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Sample records for active attitude control

  1. Attitude control with active actuator saturation prevention

    NASA Astrophysics Data System (ADS)

    Forbes, James Richard

    2015-02-01

    Spacecraft attitude control in the presence of actuator saturation is considered. The attitude controller developed has two components: a proportional component and an angular velocity component. The proportional control has a special form that depends on the attitude parameterization. The angular velocity control is realized by a strictly positive real system with its own input nonlinearity. The strictly positive real system can filter noise in the angular velocity measurement. With this control architecture the torques applied to the body are guaranteed to be below a predetermined value, thus preventing saturation of the actuators. The closed-loop equilibrium point corresponding to the desired attitude is shown to be asymptotically stable. Additionally, the control law does not require specific knowledge of the body's inertia properties, and is therefore robust to such modelling errors.

  2. Three-axis active magnetic attitude control asymptotical study

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Penkov, V. I.

    2015-05-01

    Active magnetic attitude control system providing given inertial attitude is considered. Control algorithm is constructed on the basis of a planar motion model. It decreases attitude discrepancy. Alternative approach is based on the PD-controller design. System behavior is analyzed for specific motion cases and sometimes for specific inertia tensor (axisymmetrical satellite) using averaging technique. Overall satellite angular motion is covered. Necessary attitude is found to be accessible for some control parameters. Stability is proven and optimal algorithm parameters are obtained. Floquet-based analysis is performed to verify and broaden analytical results.

  3. Study of tethered satellite active attitude control

    NASA Technical Reports Server (NTRS)

    Colombo, G.

    1982-01-01

    Existing software was adapted for the study of tethered subsatellite rotational dynamics, an analytic solution for a stable configuration of a tethered subsatellite was developed, the analytic and numerical integrator (computer) solutions for this "test case' was compared in a two mass tether model program (DUMBEL), the existing multiple mass tether model (SKYHOOK) was modified to include subsatellite rotational dynamics, the analytic "test case,' was verified, and the use of the SKYHOOK rotational dynamics capability with a computer run showing the effect of a single off axis thruster on the behavior of the subsatellite was demonstrated. Subroutines for specific attitude control systems are developed and applied to the study of the behavior of the tethered subsatellite under realistic on orbit conditions. The effect of all tether "inputs,' including pendular oscillations, air drag, and electrodynamic interactions, on the dynamic behavior of the tether are included.

  4. Attitude Control

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A Small Business Innovation Research (SBIR) contract to ITHACO, Inc. satisfied a Goddard Space Flight Center demand for a low cost altitude control system for small spacecraft. The SBIR-sponsored work resulted in the T-Wheel, built specifically for altitude control of small and medium-sized spacecraft. Another product, the T-SCANWHEEL, reduces overall system cost, minimizes mass and power and enhances reliability with a mixture of altitude control and control capacity. Additionally, the Type E Wheel is built for use on medium to large spacecraft. Through July 1996, ITHACO had delivered or was under contract for 95 T-Wheel, T-SCANWHEEL, and Type E Wheel units.

  5. Solar sail attitude control including active nutation damping in a fixed-momentum wheel satellite

    NASA Technical Reports Server (NTRS)

    Azor, Ruth

    1992-01-01

    In geostationary cruise of a momentum biased satellite, it is necessary to stabilize the roll/yaw attitude due to disturbances, caused mainly by solar radiation pressure. This work presents a roll/yaw control which is obtained by the use of solar arrays and fixed flaps as actuators, with a horizon sensor for roll measurement. The design also includes an active nutation damping.

  6. Attitude control system

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.; Rupp, C. C. (Inventor)

    1976-01-01

    An attitude control system is described in which angular rate signals are generated by rate gyros mounted closely adjacent to gimbaled engines at the rear of a vehicle. Error signals representative of a commanded change in vehicle angle or attitude are obtained from a precision inertial platform located in the nose region of the vehicle. The rate gyro derived signals dominate at high frequencies where dynamic effects become significant, and platform signals dominate at low frequencies where precision signals are required for a steady vehicle attitude. The blended signals are applied in a conventional manner to control the gimbaling of vehicle engines about control axes.

  7. Magnetic bearing momentum wheels with magnetic gimballing capability for 3-axis active attitude control and energy storage

    NASA Technical Reports Server (NTRS)

    Sindlinger, R. S.

    1977-01-01

    A 3-axis active attitude control system with only one rotating part was developed using a momentum wheel with magnetic gimballing capability as a torque actuator for all three body axes. A brief description of magnetic bearing technology is given. It is concluded that based on this technology an integrated energy storage/attitude control system with one air of counterrotating rings could reduce the complexity and weight of conventional systems.

  8. Satellite attitude control simulations

    NASA Technical Reports Server (NTRS)

    Debra, D. B.; Powell, J. D.

    1973-01-01

    Work was conducted to develop an extremely low drift rate gyroscope and a very precise star tracker. A proposed relativity satellite will measure very accurately the theoretically predicted 'relativistic' precession of the gyroscope relative to an inertial reference frame provided by the star tracker. Aspects of precision spinning attitude control are discussed together with questions of gyro operation, and the hopping mode for lunar transportation. For the attitude control system of the lunar hopper, a number of control laws were investigated. The studies indicated that some suboptimal controls should be adequate for the system.

  9. Optimality of incompletely measurable active and passive attitude control systems. [for satellites

    NASA Technical Reports Server (NTRS)

    Schiehlen, W.; Popp, K.

    1973-01-01

    Passive attitude control systems and active systems with incomplete state measurements are only suboptimal systems in the sense of optimal control theory, since optimal systems require complete state measurements or state estimations. An optimal system, then, requires additional hardware (especially in the case of flexible spacecraft) which results in higher costs. Therefore, it is a real engineering problem to determine how much an optimal system exceeds the suboptimal system, or in other words, what is the suboptimal system's degree of optimality. The problem will be treated in three steps: (1) definition of the degree of optimality for linear, time-invariant systems; (2) a computation method using the quadratic cost functional; (3) application to a gravity-gradient stabilized three-body satellite and a spinning flexible satellite.

  10. Instrument Attitude Precision Control

    NASA Technical Reports Server (NTRS)

    Juang, Jer-Nan

    2004-01-01

    A novel approach is presented in this paper to analyze attitude precision and control for an instrument gimbaled to a spacecraft subject to an internal disturbance caused by a moving component inside the instrument. Nonlinear differential equations of motion for some sample cases are derived and solved analytically to gain insight into the influence of the disturbance on the attitude pointing error. A simple control law is developed to eliminate the instrument pointing error caused by the internal disturbance. Several cases are presented to demonstrate and verify the concept presented in this paper.

  11. Weight Control Beliefs, Body Shape Attitudes, and Physical Activity among Adolescents

    ERIC Educational Resources Information Center

    Martin, Scott B.; Rhea, Deborah J.; Greenleaf, Christy A.; Judd, Doryce E.; Chambliss, Heather O.

    2011-01-01

    Background: Relatively little is known about how perceived weight controllability influences important psychological health factors among adolescents. Thus, the purpose of this study is to explore adolescents' weight controllability beliefs and how those beliefs influence weight-related attitudes and behaviors. Methods: Adolescents (N = 369, mean…

  12. The attitude control problem

    NASA Technical Reports Server (NTRS)

    Wen, John Ting-Yung; Kreutz-Delgado, Kenneth

    1991-01-01

    A general framework for the analysis of the attitude tracking control problem for a rigid body is presented. A large family of globally stable control laws is obtained by using the globally nonsingular unit quaternion representation in a Lyapunov function candidate whose form is motivated by the consideration of the total energy of the rigid body. The controllers share the common structure of a proportional-derivative feedback plus some feedforward which can be zero (the model-independent case), the Coriolis torque compensation, or an adaptive compensation. These controller structures are compared in terms of the requirement on the a priori model information, guaranteed transient performance, and robustness. The global stability of the Luh-Walker-Paul robot end-effector controller is also analyzed in this framework.

  13. Improving the Blood Pressure Control With the ProActive Attitude of Hypertensive Patients Seeking Follow-up Services

    PubMed Central

    Tang, Shangfeng; Bishwajit, Ghose; Ji, Lu; Feng, Da; Fang, Haiqing; Fu, Hang; Shao, Tian; Shao, Piaopiao; Liu, Chunyan; Feng, Zhanchun; Luba, Tegene R.

    2016-01-01

    Abstract Proactive attitude of hypertensive patients seeking follow-up services (FUS) lies at the core of self-efficacy. However, few evidence have shown the activeness of seeking FUS in the context of blood pressure control among hypertensive patients. Improvements in follow-up visits may not just by services itself cause better control of blood pressure among hypertensive patients, rather due to the patient's pro-active attitude of the patient in seeking FUS. A cross-sectional study was carried out in selected rural regions of China to explore the association between blood pressure control and sociodemographic and economic variables and activeness of hypertensive patients in seeking FUS. The primary clinical outcome for this study was blood pressure control (systolic blood pressure <140 mmHg or diastolic blood pressure <90 mmHg) Out of the total 2321 participants with hypertension aged 35 years or older participated in this survey. Number of proactive FUS seekers were 3.17 times greater than those of passive seekers (odds ratio [OR] = 3.17, 95% confidence interval [CI] = 2.56–3.93, P < 0.001). In all subgroups, hypertensive patients who were seeking FUS actively were more likely to control blood pressure better than those seeking FUS passively. Proactive attitude of seeking follow-up services can improve blood pressure control among hypertensive patients. PMID:27057859

  14. A hybrid attitude controller consisting of electromagnetic torque rods and an active fluid ring

    NASA Astrophysics Data System (ADS)

    Nobari, Nona A.; Misra, Arun K.

    2014-01-01

    In this paper, a novel hybrid actuation system for satellite attitude stabilization is proposed along with its feasibility analysis. The system considered consists of two magnetic torque rods and one fluid ring to produce the control torque required in the direction in which magnetic torque rods cannot produce torque. A mathematical model of the system dynamics is derived first. Then a controller is developed to stabilize the attitude angles of a satellite equipped with the abovementioned set of actuators. The effect of failure of the fluid ring or a magnetic torque rod is examined as well. It is noted that the case of failure of the magnetic torque rod whose torque is along the pitch axis is the most critical, since the coupling between the roll or yaw motion and the pitch motion is quite weak. The simulation results show that the control system proposed is quite fault tolerant.

  15. Magnetic bearing momentum wheels with magnetic gimballing capability for 3-axis active attitude control and energy storage

    NASA Technical Reports Server (NTRS)

    Sindlinger, R. S.

    1977-01-01

    Magnetic bearings used for the suspension of momentum wheels provide conclusive advantages: the low friction torques and the absence of abrasion allow the realization of lightweight high speed wheels with high angular momentum and energy storage capacity and virtually unlimited lifetime. The use of actively controlled bearings provides a magnetic gimballing capability by applying the external signals to the two servo loops controlling the rotational degrees of freedom. Thus, an attitude control system can be realized by using only one rotating mass for 3-axis active satellite stabilization.

  16. Skylab thruster attitude control system

    NASA Technical Reports Server (NTRS)

    Wilmer, G. E., Jr.

    1974-01-01

    Preflight activities and the Skylab mission support effort for the thruster attitude control system (TACS) are documented. The preflight activities include a description of problems and their solutions encountered in the development, qualification, and flight checkout test programs. Mission support effort is presented as it relates to system performance assessment, real-time problem solving, flight anomalies, and the daily system evaluation. Finally, the detailed flight evaluation is presented for each phase of the mission using system telemetry data. Data assert that the TACS met or exceeded design requirements and fulfilled its assigned mission objectives.

  17. Modular design attitude control system

    NASA Technical Reports Server (NTRS)

    Chichester, F. D.

    1982-01-01

    A hybrid multilevel linear quadratic regulator (ML-LQR) approach was developed and applied to the attitude control of models of the rotational dynamics of a prototype flexible spacecraft and of a typical space platform. Three axis rigid body flexible suspension models were developed for both the spacecraft and the space platform utilizing augmented body methods. Models of the spacecraft with hybrid ML-LQR attitude control and with LQR attitude control were simulated and their response with the two different types of control were compared.

  18. Predicted torque equilibrium attitude utilization for Space Station attitude control

    NASA Technical Reports Server (NTRS)

    Kumar, Renjith R.; Heck, Michael L.; Robertson, Brent P.

    1990-01-01

    An approximate knowledge of the torque equilibrium attitude (TEA) is shown to improve the performance of a control moment gyroscope (CMG) momentum management/attitude control law for Space Station Freedom. The linearized equations of motion are used in conjunction with a state transformation to obtain a control law which uses full state feedback and the predicted TEA to minimize both attitude excursions and CMG peak and secular momentum. The TEA can be computationally determined either by observing the steady state attitude of a 'controlled' spacecraft using arbitrary initial attitude, or by simulating a fixed attitude spacecraft flying in desired orbit subject to realistic environmental disturbance models.

  19. Three axis attitude control system

    NASA Technical Reports Server (NTRS)

    Studer, Philip A. (Inventor)

    1988-01-01

    A three-axis attitude control system for an orbiting body comprised of a motor driven flywheel supported by a torque producing active magnetic bearing is described. Free rotation of the flywheel is provided about its central axis and together with limited angular torsional deflections of the flywheel about two orthogonal axes which are perpendicular to the central axis. The motor comprises an electronically commutated DC motor, while the magnetic bearing comprises a radially servoed permanent magnet biased magnetic bearing capable of producing cross-axis torques on the flywheel. Three body attitude sensors for pitch, yaw and roll generate respective command signals along three mutually orthogonal axes (x, y, z) which are coupled to circuit means for energizing a set of control coils for producing torques about two of the axes (x and y) and speed control of the flywheel about the third (z) axis. An energy recovery system, which is operative during motor deceleration, is also included which permits the use of a high-speed motor to perform effectively as a reactive wheel suspended in the magnetic bearing.

  20. Active control of the attitude motion and structural vibration of a flexible satellite by jet thrusters

    NASA Astrophysics Data System (ADS)

    Lee, Mokin

    A Lagrangian formulation is used to obtain the equations of motion of a flexible satellite in a tree-type geometry. The flexible satellite model is the geosynchronous INSAT-II type satellite with a flexible balance beam and a flexible solar panel attached to the rigid main body. In deriving the equations of motion, the orbital motion, the librational motion, and the structural motion of flexible bodies are involved. The assumed-modes method is used to express the deflections of the flexible structures in the form of a finite series of space-dependent admissible functions multiplied by time-dependent amplitudes. The kinetic energy, potential energy, strain energy, and virtual work of the flexible satellite are evaluated as functions of time in terms of the generalized coordinates. Then, by substituting them into Lagrange's equations for discrete systems, the governing equations of motion of the flexible satellite are obtained as a set of second-order nonlinear ordinary differential equations. The attitude motion and the structural motion of the flexible satellite are coupled motions with one another. Uncontrolled dynamics show that the librational and structural motions are oscillatory and undamped motions. The stability and performance of the flexible satellite needs to be improved by designing control systems. A control objective is proposed to improve the stability and performance for pointing accuracy maneuver by controlling the librational motions and flexible modes simultaneously. For the control objective, a control system is synthesized, using feedback linearization control, thrust determination, thrust management, and pulse-width pulse-frequency modulation. Feedback linearization for second-order nonlinear systems is used to obtain a stable feedback control system for the pointing-accuracy control. A stable feedback control system is obtained by adjusting the diagonal matrices of the linear second-order system. Jet thrusters are used as the primary

  1. Attitude control and stabilization technology discipline

    NASA Technical Reports Server (NTRS)

    Sunkel, John W.

    1990-01-01

    Viewgraphs on attitude control and stabilization technology discipline for the Space Station Freedom are presented. Topics covered include: attitude control technologies for multi-user accommodation; flexible dynamics and control; computational control techniques; and automatic proximity operations.

  2. The Effects of Teaching Numerical Control Concepts Via Simulator Versus Non-Simulator Activities on the Achievement, Programming Proficiency and Attitude of High School Students.

    ERIC Educational Resources Information Center

    Pine, Douglas Taylor

    This study utilized 120 metalworking students and six teachers from Columbus, Ohio area high schools to ascertain the effects of teaching numerical control to industrial arts students by means of simulator-aided activities versus nonsimulator aided activities. Scores obtained from an achievement test, attitude inventory, and word address…

  3. Attitude Control Working Group report

    NASA Technical Reports Server (NTRS)

    Reid, Daniel F.; Studer, Phillip A.

    1986-01-01

    The goals were to establish the Attitude Control System (ACS) requirements, constraints, technology assessment, technology shortfalls, expected in the year 2000. These were based upon all missions, military and civil, for LEO and GEO. The critical ACS technology issues were identified and ACS programs developed to address these critical issues.

  4. Parents' Attitude towards Extracurricular Activities.

    ERIC Educational Resources Information Center

    Lam, Chi-chung; Wong, Ngai-ying

    1997-01-01

    Argues that it is important to understand parents' attitudes and perceptions of extracurricular activities to promote their involvement in them. Shows that parents in Hong Kong view extracurricular activities favorably but are more willing to invest their money than their time in promoting them. Makes suggestions for policy formation. (DSK)

  5. Noise screen for attitude control system

    NASA Technical Reports Server (NTRS)

    Rodden, John J. (Inventor); Stevens, Homer D. (Inventor); Hong, David P. (Inventor); Hirschberg, Philip C. (Inventor)

    2002-01-01

    An attitude control system comprising a controller and a noise screen device coupled to the controller. The controller is adapted to control an attitude of a vehicle carrying an actuator system that is adapted to pulse in metered bursts in order to generate a control torque to control the attitude of the vehicle in response to a control pulse. The noise screen device is adapted to generate a noise screen signal in response to the control pulse that is generated when an input attitude error signal exceeds a predetermined deadband attitude level. The noise screen signal comprises a decaying offset signal that when combined with the attitude error input signal results in a net attitude error input signal away from the predetermined deadband level to reduce further control pulse generation.

  6. Attitude orientation control for a spinning satellite

    NASA Astrophysics Data System (ADS)

    Frost, Gerald

    The Department of the Air Force, Headquarters Space Systems Division, and the National Aeronautics and Space Administration (NASA) are currently involved in litigation with Hughes Aircraft Company over the alledged infringement of the 'Williams patent,' which describes a method for attitude control of a spin-stabilized vehicle. Summarized here is pre-1960 RAND work on this subject and information obtained from RAND personnel knowledgeable on this subject. It was concluded that there is no RAND documentation that directly parallels the 'Williams patent' concept. Also, the TIROS II magnetic torque attitude control method is reviewed. The TIROS II meteorological satellite, launched on November 23, 1960, incorporated a magnetic actuation system for spin axis orientation control. The activation system was ground controlled to orient the satellite spin axis to obtain the desired pointing direction for optical and infrared sensor subsystems.

  7. Nonlinear fractional order proportion-integral-derivative active disturbance rejection control method design for hypersonic vehicle attitude control

    NASA Astrophysics Data System (ADS)

    Song, Jia; Wang, Lun; Cai, Guobiao; Qi, Xiaoqiang

    2015-06-01

    Near space hypersonic vehicle model is nonlinear, multivariable and couples in the reentry process, which are challenging for the controller design. In this paper, a nonlinear fractional order proportion integral derivative (NFOPIλDμ) active disturbance rejection control (ADRC) strategy based on a natural selection particle swarm (NSPSO) algorithm is proposed for the hypersonic vehicle flight control. The NFOPIλDμ ADRC method consists of a tracking-differentiator (TD), an NFOPIλDμ controller and an extended state observer (ESO). The NFOPIλDμ controller designed by combining an FOPIλDμ method and a nonlinear states error feedback control law (NLSEF) is to overcome concussion caused by the NLSEF and conversely compensate the insufficiency for relatively simple and rough signal processing caused by the FOPIλDμ method. The TD is applied to coordinate the contradiction between rapidity and overshoot. By attributing all uncertain factors to unknown disturbances, the ESO can achieve dynamic feedback compensation for these disturbances and thus reduce their effects. Simulation results show that the NFOPIλDμ ADRC method can make the hypersonic vehicle six-degree-of-freedom nonlinear model track desired nominal signals accurately and fast, has good stability, dynamic properties and strong robustness against external environmental disturbances.

  8. Contextual moderation of racial bias: the impact of social roles on controlled and automatically activated attitudes.

    PubMed

    Barden, Jamie; Maddux, William W; Petty, Richard E; Brewer, Marilynn B

    2004-07-01

    Three experiments tested the hypothesis that the social roles implied by specific contexts can attenuate or reverse the typical pattern of racial bias obtained on both controlled and automatic evaluation measures. Study 1 assessed evaluations of Black and Asian faces in contexts related to athlete or student roles. Study 2 compared evaluations of Black and White faces in 3 role-related contexts (prisoner, churchgoer, and factory worker). Study 3 manipulated role cues (lawyer or prisoner) within the same prison context. All 3 studies produced significant reversals of racial bias as a function of implied role on measures of both controlled and automatic evaluation. These results support the interpretation that differential evaluations based on Race x Role interactions provide one way that context can moderate both controlled and automatic racial bias. PMID:15250789

  9. Remote Spacecraft Attitude Control by Coulomb Charging

    NASA Astrophysics Data System (ADS)

    Stevenson, Daan

    The possibility of inter-spacecraft collisions is a serious concern at Geosynchronous altitudes, where many high-value assets operate in proximity to countless debris objects whose orbits experience no natural means of decay. The ability to rendezvous with these derelict satellites would enable active debris removal by servicing or repositioning missions, but docking procedures are generally inhibited by the large rotational momenta of uncontrolled satellites. Therefore, a contactless means of reducing the rotation rate of objects in the space environment is desired. This dissertation investigates the viability of Coulomb charging to achieve such remote spacecraft attitude control. If a servicing craft imposes absolute electric potentials on a nearby nonspherical debris object, it will impart electrostatic torques that can be used to gradually arrest the object's rotation. In order to simulate the relative motion of charged spacecraft with complex geometries, accurate but rapid knowledge of the Coulomb interactions is required. To this end, a new electrostatic force model called the Multi-Sphere Method (MSM) is developed. All aspects of the Coulomb de-spin concept are extensively analyzed and simulated using a system with simplified geometries and one dimensional rotation. First, appropriate control algorithms are developed to ensure that the nonlinear Coulomb torques arrest the rotation with guaranteed stability. Moreover, the complex interaction of the spacecraft with the plasma environment and charge control beams is modeled to determine what hardware requirements are necessary to achieve the desired electric potential levels. Lastly, the attitude dynamics and feedback control development is validated experimentally using a scaled down terrestrial testbed. High voltage power supplies control the potential on two nearby conductors, a stationary sphere and a freely rotating cylinder. The nonlinear feedback control algorithms developed above are implemented to

  10. Linearization of Attitude-Control Error Dynamics

    NASA Technical Reports Server (NTRS)

    Bach, Ralph; Paielli, Russell

    1993-01-01

    Direction cosines and quaternions are useful for representing rigid-body attitude because they exhibit no kinematic singularities. Each utilizes more variables than the minimum three degrees of freedom required to specify attitude. Therefore, application of a nonlinear inversion procedure to either formulation introduces singularities. Furthermore, in designing an attitude-control system, it is not appropriate to express attitude error as a difference of direction cosines (or quaternions). One should employ a measure of attitude error that not only is minimal but preserves orthogonal rotation properties as well. This note applies an inversion procedure to an appropriate measure of attitude error, so that the singularity occurs when the error reaches +/- 180 deg. This approach leads to the realization of a new model-follower attitude-control system that exhibits exact linear attitude-error dynamics.

  11. Modular design attitude control system

    NASA Technical Reports Server (NTRS)

    Chichester, F. D.

    1984-01-01

    A sequence of single axismodels and a series of reduced state linear observers of minimum order are used to reconstruct inaccessible variables pertaining to the modular attitude control of a rigid body flexible suspension model of a flexible spacecraft. The single axis models consist of two, three, four, and five rigid bodies, each interconnected by a flexible shaft passing through the mass centers of the bodies. Modal damping is added to each model. Reduced state linear observers are developed for synthesizing the inaccessible modal state variables for each modal model.

  12. Seasat-A attitude control system

    NASA Technical Reports Server (NTRS)

    Weiss, R.; Rodden, J. J.; Hendricks, R. J.

    1977-01-01

    The Seasat-A attitude control system controls the attitude of the satellite system during injection into final circular orbit after Atlas boost, during orbit adjust and trim phases, and throughout the 3-year mission. Ascent and injection guidance and attitude control are provided by the Agena spacecraft with a gyrocompassed mass expulsion system. On-orbit attitude control functions are performed by a system that has its functional roots in the gravity-gradient momentum bias technology. The paper discusses hardware, control laws, and simulation results.

  13. Spacecraft Attitude and Orbit Control Systems testing

    NASA Astrophysics Data System (ADS)

    Sonnenschein, F. J.; Schoomade, M.; Zwartbol, T.

    1995-03-01

    Contemporary AOCS are equipped with local Attitude Control Computers which provide sophisticated Attitude and Orbit Control functions, automatic Failure Detection and Isolation functions and extensive Telemetry and Telecommand handling functions. Generic models of the design, development and test life cycle approaches for such intelligent AOCS are emerging. Also knowledge of the activities to be performed and the generic design, development and test environments to be used during the different phases is accumulating. Lessons learned can be used to improve AOCS development life cycle approaches and to define new development and test environments which improve the efficiency of the design, development and test life cycle and quality of the product. The SAX (Satellite per Astronomia a raggi X) satellite is equipped with a contemporary AOCS providing the above mentioned functions. In this paper the SAX AOCS software design, development and test life cycle is described as an example of AOCS software development. Lessons learned and suggestions for possible improvements are given.

  14. Lorentz Force Based Satellite Attitude Control

    NASA Astrophysics Data System (ADS)

    Giri, Dipak Kumar; Sinha, Manoranjan

    2016-07-01

    Since the inception of attitude control of a satellite, various active and passive control strategies have been developed. These include using thrusters, momentum wheels, control moment gyros and magnetic torquers. In this present work, a new technique named Lorentz force based Coulombic actuators for the active control is proposed. This method uses electrostatic charged shells, which interact with the time varying earth's magnetic field to establish a full three axes control of the satellite. It is shown that the proposed actuation mechanism is similar to a satellite actuated by magnetic coils except that the resultant magnetic moment vanishes under two different conditions. The equation for the required charges on the the Coulomb shells attached to the satellite body axes is derived, which is in turn used to find the available control torque for actuating the satellite along the orbit. Stability of the proposed system for very high initial angular velocity and exponential stability about the origin are proved for a proportional-differential control input. Simulations are carried out to show the efficacy of the proposed system for the attitude control of the earth-pointing satellite.

  15. Nonlinear spacecraft`s gyromoment attitude control

    SciTech Connect

    Somov, Y.I.

    1994-12-31

    Nonlinear methods of attitude control for spacecraft`s spatial rotation maneuvers through the use of gyrodynes - single gimbal control moment gyroscopes - are developed. We present new results on optimizing and dynamic synthesis of the nonlinear gyromoment attitude control system for a fast-manoeuvring spacecraft with a minimum-excessive scheme of gyrodynes.

  16. RECOGNIZING FARMERS' ATTITUDES AND IMPLEMENTING NONPOINT SOURCE POLLUTION CONTROL POLICIES

    EPA Science Inventory

    This report examines the role of farmer attitudes and corresponding communication activities in the implementation of nonpoint source water pollution control programs. The report begins with an examination of the basis for and function of attitudes in influencing behavior. The ro...

  17. Linearizing feedforward/feedback attitude control

    NASA Technical Reports Server (NTRS)

    Paielli, Russell A.; Bach, Ralph E.

    1991-01-01

    An approach to attitude control theory is introduced in which a linear form is postulated for the closed-loop rotation error dynamics, then the exact control law required to realize it is derived. The nonminimal (four-component) quaternion form is used to attitude because it is globally nonsingular, but the minimal (three-component) quaternion form is used for attitude error because it has no nonlinear constraints to prevent the rotational error dynamics from being linearized, and the definition of the attitude error is based on quaternion algebra. This approach produces an attitude control law that linearizes the closed-loop rotational error dynamics exactly, without any attitude singularities, even if the control errors become large.

  18. ISS Update: Attitude Determination and Control Officer

    NASA Video Gallery

    NASA Public Affairs Officer Dan Huot talks with Attitude Determination and Control Officer (ADCO) flight controller Ann Esbeck in the Mission Control Center at Johnson Space Center. They discuss th...

  19. Adaptive mass expulsion attitude control system

    NASA Technical Reports Server (NTRS)

    Rodden, John J. (Inventor); Stevens, Homer D. (Inventor); Carrou, Stephane (Inventor)

    2001-01-01

    An attitude control system and method operative with a thruster controls the attitude of a vehicle carrying the thruster, wherein the thruster has a valve enabling the formation of pulses of expelled gas from a source of compressed gas. Data of the attitude of the vehicle is gathered, wherein the vehicle is located within a force field tending to orient the vehicle in a first attitude different from a desired attitude. The attitude data is evaluated to determine a pattern of values of attitude of the vehicle in response to the gas pulses of the thruster and in response to the force field. The system and the method maintain the attitude within a predetermined band of values of attitude which includes the desired attitude. Computation circuitry establishes an optimal duration of each of the gas pulses based on the pattern of values of attitude, the optimal duration providing for a minimal number of opening and closure operations of the valve. The thruster is operated to provide gas pulses having the optimal duration.

  20. Space Station Freedom Attitude Determination and Control System Overview

    NASA Technical Reports Server (NTRS)

    Penrod, Jeff

    1990-01-01

    Viewgraphs on Space Station Freedom attitude determination and control system overview are presented. Topics covered include: highly dynamic plant; SSF flight attitudes; effectors; inertial attitude sensors; control system performance requirements; control system functional requirements; and controller architecture.

  1. Torque equilibrium attitude control for Skylab reentry

    NASA Technical Reports Server (NTRS)

    Glaese, J. R.; Kennel, H. F.

    1980-01-01

    The method of torque equilibrium attitude control used to control the reentry of Skylab to an altitude below 150 km without the use of thruster fuel once the attitude was established is discussed. The Skylab attitude and pointing control system, which included rate gyros, sun sensors, star tracker, the Apollo telescope mount digital computer, control moment gyros and cold-gas attitude thrusters, is presented. The 12 torque equilibrium attitudes found at which aerodynamic, gravity gradient and gyroscopic torques would balance are indicated, and the three of those at which the solar power supply would be adequate for attitude control are illustrated. The equilibrium seeking method employed is then examined, and the operation and performance of the torque equilibrium attitude control system during the three weeks prior to Skylab reentry are discussed. It is concluded that the torque equilibrium attitude control method developed for Skylab was successful in performing its assigned mission, and will be valuable for the design of future, low-altitude spacecraft or tethered vehicles.

  2. Trying to trust: Brain activity during interpersonal social attitude change.

    PubMed

    Filkowski, Megan M; Anderson, Ian W; Haas, Brian W

    2016-04-01

    Interpersonal trust and distrust are important components of human social interaction. Although several studies have shown that brain function is associated with either trusting or distrusting others, very little is known regarding brain function during the control of social attitudes, including trust and distrust. This study was designed to investigate the neural mechanisms involved when people attempt to control their attitudes of trust or distrust toward another person. We used a novel control-of-attitudes fMRI task, which involved explicit instructions to control attitudes of interpersonal trust and distrust. Control of trust or distrust was operationally defined as changes in trustworthiness evaluations of neutral faces before and after the control-of-attitudes fMRI task. Overall, participants (n = 60) evaluated faces paired with the distrust instruction as being less trustworthy than faces paired with the trust instruction following the control-of-distrust task. Within the brain, both the control-of-trust and control-of-distrust conditions were associated with increased temporoparietal junction, precuneus (PrC), inferior frontal gyrus (IFG), and medial prefrontal cortex activity. Individual differences in the control of trust were associated with PrC activity, and individual differences in the control of distrust were associated with IFG activity. Together, these findings identify a brain network involved in the explicit control of distrust and trust and indicate that the PrC and IFG may serve to consolidate interpersonal social attitudes. PMID:26567160

  3. Integrated Attitude Control Based on Momentum Management for Space Station

    NASA Astrophysics Data System (ADS)

    Zhou, Li-Ni

    An integrated attitude control for attitude control, momentum management and power storage is proposed as a momentum-management-based IPACS. The integrated attitude control combines ACMM and IPACS to guarantees the momentum of CMGs and flywheels within acceptable limits as well as satisfying the requirements of attitude control and power storage. The later objective is to testify the foundation of the integrated attitude control by the fact that the momentum management of the integrated attitude control is able to keep the momentum exchange actuators including flywheels and VSCMG out of singularity. Finally, the space station attitude control task during assembly process is illustrated to testify the effectiveness of the integrated attitude control.

  4. Attitude Control Propulsion Components, Volume 1

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Effort was made to include as much engineering information on each component as possible, consistent with usefulness and catalog size limitations. The contents of this catalog contain components which were qualified for use with spacecraft monopropellant hydrazine and inert gas attitude control systems. Thrust ranges up to 44.5 N (10.0 lbf) for hydrazine and inert gas sytems were considered. Additionally, some components qualified for uses other than spacecraft attitude control are included because they are suitable for use in attitude controls systems.

  5. Miniaturized attitude control system for nanosatellites

    NASA Astrophysics Data System (ADS)

    Candini, Gian Paolo; Piergentili, Fabrizio; Santoni, Fabio

    2012-12-01

    A miniaturized attitude control system suitable for nanosatellites, developed using only commercial off-the-shelf components, is described in the paper. It is a complete and independent system to be used on board nanosatellites, allowing automated attitude control. To integrate this system into nanosatellites such as Cubesats its size has been reduced down to a cube of side about 5 cm. The result is a low cost attitude control system built with terrestrial components, integrating three micro magnetotorquers, three micro reaction wheels, three magnetometers and redundant control electronics, capable of performing automatics operations on request from the ground. The system can operate as a real time maneuvering system, executing commands sent from the ground or as a standalone attitude control system receiving the solar array status from a hosting satellite and the satellite ephemeris transmitted from the ground station. The main characteristics of the developed system and test results are depicted in this paper.

  6. Attitude Control Propulsion Components, Volume 2

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Attitude control propulsion components are described, including hydrazine thrusters, hydrazine thruster and cold gas jet valves, and pressure and temperature transducers. Component-ordered data are presented in tabular form; the manufacturer and specific space program are included.

  7. Evolution of spacecraft attitude control concepts before 1952

    NASA Technical Reports Server (NTRS)

    Roberson, R. E.

    1977-01-01

    The control of rotational motion of a spacecraft during its free flight regime is traced from pioneer space flight to the year 1952. Essentials of attitude control systems are reviewed and spin stabilization is examined. Other topics include passive stabilization and active closed loop control.

  8. Attitude Determination and Control Systems

    NASA Technical Reports Server (NTRS)

    Starin, Scott R.; Eterno, John

    2010-01-01

    The importance of accurately pointing spacecraft to our daily lives is pervasive, yet somehow escapes the notice of most people. In this section, we will summarize the processes and technologies used in designing and operating spacecraft pointing (i.e. attitude) systems.

  9. Solar Sail Attitude Control Performance Comparison

    NASA Technical Reports Server (NTRS)

    Bladt, Jeff J.; Lawrence, Dale A.

    2005-01-01

    Performance of two solar sail attitude control implementations is evaluated. One implementation employs four articulated reflective vanes located at the periphery of the sail assembly to generate control torque about all three axes. A second attitude control configuration uses mass on a gimbaled boom to alter the center-of-mass location relative to the center-of-pressure producing roll and pitch torque along with a pair of articulated control vanes for yaw control. Command generation algorithms employ linearized dynamics with a feedback inversion loop to map desired vehicle attitude control torque into vane and/or gimbal articulation angle commands. We investigate the impact on actuator deflection angle behavior due to variations in how the Jacobian matrix is incorporated into the feedback inversion loop. Additionally, we compare how well each implementation tracks a commanded thrust profile, which has been generated to follow an orbit trajectory from the sun-earth L1 point to a sub-L1 station.

  10. Integrated Attitude Control Strategy for the Asteroid Redirect Mission

    NASA Technical Reports Server (NTRS)

    Lopez, Pedro, Jr.; Price, Hoppy; San Martin, Miguel

    2014-01-01

    A deep-space mission has been proposed to redirect an asteroid to a distant retrograde orbit around the moon using a robotic vehicle, the Asteroid Redirect Vehicle (ARV). In this orbit, astronauts will rendezvous with the ARV using the Orion spacecraft. The integrated attitude control concept that Orion will use for approach and docking and for mated operations will be described. Details of the ARV's attitude control system and its associated constraints for redirecting the asteroid to the distant retrograde orbit around the moon will be provided. Once Orion is docked to the ARV, an overall description of the mated stack attitude during all phases of the mission will be presented using a coordinate system that was developed for this mission. Next, the thermal and power constraints of both the ARV and Orion will be discussed as well as how they are used to define the optimal integrated stack attitude. Lastly, the lighting and communications constraints necessary for the crew's extravehicular activity planned to retrieve samples from the asteroid will be examined. Similarly, the joint attitude control strategy that employs both the Orion and the ARV attitude control assets prior, during, and after each extravehicular activity will also be thoroughly discussed.

  11. Attitude motion of a non-attitude-controlled cylindrical satellite

    NASA Technical Reports Server (NTRS)

    Wilkinson, C. K.

    1988-01-01

    In 1985, two non-attitude-controlled satellites were each placed in a low earth orbit by the Scout Launch Vehicle. The satellites were cylindrical in shape and contained reservoirs of hydrazine fuel. Three-axis magnetometer measurements, telemetered in real time, were used to derive the attitude motion of each satellite. Algorithms are generated to deduce possible orientations (and magnitudes) of each vehicle's angular momentum for each telemetry contact. To resolve ambiguities at each contact, a force model was derived to simulate the significant long-term effects of magnetic, gravity gradient, and aerodynamic torques on the angular momentum of the vehicles. The histories of the orientation and magnitude of the angular momentum are illustrated.

  12. Power, thermal, and attitude control design interactions of the CCE/AMPTE spacecraft. [Charge Composition Explorer/Active Magnetospheric Particle Tracer Explorers

    NASA Technical Reports Server (NTRS)

    Wingate, C. A., Jr.; Allen, W. E.; Smola, J. F.; Ray, J. C.

    1982-01-01

    The power, thermal and attitude control interactions of the CCE spacecraft and the design compromises resulting from these interactions are described. These compromises result from the conflict between the plane change maneuver requirements and the final on station requirements. The resolution of these conflicts to arrive at an acceptable final design, is given and the resulting power, thermal and attitude control systems are described in some detail.

  13. Experiment D010: Ion sensing attitude control

    NASA Technical Reports Server (NTRS)

    Sagalyn, R. C.; Smiddy, M.

    1971-01-01

    The feasibility of an attitude control system that uses environmental positive ions and an electrostatic detection system to measure spacecraft pitch and yaw is studied. The secondary objective was to measure the spatial and temporal variations of ambient positively charged particles along the orbital path of the Gemini 10 and 12 spacecrafts. The results proved that the use of a horizon detector in conjunction with pitch and yaw sensors would facilitate complete description of the spacecraft position and attitude. Furthermore, with the addition of a servosystem, the unit could be used as a complete automatic attitude-control system that would be applicable from the lowest satellite altitudes up to at least 10 earth radii. Also, results established that the charge density along the trajectory of the satellite could be determined by transmission of output voltages from the individual electrometers.

  14. Vibration suppression of flexible spacecraft during attitude control

    NASA Astrophysics Data System (ADS)

    Song, Gangbing; Agrawal, Brij N.

    2001-07-01

    This paper presents a new approach to vibration reduction of flexible spacecraft during attitude control by using pulse width pulse frequency (PWPF) modulator for thruster firing and smart materials for active vibration suppression. The experiment was conducted on the Naval Postgraduate School (NPS)'s flexible spacecraft simulator (FSS), which consists of a central rigid body and an L-shape flexible appendage. A pair of on-off thrusters are used to re-orient the FSS. To actively suppress vibrations introduced to the flexible appendage, embedded piezoelectric ceramic patches are used as both sensors and actuators to detect and counter react to the induced vibration. For active vibration suppression using the piezoelectric ceramic patches, positive position feedback (PPF) control targeting at the first two flexible modes of the FSS system is used. Experimental results demonstrate the effectiveness of the control strategy of PWPF modulation for attitude control and PPF for active vibration suppression.

  15. Attitude controls for VTOL aircraft

    NASA Technical Reports Server (NTRS)

    Pauli, F. A.

    1971-01-01

    Systems consist of single duct system with two sets of reaction control nozzles, one linked mechanically to pilot's controls, and other set driven by electric servomotors commanded by preselected combinations of electrical signals.

  16. Attitude Dynamics and Control of Solar Sails

    NASA Astrophysics Data System (ADS)

    Sperber, Evan

    Solar sails are space vehicles that rely on solar radiation pressure in order to generate forces for thrust and attitude control torques. They exhibit characteristics such as large moments of inertia, fragility of various system components, and long mission durations that make attitude control a particularly difficult engineering problem. Thrust vector control (TVC) is a family of sailcraft attitude control techniques that is on a short list of strategies thought to be suitable for the primary attitude control of solar sails. Every sailcraft TVC device functions by manipulating the relative locations of the composite mass center (cm) of the sailcraft and the center of pressure (cp) of at least one of its reflectors. Relative displacement of these two points results in body torques that can be used to steer the sailcraft. This dissertation presents a strategy for the large-angle reorientation of a sailcraft using TVC. Two forms of TVC, namely the panel and ballast mass translation methods are well represented in the literature, while rigorous studies regarding a third form, gimballed mass rotation, are conspicuously absent. The gimballed mass method is physically realized by placing a ballast mass, commonly the sailcraft's scientific payload, at the tip of a gimballed boom that has its base fixed at some point on the sailcraft. A TVC algorithm will then strategically manipulate the payload boom's gimbal angles, thereby changing the projection of the sailcraft cm in the plane of the sail. This research demonstrates effective three-axis attitude control of a model sailcraft using numerical simulation of its nonlinear equations of motion. The particular TVC algorithm developed herein involves two phases---the first phase selects appropriate gimbal rates with the objective that the sailcraft be placed in the neighborhood of its target orientation. It was discovered, however that concomitantly minimizing attitude error as well as residual body rate was not possible using

  17. Mariner Mars 1971 attitude control subsystem

    NASA Technical Reports Server (NTRS)

    Edmunds, R. S.

    1974-01-01

    The Mariner Mars 1971 attitude control subsystem (ACS) is discussed. It is comprised of a sun sensor set, a Canopus tracker, an inertial reference unit, two cold gas reaction control assemblies, two rocket engine gimbal actuators, and an attitude control electronics unit. The subsystem has the following eight operating modes: (1) launch, (2) sun acquisition, (3) roll search, (4) celestial cruise, (5) all-axes inertial, (6) roll inertial, (7) commanded turn, and (8) thrust vector control. In the celestial cruise mode, the position control is held to plus or minus 0.25 deg. Commanded turn rates are plus or minus 0.18 deg/s. The attitude control logic in conjunction with command inputs from other spacecraft subsystems establishes the ACS operating mode. The logic utilizes Sun and Canopus acquisition signals generated within the ACS to perform automatic mode switching so that dependence of ground control is minimized when operating in the sun acquisition, roll search, and celestial cruise modes. The total ACS weight is 65.7 lb, and includes 5.4 lb of nitrogen gas. Total power requirements vary from 9 W for the celestial cruise mode to 54 W for the commanded turn mode.

  18. Attitude control compensator for flexible spacecraft

    NASA Technical Reports Server (NTRS)

    Goodzeit, Neil E. (Inventor); Linder, David M. (Inventor)

    1991-01-01

    An attitude control loop for a spacecraft uses a proportional-integral-derivative (PID) controller for control about an axis. The spacecraft body has at least a primary mechanical resonance. The attitude sensors are collocated, or both on the rigid portion of the spacecraft. The flexure attributable to the resonance may result in instability of the system. A compensator for the control loop has an amplitude response which includes a component which rolls off beginning at frequencies below the resonance, and which also includes a component having a notch at a notch frequency somewhat below the resonant frequency. The phase response of the compensator tends toward zero at low frequencies, and tends toward -180.degree. as frequency increases toward the notch frequency. At frequencies above the notch frequency, the phase decreases from +180.degree., becoming more negative, and tending toward -90.degree. at frequencies far above the resonance frequency. Near the resonance frequency, the compensator phase is near zero.

  19. Solar sail attitude dynamics and control

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.; Marsh, E. L.; Gunter, S. M.

    1977-01-01

    This paper describes some results of an attitude dynamics and control study for a solar sailing vehicle. This type of vehicle is currently under study and evaluation at JPL and has very high potential for interplanetary missions in and beyond the 1980s. Crucial to the success of such a vehicle would be the performance of its onboard attitude control system. Because of the vehicle's large size and its flexibility, vehicle deformations may have a potential for causing a degradation in vehicle performance. It may therefore be necessary for the control system to take into account the vehicle deformations as well as its rigid-body motions. Distributed parameter system analysis techniques are used in the paper to study certain fundamental aspects of such a control system for the sail vehicle. The techniques can, however, be more generally applicable to other large flexible vehicles.

  20. Attitude Determination and Control Systems

    NASA Technical Reports Server (NTRS)

    Starin, Scott R.; Eterno, John

    2011-01-01

    designing and operating spacecraft pointing (i.e. attitude) systems.

  1. Nonlinear attitude control of spacecraft and momentum management of control moment gyros

    NASA Astrophysics Data System (ADS)

    Oh, Hwa-Suk

    Nonlinear design procedures are presented for obtaining attitude control and momentum management laws. These are based on the Liapunov stability theorems. The Work-Energy Rate (WER) principle is extended to cover general classes of systems. It is shown that the use of the WER principle for obtaining control laws, can reduce the design efforts. The attitude control laws are designed for several types of missions, i.e., absolute attitude and relative attitude control. The momentum management as well as attitude control laws are designed for both stable and unstable spacecraft configurations which use Control Moment Gyros (CMGs) as active actuators. A large stability region is found around the local-vertical-local-horizontal (LVLH) equilibrium point, and so the designed control laws can be used even in the event of large initial attitude deviations for LVLH. In the presence of constant disturbance, the momentum is managed by seeking a Torque Equilibrium Attitude (TEA) where the disturbance torque is balanced by gravity gradient and gyroscopic torques. This is done by the use of integral feedback of the control torque, which is related to the angular momentum of the CMGs. It is shown that the unknown constant disturbance can be identified by the use of integral feedback. Cyclic disturbance rejection for the pitch axis is performed by successive stabilization and integral feedback. Theoretical results developed are verified using both experimental and numerical simulations. Experimental model of a flexible spacecraft is used to demonstrate the applicability of the WER principle and the fact that under certain conditions, a control law based on a rigid body model, can be applied to a flexible spacecraft. Using a mathematical model of the Space Station Freedom, several attitude/momentum management control laws are simulated and shown to work successfully with/without a constant disturbance torque. The control law for cyclic disturbance rejection of pitch axis attitude is

  2. Enhanced Attitude Control Experiment for SSTI Lewis Spacecraft

    NASA Technical Reports Server (NTRS)

    Maghami, Peoman G.

    1997-01-01

    The enhanced attitude control system experiment is a technology demonstration experiment on the NASA's small spacecraft technology initiative program's Lewis spacecraft to evaluate advanced attitude control strategies. The purpose of the enhanced attitude control system experiment is to evaluate the feasibility of designing and implementing robust multi-input/multi-output attitude control strategies for enhanced pointing performance of spacecraft to improve the quality of the measurements of the science instruments. Different control design strategies based on modern and robust control theories are being considered for the enhanced attitude control system experiment. This paper describes the experiment as well as the design and synthesis of a mixed H(sub 2)/H(sub infinity) controller for attitude control. The control synthesis uses a nonlinear programming technique to tune the controller parameters and impose robustness and performance constraints. Simulations are carried out to demonstrate the feasibility of the proposed attitude control design strategy. Introduction

  3. TRMM On Orbit Attitude Control System Performance

    NASA Technical Reports Server (NTRS)

    Robertson, Brent; Placanica, Sam; Morgenstern, Wendy

    1999-01-01

    This paper presents an overview of the Tropical Rainfall Measuring Mission (TRMM) Attitude Control System (ACS) along with detailed in-flight performance results for each operational mode. The TRMM spacecraft is an Earth-pointed, zero momentum bias satellite launched on November 27, 1997 from Tanegashima Space Center, Japan. TRMM is a joint mission between NASA and the National Space Development Agency (NASDA) of Japan designed to monitor and study tropical rainfall and the associated release of energy. Launched to provide a validation for poorly known rainfall data sets generated by global climate models, TRMM has demonstrated its utility by reducing uncertainties in global rainfall measurements by a factor of two. The ACS is comprised of Attitude Control Electronics (ACE), an Earth Sensor Assembly (ESA), Digital Sun Sensors (DSS), Inertial Reference Units (IRU), Three Axis Magnetometers (TAM), Coarse Sun Sensors (CSS), Magnetic Torquer Bars (MTB), Reaction Wheel Assemblies (RWA), Engine Valve Drivers (EVD) and thrusters. While in Mission Mode, the ESA provides roll and pitch axis attitude error measurements and the DSS provide yaw updates twice per orbit. In addition, the TAM in combination with the IRU and DSS can be used to provide pointing in a contingency attitude determination mode which does not rely on the ESA. Although the ACS performance to date has been highly successful, lessons were learned during checkout and initial on-orbit operation. This paper describes the design, on-orbit checkout, performance and lessons learned for the TRMM ACS.

  4. Geometric Attitude Controls And Estimations On The Special Orthogonal Group

    NASA Astrophysics Data System (ADS)

    Wu, Tse-Huai

    This dissertation is concerned with spacecraft attitude control and estimation problems from the point of view of geometric mechanics. The controllers and observers are built on the special orthogonal group without any parameterizations, where the attitude dynamics is treated in a global and unique manner. The dissertation is composed of three parts. A leader-follower attitude formation control scheme is reported such that the leader spacecraft control its absolute attitude with respect to the inertial reference frame and the follower spacecraft control relative attitude with respect to other spacecraft in the formation. The unique feature is that both the absolute attitude and the relative attitude control systems are developed directly in terms of the line-of-sight observations, where attitude determination and estimation processes are not required. Second, an angular velocity observer is developed such that the estimated angular velocity is guaranteed to converge to the true angular velocity asymptotically from almost all initial estimates. Then, the presented observer is integrated with a proportional-derivative attitude tracking controller to show a separation type property for attitude tracking in the absence of angular velocity measurements. A hybrid observer for the attitude dynamics of a rigid body is proposed to guarantee global asymptotic stability. By designing a set of attitude error functions, attitude estimates are expelled from undesired equilibria to achieve global asymptotic stability. To guarantee that the estimated attitudes evolve on the special orthogonal group, a numerical algorithm based on the Lie group method is presented.

  5. Digital attitude control for NASA sounding rockets

    NASA Astrophysics Data System (ADS)

    Martinez, Carlos

    1998-11-01

    Various configurations of Solar Pointing Control Systems have been used for NASA sounding rockets since an initial flight in December of 1967. Until now, these attitude control systems have used an analog controller. The demand for a more advanced attitude control system with better performance and flexibility leads to the testing of a digital control system. Computer aided design was used to develop the control equations and an embedded controller is used to implement these equations. The analog control system pointing performance was degraded by electrical noise and offsets getting into the sensor signals. The solution to this problem was to isolate the sun sensor from payload electrical nose and ground loops. To accomplish this the sun sensor output was digitized and the data was sent to the control system using a fiber optical cable. This control system was flown on Naval Research Laboratories rocket 36.140 and had less than 0.5 arc-second peak-to-peak jitter during the flight. With further refinements the digital system is expected to attain jitter of less than 0.2 arc- seconds peak-to-peak.

  6. Spacecraft attitude control momentum requirements analysis

    NASA Technical Reports Server (NTRS)

    Robertson, Brent P.; Heck, Michael L.

    1987-01-01

    The relationship between attitude and angular momentum control requirements is derived for a fixed attitude, Earth orbiting spacecraft with large area articulating appendages. Environmental effects such as gravity gradient, solar radiation pressure, and aerodynamic forces arising from a dynamic, rotating atmosphere are examined. It is shown that, in general, each environmental effect contributes to both cyclic and secular momentum requirements both within and perpendicular to the orbit plane. The gyroscopic contribution to the angular momentum control requirements resulting from a rotating, Earth oriented spacecraft is also discussed. Special conditions are described where one or more components of the angular momentum can be made to vanish, or become purely cyclical. Computer generated plots for a candidate space station configuration are presented to supplement the analytically derived results.

  7. The Diabetes Intention, Attitude, and Behavior Questionnaire: evaluation of a brief questionnaire to measure physical activity, dietary control, maintenance of a healthy weight, and psychological antecedents

    PubMed Central

    Traina, Shana B; Mathias, Susan D; Colwell, Hilary H; Crosby, Ross D; Abraham, Charles

    2016-01-01

    Background This study assessed measurement properties of the 17-item Diabetes Intention, Attitude, and Behavior Questionnaire (DIAB-Q), which measures intention to engage in self-care behaviors, including following a diabetes diet and engaging in appropriate physical activity. Methods The DIAB-Q includes questions based on the Theory of Planned Behavior. Items were developed using published literature, input from health care professionals, and qualitative research findings in patients with and without type 2 diabetes mellitus (T2DM). In Stage I of the study, 23 adults with T2DM were interviewed to evaluate the content and clarity of the DIAB-Q. In Stage II 1,015 individuals with T2DM completed the DIAB-Q and supplemental questionnaires, including the Short Form-36 acute (SF-36), section III of the Multidimensional Diabetes Questionnaire, the Summary of Diabetes Self-Care Activities questionnaire, and self-administered items relevant to the treatment and management of T2DM (eg, blood pressure and glycated hemoglobin [HbA1c]) at baseline and 3–7 days later. Once the DIAB-Q scale structure was determined, its test–retest reliability, construct validity, and known-groups validity were evaluated, and minimal clinically important change was estimated. Results In Stage I, the 23 respondents surveyed generally reported that the DIAB-Q was clear and comprehensive and endorsed questions as relevant to their intentions to engage in diabetes-related self-care activities. Most subjects in Stage II were male, Caucasian, and married. Mean age was 63 years. Factor analysis revealed six psychological constructs (Behavior, Planning, Intention, Perceived Behavioral Control, Attitude, and Subjective Norm). Test–retest reliability was acceptable (≥0.70) for all scales, except Perceived Behavioral Control. Construct validity was demonstrated based on correlations with diabetes-specific items/scales and the SF-36. Known-groups validity was confirmed for Behavior, Planning, and

  8. Low cost attitude control system scanwheel development

    NASA Technical Reports Server (NTRS)

    Bialke, William; Selby, Vaughn

    1991-01-01

    In order to satisfy a growing demand for low cost attitude control systems for small spacecraft, development of low cost scanning horizon sensor coupled to a low cost/low power consumption Reaction Wheel Assembly was initiated. This report addresses the details of the versatile design resulting from this effort. Tradeoff analyses for each of the major components are included, as well as test data from an engineering prototype of the hardware.

  9. Robust nonlinear attitude control of flexible spacecraft

    NASA Technical Reports Server (NTRS)

    Singh, Sahjendra N.

    1987-01-01

    This paper presents an approach to large-angle rotational maneuvers of a spacecraft-beam-tip body configuration based on nonlinear invertibility and linear feedback stabilization. A control law u sub d is derived for the decoupled control of attitude angles, lateral elastic deflections, slopes due to bending and angular deflection due to torsion at the tip of the beam using torquers and force actuators. For the stabilization of the elastic modes, a linear feedback control law u sub s is obtained based on a linearized model augmented with a servocompensator. Simulation results are presented to show that large slewing and elastic mode stabilization can be accomplished.

  10. SSS-A attitude control prelaunch analysis and operations plan

    NASA Technical Reports Server (NTRS)

    Werking, R. D.; Beck, J.; Gardner, D.; Moyer, P.; Plett, M.

    1971-01-01

    A description of the attitude control support being supplied by the Mission and Data Operations Directorate is presented. Descriptions of the computer programs being used to support the mission for attitude determination, prediction, control, and definitive attitude processing are included. In addition, descriptions of the operating procedures which will be used to accomplish mission objectives are provided.

  11. Precision attitude control for tethered satellites

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert J.; Powell, J. D.

    1993-01-01

    Tethered spacecraft are particularly well suited to serve as isolation platforms for space-borne observatories. It has previously been shown that, due to the relatively large tether force, conventional means of performing attitude control for tethered satellites are inefficient for any mission with pointing requirements more stringent than about 1 deg. A particularly effective method of implementing attitude control for tethered satellites is to use the tether tension force to generate control moments by moving the tether attach point relative to the subsatellite center of mass. This paper presents the development of a precision pointing control algorithm for tethered satellites and the simulation of the control system with laboratory hardware. The control algorithm consists of a linear quadratic regulator feedback law and a Kalman filter. The control algorithm has been shown to regulate the vehicle orientation to within 0.60 arcsec rms. This level of precision was achieved only after including a mass center estimator and accurately modeling the effects of the nonlinear attach point motion actuator.

  12. Adaptive spacecraft attitude control utilizing eigenaxis rotations

    NASA Technical Reports Server (NTRS)

    Cochran, J. E., Jr.; Colburn, B. K.; Speakman, N. O.

    1975-01-01

    Conventional and adaptive attitude control of spacecraft which use control moment gyros (CMG's) as torque sources are discussed. Control laws predicated on the assumption of a linear system are used since the spacecraft equations of motion are formulated in an 'eigenaxis system' so that they are essentially linear during 'slow' maneuvers even if large angles are involved. The overall control schemes are 'optimal' in several senses. Eigenaxis rotations and a weighted pseudo-inverse CMG steering law are used and, in the adaptive case, a Model Reference Adaptive System (MRAS) controller based on Liapunov's Second Method is adopted. To substantiate the theory, digital simulation results obtained using physical parameters of a Large Space Telescope type spacecraft are presented. These results indicate that an adaptive control law is often desirable.

  13. Adaptive Attitude Control System For Space Station

    NASA Technical Reports Server (NTRS)

    Boussalis, Dhemetrios; Bayard, David S.; Wang, Shyh J.

    1995-01-01

    Report presents theoretical foundation for attitude control system for proposed Space Station Freedom in orbit around Earth. Intended to maintain space station in torque equilibrium with designated axes of its structure aligned with local vertical, local along-trajectory horizontal, and local across-trajectory horizontal axes, respectively. System required to provide desired combination of control performance and stability in presence of disturbances (e.g., variations in masses of payloads, movements of astronauts and equipment, atmospheric drag, gravitational anomalies, and interactions with docking spacecraft).

  14. Adaptive control applied to Space Station attitude control system

    NASA Technical Reports Server (NTRS)

    Lam, Quang M.; Chipman, Richard; Hu, Tsay-Hsin G.; Holmes, Eric B.; Sunkel, John

    1992-01-01

    This paper presents an adaptive control approach to enhance the performance of current attitude control system used by the Space Station Freedom. The proposed control law was developed based on the direct adaptive control or model reference adaptive control scheme. Performance comparisons, subject to inertia variation, of the adaptive controller and the fixed-gain linear quadratic regulator currently implemented for the Space Station are conducted. Both the fixed-gain and the adaptive gain controllers are able to maintain the Station stability for inertia variations of up to 35 percent. However, when a 50 percent inertia variation is applied to the Station, only the adaptive controller is able to maintain the Station attitude.

  15. Attitude Control Subsystem for the Advanced Communications Technology Satellite

    NASA Technical Reports Server (NTRS)

    Hewston, Alan W.; Mitchell, Kent A.; Sawicki, Jerzy T.

    1996-01-01

    This paper provides an overview of the on-orbit operation of the Attitude Control Subsystem (ACS) for the Advanced Communications Technology Satellite (ACTS). The three ACTS control axes are defined, including the means for sensing attitude and determining the pointing errors. The desired pointing requirements for various modes of control as well as the disturbance torques that oppose the control are identified. Finally, the hardware actuators and control loops utilized to reduce the attitude error are described.

  16. MAP Attitude Control System Design and Analysis

    NASA Technical Reports Server (NTRS)

    Andrews, S. F.; Campbell, C. E.; Ericsson-Jackson, A. J.; Markley, F. L.; ODonnell, J. R., Jr.

    1997-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The MAP spacecraft will perform its mission in a Lissajous orbit around the Earth-Sun L(sub 2) Lagrange point to suppress potential instrument disturbances. To make a full-sky map of cosmic microwave background fluctuations, a combination fast spin and slow precession motion will be used. MAP requires a propulsion system to reach L(sub 2), to unload system momentum, and to perform stationkeeping maneuvers once at L(sub 2). A minimum hardware, power and thermal safe control mode must also be provided. Sufficient attitude knowledge must be provided to yield instrument pointing to a standard deviation of 1.8 arc-minutes. The short development time and tight budgets require a new way of designing, simulating, and analyzing the Attitude Control System (ACS). This paper presents the design and analysis of the control system to meet these requirements.

  17. Students' Attitudes toward an After-School Physical Activity Programme

    ERIC Educational Resources Information Center

    Agbuga, Bulent; Xiang, Ping; McBride, Ron

    2013-01-01

    Though considerable research on student attitudes has been conducted in physical education, little information exists concerning student attitudes toward after-school physical activity programmes. This study assessed students' attitudes toward their after-school physical activity programme located in southwest Texas, USA. Participants included 158…

  18. Globally stable control laws for the attitude maneuver problem - Tracking control and adaptive control

    NASA Technical Reports Server (NTRS)

    Wen, John T.; Kreutz, Kenneth

    1988-01-01

    An approach using a globally nonsingular representation is proposed for the attitude control problem of a rigid body. The attitude dynamics are described by the nonlinear Euler equation together with the nonlinear kinematic equations which relate a representation of attitude to the angular velocity of the body. When this approach is combined with an energy-motivated Lyapunov function, a large class of globally stable attitude control laws can be derived. This class includes model-independent tracking control, model-dependent tracking control, and adaptive control, allowing tradeoffs between controller complexity, attainable performance, and available model information.

  19. The Spartan attitude control system - Control electronics assembly

    NASA Technical Reports Server (NTRS)

    Stone, R. W.

    1986-01-01

    The Spartan attitude control system (ACS) represents an evolutionary development of the previous STRAP-5 ACS through the use of state-of-the-art microprocessors and hardware. Despite a gyro rate signal noise problem that caused the early depletion of argon gas, the Spartan 101 experiment was able to collect several hours of data from two targets. Attention is presently given to the ACS sequencer module, sensor interface box, valve driver box, control electronics software, jam tables, and sequencer programs.

  20. Operational Implementation of Mars Express Orbit and Attitude Control

    NASA Astrophysics Data System (ADS)

    Companys, V.; Keil, J.; Rivero, E.; Mueller, M.; de La Fuente, S.; Perez, P.

    On June 2nd 2003 the Mars Express spacecraft was put onto Earth escape orbit by a Soyuz rocket. Following ascend trajectory and separation from the rocket ESOC took control of the S/C. Initial attitude acquisition and solar array deployment performed nominally, leading to convergence in Sun pointing mode. The S/C established 3-axis stabilisation based on star tracker measurements and performed successfully a series of autonomous slews to direct the high gain antenna towards the Earth, thus reaching the default attitude guidance for cruise. However star tracker measurements, which had been nominally interrupted during the slews, were not recovered. Soon after, a surveillance on the inertial measurement package triggered a transition to safe mode. A challenging trip towards Mars had started. During the cruise of Mars Express the ground segment and in particular the Flight Dynamics team had to master several problems. Some of those were originated by S/C anomalies. In other occasions, as for the October solar flare event, the problem was of natural cause. Payload commissioning activities (e.g. MELACOM antenna beam characterisation, instrument calibration) involving highly tailored attitude profiles were supported during cruise. Also platform characterisation (e.g. High Gain Antenna pointing calibration, Main Engine calibration) and S/C troubleshooting (e.g. star tracker sky scans) required attitude control strategies of high complexity. Several orbit manoeuvres were executed during cruise. The spacecraft was put in collision course 50 days prior to arrival to Mars. On December 16th an accurate manoeuvre was performed to fine tune the trajectory for the release of the landing probe Beagle-2, which took place on Dec 19th . The day after lander ejection, a deflection manoeuvre put the S/C onto its final Mars arrival hyperbola. On December 25th Mars Express performed a perfect insertion manoeuvre with the 400N main engine that led to capture into Mars orbit. Eleven

  1. Chinese Teachers' Attitudes toward Teaching Physical Activity and Fitness

    ERIC Educational Resources Information Center

    Guan, Jianmin; McBride, Ron; Xiang, Ping

    2005-01-01

    In this study we examined Chinese physical educators' attitudes toward teaching physical activity and fitness. We then compared the Chinese teacher attitudes to their American counterparts. Participants were 330 Chinese elementary, middle and high school physical educators. The Teachers' Attitudes Toward Curriculum in Physical Education (TATCPE)…

  2. Dynamic and attitude control characteristics of an International Space Station

    NASA Technical Reports Server (NTRS)

    Sutter, Thomas R.; Cooper, Paul A.; Young, John W.; Mccutchen, Don K.

    1987-01-01

    The structural dynamic characteristics of the International Space Station (ISS), the interim reference configuration established for NASA's Space Station developmental program, are discussed, and a finite element model is described. Modes and frequencies of the station below 2.0 Hz are derived, and the dynamic response of the station is simulated for an external impulse load corresponding to a failed shuttle-docking maneuver. A three-axis attitude control system regulates the ISS orientation, with control moment gyros responding to attitude and attitude rate signals. No instabilities were found in the attitude control system.

  3. TSS subsatellite attitude dynamics and control laws verification programs

    NASA Technical Reports Server (NTRS)

    Venditti, Floriano

    1987-01-01

    A dynamic model of the Tethered Satellite System (TSS) and of the relevant simulation program, developed in order to provide the dynamic analysis support for the design verification of the subsatellite attitude control, is presented. Special care was spent in the satellite attitude dynamic analysis and the model was specifically conceived to this aim. The way in which the simulation results can be utilized for the verification and testing of the attitude control is also presented.

  4. Attitude and Translation Control of a Solar Sail Vehicle

    NASA Technical Reports Server (NTRS)

    Singh, Gurkirpal

    2008-01-01

    A report discusses the ability to control the attitude and translation degrees-of-freedom of a solar sail vehicle by changing its center of gravity. A movement of the spacecraft s center of mass causes solar-pressure force to apply a torque to the vehicle. At the compact core of the solar-sail vehicle lies the spacecraft bus which is a large fraction of the total vehicle mass. In this concept, the bus is attached to the spacecraft by two single degree-of-freedom linear tracks. This allows relative movement of the bus in the sail plane. At the null position, the resulting solar pressure applies no torque to the vehicle. But any deviation of the bus from the null creates an offset between the spacecraft center of mass and center of solar radiation pressure, resulting in a solar-pressure torque on the vehicle which changes the vehicle attitude. Two of the three vehicle degrees of freedom can be actively controlled in this manner. The third, the roll about the sunline, requires a low-authority vane/propulsive subsystem. Translation control of the vehicle is achieved by directing the solar-pressure-induced force in the proper inertial direction. This requires attitude control. Attitude and translation degrees-of-freedom are therefore coupled. A guidance law is proposed, which allows the vehicle to stationkeep at an appropriate point on the inertially-rotating Sun-Earth line. Power requirements for moving the bus are minimal. Extensive software simulations have been performed to demonstrate the feasibility of this concept.

  5. Attitude Control Performance of IRVE-3

    NASA Technical Reports Server (NTRS)

    Dillman, Robert A.; Gsell, Valerie T.; Bowden, Ernest L.

    2013-01-01

    The Inflatable Reentry Vehicle Experiment 3 (IRVE-3) launched July 23, 2012, from NASA Wallops Flight Facility and successfully performed its mission, demonstrating both the survivability of a hypersonic inflatable aerodynamic decelerator in the reentry heating environment and the effect of an offset center of gravity on the aeroshell's flight L/D. The reentry vehicle separated from the launch vehicle, released and inflated its aeroshell, reoriented for atmospheric entry, and mechanically shifted its center of gravity before reaching atmospheric interface. Performance data from the entire mission was telemetered to the ground for analysis. This paper discusses the IRVE-3 mission scenario, reentry vehicle design, and as-flown performance of the attitude control system in the different phases of the mission.

  6. The Relationship of Pupil Control Ideology to Students' Rights Attitudes.

    ERIC Educational Resources Information Center

    Jones, Lynn

    As a result of increased court intervention in favor of students' rights, a review of a sample of teachers concerning their attitudes about student control was examined. Taking into consideration the teachers' attitudes concerning student rights, the Pupil Control Ideology test and the Students' Rights Acceptance Scale were used as measurement…

  7. MSFC Skylab attitude and pointing control system mission evaluation

    NASA Technical Reports Server (NTRS)

    Chubb, W. B.

    1974-01-01

    The results of detailed performance analyses of the attitude and pointing control system in-orbit hardware and software on Skylab are reported. Performance is compared with requirements, test results, and prelaunch predictions. A brief history of the altitude and pointing control system evolution leading to the launch configuration is presented. The report states that the attitude and pointing system satisfied all requirements.

  8. IMP-J attitude control prelaunch analysis and operations plan

    NASA Technical Reports Server (NTRS)

    Hooper, H. L.; Mckendrew, J. B.; Repass, G. D.

    1973-01-01

    A description of the attitude control support being supplied for the Explorer 50 mission is given. Included in the document are descriptions of the computer programs being used to support attitude determination, prediction, and control for the mission and descriptions of the operating procedures that will be used to accomplish mission objectives.

  9. Application of a microprocessor to a spacecraft attitude control

    NASA Technical Reports Server (NTRS)

    Brady, D. H.; Hermann, F. W.

    1980-01-01

    The attitude control system (ACS) microprocessor development work spanned three main design areas: hardware and instruction set, ACS firmware, and hardware firmware verification testing. The processor hardware utilizes two parallel 4 bit microprocessors. The firmware includes data processing for five sensors, four attitude control laws, and telemetry and commands.

  10. New attitude penalty functions for spacecraft optimal control problems

    SciTech Connect

    Schaub, H.; Junkins, J.L.; Robinett, R.D.

    1996-03-01

    A solution of a spacecraft optimal control problem, whose cost function relies on an attitude description, usually depends on the choice of attitude coordinates used. A problem could be solved using 3-2-1 Euler angles or using classical Rodriguez parameters and yield two different ``optimal`` solutions, unless the performance index in invariant with respect to the attitude coordinate choice. Another problem arising with many attitude coordinates is that they have no sense of when a body has tumbled beyond 180{degrees} from the reference attitude. In many such cases it would be easier (i.e. cost less) to let the body complete the revolution than to force it to reverse the rotation and return to the desired attitude. This paper develops a universal attitude penalty function g() whose value is independent of the attitude coordinates chosen to represent it. Furthermore, this function will achieve its maximum value only when a principal rotation of {plus_minus}180{degrees} from the target state is performed. This will implicitly permit the g() function to sense the shortest rotational distance back to the reference state. An attitude penalty function which depends on the Modified Rodriguez Parameters (MRP) will also be presented. These recently discovered MRPs are a non-singular three-parameter set which can describe any three-attitude. This MRP penalty function is simpler than the attitude coordinate independent g() function, but retains the useful property of avoiding lengthy principal rotations of more than {plus_minus}180{degrees}.

  11. Attitude control with realization of linear error dynamics

    NASA Technical Reports Server (NTRS)

    Paielli, Russell A.; Bach, Ralph E.

    1993-01-01

    An attitude control law is derived to realize linear unforced error dynamics with the attitude error defined in terms of rotation group algebra (rather than vector algebra). Euler parameters are used in the rotational dynamics model because they are globally nonsingular, but only the minimal three Euler parameters are used in the error dynamics model because they have no nonlinear mathematical constraints to prevent the realization of linear error dynamics. The control law is singular only when the attitude error angle is exactly pi rad about any eigenaxis, and a simple intuitive modification at the singularity allows the control law to be used globally. The forced error dynamics are nonlinear but stable. Numerical simulation tests show that the control law performs robustly for both initial attitude acquisition and attitude control.

  12. Adaptive Jacobian Fuzzy Attitude Control for Flexible Spacecraft Combined Attitude and Sun Tracking System

    NASA Astrophysics Data System (ADS)

    Chak, Yew-Chung; Varatharajoo, Renuganth

    2016-07-01

    Many spacecraft attitude control systems today use reaction wheels to deliver precise torques to achieve three-axis attitude stabilization. However, irrecoverable mechanical failure of reaction wheels could potentially lead to mission interruption or total loss. The electrically-powered Solar Array Drive Assemblies (SADA) are usually installed in the pitch axis which rotate the solar arrays to track the Sun, can produce torques to compensate for the pitch-axis wheel failure. In addition, the attitude control of a flexible spacecraft poses a difficult problem. These difficulties include the strong nonlinear coupled dynamics between the rigid hub and flexible solar arrays, and the imprecisely known system parameters, such as inertia matrix, damping ratios, and flexible mode frequencies. In order to overcome these drawbacks, the adaptive Jacobian tracking fuzzy control is proposed for the combined attitude and sun-tracking control problem of a flexible spacecraft during attitude maneuvers in this work. For the adaptation of kinematic and dynamic uncertainties, the proposed scheme uses an adaptive sliding vector based on estimated attitude velocity via approximate Jacobian matrix. The unknown nonlinearities are approximated by deriving the fuzzy models with a set of linguistic If-Then rules using the idea of sector nonlinearity and local approximation in fuzzy partition spaces. The uncertain parameters of the estimated nonlinearities and the Jacobian matrix are being adjusted online by an adaptive law to realize feedback control. The attitude of the spacecraft can be directly controlled with the Jacobian feedback control when the attitude pointing trajectory is designed with respect to the spacecraft coordinate frame itself. A significant feature of this work is that the proposed adaptive Jacobian tracking scheme will result in not only the convergence of angular position and angular velocity tracking errors, but also the convergence of estimated angular velocity to

  13. Automatically-Activated Attitudes as Mechanisms for Message Effects: The Case of Alcohol Advertisements

    PubMed Central

    Goodall, Catherine E.; Slater, Michael D.

    2010-01-01

    Alcohol advertisements may influence impulsive, risky behaviors indirectly, via automatically-activated attitudes toward alcohol. Results from an experiment in which participants were exposed to either four alcohol advertisements, four control advertisements, or four drunk driving public service advertisements, suggested that alcohol advertisements had more measurable effects on implicit, than on explicit attitude measures. Moreover, there were significant indirect paths from alcohol advertisement exposure through automatically-activated alcohol attitudes on willingness to engage in risky alcohol-related behaviors, notably drinking and driving. A mechanism that may explain how these advertisements activate automatic, non-deliberative alcohol attitudes was investigated. Associative evidence was found supportive of an evaluative conditioning mechanism, in which positive responses to an alcohol advertisement may lead to more positive automatically-activated attitudes toward alcohol itself. PMID:21258609

  14. Students' Attitudes towards Control Methods in Computer-Assisted Instruction.

    ERIC Educational Resources Information Center

    Hintze, Hanne; And Others

    1988-01-01

    Describes study designed to investigate dental students' attitudes toward computer-assisted teaching as applied in programs for oral radiology in Denmark. Programs using personal computers and slide projectors with varying degrees of learner and teacher control are described, and differences in attitudes between male and female students are…

  15. Spacecraft attitude control using a smart control system

    NASA Technical Reports Server (NTRS)

    Buckley, Brian; Wheatcraft, Louis

    1992-01-01

    Traditionally, spacecraft attitude control has been implemented using control loops written in native code for a space hardened processor. The Naval Research Lab has taken this approach during the development of the Attitude Control Electronics (ACE) package. After the system was developed and delivered, NRL decided to explore alternate technologies to accomplish this same task more efficiently. The approach taken by NRL was to implement the ACE control loops using systems technologies. The purpose of this effort was to: (1) research capabilities required of an expert system in processing a classic closed-loop control algorithm; (2) research the development environment required to design and test an embedded expert systems environment; (3) research the complexity of design and development of expert systems versus a conventional approach; and (4) test the resulting systems against the flight acceptance test software for both response and accuracy. Two expert systems were selected to implement the control loops. Criteria used for the selection of the expert systems included that they had to run in both embedded systems and ground based environments. Using two different expert systems allowed a comparison of the real-time capabilities, inferencing capabilities, and the ground-based development environment. The two expert systems chosen for the evaluation were Spacecraft Command Language (SCL), and NEXTPERT Object. SCL is a smart control system produced for the NRL by Interface and Control Systems (ICS). SCL was developed to be used for real-time command, control, and monitoring of a new generation of spacecraft. NEXPERT Object is a commercially available product developed by Neuron Data. Results of the effort were evaluated using the ACE test bed. The ACE test bed had been developed and used to test the original flight hardware and software using simulators and flight-like interfaces. The test bed was used for testing the expert systems in a 'near-flight' environment

  16. Optimal periodic control for spacecraft pointing and attitude determination

    NASA Technical Reports Server (NTRS)

    Pittelkau, Mark E.

    1993-01-01

    A new approach to autonomous magnetic roll/yaw control of polar-orbiting, nadir-pointing momentum bias spacecraft is considered as the baseline attitude control system for the next Tiros series. It is shown that the roll/yaw dynamics with magnetic control are periodically time varying. An optimal periodic control law is then developed. The control design features a state estimator that estimates attitude, attitude rate, and environmental torque disturbances from Earth sensor and sun sensor measurements; no gyros are needed. The state estimator doubles as a dynamic attitude determination and prediction function. In addition to improved performance, the optimal controller allows a much smaller momentum bias than would otherwise be necessary. Simulation results are given.

  17. Children's Attitudes toward Physical Activity and Self-Esteem.

    ERIC Educational Resources Information Center

    Ewy, Stan R.

    This study was conducted to investigate attitudes toward physical activity and self-esteem of students (N=82) in grades three through five. The independent variables were gender, grade placement, and physical fitness. The dependent variables were scores from the Grade 3 Children's Attitudes Toward Physical Activity, the Revised Children's…

  18. Coupled attitude-orbit dynamics and control for displaced solar orbits

    NASA Astrophysics Data System (ADS)

    Gong, Shengping; Baoyin, Hexi; Li, Junfeng

    2009-09-01

    The paper discusses the coupled attitude-orbit dynamics of a solar sail. The equilibrium point of the coupled dynamical equations is obtained by designing the inertia of the sail. The stability of the equilibrium is analyzed through a linearization. It is found that the stability of the coupled equilibrium is determined by the stability of the attitude and orbital equilibrium point, respectively. For the sail discussed in this paper, the stability of the orbital equilibrium determines the stability of coupled system since the attitude is always marginally stable. Several numerical examples are employed to validate the conclusions. For unstable displaced orbits, active control is employed to stabilize the attitude and orbit. The results show that a small control torque can stabilize both the attitude and orbit.

  19. Torque equilibrium attitude control for Skylab reentry

    NASA Technical Reports Server (NTRS)

    Glaese, J. R.; Kennel, H. F.

    1979-01-01

    All the available torque equilibrium attitudes (most were useless from the standpoint of lack of electrical power) and the equilibrium seeking method are presented, as well as the actual successful application during the 3 weeks prior to Skylab reentry.

  20. Examination of psychological variables related to nuclear attitudes and nuclear activism

    SciTech Connect

    Roy, P.J.

    1985-01-01

    It was hypothesized that knowledge about nuclear arms developments would not be correlated with nuclear attitudes, that sense of efficacy would be positively correlated with magnitude of nuclear activism, and that death anxiety would be correlated with high level of nuclear knowledge and anti-nuclear attitudes, but not with sense of power. It was also hypothesized that positive correlations would be found between nuclear activism and political activism, knowledge of nuclear facts, and degree of adherence to anti-nuclear attitudes. One hundred and forty three women and 90 men participated in this questionnaire study. Major findings are as follows. In general, the more people knew about nuclear developments, the more anti-nuclear were their attitudes. Also, regardless of nuclear attitudes, a positive correlation was found between knowledge of nuclear facts and nuclear activism. Death anxiety and powerlessness were not correlated. There was a positive correlation between anxiety and both nuclear knowledge and anti-nuclear attitudes. A strong positive correlation was found between nuclear activism and anti-nuclear attitudes, and between political activism and nuclear activism. Internal locus of control did not correlate significantly with high sense of power or with high degree of nuclear activism.

  1. An investigation of quasi-inertial attitude control for a solar power satellite

    NASA Technical Reports Server (NTRS)

    Juang, J.-N.; Wang, S. J.

    1982-01-01

    An efficient means, a quasi-inertial attitude mode, is developed for maintaining the normal solar orientation of a space satellite for power collection in a synchronous orbit. Formulae are presented which establish the basic parametric properties for ideal quasi-inertial attitude and phasing. An active control system is necessary to compensate for the energy loss since energy dissipation in widely oscillating flexible bodies produces an instability of the quasi-inertial attitude in the sense that the spacecraft will tumble at the orbit rate. A fixed terminal time and state optimal control problem is formulated and an algorithm for determining the optimal control as a means for the periodical attitude and phase compensation is developed. The vehicle orientation affected by internal disturbance (structural flexibility) and external disturbances (e.g., drag forces) is maintained by a specialized controller design.

  2. Model-reference attitude control and reaction control jet engine placement for space shuttle

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III

    1973-01-01

    Analytical studies on the theoretical aspects of thrust vector control of large space vehicles were conducted. A system for attitude control of the space shuttle vehicle was developed. Major accomplishments of the project are: (1) investigation of a model-reference adaptive control scheme for controlling the space shuttle attitude and (2) determination of optimum placement of reaction control jet engines on space shuttles.

  3. Demonstration of Single Axis Combined Attitude Control and Energy Storage Using Two Flywheels

    NASA Technical Reports Server (NTRS)

    Kenny, Barbara H.; Jansen, Ralph; Kascak, Peter; Dever, Timothy; Santiago, Walter

    2004-01-01

    The energy storage and attitude control subsystems of the typical satellite are presently distinct and separate. Energy storage is conventionally provided by batteries, either NiCd or NiH, and active attitude control is accomplished with control moment gyros (CMGs) or reaction wheels. An overall system mass savings can be realized if these two subsystems are combined using multiple flywheels for simultaneous kinetic energy storage and momentum transfer. Several authors have studied the control of the flywheels to accomplish this and have published simulation results showing the feasibility and performance. This paper presents the first experimental results showing combined energy storage and momentum control about a single axis using two flywheels.

  4. Periodic attitude control of a slowly spinning spacecraft.

    NASA Technical Reports Server (NTRS)

    Todosiev, E. P.

    1973-01-01

    A periodic attitude control system is presented which permits control of secular errors of a slowly spinning spacecraft operating in a high disturbance environment. Attitude errors of the spin-axis are detected by sun sensors (or rate gyros) and are controlled by a periodic control law which modulates external control torques generated by mass expulsion torquers. Attitude stability during the uncontrolled periods is obtained passively via the vehicle spin momentum. Equations of motion, a system block diagram, and design parameters are presented for a typical spacecraft application. Simulation results are included which demonstrate the feasibility of the novel control concept. Salient features of the periodic control approach are implementation simplicity, excellent response, and a propellant utilization efficiency greater than 75 percent.

  5. Attitude Control Optimization for ROCSAT-2 Operation

    NASA Astrophysics Data System (ADS)

    Chern, Jeng-Shing; Wu, A.-M.

    one revolution. The purpose of this paper is to present the attitude control design optimization such that the maximum solar energy is ingested while minimum maneuvering energy is dissipated. The strategy includes the maneuvering sequence design, the minimization of angular path, the sizing of three magnetic torquers, and the trade-off of the size, number and orientations arrangement of momentum wheels.

  6. A system for spacecraft attitude control and energy storage

    NASA Technical Reports Server (NTRS)

    Shaughnessy, J. D.

    1974-01-01

    A conceptual design for a double-gimbal reaction-wheel energy-wheel device which has three-axis attitude control and electrical energy storage capability is given. A mathematical model for the three-axis gyroscope (TAG) was developed, and a system of multiple units is proposed for attitude control and energy storage for a class of spacecraft. Control laws were derived to provide the required attitude-control torques and energy transfer while minimizing functions of TAG gimbal angles, gimbal rates, reaction-wheel speeds, and energy-wheel speed differences. A control law is also presented for a magnetic torquer desaturation system. A computer simulation of a three-TAG system for an orbiting telescope was used to evaluate the concept. The results of the study indicate that all control and power requirements can be satisfied by using the TAG concept.

  7. The development and demonstration of hybrid programmable attitude control electronics

    NASA Technical Reports Server (NTRS)

    Smith, L. S.; Kopf, E. H., Jr.

    1973-01-01

    In the course of extended life attitude control system (ELACS) research sponsored by NASA a hybrid programable attitude control electronics (HYPACE) concept was developed and demonstrated. The wide variety of future planetary missions demanded a new control approach to accommodate the automatic fault tolerance and long the life requirements of such missions. HYPACE provides an adaptable, analog/digital design approach that permits preflight and in-flight accommodation of mission changes, component performance variations, and spacecraft changes, through programing. This enabled broad multimission flexibility of application in a cost effective manner. Previously, flight control computers have not been not flown on planetary missions because of weight and power problems. These problems were resolved in the design of HYPACE. The HYPACE design, which was demonstrated in breadboard form on a single-axis gas-bearing spacecraft simulation, uses a single control channel to perform the attitude control functions sequentially, thus significantly reducing the number of component parts over hard-wired designs.

  8. H∞ control option for a combined energy and attitude control system

    NASA Astrophysics Data System (ADS)

    Ban, Ying Siang; Varatharajoo, Renuganth

    2013-10-01

    A combined energy and attitude control system (CEACS) is a hybrid system that uses flywheels to store energy and provide a simultaneous attitude control in satellites. Previous work appeared in Advances in Space Research (ASR) employing the proportional-derivative (PD) control has proven that CEACS works well and achieves its mission requirement. However, the in-orbit system performance uncertainties present a challenge to the CEACS attitude pointing capability. Thus, this paper complements the previous mentioned work, and focuses on employing the H∞ optimal attitude control solution for the CEACS attitude control enhancement. The mathematical model and numerical treatments for the CEACS H∞ control architecture are presented. Numerical results show that a better attitude pointing accuracy at least up to 0.043° can be achieved with the H∞ control method.

  9. Attitude Control System Design for the Solar Dynamics Observatory

    NASA Technical Reports Server (NTRS)

    Starin, Scott R.; Bourkland, Kristin L.; Kuo-Chia, Liu; Mason, Paul A. C.; Vess, Melissa F.; Andrews, Stephen F.; Morgenstern, Wendy M.

    2005-01-01

    The Solar Dynamics Observatory mission, part of the Living With a Star program, will place a geosynchronous satellite in orbit to observe the Sun and relay data to a dedicated ground station at all times. SDO remains Sun- pointing throughout most of its mission for the instruments to take measurements of the Sun. The SDO attitude control system is a single-fault tolerant design. Its fully redundant attitude sensor complement includes 16 coarse Sun sensors, a digital Sun sensor, 3 two-axis inertial reference units, 2 star trackers, and 4 guide telescopes. Attitude actuation is performed using 4 reaction wheels and 8 thrusters, and a single main engine nominally provides velocity-change thrust. The attitude control software has five nominal control modes-3 wheel-based modes and 2 thruster-based modes. A wheel-based Safehold running in the attitude control electronics box improves the robustness of the system as a whole. All six modes are designed on the same basic proportional-integral-derivative attitude error structure, with more robust modes setting their integral gains to zero. The paper details the mode designs and their uses.

  10. Three-Axis Attitude Control With a Single Wheel

    NASA Technical Reports Server (NTRS)

    Studer, P. A.

    1987-01-01

    Single-device attitude-control system provides stabilization along three axes. Flywheel connected to electronically controlled motor rotates on magnetic bearing. At high rotational speed, small angular displacements about x and y axes, in response to control signals enable storage of relatively large amounts of angular momentum. Angular momentum about z axis stored in changes in rotational speed.

  11. Design study for LANDSAT D attitude control system

    NASA Technical Reports Server (NTRS)

    Iwens, R. P.; Bernier, G. E.; Hofstadter, R. F.

    1976-01-01

    A design and performance evaluation is presented for the LANDSAT D attitude control system (ACS). Control and configuration of the gimballed Ku-band antenna system for communication with the tracking and data relay satellite (TDRS). Control of the solar array drive considered part of the ACS is also addressed.

  12. Model reference adaptive attitude control of spacecraft using reaction wheels

    NASA Technical Reports Server (NTRS)

    Singh, Sahjendra N.

    1986-01-01

    A nonlinear model reference adaptive control law for large angle rotational maneuvers of spacecraft using reaction wheels in the presence of uncertainty is presented. The derivation of control law does not require any information on the values of the system parameters and the disturbance torques acting on the spacecraft. The controller includes a dynamic system in the feedback path. The control law is a nonlinear function of the attitude error, the rate of the attitude error, and the compensator state. Simulation results are prsented to show that large angle rotational maneuvers can be performed in spite of the uncertainty in the system.

  13. Low drag attitude control for Skylab orbital lifetime extension

    NASA Technical Reports Server (NTRS)

    Glaese, J. R.; Kennel, H. F.

    1981-01-01

    In the fall of 1977 it was determined that Skylab had started to tumble and that the original orbit lifetime predictions were much too optimistic. A decision had to be made whether to accept an early uncontrolled reentry with its inherent risks or try to attempt to control Skylab to a lower drag attitude in the hope that there was enough time to develop a Teleoperator Retrieval System, bring it up on the Space Shuttle and then decide whether to boost Skylab to a higher longer life orbit or to reenter it in a controlled fashion. The end-on-velocity (EOVV) control method is documented, which was successfully applied for about half a year to keep Skylab in a low drag attitude with the aid of the control moment gyros and a minimal expenditure of attitude control gas.

  14. Attitude control schemes for the first recovery mission of India

    NASA Astrophysics Data System (ADS)

    Philip, N. K.; Chinnaponnu, V.; Krishnakumar, E.; Natarajan, P.; Agrawal, V. K.; Malik, N. K.

    2009-01-01

    This paper describes the attitude control schemes for the various phases such as acquisition, on-orbit, orbit maneuver, de-boost maneuvers and coast phases of the India's first recovery mission Space Capsule Recovery Experiment-I (SRE-1). During the on-orbit phase, the SRE was configured to point the negative roll axis to Sun. The attitude referencing of SRE-1 was based on dry tuned gyros with updates from the attitude determined using on-board Sun sensors and magnetometer. For attitude acquisition, attitude maneuvers and for providing the velocity corrections for de-orbiting operations; a set of eight thrusters grouped in functionally redundant blocks were used. The control scheme with thrusters was based on proportional derivative controller with a modulator. In order to ensure micro-gravity environment during the on-orbit payload operations a linear quadratic regulator (LQR) based control scheme was designed to drive an orthogonal configuration of magnetic torquers which in turn produced three-axis control torque with the interaction of Earth's magnetic field. Proportional derivative control scheme with modulator was designed to track the steering commands during the velocity reduction as well as during the coasting phase of the de-orbiting operations. A novel thruster failure detection, isolation and reconfiguration scheme implemented on-board for the de-orbiting phase is also discussed in this paper.

  15. Two Axis Pointing System (TAPS) attitude acquisition, determination, and control

    NASA Technical Reports Server (NTRS)

    Azzolini, John D.; Mcglew, David E.

    1990-01-01

    The Two Axis Pointing System (TAPS) is a 2 axis gimbal system designed to provide fine pointing of Space Transportation System (STS) borne instruments. It features center-of-mass instrument mounting and will accommodate instruments of up to 1134 kg (2500 pounds) which fit within a 1.0 by 1.0 by 4.2 meter (40 by 40 by 166 inch) envelope. The TAPS system is controlled by a microcomputer based Control Electronics Assembly (CEA), a Power Distribution Unit (PDU), and a Servo Control Unit (SCU). A DRIRU-II inertial reference unit is used to provide incremental angles for attitude propagation. A Ball Brothers STRAP star tracker is used for attitude acquisition and update. The theory of the TAPS attitude determination and error computation for the Broad Band X-ray Telescope (BBXRT) are described. The attitude acquisition is based upon a 2 star geometric solution. The acquisition theory and quaternion algebra are presented. The attitude control combines classical position, integral and derivative (PID) control with techniques to compensate for coulomb friction (bias torque) and the cable harness crossing the gimbals (spring torque). Also presented is a technique for an adaptive bias torque compensation which adjusts to an ever changing frictional torque environment. The control stability margins are detailed, with the predicted pointing performance, based upon simulation studies. The TAPS user interface, which provides high level operations commands to facilitate science observations, is outlined.

  16. Robustness and Actuator Bandwidth of MRP-Based Sliding Mode Control for Spacecraft Attitude Control Problems

    NASA Astrophysics Data System (ADS)

    Keum, Jung-Hoon; Ra, Sung-Woong

    2009-12-01

    Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters (MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

  17. ISS Contingency Attitude Control Recovery Method for Loss of Automatic Thruster Control

    NASA Technical Reports Server (NTRS)

    Bedrossian, Nazareth; Bhatt, Sagar; Alaniz, Abran; McCants, Edward; Nguyen, Louis; Chamitoff, Greg

    2008-01-01

    In this paper, the attitude control issues associated with International Space Station (ISS) loss of automatic thruster control capability are discussed and methods for attitude control recovery are presented. This scenario was experienced recently during Shuttle mission STS-117 and ISS Stage 13A in June 2007 when the Russian GN&C computers, which command the ISS thrusters, failed. Without automatic propulsive attitude control, the ISS would not be able to regain attitude control after the Orbiter undocked. The core issues associated with recovering long-term attitude control using CMGs are described as well as the systems engineering analysis to identify recovery options. It is shown that the recovery method can be separated into a procedure for rate damping to a safe harbor gravity gradient stable orientation and a capability to maneuver the vehicle to the necessary initial conditions for long term attitude hold. A manual control option using Soyuz and Progress vehicle thrusters is investigated for rate damping and maneuvers. The issues with implementing such an option are presented and the key issue of closed-loop stability is addressed. A new non-propulsive alternative to thruster control, Zero Propellant Maneuver (ZPM) attitude control method is introduced and its rate damping and maneuver performance evaluated. It is shown that ZPM can meet the tight attitude and rate error tolerances needed for long term attitude control. A combination of manual thruster rate damping to a safe harbor attitude followed by a ZPM to Stage long term attitude control orientation was selected by the Anomaly Resolution Team as the alternate attitude control method for such a contingency.

  18. Advanced Integrated Power and Attitude Control System (IPACS) study

    NASA Technical Reports Server (NTRS)

    Oglevie, R. E.; Eisenhaure, D. B.

    1985-01-01

    Integrated Power and Attitude Control System (IPACS) studies performed over a decade ago established the feasibility of simultaneously satisfying the demands of energy storage and attitude control through the use of rotating flywheels. It was demonstrated that, for a wide spectrum of applications, such a system possessed many advantages over contemporary energy storage and attitude control approaches. More recent technology advances in composite material rotors, magnetic suspension systems, and power control electronics have triggered new optimism regarding the applicability and merits of this concept. This study is undertaken to define an advanced IPACS and to evaluate its merits for a space station application. System and component designs are developed to establish the performance of this concept and system trade studies conducted to examine the viability of this approach relative to conventional candidate systems. It is clearly demonstrated that an advanced IPACS concept is not only feasible, but also offers substantial savings in mass and life-cycle cost for the space station mission.

  19. NASA Workshop on Hybrid (Mixed-Actuator) Spacecraft Attitude Control

    NASA Technical Reports Server (NTRS)

    Dennehy, Cornelius J.; Kunz, Nans

    2014-01-01

    At the request of the Science Mission Directorate Chief Engineer, the NASA Technical Fellow for Guidance, Navigation & Control assembled and facilitated a workshop on Spacecraft Hybrid Attitude Control. This multi-Center, academic, and industry workshop, sponsored by the NASA Engineering and Safety Center (NESC), was held in April 2013 to unite nationwide experts to present and discuss the various innovative solutions, techniques, and lessons learned regarding the development and implementation of the various hybrid attitude control system solutions investigated or implemented. This report attempts to document these key lessons learned with the 16 findings and 9 NESC recommendations.

  20. On-board attitude determination and control algorithms for SAMPEX

    NASA Technical Reports Server (NTRS)

    Flatley, Thomas W.; Forden, Josephine K.; Henretty, Debra A.; Lightsey, E. Glenn; Markley, F. Landis

    1990-01-01

    Algorithms for onboard attitude determination and control of the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) were developed. The algorithms include spacecraft ephemeris and geomagnetic field models, attitude determination with 2 degree accuracy, control of pitch axis pointing to the sun and yaw axis pointing away from the Earth to achieve control of pitch axis within 5 degrees of sunline, momentum unloading, and nutation damping. The closed loop simulations were performed on a VAX 8830 using a prototype version of the on-board software.

  1. Applications software supporting the Spartan Attitude Control System

    NASA Technical Reports Server (NTRS)

    Stone, R. W.

    1986-01-01

    The native software supporting a single mission for the Spartan Attitude Control System can require up to 40,000 lines of code. Most of this must be rewritten for each mission. Control system engineers use an array of Applications Software Packages residing in ground computers to write each mission's flight software. These Applications Packages are written in the 'C' programming language and run under the UNIX Operating System. This paper discusses each of the Attitude Control Applications Software Packages, and describes the purpose and design of each.

  2. Inquiry-Based Laboratory Activities in Electrochemistry: High School Students' Achievements and Attitudes

    NASA Astrophysics Data System (ADS)

    Acar Sesen, Burcin; Tarhan, Leman

    2013-02-01

    This study aimed to investigate the effects of inquiry-based laboratory activities on high school students' understanding of electrochemistry and attitudes towards chemistry and laboratory work. The participants were 62 high school students (average age 17 years) in an urban public high school in Turkey. Students were assigned to experimental ( N = 30) and control groups ( N = 32). The experimental group was taught using inquiry-based laboratory activities developed by the researchers and the control group was instructed using traditional laboratory activities. The results of the study indicated that instruction based on inquiry-based laboratory activities caused a significantly better acquisition of scientific concepts related to electrochemistry, and produced significantly higher positive attitudes towards chemistry and laboratory. In the light of the findings, it is suggested that inquiry-based laboratory activities should be developed and applied to promote students' understanding in chemistry subjects and to improve their positive attitudes.

  3. Weight Control: Attitudes of Dieters and Change Agents.

    ERIC Educational Resources Information Center

    Parham, Ellen S.; And Others

    1991-01-01

    Survey explores attitudes toward weight loss/weight control among 2 groups of change agents--40 dietitians and 42 fitness instructors--and among 96 people trying to lose weight. Significant differences were found in terms of importance in weight control of diet, drugs, exercise, religion, and will power; in importance of being of normal weight;…

  4. Factors That Affect Patient Attitudes toward Infection Control Measures.

    ERIC Educational Resources Information Center

    Jones, Daniel J.; And Others

    1991-01-01

    A study investigated patient attitudes toward different disease control measures taken in dental school clinics (n=272 patients) and private practices (n=107 patients). Variables examined included sex, age, educational background, and knowledge of infectious diseases. Patients tended to accept the control measures being used in each context. (MSE)

  5. Precision Attitude Control for the BETTII Balloon-Borne Interferometer

    NASA Technical Reports Server (NTRS)

    Benford, Dominic J.; Fixsen, Dale J.; Rinehart. Stephen

    2012-01-01

    The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared interferometer to fly on a high altitude balloon. Operating at wavelengths of 30-90 microns, BETTII will obtain spatial and spectral information on science targets at angular resolutions down to less than half an arcsecond, a capability unmatched by other far-infrared facilities. This requires attitude control at a level ofless than a tenth of an arcsecond, a great challenge for a lightweight balloon-borne system. We have designed a precision attitude determination system to provide gondola attitude knowledge at a level of 2 milliarcseconds at rates up to 100Hz, with accurate absolute attitude determination at the half arcsecond level at rates of up to 10Hz. A mUlti-stage control system involving rigid body motion and tip-tilt-piston correction provides precision pointing stability to the level required for the far-infrared instrument to perform its spatial/spectral interferometry in an open-loop control. We present key aspects of the design of the attitude determination and control and its development status.

  6. Attitude Dynamics and Control of Solar Sails with Articulated Vanes

    NASA Technical Reports Server (NTRS)

    Mettler, Edward; Acikmese, A. Behcet; Ploen, Scott R.

    2005-01-01

    In this paper we develop a robust nonlinear algorithm for the attitude control of a solar sailcraft with M single degree-of-freedom articulated control vanes. A general attitude controller that tracks an admissible trajectory while rejecting disturbances such as torques due to center-of-mass to center-of-pressure offsets is applied to this problem. We then describe a methodology based on nonlinear programming to allocate the required control torques among the control vanes. A simplified allocation strategy is then applied to a solar sail with four articulated control vanes, and simulation results are given. The performance of the control algorithm and possible limitations of vane-only control are then discussed.

  7. Precision attitude control of the Gravity Probe B satellite

    NASA Astrophysics Data System (ADS)

    Conklin, J. W.; Adams, M.; Bencze, W. J.; DeBra, D. B.; Green, G.; Herman, L.; Holmes, T.; Muhlfelder, B.; Parkinson, B. W.; Silbergleit, A. S.; Kirschenbaum, J.

    2015-11-01

    The Gravity Probe B satellite used ultra-precise gyroscopes in low Earth orbit to compare the orientation of the local inertial reference frame with that of distant space in order to test predictions of general relativity. The experiment required that the Gravity Probe B spacecraft have milliarcsecond-level attitude knowledge for the science measurement, and milliarcsecond-level control to minimize classical torques acting on the science gyroscopes. The primary sensor was a custom Cassegrainian telescope, which measured the pitch and yaw angles of the experiment package with respect to a guide star. The spacecraft rolled uniformly about the direction to the guide star, and the roll angle was measured by star trackers. Attitude control was performed with sixteen proportional thrusters that used boil-off from the experiment’s liquid Helium cryogen as propellant. This paper summarizes the attitude control system’s design and on-orbit performance.

  8. Attitude sensors and attitude-control concepts for next-generation spacecraft

    NASA Astrophysics Data System (ADS)

    Balteas, N.; Simon, C.

    The design concept of the attitude sensor being developed for the Tubsat experimental satellite is discussed and illustrated with drawings, diagrams, and photographs. The device is based on a CCD-detector star sensor which determines the attitude angle and the angular velocity of the spacecraft on the basis of any arbitrary star configuration (rather than from the position of a particular star or the earth or sun). The components include a single-chip microcomputer, a D/A converter, the CCD, and control and readout electronics. The sensor operates either in a barbecue mode (to stabilize the rotation rate) or a sun-oriented triaxially stabilized mode (to maintain, during eclipse periods, the attitude set by an analogous sun sensor while the sun is visible). The resolution of the sensor in the latter mode is less than 0.1 deg.

  9. HEAO attitude reference design. [for satellite attitude control and determination subsystem

    NASA Technical Reports Server (NTRS)

    Hoffman, D. P.; Mcelroy, T. T.

    1978-01-01

    The paper deals with the precision onboard attitude reference implemented as part of the attitude control and determination subsystem for the three High Energy Astronomy Observatories (HEAO-A, HEAO-B, and HEAO-C) in the HEAO scientific spacecraft program. The first observatory (HEAO-A, designated HEAO-1 when in orbit) was launched successfully into near-earth orbit on August 12, 1977. The HEAO attitude reference, analysis techniques for performance prediction, and flight results from the HEAO-1 observatory during its first months of operation. The HEAO-B design is specifically described and analyzed in terms of gyro processing, kinematic integration, ground update algorithm, and star tracker update algorithm. Attitude reference performance estimates are also discussed. It is shown that the orbital performance of the attitude reference correlates very well with the developmental predictions, thereby validating the analytical techniques used during the development. This validation provides a firm basis from which to extrapolate to other applications and related design concepts.

  10. Control and synchronization of Chaotic Attitude Control of Satellite with Backstepping controller

    NASA Astrophysics Data System (ADS)

    Kemih, K.; Halimi, M.; Ghanes, M.; Fanit, H.; Salit, H.

    2014-06-01

    A backstepping control system is proposed to control and synchronize the attitude dynamics of a satellite subjected to deterministic external perturbations which induce chaotic motion when no control is affected in this paper. The proposed method is a systematic recursive design approach based on the choice of Lyapunov functions for constructing feedback control laws. The effectiveness of the proposed control scheme is verified by the simulated results.

  11. Application of square-root filtering for spacecraft attitude control

    NASA Technical Reports Server (NTRS)

    Sorensen, J. A.; Schmidt, S. F.; Goka, T.

    1978-01-01

    Suitable digital algorithms are developed and tested for providing on-board precision attitude estimation and pointing control for potential use in the Landsat-D spacecraft. These algorithms provide pointing accuracy of better than 0.01 deg. To obtain necessary precision with efficient software, a six state-variable square-root Kalman filter combines two star tracker measurements to update attitude estimates obtained from processing three gyro outputs. The validity of the estimation and control algorithms are established, and the sensitivity of their performance to various error sources and software parameters are investigated by detailed digital simulation. Spacecraft computer memory, cycle time, and accuracy requirements are estimated.

  12. The Microwave Anisotropy Probe (MAP) Attitude Control System

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Ericsson, Aprille J.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an Inertial Reference Unit, two Autonomous Star Trackers, a Digital Sun Sensor, twelve Coarse Sun Sensors, three Reaction Wheel Assemblies, and a propulsion system. This paper describes the design of the attitude control system that carries out this mission and presents some early flight experience.

  13. Precise attitude control of the Stanford relativity satellite.

    NASA Technical Reports Server (NTRS)

    Bull, J. S.; Debra, D. B.

    1973-01-01

    A satellite being designed by the Stanford University to measure (with extremely high precision) the effect of General Relativity is described. Specifically, the satellite will measure two relativistic precessions predicted by the theory: the geodetic effect (6.9 arcsec/yr), due solely to motion about the earth, and the motional effect (0.05 arcsec/yr), due to rotation of the earth. The gyro design requirements, including the requirement for precise attitude control and a dynamic model for attitude control synthesis, are discussed. Closed loop simulation of the satellite's natural dynamics on an analog computer is described.

  14. Flight performance of Skylab attitude and pointing control system

    NASA Technical Reports Server (NTRS)

    Chubb, W. B.; Kennel, H. F.; Rupp, C. C.; Seltzer, S. M.

    1975-01-01

    The Skylab attitude and pointing control system (APCS) requirements are briefly reviewed and the way in which they became altered during the prelaunch phase of development is noted. The actual flight mission (including mission alterations during flight) is described. The serious hardware failures that occurred, beginning during ascent through the atmosphere, also are described. The APCS's ability to overcome these failures and meet mission changes are presented. The large around-the-clock support effort on the ground is discussed. Salient design points and software flexibility that should afford pertinent experience for future spacecraft attitude and pointing control system designs are included.

  15. Attitudes toward population control in Santiago, Chile.

    PubMed

    Hall, M F

    1975-01-01

    This article explores Chilean attitudes toward the national population's size and rate of growth, as indicated by a special survey conducted for this purpose. The survey sample consisted of 1,410 men 20 to 54 years of age in urban Santiago, who were separated into six categories on the basis of their education and socioeconomic status. The subjects were interviewed by 36 students from the University of Chile who utilized a prepared questionnaire including both open-ended and multiple-choice questions. The results clearly indicate that men in the lower socioeconomic categories tended to know less about the population's size and growth than their better-off counterparts. Nevertheless, they more often felt that Chile had "too many" inhabitants, that recent population growth had been rapid, and that this rate of growth should be reduced. PMID:1212535

  16. An investigation of nonlinear control of spacecraft attitude

    NASA Astrophysics Data System (ADS)

    Binette, Mark Richard

    The design of controllers subject to the nonlinear H-infinity criterion is explored. The plants to be controlled are the attitude motion of spacecraft, subject to some disturbance torque. Two cases are considered: the regulation about an inertially-fixed direction, and an Earth-pointing spacecraft in a circular orbit, subject to the gravity-gradient torque. The spacecraft attitude is described using the modified Rodrigues parameters. A series of controllers are designed using the nonlinear H-infinity control criterion, and are subsequently generated using a Taylor series expansion to approximate solutions of the relevant Hamilton-Jacobi equations. The controllers are compared, using both input-output and initial condition simulations. A proof is used to demonstrate that the linearized controller solves the H-infinity control problem for the inertial pointing problem when describing the plant using the modified Rodrigues parameters.

  17. Youth Attitudes towards Tobacco Control Laws: The Influence of Smoking Status and Grade in School

    ERIC Educational Resources Information Center

    Williams, Terrinieka T.; Jason, Leonard A.; Pokorny, Steven B.

    2008-01-01

    This study examined adolescent attitudes towards tobacco control laws. An exploratory factor analysis, using surveys from over 9,000 students, identified the following three factors: (1) youth attitudes towards the efficacy of tobacco control laws, (2) youth attitudes towards tobacco possession laws and (3) youth attitudes towards tobacco sales…

  18. Prospects of Relative Attitude Control Using Coulomb Actuation

    NASA Astrophysics Data System (ADS)

    Schaub, Hanspeter; Stevenson, Daan

    2013-12-01

    The relative attitude is studied between two charge controlled spacecraft being held at a fixed separation distance. While one body has a spherical shape, the 2nd body is assumed to be non-spherical and tumbling. The attitude control goal is to arrest the rotation of the 2nd body. While prior work has identified the existence of torques between charged bodies, this is the first analytical study on a charged feedback attitude control. Using the recently developed multi-sphere method to provide a simplified electrostatic force and torque model between non-spherical shapes, Lyapunov theory is used to develop a stabilizing attitude control using spacecraft potential as the control variable. Zero and non-zero equilibrium potentials are considered, with the later suitable for the electrostatic tug concept. With a pulling configuration, the cylinder will come to rest with the long axis aligned with the inter-vehicle axis in a stable configuration. For a pusher, the cylinder will settle 90 degrees rotated from this axis. Numerical simulations illustrate the control performance.

  19. A novel single thruster control strategy for spacecraft attitude stabilization

    NASA Astrophysics Data System (ADS)

    Godard; Kumar, Krishna Dev; Zou, An-Min

    2013-05-01

    Feasibility of achieving three axis attitude stabilization using a single thruster is explored in this paper. Torques are generated using a thruster orientation mechanism with which the thrust vector can be tilted on a two axis gimbal. A robust nonlinear control scheme is developed based on the nonlinear kinematic and dynamic equations of motion of a rigid body spacecraft in the presence of gravity gradient torque and external disturbances. The spacecraft, controlled using the proposed concept, constitutes an underactuated system (a system with fewer independent control inputs than degrees of freedom) with nonlinear dynamics. Moreover, using thruster gimbal angles as control inputs make the system non-affine (control terms appear nonlinearly in the state equation). This necessitates the control algorithms to be developed based on nonlinear control theory since linear control methods are not directly applicable. The stability conditions for the spacecraft attitude motion for robustness against uncertainties and disturbances are derived to establish the regions of asymptotic 3-axis attitude stabilization. Several numerical simulations are presented to demonstrate the efficacy of the proposed controller and validate the theoretical results. The control algorithm is shown to compensate for time-varying external disturbances including solar radiation pressure, aerodynamic forces, and magnetic disturbances; and uncertainties in the spacecraft inertia parameters. The numerical results also establish the robustness of the proposed control scheme to negate disturbances caused by orbit eccentricity.

  20. Precision tethered satellite attitude control. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert J.

    1990-01-01

    Tethered spacecraft possess unique dynamic characteristics which make them advantageous for certain classes of experiments. One use for which tethers are particularly well suited is to provide an isolated platform for spaceborne observatories. The advantages of tethering a pointing platform 1 or 2 km from a space shuttle or space station are that, compared to placing the observatory on the parent spacecraft, vibrational disturbances are attenuated and contamination is eliminated. In practice, all satellites have some requirement on the attitude control of the spacecraft, and tethered satellites are no exception. It has previously been shown that conventional means of performing attitude control for tethered satellites are insufficient for any mission with pointing requirements more stringent than about 1 deg. This is due mainly to the relatively large force applied by the tether to the spacecraft. A particularly effective method of implementing attitude control for tethered satellites is to use this tether tension force to generate control torques by moving the tether attach point relative to the subsatellite center of mass. A demonstration of this attitude control technique on an astrophysical pointing platform has been proposed for a space shuttle flight test project and is referred to as the Kinetic Isolation Tether Experiment (KITE).

  1. Dual-spin attitude control for outer planet missions

    NASA Technical Reports Server (NTRS)

    Ward, R. S.; Tauke, G. J.

    1977-01-01

    The applicability of dual-spin technology to a Jupiter orbiter with probe mission was investigated. Basic mission and system level attitude control requirements were established and preliminary mechanization and control concepts developed. A comprehensive 18-degree-of-freedom digital simulation was utilized extensively to establish control laws, study dynamic interactions, and determined key sensitivities. Fundamental system/subsystem constraints were identified, and the applicability of dual-spin technology to a Jupiter orbiter with probe mission was validated.

  2. Spin-stabilized satellite magnetic attitude control scheme without initial detumbling

    NASA Astrophysics Data System (ADS)

    Roldugin, D. S.; Testani, P.

    2014-01-01

    The angular motion of an axisymmetrical satellite equipped with an active magnetic attitude control system is considered. The dynamics of the satellite are analytically studied on the whole control loop. The control loop is as follows: preliminary reorientation along with nutation damping, spinning about the axis of symmetry, then precise reorientation of the axis of symmetry in inertial space. Reorientation starts right after separation from the launch vehicle. Active magnetic attitude control system time-response with respect to its parameters is analyzed. It is proven that low-inclined orbit forces low control system time-response. Comparison with the common control scheme shows the time-response gain. Numerical analysis of the disturbances effect is carried out and good pointing accuracy is proved.

  3. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    NASA Technical Reports Server (NTRS)

    Burk, Thomas A.

    2013-01-01

    The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

  4. Low cost attitude control system reaction wheel development

    NASA Technical Reports Server (NTRS)

    Bialke, William

    1991-01-01

    In order to satisfy a growing demand for low cost attitude control systems for small spacecraft, development of a low power and low cost Reaction Wheel Assembly was initiated. The details of the versatile design resulting from this effort are addressed. Tradeoff analyses for each of the major components are included, as well as test data from an engineering prototype of the hardware.

  5. Attitudes about Arms Control and Effects of "The Day After."

    ERIC Educational Resources Information Center

    Nelson, Linden L.; Slem, Charles M.

    An 18-item questionnaire was designed to investigate relationships between attitude towards arms control and beliefs about nuclear weapon effects, probability of war, Soviet goals, and the importance of nuclear arms superiority. Effects of the television movie, "The Day After," were also assessed by administering the questionnaire eight days…

  6. Attitudes toward Nutrition, Locus of Control and Smoking Behavior.

    ERIC Educational Resources Information Center

    Corfield, V. Kilian; And Others

    Research has shown that many behaviors previously thought to be purely psychological in origin do, in fact, have a physiological basis. To examine the relationship of smoking behavior to locus of control, and to attitudes toward, knowledge about, and behavior with respect to nutrition, 116 Canadian undergraduate students completed the Nutrition…

  7. Community Involvement, Perceived Control, and Attitudes toward Aging among Lesbians and Gay Men

    ERIC Educational Resources Information Center

    Hostetler, Andrew J.

    2012-01-01

    A person-environment approach was used to explore the relationship between community involvement and attitudes toward aging among middle-age and older lesbians and gay men. Specifically, this study investigated the relationships between participation in gay community activities, perceived control, and aging-related concerns among two…

  8. The SAS-3 attitude control system

    NASA Technical Reports Server (NTRS)

    Mobley, F. F.; Konigsberg, R.; Fountain, G. H.

    1975-01-01

    SAS-3 uses a reaction wheel to provide torque to control the spin rate. If the wheel speed becomes too great or too small, it must be restored to its nominal rate by momentum dumping which is done by magnetic torquing against the earth's magnetic field by the satellite's magnetic coils. A small rate-integrating gyro is used to sense the spin rate so that closed loop control of the spin rate can be achieved. These various systems are described in detail including the reaction wheel system, the gyro system, along with control modes (spin rate control and the star lock mode).

  9. Graduate Nursing Students' Attitudes Toward Sexually Active Older Persons.

    ERIC Educational Resources Information Center

    Damrosch, Shirley Petchel

    1984-01-01

    Reviewed empirical evidence relevant to taboos for aged sexuality and measured the attitudes of 114 graduate nursing students toward a 68-year-old woman. Nurses read a vignette which either contained or excluded information about the woman's sexual activity and exhibited a statistically significant bias favoring the sexually active version. (JAC)

  10. Active Learning's Effect upon Preservice Teachers' Attitudes toward Inclusion.

    ERIC Educational Resources Information Center

    Andrews, Sharon; Clementson, John J.

    The purpose of this study was to determine the effect of active learning techniques and the use of supplemental literature dealing with disabilities in a required introduction to education and special education course on preservice teachers (N=67) attitudes toward inclusion. The active learning techniques included participation in simulation…

  11. Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters

    NASA Technical Reports Server (NTRS)

    Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith

    2016-01-01

    NASA is providing preliminary design and requirements for the Space Launch System Exploration Upper Stage (EUS). The EUS will provide upper stage capability for vehicle ascent as well as on-orbit control capability. Requirements include performance of on-orbit burn to provide Orion vehicle with escape velocity. On-orbit attitude control is accommodated by a on-off Reaction Control System (RCS). Paper provides overview of approaches for design and stability of an attitude control system using a RCS.

  12. Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter

    NASA Technical Reports Server (NTRS)

    Calhoun, Philip C.; Garrick, Joseph C.

    2007-01-01

    The Lunar Reconnaissance Orbiter (LRO) mission is the first of a series of lunar robotic spacecraft scheduled for launch in Fall 2008. LRO will spend at least one year in a low altitude polar orbit around the Moon, collecting lunar environment science and mapping data to enable future human exploration. The LRO employs a 3-axis stabilized attitude control system (ACS) whose primary control mode, the "Observing mode", provides Lunar Nadir, off-Nadir, and Inertial fine pointing for the science data collection and instrument calibration. The controller combines the capability of fine pointing with that of on-demand large angle full-sky attitude reorientation into a single ACS mode, providing simplicity of spacecraft operation as well as maximum flexibility for science data collection. A conventional suite of ACS components is employed in this mode to meet the pointing and control objectives. This paper describes the design and analysis of the primary LRO fine pointing and attitude re-orientation controller function, known as the "Observing mode" of the ACS subsystem. The control design utilizes quaternion feedback, augmented with a unique algorithm that ensures accurate Nadir tracking during large angle yaw maneuvers in the presence of high system momentum and/or maneuver rates. Results of system stability analysis and Monte Carlo simulations demonstrate that the observing mode controller can meet fine pointing and maneuver performance requirements.

  13. Voyager Saturn encounter attitude and articulation control experience

    NASA Technical Reports Server (NTRS)

    Carlisle, G.; Hill, M.

    1981-01-01

    The Voyager attitude and articulation control system is designed for a three-axis stabilized spacecraft; it uses a biasable sun sensor and a Canopus Star Tracker (CST) for celestial control, as well as a dry inertial reference unit, comprised of three dual-axis dry gryos, for inertial control. A series of complex maneuvers was required during the first of two Voyager spacecraft encounters with Saturn (November 13, 1980); these maneuvers involved rotating the spacecraft simultaneously about two or three axes while maintaining accurate pointing of the scan platform. Titan and Saturn earth occulation experiments and a ring scattering experiment are described. Target motion compensation and the effects of celestial sensor interference are also considered. Failure of the CST, which required an extensive reevaluation of the star reference and attitude control mode strategy, is discussed. Results analyzed thus far show that the system performed with high accuracy, gathering data deeper into Saturn's atmosphere than on any previous planetary encounter.

  14. Inversion Of Dynamical Equations For Control Of Attitude

    NASA Technical Reports Server (NTRS)

    Bach, Ralph; Paielli, Russell

    1995-01-01

    Method of inverting nonlinear equations of rotational dynamics of rigid body used to design feedback control of orientation of body. Applicable to both direction-cosine and quaternion formulations suitable for large-angle maneuvers. Exploiting some apparently little-known properties of direction cosine and quaternion formulations, method leads to equations for model-follower control system that exhibits exactly linear attitude-error dynamics. Quarternion system more robust in responding to large roll-angle commands.

  15. Minimizing attitude control fuel in space manipulator systems

    NASA Technical Reports Server (NTRS)

    Dubowsky, Steven; Torres, Miguel A.

    1990-01-01

    Techniques are presented for finding space manipulator motions which result in reduced spacecraft dynamic disturbances. Although a spacecraft's attitude control reaction jets can compensate for these disturbances, reaction jet fuel is a limited resource and excessive disturbances would limit the life of a space manipulator. A graphical tool called the Enhanced Disturbance Map (EDM) is presented and is demonstrated as an aid in developing planning and control algorithms to solve this complex problem.

  16. Flexible spacecraft maneuver - Inverse attitude control and modal stabilization

    NASA Technical Reports Server (NTRS)

    Singh, Sahjendra N.

    1988-01-01

    A control law is presented for three-axis rotational maneuvers of a spacecraft (orbiter)-beam-tip body (antenna or a reflector) configuration based on nonlinear inversion and modal velocity feedback. Using invertibility and functional reproducibility results, a decoupling attitude control law is presented such that, in the closed-loop system, the attitude angles of the spacecraft are independently controlled using the control moments acting on the space vehicle. This controller asymptotically decouples the flexible dynamics from the rigid one and also allows the decomposition of the elastic dynamics into two subsystems representing the transverse deflections of the beam in two orthogonal planes. These low-order subsystems are used for derivation of a modal velocity feedback stabilizer using the force and moment actuators at the end body. Simulation results are presented to show that, in the closed-loop system, attitude control and elastic mode stabilization are accomplished in spite of the parameter uncertainty and disturbance torque input in the system.

  17. Preliminary Attitude Control Studies for the ASTER Mission

    NASA Astrophysics Data System (ADS)

    Victorino Sarli, Bruno; Luís da Silva, André; Paglione, Pedro

    2013-10-01

    This work discusses an attitude control study for the ASTER mission, the first Brazilian mission to the deep space. The study is part of a larger scenario that is the development of optimal trajectories to navigate in the 2001 SN263 asteroid system, together with the generation of orbit and attitude controllers for autonomous operation. The spacecraft attitude is defined from the orientation of the body reference system to the Local Vertical Local Horizontal (LVLH) of a circular orbit around the Alpha asteroid. The rotational equations of motion involve the dynamic equations, where the three angular speeds are generated from a set of three reaction wheels and the gravitational torque. The rotational kinematics is represented in the Euler angles format. The controller is developed via the linear quadratic regulator approach with output feedback. It involves the generation of a stability augmentation (SAS) loop and a tracking outer loop, with a compensator of desired structure. It was chosen the feedback of the p, q and r angular speeds in the SAS, one for each reaction wheel. In the outer loop, it was chosen a proportional integral compensator. The parameters are tuned using a numerical minimization that represents a linear quadratic cost, with weightings in the tracking error and controls. Simulations are performed with the nonlinear model. For small angle manoeuvres, the linear results with reaction wheels or thrusters are reasonable, but, for larger manoeuvres, nonlinear control techniques shall be applied, for example, the sliding mode control.

  18. Attitude control of a spinning rocket via thrust vectoring

    SciTech Connect

    White, J.E.

    1990-12-19

    Two controllers are developed to provide attitude control of a spinning rocket that has a thrust vectoring capability. The first controller has a single-input/single-output design that ignores the gyroscopic coupling between the control channels. The second controller has a multi-input/multi-output structure that is specifically intended to account for the gyroscopic coupling effects. A performance comparison between the two approached is conducted for a range of roll rates. Each controller is tested for the ability to track step commands, and for the amount of coupling impurity. Both controllers are developed via a linear-quadratic-regulator synthesis procedure, which is motivated by the multi-input/multi-output nature of second controller. Time responses and a singular value analysis are used to evaluate controller performance. This paper describes the development and comparison of two controllers that are designed to provide attitude control of a spinning rocket that is equipped with thrust vector control. 12 refs., 13 figs., 2 tabs.

  19. The Attitude Control System for the Wilkinson Microwave Anisotropy Probe

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe mission produces a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an inertial reference unit, two star trackers, a digital sun sensor, twelve coarse sun sensors, three reaction wheel assemblies, and a propulsion system. Sufficient attitude knowledge is provided to yield instrument pointing to a standard deviation (l sigma) of 1.3 arc-minutes per axis. In addition, the spacecraft acquires and holds the sunline at initial acquisition and in the event of a failure, and slews to the proper orbit adjust orientations and to the proper off-sunline attitude to start the compound spin. This paper presents an overview of the design of the attitude control system to carry out this mission and presents some early flight experience.

  20. Method for controlling a vehicle attitude

    SciTech Connect

    Ise, K.; Minegishi, H.; Harada, H.

    1989-02-14

    This patent describes a method for controlling a suspension characteristic of a vehicle comprising the steps of: detecting a slippage of the one drive wheel of the vehicle; determining whether or not the detected slippage is greater than a reference value; controlling a drive force of the drive wheel by means of the braking system when the slippage is determined to be greater than the reference value; and altering an original state suspension characteristic of at least the drive wheel to a harder state when the slippage is determined to be greater than the reference value.

  1. Attitude-Control Algorithm for Minimizing Maneuver Execution Errors

    NASA Technical Reports Server (NTRS)

    Acikmese, Behcet

    2008-01-01

    A G-RAC attitude-control algorithm is used to minimize maneuver execution error in a spacecraft with a flexible appendage when said spacecraft must induce translational momentum by firing (in open loop) large thrusters along a desired direction for a given period of time. The controller is dynamic with two integrators and requires measurement of only the angular position and velocity of the spacecraft. The global stability of the closed-loop system is guaranteed without having access to the states describing the dynamics of the appendage and with severe saturation in the available torque. Spacecraft apply open-loop thruster firings to induce a desired translational momentum with an extended appendage. This control algorithm will assist this maneuver by stabilizing the attitude dynamics around a desired orientation, and consequently minimize the maneuver execution errors.

  2. Compassionate attitude towards others' suffering activates the mesolimbic neural system.

    PubMed

    Kim, Ji-Woong; Kim, Sung-Eun; Kim, Jae-Jin; Jeong, Bumseok; Park, Chang-Hyun; Son, Ae Ree; Song, Ji Eun; Ki, Seon Wan

    2009-08-01

    Compassion is one of the essential components which enable individuals to enter into and maintain relationships of caring. Compassion tends to motivate us to help people who are emotionally suffering. It is also known that a feeling of intrinsic reward may occur as a result of experiencing compassion for others. We conducted this study to understand the neural nature of compassion for other people's emotional state. Twenty-one healthy normal volunteers participated in this study. We used a 2 x 2 factorial design in which each subject was asked to assume a compassionate attitude or passive attitude while viewing the sad or neutral facial affective pictures during functional magnetic imaging. The main effect of a compassionate attitude was observed in the medial frontal cortex, the subgenual frontal cortex, the inferior frontal cortex and the midbrain regions. A test of the interaction between a compassionate attitude and sad facial affect revealed significant activations in the midbrain-ventral striatum/septal network region. The results of this study suggest that taking a compassionate attitude towards other people's sad expressions modulate the activities of the midbrain-ventral striatum/septal region network, which is known to play a role in the prosocial/social approach motivation and its accompanied rewarding feeling. PMID:19428038

  3. Elizabethan birth control and Puritan attitudes.

    PubMed

    Schnucker, R V

    1975-01-01

    During the Elizabethan era there was a considerable body of knowledge concerning birth control techniques including coitus interruptus, penis ointments, pessaries, purgatives, genital baths and bloodletting. Works were available describing the symptons and causes of abortion and reporting some abortifacients. The Puritans were aware of birth control techniques, but were opposed to them for several reasons: 1) it would go against the biblical injunction to be fruitful and multiply; 2) birth control frustrated the creation of what was in the image of God; 3) fecundity was a blessing and should not be thwarted; 4) the society of the elect should be increased; and 5) through childbirth a woman could atone for Eve's original sin. Although some Puritans recognized that marriage was for comfort and solace as well as for the bearing of progeny, birth control was frowned upon, the the Puritan clergy practiced what it preached. In a random sample of Puritan clergy there was an average of 6.8 children born per family, which was higher than the average to be found among English nobility of the same period. PMID:11619425

  4. The control of space manipulators subject to spacecraft attitude control saturation limits

    NASA Technical Reports Server (NTRS)

    Dubowsky, S.; Vance, E. E.; Torres, M. A.

    1989-01-01

    The motions of robotic manipulators mounted on spacecraft can disturb the spacecraft's positions and attitude. These disturbances can surpass the ability of the system's attitude control reaction jets to control them, for the disturbances increase as manipulator speeds increase. If the manipulator moves too quickly the resulting disturbances can exceed the saturation levels of the reaction jets, causing excessive spacecraft motions. A method for planning space manipulator's motions is presented, so that tasks can be performed as quickly as possible without saturating the system's attitude control jets.

  5. Fully magnetic sliding mode control for acquiring three-axis attitude

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Penkov, V. I.; Tkachev, S. S.; Mashtakov, Y. V.

    2016-04-01

    Satellite equipped with purely magnetic attitude control system is considered. Sliding mode control is used to achieve three-axis satellite attitude. Underactuation problem is solved for transient motion. Necessary attitude is acquired by proper sliding manifold construction. Satellite motion on the manifold is executed with magnetic control system. One manifold construction approach is proposed and discussed. Numerical examples are provided.

  6. Locus of Control and Attitude toward Eating in a Female College Population.

    ERIC Educational Resources Information Center

    Groth-Marnat, Gary; Scumaker, Jack F.

    1988-01-01

    Investigated relationship between locus of control and attitude to food intake in 101 female college students. Results indicated that locus of control was unable to predict attitudes toward eating and fear of becoming overweight. Thesis that locus of control would be related to attitude toward food intake was not supported. (Author/NB)

  7. Flexible Dynamics and Attitude Control of a Square Solar Sail

    NASA Astrophysics Data System (ADS)

    Choi, Mirue

    This thesis presents a comprehensive analysis of attitude and structural dynamics of a square solar sail. In particular, this research examines the use of corner-attached reflective vanes to control the attitude of the spacecraft. An introduction to known solar sail designs is given, then the mathematics involved in calculating solar radiation pressure forces are presented. A detailed derivation and implementation of the unconstrained nonlinear flexible structural dynamics with Finite Element Method (FEM) models are explored, with several sample simulations of published large deflection experiments used as verification measures. To simulate the inability of a thin membrane to resist compression, the sail membrane elements are augmented with a method that approximates the wrinkling and the slacking dynamics, which is followed by a simulation of another well-known experiment as a verification measure. Once the structural dynamics are established, the usage of the tip vanes is explored. Specifically, a control allocation problem formed by having two degrees of freedom for each tip vane is defined and an efficient solution to this problem is presented, allowing desired control torques to be converted to appropriate vane angles. A randomized testing mechanism is implemented to show the efficacy of this algorithm. The sail shadowing problem is explored as well, where a component of the spacecraft casts shadow upon the sail and prevents solar radiation pressure force from being produced. A method to calculate the region of shadow is presented, and two different shadowing examples are examined --- due to the spacecraft bus, and due to the sail itself. Combining all of the above, an attitude control simulation of the sail model is presented. A simple PD controller combined with the control allocation scheme is used to provide the control torque for the sail, with which the spacecraft must orient towards a number of pre-specified attitude targets. Several attitude

  8. Attitudes Toward Physical Activity of Champion Women Basketball Players.

    ERIC Educational Resources Information Center

    Corbin, Charles B.

    This study was undertaken to determine which attitudes were central to the motivation of women involved in championship basketball competition. Seventy-five women members of teams represented in national basketball championships served as subjects for this experiment. In addition, a control group of 212 women was randomly selected from physical…

  9. Attitude Control System Design for Fast Rest-to-Rest Attitude Maneuver

    NASA Astrophysics Data System (ADS)

    Sakai, S.-I.; Bando, N.; Hashimoto, T.; Murata, Y.; Mochizuki, N.; Nakamura, T.; Kamiya, T.; Ogura, N.; Maeda, K.

    2009-08-01

    The VSOP-2 project is a new space VLBI (very long baseline interferometer) radio astronomy mission, proposed to inherit the fruitful success of the VSOP mission with the HALCA satellite. One of the most important advances of VSOP-2 is the use of higher observation frequency, which requires fast alternating observation of a target and calibrator in order to remove the phase changes caused by the atmosphere. Typically, both sources must be observed within 60 sec, and this switching must be carried out over many hours. ``ASTRO-G" is a satellite planned for this VSOP-2 project, and one of technical challenges is to achieve such fast rest-to-rest maneuvers, and the proper hardware must be selected to account for this fast attitude maneuver. The controlled momentum gyro (CMG) is an actuator that provides high torque with small power consumption, and the fiber optical gyro is a sensor able to measure the high angular velocity with excellent accuracy. This paper first describes these components for attitude control. Another challenge of the ASTRO-G's attitude control system is to design the switching for the flexible mode of the satellite structure, containing a large deployable reflector and a large solar panel. These produce resonances with fast switching and these must be attenuated. To achieve high agility in a flexible satellite, the controller design is crucial. One design feature is a novel robust input shaper named ``nil mode exciting profiler". Another feature is the feedback controller design. The paper describes these features and other potential problems with fast switching..

  10. Measurement of the Construct of Attitude Toward Student Activism.

    ERIC Educational Resources Information Center

    Gold, Joel A.; And Others

    The study measures individual differences in attitude toward student activism on an 18-item Likert type scale. A validity comparison of a known extreme group with a sample from the general student population yielded a significant difference between the means of the groups. Construct validity was evaluated by first testing the differences between…

  11. The Empirical Attitude, Material Practice and Design Activities

    ERIC Educational Resources Information Center

    Apedoe, Xornam; Ford, Michael

    2010-01-01

    This article is an argument about something that is both important and severely underemphasized in most current science curricula. The empirical attitude, fundamental to science since Galileo, is a habit of mind that motivates an active search for feedback on our ideas from the material world. Although more simple views of science manifest the…

  12. Triana Safehold: A New Gyroless, Sun-Pointing Attitude Controller

    NASA Technical Reports Server (NTRS)

    Chen, J.; Morgenstern, Wendy; Garrick, Joseph

    2001-01-01

    Triana is a single-string spacecraft to be placed in a halo orbit about the sun-earth Ll Lagrangian point. The Attitude Control Subsystem (ACS) hardware includes four reaction wheels, ten thrusters, six coarse sun sensors, a star tracker, and a three-axis Inertial Measuring Unit (IMU). The ACS Safehold design features a gyroless sun-pointing control scheme using only sun sensors and wheels. With this minimum hardware approach, Safehold increases mission reliability in the event of a gyroscope anomaly. In place of the gyroscope rate measurements, Triana Safehold uses wheel tachometers to help provide a scaled estimation of the spacecraft body rate about the sun vector. Since Triana nominally performs momentum management every three months, its accumulated system momentum can reach a significant fraction of the wheel capacity. It is therefore a requirement for Safehold to maintain a sun-pointing attitude even when the spacecraft system momentum is reasonably large. The tachometer sun-line rate estimation enables the controller to bring the spacecraft close to its desired sun-pointing attitude even with reasonably high system momentum and wheel drags. This paper presents the design rationale behind this gyroless controller, stability analysis, and some time-domain simulation results showing performances with various initial conditions. Finally, suggestions for future improvements are briefly discussed.

  13. Wheel configurations for combined energy storage and attitude control systems

    NASA Technical Reports Server (NTRS)

    Oglevie, R. E.

    1985-01-01

    Integrated power and attitude control system (IPACS) studies performed over a decade ago established the feasibility of simultaneously storing electrical energy in wheels and utilizing the resulting momentum for spacecraft attitude control. It was shown that such a system possessed many advantages over other contemporary energy storage and attitude control systems in many applications. More recent technology advances in composite rotors, magnetic bearings, and power control electronics have triggered new optimism regarding the feasibility and merits of such a system. This paper presents the results of a recent study whose focus was to define an advanced IPACS and to evaluate its merits for the Space Station application. Emphasis is given to the selection of the wheel configuration to perform the combined functions. A component design concept is developed to establish the system performance capability. A system-level trade study, including life-cycle costing, is performed to define the merits of the system relative to two other candidate systems. It is concluded that an advanced IPACS concept is not only feasible but offers substantial savings in mass and life-cycle cost.

  14. SP-100 attitude control pathfinder study. Technical information report

    SciTech Connect

    Eke, F.O.; Graff, S.H.; Laskin, R.A.; Swan, P.A.

    1984-03-01

    This report delineates the scope of Jet Propulsion Laboratory`s FY`83 effort in the attitude control area in support of the SP-100 program. Dynamic modeling of the baseline beam configuration has been conducted and is presented herein. As a first cut, the beam is treated as rigid. Its inherent flexibility is then integrated via the hybrid coordinates method. Using the resulting dynamical equations, a preliminary look at attitude control is taken. Only one axis of rotational one flexible mode are included. An alternative to the beam configuration is one that envisions connecting basebody to user via a long, lightweight, flexible tether. A literature search has been conducted in this area and the resulting bibliography is presented. The tether option is not considered viable near term. However, it offers several potentially significant advantages and thus deserves serious consideration for the next generation space power system. This report also treats attitude control constraints imposed by the high temperature and radiation environment and addresses the issue of hardware requirements and availability. Recommendations for FY`84 tasks include assembling and exercising a simulation program for the beam configuration dynamic model and conducting a technology assessment in the area of tether dynamics and control.

  15. 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.

  16. Optimal spacecraft attitude control using collocation and nonlinear programming

    NASA Astrophysics Data System (ADS)

    Herman, A. L.; Conway, B. A.

    1992-10-01

    Direct collocation with nonlinear programming (DCNLP) is employed to find the optimal open-loop control histories for detumbling a disabled satellite. The controls are torques and forces applied to the docking arm and joint and torques applied about the body axes of the OMV. Solutions are obtained for cases in which various constraints are placed on the controls and in which the number of controls is reduced or increased from that considered in Conway and Widhalm (1986). DCLNP works well when applied to the optimal control problem of satellite attitude control. The formulation is straightforward and produces good results in a relatively small amount of time on a Cray X/MP with no a priori information about the optimal solution. The addition of joint acceleration to the controls significantly reduces the control magnitudes and optimal cost. In all cases, the torques and acclerations are modest and the optimal cost is very modest.

  17. Magnetic bearing reaction wheel. [for spacecraft attitude control

    NASA Technical Reports Server (NTRS)

    Sabnis, A.; Schmitt, F.; Smith, L.

    1976-01-01

    The results of a program for the development, fabrication and functional test of an engineering model magnetically suspended reaction wheel are described. The reaction wheel develops an angular momentum of + or - 0.5 foot-pound-second and is intended for eventual application in the attitude control of long-life interplanetary and orbiting spacecraft. A description of the wheel design and its major performance characteristics is presented. Recommendations for flight prototype development are made.

  18. Fault tolerant programmable digital attitude control electronics study

    NASA Technical Reports Server (NTRS)

    Sorensen, A. A.

    1974-01-01

    The attitude control electronics mechanization study to develop a fault tolerant autonomous concept for a three axis system is reported. Programmable digital electronics are compared to general purpose digital computers. The requirements, constraints, and tradeoffs are discussed. It is concluded that: (1) general fault tolerance can be achieved relatively economically, (2) recovery times of less than one second can be obtained, (3) the number of faulty behavior patterns must be limited, and (4) adjoined processes are the best indicators of faulty operation.

  19. Hardware and software implementation of a low power attitude control and determination system for cubesats

    NASA Astrophysics Data System (ADS)

    Frey, Jesse

    In recent years there has been a growing interest in smaller satellites. Smaller satellites are cheaper to build and launch than larger satellites. One form factor, the CubeSat, is especially popular with universities and is a 10~cm cube. Being smaller means that the mass and power budgets are tighter and as such new ways must be developed to cope with these constraints. Traditional attitude control systems often use reaction wheels with gas thrusters which present challenges on a CubeSat. Many CubeSats use magnetic attitude control which uses the Earth's magnetic field to torque the satellite into the proper orientation. Magnetic attitude control systems fall into two main categories: active and passive. Active control is often achieved by running current through a coil to produce a dipole moment, while passive control uses the dipole moment from permanent magnets that consume no power. This thesis describes a system that uses twelve hard magnetic torquers along with a magnetometer. The torquers only consume current when their dipole moment is flipped, thereby significantly reducing power requirements compared with traditional active control. The main focus of this thesis is on the design, testing and fabrication of CubeSat hardware and software in preparation for launch.

  20. Entry Attitude Controller for the Mars Science Laboratory

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul B.; SanMartin, A. Miguel; Wong, Edward C.

    2007-01-01

    This paper describes the preliminary concept for the RCS 3-axis attitude controller for the exo-atmospheric and guided entry phases of the Mars Science Laboratory Entry, Descend and Landing. The entry controller is formulated as three independent channels in the control frame, which is nominally aligned with the stability frame. Each channel has a feedfoward and a feedback. The feedforward path enables fast response to large bank commands. The feedback path stabilizes the vehicle angle of attack and sideslip around its trim position, and tracks bank commands. The feedback path has a PD/D structure with deadbands that minimizes fuel usage. The performance of this design is demonstrated via simulation.

  1. Position and attitude tracking control for a quadrotor UAV.

    PubMed

    Xiong, Jing-Jing; Zheng, En-Hui

    2014-05-01

    A synthesis control method is proposed to perform the position and attitude tracking control of the dynamical model of a small quadrotor unmanned aerial vehicle (UAV), where the dynamical model is underactuated, highly-coupled and nonlinear. Firstly, the dynamical model is divided into a fully actuated subsystem and an underactuated subsystem. Secondly, a controller of the fully actuated subsystem is designed through a novel robust terminal sliding mode control (TSMC) algorithm, which is utilized to guarantee all state variables converge to their desired values in short time, the convergence time is so small that the state variables are acted as time invariants in the underactuated subsystem, and, a controller of the underactuated subsystem is designed via sliding mode control (SMC), in addition, the stabilities of the subsystems are demonstrated by Lyapunov theory, respectively. Lastly, in order to demonstrate the robustness of the proposed control method, the aerodynamic forces and moments and air drag taken as external disturbances are taken into account, the obtained simulation results show that the synthesis control method has good performance in terms of position and attitude tracking when faced with external disturbances. PMID:24534327

  2. Civic Engagement Assessment: Linking Activities to Attitudes

    ERIC Educational Resources Information Center

    Terkla, Dawn Geronimo; O'Leary, Lisa S.; Wilson, Nancy E.; Diaz, Ande

    2007-01-01

    Recently, higher education has witnessed a renewed commitment to the mission of preparing students for lives of active citizenship. Under the leadership of President Lawrence S. Bacow, Tufts University (Medford, Massachusetts) has articulated an institutional mission that embraces three areas of focus: active citizenship, internationalism, and…

  3. MAP Attitude Control System Design and Flight Performance

    NASA Technical Reports Server (NTRS)

    Andrews, S. F.; ODonnell, J. R.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. To make a full-sky map of cosmic microwave background fluctuations, a combination fast spin and slow precession motion will be used that will cover the entire celestial sphere in six months. The spin rate should be an order of magnitude higher than the precession rate, and each rate should be tightly controlled. The sunline angle should be 22.5 +/- 0.25 deg. Sufficient attitude knowledge must be provided to yield instrument pointing to a standard deviation of 1.3 arc-minutes RSS three axes. In addition, the spacecraft must be able to acquire and hold the sunline at initial acquisition, and in the event of a failure. Finally. the spacecraft must be able to slew to the proper burn orientations and to the proper off-sunline attitude to start the compound spin. The design and flight performance of the Attitude Control System on MAP that meets these requirements will be discussed.

  4. Attitude Control for a Solar-Sail Spacecraft

    NASA Technical Reports Server (NTRS)

    Mettler, Edward; Ploen, Scott

    2004-01-01

    A report discusses the attitude-control system of a proposed spacecraft that would derive at least part of its propulsion from a solar sail. The spacecraft would include a bus module containing three or more reaction wheels, a boom attached at one end to the bus module and attached at its other end to a two-degree-of-freedom (DOF) gimbal at the nominal center of mass of a sail module. Each DOF of the gimbal could be independently locked against rotation or allowed to rotate freely. By using the reaction wheels to rotate the bus when at least one gimbal DOF was in the free state, the center of mass (CM) of the spacecraft could be shifted relative to the center of pressure (CP) on the solar sail. The resulting offset between the CM and CP would result in a solar torque, which could be used to change the attitude of the spacecraft. The report discusses numerous aspects of the dynamics and kinematics of the spacecraft, along with the relationships between these aspects and the designs of such attitude-control- system components as sensors, motors, brakes, clutches, and gimbals.

  5. Robust attitude control for Cassini spacecraft flying by Titan

    NASA Technical Reports Server (NTRS)

    Chiang, R.; Lisman, S.; Wong, E.; Enright, P.; Breckenridge, W.; Jahanshahi, M.

    1993-01-01

    This paper summarizes a few years attitude control design work on Cassini spacecraft with emphasis on the mission of Titan flyby. The study consists of modeling of the spacecraft dynamics, fuel sloshing, aerodynamic disturbance, controller design, nonlinear simulation, and establishing geometric command profiles. Both classical bang-bang control and modern robust H-infinity control have been designed and evaluated in nonlinear simulation to access the system tracking performance. Design procedures as well as their critical design issues are discussed in detail. Full model nonlinear simulations indicate that a simple 12-state H-infinity controller achieves better radar tracking performance than the classical bang-bang controller with less fuel throughout the flyby mission. Detailed robustness analysis of both designs will be published elsewhere.

  6. Fuzzy attitude control for a nanosatellite in leo orbit

    NASA Astrophysics Data System (ADS)

    Calvo, Daniel; Laverón-Simavilla, Ana; Lapuerta, Victoria; Aviles, Taisir

    Fuzzy logic controllers are flexible and simple, suitable for small satellites Attitude Determination and Control Subsystems (ADCS). In this work, a tailored fuzzy controller is designed for a nanosatellite and is compared with a traditional Proportional Integrative Derivative (PID) controller. Both control methodologies are compared within the same specific mission. The orbit height varies along the mission from injection at around 380 km down to a 200 km height orbit, and the mission requires pointing accuracy over the whole time. Due to both the requirements imposed by such a low orbit, and the limitations in the power available for the attitude control, a robust and efficient ADCS is required. For these reasons a fuzzy logic controller is implemented as the brain of the ADCS and its performance and efficiency are compared to a traditional PID. The fuzzy controller is designed in three separated controllers, each one acting on one of the Euler angles of the satellite in an orbital frame. The fuzzy memberships are constructed taking into account the mission requirements, the physical properties of the satellite and the expected performances. Both methodologies, fuzzy and PID, are fine-tuned using an automated procedure to grant maximum efficiency with fixed performances. Finally both methods are probed in different environments to test their characteristics. The simulations show that the fuzzy controller is much more efficient (up to 65% less power required) in single maneuvers, achieving similar, or even better, precision than the PID. The accuracy and efficiency improvement of the fuzzy controller increase with orbit height because the environmental disturbances decrease, approaching the ideal scenario. A brief mission description is depicted as well as the design process of both ADCS controllers. Finally the validation process and the results obtained during the simulations are described. Those results show that the fuzzy logic methodology is valid for small

  7. Multimode attitude and orbit control for the Atmosphere Explorer spacecraft

    NASA Technical Reports Server (NTRS)

    Stewart, B.

    1975-01-01

    The orbit profile for the Atmosphere Explorer requires a velocity adjust capability of 2000 ft/sec/sec and individual maneuvers of up to 24 ft/sec in magnitude. This requirement is met by a monopropellant hydrazine propulsion subsystem which also provides, by virtue of the tank arrangement, a means of adjusting the spacecraft center of mass in orbit, thereby minimizing external disturbance torques. The attitude control subsystem is of the momentum bias type. A large internal flywheel furnishes gyroscopic stiffness and permits rapid changes in operating mode (despun to spinning mode) by controlled interchange of momentum between the flywheel and the spacecraft main body.

  8. Social activities, self-efficacy, game attitudes, and game addiction.

    PubMed

    Jeong, Eui Jun; Kim, Doo Hwan

    2011-04-01

    This study examines whether social activities with parents, online and offline social self-efficacy, and attitudes toward gaming are associated with the degree of game addiction among adolescents. Using data from a survey of 600 middle- and high-school students in South Korea, we tested the relationships of personal characteristics (grade point average and time spent on gaming each day), social self-efficacy (both on- and offline), general social activities (with parents, friends, and teachers), gaming activities with parents, and attitudes toward gaming (those of self, parents, friends, and teachers) with the degree of game addiction. In addition, we conducted ANOVA tests to determine the differences among three groups: non-addicts (NA), possible (mild or moderate) addicts (PA), and Internet addicts (IA). The results show that social self-efficacy in the real world (offline) was negatively related with the degree of game addiction, whereas social self-efficacy in the virtual world (online) indicated a positive association. Social activities with parents are negatively associated with game addiction, although no relationship is found between gaming activities with parents and game addiction. Parental attitude toward gaming has a negative relationship with the addiction. Results and implications are discussed. PMID:21067285

  9. Integrated Power and Attitude Control for a Spacecraft with Flywheels and Control Moment Gyroscopes

    NASA Technical Reports Server (NTRS)

    Roithmayr, Carlos M.; Karlgaard, Christopher D.; Kumar, Renjith R.; Bose, David M.

    2003-01-01

    A law is designed for simultaneous control of the orientation of an Earth-pointing spacecraft, the energy stored by counter-rotating flywheels, and the angular momentum of the flywheels and control moment gyroscopes used together as all integrated set of actuators for attitude control. General. nonlinear equations of motion are presented in vector-dyadic form, and used to obtain approximate expressions which are then linearized in preparation for design of control laws that include feedback of flywheel kinetic energy error as it means of compensating for damping exerted by rotor bearings. Two flywheel 'steering laws' are developed such that torque commanded by all attitude control law is achieved while energy is stored or discharged at the required rate. Using the International Space Station as an example, numerical simulations are performed to demonstrate control about a torque equilibrium attitude and illustrate the benefits of kinetic energy error feedback.

  10. Nonlinear attitude control of flexible spacecraft under disturbance torque

    NASA Technical Reports Server (NTRS)

    Singh, Sahjendra N.

    1986-01-01

    A control law for large-angle single-axis rotational maneuvers of a spacecraft-beam-tip body (an antenna or a reflector) configuration is presented. It is assumed that an unknown but bounded disturbance torque is acting on the spacecraft. A model reference adaptive torque control law is derived for the slewing of the space vehicle. This controller includes a dynamic system in the feedback path and requires only attitude angle and rate of the space vehicle for feedback. For damping out the elastic motion excited by the slewing maneuver, a stabilizer is designed assuming that a torquer and a force actuator are available at the tip body. The stabilizer uses only the flexible modes for the synthesis of the control law. Simulation results are presented to show that fast, large-angle rotational maneuvers can be performed using the adaptive controller and the stabilizer in spite of the presence of continuously acting unknown torque on the spacecraft.

  11. Design development of the Apollo command and service module thrust vector attitude control systems

    NASA Technical Reports Server (NTRS)

    Peters, W. H.

    1978-01-01

    Development of the Apollo thrust vector control digital autopilot (TVC DAP) was summarized. This is the control system that provided pitch and yaw attitude control during velocity change maneuvers using the main rocket engine on the Apollo service module. A list of ten primary functional requirements for this control system are presented, each being subordinate to a more general requirement appearing earlier on the list. Development process functions were then identified and the essential information flow paths were explored. This provided some visibility into the particular NASA/contractor interface, as well as relationships between the many individual activities.

  12. A New Approach to Attitude Stability and Control for Low Airspeed Vehicles

    NASA Technical Reports Server (NTRS)

    Lim, K. B.; Shin, Y-Y.; Moerder, D. D.; Cooper, E. G.

    2004-01-01

    This paper describes an approach for controlling the attitude of statically unstable thrust-levitated vehicles in hover or slow translation. The large thrust vector that characterizes such vehicles can be modulated to provide control forces and moments to the airframe, but such modulation is accompanied by significant unsteady flow effects. These effects are difficult to model, and can compromise the practical value of thrust vectoring in closed-loop attitude stability, even if the thrust vectoring machinery has sufficient bandwidth for stabilization. The stabilization approach described in this paper is based on using internal angular momentum transfer devices for stability, augmented by thrust vectoring for trim and other "outer loop" control functions. The three main components of this approach are: (1) a z-body axis angular momentum bias enhances static attitude stability, reducing the amount of control activity needed for stabilization, (2) optionally, gimbaled reaction wheels provide high-bandwidth control torques for additional stabilization, or agility, and (3) the resulting strongly coupled system dynamics are controlled by a multivariable controller. A flight test vehicle is described, and nonlinear simulation results are provided that demonstrate the efficiency of the approach.

  13. attitude control design for the solar polar orbit radio telesope

    NASA Astrophysics Data System (ADS)

    Gao, D.; Zheng, J.

    This paper studies the attitude dynamics and control of the Solar Polar Orbit Radio Telescope SPORT The SPORT which consists of one parent satellite and eight tethered satellites runs around the Sun in a polar orbit The parent satellite locates at the mass center of the constellation and tethered satellites which are tied with the parent satellite through a non-electric rope rotate around the parent satellite It is also supposed that the parent satellite and all tethered satellites are in a plane when the constellation works begin figure htbp centerline includegraphics width 3 85in height 2 38in 75271331 6a6eb71057 doc1 eps label fig1 end figure Fig 1 the SPORT constellation Firstly this paper gives the dynamic equations of the tethered satellite and the parent satellite From the dynamic characteristic of the tethered satellite we then find that the roll axis is coupled with the yaw axis The control torque of the roll axis can control the yaw angle But the control torque of the roll axis and pitch axis provided by the tether is very small it can not meet the accuracy requirement of the yaw angle In order to improve the attitude pointing accuracy of the tethered satellite a gradient pole is set in the negative orientation of the yaw axis The gradient pole can improve not only the attitude accuracy of roll angle and pitch angle but also that of the yaw angle indirectly As to the dynamic characteristic of the parent satellite the roll axis is coupled with the pitch axis due to the spinning angular velocity At the same

  14. Cosmic Background Explorer (COBE) transfer orbit attitude control system

    NASA Technical Reports Server (NTRS)

    Placanica, Samuel J.; Flatley, Thomas W.

    1986-01-01

    The Cosmic Background Explorer (COBE) spacecraft will be launched by the Shuttle from Vandenberg AFB into a 300 km altitude, 99 deg inclination, 6 a.m. or 6 p.m. ascending node orbit. After release from the Remote Manipulator System (RMS) arm, an on-board monopropellant hydrazine propulsion system will raise the orbit altitude to 900 km. The spacecraft continuously spins during transfer orbit operations with the spin axis nominally horizontal and in or near the orbit plane. The blowdown propulsion system consists of twelve 5 lb thrusters (3 'spin', 3 'despin', and 6 'axial') with the latter providing initially 30 lb of force parallel to the spin axis for orbit raising. The spin/despin jets provide a constant roll rate during the transfer orbit phase of the mission and the axials control pitch and yaw. The axial thrusters are pulsed on for attitude control during coast periods and are normally on- and off-modulated for control during orbit raising. Attitude sensors employed in the control loops include an array of two-axis digital sun sensors and three planar earth scanners for position measurements, as well as six gyroscopes for rate information. System redundancy is achieved by means of unique three-axes-in-a-plane geometry. This triaxial concept results in a fail-safe operational system with no performance degradation for many different component failure modes.

  15. A Comparison of Upper Elementary School Children's Attitudes toward Physical Activity.

    ERIC Educational Resources Information Center

    Folsom-Meek, Sherry L.

    This study was conducted to compare upper elementary school children's attitudes toward physical activity, by grade level and gender across six attitude scale subdomains in order to assist physical education teachers in planning programs designed to foster positive attitudes toward physical activity. Subjects (N=429) were 243 girls and 186 boys in…

  16. Galileo attitude and articulation control subsystem closed loop testing

    NASA Technical Reports Server (NTRS)

    Lembeck, M. F.; Pignatano, N. D.

    1983-01-01

    In order to ensure the reliable operation of the Attitude and Articulation Control Subsystem (AACS) which will guide the Galileo spacecraft on its two and one-half year journey to Jupiter, the AACS is being rigorously tested. The primary objectives of the test program are the verification of the AACS's form, fit, and function, especially with regard to subsystem external interfaces and the functional operation of the flight software. Attention is presently given to the Galileo Closed Loop Test System, which simulates the dynamic and 'visual' flight environment for AACS components in the laboratory.

  17. Propulsion Options for Primary Thrust and Attitude Control of Microspacecraft

    NASA Technical Reports Server (NTRS)

    deGroot, W. A.

    1998-01-01

    Order of magnitude decreases in the size of scientific satellites and spacecraft could provide concurrent decreases in mission costs because of lower launch and fabrication costs. Although many subsystems are amenable to dramatic size reductions, miniaturization of the propulsion subsystems is not straightforward. There are a range of requirements for both primary and attitude control propulsion, dictated by mission requirements, satellite size, and power restrictions. Many of the established propulsion technologies can not currently be applied to microspacecraft. Because of this, micro-electromechanical systems (MEMS) fabrication technology is being explored as a path for miniaturization.

  18. Attitude Changes of Specialist Students of Physical Education towards Physical Activity during Teacher-Training Courses.

    ERIC Educational Resources Information Center

    Barrell, G. V.; Holt, D.

    1982-01-01

    A longitudinal investigation of the attitudes towards physical activity of specialist students of physical education was undertaken during a course of training teachers. Significant changes of attitude with time were noted, particularly in the Vertigo and Ascetic dimensions. (Author)

  19. Pulsed Plasma Thrusters for Small Spacecraft Attitude Control

    NASA Technical Reports Server (NTRS)

    McGuire, Melissa L.; Myers, Roger M.

    1996-01-01

    Pulsed plasma thrusters (PPT's) are a new option for attitude control of a small spacecraft and may result in reduced attitude control system (ACS) mass and cost. The primary purpose of an ACS is to orient the spacecraft configuration to the desired accuracy in inertial space. The ACS functions for which the PPT system will be analyzed include disturbance torque compensation and slewing maneuvers such as sun acquisition for which the small impulse bit and high specific impulse of the PPT offers unique advantages. The NASA Lewis Reserach Center (LeRC) currently has a contracted flight PPT system development program in place with Olin Aerospace and a delivery date of October 1997. The PPT system in this study are based upon the work being done under the NASA LeRC program. Analysis of the use of PPT's for ACS showed that the replacement of the standard momentum wheels and torque rods systems with a PTT system to perform the altitude control maneuvers on a small low Earth orbiting spacecraft reduced the ACS mass by 50 to 75 percent with no increase in required power level over comparable wheel-based systems.

  20. An Attitude Control of Flexible Spacecraft Using Fuzzy-PID Controller

    NASA Astrophysics Data System (ADS)

    Park, Jong-Oh; Im, Young-Do

    This primary objective of this study is to demonstrate simulation and ground-based experiment for the attitude control of flexible spacecraft. A typical spacecraft structure consists of the rigid body and flexible appendages which are large flexible solar panels, parabolic antennas built from light materials in order to reduce their weight. Therefore the attitude control has a big problem because these appendages induce structural vibration under the excitation of external forces. A single-axis rotational simulator with a flexible arm is constructed with on-off air thrusters and reaction wheel as actuation. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The experiment of flexible spacecraft attitude control is performed using only the reaction wheel. Using the reaction wheel the performance of the fuzzy-PID controller is illustrated by simulation and experimental results for a single-axis rotational simulator.

  1. Asian American Midlife Women’s Attitudes toward Physical Activity

    PubMed Central

    Im, Eun-Ok; Ko, Young; Hwang, Hyenam; Chee, Wonshik; Stuifbergen, Alexa; Lee, Hannah; Chee, Eunice

    2012-01-01

    Objectives To explore Asian American midlife women’s attitudes toward physical activity using a feminist perspective. Design A qualitative online forum study. Settings Internet communities/groups for midlife women and ethnic minorities. Participants A total of 17 Asian American women recruited through the internet using a convenience sampling method. Methods A six-month qualitative online forum was conducted using 17 online forum topics. The data were analyzed using thematic analysis. Results Three major themes related to Asian American midlife women’s attitudes toward physical activity were extracted from the data: keeping traditions, not a priority, and not for Asian girls. Because Asian American midlife women were busy in keeping their cultural traditions, they rarely found time for physical activity. The women gave the highest priority to their children, and physical activity was the lowest priority in their busy lives. Also, the women were rarely encouraged to participate in physical activity during their childhoods, and they perceived that their weak and small bodies were not appropriate for physical activity. Conclusions Several implications for future development of physical activity promotion programs for this specific population have been suggested based on the findings. PMID:22789126

  2. Attitude and translation control of a low-altitude Gravsat

    NASA Technical Reports Server (NTRS)

    Ray, J. C.; Jenkins, R. E.; Debra, D. B.; Van Patten, R. A.; Junkins, J. L.

    1982-01-01

    Dynamic simulation of the Gravsat's attitude and translation control system is used to provide an upper bound for the fuel supply and test the feasibility of the preliminary design. A preliminary design is made for the disturbance compensation system (DISCOS) sensor, the thruster control laws, reaction wheel control laws, and the onboard state estimators. The sensor analysis and noise measurements show no problems in scaling the Triad navigation satellite sensor design up to meet the Gravsat requirements, except for proof mass center-of-mass offset. A promising technique is proposed to measure and eliminate this error. The covariance analysis confirms that a sophisticated post-flight data fit will be necessary to reconstruct a scientifically useful proof mass state. The DISCOS sensor will have to be continuously calibrated from the inflight data to achieve this reconstruction.

  3. Backup Attitude Control Algorithms for the MAP Spacecraft

    NASA Technical Reports Server (NTRS)

    ODonnell, James R., Jr.; Andrews, Stephen F.; Ericsson-Jackson, Aprille J.; Flatley, Thomas W.; Ward, David K.; Bay, P. Michael

    1999-01-01

    The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The MAP spacecraft will perform its mission, studying the early origins of the universe, in a Lissajous orbit around the Earth-Sun L(sub 2) Lagrange point. Due to limited mass, power, and financial resources, a traditional reliability concept involving fully redundant components was not feasible. This paper will discuss the redundancy philosophy used on MAP, describe the hardware redundancy selected (and why), and present backup modes and algorithms that were designed in lieu of additional attitude control hardware redundancy to improve the odds of mission success. Three of these modes have been implemented in the spacecraft flight software. The first onboard mode allows the MAP Kalman filter to be used with digital sun sensor (DSS) derived rates, in case of the failure of one of MAP's two two-axis inertial reference units. Similarly, the second onboard mode allows a star tracker only mode, using attitude and derived rate from one or both of MAP's star trackers for onboard attitude determination and control. The last backup mode onboard allows a sun-line angle offset to be commanded that will allow solar radiation pressure to be used for momentum management and orbit stationkeeping. In addition to the backup modes implemented on the spacecraft, two backup algorithms have been developed in the event of less likely contingencies. One of these is an algorithm for implementing an alternative scan pattern to MAP's nominal dual-spin science mode using only one or two reaction wheels and thrusters. Finally, an algorithm has been developed that uses thruster one shots while in science mode for momentum management. This algorithm has been developed in case system momentum builds up faster than anticipated, to allow adequate momentum management while minimizing interruptions to science. In this paper, each mode and

  4. Rotating Space Debris Tracking Based on The Orbit-Attitude Coordinated Control

    NASA Astrophysics Data System (ADS)

    Wang, Shuquan; Zhu, Lingchao

    2016-07-01

    This paper investigates the rotating space debris tracking problem. Active capturing and removal of space debris are challenging because the space debris is noncoorperating. The scenario considered is that a rotating space debris is the target to be captured by a spacecraft with a robotic arm. One rough approach is to capture the space debris with a strong arm then detumble the rotation of the whole system using the attitude control system on board. In this way the arm and the spacecraft have to be strong enough to withstand the impact caused by the relative orbital and attitude motions. Another way is to at first track the motion of the characterized surface, which should be easier to capture, of the debris. Then the robotic arm is engaged to capture the debris. In this way, the impact applied on the robotic arm is greatly reduced such that the possibility of causing new debris is also reduced. The orbit-attitude coordinated controller is developed to track the motion of the space debris. The controller is assymptotically stable without considering the boundness of the control efforts. The stability in the situation of bounded control inputs is analyzed. Analytical criterion for a successful tracking is obtained in the situation that rotational motion of the space debris is percession.

  5. Pushing the Limits of Cubesat Attitude Control: A Ground Demonstration

    NASA Technical Reports Server (NTRS)

    Sanders, Devon S.; Heater, Daniel L.; Peeples, Steven R.; Sules. James K.; Huang, Po-Hao Adam

    2013-01-01

    A cubesat attitude control system (ACS) was designed at the NASA Marshall Space Flight Center (MSFC) to provide sub-degree pointing capabilities using low cost, COTS attitude sensors, COTS miniature reaction wheels, and a developmental micro-propulsion system. The ACS sensors and actuators were integrated onto a 3D-printed plastic 3U cubesat breadboard (10 cm x 10 cm x 30 cm) with a custom designed instrument board and typical cubesat COTS hardware for the electrical, power, and data handling and processing systems. In addition to the cubesat development, a low-cost air bearing was designed and 3D printed in order to float the cubesat in the test environment. Systems integration and verification were performed at the MSFC Small Projects Rapid Integration & Test Environment laboratory. Using a combination of both the miniature reaction wheels and the micro-propulsion system, the open and closed loop control capabilities of the ACS were tested in the Flight Robotics Laboratory. The testing demonstrated the desired sub-degree pointing capability of the ACS and also revealed the challenges of creating a relevant environment for development testin

  6. Controlling Attitude of a Solar-Sail Spacecraft Using Vanes

    NASA Technical Reports Server (NTRS)

    Mettler, Edward; Acikmese, Ahmet; Ploen, Scott

    2006-01-01

    A paper discusses a concept for controlling the attitude and thrust vector of a three-axis stabilized Solar Sail spacecraft using only four single degree-of-freedom articulated spar-tip vanes. The vanes, at the corners of the sail, would be turned to commanded angles about the diagonals of the square sail. Commands would be generated by an adaptive controller that would track a given trajectory while rejecting effects of such disturbance torques as those attributable to offsets between the center of pressure on the sail and the center of mass. The controller would include a standard proportional + derivative part, a feedforward part, and a dynamic component that would act like a generalized integrator. The controller would globally track reference signals, and in the presence of such control-actuator constraints as saturation and delay, the controller would utilize strategies to cancel or reduce their effects. The control scheme would be embodied in a robust, nonlinear algorithm that would allocate torques among the vanes, always finding a stable solution arbitrarily close to the global optimum solution of the control effort allocation problem. The solution would include an acceptably small angle, slow limit-cycle oscillation of the vanes, while providing overall thrust vector pointing stability and performance.

  7. Spacecraft attitude control using neuro-fuzzy approximation of the optimal controllers

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Woo; Park, Sang-Young; Park, Chandeok

    2016-01-01

    In this study, a neuro-fuzzy controller (NFC) was developed for spacecraft attitude control to mitigate large computational load of the state-dependent Riccati equation (SDRE) controller. The NFC was developed by training a neuro-fuzzy network to approximate the SDRE controller. The stability of the NFC was numerically verified using a Lyapunov-based method, and the performance of the controller was analyzed in terms of approximation ability, steady-state error, cost, and execution time. The simulations and test results indicate that the developed NFC efficiently approximates the SDRE controller, with asymptotic stability in a bounded region of angular velocity encompassing the operational range of rapid-attitude maneuvers. In addition, it was shown that an approximated optimal feedback controller can be designed successfully through neuro-fuzzy approximation of the optimal open-loop controller.

  8. ATS-6 engineering performance report. Volume 2: Orbit and attitude controls

    NASA Technical Reports Server (NTRS)

    Wales, R. O. (Editor)

    1981-01-01

    Attitude control is reviewed, encompassing the attitude control subsystem, spacecraft attitude precision pointing and slewing adaptive control experiment, and RF interferometer experiment. The spacecraft propulsion system (SPS) is discussed, including subsystem, SPS design description and validation, orbital operations and performance, in-orbit anomalies and contingency operations, and the cesium bombardment ion engine experiment. Thruster failure due to plugging of the propellant feed passages, a major cause for mission termination, are considered among the critical generic failures on the satellite.

  9. ATTDES: An Expert System for Satellite Attitude Determination and Control. 2

    NASA Technical Reports Server (NTRS)

    Mackison, Donald L.; Gifford, Kevin

    1996-01-01

    The design, analysis, and flight operations of satellite attitude determintion and attitude control systems require extensive mathematical formulations, optimization studies, and computer simulation. This is best done by an analyst with extensive education and experience. The development of programs such as ATTDES permit the use of advanced techniques by those with less experience. Typical tasks include the mission analysis to select stabilization and damping schemes, attitude determination sensors and algorithms, and control system designs to meet program requirements. ATTDES is a system that includes all of these activities, including high fidelity orbit environment models that can be used for preliminary analysis, parameter selection, stabilization schemes, the development of estimators covariance analyses, and optimization, and can support ongoing orbit activities. The modification of existing simulations to model new configurations for these purposes can be an expensive, time consuming activity that becomes a pacing item in the development and operation of such new systems. The use of an integrated tool such as ATTDES significantly reduces the effort and time required for these tasks.

  10. Health literacy and parent attitudes about weight control for children.

    PubMed

    Liechty, Janet M; Saltzman, Jaclyn A; Musaad, Salma M

    2015-08-01

    The purpose of this study was to examine associations between parental health literacy and parent attitudes about weight control strategies for young children. Parental low health literacy has been associated with poor child health outcomes, yet little is known about its relationship to child weight control and weight-related health information-seeking preferences. Data were drawn from the STRONG Kids Study, a Midwest panel survey among parents of preschool aged children (n = 497). Parents endorsed an average of 4.3 (SD =2.8) weight loss strategies, 53% endorsed all three recommended weight loss strategies for children, and fewer than 1% of parents endorsed any unsafe strategies. Parents were most likely to seek child weight loss information from healthcare professionals but those with low (vs. adequate) health literacy were significantly less likely to use the Internet or books and more likely to use minister/clergy as sources. Poisson and logistic regressions showed that higher health literacy was associated with endorsement of more strategies overall, more recommended strategies, and greater odds of endorsing each specific recommended strategy for child weight control, after adjusting for parent age, education, race/ethnicity, income, marital status, weight concern, and child BMI percentile. Findings suggest that health literacy impacts parental views about child weight loss strategies and health information-seeking preferences. Pediatric weight loss advice to parents should include assessment of parent attitudes and prior knowledge about child weight control and facilitate parent access to reliable sources of evidence-informed child weight control information. PMID:25868552

  11. Multivariable control theory applied to hierarchial attitude control for planetary spacecraft

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III; Russell, D. W.

    1972-01-01

    Multivariable control theory is applied to the design of a hierarchial attitude control system for the CARD space vehicle. The system selected uses reaction control jets (RCJ) and control moment gyros (CMG). The RCJ system uses linear signal mixing and a no-fire region similar to that used on the Skylab program; the y-axis and z-axis systems which are coupled use a sum and difference feedback scheme. The CMG system uses the optimum steering law and the same feedback signals as the RCJ system. When both systems are active the design is such that the torques from each system are never in opposition. A state-space analysis was made of the CMG system to determine the general structure of the input matrices (steering law) and feedback matrices that will decouple the axes. It is shown that the optimum steering law and proportional-plus-rate feedback are special cases. A derivation of the disturbing torques on the space vehicle due to the motion of the on-board television camera is presented. A procedure for computing an upper bound on these torques (given the system parameters) is included.

  12. Gaining control over responses to implicit attitude tests: Implementation intentions engender fast responses on attitude-incongruent trials.

    PubMed

    Webb, Thomas L; Sheeran, Paschal; Pepper, John

    2012-03-01

    The present research investigated whether forming implementation intentions could promote fast responses to attitude-incongruent associations (e.g., woman-manager) and thereby modify scores on popular implicit measures of attitude. Expt 1 used the Implicit Association Test (IAT) to measure associations between gender and science versus liberal arts. Planning to associate women with science engendered fast responses to this category-attribute pairing and rendered summary scores more neutral compared to standard IAT instructions. Expt 2 demonstrated that forming egalitarian goal intentions is not sufficient to produce these effects. Expt 3 extended these findings to a different measure of implicit attitude (the Go/No-Go Association Task) and a different stereotypical association (Muslims-terrorism). In Expt 4, managers who planned to associate women with superordinate positions showed more neutral IAT scores relative to non-planners and effects were maintained 3 weeks later. In sum, implementation intentions enable people to gain control over implicit attitude responses. PMID:22435844

  13. Neural network-based distributed attitude coordination control for spacecraft formation flying with input saturation.

    PubMed

    Zou, An-Min; Kumar, Krishna Dev

    2012-07-01

    This brief considers the attitude coordination control problem for spacecraft formation flying when only a subset of the group members has access to the common reference attitude. A quaternion-based distributed attitude coordination control scheme is proposed with consideration of the input saturation and with the aid of the sliding-mode observer, separation principle theorem, Chebyshev neural networks, smooth projection algorithm, and robust control technique. Using graph theory and a Lyapunov-based approach, it is shown that the distributed controller can guarantee the attitude of all spacecraft to converge to a common time-varying reference attitude when the reference attitude is available only to a portion of the group of spacecraft. Numerical simulations are presented to demonstrate the performance of the proposed distributed controller. PMID:24807141

  14. Attitude tracking control for spacecraft formation with time-varying delays and switching topology

    NASA Astrophysics Data System (ADS)

    Yang, Hongjiu; You, Xiu; Hua, Changchun

    2016-09-01

    This paper investigates attitude dynamic tracking control for spacecraft formation in the presence of unmeasurable velocity information with time-varying delays and switching topology. Based on an extended state observer, a nonlinear attitude tracking control approach is developed for spacecraft attitude model formulated by Euler-Lagrangian equations. The attitude tracking controller allows for external disturbances and absence of angular velocity information. Both auto-stable region techniques and a Lyapunov function approach are developed to prove ultimately bounded tracking. Simulation results demonstrate effectiveness of the nonlinear control techniques proposed in this paper.

  15. Attitude control requirements for various solar sail missions

    NASA Technical Reports Server (NTRS)

    Williams, Trevor

    1990-01-01

    The differences are summarized between the attitude control requirements for various types of proposed solar sail missions (Earth orbiting; heliocentric; asteroid rendezvous). In particular, it is pointed out that the most demanding type of mission is the Earth orbiting one, with the solar orbit case quite benign and asteroid station keeping only slightly more difficult. It is then shown, using numerical results derived for the British Solar Sail Group Earth orbiting design, that the disturbance torques acting on a realistic sail can completely dominate the torques required for nominal maneuvering of an 'ideal' sail. This is obviously an important consideration when sizing control actuators; not so obvious is the fact that it makes the standard rotating vane actuator unsatisfactory in practice. The reason for this is given, and a set of new actuators described which avoids the difficulty.

  16. Robust attitude control design for spacecraft under assigned velocity and control constraints.

    PubMed

    Hu, Qinglei; Li, Bo; Zhang, Youmin

    2013-07-01

    A novel robust nonlinear control design under the constraints of assigned velocity and actuator torque is investigated for attitude stabilization of a rigid spacecraft. More specifically, a nonlinear feedback control is firstly developed by explicitly taking into account the constraints on individual angular velocity components as well as external disturbances. Considering further the actuator misalignments and magnitude deviation, a modified robust least-squares based control allocator is employed to deal with the problem of distributing the previously designed three-axis moments over the available actuators, in which the focus of this control allocation is to find the optimal control vector of actuators by minimizing the worst-case residual error using programming algorithms. The attitude control performance using the controller structure is evaluated through a numerical example. PMID:23618744

  17. The Effect of Using Alternative Assessment Activities on Students' Success and Attitudes in Science and Technology Course

    ERIC Educational Resources Information Center

    Kirikkaya, Esma Bulus; Vurkaya, Gurbet

    2011-01-01

    The pre-test and post-test quasi-experimental design with control group was used in this study, in which the impact of alternative assessment activities on students' academic achievement levels and attitudes were explored by employing these activities in the unit "Electricity in Our Lives" of the Science and Technology Course. The research was…

  18. Motor Control of Two Flywheels Enabling Combined Attitude Control and Bus Regulation

    NASA Technical Reports Server (NTRS)

    Kenny, Barbara H.

    2004-01-01

    This presentation discussed the flywheel technology development work that is ongoing at NASA GRC with a particular emphasis on the flywheel system control. The "field orientation" motor/generator control algorithm was discussed and explained. The position-sensorless angle and speed estimation algorithm was presented. The motor current response to a step change in command at low (10 kRPM) and high (60 kRPM) was discussed. The flywheel DC bus regulation control was explained and experimental results presented. Finally, the combined attitude control and energy storage algorithm that controls two flywheels simultaneously was presented. Experimental results were shown that verified the operational capability of the algorithm. shows high speed flywheel energy storage (60,000 RPM) and the successful implementation of an algorithm to simultaneously control both energy storage and a single axis of attitude with two flywheels. Overall, the presentation demonstrated that GRC has an operational facility that

  19. CMC 20N thruster for hermes attitude control

    NASA Astrophysics Data System (ADS)

    Mathieu, A. C.

    Ceramic Matrix Composite materials (CMC) have been developped by SEP Solid Propulsion an Composite Materials Division in Le Haillan since the seventies for solid propulsion applications. In the race to create a new generation of small high performance bipropellant engines, SEP has opted for Ceramic Matrix Composite (CMC) such as SEPCARBINOX (R) or CERASEP (R), as combustion chamber and nozzle material. The main advantage of these composites is enabling increase of maximum combustion temperature to 1600°C without requiring anti-oxydation coatings, and with improved resistance to thermal cycles. SEP's Defense and Space group started preliminary work on choosing the composite materials best adapted to liquid bipropellant engines in 1983. Based on some 30 5N thrust combustion chambers, about 20 different materials were evaluated during firing tests. Next, using different combustion chambers sizes, SEP implemented a program designed to demonstrate the endurance of this material, and initiated a study on producing larger size parts including large area ratio nozzles. This program comprised the production and testing of combustion chambers rated at 200N and 6000N, associated with injectors derived from other applications. Finaly, in order to simulate the operating conditions experienced by certain motors on HERMES spaceplane, tests of the 200N motor were also carried out with an external thermal protection system. As of end 1987, designers had set the thrust level required for the HERMES attitude control system at between 10 and 30N. SEP therefore decided to focus further work on 20N-thrust engines, a choice which took into consideration the potential applications of this thrust level for satellite attitude control systems. Starting in mid-1988 and continuing until fall 1990, this program is designed to validate before going into final qualification all technologies required for the two planned applications: - the HERMES spaceplane, which has several thrusters integrated

  20. Reusable Reentry Satellite (RRS) system design study. Phase B, appendix E: Attitude control system study

    NASA Technical Reports Server (NTRS)

    1991-01-01

    A study which consisted of a series of design analyses for an Attitude Control System (ACS) to be incorporated into the Re-usable Re-entry Satellite (RRS) was performed. The main thrust of the study was associated with defining the control laws and estimating the mass and power requirements of the ACS needed to meet the specified performance goals. The analyses concentrated on the different on-orbit control modes which start immediately after the separation of the RRS from the launch vehicle. The three distinct on-orbit modes considered for these analyses are as follows: (1) Mode 1 - A Gravity Gradient (GG) three-axis stabilized spacecraft with active magnetic control; (2) Mode 2 - A GG stabilized mode with a controlled yaw rotation rate ('rotisserie') using three-axis magnetic control and also incorporating a 10 N-m-s momentum wheel along the (Z) yaw axis; and (3) Mode 3 - A spin stabilized mode of operation with the spin about the pitch (Y) axis, incorporating a 20 N-m-s momentum wheel along the pitch (Y) axis and attitude control via thrusters. To investigate the capabilities of the different controllers in these various operational modes, a series of computer simulations and trade-off analyses have been made to evaluate the achievable performance levels, and the necessary mass and power requirements.

  1. Passive radiative cooling of a HTS coil for attitude orbit control in micro-spacecraft

    NASA Astrophysics Data System (ADS)

    Inamori, Takaya; Ozaki, Naoya; Saisutjarit, Phongsatorn; Ohsaki, Hiroyuki

    2015-02-01

    This paper proposes a novel radiative cooling system for a high temperature superconducting (HTS) coil for an attitude orbit control system in nano- and micro-spacecraft missions. These days, nano-spacecraft (1-10 kg) and micro-spacecraft (10-100 kg) provide space access to a broader range of spacecraft developers and attract interest as space development applications. In planetary and high earth orbits, most previous standard-size spacecraft used thrusters for their attitude and orbit control, which are not available for nano- and micro-spacecraft missions because of the strict power consumption, space, and weight constraints. This paper considers orbit and attitude control methods that use a superconducting coil, which interacts with on-orbit space plasmas and creates a propulsion force. Because these spacecraft cannot use an active cooling system for the superconducting coil because of their mass and power consumption constraints, this paper proposes the utilization of a passive radiative cooling system, in which the superconducting coil is thermally connected to the 3 K cosmic background radiation of deep space, insulated from the heat generation using magnetic holders, and shielded from the sun. With this proposed cooling system, the HTS coil is cooled to 60 K in interplanetary orbits. Because the system does not use refrigerators for its cooling system, the spacecraft can achieve an HTS coil with low power consumption, small mass, and low cost.

  2. The instrument pointing system: Precision attitude control in space

    NASA Astrophysics Data System (ADS)

    Hartmann, Ralf; Woelker, Albrecht

    1990-06-01

    The Spacelab Instrument Pointing System (IPS) is a three axes gimbal system providing pointing and stabilization in the arcsec range to a variety of space experiments with a mass of up to 7000 kg. The IPS demonstrated its control performance during the maiden flight in July 1985, the Spacelab 2 mission on board the Space Shuttle Challenger. The most challenging problem for attitude control in space is the disturbance compensation in the presence of structural flexibilities. Kalman filtering based on optical sensor and gyro measurements as well as flexible mode attenuation and feedforward control were indispensable to achieve high precision. To further enhance the IPS pointing performance and versatility, a new, more autonomous computer and sensor concept has been conceived providing the capacity for a higher degree of automation as well as improved pointing and closed loop tracking control. The autonomy and control capacity of the enhanced IPS establish the basis to accommodate the IPS as long-term available tracking and pointing platform on the International Space Station Freedom (ISF).

  3. Integrated Power/Attitude Control System (IPACS) technology experiment

    NASA Technical Reports Server (NTRS)

    Keckler, C. R.

    1984-01-01

    An experiment is proposed that will perform the tasks associated with the control and energy storage/power generation functions attendant to space operations. It was shown in past studies that the integration of these functions into one system can result in significant weight, volume, and cost savings. The Integrated Power/Attitude Control System (IPACS) concept is discussed. During orbit day, power is derived from the solar cell arrays and, after appropriate conditioning, is used to operate the spacecraft subsystems, including the control system. In conventional approaches, a part of the collected solar energy is stored in a bank of batteries to permit operation of the vehicle's systems during orbit night. In the IPACS concept, the solar energy is stored in the spinning flywheels of the control system in the form of kinetic energy. During orbit night, the wheels are despun and, through the use of a wheel-shaft mounted generator, power is generated for the onboard subsystems. Operating these flywheels over a 50-percent speed variation permits the extraction of 75 percent of the stored energy while at the same time preserving 50 percent of the momentum capacity for control of the vehicle. Batteries can therefore be eliminated and significant weight and volume savings realized.

  4. Variability in automatic activation as an unobtrusive measure of racial attitudes: a bona fide pipeline?

    PubMed

    Fazio, R H; Jackson, J R; Dunton, B C; Williams, C J

    1995-12-01

    The research examines an unobtrusive measure of racial attitudes based on the evaluations that are automatically activated from memory on the presentation of Black versus White faces. Study 1, which concerned the technique's validity, obtained different attitude estimates for Black and White participants and also revealed that the variability among White participants was predictive of other race-related judgments and behavior. Study 2 concerned the lack of correspondence between the unobtrusive estimates and Modern Racism Scale (MRS) scores. The reactivity of the MRS was demonstrated in Study 3. Study 4 observed an interaction between the unobtrusive estimates and an individual difference in motivation to control prejudiced reactions when predicting MRS scores. The theoretical implications of the findings for consideration of automatic and controlled components of racial prejudice are discussed, as is the status of the MRS. PMID:8531054

  5. Anti-sway control of tethered satellite systems using attitude control of the main satellite

    NASA Astrophysics Data System (ADS)

    Yousefian, Peyman; Salarieh, Hassan

    2015-06-01

    In this study a new method is introduced to suppress libration of a tethered satellite system (TSS). It benefits from coupling between satellites and tether libration dynamics. The control concept uses the main satellite attitude maneuvers to suppress librational motion of the tether, and the main satellite's actuators for attitude control are used as the only actuation in the system. The study considers planar motion of a two body TSS system in a circular orbit and it is assumed that the tether's motion will not change it. Governing dynamic equations of motion are derived using the extended Lagrange method. Controllability of the system around the equilibrium state is studied and a linear LQG controller is designed to regulate libration of the system. Tether tension and satellite attitude are assumed as only measurable outputs of the system. The Extended Kalman Filter (EKF) is used to estimate states of the system to be used as feedback to the controller. The designed controller and observer are implemented to the nonlinear plant and simulations demonstrate that the controller lead to reduction of the tether libration propoerly. By the way, because the controller is linear, it is applicable only at low amplitudes in the vicinity of equilibrium point. To reach global stability, a nonlinear controller is demanded.

  6. A sun gate for Galileo spacecraft attitude control

    NASA Technical Reports Server (NTRS)

    Mobasser, Sohrab; Weisenberg, David

    1990-01-01

    The combination of a sun sensor called a sun gate (SG) and a digital programmable signal processor on the Galileo spacecraft attitude and articulation control subsystem (AACS) will orient the rotation axis of the spacecraft toward the sun to satisfy a new requirement imposed by the new spacecraft trajectory. The combination will continuously monitor the pointing direction of the rotation axis, and any off-sun excursions of more than a preset threshold will be detected, triggering appropriate actions by the flight software to prevent off-sun cone angles of more than 14 deg. The design of the SG is described in detail, its principle of operation is given, and the flight software processing of the SG output is discussed.

  7. Fault Detection and Correction for the Solar Dynamics Observatory Attitude Control System

    NASA Technical Reports Server (NTRS)

    Starin, Scott R.; Vess, Melissa F.; Kenney, Thomas M.; Maldonado, Manuel D.; Morgenstern, Wendy M.

    2007-01-01

    The Solar Dynamics Observatory is an Explorer-class mission that will launch in early 2009. The spacecraft will operate in a geosynchronous orbit, sending data 24 hours a day to a devoted ground station in White Sands, New Mexico. It will carry a suite of instruments designed to observe the Sun in multiple wavelengths at unprecedented resolution. The Atmospheric Imaging Assembly includes four telescopes with focal plane CCDs that can image the full solar disk in four different visible wavelengths. The Extreme-ultraviolet Variability Experiment will collect time-correlated data on the activity of the Sun's corona. The Helioseismic and Magnetic Imager will enable study of pressure waves moving through the body of the Sun. The attitude control system on Solar Dynamics Observatory is responsible for four main phases of activity. The physical safety of the spacecraft after separation must be guaranteed. Fine attitude determination and control must be sufficient for instrument calibration maneuvers. The mission science mode requires 2-arcsecond control according to error signals provided by guide telescopes on the Atmospheric Imaging Assembly, one of the three instruments to be carried. Lastly, accurate execution of linear and angular momentum changes to the spacecraft must be provided for momentum management and orbit maintenance. In thsp aper, single-fault tolerant fault detection and correction of the Solar Dynamics Observatory attitude control system is described. The attitude control hardware suite for the mission is catalogued, with special attention to redundancy at the hardware level. Four reaction wheels are used where any three are satisfactory. Four pairs of redundant thrusters are employed for orbit change maneuvers and momentum management. Three two-axis gyroscopes provide full redundancy for rate sensing. A digital Sun sensor and two autonomous star trackers provide two-out-of-three redundancy for fine attitude determination. The use of software to maximize

  8. AE-C attitude determination and control prelaunch analysis and operations plan

    NASA Technical Reports Server (NTRS)

    Werking, R. D.; Headrick, R. D.; Manders, C. F.; Woolley, R. D.

    1973-01-01

    A description of attitude control support being supplied by the Mission and Data Operations Directorate is presented. Included are descriptions of the computer programs being used to support the missions for attitude determination, prediction, and control. In addition, descriptions of the operating procedures which will be used to accomplish mission objectives are provided.

  9. The Effects of Perceived Locus of Control and Social Influence Techniques on Attitude Change.

    ERIC Educational Resources Information Center

    Sherman, Steven J.

    This study deals with the interaction between social influence technique and locus of control, internal or external to oneself, on attitude change. In a persuasive communication situation, where effectiveness depends on the receiver feelings controlled and subject to influence from outside sources, externals ought to show more attitude change than…

  10. Satellite Dynamic Damping via Active Force Control Augmentation

    NASA Astrophysics Data System (ADS)

    Varatharajoo, Renuganth

    2012-07-01

    An approach that incorporates the Active Force Control (AFC) technique into a conventional Proportional-Derivative (PD) controller is proposed for a satellite active dynamic damping towards a full attitude control. The AFC method has been established to facilitate a robust motion control of dynamical systems in the presence of disturbances, parametric uncertainties and changes that are commonly prevalent in the real-world environment. The usefulness of the method can be extended by introducing intelligent mechanisms to approximate the mass or inertia matrix of the dynamic system to trigger the compensation effect of the controller. AFC is a technique that relies on the appropriate estimation of the inertial or mass parameters of the dynamic system and the measurements of the acceleration and force signals induced by the system if practical implementation is ever considered. In AFC, it is shown that the system subjected to a number of disturbances remains stable and robust via the compensating action of the control strategy. We demonstrate that it is possible to design a spacecraft attitude feedback controller that will ensure the system dynamics set point remains unchanged even in the presence of the disturbances provided that the actual disturbances can be modeled effectively. In order to further facilitate this analysis, a combined energy and attitude control system (CEACS) is proposed as a model satellite attitude control actuator. All the governing equations are established and the proposed satellite attitude control architecture is made amenable to numerical treatments. The results show that the PD-AFC attitude damping performances are superiorly better than that of the solely PD type. It is also shown that the tunings of the AFC system gains are crucial to ensure a better attitude damping performance and this process is mandatory for AFC systems. Finally, the results demonstrate an important satellite dynamic damping enhancement capability using the AFC

  11. The Role of Episodic Memory in Controlled Evaluative Judgments about Attitudes: An Event-Related Potential Study

    ERIC Educational Resources Information Center

    Johnson, Ray, Jr.; Simon, Elizabeth J.; Henkell, Heather; Zhu, John

    2011-01-01

    Event-related potentials (ERPs) are unique in their ability to provide information about the timing of activity in the neural networks that perform complex cognitive processes. Given the dearth of extant data from normal controls on the question of whether attitude representations are stored in episodic or semantic memory, the goal here was to…

  12. The attitude control of fixed-wing MAVS in turbulent environments

    NASA Astrophysics Data System (ADS)

    Mohamed, Abdulghani; Massey, Kevin; Watkins, Simon; Clothier, Reece

    2014-04-01

    The small scale and portability of fixed-wing Micro Aerial Vehicles lend them to many unique applications, however their utility is often limited by ineffective attitude control in turbulent environments. The performance of attitude control systems themselves are affected by a variety of factors. Assessment of this system’s performance needs to be viewed in relation to the MAVs’ unique constraints. Certain aspects and limitations of MAV attitude control related issues are addressed in the literature, but to fully address the degradation of utility, the entire system must be examined. These issues can only be fully addressed when considering them concurrently. There is no framework for defining the attitude control problem explicitly for MAVs. This paper attempts to (1) Define the MAV attitude control problem with respect to the unique constraints imposed by this class of Unmanned Aircraft; (2) Review current design trends of MAVs with respect to vulnerability to atmospheric turbulence.

  13. Orion Launch Abort Vehicle Attitude Control Motor Testing

    NASA Technical Reports Server (NTRS)

    Murphy, Kelly J.; Brauckmann, Gregory J.; Paschal, Keith B.; Chan, David T.; Walker, Eric L.; Foley, Robert; Mayfield, David; Cross, Jared

    2011-01-01

    Current Orion Launch Abort Vehicle (LAV) configurations use an eight-jet, solid-fueled Attitude Control Motor (ACM) to provide required vehicle control for all proposed abort trajectories. Due to the forward position of the ACM on the LAV, it is necessary to assess the effects of jet-interactions (JI) between the various ACM nozzle plumes and the external flow along the outside surfaces of the vehicle. These JI-induced changes in flight control characteristics must be accounted for in developing ACM operations and LAV flight characteristics. A test program to generate jet interaction aerodynamic increment data for multiple LAV configurations was conducted in the NASA Ames and NASA Langley Unitary Plan Wind Tunnels from August 2007 through December 2009. Using cold air as the simulant gas, powered subscale models were used to generate interaction data at subsonic, transonic, and supersonic test conditions. This paper presents an overview of the complete ACM JI experimental test program for Orion LAV configurations, highlighting ACM system modeling, nozzle scaling assumptions, experimental test techniques, and data reduction methodologies. Lessons learned are discussed, and sample jet interaction data are shown. These data, in conjunction with computational predictions, were used to create the ACM JI increments for all relevant flight databases.

  14. Multiple degree-of-freedom tracking for attitude control of an experimental system on tether-stabilized platform

    NASA Astrophysics Data System (ADS)

    Angrilli, Francesco; Baglioni, Pietro; Bianchini, Gianandrea; da Forno, Roberto; Fanti, Giulio; Mozzi, Massimo

    1991-08-01

    A study has been conducted about attitude control and pointing of an optical instrument (a Schmidt-type telescope) connected to the space station via a tether 2 to 10 km long, mounted on a platform. The tether plays a multifunctional role, including elastic suspension and data and power transmission. It will insulate the platform from dynamic noise, light, and other pollution from the space station. Furthermore, stabilization and active attitude control will be achieved by moving the attachment point of the tether with respect to the platform itself. A bi- dimensional model of this system has been realized and tested in the laboratory. The measurement and control concept that works on the basis of a computer vision system is discussed. The system is used to stabilize a platform floating on an air table attached to a fixed point through a tether, via a closed loop position control circuit. This is achieved through a CCD camera (768 X 512 pixels), an image processing software, and a dc motor with encoder which controls the attitude of the platform moving its attachment point. The tracking function is realized via a multiple windows technique using an algorithm based on the linearized equations of motion of the platform. The performance of the overall system is presented. An analysis of system characteristics with respect to a real application is carried out. In particular, the possibility of achieving stabilization and active attitude control of such a system by moving the attach point of the tether has been investigated.

  15. Spacecraft methods and structures with enhanced attitude control that facilitates gyroscope substitutions

    NASA Technical Reports Server (NTRS)

    Li, Rongsheng (Inventor); Kurland, Jeffrey A. (Inventor); Dawson, Alec M. (Inventor); Wu, Yeong-Wei A. (Inventor); Uetrecht, David S. (Inventor)

    2004-01-01

    Methods and structures are provided that enhance attitude control during gyroscope substitutions by insuring that a spacecraft's attitude control system does not drive its absolute-attitude sensors out of their capture ranges. In a method embodiment, an operational process-noise covariance Q of a Kalman filter is temporarily replaced with a substantially greater interim process-noise covariance Q. This replacement increases the weight given to the most recent attitude measurements and hastens the reduction of attitude errors and gyroscope bias errors. The error effect of the substituted gyroscopes is reduced and the absolute-attitude sensors are not driven out of their capture range. In another method embodiment, this replacement is preceded by the temporary replacement of an operational measurement-noise variance R with a substantially larger interim measurement-noise variance R to reduce transients during the gyroscope substitutions.

  16. Finite-time output feedback attitude coordination control for formation flying spacecraft without unwinding

    NASA Astrophysics Data System (ADS)

    Guo, Yong; Song, Shen-Min; Li, Xue-Hui

    2016-05-01

    In this paper, two finite-time attitude coordinated controllers for formation flying spacecraft are investigated based on rotation matrix. Because rotation matrix can represent the set of attitudes both globally and uniquely, the two controllers can deal with unwinding that can result in extra fuel consumption. To address the lack of angular velocity measurement, the second attitude coordinated controller is given by using a novel filter. Through homogeneous method and Lyapunov theories, it is shown that the proposed controllers can achieve the finite-time stability. Numerical simulations also demonstrate that the proposed control schemes are effective.

  17. The Effect of Physical Activity on Science Competence and Attitude towards Science Content

    NASA Astrophysics Data System (ADS)

    Klinkenborg, Ann Maria

    This study examines the effect of physical activity on science instruction. To combat the implications of physical inactivity, schools need to be willing to consider all possible opportunities for students to engage in moderate-to-vigorous physical activity (MVPA). Integrating physical activity with traditional classroom content is one instructional method to consider. Researchers have typically focused on integration with English/language arts (ELA) and mathematics. The purpose of this study was to determine the effect of physical activity on science competence and attitude towards science. Fifty-three third grade children participated in this investigation; one group received science instruction with a physical activity intervention while the other group received traditional science instruction. Participants in both groups completed a modified version of What I Really Think of Science attitude scale (Pell & Jarvis, 2001) and a physical science test of competence prior to and following the intervention. Children were videotaped during science instruction and their movement coded to measure the proportion of time spent in MVPA. Results revealed that children in the intervention group demonstrated greater MVPA during the instructional period. A moderate to large effect size (partial eta squared = .091) was seen in the intervention group science competence post-test indicating greater understanding of force, motion, work, and simple machines concepts than that of the control group who were less physically active. There was no statistically significant attitude difference between the intervention and control groups post-test, (F(1,51) = .375, p = .543). These results provide evidence that integration can effectively present physical science content and have a positive impact on the number of minutes of health-enhancing physical activity in a school day.

  18. Development of the Galileo Attitude and Articulation Control Subsystem flight software

    NASA Technical Reports Server (NTRS)

    Krasner, S. M.

    1982-01-01

    The ongoing design and implementation of the Project Galileo Attitude and Articulation Control Subsystem (AACS) flight software is outlined, as well as the more important problems that were experienced in the development of this software. The important characteristics of the Galileo spacecraft are described, as are the major requirements driving the software design. The important features of the design are stated and discussed, and a modes and tasks transition diagram is presented. The AACS software implementation is covered, and the algorithms active in each task are shown. Finally, some of the design and management techniques used in the course of the software development are discussed.

  19. The Software Design for the Wide-Field Infrared Explorer Attitude Control System

    NASA Technical Reports Server (NTRS)

    Anderson, Mark O.; Barnes, Kenneth C.; Melhorn, Charles M.; Phillips, Tom

    1998-01-01

    The Wide-Field Infrared Explorer (WIRE), currently scheduled for launch in September 1998, is the fifth of five spacecraft in the NASA/Goddard Small Explorer (SMEX) series. This paper presents the design of WIRE's Attitude Control System flight software (ACS FSW). WIRE is a momentum-biased, three-axis stabilized stellar pointer which provides high-accuracy pointing and autonomous acquisition for eight to ten stellar targets per orbit. WIRE's short mission life and limited cryogen supply motivate requirements for Sun and Earth avoidance constraints which are designed to prevent catastrophic instrument damage and to minimize the heat load on the cryostat. The FSW implements autonomous fault detection and handling (FDH) to enforce these instrument constraints and to perform several other checks which insure the safety of the spacecraft. The ACS FSW implements modules for sensor data processing, attitude determination, attitude control, guide star acquisition, actuator command generation, command/telemetry processing, and FDH. These software components are integrated with a hierarchical control mode managing module that dictates which software components are currently active. The lowest mode in the hierarchy is the 'safest' one, in the sense that it utilizes a minimal complement of sensors and actuators to keep the spacecraft in a stable configuration (power and pointing constraints are maintained). As higher modes in the hierarchy are achieved, the various software functions are activated by the mode manager, and an increasing level of attitude control accuracy is provided. If FDH detects a constraint violation or other anomaly, it triggers a safing transition to a lower control mode. The WIRE ACS FSW satisfies all target acquisition and pointing accuracy requirements, enforces all pointing constraints, provides the ground with a simple means for reconfiguring the system via table load, and meets all the demands of its real-time embedded environment (16 MHz Intel

  20. Single Axis Attitude Control and DC Bus Regulation with Two Flywheels

    NASA Technical Reports Server (NTRS)

    Kascak, Peter E.; Jansen, Ralph H.; Kenny, Barbara; Dever, Timothy P.

    2002-01-01

    A computer simulation of a flywheel energy storage single axis attitude control system is described. The simulation models hardware which will be experimentally tested in the future. This hardware consists of two counter rotating flywheels mounted to an air table. The air table allows one axis of rotational motion. An inertia DC bus coordinator is set forth that allows the two control problems, bus regulation and attitude control, to be separated. Simulation results are presented with a previously derived flywheel bus regulator and a simple PID attitude controller.

  1. Hands-on Activities versus Worksheets in Reinforcing Physical Science Principles: Effects on Student Achievement and Attitude.

    ERIC Educational Resources Information Center

    Johnson, Donald M.; Wardlow, George W.; Franklin, Timothy D.

    1997-01-01

    A group of 132 agricultural science students were divided into an experimental group who completed hands-on activities on Ohm's Law and incline plane and a control group who completed worksheets. There were no significant differences in immediate or follow-up measures of achievement. Hands-on students had significantly more positive attitudes. (SK)

  2. Effects of Requiring Physical Fitness in a Lecture-Based College Course: Students' Attitudes toward Physical Activity

    ERIC Educational Resources Information Center

    Esslinger, Keri A.; Grimes, Amanda R.; Pyle, Elizabeth

    2016-01-01

    In this study, we investigated students' attitudes toward physical activity (PA) when including a required PA component in a university-required personal wellness class. The study included (a) an experimental group of students enrolled in a personal wellness course in which there was a required PA requirement and (b) a control group of students…

  3. Integrated Orbit and Attitude Control for a Nanosatellite with Power Constraints

    NASA Technical Reports Server (NTRS)

    Naasz, Bo; Hall, Christopher; Berry, Matthew; Hy-Young, Kim

    2003-01-01

    Small satellites tend to be power-limited, so that actuators used to control the orbit and attitude must compete with each other as well as with other subsystems for limited electrical power. The Virginia Tech nanosatellite project, HokieSat, must use its limited power resources to operate pulsed-plasma thrusters for orbit control and magnetic torque coils for attitude control, while also providing power to a GPS receiver, a crosslink transceiver, and other subsystems. The orbit and attitude control strategies were developed independently. The attitude control system is based on an application of Linear Quadratic Regulator (LQR) to an averaged system of equations, whereas the orbit control is based on orbit element feedback. In this paper we describe the strategy for integrating these two control systems and present simulation results to verify the strategy.

  4. Decentralized sliding-mode control for spacecraft attitude synchronization under actuator failures

    NASA Astrophysics Data System (ADS)

    Wu, Baolin; Wang, Danwei; Poh, Eng Kee

    2014-12-01

    This paper examines attitude synchronization and tracking problems with model uncertainties, external disturbances, actuator failures and control torque saturation. Two decentralized sliding mode control laws are proposed and analyzed based on algebraic graph theory. Using Barbalat's Lemma, it is shown that the control laws guarantee each spacecraft approaches the desired time-varying attitude and angular velocity while maintaining attitude synchronization among the other spacecraft in the formation. The first controller is designed in the presence of model uncertainties, external disturbances, and actuator failures. The results are extended to the case with control input saturation in the second controller. Both control laws do not require online identification of failures. Numerical simulations are presented to show the effectiveness of the proposed attitude synchronization and tracking approaches.

  5. X-33 Attitude Control System Design for Ascent, Transition, and Entry Flight Regimes

    NASA Technical Reports Server (NTRS)

    Hall, Charles E.; Gallaher, Michael W.; Hendrix, Neal D.

    1998-01-01

    The Vehicle Control Systems Team at Marshall Space Flight Center, Systems Dynamics Laboratory, Guidance and Control Systems Division is designing under a cooperative agreement with Lockheed Martin Skunkworks, the Ascent, Transition, and Entry flight attitude control system for the X-33 experimental vehicle. Ascent flight control begins at liftoff and ends at linear aerospike main engine cutoff (NECO) while Transition and Entry flight control begins at MECO and concludes at the terminal area energy management (TAEM) interface. TAEM occurs at approximately Mach 3.0. This task includes not only the design of the vehicle attitude control systems but also the development of requirements for attitude control system components and subsystems. The X-33 attitude control system design is challenged by a short design cycle, the design environment (Mach 0 to about Mach 15), and the X-33 incremental test philosophy. The X-33 design-to-launch cycle of less than 3 years requires a concurrent design approach while the test philosophy requires design adaptation to vehicle variations that are a function of Mach number and mission profile. The flight attitude control system must deal with the mixing of aerosurfaces, reaction control thrusters, and linear aerospike engine control effectors and handle parasitic effects such as vehicle flexibility and propellant sloshing from the uniquely shaped propellant tanks. The attitude control system design is, as usual, closely linked to many other subsystems and must deal with constraints and requirements from these subsystems.

  6. Propellantless Attitude Control of Solar Sail Technology Utilizing Reflective Control Devices

    NASA Technical Reports Server (NTRS)

    Munday, Jeremy

    2016-01-01

    Solar sails offer an opportunity for a CubeSatscale, propellant-free spacecraft technology that enables long-term and long-distance missions not possible with traditional methods. Solar sails operate using the transfer of linear momentum from photons of sunlight reflected from the surface of the sail. To propel the spacecraft, no mechanically moving parts, thrusters, or propellant are needed. However, attitude control, or orientation, is still performed using traditional methods involving reaction wheels and propellant ejection, which severely limit mission lifetime. For example, the current state of the art solutions employed by upcoming missions couple solar sails with a state of the art propellant ejection gas system. Here, the use of the gas thruster has limited the lifetime of the mission. To solve the limited mission lifetime problem, the Propellantless Attitude Control of Solar Sail Technology Utilizing Reflective Control Devices project team is working on propellantless attitude control using thin layers of material, an optical film, electrically switchable from transparent to reflective. The technology is based on a polymer-dispersed liquid crystal (PDLC), which allows this switch upon application of a voltage. This technology removes the need for propellant, which reduces weight and cost while improving performance and lifetime.

  7. Maternal and Paternal Psychological Control as Moderators of the Link between Peer Attitudes and Adolescents' Risky Sexual Behavior

    ERIC Educational Resources Information Center

    Oudekerk, Barbara A.; Allen, Joseph P.; Hafen, Christopher A.; Hessel, Elenda T.; Szwedo, David E.; Spilker, Ann

    2014-01-01

    Maternal and paternal psychological control, peer attitudes, and the interaction of psychological control and peer attitudes at age 13 were examined as predictors of risky sexual behavior before age 16 in a community sample of 181 youth followed from age 13 to 16. Maternal psychological control moderated the link between peer attitudes and sexual…

  8. Flight Performance of Skylab Attitude and Pointing Control System

    NASA Technical Reports Server (NTRS)

    Chubb, W. B.; Kennel, H. F.; Rupp, C. C.; Seltzer, S. M.

    1975-01-01

    In 1967 a paper at the AIAA Guidance, Control and Flight Dynamics Conference in Huntsville, Ala. presented for the first time the prot)osed SKYLAB Attitude and Pointing Control System (APCS) The system requirements, Apollo Telescope Mount (ATM) configuration, control philosophy, and operational modes were presented and the APCS described. The Initial mission and system design requirements changed during the period of time before the SKYLAB was launched. This paper will review the Initial and final APCS requirements and goals and their relationship. The actual flight mission (and Its alterations during the flight) and known achieved APCS performance will then be presented. SKYLAB was a tremendous success in furthering man's scientific knowledge; but perhaps SKYLAB will be remembered more for the anomalies and the efforts undertaken to solve them. On May 14, 1973, the unmanned SKYLAB Orbital Workshop (OWS) was launched from Cape Kennedy. Serious hardware failures began to occur during ascent through the atmosphere and their spectre continued to haunt both the astronauts and their ground based support team. Nor were these the only surprises affecting the design and operation of the APCS. Mission requirements for pointing to various stellar targets and to nadir for earth resources experiments were added after the hardware was designed. The chance appearance of comet Kohoutek during the SKYLAB operational life-time caused NASA to add comet observation to the mission requirements and to adjust the time when the third crew would man the SKYLAB. The development of new procedures and software for the opportunity to observe this visitor to our solar system is described.

  9. Child physical activity and parent-child attitude congruence of athletic competence and activity type

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our purpose was to evaluate parental influence on child physical activity (PA) through parental beliefs on child competence and importance of specific types of PA. Utilizing Eccles' expectancy-value model of task choice, the study examined parent-child attitude congruence and whether task value bel...

  10. Simultaneous calibrations of Voyager celestial and inertial attitude control systems in flight

    NASA Technical Reports Server (NTRS)

    Jahanshahi, M. H.

    1982-01-01

    A mathematical description of the data reduction technique used to simultaneously calibrate the Voyager celestial and inertial attitude control subsystems is given. It is shown that knowledge of the spacecraft limit cycle motion, as measured by the celestial and the inertial sensors, is adequate to result in the estimates of a selected number of errors which adversely affect the spacecraft attitude knowledge.

  11. Changes in Short-Term Attitudes Toward Physical Activity and Exercise of University Personal Wellness Students

    ERIC Educational Resources Information Center

    Mack, Mick G.; Shaddox, Lea Ann

    2004-01-01

    This study examined the attitudes toward physical activity and exercise of university students enrolled in Personal Wellness classes. 1,625 undergraduate students completed the Attitudes Toward Exercise and Physical Activity (ATEPA) inventory on the first and last day of the class. Paired-samples t test results comparing the mean pretest ATEPA…

  12. Parental Attitudes and Young People's Online Sexual Activities

    ERIC Educational Resources Information Center

    Sorbring, Emma; Hallberg, Jonas; Bohlin, Margareta; Skoog, Therése

    2015-01-01

    Parental attitudes towards young people's sexuality in traditional (i.e. non-online media) settings have been associated with young people's sexual activities. In this study, we explored the association between key parent and youth characteristics and parental attitudes towards young people's online sexual activities. We also…

  13. Attitude control/momentum management of the Space Station Freedom for large angle torque-equilibrium-attitude configurations

    NASA Technical Reports Server (NTRS)

    Parlos, Alexander G.; Sunkel, John W.

    1990-01-01

    An attitude-control and momentum-management (ACMM) system for the Space Station in a large-angle torque-equilibrium-attitude (TEA) configuration is developed analytically and demonstrated by means of numerical simulations. The equations of motion for a rigid-body Space Station model are outlined; linearized equations for an arbitrary TEA (resulting from misalignment of control and body axes) are derived; the general requirements for an ACMM are summarized; and a pole-placement linear-quadratic regulator solution based on scheduled gains is proposed. Results are presented in graphs for (1) simulations based on configuration MB3 (showing the importance of accounting for the cross-inertia terms in the TEA estimate) and (2) simulations of a stepwise change from configuration MB3 to the 'assembly complete' stage over 130 orbits (indicating that the present ACCM scheme maintains sufficient control over slowly varying Space Station dynamics).

  14. Nonlinear Attitude Control of Planar Structures in Space Using Only Internal Controls

    NASA Technical Reports Server (NTRS)

    Reyhanoglu, Mahmut; Mcclamroch, N. Harris

    1993-01-01

    An attitude control strategy for maneuvers of an interconnection of planar bodies in space is developed. It is assumed that there are no exogeneous torques and that torques generated by joint motors are used as means of control so that the total angular momentum of the multibody system is a constant, assumed to be zero. The control strategy utilizes the nonintegrability of the expression for the angular momentum. Large angle maneuvers can be designed to achieve an arbitrary reorientation of the multibody system with respect to an inertial frame. The theoretical background for carrying out the required maneuvers is summarized.

  15. Feedback control and steering laws for spacecraft using Canfield joint attitude manipulators

    NASA Astrophysics Data System (ADS)

    Moyer, Eamonn James

    A novel attitude control system using a reaction wheel mounted on a Canfield joint is introduced. The rotational equations of motion for a rigid body spacecraft equipped with a pair of Canfield joint attitude manipulators are derived. Stable feedback laws are developed for attitude control and momentum management of the spacecraft using Lyapunov theory. Steering laws to find the gimbal rates and accelerations to generate the torque required for a maneuver are derived in both a linear and a nonlinear form. Numerical simulations of representative spacecraft reorientation maneuvers demonstrate the utility of the control and steering laws developed in this research. The singularity problem associated with traditional configurations of single-gimbal control moment gyroscopes is discussed in relation to the attitude control system being presented.

  16. Attitude and vibration control of a large flexible space-based antenna

    NASA Technical Reports Server (NTRS)

    Joshi, S. M.

    1982-01-01

    Control systems synthesis is considered for controlling the rigid body attitude and elastic motion of a large deployable space-based antenna. Two methods for control systems synthesis are considered. The first method utilizes the stability and robustness properties of the controller consisting of torque actuators and collocated attitude and rate sensors. The second method is based on the linear-quadratic-Gaussian control theory. A combination of the two methods, which results in a two level hierarchical control system, is also briefly discussed. The performance of the controllers is analyzed by computing the variances of pointing errors, feed misalignment errors and surface contour errors in the presence of sensor and actuator noise.

  17. Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters

    NASA Technical Reports Server (NTRS)

    Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith

    2015-01-01

    Principles for the design and stability of a spacecraft on-orbit attitude control system employing on-off Reaction Control System (RCS) thrusters is presented. Both the vehicle dynamics and the control system actuators are inherently nonlinear, hence traditional linear control system design approaches are not directly applicable. This paper has three main aspects: It summarizes key RCS control System design principles from the Space Shuttle and Space Station programs, it demonstrates a new approach to develop a linear model of a phase plane control system using describing functions, and applies each of these to the initial development of the NASA's next generation of upper stage vehicles. Topics addressed include thruster hardware specifications, phase plane design and stability, jet selection approaches, filter design metrics, and automaneuver logic.

  18. Reusable Launch Vehicle Attitude Control Using a Time-Varying Sliding Mode Control Technique

    NASA Technical Reports Server (NTRS)

    Shtessel, Yuri B.; Zhu, J. Jim; Daniels, Dan; Jackson, Scott (Technical Monitor)

    2002-01-01

    In this paper we present a time-varying sliding mode control (TVSMC) technique for reusable launch vehicle (RLV) attitude control in ascent and entry flight phases. In ascent flight the guidance commands Euler roll, pitch and yaw angles, and in entry flight it commands the aerodynamic angles of bank, attack and sideslip. The controller employs a body rate inner loop and the attitude outer loop, which are separated in time-scale by the singular perturbation principle. The novelty of the TVSMC is that both the sliding surface and the boundary layer dynamics can be varied in real time using the PD-eigenvalue assignment technique. This salient feature is used to cope with control command saturation and integrator windup in the presence of severe disturbance or control effector failure, which enhances the robustness and fault tolerance of the controller. The TV-SMC ascent and descent designs are currently being tested with high fidelity, 6-DOF dispersion simulations. The test results will be presented in the final version of this paper.

  19. A linear quadratic tracker for Control Moment Gyro based attitude control of the Space Station

    NASA Technical Reports Server (NTRS)

    Kaidy, J. T.

    1986-01-01

    The paper discusses a design for an attitude control system for the Space Station which produces fast response, with minimal overshoot and cross-coupling with the use of Control Moment Gyros (CMG). The rigid body equations of motion are linearized and discretized and a Linear Quadratic Regulator (LQR) design and analysis study is performed. The resulting design is then modified such that integral and differential terms are added to the state equations to enhance response characteristics. Methods for reduction of computation time through channelization are discussed as well as the reduction of initial torque requirements.

  20. Evaluation of Assembly Simulators Used in Closed Loop Attitude Control System Testing

    NASA Technical Reports Server (NTRS)

    Bunn, Jason Christopher

    1997-01-01

    The Cassini Spacecraft's Attitude and Articulation Control Subsystem has been tested extensively at the Jet Propulsion Laboraroty in Pasadena, California. Three of the subsystem's assemblies have been tested using assembly simulators in place of actural hardware.

  1. Attitude Control System for Low-Speed CubeSat Centrifuge to Simulate Asteroid Surface Conditions

    NASA Astrophysics Data System (ADS)

    Saumil, S.; Cannady, A.; Alizadeh, I.; Thangavelautham, J.; Asphaug, E.

    2015-01-01

    AOSat is a 3U CubeSat based centrifuge that will be launched into low Earth orbit in the 2015-2016 timeframe. This unique platform poses some fundamental challenges and opportunities in attitude control system development.

  2. Flight Technology Improvement. [spaceborne optical radiometric instruments, attitude control, and electromechanical and power subsystems

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Shortcomings in spaceborne instrumentation technology are analyzed and recommendations are given for corrections and technology development. The technologies discussed are optical radiometric instruments and calibration, attitude control and determination, and electromechanical and power subsystems.

  3. Interior and exterior ballistics coupled optimization with constraints of attitude control and mechanical-thermal conditions

    NASA Astrophysics Data System (ADS)

    Liang, Xin-xin; Zhang, Nai-min; Zhang, Yan

    2016-07-01

    For solid launch vehicle performance promotion, a modeling method of interior and exterior ballistics associated optimization with constraints of attitude control and mechanical-thermal condition is proposed. Firstly, the interior and external ballistic models of the solid launch vehicle are established, and the attitude control model of the high wind area and the stage of the separation is presented, and the load calculation model of the drag reduction device is presented, and thermal condition calculation model of flight is presented. Secondly, the optimization model is established to optimize the range, which has internal and external ballistic design parameters as variables selected by sensitivity analysis, and has attitude control and mechanical-thermal conditions as constraints. Finally, the method is applied to the optimal design of a three stage solid launch vehicle simulation with differential evolution algorithm. Simulation results are shown that range capability is improved by 10.8%, and both attitude control and mechanical-thermal conditions are satisfied.

  4. The results of flight tests of an attitude control system for the Chibis-M microsatellite

    NASA Astrophysics Data System (ADS)

    Ivanov, D. S.; Ivlev, N. A.; Karpenko, S. O.; Ovchinnikov, M. Yu.; Roldugin, D. S.; Tkachev, S. S.

    2014-05-01

    The attitude control system of the Chibis-M microsatellite is described. Results of flight experiments on damping the initial angular velocity (made using magnetorquers) are considered, as well as stabilization in the orbital referece frame, and orientation of solar arrays toward the Sun using reaction wheels. The operation of algorithms of satellite attitude determination on sunlit and shadow segments of the orbit is also under study. The general logic of operation of the attitude control system in automatic mode is presented and discussed.

  5. A preliminary 6 DOF attitude and translation control system design for Starprobe

    NASA Technical Reports Server (NTRS)

    Mak, P.; Mettler, E.; Vijayarahgavan, A.

    1981-01-01

    The extreme thermal environment near perihelion and the high-accuracy gravitational science experiments impose unique design requirements on various subsystems of Starprobe. This paper examines some of these requirements and their impact on the preliminary design of a six-degree-of-freedom attitude and translational control system. Attention is given to design considerations, the baseline attitude/translational control system, system modeling, and simulation studies.

  6. Elementary School Students' Self-Determination in Physical Education and Attitudes toward Physical Activity

    ERIC Educational Resources Information Center

    Chen, Weiyun; Hypnar, Andrew J.

    2015-01-01

    Motivations for and positive attitudes toward physical activity (PA) developed during childhood are likely to be carried over to adulthood. The purpose of this study was to examine the relationship between three psychological needs satisfaction, motivational regulations in physical education (PE), and attitudes toward participation in leisure-time…

  7. Relationships between Personal Biography and Changes in Preservice Classroom Teachers' Physical Activity Promotion Competence and Attitudes

    ERIC Educational Resources Information Center

    Webster, Collin A.

    2011-01-01

    Personal biography influences preservice classroom teachers' (PCT) perceptions and attitudes related to school-based physical activity promotion (SPAP). Using an uncontrolled prepost design, this study investigated associations between biographical variables and changes in PCTs' SPAP attitudes and perceived competence while enrolled in a 16-week…

  8. Gender Differences on Attitudes, Computer Use and Physical Activity among Greek University Students

    ERIC Educational Resources Information Center

    Bebetsos, Evangelos; Antoniou, Panagiotis

    2009-01-01

    The aim of this study was to discover any possible relation(s) between the subject of computer, the involvement in physical activity examine and the attitudes of Greek Physical Education students, divided by gender. The sample consisted of 165 freshmen students, 93 males and 72 females. They completed: a) the "Computer Attitude Scale"…

  9. Development of Positive Racial Attitudes, Knowledges, and Activities in Pre-Service Social Studies Teachers.

    ERIC Educational Resources Information Center

    Swick, Kevin J.; Lamb, Morris L.

    Information on aspects of social studies teachers' racial attitudes, knowledges, and skill in implementing relevant ethnic-racial activities in the classroom are presented. Major research studies that have examined teacher attitudes toward black and other minority group children are discussed along with information on programs that have attempted…

  10. Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters

    NASA Technical Reports Server (NTRS)

    Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith

    2016-01-01

    Basic principles for the design and stability of a spacecraft on-orbit attitude control system employing on-off Reaction Control System (RCS) thrusters are presented. Both vehicle dynamics and the control system actuators are inherently nonlinear, hence traditional linear control system design approaches are not directly applicable. This paper has two main aspects: It summarizes key RCS design principles from earlier NASA vehicles, notably the Space Shuttle and Space Station programs, and introduces advances in the linear modelling and analyses of a phase plane control system derived in the initial development of the NASA's next upper stage vehicle, the Exploration Upper Stage (EUS). Topics include thruster hardware specifications, phase plane design and stability, jet selection approaches, filter design metrics, and RCS rotational maneuver logic.

  11. Sliding mode attitude control with L 2-gain performance and vibration reduction of flexible spacecraft with actuator dynamics

    NASA Astrophysics Data System (ADS)

    Hu, Qinglei

    2010-09-01

    This paper presents a dual-stage control system design method for the rotational maneuver control and vibration stabilization of a flexible spacecraft. In this design approach, the sub-systems of attitude control and vibration suppression are designed separately using the low order model. Based on the sliding mode control (SMC) theory, a discontinuous attitude control law in the form of the input voltage of the reaction wheel is derived to control the orientation of the spacecraft, incorporating the L 2-gain performance criterion constraint. The resulting closed-loop system is proven to be uniformly ultimately bounded stability and the effect of the external disturbance on both attitude quaternion and angular velocity can be attenuated to the prescribed level as well. In addition, an adaptive version of the control law is designed for adapting the unknown upper bounds of the lumped disturbance such that the limitation of knowing the bound of the disturbance in advance is released. For actively suppressing the induced vibration, strain rate feedback control method is also investigated by using piezoelectric materials as additional sensors and actuators bonded on the surface of the flexible appendages. Numerical simulations are performed to show that rotational maneuver and vibration suppression are accomplished in spite of the presence of disturbance and uncertainty.

  12. Overview of the Miniature Sensor Technology Integration (MSTI) spacecraft attitude control system

    NASA Technical Reports Server (NTRS)

    Mcewen, Rob

    1994-01-01

    Msti2 is a small, 164 kg (362 lb), 3-axis stabilized, low-Earth-orbiting satellite whose mission is missile booster tracking. The spacecraft is actuated by 3 reaction wheels and 12 hot gas thrusters. It carries enough fuel for a projected life of 6 months. The sensor complement consists of a Horizon Sensor, a Sun Sensor, low-rate gyros, and a high rate gyro for despin. The total pointing control error allocation is 6 mRad (.34 Deg), and this is while tracking a target on the Earth's surface. This paper describes the Attitude Control System (ACS) algorithms which include the following: attitude acquisition (despin, Sun and Earth acquisition), attitude determination, attitude control, and linear stability analysis.

  13. A Low-Cost Attitude Determination and Control System for the UYS-1 nanosatellite

    NASA Astrophysics Data System (ADS)

    de Oliveira, G. F.; Ishihara, J. Y.; Borges, R. A.; Ferreira, H. C.; Kulabukhov, A. M.; Larin, V. A.; Belikov, V. V.

    This paper considers the development of a Low-Cost Attitude Determination and Control Subsystem (LCADCS) for the first Ukrainian University Nanosatellite, UYS-1. For the attitude determination part, an attitude determination framework is implemented to combine all available data at each time sample using a modified Unscented Kalman Filter, based on the Unscented Quaternion Estimator (USQUE). For the attitude control part, the subsystem should rely only on magnetic actuation with magnetorquers operating in a relay mode. A proposed control strategy is presented. The choice of hardware and algorithms is addressed observing the LCADCS requirements, theoretical and practical considerations, ease of implementation, and time and cost budgets inherent to small-satellite projects. The validity and performance of the general proposed systems are evaluated using computer simulations.

  14. Precision Integrated Power and Attitude Control System (IPACS) in the Presence of Dynamic Uncertainty

    NASA Astrophysics Data System (ADS)

    Kim, D.; MacKunis, W.; Fitz-Coy, N.; Dixon, W. E.

    2011-01-01

    An adaptive robust integrated power and attitude control system (IPACS) is presented for a variable speed control moment gyroscope (VSCMG)-actuated satellite. The developed IPACS method is capable of achieving precision attitude control while simultaneously achieving asymptotic power tracking for a rigid-body satellite in the presence of uncertain friction in the VSCMG gimbals and wheels. In addition, the developed controller compensates for the effects of uncertain, time-varying satellite inertia properties. Some challenges encountered in the control design are that the control input is premultiplied by a nonsquare, time-varying, nonlinear, uncertain matrix and is embedded in a discontinuous nonlinear. Globally uniformly ultimately bounded attitude tracking and asymptotic power tracking results are proven via Lyapunov stability analyses, and simulation results are provided to demonstrate the performance of the controller.

  15. Implicit attitudes towards homosexuality: reliability, validity, and controllability of the IAT.

    PubMed

    Banse, R; Seise, J; Zerbes, N

    2001-01-01

    Two experiments were conducted to investigate the psychometric properties of an Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) that was adapted to measure implicit attitudes towards homosexuality. In a first experiment, the validity of the Homosexuality-IAT was tested using a known group approach. Implicit and explicit attitudes were assessed in heterosexual and homosexual men and women (N = 101). The results provided compelling evidence for the convergent and discriminant validity of the Homosexuality-IAT as a measure of implicit attitudes. No evidence was found for two alternative explanations of IAT effects (familiarity with stimulus material and stereotype knowledge). The internal consistency of IAT scores was satisfactory (alpha s > .80), but retest correlations were lower. In a second experiment (N = 79) it was shown that uninformed participants were able to fake positive explicit but not implicit attitudes. Discrepancies between implicit and explicit attitudes towards homosexuality could be partially accounted for by individual differences in the motivation to control prejudiced behavior, thus providing independent evidence for the validity of the implicit attitude measure. Neither explicit nor implicit attitudes could be changed by persuasive messages. The results of both experiments are interpreted as evidence for a single construct account of implicit and explicit attitudes towards homosexuality. PMID:11392982

  16. Coupled attitude-orbit dynamics and control for an electric sail in a heliocentric transfer mission.

    PubMed

    Huo, Mingying; Zhao, Jun; Xie, Shaobiao; Qi, Naiming

    2015-01-01

    The paper discusses the coupled attitude-orbit dynamics and control of an electric-sail-based spacecraft in a heliocentric transfer mission. The mathematical model characterizing the propulsive thrust is first described as a function of the orbital radius and the sail angle. Since the solar wind dynamic pressure acceleration is induced by the sail attitude, the orbital and attitude dynamics of electric sails are coupled, and are discussed together. Based on the coupled equations, the flight control is investigated, wherein the orbital control is studied in an optimal framework via a hybrid optimization method and the attitude controller is designed based on feedback linearization control. To verify the effectiveness of the proposed control strategy, a transfer problem from Earth to Mars is considered. The numerical results show that the proposed strategy can control the coupled system very well, and a small control torque can control both the attitude and orbit. The study in this paper will contribute to the theory study and application of electric sail. PMID:25950179

  17. Coupled Attitude-Orbit Dynamics and Control for an Electric Sail in a Heliocentric Transfer Mission

    PubMed Central

    Huo, Mingying; Zhao, Jun; Xie, Shaobiao; Qi, Naiming

    2015-01-01

    The paper discusses the coupled attitude-orbit dynamics and control of an electric-sail-based spacecraft in a heliocentric transfer mission. The mathematical model characterizing the propulsive thrust is first described as a function of the orbital radius and the sail angle. Since the solar wind dynamic pressure acceleration is induced by the sail attitude, the orbital and attitude dynamics of electric sails are coupled, and are discussed together. Based on the coupled equations, the flight control is investigated, wherein the orbital control is studied in an optimal framework via a hybrid optimization method and the attitude controller is designed based on feedback linearization control. To verify the effectiveness of the proposed control strategy, a transfer problem from Earth to Mars is considered. The numerical results show that the proposed strategy can control the coupled system very well, and a small control torque can control both the attitude and orbit. The study in this paper will contribute to the theory study and application of electric sail. PMID:25950179

  18. Student Cheating and Attitude: A Function of Classroom Control Technique.

    ERIC Educational Resources Information Center

    Houser, Betsy Bosak

    1982-01-01

    In teachers' classroom utilization of certain means of social influence, coercive power was found to produce the least cheating and the most favorable student attitudes, compared to reward and five other power base strategies utilized. Precautions as to the interpretation and possible application of the findings are discussed. (Author/CM)

  19. Student Compliance and Attitude: A Function of Classroom Control Technique.

    ERIC Educational Resources Information Center

    Houser, Betsy B.

    This paper examines the effects of a teacher's classroom utilization of certain means of social influence or bases of social power (reward, coercive, referent, legitimate, and informational) upon: (1) level of student compliance, and (2) attitude of the student toward the teacher. A total of 588 white, middle-class fourth, fifth, and sixth grade…

  20. Attitude Control for an Aero-Vehicle Using Vector Thrusting and Variable Speed Control Moment Gyros

    NASA Technical Reports Server (NTRS)

    Shin, Jong-Yeob; Lim, K. B.; Moerder, D. D.

    2005-01-01

    Stabilization of passively unstable thrust-levitated vehicles can require significant control inputs. Although thrust vectoring is a straightforward choice for realizing these inputs, this may lead to difficulties discussed in the paper. This paper examines supplementing thrust vectoring with Variable-Speed Control Moment Gyroscopes (VSCMGs). The paper describes how to allocate VSCMGs and the vectored thrust mechanism for attitude stabilization in frequency domain and also shows trade-off between vectored thrust and VSCMGs. Using an H2 control synthesis methodology in LMI optimization, a feedback control law is designed for a thrust-levitated research vehicle and is simulated with the full nonlinear model. It is demonstrated that VSCMGs can reduce the use of vectored thrust variation for stabilizing the hovering platform in the presence of strong wind gusts.

  1. Application of SDRE technique to orbital and attitude control of spacecraft formation flying

    NASA Astrophysics Data System (ADS)

    Massari, Mauro; Zamaro, Mattia

    2014-01-01

    This paper proposes the application of a nonlinear control technique for coupled orbital and attitude relative motion of formation flying. Recently, mission concepts based on the formations of spacecraft that require an increased performance level for in-space maneuvers and operations, have been proposed. In order to guarantee the required performance level, those missions will be characterized by very low inter-satellite distance and demanding relative pointing requirements. Therefore, an autonomous control with high accuracy will be required, both for the control of relative distance and relative attitude. The control system proposed in this work is based on the solution of the State-Dependent Riccati Equation (SDRE), which is one of the more promising nonlinear techniques for regulating nonlinear systems in all the major branches of engineering. The coupling of the relative orbital and attitude motion is obtained considering the same set of thrusters for the control of both orbital and attitude relative dynamics. In addition, the SDRE algorithm is implemented with a timing update strategy both for the controller and the proposed nonlinear filter. The proposed control system approach has been applied to the design of a nonlinear controller for an up-to-date formation mission, which is ESA Proba-3. Numerical simulations considering a tracking signal for both orbital and attitude relative maneuver during an operative orbit of the mission are presented.

  2. Influence of attitude control on transfer mission for a flexible solar sail

    NASA Astrophysics Data System (ADS)

    Jin, Zhang; Tianshu, Wang; Shengping, Gong

    2014-04-01

    A solar-photon sail space vehicle, or a sailcraft, is a new type of vehicle apt also for deep-space exploration. A sailcraft is pushed by the pressure of the solar irradiance on the sail. The sailcraft has large and highly flexible structure, and its motion involves a coupling of the orbit, the attitude and structural vibration. Based on the coupling effect of the orbit and the attitude, the theory of time-optimal control is used to design the transfer trajectory from an earth-centric orbit to a heliocentric polar orbit. This paper establishes the reduced dynamic model for a flexible solar sail with foreshortening deformation and coupling of its attitude and vibration. In the process of attitude control, the sailcraft will generate orbital deviations from the designed orbit as well as structural vibration. This is especially true when the sailcraft makes large-angle maneuvers: larger orbital deviations and structural vibrations are generated. When initial deviations and solar pressure disturbance torques are considered, the process of attitude control leads to greater accumulated error in the transfer trajectory, which demonstrates that the process of attitude control is important to the sailcraft mission.

  3. A jet controlled magnetic referenced attitude control system for spinning payloads

    NASA Technical Reports Server (NTRS)

    Celmer, J. J.; Donohue, J. H.; Placanica, S. J.

    1982-01-01

    An attitude control system was designed permitting large angle acquisition and alignment of the principle axis of a spinning payload to within 1 degree of the earth's magnetic field. Signals from magnetometer and gyro sensors are fed to the control algorithm to generate commands for the jet thrusters. The algorithm contains a cross axis magnetometer signal to prevent a large angle magnetometer signal to prevent a large angle equilibrium solution. The acquisition will occur within 50 seconds from initial precession and nutation angles of 30 degrees. An electronic spin filter passes signals at spin and nutation frequencies and rejects bias signals due to sensor misalignment and principle axis offset. Describing function analysis and total analog simulation techniques were used. The flight ACS hardware was interfaced with the analog computer simulation for design and verification. The controller has flown on four successful missions.

  4. Gender, Religiosity, Sexual Activity, Sexual Knowledge, and Attitudes Toward Controversial Aspects of Sexuality.

    PubMed

    Sümer, Zeynep Hatipoğlu

    2015-12-01

    The purpose of this study is to examine the role of gender, religiosity, sexual activity, and sexual knowledge in predicting attitudes toward controversial aspects of sexuality among Turkish university students. Participants were 162 female and 135 male undergraduate students who were recruited on a volunteer basis from an urban state university in Turkey. The SKAT-A Attitude Scale along with background information form, sexual activities inventory, and sexual knowledge scale were administered to the participants. Simultaneous multiple regression analyses revealed that religiosity, particularly attendance to religious services was the most significant predictor in explaining university students' attitudes toward masturbation, abortion, homosexuality, pornography, and sexual coercion. PMID:24510128

  5. Nature and operation of attitudes.

    PubMed

    Ajzen, I

    2001-01-01

    This survey of attitude theory and research published between 1996 and 1999 covers the conceptualization of attitude, attitude formation and activation, attitude structure and function, and the attitude-behavior relation. Research regarding the expectancy-value model of attitude is considered, as are the roles of accessible beliefs and affective versus cognitive processes in the formation of attitudes. The survey reviews research on attitude strength and its antecedents and consequences, and covers progress made on the assessment of attitudinal ambivalence and its effects. Also considered is research on automatic attitude activation, attitude functions, and the relation of attitudes to broader values. A large number of studies dealt with the relation between attitudes and behavior. Research revealing additional moderators of this relation is reviewed, as are theory and research on the link between intentions and actions. Most work in this context was devoted to issues raised by the theories of reasoned action and planned behavior. The present review highlights the nature of perceived behavioral control, the relative importance of attitudes and subjective norms, the utility of adding more predictors, and the roles of prior behavior and habit. PMID:11148298

  6. Exploiting environmental torques for attitude control and determination of spin stabilized satellites

    NASA Technical Reports Server (NTRS)

    Gluck, R.

    1974-01-01

    Design techniques are presented which exploit environmental torques for attitude control and determination of spin stabilized satellites. The techniques are applicable to satellite missions where the dominant environmental torques are well understood and lend themselves to accurate analytical modeling. The techniques were applied to the Particles and Fields subsatellites of the Apollo 15 and 16 spacecraft and the flight results show good agreement with the attitude determination estimates obtained.

  7. Investigation on attitude disturbance control and vibration suppression for fuel-filled flexible spacecraft

    NASA Astrophysics Data System (ADS)

    Song, Xiao-Juan; Yue, Bao-Zeng; Wu, Wen-Jun

    2015-08-01

    This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft subjected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton's principle. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superimposed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liquid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algorithm would suppress the residual vibration.

  8. Crew exploration vehicle (CEV) attitude control using a neural-immunology/memory network

    NASA Astrophysics Data System (ADS)

    Weng, Liguo; Xia, Min; Wang, Wei; Liu, Qingshan

    2015-01-01

    This paper addresses the problem of the crew exploration vehicle (CEV) attitude control. CEVs are NASA's next-generation human spaceflight vehicles, and they use reaction control system (RCS) jet engines for attitude adjustment, which calls for control algorithms for firing the small propulsion engines mounted on vehicles. In this work, the resultant CEV dynamics combines both actuation and attitude dynamics. Therefore, it is highly nonlinear and even coupled with significant uncertainties. To cope with this situation, a neural-immunology/memory network is proposed. It is inspired by the human memory and immune systems. The control network does not rely on precise system dynamics information. Furthermore, the overall control scheme has a simple structure and demands much less computation as compared with most existing methods, making it attractive for real-time implementation. The effectiveness of this approach is also verified via simulation.

  9. Spontaneous prejudice in context: variability in automatically activated attitudes.

    PubMed

    Wittenbrink, B; Judd, C M; Park, B

    2001-11-01

    The goal of the research reported in this article was to examine whether automatic group attitudes and stereotypes, commonly thought to be fixed responses to a social category cue, are sensitive to changes in the situational context. Two experiments demonstrated such variability of automatic responses due to changes in the stimulus context. In Study 1 White participants' implicit attitudes toward Blacks varied as a result of exposure to either a positive (a family barbecue) or a negative (a gang incident) stereotypic situation. Study 2 demonstrated similar context effects under clearly automatic processing conditions. Here, the use of different background pictures (church interior vs. street corner) for Black and White face primes affected participants' racial attitudes as measured by a sequential priming task. Implications for the concept of automaticity in social cognition are discussed. PMID:11708559

  10. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    SciTech Connect

    Woronowicz, M. S.

    2011-05-20

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm{sup 3}. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  11. A solenoid failure detection system for cold gas attitude control jet valves

    NASA Technical Reports Server (NTRS)

    Johnston, P. A.

    1970-01-01

    The development of a solenoid valve failure detection system is described. The technique requires the addition of a radioactive gas to the propellant of a cold gas jet attitude control system. Solenoid failure is detected with an avalanche radiation detector located in the jet nozzle which senses the radiation emitted by the leaking radioactive gas. Measurements of carbon monoxide leakage rates through a Mariner type solenoid valve are presented as a function of gas activity and detector configuration. A cylindrical avalanche detector with a factor of 40 improvement in leak sensitivity is proposed for flight systems because it allows the quantity of radioactive gas that must be added to the propellant to be reduced to a practical level.

  12. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Technical Reports Server (NTRS)

    Woronowicz, M. S.

    2010-01-01

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cu cm. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  13. Linking Prenatal Androgens to Gender-Related Attitudes, Identity, and Activities: Evidence From Girls With Congenital Adrenal Hyperplasia.

    PubMed

    Endendijk, Joyce J; Beltz, Adriene M; McHale, Susan M; Bryk, Kristina; Berenbaum, Sheri A

    2016-10-01

    Key questions for developmentalists concern the origins of gender attitudes and their implications for behavior. We examined whether prenatal androgen exposure was related to gender attitudes, and whether and how the links between attitudes and gendered activity interest and participation were mediated by gender identity and moderated by hormones. Gender attitudes (i.e., gender-role attitudes and attitudes about being a girl), gender identity, and gender-typed activities were reported by 54 girls aged 10-13 years varying in degree of prenatal androgen exposure, including 40 girls with classical congenital adrenal hyperplasia (C-CAH) exposed to high prenatal androgens and 14 girls with non-classical (NC) CAH exposed to low, female-typical, prenatal androgens. Both girls with C-CAH and NC-CAH reported positive attitudes about being a girl and egalitarian gender attitudes, consistent with their female-typical gender identity. In contrast, girls with C-CAH had more male-typed activity interest and participation than girls with NC-CAH. Gender attitudes were linked to activities in both groups, with gender identity mediating the links. Specifically, gender-role attitudes and positive attitudes about being a girl were associated with feminine gender identity, which in turn was associated with decreased male-typed activity interests and participation, and increased female-typed activity interests. Our results are consistent with schema theories, with attitudes more closely associated with gender identity than with prenatal androgens. PMID:26940967

  14. A preliminary analysis of barriers, intentions, and attitudes towards moderate physical activity in women who are overweight.

    PubMed

    Jewson, Elizabeth; Spittle, Michael; Casey, Meghan

    2008-11-01

    Physical activity is important for the health of all individuals, however, the determinants of physical activity behaviour for women who are overweight remain largely unexplored. The purpose of this investigation was to explore a range of factors that influence participation in physical activity for a group of women who are overweight. Participants were 30 women, aged 25-71 years, with a mean age of 46.8 years (+12.95) and an average BMI of 31.2kg/m(2) (+5.6). Self-reported level of physical activity, perceived barriers and facilitators of physical activity, attitudes, intentions and perceived behavioural control to physical activity were measured. Seventeen participants were generally active, with self-reported moderate physical activity of 218.53min (+/-113.82) in the last 7 days; whereas 13 participants were reportedly less active 43.46 (+/-42.98)min. Active participants were more likely to identify social reasons for participating in physical activity, while inactive participants perceived that their laziness prevented them from being physically active. There were no significant differences between active and inactive overweight women for attitude, intention or subjective norm for moderate-intensity physical activity. There was a significant difference between these women in perceived behavioural control (p=.014) for moderate-intensity physical activity, as women who felt more in control of their physical activity behaviour were more likely to engage in physical activity than inactive women. Future research should investigate interventions to increase behavioural control of moderate-intensity physical activity in women who are overweight. PMID:17884730

  15. Design and simulation of satellite attitude control system based on Simulink and VR

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Gan, Qingbo; Kang, Jingshu

    2016-01-01

    In order to research satellite attitude control system design and visual simulation, the simulation framework of satellite dynamics and attitude control using Simulink were established. The design of satellite earth-oriented control system based on quaternion feedback was completed. The 3D scene based on VR was created and models in the scene were driven by simulation data of Simulink. By coordinate transformation. successful observing the scene in inertial coordinate system, orbit coordinate system and body coordinate system. The result shows that application of simulation method of Simulink combined with VR in the design of satellite attitude control system field, has the advantages of high confidence level, hard real-time property, multi-perspective and multi-coordinate system observing the scene, and improves the comprehensibility and accuracy of the design.

  16. Attitude control of a space structure using a 3-R rigid manipulator

    NASA Astrophysics Data System (ADS)

    Mukherjee, Ranjan; Zurowski, Mary

    The attitude control of space structures is an important problem. There has been considerable research in this area that has focussed on the use of momentum exchange devices. In this paper, we propose to control the attitude of space structures using a serial three-link PUMA-type manipulator that can be mounted on the space structure. This unconventional method of attitude control exploits the nonholonomic nature of the constraints that arise due to the conservation of angular momentum. We adopt a surface integral approach for the motion planning of the manipulator that will reorient the space structure in any desired way. The salient features of our algorithm are: (a) it is possible to mathematically prove the controllability of the system; (b) The motion of the manipulator can be planned amidst additional constraints like joint limits of the manipulator; and (c) the algorithm can be easily extended for application to flexible space structures.

  17. On prediction of longitudinal attitude of planing craft based on controllable hydrofoils

    NASA Astrophysics Data System (ADS)

    Ling, Hongjie; Wang, Zhidong; Wu, Na

    2013-09-01

    The purpose of this research study was to examine the attitude response of a planing craft under the controllable hydrofoils. Firstly, a non-linear longitudinal attitude model was established. In the mathematical model, effects of wind loads were considered. Both the wetted length and windward area varied in different navigation conditions. Secondly, control strategies for hydrofoils were specified. Using the above strategies, the heave and trim of the planing craft was adjusted by controllable hydrofoils. Finally, a simulation program was developed to predict the longitudinal attitudes of the planing craft with wind loads. A series of simulations were performed and effects of control strategies on longitudinal attitudes were analyzed. The results show that under effects of wind loads, heave of fixed hydrofoils planing craft decreased by 6.3%, and pitch increased by 8.6% when the main engine power was constant. Heave decreased by less than 1% and trim angle decreased by 1.7% as a result of using variable attack angle hydrofoils; however, amplitude changes of heave and pitch were less than 1% under the control of changeable attack angle hydrofoils and longitudinal attitude.

  18. Linear parameter varying switching attitude control for a near space hypersonic vehicle with parametric uncertainties

    NASA Astrophysics Data System (ADS)

    Huang, Yiqing; Sun, Changyin; Qian, Chengshan; Wang, Li

    2015-12-01

    This paper deals with the problem of linear parameter varying (LPV) switching attitude control for a near space hypersonic vehicle (NSHV) with parametric uncertainties. First, due to the enormous complexity of the NSHV nonlinear attitude dynamics, a slow-fast loop polytopic LPV attitude model is developed by using Jacobian linearisation and the tensor product model transformation approach. Second, for the purpose of less conservative attitude controller design, the flight envelope is divided into four subregions. For each parameter subregion, slow-loop and fast-loop LPV controllers are designed. By the defined switching character function, these slow-fast loop LPV controllers are then switched in order to guarantee the closed-loop NSHV system to be asymptotically stable and satisfy a specified tracking performance criterion. The condition of LPV switching attitude controller synthesis is given in terms of linear matrix inequalities, which can be readily solved via standard numerical software, and the robust stability analysis of the closed-loop NSHV system is verified based on multiple Lypapunov functions. Finally, numerical simulations have demonstrated the effectiveness of the proposed approach.

  19. Combined control of fast attitude maneuver and stabilization for large complex spacecraft

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Zhang, Jing-Rui

    2013-12-01

    In remote sensing or laser communication space missions, spacecraft need fast maneuver and fast stabilization in order to accomplish agile imaging and attitude tracking tasks. However, fast attitude maneuvers can easily cause elastic deformations and vibrations in flexible appendages of the spacecraft. This paper focuses on this problem and deals with the combined control of fast attitude maneuver and stabilization for large complex spacecraft. The mathematical model of complex spacecraft with flexible appendages and momentum bias actuators on board is presented. Based on the plant model and combined with the feedback controller, modal parameters of the closed-loop system are calculated, and a multiple mode input shaper utilizing the modal information is designed to suppress vibrations. Aiming at reducing vibrations excited by attitude maneuver, a quintic polynomial form rotation path planning is proposed with constraints on the actuators and the angular velocity taken into account. Attitude maneuver simulation results of the control systems with input shaper or path planning in loop are separately analyzed, and based on the analysis, a combined control strategy is presented with both path planning and input shaper in loop. Simulation results show that the combined control strategy satisfies the complex spacecraft's requirement of fast maneuver and stabilization with the actuators' torque limitation satisfied at the same time.

  20. Attitude control study for a large flexible spacecraft using a Solar Electric Propulsion System (SEPS)

    NASA Technical Reports Server (NTRS)

    Tolivar, A. F.; Key, R. W.

    1980-01-01

    The attitude control performance of the solar electric propulsion system (SEPS) was evaluated. A thrust vector control system for powered flight control was examined along with a gas jet reaction control system, and a reaction wheel system, both of which have been proposed for nonpowered flight control. Comprehensive computer simulations of each control system were made and evaluated using a 30 mode spacecraft model. Results obtained indicate that thrust vector control and reaction wheel systems offer acceptable smooth proportional control. The gas jet control system is shown to be risky for a flexible structure such as SEPS, and is therefore, not recommended as a primary control method.

  1. A Nonlinear Spacecraft Attitude Controller and Observer with an Unknown Constant Gyro Bias and Gyro Noise

    NASA Technical Reports Server (NTRS)

    Deutschmann, Julie; Sanner, Robert M.

    2001-01-01

    A nonlinear control scheme for attitude control of a spacecraft is combined with a nonlinear gyro bias observer for the case of constant gyro bias, in the presence of gyro noise. The observer bias estimates converge exponentially to a mean square bound determined by the standard deviation of the gyro noise. The resulting coupled, closed loop dynamics are proven to be globally stable, with asymptotic tracking which is also mean square bounded. A simulation of the proposed observer-controller design is given for a rigid spacecraft tracking a specified, time-varying attitude sequence to illustrate the theoretical claims.

  2. Smoking behaviours and attitudes toward tobacco control among assistant environmental health officer trainees.

    PubMed

    Tee, G H; Gurpreet, K; Hairi, N N; Zarihah, Z; Fadzilah, K

    2013-12-01

    Assistant environmental health officers (AEHO) are health care providers (HCPs) who act as enforcers, educators and trusted role models for the public. This is the first study to explore smoking behaviour and attitudes toward tobacco control among future HCPs. Almost 30% of AEHO trainees did not know the role of AEHOs in counselling smokers to stop smoking, but 91% agreed they should not smoke before advising others not to do so. The majority agreed that tobacco control regulations may be used as a means of reducing the prevalence of smoking. Future AEHOs had positive attitudes toward tobacco regulations but lacked understanding of their responsibility in tobacco control measures. PMID:24200284

  3. Spacecraft Hybrid (Mixed-Actuator) Attitude Control Experiences on NASA Science Missions

    NASA Technical Reports Server (NTRS)

    Dennehy, Cornelius J.

    2014-01-01

    There is a heightened interest within NASA for the design, development, and flight implementation of mixed-actuator hybrid attitude control systems for science spacecraft that have less than three functional reaction wheel actuators. This interest is driven by a number of recent reaction wheel failures on aging, but what could be still scientifically productive, NASA spacecraft if a successful hybrid attitude control mode can be implemented. Over the years, hybrid (mixed-actuator) control has been employed for contingency attitude control purposes on several NASA science mission spacecraft. This paper provides a historical perspective of NASA's previous engineering work on spacecraft mixed-actuator hybrid control approaches. An update of the current situation will also be provided emphasizing why NASA is now so interested in hybrid control. The results of the NASA Spacecraft Hybrid Attitude Control Workshop, held in April of 2013, will be highlighted. In particular, the lessons learned captured from that workshop will be shared in this paper. An update on the most recent experiences with hybrid control on the Kepler spacecraft will also be provided. This paper will close with some future considerations for hybrid spacecraft control.

  4. Long-term stability of GOES-8 and -9 attitude control

    NASA Astrophysics Data System (ADS)

    Carr, James L.

    1996-10-01

    An independent audit of the in-orbit behavior of the GOES-8 and GOES-9 satellites has been conducted for the NASA/GSFC. This audit utilized star and landmark observations from the GOES imager to determine long-term histories for spacecraft attitude, orbital position, and instrument internal misalignments. The paper presents results from this audit. Long-term drifts are found in the attitude histories, whereas the misalignment histories are shown to be diurnally stable. The GOES image navigation and registration system is designed to compensate for instrument internal misalignments, and both the diurnally repeatable and drift components of the attitude. Correlations between GOES-8 and GOES-9 long-term roll and pitch drifts implicate the Earth sensor as the origin of these observed drifts. This results clearly demonstrates the enhanced registration stability to be obtained with stellar inertial attitude determination replacing or supplementing Earth sensor control on future GOES missions.

  5. Concept design, modeling and station-keeping attitude control of an earth observation platform

    NASA Astrophysics Data System (ADS)

    Yang, Yueneng; Wu, Jie; Zheng, Wei

    2012-11-01

    The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.

  6. Structural control interaction for an LSS attitude control system using thrusters and reaction wheels

    NASA Astrophysics Data System (ADS)

    da Fonseca, Ijar M.; Bainum, Peter M.; da Silva, Adenilson R.

    2007-05-01

    This work provides some important information about control structure interaction (CSI) for a large space structure (LSS) attitude control subsystem (ACS) comprised of thrusters and reaction wheels. The LSS physical model is assumed as a rigid long tubular beam as the main bus with two attached long flexible solar panels. Two thrusters (one at each tip of the LSS) are used for large amplitude maneuvers and the reaction wheels for fine control. Lagrange's formulations for generalized and quasi-coordinates were used to derive the equations of motion. The gravity gradient, the solar pressure and the drag were included in the mathematical model as external perturbations. The assumed modes discretization method has been used to model the solar array elastic displacements so as to obtain a set of ordinary differential equations to describe the LSS motion. Different control strategies were implemented to analyze the CSI for two configurations, fine and coarse control. The MatLab/Simulink platform has been used for the computational simulations. The results are in agreement with the CSI theory in that thruster firings excite the solar panel vibrations and that the elastic vibration is an important issue to be taken into account for LSS ACS performance evaluation for both fine and coarse control. In spite of the CSI the maneuver objectives have been accomplished with results that meet the mission criteria.

  7. A Coupled Nonlinear Spacecraft Attitude Controller/Observer With an Unknown Constant Gyro Bias

    NASA Technical Reports Server (NTRS)

    Deutschmann, Julie; Sanner, Robert M.; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    A nonlinear control scheme for attitude control of a spacecraft is combined with a nonlinear gyro bias observer for the case of constant gyro bias. The closed loop system is proven to be globally stable, with zero tracking error, thus proving a separation principle for the given system. The nonlinear observer incorporates persistency of excitation, resulting in exponential convergence of the gyro bias error.

  8. Attitudes of Israeli Jewish and Arab High School Students toward Alcohol Control Measures.

    ERIC Educational Resources Information Center

    Weiss, Shoshana

    1999-01-01

    Explores the attitudes of adolescents (N=2,186) of four religions in the north of Israel toward eight alcohol measures. Findings indicate that the majority of the respondents tend to enhance alcohol control measures and driving issues, but only about a third tend to enhance alcohol control measures in the other domains. (Author/MKA)

  9. Smoking Behaviors and Attitudes During Adolescence Prospectively Predict Support for Tobacco Control Policies in Adulthood

    PubMed Central

    Chassin, Laurie; Presson, Clark C.

    2012-01-01

    Introduction: Several cross-sectional studies have examined factors associated with support for tobacco control policies. The current study utilized a longitudinal design to test smoking status and attitude toward smoking measured in adolescence as prospective predictors of support for tobacco control policies measured in adulthood. Methods: Participants (N = 4,834) were from a longitudinal study of a Midwestern community-based sample. Hierarchical multiple regression analyses tested adolescent smoking status and attitude toward smoking as prospective predictors (after controlling for sociodemographic factors, adult smoking status, and adult attitude toward smoking) of support for regulation of smoking in public places, discussion of the dangers of smoking in public schools, prohibiting smoking in bars, eliminating smoking on television and in movies, prohibiting smoking in restaurants, and increasing taxes on cigarettes. Results: Participants who smoked during adolescence demonstrated more support for discussion of the dangers of smoking in public schools and less support for increasing taxes on cigarettes but only among those who smoked as adults. Those with more positive attitudes toward smoking during adolescence demonstrated less support as adults for prohibiting smoking in bars and eliminating smoking on television and in movies. Moreover, a significant interaction indicated that those with more positive attitudes toward smoking as adolescents demonstrated less support as adults for prohibiting smoking in restaurants, but only if they became parents as adults. Conclusions: This study’s findings suggest that interventions designed to deter adolescent smoking may have future benefits in increasing support for tobacco control policies. PMID:22193576

  10. International Space Station Attitude Control and Energy Storage Experiment: Effects of Flywheel Torque

    NASA Technical Reports Server (NTRS)

    Roithmayr, Carlos M.

    1999-01-01

    The Attitude Control and Energy Storage Experiment is currently under development for the International Space Station; two counter-rotating flywheels will be levitated with magnetic bearings and placed in vacuum housings. The primary objective of the experiment is to store and discharge energy, in combination with existing batteries, into the electrical power system. The secondary objective is to use the flywheels to exert torque on the Station; a simple torque profile has been designed so that the Station's Control Moment Gyroscopes will be assisted in maintaining torque equilibrium attitude. Two energy storage contingencies could result in the inadvertent application of torque by the flywheels to the Station: an emergency shutdown of one flywheel rotor while the other remains spinning, and energy storage with only one rotor instead of the counterrotating pair. Analysis of these two contingencies shows that attitude control and the microgravity environment will not be adversely affected.

  11. Perception of Locus of Control as a Predictor of Attitude Toward Students' Evaluation of University Faculty. AIR Forum Paper 1978.

    ERIC Educational Resources Information Center

    Kohler, Emmett T.; Christal, Melodie E.

    Student and faculty attitudes about faculty evaluation and the relationship of the attitudes to the concept of locus of control were investigated. Student respondents consisted of 172 males and 256 females, and 108 faculty responses were received. The measure of locus of control closely resembles the Rotter Internal-External Control Scale. Student…

  12. Development of a Hardware-in-the-loop Simulator for Spacecraft Attitude Control Using Thrusters

    NASA Astrophysics Data System (ADS)

    Koh, Dong-Wook; Park, Sang-Young; Kim, Do-Hee; Choi, Kyu-Hong

    2009-03-01

    In this study, a Hardware-In-the-Loop (HIL) simulator using thrusters is developed to validate the spacecraft attitude system. To control the attitude of the simulator, eight cold gas thrusters are aligned with roll, pitch and yaw axis. Also linear actuators are applied to the HIL simulator for automatic mass balancing to compensate the center of mass offset from the center of rotation. The HIL simulator consists of an embedded computer (Onboard PC) for simulator system control, a wireless adapter for wireless network, a rate gyro sensor to measure 3-axis attitude of the simulator, an inclinometer to measure horizontal attitude, and a battery set to supply power for the simulator independently. For the performance test of the HIL simulator, a bang-bang controller and Pulse-Width Pulse-Frequency (PWPF) modulator are evaluated successfully. The maneuver of 68 deg. in yaw axis is tested for the comparison of the both controllers. The settling time of the bang-bang controller is faster than that of the PWPF modulator by six seconds in the experiment. The required fuel of the PWPF modulator is used as much as 51% of bang-bang controller in the experiment. Overall, the HIL simulator is appropriately developed to validate the control algorithms using thrusters.

  13. Dynamics and Control of Attitude, Power, and Momentum for a Spacecraft Using Flywheels and Control Moment Gyroscopes

    NASA Technical Reports Server (NTRS)

    Roithmayr, Carlos M.; Karlgaard, Christopher D.; Kumar, Renjith R.; Seywald, Hans; Bose, David M.

    2003-01-01

    Several laws are designed for simultaneous control of the orientation of an Earth-pointing spacecraft, the energy stored by counter-rotating flywheels, and the angular momentum of the flywheels and control moment gyroscopes used together as an integrated set of actuators for attitude control. General, nonlinear equations of motion are presented in vector-dyadic form, and used to obtain approximate expressions which are then linearized in preparation for design of control laws that include feedback of flywheel kinetic energy error as a means of compensating for damping exerted by rotor bearings. Two flywheel steering laws are developed such that torque commanded by an attitude control law is achieved while energy is stored or discharged at the required rate. Using the International Space Station as an example, numerical simulations are performed to demonstrate control about a torque equilibrium attitude, and illustrate the benefits of kinetic energy error feedback. Control laws for attitude hold are also developed, and used to show the amount of propellant that can be saved when flywheels assist the CMGs. Nonlinear control laws for large-angle slew maneuvers perform well, but excessive momentum is required to reorient a vehicle like the International Space Station.

  14. Physical Activity Attitudes, Preferences, and Practices in African American, Hispanic, and Caucasian Girls

    ERIC Educational Resources Information Center

    Grieser, Mira; Vu, Maihan B.; Bedimo-Rung, Ariane L.; Neumark-Sztainer, Dianne; Moody, Jamie; Young, Deborah Rohm; Moe, Stacey G.

    2006-01-01

    Physical activity levels in girls decline dramatically during adolescence, most profoundly among minorities. To explore ethnic and racial variation in attitudes toward physical activity, semistructured interviews (n = 80) and physical activity checklists (n = 130) are conducted with African American, Hispanic, and Caucasian middle school girls in…

  15. Attitudes towards the outgroup are predicted by activity in the precuneus in Arabs and Israelis.

    PubMed

    Bruneau, Emile G; Saxe, Rebecca

    2010-10-01

    The modern socio-political climate is defined by conflict between ethnic, religious and political groups: Bosnians and Serbs, Tamils and Singhalese, Irish Catholics and Protestants, Israelis and Arabs. One impediment to the resolution of these conflicts is the psychological bias that members of each group harbor towards each other. These biases, and their neural bases, are likely different from the commonly studied biases towards racial outgroups. We presented Arab, Israeli and control individuals with statements about the Middle East from the perspective of the ingroup or the outgroup. Subjects rated how 'reasonable' each statement was, during fMRI imaging. Increased activation in the precuneus (PC) while reading pro-outgroup vs. pro-ingroup statements correlated strongly with both explicit and implicit measures of negative attitudes towards the outgroup; other brain regions that were involved in reasoning about emotionally-laden information did not show this pattern. PMID:20510370

  16. Attitude-control model identification of on-orbit satellites actuated by reaction wheels

    NASA Astrophysics Data System (ADS)

    Geng, Li-Hui; Xiao, De-Yun; Wang, Qian; Zhang, Tao; Song, Jing-Yan

    2010-03-01

    With the long-term running of an on-orbit satellite, parameters in its attitude model are naturally altered due to the wastage of on-board components and the consumption of propellants or pay loads. In order to obtain high-accuracy attitude-control models and improve the on-orbit adaptation of an attitude controller, identification of an on-orbit satellite becomes another available approach. Due to the effect of exogenous disturbing torques and the measurement noises, estimation of the attitude-control models is eventually converted into that of an errors-in-variables model (EIVM). Since any a priori information on disturbing noises is not known in the on-orbit environment, an L2-optimal identification algorithm is proposed to estimate a generalized attitude model (GAM) for the satellite and then the corresponding noise model (NM) can be readily given by a model transformation to the GAM. During the parameter optimization for GAM, v-gap metric is employed as a minimization criterion to reduce the conservativeness of the resulting model and the optimization problem can be solved by linear matrix inequalities (LMIs). Finally, the testbed of a micro-satellite simulator is utilized to demonstrate the effectiveness of the proposed identification algorithm.

  17. Flight test evaluation of a separate surface attitude command control system on a Beech 99 airplane

    NASA Technical Reports Server (NTRS)

    Gee, S. W.; Jenks, G. E.; Roskam, J.; Stone, R. L.

    1976-01-01

    A joint NASA/university/industry program was conducted to flight evaluate a potentially low cost separate surface implementation of attitude command in a Beech 99 airplane. Saturation of the separate surfaces was the primary cause of many problems during development. Six experienced professional pilots made simulated instrument flight evaluations in light-to-moderate turbulence. They were favorably impressed with the system, particularly with the elimination of control force transients that accompanied configuration changes. For ride quality, quantitative data showed that the attitude command control system resulted in all cases of airplane motion being removed from the uncomfortable ride region.

  18. Self-control, perceived opportunity, and attitudes as predictors of academic dishonesty.

    PubMed

    Bolin, Aaron U

    2004-03-01

    Academic dishonesty is a persistent and pervasive problem on college campuses. Researchers have suggested a variety of factors that influence academic dishonesty. The present study is an examination of the roles of self-control, attitude toward academic dishonesty, and perceived opportunity in predicting academic dishonesty. The dataset consisted of 853 survey responses from university students across the United States. The results showed that attitude toward academic dishonesty mediated the relationship between self-control and academic dishonesty and also between perceived opportunity and academic dishonesty. Implications of these findings are briefly discussed. PMID:15218783

  19. Attitude control system conceptual design for the X-ray timing explorer

    NASA Technical Reports Server (NTRS)

    Bauer, Frank H.; Femiano, Michael D.; Mosier, Gary E.

    1992-01-01

    The X-ray Timing Explorer (XTE) satellite is the next in a long series of Explorer-class missions developed by NASA. It will study the structure and dynamics of compact X-ray sources, neutron stars, white dwarfs, and other stellar objects with X-ray energy emissions. The demanding pointing requirement of XTE are driving the attitude control system design. This design is further complicated by large moving instruments which impart significant momentum on the spacecraft. The attitude control system concept to meet the XTE science objectives is discussed.

  20. The 6670-Newton attitude-control thruster using hydrogen-oxygen propellant

    NASA Technical Reports Server (NTRS)

    Gordon, L. H.

    1977-01-01

    The development of a reusable, attitude-control propulsion system for the space transportation system is discussed. A flight weight, gaseous oxygen attitude control thruster assembly was tested to obtain data on cyclic life, thermal and hydraulic characteristics, pulse response, and performance. The basic thruster components were tested in excess of 51,000 pulses and 660 seconds, steady state, with no degradation of the 93 percent characteristic exhaust velocity efficiency level. Nominal operating conditions were a chamber pressure of 207 N sq cm (300 psia), a mixture ratio of 4.0, a pulse width of 100 ms, and a pulse frequency of 2 Hz.

  1. Implicit and Explicit Attitudes Predict Smoking Cessation: Moderating Effects of Experienced Failure to Control Smoking and Plans to Quit

    PubMed Central

    Chassin, Laurie; Presson, Clark C.; Sherman, Steven J.; Seo, Dong-Chul; Macy, Jon

    2010-01-01

    The current study tested implicit and explicit attitudes as prospective predictors of smoking cessation in a Midwestern community sample of smokers. Results showed that the effects of attitudes significantly varied with levels of experienced failure to control smoking and plans to quit. Explicit attitudes significantly predicted later cessation among those with low (but not high or average) levels of experienced failure to control smoking. Conversely, however, implicit attitudes significantly predicted later cessation among those with high levels of experienced failure to control smoking, but only if they had a plan to quit. Because smoking cessation involves both controlled and automatic processes, interventions may need to consider attitude change interventions that focus on both implicit and explicit attitudes. PMID:21198227

  2. Design and Integration of an All-Magnetic Attitude Control System for FASTSAT-HSV01's Multiple Pointing Objectives

    NASA Technical Reports Server (NTRS)

    DeKock, Brandon; Sanders, Devon; Vanzwieten, Tannen; Capo-Lugo, Pedro

    2011-01-01

    The FASTSAT-HSV01 spacecraft is a microsatellite with magnetic torque rods as it sole attitude control actuator. FASTSAT s multiple payloads and mission functions require the Attitude Control System (ACS) to maintain Local Vertical Local Horizontal (LVLH)-referenced attitudes without spin-stabilization, while the pointing errors for some attitudes be significantly smaller than the previous best-demonstrated for this type of control system. The mission requires the ACS to hold multiple stable, unstable, and non-equilibrium attitudes, as well as eject a 3U CubeSat from an onboard P-POD and recover from the ensuing tumble. This paper describes the Attitude Control System, the reasons for design choices, how the ACS integrates with the rest of the spacecraft, and gives recommendations for potential future applications of the work.

  3. Nonlinear observer/controller designs for spacecraft attitude control systems with uncalibrated gyros

    NASA Astrophysics Data System (ADS)

    Thienel, Julie K.

    Gyroscopes, or gyros, are vital sensors in spacecraft onboard attitude control systems. Gyro measurements are corrupted, though, due to errors in alignment and scale factor, biases, and noise. This work proposes a class of adaptive nonlinear observers for calibration of spacecraft gyros. Observers for each of the calibration parameters are separately developed, then combined. Lyapunov stability analysis is used to demonstrate the stability and convergence properties of each design. First, an observer to estimate gyro bias is developed, both with and without added noise effects. The observer is shown to be exponentially stable without any additional conditions. Next a scale factor observer is developed, followed by an alignment observer. The scale factor and alignment observers are both shown to be Lyapunov stable. Additionally, if the angular velocity meets a persistency of excitation (PE) condition, the scale factor and alignment observers are exponentially stable. Finally, the three observers are combined, and the combination is shown to be stable, with exponential stability if the angular velocity is persistently exciting. The specific PE condition for each observer is given in detail. Next, the adaptive observers are combined with a class of nonlinear control algorithms designed to asymptotically track a general time-varying reference attitude. This algorithm requires feedback from rate sensors, such as gyros. The miscalibration discussed above will seriously degrade the performance of these controllers. While the adaptive observers can eliminate this miscalibration, it is not immediately clear that the observers can be safely combined with the controller in this case. There is, in general, no "separation principle" for nonlinear systems, as there is for linear systems. However, Lyapunov analysis of the coupled controller-observer dynamics shows that the closed-loop system will be stable for the class of observers proposed. With only gyro bias miscalibration

  4. Design and analysis of a moment control unit for agile satellite with high attitude stability requirement

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Li, Mou; Song, Zhuoyue; Shan, Jinjun; Guan, Xin; Tang, Liang

    2016-05-01

    A moment control unit is developed and verified by numerical simulation. This moment control unit is employed as an actuator for the satellite attitude control. It contains four control moment gyroscopes (CMGs) to realize the rapid attitude maneuver and a vibration isolation system for each CMG. This unit can not only reduce the required electronics for each CMG and thus the weight, but also improve the stability of the satellite attitude. The design of the structure is presented first. This structure not only holds and protects the CMGs, but also isolates the vibrations caused by each CMG. Then, a dynamic model of a single CMG with a vibration isolation system is formulated, and the time- and frequency-domain characteristics of this dynamic model are discussed. Numerical simulations of a satellite attitude control example are then used to evaluate the system. The new moment control unit occupies less volume than previous designs, and the results show that the new design improves satellite pointing performance because of the vibration isolation.

  5. Topics in constrained optimal control: Spacecraft formation flying, constrained attitude control, and rank minimization problems

    NASA Astrophysics Data System (ADS)

    Kim, Yoonsoo

    This dissertation focuses on cooperative control between multiple agents (e.g., spacecraft, UAVs). In particular, motivated by future NASA's multiple spacecraft missions, we have been guided to consider fundamental aspects of spacecraft formation flying, including collision avoidance issues; constraints on the relative position and attitude. In this venue, we have realized that one of the main challenges is dealing with nonconvex state constraints. In this dissertation, we will address such complications using classical control theory, heuristic techniques, and more recent semidefinite programming-based approaches. We then proceed to consider communication and interspacecraft sensing issues in multiple agent dynamic system setting. In this direction, we will study (1) how conventional control techniques should be augmented to meet our design objectives when the information flow between multiple agents is taken into account; (2) which information structures (e.g., information graphs) yield best performance guarantees in terms of stability, robustness, or fast agreement. In this work, we provide theoretical answers to these problems. Moreover, as many design problems involving information networks and graphs lead to combinatorial problems, which can be formulated as rank optimization problems over matrices, we consider these class of problems in this dissertation. Rank optimization problems also arise in system theory and are considered to be of paramount importance in modern control synthesis problems.

  6. Cassini Attitude Control Operations - Guidelines Levied on Science to Extend Reaction Wheel Life

    NASA Technical Reports Server (NTRS)

    Mittelsteadt, Carson O.

    2011-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. Cassini deployed the European-built Huygens probe, which descended through the Titan atmosphere (Saturn's largest moon) and landed on its surface on January 14, 2005. The Cassini mission has recently been approved by NASA to continue through September of 2017. This 7-year extension is called the Solstice mission and it presents challenges to the spacecraft operations team and its ability to maintain the health of the spacecraft. To keep the spacecraft healthy for 7 more years, the spacecraft team must carefully manage hydrazine use (about 48% of the 132 kg launch load remains as of January 2011). A vital part of conserving hydrazine is to use the reaction wheel assembly (RWA) control system for precise pointing and slews wherever possible. In any given week, the Cassini spacecraft is commanded to use RWA control about 99% of the time, with about 1% of the time requiring reaction control system (RCS) thruster control (to perform Delta V course corrections or to bias the RWA momentum). Such extensive use of the RWA hardware throughout the mission requires that the RWAs be operated in a way that minimizes degradation in the RWA electronics, DC motor, and spin bearing for each reaction wheel. Three consumables in particular have been identified for the RWAs: (1) Total number of revolutions for each RWA. (2) Time spent at very low wheel speeds. At these low speeds, good elasto-hydrodynamic (EHD) film lubrication may be compromised. (3) Total number of on/off power cycles. The second of these consumables, minimizing the time spent at very low wheel speeds, is especially important to keep the spin bearing healthy and well-lubricated. These consumables are actively managed by the attitude control operations team throughout the mission. One vital management

  7. Analysis of the TDRS multiple access system for possible use as an attitude control system sensor

    NASA Technical Reports Server (NTRS)

    Blevins, Bruce Allyn; Sank, Victor J.

    1993-01-01

    A member of the constellation of TDR satellites (TDRS) has experienced a failure of its prime earth sensor. Failure of the remaining earth sensor could result in the inability of the satellite to control its attitude and provide user services. Loss of the satellite would be a serious event. The multiple access (MA) antenna array on the TDRS has been proposed for use as a backup sensor for the attitude control system. This paper describes our analysis of the performance of the MA array as an interferometer used for accurate attitude determination. A least squares fit of a plane to the MA phase information appears to represent the TDRS body roll and pitch within about 0.1 deg. This is sufficient for SGL pointing and MA and SSA user services. Analytic improvements that include ionospheric correction may yield sufficient accuracy for KSA user services.

  8. Attitude control/momentum management and payload pointing in advanced space vehicles

    NASA Technical Reports Server (NTRS)

    Parlos, Alexander G.; Jayasuriya, Suhada

    1990-01-01

    The design and evaluation of an attitude control/momentum management system for highly asymmetric spacecraft configurations are presented. The preliminary development and application of a nonlinear control system design methodology for tracking control of uncertain systems, such as spacecraft payload pointing systems are also presented. Control issues relevant to both linear and nonlinear rigid-body spacecraft dynamics are addressed, whereas any structural flexibilities are not taken into consideration. Results from the first task indicate that certain commonly used simplifications in the equations of motions result in unstable attitude control systems, when used for highly asymmetric spacecraft configurations. An approach is suggested circumventing this problem. Additionally, even though preliminary results from the second task are encouraging, the proposed nonlinear control system design method requires further investigation prior to its application and use as an effective payload pointing system design technique.

  9. Attitude Controller for the Atmospheric Entry of the Mars Science Laboratory

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul B.; San Martin, A. Miguel; Wong, Edward C.

    2008-01-01

    This paper describes the attitude controller for the atmospheric entry of the Mars Science Laboratory (MSL). The controller will command 8 RCS thrusters to control the 3- axis attitude of the entry capsule. The Entry Controller is formulated as three independent channels in the control frame, which is nominally aligned with the stability frame. Each channel has a feedfoward and a feedback path. The feedforward path enables fast response to large bank commands. The feedback path stabilizes the vehicle angle of attack and sideslip around its trim position, and tracks bank commands. The feedback path has a PD/D control structure with deadbands that minimizes fuel usage. The performance of this design is demonstrated via computer simulations.

  10. TRMM Re-Entry Planning: Attitude Determination and Control During Thruster Modes

    NASA Technical Reports Server (NTRS)

    DeWeese, Keith

    2005-01-01

    The Tropical Rainfall Measuring Mission (TRMM) spacecraft has been undergoing design for a controlled re-entry to Earth. During simulation of the re-entry plan, there was evidence of errors in the attitude determination algorithms during thruster modes. These errors affected the bum efficiency, and thus planning, during re-entry. During thruster modes, the spacecraft attitude is controlled off of integrated Gyro Error Angles that were designed to closely follow the nominal spacecraft pointing frame (Tip Frame). These angles, however, were not exactly mapped to the Tip Frame from the Body Frame. Additionally, in the initial formulation of the thruster mode attitude determination algorithms, several assumptions and approximations were made to conserve processor speed. These errors became noticeable and significant when simulating bums of much longer duration (-10 times) than had been produced in flight. A solution is proposed that uses attitude determination information from a propagated extended Kalman filter that already exists in the TRMM thruster modes. This attitude information is then used to rotate the Gyro Error Angles into the Tip Frame. An error analysis is presented that compares the two formulations. The new algorithm is tested using the TRMM High-Fidelity Simulator and verified with the TRMM Software Testing and Training Facility. Simulation results for both configurations are also presented.

  11. Techniques for monitoring and controlling yaw attitude of a GPS satellite

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M. (Inventor); Bar-Sever, Yoaz (Inventor); Zumberge, James (Inventor); Bertiger, William I. (Inventor); Muellerschoen, Ronald J. (Inventor); Wu, Sien-Chong (Inventor); Hurst, Kenneth (Inventor); Blewitt, Geoff (Inventor); Yunck, Thomas (Inventor); Thornton, Catherine (Inventor)

    2001-01-01

    Techniques for monitoring and controlling yawing of a GPS satellite in an orbit that has an eclipsing portion out of the sunlight based on the orbital conditions of the GPS satellite. In one embodiment, a constant yaw bias is generated in the attitude control system of the GPS satellite to control the yawing of the GPS satellite when it is in the shadow of the earth.

  12. Attitude control system of the Delfi-n3Xt satellite

    NASA Astrophysics Data System (ADS)

    Reijneveld, J.; Choukroun, D.

    2013-12-01

    This work is concerned with the development of the attitude control algorithms that will be implemented on board of the Delfi-n3xt nanosatellite, which is to be launched in 2013. One of the mission objectives is to demonstrate Sun pointing and three axis stabilization. The attitude control modes and the associated algorithms are described. The control authority is shared between three body-mounted magnetorquers (MTQ) and three orthogonal reaction wheels. The attitude information is retrieved from Sun vector measurements, Earth magnetic field measurements, and gyro measurements. The design of the control is achieved as a trade between simplicity and performance. Stabilization and Sun pointing are achieved via the successive application of the classical Bdot control law and a quaternion feedback control. For the purpose of Sun pointing, a simple quaternion estimation scheme is implemented based on geometric arguments, where the need for a costly optimal filtering algorithm is alleviated, and a single line of sight (LoS) measurement is required - here the Sun vector. Beyond the three-axis Sun pointing mode, spinning Sun pointing modes are also described and used as demonstration modes. The three-axis Sun pointing mode requires reaction wheels and magnetic control while the spinning control modes are implemented with magnetic control only. In addition, a simple scheme for angular rates estimation using Sun vector and Earth magnetic measurements is tested in the case of gyro failures. The various control modes performances are illustrated via extensive simulations over several orbits time spans. The simulated models of the dynamical space environment, of the attitude hardware, and the onboard controller logic are using realistic assumptions. All control modes satisfy the minimal Sun pointing requirements allowed for power generation.

  13. Classical and higher-order sliding mode attitude control for launch vehicle systems

    NASA Astrophysics Data System (ADS)

    Stott, James Edward, Jr.

    In determining flight controls for launch vehicle systems, several things must be taken into account. Launch vehicle systems can be expendable or reusable, carry crew or cargo, etc. Each of these launch vehicles maneuvers through a wide range of flight conditions and different mission profiles. Crewed vehicles must adhere to human rating requirements which limit the angular rates. Reusable launch vehicle systems must take into account actuator saturation during entry. Wind disturbances and plant uncertainties are major perturbations to the nominal state of any launch vehicle. An ideal controller is one that is robust enough to handle these uncertainties and external disturbances with limited control authority. One major challenge that exists in the design of these vehicles is the updating of old autopilot technology to new robust designs while also taking into account the different type of launch vehicle system employed. Sliding mode control algorithms that are inherently robust to external disturbances and plant uncertainties are very good candidates for improving the robustness and accuracy of the flight control systems. This dissertation focuses on systematically studying and developing a 'toolbox' of classical and higher-order sliding mode attitude control algorithms for different types of launch vehicle systems operating in uncertain conditions, including model uncertainties, actuator malfunctions, and external perturbations such as wind gusts. The developed toolbox comprises of time-varying sliding variables, classical and higher-order sliding mode attitude control algorithms, and observer techniques that yield novel sliding mode attitude control architectures. The proposed control toolbox allows achieving even higher standards of performance, reliability, safety, operability, and cost for launch vehicles over the current state of the art. Case studies include controlling the X-33 and SLV-X Launch Vehicles studied under NASA's Space Launch Initiative (SLI

  14. Attitude Control of a Small Coaxial Helicopter with a Bell Type Stabilizer Bar

    NASA Astrophysics Data System (ADS)

    Sunada, Shigeru; Hirosue, Wataru; Kawashima, Kenta

    We analyzed the small coaxial helicopter recently developed for entertainment. The upper rotor is connected with a stabilizer bar alone and the lower rotor is not connected with it. The cyclic pitch of the upper rotor is controlled by this stabilizer bar, and that of the lower rotor is controlled by servo motors. We investigated how this stabilizer bar varies the cyclic pitch of the upper rotor and how it contributes to attitude control of a fuselage.

  15. Attitude control of geostationary satellites with double gimballed momentum wheels

    NASA Astrophysics Data System (ADS)

    Schulz, G.; Lange, T.

    1981-11-01

    Conventional control methods are generalized using state vector feedback design procedures. Alternatively, a decoupled control method using a nondiagonal inertia tensor was derived. These are confronted to modern control theory design method with observer, where especially the insensitivity with respect to variants of the moments of inertia was demonstrated.

  16. The Attitudes & Beliefs on Classroom Control Inventory-Revised and Revisited: A Continuation of Construct Validation

    ERIC Educational Resources Information Center

    Martin, Nancy K.; Yin, Zenong; Mayall, Hayley

    2008-01-01

    The purpose of this study was to report the psychometric properties of the revised Attitudes and Beliefs of Classroom Control Inventory (ABCC-R). Data were collected from 489 participants via the ABCC-R, Teacher Efficacy Scale, Problems in School Questionnaire, and a demographic questionnaire. Results were in keeping with the construct. The…

  17. Children's Eating Attitudes and Behaviour: A Study of the Modelling and Control Theories of Parental Influence

    ERIC Educational Resources Information Center

    Brown, Rachael; Ogden, Jane

    2004-01-01

    The present study compared the modelling and control theories of parental influence on children's eating attitudes and behaviour with a focus on snack foods. Matched questionnaires describing reported snack intake, eating motivations and body dissatisfaction were completed by 112 parent/child pairs. Parents completed additional items relating to…

  18. MSFC Skylab Orbital Workshop, volume 2. [design and development of electrical systems and attitude control system

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The design and development of the Skylab Orbital Workshop are discussed. The subjects considered are: (1) thrust attitude control system, (2) solar array system, (3) electrical power distribution system, (4) communication and data acquisition system, (5) illumination system, and (6) caution and warning system.

  19. Interrelationships of Study Habits and Attitudes, Locus of Control, Motivation Achievement Tendencies and Academic Achievement.

    ERIC Educational Resources Information Center

    Gadzella, Bernadette M.; And Others

    The study investigated (a) relationships between measures on study habits and attitudes, locus of control, achieving tendency, and semester grade-point averages (SGPA), (b) differences between the sexes on the above mentioned variables, and (c) best predictor of SGPA. The subjects were 39 males and 81 females. There were a number of significant…

  20. Tobacco Control Policy Advocacy Attitudes and Self-Efficacy among Ethnically Diverse High School Students

    ERIC Educational Resources Information Center

    Ramirez, Amelie G.; Velez, Luis F.; Chalela, Patricia; Grussendorf, Jeannie; McAlister, Alfred L.

    2006-01-01

    This study applied self-efficacy theory to assess empowerment to advocate on behalf of tobacco control policies. The Youth Tobacco Survey with added policy advocacy self-efficacy, attitudes, and outcome expectations scales was given to 9,177 high school students in Texas. Asians showed the lowest prevalence of experimentation and current smoking,…

  1. Using Automatic Code Generation in the Attitude Control Flight Software Engineering Process

    NASA Technical Reports Server (NTRS)

    McComas, David; O'Donnell, James R., Jr.; Andrews, Stephen F.

    1999-01-01

    This paper presents an overview of the attitude control subsystem flight software development process, identifies how the process has changed due to automatic code generation, analyzes each software development phase in detail, and concludes with a summary of our lessons learned.

  2. Fraternity Hazing Revisited: Current Alumni and Active Member Attitudes Toward Hazing.

    ERIC Educational Resources Information Center

    Baier, John L.; Williams, Patrick S.

    1983-01-01

    Studied hazing practices at a large university and compared active and alumni fraternity members' (N=259) attitudes towards them. Results showed alumni accepted hazing more than active members. Most members believed hazing served a valuable purpose and did not create problems in their own chapter. (WAS)

  3. Comparing Primary Student Teachers' Attitudes, Subject Knowledge and Pedagogical Content Knowledge Needs in a Physics Activity

    ERIC Educational Resources Information Center

    Johnston, Jane; Ahtee, Maija

    2006-01-01

    This research explores and compares primary student teachers' attitudes, subject knowledge and pedagogical content knowledge (PCK) in physics in two institutions in England and Finland, using a practical physics activity and questionnaire. Teaching of physics activities was rated unpopular both in Finland and England, although English students…

  4. An Exploration of the Character, Expressive Qualities and Attitudes towards Arts Activities of Exceptional Adolescent Students.

    ERIC Educational Resources Information Center

    Sturgess, Pamela A.

    A study examined the character, expressive qualities, and attitudes toward art (performing and visual) activities of handicapped Canadian adolescents (N=30) to determine how well current teaching of the arts meets the needs and expectations of these students. A review of literature on arts activities and exceptional students contributed to the…

  5. Multiagent Attitude Control System for Satellites Based in Momentum Wheels and Event-Driven Synchronization

    NASA Astrophysics Data System (ADS)

    Garcia, Juan L.; Moreno, Jose Sanchez

    2012-12-01

    Attitude control is a requirement always present in spacecraft design. Several kinds of actuators exist to accomplish this control, being momentum wheels one of the most employed. Usually satellites carry redundant momentum wheels to handle any possible single failure, but the controller remains as a single centralized element, posing problems in case of failures. In this work a decentralized agent-based event-driven algorithm for attitude control is presented as a possible solution. Several agents based in momentum wheels will interact among them to accomplish the satellite control. A simulation environment has been developed to analyze the behavior of this architecture. This environment has been made available through the web page http://www.dia.uned.es.

  6. Fuzzy based attitude controller for flexible spacecraft with on/off thrusters

    NASA Technical Reports Server (NTRS)

    Knapp, Roger G.; Adams, Neil J.

    1993-01-01

    A fuzzy-based attitude controller is designed for attitude control of a generic spacecraft with on/off thrusters. The controller is comprised of packages of rules dedicated to addressing different objectives (e.g., disturbance rejection, low fuel consumption, avoiding the excitation of flexible appendages, etc.). These rule packages can be inserted or removed depending on the requirements of the particular spacecraft and are parameterized based on vehicle parameters such as inertia or operational parameters such as the maneuvering rate. Individual rule packages can be 'weighted' relative to each other to emphasize the importance of one objective relative to another. Finally, the fuzzy controller and rule packages are demonstrated using the high-fidelity Space Shuttle Interactive On-Orbit Simulator (IOS) while performing typical on-orbit operations and are subsequently compared with the existing shuttle flight control system performance.

  7. High performance two degrees of freedom attitude control for solar sails

    NASA Astrophysics Data System (ADS)

    Romagnoli, Daniele; Oehlschlägel, Thimo

    2011-12-01

    The purpose of this paper is to present a high performance solar sail attitude controller which uses ballast masses moving inside the sail's booms as actuators and to demonstrate its ability of performing time efficient reorientation maneuvers. The proposed controller consists of a combination of a feedforward and a feedback controller, which takes advantage of the feedforward's fast response and the feedback's ability of responding to unpredicted disturbances. The feedforward controller considers the attitude dynamics of the sailcraft as well as the disturbance torque due to the center of pressure offset to the center of mass of the sailcraft. Additional disturbance torques, like those coming from the environment or from asymmetry of the spacecraft structure, are then handled by the feedback controller. Simulation performance results are finally compared against results available in the literature.

  8. Flight test evaluation of a separate surface attitude command control system on a Beech 99 airplane

    NASA Technical Reports Server (NTRS)

    Gee, S. W.; Jenks, G. E.; Roskam, J.; Stone, R. L.

    1976-01-01

    A joint NASA/university/industry program was conducted to flight evaluate a potentially low cost separate surface implementation of attitude command in a Beech 99 airplane. Saturation of the separate surfaces was the primary cause of many problems during development. Six experienced professional pilots who made simulated instrument flight evaluations experienced improvements in airplane handling qualities in the presence of turbulence and a reduction in pilot workload. For ride quality, quantitative data show that the attitude command control system results in all cases of airplane motion being removed from the uncomfortable ride region.

  9. "This World Is So Beautiful....": Feelings and Attitudes in Environmental Education. Instructional Activities Series IA/S-15.

    ERIC Educational Resources Information Center

    Allen, Rodney F.

    This activity is one of a series of 17 teacher-developed instructional activities for geography at the secondary-grade level described in SO 009 140. The activity investigates the rationale and means for including attitudes, feelings, and emotions in the environmental education curriculum. Explanation is given about the role of attitudes and…

  10. Helicopter gust alleviation, attitude stabilization, and vibration alleviation using individual-blade-control through a conventional swash plate

    NASA Technical Reports Server (NTRS)

    Ham, N. D.

    1985-01-01

    The novel active control system presented for helicopter rotor aerodynamic and aeroelastic problems involves the individual control of each blade in the rotating frame over a wide range of frequencies (up to the sixth harmonic of rotor speed). This Individual Blade Control (IBC) system controls blade pitch by means of broadband electrohydraulic actuators attached to the swash plate (in the case of three blades) or individually to each blade, using acceleratometer signals to furnish control commands to the actuators. Attention is given to IBC's application to blade lag, flapping, and bending dynamics. It is shown that gust alleviation, attitude stabilization, vibration alleviation, and air/ground resonance suppression, are all achievable with a conventional helicopter swash plate.

  11. Predicting private and public helping behaviour by implicit attitudes and the motivation to control prejudiced reactions.

    PubMed

    Gabriel, Ute; Banse, Rainer; Hug, Florian

    2007-06-01

    The role of individual differences in implicit attitudes toward homosexuals and motivation to control prejudiced reactions (MCPR) in predicting private and public helping behaviour was investigated. After assessing the predictor variables, 69 male students were informed about a campaign of a local gay organization. They were provided with an opportunity to donate money and sign a petition in the presence (public setting) or absence (private setting) of the experimenter. As expected, more helping behaviour was shown in the public than in the private setting. However, while the explicit cognitive attitude accounted for helping behaviour in both settings, an implicit attitude x MCPR interaction accounted for additional variability of helping in the public setting only. Three different mediating processes are discussed as possible causes of the observed effects. PMID:17565787

  12. Fault tolerant small satellite attitude control using adaptive non-singular terminal sliding mode

    NASA Astrophysics Data System (ADS)

    Cao, Lu; Chen, XiaoQian; Sheng, Tao

    2013-06-01

    The Attitude Control System (ACS) plays a pivotal role in the whole performance of the spacecraft on the orbit; therefore, it is vitally important to design the control system with the performance of rapid response, high control precision and insensitive to external perturbations. In the first place, this paper proposes two adaptive nonlinear control algorithms based on the sliding mode control (SMC), which are designed for small satellite attitude control system. The nonlinear dynamics describing the attitude of small satellite is considered in a circle reference orbit, and the stability of the closed-loop system in the presence of external perturbations is investigated. Then, in order to account for accidental or degradation fault in satellite actuators, the fault-tolerant control schemes are presented. Hence, two adaptive fault-tolerant control laws (continuous sliding mode control and non-singular terminal sliding mode control) are developed by adopting the nonlinear analytical model to describe the system, which can guarantee global asymptotic convergence of the attitude control error with the existence of unknown external perturbations. The nonlinear hyperplane based Terminal sliding mode is introduced into the control law design; therefore, the system convergence performance improves and the control error is convergent in "finite time". As a result, the study on the non-singular terminal sliding mode control is the emphasis and the continuous sliding mode control is used to compare with the non-singular terminal sliding mode control. Meanwhile, an adaptive fuzzy algorithm has been proposed to suppress the chattering phenomenon. Moreover, several numerical examples are presented to demonstrate the efficacy of the proposed controllers by correcting for the external perturbations. Simulation results confirm that the suggested methodologies yield high control precision in control. In addition, actuator degradation, actuator stuck and actuator failure for a

  13. Attitude control of the space construction base: A modular approach

    NASA Technical Reports Server (NTRS)

    Oconnor, D. A.

    1982-01-01

    A planar model of a space base and one module is considered. For this simplified system, a feedback controller which is compatible with the modular construction method is described. The systems dynamics are decomposed into two parts corresponding to base and module. The information structure of the problem is non-classical in that not all system information is supplied to each controller. The base controller is designed to accommodate structural changes that occur as the module is added and the module controller is designed to regulate its own states and follow commands from the base. Overall stability of the system is checked by Liapunov analysis and controller effectiveness is verified by computer simulation.

  14. Attitude Determination and Control Subsystem (ADCS) Preparations for the EPOXI Flyby of Comet Haley 2

    NASA Technical Reports Server (NTRS)

    Luna, Michael E.; Collins, Stephen M.

    2011-01-01

    On November 4, 2010 the already "in-flight" Deep Impact spacecraft flew within 700km of comet 103P/Hartley 2 as part of its extended mission EPOXI, the 5th time to date any spacecraft visited a comet. In 2005, the spacecraft had previously imaged a probe impact comet Tempel 1. The EPOXI flyby marked the first time in history that two comets were explored with the same instruments on a re-used spacecraft-with hardware and software originally designed and optimized for a different mission. This made the function of the attitude determination and control subsystem (ADCS) critical to the successful execution of the EPOXI flyby. As part of the spacecraft team preparations, the ADCS team had to perform thorough sequence reviews, key spacecraft activities and onboard calibrations. These activities included: review of background sequences for the initial conditions vector, sun sensor coefficients, and reaction wheel assembly (RWA) de-saturations; design and execution of 10 trajectory correction maneuvers; science calibration of the two telescope instruments; a flight demonstration of the fastest turns conducted by the spacecraft between Earth and comet point; and assessment of RWA health (given RWA problems on other spacecraft).

  15. Coupled Attitude and Orbit Dynamics and Control in Formation Flying Systems

    NASA Technical Reports Server (NTRS)

    Xu, Yun-Jun; Fitz-Coy, Norman; Mason, Paul

    2003-01-01

    Formation flying systems can range from global constellations offering extended service coverage to clusters of highly coordinated vehicles that perform distributed sensing. Recently, the use of groups of micro-satellites in the areas of near Earth explorations, deep space explorations, and military applications has received considerable attention by researchers and practitioners. To date, most proposed control strategies are based on linear models (e.g., Hill-Clohessy-Wiltshire equations) or nonlinear models that are restricted to circular reference orbits. Also, all models in the literature are uncoupled between relative position and relative attitude. In this paper, a generalized dynamic model is proposed. The reference orbit is not restricted to the circular case. In this formulation, the leader or follower satellite can be in either a circular or an elliptic orbit. In addition to maintaining a specified relative position, the satellites are also required to maintain specified relative attitudes. Thus the model presented couples vehicle attitude and orbit requirements. Orbit perturbations are also included. In particular, the J(sub 2) effects are accounted in the model. Finally, a sliding mode controller is developed and used to control the relative attitude of the formation and the simulation results are presented.

  16. Spacecraft attitude maneuver using two single-gimbal control moment gyros

    NASA Astrophysics Data System (ADS)

    Kasai, Shinya; Kojima, Hirohisa; Satoh, Mitsunori

    2013-03-01

    In this paper, arbitrary rest-to-rest attitude maneuver problems for a satellite using two single-gimbal control moment gyros (2SGCMGs) are considered. Although single-gimbal control moment gyros are configured in the same manner as the traditional pyramid-array CMG, only two CMGs are assumed to be available. Attitude maneuver problems are similar to problems involving two reaction wheels (RWs) from the viewpoint of the number of actuators. In other words, the problem treated herein is a kind of underactuated problem. Although 2SGCMGs can generate torques around all axes, they cannot generate torques around each axis independently. Therefore, control methods designed for a satellite using two reaction wheels cannot be applied to three-axis attitude maneuver problems for a satellite using 2SGCMGs. In this paper, for simplicity, maneuvers around the x- and z-axes are first considered, and then a maneuver around the y-axis due to the corning effect resulting from the maneuver around the x- and z-axes is considered. Since maneuvers around each axis are established by the proposed method, arbitrary attitude maneuvers can be achieved using 2SGCMGs. In addition, the maneuvering angles around the z- and x-axes, which are required in order to maneuver around the y-axis, are analytically determined, and the total time required for maneuvering around the y-axis is then analyzed numerically.

  17. Functional evaluation of the Galileo attitude and articulation control subsystem using FUNSIM. [Functional Simulator

    NASA Technical Reports Server (NTRS)

    Namiri, M. K.

    1984-01-01

    The functional performance of the Galileo spacecraft's attitude and articulation control subsystem is evaluated. The tests are performed utilizing the simulation program developed on an IBM 370 system known as the Functional Simulation (FUNSIM). FUNSIM is an entirely software-based simulation which uses the actual flight software in HAL/S and simulated spacecraft dynamics in FORTRAN language. A description of how the test cases were selected to verify that the algorithms perform functionally correctly, and a summary of the problems encountered are included in the paper. The benefits of having an alternative test bed such as FUNSIM to the real-time simulation test beds which utilize the spacecraft hardware components in discovering the problems are described. A sample test case which shows that the desired tasks were performed functionally correctly is included in the paper. The commands in this test are selected to start the dual-spin spacecraft initially in launch mode and lead it all the way to inertial mode. Major attitude control algorithms such as rotor and platform attitude estimators, clock and core platform attitude estimators, clock and core platform controllers, and the command turn and burn are examined.

  18. Attitude control system design of a satellite with a magnetically suspended momentum wheel based on two-degree-of-freedom control system theory

    NASA Astrophysics Data System (ADS)

    Hashimoto, T.; Hamasaki, T.; Nakatani, I.; Ninomiya, K.

    By adopting as an actuator a momentum wheel with fully actively controlled magnetic bearings, abbreviated as MBMW hereafter, three-axis-attitude of a satellite can be controlled efficiently by one single wheel. This usually contributes to the system-weight reduction. However, a magnetic bearing system is inherently nonlinear and bias current is normally required to linearize the bearing characteristics, causing increased power consumption in the suspension system. In this paper, by applying the so-called two-DOF control system theory and introducing complex state-variables to seemingly reduce the dimension of the system, we formulate and propose a design method of both an attitude control system of a satellite adopting a MBMW and a control scheme of the MBMW bearing-system, for which the nonlinearity of magnetic bearings is compensated by the robust controller. The proposed approach provides an explicit design method for a high-performance pointing control system for a class of three-axis stabilized satellites. The usefulness of the design method and the effectiveness of the control system are confirmed by computer simulations for a high energy solar physics observation mission.

  19. Robust adaptive relative position and attitude control for spacecraft autonomous proximity.

    PubMed

    Sun, Liang; Huo, Wei; Jiao, Zongxia

    2016-07-01

    This paper provides new results of the dynamical modeling and controller designing for autonomous close proximity phase during rendezvous and docking in the presence of kinematic couplings and model uncertainties. A globally defined relative motion mechanical model for close proximity operations is introduced firstly. Then, in spite of the kinematic couplings and thrust misalignment between relative rotation and relative translation, robust adaptive relative position and relative attitude controllers are designed successively. Finally, stability of the overall system is proved that the relative position and relative attitude are uniformly ultimately bounded, and the size of the ultimate bound can be regulated small enough by control system parameters. Performance of the controlled overall system is demonstrated via a representative numerical example. PMID:26993103

  20. In-flight measured human pilot describing function and remnant for pitch attitude control

    NASA Technical Reports Server (NTRS)

    Mooij, H. A.

    1973-01-01

    Flight tests have been performed with a variable pitch-rate-command/attitude-hold flight control system in a Beechoraft Queen air-80 aircraft. Some results of in-flight measured runs for two pilots controlling typical easy and difficult dynamics are presented together with the initial results of the same tracking experiment performed on a ground-based flight simulator. Results are compared with results of other investigators using fixed-base flight simulators.

  1. Spacecraft attitude pulse-width control at initial, service and emergency modes

    NASA Astrophysics Data System (ADS)

    Somov, Sergey

    2012-11-01

    Problems of nonlinear modeling, dynamic analysis and simulation of spatial motion by a spacecraft with a flexible weak damping structure, are considered. Attitude motion of a flexible spacecraft with pulse-width control, spin-up rotors of six single-gimbal control moment gyros (CMGs) at the initial, service and emergency modes, is studied. Results on analysis of the spacecraft nutation and flexible oscillations, are represented.

  2. Performance quantification of heliogyro solar sails using structural, attitude, and orbital dynamics and control analysis

    NASA Astrophysics Data System (ADS)

    Guerrant, Daniel Vernon

    Solar sails enable or enhance exploration of a variety of destinations both within and without the solar system. The heliogyro solar sail architecture divides the sail into blades spun about a central hub and centrifugally stiffened. The resulting structural mass savings can often double acceleration verses kite-type square sails of the same mass. Pitching the blades collectively and cyclically, similar to a helicopter, creates attitude control moments and vectors thrust. The principal hurdle preventing heliogyros' implementation is the uncertainty in their dynamics. This thesis investigates attitude, orbital and structural control using a combination of analytical studies and simulations. Furthermore, it quantifies the heliogyro's ability to create attitude control moments, change the thrust direction, and stably actuate blade pitch. This provides engineers a toolbox from which to estimate the heliogyro's performance and perform trades during preliminary mission design. It is shown that heliogyros can create an attitude control moment in any direction from any orientation. While their large angular momentum limits attitude slewing to only a few degrees per hour, cyclic blade pitching can slew the thrust vector within a few minutes. This approach is only 13% less efficient than slewing a square sail during Earth escape, so it does not offset the overall acceleration benefits of heliogyros. Lastly, a root pitch motor should be able to settle torsional disturbances within a few rotations and achieve thrust performance comparable to that of flat blades. This work found no significant dynamic hurdles for heliogyros, and it provides key insight into their practical capabilities and limitations for future mission designers.

  3. Application of fuzzy logic-neural network based reinforcement learning to proximity and docking operations: Attitude control results

    NASA Technical Reports Server (NTRS)

    Jani, Yashvant

    1992-01-01

    As part of the RICIS activity, the reinforcement learning techniques developed at Ames Research Center are being applied to proximity and docking operations using the Shuttle and Solar Max satellite simulation. This activity is carried out in the software technology laboratory utilizing the Orbital Operations Simulator (OOS). This report is deliverable D2 Altitude Control Results and provides the status of the project after four months of activities and outlines the future plans. In section 2 we describe the Fuzzy-Learner system for the attitude control functions. In section 3, we provide the description of test cases and results in a chronological order. In section 4, we have summarized our results and conclusions. Our future plans and recommendations are provided in section 5.

  4. Active control of convection

    SciTech Connect

    Bau, H.H.

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  5. Adaptive attitude controller for a satellite based on neural network in the presence of unknown external disturbances and actuator faults

    NASA Astrophysics Data System (ADS)

    Fazlyab, Ali Reza; Fani Saberi, Farhad; Kabganian, Mansour

    2016-01-01

    In this paper, an adaptive attitude control algorithm is developed based on neural network for a satellite. The proposed attitude control is based on nonlinear modified Rodrigues parameters feedback control in the presence of unknown terms like external disturbances and actuator faults. In order to eliminate the effect of the uncertainties, a multilayer neural network with a new learning rule will be designed appropriately. In this method, asymptotic stability of the proposed algorithm has been proven in the presence of unknown terms based on Lyapunov stability theorem. Finally, the performance of the designed attitude controller is investigated by simulations.

  6. The combined energy and attitude control system for small satellites—Earth observation missions

    NASA Astrophysics Data System (ADS)

    Varatharajoo, Renuganth; Fasoulas, Stefanos

    2005-01-01

    Small satellites are becoming the preferred option for low-cost Earth observation missions. However, the projected requirements have increased for the missions, which require more sophisticated and additional payloads nowadays. As a result, this would most probably be cumbersome and critical for the overall satellite mass/volume budgets. In this article, the idea of combining the energy storage and attitude control systems is presented in order to reduce the number of subsystems onboard. Such a system consists of a double counterrotating flywheel unit serving simultaneously for the satellite energy and attitude management. First, numerical treatments were conducted for the rotors to determine a failure-free condition corresponding to their stresses and natural frequencies. Further, the mathematical models describing the energy and attitude control are established, and the system onboard architecture is implemented. Numerical simulations for the developed architecture were conducted taking into account the ideal and non-ideal cases. The simulation results are discussed especially from the energy and attitude standpoints. The system performance complies with the mission requirements. Thus, this end-to-end system demonstration indicates that the combined system is judiciously feasible, and is a potential combined subsystem for small satellites.

  7. Adaptive Attitude Control of the Crew Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Muse, Jonathan

    2010-01-01

    An H(sub infinity)-NMA architecture for the Crew Launch Vehicle was developed in a state feedback setting. The minimal complexity adaptive law was shown to improve base line performance relative to a performance metric based on Crew Launch Vehicle design requirements for all most all of the Worst-on-Worst dispersion cases. The adaptive law was able to maintain stability for some dispersions that are unstable with the nominal control law. Due to the nature of the H(sub infinity)-NMA architecture, the augmented adaptive control signal has low bandwidth which is a great benefit for a manned launch vehicle.

  8. A Coupled Nonlinear Spacecraft Attitude Controller and Observer with an Unknown Gyro Misalignment and Gyro Bias

    NASA Technical Reports Server (NTRS)

    Thienel, Julie; Sanner, Robert M.

    2002-01-01

    A nonlinear control scheme for attitude control of a spacecraft is combined with a nonlinear gyro misalignment and bias observer for the case of constant gyro misalignment and bias. A persistency of excitation analysis shows the observer gyro bias estimates converge to the true bias values exponentially fast. The convergence of the misalignment estimates is also presented. Then; the resulting coupled, closed loop dynamics are proven by a Lyapunov analysis to be globally stable, with asymptotically perfect tracking. The analysis is extended to consider the effects of noise in addition to the gyro misalignment and bias. A simulation of the proposed observer-controller design is given for a rigid spacecraft tracking a specified, time-varying attitude sequence to illustrate the theoretical claims.

  9. [Attitude and perceived control of the elderly towards the consumption of anxiolytic, sedative and hypnotic medications].

    PubMed

    Guindon, Marilyn; Cappeliez, Philippe

    2011-03-01

    This study examines the importance of variables from the Theory of Planned Behaviour (i.e., attitudes toward behaviour, subjective norms, and perceived control) for the prediction of consumption of anxiolytic and sedative-hypnotic (ASH) medications in a sample of older persons, aged 69 years on average, 62 consumers and 92 non-consumers. A favourable attitude toward ASH and a sense of having less control regarding these drugs predict both current usage and intention to continue. Perceived control predicts intention to start consumption of ASH in current non-consumers. This study underlines the importance of considering the role of the older person's decisional power in the consumption of these medications. PMID:21470438

  10. Development of a Hardware-In-Loop (HIL) Simulator for Spacecraft Attitude Control Using Momentum Wheels

    NASA Astrophysics Data System (ADS)

    Kim, Dohee; Park, Sang-Young; Kim, Jong-Woo; Choi, Kyu-Hong

    2008-12-01

    In this paper, a Hardware-In-the-Loop simulator to simulate attitude control of spacecraft using momentum wheels is developed. The simulator consists of a spherical air bearing system allowing rotation and tilt in all three axes, three momentum wheels for actuation, and an AHRS (Attitude Heading Reference System). The simulator processes various types of data in PC104 and wirelessly communicates with a host PC using TCP/IP protocol. A simple low-cost momentum wheel assembly set and its drive electronics are also developed. Several experiments are performed to test the performance of the momentum wheels. For the control performance test of the simulator, a PID controller is implemented. The results of experimental demonstrations confirm the feasibility and validity of the Hardware-In-the-Loop simulator developed in the current study.

  11. Active weld control

    NASA Technical Reports Server (NTRS)

    Powell, Bradley W.; Burroughs, Ivan A.

    1994-01-01

    Through the two phases of this contract, sensors for welding applications and parameter extraction algorithms have been developed. These sensors form the foundation of a weld control system which can provide action weld control through the monitoring of the weld pool and keyhole in a VPPA welding process. Systems of this type offer the potential of quality enhancement and cost reduction (minimization of rework on faulty welds) for high-integrity welding applications. Sensors for preweld and postweld inspection, weld pool monitoring, keyhole/weld wire entry monitoring, and seam tracking were developed. Algorithms for signal extraction were also developed and analyzed to determine their application to an adaptive weld control system. The following sections discuss findings for each of the three sensors developed under this contract: (1) weld profiling sensor; (2) weld pool sensor; and (3) stereo seam tracker/keyhole imaging sensor. Hardened versions of these sensors were designed and built under this contract. A control system, described later, was developed on a multiprocessing/multitasking operating system for maximum power and flexibility. Documentation for sensor mechanical and electrical design is also included as appendices in this report.

  12. Design of the EO-1 Pulsed Plasma Thruster Attitude Control Experiment

    NASA Technical Reports Server (NTRS)

    Zakrzwski, Charles; Sanneman, Paul; Hunt, Teresa; Blackman, Kathie; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    The Pulsed Plasma Thruster (PPT) Experiment on the Earth Observing 1 (EO-1) spacecraft has been designed to demonstrate the capability of a new generation PPT to perform spacecraft attitude control. The PPT is a small, self-contained pulsed electromagnetic Propulsion system capable of delivering high specific impulse (900-1200 s), very small impulse bits (10-1000 micro N-s) at low average power (less than 1 to 100 W). EO-1 has a single PPT that can produce torque in either the positive or negative pitch direction. For the PPT in-flight experiment, the pitch reaction wheel will be replaced by the PPT during nominal EO-1 nadir pointing. A PPT specific proportional-integral-derivative (PID) control algorithm was developed for the experiment. High fidelity simulations of the spacecraft attitude control capability using the PPT were conducted. The simulations, which showed PPT control performance within acceptable mission limits, will be used as the benchmark for on-orbit performance. The flight validation will demonstrate the ability of the PPT to provide precision pointing resolution. response and stability as an attitude control actuator.

  13. Attitude control system design using a flywheel suspended by two gimbals

    NASA Astrophysics Data System (ADS)

    Peres, R. W.; Ricci, M. C.

    2015-10-01

    This work presents the attitude control system design procedures for a three axis stabilized satellite in geostationary orbit, which contains a flywheel suspended by two gimbals. The use of a flywheel with two DOFs is an interesting option because with only one device it's possible to control the torques about vehicle's three axes; through the wheel speed control and gyrotorquing phenomenon with two DOFs. If the wheel size and speed are determined properly it's possible to cancel cyclic torques using gas jets only periodically to cancel secular disturbance torques. The system, based on a flywheel, takes only one pitch/roll (earth) sensor to maintain precise attitude, unlike mass expulsion based control systems, which uses propellants continuously, beyond roll, pitch and yaw sensors. It is considered the satellite is in nominal orbit and, therefore, that the attitude's acquisition phase has already elapsed. Control laws and system parameters are determined in order to cancel the solar pressure radiation disturbance torque and the torque due to misalignment of the thrusters. Stability is analyzed and step and cyclic responses are obtained.

  14. Physical Performance, Sex, and Race as Factors in the Attitude of Intermediate School Children Toward Physical Activity.

    ERIC Educational Resources Information Center

    Greensley, Roy J.; Gronbech, C. Eric

    For this study, the physical performance levels of 73 children in grades 4-6 were assessed, and each individual was administered an adaptation of Kenyon's Attitude Toward Physical Activity (ATPA) survey. This instrument measured selected attitudes related to physical activities: social, health and fitness, risk, aesthetic, catharsis, ascetic,…

  15. Assessing General and Specific Attitudes in Human Learning Behavior: An Activity Perspective and a Multilevel Modeling Approach

    ERIC Educational Resources Information Center

    Sun, Jun; Willson, Victor L.

    2008-01-01

    This article proposes a multilevel modeling approach to study the general and specific attitudes formed in human learning behavior. Based on the premises of activity theory, it conceptualizes the unit of analysis for attitude measurement as a scalable and evolving activity system rather than a single action. Measurement issues related to this…

  16. A ground test program to support condition monitoring of a spacecraft attitude control propulsion system

    NASA Technical Reports Server (NTRS)

    Clark, Douglas J.; Lester, Robert W.; Baroth, Edmund C.; Coleman, Arthur L.

    1991-01-01

    The Comet Rendezvous Asteroid Flyby (CRAF) mission involves seven years of flight from 0.6 to 4.57 Astronomical Units (AU), followed by about 915 days of maneuvering around a comet. Ground testing will characterize the very critical attitude control system thrusters' fuel consumption and performance for all anticipated fuel temperatures over thruster life. The ground test program characterization will support flight condition monitoring. A commercial software application hosted on a commercial microcomputer will control ground test operations and data acquisition using a newly designed thrust stand. The data acquisition and control system uses a graphics-based language and features a visual interface to integrate data acquisition and control.

  17. The Role of Biographical Characteristics in Preservice Classroom Teachers' School Physical Activity Promotion Attitudes

    ERIC Educational Resources Information Center

    Webster, Collin A.; Monsma, Eva; Erwin, Heather E.

    2010-01-01

    Recommendations for increasing children's daily physical activity (PA) call on classroom teachers to assume an activist role at school. This study examined relationships among preservice classroom teachers' (PCT; n = 247) biographical characteristics, perceptions and attitudes regarding school PA promotion (SPAP). Results indicated participants…

  18. Knowledge, Attitudes and Practices of Clinicians in Promoting Physical Activity to Prostate Cancer Survivors

    ERIC Educational Resources Information Center

    Spellman, Claire; Craike, Melinda; Livingston, Patricia M.

    2014-01-01

    Objectives: This study examined the knowledge, attitudes and practices of clinicians in promoting physical activity to prostate cancer survivors. Design: A purposeful sample was used and cross-sectional data were collected using an anonymous, self-reported online questionnaire or an identical paper-based questionnaire. Settings: Health services…

  19. Factors Influencing Attitudes toward Sexual Activity among Early Adolescents in Japan

    ERIC Educational Resources Information Center

    Nagamatsu, Miyuki; Yamawaki, Niwako; Sato, Takeshi; Nakagawa, Aki; Saito, Hisako

    2013-01-01

    The purpose of this study was to examine factors influencing attitudes toward sexual activity among early adolescents in Japan. A total of 1,551 students aged 12 to 14 years at 4 junior high schools were divided into either a conservative or liberal group. Results of chi-square tests showed that the liberal group had higher percentages of students…

  20. Investigating Pre-Service Early Childhood Teachers' Attitudes towards the Computer Based Education in Science Activities

    ERIC Educational Resources Information Center

    Yilmaz, Nursel; Alici, Sule

    2011-01-01

    The purpose of this study was to investigate pre-service early childhood teachers' attitudes towards using Computer Based Education (CBE) while implementing science activities. More specifically, the present study examined the effect of different variables such as gender, year in program, experience in preschool, owing a computer, and the…

  1. Attitudes toward the Participation of Individuals with Disabilities in Physical Activity: A Review

    ERIC Educational Resources Information Center

    Hutzler, Yeshayahu

    2003-01-01

    This review covers articles published during the recent two decades on attitudes toward the participation of individuals with disabilities in physical activity. Research literature has been retrieved and analyzed by content and quality, across research type categories (cross sectional vs. intervention) and members of the participation context…

  2. Investigating Learner Attitudes toward E-Books as Learning Tools: Based on the Activity Theory Approach

    ERIC Educational Resources Information Center

    Liaw, Shu-Sheng; Huang, Hsiu-Mei

    2016-01-01

    This paper investigates the use of e-books as learning tools in terms of learner satisfaction, usefulness, behavioral intention, and learning effectiveness. Based on the activity theory approach, this research develops a research model to understand learner attitudes toward e-books in two physical sizes: 10? and 7?. Results suggest that screen…

  3. Physical Education Teacher Attitudes towards the Effectiveness of Sport Activities in Northern-East Badia

    ERIC Educational Resources Information Center

    Al-Oun, Ismael Sood

    2015-01-01

    The purpose of this study is to investigate physical education teacher attitudes towards the effectiveness of sport activities in north-east Badia. The study population consisted of all teachers of physical education who are studying curriculum of physical education in schools affiliated to the Directorate of Education of the brigade desert…

  4. Science Attitude Change in Preservice Elementary Teachers during an Activity-Oriented Biology Course.

    ERIC Educational Resources Information Center

    Kramer, David C.

    1979-01-01

    Investigates the effect of an activity-oriented biology course on the science attitudes of preservice elementary teachers. Forty-nine students enrolled in this course during the winter and spring quarter of 1977 at St. Cloud State University, Minnesota participated in this study. (HM)

  5. Inquiry-Based Laboratory Activities in Electrochemistry: High School Students' Achievements and Attitudes

    ERIC Educational Resources Information Center

    Sesen, Burcin Acar; Tarhan, Leman

    2013-01-01

    This study aimed to investigate the effects of inquiry-based laboratory activities on high school students' understanding of electrochemistry and attitudes towards chemistry and laboratory work. The participants were 62 high school students (average age 17 years) in an urban public high school in Turkey. Students were assigned to experimental (N =…

  6. Active Control of Engine Dynamics

    NASA Astrophysics Data System (ADS)

    2002-11-01

    Active control can alleviate design constraints and improve the response to operational requirements in gas turbines. The Course presented the state-of-the-art including experimental, theoretical knowledge and practical information. Topics treated: stability characteristics; active control approaches; robustness and fundamental limits; combustion systems processes; combustor dynamics; compression system dynamics models; diagnostics and control of compression instabilities; sensor and actuator architectures; R&D needs of future prospects. The course has shown that for combustion systems, as well as in actuator and sensor technologies the active control approach is a viable option even at full scale with potential for aero engines and air breathing missiles.

  7. Attitude Determination and Control Subsystem (ADCS) Preparations for the EPOXI Flyby of Comet Hartley 2

    NASA Technical Reports Server (NTRS)

    Luna, Michael E.; Collins, Steven M.

    2011-01-01

    On November 4, 2010 the former "Deep Impact" spacecraft, renamed "EPOXI" for its extended mission, flew within 700km of comet 103P/Hartley 2. In July 2005, the spacecraft had previously imaged a probe impact of comet Tempel 1. The EPOXI flyby was the fifth close encounter of a spacecraft with a comet nucleus and marked the first time in history that two comet nuclei were imaged at close range with the same suite of onboard science instruments. This challenging objective made the function of the attitude determination and control subsystem (ADCS) critical to the successful execution of the EPOXI flyby.As part of the spacecraft flyby preparations, the ADCS operations team had to perform meticulous sequence reviews, implement complex spacecraft engineering and science activities and perform numerous onboard calibrations. ADCS contributions included design and execution of 10 trajectory correction maneuvers, the science calibration of the two telescopic instruments, an in-flight demonstration of high-rate turns between Earth and comet point, and an ongoing assessment of reaction wheel health. The ADCS team was also responsible for command sequences that included updates to the onboard ephemeris and sun sensor coefficients and implementation of reaction wheel assembly (RWA) de-saturations.

  8. Some optimal considerations in attitude control systems. [evaluation of value of relative weighting between time and fuel for relay control law

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III

    1973-01-01

    The conventional six-engine reaction control jet relay attitude control law with deadband is shown to be a good linear approximation to a weighted time-fuel optimal control law. Techniques for evaluating the value of the relative weighting between time and fuel for a particular relay control law is studied along with techniques to interrelate other parameters for the two control laws. Vehicle attitude control laws employing control moment gyros are then investigated. Steering laws obtained from the expression for the reaction torque of the gyro configuration are compared to a total optimal attitude control law that is derived from optimal linear regulator theory. This total optimal attitude control law has computational disadvantages in the solving of the matrix Riccati equation. Several computational algorithms for solving the matrix Riccati equation are investigated with respect to accuracy, computational storage requirements, and computational speed.

  9. Attitudes toward physical activity and exercise: comparison of memory clinic patients and their caregivers and prediction of activity levels.

    PubMed

    O'Connell, Megan E; Dal Bello-Haas, Vanina; Crossley, Margaret; Morgan, Debra G

    2015-01-01

    Regular physical activity and exercise (PA&E) reduces cognitive aging, may delay dementia onset, and for persons with dementia, may slow progression and improve quality of life. Memory clinic patients and caregivers described their PA&E and completed the Older Persons' Attitudes Toward Physical Activity and Exercise Questionnaire (OPAPAEQ). Caregivers and patients differed in their PA&E attitudes: patients were less likely to believe in the importance of PA&E for health promotion. PA&E attitudes were explored as predictors of self-reported exercise habits. Belief in the importance of high intensity exercise for health maintenance was the only variable that significantly predicted engagement in regular PA&E. Moreover, caregivers' attitudes toward high intensity exercise predicted memory patients' participation in PA&E. These findings may aid in development of exercise interventions for people with memory problems, and suggest that modification of specific attitudes toward exercise is an important component to ensure maximum participation and engagement in PA&E. PMID:24451476

  10. Design of a high density cold gas attitude control system

    NASA Technical Reports Server (NTRS)

    Hall, Sarah E.; Lewis, Mark J.; Akin, David L.

    1993-01-01

    A comparison of the experimental results of a nitrous oxide cold gas thruster with the predicted performance from a numerical simulation of nozzle operations is discussed. Tests were conducted in a vacuum chamber to verify analytical predictions of both nitrogen and nitrous oxide. Preliminary results indicate an Isp for N2O of 61, and an Isp of 69 for N2. Based on the results of this research, parameters are presented for a nitrous oxide-based reaction control system for a small spacecraft currently under development.

  11. Air-bearing-based satellite attitude dynamics simulator for control software research and development

    NASA Astrophysics Data System (ADS)

    Agrawal, Brij N.; Rasmussen, Richard E.

    2001-08-01

    A Satellite Attitude Dynamics Simulator (SADS) has been developed to facilitate the research and development of spacecraft flight attitude control software at the Naval Postgraduate School in Monterey, CA. The simulator provides a real-time 3 degree of freedom (3DOF) synthetic spacecraft hardware-in-the-loop environment, that includes realistic angular motions, sensor-effector delays, and control torque profiles. Control software, entered into a notebook PC mounted on the equipment platform, is input as high level object oriented code, allowing rapid code development and thorough post-test analysis. Three flight-like reaction wheels and eight cold-gas thrusters that are mounted to the SADS equipment platform provide motion simulation torque. The equipment platform is suspended in air by a spherical segment air bearing. This virtually frictionless suspension allows free rotation of the equipment platform about any rotation axis. Three separate sets of sensors, three single-axis rate gyros, a three-axis magnetometer, and a two-axis sun sensor monitor SADS platform motion. This paper discusses the SADS design, and the practical uses of this simulator for satellite attitude control system software research and development.

  12. Inertial attitude control of a bat-like morphing-wing air vehicle.

    PubMed

    Colorado, J; Barrientos, A; Rossi, C; Parra, C

    2013-03-01

    This paper presents a novel bat-like unmanned aerial vehicle inspired by the morphing-wing mechanism of bats. The goal of this paper is twofold. Firstly, a modelling framework is introduced for analysing how the robot should manoeuvre by means of changing wing morphology. This allows the definition of requirements for achieving forward and turning flight according to the kinematics of the wing modulation. Secondly, an attitude controller named backstepping+DAF is proposed. Motivated by biological evidence about the influence of wing inertia on the production of body accelerations, the attitude control law incorporates wing inertia information to produce desired roll (ϕ) and pitch (θ) acceleration commands (desired angular acceleration function (DAF)). This novel control approach is aimed at incrementing net body forces (F(net)) that generate propulsion. Simulations and wind-tunnel experimental results have shown an increase of about 23% in net body force production during the wingbeat cycle when the wings are modulated using the DAF as a part of the backstepping control law. Results also confirm accurate attitude tracking in spite of high external disturbances generated by aerodynamic loads at airspeeds up to 5 ms⁻¹. PMID:23211685

  13. Effect of an institutional development plan for user participation on professionals' knowledge, practice, and attitudes. A controlled study

    PubMed Central

    2011-01-01

    Background Governments in several countries attempt to strengthen user participation through instructing health care organisations to plan and implement activities such as user representation in administrational boards, improved information to users, and more individual user participation in clinical work. The professionals are central in implementing initiatives to enhance user participation in organisations, but no controlled studies have been conducted on the effect on professionals from implementing institutional development plans. The objective was to investigate whether implementing a development plan intending to enhance user participation in a mental health hospital had any effect on the professionals' knowledge, practice, or attitudes towards user participation. Methods This was a non-randomized controlled study including professionals from three mental health hospitals in Central Norway. A development plan intended to enhance user participation was implemented in one of the hospitals as a part of a larger re-organizational process. The plan included i.e. establishing a patient education centre and a user office, purchasing of user expertise, appointing contact professionals for next of kin, and improving of the centre's information and the professional culture. The professionals at the intervention hospital thus constituted the intervention group, while the professionals at two other hospitals participated as control group. All professionals were invited to answer the Consumer Participation Questionnaire (CPQ) and additional questions, focusing on knowledge, practice, and attitudes towards user participation, two times with a 16 months interval. Results A total of 438 professionals participated (55% response rate). Comparing the changes in the intervention group with the changes in the control group revealed no statistically significant differences at a 0.05 level. The implementation of the development plan thus had no measurable effect on the

  14. Enhancing Primary School Students' Knowledge about Global Warming and Environmental Attitude Using Climate Change Activities

    NASA Astrophysics Data System (ADS)

    Karpudewan, Mageswary; Roth, Wolff-Michael; Abdullah, Mohd Nor Syahrir Bin

    2015-01-01

    Climate change generally and global warming specifically have become a common feature of the daily news. Due to widespread recognition of the adverse consequences of climate change on human lives, concerted societal effort has been taken to address it (e.g. by means of the science curriculum). This study was designed to test the effect that child-centred, 5E learning cycle-based climate change activities would have over more traditional teacher-centred activities on Malaysian Year 5 primary students (11 years). A quasi-experimental design involving a treatment (n = 55) and a group representing typical teaching method (n = 60) was used to measure the effectiveness of these activities on (a) increasing children's knowledge about global warming; (b) changing their attitudes to be more favourable towards the environment and (c) identify the relationship between knowledge and attitude that exist in this study. Statistically significant differences in favour of the treatment group were detected for both knowledge and environmental attitudes. Non-significant relationship was identified between knowledge and attitude in this study. Interviews with randomly selected students from treatment and comparison groups further underscore these findings. Implications are discussed.

  15. Leisure activities and attitude of institutionalized elderly people: a basis for nursing practice1

    PubMed Central

    de Castro, Vivian Carla; Carreira, Lígia

    2015-01-01

    Aim: to identify the leisure activities performed in Long-Stay Institutions for the Elderly (LSIEs), registered in the city of Maringá-PR, Brazil, and to analyze the attitude of the elderly people toward leisure promoted by the institutions. METHOD: this was a descriptive and transversal study with a quantitative approach, carried out with 97 elderly people, through the establishment of the socio-demographic profile and the application of the Leisure Attitude Scale. The data was subjected to descriptive statistical analysis, association tests (chi-square or Fisher's) and Spearman's correlation. RESULTS: males, aged 80 or over, widowed, with one to eight years of study, who had a monthly income were predominant. Age group and income were significantly associated with the performance of leisure activities. The results reflected the positive attitude of the elderly people in relation to leisure activities, except in the behavioral component. CONCLUSION: the findings of this study indicate the need for further investigation into the difficulties linked to the attitude toward leisure in the behavioral component, considering aspects such as individual concepts of leisure and the health status of the elderly people. PMID:26039302

  16. Design study for LANDSAT-D attitude control system

    NASA Technical Reports Server (NTRS)

    Iwens, R. P.; Bernier, G. E.; Hofstadter, R. F.; Mayo, R. A.; Nakano, H.

    1977-01-01

    The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse.

  17. Analysis of Pan-European attitudes to the eradication and control of bovine viral diarrhoea.

    PubMed

    Heffernan, C; Misturelli, F; Nielsen, L; Gunn, G J; Yu, J

    2009-02-01

    At present, national-level policies concerning the eradication and control of bovine viral diarrhoea (BVD) differ widely across Europe. Some Scandinavian countries have enacted strong regulatory frameworks to eradicate the disease, whereas other countries have few formal policies. To examine these differences, the attitudes of stakeholders and policy makers in 17 European countries were investigated. A web-based questionnaire was sent to policy makers, government and private sector veterinarians, and representatives of farmers' organisations. In total, 131 individuals responded to the questionnaire and their responses were analysed by applying a method used in sociolinguistics: frame analysis. The results showed that the different attitudes of countries that applied compulsory or voluntary frameworks were associated with different views about the attribution or blame for BVD and the roles ascribed to farmers and other stakeholders in its eradication and control. PMID:19202168

  18. Attitudes towards smoking and tobacco control among pre-clinical medical students in Malaysia.

    PubMed

    Tee, G H; Hairi, N N; Hairi, F

    2012-08-01

    Physicians should play a leading role in combatting smoking; information on attitudes of future physicians towards tobacco control measures in a middle-income developing country is limited. Of 310 future physicians surveyed in a medical school in Malaysia, 50% disagreed that it was a doctor's duty to advise smokers to stop smoking; 76.8% agreed that physicians should not smoke before advising others not to smoke; and 75% agreed to the ideas of restricting the sale of cigarettes to minors, making all public places smoke-free and banning advertising of tobacco-related merchandise. Future physicians had positive attitudes towards tobacco regulations but had not grasped their responsibilities in tobacco control measures. PMID:22668450

  19. Simulation and simulator development of a separate surface attitude command control system for light aircraft

    NASA Technical Reports Server (NTRS)

    Roskam, J.

    1976-01-01

    A detailed description is presented of the simulation philosophy and process used in the development of a Separate Surface Attitude Command control system (SSAC) for a Beech Model 99 Airliner. The intent of this system is to provide complete three axes stability augmentation at low cost and without the need for system redundancy. The system, although aimed at the general aviation market, also has applications to certain military airplanes as well as to miniature submarines.

  20. Development of a coupled expert system for the spacecraft attitude control problem

    NASA Technical Reports Server (NTRS)

    Kawamura, K.; Beale, G.; Schaffer, J.; Hsieh, B.-J.; Padalkar, S.; Rodriguezmoscoso, J.; Vinz, F.; Fernandez, K.

    1987-01-01

    A majority of the current expert systems focus on the symbolic-oriented logic and inference mechanisms of artificial intelligence (AI). Common rule-based systems employ empirical associations and are not well suited to deal with problems often arising in engineering. Described is a prototype expert system which combines both symbolic and numeric computing. The expert system's configuration is presented and its application to a spacecraft attitude control problem is discussed.

  1. Geostationary Satellite (GSAT) Failure; an Analysis and Possible Attitude Control Remedy

    NASA Astrophysics Data System (ADS)

    Kumar, Krishna; Singh, Sanjay

    A geostationary satellite has reportedly failed during its orbit raising maneuvers from the GTO to its final stationary ring. It was felt that the failure was possibly caused by differential propellant rates of flow from the symmetrically placed pair of liquid tanks on either side of the center of mass. Alternatively even the initial fixed center-of-mass offset could have led to the same outcome. The investigation presented here models the problem as one of attitude motion by separately treating the system mass into two parts: fixed mass structure including the motor tanks and differentially shrinking bodies of liquid propellant. The system with variable mass is assumed to undergo pitching librations under the influence of thrust moments about the shifting center of mass in the orbital plane. The detailed numerical simulation is undertaken to assess the influence of pitching excitation caused by asymmetric thrusting. The effect of this attitude motion on possible reduction in velocity increment due to thrust misalignment is found to be quite significant. Besides some additional attitude control fuel may also be required to undo the pitching excitation. The simulation carried out here for the case of fixed center-of-mass offset leads to the same general adverse behavior. Finally, a suitable feedback control strategy proposed here is employed to regulate the differential flow rate in symmetrically placed pair of liquid tanks on either side of the center of mass in order to eliminate the adverse effect of the moving center of mass and instead make judicious use for attitude control. It is shown that the feedback control of fuel flow rate in this design with symmetrically laid liquid tanks can help in conserving the fuel, the precious commodity on board and thus significantly enhance the performance of orbit raising maneuvers and hence much higher reliability for mission success.

  2. A computer simulation of Skylab dynamics and attitude control for performance verification and operational support

    NASA Technical Reports Server (NTRS)

    Buchanan, H.; Nixon, D.; Joyce, R.

    1974-01-01

    A simulation of the Skylab attitude and pointing control system (APCS) is outlined and discussed. Implementation is via a large hybrid computer and includes those factors affecting system momentum management, propellant consumption, and overall vehicle performance. The important features of the flight system are discussed; the mathematical models necessary for this treatment are outlined; and the decisions involved in implementation are discussed. A brief summary of the goals and capabilities of this tool is also included.

  3. Analytic investigation of the AEM-A/HCMM attitude control system performance. [Application Explorer Missions/Heat Capacity Mapping Mission

    NASA Technical Reports Server (NTRS)

    Lerner, G. M.; Huang, W.; Shuster, M. D.

    1977-01-01

    The Heat Capacity Mapping Mission (HCMM), scheduled for launch in 1978, will be three-axis stabilized relative to the earth in a 600-kilometer altitude, polar orbit. The autonomous attitude control system consists of three torquing coils and a momentum wheel driven in response to error signals computed from data received from an infrared horizon sensor and a magnetometer. This paper presents a simple model of the attitude dynamics and derives the equations that determine the stability of the system during both attitude acquisition (acquisition-mode) and mission operations (mission-mode). Modifications to the proposed mission-mode control laws which speed the system's response to transient attitude errors and reduce the steady-state attitude errors are suggested. Numerical simulations are performed to validate the results obtained with the simple model.

  4. Cassini Attitude Control Flight Software: from Development to In-Flight Operation

    NASA Technical Reports Server (NTRS)

    Brown, Jay

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Flight Software (FSW) has achieved its intended design goals by successfully guiding and controlling the Cassini-Huygens planetary mission to Saturn and its moons. This paper describes an overview of AACS FSW details from early design, development, implementation, and test to its fruition of operating and maintaining spacecraft control over an eleven year prime mission. Starting from phases of FSW development, topics expand to FSW development methodology, achievements utilizing in-flight autonomy, and summarize lessons learned during flight operations which can be useful to FSW in current and future spacecraft missions.

  5. A high precision attitude determination and control system for the UYS-1 nanosatellite

    NASA Astrophysics Data System (ADS)

    Chaurais, J. R.; Ferreira, H. C.; Ishihara, J. Y.; Borges, R. A.; Kulabukhov, A. M.; Larin, V. A.; Belikov, V. V.

    This paper presents the design of a high precision attitude determination and control system for the UYS-1 Ukrainian nanosatellite. Its main task is the 3-axis stabilization with less than 0.5° angle errors, so the satellite may take high precision photos of Earth's surface. To accomplish this task, this system comprises a star tracker and three reaction wheels. To avoid external disturbances and actuators faults, a PD-type and a PID-type robust controllers are simulated and the results are compared to an empirically adjusted PD controller.

  6. A controlled experiment to evaluate the impact of summer research experiences on attitudes towards science in high school aged students

    NASA Astrophysics Data System (ADS)

    White, M. A.; Tcherednichenko, I.; Hamar, M.; Taylor, M. J.; Litizzette, L.

    2006-12-01

    United States funding agencies increasingly are supporting activities designed to increase the enrollment of United States high school students in science, math, or engineering careers. However, in many cases, the likely outcomes of educational activities are unknown. A common approach within the physical and natural sciences is to provide high school aged students with a summer research experience, with the expectation that such experiences will increase student interest in science, possibly as a career choice. With funding support from the National Aeronautics and Space Administration New Investigator Grant program, we conducted a controlled experiment to test this assumption. In collaboration with Mountain Crest High School in Logan, UT, we recruited 40 students currently enrolled in science courses, assessed attitudes towards science (with informed consent), and randomly assigned 20 students to a control group and 20 students to an experimental group. Students in the experimental group were paired with faculty and graduate students in a wide range of field and laboratory research groups in natural resources and biology. Students were employed in at least two different research groups for an average of 30-40 hours per week for eight weeks in the summer of 2006. Following the completion of the summer work experience, we again assessed attitudes towards science in both groups and gathered additional information from the experimental group on satisfaction with the work experience and reasons for participating. Results are presented and discussed.

  7. Decentralized diagnosis in a spacecraft attitude determination and control system

    NASA Astrophysics Data System (ADS)

    Pérez, C. G.; Travé-Massuyès, L.; Chanthery, E.; Sotomayor, J.

    2015-11-01

    In model-based diagnosis (MBD), structural models can provide useful information for fault diagnosis and fault-tolerant control design. In particular, they are known for supporting the design of analytical redundancy relations (ARRs) which are widely used to generate residuals for diagnosis. On the other hand, systems are increasingly complex whereby it is necessary to develop decentralized architectures to perform the diagnosis task. Decentralized diagnosis is of interest for on-board systems as a way to reduce computational costs or for large geographically distributed systems that require to minimizing data transfer. Decentralized solutions allow proper separation of industrial knowledge, provided that inputs and outputs are clearly defined. This paper builds on the results of [1] and proposes an optimized approach for decentralized fault-focused residual generation. It also introduce the concept of Fault-Driven Minimal Structurally-Overdetermined set (FMSO) ensuring minimal redundancy. The method decreases communication cost involved in decentralization with respect to the algorithm proposed in [1] while still maintaining the same isolation properties as the centralized approach as well as the isolation on request capability.

  8. Attitudes towards exercise and physical activity behaviours in Greek schoolchildren after a year long health education intervention

    PubMed Central

    Christodoulos, A D; Douda, H T; Polykratis, M; Tokmakidis, S P

    2006-01-01

    Objective To examine the short term effects of a health education programme on Greek primary schoolchildren Methods The school based intervention programme was applied to 29 children in the 6th grade of the 2nd Primary School of Agios Stefanos (∼12 000 inhabitants); 49 pupils from the 1st Primary School constituted the control group. To assess the effectiveness of the intervention, attitude and behavioural variables were measured before and after the intervention. Results After adjustment for initial differences in the assessed variables, pupils who took part in the intervention had more positive attitudes towards physical activity than the control group and scored significantly more highly on their intention to participate in physical activity. Moreover, pupils in the intervention group reported more hours/week spent in organised physical activities than pupils in the control group (mean (SD) 3.54 (0.32) v 2.54 (0.26), p<0.020). Finally, a higher proportion of pupils in the intervention classes matched the recommendations of 60 minutes of moderate to vigorous physical activity daily (77.4% v 55.1%, p<0.043). Conclusions Within the limitations of the study, the data show that school health education programmes have the potential to slow the age related decline in physical activity and help pupils establish lifelong, healthy physical activity patterns. Promoting healthy habits and physical activity behaviours during childhood may prevent some of the leading causes of morbidity and mortality in the Greek population, and also decrease direct healthcare costs and improve quality of life. PMID:16556796

  9. The Implementation of Satellite Attitude Control System Software Using Object Oriented Design

    NASA Technical Reports Server (NTRS)

    Reid, W. Mark; Hansell, William; Phillips, Tom; Anderson, Mark O.; Drury, Derek

    1998-01-01

    NASA established the Small Explorer (SNMX) program in 1988 to provide frequent opportunities for highly focused and relatively inexpensive space science missions. The SMEX program has produced five satellites, three of which have been successfully launched. The remaining two spacecraft are scheduled for launch within the coming year. NASA has recently developed a prototype for the next generation Small Explorer spacecraft (SMEX-Lite). This paper describes the object-oriented design (OOD) of the SMEX-Lite Attitude Control System (ACS) software. The SMEX-Lite ACS is three-axis controlled and is capable of performing sub-arc-minute pointing. This paper first describes high level requirements governing the SMEX-Lite ACS software architecture. Next, the context in which the software resides is explained. The paper describes the principles of encapsulation, inheritance, and polymorphism with respect to the implementation of an ACS software system. This paper will also discuss the design of several ACS software components. Specifically, object-oriented designs are presented for sensor data processing, attitude determination, attitude control, and failure detection. Finally, this paper will address the establishment of the ACS Foundation Class (AFC) Library. The AFC is a large software repository, requiring a minimal amount of code modifications to produce ACS software for future projects.

  10. Development and test of the ASAT Bipropellant Attitude Control System (ACS) engine

    NASA Astrophysics Data System (ADS)

    Hodge, K. F.; Allen, K. A.; Hemmings, B.

    1993-06-01

    The recent Kinetic Energy Anti-Satellite (KE ASAT) Bipropellant Attitude Control System (ACS) Engine testing demonstrated and characterized performance and operational durability. Within the ASAT mission, the bipropellant engines are used to despin the missile after shroud deployment and to provide attitude control of the Kill Vehicle (KV) during all phases of the KV free flight. These engines provide all attitude control thrust from booster separation until target intercept. The ASAT ACS engine is unique both in the amount of on-time that the engine sees during a tactical mission scenario and the high thermal loads which result from performing two diametrically opposed missions with a single thruster - long steady state burns and very short response time pulse mode operations. Two flightweight ASAT ACS Bipropellant engines were individually tested in a developmental test program. Testing was conducted at ambient conditions. Hot-fire testing consisted of steady-state, mission duty cycle (MDC), Chamber Pressure (Pc) excursion, mixture ratio excursion, and pulse performance. Testing was conducted by Rockwell's Rocketdyne Division at the Santa Susana Field Laboratory (SSFL), Systems Test Laboratory IV (STL IV), Cell 37A. Two additional engine tests are planned and will include altitude testing. This paper will summarize engine development, component development testing, valve orificing and cold flow calibration, and engine hot-fire testing approach and results.

  11. Predicting healthcare employees' participation in an office redesign program: Attitudes, norms and behavioral control

    PubMed Central

    Mohr, David C; Lukas, Carol VanDeusen; Meterko, Mark

    2008-01-01

    Background The study examined the extent to which components based on a modified version of the theory of planned behavior explained employee participation in a new clinical office program designed to reduce patient waiting times in primary care clinics. Methods We regressed extent of employee participation on attitudes about the program, group norms, and perceived behavioral control along with individual and clinic characteristics using a hierarchical linear mixed model. Results Perceived group norms were one of the best predictors of employee participation. Attitudes about the program were also significant, but to a lesser degree. Behavioral control, however, was not a significant predictor. Respondents with at least one year of clinic tenure, or who were team leaders, first line supervisor, or managers had greater participation rates. Analysis at the clinic level indicated clinics with scores in the highest quartile clinic scores on group norms, attitudes, and behavioral control scores were significantly higher on levels of overall participation than clinics in the lowest quartile. Conclusion Findings suggest that establishing strong norms and values may influence employee participation in a change program in a group setting. Supervisory level was also significant with greater responsibility being associated with greater participation. PMID:18976505

  12. A Simple Attitude Control of Quadrotor Helicopter Based on Ziegler-Nichols Rules for Tuning PD Parameters

    PubMed Central

    He, ZeFang

    2014-01-01

    An attitude control strategy based on Ziegler-Nichols rules for tuning PD (proportional-derivative) parameters of quadrotor helicopters is presented to solve the problem that quadrotor tends to be instable. This problem is caused by the narrow definition domain of attitude angles of quadrotor helicopters. The proposed controller is nonlinear and consists of a linear part and a nonlinear part. The linear part is a PD controller with PD parameters tuned by Ziegler-Nichols rules and acts on the quadrotor decoupled linear system after feedback linearization; the nonlinear part is a feedback linearization item which converts a nonlinear system into a linear system. It can be seen from the simulation results that the attitude controller proposed in this paper is highly robust, and its control effect is better than the other two nonlinear controllers. The nonlinear parts of the other two nonlinear controllers are the same as the attitude controller proposed in this paper. The linear part involves a PID (proportional-integral-derivative) controller with the PID controller parameters tuned by Ziegler-Nichols rules and a PD controller with the PD controller parameters tuned by GA (genetic algorithms). Moreover, this attitude controller is simple and easy to implement. PMID:25614879

  13. Design and validation of inverse optimisation software for the attitude control of microsatellites

    NASA Astrophysics Data System (ADS)

    Horri, N. M.; Palmer, P.; Roberts, M.

    2011-12-01

    The capabilities of microsatellite attitude control hardware have considerably evolved during the last two decades. However, three axis attitude control software is still predominantly based on the conservative use of standard flight proven PD type controllers, which are known to be limited in terms of rapidity for a prescribed level of energy consumption. Microsatellites are therefore typically not as agile as they could be. This conservatism is due to the complexity of implementing global numerical optimisation techniques to satellite attitude control. In this paper, we consider the model of a low earth orbiting microsatellite with a four wheel configuration, where the speed of one of the wheels is kept constant to provide a momentum bias and guarantee gyroscopic stiffness to disturbances. A geometric optimal control approach is presented, which circumvents the tedious tasks of numerically solving online the nonlinear optimisation problem. The approach is based on the design of suboptimal phase space trajectories. The phase space trajectory of a standard linear controller, typically a PD law with gyro-compensation, is used as a benchmark. The proposed inverse optimal control technique is then used to enforce higher convergence rate constraints than the benchmark law, without increasing the total energy consumption. The convergence rate of a Lyapunov function under the effect of the optimal controller outperforms the convergence rate of the same function under PD control and keeps increasing until a design settling time limit is reached. Guidelines are given for the tuning of the controller. The optimal attitude control algorithms are validated on a microsatellite software simulator in collaboration with the space company Surrey Satellite Technology Limited (SSTL). The software simulator incorporates a precise model of the effects of estimation errors, noise, external disturbances, sampling and actuator dynamics. The software is similar to the flight software of

  14. Nurses' Perceptions and Attitudes Toward Use of Oral Patient-Controlled Analgesia.

    PubMed

    Riemondy, Susan; Gonzalez, Lorie; Gosik, Kirk; Ricords, Amy; Schirm, Victoria

    2016-04-01

    Patient-controlled analgesia (PCA) administered intravenously is a generally well-accepted therapy by nurses and patients. PCA devices are now available for oral medications, allowing patients to self-administer pain pills without requesting them from the nurse. Successful introduction of new pain medication delivery devices can depend on nurses' knowledge and attitudes. The aim of this institutional review board approved project was to evaluate nurses' perceptions and attitudes toward using an oral PCA device for patients' pain. A 4-week study was designed and conducted at an academic medical center on an orthopedic unit and a women's health unit. Nurse participants received education on using the oral PCA device and were invited to complete a pre- and poststudy knowledge and attitude survey regarding pain management. Nurses and patients also completed a questionnaire about perceptions related to using the oral PCA device. Findings showed that nurses' attitudes toward using the oral PCA device were less favorable than those of patients, suggesting that nurses may require additional education for acceptance of this device. Results from 37 nurses showed improvement in overall knowledge and attitudes, from 70.8% pretest to 74.2% post-test. Although improvement was not statistically significant (p = .1637), two items showed significant improvement. Knowledge about the effectiveness of NSAIDS was 27.5% pretest compared with 60.0% post-test (p = .0028); and understanding about use of opioids in patients with a history of substance abuse was 50% pretest compared with 70% post-test (p = .0531). Helping nurses overcome the perceived barriers to use of an oral PCA device has potential implications for better pain management as well as enhanced patient satisfaction. PMID:27091584

  15. The Middeck Active Control Experiment (MACE)

    NASA Technical Reports Server (NTRS)

    Miller, David W.; Sepe, Raymond B.; Rey, Daniel; Saarmaa, Erik; Crawley, Edward F.

    1993-01-01

    The Middeck Active Control Experiment (MACE) is a NASA In-Step and Control Structure Interaction (CSI) Office funded Shuttle middeck experiment. The objective is to investigate the extent to which closed-loop behavior of flexible spacecraft in zero-gravity (0-g) can be predicted. This prediction becomes particularly difficult when dynamic behavior during ground testing exhibits extensive suspension and direct gravity coupling. On-orbit system identification and control reconfiguration is investigated to improve performance which would otherwise be limited due to errors in prediction. The program is presently in its preliminary design phase with launch expected in the summer of 1994. The MACE test article consists of three attitude control torque wheels, a two axis gimballing payload, inertial sensors and a flexible support structure. With the acquisition of a second payload, this will represent a multiple payload platform with significant structural flexibility. This paper presents on-going work in the areas of modelling and control of the MACE test article in the zero and one-gravity environments. Finite element models, which include suspension and gravity effects, and measurement models, derived from experimental data, are used as the basis for Linear Quadratic Gaussian controller designs. Finite element based controllers are analytically used to study the differences in closed-loop performance as the test article transitions between the 0-g and 1-g environments. Measurement based controllers are experimentally applied to the MACE test article in the 1-g environment and achieve over an order of magnitude improvement in payload pointing accuracy when disturbed by a broadband torque disturbance. The various aspects of the flight portion of the experiment are also discussed.

  16. The Middeck Active Control Experiment (MACE)

    NASA Astrophysics Data System (ADS)

    Miller, David W.; Sepe, Raymond B.; Rey, Daniel; Saarmaa, Erik; Crawley, Edward F.

    1993-02-01

    The Middeck Active Control Experiment (MACE) is a NASA In-Step and Control Structure Interaction (CSI) Office funded Shuttle middeck experiment. The objective is to investigate the extent to which closed-loop behavior of flexible spacecraft in zero-gravity (0-g) can be predicted. This prediction becomes particularly difficult when dynamic behavior during ground testing exhibits extensive suspension and direct gravity coupling. On-orbit system identification and control reconfiguration is investigated to improve performance which would otherwise be limited due to errors in prediction. The program is presently in its preliminary design phase with launch expected in the summer of 1994. The MACE test article consists of three attitude control torque wheels, a two axis gimballing payload, inertial sensors and a flexible support structure. With the acquisition of a second payload, this will represent a multiple payload platform with significant structural flexibility. This paper presents on-going work in the areas of modelling and control of the MACE test article in the zero and one-gravity environments. Finite element models, which include suspension and gravity effects, and measurement models, derived from experimental data, are used as the basis for Linear Quadratic Gaussian controller designs. Finite element based controllers are analytically used to study the differences in closed-loop performance as the test article transitions between the 0-g and 1-g environments. Measurement based controllers are experimentally applied to the MACE test article in the 1-g environment and achieve over an order of magnitude improvement in payload pointing accuracy when disturbed by a broadband torque disturbance. The various aspects of the flight portion of the experiment are also discussed.

  17. Design, dynamics and control of an Adaptive Singularity-Free Control Moment Gyroscope actuator for microspacecraft Attitude Determination and Control System

    NASA Astrophysics Data System (ADS)

    Viswanathan, Sasi Prabhakaran

    Design, dynamics, control and implementation of a novel spacecraft attitude control actuator called the "Adaptive Singularity-free Control Moment Gyroscope" (ASCMG) is presented in this dissertation. In order to construct a comprehensive attitude dynamics model of a spacecraft with internal actuators, the dynamics of a spacecraft with an ASCMG, is obtained in the framework of geometric mechanics using the principles of variational mechanics. The resulting dynamics is general and complete model, as it relaxes the simplifying assumptions made in prior literature on Control Moment Gyroscopes (CMGs) and it also addresses the adaptive parameters in the dynamics formulation. The simplifying assumptions include perfect axisymmetry of the rotor and gimbal structures, perfect alignment of the centers of mass of the gimbal and the rotor etc. These set of simplifying assumptions imposed on the design and dynamics of CMGs leads to adverse effects on their performance and results in high manufacturing cost. The dynamics so obtained shows the complex nonlinear coupling between the internal degrees of freedom associated with an ASCMG and the spacecraft bus's attitude motion. By default, the general ASCMG cluster can function as a Variable Speed Control Moment Gyroscope, and reduced to function in CMG mode by spinning the rotor at constant speed, and it is shown that even when operated in CMG mode, the cluster can be free from kinematic singularities. This dynamics model is then extended to include the effects of multiple ASCMGs placed in the spacecraft bus, and sufficient conditions for non-singular ASCMG cluster configurations are obtained to operate the cluster both in VSCMG and CMG modes. The general dynamics model of the ASCMG is then reduced to that of conventional VSCMGs and CMGs by imposing the standard set of simplifying assumptions used in prior literature. The adverse effects of the simplifying assumptions that lead to the complexities in conventional CMG design, and

  18. Factors associated with attitude toward premarital sexual activities among school-going adolescents in Kelantan, Malaysia.

    PubMed

    Rahman, Azriani Abdul; Rahman, Razlina Abdul; Ismail, Shaiful Bahari; Ibrahim, Mohd Ismail; Ali, Siti Hawa; Salleh, Halim; Wan Muda, Wan Abdul Manan

    2015-03-01

    The objective of this cross-sectional study was to determine the factors associated with the attitudes toward premarital sexual activities among school-going adolescents in Kelantan, Malaysia. It was conducted among 1032 secondary school students using a self-administered validated questionnaire. Multiple logistic regression revealed that the risk factors for having permissive attitudes toward practice of premarital sexual activities were male students (odds ratio [OR] = 1.83; 95% confidence interval [CI] = 1.34-2.48), being less religious (OR = 2.02; 95% CI = 1.49-2.73), and younger age group of students (13 to 14 years old; OR = 1.42; 95% CI = 1.05-1.92). Having good knowledge on sexual and reproductive health was a protective factor against permissive sexual attitude (OR = 0.27; 95% CI = 0.20-0.36). In conclusion, male and young adolescents were at risk of having permissive attitudes toward sexual behaviors, but good knowledge on sexual and reproductive health and being more religious may protect them from it. PMID:22751680

  19. Controls Considerations for Turbine Active Clearance Control

    NASA Technical Reports Server (NTRS)

    Melcher, Kevin J.

    2004-01-01

    This presentation discusses active control of turbine tip clearance from a control systems perspective. It is a subset of charts that were presented at the 2003 meeting of the International Society of Air Breathing Engines which was held August 31 through September 5 in Cleveland, Ohio. The associated reference paper is cited at the end of the presentation. The presentation describes active tip clearance control research being conducted by NASA to improve turbine engine systems. The target application for this effort is commercial aircraft engines. However, it is believed that the technologies developed as part of this research will benefit a broad spectrum of current and future turbomachinery. The first part of the presentation discusses the concept of tip clearance, problems associated with it, and the benefits of controlling it. It lays out a framework for implementing tip clearance controls that enables the implementation to progress from purely analytical to hardware-in-the-loop to fully experimental. And it briefly discusses how the technologies developed will be married to the previously described ACC Test Rig for hardware-in-the-loop demonstrations. The final portion of the presentation, describes one of the key technologies in some detail by presenting equations and results for a functional dynamic model of the tip clearance phenomena. As shown, the model exhibits many of the clearance dynamics found in commercial gas turbine engines. However, initial attempts to validate the model identified limitations that are being addressed to make the model more realistic.

  20. A Comparison of Attitudes and Exercise Habits of Alumni from Colleges with Varying Degrees of Physical Education Activity Programs.

    ERIC Educational Resources Information Center

    Adams, Thomas M.; Brynteson, Paul

    1992-01-01

    Study compared the exercise attitudes and habits of alumni from four colleges with varying physical education activity (PEA) requirements. Survey results indicated the type of PEA programs offered influenced alumni attitudes toward fitness and exercise behaviors. Students from colleges with higher PEA requirements had more positive exercise…

  1. Urban Middle School African American Girls' Attitudes toward Physical Education and Out-of-School Physical Activity Levels

    ERIC Educational Resources Information Center

    Ramsey, Victor

    2012-01-01

    The purposes of this two-part study were (1) to investigate urban middle school African American girls' physical activity levels and their relationships to attitudes and, (2) to explore urban middle school African American girls' attitude toward physical education. A total of (N = 649) African American girls from 14 New York City middle…

  2. Perceptions of siblings’ sexual activity predict sexual attitudes among at-risk adolescents

    PubMed Central

    Almy, Brandon; Long, Kristin; Lobato, Debra; Plante, Wendy; Kao, Barbara; Houck, Christopher

    2014-01-01

    Objective Most American youth have siblings. This study examined the influence of early adolescents’ perceptions of their older sibling’s sexual activity on their own sexual attitudes and behaviors. Method Early adolescents (ages 12–14) at risk for emotional/behavioral problems reported on attitudes towards sex, sexual behaviors, perception of older siblings’ and peers’ sexual activity, and perceived parental approval toward sex. The sample was divided into three groups: teens who thought their older sibling was not having sex (N = 119), teens who believed their sibling was sexually active (N = 55) and teens without an older sibling (N = 170). Results Teens who thought their older sibling was not having sex scored higher in valuing abstinence and lower on perceptions of peer sex and maternal approval toward sex than teens who perceived their sibling to be having sex and teens without an older sibling. With regard to behaviors, teens who thought their older sibling was not having sex were less likely to endorse making out, touching genitals, oral sex, and vaginal sex compared to teens who thought their older sibling was having sex. Conclusion Perceptions that older siblings abstain from sexual activity may be a protective factor for more conservative attitudes towards sex and decreased sexual activity among young, at-risk teens. A single question about perceptions of siblings’ sexual behaviors can be integrated into healthcare visits to introduce conversations about age-appropriate sexual decision-making. PMID:25741948

  3. Attitudes and Motivations of Polish Students towards Entrepreneurial Activity

    ERIC Educational Resources Information Center

    Jones, Paul; Miller, Christopher; Jones, Amanda; Packham, Gary; Pickernell, David; Zbierowski, Przemyslaw

    2011-01-01

    Purpose: The Polish economy is continuing its expansion through the adoption of free market economics in the post-communist era. To encourage this growth in a future where difficult global economic conditions are likely to persist, it is essential that entrepreneurial activity is encouraged within the next generation of graduates. This study aims…

  4. A neural network approach to fault detection in spacecraft attitude determination and control systems

    NASA Astrophysics Data System (ADS)

    Schreiner, John N.

    This thesis proposes a method of performing fault detection and isolation in spacecraft attitude determination and control systems. The proposed method works by deploying a trained neural network to analyze a set of residuals that are defined such that they encompass the attitude control, guidance, and attitude determination subsystems. Eight neural networks were trained using either the resilient backpropagation, Levenberg-Marquardt, or Levenberg-Marquardt with Bayesian regularization training algorithms. The results of each of the neural networks were analyzed to determine the accuracy of the networks with respect to isolating the faulty component or faulty subsystem within the ADCS. The performance of the proposed neural network-based fault detection and isolation method was compared and contrasted with other ADCS FDI methods. The results obtained via simulation showed that the best neural networks employing this method successfully detected the presence of a fault 79% of the time. The faulty subsystem was successfully isolated 75% of the time and the faulty components within the faulty subsystem were isolated 37% of the time.

  5. A study of attitude control concepts for precision-pointing non-rigid spacecraft

    NASA Technical Reports Server (NTRS)

    Likins, P. W.

    1975-01-01

    Attitude control concepts for use onboard structurally nonrigid spacecraft that must be pointed with great precision are examined. The task of determining the eigenproperties of a system of linear time-invariant equations (in terms of hybrid coordinates) representing the attitude motion of a flexible spacecraft is discussed. Literal characteristics are developed for the associated eigenvalues and eigenvectors of the system. A method is presented for determining the poles and zeros of the transfer function describing the attitude dynamics of a flexible spacecraft characterized by hybrid coordinate equations. Alterations are made to linear regulator and observer theory to accommodate modeling errors. The results show that a model error vector, which evolves from an error system, can be added to a reduced system model, estimated by an observer, and used by the control law to render the system less sensitive to uncertain magnitudes and phase relations of truncated modes and external disturbance effects. A hybrid coordinate formulation using the provided assumed mode shapes, rather than incorporating the usual finite element approach is provided.

  6. Large scale static tests of a tilt-nacelle V/STOL propulsion/attitude control system

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The concept of a combined V/STOL propulsion and aircraft attitude control system was subjected to large scale engine tests. The tilt nacelle/attitude control vane package consisted of the T55 powered Hamilton Standard Q-Fan demonstrator. Vane forces, moments, thermal and acoustic characteristics as well as the effects on propulsion system performance were measured under conditions simulating hover in and out of ground effect.

  7. Infrared horizon sensor modeling for attitude determination and control: Analysis and mission experience

    NASA Technical Reports Server (NTRS)

    Phenneger, M. C.; Singhal, S. P.; Lee, T. H.; Stengle, T. H.

    1985-01-01

    The work performed by the Attitude Determination and Control Section at the National Aeronautics and Space Administration/Goddard Space Flight Center in analyzing and evaluating the performance of infrared horizon sensors is presented. The results of studies performed during the 1960s are reviewed; several models for generating the Earth's infrared radiance profiles are presented; and the Horizon Radiance Modeling Utility, the software used to model the horizon sensor optics and electronics processing to computer radiance-dependent attitude errors, is briefly discussed. Also provided is mission experience from 12 spaceflight missions spanning the period from 1973 to 1984 and using a variety of horizon sensing hardware. Recommendations are presented for future directions for the infrared horizon sensing technology.

  8. Parental attitudes about sexual education: cross-cultural differences and covariate controls.

    PubMed

    Abramson, P R; Moriuchi, K D; Waite, M S; Perry, L B

    1983-10-01

    Cross-cultural differences in parental attitudes and experiences of childhood sexual education were examined. Parental attitudes and experiences were isolated for study because of their significance as a vehicle for transmitting culturally prescribed norms. The present study also tested for artifactual differences between cultures, in terms of explaining the differences with concomitant variability. Couples with children ranging in age from 1 to 10 were utilized and were drawn from four subcultures (Mexican-American, N = 22, Black American, N = 20, Caucasian American, N = 27, and Japanese-American, N = 18). The most salient and consistent finding was the pronounced significance of the covariate controls (especially father's education and mother's religiosity). That is, although a few cross-cultural effects remained significant despite the influence of a covariate, most of the findings were biased by a concomitant (i.e., demographic) variable. PMID:6651506

  9. Attitude control requirements for an earth-orbital solar electric propulsion stage

    NASA Technical Reports Server (NTRS)

    Oglevie, R. E.; Andrews, P. D.; Jasper, T. P.

    1975-01-01

    Solar Electric Propulsion Stage (SEPS) application in earth orbit requires considerably more maneuvering for thrust vector steering and solar array pointing than planetary missions. Attitude maneuver requirements for geosynchronous and low earth-orbital missions are presented. Situations which result in optimum steering torque requirements exceeding the capability of current SEPS configurations are defined. Sub-optimal steering techniques are defined which reduce the geosynchronous mission torque requirements to acceptable levels with negligible performance penalties. Some low earth-orbital flight regimes with earth shadowing are found to result in much larger torque requirements and impose significant mechanization penalties if serious performance losses are to be avoided. Alternative attitude control mechanization techniques are defined for these cases.

  10. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    NASA Technical Reports Server (NTRS)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  11. Attitudes toward Placebo-Controlled Clinical Trials of Patients with Schizophrenia in Japan

    PubMed Central

    Sugawara, Norio; Ishioka, Masamichi; Tsuchimine, Shoko; Tsuruga, Koji; Sato, Yasushi; Furukori, Hanako; Kudo, Shuhei; Tomita, Tetsu; Nakagami, Taku; Yasui-Furukori, Norio

    2015-01-01

    Background Although the use of placebo in clinical trials of schizophrenia patients is controversial because of medical and ethical concerns, placebo-controlled clinical trials are commonly used in the licensing of new drugs. Aims The objective of this study was to assess the attitudes toward placebo-controlled clinical trials among patients with schizophrenia in Japan. Method Using a cross-sectional design, we recruited patients (n = 251) aged 47.7±13.2 (mean±SD) with a DSM-IV diagnosis of schizophrenia or schizoaffective disorder who were admitted to six psychiatric hospitals from December 2013 to March 2014. We employed a 14-item questionnaire specifically developed to survey patients' attitudes toward placebo-controlled clinical trials. Results The results indicated that 33% of the patients would be willing to participate in a placebo-controlled clinical trial. Expectations for improvement of disease, a guarantee of hospital treatment continuation, and encouragement by family or friends were associated with the willingness to participate in such trials, whereas a belief of additional time required for medical examinations was associated with non-participation. Conclusions Fewer than half of the respondents stated that they would be willing to participate in placebo-controlled clinical trials. Therefore, interpreting the results from placebo-controlled clinical trials could be negatively affected by selection bias. PMID:26600382

  12. Mission management, planning, and cost: PULSE Attitude And Control Systems (AACS)

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The Pluto unmanned long-range scientific explorer (PULSE) is a probe that will do a flyby of Pluto. It is a low weight, relatively low costing vehicle which utilizes mostly off-the-shelf hardware, but not materials or techniques that will be available after 1999. A design, fabrication, and cost analysis is presented. PULSE will be launched within the first decade of the twenty-first century. The topics include: (1) scientific instrumentation; (2) mission management, planning, and costing; (3) power and propulsion systems; (4) structural subsystem; (5) command, control, and communication; and (6) attitude and articulation control.

  13. Balloon infrared astronomy platform (BIRAP). [development and characteristics of a balloon-borne attitude control system

    NASA Technical Reports Server (NTRS)

    Greeb, M. E.; True, G. A.

    1974-01-01

    The development of a balloon-borne attitude control system for infrared astronomy studies is discussed. The Balloon Infrared Astronomy Platform (BIRAP) is the result of the development effort. The BIRAP uses electronic gimballing for the offset pointing which eliminates a set of mechanical gimbals. Guide stars with visual magnitudes as low as plus 6 are used for fine tracking assuring that all areas of the sky can be covered. The BIRAP control concept uses a closed loop system in the airborne equipment with automatic update through a command link that can be operated either manually or automatically by a ground based computer.

  14. Simulation of flexible appendage interactions with Mariner Venus/Mercury attitude control and science platform pointing

    NASA Technical Reports Server (NTRS)

    Fleischer, G. E.

    1973-01-01

    A new computer subroutine, which solves the attitude equations of motion for any vehicle idealized as a topological tree of hinge-connected rigid bodies, is used to simulate and analyze science instrument pointing control interaction with a flexible Mariner Venus/Mercury (MVM) spacecraft. The subroutine's user options include linearized or partially linearized hinge-connected models whose computational advantages are demonstrated for the MVM problem. Results of the pointing control/flexible vehicle interaction simulations, including imaging experiment pointing accuracy predictions and implications for MVM science sequence planning, are described in detail.

  15. Comparison of thruster configurations in attitude control systems. M.S. Thesis. Progress Report

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III; Drinkard, D. M., Jr.; White, L. R.; Chakravarthi, K. R.

    1973-01-01

    Several aspects concerning reaction control jet systems as used to govern the attitude of a spacecraft were considered. A thruster configuration currently in use was compared to several new configurations developed in this study. The method of determining the error signals which control the firing of the thrusters was also investigated. The current error determination procedure is explained and a new method is presented. Both of these procedures are applied to each of the thruster configurations which are developed and comparisons of the two methods are made.

  16. Pitch attitude, flight path, and airspeed control during approach and landing of a powered lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Innis, R. C.

    1972-01-01

    Analytical investigations and piloted moving base simulator evaluations were conducted for manual control of pitch attitude, flight path, and airspeed for the approach and landing of a powered lift jet STOL aircraft. Flight path and speed response characteristics were described analytically and were evaluated for the simulation experiments which were carried out on a large motion simulator. The response characteristics were selected and evaluated for a specified path and speed control technique. These charcteristics were: (1) the initial pitch response and steady pitch rate sensitivity for control of attitude with a pitch rate command/ attitude hold system, (2) the initial flight path response, flight path overshoot, and flight path-airspeed coupling in response to a change in thrust, and (3) the sensitivity of airspeed to pitch attitude changes. Results are presented in the form of pilot opinion ratings and commentary, substantiated where appropriate by response time histories and aircraft states at the point of touchdown.

  17. Robust momentum management and attitude control system for the Space Station

    NASA Technical Reports Server (NTRS)

    Rhee, Ihnseok; Speyer, Jason L.

    1992-01-01

    A game theoretic controller is synthesized for momentum management and attitude control of the Space Station in the presence of uncertainties in the moments of inertia. Full state information is assumed since attitude rates are assumed to be very accurately measured. By an input-output decomposition of the uncertainty in the system matrices, the parameter uncertainties in the dynamic system are represented as an unknown gain associated with an internal feedback loop (IFL). The input and output matrices associated with the IFL form directions through which the uncertain parameters affect system response. If the quadratic form of the IFL output augments the cost criterion, then enhanced parameter robustness is anticipated. By considering the input and the input disturbance from the IFL as two noncooperative players, a linear-quadratic differential game is constructed. The solution in the form of a linear controller is used for synthesis. Inclusion of the external disturbance torques results in a dynamic feedback controller which consists of conventional PID (proportional integral derivative) control and cyclic disturbance rejection filters. It is shown that the game theoretic design allows large variations in the inertias in directions of importance.

  18. A robust momentum management and attitude control system for the space station

    NASA Technical Reports Server (NTRS)

    Speyer, J. L.; Rhee, Ihnseok

    1991-01-01

    A game theoretic controller is synthesized for momentum management and attitude control of the Space Station in the presence of uncertainties in the moments of inertia. Full state information is assumed since attitude rates are assumed to be very assurately measured. By an input-output decomposition of the uncertainty in the system matrices, the parameter uncertainties in the dynamic system are represented as an unknown gain associated with an internal feedback loop (IFL). The input and output matrices associated with the IFL form directions through which the uncertain parameters affect system response. If the quadratic form of the IFL output augments the cost criterion, then enhanced parameter robustness is anticipated. By considering the input and the input disturbance from the IFL as two noncooperative players, a linear-quadratic differential game is constructed. The solution in the form of a linear controller is used for synthesis. Inclusion of the external disturbance torques results in a dynamic feedback controller which consists of conventional PID (proportional integral derivative) control and cyclic disturbance rejection filters. It is shown that the game theoretic design allows large variations in the inertias in directions of importance.

  19. An approach to the design and implementation of spacecraft attitude control systems

    NASA Technical Reports Server (NTRS)

    ODonnell, James R., Jr.; Mangus, David J.

    1998-01-01

    Over 39 years and a long list of missions, the guidance, navigation, and control (GN&C) groups at the Goddard Space Flight Center have gradually developed approaches to the design and implementation of successful spacecraft attitude control systems. With the recent creation of the Guidance, Navigation, and Control Center at Goddard, there is a desire to document some of these design practices to help to ensure their consistent application in the future. In this paper, we will discuss the beginnings of this effort, drawing primarily on the experience of one of the past attitude control system (ACS) groups at Goddard (what was formerly known as Code 712, the Guidance, Navigation, and Control Branch). We will discuss the analysis and design methods and criteria used, including guidelines for linear and nonlinear analysis, as well as the use of low- and high-fidelity simulation for system design and verification of performance. Descriptions of typical ACS sensor and actuator hardware will be shown, and typical sensor/actuator suites for a variety of mission types detailed. A description of the software and hardware test effort will be given, along with an attempt to make some qualitative estimates on how much effort is involved. The spacecraft and GN&C subsystem review cycles will be discussed, giving an outline of what design reviews are typically held and what information should be presented at each stage. Finally, we will point out some of the lessons learned at Goddard.

  20. An Approach to the Design and Implementation of Spacecraft Attitude Control Systems

    NASA Technical Reports Server (NTRS)

    ODonnell, James R., Jr.; Mangus, David J.

    1998-01-01

    Over 39 years and a long list of missions, the guidance, navigation, and control (GN&C) groups at the Goddard Space Flight Center have gradually developed approaches to the design and implementation of successful spacecraft attitude control systems. With the recent creation of the Guidance, Navigation, and Control Center at Goddard, there is a desire to document some of these design practices to help to ensure their consistent application in the future. In this paper, we will discuss the beginnings of this effort, drawing primarily on the experience of one of the past attitude control system (ACS) groups at Goddard (what was formerly known as Code 712, the Guidance, Navigation, and Control Branch). We will discuss the analysis and design methods and criteria used, including guidelines for linear and nonlinear analysis, as well as the use of low- and high-fidelity simulation for system design and verification of performance. Descriptions of typical ACS sensor and actuator hardware will be shown, and typical sensor/actuator suites for a variety of mission types detailed. A description of the software and hardware test effort will be given, along with an attempt to make some qualitative estimates on how much effort is involved. The spacecraft and GN&C subsystem review cycles will be discussed, giving an outline of what design reviews are typically held and .what information should be presented at each stage. Finally, we will point out some of the lessons learned at Goddard.

  1. Optical control of antibacterial activity

    NASA Astrophysics Data System (ADS)

    Velema, Willem A.; van der Berg, Jan Pieter; Hansen, Mickel J.; Szymanski, Wiktor; Driessen, Arnold J. M.; Feringa, Ben L.

    2013-11-01

    Bacterial resistance is a major problem in the modern world, stemming in part from the build-up of antibiotics in the environment. Novel molecular approaches that enable an externally triggered increase in antibiotic activity with high spatiotemporal resolution and auto-inactivation are highly desirable. Here we report a responsive, broad-spectrum, antibacterial agent that can be temporally activated with light, whereupon it auto-inactivates on the scale of hours. The use of such a ‘smart’ antibiotic might prevent the build-up of active antimicrobial material in the environment. Reversible optical control over active drug concentration enables us to obtain pharmacodynamic information. Precisely localized control of activity is achieved, allowing the growth of bacteria to be confined to defined patterns, which has potential for the development of treatments that avoid interference with the endogenous microbial population in other parts of the organism.

  2. Demonstration of Active Combustion Control

    NASA Technical Reports Server (NTRS)

    Lovett, Jeffrey A.; Teerlinck, Karen A.; Cohen, Jeffrey M.

    2008-01-01

    The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.

  3. Improving psychology students' attitudes toward people with schizophrenia: A quasi-randomized controlled study.

    PubMed

    Magliano, Lorenza; Rinaldi, Angela; Costanzo, Regina; De Leo, Renata; Schioppa, Giustina; Petrillo, Miriam; Read, John

    2016-01-01

    Despite scientific evidence that the majority of people with schizophrenia (PWS) have personal histories of traumatic life events and adversities, their needs for psychological support often remain unmet. Poor availability of nonpharmacological therapies in schizophrenia may be partly because of professionals' attitudes toward people diagnosed with this disorder. As future health professionals, psychology students represent a target population for efforts to increase the probability that PWS will be offered effective psychological therapies. This quasi-randomized controlled study investigated the effect of an educational intervention, addressing common prejudices via scientific evidence and prerecorded audio-testimony from PWS, on the attitudes of psychology students toward PWS. Students in their fifth year of a master's degree in Psychology at the Second University of Naples, Italy were randomly assigned to an experimental group-which attended two 3-hr sessions a week apart-or to a control group. Compared with their baseline assessment, at 1-month reassessment the 76 educated students endorsed more psychosocial causes and more of them recommended psychologists in the treatment of schizophrenia. They were also more optimistic about recovery, less convinced that PWS are recognizable and unpredictable, and more convinced that treatments, pharmacological and psychological, are useful. No significant changes were found, from baseline to 1-month reassessment, in the 112 controls. At 1-month reassessment, educated students were more optimistic about recovery and less convinced that PWS are unpredictable than controls. These findings suggest that psychology students' attitudes toward PWS can be improved by training initiatives including education and indirect contact with users. (PsycINFO Database Record PMID:26963178

  4. Attitude control of the LACE satellite: A gravity gradient stabilized spacecraft

    NASA Technical Reports Server (NTRS)

    Ivory, J. E.; Campion, R. E.; Bakeris, D. F.

    1993-01-01

    The Low-power Atmospheric Compensation Experiment (LACE) satellite was launched in February 1990 by the Naval Research Laboratory. The spacecraft's pitch and roll are maintained with a gravity gradient boom and a magnetic damper. There are two other booms with much smaller tip masses, one in the velocity direction (lead boom) of variable length and the other in the opposite direction (balance boom) also of variable length. In addition, the system uses a momentum wheel with its axis perpendicular to the plane of the orbit to control yaw and keep these booms in the orbital plane. The primary LACE experiment requires that the lead boom be moved to lengths varying from 4.6 m to 45.7 m. This and other onboard experiments require that the spacecraft attitude remain within tight constraints while operating. The problem confronting the satellite operators was to move the lead boom without inducing a net spacecraft attitude disturbance. A description of a method used to change the length of the lead boom while minimizing the disturbance to the attitude of the spacecraft is given. Deadbeating to dampen pitch oscillations has also been accomplished by maneuvering either the lead or balance boom and is discussed.

  5. Attitudes towards health and physical activity in the elderly. Effects of a physical training program.

    PubMed

    Sidney, K H; Shephard, R J

    1976-01-01

    Attitudes towards physical activity, perceived health, body image, anxiety and life satisfaction have been studied in men and women 60 years of age and older, volunteering for progressive endurance training. Relative to other studies of younger volunteers, the senior citizens placed more value upon activity as "an esthetic experience" and as "a means to health and fitness" showing less interest in "the pursuit of vertigo." Many non-participants and "drop-outs" perceived their current fitness as satisfactory. Subjects who selected a low frequency and low intensity of training were obese, with high Cornell Medical Index (CMI) scores on both organic and psychological scales. After 14 weeks of conditioning, 83% of subjects reported improvements in well-being. However, CMI scores were reduced on only one of twelve organic scales and none of the behavior, mood and feeling scales. Neugarten's Life Satisfaction Index, Kenyon's Body Image scales, and McPherson's the Real Me scores remained unchanged, but there was a decrease of Manifest Anxiety (Taylor scale) and a greater regard for physical activity as "the relief of tension." When subjects were classed according to changes in aerobic power, between group differences were found for "Real Me" scores and for three of Kenyon's attitude scales. Persons who trained frequently and intensively showed improvements for body image and for five of Kenyon's attitude scales. PMID:1011965

  6. Attitudes towards health and physical activity in the elderly. Effects of a physical training program.

    PubMed

    Sidney, K H; Shephard, R J

    1976-01-01

    Attitudes towards physical activity, perceived health, body image, anxiety and life satisfaction have been studied in men and women 60 years of age and older, volunteering for progressive endurance training. Relative to other studies of younger volunteers, the senior citizens placed more value upon activity as "an esthetic experience" and as "a means to health and fitness" showing less interest in "the pursuit of vertigo." Many non-participants and "drop-outs" perceived their current fitness as satisfactory. Subjects who selected a low frequency and low intensity of training were obese, with high Cornell Medical Index (CMI) scores on both organic and psychological scales. After 14 weeks of conditioning, 83% of subjects reported improvements in well-being. However, CMI scores were reduced on only one of twelve organic scales and none of the behavior, mood and feeling scales. Neugarten's Life Satisfaction Index, Kenyon's Body Image scales, and McPherson's the Real Me scores remained unchanged, but there was a decrease of Manifest Anxiety (Taylor scale) and a greater regard of physical activity as "the relief of tension." When subjects were classed according to changes in aerobic power, between group differences were found for "Real Me" scores and for three of Kenyon's attitude scales. Persons who trained frequently and intensively showed improvements for body image and for five of Kenyon's attitude scales. PMID:1011964

  7. Active Flow Control Activities at NASA Langley

    NASA Technical Reports Server (NTRS)

    Anders, Scott G.; Sellers, William L., III; Washburn, Anthony E.

    2004-01-01

    NASA Langley continues to aggressively investigate the potential advantages of active flow control over more traditional aerodynamic techniques. This paper provides an update to a previous paper and describes both the progress in the various research areas and the significant changes in the NASA research programs. The goals of the topics presented are focused on advancing the state of knowledge and understanding of controllable fundamental mechanisms in fluids as well as to address engineering challenges. An organizational view of current research activities at NASA Langley in active flow control as supported by several projects is presented. On-center research as well as NASA Langley funded contracts and grants are discussed at a relatively high level. The products of this research are to be demonstrated either in bench-top experiments, wind-tunnel investigations, or in flight as part of the fundamental NASA R&D program and then transferred to more applied research programs within NASA, DOD, and U.S. industry.

  8. Evaluation and modeling of autonomous attitude thrust control for the Geostation Operational Environmental Satellite (GOES)-8 orbit determination

    NASA Technical Reports Server (NTRS)

    Forcey, W.; Minnie, C. R.; Defazio, R. L.

    1995-01-01

    The Geostationary Operational Environmental Satellite (GOES)-8 experienced a series of orbital perturbations from autonomous attitude control thrusting before perigee raising maneuvers. These perturbations influenced differential correction orbital state solutions determined by the Goddard Space Flight Center (GSFC) Goddard Trajectory Determination System (GTDS). The maneuvers induced significant variations in the converged state vector for solutions using increasingly longer tracking data spans. These solutions were used for planning perigee maneuvers as well as initial estimates for orbit solutions used to evaluate the effectiveness of the perigee raising maneuvers. This paper discusses models for the incorporation of attitude thrust effects into the orbit determination process. Results from definitive attitude solutions are modeled as impulsive thrusts in orbit determination solutions created for GOES-8 mission support. Due to the attitude orientation of GOES-8, analysis results are presented that attempt to absorb the effects of attitude thrusting by including a solution for the coefficient of reflectivity, C(R). Models to represent the attitude maneuvers are tested against orbit determination solutions generated during real-time support of the GOES-8 mission. The modeling techniques discussed in this investigation offer benefits to the remaining missions in the GOES NEXT series. Similar missions with large autonomous attitude control thrusting, such as the Solar and Heliospheric Observatory (SOHO) spacecraft and the INTELSAT series, may also benefit from these results.

  9. Fractional active disturbance rejection control.

    PubMed

    Li, Dazi; Ding, Pan; Gao, Zhiqiang

    2016-05-01

    A fractional active disturbance rejection control (FADRC) scheme is proposed to improve the performance of commensurate linear fractional order systems (FOS) and the robust analysis shows that the controller is also applicable to incommensurate linear FOS control. In FADRC, the traditional extended states observer (ESO) is generalized to a fractional order extended states observer (FESO) by using the fractional calculus, and the tracking differentiator plus nonlinear state error feedback are replaced by a fractional proportional-derivative controller. To simplify controller tuning, the linear bandwidth-parameterization method has been adopted. The impacts of the observer bandwidth ωo and controller bandwidth ωc on system performance are then analyzed. Finally, the FADRC stability and frequency-domain characteristics for linear single-input single-output FOS are analyzed. Simulation results by FADRC and ADRC on typical FOS are compared to demonstrate the superiority and effectiveness of the proposed scheme. PMID:26928516

  10. Body-fixed orbit-attitude hovering control over an asteroid using non-canonical Hamiltonian structure

    NASA Astrophysics Data System (ADS)

    Wang, Yue; Xu, Shijie

    2015-12-01

    The orbit-attitude hovering means that both the position and attitude of the spacecraft are kept to be stationary in the asteroid body-fixed frame. The orbit-attitude hovering is discussed in the framework of the gravitationally coupled orbit-attitude dynamics, also called the full dynamics, in which the spacecraft is modeled as a rigid body to take into account the gravitational orbit-attitude coupling naturally. A feedback hovering control law is proposed by using the non-canonical Hamiltonian structure of the problem, which is consisted of two potential shapings and one energy dissipation. The first potential shaping is to create an artificial equilibrium at the desired hovering position-attitude. Then, the second potential shaping modifies the potential further so that the artificial equilibrium is a minimum of the modified Hamiltonian on the invariant manifold. Finally, the energy dissipation leads the motion to converge asymptotically to the minimum of the modified Hamiltonian, i.e., the artificial equilibrium for hovering. The feasibility of the hovering control law is verified through numerical simulations. The proposed hovering control law has a simple form and can be implemented by the spacecraft autonomously with little computation. This feature can be attributed to the utilization of the Hamiltonian structure and natural dynamical behaviors of the system in the control law design.

  11. Electric propulsion. [pulsed plasma thruster and electron bombardment ion engine for MSAT attitude control and stationkeeping

    NASA Technical Reports Server (NTRS)

    1982-01-01

    An alternative propulsion subsystem for MSAT is presented which has a potential of reducing the satellite weight by more than 15%. The characteristics of pulsed plasma and ion engines are described and used to estimate of the mass of the propellant and thrusters for attitude control and stationkeeping functions for MSAT. Preliminary estimates indicate that the electric propulsion systems could also replace the large momentum wheels necessary to counteract the solar pressure; however, the fine pointing wheels would be retained. Estimates also show that either electric propulsion system can save approximately 18% to 20% of the initial 4,000 kg mass. The issues that require further experimentation are mentioned.

  12. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael

    2011-01-01

    We have learned it is conceivable that the Neutral Mass Spectrometer on board the Lunarr Atmosphere Dust Environment Explorer (LADEE) could measure gases from surface-reflected Attitude Control System (ACS) thruster plume. At minimum altitude, the measurement would be maximized, and gravitational influence minimized ("short" time-of-flight (TOF) situation) Could use to verify aspects of thruster plume modeling Model the transient disturbance to NMS measurements due to ACS gases reflected from lunar surface Observe evolution of various model characteristics as measured by NMS Species magnitudes, TOF measurements, angular distribution, species separation effects

  13. Cassini Attitude Control Fault Protection Design: Launch to End of Prime Mission Performance

    NASA Technical Reports Server (NTRS)

    Meakin, Peter C.

    2008-01-01

    The Cassini Attitude and Articulation Control Subsystem (AACS) Fault Protection (FP) has been successfully supporting operations for over 10 years from launch through the end of the prime mission. Cassini's AACS FP is complex, containing hundreds of error monitors and thousands of tunable parameters. Since launch there have been environmental, hardware, personnel and mission event driven changes which have required AACS FP to adapt and be robust to a variety of scenarios. This paper will discuss the process of monitoring, maintaining and updating the AACS FP during Cassini's lengthy prime mission as well as provide some insight into lessons learned during tour operations.

  14. Use of the MATRIXx Integrated Toolkit on the Microwave Anisotropy Probe Attitude Control System

    NASA Technical Reports Server (NTRS)

    Ward, David K.; Andrews, Stephen F.; McComas, David C.; ODonnell, James R., Jr.

    1999-01-01

    Recent advances in analytical software tools allow the analysis, simulation, flight code, and documentation of an algorithm to be generated from a single source, all within one integrated analytical design package. NASA's Microwave Anisotropy Probe project has used one such package, Integrated Systems' MATRIXx suite, in the design of the spacecraft's Attitude Control System. The project's experience with the linear analysis, simulation, code generation, and documentation tools will be presented and compared with more traditional development tools. In particular, the quality of the flight software generated will be examined in detail. Finally, lessons learned on each of the tools will be shared.

  15. Structural dynamics and attitude control study of early manned capability space station configurations

    NASA Technical Reports Server (NTRS)

    Ayers, J. Kirk; Cirillo, William M.; Giesy, Daniel P.; Hitchcock, Jay C.; Kaszubowski, Martin J.; Raney, J. Philip

    1987-01-01

    A study was performed to determine the vibration and attitude control characteristics of critical space station configurations featuring early manned capability during buildup from initial user support through the operations capability reference station. Five configurations were selected and were examined thus determining the changes that are likely to occur in the characteristics of the system as the station progresses from a single boom structure to a mature, dual keel, operations capability reference station. Both 9 foot and 5 meter truss bay sizes were investigated. All configurations analyzed were stable; however, the 5 meter truss bay size structure exhibited superior stability characteristics.

  16. Vega roll and attitude control system algorithms trade-off study

    NASA Astrophysics Data System (ADS)

    Paulino, N.; Cuciniello, G.; Cruciani, I.; Corraro, F.; Spallotta, D.; Nebula, F.

    2013-12-01

    This paper describes the trade-off study for the selection of the most suitable algorithms for the Roll and Attitude Control System (RACS) within the FPS-A program, aimed at developing the new Flight Program Software of VEGA Launcher. Two algorithms were analyzed: Switching Lines (SL) and Quaternion Feedback Regulation. Using a development simulation tool that models two critical flight phases (Long Coasting Phase (LCP) and Payload Release (PLR) Phase), both algorithms were assessed with Monte Carlo batch simulations for both of the phases. The statistical outcomes of the results demonstrate a 100 percent success rate for Quaternion Feedback Regulation, and support the choice of this method.

  17. Attitude control and drag compensation propulsion system for Gravity Probe-B spacecraft

    NASA Technical Reports Server (NTRS)

    Blount, D. H.

    1983-01-01

    An on board propulsion system for attitude control and drag compensation is presented which uses helium boiloff gas from an experiment package dewar as propellant. This boiloff gas would normally be vented nonpropulsively. Use of a small allowable temperature range in the dewar is exploited to store helium and accommodate incompatibilities in dewar heat leak and thruster demand flow over periods of more than one orbit. A relatively detailed thermodynamics analysis of the two phase helium dewar and simulation of pressure loss through the helium distribution system is included.

  18. Outreach as seen by the Spanish professional astronomers: a survey of beliefs, attitudes, and activities

    NASA Astrophysics Data System (ADS)

    Rodríguez Hidalgo, I.; Díaz Vilela, L. F.

    A survey of outreach related beliefs, attitudes, and activities of the Spanish professional astronomers is presented. More than one hundred scientists answered an ad-hoc drawn up questionnaire, whose results have been analysed statistically. This feedback form is an improved version of that used in a previous research carried out by the authors with a sample of members of the Instituto de Astrofísica de Canarias (Díaz Vilela & Rodríguez Hidalgo 2005). Some of the studied items are the actual time and effort devoted to outreach by a researcher, the role of outreach within his work, the valuation of outreach activities in his curriculum, socially, or economically, the opinion about who should have the responsibility of organising and performing popularisation tasks, etc. Three kinds of studies have been performed: the descriptive one is based on the frequencies and means of variables; a Principal Component Analysis was applied to get a shorter number of belief-attitude dimensions; and an inferential one, derived from a Multiple Regression Analysis which provides a reliable description of the beliefs-attitudes scale grouping outreach related beliefs into 6 components, 3 of them more significant. A simple regression allows us to predict about a 50% of the variance of the outreach practices.

  19. Extended Active Disturbance Rejection Controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2016-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  20. Extended Active Disturbance Rejection Controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2014-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  1. Extended active disturbance rejection controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2012-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  2. Inverse free steering law for small satellite attitude control and power tracking with VSCMGs

    NASA Astrophysics Data System (ADS)

    Malik, M. S. I.; Asghar, Sajjad

    2014-01-01

    Recent developments in integrated power and attitude control systems (IPACSs) for small satellite, has opened a new dimension to more complex and demanding space missions. This paper presents a new inverse free steering approach for integrated power and attitude control systems using variable-speed single gimbal control moment gyroscope. The proposed inverse free steering law computes the VSCMG steering commands (gimbal rates and wheel accelerations) such that error signal (difference in command and output) in feedback loop is driven to zero. H∞ norm optimization approach is employed to synthesize the static matrix elements of steering law for a static state of VSCMG. Later these matrix elements are suitably made dynamic in order for the adaptation. In order to improve the performance of proposed steering law while passing through a singular state of CMG cluster (no torque output), the matrix element of steering law is suitably modified. Therefore, this steering law is capable of escaping internal singularities and using the full momentum capacity of CMG cluster. Finally, two numerical examples for a satellite in a low earth orbit are simulated to test the proposed steering law.

  3. Study of a Satellite Attitude Control System Using Integrating Gyros as Torque Sources

    NASA Technical Reports Server (NTRS)

    White, John S.; Hansen, Q. Marion

    1961-01-01

    This report considers the use of single-degree-of-freedom integrating gyros as torque sources for precise control of satellite attitude. Some general design criteria are derived and applied to the specific example of the Orbiting Astronomical Observatory. The results of the analytical design are compared with the results of an analog computer study and also with experimental results from a low-friction platform. The steady-state and transient behavior of the system, as determined by the analysis, by the analog study, and by the experimental platform agreed quite well. The results of this study show that systems using integrating gyros for precise satellite attitude control can be designed to have a reasonably rapid and well-damped transient response, as well as very small steady-state errors. Furthermore, it is shown that the gyros act as rate sensors, as well as torque sources, so that no rate stabilization networks are required, and when no error sensor is available, the vehicle is still rate stabilized. Hence, it is shown that a major advantage of a gyro control system is that when the target is occulted, an alternate reference is not required.

  4. Farmer attitudes to vaccination and culling of badgers in controlling bovine tuberculosis.

    PubMed

    Warren, M; Lobley, M; Winter, M

    2013-07-13

    Controversy persists in England, Wales and Northern Ireland concerning methods of controlling the transmission of bovine tuberculosis (bTB) between badgers and cattle. The National Trust, a major land-owning heritage organisation, in 2011, began a programme of vaccinating badgers against bTB on its Killerton Estate in Devon. Most of the estate is farmed by 18 tenant farmers, who thus have a strong interest in the Trust's approach, particularly as all have felt the effects of the disease. This article reports on a study of the attitudes to vaccination of badgers and to the alternative of a culling programme, using face-to-face interviews with 14 of the tenants. The results indicated first that the views of the respondents were more nuanced than the contemporary public debate about badger control would suggest. Secondly, the attitude of the interviewees to vaccination of badgers against bTB was generally one of resigned acceptance. Thirdly, most respondents would prefer a combination of an effective vaccination programme with an effective culling programme, the latter reducing population of density sufficiently (and preferably targeting the badgers most likely to be diseased) for vaccination to have a reasonable chance of success. While based on a small sample, these results will contribute to the vigorous debate concerning contrasting policy approaches to bTB control in England, Wales and Northern Ireland. PMID:23775132

  5. Experiments with optical instruments. [attitude control and docking of Soyuz T-4 with Salyut 6

    NASA Technical Reports Server (NTRS)

    Savinykh, V.

    1983-01-01

    Photography was used to document known defects of the periscopic instrument used to check spacecrews in the descent module of the Soyuz T-4. The screen of the altitude control unit was also photographed and revealed glare in the central field of vision. A light filter was installed in the peripheral window to observe the Sun and horizon of the Earth. Checking attitude control by means of polaroids enabled a 5 further advance (500 km) into the zone of shadow. The attitude control unit was used to check the orbital orientation with respect to the vertical during the night segment of flight. A lens screen was used for the emission glow of the atmosphere at an altitude of about 100 km. Docking of the Soyuz T-4 was observed by means of an onboard display, a television camera, and a sighting device. From a distance of about 5 km, the space station could be seen as a bright dot in the sighting device. Docking occurred in shadow.

  6. Improved ITOS attitude control system with Hall generator brushless motor and earth-splitting technique

    NASA Technical Reports Server (NTRS)

    Peacock, W. M.

    1971-01-01

    The ITOS with an improved attitude control system is described. A Hall generator brushless dc torque motor will replace the brush dc torque motor on ITOS-I and ITOS-A (NOAA-1). The four attitude horizon sensors will be replaced with two CO2 sensors for better horizon definition. An earth horizon splitting technique will be used to keep the earth facing side of the satellite toward earth even if the desired circular orbit is not achieved. The external appearance of the pitch control subsystem differs from TIROS-M (ITOS-1) and ITOS-A (NOAA-1) in that two instead of one pitch control electronics (PCE) boxes are used. Two instead of four horizon sensors will be used and one instead of two mirrors will be used for sensor scanning. The brushless motor will eliminate the requirement for brushes, strain gages and the telemetry for the brush wear. A single rotating flywheel, supported by a single bearing provides the gyroscopic stability and the required momentum interchange to keep one side of the satellite facing the earth. Magnetic torquing against the earth's magnetic field eliminates the requirement for expendable propellants which would limit satellite life in orbit.

  7. Eating on impulse: Implicit attitudes, self-regulatory resources, and trait self-control as determinants of food consumption.

    PubMed

    Wang, Yan; Wang, Lei; Cui, Xianghua; Fang, Yuan; Chen, Qianqiu; Wang, Ya; Qiang, Yao

    2015-12-01

    Self-regulatory resources and trait self-control have been found to moderate the impulse-behavior relationship. The current study investigated whether the interaction of self-regulatory resources and trait self-control moderates the association between implicit attitudes and food consumption. One hundred twenty female participants were randomly assigned to either a depletion condition in which their self-regulatory resources were reduced or a no-depletion condition. Participants' implicit attitudes for chocolate were measured with the Single Category Implicit Association Test and self-report measures of trait self-control were collected. The dependent variable was chocolate consumption in an ostensible taste and rate task. Implicit attitudes predicted chocolate consumption in depleted participants but not in non-depleted participants. However, this predictive power of implicit attitudes on eating in depleted condition disappeared in participants with high trait self-control. Thus, trait self-control and self-regulatory resources interact to moderate the prediction of implicit attitude on eating behavior. Results suggest that high trait self-control buffers the effect of self-regulatory depletion on impulsive eating. PMID:26402043

  8. Study of interaction between solar arrays and attitude - orbit control. Volume 1: Technical Report

    NASA Astrophysics Data System (ADS)

    Annett, R. J.

    1980-04-01

    Interface criteria for the specification of solar arrays and attitude control systems for given mission profiles were defined for an Earth observation satellite, a high accuracy, heavy pointing platform and a heavy, geostationary, communications satellite. A double roll-out, a hybrid and an ultra-lightweight panel array were chosen with power levels varying from 1 1/4 kW to 3 kW per wing. Mathematical techniques were developed to modify the array modal data to enable the array design to be performed independently of the center body and general system parameters. The dynamic interaction between the array flexure and various controller algorithms was examined by analytical and simulation techniques and the limits of applicability of specific algorithms are defined. The impact of these modal parameter boundaries are re-evaluated in terms of allowable domains for the dominant structural parameters. Allowable array configurations are shown for given controller algorithms for specific mission senarios.

  9. Distributed event-triggered cooperative attitude control of multiple rigid bodies with leader-follower architecture

    NASA Astrophysics Data System (ADS)

    Weng, Shengxuan; Yue, Dong

    2016-02-01

    In this note, the distributed event-triggered cooperative attitude control of multiple rigid bodies with leader-follower architecture is investigated, where both the cases of static and dynamic leaders are all considered. Two distributed triggering procedures are first introduced for the followers and leaders, and then the distributed cooperative controllers are designed under the proposed triggering schemes. Under the designed controllers with the event-triggered strategies, it is shown that the orientations of followers converge to the convex hull formed by the desired leaders' orientations with zero angular velocities. Moreover, the communication pressure in network is reduced and the energy of each agent is saved. Simulation results show the effectiveness of the proposed method.

  10. A spectral identification technique for adaptive attitude control and pointing of the Space Telescope

    NASA Technical Reports Server (NTRS)

    Teuber, D. L.

    1976-01-01

    The Space Telescope is a 2.4 m class aperture optical telescope having near-diffraction-limited performance. It will be placed into earth orbit by 1980 via the Space Shuttle. The problem considered is how to achieve negligible degradation of the astronomy imaging capability (to 0.005 arc second) due to smearing by pointing motions during observations. Initially, pointing instability sources were identified and a linear stability was used to assess the magnitude of elastic body modes and to design control system compensation regions necessary for subsequent adaptive control. A spectral identification technique for this adaptive attitude control and pointing has been investigated that will alleviate requirements for comprehensive dynamic ground testing. Typical all-digital simulation results describing motions of the telescope line of sight are presented.

  11. System design of the Pioneer Venus spacecraft. Volume 9: Attitude control/mechanisms subsystems studies

    NASA Technical Reports Server (NTRS)

    Neil, A. L.

    1973-01-01

    The Pioneer Venus mission study was conducted for a probe spacecraft and an orbiter spacecraft to be launched by either a Thor/Delta or an Atlas/Centaur launch vehicle. Both spacecraft are spin stabilized. The spin speed is controlled by ground commands to as low as 5 rpm for science instrument scanning on the orbiter and as high as 71 rpm for small probes released from the probe bus. A major objective in the design of the attitude control and mechanism subsystem (ACMS) was to provide, in the interest of costs, maximum commonality of the elements between the probe bus and orbiter spacecraft configurations. This design study was made considering the use of either launch vehicle. The basic functional requirements of the ACMS are derived from spin axis pointing and spin speed control requirements implicit in the acquisition, cruise, encounter and orbital phases of the Pioneer Venus missions.

  12. Fault tolerant attitude sensing and force feedback control for unmanned aerial vehicles

    NASA Astrophysics Data System (ADS)

    Jagadish, Chirag

    Two aspects of an unmanned aerial vehicle are studied in this work. One is fault tolerant attitude determination and the other is to provide force feedback to the joy-stick of the UAV so as to prevent faulty inputs from the pilot. Determination of attitude plays an important role in control of aerial vehicles. One way of defining the attitude is through Euler angles. These angles can be determined based on the measurements of the projections of the gravity and earth magnetic fields on the three body axes of the vehicle. Attitude determination in unmanned aerial vehicles poses additional challenges due to limitations of space, payload, power and cost. Therefore it provides for almost no room for any bulky sensors or extra sensor hardware for backup and as such leaves no room for sensor fault issues either. In the face of these limitations, this study proposes a fault tolerant computing of Euler angles by utilizing multiple different computation methods, with each method utilizing a different subset of the available sensor measurement data. Twenty-five such methods have been presented in this document. The capability of computing the Euler angles in multiple ways provides a diversified redundancy required for fault tolerance. The proposed approach can identify certain sets of sensor failures and even separate the reference fields from the disturbances. A bank-to-turn maneuver of the NASA GTM UAV is used to demonstrate the fault tolerance provided by the proposed method as well as to demonstrate the method of determining the correct Euler angles despite interferences by inertial acceleration disturbances. Attitude computation is essential for stability. But as of today most UAVs are commanded remotely by human pilots. While basic stability control is entrusted to machine or the on-board automatic controller, overall guidance is usually with humans. It is therefore the pilot who sets the command/references through a joy-stick. While this is a good compromise between

  13. Control of nonlinear systems with applications to constrained robots and spacecraft attitude stabilization

    NASA Technical Reports Server (NTRS)

    Krishnan, Hariharan

    1993-01-01

    This thesis is organized in two parts. In Part 1, control systems described by a class of nonlinear differential and algebraic equations are introduced. A procedure for local stabilization based on a local state realization is developed. An alternative approach to local stabilization is developed based on a classical linearization of the nonlinear differential-algebraic equations. A theoretical framework is established for solving a tracking problem associated with the differential-algebraic system. First, a simple procedure is developed for the design of a feedback control law which ensures, at least locally, that the tracking error in the closed loop system lies within any given bound if the reference inputs are sufficiently slowly varying. Next, by imposing additional assumptions, a procedure is developed for the design of a feedback control law which ensures that the tracking error in the closed loop system approaches zero exponentially for reference inputs which are not necessarily slowly varying. The control design methodologies are used for simultaneous force and position control in constrained robot systems. The differential-algebraic equations are shown to characterize the slow dynamics of a certain nonlinear control system in nonstandard singularly perturbed form. In Part 2, the attitude stabilization (reorientation) of a rigid spacecraft using only two control torques is considered. First, the case of momentum wheel actuators is considered. The complete spacecraft dynamics are not controllable. However, the spacecraft dynamics are small time locally controllable in a reduced sense. The reduced spacecraft dynamics cannot be asymptotically stabilized using continuous feedback, but a discontinuous feedback control strategy is constructed. Next, the case of gas jet actuators is considered. If the uncontrolled principal axis is not an axis of symmetry, the complete spacecraft dynamics are small time locally controllable. However, the spacecraft attitude

  14. Dual control active superconductive devices

    DOEpatents

    Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

    1993-07-20

    A superconducting active device has dual control inputs and is constructed such that the output of the device is effectively a linear mix of the two input signals. The device is formed of a film of superconducting material on a substrate and has two main conduction channels, each of which includes a weak link region. A first control line extends adjacent to the weak link region in the first channel and a second control line extends adjacent to the weak link region in the second channel. The current flowing from the first channel flows through an internal control line which is also adjacent to the weak link region of the second channel. The weak link regions comprise small links of superconductor, separated by voids, through which the current flows in each channel. Current passed through the control lines causes magnetic flux vortices which propagate across the weak link regions and control the resistance of these regions. The output of the device taken across the input to the main channels and the output of the second main channel and the internal control line will constitute essentially a linear mix of the two input signals imposed on the two control lines. The device is especially suited to microwave applications since it has very low input capacitance, and is well suited to being formed of high temperature superconducting materials since all of the structures may be formed coplanar with one another on a substrate.

  15. Racism, Gun Ownership and Gun Control: Biased Attitudes in US Whites May Influence Policy Decisions

    PubMed Central

    O’Brien, Kerry; Forrest, Walter; Lynott, Dermot; Daly, Michael

    2013-01-01

    Objective Racism is related to policies preferences and behaviors that adversely affect blacks and appear related to a fear of blacks (e.g., increased policing, death penalty). This study examined whether racism is also related to gun ownership and opposition to gun controls in US whites. Method The most recent data from the American National Election Study, a large representative US sample, was used to test relationships between racism, gun ownership, and opposition to gun control in US whites. Explanatory variables known to be related to gun ownership and gun control opposition (i.e., age, gender, education, income, conservatism, anti-government sentiment, southern vs. other states, political identification) were entered in logistic regression models, along with measures of racism, and the stereotype of blacks as violent. Outcome variables included; having a gun in the home, opposition to bans on handguns in the home, support for permits to carry concealed handguns. Results After accounting for all explanatory variables, logistic regressions found that for each 1 point increase in symbolic racism there was a 50% increase in the odds of having a gun at home. After also accounting for having a gun in the home, there was still a 28% increase in support for permits to carry concealed handguns, for each one point increase in symbolic racism. The relationship between symbolic racism and opposition to banning handguns in the home (OR1.27 CI 1.03,1.58) was reduced to non-significant after accounting for having a gun in the home (OR1.17 CI.94,1.46), which likely represents self-interest in retaining property (guns). Conclusions Symbolic racism was related to having a gun in the home and opposition to gun control policies in US whites. The findings help explain US whites’ paradoxical attitudes towards gun ownership and gun control. Such attitudes may adversely influence US gun control policy debates and decisions. PMID:24204867

  16. Active Interior Noise Control Studies

    NASA Technical Reports Server (NTRS)

    Park, J.; Veeramani, S.; Sampath, A.; Balachandran, B.; Wereley, N.

    1996-01-01

    Analytical and experimental investigations into the control of noise in the interior of a three-dimensional enclosure with a flexible boundary are presented. The rigid boundaries are constructed from acrylic material, and in the different cases considered the flexible boundary is constructed from either aluminum or composite material. Noise generated by an external speaker is transmitted into the enclosure through the flexible boundary and active control is realized by using Lead Zirconate Titanate (PZT) piezoelectric actuators bonded to the flexible boundary. Condenser microphones are used for noise measurements inside and outside the enclosure. Minimization schemes for global and local noise control in the presence of a harmonic disturbance are developed and discussed. In the experiments, analog feedforward control is implemented by using the harmonic disturbance as a reference signal.

  17. Investigations of an integrated angular velocity measurement and attitude control system for spacecraft using magnetically suspended double-gimbal CMGs

    NASA Astrophysics Data System (ADS)

    Zheng, Shiqiang; Han, Bangcheng

    2013-06-01

    This paper presents an integrated angular velocity measurement and attitude control system of spacecraft using magnetically suspended double-gimbal control moment gyros (MSDGCMGs). The high speed rotor of MSDGCMG is alleviated by a five-degree-of-freedom permanent magnet biased AMB control system. With this special rotor supported manner, the MSDGCMG has the function of attitude rate sensing as well as attitude control. This characteristic provides a new approach to a compact light-weight spacecraft design, which can combine these two functions into a single device. This paper discusses the principles and implementations of AMB-based angular velocity measurement. Spacecraft dynamics with DGMSCMG actuators, including the dynamics of magnetically suspended high-speed rotor, the dynamics of inner gimbal and outer gimbal, as well as the determination method of spacecraft angular velocity are modeled, respectively. The effectiveness of the proposed integrated system is also validated numerically and experimentally.

  18. Integrated Orbit and Attitude Control for a Nanosatellite with Power Constraints

    NASA Technical Reports Server (NTRS)

    Berry, Matthew M.; Naasz, Bo J.; Kim, Hye-Young; Hall, Christopher D.

    2002-01-01

    HokieSat is a NASA Goddard sponsored spacecraft currently being built by students at Virginia Tech. HokieSat is part of the Ionospheric Observation Nanosatellite Formation (ION-F) project. The project involves spacecraft built by three schools: Virginia Tech (VT), Utah State University (USU), and University of Washington (UW). The three spacecraft are similar in design and will perform formation flying demonstrations, and make ionospheric measurements. HokieSat uses Pulsed Plasma Thrusters (PPTs) to maintain its position in the formation. There are two pairs of PPTs on HokieSat; their position on HokieSat's hexagonal cross-section is shown. Thrusters T(sub 2) and T(sub 3) provide translation control, and Thrusters TI and T4 can provide yaw steering. Any thruster can be fired individually. However because they share a capacitor, thrusters T(sub 1) and T(sub 2) or thrusters T(sub 3) and T(sub 4) cannot be fired simultaneously. Thrusters T(sub 2) T(sub 3) can be fired simultaneously, as well as thrusters T(sub 1) and T(sub 4). Each thruster provides an impulse-bit of 56 micronN-s and fires at a rate of 1 Hz. For translation control thrusters T2 and T3 are fired together providing an impulse-bit of 112 micronN-s. All four thrusters are positioned slightly above the center of mass, and therefore exert a torque on the spacecraft. Because there are no thrusters in the zenith-nadir directions, and the communication system requires that the spacecraft remain nadir-pointing, there is no way to thrust in the radial direction. The attitude of HokieSat is controlled by 3 orthogonal magnetic torque coils. Attitude control is achieved by forcing a current through the torque coils, which interacts with the Earth's magnetic field and creates a torque. Due to magnetic field interactions between the coils and PPTs, the two actuator systems cannot be used simultaneously, and any attitude or orbit control must be performed in a piecewise fashion. Power limitations place an additional

  19. Adaptive feedback active noise control

    NASA Astrophysics Data System (ADS)

    Kuo, Sen M.; Vijayan, Dipa

    Feedforward active noise control (ANC) systems use a reference sensor that senses a reference input to the controller. This signal is assumed to be unaffected by the secondary source and is a good measure of the undesired noise to be cancelled by the system. The reference sensor may be acoustic (e.g., microphone) or non-acoustic (e.g., tachometer, optical transducer). An obvious problem when using acoustic sensors is that the reference signal may be corrupted by the canceling signal generated by the secondary source. This problem is known as acoustic feedback. One way of avoiding this is by using a feedback active noise control (FANC) system which dispenses with the reference sensor. The FANC technique originally proposed by Olson and May employs a high gain negative feedback amplifier. This system suffered from the drawback that the error microphone had to be placed very close to the loudspeaker. The operation of the system was restricted to low frequency range and suffered from instability due to the possibility of positive feedback. Feedback systems employing adaptive filtering techniques for active noise control were developed. This paper presents the FANC system modeled as an adaptive prediction scheme.

  20. Fault tolerant attitude control for small unmanned aircraft systems equipped with an airflow sensor array.

    PubMed

    Shen, H; Xu, Y; Dickinson, B T

    2014-01-01

    Inspired by sensing strategies observed in birds and bats, a new attitude control concept of directly using real-time pressure and shear stresses has recently been studied. It was shown that with an array of onboard airflow sensors, small unmanned aircraft systems can promptly respond to airflow changes and improve flight performances. In this paper, a mapping function is proposed to compute aerodynamic moments from the real-time pressure and shear data in a practical and computationally tractable formulation. Since many microscale airflow sensors are embedded on the small unmanned aircraft system surface, it is highly possible that certain sensors may fail. Here, an adaptive control system is developed that is robust to sensor failure as well as other numerical mismatches in calculating real-time aerodynamic moments. The advantages of the proposed method are shown in the following simulation cases: (i) feedback pressure and wall shear data from a distributed array of 45 airflow sensors; (ii) 50% failure of the symmetrically distributed airflow sensor array; and (iii) failure of all the airflow sensors on one wing. It is shown that even if 50% of the airflow sensors have failures, the aircraft is still stable and able to track the attitude commands. PMID:25405953

  1. Venusian atmospheric and Magellan properties from attitude control data. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Croom, Christopher A.; Tolson, Robert H.

    1994-01-01

    Results are presented of the study of the Venusian atmosphere, Magellan aerodynamic moment coefficients, moments of inertia, and solar moment coefficients. This investigation is based upon the use of attitude control data in the form of reaction wheel speeds from the Magellan spacecraft. As the spacecraft enters the upper atmosphere of Venus, measurable torques are experienced due to aerodynamic effects. Solar and gravity gradient effects also cause additional torques throughout the orbit. In order to maintain an inertially fixed attitude, the control system counteracts these torques by changing the angular rates of three reaction wheels. Model reaction wheel speeds are compared to observed Magellan reaction wheel speeds through a differential correction procedure. This method determines aerodynamic, atmospheric, solar pressure, and mass moment of inertia parameters. Atmospheric measurements include both base densities and scale heights. Atmospheric base density results confirm natural variability as measured by the standard orbital decay method. Potential inconsistencies in free molecular aerodynamic moment coefficients are identified. Moments of inertia are determined with a precision better than 1 percent of the largest principal moment of inertia.

  2. Estimation of Gravitation Parameters of Saturnian Moons Using Cassini Attitude Control Flight Data

    NASA Technical Reports Server (NTRS)

    Krening, Samantha C.

    2013-01-01

    A major science objective of the Cassini mission is to study Saturnian satellites. The gravitational properties of each Saturnian moon is of interest not only to scientists but also to attitude control engineers. When the Cassini spacecraft flies close to a moon, a gravity gradient torque is exerted on the spacecraft due to the mass of the moon. The gravity gradient torque will alter the spin rates of the reaction wheels (RWA). The change of each reaction wheel's spin rate might lead to overspeed issues or operating the wheel bearings in an undesirable boundary lubrication condition. Hence, it is imperative to understand how the gravity gradient torque caused by a moon will affect the reaction wheels in order to protect the health of the hardware. The attitude control telemetry from low-altitude flybys of Saturn's moons can be used to estimate the gravitational parameter of the moon or the distance between the centers of mass of Cassini and the moon. Flight data from several low altitude flybys of three Saturnian moons, Dione, Rhea, and Enceladus, were used to estimate the gravitational parameters of these moons. Results are compared with values given in the literature.

  3. Analysis of state-of-the-art single-thruster attitude control techniques for spinning penetrator

    NASA Astrophysics Data System (ADS)

    Raus, Robin; Gao, Yang; Wu, Yunhua; Watt, Mark

    2012-07-01

    The attitude dynamics and manoeuvre survey in this paper is performed for a mission scenario involving a penetrator-type spacecraft: an axisymmetric prolate spacecraft spinning around its minor axis of inertia performing a 90° spin axis reorientation manoeuvre. In contrast to most existing spacecraft only one attitude control thruster is available, providing a control torque perpendicular to the spin axis. Having only one attitude thruster on a spinning spacecraft could be preferred for spacecraft simplicity (lower mass, lower power consumption etc.), or it could be imposed in the context of redundancy/contingency operations. This constraint does yield restrictions on the thruster timings, depending on the ratio of minor to major moments of inertia among other parameters. The Japanese Lunar-A penetrator spacecraft proposal is a good example of such a single-thruster spin-stabilised prolate spacecraft. The attitude dynamics of a spinning rigid body are first investigated analytically, then expanded for the specific case of a prolate and axisymmetric rigid body and finally a cursory exploration of non-rigid body dynamics is made. Next two well-known techniques for manoeuvring a spin-stabilised spacecraft, the Half-cone/Multiple Half-cone and the Rhumb line slew, are compared with two new techniques, the Sector-Arc Slew developed by Astrium Satellites and the Dual-cone developed at Surrey Space Centre. Each technique is introduced and characterised by means of simulation results and illustrations based on the penetrator mission scenario and a brief robustness analysis is performed against errors in moments of inertia and spin rate. Also, the relative benefits of each slew algorithm are discussed in terms of slew accuracy, energy (propellant) efficiency and time efficiency. For example, a sequence of half-cone manoeuvres (a Multi-half-cone manoeuvre) tends to be more energy-efficient than one half-cone for the same final slew angle, but more time-consuming. As another

  4. A SURVEY OF CROSS-INFECTION CONTROL PROCEDURES: KNOWLEDGE AND ATTITUDES OF TURKISH DENTISTS

    PubMed Central

    Yüzbaşioglu, Emir; Saraç, Duygu; Canbaz, Sevgi; Saraç, Y. Şinasi; Cengiz, Seda

    2009-01-01

    Objectives: The objective of this study was to investigate the knowledge, attitudes and behavior of Turkish dentists in Samsun City regarding cross-infection control. Material and methods: A questionnaire was designed to obtain information about procedures used for the prevention of cross-infection in dental practices and determine the attitudes and perceptions of respondent dental practitioners to their procedures. The study population included all dentists in the city of Samsun, Turkey, in April 2005 (n=184). The questionnaire collected data on sociodemographic characteristics, knowledge and practice of infection control procedures, sterilization, wearing of gloves, mask, use of rubber dam, method of storing instruments and disposal methods of contaminated material, etc. Questionnaire data was entered into a computer and analyzed by SPSS statistical software. Results: From the 184 dentists to whom the questionnaires were submitted, 135 participated in the study (overall response rate of 73.36%). As much as 74.10% dentists expressed concern about the risk of cross-infection from patients to themselves and their dental assistants. Forty-three percent of the participants were able to define "cross-infection" correctly. The greatest majority of the respondents (95.60%) stated that all patients have to be considered as infectious and universal precautions must apply to all of them. The overall responses to the questionnaire showed that the dentists had moderate knowledge of infection control procedures. Conclusions: Improved compliance with recommended infection control procedures is required for all dentists evaluated in the present survey. Continuing education programs and short-time courses about cross-infection and infection control procedures are suitable to improve the knowledge of dentists. PMID:20027427

  5. Infection Control Knowledge, Attitudes, and Practices among Healthcare Workers in Addis Ababa, Ethiopia

    PubMed Central

    Tenna, Admasu; Stenehjem, Edward A.; Margoles, Lindsay; Kacha, Ermias; Blumberg, Henry M.; Kempker, Russell R.

    2014-01-01

    Objective To better understand hospital infection control practices in Ethiopia. Design A cross-sectional evaluation of healthcare worker (HCW) knowledge, attitudes and practices about hand hygiene and tuberculosis (TB) infection control measures. Methods An anonymous, 76-item questionnaire was administered to HCWs at two university hospitals in Addis Ababa, Ethiopia. Knowledge items were scored as correct/incorrect. Attitude and practice items were assessed using a Likert scale. Results 261 surveys were completed by physicians (51%) and nurses (49%). Fifty-one percent of respondents were male; mean age was 30 years. While hand hygiene knowledge was fair, self-reported practice was suboptimal. Physicians reported performing hand hygiene 7% and 48% before and after patient contact, respectively. Barriers for performing hand hygiene included lack of hand hygiene agents (77%), sinks (30%), proper training (50%), and irritation and dryness (67%) caused by hand sanitizer made per WHO formulation. TB infection control knowledge was excellent (>90% correct). Most HCWs felt at high risk for occupational acquisition of TB (71%) and that proper TB infection control can prevent nosocomial transmission (92%). Only 12% of HCWs regularly wore a mask when caring for TB patients. Only 8% of HCWs reported masks were regularly available and 76% cited a lack of infrastructure to isolate suspected/known TB patients. Conclusions Training HCWs about the importance and proper practice of hand hygiene along with improving hand sanitizer options may improve patient safety. Additionally, enhanced infrastructure is needed to improve TB infection control practices and allay HCW concerns about acquiring TB in the hospital. PMID:24225614

  6. Evaluating Resident Physicians' Knowledge, Attitude, and Practice Regarding the Pain Control in Cancer Patients

    PubMed Central

    Hashemi, Masoud; Akbari, Mohammad Esmaeil; Razavi, Seyed Sajad; Saadat-Niaki, Asadollah; Hoseini Khameneh, Seyed Mehdi

    2015-01-01

    Background Pain has been one of the most debilitating symptoms of cancer. The aim of this study was to evaluate residents' knowledge, attitude, and practice regarding pain control in cancer patients. Methods In a descriptive study, 69 randomly selected third-year various residents practicing in teaching hospitals of Shahid Beheshti School of medicine participated in this study. They have provided their demographic characteristics and completed a questionnaire, based on their “knowledge”, “attitude” and “practice” regarding cancer pain and its management. Data analysis has performed using SPSS v.19. A p value of less than 0.05 has considered as significant. Results Obtained Data from 69 participants including 32 anesthesiology residents has included to our study. The average scores were 35.8±6.1 (ranging from 20 to 49) for the residents' attitude, 25.1±9.1 (ranging from 0 to 53) for their knowledge and 11.2±4.1 (ranging from 0 to 17) for their practice. The overall scores of the questions have related to attitude and knowledge were higher for residents of anesthesiology but the difference was not statistically significant (A: 37.1±4.9 vs. 34.7±6.8, p=0.106, K: 27.2±11.8 vs. 23.3±5.6, p=0.076). The average score for questions on physician' practice was significantly higher in residents of anesthesiology (P: 12.8±3.2 vs. 9.7±4.2, p=0.001). Conclusion In order to provide patients with adequate pain relief, it has seemed advisable for medical schools to focus on improving the educational curriculum and integrating it into clinical practice. PMID:25821565

  7. Novel Active Combustion Control Valve

    NASA Technical Reports Server (NTRS)

    Caspermeyer, Matt

    2014-01-01

    This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

  8. Testing of the on-board attitude determination and control algorithms for SAMPEX

    NASA Technical Reports Server (NTRS)

    Mccullough, Jon D.; Flatley, Thomas W.; Henretty, Debra A.; Markley, F. Landis; San, Josephine K.

    1993-01-01

    Algorithms for on-board attitude determination and control of the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) have been expanded to include a constant gain Kalman filter for the spacecraft angular momentum, pulse width modulation for the reaction wheel command, an algorithm to avoid pointing the Heavy Ion Large Telescope (HILT) instrument boresight along the spacecraft velocity vector, and the addition of digital sun sensor (DSS) failure detection logic. These improved algorithms were tested in a closed-loop environment for three orbit geometries, one with the sun perpendicular to the orbit plane, and two with the sun near the orbit plane - at Autumnal Equinox and at Winter Solstice. The closed-loop simulator was enhanced and used as a truth model for the control systems' performance evaluation and sensor/actuator contingency analysis. The simulations were performed on a VAX 8830 using a prototype version of the on-board software.

  9. Cassini Spacecraft In-Flight Swap to Backup Attitude Control Thrusters

    NASA Technical Reports Server (NTRS)

    Bates, David M.

    2010-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 and arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. In order to meet the challenging attitude control and navigation requirements of the orbit profile at Saturn, Cassini is equipped with a monopropellant thruster based Reaction Control System (RCS), a bipropellant Main Engine Assembly (MEA) and a Reaction Wheel Assembly (RWA). In 2008, after 11 years of reliable service, several RCS thrusters began to show signs of end of life degradation, which led the operations team to successfully perform the swap to the backup RCS system, the details and challenges of which are described in this paper. With some modifications, it is hoped that similar techniques and design strategies could be used to benefit other spacecraft.

  10. Electrospray Thrusters for Attitude Control of a 1-U CubeSat

    NASA Astrophysics Data System (ADS)

    Timilsina, Navin

    With a rapid increase in the interest in use of nanosatellites in the past decade, finding a precise and low-power-consuming attitude control system for these satellites has been a real challenge. In this thesis, it is intended to design and test an electrospray thruster system that could perform the attitude control of a 1-unit CubeSat. Firstly, an experimental setup is built to calculate the conductivity of different liquids that could be used as propellants for the CubeSat. Secondly, a Time-Of-Flight experiment is performed to find out the thrust and specific impulse given by these liquids and hence selecting the optimum propellant. On the other hand, a colloidal thruster system for a 1-U CubeSat is designed in Solidworks and fabricated using Lathe and CNC Milling Machine. Afterwards, passive propellant feeding is tested in this thruster system. Finally, the electronic circuit and wireless control system necessary to remotely control the CubeSat is designed and the final testing is performed. Among the propellants studied, Ethyl ammonium nitrate (EAN) was selected as the best propellant for the CubeSat. Theoretical design and fabrication of the thruster system was performed successfully and so was the passive propellant feeding test. The satellite was assembled for the final experiment but unfortunately the microcontroller broke down during the first test and no promising results were found out. However, after proving that one thruster works with passive feeding, it could be said that the ACS testing would have worked if we had performed vacuum compatibility tests for other components beforehand.

  11. Analysis and experiments for delay compensation in attitude control of flexible spacecraft

    NASA Astrophysics Data System (ADS)

    Sabatini, Marco; Palmerini, Giovanni B.; Leonangeli, Nazareno; Gasbarri, Paolo

    2014-11-01

    Space vehicles are often characterized by highly flexible appendages, with low natural frequencies which can generate coupling phenomena during orbital maneuvering. The stability and delay margins of the controlled system are deeply affected by the presence of bodies with different elastic properties, assembled to form a complex multibody system. As a consequence, unstable behavior can arise. In this paper the problem is first faced from a numerical point of view, developing accurate multibody mathematical models, as well as relevant navigation and control algorithms. One of the main causes of instability is identified with the unavoidable presence of time delays in the GNC loop. A strategy to compensate for these delays is elaborated and tested using the simulation tool, and finally validated by means of a free floating platform, replicating the flexible spacecraft attitude dynamics (single axis rotation). The platform is equipped with thrusters commanded according to the on-off modulation of the Linear Quadratic Regulator (LQR) control law. The LQR is based on the estimate of the full state vector, i.e. including both rigid - attitude - and elastic variables, that is possible thanks to the on line measurement of the flexible displacements, realized by processing the images acquired by a dedicated camera. The accurate mathematical model of the system and the rigid and elastic measurements enable a prediction of the state, so that the control is evaluated taking the predicted state relevant to a delayed time into account. Both the simulations and the experimental campaign demonstrate that by compensating in this way the time delay, the instability is eliminated, and the maneuver is performed accurately.

  12. Integrated Power/Attitude Control System (IPACS) study. Volume 1: Feasibility studies. [application of flywheels for power storage and generation

    NASA Technical Reports Server (NTRS)

    Notti, J. E.; Cormack, A., III; Schmill, W. C.

    1974-01-01

    An Integrated Power/Attitude Control System (IPACS) concept consisting of an array of spinning flywheels, with or without gimbals, capable of performing the dual function of power storage and generation, as well as attitude control has been investigated. This system provides attitude control through momentum storage, and replaces the storage batteries onboard the spacecraft. The results of the investigation are presented in two volumes. The trade-off studies performed to establish the feasibility, cost effectiveness, required level of development, and boundaries of application of IPACS to a wide variety of spacecraft are discussed. The conceptual designs for a free-flying research application module (RAM), and for a tracking and data relay satellite (TDRS) are presented. Results from dynamic analyses and simulations of the IPACS conceptual designs are included.

  13. Knowledge, Attitude, Practice, and Status of Infection Control among Iranian Dentists and Dental Students: A Systematic Review

    PubMed Central

    Moradi Khanghahi, Behnam; Jamali, Zahra; Pournaghi Azar, Fatemeh; Naghavi Behzad, Mohammad; Azami-Aghdash, Saber

    2013-01-01

    Background and aims Infection control is an important issue in dentistry, and the dentists are primarily responsible for observing the relevant procedures. Therefore, the present study evaluated knowledge, attitude, practice, and status of infection control among Iranian dentists through systematic review of published results. Materials and methods In this systematic review, the required data was collected searching for keywords including infection, infection control, behavior, performance, practice, attitude, knowledge, dent*, prevention, Iran* and their Persian equivalents in PubMed, Science Direct, Iranmedex, SID, Medlib, and Magiran databases with a time limit of 1985 to 2012. Out of 698 articles, 15 completely related articles were finally considered and the rest were excluded due to lake of relev-ance to the study goals. The required data were extracted and summarized in an Extraction Table and were analyzed ma-nually. Results Evaluating the results of studies indicated inappropriate knowledge, attitude, and practice regarding infection control among Iranian dentists and dental students. Using personal protection devices and observing measures required for infection control were not in accordance with global standards. Conclusion The knowledge, attitudes, and practice of infection control in Iranian dental settings were found to be inadequate. Therefore, dentists should be educated more on the subject and special programs should be in place to monitor the dental settings for observing infection control standards. PMID:23875081

  14. MERCATOR: Methods and Realization for Control of the Attitude and the Orbit of spacecraft

    NASA Technical Reports Server (NTRS)

    Tavernier, Gilles; Campan, Genevieve

    1993-01-01

    Since 1974, CNES has been involved in geostationary positioning. Among different entities participating in operations and their preparation, the Flight Dynamics Center (FDC) is in charge of performing the following tasks: orbit determination; attitude determination; computation, monitoring, and calibration of orbit maneuvers; computation, monitoring, and calibration of attitude maneuvers; and operational predictions. In order to fulfill this mission, the FDC receives telemetry from the satellite and localization measurements from ground stations (e.g., CNES, NASA, INTELSAT). These data are processed by space dynamics programs integrated in the MERCATOR system which is run on SUN workstations (UNIX O.S.). The main features of MERCATOR are redundancy, modularity, and flexibility: efficient, flexible, and user friendly man-machine interface; and four identical SUN stations redundantly linked in an Ethernet network. Each workstation can perform all the tasks from data acquisition to computation results dissemination through a video network. A team of four engineers can handle the space mechanics aspects of a complete geostationary positioning from the injection into a transfer orbit to the final maneuvers in the station-keeping window. MERCATOR has been or is to be used for operations related to more than ten geostationary positionings. Initially developed for geostationary satellites, MERCATOR's methodology was also used for satellite control centers and can be applied to a wide range of satellites and to future manned missions.

  15. Changes in Primary School Children's Behaviour, Knowledge, Attitudes, and Environments Related to Nutrition and Physical Activity.

    PubMed

    Magarey, Anthea Margaret; Pettman, Tahna Lee; Wilson, Annabelle; Mastersson, Nadia

    2013-01-01

    Rigorous evaluation of large-scale community-based obesity interventions can provide important guidance to policy and decision makers. The eat well be active (ewba) Community Programs, a five-year multilevel, multistrategy community-based obesity intervention targeting children in a range of settings, was delivered in two communities. A comprehensive mixed-methods evaluation using a quasiexperimental design with nonmatched comparison communities was undertaken. This paper describes the changes in primary school children's attitudes, behaviours, knowledge, and environments associated with healthy eating and physical activity, based on data from six questionnaires completed pre- and postintervention by students, parents, and school representatives. As self-reported by students in years from five to seven there were few significant improvements over time in healthy eating and physical activity behaviours, attitudes, knowledge, and perceived environments, and there were few changes in the home environment (parent report). Overall there were considerably more improvements in intervention compared with comparison schools affecting all environmental areas, namely, policy, physical, financial, and sociocultural, in addition to improvements in teacher skill and knowledge. These improvements in children's learning environments are important and likely to be sustainable as they reflect a change of school culture. More sensitive evaluation tools may detect behaviour changes. PMID:24555153

  16. Attitude computation system

    NASA Technical Reports Server (NTRS)

    Werking, R. D.

    1973-01-01

    An attitude computation facility for the control of unmanned satellite missions is reported. The system's major components include: the ability to transfer the attitude data from the control center to the attitude computer at a rate of 2400 bps; an attitude computation center which houses communications, closed circuit TV, graphics devices and a data evaluation area; and the use of interactive graphics devices to schedule jobs and to control program flow.

  17. Neuronal activity controls transsynaptic geometry.

    PubMed

    Glebov, Oleg O; Cox, Susan; Humphreys, Lawrence; Burrone, Juan

    2016-01-01

    The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792

  18. Neuronal activity controls transsynaptic geometry

    PubMed Central

    Glebov, Oleg O.; Cox, Susan; Humphreys, Lawrence; Burrone, Juan

    2016-01-01

    The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792

  19. Predicting condom use attitudes, norms, and control beliefs in Hispanic problem behavior youth: the effects of family functioning and parent-adolescent communication about sex on condom use.

    PubMed

    Malcolm, Shandey; Huang, Shi; Cordova, David; Freitas, Derek; Arzon, Margaret; Jimenez, Giselle Leon; Pantin, Hilda; Prado, Guillermo

    2013-08-01

    Hispanic problem behavior youth are at an increased risk of engaging in HIV risk behaviors, including low condom use. However, relatively little research has examined factors that affect condom use in this population. Although research indicates that family processes, such as higher levels of family functioning and open parent-adolescent communication about sex, and condom use attitudes, norms, and control beliefs as depicted by the theory of planned behavior have an effect on condom use behaviors, the combination of the two factors has received minimal attention. The purpose of this study was to examine the effect of family functioning on condom use intentions and behaviors through communication about sex and condom use attitudes, parental norms, and control beliefs. A cross-sectional study of 171 predominately male (73.1%) sexually active Hispanic problem behavior adolescents (mean age = 14.88 years) was conducted. Structural equation modeling was used to test the study hypothesis. Findings largely support the overall model and suggest that family functioning had an indirect effect on condom use intention and behavior through communication about sex, condom use attitudes, and control beliefs. Family functioning, however, did not have an indirect effect on condom use intention and behavior through communication about sex and parental norms. Implications for prevention science and future research are discussed. PMID:22561377

  20. Predicting Condom Use Attitudes, Norms, and Control Beliefs in Hispanic Problem Behavior Youth: The Effects of Family Functioning and Parent–Adolescent Communication About Sex on Condom Use

    PubMed Central

    Malcolm, Shandey; Huang, Shi; Cordova, David; Freitas, Derek; Arzon, Margaret; Jimenez, Giselle Leon; Pantin, Hilda; Prado, Guillermo

    2012-01-01

    Hispanic problem behavior youth are at an increased risk of engaging in HIV risk behaviors, including low condom use. However, relatively little research has examined factors that affect condom use in this population. Although research indicates that family processes, such as higher levels of family functioning and open parent–adolescent communication about sex, and condom use attitudes, norms, and control beliefs as depicted by the theory of planned behavior have an effect on condom use behaviors, the combination of the two factors has received minimal attention. The purpose of this study was to examine the effect of family functioning on condom use intentions and behaviors through communication about sex and condom use attitudes, parental norms, and control beliefs. A cross-sectional study of 171 predominately male (73.1%) sexually active Hispanic problem behavior adolescents (mean age = 14.88 years) was conducted. Structural equation modeling was used to test the study hypothesis. Findings largely support the overall model and suggest that family functioning had an indirect effect on condom use intention and behavior through communication about sex, condom use attitudes, and control beliefs. Family functioning, however, did not have an indirect effect on condom use intention and behavior through communication about sex and parental norms. Implications for prevention science and future research are discussed. PMID:22561377