperature, the received light is transmitted out of the thermal control device via the optical filter, without being passed to the absorption element.

  8. Using Feedback for Coherent Control of Quantum Systems

    NASA Astrophysics Data System (ADS)

    Weinacht, Thomas

    2001-05-01

    The control of atoms and molecules using coherent light fields has been a longstanding goal in chemical physics. I will discuss experiments which use a programmable pulse shaper to control the quantum state of electronic wavepackets in Rydberg atoms and nuclear dynamics in molecular liquids. The shape of Rydberg wavepackets was controlled by using tailored ultrafast laser pulses to excite a beam of cesium atoms. The quantum state of these atoms was measured using holographic techniques borrowed from optics. The experiments with molecular liquids involved the contstruction of an automated learning machine. A Genetic Algorithm directed the choice of shaped pulses which interacted with the molecular system inside a learning control loop. Analysis of successful pulse shapes that were found by the algorithm yield insight into the systems being controlled.

  9. Scheduling of network access for feedback-based embedded systems

    NASA Astrophysics Data System (ADS)

    Liberatore, Vincenzo

    2002-07-01

    nd communication capabilities. Examples range from smart dust embedded in building materials to networks of appliances in the home. Embedded devices will be deployed in unprecedented numbers, will enable pervasive distributed computing, and will radically change the way people interact with the surrounding environment [EGH00a]. The paper targets embedded systems and their real-time (RT) communication requirements. RT requirements arise from the

  10. Feedback invariants for linear systems defined over rings

    NASA Technical Reports Server (NTRS)

    Byrnes, C. I.

    1979-01-01

    A coefficient-assignability theorem is presented for systems defined over a commutative ring with 1. The conditions examined include all the general results on coefficient-assignability available in the literature. It is concluded that the proposed techniques are not effective for the case of the weaker property of pole placement when it is assumed that the commutative ring is a PID. Morse's well-known theorem seems to be the best result available for this situation.

  11. Improving patient safety incident reporting systems by focusing upon feedback - lessons from English and Welsh trusts.

    PubMed

    Wallace, Louise M; Spurgeon, Peter; Benn, Jonathan; Koutantji, Maria; Vincent, Charles

    2009-08-01

    This paper describes practical implications and learning from a multi-method study of feedback from patient safety incident reporting systems. The study was performed using the Safety Action and Information Feedback from Incident Reporting model, a model of the requirements of the feedback element of a patient safety incident reporting and learning system, derived from a scoping review of research and expert advice from world leaders in safety in high-risk industries. We present the key findings of the studies conducted in the National Health Services (NHS) trusts in England and Wales in 2006. These were a survey completed by risk managers for 351 trusts in England and Wales, three case studies including interviews with staff concerning an example of good practice feedback and an audit of 90 trusts clinical risk staff newsletters. We draw on an Expert Workshop that included 71 experts from the NHS, from regulatory bodies in health care, Royal Colleges, Health and Safety Executive and safety agencies in health care and high-risk industries (commercial aviation, rail and maritime industries). We draw recommendations of enduring relevance to the UK NHS that can be used by trust staff to improve their systems. The recommendations will be of relevance in general terms to health services worldwide. PMID:19633181

  12. Stereo Camera Based Virtual Cane System with Identifiable Distance Tactile Feedback for the Blind

    PubMed Central

    Kim, Donghun; Kim, Kwangtaek; Lee, Sangyoun

    2014-01-01

    In this paper, we propose a new haptic-assisted virtual cane system operated by a simple finger pointing gesture. The system is developed by two stages: development of visual information delivery assistant (VIDA) with a stereo camera and adding a tactile feedback interface with dual actuators for guidance and distance feedbacks. In the first stage, user's pointing finger is automatically detected using color and disparity data from stereo images and then a 3D pointing direction of the finger is estimated with its geometric and textural features. Finally, any object within the estimated pointing trajectory in 3D space is detected and the distance is then estimated in real time. For the second stage, identifiable tactile signals are designed through a series of identification experiments, and an identifiable tactile feedback interface is developed and integrated into the VIDA system. Our approach differs in that navigation guidance is provided by a simple finger pointing gesture and tactile distance feedbacks are perfectly identifiable to the blind. PMID:24932864

  13. A sensory feedback system for prosthetic hand based on evoked tactile sensation.

    PubMed

    Liu, X X; Chai, G H; Qu, H E; Lan, N

    2015-08-01

    The lack of reliable sensory feedback has been one of the barriers in prosthetic hand development. Restoring sensory function from prosthetic hand to amputee remains a great challenge to neural engineering. In this paper, we present the development of a sensory feedback system based on the phenomenon of evoked tactile sensation (ETS) at the stump skin of residual limb induced by transcutaneous electrical nerve stimulation (TENS). The system could map a dynamic pattern of stimuli to an electrode placed on the corresponding projected finger areas on the stump skin. A pressure transducer placed at the tip of prosthetic fingers was used to sense contact pressure, and a high performance DSP processor sampled pressure signals, and calculated the amplitude of feedback stimulation in real-time. Biphasic and charge-balanced current pulses with amplitude modulation generated by a multi-channel laboratory stimulator were delivered to activate sensory nerves beneath the skin. We tested this sensory feedback system in amputee subjects. Preliminary results showed that the subjects could perceive different levels of pressure at the tip of prosthetic finger through evoked tactile sensation (ETS) with distinct grades and modalities. We demonstrated the feasibility to restore the perceptual sensation from prosthetic fingers to amputee based on the phenomenon of evoked tactile sensation (ETS) with TENS. PMID:26736798

  14. Augmented Feedback System to Support Physical Therapy of Non-specific Low Back Pain

    NASA Astrophysics Data System (ADS)

    Brodbeck, Dominique; Degen, Markus; Stanimirov, Michael; Kool, Jan; Scheermesser, Mandy; Oesch, Peter; Neuhaus, Cornelia

    Low back pain is an important problem in industrialized countries. Two key factors limit the effectiveness of physiotherapy: low compliance of patients with repetitive movement exercises, and inadequate awareness of patients of their own posture. The Backtrainer system addresses these problems by real-time monitoring of the spine position, by providing a framework for most common physiotherapy exercises for the low back, and by providing feedback to patients in a motivating way. A minimal sensor configuration was identified as two inertial sensors that measure the orientation of the lower back at two points with three degrees of freedom. The software was designed as a flexible platform to experiment with different hardware, and with various feedback modalities. Basic exercises for two types of movements are provided: mobilizing and stabilizing. We developed visual feedback - abstract as well as in the form of a virtual reality game - and complemented the on-screen graphics with an ambient feedback device. The system was evaluated during five weeks in a rehabilitation clinic with 26 patients and 15 physiotherapists. Subjective satisfaction of subjects was good, and we interpret the results as encouraging indication for the adoption of such a therapy support system by both patients and therapists.

  15. Two time scale output feedback regulation for ill-conditioned systems

    NASA Technical Reports Server (NTRS)

    Calise, A. J.; Moerder, D. D.

    1986-01-01

    Issues pertaining to the well-posedness of a two time scale approach to the output feedback regulator design problem are examined. An approximate quadratic performance index which reflects a two time scale decomposition of the system dynamics is developed. It is shown that, under mild assumptions, minimization of this cost leads to feedback gains providing a second-order approximation of optimal full system performance. A simplified approach to two time scale feedback design is also developed, in which gains are separately calculated to stabilize the slow and fast subsystem models. By exploiting the notion of combined control and observation spillover suppression, conditions are derived assuring that these gains will stabilize the full-order system. A sequential numerical algorithm is described which obtains output feedback gains minimizing a broad class of performance indices, including the standard LQ case. It is shown that the algorithm converges to a local minimum under nonrestrictive assumptions. This procedure is adapted to and demonstrated for the two time scale design formulations.

  16. Improved optical feedback reference tracking for diamagnetically levitating motor system

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Chih; Vu, Jefferey; Khanna, Shrey

    2011-04-01

    This paper describes the design and fabrication of an optical sensor to sense vertical displacement of a diamagnetically stabilized levitating rotor. The planar rotor described in this paper rotates due to nine electromagnetic coils evenly spaced around the rotor. A driving circuit allows current to flow through the coils one phase at a time. This produces a magnetic field strong enough to spin the rotor. However, instability due to a number of factors is prevalent in the present system. This instability is observed as vertical and horizontal displacement of the levitating rotor. The purpose of an additional optical sensor is to measure and record this vertical displacement and combine it with topsensing optical measurements in order to create a three-dimensional optical sensing mechanism around the rotor.

  17. Single state feedback stabilization of unified chaotic systems and circuit implementation

    NASA Astrophysics Data System (ADS)

    Jing, Chun-Guo; He, Ping; Fan, Tao; Li, Yangmin; Chen, Changzhong; Song, Xin

    2014-11-01

    This paper focuses on the single state feedback stabilization problem of unified chaotic system and circuit implementation. Some stabilization conditions will be derived via the single state feedback control scheme. The robust performance of controlled unified chaotic systems with uncertain parameter will be investigated based on maximum and minimum analysis of uncertain parameter, the robust controller which only requires information of a state of the system is proposed and the controller is linear. Both the unified chaotic system and the designed controller are synthesized and implemented by an analog electronic circuit which is simpler because only three variable resistors are required to be adjusted. The numerical simulation and control in MATLAB/Simulink is then provided to show the effectiveness and feasibility of the proposed method which is robust against some uncertainties. The results presented in this paper improve and generalize the corresponding results of recent works.

  18. An open-structure electrowetting-based reflective display with a feedback system

    NASA Astrophysics Data System (ADS)

    Choi, Seungyul; Lee, Junghoon

    2015-11-01

    Electrowetting-based reflective displays have long been considered a promising display choice for electronic paper applications due to their fast operating speeds and high color contrasts. However, they still require several improvements in terms of their packaging process, color contrast, and reliability. This study investigates such enhancements via an open-structure design and a capacitive feedback system. It has a femto-farad level resolution and demonstrates a high operating speed (approximately 10 ms), effective ink dosing, and large color area change (approximately 92%). The feedback system for the precise control of the color area is verified by testing under a wide range of interfacial tension. The system reduces the deviation of color contrast by 85%. Working with high fidelity with large disturbances, which are represented by interfacial variations, the system shows robust performance against other disturbances, such as temperature variation and contact angle hysteresis.

  19. Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

    2010-01-01

    A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, Ohio. This is a closed-cycle system that incorporates an electrically heated reactor core module, turboalternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

  20. A Real-Time Analysis and Feedback System for Quality Control of Dam Foundation Grouting Engineering

    NASA Astrophysics Data System (ADS)

    Zhong, D. H.; Yan, F. G.; Li, M. C.; Huang, C. X.; Fan, K.; Tang, J. F.

    2015-09-01

    Real-time analysis and feedback systems play a vital role in obtaining good results from grouting processes. However, when there are intense construction schedules and complex geological structures, it is difficult for existing systems to provide to site engineers, prior to the borehole construction, prompt and accurate feedback, such as detailed geological information about grouting boreholes, which limits the use of such systems in practical applications. This paper proposes combining a three-dimensional (3D) geological model with real-time data collection technology in a system for both monitoring grouting, and providing analysis and feedback. This integrated grouting model, which comprises the geological model, the grouting borehole model and the grouting parameter database set, can be coupled and associated dynamically with grouting data. Additionally, the following methods are applied in this system: real-time grouting data processing and a monitoring alarm, prediction and visualization of geological conditions, forecasting of rock uplift, and visualization analysis of grouting parameters. The application of this system in Hydropower Project A, China is used as a case study. The predictions of geological conditions are closely matched with the actual situation, and this system can be used to monitor construction processes remotely and to help site engineers to design reasonable construction plans, optimize layouts for grouting boreholes and adjust construction measures.

  1. Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

    2009-01-01

    A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, OH. This is a closed-cycle system that incorporates an electrically heated reactor core module, turbo alternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

  2. The Differential Effects of Elaborate Feedback and Basic Feedback on Student Performance in a Modified, Personalized System of Instruction Course

    ERIC Educational Resources Information Center

    Chase, Jared A.; Houmanfar, Ramona

    2009-01-01

    Educators in large-enrollment courses are faced with the challenge of effectively disseminating information to their students to ensure that they learn the content provided. A related issue involves the means by which instructors evaluate student performance. Offering effective forms of performance feedback may be one technique to provide students…

  3. A Comparison of the Effects of Feedback and Prompts on Safe Sitting Posture: Utilizing an Automated Observation and Feedback System

    ERIC Educational Resources Information Center

    Moon, Kwangsu; Oah, Shezeen

    2013-01-01

    This study used an ABCB within-subjects design to examine the relative effects of feedback and prompts on safe sitting posture. Participants were three office workers. The dependent variables were the percentages of time the participants spent in four safe individual body positions and in the safe overall sitting posture. After baseline (A),…

  4. An investigation of optical feedback to extend the frequency response of solid-state detector systems

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.

    1972-01-01

    A primary limitation of many solid-state photodetectors used in electro-optical systems such as the facsimile camera is their slow response in converting light intensities into electrical signals. An optical feedback technique is presented which can extend the frequency response of systems that use these detectors by orders of magnitude without significantly degrading their signal-to-noise performance. This technique is analyzed to predict improvement, implemented, and evaluated to verify analytical results.

  5. Incomplete state feedback for systems with parameter uncertainty and random disturbances

    NASA Technical Reports Server (NTRS)

    Basuthakur, S.

    1972-01-01

    A unified design philosophy is presented for limited state feedback control problems with parameter uncertainty for both deterministic and stochastic problems. Two approaches are considered: linear compensator for the deterministic problem with parameter uncertainty, and for the single input-single output system with parameter uncertainty, a model on order equal to that of the system less the number of zeroes. The limitations of these approaches are discussed along with suggestions for further research.

  6. Investigating feedbacks in human-landscape systems: Lessons following a wildfire in Colorado, USA

    NASA Astrophysics Data System (ADS)

    Chin, Anne; An, Li; Florsheim, Joan L.; Laurencio, Laura R.; Marston, Richard A.; Solverson, Anna P.; Simon, Gregory L.; Stinson, Emily; Wohl, Ellen

    2016-01-01

    As human interactions with Earth systems continue to intensify, understanding the complex relationships among human activity, landscape change, and societal responses to those changes becomes increasingly important. Interdisciplinary research centered on the theme of "feedbacks" in human-landscape systems serves as a promising focus for unraveling these interactions. This paper examines the specific case of the 2012 Waldo Canyon Fire of Colorado, where human responses after the fire to perceived threats of hydro-geomorphological hazards included construction of tall fences at the base of a burned watershed. These actions prompted feedbacks that promoted further landscape change that ultimately increased those hazards, rather than dampening the hydro-geomorphological effects of fire. Geomorphic analysis showed that the fences trapped particles that would naturally move through the system by flows with recurrence intervals greater than 3.3 years. With the particles blocked by the fences, the channel downstream became erosive, because it was devoid of large particles that produce substantial hydraulic resistance. Channel incision prompted a second human response to pave the eroding channel, which led to further incision downstream. This cycle of positive feedbacks between human decision-making and landscape change eventually led to a complete channelization of the stream channel downstream of the fences. The explanation for the transformation of the post-fire landscape therefore lies in the interacting human impacts and feedbacks, rather than the expected post-fire hydro-geomorphological adjustments. An initial agent-based model, capable of integrating social and hydro-geomorphological data, simulates these interacting impacts and feedbacks. Further refinement with more complete data input, especially pertaining to human decision making at individual or local levels, is required to fully demonstrate the utility and promise of this tool for application to geomorphic

  7. A switched state feedback law for the stabilization of LTI systems.

    SciTech Connect

    Santarelli, Keith R.

    2009-09-01

    Inspired by prior work in the design of switched feedback controllers for second order systems, we develop a switched state feedback control law for the stabilization of LTI systems of arbitrary dimension. The control law operates by switching between two static gain vectors in such a way that the state trajectory is driven onto a stable n - 1 dimensional hyperplane (where n represents the system dimension). We begin by briefly examining relevant geometric properties of the phase portraits in the case of two-dimensional systems to develop intuition, and we then show how these geometric properties can be expressed as algebraic constraints on the switched vector fields that are applicable to LTI systems of arbitrary dimension. We then derive necessary and sufficient conditions to ensure stabilizability of the resulting switched system (characterized primarily by simple conditions on eigenvalues), and describe an explicit procedure for designing stabilizing controllers. We then show how the newly developed control law can be applied to the problem of minimizing the maximal Lyapunov exponent of the corresponding closed-loop state trajectories, and we illustrate the closed-loop transient performance of these switched state feedback controllers via multiple examples.

  8. Mesoscale Coupled Ocean-Atmosphere Feedbacks in Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Putrasahan, Dian Ariyani

    The focus of this dissertation is on studying ocean-atmosphere (OA) interactions in the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using satellite observations and the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This technique provides insights to spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean. For the HCS, the use of downscaled forcing from SCOAR, as compared to NCEP Reanalysis 2, proves to be more appropriate in quantifying wind-driven upwelling indices along the coast of Peru and Chile. The difference in their wind stress distribution has significant impact on the wind-driven upwelling processes and total upwelling transport along the coast. Although upwelling induced by coastal Ekman transport dominates the wind-driven upwelling along coastal areas, Ekman pumping can account for 30% of the wind-driven upwelling in several coastal locations. Control SCOAR shows significant SST-wind stress coupling during fall and winter, while Smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air-sea coupling in HCS. The SST-wind stress coupling however, did not produce any rectified response on the ocean eddies. Coupling between SST, wind speed and latent heat flux is insignificant on large-scale coupling and full coupling mode. On the other hand, coupling between these three variables are significant on the mesoscale for most of the model run, which suggests that mesoscale SST affects latent heat through direct flux anomalies as well as indirectly through stability changes on the

  9. Next Generation Environmentally-Friendly Driving Feedback Systems Research and Development

    SciTech Connect

    Barth, Matthew; Boriboonsomsin, Kanok

    2014-12-31

    The objective of this project is to design, develop, and demonstrate a next-generation, federal safety- and emission-complaint driving feedback system that can be deployed across the existing vehicle fleet and improve fleet average fuel efficiency by at least 2%. The project objective was achieved with the driving feedback system that encourages fuel-efficient vehicle travel and operation through: 1) Eco-Routing Navigation module that suggests the most fuel-efficient route from one stop to the next, 2) Eco-Driving Feedback module that provides sensible information, recommendation, and warning regarding fuel-efficient vehicle operation, and 3) Eco-Score and Eco-Rank module that provides a means for driving performance tracking, self-evaluation, and peer comparison. The system also collects and stores vehicle travel and operation data, which are used by Algorithm Updating module to customize the other modules for specific vehicles and adapts them to specific drivers over time. The driving feedback system was designed and developed as an aftermarket technology that can be retrofitted to vehicles in the existing fleet. It consists of a mobile application for smart devices running Android operating system, a vehicle on-board diagnostics connector, and a data server. While the system receives and utilizes real-time vehicle and engine data from the vehicle’s controller area network bus through the vehicle’s on-board diagnostic connector, it does not modify or interfere with the vehicle’s controller area network bus, and thus, is in compliance with federal safety and emission regulations. The driving feedback system was demonstrated and then installed on 45 vehicles from three different fleets for field operational test. These include 15 private vehicles of the general public, 15 pickup trucks of the California Department of Transportation that are assigned to individual employees for business use, and 15 shuttle buses of the Riverside Transit Agency that are used

  10. Cross Feedback Control of a Magnetic Bearing System: Controller Design Considering Gyroscopic Effects

    NASA Technical Reports Server (NTRS)

    Ahrens, Markus; Kucera, Ladislav

    1996-01-01

    For flywheel rotors or other rotors with significant ratios of moments of inertia, the influence of gyroscopic effects has to be considered. While conservative or damped systems remain stable even under gyroscopic effects, magnetically suspended rotors can be destabilized with increasing rotational speed. The influence of gyroscopic effects on the stability and behavior of a magnetic bearing system is analyzed. The analysis is carried out with a rigid body model for the rotor and a nonlinear model for the magnetic bearing and its amplifier. Cross feedback control can compensate gyroscopic effects. This compensation leads to better system performance and can avoid instability. Furthermore, the implementation of this compensation is simple. The main structure of a decentralized controller can still be used. It has only to be expanded by the cross feedback path.

  11. Adaptive Output-Feedback Neural Control of Switched Uncertain Nonlinear Systems With Average Dwell Time.

    PubMed

    Long, Lijun; Zhao, Jun

    2015-07-01

    This paper investigates the problem of adaptive neural tracking control via output-feedback for a class of switched uncertain nonlinear systems without the measurements of the system states. The unknown control signals are approximated directly by neural networks. A novel adaptive neural control technique for the problem studied is set up by exploiting the average dwell time method and backstepping. A switched filter and different update laws are designed to reduce the conservativeness caused by adoption of a common observer and a common update law for all subsystems. The proposed controllers of subsystems guarantee that all closed-loop signals remain bounded under a class of switching signals with average dwell time, while the output tracking error converges to a small neighborhood of the origin. As an application of the proposed design method, adaptive output feedback neural tracking controllers for a mass-spring-damper system are constructed. PMID:25122844

  12. Quantitative Feedback Theory (QFT) applied to the design of a rotorcraft flight control system

    NASA Technical Reports Server (NTRS)

    Hess, R. A.; Gorder, P. J.

    1992-01-01

    Quantitative Feedback Theory describes a frequency-domain technique for the design of multi-input, multi-output control systems which meet time or frequency domain performance criteria when specified uncertainty exists in the linear description of the vehicle dynamics. Quantitative Feedback Theory is applied to the design of the longitudinal flight control system for a linear uncertain model of the AH-64 rotorcraft. In this model, the uncertainty is assigned, and is assumed to be attributable to actual uncertainty in the dynamic model and to the changes in the vehicle aerodynamic characteristics which occur near hover. The model includes an approximation to the rotor and actuator dynamics. The design example indicates the manner in which handling qualities criteria may be incorporated into the design of realistic rotorcraft control systems in which significant uncertainty exists in the vehicle model.

  13. On the interaction structure of linear multi-input feedback control systems. M.S. Thesis; [problem solving, lattices (mathematics)

    NASA Technical Reports Server (NTRS)

    Wong, P. K.

    1975-01-01

    The closely-related problems of designing reliable feedback stabilization strategy and coordinating decentralized feedbacks are considered. Two approaches are taken. A geometric characterization of the structure of control interaction (and its dual) was first attempted and a concept of structural homomorphism developed based on the idea of 'similarity' of interaction pattern. The idea of finding classes of individual feedback maps that do not 'interfere' with the stabilizing action of each other was developed by identifying the structural properties of nondestabilizing and LQ-optimal feedback maps. Some known stability properties of LQ-feedback were generalized and some partial solutions were provided to the reliable stabilization and decentralized feedback coordination problems. A concept of coordination parametrization was introduced, and a scheme for classifying different modes of decentralization (information, control law computation, on-line control implementation) in control systems was developed.

  14. Expression Optimization and Inducible Negative Feedback in Cell-Free Systems

    SciTech Connect

    Karig, David K; Iyer, Sukanya; Simpson, Michael L; Doktycz, Mitchel John

    2012-01-01

    Synthetic biology offers great promise to a variety of applications through the forward engineering of biological function. Most efforts in this field have focused on employing living cells. Cell-free approaches, on the other hand, offer simpler and more flexible contexts, but few synthetic systems based on cell-free protein expression have been constructed. Here, we evaluate cell-free regulatory systems based on T7 promoter driven expression, and we demonstrate negative feedback, an essential motif in many natural and engineered systems. First, we characterize variants of TetR and LacI repressible T7 promoters in a cell-free context and examine sequence elements that determine expression efficiency. Then, we explore different approaches for composing regulatory systems, leading to the implementation of inducible negative feedback in E. coli extracts and in the minimal PURE system, which consists of purified proteins necessary for transcription and translation. Our quantitative cell-free component characterizations and demonstration of negative feedback embody important steps on the path to harnessing biological function in a bottom up fashion.

  15. A methodology for the synthesis of robust feedback systems. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Milich, David Albert

    1988-01-01

    A new methodology is developed for the synthesis of linear, time-variant (LTI) controllers for multivariable LTI systems. The resulting closed-loop system is nominally stable and exhibits a known level of performance. In addition, robustness of the feedback system is guaranteed, i.e., stability and performance are retained in the presence of multiple unstructured uncertainty blocks located at various points in the feedback loop. The design technique is referred to as the Causality Recovery Methodology (CRM). The CRM relies on the Youla parameterization of all stabilizing compensators to ensure nominal stability of the feedback system. A frequency-domain inequality in terms of the structured singular value mu defines the robustness specification. The optimal compensator, with respect to the mu condition, is shown to be noncausal in general. The aim of the CRM is to find a stable, causal transfer function matrix that approximates the robustness characteristics of the optimal solution. The CRM, via a series of infinite-dimensional convex programs, produces a closed-loop system whose performance robustness is at least as good as that of any initial design. The algorithm is approximated by a finite dimensional process for the purposes of implementation. Two numerical examples confirm the potential viability of the CRM concept; however, the robustness improvement comes at the expense of increased computational burden and compensator complexity.

  16. Effect of intermittent feedback control on robustness of human-like postural control system.

    PubMed

    Tanabe, Hiroko; Fujii, Keisuke; Suzuki, Yasuyuki; Kouzaki, Motoki

    2016-01-01

    Humans have to acquire postural robustness to maintain stability against internal and external perturbations. Human standing has been recently modelled using an intermittent feedback control. However, the causality inside of the closed-loop postural control system associated with the neural control strategy is still unknown. Here, we examined the effect of intermittent feedback control on postural robustness and of changes in active/passive components on joint coordinative structure. We implemented computer simulation of a quadruple inverted pendulum that is mechanically close to human tiptoe standing. We simulated three pairs of joint viscoelasticity and three choices of neural control strategies for each joint: intermittent, continuous, or passive control. We examined postural robustness for each parameter set by analysing the region of active feedback gain. We found intermittent control at the hip joint was necessary for model stabilisation and model parameters affected the robustness of the pendulum. Joint sways of the pendulum model were partially smaller than or similar to those of experimental data. In conclusion, intermittent feedback control was necessary for the stabilisation of the quadruple inverted pendulum. Also, postural robustness of human-like multi-link standing would be achieved by both passive joint viscoelasticity and neural joint control strategies. PMID:26931281

  17. Effect of intermittent feedback control on robustness of human-like postural control system

    NASA Astrophysics Data System (ADS)

    Tanabe, Hiroko; Fujii, Keisuke; Suzuki, Yasuyuki; Kouzaki, Motoki

    2016-03-01

    Humans have to acquire postural robustness to maintain stability against internal and external perturbations. Human standing has been recently modelled using an intermittent feedback control. However, the causality inside of the closed-loop postural control system associated with the neural control strategy is still unknown. Here, we examined the effect of intermittent feedback control on postural robustness and of changes in active/passive components on joint coordinative structure. We implemented computer simulation of a quadruple inverted pendulum that is mechanically close to human tiptoe standing. We simulated three pairs of joint viscoelasticity and three choices of neural control strategies for each joint: intermittent, continuous, or passive control. We examined postural robustness for each parameter set by analysing the region of active feedback gain. We found intermittent control at the hip joint was necessary for model stabilisation and model parameters affected the robustness of the pendulum. Joint sways of the pendulum model were partially smaller than or similar to those of experimental data. In conclusion, intermittent feedback control was necessary for the stabilisation of the quadruple inverted pendulum. Also, postural robustness of human-like multi-link standing would be achieved by both passive joint viscoelasticity and neural joint control strategies.

  18. Effect of intermittent feedback control on robustness of human-like postural control system

    PubMed Central

    Tanabe, Hiroko; Fujii, Keisuke; Suzuki, Yasuyuki; Kouzaki, Motoki

    2016-01-01

    Humans have to acquire postural robustness to maintain stability against internal and external perturbations. Human standing has been recently modelled using an intermittent feedback control. However, the causality inside of the closed-loop postural control system associated with the neural control strategy is still unknown. Here, we examined the effect of intermittent feedback control on postural robustness and of changes in active/passive components on joint coordinative structure. We implemented computer simulation of a quadruple inverted pendulum that is mechanically close to human tiptoe standing. We simulated three pairs of joint viscoelasticity and three choices of neural control strategies for each joint: intermittent, continuous, or passive control. We examined postural robustness for each parameter set by analysing the region of active feedback gain. We found intermittent control at the hip joint was necessary for model stabilisation and model parameters affected the robustness of the pendulum. Joint sways of the pendulum model were partially smaller than or similar to those of experimental data. In conclusion, intermittent feedback control was necessary for the stabilisation of the quadruple inverted pendulum. Also, postural robustness of human-like multi-link standing would be achieved by both passive joint viscoelasticity and neural joint control strategies. PMID:26931281

  19. The role of time delay in adaptive cellular negative feedback systems.

    PubMed

    Lapytsko, Anastasiya; Schaber, Jörg

    2016-06-01

    Adaptation in cellular systems is often mediated by negative feedbacks, which usually come with certain time delays causing several characteristic response patterns including an overdamped response, damped or sustained oscillations. Here, we analyse generic two-dimensional delay differential equations with delayed negative feedback describing the dynamics of biochemical adaptive signal-response networks. We derive explicit thresholds and boundaries showing how time delay determines characteristic response patterns of these networks. Applying our theoretical analyses to concrete data we show that adaptation to osmotic stress in yeast is optimal in the sense of minimizing adaptation time without causing oscillatory behaviour, i.e., a critically damped response. In addition, our framework demonstrates that a slight increase of time delay in the NF-κB system might induce a switch from damped to sustained oscillatory behaviour. Thus, we demonstrate how delay differential equations can be used to explicitly study the delay in biochemical negative feedback systems. Our analysis also provides insight into how time delay may tune biological signal-response patterns and control the systems behaviour. PMID:26995333

  20. Implementation of an Automated Grading System with an Adaptive Learning Component to Affect Student Feedback and Response Time

    ERIC Educational Resources Information Center

    Matthews, Kevin; Janicki, Thomas; He, Ling; Patterson, Laurie

    2012-01-01

    This research focuses on the development and implementation of an adaptive learning and grading system with a goal to increase the effectiveness and quality of feedback to students. By utilizing various concepts from established learning theories, the goal of this research is to improve the quantity, quality, and speed of feedback as it pertains…

  1. Assessing Online Textual Feedback to Support Student Intrinsic Motivation Using a Collaborative Text-Based Dialogue System: A Qualitative Study

    ERIC Educational Resources Information Center

    Shroff, Ronnie H.; Deneen, Christopher

    2011-01-01

    This paper assesses textual feedback to support student intrinsic motivation using a collaborative text-based dialogue system. A research model is presented based on research into intrinsic motivation, and the specific construct of feedback provides a framework for the model. A qualitative research methodology is used to validate the model.…

  2. Development and Piloting of a Classroom-Focused Measurement Feedback System.

    PubMed

    Nadeem, Erum; Cappella, Elise; Holland, Sibyl; Coccaro, Candace; Crisonino, Gerard

    2016-05-01

    The present study used a community partnered research method to develop and pilot a classroom-focused measurement feedback system (MFS) for school mental health providers to support teachers' use of effective universal and target classroom practices related to student emotional and behavioral issues. School personnel from seven urban elementary and middle school classrooms participated. Phase I involved development and refinement of the system through a baseline needs assessment and rapid-cycle feedback. Phase II involved detailed case study analysis of pre-to-post quantitative and implementation process data. Results suggest that teachers who used the dashboard along with consultation showed improvement in observed classroom organization and emotional support. Results also suggest that MFS use was tied closely to consultation dose, and that broader support at the school level was critical. Classroom-focused MFSs are a promising tool to support classroom improvement, and warrant future research focused on their effectiveness and broad applicability. PMID:25894312

  3. Stabilization of an inverted pendulum-cart system by fractional PI-state feedback.

    PubMed

    Bettayeb, M; Boussalem, C; Mansouri, R; Al-Saggaf, U M

    2014-03-01

    This paper deals with pole placement PI-state feedback controller design to control an integer order system. The fractional aspect of the control law is introduced by a dynamic state feedback as u(t)=K(p)x(t)+K(I)I(α)(x(t)). The closed loop characteristic polynomial is thus fractional for which the roots are complex to calculate. The proposed method allows us to decompose this polynomial into a first order fractional polynomial and an integer order polynomial of order n-1 (n being the order of the integer system). This new stabilization control algorithm is applied for an inverted pendulum-cart test-bed, and the effectiveness and robustness of the proposed control are examined by experiments. PMID:24315056

  4. Rotorcraft control system design for uncertain vehicle dynamics using quantitative feedback theory

    NASA Technical Reports Server (NTRS)

    Hess, R. A.

    1994-01-01

    Quantitative Feedback Theory describes a frequency-domain technique for the design of multi-input, multi-output control systems which must meet time or frequency domain performance criteria when specified uncertainty exists in the linear description of the vehicle dynamics. This theory is applied to the design of the longitudinal flight control system for a linear model of the BO-105C rotorcraft. Uncertainty in the vehicle model is due to the variation in the vehicle dynamics over a range of airspeeds from 0-100 kts. For purposes of exposition, the vehicle description contains no rotor or actuator dynamics. The design example indicates the manner in which significant uncertainty exists in the vehicle model. The advantage of using a sequential loop closure technique to reduce the cost of feedback is demonstrated by example.

  5. Static output feedback for partial eigenstructure assignment of undamped vibration systems

    NASA Astrophysics Data System (ADS)

    Zhang, Jiafan; Ye, Jianping; Ouyang, Huajiang

    2016-02-01

    A novel method for partial eigenstructure assignment of undamped vibration systems using acceleration and displacement output feedback is presented in this paper. It is based on modifications of mass and stiffness that preserve partial eigenstructure. A numerical algorithm for determining the required control gain matrices of acceleration and displacement output feedback, which assign the desired eigenstructure, is developed. This algorithm is easy to implement, and works directly on the second-order system model. More importantly, the algorithm allows the output matrix and the input matrix to be specified beforehand and also leads naturally to a small norm solution of the gain matrices. Finally, some numerical results are presented to demonstrate the effectiveness and accuracy of the proposed algorithm.

  6. Piecewise Function Feedback Strategy in Intelligent Traffic Systems with a Speed Limit Bottleneck

    NASA Astrophysics Data System (ADS)

    Chen, Bokui; Sun, Xiaoyan; Wei, Hua; Dong, Chuanfei; Wang, Binghong

    The road capacity can be greatly improved if an appropriate and effective information feedback strategy is adopted in the traffic system. In this paper, a strategy called piecewise function feedback strategy (PFFS) is introduced and applied into an asymmetrical two-route scenario with a speed limit bottleneck in which the dynamic information can be generated and displayed on the information board to guide road users to make a choice. Meanwhile, the velocity-dependent randomization (VDR) mechanism is adopted which can better reflect the dynamic behavior of vehicles in the system than NS mechanism. Simulation results adopting PFFS have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the previous strategies.

  7. Linear stable unity-feedback system - Necessary and sufficient conditions for stability under nonlinear plant perturbations

    NASA Technical Reports Server (NTRS)

    Desoer, C. A.; Kabuli, M. G.

    1989-01-01

    The authors consider a linear (not necessarily time-invariant) stable unity-feedback system, where the plant and the compensator have normalized right-coprime factorizations. They study two cases of nonlinear plant perturbations (additive and feedback), with four subcases resulting from: (1) allowing exogenous input to Delta P or not; 2) allowing the observation of the output of Delta P or not. The plant perturbation Delta P is not required to be stable. Using the factorization approach, the authors obtain necessary and sufficient conditions for all cases in terms of two pairs of nonlinear pseudostate maps. Simple physical considerations explain the form of these necessary and sufficient conditions. Finally, the authors obtain the characterization of all perturbations Delta P for which the perturbed system remains stable.

  8. Synthesis of minimum-time feedback laws for dynamic systems using neural networks

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Smyth, Padhraic

    1994-01-01

    The paper presents the synthesis of neural network based feedback laws for dynamic systems using the computed optimal and time histories of the state and control variables. The efficacy of the proposed approach has been successfully demonstrated on a minimum time orbit injection problem. If the method is found to be effective to real life problems with many state and control variables, it can used for a variety of guidance and control problems.

  9. Optimized feedback control system modeling of resistive wall modes for burning plasmas experiments

    NASA Astrophysics Data System (ADS)

    Katsuro-Hopkins, Oksana Nikolaevna

    A numerical study of active feedback control system performance and optimization for tokamak Resistive Wall Modes (RWM) is the subject of this thesis. The ability to accurately model and predict the performance of an active MHD control systems is critical to present and future advanced confinement scenarios and fusion reactor design studies. The computer code VALEN has been designed to calculate the performance of a MHD feedback control system in an arbitrary geometry. The simulation of realistic effects in feedback systems, such as noise, time delays and filters is of particular importance. In this work realistic measurement noise analysis was added to VALEN and used to design the RWM feedback control amplifier power level for the DIII-D experiment. Modern control theory based on a state-space formulation obtained from VALEN was applied to design an Optimal Controller and Observer based on a reduced VALEN model. A quantitative low order model of the VALEN state space was derived from the high dimensional intrinsic state space structure of the VALEN using methods of a balanced realization and matched DC gain truncation. These techniques for the design of an optimal controller and optimal observer were applied to models of the DIII-D and ITER experiments and showed an order of magnitude reduction of the required control coil current and voltage in the presence of white noise as compared to a traditional, classical PID controller. This optimal controller for the ITER burning plasma experiment was robust from the no-wall pressure limit to a pressure value well above those achieved with a classical PID controller and could approach the ideal wall limit.

  10. Expert verification of the knowledge base of FEED--a feedback expert system for EMS documentation.

    PubMed

    Saini, Devashish; Orthner, Helmuth F; Berner, Eta S; Mirza, Muzna; Godwin, Charles J; Brown, Todd B

    2008-01-01

    Feedback Expert System for Emergency Medical Services (EMS) Documentation (FEED) has a rule-based knowledge base (KB) that was verified against specifications in a focus group consisting of six experts. The focus group suggested changes in almost all rules discussed, indicating that the KB did not meet specifications at that stage of development. However, enough information was gathered to address these issues in the next iteration of development. PMID:18999259

  11. Implementation status of the global and local beam position feedback systems for the Advanced Photon Source storage ring

    SciTech Connect

    Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Kirchman, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A.J.

    1995-07-01

    The Advanced Photon Source (APS) is implementing an extensive beam position feedback system for both global and local stabilization of particle and photon beams based on digital signal processing. The description and operational experience of the system will be given in this paper. In particular, we will discuss the underlying fundamental principles, hardware layout, controls interface, and automatic software generation for multiple digital signal processors (DSPS) distributed in 20 VME crates around the ring. The feedback system runs at 4-kHz sampling frequency in order to achieve the correction bandwidth of approximately 100 Hz. For the maximum correction efficiency and resolution of conflicts among multiple local feedback systems due to the local bump closure error, the global and local feedback systems are combined into a single unified system. This novel approach is made possible through data sharing among the global and local systems via the fiber-optically networked reflective memories.

  12. Stability and Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback

    NASA Astrophysics Data System (ADS)

    Liu, Shuang; Zhao, Shuang-Shuang; Wang, Zhao-Long; Li, Hai-Bin

    2015-01-01

    The stability and the Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback are studied. By considering the energy in the air-gap field of the AC motor, the dynamical equation of the electromechanical coupling transmission system is deduced and a time delay feedback is introduced to control the dynamic behaviors of the system. The characteristic roots and the stable regions of time delay are determined by the direct method, and the relationship between the feedback gain and the length summation of stable regions is analyzed. Choosing the time delay as a bifurcation parameter, we find that the Hopf bifurcation occurs when the time delay passes through a critical value. A formula for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions is given by using the normal form method and the center manifold theorem. Numerical simulations are also performed, which confirm the analytical results. Project supported by the National Natural Science Foundation of China (Grant No. 61104040), the Natural Science Foundation of Hebei Province, China (Grant No. E2012203090), and the University Innovation Team of Hebei Province Leading Talent Cultivation Project, China (Grant No. LJRC013).

  13. Modified neural dynamic surface approach to output feedback of MIMO nonlinear systems.

    PubMed

    Sun, Guofa; Li, Dongwu; Ren, Xuemei

    2015-02-01

    We report an adaptive output feedback dynamic surface control (DSC), maintaining the prescribed performance, for a class of uncertain nonlinear systems with multiinput and multioutput. Designing neural network observers and modifying the DSC method achieves several control objectives. First, to achieve output feedback control, the finite-time echo state networks (ESN) observer with fast convergence is designed to obtain the online system states. Thus, the immeasurable states in traditional state feedback control are estimated and the unknown functions are approximated by ESN. Then, a modified DSC approach is developed by introducing a high-order sliding mode differentiator to replace the first-order filter in each step. Thus, the effect of filter performance on closed-loop stability is reduced. Furthermore, the input to state stability guarantees that all signals of the whole closed-loop system are semiglobally uniformly ultimately bounded. Specifically, the performance functions make the tracking errors converge to a compact set around equilibrium. Two numerical examples illustrated the proposed control scheme with satisfactory results. PMID:25608286

  14. Stochastic thermodynamics of Langevin systems under time-delayed feedback control: Second-law-like inequalities.

    PubMed

    Rosinberg, M L; Munakata, T; Tarjus, G

    2015-04-01

    Response lags are generic to almost any physical system and often play a crucial role in the feedback loops present in artificial nanodevices and biological molecular machines. In this paper, we perform a comprehensive study of small stochastic systems governed by an underdamped Langevin equation and driven out of equilibrium by a time-delayed continuous feedback control. In their normal operating regime, these systems settle in a nonequilibrium steady state in which work is permanently extracted from the surrounding heat bath. By using the Fokker-Planck representation of the dynamics, we derive a set of second-law-like inequalities that provide bounds to the rate of extracted work. These inequalities involve additional contributions characterizing the reduction of entropy production due to the continuous measurement process. We also show that the non-Markovian nature of the dynamics requires a modification of the basic relation linking dissipation to the breaking of time-reversal symmetry at the level of trajectories. The modified relation includes a contribution arising from the acausal character of the reverse process. This, in turn, leads to another second-law-like inequality. We illustrate the general formalism with a detailed analytical and numerical study of a harmonic oscillator driven by a linear feedback, which describes actual experimental setups. PMID:25974446

  15. Stochastic thermodynamics of Langevin systems under time-delayed feedback control: Second-law-like inequalities

    NASA Astrophysics Data System (ADS)

    Rosinberg, M. L.; Munakata, T.; Tarjus, G.

    2015-04-01

    Response lags are generic to almost any physical system and often play a crucial role in the feedback loops present in artificial nanodevices and biological molecular machines. In this paper, we perform a comprehensive study of small stochastic systems governed by an underdamped Langevin equation and driven out of equilibrium by a time-delayed continuous feedback control. In their normal operating regime, these systems settle in a nonequilibrium steady state in which work is permanently extracted from the surrounding heat bath. By using the Fokker-Planck representation of the dynamics, we derive a set of second-law-like inequalities that provide bounds to the rate of extracted work. These inequalities involve additional contributions characterizing the reduction of entropy production due to the continuous measurement process. We also show that the non-Markovian nature of the dynamics requires a modification of the basic relation linking dissipation to the breaking of time-reversal symmetry at the level of trajectories. The modified relation includes a contribution arising from the acausal character of the reverse process. This, in turn, leads to another second-law-like inequality. We illustrate the general formalism with a detailed analytical and numerical study of a harmonic oscillator driven by a linear feedback, which describes actual experimental setups.

  16. Dynamical systems with multiple long-delayed feedbacks: Multiscale analysis and spatiotemporal equivalence.

    PubMed

    Yanchuk, Serhiy; Giacomelli, Giovanni

    2015-10-01

    Dynamical systems with multiple, hierarchically long-delayed feedback are introduced and studied extending our previous work [Yanchuk and Giacomelli, Phys. Rev. Lett. 112, 174103 (2014)]. Focusing on the phenomenological model of a Stuart-Landau oscillator with two feedbacks, we show the multiscale properties of its dynamics and demonstrate them by means of a space-time representation. For sufficiently long delays, we derive a normal form describing the system close to the destabilization. The space and temporal variables, which are involved in the space-time representation, correspond to suitable time scales of the original system. The physical meaning of the results, together with the interpretation of the description at different scales, is presented and discussed. In particular, it is shown how this representation uncovers hidden multiscale patterns such as spirals or spatiotemporal chaos. The effect of the delay size and the features of the transition between small and large delays is also analyzed. Finally, we comment on the application of the method and on its extension to an arbitrary, but finite, number of delayed feedback terms. PMID:26565300

  17. Nonlinear analysis, design and vibration isolation for a bilinear system with time-delayed cubic velocity feedback

    NASA Astrophysics Data System (ADS)

    Gao, X.; Chen, Q.

    2014-03-01

    This paper combines cubic nonlinearity and time delay to improve the performance of vibration isolation. Nonlinear dynamics properties, design methodology and isolation performance are studied for a piecewise bilinear vibration isolation system with the time-delayed cubic velocity feedback control. By the multi-scale perturbation method, the equivalent stiffness and damping are first defined to interpret the effect of feedback control loop on dynamics behaviours, such as frequency island phenomenon. Then, a design criterion is proposed to suppress the jump phenomenon induced by the saddle-node bifurcation. With the purpose of obtaining the desirable vibration isolation performance, stability conditions are obtained to find appropriate feedback parameters including gain and time delay. Last, the influence of the feedback parameters on vibration transmissibility is assessed. Results show that the strategy developed in this paper is practicable and feedback parameters are significant factors to alter dynamics behaviours, and more importantly, to improve the isolation effectiveness for the bilinear isolation system.

  18. Delayed-state-derivative feedback for improving consensus performance of second-order delayed multi-agent systems

    NASA Astrophysics Data System (ADS)

    Wu, Zhihai; Fang, Huajing

    2012-01-01

    In this article, delayed-state-derivative feedback is introduced into the existing delayed consensus protocol for improving the robustness against communication delay and the convergence speed of reaching the consensus simultaneously. Frequency-domain analysis and algebra graph theory are employed to derive the sufficient and necessary condition guaranteeing the second-order delayed multi-agent system applying the consensus protocol with the delayed-state-derivative feedback to achieve the stationary consensus asymptotically. It is proved that introducing delayed-state-derivative feedback with the proper intensity can improve the robustness against communication delay and that for two particular kinds of second-order delayed multi-agent systems, introducing the delayed-state-derivative feedback can also accelerate the convergence speed, provided that the intensity of the delayed-state-derivative feedback is chosen properly. Simulations are provided to demonstrate the effectiveness of the theoretical results.

  19. A Self-regulatory System of Interlinked Signaling Feedback Loops Controls Mouse Limb Patterning

    NASA Astrophysics Data System (ADS)

    Benazet, Jean-Denis; Bischofberger, Mirko; Tiecke, Eva; Gonalves, Alexandre; Martin, James F.; Zuniga, Aime; Naef, Felix; Zeller, Rolf

    Developmental pathways need to be robust against environmental and genetic variation to enable reliable morphogenesis. Here, we take a systems biology approach to explain how robustness is achieved in the developing mouse limb, a classical model of organogenesis. By combining quantitative genetics with computational modeling we established a computational model of multiple interlocked feedback modules, involving sonic hedgehog (SHH) morphogen, fibroblast growth factor (FGFs) signaling, bone morphogenetic protein (BMP) and its antagonist GREM1. Earlier modeling work had emphasized the versatile kinetic characteristics of interlocked feedback loops operating at different time scales. Here we develop and then validate a similar computational model to show how BMP4 first initiates and SHH then propagates feedback in the network through differential transcriptional regulation of Grem1 to control digit specification. This switch occurs by linking a fast BMP4/GREM1 module to a slower SHH/GREM1/FGF feedback loop. Simulated gene expression profiles modeled normal limb development as well those of single-gene knockouts. Sensitivity analysis showed how the model was robust and insensitive to variability in parameters. A surprising prediction of the model was that an early Bmp4 signal is essential to kick-start Grem1 expression and the digit specification system. We experimentally validated the prediction using inducible alleles and showed that early, but not late, removal of Bmp4 dramatically disrupted limb development. Sensitivity analysis showed how robustness emerges from this circuitry. This study shows how modeling and computation can help us understand how self-regulatory signaling networks achieve robust regulation of limb development, by exploiting interconnectivity among the three signaling pathways. We expect that similar computational analyses will shed light on the origins of robustness in other developmental systems, and I will discuss some recent examples from

  20. Study of the DEF Feedback Control System in AC Operation of Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Wang, Hua; Luo, Jiarong; Yuan, Qiping; Xu, Congdong

    2007-02-01

    AC operation with multiple full cycles has been successfully performed on the superconducting tokamak HT-7. In the experiment, it was discovered that the saturation of the transformer magnetic flux with DEF, a signal name, was one of key aspects that affected the AC operation. The conditions of DEF were examined through the DEF feedback control system. By controlling the working patterns of the subsystems, namely the poloidal field control system and density control system, it was guaranteed that DEF would remain in the non-saturated status.

  1. Quantum Coherent Feedback Control for Generation System of Optical Entangled State

    PubMed Central

    Zhou, Yaoyao; Jia, Xiaojun; Li, Fang; Yu, Juan; Xie, Changde; Peng, Kunchi

    2015-01-01

    The non-measurement based coherent feedback control (CFC) is a control method without introducing any backaction noise into the controlled system, thus is specially suitable to manipulate various quantum optical systems for preparing nonclassical states of light. By simply tuning the transmissivity of an optical controller in a CFC loop attached to a non-degenerate optical parametric amplifier (NOPA), the quantum entanglement degree of the output optical entangled state of the system is improved. At the same time, the threshold pump power of the NOPA is reduced also. The experimental results are in reasonable agreement with the theoretical expectation. PMID:26047357

  2. Audio Feedback -- Better Feedback?

    ERIC Educational Resources Information Center

    Voelkel, Susanne; Mello, Luciane V.

    2014-01-01

    National Student Survey (NSS) results show that many students are dissatisfied with the amount and quality of feedback they get for their work. This study reports on two case studies in which we tried to address these issues by introducing audio feedback to one undergraduate (UG) and one postgraduate (PG) class, respectively. In case study one…

  3. Output-feedback sampled-data control design for linear parameter-varying systems with delay

    NASA Astrophysics Data System (ADS)

    Ramezanifar, Amin; Mohammadpour, Javad; Grigoriadis, Karolos M.

    2014-12-01

    In this paper, we address the sampled-data output-feedback control design problem for continuous-time linear parameter-varying systems with time-varying delay in the system states. Due to the combination of the plant's continuous-time dynamics and the controller's discrete-time dynamics connected through A/D and D/A converter devices, the closed-loop system is a hybrid system. In order to analyse this hybrid system from stability and performance perspectives we use the input-delay approach to map the closed-loop system into the continuous-time domain with delay in the states. This results in a closed-loop system containing two types of delays, the system internal delay and the one imposed by the mapping. Next, we use delay-dependent conditions for analysis of stability and ?-norm performance which result in a sampled-data control synthesis procedure. The proposed output-feedback sampled-data controller is obtained based on the solution to a linear matrix inequality optimisation problem using a set of appropriately defined slack variables. A numerical example of a milling machine is presented to demonstrate the viability of the proposed sampled-data control design method to satisfy the stability and performance objectives even with a varying sampling rate.

  4. State feedback control of real-time discrete event systems with infinite states

    NASA Astrophysics Data System (ADS)

    Park, Seong-Jin; Cho, Kwang-Hyun

    2015-05-01

    In this paper, we study a state feedback supervisory control of timed discrete event systems (TDESs) with infinite number of states modelled as timed automata. To this end, we represent a timed automaton with infinite number of untimed states (called locations) by a finite set of conditional assignment statements. Predicates and predicate transformers are employed to finitely represent the behaviour and specification of a TDES with infinite number of locations. In addition, the notion of clock regions in timed automata is used to identify the reachable states of a TDES with an infinite time space. For a real-time specification described as a predicate, we present the controllability condition for the existence of a state feedback supervisor that restricts the behaviour of the controlled TDES within the specification.

  5. Measurement of thermal expansion coefficients of materials based on Nd:YVO4 laser feedback systems

    NASA Astrophysics Data System (ADS)

    Ding, Yingchun; Zheng, Fasong; Lin, Jing; Tan, Yidong

    2015-07-01

    The noncooperative and high sensitivity optical displacement measurement technology is very relevant to the study and the determination of high-precision thermal expansion coefficients (TECs) of materials. This paper describes a measurement technology based on Nd:YVO4 laser feedback systems, which can realize fully non- contact measurement of many kinds of materials with surface reflectivity greater than 10-5. A muffle furnace is designed with two coaxial holes opened on the opposite furnace walls. This length determination technique is based on the frequency-shifted optical feedback effects and the heterodyne phase measurement technique. For validation, the samples are determined in the temperature range 298 to 748K, confirming high sensitivity non- contact measurement of the materials and demonstrating TEC-measurement capabilities with uncertainties in the range of 10-7 or less.

  6. Stability robustness improvement of direct eigenspace assignment based feedback systems using singular value sensitivities

    NASA Technical Reports Server (NTRS)

    Garg, Sanjay

    1989-01-01

    A methodology to improve the stability robustness of feedback control systems designed using direct eigenspace assignment techniques is presented. The method consists of considering the sensitivity of the minimum singular value of the return difference transfer matrix at the plant input to small changes in the desired closed-loop eigenvalues and the specified elements of the desired closed-loop eigenvectors. Closed-form expressions for the gradient of the minimum return difference singular value with respect to desired closed-loop eigenvalue and eigenvector parameters are derived. Closed-form expressions for the gradients of the control feedback gains with respect to the specified eigenspace parameters are obtained as an intermediate step. The use of the gradient information to improve the guaranteed gain and phase margins in eigenspace assignment based designs is demonstrated by application to an advanced fighter aircraft.

  7. A Comparison of Computerized and Psychometric Feedback of the Results of the California Occcupational Preference System.

    ERIC Educational Resources Information Center

    Bringmann, Wolfgang, G.; Christian, James K.

    The practice of not sharing tests results with clients may soon be in conflict with the Ethical Standards for Psychologist (sic). Studies using self-validation of feedback information to study feedback parameters have shown that the form of feedback is less important than the content. To investigate direct feedback of test results by computer, the…

  8. Conversion of linear time-invariant time-delay feedback systems into delay-differential equations with commensurate delays

    NASA Astrophysics Data System (ADS)

    Yamazaki, Tatsuya; Hagiwara, Tomomichi

    2014-08-01

    A new stability analysis method of time-delay systems (TDSs) called the monodromy operator approach has been studied under the assumption that a TDS is represented as a time-delay feedback system consisting of a finite-dimensional linear time-invariant (LTI) system and a pure delay. For applying this approach to TDSs described by delay-differential equations (DDEs), the problem of converting DDEs into representation as time-delay feedback systems has been studied. With regard to such a problem, it was shown that, under discontinuous initial functions, it is natural to define the solutions of DDEs in two different ways, and the above conversion problem was solved for each of these two definitions. More precisely, the solution of a DDE was represented as either the state of the finite-dimensional part of a time-delay feedback system or a part of the output of another time-delay feedback system, depending on which definition of the DDE solution one is talking about. Motivated by the importance in establishing a thorough relationship between time-delay feedback systems and DDEs, this paper discusses the opposite problem of converting time-delay feedback systems into representation as DDEs, including the discussions about the conversion of the initial conditions. We show that the state of (the finite-dimensional part of) a time-delay feedback system can be represented as the solution of a DDE in the sense of one of the two definitions, while its 'essential' output can be represented as that of another DDE in the sense of the other type of definition. Rigorously speaking, however, it is also shown that the latter representation is possible regardless of the initial conditions, while some initial condition could prevent the conversion into the former representation. This study hence establishes that the representation of TDSs as time-delay feedback systems possesses higher ability than that with DDEs, as description methods for LTI TDSs with commensurate delays.

  9. Control Quality of a Feedback Control System under Cyclostationary Noise in Power Line Communication

    NASA Astrophysics Data System (ADS)

    Carrizo, Cesar; Kobayashi, Kentaro; Okada, Hiraku; Katayama, Masaaki

    This paper discusses a control system that employs a power line to transfer signals to control the motion of a single machine, and explores the influence of packet losses on the quality of the control. As an example of a controlled system, a controller with a rotary inverted pendulum as a controlled object, is considered. The feedback loop in between is the power line. The control performance is evaluated in the power line cyclostationary noise environment and compared against the performance in a stationary noise environment. As a result, it is confirmed that the power line and its cyclostationary noise features present an advantage against transmission in a channel with stationary noise.

  10. Cooperative linear output regulation for networked systems by dynamic measurement output feedback

    NASA Astrophysics Data System (ADS)

    Li, Shaobao; Feng, Gang; Wang, Juan; Luo, Xiaoyuan; Guan, Xinping

    2016-04-01

    This paper investigates the cooperative linear output regulation problem of a class of heterogeneous networked systems with a common reference input but with different disturbances for individual nodes. A novel distributed control law is presented based on dynamic measurement output feedback. It is shown that the overall networked closed-loop control system is asymptotically stable and the output regulation errors asymptotically approach zero as time goes to infinity under a sufficient and necessary condition. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed control law.

  11. Mimicking Biological Delivery Through Feedback-Controlled Drug Release Systems Based on Molecular Imprinting

    PubMed Central

    Kryscio, David R.; Peppas, Nicholas A.

    2015-01-01

    Intelligent drug delivery systems (DDS) are able to rapidly detect a biological event and respond appropriately by releasing a therapeutic agent; thus, they are advantageous over their conventional counterparts. Molecular imprinting is a promising area that generates a polymeric network which can selectively recognize a desired analyte. This field has been studied for a variety of applications over a long period of time, but only recently has it been investigated for biomedical and pharmaceutical applications. Recent work in the area of molecularly imprinted polymers in drug delivery highlights the potential of these recognitive networks as environmentally responsive DDS that can ultimately lead to feedback controlled recognitive release systems. PMID:26500352

  12. An Automated Mouse Tail Vascular Access System by Vision and Pressure Feedback

    PubMed Central

    Chang, Yen-Chi; Berry-Pusey, Brittany; Yasin, Rashid; Vu, Nam; Maraglia, Brandon; Chatziioannou, Arion X.; Tsao, Tsu-Chin

    2015-01-01

    This paper develops an automated vascular access system (A-VAS) with novel vision-based vein and needle detection methods and real-time pressure feedback for murine drug delivery. Mouse tail vein injection is a routine but critical step for preclinical imaging applications. Due to the small vein diameter and external disturbances such as tail hair, pigmentation, and scales, identifying vein location is difficult and manual injections usually result in poor repeatability. To improve the injection accuracy, consistency, safety, and processing time, A-VAS was developed to overcome difficulties in vein detection noise rejection, robustness in needle tracking, and visual servoing integration with the mechatronics system. PMID:26478693

  13. Simulation Results of a Feedback Control System to Damp Electron Cloud Single-Bunch Transverse Instabilities In The Cern SPS

    SciTech Connect

    Secondo, R.; Vay, J. L.; Venturini, M.; Fox, J. D.; Rivetta, C. H.; Hofle, W.

    2011-03-28

    Transverse Single-Bunch Instabilities due to the Electron Cloud effect are limiting the operation at high current of the SPS at CERN. Recently a high-bandwidth Feedback System has been proposed as a possible solution to stabilize the beam and is currently under study. We analyze the dynamics of the bunch actively damped with a simple model of the Feedback in the macro-particle code WARP, in order to investigate the limitations of the System such as the minimum amount of power required to maintain stability. We discuss the feedback model, report on simulation results and present our plans for further development of the numerical model.

  14. Modeling and control of non-square MIMO system using relay feedback.

    PubMed

    Kalpana, D; Thyagarajan, T; Gokulraj, N

    2015-11-01

    This paper proposes a systematic approach for the modeling and control of non-square MIMO systems in time domain using relay feedback. Conventionally, modeling, selection of the control configuration and controller design of non-square MIMO systems are performed using input/output information of direct loop, while the output of undesired responses that bears valuable information on interaction among the loops are not considered. However, in this paper, the undesired response obtained from relay feedback test is also taken into consideration to extract the information about the interaction between the loops. The studies are performed on an Air Path Scheme of Turbocharged Diesel Engine (APSTDE) model, which is a typical non-square MIMO system, with input and output variables being 3 and 2 respectively. From the relay test response, the generalized analytical expressions are derived and these analytical expressions are used to estimate unknown system parameters and also to evaluate interaction measures. The interaction is analyzed by using Block Relative Gain (BRG) method. The model thus identified is later used to design appropriate controller to carry out closed loop studies. Closed loop simulation studies were performed for both servo and regulatory operations. Integral of Squared Error (ISE) performance criterion is employed to quantitatively evaluate performance of the proposed scheme. The usefulness of the proposed method is demonstrated on a lab-scale Two-Tank Cylindrical Interacting System (TTCIS), which is configured as a non-square system. PMID:26453020

  15. eMed Teamwork: a self-moderating system to gather peer feedback for developing and assessing teamwork skills.

    PubMed

    Hughes, Chris; Toohey, Susan; Velan, Gary

    2008-02-01

    Students in the six-year undergraduate medicine program at UNSW must submit a portfolio which demonstrates inter alia their development in teamwork skills. Much of the feedback they need to develop these skills, as well as the evidence they require to document their achievements, can only come from their peers. The eMed Teamwork system, developed for this purpose, is a computer-based system which gathers feedback from peers in project groups. The feedback submitted to the system is available to the recipient for formative purposes, and becomes part of both the author's and the recipient's portfolios for later summative assessment. This dual use ensures that the feedback is thoughtful and constructive and the system operates without significant moderation by teachers. PMID:18278642

  16. Innovative system for real-time ergonomic feedback in industrial manufacturing.

    PubMed

    Vignais, Nicolas; Miezal, Markus; Bleser, Gabriele; Mura, Katharina; Gorecky, Dominic; Marin, Frédéric

    2013-07-01

    This work presents a system that permits a real-time ergonomic assessment of manual tasks in an industrial environment. First, a biomechanical model of the upper body has been developed by using inertial sensors placed at different locations on the upper body. Based on this model, a computerized RULA ergonomic assessment was implemented to permit a global risk assessment of musculoskeletal disorders in real-time. Furthermore, local scores were calculated per segment, e.g. the neck region, and gave information on the local risks for musculoskeletal disorders. Visual information was fed back to the user by using a see-through head mounted display. Additional visual highlighting and auditory warnings were provided when some predefined thresholds were exceeded. In a user study (N = 12 participants) a group with the RULA feedback was compared to a control group. Results demonstrate that the real-time ergonomic feedback significantly decreased the outcome of both globally as well as locally hazardous RULA values that are associated with increased risk for musculoskeletal disorders. Task execution time did not differ between groups. The real-time ergonomic tool introduced in this study has the potential to considerably reduce the risk of musculoskeletal disorders in industrial settings. Implications for ergonomics in manufacturing and user feedback modalities are further discussed. PMID:23261177

  17. Rule-Based Cell Systems Model of Aging using Feedback Loop Motifs Mediated by Stress Responses

    PubMed Central

    Kriete, Andres; Bosl, William J.; Booker, Glenn

    2010-01-01

    Investigating the complex systems dynamics of the aging process requires integration of a broad range of cellular processes describing damage and functional decline co-existing with adaptive and protective regulatory mechanisms. We evolve an integrated generic cell network to represent the connectivity of key cellular mechanisms structured into positive and negative feedback loop motifs centrally important for aging. The conceptual network is casted into a fuzzy-logic, hybrid-intelligent framework based on interaction rules assembled from a priori knowledge. Based upon a classical homeostatic representation of cellular energy metabolism, we first demonstrate how positive-feedback loops accelerate damage and decline consistent with a vicious cycle. This model is iteratively extended towards an adaptive response model by incorporating protective negative-feedback loop circuits. Time-lapse simulations of the adaptive response model uncover how transcriptional and translational changes, mediated by stress sensors NF-κB and mTOR, counteract accumulating damage and dysfunction by modulating mitochondrial respiration, metabolic fluxes, biosynthesis, and autophagy, crucial for cellular survival. The model allows consideration of lifespan optimization scenarios with respect to fitness criteria using a sensitivity analysis. Our work establishes a novel extendable and scalable computational approach capable to connect tractable molecular mechanisms with cellular network dynamics underlying the emerging aging phenotype. PMID:20585546

  18. Track-to-track association in decentralized tracking systems with feedback

    NASA Astrophysics Data System (ADS)

    Malmberg, Anders; Karlsson, Mathias

    2000-07-01

    In air combat, information advantage over the opponent is vital for the success of the operation. For that reason, modern fighter aircraft have extensive sensor suites to track other objects. In order to form a unified picture of the vicinity; all sensor information is fused. Since system modularity and high computational performance are key issues in the application, a decentralized tracking approach, where the information from the decentralized trackers is fused in a central node, is preferable. Furthermore, in order to improve the sensor tracking performance, it is often desired to feed back information to the sensors from the central node. In this paper, track-to-track association in such a decentralized tracking system with feedback is addressed. The central fusion node has to associate the sensor tracks to each other to be able to fuse them. In a system without feedback, the track-to-track association algorithm bases its conclusions on the assumption that the estimation errors of the tracks from different local trackers are not correlated. However, when information is fed back to the local trackers, this assumption is not valid, since the sensor tracks then consist of common information. System configurations that deal with this problem are proposed and tested in a fighter aircraft application. One approach is to extract the uncorrelated information from the sensor data and use that in the association process. Another approach is to keep parallel trackers in the sensors that only contain the local sensor information. Both approaches produce sensor tracks that contain the same information as the sensor tracks in a system without feedback. Also, a track-to-track association algorithm that recursively uses information from multiple time steps is proposed. The use of multiple time step data separates it from conventional track-to-track association algorithms that mostly use only current information. The result is an algorithm that improves the performance and

  19. [Quality assurance in heart surgery: 8 years experience with a "feedback-control" system in Heidelberg].

    PubMed

    Vahl, C F; Meinzer, P; Thomas, G; Osswald, B R; Hagl, S

    1996-12-01

    An important aspect of quality assurance in cardiac surgery covers the epidemiological analysis of patient data. After an 8 year period of clinical experience with quality assurance, we summarize and evaluate current concepts and actual experiences regarding a special type of database application and organisation ("feedback-control-system") for quality assurance. It had been developed to meet and solve the problems related to the data acquisition process, that are typically present in the clinical routine of quality assurance. In 1988 the "feedback-control-system" was designed and implemented in the Department of Cardiac Surgery at Heidelberg University. Since then it had been continuously improved and adapted to satisfy current needs in cardiac surgery. More than 1500 items are now recorded routinely per patient. At present, detailed information of more than 10,000 patients is available for the specific methods of analysis in the field of quality assurance. The basic concept included 1. the integration of the data acquisition in the daily clinical routine, 2. the evaluation and improvement of collected data material by means of "output-functions", that require previously recorded reliable data (that is automatically computer generated operation reports, letters, statistics, accounting etc.), and 3. to ensure that the medical and non-medical staff members participate in the advantages and the responsibilities of the data-base system for quality assurance. Analyses of perioperative risks and results, early discovery of trends, identification of special subpopulations receiving special types of treatment in cardiac surgery etc. have now become a regularly performed tool in clinical routine. This includes the availability of "problem profiles", "trend analysis", the use of simple concluding statistics as well as the calculation of multivariable models. This internal quality assurance is completed by "multicentric" comparisons with further hospitals already using the

  20. Design and characteristics evaluation of a novel teleoperated robotic catheterization system with force feedback for vascular interventional surgery.

    PubMed

    Guo, Jian; Guo, Shuxiang; Yu, Yang

    2016-10-01

    In this paper, we proposed a novel master-slave robotic catheterization system with force feedback for VIS (Vascular Interventional Surgery). The force feedback to the operator on the master side is the key factor to improve the safety during VIS. The developed system used the MR (magneto rheological) fluid to realize force feedback, and it used the developed multidimensional monitoring interface to realize the visualization of force feedback, the developed multidimensional monitoring interface can monitor the motion information of the catheter and contact force between catheter tip or side wall and blood vessel wall, and the motion data of the catheter was collected and generated diagram for reference to surgeon. We have developed a force sensor array to detect the contact force between catheter tip or side wall and blood vessel wall. The force information was detected by the developed contact force sensor array when the catheter contacted with the blood vessel. The force feedback and multidimensional information monitoring interface evaluation experiments were done, the tracking characteristic evaluation experiments were also carried out, the experimental results indicated that the developed novel robotic catheterization system with force feedback and visualization of force feedback is effective for VIS, it can improve the safety during VIS. PMID:27499092

  1. Global sampled-data output feedback stabilisation for a class of nonlinear systems with unknown output function

    NASA Astrophysics Data System (ADS)

    Zhai, Jun-yong; Du, Hai-bo; Fei, Shu-min

    2016-03-01

    This paper discusses the problem of global sampled-data output feedback stabilisation for a class of nonlinear systems whose output function is unknown. A systematic design scheme is developed to construct a linear output feedback control law in sampled-data form. An explicit formula for the maximum allowable sampling period is computed to guarantee global stability of the uncertain nonlinear systems under the proposed controller with appropriate gains. Two examples are given to demonstrate the effectiveness of the proposed design procedure.

  2. Design of feedback control systems for unstable plants with saturating actuators

    NASA Technical Reports Server (NTRS)

    Kapasouris, Petros; Athans, Michael; Stein, Gunter

    1988-01-01

    A new control design methodology is introduced for multi-input/multi-output systems with unstable open loop plants and saturating actuators. A control system is designed using well known linear control theory techniques and then a reference prefilter is introduced so that when the references are sufficiently small, the control system operates linearly as designated. For signals large enough to cause saturations, the control law is modified in such a way to ensure stability and to preserve, to the extent possible, the behavior of the linear control design. Key benefits of this methodology are: the modified feedback system never produces saturating control signals, integrators and/or slow dynamics in the compensator never windup, the directionaL properties of the controls are maintained, and the closed loop system has certain guaranteed stability properties. The advantages of the new design methodology are illustrated in the simulation of an approximation of the AFTI-16 (Advanced Fighter Technology Integration) aircraft multivariable longitudinal dynamics.

  3. Stochastic linearisation approach to performance analysis of feedback systems with asymmetric nonlinear actuators and sensors

    NASA Astrophysics Data System (ADS)

    Kabamba, P. T.; Meerkov, S. M.; Ossareh, H. R.

    2015-01-01

    This paper considers feedback systems with asymmetric (i.e., non-odd functions) nonlinear actuators and sensors. While the stability of such systems can be investigated using the theory of absolute stability and its extensions, the current paper provides a method for their performance analysis, i.e., reference tracking and disturbance rejection. Similar to the case of symmetric nonlinearities considered in earlier work, the development is based on the method of stochastic linearisation (which is akin to the describing functions, but intended to study general properties of dynamics, rather than periodic regimes). Unlike the symmetric case, however, the nonlinearities considered here must be approximated not only by a quasilinear gain, but a quasilinear bias as well. This paper derives transcendental equations for the quasilinear gain and bias, provides necessary and sufficient conditions for existence of their solutions, and, using simulations, investigates the accuracy of these solutions as a tool for predicting the quality of reference tracking and disturbance rejection. The method developed is then applied to performance analysis of specific systems, and the effect of asymmetry on their behaviour is investigated. In addition, this method is used to justify the recently discovered phenomenon of noise-induced loss of tracking in feedback systems with PI controllers, anti-windup, and sensor noise.

  4. Numerical algorithms for computations of feedback laws arising in control of flexible systems

    NASA Technical Reports Server (NTRS)

    Lasiecka, Irena

    1989-01-01

    Several continuous models will be examined, which describe flexible structures with boundary or point control/observation. Issues related to the computation of feedback laws are examined (particularly stabilizing feedbacks) with sensors and actuators located either on the boundary or at specific point locations of the structure. One of the main difficulties is due to the great sensitivity of the system (hyperbolic systems with unbounded control actions), with respect to perturbations caused either by uncertainty of the model or by the errors introduced in implementing numerical algorithms. Thus, special care must be taken in the choice of the appropriate numerical schemes which eventually lead to implementable finite dimensional solutions. Finite dimensional algorithms are constructed on a basis of a priority analysis of the properties of the original, continuous (infinite diversional) systems with the following criteria in mind: (1) convergence and stability of the algorithms and (2) robustness (reasonable insensitivity with respect to the unknown parameters of the systems). Examples with mixed finite element methods and spectral methods are provided.

  5. The impact of immediate or delayed feedback on driving behaviour in a simulated Pay-As-You-Drive system.

    PubMed

    Dijksterhuis, Chris; Lewis-Evans, Ben; Jelijs, Bart; de Waard, Dick; Brookhuis, Karel; Tucha, Oliver

    2015-02-01

    Pay-As-You-Drive (PAYD) insurance links an individual's driving behaviour to the insurance fee that they pay, making car insurance more actuarially accurate. The best known PAYD insurance format is purely mileage based and is estimated to reduce accidents by about 15% (Litman, 2011). However, these benefits could be further enhanced by incorporating a wider range of driving behaviours, such as lateral and longitudinal accelerations and speeding behaviour, thereby stimulating not only a safe but also an eco-friendly driving style. Currently, feedback on rewards and driver behaviour is mostly provided through a web-based interface, which is presented temporally separated from driving. However, providing immediate feedback within the vehicle itself could elicit more effect. To investigate this hypothesis, two groups of 20 participants drove with a behavioural based PAYD system in a driving simulator and were provided with either delayed feedback through a website, or immediate feedback through an in-car interface, allowing them to earn up to €6 extra. To be clear, every participant in the web group did actually view their feedback during the one week between sessions. Results indicate clear driving behaviour improvements for both PAYD groups as compared to baseline rides and an equal sized control group. After both PAYD groups had received feedback, the initial advantage of the in-car group was reduced substantially. Taken together with usability ratings and driving behaviours in specific situations these results show a moderate advantage of using immediate in-car feedback. However, the study also showed that under conditions of feedback certainty, the effectiveness of delayed feedback approaches that of immediate feedback as compared to a naïve control group. PMID:25460096

  6. A software module for implementing auditory and visual feedback on a video-based eye tracking system

    NASA Astrophysics Data System (ADS)

    Rosanlall, Bharat; Gertner, Izidor; Geri, George A.; Arrington, Karl F.

    2016-05-01

    We describe here the design and implementation of a software module that provides both auditory and visual feedback of the eye position measured by a commercially available eye tracking system. The present audio-visual feedback module (AVFM) serves as an extension to the Arrington Research ViewPoint EyeTracker, but it can be easily modified for use with other similar systems. Two modes of audio feedback and one mode of visual feedback are provided in reference to a circular area-of-interest (AOI). Auditory feedback can be either a click tone emitted when the user's gaze point enters or leaves the AOI, or a sinusoidal waveform with frequency inversely proportional to the distance from the gaze point to the center of the AOI. Visual feedback is in the form of a small circular light patch that is presented whenever the gaze-point is within the AOI. The AVFM processes data that are sent to a dynamic-link library by the EyeTracker. The AVFM's multithreaded implementation also allows real-time data collection (1 kHz sampling rate) and graphics processing that allow display of the current/past gaze-points as well as the AOI. The feedback provided by the AVFM described here has applications in military target acquisition and personnel training, as well as in visual experimentation, clinical research, marketing research, and sports training.

  7. Feedbacks between climate, CO2 and N2O quantified by a fully coupled Earth system model

    NASA Astrophysics Data System (ADS)

    Kracher, D.; Reick, C. H.

    2013-12-01

    Climate change is evoked by an anthropogenic increase of green house gases (GHG) in the atmosphere, induced by direct emissions from industrial processes or indirectly due to human impacts on ecosystems. Those indirect GHG emissions are strongly influenced by climatic conditions implying several feedback loops in the climate - carbon (C) - nitrogen (N) system. In our study we aim at quantifying the climate - nitrous oxide (N2O) feedback strength in comparison to other feedback mechanisms by applying an Earth system model with explicit representation of interactive N2O in the atmosphere-land-ocean system. Beside the feedbacks emerging due to the temperature sensitivity of biogenic CO2 and N2O emissions, another feedback addressed arises from additional inter-linkages between climate and C and N cycles. Future increased atmospheric CO2 leads to enhanced primary productivity ('CO2 fertilization') causing changes in N availability in the different land and ocean ecosystems. As N2O emissions are driven by availability of N, increased atmospheric CO2 concentrations will impact the climate system also via modifications in N2O emissions. Those changes in N2O emissions will feed back to the climate and will hence also modify the natural biogenic release of CO2 into the atmosphere. This and other associated feedbacks are quantified by applying MPI-ESM, the Earth system model of the Max Planck Institute for Meteorology in Hamburg. MPI-ESM is an atmosphere and ocean global circulation model with model components for land and ocean biogeochemistry. For both CO2 and N2O, land-atmosphere and ocean-atmosphere exchange as well as atmospheric transport are simulated explicitly. Hence, different feedback components in the climate-C-N system can be quantified by cutting artificially single feedback pathways in the model.

  8. Bifurcation Analysis and Chaos Control in a Modified Finance System with Delayed Feedback

    NASA Astrophysics Data System (ADS)

    Yang, Jihua; Zhang, Erli; Liu, Mei

    2016-06-01

    We investigate the effect of delayed feedback on the finance system, which describes the time variation of the interest rate, for establishing the fiscal policy. By local stability analysis, we theoretically prove the existences of Hopf bifurcation and Hopf-zero bifurcation. By using the normal form method and center manifold theory, we determine the stability and direction of a bifurcating periodic solution. Finally, we give some numerical solutions, which indicate that when the delay passes through certain critical values, chaotic oscillation is converted into a stable equilibrium or periodic orbit.

  9. Fuzzy logic based feedback control system for laser beam pointing stabilization.

    PubMed

    Singh, Ranjeet; Patel, Kiran; Govindarajan, J; Kumar, Ajai

    2010-09-20

    This paper reports a fuzzy logic based feedback control system for beam pointing stabilization of a high-power nanosecond Nd:YAG laser operating at 30 Hz. This is achieved by generating the correcting signal for each consequent pulse from the error in the pointing position of the previous laser pulse. We have successfully achieved a reduction of beam position fluctuation from ±60 to ±5.0 μrad without the focusing optics and ±0.9 μrad with focusing optics. PMID:20856289

  10. A feedback control strategy for the airfoil system under non-Gaussian colored noise excitation

    SciTech Connect

    Huang, Yong E-mail: taogang@njust.edu.cn; Tao, Gang E-mail: taogang@njust.edu.cn

    2014-09-01

    The stability of a binary airfoil with feedback control under stochastic disturbances, a non-Gaussian colored noise, is studied in this paper. First, based on some approximated theories and methods the non-Gaussian colored noise is simplified to an Ornstein-Uhlenbeck process. Furthermore, via the stochastic averaging method and the logarithmic polar transformation, one dimensional diffusion process can be obtained. At last by applying the boundary conditions, the largest Lyapunov exponent which can determine the almost-sure stability of the system and the effective region of control parameters is calculated.

  11. A feedback control strategy for the airfoil system under non-Gaussian colored noise excitation.

    PubMed

    Huang, Yong; Tao, Gang

    2014-09-01

    The stability of a binary airfoil with feedback control under stochastic disturbances, a non-Gaussian colored noise, is studied in this paper. First, based on some approximated theories and methods the non-Gaussian colored noise is simplified to an Ornstein-Uhlenbeck process. Furthermore, via the stochastic averaging method and the logarithmic polar transformation, one dimensional diffusion process can be obtained. At last by applying the boundary conditions, the largest Lyapunov exponent which can determine the almost-sure stability of the system and the effective region of control parameters is calculated. PMID:25273197

  12. Capabilities and Characteristics of Digital Measurement Feedback Systems: Results from a Comprehensive Review.

    PubMed

    Lyon, Aaron R; Lewis, Cara C; Boyd, Meredith R; Hendrix, Ethan; Liu, Freda

    2016-05-01

    Measurement feedback systems (MFS) are a class of health information technology (HIT) that function as an implementation support strategy for integrating measurement based care or routine outcome monitoring into clinical practice. Although many MFS have been developed, little is known about their functions. This paper reports findings from an application of health information technology-academic and commercial evaluation (HIT-ACE), a systematic and consolidated evaluation method, to MFS designed for use in behavioral healthcare settings. Forty-nine MFS were identified and subjected to systematic characteristic and capability coding. Results are presented with respect to the representation of characteristics and capabilities across MFS. PMID:26860952

  13. A robust rotorcraft flight control system design methodology utilizing quantitative feedback theory

    NASA Technical Reports Server (NTRS)

    Gorder, Peter James

    1993-01-01

    Rotorcraft flight control systems present design challenges which often exceed those associated with fixed-wing aircraft. First, large variations in the response characteristics of the rotorcraft result from the wide range of airspeeds of typical operation (hover to over 100 kts). Second, the assumption of vehicle rigidity often employed in the design of fixed-wing flight control systems is rarely justified in rotorcraft where rotor degrees of freedom can have a significant impact on the system performance and stability. This research was intended to develop a methodology for the design of robust rotorcraft flight control systems. Quantitative Feedback Theory (QFT) was chosen as the basis for the investigation. Quantitative Feedback Theory is a technique which accounts for variability in the dynamic response of the controlled element in the design robust control systems. It was developed to address a Multiple-Input Single-Output (MISO) design problem, and utilizes two degrees of freedom to satisfy the design criteria. Two techniques were examined for extending the QFT MISO technique to the design of a Multiple-Input-Multiple-Output (MIMO) flight control system (FCS) for a UH-60 Black Hawk Helicopter. In the first, a set of MISO systems, mathematically equivalent to the MIMO system, was determined. QFT was applied to each member of the set simultaneously. In the second, the same set of equivalent MISO systems were analyzed sequentially, with closed loop response information from each loop utilized in subsequent MISO designs. The results of each technique were compared, and the advantages of the second, termed Sequential Loop Closure, were clearly evident.

  14. Low-noise and high-speed photodetection system using optical feedback with a current amplification function

    NASA Astrophysics Data System (ADS)

    Akiba, M.

    2015-09-01

    A photodetection system with an optical-feedback circuit accompanied by current amplification was fabricated to minimize the drawbacks associated with a transimpedance amplifier (TIA) with a very high resistance feedback resistor. Current amplification was implemented by extracting an output light from the same light source that emitted the feedback light. The current gain corresponds to the ratio of the photocurrent created by the output light to that created by the feedback light because the feedback current value is identical to the input photocurrent value generated by an input light to be measured. The current gain has no theoretical limit. The output light was detected by a photodiode with a TIA having a small feedback resistance. The expression for the input-referred noise current of the optical-feedback photodetection system was derived, and the trade-off between sensitivity and response, which is a characteristic of TIA, was found to considerably improve. An optical-feedback photodetection system with an InGaAs pin photodiode was fabricated. The measured noise equivalent power of the system was 1.7 fW/Hz1/2 at 10 Hz and 1.3 μm, which is consistent with the derived expression. The time response of the system was found to deteriorate with decreasing photocurrent. The 50% rise time for a light pulse input increased from 3.1 μs at a photocurrent of 10 nA to 15 μs at photocurrents below 10 pA. The bandwidth of the input-referred noise current was 7 kHz, which is consistent with rise times below 10 pA.

  15. System Simulation by Recursive Feedback: Coupling a Set of Stand-Alone Subsystem Simulations

    NASA Technical Reports Server (NTRS)

    Nixon, D. D.

    2001-01-01

    Conventional construction of digital dynamic system simulations often involves collecting differential equations that model each subsystem, arran g them to a standard form, and obtaining their numerical gin solution as a single coupled, total-system simultaneous set. Simulation by numerical coupling of independent stand-alone subsimulations is a fundamentally different approach that is attractive because, among other things, the architecture naturally facilitates high fidelity, broad scope, and discipline independence. Recursive feedback is defined and discussed as a candidate approach to multidiscipline dynamic system simulation by numerical coupling of self-contained, single-discipline subsystem simulations. A satellite motion example containing three subsystems (orbit dynamics, attitude dynamics, and aerodynamics) has been defined and constructed using this approach. Conventional solution methods are used in the subsystem simulations. Distributed and centralized implementations of coupling have been considered. Numerical results are evaluated by direct comparison with a standard total-system, simultaneous-solution approach.

  16. Optimal feedback control of strongly non-linear systems excited by bounded noise

    NASA Astrophysics Data System (ADS)

    Zhu, W. Q.; Huang, Z. L.; Ko, J. M.; Ni, Y. Q.

    2004-07-01

    A strategy for non-linear stochastic optimal control of strongly non-linear systems subject to external and/or parametric excitations of bounded noise is proposed. A stochastic averaging procedure for strongly non-linear systems under external and/or parametric excitations of bounded noise is first developed. Then, the dynamical programming equation for non-linear stochastic optimal control of the system is derived from the averaged Itô equations by using the stochastic dynamical programming principle and solved to yield the optimal control law. The Fokker-Planck-Kolmogorov equation associated with the fully completed averaged Itô equations is solved to give the response of optimally controlled system. The application and effectiveness of the proposed control strategy are illustrated with the control of cable vibration in cable-stayed bridges and the feedback stabilization of the cable under parametric excitation of bounded noise.

  17. Stabilizing a multimachine power system via decentralized feedback linearizing excitation control

    SciTech Connect

    Chapman, J.W.; Ilic, M.D. ); King, C.A. ); Eng, L. ); Kaufman, H. )

    1993-08-01

    A new controller for the generator excitation system is described that uses a combination of feedback linearization and the observation decoupled state space. This creates a controller that can be realistically implemented using only local measurements, and whose performance is consistent with respect to changes in network configuration, loading and power transfer conditions. The control differs in this respect from linear constant-gain controllers such as power system stabilizers, whose characteristics can vary significantly with changes in operating conditions. The design is well-suited to a multimachine setting, in that it is not based on an infinite-bus approximation. Simulations are performed on a 38-bus reduced model of the Northeast Power Coordinating Council system and benchmarked against simulations in which automatic voltage regulators with power system stabilizers are substituted in place of the nonlinear controls.

  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. Targeted Help for Spoken Dialogue Systems: Intelligent Feedback Improves Naive Users' Performance

    NASA Technical Reports Server (NTRS)

    Hockey, Beth Ann; Lemon, Oliver; Campana, Ellen; Hiatt, Laura; Aist, Gregory; Hieronymous, Jim; Gruenstein, Alexander; Dowding, John

    2003-01-01

    We present experimental evidence that providing naive users of a spoken dialogue system with immediate help messages related to their out-of-coverage utterances improves their success in using the system. A grammar-based recognizer and a Statistical Language Model (SLM) recognizer are run simultaneously. If the grammar-based recognizer suceeds, the less accurate SLM recognizer hypothesis is not used. When the grammar-based recognizer fails and the SLM recognizer produces a recognition hypothesis, this result is used by the Targeted Help agent to give the user feed-back on what was recognized, a diagnosis of what was problematic about the utterance, and a related in-coverage example. The in-coverage example is intended to encourage alignment between user inputs and the language model of the system. We report on controlled experiments on a spoken dialogue system for command and control of a simulated robotic helicopter.

  20. Inversion-free decentralised quantitative feedback design of large-scale systems

    NASA Astrophysics Data System (ADS)

    Labibi, B.; Mahdi Alavi, S. M.

    2016-06-01

    In this paper, a new method for robust decentralised control of multi-input multi-output (MIMO) systems using quantitative feedback theory (QFT) is suggested. The proposed method does not need inversion of the plant transfer function matrix in the design process. For a given system, an equivalent descriptor system representation is defined. By using this representation, sufficient conditions for closed-loop diagonal dominance over the uncertainty space are obtained. These conditions transform the original MIMO system into a set of isolated multi-input single-output (MISO) subsystems. Then, the local controllers are designed by using the typical MISO QFT technique for each isolated subsystem to satisfy the predefined desired specifications and the closed-loop diagonal dominance sufficient conditions. The proposed technique is less conservative in comparison to the approaches using the over-bounding concept in the design procedure. The effectiveness of the proposed technique is finally assessed on a MIMO Scara robot.

  1. Exponential and polynomial stability of an elastic Bresse system with two locally distributed feedbacks

    NASA Astrophysics Data System (ADS)

    Wehbe, Ali; Youssef, Wael

    2010-10-01

    In this paper, we study the energy decay rate for the elastic Bresse system in one-dimensional bounded domain. The physical system consists of three wave equations. The two wave equations about the rotation angle and the longitudinal displacement are damped by two locally distributed feedbacks at the neighborhood of the boundary. Then indirect damping is applied to the equation for the transverse displacement of the beam through the coupling terms. We will establish the exponential stability for this system in the case of the same speed of propagation in the equation for the vertical displacement and the equation for the rotation angle of the system. When the wave speeds are different, nonexponential decay rate is proved and a polynomial-type decay rate is obtained. The frequency domain method and the multiplier technique are applied.

  2. Exponential and polynomial stability of an elastic Bresse system with two locally distributed feedbacks

    SciTech Connect

    Wehbe, Ali; Youssef, Wael

    2010-10-15

    In this paper, we study the energy decay rate for the elastic Bresse system in one-dimensional bounded domain. The physical system consists of three wave equations. The two wave equations about the rotation angle and the longitudinal displacement are damped by two locally distributed feedbacks at the neighborhood of the boundary. Then indirect damping is applied to the equation for the transverse displacement of the beam through the coupling terms. We will establish the exponential stability for this system in the case of the same speed of propagation in the equation for the vertical displacement and the equation for the rotation angle of the system. When the wave speeds are different, nonexponential decay rate is proved and a polynomial-type decay rate is obtained. The frequency domain method and the multiplier technique are applied.

  3. A transverse bunch by bunch feedback system for Pohang Light Source upgrade

    SciTech Connect

    Lee, E.-H.; Kim, D.-T.; Huang, J.-Y.; Shin, S.; Nakamura, T.; Kobayashi, K.

    2014-12-15

    The Pohang Light Source upgrade (PLS-II) project has successfully upgraded the Pohang Light Source (PLS). The main goals of the PLS-II project are to increase the beam energy to 3 GeV, increase the number of insertion devices by a factor of two (20 IDs), increase the beam current to 400 mA, and at the same time reduce the beam emittance to below 10 nm by using the existing PLS tunnel and injection system. Among 20 insertion devices, 10 narrow gap in-vacuum undulators are in operation now and two more in-vacuum undulators are to be installed later. Since these narrow gap in-vacuum undulators are most likely to produce coupled bunch instability by the resistive wall impedance and limit the stored beam current, a bunch by bunch feedback system is implemented to suppress coupled bunch instability in the PLS-II. This paper describes the scheme and performance of the PLS-II bunch by bunch feedback system.

  4. A Portable Gait Asymmetry Rehabilitation System for Individuals with Stroke Using a Vibrotactile Feedback

    PubMed Central

    Afzal, Muhammad Raheel; Oh, Min-Kyun; Lee, Chang-Hee; Park, Young Sook; Yoon, Jungwon

    2015-01-01

    Gait asymmetry caused by hemiparesis results in reduced gait efficiency and reduced activity levels. In this paper, a portable rehabilitation device is proposed that can serve as a tool in diagnosing gait abnormalities in individuals with stroke and has the capability of providing vibration feedback to help compensate for the asymmetric gait. Force-sensitive resistor (FSR) based insoles are used to detect ground contact and estimate stance time. A controller (Arduino) provides different vibration feedback based on the gait phase measurement. It also allows wireless interaction with a personal computer (PC) workstation using the XBee transceiver module, featuring data logging capabilities for subsequent analysis. Walking trials conducted with healthy young subjects allowed us to observe that the system can influence abnormality in the gait. The results of trials showed that a vibration cue based on temporal information was more effective than intensity information. With clinical experiments conducted for individuals with stroke, significant improvement in gait symmetry was observed with minimal disturbance caused to the balance and gait speed as an effect of the biofeedback. Future studies of the long-term rehabilitation effects of the proposed system and further improvements to the system will result in an inexpensive, easy-to-use, and effective rehabilitation device. PMID:26161398

  5. A Portable Gait Asymmetry Rehabilitation System for Individuals with Stroke Using a Vibrotactile Feedback.

    PubMed

    Afzal, Muhammad Raheel; Oh, Min-Kyun; Lee, Chang-Hee; Park, Young Sook; Yoon, Jungwon

    2015-01-01

    Gait asymmetry caused by hemiparesis results in reduced gait efficiency and reduced activity levels. In this paper, a portable rehabilitation device is proposed that can serve as a tool in diagnosing gait abnormalities in individuals with stroke and has the capability of providing vibration feedback to help compensate for the asymmetric gait. Force-sensitive resistor (FSR) based insoles are used to detect ground contact and estimate stance time. A controller (Arduino) provides different vibration feedback based on the gait phase measurement. It also allows wireless interaction with a personal computer (PC) workstation using the XBee transceiver module, featuring data logging capabilities for subsequent analysis. Walking trials conducted with healthy young subjects allowed us to observe that the system can influence abnormality in the gait. The results of trials showed that a vibration cue based on temporal information was more effective than intensity information. With clinical experiments conducted for individuals with stroke, significant improvement in gait symmetry was observed with minimal disturbance caused to the balance and gait speed as an effect of the biofeedback. Future studies of the long-term rehabilitation effects of the proposed system and further improvements to the system will result in an inexpensive, easy-to-use, and effective rehabilitation device. PMID:26161398

  6. Adaptive Neural Control for a Class of Pure-Feedback Nonlinear Systems via Dynamic Surface Technique.

    PubMed

    Liu, Zongcheng; Dong, Xinmin; Xue, Jianping; Li, Hongbo; Chen, Yong

    2016-09-01

    This brief addresses the adaptive control problem for a class of pure-feedback systems with nonaffine functions possibly being nondifferentiable. Without using the mean value theorem, the difficulty of the control design for pure-feedback systems is overcome by modeling the nonaffine functions appropriately. With the help of neural network approximators, an adaptive neural controller is developed by combining the dynamic surface control (DSC) and minimal learning parameter (MLP) techniques. The key features of our approach are that, first, the restrictive assumptions on the partial derivative of nonaffine functions are removed, second, the DSC technique is used to avoid "the explosion of complexity" in the backstepping design, and the number of adaptive parameters is reduced significantly using the MLP technique, third, smooth robust compensators are employed to circumvent the influences of approximation errors and disturbances. Furthermore, it is proved that all the signals in the closed-loop system are semiglobal uniformly ultimately bounded. Finally, the simulation results are provided to demonstrate the effectiveness of the designed method. PMID:26277010

  7. Simulation of e-cloud driven instability and its attenuation using a simulated feedback system in the CERN SPS

    SciTech Connect

    Vay, J.-L.; Furman, M. A.

    2010-12-13

    Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS, and a feedback system to control the single-bunch instabilities is under active development. We present the latest improvements to the WARP-POSINST simulation framework and feedback model, and its application to the self-consistent simulations of two consecutive bunches interacting with an electron cloud in the SPS. Simulations using an idealized feedback system exhibit adequate mitigation of the instability providing that the cutoff of the feedback bandwidth is at or above 450 MHz. Artifacts from numerical noise of the injected distribution of electrons in the modeling of portions of bunch trains are discussed, and benchmarking of WARP against POSINST and HEADTAIL are presented.

  8. Feedback analysis and design of RF power links for low-power bionic systems.

    PubMed

    Baker, M W; Sarpeshkar, R

    2007-03-01

    This paper presents a feedback-loop technique for analyzing and designing RF power links for transcutaneous bionic systems, i.e., between an external RF coil and an internal RF coil implanted inside the body. The feedback techniques shed geometric insight into link design and minimize algebraic manipulations. We demonstrate that when the loop transmission of the link's feedback loop is -1, the link is critically coupled, i.e., the magnitude of the voltage transfer function across the link is maximal. We also derive an optimal loading condition that maximizes the energy efficiency of the link and use it as a basis for our link design. We present an example of a bionic implant system designed for load power consumptions in the 1-10-mW range, a low-power regime not significantly explored in prior designs. Such low power levels add to the challenge of link efficiency, because the overhead associated with switching losses in power amplifiers at the link input and with rectifiers at the link output significantly degrade link efficiency. We describe a novel integrated Class-E power amplifier design that uses a simple control strategy to minimize such losses. At 10-mW load power consumption, we measure overall link efficiencies of 74% and 54% at 1- and 10-mm coil separations, respectively, in good agreement with our theoretical predictions of the link's efficiency. At 1-mW load power consumption, we measure link efficiencies of 67% and 51% at 1- and 10-mm coil separations, respectively, also in good accord with our theoretical predictions. In both cases, the link's rectified output dc voltage varied by less than 16% over link distances that ranged from 2 to 10 mm. PMID:23851518

  9. Sahara Heat Low Perturbations and Water Vapor in the Sahel: A Positive Feedback System

    NASA Astrophysics Data System (ADS)

    Caughman, L.; Evan, A. T.

    2013-12-01

    It is necessary to understand the drivers and feedbacks of global desertification, motivated by the increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change. Climate change and land dynamics are the perturbations that are major drivers of an ecosystem shift to a ';';desertified'' state. This shift is typically sustained by positive feedbacks, which stabilize the system in the new state. This research focuses on changes in precipitation resulting from land-atmosphere interactions and changes in vegetation cover. We concentrate on the Sahel region of Africa (a strip of land that is a transitional area between the Sahara desert to the North and the rain forest to the South). It is a dry land, semi arid environment and is a bistable ecosystem that can either be in the state of 'dry' or 'wet'. After an abnormally wet/high precipitation period in the 1950s the Sahel experienced terrible droughts and desertification which peaked in the 1980s. Since then, precipitation has gradually increased and a sinusoidal model has been shown run on a multi decadal cycle. Discrepancies in the data exist, however, and although the overall cycle has been modeled well, the large inter-annual fluctuations in precipitation have yet to be sufficiently modeled or explained. This research offers new evidence as to why such a phenomenon exists and attempts to attribute this behavior to a coupled land-atmosphere feedback system, linking together changes in vegetation cover and precipitation in the Sahel. Using the model output data from a high resolution Weather Research and Forecasting (WRF) model to look at Africa and compare the difference between perturbations and the mean, this research asserts that when the surface of the Saharan Heat Low (SHL) becomes extremely hot the pressure drops substantially. Subsequently, due to the West African Monsoon system, air rushes in from high-pressure areas, and pulls monsoon precipitation

  10. A Fuzzy Feed-Forward/Feedback Control System for a Three-Phase Oil Field Centrifuge.

    SciTech Connect

    Parkinson, W. J. ,; Smith, R. E.; Mortensen, F. N.; Wantuck, P. J.; Ross, Timothy J.; Jamshidi, Mohammad; Miller, N.

    2002-01-01

    A set of fuzzy controllers was designed and applied to a commercial three-phase oil field centrifuge. This centrifuge is essentially a one of a kind unit. It is used to recover oil from tank bottoms and oil field and/or refinery sludge. It is unique because it can separate oily emulsions into three separate phases, oil, water, and solids, in one operation. The centrifuge is a large but portable device. It is moved form site to site and is used to separate a large variety of waste emulsions. The centrifuge feedstock varies significantly from site to site and often varies significantly during the daily operation. In this application, fuzzy logic was used on a class of problems not easily solved by classical control techniques. The oil field centrifuge is a highly nonlinear system, with a time varying input. We have been unable to develop a physical-mathematical model of the portion of the centrifuge operation that actually separates the oil, water, and solids. For this portion of the operation we developed a fuzzy feedback control system that modeled a skilled operator's knowledge and actions as opposed to the physical model of the centrifuge itself. Because of the variable feed we had to develop a feed-forward controller that would sense and react to feed changes prior to the time that the actual change reached the centrifuge separation unit. This portion of the control system was also a fuzzy controller designed around the knowledge of a skilled operator. In addition to the combined feed-forward and feedback control systems, we developed a soft-sensor that was used to determine the value of variables needed for the feed-forward control system. These variables could not actually be measured but were calculated from the measurement of other variables. The soft-sensor was developed with a combination of a physical model of the feed system and a skilled operator's expert knowledge. Finally the entire control system is tied together with a fuzzy-SPC (Statistical Process

  11. Simulation of E-Cloud Driven Instability And Its Attenuation Using a Feedback System in the CERN SPS

    SciTech Connect

    Vay, Jean-Luc; Byrd, John; Furman, Miguel; Penn, Gregory; Secondo, Raffaello; Venturini, Marco Fox, John; Rivetta, Claudio; /SLAC

    2012-07-06

    Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS, and a feedback system to control the instabilities is under active development. We present the latest improvements to the Warp-Posinst simulation framework and feedback model, and its application to the self-consistent simulations of two consecutive bunches interacting with an electron cloud in the SPS.

  12. SIMULATION OF E-CLOUD DRIVEN INSTABILITY AND ITS ATTENUATION USING A FEEDBACK SYSTEM IN THE CERN SPS

    SciTech Connect

    Vay, J.-L.; Byrd, J. M.; Furman, M. A.; Secondo, R.; Venturini, M.; Fox, J. D.; Rivetta, C. H.; Hofle, W.

    2010-05-03

    Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS [1], and a feedback system to control the instabilities is under active development [2]. We present the latest improvements to the Warp-Posinst simulation framework and feedback model, and its application to the self-consistent simulations of two consecutive bunches interacting with an electron cloud in the SPS.

  13. Feedback control of digital chaotic systems with application to pseudorandom number generator

    NASA Astrophysics Data System (ADS)

    Deng, Yashuang; Hu, Hanping; Liu, Lingfeng

    2015-07-01

    The dynamical properties will degrade when chaotic systems are implemented in digital computers with finite precisions, and such degradation often has serious negative influence on some digital chaos-based systems. Degradation reduction for a class of digital chaotic systems is investigated in this paper. A varying parameter control method is proposed based on the state feedback control technology at first. Then two chaotic maps are applied to verify its validity. Finally, a novel pseudorandom number generator is constructed, which can pass all the tests of NIST SP800-22 at both level-one and level-two approaches and also most of the tests of TestU01. Moreover, it performs better than some existing pseudorandom number generators. Thus, it has acceptable quality of randomness and can be used for cryptography and other applications.

  14. Application of Design Methodologies for Feedback Compensation Associated with Linear Systems

    NASA Technical Reports Server (NTRS)

    Smith, Monty J.

    1996-01-01

    The work that follows is concerned with the application of design methodologies for feedback compensation associated with linear systems. In general, the intent is to provide a well behaved closed loop system in terms of stability and robustness (internal signals remain bounded with a certain amount of uncertainty) and simultaneously achieve an acceptable level of performance. The approach here has been to convert the closed loop system and control synthesis problem into the interpolation setting. The interpolation formulation then serves as our mathematical representation of the design process. Lifting techniques have been used to solve the corresponding interpolation and control synthesis problems. Several applications using this multiobjective design methodology have been included to show the effectiveness of these techniques. In particular, the mixed H 2-H performance criteria with algorithm has been used on several examples including an F-18 HARV (High Angle of Attack Research Vehicle) for sensitivity performance.

  15. Robust control of nonlinear flexible multibody systems using quaternion feedback and dissipative compensation

    NASA Technical Reports Server (NTRS)

    Kelkar, Atul G.; Joshi, Suresh M.

    1994-01-01

    Global asymptotic stability of a class of nonlinear multibody flexible space-stnuctures under dissipative compensation is established. Two cases are considered. The first case allows unlimited nonlinear motions of the entire system and uses quaternion feedback. The second case assumes that the central body motion is in the linear range although the other bodies can undergo unrestricted nonlinear motion. The stability is proved to be robust to the inherent modeling nonlinearities and uncertainties. Furthermore for the second case the stability is also shown to be robust to certain actuator and sensor nonlinearities. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems. The results are applicable to a wide class of systems including flexible space-structures with articulated flexible appendages.

  16. Robust control of nonlinear flexible multibody systems using quaternion feedback and dissipative compensation

    NASA Technical Reports Server (NTRS)

    Kelkar, Atul G.; Joshi, Suresh M.

    1994-01-01

    Global asymptotic stability of a class of nonlinear multibody flexible space structures under dissipative compensation is established. Two cases are considered. The first case allows unlimited nonlinear motions of the entire system and uses quaternion feedback. The second case assumes that the central body motion is in the linear range although the other bodies can undergo unrestricted nonlinear motion. The stability is proved to be robust to the inherent modeling nonlinearities and uncertainties. Furthermore, for the second case, the stability is also shown to be robust to certain actuator and sensor nonlinearities. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems. The results are applicable to a wide class of systems, including flexible space structures with articulated flexible appendages.

  17. Act-and-wait time-delayed feedback control of nonautonomous systems

    NASA Astrophysics Data System (ADS)

    Pyragas, Viktoras; Pyragas, Kestutis

    2016-07-01

    Act-and-wait modification of a time-delayed feedback control (TDFC) algorithm is proposed to stabilize unstable periodic orbits in nonautonomous dynamical systems. Due to periodical switching on and off the control perturbation, an infinite-dimensional function space of the TDFC system is reduced to the finite-dimensional state space. As a result the number of Floquet exponents defining the stability of the controlled orbit remains the same as for the control-free system. The values of these exponents can be effectively manipulated by the variation of control parameters. We demonstrate the advantages of the modification for the chaotic nonautonomous Duffing oscillator with diagonal and nondiagonal control matrices. In both cases very deep minima of the spectral abscissa of Floquet exponents have been attained. The advantage of the modification is particularly remarkable for the nondiagonal coupling; in this case the conventional TDFC fails, whereas the modified version works.

  18. Act-and-wait time-delayed feedback control of nonautonomous systems.

    PubMed

    Pyragas, Viktoras; Pyragas, Kestutis

    2016-07-01

    Act-and-wait modification of a time-delayed feedback control (TDFC) algorithm is proposed to stabilize unstable periodic orbits in nonautonomous dynamical systems. Due to periodical switching on and off the control perturbation, an infinite-dimensional function space of the TDFC system is reduced to the finite-dimensional state space. As a result the number of Floquet exponents defining the stability of the controlled orbit remains the same as for the control-free system. The values of these exponents can be effectively manipulated by the variation of control parameters. We demonstrate the advantages of the modification for the chaotic nonautonomous Duffing oscillator with diagonal and nondiagonal control matrices. In both cases very deep minima of the spectral abscissa of Floquet exponents have been attained. The advantage of the modification is particularly remarkable for the nondiagonal coupling; in this case the conventional TDFC fails, whereas the modified version works. PMID:27575117

  19. Computer program for single input-output, single-loop feedback systems

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Additional work is reported on a completely automatic computer program for the design of single input/output, single loop feedback systems with parameter uncertainly, to satisfy time domain bounds on the system response to step commands and disturbances. The inputs to the program are basically the specified time-domain response bounds, the form of the constrained plant transfer function and the ranges of the uncertain parameters of the plant. The program output consists of the transfer functions of the two free compensation networks, in the form of the coefficients of the numerator and denominator polynomials, and the data on the prescribed bounds and the extremes actually obtained for the system response to commands and disturbances.

  20. Noise-controlled bistability in an excitable system with positive feedback

    NASA Astrophysics Data System (ADS)

    Kromer, Justus A.; Pinto, Reynaldo D.; Lindner, Benjamin; Schimansky-Geier, Lutz

    2014-10-01

    We study the interplay between noise and a positive feedback mechanism in an excitable system that generates events. We show that such a system can exhibit a bistability in the dynamics of the event generation (states of low and high activity). The stability of the two states is determined by the strength of the noise such that a change of noise intensity permits complete control over the probabilities with which the two states are occupied. The bistability also has strong implications for the regularity of the event generation. While the irregularity of the interevent interval (short-time variability) and the asymptotic Fano factor of the event count (long-time variability) are limited if the system is only in one of the two states, we show that both measures of variability display giant values if both states are equally likely. The long-time variability is additionally amplified by long-range positive correlations of the interevent intervals.

  1. Output feedback adaptive fuzzy control of uncertain MIMO nonlinear systems with unknown input nonlinearities.

    PubMed

    Shahnazi, Reza

    2015-01-01

    An adaptive fuzzy output feedback controller is proposed for a class of uncertain MIMO nonlinear systems with unknown input nonlinearities. The input nonlinearities can be backlash-like hysteresis or dead-zone. Besides, the gains of unknown input nonlinearities are unknown nonlinear functions. Based on universal approximation theorem, the unknown nonlinear functions are approximated by fuzzy systems. The proposed method does not need the availability of the states and an observer based on strictly positive real (SPR) theory is designed to estimate the states. An adaptive robust structure is used to cope with fuzzy approximation error and external disturbances. The semi-global asymptotic stability of the closed-loop system is guaranteed via Lyapunov approach. The applicability of the proposed method is also shown via simulations. PMID:25104646

  2. The Effect of Positive Feedback in a Constraint-Based Intelligent Tutoring System

    ERIC Educational Resources Information Center

    Mitrovic, Antonija; Ohlsson, Stellan; Barrow, Devon K.

    2013-01-01

    Tutoring technologies for supporting learning from errors via negative feedback are highly developed and have proven their worth in empirical evaluations. However, observations of empirical tutoring dialogs highlight the importance of positive feedback in the practice of expert tutoring. We hypothesize that positive feedback works by reducing…

  3. Feedback system of a liquid-nitrogen-cooled double-crystal monochromator: design and performances.

    PubMed

    Proux, Olivier; Nassif, Vivian; Prat, Alain; Ulrich, Olivier; Lahera, Eric; Biquard, Xavier; Menthonnex, Jean Jacques; Hazemann, Jean Louis

    2006-01-01

    A new set-up is reported of an indirect cryogenic cooling system for a double-crystal monochromator which runs on the BM30b/FAME beamline at the ESRF (Grenoble, France). This device has been conceived to limit the vibrations on the first diffracting crystal and to maintain it at a constant temperature. These points are crucial for maximizing the beamline stability. Moreover, the relative angular position of the second crystal can be dynamically adjusted by a piezoelectric transducer coupled with a feedback system in order to always be at the maximum of the rocking curve during an X-ray absorption spectroscopy scan. The temperature is stabilized to an accuracy of 0.01 degrees , with two principal consequences. The energy resolution is close to the theoretical value [DeltaE/E = 5.6 x 10(-6) for Si(220)] and the precision of the energy positioning is extremely good even if the power load changes. A feedback mechanism allows a permanent and automatic optimization of the angle between the two crystals of the monochromator. The intensity of the monochromatic beam remains optimized (i) when the intensity of the electron beam decreases in the storage ring and (ii) during an energy scan. PMID:16371709

  4. Low-bit rate feedback strategies for iterative IA-precoded MIMO-OFDM-based systems.

    PubMed

    Teodoro, Sara; Silva, Adão; Dinis, Rui; Gameiro, Atílio

    2014-01-01

    Interference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the other BSs through a limited-capacity backhaul network. This information is then used by BSs to perform the overall IA design. With the proposed strategies, we only need to send part of the CSI information, and this can even be sent only once for a set of data blocks transmitted over time-varying channels. These strategies are applied to iterative MMSE-based IA techniques for the downlink of broadband wireless OFDM systems with limited feedback. A new robust iterative IA technique, where channel quantization errors are taken into account in IA design, is also proposed and evaluated. With our proposed strategies, we need a small number of quantization bits to transmit and share the CSI, when comparing with the techniques used in previous works, while allowing performance close to the one obtained with perfect channel knowledge. PMID:24678274

  5. Low-Bit Rate Feedback Strategies for Iterative IA-Precoded MIMO-OFDM-Based Systems

    PubMed Central

    Teodoro, Sara; Silva, Adão; Dinis, Rui; Gameiro, Atílio

    2014-01-01

    Interference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the other BSs through a limited-capacity backhaul network. This information is then used by BSs to perform the overall IA design. With the proposed strategies, we only need to send part of the CSI information, and this can even be sent only once for a set of data blocks transmitted over time-varying channels. These strategies are applied to iterative MMSE-based IA techniques for the downlink of broadband wireless OFDM systems with limited feedback. A new robust iterative IA technique, where channel quantization errors are taken into account in IA design, is also proposed and evaluated. With our proposed strategies, we need a small number of quantization bits to transmit and share the CSI, when comparing with the techniques used in previous works, while allowing performance close to the one obtained with perfect channel knowledge. PMID:24678274

  6. Laser 3-D measuring system and real-time visual feedback for teaching and correcting breathing

    NASA Astrophysics Data System (ADS)

    Povšič, Klemen; Fležar, Matjaž; Možina, Janez; Jezeršek, Matija

    2012-03-01

    We present a novel method for real-time 3-D body-shape measurement during breathing based on the laser multiple-line triangulation principle. The laser projector illuminates the measured surface with a pattern of 33 equally inclined light planes. Simultaneously, the camera records the distorted light pattern from a different viewpoint. The acquired images are transferred to a personal computer, where the 3-D surface reconstruction, shape analysis, and display are performed in real time. The measured surface displacements are displayed with a color palette, which enables visual feedback to the patient while breathing is being taught. The measuring range is approximately 400×600×500 mm in width, height, and depth, respectively, and the accuracy of the calibrated apparatus is +/-0.7 mm. The system was evaluated by means of its capability to distinguish between different breathing patterns. The accuracy of the measured volumes of chest-wall deformation during breathing was verified using standard methods of volume measurements. The results show that the presented 3-D measuring system with visual feedback has great potential as a diagnostic and training assistance tool when monitoring and evaluating the breathing pattern, because it offers a simple and effective method of graphical communication with the patient.

  7. Cell cycle dynamics in a response/signalling feedback system with a gap

    PubMed Central

    Gong, Xue; Buckalew, Richard; Young, Todd; Boczko, Erik

    2014-01-01

    We consider a dynamical model of cell cycles of n cells in a culture in which cells in one specific phase (S for signalling) of the cell cycle produce chemical agents that influence the growth/cell cycle progression of cells in another phase (R for responsive). In the case that the feedback is negative, it is known that subpopulations of cells tend to become clustered in the cell cycle; while for a positive feedback, all the cells tend to become synchronized. In this paper, we suppose that there is a gap between the two phases. The gap can be thought of as modelling the physical reality of a time delay in the production and action of the signalling agents. We completely analyse the dynamics of this system when the cells are arranged into two cell cycle clusters. We also consider the stability of certain important periodic solutions in which clusters of cells have a cyclic arrangement and there are just enough clusters to allow interactions between them. We find that the inclusion of a small gap does not greatly alter the global dynamics of the system; there are still large open sets of parameters for which clustered solutions are stable. Thus, we add to the evidence that clustering can be a robust phenomenon in biological systems. However, the gap does effect the system by enhancing the stability of the stable clustered solutions. We explain this phenomenon in terms of contraction rates (Floquet exponents) in various invariant subspaces of the system. We conclude that in systems for which these models are reasonable, a delay in signalling is advantageous to the emergence of clustering. PMID:24963979

  8. Inferring Instantaneous, Multivariate and Nonlinear Sensitivities for the Analysis of Feedback Processes in a Dynamical System: Lorenz Model Case Study

    NASA Technical Reports Server (NTRS)

    Aires, Filipe; Rossow, William B.; Hansen, James E. (Technical Monitor)

    2001-01-01

    A new approach is presented for the analysis of feedback processes in a nonlinear dynamical system by observing its variations. The new methodology consists of statistical estimates of the sensitivities between all pairs of variables in the system based on a neural network modeling of the dynamical system. The model can then be used to estimate the instantaneous, multivariate and nonlinear sensitivities, which are shown to be essential for the analysis of the feedbacks processes involved in the dynamical system. The method is described and tested on synthetic data from the low-order Lorenz circulation model where the correct sensitivities can be evaluated analytically.

  9. FPGA-based LLRF control module for x-ray free electron laser and TESLA feedback system

    NASA Astrophysics Data System (ADS)

    Giergusiewicz, Wojciech; Kierzkowski, Krzysztof; Pozniak, Krzysztof T.; Romaniuk, Ryszard S.

    2005-02-01

    The paper introduces a dedicated LLRF control module developed for the Free Electron Laser (FEL) called internally also the "TESLA Test Facility phase II" because of some daring scientific plans to build in the future the X-ray Free Electron Laser (XFEL) as well as the TESLA project. This DSP-board has been dedicated for electron beam gun called RF-gun feedback system and also for the cavity (superconducting electromagnetic resonator) feedback system and cavity simulator implemented in one DSP system chip. The system for the elctromagnetic field parameters control is meant as the feedback system -- in this document. The board is based on a large modern Field Programmble Gate Array (FPGA) chip by "Xilinx" and fast Analog to Digital Converters (ADC) and Digital to Analog converters (DAC) by "Analog Devices."

  10. Observation, control, and modal analysis of longitudinal coupled-bunch instabilities in the ALS via a digital feedback system

    SciTech Connect

    Fox, J.D.; Claus, R.; Hindi, H.; Linscott, I.; Prabhakar, S.; Ross, W.; Teytelman, D.; Drago, A.; Serio, M.; Byrd, J.; Corlett, J.; Stover, G.

    1997-01-01

    The operation of a longitudinal multibunch damping system using digital signal processing (DSP) techniques is shown via measurements from the Lawrence Berkeley Laboratory (LBL) Advanced Light Source (ALS). The feedback system (developed for use by PEP-II, ALS, and DA{Phi}NE) uses a parallel array of signal processors to implement a bunch-by-bunch feedback system for sampling rates up to 500 MHz. The programmable DSP system allows feedback control as well as accelerator diagnostics. A diagnostic technique is illustrated which uses the DSP system to excite and then damp the beam. The resulting 12-ms time domain transient is Fourier analyzed to provide the simultaneous measurement of growth rates and damping rates of all unstable coupled-bunch beam modes. {copyright} {ital 1997 American Institute of Physics.}

  11. Synthesis of a non-linear feedback system with significant plant-ignorance for prescribed time-domain tolerances

    NASA Technical Reports Server (NTRS)

    Krishnan, K. R.; Horowitz, I. M.

    1973-01-01

    The problem considered is the design of a feedback system containing a linear, time invariant, minimum phase plant, whose parameters are known only within given bounds, such that the time response of the system remains within specified limits. A quasi-optimal design, for given design constraints, is one which minimizes the effect of white sensor noise on the input to the plant. An investigation was conducted on the use of the non linear device known as the Clegg integrator in the design of such a system. The describing function of the Clegg integrator has the same magnitude characteristic, apart from a scale factor, as the linear integrator, but has 52 deg less phase-lag, at all frequencies, than the linear integrator; thus, when used in a feedback system, it provides a larger stability margin than the linear integrator. This property allows the nonlinear feedback system to be designed so that the sensor noise is attenuated more than in the linear design.

  12. Observational constraints on atmospheric radiaitve feedbacks: absolute accuracy and next-generation observing systems

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Hanssen, L. M.; Mekhontsev, S.; Anderson, J.

    2012-12-01

    The central role of atmospheric radiative feedbacks to understanding and projecting climate change calls for a robust observational system. Recent studies have shown the value of space-based measurements for putting quantitative constraints on a range of radiative feedback processes through a fingerprinting method applied to long-term observational records. More recent work has suggested the value of demonstrably accurate measurements to disentangle model error from observational uncertainties within reanalysis systems, potentially yielding improved representations of feedback processes within just a few years. Both of these methods rely on space-based measurements that can be objectively tested for accuracy on-orbit. A new class of mission has been proposed that incorporates the same type of empirical tests for accuracy as used in the laboratory into a space-based sensor. One example of such a mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO), a new mission suggested by the 2006 National Research Council Decadal Survey. CLARREO includes three sensor types: thermal infrared, microwave, and reflected shortwave. This paper presents a laboratory demonstration of prototype systems for testing the on-orbit accuracy of a thermal infrared sensor for CLARREO. These systems utilize infrared lasers to provide monochromatic light sources to quantitatively determine the optical properties of materials. These infrared optical properties are major determinants of the on-orbit radiometric performance of a thermal infrared sensor. For this reason, reliable quantitative information (including uncertainty) that tracks any changes in relevant infrared materials over the mission lifetime is essential to objective assessment of instrument accuracy. The practicality of mid-infrared lasers for these applications is due to the availability and continued evolution of compact, high-efficiency Quantum Cascade Lasers (QCLs). These lasers can provide over 100 m

  13. Development of a flow feedback pulse duplicator system with rhesus monkey arterial input impedance characteristics

    NASA Technical Reports Server (NTRS)

    Schaub, J. D.; Koenig, S. C.; Schroeder, M. J.; Ewert, D. L.; Drew, G. A.; Swope, R. D.; Convertino, V. A. (Principal Investigator)

    1999-01-01

    An in vitro pulsatile pump flow system that is capable of producing physiologic pressures and flows in a mock circulatory system tuned to reproduce the first nine harmonics of the input impedance of a rhesus monkey was developed and tested. The system was created as a research tool for evaluating cardiovascular function and for the design, testing, and evaluation of electrical-mechanical cardiovascular models and chronically implanted sensors. The system possesses a computerized user interface for controlling a linear displacement pulsatile pump in a controlled flow loop format to emulate in vivo cardiovascular characteristics. Evaluation of the pump system consisted of comparing its aortic pressure and flow profiles with in vivo rhesus hemodynamic waveforms in the time and frequency domains. Comparison of aortic pressure and flow data between the pump system and in vivo data showed good agreement in the time and frequency domains, however, the pump system produced a larger pulse pressure. The pump system can be used for comparing cardiovascular parameters with predicted cardiovascular model values and for evaluating such items as vascular grafts, heart valves, biomaterials, and sensors. This article describes the development and evaluation of this feedback controlled cardiovascular dynamics simulation modeling system.

  14. Development of a flow feedback pulse duplicator system with rhesus monkey arterial input impedance characteristics.

    PubMed

    Schaub, J D; Koenig, S C; Schroeder, M J; Ewert, D L; Drew, G A; Swope, R D

    1999-01-01

    An in vitro pulsatile pump flow system that is capable of producing physiologic pressures and flows in a mock circulatory system tuned to reproduce the first nine harmonics of the input impedance of a rhesus monkey was developed and tested. The system was created as a research tool for evaluating cardiovascular function and for the design, testing, and evaluation of electrical-mechanical cardiovascular models and chronically implanted sensors. The system possesses a computerized user interface for controlling a linear displacement pulsatile pump in a controlled flow loop format to emulate in vivo cardiovascular characteristics. Evaluation of the pump system consisted of comparing its aortic pressure and flow profiles with in vivo rhesus hemodynamic waveforms in the time and frequency domains. Comparison of aortic pressure and flow data between the pump system and in vivo data showed good agreement in the time and frequency domains, however, the pump system produced a larger pulse pressure. The pump system can be used for comparing cardiovascular parameters with predicted cardiovascular model values and for evaluating such items as vascular grafts, heart valves, biomaterials, and sensors. This article describes the development and evaluation of this feedback controlled cardiovascular dynamics simulation modeling system. PMID:10445741

  15. Modal self-excitation by nonlinear acceleration feedback in a class of mechanical systems

    NASA Astrophysics Data System (ADS)

    Malas, Anindya; Chatterjee, S.

    2016-08-01

    The article proposes an acceleration feedback based technique for exciting modal self-oscillation in a class of multi degrees-of-freedom mechanical systems. The controller comprises a bank of second-order filters and the control law is formulated as the nonlinear function of the filter output. A design methodology is developed to excite self-oscillation in any desired mode or combination of modes (mixed-mode oscillation). The choice of control parameters takes into account the control cost and robustness of the controller. The effects of structural damping on the system performance are also studied. Analytical results are confirmed by numerical simulations. An adaptive control is proposed to maintain the oscillation amplitude at the desired level.

  16. Note: Design of a laser feedback interferometer with double diffraction system

    SciTech Connect

    Guo, Dongmei Wang, Ming

    2015-09-15

    A novel laser feedback interferometer with double diffraction system is proposed in this paper. A beam emitted from the laser is incident onto a transmission grating. The mth order beam is vertically reflected by a mirror and diffracted again by the grating. The double-diffracted beam returns into the laser cavity and mixes with the light inside the active cavity, thus generating a modulation of both the amplitude and the frequency of the lasing field. Theoretical analysis and experimental observations show that the output signal of the proposed system depends on the grating pitch and the direction of the phase movement can be obtained from inclination of the interference signal. It provides a potential displacement sensor with high stability and quite a compact configuration.

  17. Assisting the Visually Impaired: Obstacle Detection and Warning System by Acoustic Feedback

    PubMed Central

    Rodríguez, Alberto; Yebes, J. Javier; Alcantarilla, Pablo F.; Bergasa, Luis M.; Almazán, Javier; Cela, Andrés

    2012-01-01

    The aim of this article is focused on the design of an obstacle detection system for assisting visually impaired people. A dense disparity map is computed from the images of a stereo camera carried by the user. By using the dense disparity map, potential obstacles can be detected in 3D in indoor and outdoor scenarios. A ground plane estimation algorithm based on RANSAC plus filtering techniques allows the robust detection of the ground in every frame. A polar grid representation is proposed to account for the potential obstacles in the scene. The design is completed with acoustic feedback to assist visually impaired users while approaching obstacles. Beep sounds with different frequencies and repetitions inform the user about the presence of obstacles. Audio bone conducting technology is employed to play these sounds without interrupting the visually impaired user from hearing other important sounds from its local environment. A user study participated by four visually impaired volunteers supports the proposed system. PMID:23247413

  18. Real-time feedback control for high-intensity focused ultrasound system using localized motion imaging

    NASA Astrophysics Data System (ADS)

    Sugiyama, Ryusuke; Kanazawa, Kengo; Seki, Mika; Azuma, Takashi; Sasaki, Akira; Takeuchi, Hideki; Fujiwara, Keisuke; Itani, Kazunori; Tamano, Satoshi; Yoshinaka, Kiyoshi; Takagi, Shu; Matsumoto, Yoichiro

    2015-07-01

    High-intensity focused ultrasound (HIFU) is one of the noninvasive treatment for tumors. Visualizing the treated area inside the human body is necessary to control the HIFU exposure. Localized motion imaging (LMI) using ultrasound to induce and detect tissue deformation is one technique to detect a change in tissue stiffness caused by thermal coagulation. In experiments with porcine liver, LMI has shown to detect deformation with less than 20% accuracy. We have developed a prototype feedback control system using real-time LMI. In this system, coagulation size was measured every 1 s and controlled to correspond to a targeted size. The typical size error was reduced to 14% from 35%. LMI displacements in normal and coagulated tissues were sufficiently different to discriminate between coagulated areas and noncoagulated ones after HIFU sonication and to visualize treated areas after HIFU treatment.

  19. Feedback controlled laser system for safe and efficient reshaping of nasal cartilage

    NASA Astrophysics Data System (ADS)

    Sobol, Emil; Sviridov, Alexander; Svistushkin, Valery; Vorobieva, Natalia

    2010-02-01

    Laser septochondrocorrection (LSC) is a non-invasive, bloodless, painless procedure which takes only 10 minutes to complete and can be performed in outpatient settings. The efficacy and safety of this technology can be guarantied with the feed-back control system monitoring tissue characteristics in the course of laser treatment. Laser medical equipment for septochondrocorrection includes an Erbium doped glass fiber laser, special instrument, opto thermo mechanical contactor, and feed back control system measuring temperature on the nasal septum surface and switching the laser off when preset value of temperature is achieved. To the date LSC procedure has been applied for 380 patients, aging from 12 until 68 years. The new laser equipment LRC-701 manufactured by Arcuo Medical Inc. was tested for 106 patients in Moscow and for 64 patients in Crete. The positive results habe been obtained for 95 percent of the patients with two years follow-up. No age limitation, no complications and negative secondary effects were observed.

  20. Generation of sub-Poisson light in a negative feedback and cascade three-level system

    NASA Astrophysics Data System (ADS)

    Chai, Jinhua; Guo, Guangcan

    1992-10-01

    The aim of this paper is to try to find out the possibility of reducing the photon number noise in an optically pumped three-level atomic system. Consider a three-level atomic system. The atomic transition between level 1 and level 3 is forbidden. Each atom is incoherently excited to upper level 3 from level 1, transits to level 1 through intermediate level 2, and emits photons at frequency (omega) 1 and (omega) 2. We place the atoms with the above feature into an oscillator and may obtain two coherent light beams, whose frequency are (omega) 1 and (omega) 2, respectively. There may be some correlation between these two light beams. We make one beam to control the pump source by a feedback loop and expect to reduce the noise of photon number of the other beam.

  1. Implementing for Sustainability: Promoting Use of a Measurement Feedback System for Innovation and Quality Improvement.

    PubMed

    Douglas, Susan; Button, Suzanne; Casey, Susan E

    2016-05-01

    Measurement feedback systems (MFSs) are increasingly recognized as evidence-based treatments for improving mental health outcomes, in addition to being a useful administrative tool for service planning and reporting. Promising research findings have driven practice administrators and policymakers to emphasize the incorporation of outcomes monitoring into electronic health systems. To promote MFS integrity and protect against potentially negative outcomes, it is vital that adoption and implementation be guided by scientifically rigorous yet practical principles. In this point of view, the authors discuss and provide examples of three user-centered and theory-based principles: emphasizing integration with clinical values and workflow, promoting administrative leadership with the 'golden thread' of data-informed decision-making, and facilitating sustainability by encouraging innovation. In our experience, enacting these principles serves to promote sustainable implementation of MFSs in the community while also allowing innovation to occur, which can inform improvements to guide future MFS research. PMID:25344848

  2. Synthesis of feedback systems with large plant ignorance for prescribed time domain tolerances

    NASA Technical Reports Server (NTRS)

    Horowitz, I. M.; Sidi, M.

    1971-01-01

    There is given a minimum-phase plant transfer function, with prescribed bounds on its parameter values. The plant is imbedded in a two-degree-of freedom feedback system, which is to be designed such that the system time response to a deterministic input lies within specified boundaries. Subject to the above, the design should be such as to minimize the effect of sensor noise at the input to the plant. This report presents a design procedure for this purpose, based on frequency response concepts. The time-domain tolerances are translated into equivalent frequency response tolerances. The latter lead to bounds on the loop transmission function in the form of continuous curves on the Nichols chart. The properties of the loop transmission function which satisfy these bounds with minimum effect of sensor noise, are derived.

  3. Synchronised output regulation of leader-following heterogeneous networked systems via error feedback

    NASA Astrophysics Data System (ADS)

    Li, Yanjun; Wang, Xuejie; Xiang, Ji; Wei, Wei

    2016-03-01

    A dynamic error feedback controller is presented for the synchronised output regulation (SOR) of leader-following heterogeneous linear networked systems. The nodes in the networked systems are divided into two kinds: the leader node accessible to the regulated error and the following nodes inaccessible to the regulated error but accessible to the relative output errors with respect to their neighbouring nodes. By using the small-gain theorem, a sufficient criterion for the SOR problem is developed for more general networks. This criterion can be regarded as imposing an additional H∞ constraint on the classical output regulation problem. The synthesis problem is then addressed by means of linear matrix inequality technique. The efficacy of the analytic results is illustrated by simulation examples.

  4. Kinetics of constant gravitropic stimulus responses in Arabidopsis roots using a feedback system

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Wolverton, C.; Ishikawa, H.; Evans, M. L.

    2000-01-01

    The study of gravitropism is hindered by the fact that as a root responds, the gravitational stimulus changes. Using a feedback system to connect a rotating stage platform to a video digitizer system, we were able to maintain a constant angle of gravistimulation to Arabidopsis roots for long time periods. The rate of curvature approximated the sine rule for angles of stimulation between 20 degrees and 120 degrees. For a given angle of stimulation, the rate of curvature also remained constant, with no observed diminishment of the response. Although previous reports of Arabidopsis root gravitropism suggest latent periods of approximately 30 min, using a smooth mechanical stage to reorient the root, we observed a mean time lag of approximately 10 min. This more rapid onset of curvature can, in part, be explained by reduced mechanical perturbation during the process of gravistimulation. This suggests that mechanical stimulation associated with rapid root re-orientation may confound investigations of early gravitropic events.

  5. Robust fixed-order dynamic output feedback controller design for nonlinear uncertain suspension system

    NASA Astrophysics Data System (ADS)

    Badri, Pouya; Amini, Amir; Sojoodi, Mahdi

    2016-12-01

    This paper deals with designing a robust fixed-order non-fragile dynamic output feedback controller for active suspension system of a quarter-car, by means of convex optimization and linear matrix inequalities (LMIs). Our purpose is to design a low-order controller that keeps the desired design specifications besides the simplicity of the implementation. The proposed controller is capable of asymptotically stabilizing the closed-loop system and developing H∞ control, despite model uncertainties and nonlinear dynamics of the quarter-car as well as the norm bounded perturbations of controller parameters. Furthermore, controller parameters are prevented from taking very large and undesirable amounts through appropriate LMI constraints. Finally, a numerical example is presented to show the effectiveness of the proposed method by comparing it with similar works.

  6. Adaptive Fuzzy Control of Strict-Feedback Nonlinear Time-Delay Systems With Unmodeled Dynamics.

    PubMed

    Yin, Shen; Shi, Peng; Yang, Hongyan

    2016-08-01

    In this paper, an approximated-based adaptive fuzzy control approach with only one adaptive parameter is presented for a class of single input single output strict-feedback nonlinear systems in order to deal with phenomena like nonlinear uncertainties, unmodeled dynamics, dynamic disturbances, and unknown time delays. Lyapunov-Krasovskii function approach is employed to compensate the unknown time delays in the design procedure. By combining the advances of the hyperbolic tangent function with adaptive fuzzy backstepping technique, the proposed controller guarantees the semi-globally uniformly ultimately boundedness of all the signals in the closed-loop system from the mean square point of view. Two simulation examples are finally provided to show the superior effectiveness of the proposed scheme. PMID:26302525

  7. Robust path integration in the entorhinal grid cell system with hippocampal feed-back.

    PubMed

    Samu, Dávid; Eros, Péter; Ujfalussy, Balázs; Kiss, Tamás

    2009-07-01

    Animals are able to update their knowledge about their current position solely by integrating the speed and the direction of their movement, which is known as path integration. Recent discoveries suggest that grid cells in the medial entorhinal cortex might perform some of the essential underlying computations of path integration. However, a major concern over path integration is that as the measurement of speed and direction is inaccurate, the representation of the position will become increasingly unreliable. In this paper, we study how allothetic inputs can be used to continually correct the accumulating error in the path integrator system. We set up the model of a mobile agent equipped with the entorhinal representation of idiothetic (grid cell) and allothetic (visual cells) information and simulated its place learning in a virtual environment. Due to competitive learning, a robust hippocampal place code emerges rapidly in the model. At the same time, the hippocampo-entorhinal feed-back connections are modified via Hebbian learning in order to allow hippocampal place cells to influence the attractor dynamics in the entorhinal cortex. We show that the continuous feed-back from the integrated hippocampal place representation is able to stabilize the grid cell code. PMID:19381679

  8. Continuous flow total artificial heart: modeling and feedback control in a mock circulatory system.

    PubMed

    Khalil, Hassan A; Kerr, Daniel T; Franchek, Matthew A; Metcalfe, Ralph W; Benkowski, Robert J; Cohn, William E; Tuzun, Egemen; Radovancevic, Branislav; Frazier, O H; Kadipasaoglu, Kamuran A

    2008-01-01

    We developed a mock circulatory loop and used mathematical modeling to test the in vitro performance of a physiologic flow control system for a total artificial heart (TAH). The TAH was constructed from two continuous flow pumps. The objective of the control system was to maintain loop flow constant in response to changes in outflow resistance of either pump. Baseline outflow resistances of the right (pulmonary vascular resistance) and the left (systemic vascular resistance) pumps were set at 2 and 18 Wood units, respectively. The corresponding circuit flow was 4 L/min. The control system consisted of two digital integral controllers, each regulating the voltage, hence, the rotational speed of one of the pumps. The in vitro performance of the flow control system was validated by increasing systemic and pulmonary vascular resistances in the mock loop by 4 and 8 Wood units (simulating systemic and pulmonary hypertension conditions), respectively. For these simulated hypertensive states, the flow controllers regulated circuit flow back to 4 L/min within seconds by automatically adjusting the rotational speed of either or both pumps. We conclude that this multivariable feedback mechanism may constitute an adequate supplement to the inherent pressure sensitivity of rotary blood pumps for the automatic flow control and left-right flow balance of a dual continuous flow pump TAH system. PMID:18496274

  9. From Demonstration System to Prototype: ShakeAlert Beta Users Provide Feedback to Improve Alert Delivery

    NASA Astrophysics Data System (ADS)

    Strauss, J. A.; Vinci, M.; Steele, W. P.; Allen, R. M.; Hellweg, M.

    2013-12-01

    Earthquake Early Warning (EEW) is a system that can provide a few to tens of seconds to minutes of warning prior to ground shaking at a given location. The goal and purpose of such a system is to reduce the damage, costs, and casualties resulting from an earthquake. A prototype earthquake early warning system (ShakeAlert) is in development by the UC Berkeley Seismological Laboratory, Caltech, ETH Zurich, University of Washington, and the USGS. Events are published to the UserDisplay--ShakeAlert's Java based graphical interface, which is being tested by a small group of beta users throughout California. The beta users receive earthquake alerts in real-time and are providing feedback on their experiences. For early warning alerts to be useful, people, companies, and institutions must know beforehand what actions they will perform when they receive the information. Beta user interactions allow the ShakeAlert team to discern: which alert delivery options are most effective, what changes would make the UserDisplay more useful in a pre-disaster situation, and most importantly, what actions users plan to take for various scenarios. We also collect feedback detailing costs of implementing actions and challenges within the beta user organizations, as well as anticipated benefits and savings. Thus, creating a blueprint for a fully operational system that will meet the needs of the public. New California users as well as the first group of Pacific Northwest users are slated to join the ShakeAlert beta test group in the fall of 2013.

  10. Analysis of a dc bus system with a nonlinear constant power load and its delayed feedback control.

    PubMed

    Konishi, Keiji; Sugitani, Yoshiki; Hara, Naoyuki

    2014-02-01

    This paper tackles a destabilizing problem of a direct-current (dc) bus system with constant power loads, which can be considered a fundamental problem of dc power grid networks. The present paper clarifies scenarios of the destabilization and applies the well-known delayed-feedback control to the stabilization of the destabilized bus system on the basis of nonlinear science. Further, we propose a systematic procedure for designing the delayed feedback controller. This controller can converge the bus voltage exactly on an unstable operating point without accurate information and can track it using tiny control energy even when a system parameter, such as the power consumption of the load, is slowly varied. These features demonstrate that delayed feedback control can be considered a strong candidate for solving the destabilizing problem. PMID:25353544

  11. Observer-based adaptive neural dynamic surface control for a class of non-strict-feedback stochastic nonlinear systems

    NASA Astrophysics Data System (ADS)

    Yu, Zhaoxu; Li, Shugang; Li, Fangfei

    2016-01-01

    The problem of adaptive output feedback stabilisation is addressed for a more general class of non-strict-feedback stochastic nonlinear systems in this paper. The neural network (NN) approximation and the variable separation technique are utilised to deal with the unknown subsystem functions with the whole states. Based on the design of a simple input-driven observer, an adaptive NN output feedback controller which contains only one parameter to be updated is developed for such systems by using the dynamic surface control method. The proposed control scheme ensures that all signals in the closed-loop systems are bounded in probability and the error signals remain semi-globally uniformly ultimately bounded in fourth moment (or mean square). Two simulation examples are given to illustrate the effectiveness of the proposed control design.

  12. [Development of an Analgesia Therapy System for Delivery Based on Bio-feedback Transcuataneous Electrical Nerve Stimulation].

    PubMed

    Deng Songbo; Lu Yaosheng; Fang, Kun; Qin, Ruyi; Lin, Zhan

    2015-06-01

    Transcuataneous electrical nerve stimulation (TENS) analgesia as a non-drug method has received people's more and more attention recently. Considering problems of existing products, such as unstable performance and unsatisfied effectiveness, we developed a new analgesia therapy system for delivery based on bio-feedback TENS in our laboratory. We proposed a new idea for stimulation signal design, that is, we modulated a middle frequency signal by a traditional low frequency TENS wave in the new system. We designed different prescription waves for pain relief during a uterine contraction or massage between contractions. In the end, a bio-feedback TENS method was proposed, in which the waveforms of stimulation signals were selected and their parameters were modified automatically based on feedback from uterine pressure, etc. It was proved through quality tests and clinical trials that the system had good performance and satisfied analgesia effectiveness. PMID:26485994

  13. Paired-Associate and Feedback-Based Weather Prediction Tasks Support Multiple Category Learning Systems.

    PubMed

    Li, Kaiyun; Fu, Qiufang; Sun, Xunwei; Zhou, Xiaoyan; Fu, Xiaolan

    2016-01-01

    It remains unclear whether probabilistic category learning in the feedback-based weather prediction task (FB-WPT) can be mediated by a non-declarative or procedural learning system. To address this issue, we compared the effects of training time and verbal working memory, which influence the declarative learning system but not the non-declarative learning system, in the FB and paired-associate (PA) WPTs, as the PA task recruits a declarative learning system. The results of Experiment 1 showed that the optimal accuracy in the PA condition was significantly decreased when the training time was reduced from 7 to 3 s, but this did not occur in the FB condition, although shortened training time impaired the acquisition of explicit knowledge in both conditions. The results of Experiment 2 showed that the concurrent working memory task impaired the optimal accuracy and the acquisition of explicit knowledge in the PA condition but did not influence the optimal accuracy or the acquisition of self-insight knowledge in the FB condition. The apparent dissociation results between the FB and PA conditions suggested that a non-declarative or procedural learning system is involved in the FB-WPT and provided new evidence for the multiple-systems theory of human category learning. PMID:27445958

  14. Paired-Associate and Feedback-Based Weather Prediction Tasks Support Multiple Category Learning Systems

    PubMed Central

    Li, Kaiyun; Fu, Qiufang; Sun, Xunwei; Zhou, Xiaoyan; Fu, Xiaolan

    2016-01-01

    It remains unclear whether probabilistic category learning in the feedback-based weather prediction task (FB-WPT) can be mediated by a non-declarative or procedural learning system. To address this issue, we compared the effects of training time and verbal working memory, which influence the declarative learning system but not the non-declarative learning system, in the FB and paired-associate (PA) WPTs, as the PA task recruits a declarative learning system. The results of Experiment 1 showed that the optimal accuracy in the PA condition was significantly decreased when the training time was reduced from 7 to 3 s, but this did not occur in the FB condition, although shortened training time impaired the acquisition of explicit knowledge in both conditions. The results of Experiment 2 showed that the concurrent working memory task impaired the optimal accuracy and the acquisition of explicit knowledge in the PA condition but did not influence the optimal accuracy or the acquisition of self-insight knowledge in the FB condition. The apparent dissociation results between the FB and PA conditions suggested that a non-declarative or procedural learning system is involved in the FB-WPT and provided new evidence for the multiple-systems theory of human category learning. PMID:27445958

  15. IDENTIFICATION OF NONLINEARITIES IN AN 8-DOF SYSTEM THROUGH SPECTRAL FEEDBACK

    SciTech Connect

    B. ARCAND; J. WAIT

    2000-08-01

    The accurate detection and characterization of nonlinearities associated with damage in structural systems is an area of vibration analysis that is being widely researched. In this paper, nonlinear behavior is considered a potential indicator of damage. Most conventional damage detection methods, such as those based on resonant frequencies and mode shapes, do not accurately identify the location and extent of nonlinearities present in a given structural system. As an extension of previous work at LANL, an effort is made to validate a damage detection method proposed by Adams. This method states that the frequency response function (FRF) matrix obtained from a low-level vibration test approximates the underlying linear FRF matrix of the system. The nonlinear systems' responses to high level excitation are combined with the linear FRF in a classic feedback loop to obtain the contributions of nonlinear internal forces. The temporal and spatial characteristics of the nonlinearities present in a structural system are identified. An 8-DOF system is used as a test case to validate the aforementioned method. Results of the tests and important issues concerning the method are presented.

  16. Investigation of rotational skin stretch for proprioceptive feedback with application to myoelectric systems.

    PubMed

    Wheeler, Jason; Bark, Karlin; Savall, Joan; Cutkosky, Mark

    2010-02-01

    We present a new wearable haptic device that provides a sense of position and motion by inducing rotational skin stretch on the user's skin. In the experiments described in this paper, the device was used to provide proprioceptive feedback from a virtual prosthetic arm controlled with myoelectric sensors on the bicep and tricep muscles in 15 able-bodied participants. Targeting errors in blind movements with the haptic device were compared to cases where no feedback and contralateral proprioception were provided. Average errors were lower with the device than with no feedback but larger than with contralateral proprioceptive feedback. Participants also had lower visual demand with the device than with no feedback while tracking a 30 ( degrees ) moving range. The results indicate that the rotational skin stretch may ultimately be effective for proprioceptive feedback in myoelectric prostheses, particularly when vision is otherwise occupied. PMID:20071271

  17. Delay-feedback control strategy for reducing CO2 emission of traffic flow system

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Dong; Zhu, Wen-Xing

    2015-06-01

    To study the signal control strategy for reducing traffic emission theoretically, we first presented a kind of discrete traffic flow model with relative speed term based on traditional coupled map car-following model. In the model, the relative speed difference between two successive running cars is incorporated into following vehicle's acceleration running equation. Then we analyzed its stability condition with discrete control system stability theory. Third, we designed a delay-feedback controller to suppress traffic jam and decrease traffic emission based on modern controller theory. Last, numerical simulations are made to support our theoretical results, including the comparison of models' stability analysis, the influence of model type and signal control on CO2 emissions. The results show that the temporal behavior of our model is superior to other models, and the traffic signal controller has good effect on traffic jam suppression and traffic CO2 emission, which fully supports the theoretical conclusions.

  18. Effects of endogenous proteins and microRNA target sequence in a positive feedback system.

    PubMed

    Kanda, Genki N; Togashi, Ryohei; Harashima, Hideyoshi; Kamiya, Hiroyuki

    2012-01-01

    A positive feedback system, using GAL4-vp16 (a fusion protein of yeast GAL4 and herpes simplex virus vp16) as an activator and firefly luciferase as a reporter, maintained luciferase expression for 7 d in mice. However, the luciferase expression decreased after 7 d, and this phenomenon could be caused by immunoreactions against these exogenous proteins. This hypothesis was examined by the following three strategies, designed to avoid the putative immunoreactions: (i) use of the endogenous secreted alkaline phosphatase (SEAP) protein as a reporter, (ii) replacement of vp16 with endogenous transcription factors, and (iii) insertion of the target sequence of microRNA expressed in cells of hematopoietic origin, to suppress GAL4-vp16 expression in antigen-presenting cells. The results obtained in this study suggested that silencing would be induced by mechanism(s) besides immunoreactions against reporter and activator proteins. PMID:22975505

  19. The dipole corrector magnets for the RHIC fast global orbit feedback system

    SciTech Connect

    Thieberger, P.; Arnold, L.; Folz, C.; Hulsart, R.; Jain, A.; Karl, R.; Mahler, G.; Meng, W.; Mernick, K.; Michnoff, R.; Minty, M.; Montag, C.; Ptitsyn, V.; Ritter, J.; Smart, L.; Tuozzolo, J.; White, J.

    2011-03-28

    The recently completed RHIC fast global orbit feedback system uses 24 small 'window-frame' horizontal dipole correctors. Space limitations dictated a very compact design. The magnetic design and modelling of these laminated yoke magnets is described as well as the mechanical implementation, coil winding, vacuum impregnation, etc. Test procedures to determine the field quality and frequency response are described. The results of these measurements are presented and discussed. A small fringe field from each magnet, overlapping the opposite RHIC ring, is compensated by a correction winding placed on the opposite ring's magnet and connected in series with the main winding of the first one. Results from measurements of this compensation scheme are shown and discussed.

  20. Stability and chaotification of vibration isolation floating raft systems with time-delayed feedback control.

    PubMed

    Li, Y L; Xu, D L; Fu, Y M; Zhou, J X

    2011-09-01

    This paper presents a systematic study on the stability of a two-dimensional vibration isolation floating raft system with a time-delayed feedback control. Based on the generalized Sturm criterion, the critical control gain for the delay-independent stability region and critical time delays for the stability switches are derived. The critical conditions can provide a theoretical guidance of chaotification design for line spectra reduction. Numerical simulations verify the correctness of the approach. Bifurcation analyses reveal that chaotification is more likely to occur in unstable region defined by these critical conditions, and the stiffness of the floating raft and mass ratio are the sensitive parameters to reduce critical control gain. PMID:21974650

  1. A neighboring optimal feedback control scheme for systems using discontinuous control.

    NASA Technical Reports Server (NTRS)

    Foerster, R. E.; Flugge-Lotz, I.

    1971-01-01

    The calculation and implementation of the neighboring optimal feedback control law for multiinput, nonlinear dynamical systems, using discontinuous control, is discussed. An initialization procedure is described which removes the requirement that the neighboring initial state be in the neighborhood of the nominal initial state. This procedure is a bootstrap technique for determining the most appropriate control-law gain for the neighboring initial state. The mechanization of the neighboring control law described is closed loop in that the concept of time-to-go is utilized in the determination of the control-law gains appropriate for each neighboring state. The gains are chosen such that the time-to-go until the next predicted switch time or predicted final time is the same for both the neighboring and nominal trajectories. The procedure described is utilized to solve the minimum-time satellite attitude-acquisition problem.

  2. Noise-induced standing waves in oscillatory systems with time-delayed feedback

    NASA Astrophysics Data System (ADS)

    Stich, Michael; Chattopadhyay, Amit K.

    2016-05-01

    In oscillatory reaction-diffusion systems, time-delay feedback can lead to the instability of uniform oscillations with respect to formation of standing waves. Here, we investigate how the presence of additive, Gaussian white noise can induce the appearance of standing waves. Combining analytical solutions of the model with spatiotemporal simulations, we find that noise can promote standing waves in regimes where the deterministic uniform oscillatory modes are stabilized. As the deterministic phase boundary is approached, the spatiotemporal correlations become stronger, such that even small noise can induce standing waves in this parameter regime. With larger noise strengths, standing waves could be induced at finite distances from the (deterministic) phase boundary. The overall dynamics is defined through the interplay of noisy forcing with the inherent reaction-diffusion dynamics.

  3. Robust pole assignment for synthesizing feedback control systems using recurrent neural networks.

    PubMed

    Le, Xinyi; Wang, Jun

    2014-02-01

    This paper presents a neurodynamic optimization approach to robust pole assignment for synthesizing linear control systems via state and output feedback. The problem is formulated as a pseudoconvex optimization problem with robustness measure: i.e., the spectral condition number as the objective function and linear matrix equality constraints for exact pole assignment. Two coupled recurrent neural networks are applied for solving the formulated problem in real time. In contrast to existing approaches, the exponential convergence of the proposed neurodynamics to global optimal solutions can be guaranteed even with lower model complexity in terms of the number of variables. Simulation results of the proposed neurodynamic approach for 11 benchmark problems are reported to demonstrate its superiority. PMID:24807036

  4. Psycho-physiological assessment of a prosthetic hand sensory feedback system based on an auditory display: a preliminary study

    PubMed Central

    2012-01-01

    Background Prosthetic hand users have to rely extensively on visual feedback, which seems to lead to a high conscious burden for the users, in order to manipulate their prosthetic devices. Indirect methods (electro-cutaneous, vibrotactile, auditory cues) have been used to convey information from the artificial limb to the amputee, but the usability and advantages of these feedback methods were explored mainly by looking at the performance results, not taking into account measurements of the user’s mental effort, attention, and emotions. The main objective of this study was to explore the feasibility of using psycho-physiological measurements to assess cognitive effort when manipulating a robot hand with and without the usage of a sensory substitution system based on auditory feedback, and how these psycho-physiological recordings relate to temporal and grasping performance in a static setting. Methods 10 male subjects (26+/-years old), participated in this study and were asked to come for 2 consecutive days. On the first day the experiment objective, tasks, and experiment setting was explained. Then, they completed a 30 minutes guided training. On the second day each subject was tested in 3 different modalities: Auditory Feedback only control (AF), Visual Feedback only control (VF), and Audiovisual Feedback control (AVF). For each modality they were asked to perform 10 trials. At the end of each test, the subject had to answer the NASA TLX questionnaire. Also, during the test the subject’s EEG, ECG, electro-dermal activity (EDA), and respiration rate were measured. Results The results show that a higher mental effort is needed when the subjects rely only on their vision, and that this effort seems to be reduced when auditory feedback is added to the human-machine interaction (multimodal feedback). Furthermore, better temporal performance and better grasping performance was obtained in the audiovisual modality. Conclusions The performance improvements when using

  5. Estimating Climate System Feedbacks and Sensitivities using Linear Inverse Modeling versus the Fluctuation-Dissipation Theorem

    NASA Astrophysics Data System (ADS)

    Sardeshmukh, P. D.; Penland, M. C.

    2011-12-01

    Improving climate predictions from subseasonal to centennial scales, including responses to projected increases of greenhouse gases (GHGs) and other radiative forcings, is the outstanding challenge in climate science today. Despite decades of model development, however, comprehensive coupled atmosphere-ocean models remain deficient in many respects in this regard, and also disagree substantially among themselves. They differ in their representations of ENSO and longer-term oceanic variability, and also generate substantially different global and regional climate responses to radiative forcing. A key global metric, global climate sensitivity (defined as the globally averaged equilibrium surface temperature response to a doubling of carbon dioxide), differs by more than a factor of three among the models, which is highly inconvenient for climate policy. To discriminate between the models and also possibly to improve them, independent estimations of climate sensitivities and feedbacks from knowledge of observed past system behavior would be highly desirable. There are two apparently distinct approaches currently available to accomplish this: the Fluctuation-Dissipation Theorem (FDT) and Linear Inverse Modeling (LIM). Both use knowledge of the time-lag covariance matrices C(tau) of the system. The former estimates the system response matrix R for small external forcing using C(tau) integrated from zero to infinite lag, whereas the latter estimates it using C(tau) for a single lag, tau-0. If C(tau) decays exponentially with lag, the two approaches are formally identical. The authors and others have demonstrated in numerous publications that C(tau) does indeed decay approximately exponentially with lag in the climate system, and have used this property to construct forecast models that remain highly competitive with state-of-the-art comprehensive subseasonal and seasonal forecast models. A practical difficulty with using the FDT to estimate R is that it requires accurate

  6. Cry-wolf signals emerging from coevolutionary feedbacks in a tritrophic system.

    PubMed

    Yamauchi, Atsushi; van Baalen, Minus; Kobayashi, Yutaka; Takabayashi, Junji; Shiojiri, Kaori; Sabelis, Maurice W

    2015-11-01

    For a communication system to be stable, senders should convey honest information. Providing dishonest information, however, can be advantageous to senders, which imposes a constraint on the evolution of communication systems. Beyond single populations and bitrophic systems, one may ask whether stable communication systems can evolve in multitrophic systems. Consider cross-species signalling where herbivore-induced plant volatiles (HIPVs) attract predators to reduce the damage from arthropod herbivores. Such plant signals may be honest and help predators to identify profitable prey/plant types via HIPV composition and to assess prey density via the amount of HIPVs. There could be selection for dishonest signals that attract predators for protection from possible future herbivory. Recently, we described a case in which plants release a fixed, high amount of HIPVs independent of herbivore load, adopting what we labelled a 'cry-wolf' strategy. To understand when such signals evolve, we model coevolutionary interactions between plants, herbivores and predators, and show that both 'honest' and 'cry-wolf' types can emerge, depending on the assumed plant-herbivore encounter rates and herbivore population density. It is suggested that the 'cry-wolf' strategy may have evolved to reduce the risk of heavy damage in the future. Our model suggests that eco-evolutionary feedback loops involving a third species may have important consequences for the stability of this outcome. PMID:26538597

  7. Space-Frequency Block Code with Matched Rotation for MIMO-OFDM System with Limited Feedback

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Abhayapala, Thushara D.; Jayalath, Dhammika; Smith, David; Athaudage, Chandra

    2009-12-01

    This paper presents a novel matched rotation precoding (MRP) scheme to design a rate one space-frequency block code (SFBC) and a multirate SFBC for MIMO-OFDM systems with limited feedback. The proposed rate one MRP and multirate MRP can always achieve full transmit diversity and optimal system performance for arbitrary number of antennas, subcarrier intervals, and subcarrier groupings, with limited channel knowledge required by the transmit antennas. The optimization process of the rate one MRP is simple and easily visualized so that the optimal rotation angle can be derived explicitly, or even intuitively for some cases. The multirate MRP has a complex optimization process, but it has a better spectral efficiency and provides a relatively smooth balance between system performance and transmission rate. Simulations show that the proposed SFBC with MRP can overcome the diversity loss for specific propagation scenarios, always improve the system performance, and demonstrate flexible performance with large performance gain. Therefore the proposed SFBCs with MRP demonstrate flexibility and feasibility so that it is more suitable for a practical MIMO-OFDM system with dynamic parameters.

  8. Feedback-Based, System-Level Properties of Vertebrate-Microbial Interactions

    PubMed Central

    Rivas, Ariel L.; Jankowski, Mark D.; Piccinini, Renata; Leitner, Gabriel; Schwarz, Daniel; Anderson, Kevin L.; Fair, Jeanne M.; Hoogesteijn, Almira L.; Wolter, Wilfried; Chaffer, Marcelo; Blum, Shlomo; Were, Tom; Konah, Stephen N.; Kempaiah, Prakash; Ong’echa, John M.; Diesterbeck, Ulrike S.; Pilla, Rachel; Czerny, Claus-Peter; Hittner, James B.; Hyman, James M.; Perkins, Douglas J.

    2013-01-01

    Background Improved characterization of infectious disease dynamics is required. To that end, three-dimensional (3D) data analysis of feedback-like processes may be considered. Methods To detect infectious disease data patterns, a systems biology (SB) and evolutionary biology (EB) approach was evaluated, which utilizes leukocyte data structures designed to diminish data variability and enhance discrimination. Using data collected from one avian and two mammalian (human and bovine) species infected with viral, parasite, or bacterial agents (both sensitive and resistant to antimicrobials), four data structures were explored: (i) counts or percentages of a single leukocyte type, such as lymphocytes, neutrophils, or macrophages (the classic approach), and three levels of the SB/EB approach, which assessed (ii) 2D, (iii) 3D, and (iv) multi-dimensional (rotating 3D) host-microbial interactions. Results In all studies, no classic data structure discriminated disease-positive (D+, or observations in which a microbe was isolated) from disease-negative (D–, or microbial-negative) groups: D+ and D– data distributions overlapped. In contrast, multi-dimensional analysis of indicators designed to possess desirable features, such as a single line of observations, displayed a continuous, circular data structure, whose abrupt inflections facilitated partitioning into subsets statistically significantly different from one another. In all studies, the 3D, SB/EB approach distinguished three (steady, positive, and negative) feedback phases, in which D– data characterized the steady state phase, and D+ data were found in the positive and negative phases. In humans, spatial patterns revealed false-negative observations and three malaria-positive data classes. In both humans and bovines, methicillin-resistant Staphylococcus aureus (MRSA) infections were discriminated from non-MRSA infections. Conclusions More information can be extracted, from the same data, provided that data are

  9. Output-feedback IDA stabilisation of an SMIB system using a TCSC

    NASA Astrophysics Data System (ADS)

    Espinosa-Pérez, Gerardo; Maya-Ortíz, Paul; Dòria-Cerezo, Arnau; Moreno, Jaime A.

    2010-12-01

    Interconnection and damping assignment (IDA) passivity-based control (PBC) is currently a well-known viable alternative for solving regulation control problems of a wide class of nonlinear systems. However, a distinctive feature that, in spite of its appearance under several applications, has not been exhaustively exploited, is the flexibility that this technique exhibits for designing output-feedback controllers (OFCs). The purpose of this article is to illustrate this attractive characteristic by approaching the (practically important) case study given by the improvement of the transient stability properties of power systems. The particular system composed by a synchronous generator connected to an infinite bus via a thyristor controlled series capacitor is considered. Two OFCs are presented, one that does not involve the unmeasurable state and another that, although including this state, presents some input-to-state stability properties that allow for establishing a sort of separation principle concerning an observer-based structure for the closed-loop system. The advantages of both controllers are illustrated by numerical simulations when a three-phase short circuit at the generator bus is induced.

  10. Adaptive Neural Output Feedback Control of Output-Constrained Nonlinear Systems With Unknown Output Nonlinearity.

    PubMed

    Liu, Zhi; Lai, Guanyu; Zhang, Yun; Chen, Chun Lung Philip

    2015-08-01

    This paper addresses the problem of adaptive neural output-feedback control for a class of special nonlinear systems with the hysteretic output mechanism and the unmeasured states. A modified Bouc-Wen model is first employed to capture the output hysteresis phenomenon in the design procedure. For its fusion with the neural networks and the Nussbaum-type function, two key lemmas are established using some extended properties of this model. To avoid the bad system performance caused by the output nonlinearity, a barrier Lyapunov function technique is introduced to guarantee the prescribed constraint of the tracking error. In addition, a robust filtering method is designed to cancel the restriction that all the system states require to be measured. Based on the Lyapunov synthesis, a new neural adaptive controller is constructed to guarantee the prescribed convergence of the tracking error and the semiglobal uniform ultimate boundedness of all the signals in the closed-loop system. Simulations are implemented to evaluate the performance of the proposed neural control algorithm in this paper. PMID:25915964

  11. Systemic risk in multiplex networks with asymmetric coupling and threshold feedback

    NASA Astrophysics Data System (ADS)

    Burkholz, Rebekka; Leduc, Matt V.; Garas, Antonios; Schweitzer, Frank

    2016-06-01

    We study cascades on a two-layer multiplex network, with asymmetric feedback that depends on the coupling strength between the layers. Based on an analytical branching process approximation, we calculate the systemic risk measured by the final fraction of failed nodes on a reference layer. The results are compared with the case of a single layer network that is an aggregated representation of the two layers. We find that systemic risk in the two-layer network is smaller than in the aggregated one only if the coupling strength between the two layers is small. Above a critical coupling strength, systemic risk is increased because of the mutual amplification of cascades in the two layers. We even observe sharp phase transitions in the cascade size that are less pronounced on the aggregated layer. Our insights can be applied to a scenario where firms decide whether they want to split their business into a less risky core business and a more risky subsidiary business. In most cases, this may lead to a drastic increase of systemic risk, which is underestimated in an aggregated approach.

  12. Feedbacks, Bifurcations, and Cell Fate Decision-Making in the p53 System.

    PubMed

    Hat, Beata; Kochańczyk, Marek; Bogdał, Marta N; Lipniacki, Tomasz

    2016-02-01

    The p53 transcription factor is a regulator of key cellular processes including DNA repair, cell cycle arrest, and apoptosis. In this theoretical study, we investigate how the complex circuitry of the p53 network allows for stochastic yet unambiguous cell fate decision-making. The proposed Markov chain model consists of the regulatory core and two subordinated bistable modules responsible for cell cycle arrest and apoptosis. The regulatory core is controlled by two negative feedback loops (regulated by Mdm2 and Wip1) responsible for oscillations, and two antagonistic positive feedback loops (regulated by phosphatases Wip1 and PTEN) responsible for bistability. By means of bifurcation analysis of the deterministic approximation we capture the recurrent solutions (i.e., steady states and limit cycles) that delineate temporal responses of the stochastic system. Direct switching from the limit-cycle oscillations to the "apoptotic" steady state is enabled by the existence of a subcritical Neimark-Sacker bifurcation in which the limit cycle loses its stability by merging with an unstable invariant torus. Our analysis provides an explanation why cancer cell lines known to have vastly diverse expression levels of Wip1 and PTEN exhibit a broad spectrum of responses to DNA damage: from a fast transition to a high level of p53 killer (a p53 phosphoform which promotes commitment to apoptosis) in cells characterized by high PTEN and low Wip1 levels to long-lasting p53 level oscillations in cells having PTEN promoter methylated (as in, e.g., MCF-7 cell line). PMID:26928575

  13. Feedbacks, Bifurcations, and Cell Fate Decision-Making in the p53 System

    PubMed Central

    Bogdał, Marta N.; Lipniacki, Tomasz

    2016-01-01

    The p53 transcription factor is a regulator of key cellular processes including DNA repair, cell cycle arrest, and apoptosis. In this theoretical study, we investigate how the complex circuitry of the p53 network allows for stochastic yet unambiguous cell fate decision-making. The proposed Markov chain model consists of the regulatory core and two subordinated bistable modules responsible for cell cycle arrest and apoptosis. The regulatory core is controlled by two negative feedback loops (regulated by Mdm2 and Wip1) responsible for oscillations, and two antagonistic positive feedback loops (regulated by phosphatases Wip1 and PTEN) responsible for bistability. By means of bifurcation analysis of the deterministic approximation we capture the recurrent solutions (i.e., steady states and limit cycles) that delineate temporal responses of the stochastic system. Direct switching from the limit-cycle oscillations to the “apoptotic” steady state is enabled by the existence of a subcritical Neimark—Sacker bifurcation in which the limit cycle loses its stability by merging with an unstable invariant torus. Our analysis provides an explanation why cancer cell lines known to have vastly diverse expression levels of Wip1 and PTEN exhibit a broad spectrum of responses to DNA damage: from a fast transition to a high level of p53 killer (a p53 phosphoform which promotes commitment to apoptosis) in cells characterized by high PTEN and low Wip1 levels to long-lasting p53 level oscillations in cells having PTEN promoter methylated (as in, e.g., MCF-7 cell line). PMID:26928575

  14. Examining vegetation feedbacks on global warming in the Community Earth System Model

    NASA Astrophysics Data System (ADS)

    Pu, Bing; Dickinson, Robert E.

    2012-10-01

    Leaves close their stomates in response to increases of CO2. Such a rapid physiological response is included in the land component of comprehensive climate models. However, observational studies have shown that they can further close their stomates as a consequence of "down-regulation," further reducing canopy conductance. However, they may also increase the area of their leaves, hence increasing their canopy conductance. Changes of canopy conductance change surface ET, a reduction leading to surface warming. A simulation considering these mechanisms of modifying canopy conductance is carried out for the assumption of a doubled atmospheric CO2concentration, using the Community Earth System model. It finds that down-regulation as formulated in previous studies could have as large a warming impact on land temperatures as the standard leaf physiological response. Increases in LAI, if they were to occur, appear to have but a small cooling effect. The reduction of latent cooling in the model is amplified by a reduction of low-level cloud cover, hence enhanced net absorption of solar radiation. Reduction of low level cloudiness appears to be necessary to maintain global radiation balance as reported in a previous study. Over mid to high latitudes, decreases in surface albedo associated with reduced snow cover also contribute to amplifying the warming. The physiological feedbacks of leaf stomates in the simulation increase warming by 0.6 ± 0.2°C over land and 0.3 ± 0.1°C globally, not inconsistent with previous studies. Enhanced interhemispheric temperature differences weaken the southward shift of the ITCZ associated with CO2radiative warming. Regions with relatively high LAI tend to have greater vegetation feedback; but increases in large-scale precipitation may weaken this local warming effect.

  15. Student Feedback Systems in Higher Education: A Focused Literature Review and Environmental Scan

    ERIC Educational Resources Information Center

    Alderman, Lyn; Towers, Stephen; Bannah, Sylvia

    2012-01-01

    In recent times, higher education institutions have paid increasing attention to the views of students to obtain feedback on their experience of learning and teaching through internal surveys. This article reviews research in the field and reports on practices in other Australian universities. Findings demonstrate that while student feedback is…

  16. Learning from adaptive neural dynamic surface control of strict-feedback systems.

    PubMed

    Wang, Min; Wang, Cong

    2015-06-01

    Learning plays an essential role in autonomous control systems. However, how to achieve learning in the nonstationary environment for nonlinear systems is a challenging problem. In this paper, we present learning method for a class of n th-order strict-feedback systems by adaptive dynamic surface control (DSC) technology, which achieves the human-like ability of learning by doing and doing with learned knowledge. To achieve the learning, this paper first proposes stable adaptive DSC with auxiliary first-order filters, which ensures the boundedness of all the signals in the closed-loop system and the convergence of tracking errors in a finite time. With the help of DSC, the derivative of the filter output variable is used as the neural network (NN) input instead of traditional intermediate variables. As a result, the proposed adaptive DSC method reduces greatly the dimension of NN inputs, especially for high-order systems. After the stable DSC design, we decompose the stable closed-loop system into a series of linear time-varying perturbed subsystems. Using a recursive design, the recurrent property of NN input variables is easily verified since the complexity is overcome using DSC. Subsequently, the partial persistent excitation condition of the radial basis function NN is satisfied. By combining a state transformation, accurate approximations of the closed-loop system dynamics are recursively achieved in a local region along recurrent orbits. Then, the learning control method using the learned knowledge is proposed to achieve the closed-loop stability and the improved control performance. Simulation studies are performed to demonstrate the proposed scheme can not only reuse the learned knowledge to achieve the better control performance with the faster tracking convergence rate and the smaller tracking error but also greatly alleviate the computational burden because of reducing the number and complexity of NN input variables. PMID:25069127

  17. Computation of optimal output-feedback compensators for linear time-invariant systems

    NASA Technical Reports Server (NTRS)

    Platzman, L. K.

    1972-01-01

    The control of linear time-invariant systems with respect to a quadratic performance criterion was considered, subject to the constraint that the control vector be a constant linear transformation of the output vector. The optimal feedback matrix, f*, was selected to optimize the expected performance, given the covariance of the initial state. It is first shown that the expected performance criterion can be expressed as the ratio of two multinomials in the element of f. This expression provides the basis for a feasible method of determining f* in the case of single-input single-output systems. A number of iterative algorithms are then proposed for the calculation of f* for multiple input-output systems. For two of these, monotone convergence is proved, but they involve the solution of nonlinear matrix equations at each iteration. Another is proposed involving the solution of Lyapunov equations at each iteration, and the gradual increase of the magnitude of a penalty function. Experience with this algorithm will be needed to determine whether or not it does, indeed, possess desirable convergence properties, and whether it can be used to determine the globally optimal f*.

  18. The amazing evolutionary dynamics of non-linear optical systems with feedback

    NASA Astrophysics Data System (ADS)

    Yaroslavsky, Leonid

    2013-09-01

    Optical systems with feedback are, generally, non-linear dynamic systems. As such, they exhibit evolutionary behavior. In the paper we present results of experimental investigation of evolutionary dynamics of several models of such systems. The models are modifications of the famous mathematical "Game of Life". The modifications are two-fold: "Game of Life" rules are made stochastic and mutual influence of cells is made spatially non-uniform. A number of new phenomena in the evolutionary dynamics of the models are revealed: - "Ordering of chaos". Formation, from seed patterns, of stable maze-like patterns with chaotic "dislocations" that resemble natural patterns, such as skin patterns of some animals and fishes, see shell, fingerprints, magnetic domain patterns and alike, which one can frequently find in the nature. These patterns and their fragments exhibit a remarkable capability of unlimited growth. - "Self-controlled growth" of chaotic "live" formations into "communities" bounded, depending on the model, by a square, hexagon or octagon, until they reach a certain critical size, after which the growth stops. - "Eternal life in a bounded space" of "communities" after reaching a certain size and shape. - "Coherent shrinkage" of "mature", after reaching a certain size, "communities" into one of stable or oscillating patterns preserving in this process isomorphism of their bounding shapes until the very end.

  19. Modelling diffusion feedbacks between technology performance, cost and consumer behaviour for future energy-transport systems

    NASA Astrophysics Data System (ADS)

    Tran, Martino; Brand, Christian; Banister, David

    2014-04-01

    Emerging technologies will have important impacts on sustainability objectives. Yet little is known about the explicit feedbacks between consumer behaviour and technological change, and the potential impact on mass market penetration. We use the UK as a case-study to explore the dynamic interactions between technology supply, performance, cost, and heterogeneous consumer behaviour and the resulting influence on long term market diffusion. Simulations of competing vehicle technologies indicate that petrol hybrids (HEVs) dominate the market over the long-term because they benefit from improved performance and are able to reach the steep part of the diffusion curve by 2025 while competing technologies remain in the early stages of growth and are easier to displace in the market. This is due to the cumulative build-up of stock and slow fleet turnover creating inertia in the technological system. Consequently, it will be difficult to displace incumbent technologies because of system inertia, cumulative growth in stock, long operational life, and consumer risk aversion to new unproven technologies. However, when accounting for both technological and behavioural change, simulations indicate that if investment can reach 30-40% per annum growth in supply, combined with steady technology improvements, and more sophisticated agent decision making such as accounting for full technology lifecycle cost and performance, full battery electric vehicles could displace the incumbent system by 2050.

  20. 'Hybrid-PLEMO', rehabilitation system for upper limbs with active / passive force feedback mode.

    PubMed

    Kikuchi, Takehito; Jin, Ying; Fukushima, Kazuki; Akai, Hiroki; Furusho, Junji

    2008-01-01

    Several rehabilitation robots for upper limbs have been proposed so far, and clinical effectiveness was reported in several studies for the aged people or patients with stroke. However most of them have only 2-DOF for its active motion. It is important for designing a rehabilitation system which trains in the 3-DOF space because the upper limbs of humans works in 3-DOF space even expect for the wrist. We developed the quasi 3-DOF rehabilitation system which has 2-DOF force-feedback function in working plane but its working plane can be adjusted the inclination. And we named it Hybrid-PLEMO for it can be switched between active type and passive type. Hybrid-PLEMO is a compact, low-cost rehabilitation system for upper limbs with high safety by using ER brakes or ER actuators. Additionally, in Hybrid-PLEMO, we take direct-drive linkage mechanism by adding sub links. In this paper, we describe the mechanism and haptic control of Hybrid-PLEMO. PMID:19163078

  1. A general non-equilibrium framework for the parameterization of positive and negative feedbacks in atmospheric systems

    NASA Astrophysics Data System (ADS)

    Garrett, T. J.

    2012-12-01

    For any identifiable system, regardless of its complexity or scale, evolution can be treated as a spontaneous thermodynamic response to a local convergence of down-gradient material flows. In climate studies, examples of identifiable systems might include cloud cover or the global incidence of temperatures warmer than a certain threshold. Here it is shown how the time-dependent evolution of such systems is constrained by positive and negative feedbacks that fall into a few mathematically distinct modes. In general, evolution depends on the time integral of past flows and the current availability of material and energetic resources. More specifically, negative feedbacks arise from the depletion or predation of the material and potential energy reservoirs that supply the system. Positive feedbacks are due to either new reservoir "discovery" or system expansion into existing reservoirs. When positive feedbacks dominate, the time dependent response of system growth falls into a few clearly identifiable behaviors that include a law of diminishing returns, logistic behavior, and, if reservoirs are expanding very rapidly, unstable super-exponential or explosive growth. For open systems (e.g. radiative flows in our atmosphere) that have a resolved sink as well as a source, oscillatory behavior emerges and can be characterized in terms of a slightly modified form of the predator-prey equations commonly employed in ecology. The perturbation formulation of these equations is equivalent to a damped simple harmonic oscillator. Specific examples of non-equilibrium positive and negative feedback response can be described for the sudden development of rain and the oscillatory evolution of open-celled stratocumulus cloud decks.

  2. Suppressing decoherence and improving entanglement by quantum-jump-based feedback control in two-level systems

    SciTech Connect

    Hou, S. C.; Huang, X. L.; Yi, X. X.

    2010-07-15

    We study the quantum-jump-based feedback control on the entanglement shared between two qubits with one of them subject to decoherence while the other qubit is under the control. This situation is very relevant to a quantum system consisting of nuclear and electron spins in solid states. The possibility of prolonging the coherence time of the dissipative qubit is also explored. Numerical simulations show that the quantum-jump-based feedback control can improve the entanglement between the qubits and prolong the coherence time for the qubit subject directly to decoherence.

  3. A feedback control loop for autonomous time synchronisation for mobile satellite systems, including satellites in any Earth orbit

    NASA Astrophysics Data System (ADS)

    Soprano, C.

    This paper presents the preliminary results of the design, analysis and simulation of a feedback control-loop for application to autonomous epoch synchronization in a satellite mobile synchronous communications system which includes communications satellites in non-geostationary Earth orbits and fast-moving mobile users.

  4. Development of a Media Driven Online Assessment System: Improving Quality, Frequency, and Deployment of Grades and Feedback in Higher Education

    ERIC Educational Resources Information Center

    Jaurez, James J.

    2013-01-01

    Information communication technologies (ICT) in education is an expanding field, and within this field there is a need for development of effective systems for faculty and learners to communicate feedback and assess performance. The increasing migration of many academic disciplines and courses to an online format has prompted an increased need for…

  5. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Markov Quantum Feedback Control Based on Homodyne Measurement of a Two-Qubit System

    NASA Astrophysics Data System (ADS)

    Zhu, Jing-Min; Wang, Shun-Jin

    2010-09-01

    We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is (i) to solve the feedback-modified master equation, (ii) to demonstrate the ability of feedback control based on the solutions, and (iii) to pick out different steady states by choosing different driving strengths and feedback strengths to counteract the effects of both damping and the measurement back-action on the system. We further investigate some properties of the equilibrium steady state, its distribution probability and entanglement vs. the driving and feedback amplitudes. We find that in our feedback model feedback plays a negative role in producing entanglement.

  6. Force feedback system using magneto-rheological fluids for telerobotic surgery

    NASA Astrophysics Data System (ADS)

    Neelakantan, Vijay A.; Washington, Gregory N.; Wolf, Randall K.

    2002-07-01

    Force feedback is a new technology that has great potential in human-machine interfaces. While guiding the end effector of a robot through an environment using a hand-held actuator, force feedback is needed to make the user feel the environment conditions like stiffness along which the end effector moves. This along with the already available visual feedback will allow the user to guide the robot exactly along the path that he or she intends thereby enhancing the performance. Easily controllable actuators that give quick response at the user end are needed here. This paper demonstrates the effectiveness of MR fluid devices in such force feedback applications. The force-feedback experiment includes a simple setup that depicts a typical situation wherein a user controls the movement of an external linear hydraulic actuator using a MR sponge damper. Force and displacement sensors sense the environment conditions along which the end effector of the hydraulic actuator moves. This information is then used to control the MR damper to provide appropriate force feedback to the user. The setup is tested with different environments like springs with various stiffnesses and for extreme cases with mechanical stops thereby demonstrating the flexibility in using MR sponge dampers for various force feedback applications.

  7. Kuiper Airborne Observatory's Telescope Stabilization System: Disturbance Sensitivity Reduction Via Velocity Loop Feedback

    NASA Technical Reports Server (NTRS)

    Lawrence, David P.; Tsui, K. C.; Tucker, John; Mancini, Ronald E. (Technical Monitor)

    1995-01-01

    In July of 1994 the Kuiper Airborne Observatory's (KAO) Telescope Stabilization System (TSS) was upgraded to meet performance goals necessary to view the Shoemaker-Levy 9 comet collision with Jupiter. The KAO is a modified C-141 Aircraft supporting a 36 inch Infrared telescope used to gather and analyze astronomical data. Before the upgrade, the TSS exhibited approximately a 10 arc-second resolution pointing accuracy. The majority of the inaccuracy was attributable to aircraft vibration and wind buffeting entering through the aircraft's telescope door opening; in other words, the TSS was overly sensitive to external disturbances. Because of power limitations and noise requirements, improving the pointing accuracy of the telescope required more sophistication than simply raising the bandwidth as some classical control strategies might suggest. Instead, relationships were developed between the disturbance sensitivity and closed loop transfer functions. These relationships suggested that employing velocity feedback along with an increase in current loop gain would dramatically improve the pointing resolution of the TSS by decreasing the control system's sensitivity to external disturbances. With the implementation of some classical control techniques and the above philosophy, the KAO's TSS's resolution was improved to approximately 2-3 arc-seconds.

  8. The P0 feedback control system blurs the line between IOC and FPGA.

    SciTech Connect

    DiMonte, N.; APS Engineering Support Division

    2008-01-01

    The P0 Feedback system is a new design at the Advanced Photon Source (APS) primarily intended to stabilize a single bunch in order to operate at a higher accumulated charge. The algorithm for this project required a high-speed DSP solution for a single channel that would make adjustments on a turn-by-turn basis. A field programmable gate array (FPGA) solution was selected that not only met the requirements of the project but far exceeded them. By using a single FPGA, we were able to adjust up to 324 bunches on two separate channels with a total computational time of {approx} 6 x 10{sup 9} multiply- accumulate operations per second. The IOC is a Coldfire CPU tightly coupled to the FPGA, providing dedicated control and monitoring of the system through EPICS [1] process variables. One of the benefits of this configuration is having a four-channel scope in the FPGA that can be monitored on a continuous basis.

  9. Data-driven output-feedback fault-tolerant L2 control of unknown dynamic systems.

    PubMed

    Wang, Jun-Sheng; Yang, Guang-Hong

    2016-07-01

    This paper studies the data-driven output-feedback fault-tolerant L2-control problem for unknown dynamic systems. In a framework of active fault-tolerant control (FTC), three issues are addressed, including fault detection, controller reconfiguration for optimal guaranteed cost control, and tracking control. According to the data-driven form of observer-based residual generators, the system state is expressed in the form of the measured input-output data. On this basis, a model-free approach to L2 control of unknown linear time-invariant (LTI) discrete-time plants is given. To achieve tracking control, a design method for a pre-filter is also presented. With the aid of the aforementioned results and the input-output data-based time-varying value function approximation structure, a data-driven FTC scheme ensuring L2-gain properties is developed. To illustrate the effectiveness of the proposed methodology, two simulation examples are employed. PMID:27178710

  10. Error-based autofocus system using image feedback in a liquid-filled diaphragm lens

    NASA Astrophysics Data System (ADS)

    Abdullah, Soran J.; Ratnam, Mani Maran; Samad, Zahurin

    2009-12-01

    A liquid-filled diaphragm (LFD) lens system that uses image feedback for automatic focus control has been designed and developed. The edge slope width (ESW) of the pixel intensity profile across a binary target was selected as the focus measure parameter. An algorithm was developed to achieve single- and dual-direction autofocus control. An improved autofocus method, which is based on the error between the expected ESW value for a focused image and the ESW value for the current (unfocused) image, was introduced to improve the performance of the system. An empirical equation of the focus measure error was used to predict the number of autofocus operation steps required to approach a near-focus region. A stepper motor was used for actuating a syringe-driven pump mechanism that injects or withdraws fluid into (or out of) the fluid lens chamber. The lens diaphragm was made of polydimethylsiloxane (PDMS) polymer that covers the fluid chamber. A monochrome CCD camera was attached to the LFD lens to capture live images of the target. The autofocus experiments carried out using the new differential error-based algorithm proved the viability of the algorithm in determining the near-focus region. A maximum reduction of time operation was also recorded to be 40 s in comparison with the normal autofocus algorithm.

  11. Focused ultrasound thermal therapy system with ultrasound image guidance and temperature measurement feedback.

    PubMed

    Lin, Kao-Han; Young, Sun-Yi; Hsu, Ming-Chuan; Chan, Hsu; Chen, Yung-Yaw; Lin, Win-Li

    2008-01-01

    In this study, we developed a focused ultrasound (FUS) thermal therapy system with ultrasound image guidance and thermocouple temperature measurement feedback. Hydraulic position devices and computer-controlled servo motors were used to move the FUS transducer to the desired location with the measurement of actual movement by linear scale. The entire system integrated automatic position devices, FUS transducer, power amplifier, ultrasound image system, and thermocouple temperature measurement into a graphical user interface. For the treatment procedure, a thermocouple was implanted into a targeted treatment region in a tissue-mimicking phantom under ultrasound image guidance, and then the acoustic interference pattern formed by image ultrasound beam and low-power FUS beam was employed as image guidance to move the FUS transducer to have its focal zone coincident with the thermocouple tip. The thermocouple temperature rise was used to determine the sonication duration for a suitable thermal lesion as a high power was turned on and ultrasound image was used to capture the thermal lesion formation. For a multiple lesion formation, the FUS transducer was moved under the acoustic interference guidance to a new location and then it sonicated with the same power level and duration. This system was evaluated and the results showed that it could perform two-dimensional motion control to do a two-dimensional thermal therapy with a small localization error 0.5 mm. Through the user interface, the FUS transducer could be moved to heat the target region with the guidance of ultrasound image and acoustic interference pattern. The preliminary phantom experimental results demonstrated that the system could achieve the desired treatment plan satisfactorily. PMID:19163216

  12. [A Methane Detection System Using Distributed Feedback Laser at 1 654 nm].

    PubMed

    Li, Bin; Liu, Hui-fang; He, Qi-xin; Zhai, Bing; Pan, Jiao-qing; Zheng, Chuan-tao; Wang, Yi-ding

    2016-01-01

    A methane (CH4) detection system based on tunable diode laser absorption spectroscopy (TDLAS) technique was experimentally demonstrated. A distributed feedback (DFB) laser around 1 654 nm, an open reflective sensing probe and two InGaAs photodiodes were adopted in the system. The electrical part of the system mainly includes the laser temperature control & modulation module and the orthogonal lock-in amplifier module. Temperature and spectrum tests on the DFB laser indicate that, the laser temperature fluctuation can be limited to the range of -0.02-0.02 degrees C, the laser's emitting wavelength varies linearly with the temperature and injection current, and also good operation stability of the laser was observed through experiments. Under a constant working temperature, the center wavelength of the laser is varied linearly by adjusting the driving current. Meanwhile, a 5 kHz sine wave signal and a 10 Hz saw wave signal were provided by the driving circuit for the harmonic extraction purpose. The developed orthogonal lock-in amplifier can extract the If and 2f harmonic signals with the extraction error of 3.55% and 5% respectively. By using the open optical probe, the effective optical pass length was doubled to 40 cm. Gas detection experiment was performed to derive the relation between the harmonic amplitude and the gas concentration. As the concentration increases from 1% to 5%, the amplitudes of the 1f harmonic and the 2f harmonic signal were obtained, and good linear ration between the concentration and the amplitude ratio was observed, which proves the normal function of the developed detection system. This system is capable to detect other trace gases by using relevant DFB lasers. PMID:27228733

  13. Neural cryptography with feedback

    NASA Astrophysics Data System (ADS)

    Ruttor, Andreas; Kinzel, Wolfgang; Shacham, Lanir; Kanter, Ido

    2004-04-01

    Neural cryptography is based on a competition between attractive and repulsive stochastic forces. A feedback mechanism is added to neural cryptography which increases the repulsive forces. Using numerical simulations and an analytic approach, the probability of a successful attack is calculated for different model parameters. Scaling laws are derived which show that feedback improves the security of the system. In addition, a network with feedback generates a pseudorandom bit sequence which can be used to encrypt and decrypt a secret message.

  14. On integral input-to-state stability for a feedback interconnection of parameterised discrete-time systems

    NASA Astrophysics Data System (ADS)

    Noroozi, N.; Khayatian, A.; Ahmadizadeh, S.; Karimi, H. R.

    2016-05-01

    This paper addresses integral input-to-state stability (iISS) for a feedback interconnection of parameterised discrete-time systems involving two subsystems. Particularly, we give a construction for a smooth iISS Lyapunov function for the whole system from the sum of nonlinearly weighted Lyapunov functions of individual subsystems. Motivations for such a construction are given. We consider two main cases. The first one investigates iISS for the whole system when both subsystems are iISS. The second one gives iISS for the interconnected system when one of subsystems is allowed to be input-to-state stable. The approach is also valid for both discrete-time cascades and a feedback interconnection of iISS and static systems. Examples are given to illustrate the effectiveness of the results.

  15. Reliable Control Using Disturbance Observer and Equivalent Transfer Function for Position Servo System in Current Feedback Loop Failure

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kaoru; Nakamura, Taro; Osumi, Hisashi

    A reliable control method is proposed for multiple loop control system. After a feedback loop failure, such as case of the sensor break down, the control system becomes unstable and has a big fluctuation even if it has a disturbance observer. To cope with this problem, the proposed method uses an equivalent transfer function (ETF) as active redundancy compensation after the loop failure. The ETF is designed so that it does not change the transfer function of the whole system before and after the loop failure. In this paper, the characteristic of reliable control system that uses an ETF and a disturbance observer is examined by the experiment that uses the DC servo motor for the current feedback loop failure in the position servo system.

  16. Underspecification-Based Grammatical Feedback Generation Tailored to the Learner's Current Acquisition Level in an e-Learning System for German as Second Language

    ERIC Educational Resources Information Center

    Harbusch, Karin; Cameran, Christel-Joy; Härtel, Johannes

    2014-01-01

    We present a new feedback strategy implemented in a natural language generation-based e-learning system for German as a second language (L2). Although the system recognizes a large proportion of the grammar errors in learner-produced written sentences, its automatically generated feedback only addresses errors against rules that are relevant at…

  17. Implementation and Impact of an Automated Group Monitoring and Feedback System to Promote Hand Hygiene Among Health Care Personnel

    PubMed Central

    Conway, Laurie J.; Riley, Linda; Saiman, Lisa; Cohen, Bevin; Alper, Paul; Larson, Elaine L.

    2015-01-01

    Article-at-a-Glance Background Despite substantial evidence to support the effectiveness of hand hygiene for preventing health care–associated infections, hand hygiene practice is often inadequate. Hand hygiene product dispensers that can electronically capture hand hygiene events have the potential to improve hand hygiene performance. A study on an automated group monitoring and feedback system was implemented from January 2012 through March 2013 at a 140-bed community hospital. Methods An electronic system that monitors the use of sanitizer and soap but does not identify individual health care personnel was used to calculate hand hygiene events per patient-hour for each of eight inpatient units and hand hygiene events per patient-visit for the six outpatient units. Hand hygiene was monitored but feedback was not provided during a six-month baseline period and three-month rollout period. During the rollout, focus groups were conducted to determine preferences for feedback frequency and format. During the six-month intervention period, graphical reports were e-mailed monthly to all managers and administrators, and focus groups were repeated. Results After the feedback began, hand hygiene increased on average by 0.17 events/patient-hour in inpatient units (interquartile range = 0.14, p = .008). In outpatient units, hand hygiene performance did not change significantly. A variety of challenges were encountered, including obtaining accurate census and staffing data, engendering confidence in the system, disseminating information in the reports, and using the data to drive improvement. Conclusions Feedback via an automated system was associated with improved hand hygiene performance in the short term. PMID:25252389

  18. Concepts for the design of a completely active helicopter isolation system using output vector feedback

    NASA Technical Reports Server (NTRS)

    Schulz, G.

    1977-01-01

    The theory of output vector feedback (a few measured quantities) is used to derive completely active oscillation isolation functions for helicopters. These feedback controller concepts are tested with various versions of the BO 105 helicopter and their performance is demonstrated. A compensation of the vibrational excitations from the rotor and harmonics of the number of blades are considered. There is also a fast and automatic trim function for maneuvers.

  19. Arctic Hydrology and the role of feedbacks in the climate system (Invited)

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.

    2009-12-01

    The effects of a warming climate on the terrestrial regions of the Arctic are already quite apparent and impacts to the hydrologic system are also quite evident. The broadest impacts to the terrestrial arctic regions will result through consequent effects of changing permafrost structure and extent. As the climate differentially warms in summer and winter, the permafrost will become warmer, the active layer (the layer of soil above the permafrost that annually experiences freeze and thaw) will become thicker, the lower boundary of permafrost will become shallower and permafrost extent will decrease in area. These simple structural changes will affect every aspect of the surface water and energy balances and local ecology. Surface moisture and surface temperature are the main driving variables in local terrestrial and atmospheric linkages. Surface temperature is the linchpin in energy fluxes since it links atmospheric thermal gradients, forcing convective heat transfer, with the subsurface thermal gradients, driving conductive heat transfer. Soil moisture exerts a strong influence upon energy fluxes through controls on evaporative heat flux, phase change in thawing of permafrost, and indirect effects on thermal conductivity. In order to understand and predict ecosystem responses to a changing climate and the resultant feedbacks, it is critical to quantify the dynamic interactions of soil moisture and temperature with changes in permafrost as a function of climatic processes, landscape type, and vegetation. In future climate scenarios, the Arctic is expected to be warmer, and experience greater precipitation. With the lengthening of the summer season, however, more of this precipitation will occur as rain. The periods of potential evaporation, and transpiration will also increase. Oddly enough, even now, the Arctic may be considered a desert. The vast wetlands that cover large portions of Alaska, Canada and Siberia exist because permafrost prevents soil moisture and

  20. Acceleration feedback control (AFC) enhanced by disturbance observation and compensation (DOC) for high precision tracking in telescope systems

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Cai, Hua-Xiang; Huang, Yong-Mei; Ge, Liang; Tang, Tao; Su, Yan-Rui; Liu, Xiang; Li, Jin-Ying; He, Dong; Du, Sheng-Ping; Ling, Yu

    2016-08-01

    In this paper, a cascade acceleration feedback control (AFC) enhanced by a disturbance observation and compensation (DOC) method is proposed to improve the tracking precision of telescope systems. Telescope systems usually suffer some uncertain disturbances, such as wind load, nonlinear friction and other unknown disturbances. To ensure tracking precision, an acceleration feedback loop which can increase the stiffness of such a system is introduced. Moreover, to further improve the tracking precision, we introduce the DOC method which can accurately estimate the disturbance and compensate it. Furthermore, the analysis of tracking accuracy used by this method is proposed. Finally, a few comparative experimental results show that the proposed control method has excellent performance for reducing the tracking error of a telescope system.

  1. Polarization and wavelength insensitive optical feedback control systems for stabilizing CO2 lasers

    NASA Astrophysics Data System (ADS)

    Jebali, M. A.

    2016-03-01

    Power scaling of multi-kilowatt fiber lasers has been driving the development of glass and fiber processing technology. Designed for processing of large diameter fibers, this technology is used for the fabrication of fiber-based components such as end-pump and side pump combiners, large diameter endcaps, ball lenses for collimators and focusers… The use of 10.6um CO2 lasers as a heating element provides incomparable flexibility, process control and repeatability when compared to conventional heating methods. This low maintenance technology provides an accurate, adjustable and uniform heating area by absorption of fused silica of the 10.6m laser radiation. However, commercially available CO2 lasers can experience power, polarization and mode instability, which becomes important at 20W levels and higher of output power. This paper presents a polarization and wavelength insensitive optical feedback control system for stabilizing commercially available CO2 lasers. Less than 1% power fluctuation was achieved at different laser power levels, ranging from as 5 to 40W.

  2. Through-wafer optical probe characterization for microelectromechanical systems positional state monitoring and feedback control

    NASA Astrophysics Data System (ADS)

    Dawson, Jeremy M.; Chen, Jingdong; Brown, Kolin S.; Famouri, Parviz F.; Hornak, Lawrence A.

    2000-12-01

    Implementation of closed-loop microelectromechanical system (MEMS) control enables mechanical microsystems to adapt to the demands of the environment that they are actuating, opening a broad range of new opportunities for future MEMS applications. Integrated optical microsystems have the potential to enable continuous in situ optical interrogation of MEMS microstructure position fully decoupled from the means of mechanical actuation that is necessary for realization of feedback control. We present the results of initial research evaluating through-wafer optical microprobes for surface micromachined MEMS integrated optical position monitoring. Results from the through-wafer free-space optical probe of a lateral comb resonator fabricated using the multiuser MEMS process service (MUMPS) indicate significant positional information content with an achievable return probe signal dynamic range of up to 80% arising from film transmission contrast. Static and dynamic deflection analysis and experimental results indicate a through-wafer probe positional signal sensitivity of 40 mV/micrometers for the present setup or 10% signal change per micrometer. A simulation of the application of nonlinear sliding control is presented illustrating position control of the lateral comb resonator structure given the availability of positional state information.

  3. Intrinsic Negative Feedback Governs Activation Surge in Two-Component Regulatory Systems

    PubMed Central

    Yeo, Won-Sik; Zwir, Igor; Huang, Henry V.; Shin, Dongwoo; Kato, Akinori; Groisman, Eduardo A.

    2013-01-01

    SUMMARY PhoP and PhoQ comprise a two-component system in the bacterium Salmonella enterica. PhoQ is the sensor kinase/phosphatase that modifies the phosphorylation state of the regulator PhoP in response to stimuli. The amount of phosphorylated PhoP surges after activation, then declines to reach a steady-state level. We now recapitulate this surge in vitro by incubating PhoP and PhoQ with ATP and ADP. Mathematical modeling identified PhoQ’s affinity for ADP as the key parameter dictating phosphorylated PhoP levels, as ADP promotes PhoQ’s phosphatase activity toward phosphorylated PhoP. The lid covering the nucleotide-binding pocket of PhoQ governs the kinase to phosphatase switch because a lid mutation that decreased ADP binding compromised PhoQ’s phosphatase activity in vitro and resulted in sustained expression of PhoP-dependent mRNAs in vivo. This feedback mechanism may curtail futile ATP consumption because ADP not only stimulates PhoQ’s phosphatase activity but also inhibits ATP binding necessary for the kinase reaction. PMID:22325356

  4. Dominant pole and eigenstructure assignment for positive systems with state feedback

    NASA Astrophysics Data System (ADS)

    Li, Zhao; Lam, James

    2016-09-01

    In this paper, the dominant pole assignment problem, the dominant eigenstructure assignment problem and the robust dominant pole assignment problem for linear time-invariant positive systems with state feedback are considered. The dominant pole assignment problem is formulated as a linear programming problem, and the dominant eigenstructure problem is formulated as a quasiconvex optimisation problem with linear constraints. The robust dominant pole assignment problem is formulated as a non-convex optimisation problem with non-linear constraints which is solved using particle swarm optimisation (PSO) with an efficient scheme which employs the dominant eigenstructure assignment technique to accelerate the convergence of the PSO procedure. Each of the three problems can be further constrained by requiring that the controller has a pre-specified structure, or the gain matrix have both elementwise upper and lower bounds. These constraints can be incorporated into the proposed scheme without increasing the complexity of the algorithms. Both the continuous-time case and the discrete-time case are treated in the paper.

  5. SOS based robust H(∞) fuzzy dynamic output feedback control of nonlinear networked control systems.

    PubMed

    Chae, Seunghwan; Nguang, Sing Kiong

    2014-07-01

    In this paper, a methodology for designing a fuzzy dynamic output feedback controller for discrete-time nonlinear networked control systems is presented where the nonlinear plant is modelled by a Takagi-Sugeno fuzzy model and the network-induced delays by a finite state Markov process. The transition probability matrix for the Markov process is allowed to be partially known, providing a more practical consideration of the real world. Furthermore, the fuzzy controller's membership functions and premise variables are not assumed to be the same as the plant's membership functions and premise variables, that is, the proposed approach can handle the case, when the premise of the plant are not measurable or delayed. The membership functions of the plant and the controller are approximated as polynomial functions, then incorporated into the controller design. Sufficient conditions for the existence of the controller are derived in terms of sum of square inequalities, which are then solved by YALMIP. Finally, a numerical example is used to demonstrate the validity of the proposed methodology. PMID:24108002

  6. Methane leakage from evolving petroleum systems: Masses, rates and inferences for climate feedback

    NASA Astrophysics Data System (ADS)

    Berbesi, L. A.; di Primio, R.; Anka, Z.; Horsfield, B.; Wilkes, H.

    2014-02-01

    The immense mass of organic carbon contained in sedimentary systems, currently estimated at 1.56×1010 Tg (Des Marais et al., 1992), bears the potential of affecting global climate through the release of thermally or biologically generated methane to the atmosphere. Here we investigate the potential of naturally-occurring gas leakage, controlled by petroleum generation and degradation as a forcing mechanism for climate at geologic time scales. We addressed the potential methane contributions to the atmosphere during the evolution of petroleum systems in two different, petroliferous geological settings: the Western Canada Sedimentary Basin (WCSB) and the Central Graben area of the North Sea. Besides 3D numerical simulation, different types of mass balance and theoretical approaches were applied depending on the data available and the processes taking place in each basin. In the case of the WCSB, we estimate maximum thermogenic methane leakage rates in the order of 10-2-10-3 Tg/yr, and maximum biogenic methane generation rates of 10-2 Tg/yr. In the case of the Central Graben, maximum estimates for thermogenic methane leakage are in the order in 10-3 Tg/yr. Extrapolation of our results to a global scale suggests that, at least as a single process, thermal gas generation in hydrocarbon kitchen areas would not be able to influence climate, although it may contribute to a positive feedback. Conversely, only the sudden release of subsurface methane accumulations, formed over geologic timescales, can possibly allow for petroleum systems to exert an effect on climate.

  7. Global output regulation of a class of lower triangular nonlinear systems with unknown control direction via output feedback

    NASA Astrophysics Data System (ADS)

    Li, Ranran

    2016-05-01

    In this paper, we study the global output regulation problem of a class of lower triangular systems under measurement output feedback. A novel high-gain filter is proposed to estimate the unmeasured states of the systems. Furthermore, we integrate the robust stabilisation technique and Nussbaumgain technique to achieve asymptotic regulation when the control direction is unknown. The simulation results illustrate the effectiveness of the proposed method.

  8. Experimental study on active vibration control using genetic algorithm-based system identification and optimized positive position feedback

    NASA Astrophysics Data System (ADS)

    Orszulik, Ryan R.; Shan, Jinjun

    2012-12-01

    A genetic algorithm is implemented to identify the transfer function of an experimental system consisting of a flexible manipulator with a collocated piezoelectric sensor/actuator pair. A multi-mode positive position feedback controller is then designed based upon the identified transfer function. To this end, the same iteratively implemented genetic algorithm is used to optimize all controller parameters by minimization of the closed loop H∞-norm. The designed controller is then applied for vibration suppression on the experimental system.

  9. Coordination of the Arc Regulatory System and Pheromone-Mediated Positive Feedback in Controlling the Vibrio fischeri lux Operon

    PubMed Central

    Septer, Alecia N.; Stabb, Eric V.

    2012-01-01

    Bacterial pheromone signaling is often governed both by environmentally responsive regulators and by positive feedback. This regulatory combination has the potential to coordinate a group response among distinct subpopulations that perceive key environmental stimuli differently. We have explored the interplay between an environmentally responsive regulator and pheromone-mediated positive feedback in intercellular signaling by Vibrio fischeri ES114, a bioluminescent bacterium that colonizes the squid Euprymna scolopes. Bioluminescence in ES114 is controlled in part by N-(3-oxohexanoyl)-L-homoserine lactone (3OC6), a pheromone produced by LuxI that together with LuxR activates transcription of the luxICDABEG operon, initiating a positive feedback loop and inducing luminescence. The lux operon is also regulated by environmentally responsive regulators, including the redox-responsive ArcA/ArcB system, which directly represses lux in culture. Here we show that inactivating arcA leads to increased 3OC6 accumulation to initiate positive feedback. In the absence of positive feedback, arcA-mediated control of luminescence was only ∼2-fold, but luxI-dependent positive feedback contributed more than 100 fold to the net induction of luminescence in the arcA mutant. Consistent with this overriding importance of positive feedback, 3OC6 produced by the arcA mutant induced luminescence in nearby wild-type cells, overcoming their ArcA repression of lux. Similarly, we found that artificially inducing ArcA could effectively repress luminescence before, but not after, positive feedback was initiated. Finally, we show that 3OC6 produced by a subpopulation of symbiotic cells can induce luminescence in other cells co-colonizing the host. Our results suggest that even transient loss of ArcA-mediated regulation in a sub-population of cells can induce luminescence in a wider community. Moreover, they indicate that 3OC6 can communicate information about both cell density and the state of

  10. Evaluating Effectiveness of Modeling Motion System Feedback in the Enhanced Hess Structural Model of the Human Operator

    NASA Technical Reports Server (NTRS)

    Zaychik, Kirill; Cardullo, Frank; George, Gary; Kelly, Lon C.

    2009-01-01

    In order to use the Hess Structural Model to predict the need for certain cueing systems, George and Cardullo significantly expanded it by adding motion feedback to the model and incorporating models of the motion system dynamics, motion cueing algorithm and a vestibular system. This paper proposes a methodology to evaluate effectiveness of these innovations by performing a comparison analysis of the model performance with and without the expanded motion feedback. The proposed methodology is composed of two stages. The first stage involves fine-tuning parameters of the original Hess structural model in order to match the actual control behavior recorded during the experiments at NASA Visual Motion Simulator (VMS) facility. The parameter tuning procedure utilizes a new automated parameter identification technique, which was developed at the Man-Machine Systems Lab at SUNY Binghamton. In the second stage of the proposed methodology, an expanded motion feedback is added to the structural model. The resulting performance of the model is then compared to that of the original one. As proposed by Hess, metrics to evaluate the performance of the models include comparison against the crossover models standards imposed on the crossover frequency and phase margin of the overall man-machine system. Preliminary results indicate the advantage of having the model of the motion system and motion cueing incorporated into the model of the human operator. It is also demonstrated that the crossover frequency and the phase margin of the expanded model are well within the limits imposed by the crossover model.

  11. Reduced-order observer-based output feedback control of nonlinear time-delay systems with prescribed performance

    NASA Astrophysics Data System (ADS)

    Hua, Changchun; Zhang, Liuliu; Guan, Xinping

    2016-04-01

    This paper studies the problem of output feedback control for a class of nonlinear time-delay systems with prescribed performance. The system is in the form of triangular structure with unmodelled dynamics. First, we introduce a reduced-order observer to provide the estimate of the unmeasured states. Then, by setting a new condition with the performance function, we design the state transformation with prescribed performance control. By employing backstepping method, we construct the output feedback controller. It is proved that the resulting closed-loop system is asymptotically stable and both transient and steady-state performance of the output are preserved with the changing supply function idea. Finally, a simulation example is conducted to show the effectiveness of the main results.

  12. Online adaptive policy learning algorithm for H∞ state feedback control of unknown affine nonlinear discrete-time systems.

    PubMed

    Zhang, Huaguang; Qin, Chunbin; Jiang, Bin; Luo, Yanhong

    2014-12-01

    The problem of H∞ state feedback control of affine nonlinear discrete-time systems with unknown dynamics is investigated in this paper. An online adaptive policy learning algorithm (APLA) based on adaptive dynamic programming (ADP) is proposed for learning in real-time the solution to the Hamilton-Jacobi-Isaacs (HJI) equation, which appears in the H∞ control problem. In the proposed algorithm, three neural networks (NNs) are utilized to find suitable approximations of the optimal value function and the saddle point feedback control and disturbance policies. Novel weight updating laws are given to tune the critic, actor, and disturbance NNs simultaneously by using data generated in real-time along the system trajectories. Considering NN approximation errors, we provide the stability analysis of the proposed algorithm with Lyapunov approach. Moreover, the need of the system input dynamics for the proposed algorithm is relaxed by using a NN identification scheme. Finally, simulation examples show the effectiveness of the proposed algorithm. PMID:25095274

  13. A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-VLLC integration

    NASA Astrophysics Data System (ADS)

    Tsai, Wen-Shing; Lu, Hai-Han; Li, Chung-Yi; Chen, Bo-Rui; Lin, Hung-Hsien; Lin, Dai-Hua

    2016-04-01

    A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-visible laser light communication (VLLC) integration is proposed and experimentally demonstrated. To be the first one of its kind in employing light injection and optoelectronic feedback techniques in a fiber-VLLC integration lightwave transmission system, the light is successfully directly modulated with Community Access Television (CATV), 16-QAM, and 16-QAM-OFDM signals. Over a 40 km SMF and a 10 m free-space VLLC transport, good performances of carrier-to-noise ratio (CNR)/composite second-order (CSO)/composite triple-beat (CTB)/bit error rate (BER) are achieved for CATV/16-QAM/16-QAM-OFDM signals transmission. Such a hybrid lightwave transmission system would be very useful since it can provide broadband integrated services including CATV, Internet, and telecommunication services over both distribute fiber and in-building networks.

  14. Accurate chromatic control and color rendering optimization in LED lighting systems using junction temperature feedback

    NASA Astrophysics Data System (ADS)

    Sisto, Marco Michele; Gauvin, Jonny

    2014-09-01

    Accurate color control of LED lighting systems is a challenging task: noticeable chromaticity shifts are commonly observed in mixed-color and phosphor converted LEDs due to intensity dimming. Furthermore, the emitted color varies with the LED temperature. We present a novel color control method for tri-chromatic and tetra-chromatic LEDs, which enable to set and maintain the LED emission at a target color, or combination of correlated color temperature (CCT) and intensity. The LED color point is maintained over variations in the LED junctions' temperatures and intensity dimming levels. The method does not require color feedback sensors, so to minimize system complexity and cost, but relies on estimation of the LED junctions' temperatures from the junction voltages. If operated with tetra-chromatic LEDs, the method allows meeting an additional optimization criterion: for example, the maximization of a color rendering metric like the Color Rendering Index (CRI) or the Color Quality Scale (CQS), thus providing a high quality and clarity of colors on the surface illuminated by the LED. We demonstrate the control of a RGBW LED at target D65 white point with CIELAB color difference metric triangle;a,bE < 1 for simultaneous variations of flux from approximately 30 lm to 100 lm and LED heat sink temperature from 25°C to 58°C. In the same conditions, we demonstrate a CCT error <1%. Furthermore, the method allows varying the LED CCT from 5500K to 8000K while maintaining luminance within 1% of target. Further work is ongoing to evaluate the stability of the method over LED aging.

  15. Experimental study of a semi-passive ventilation grille with a feedback control system

    NASA Astrophysics Data System (ADS)

    D'Orazio, A.; Fontana, L.; Salata, F.

    2011-08-01

    The diffusion of window frames with low air permeability, due to the energy saving regulations, has implied in several cases the worsening of the indoor microclimate and air quality. On the other hand, air-tight window frames imply uncontrolled and too high air change rates. The mechanical ventilation not always is a practicable solution because of economic reasons and because it implies energy waste. Various Italian and European environmental and energetic laws take into consideration and promote the use of controlled natural ventilation, though this definition is not associated to well defined and tested technical solutions. An adequate solution can be achieved by using semi-passive self adjustable ventilation devices, able to ensure controlled changes of indoor air. In this paper, a semi-passive damper with a feedback control system is proposed and its behavior is investigated by means of experimental study. The presented semi-passive grille allows to control the air flow rate, injected into the room by natural or artificial pressure gradient, more effectively than the usual passive ventilation grilles made available by the present industrial production. However, since the semi-passive grille has a one-way flow, in the natural ventilation of a flat the proper functioning of the system could be ensured with a more complex configuration, with respect to the passive self-regulating grilles, able to limit the flow of fresh air in the presence of high levels of Δp; conversely, it could have widespread use in applications requiring a more accurate control of airflow in case of mechanical ventilation plants.

  16. Feedback Is a Two-Way Street

    ERIC Educational Resources Information Center

    Tovani, Cris

    2012-01-01

    In this article, the author shares her experience that illustrates that the feedback students give is just as important as the feedback they get. For her, the idea that students giving her feedback was more powerful than her giving them feedback sounded too good to be true. If she could come up with a system to regularly collect feedback that did…

  17. Design of multivariable feedback control systems via spectral assignment using reduced-order models and reduced-order observers

    NASA Technical Reports Server (NTRS)

    Mielke, R. R.; Tung, L. J.; Carraway, P. I., III

    1984-01-01

    The feasibility of using reduced order models and reduced order observers with eigenvalue/eigenvector assignment procedures is investigated. A review of spectral assignment synthesis procedures is presented. Then, a reduced order model which retains essential system characteristics is formulated. A constant state feedback matrix which assigns desired closed loop eigenvalues and approximates specified closed loop eigenvectors is calculated for the reduced order model. It is shown that the eigenvalue and eigenvector assignments made in the reduced order system are retained when the feedback matrix is implemented about the full order system. In addition, those modes and associated eigenvectors which are not included in the reduced order model remain unchanged in the closed loop full order system. The full state feedback design is then implemented by using a reduced order observer. It is shown that the eigenvalue and eigenvector assignments of the closed loop full order system rmain unchanged when a reduced order observer is used. The design procedure is illustrated by an actual design problem.

  18. Design of multivariable feedback control systems via spectral assignment using reduced-order models and reduced-order observers

    NASA Technical Reports Server (NTRS)

    Mielke, R. R.; Tung, L. J.; Carraway, P. I., III

    1985-01-01

    The feasibility of using reduced order models and reduced order observers with eigenvalue/eigenvector assignment procedures is investigated. A review of spectral assignment synthesis procedures is presented. Then, a reduced order model which retains essential system characteristics is formulated. A constant state feedback matrix which assigns desired closed loop eigenvalues and approximates specified closed loop eigenvectors is calculated for the reduced order model. It is shown that the eigenvalue and eigenvector assignments made in the reduced order system are retained when the feedback matrix is implemented about the full order system. In addition, those modes and associated eigenvectors which are not included in the reduced order model remain unchanged in the closed loop full order system. The fulll state feedback design is then implemented by using a reduced order observer. It is shown that the eigenvalue and eigenvector assignments of the closed loop full order system remain unchanged when a reduced order observer is used. The design procedure is illustrated by an actual design problem.

  19. Development of the Mayo Investigational Neuromodulation Control System: toward a closed-loop electrochemical feedback system for deep brain stimulation

    PubMed Central

    Chang, Su-Youne; Kimble, Christopher J.; Kim, Inyong; Paek, Seungleal B.; Kressin, Kenneth R.; Boesche, Joshua B.; Whitlock, Sidney V.; Eaker, Diane R.; Kasasbeh, Aimen; Horne, April E.; Blaha, Charles D.; Bennet, Kevin E.; Lee, Kendall H.

    2014-01-01

    Object Conventional deep brain stimulation (DBS) devices continue to rely on an open-loop system in which stimulation is independent of functional neural feedback. The authors previously proposed that as the foundation of a DBS “smart” device, a closed-loop system based on neurochemical feedback, may have the potential to improve therapeutic outcomes. Alterations in neurochemical release are thought to be linked to the clinical benefit of DBS, and fast-scan cyclic voltammetry (FSCV) has been shown to be effective for recording these evoked neurochemical changes. However, the combination of FSCV with conventional DBS devices interferes with the recording and identification of the evoked analytes. To integrate neurochemical recording with neurostimulation, the authors developed the Mayo Investigational Neuromodulation Control System (MINCS), a novel, wirelessly controlled stimulation device designed to interface with FSCV performed by their previously described Wireless Instantaneous Neurochemical Concentration Sensing System (WINCS). Methods To test the functionality of these integrated devices, various frequencies of electrical stimulation were applied by MINCS to the medial forebrain bundle of the anesthetized rat, and striatal dopamine release was recorded by WINCS. The parameters for FSCV in the present study consisted of a pyramidal voltage waveform applied to the carbon-fiber microelectrode every 100 msec, ramping between −0.4 V and +1.5 V with respect to an Ag/AgCl reference electrode at a scan rate of either 400 V/sec or 1000 V/sec. The carbon-fiber microelectrode was held at the baseline potential of −0.4 V between scans. Results By using MINCS in conjunction with WINCS coordinated through an optic fiber, the authors interleaved intervals of electrical stimulation with FSCV scans and thus obtained artifact-free wireless FSCV recordings. Electrical stimulation of the medial forebrain bundle in the anesthetized rat by MINCS elicited striatal dopamine

  20. Changing permafrost in a warming world and feedbacks to the Earth system

    NASA Astrophysics Data System (ADS)

    Grosse, Guido; Goetz, Scott; McGuire, A. Dave; Romanovsky, Vladimir E.; Schuur, Edward A. G.

    2016-04-01

    The permafrost component of the cryosphere is changing dramatically, but the permafrost region is not well monitored and the consequences of change are not well understood. Changing permafrost interacts with ecosystems and climate on various spatial and temporal scales. The feedbacks resulting from these interactions range from local impacts on topography, hydrology, and biology to complex influences on global scale biogeochemical cycling. This review contributes to this focus issue by synthesizing its 28 multidisciplinary studies which provide field evidence, remote sensing observations, and modeling results on various scales. We synthesize study results from a diverse range of permafrost landscapes and ecosystems by reporting key observations and modeling outcomes for permafrost thaw dynamics, identifying feedbacks between permafrost and ecosystem processes, and highlighting biogeochemical feedbacks from permafrost thaw. We complete our synthesis by discussing the progress made, stressing remaining challenges and knowledge gaps, and providing an outlook on future needs and research opportunities in the study of permafrost-ecosystem-climate interactions.

  1. Review and synthesis: Changing permafrost in a warming world and feedbacks to the Earth System

    USGS Publications Warehouse

    Grosse, Guido; Goetz, Scott; McGuire, Anthony; Romanovsky, Vladimir E.; Schuur, Edward A.G.

    2016-01-01

    The permafrost component of the cryosphere is changing dramatically, but the permafrost region is not well monitored and the consequences of change are not well understood. Changing permafrost interacts with ecosystems and climate on various spatial and temporal scales. The feedbacks resulting from these interactions range from local impacts on topography, hydrology, and biology to complex influences on global scale biogeochemical cycling. This review contributes to this focus issue by synthesizing its 28 multidisciplinary studies which provide field evidence, remote sensing observations, and modeling results on various scales. We synthesize study results from a diverse range of permafrost landscapes and ecosystems by reporting key observations and modeling outcomes for permafrost thaw dynamics, identifying feedbacks between permafrost and ecosystem processes, and highlighting biogeochemical feedbacks from permafrost thaw. We complete our synthesis by discussing the progress made, stressing remaining challenges and knowledge gaps, and providing an outlook on future needs and research opportunities in the study of permafrost–ecosystem–climate interactions.

  2. Multi-input control-affine systems static feedback equivalent to a triangular form and their flatness

    NASA Astrophysics Data System (ADS)

    Li, Shunjie; Nicolau, Florentina; Respondek, Witold

    2016-01-01

    In this paper, we give a complete geometric characterisation of systems locally static feedback equivalent to a triangular form compatible with the chained form, for m = 1, respectively with the m-chained form, for m ≥ 2, where the number of controls is m + 1. They are x-flat systems. We provide a system of first-order PDE's to be solved in order to find all x-flat outputs, for m = 1, respectively all minimal x-flat outputs, for m ≥ 2. We illustrate our results by examples, in particular, by an application to a mechanical system: the coin rolling without slipping on a moving table.

  3. Regulation of release factor expression using a translational negative feedback loop: a systems analysis.

    PubMed

    Betney, Russell; de Silva, Eric; Mertens, Christina; Knox, Yvonne; Krishnan, J; Stansfield, Ian

    2012-12-01

    The essential eukaryote release factor eRF1, encoded by the yeast SUP45 gene, recognizes stop codons during ribosomal translation. SUP45 nonsense alleles are, however, viable due to the establishment of feedback-regulated readthrough of the premature termination codon; reductions in full-length eRF1 promote tRNA-mediated stop codon readthrough, which, in turn, drives partial production of full-length eRF1. A deterministic mathematical model of this eRF1 feedback loop was developed using a staged increase in model complexity. Model predictions matched the experimental observation that strains carrying the mutant SUQ5 tRNA (a weak UAA suppressor) in combination with any of the tested sup45(UAA) nonsense alleles exhibit threefold more stop codon readthrough than that of an SUQ5 yeast strain. The model also successfully predicted that eRF1 feedback control in an SUQ5 sup45(UAA) mutant would resist, but not completely prevent, imposed changes in eRF1 expression. In these experiments, the introduction of a plasmid-borne SUQ5 copy into a sup45(UAA) SUQ5 mutant directed additional readthrough and full-length eRF1 expression, despite feedback. Secondly, induction of additional sup45(UAA) mRNA expression in a sup45(UAA) SUQ5 strain also directed increased full-length eRF1 expression. The autogenous sup45 control mechanism therefore acts not to precisely control eRF1 expression, but rather as a damping mechanism that only partially resists changes in release factor expression level. The validated model predicts that the degree of feedback damping (i.e., control precision) is proportional to eRF1 affinity for the premature stop codon. The validated model represents an important tool to analyze this and other translational negative feedback loops. PMID:23104998

  4. Regulation of release factor expression using a translational negative feedback loop: A systems analysis

    PubMed Central

    Betney, Russell; de Silva, Eric; Mertens, Christina; Knox, Yvonne; Krishnan, J.; Stansfield, Ian

    2012-01-01

    The essential eukaryote release factor eRF1, encoded by the yeast SUP45 gene, recognizes stop codons during ribosomal translation. SUP45 nonsense alleles are, however, viable due to the establishment of feedback-regulated readthrough of the premature termination codon; reductions in full-length eRF1 promote tRNA-mediated stop codon readthrough, which, in turn, drives partial production of full-length eRF1. A deterministic mathematical model of this eRF1 feedback loop was developed using a staged increase in model complexity. Model predictions matched the experimental observation that strains carrying the mutant SUQ5 tRNA (a weak UAA suppressor) in combination with any of the tested sup45UAA nonsense alleles exhibit threefold more stop codon readthrough than that of an SUQ5 yeast strain. The model also successfully predicted that eRF1 feedback control in an SUQ5 sup45UAA mutant would resist, but not completely prevent, imposed changes in eRF1 expression. In these experiments, the introduction of a plasmid-borne SUQ5 copy into a sup45UAA SUQ5 mutant directed additional readthrough and full-length eRF1 expression, despite feedback. Secondly, induction of additional sup45UAA mRNA expression in a sup45UAA SUQ5 strain also directed increased full-length eRF1 expression. The autogenous sup45 control mechanism therefore acts not to precisely control eRF1 expression, but rather as a damping mechanism that only partially resists changes in release factor expression level. The validated model predicts that the degree of feedback damping (i.e., control precision) is proportional to eRF1 affinity for the premature stop codon. The validated model represents an important tool to analyze this and other translational negative feedback loops. PMID:23104998

  5. Linear quantum feedback networks

    NASA Astrophysics Data System (ADS)

    Gough, J. E.; Gohm, R.; Yanagisawa, M.

    2008-12-01

    The mathematical theory of quantum feedback networks has recently been developed [J. Gough and M. R. James, e-print arXiv:0804.3442v2] for general open quantum dynamical systems interacting with bosonic input fields. In this article we show, for the special case of linear dynamical Markovian systems with instantaneous feedback connections, that the transfer functions can be deduced and agree with the algebraic rules obtained in the nonlinear case. Using these rules, we derive the transfer functions for linear quantum systems in series, in cascade, and in feedback arrangements mediated by beam splitter devices.

  6. Design procedure for satisfying time domain bounds for nonminimum-phase systems. [feedback control systems

    NASA Technical Reports Server (NTRS)

    Ostheimer, W. D.

    1972-01-01

    Design techniques are presented applicable to nonminimum-phase systems. They are designed to handle plants with one right-half-plane zero which may vary, and any other variation of the plant parameters within known limits. The specifications that must be designed are given as a set of step response bounds in the time domain. A completed design will yield responses that stay within the time domain bounds at all times and utilize the entire region of allowed variation.

  7. Parallel Multistage Decision Feedback Equalizer for Single-Carrier Layered Space-Time Systems in Frequency-Selective Channels

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Wang, Haifeng; Cheng, Shixin; Chen, Ming

    2004-12-01

    Space-time transmission techniques can greatly increase the spectral efficiency. In this paper, a parallel multistage decision feedback equalizer (PMDFE) is proposed for single-carrier layered space-time systems with a fixed cyclic prefix over frequency-selective channels. It is composed of a parallel interference canceller, a multiple-input single-output decision feedback equalizer (MISO-DFE), and a linear combiner. The soft output of the MISO-DFE is linearly combined with the previous tentative soft decision. In addition, an algorithm is proposed to obtain tentative soft and hard decisions for initializing the equalizer. The initializing complexity of the PMDFE is lower than that of MIMO-OFDM. Simulation results show that the PMDFE outperforms MIMO-OFDM and previously existing equalizers for single-carrier layered space-time systems.

  8. Non-fragile H∞ dynamic output feedback control for uncertain Takagi-Sugeno fuzzy systems with time-varying delay

    NASA Astrophysics Data System (ADS)

    Huang, Sheng-Juan; Yang, Guang-Hong

    2016-09-01

    This paper mainly focuses on the problem of non-fragile H∞ dynamic output feedback control for a class of uncertain Takagi-Sugeno fuzzy systems with time-varying state delay. Based on a new type of Lyapunov-Krasovskii functional without ignoring any subtle integral terms in the derivatives, a less conservative dynamic output feedback controller with additive gain variations is designed, which guarantees that the closed-loop fuzzy system is asymptotically stable and satisfies a prescribed H∞-performance level. Furthermore, the obtained parameter-dependent conditions are given in terms of solution to a set of linear matrix inequalities, which improve some existing relevant results. Finally, numerical examples are given to illustrate the effectiveness and merits of the proposed method.

  9. Performance optimization of force feedback control system in virtual vascular intervention surgery.

    PubMed

    Hu, Zhi; Cai, Ping; Qin, Peng; Xie, Le

    2014-01-01

    In virtual surgery of minimally invasive vascular intervention, the force feedback is transmitted through the flexible guide wire. The disturbance caused by the flexible deformation would affect the fidelity of the VR (virtual reality) training. SMC (sliding mode control) strategy with delayed-output observer is adopted to suppress the effect of flexible deformation. In this study, the control performance of the strategy is assessed when the length of guide wire between actuator and the operating point changes. The performance assessment results demonstrate the effectiveness of the proposed method and find the optimal length of guide wire for the force feedback control. PMID:25254063

  10. Performance Optimization of Force Feedback Control System in Virtual Vascular Intervention Surgery

    PubMed Central

    Cai, Ping; Qin, Peng; Xie, Le

    2014-01-01

    In virtual surgery of minimally invasive vascular intervention, the force feedback is transmitted through the flexible guide wire. The disturbance caused by the flexible deformation would affect the fidelity of the VR (virtual reality) training. SMC (sliding mode control) strategy with delayed-output observer is adopted to suppress the effect of flexible deformation. In this study, the control performance of the strategy is assessed when the length of guide wire between actuator and the operating point changes. The performance assessment results demonstrate the effectiveness of the proposed method and find the optimal length of guide wire for the force feedback control. PMID:25254063

  11. Nonlinear Time Delayed Feedback Control of Aeroelastic Systems: A Functional Approach

    NASA Technical Reports Server (NTRS)

    Marzocca, Piergiovanni; Librescu, Liviu; Silva, Walter A.

    2003-01-01

    In addition to its intrinsic practical importance, nonlinear time delayed feedback control applied to lifting surfaces can result in interesting aeroelastic behaviors. In this paper, nonlinear aeroelastic response to external time-dependent loads and stability boundary for actively controlled lifting surfaces, in an incompressible flow field, are considered. The structural model and the unsteady aerodynamics are considered linear. The implications of the presence of time delays in the linear/nonlinear feedback control and of geometrical parameters on the aeroelasticity of lifting surfaces are analyzed and conclusions on their implications are highlighted.

  12. On the periodic coordination of linear stochastic systems. [open-loop and closed-loop feedback optimal control

    NASA Technical Reports Server (NTRS)

    Chong, C.-Y.; Athans, M.

    1975-01-01

    The decentralized stochastic control of a linear dynamic system consisting of several subsystems is considered. A two-level approach is used by the introduction of a coordinator who collects measurements from the local controllers periodically and in return transmits coordinating parameters. Two types of coordination are considered: open-loop feedback and closed loop. The resulting control laws are found to be intuitively attractive.

  13. An Augmented Lecture Feedback System to Support Learner and Teacher Communication

    ERIC Educational Resources Information Center

    Zarraonandia, Telmo; Aedo, Ignacio; Diaz, Paloma; Montero, Alvaro

    2013-01-01

    In this paper, it is advocated that the feedback loop between learners and teachers could be improved by making use of augmented reality (AR) techniques. The bidirectional communication between teacher and learners is sometimes hampered by students' fear of showing themselves up in front of their classmates. In order to overcome this problem,…

  14. Multigroup 3-Dimensional Neutron Diffusion Nodal Code System with Thermohydraulic Feedbacks.

    Energy Science and Technology Software Center (ESTSC)

    1994-02-07

    Version 01 GNOMER is a program which solves the multigroup neutron diffusion equation on coarse mesh in 1D, 2D, and 3D Cartesian geometry. The program is designed to calculate the global core power distributions (with thermohydraulic feedbacks) as well as power distributions and homogenized cross sections over a fuel assembly.

  15. Adult Vocational Education Follow Through. A System for Participant Feedback for Decision Makers. Final Report.

    ERIC Educational Resources Information Center

    White, Thomas R.

    The objectives of this project were (1) to develop participant feedback materials that can be used by local adult vocational education (AVE) administrators for program planning, implementation, and evaluation and (2) to determine why participants enroll in AVE programs. A follow-up survey which contained key items from the follow-through system…

  16. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

    1998-05-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

  17. Formative Feedback Using Pseudo Peer Diagrams: Evaluating System Equilibrium of Buoyancy Forces

    ERIC Educational Resources Information Center

    Li, Sensen

    2013-01-01

    This study introduces an innovative instructional method, called "pseudo peer diagram" (PPD), where students employ executive skills to compare and contrast their work with others' as a formative feedback mechanism. The focus of this study is how students compare and contrast their own diagrams with the pseudo peer diagrams as a stimulus…

  18. A Parallel Relational Database Management System Approach to Relevance Feedback in Information Retrieval.

    ERIC Educational Resources Information Center

    Lundquist, Carol; Frieder, Ophir; Holmes, David O.; Grossman, David

    1999-01-01

    Describes a scalable, parallel, relational database-drive information retrieval engine. To support portability across a wide range of execution environments, all algorithms adhere to the SQL-92 standard. By incorporating relevance feedback algorithms, accuracy is enhanced over prior database-driven information retrieval efforts. Presents…

  19. The Implementation of an Automated Assessment Feedback and Quality Assurance System for ICT Courses

    ERIC Educational Resources Information Center

    Debuse, J.; Lawley, M.; Shibl, R.

    2007-01-01

    Providing detailed, constructive and helpful feedback is an important contribution to effective student learning. Quality assurance is also required to ensure consistency across all students and reduce error rates. However, with increasing workloads and student numbers these goals are becoming more difficult to achieve. An automated feedback…

  20. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchick, A.M.; Gold, D.M.; Darrown, C.B.; Da Silva, L.B.

    1998-01-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  1. Noise-resistant system of concealed information transfer on a chaotic delayed feedback oscillator with switchable delay time

    NASA Astrophysics Data System (ADS)

    Kul'minskii, D. D.; Ponomarenko, V. I.; Karavaev, A. S.; Prokhorov, M. D.

    2016-05-01

    We propose a system of concealed information transfer based on a delayed feedback oscillator with switchable chaotic regimes. The proposed system is analyzed numerically and experimentally. The dependences of the bit error rate during transmission of a binary information signal on the signal-to-noise ratio, attenuation of the signal in the communication channel, and the duration of the time interval during which a bit is transferred are constructed. The high stability of the system to noise and amplitude distortions of a signal in the communication channel is demonstrated.

  2. Feedback: Focusing Attention on Engagement

    ERIC Educational Resources Information Center

    Price, Margaret; Handley, Karen; Millar, Jill

    2011-01-01

    Within many higher education systems there is a search for means to increase levels of student satisfaction with assessment feedback. This article suggests that the search is under way in the wrong place by concentrating on feedback as a product rather than looking more widely to feedback as a long-term dialogic process in which all parties are…

  3. Vegetation-climate feedback causes reduced precipitation in CMIP5 regional Earth system model simulation over Africa

    NASA Astrophysics Data System (ADS)

    Wu, Minchao; Smith, Benjamin; Schurgers, Guy; Lindström, Joe; Rummukainen, Markku; Samuelsson, Patrick

    2013-04-01

    Terrestrial ecosystems have been demonstrated to play a significant role within the climate system, amplifying or dampening climate change via biogeophysical and biogeochemical exchange with the atmosphere and vice versa (Cox et al. 2000; Betts et al. 2004). Africa is particularly vulnerable to climate change and studies of vegetation-climate feedback mechanisms on Africa are still limited. Our study is the first application of A coupled Earth system model at regional scale and resolution over Africa. We applied a coupled regional climate-vegetation model, RCA-GUESS (Smith et al. 2011), over the CORDEX Africa domain, forced by boundary conditions from a CanESM2 CMIP5 simulation under the RCP8.5 future climate scenario. The simulations were from 1961 to 2100 and covered the African continent at a horizontal grid spacing of 0.44°. RCA-GUESS simulates changes in the phenology, productivity, relative cover and population structure of up to eight plant function types (PFTs) in response to forcing from the climate part of the model. These vegetation changes feedback to simulated climate through dynamic adjustments in surface energy fluxes and surface properties. Changes in the net ecosystem-atmosphere carbon flux and its components net primary production (NPP), heterotrophic respiration and emissions from biomass burning were also simulated but do not feedback to climate in our model. Constant land cover was assumed. We compared simulations with and without vegetation feedback switched "on" to assess the influence of vegetation-climate feedback on simulated climate, vegetation and ecosystem carbon cycling. Both positive and negative warming feedbacks were identified in different parts of Africa. In the Sahel savannah zone near 15°N, reduced vegetation cover and productivity, and mortality caused by a deterioration of soil water conditions led to a positive warming feedback mediated by decreased evapotranspiration and increased sensible heat flux between vegetation and

  4. Translational recoding as a feedback controller: systems approaches reveal polyamine-specific effects on the antizyme ribosomal frameshift.

    PubMed

    Rato, Claudia; Amirova, Svetlana R; Bates, Declan G; Stansfield, Ian; Wallace, Heather M

    2011-06-01

    The antizyme protein, Oaz1, regulates synthesis of the polyamines putrescine, spermidine and spermine by controlling stability of the polyamine biosynthetic enzyme, ornithine decarboxylase. Antizyme mRNA translation depends upon a polyamine-stimulated +1 ribosomal frameshift, forming a complex negative feedback system in which the translational frameshifting event may be viewed in engineering terms as a feedback controller for intracellular polyamine concentrations. In this article, we present the first systems level study of the characteristics of this feedback controller, using an integrated experimental and modeling approach. Quantitative analysis of mutant yeast strains in which polyamine synthesis and interconversion were blocked revealed marked variations in frameshift responses to the different polyamines. Putrescine and spermine, but not spermidine, showed evidence of co-operative stimulation of frameshifting and the existence of multiple ribosome binding sites. Combinatorial polyamine treatments showed polyamines compete for binding to common ribosome sites. Using concepts from enzyme kinetics and control engineering, a mathematical model of the translational controller was developed to describe these complex ribosomal responses to combinatorial polyamine effects. Each one of a range of model predictions was successfully validated against experimental frameshift frequencies measured in S-adenosylmethionine-decarboxylase and antizyme mutants, as well as in the wild-type genetic background. PMID:21303766

  5. SU-E-J-196: Implementation of An In-House Visual Feedback System for Motion Management During Radiation Therapy

    SciTech Connect

    Nguyen, V; James, J; Wang, B; Ellerbusch, D

    2015-06-15

    Purpose: To describe an in-house video goggle feedback system for motion management during simulation and treatment of radiation therapy patients. Methods: This video goggle system works by splitting and amplifying the video output signal directly from the Varian Real-Time Position Management (RPM) workstation or TrueBeam imaging workstation into two signals using a Distribution Amplifier. The first signal S[1] gets reconnected back to the monitor. The second signal S[2] gets connected to the input of a Video Scaler. The S[2] signal can be scaled, cropped and panned in real time to display only the relevant information to the patient. The output signal from the Video Scaler gets connected to an HDMI Extender Transmitter via a DVI-D to HDMI converter cable. The S[2] signal can be transported from the HDMI Extender Transmitter to the HDMI Extender Receiver located inside the treatment room via a Cat5e/6 cable. Inside the treatment room, the HDMI Extender Receiver is permanently mounted on the wall near the conduit where the Cat5e/6 cable is located. An HDMI cable is used to connect from the output of the HDMI Receiver to the video goggles. Results: This video goggle feedback system is currently being used at two institutions. At one institution, the system was just recently implemented for simulation and treatments on two breath-hold gated patients with 8+ total fractions over a two month period. At the other institution, the system was used to treat 100+ breath-hold gated patients on three Varian TrueBeam linacs and has been operational for twelve months. The average time to prepare the video goggle system for treatment is less than 1 minute. Conclusion: The video goggle system provides an efficient and reliable method to set up a video feedback signal for radiotherapy patients with motion management.

  6. Soil Warming Alters the Nitrogen Cycle: Ecosystem Implications and Feedbacks to the Climate System

    NASA Astrophysics Data System (ADS)

    Butler, S. M.; Melillo, J. M.; Johnson, J. E.; Mohan, J. E.; Steudler, P. A.; Bowles, F. P.

    2008-12-01

    Increases in soil temperatures associated with global warming have the potential to accelerate nitrogen turnover in soils, which could alter other biogeochemical processes and eventually affect the structure of these forests. Over the past five years we have been studying soil and plant responses to soil warming in large plots in a deciduous stand at Harvard Forest in central Massachusetts. We have heated the soil 5°C above ambient and measured nitrogen cycling parameters including in situ net nitrogen mineralization and nitrification, nitrogen leaching and nitrous oxide (N2O) fluxes. We have also measured various aspects of the carbon cycle including soil respiration and carbon accumulation in vegetation. Over the first five years of the study, we observed a mean annual increase in the net nitrogen mineralized in the warmed plot of 23.8 kg N ha-1. While nitrification rates were low throughout the five years in the control plot, they increased in the warmed plot to account for over 25% of the total net nitrogen mineralized in year five. The increase in nitrogen mineralization stimulated tree growth and carbon storage in woody tissue in the warmed plot. The increased carbon storage in the trees compensated for more than half of the carbon lost from the soils due to accelerated decay of soil organic matter and so reduced the magnitude of the positive feedback to the climate system due to soil warming. We hypothesize that the increase in nitrification we observed will eventually "open" the nitrogen cycle and make gaseous and solution losses more likely. To date, however, we have measured no major losses of nitrous oxide or solution losses of nitrate in response to soil warming. Trees with the capacity to use nitrate may have a competitive advantage in a warmer world. Nitrate-using plants have an inducible enzyme that transforms nitrate to ammonium, a key building block for producing essential amino acids and proteins. Studies by our research group and by others have

  7. A betatron tune measurement system based on bunch-by-bunch transverse feedback at the Duke storage ring

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Z. Wu, W.; Li, Jing-Yi; He, Duo-Hui; K. Wu, Y.

    2013-07-01

    To combat electron beam instabilities, a digital bunch-by-bunch transverse feedback (TFB) system has been developed for the Duke storage ring. While it is capable of suppressing transverse beam instabilities for multibunch operation, the TFB system has not been needed for typical operation of the Duke storage ring. To explore the great potential of this system, we have developed beam diagnostic techniques using the TFB, in particular, the TFB based tune measurement techniques. The tune measurement technique allows us to conduct fast chromaticity measurements, compared with the existing chromaticity measurement system using a network analyzer. This new tune measurement system also enables us to measure the bunch tune for multibunch operation of the Duke storage ring. With the TFB based tune measurement system, we have studied the tune stability of the electron beam in the Duke storage ring. This tune system has also been used to calibrate the tune knob for the Duke storage ring.

  8. Computation of output feedback gains for linear stochastic systems using the Zangnill-Powell Method

    NASA Technical Reports Server (NTRS)

    Kaufman, H.

    1975-01-01

    Because conventional optimal linear regulator theory results in a controller which requires the capability of measuring and/or estimating the entire state vector, it is of interest to consider procedures for computing controls which are restricted to be linear feedback functions of a lower dimensional output vector and which take into account the presence of measurement noise and process uncertainty. To this effect a stochastic linear model has been developed that accounts for process parameter and initial uncertainty, measurement noise, and a restricted number of measurable outputs. Optimization with respect to the corresponding output feedback gains was then performed for both finite and infinite time performance indices without gradient computation by using Zangwill's modification of a procedure originally proposed by Powell. Results using a seventh order process show the proposed procedures to be very effective.

  9. Disturbance observer based fault estimation and dynamic output feedback fault tolerant control for fuzzy systems with local nonlinear models.

    PubMed

    Han, Jian; Zhang, Huaguang; Wang, Yingchun; Liu, Yang

    2015-11-01

    This paper addresses the problems of fault estimation (FE) and fault tolerant control (FTC) for fuzzy systems with local nonlinear models, external disturbances, sensor and actuator faults, simultaneously. Disturbance observer (DO) and FE observer are designed, simultaneously. Compared with the existing results, the proposed observer is with a wider application range. Using the estimation information, a novel fuzzy dynamic output feedback fault tolerant controller (DOFFTC) is designed. The controller can be used for the fuzzy systems with unmeasurable local nonlinear models, mismatched input disturbances, and measurement output affecting by sensor faults and disturbances. At last, the simulation shows the effectiveness of the proposed methods. PMID:26456728

  10. Virtual patients feedback system--a concept to support students and educators.

    PubMed

    Yilmaz, Arzu; Haag, Martin

    2014-01-01

    Assessments deliver information about the knowledge level of a student. Formative assessments' main purposes are to identify student's weaknesses and strengths, and support educators in the planning process of their instruction. In this paper a graphical user interface concept is presented to provide feedback with the aid of the editing results of medical students, who train with Virtual Patient, which is a computer-based simulation of patient care. PMID:24825696

  11. Tool actuation and force feedback on robot-assisted microsurgery system

    NASA Technical Reports Server (NTRS)

    Das, Hari (Inventor); Ohm, Tim R. (Inventor); Boswell, Curtis D. (Inventor); Steele, Robert D. (Inventor)

    2002-01-01

    An input control device with force sensors is configured to sense hand movements of a surgeon performing a robot-assisted microsurgery. The sensed hand movements actuate a mechanically decoupled robot manipulator. A microsurgical manipulator, attached to the robot manipulator, is activated to move small objects and perform microsurgical tasks. A force-feedback element coupled to the robot manipulator and the input control device provides the input control device with an amplified sense of touch in the microsurgical manipulator.

  12. Adaptive Neural Stabilizing Controller for a Class of Mismatched Uncertain Nonlinear Systems by State and Output Feedback.

    PubMed

    Arefi, Mohammad Mehdi; Jahed-Motlagh, Mohammad Reza; Karimi, Hamid Reza

    2015-08-01

    In this paper, first, an adaptive neural network (NN) state-feedback controller for a class of nonlinear systems with mismatched uncertainties is proposed. By using a radial basis function NN (RBFNN), a bound of unknown nonlinear functions is approximated so that no information about the upper bound of mismatched uncertainties is required. Then, an observer-based adaptive controller based on RBFNN is designed to stabilize uncertain nonlinear systems with immeasurable states. The state-feedback and observer-based controllers are based on Lyapunov and strictly positive real-Lyapunov stability theory, respectively, and it is shown that the asymptotic convergence of the closed-loop system to zero is achieved while maintaining bounded states at the same time. The presented methods are more general than the previous approaches, handling systems with no restriction on the dimension of the system and the number of inputs. Simulation results confirm the effectiveness of the proposed methods in the stabilization of mismatched nonlinear systems. PMID:25265641

  13. Influence of the feedback loops in the trp operon of B. subtilis on the system dynamic response and noise amplitude.

    PubMed

    Zamora-Chimal, Criseida; Santillán, Moisés; Rodríguez-González, Jesús

    2012-10-01

    In this paper we introduce a mathematical model for the tryptophan operon regulatory pathway in Bacillus subtilis. This model considers the transcription-attenuation, and the enzyme-inhibition regulatory mechanisms. Special attention is paid to the estimation of all the model parameters from reported experimental data. With the aid of this model we investigate, from a mathematical-modeling point of view, whether the existing multiplicity of regulatory feedback loops is advantageous in some sense, regarding the dynamic response and the biochemical noise in the system. The tryptophan operon dynamic behavior is studied by means of deterministic numeric simulations, while the biochemical noise is analyzed with the aid of stochastic simulations. The model feasibility is tested comparing its stochastic and deterministic results with experimental reports. Our results for the wildtype and for a couple of mutant bacterial strains suggest that the enzyme-inhibition feedback loop, dynamically accelerates the operon response, and plays a major role in the reduction of biochemical noise. Also, the transcription-attenuation feedback loop makes the trp operon sensitive to changes in the endogenous tryptophan level, and increases the amplitude of the biochemical noise. PMID:22713856

  14. Feedback as Real-Time Constructions

    ERIC Educational Resources Information Center

    Keiding, Tina Bering; Qvortrup, Ane

    2014-01-01

    This article offers a re-description of feedback and the significance of time in feedback constructions based on systems theory. It describes feedback as internal, real-time constructions in a learning system. From this perspective, feedback is neither immediate nor delayed, but occurs in the very moment it takes place. This article argues for a…

  15. Native and non-native ruderals experience similar plant-soil feedbacks and neighbor effects in a system where they coexist.

    PubMed

    Chiuffo, Mariana C; MacDougall, Andrew S; Hierro, José L

    2015-11-01

    Recent applications of coexistence theory to plant invasions posit that non-natives establish in resident communities through either niche differences or traits conferring them with fitness advantages, the former being associated with coexistence and the latter with dominance and competitive exclusion. Plant-soil feedback is a mechanism that is known to explain both coexistence and dominance. In a system where natives and non-natives appear to coexist, we explored how plant-soil feedbacks affect the performance of nine native and nine non-native ruderal species-the prevalent life-history strategy among non-natives-when grown alone and with a phytometer. We also conducted field samplings to estimate the abundance of the 18 species, and related feedbacks to abundances. We found that groups of native and non-native ruderals displayed similar frequencies of negative, positive, and neutral feedbacks, resulting in no detectable differences between natives and non-natives. Likewise, the phytometer exerted comparable negative impacts on native and non-native plants, which were unchanged by plant-soil feedbacks. Finally, feedbacks explained plant abundances only after removing one influential species which exhibited strong positive feedbacks but low abundance. Importantly, however, four out of five species with negative feedbacks were rare in the field. These findings suggest that soil feedbacks and plant-plant interactions do not confer an advantage to non-native over native species, but do contribute to the observed coexistence of these groups in the system. By comparing natives and non-natives with overlapping abundances and strategies, our work broadens understanding of the consequences of plant-soil feedbacks in plant invasion and, more generally, coexistence within plant communities. PMID:26209047

  16. Accelerator Diagnostic Techniques Using Time-Domain Data from a Bunch-by-bunch Longitudinal Feedback System

    SciTech Connect

    Teytelman, Dmitry

    2000-03-30

    A programmable DSP-based longitudinal damping system has been developed for the PEP-II/DAFNE/ALS machines. The DSP-based architecture allows feedback functions to coexist with data acquisition or instrumentation algorithms. The fast sampling rates in these systems (500 MHz) in conjunction with the large distributed memory of the DSP processors make possible several novel beam diagnostics complementary to traditional narrowband spectral measurements. Instantaneous spectral measurements of 250 MHz span with 70 Hz resolution can be made from 14 ms time domain data records captured by the DSP system. The authors present techniques developed for the measurement of modal growth and damping rates and other beam and system diagnostics (calibrations, measurements of the system noise floor). Results from the Advanced Light Source and PEP-II are presented to illustrate these techniques.

  17. GREENCYCLESII: A European Initial Training Network on anticipating climate change and biospheric feedbacks within the Earth system to 2200

    NASA Astrophysics Data System (ADS)

    Jones, B. C.

    2013-12-01

    GREENCYCLESII is a European Marie Curie FP7 Initial Training Network which aims to improve current understanding of the impacts of climate-biogeochemistry feedbacks on the evolution of the Earth system over the next two centuries and foster the next generation of Earth system scientists. The project started in 2010 and 15 European research centres in 8 different countries are collaborating to provide training for 30 network fellows. Workshops, mini-conferences, and a summer school have brought the fellows together with senior scientists to discuss and learn about the Earth system and current scientific efforts. Each fellow is undertaking a jointly-supervised science project, and these are yielding major advances in our ability to model the coupled Earth system. GREENCYCLESII has a particular focus on the role of biological processes within the global carbon cycle. Work packages cover the themes of global datasets for model benchmarking, marine processes, terrestrial processes, high-latitude feedbacks, and coupled modelling. This poster will highlight a selection of the key scientific findings that have arisen from the network so far.

  18. A European Initial Training Network on anticipating climate change and biospheric feedbacks within the Earth system to 2200: GREENCYCLESII

    NASA Astrophysics Data System (ADS)

    Friend, Andrew D.; Jones, Bethan

    2013-04-01

    GREENCYCLESII is a Marie Curie FP7 Initial Training Network which aims to improve current understanding of the impacts of climate-biogeochemistry feedbacks on the evolution of the Earth system over the next two Centuries and foster the next generation of Earth system scientists. 15 European research centres are collaborating on providing training and hosting of network Fellows. The project started in 2010 and 30 Fellows have joined the network across 8 countries. Workshops, mini-conferences, and a summer school have brought the Fellows together with network and outside senior scientists to explore the Earth system. Science projects are yielding major advances in our ability to model the coupled Earth system, with a particular focus on the role of biological processes within the global carbon cycle. Work packages cover the themes of global datasets for model benchmarking, marine processes, terrestrial processes, high-latitude feedbacks, and coupled modelling. This poster will highlight a selection of the key scientific findings to have arisen from the network so far.

  19. An Autonomous Sensor System Architecture for Active Flow and Noise Control Feedback

    NASA Technical Reports Server (NTRS)

    Humphreys, William M, Jr.; Culliton, William G.

    2008-01-01

    Multi-channel sensor fusion represents a powerful technique to simply and efficiently extract information from complex phenomena. While the technique has traditionally been used for military target tracking and situational awareness, a study has been successfully completed that demonstrates that sensor fusion can be applied equally well to aerodynamic applications. A prototype autonomous hardware processor was successfully designed and used to detect in real-time the two-dimensional flow reattachment location generated by a simple separated-flow wind tunnel model. The success of this demonstration illustrates the feasibility of using autonomous sensor processing architectures to enhance flow control feedback signal generation.

  20. Hybrid Stochastic Search Technique based Suboptimal AGC Regulator Design for Power System using Constrained Feedback Control Strategy

    NASA Astrophysics Data System (ADS)

    Ibraheem, Omveer, Hasan, N.

    2010-10-01

    A new hybrid stochastic search technique is proposed to design of suboptimal AGC regulator for a two area interconnected non reheat thermal power system incorporating DC link in parallel with AC tie-line. In this technique, we are proposing the hybrid form of Genetic Algorithm (GA) and simulated annealing (SA) based regulator. GASA has been successfully applied to constrained feedback control problems where other PI based techniques have often failed. The main idea in this scheme is to seek a feasible PI based suboptimal solution at each sampling time. The feasible solution decreases the cost function rather than minimizing the cost function.