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  • 1
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    Spatial operator factorization and inversion of the manipulator mass matrix (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper advances two linear operator factorizations of the manipulator mass matrix. Embedded in the factorizations are many of the techniques that are regarded as very efficient computational solutions to inverse and forward dynamics problems. The operator factorizations provide a high-level architectural understanding of the mass matrix and its inverse, which is not visible in the detailed algorithms. They also lead to a new approach to the development of computer programs or organize complexity in robot dynamics.
    Keywords: MECHANICAL ENGINEERING
    Type: IEEE Transactions on Robotics and Automation (ISSN 1042-296X); 8; 65-76
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  • 2
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    JPL space robotics: Present accomplishments and future thrusts (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Complex missions require routine and unscheduled inspection for safe operation. The purpose of research in this task is to facilitate structural inspection of the planned Space Station while mitigating the need for extravehicular activity (EVA), and giving the operator supervisory control over detailed and somewhat mundane, but important tasks. The telerobotic system enables inspection relative to a given reference (e.g., the status of the facility at the time of the last inspection) and alerts the operator to potential anomalies for verification and action. There are two primary objectives of this project: (1) To develop technologies that enable well-integrated NASA ground-to-orbit telerobotics operations, and (2) to develop a prototype common architecture workstation which implements these capabilities for other NASA technology projects and planned NASA flight applications. This task develops and supports three telerobot control modes which are applicable to time delay operation: Preview teleoperation, teleprogramming, and supervised autonomy.
    Keywords: MECHANICAL ENGINEERING
    Type: Third International Symposium on Artificial Intelligence, Robotics, and Automation for Space 1994; p 131-134
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  • 3
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    Space Station Freedom seal leakage rate analysis and testing summary: Air leaks in ambient versus vacuum exit conditions (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report is intended to reveal the apparent relationship of air seal leakage rates between 2 atmospheres (atm) to 1 atm and 1 atm to vacuum conditions. Gas dynamics analysis is provided as well as data summarizing the MSFC test report, 'Space Station Freedom (S.S. Freedom) Seal Flaw Study With Delta Pressure Leak Rate Comparison Test Report'.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-103604 , NAS 1.15:103604
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  • 4
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    System considerations for a magnetically suspended flywheel (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper presents the system considerations of a magnetically suspended energy storage system. The key technologies for system success are presented in a technology flowchart. The key areas identified and discussed include: the active bearing control system, the back-up touchdown bearings, and the flywheel dynamic performance and balancing. Two possible hardware designs are described which have been identified as having characteristics suitable for energy storage in low earth orbit spacecraft. Finally, a matrix of the key technologies versus the various prototype designs is presented to show the current progress of inertial energy storage, and to show the direction of future work.
    Keywords: MECHANICAL ENGINEERING
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  • 5
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    Spatially random models, estimation theory, and robot arm dynamics (1987)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Spatially random models provide an alternative to the more traditional deterministic models used to describe robot arm dynamics. These alternative models can be used to establish a relationship between the methodologies of estimation theory and robot dynamics. A new class of algorithms for many of the fundamental robotics problems of inverse and forward dynamics, inverse kinematics, etc. can be developed that use computations typical in estimation theory. The algorithms make extensive use of the difference equations of Kalman filtering and Bryson-Frazier smoothing to conduct spatial recursions. The spatially random models are very easy to describe and are based on the assumption that all of the inertial (D'Alembert) forces in the system are represented by a spatially distributed white-noise model. The models can also be used to generate numerically the composite multibody system inertia matrix. This is done without resorting to the more common methods of deterministic modeling involving Lagrangian dynamics, Newton-Euler equations, etc. These methods make substantial use of human knowledge in derivation and minipulation of equations of motion for complex mechanical systems.
    Keywords: MECHANICAL ENGINEERING
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the Workshop on Space Telerobotics, Volume 2; p 177-184
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  • 6
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    Controlling under-actuated robot arms using a high speed dynamics process (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The invention controls an under-actuated manipulator by first obtaining predetermined active joint accelerations of the active joints and the passive joint friction forces of the passive joints, then computing articulated body qualities for each of the joints from the current positions of the links, and finally computing from the articulated body qualities and from the active joint accelerations and the passive joint forces, active joint forces of the active joints. Ultimately, the invention transmits servo commands to the active joint forces thus computed to the respective ones of the joint servos. The computation of the active joint forces is accomplished using a recursive dynamics algorithm. In this computation, an inward recursion is first carried out for each link, beginning with the outermost link in order to compute the residual link force of each link from the active joint acceleration if the corresponding joint is active, or from the known passive joint force if the corresponding joint is passive. Then, an outward recursion is carried out for each link in which the active joint force is computed from the residual link force if the corresponding joint is active or the passive joint acceleration is computed from the residual link force if the corresponding joint is passive.
    Keywords: MECHANICAL ENGINEERING
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  • 7
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    Controlling flexible robot arms using a high speed dynamics process (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Described here is a robot controller for a flexible manipulator arm having plural bodies connected at respective movable hinges, and flexible in plural deformation modes. It is operated by computing articulated body qualities for each of the bodies from the respective modal spatial influence vectors, obtaining specified body forces for each of the bodies, and computing modal deformation accelerations of the nodes and hinge accelerations of the hinges from the specified body forces, from the articulated body quantities and from the modal spatial influence vectors. In one embodiment of the invention, the controller further operates by comparing the accelerations thus computed to desired manipulator motion to determine a motion discrepancy, and correcting the specified body forces so as to reduce the motion discrepancy. The manipulator bodies and hinges are characterized by respective vectors of deformation and hinge configuration variables. Computing modal deformation accelerations and hinge accelerations is carried out for each of the bodies, beginning with the outermost body by computing a residual body force from a residual body force of a previous body, computing a resultant hinge acceleration from the body force, and then, for each one of the bodies beginning with the innermost body, computing a modal body acceleration from a modal body acceleration of a previous body, computing a modal deformation acceleration and hinge acceleration from the resulting hinge acceleration and from the modal body acceleration.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:NPO-18499-1-CU
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  • 8
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    Recursive forward dynamics for multiple robot arms moving a common task object (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Recursive forward dynamics algorithms are developed for an arbitrary number of robot arms moving a commonly held object. The multiarm forward dynamics problem is to find the angular accelerations at the joints and the contact forces that the arms impart to the task object. The problem also involves finding the acceleration of this object. The multiarm forward dynamics solutions provide a thorough physical and mathematical understanding of the way several arms behave in response to a set of applied joint moments. Such an understanding simplifies and guides the subsequent control design and experimentation process. The forward dynamics algorithms also provide the necessary analytical foundation for conducting analysis and simulation studies. The multiarm algorithms are based on the filtering and smoothing approach recently advanced for single-arm dynamics, and they can be built up modularly from the single-arm algorithms. The algorithms compute recursively the joint-angle accelerations, the contact forces, and the task-object accelerations. Algorithms are also developed to evaluate in closed form the linear transformations from the active joint moments to the joint-angle accelerations, to the task-object accelerations., and to the task-object contact forces. A possible computing architecture is presented as a precursor to a more complete investigation of the computational performance of the dynamics algorithms.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-182526 , JPL-PUBL-88-6 , NAS 1.26:182526
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  • 9
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    Magnetic bearings for inertial energy storage (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Advanced flywheels utilizing high strength fibers must operate at high rotational speeds and as such must operate in vacuum to reduce windage losses. The utilization of magnetic bearings in the flywheels overcome lubrication and seal problems, resulting in an energy storage system offering potential improvements over conventional electrochemical energy storage. Magnetic bearings evolved in the 1950s from the simple application of permanent magnets positioned to exert repulsive forces to the present where permanent magnets and electromagnets have been combined to provide axial and radial suspension. Further development of magnetic suspension has led to the design of a shaftless flywheel system for aerospace application. Despite the lack of proof of concept, integrated magnetic suspension in inertial storage systems can provide significant performance improvements to warrant development and tests.
    Keywords: MECHANICAL ENGINEERING
    Type: IECEC ''87; Aug 10, 1987 - Aug 14, 1987; Philadelphia, PA; United States
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  • 10
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    Recursive dynamics for geared robot manipulators (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The authors consider the dynamical modeling of robot manipulators whose joint actuators consist of motors driving the joints through gears. The dynamical models for such manipulators are significantly more complex than those for direct drive manipulators. The authors develop recursive O(n) inverse and forward dynamics algorithms as well as recursive O(n2) algorithms for the computation of the mass matrix for geared manipulators. It is shown that, despite the added complexity of the dynamical models for geared manipulators, the algorithms closely resemble the corresponding algorithms for direct drive manipulators, and that the additional algorithmic or computational complexity is relatively insignificant. As a consequence, with little additional cost, existing direct drive algorithms can be easily extended to handle the effects of gearing at the joints.
    Keywords: MECHANICAL ENGINEERING
    Type: IEEE Conference on Decision and Control; Dec 05, 1990 - Dec 07, 1990; Honolulu, HI; United States
    Format: text
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