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  • 1
    Electronic Resource
    Electronic Resource
    A mathematical model of the adaptive control of human arm motions (1999)
    Springer
    Biological cybernetics 80 (1999), S. 369-382 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. This paper discusses similarities between models of adaptive motor control suggested by recent experiments with human and animal subjects, and the structure of a new control law derived mathematically from nonlinear stability theory. In both models, the control actions required to track a specified trajectory are adaptively assembled from a large collection of simple computational elements. By adaptively recombining these elements, the controllers develop complex internal models which are used to compensate for the effects of externally imposed forces or changes in the physical properties of the system. On a motor learning task involving planar, multi-joint arm motions, the simulated performance of the mathematical model is shown to be qualitatively similar to observed human performance, suggesting that the model captures some of the interesting features of the dynamics of low-level motor adaptation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050532
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    Paper (German National Licenses)
    Fulltext
  • 2
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    A mathematical model of the adaptive control of human arm motions (1999)
    Springer
    Details
    Publication Date: 1999-05-11
    Print ISSN: 0340-1200
    Electronic ISSN: 1432-0770
    Topics: Biology , Computer Science , Physics
    Published by Springer
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    PAPER CURRENT
  • 3
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    Stable adaptive neurocontrollers for spacecraft and space robots (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper reviews recently developed techniques of adaptive nonlinear control using neural networks, and demonstrates their application to two important practical problems in orbital operations. An adaptive neurocontroller is first developed for spacecraft attitude control applications, and then the same design, slightly modified, is shown to be effective in the control of free-floating orbital manipulators. The algorithms discussed have guaranteed stability and convergence properties, and thus constitute viable alternatives to existing control methodologies. Simulation results are presented demonstrating the performance of each algorithm with representative dynamic models.
    Keywords: CYBERNETICS
    Type: NASA. Goddard Space Flight Center, The 1995 Goddard Conference on Space Applications of Artificial Intelligence and Emerging Information Technologies; p 131-142
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    A Nonlinear Spacecraft Attitude Controller and Observer with an Unknown Constant Gyro Bias and Gyro Noise (2001)
    In:  CASI
    Details
    Publication Date: 2017-09-27
    Description: 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.
    Keywords: Instrumentation and Photography
    Type: 2001 Flight Mechanics Symposium; 249-257; NASA/CP-2001-209986
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    NASA TECHNICAL REPORTS
  • 5
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    A Non-Linear Approach to Spacecraft Trajectory Control in the Vicinity of a Libration Point (2001)
    In:  CASI
    Details
    Publication Date: 2017-09-27
    Description: An expanding interest in mission design strategies that exploit libration point regions demands the continued development of enhanced, efficient, control algorithms for station-keeping and formation maintenance. This paper discusses the development of a non-linear, station-keeping, control algorithm for trajectories in the vicinity of a libration point. The control law guarantees exponential convergence, based on a Lyaponov analysis. Controller performance is evaluated using FreeFlyer(R) and MATLAB(R) for a spacecraft stationed near the L2 libration point in the Earth-Moon system, tracking a pre-defined reference trajectory. Evaluation metrics are fuel usage and tracking accuracy. Simulation results are compared with a linear-based controller for a spacecraft tracking the same reference trajectory. Although the analysis is framed in the context of station-keeping, the control algorithm is equally applicable to a formation flying problem with an appropriate definition of the reference trajectory.
    Keywords: Spacecraft Design, Testing and Performance
    Type: 2001 Flight Mechanics Symposium; 15-24; NASA/CP-2001-209986
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  • 6
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    Hubble Space Telescope Angular Velocity Estimation During the Robotic Servicing Mission (2005)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: In 2004 NASA began investigation of a robotic servicing mission for the Hubble Space Telescope (HST). Such a mission would require estimates of the HST attitude and rates in order to achieve a capture by the proposed Hubble robotic vehicle (HRV). HRV was to be equipped with vision-based sensors, capable of estimating the relative attitude between HST and HRV. The inertial HST attitude is derived from the measured relative attitude and the HRV computed inertial attitude. However, the relative rate between HST and HRV cannot be measured directly. Therefore, the HST rate with respect to inertial space is not known. Two approaches are developed to estimate the HST rates. Both methods utilize the measured relative attitude and the HRV inertial attitude and rates. First, a nonlinear estimator is developed. The nonlinear approach estimates the HST rate through an estimation of the inertial angular momentum. The development includes an analysis of the estimator stability given errors in the measured attitude. Second, a linearized approach is developed. The linearized approach is a pseudo-linear Kalman filter. Simulation test results for both methods are given, including scenarios with erroneous measured attitudes. Even though the development began as an application for the HST robotic servicing mission, the methods presented are applicable to any rendezvous/capture mission involving a non-cooperative target spacecraft.
    Keywords: Space Sciences (General)
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Formation Control for the MAXIM Mission (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Over the next twenty years, a wave of change is occurring in the space-based scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today s technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. MAXIM formation flying requirements are on the order of microns, while Stellar Imager mission requirements are on the order of nanometers. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; and (2) the development of linearized equations of relative motion for a formation operating in an n-body gravitational field. Linearized equations of motion provide the ground work for linear formation control designs.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings from the 2nd International Symposium on Formation Flying Missions and Technologies; NASA/CP-2005-212781
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Nonlinear Observers for Gyro Calibration Coupled with a Nonlinear Control Algorithm (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Nonlinear observers for gyro calibration are presented. The first observer estimates a constant gyro bias. The second observer estimates scale factor errors. The third observer estimates the gyro alignment for three orthogonal gyros. The observers are then combined. The convergence properties of all three observers, and the combined observers, are discussed. Additionally, all three observers are coupled with a nonlinear control algorithm. The stability of each of the resulting closed loop systems is analyzed. Simulated test results are presented for each system.
    Keywords: Aircraft Stability and Control
    Type: AAS Guidance and Control Conference; Feb 01, 2004; Breckenridge, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Linear State-Space Representation of the Dynamics of Relative Motion, Based on Restricted Three Body Dynamics (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Precision Formation Flying is an enabling technology for a variety of proposed space-based observatories, including the Micro-Arcsecond X-ray Imaging Mission (MAXIM) , the associated MAXIM pathfinder mission, Stellar Imager (SI) and the Terrestrial Planet Finder (TPF). An essential element of the technology is the control algorithm, requiring a clear understanding of the dynamics of relative motion. This paper examines the dynamics of relative motion in the context of the Restricted Three Body Problem (RTBP). The natural dynamics of relative motion are presented in their full nonlinear form. Motivated by the desire to apply linear control methods, the dynamics equations are linearized and presented in state-space form. The stability properties are explored for regions in proximity to each of the libration points in the Earth/Moon - Sun rotating frame. The dynamics of relative motion are presented in both the inertial and rotating coordinate frames.
    Keywords: Spacecraft Design, Testing and Performance
    Type: AIAA Guidance and Control Conference; Aug 16, 2004 - Aug 19, 2004; Providence, RI; United States
    Format: application/pdf
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  • 10
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    A Nonlinear Adaptive Filter for Gyro Thermal Bias Error Cancellation (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Deterministic errors in angular rate gyros, such as thermal biases, can have a significant impact on spacecraft attitude knowledge. In particular, thermal biases are often the dominant error source in MEMS gyros after calibration. Filters, such as J\,fEKFs, are commonly used to mitigate the impact of gyro errors and gyro noise on spacecraft closed loop pointing accuracy, but often have difficulty in rapidly changing thermal environments and can be computationally expensive. In this report an existing nonlinear adaptive filter is used as the basis for a new nonlinear adaptive filter designed to estimate and cancel thermal bias effects. A description of the filter is presented along with an implementation suitable for discrete-time applications. A simulation analysis demonstrates the performance of the filter in the presence of noisy measurements and provides a comparison with existing techniques.
    Keywords: Spacecraft Design, Testing and Performance
    Type: GSFC.CP.5989.2012 , GSFC.CP.6788.2012 , AIAA Guidance, Navigation, and Control Conference; Aug 13, 2012 - Aug 16, 2012; Minneapolis, MN; United States
    Format: application/pdf
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