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  • 1
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    Linearization of manipulator dynamics using spatial operators (1993)
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    Publication Date: 2011-08-24
    Description: Linearized dynamics models for manipulators are useful in robot analysis, motion planning, and control applications. Techniques from the spatial operator algebra are used to obtain closed form operator expressions for two types of linearized dynamics models, the linearized inverse and forward dynamics models. Spatially recursive algorithms of O(n) and O(n-squared) complexity for the computation of the perturbation vector and coefficient matrices for the linearized inverse dynamics model are developed first. Subsequently, operator factorization and inversion identities are used to develop corresponding closed-form expressions for the linearized forward dynamics model (LFDM). Once again, these are used to develop algorithms of O(n) and O(n-squared) complexity for the computation of the perturbation vector and the coefficient matrices. The algorithms for the LFDM do not require the explicit computation of the mass matrix nor its numerical inversion and are also of lower complexity than the conventional O(n-cubed) algorithms.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Systems, Man, and Cybernetics (ISSN 0018-9472); 23; 1; p. 239-248.
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  • 2
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    Recursive flexible multibody system dynamics using spatial operators (1992)
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    Publication Date: 2011-08-24
    Description: This paper uses spatial operators to develop new spatially recursive dynamics algorithms for flexible multibody systems. The operator description of the dynamics is identical to that for rigid multibody systems. Assumed-mode models are used for the deformation of each individual body. The algorithms are based on two spatial operator factorizations of the system mass matrix. The first (Newton-Euler) factorization of the mass matrix leads to recursive algorithms for the inverse dynamics, mass matrix evaluation, and composite-body forward dynamics for the systems. The second (innovations) factorization of the mass matrix, leads to an operator expression for the mass matrix inverse and to a recursive articulated-body forward dynamics algorithm. The primary focus is on serial chains, but extensions to general topologies are also described. A comparison of computational costs shows that the articulated-body, forward dynamics algorithm is much more efficient than the composite-body algorithm for most flexible multibody systems.
    Keywords: CYBERNETICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 15; 6; p. 1453-1466.
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  • 3
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    Spatial operator approach to flexible manipulator inverse and forward dynamics (1990)
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    Publication Date: 2011-08-19
    Description: This study extends to flexible multibody manipulators the recent results of the author on the use of spatially recursive filtering and smoothing techniques for robot arm dynamics. The configuration analyzed is that of a mechanical system of flexible bodies joined together by articulated joints. The inverse and forward dynamics problems are solved using the techniques of spatially recursive Kalman filtering and smoothing. The algorithms are easily developed using a set of identities associated with mass matrix factorization and inversion. The identities are easily derived using a spatial operator algebra developed by the author.
    Keywords: CYBERNETICS
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  • 4
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    A spatial operator algebra for manipulator modeling and control (1991)
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    Publication Date: 2011-08-19
    Description: A recently developed spatial operator algebra for manipulator modeling, control, and trajectory design is discussed. The elements of this algebra are linear operators whose domain and range spaces consist of forces, moments, velocities, and accelerations. The effect of these operators is equivalent to a spatial recursion along the span of a manipulator. Inversion of operators can be efficiently obtained via techniques of recursive filtering and smoothing. The operator algebra provides a high-level framework for describing the dynamic and kinematic behavior of a manipulator and for control and trajectory design algorithms. The interpretation of expressions within the algebraic framework leads to enhanced conceptual and physical understanding of manipulator dynamics and kinematics.
    Keywords: CYBERNETICS
    Type: International Journal of Robotics Research (ISSN 0278-3649); 10; 371-381
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  • 5
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    Kalman filtering, smoothing, and recursive robot arm forward and inverse dynamics (1987)
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    Publication Date: 2011-08-19
    Description: The recursive difference equations of Kalman filtering and Bryson-Frazier fixed time-interval smoothing, arising in the state estimation theory for linear state space systems, are used here to solve problems of serial manipulator inverse and forward dynamics. The configuration analyzed is that of a joint connected N-link serial manipulator attached to an immobile base. The equivalence between the filtering and smoothing techniques from state estimation theory and recursive robot dynamics methods is demonstrated. Several areas for future research are suggested.
    Keywords: CYBERNETICS
    Type: IEEE Journal of Robotics and Automation (ISSN 0882-4967); RA-3; 624-639
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  • 6
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    Recursive forward dynamics for multiple robot arms moving a common task object (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recursive forward dynamics algorithms are developed and presented 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: CYBERNETICS
    Type: IEEE Transactions on Robotics and Automation (ISSN 1042-296X); 5; 510-521
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  • 7
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    Beyond the Kirchhoff approximation (1989)
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    Publication Date: 2011-08-19
    Description: The three most successful models for describing scattering from random rough surfaces are the Kirchhoff approximation (KA), the small-perturbation method (SPM), and the two-scale-roughness (or composite roughness) surface-scattering (TSR) models. In this paper it is shown how these three models can be derived rigorously from one perturbation expansion based on the extinction theorem for scalar waves scattering from perfectly rigid surface. It is also shown how corrections to the KA proportional to the surface curvature and higher-order derivatives may be obtained. Using these results, the scattering cross section is derived for various surface models.
    Keywords: PHYSICS (GENERAL)
    Type: Radio Science (ISSN 0048-6604); 24; 681-693
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  • 8
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    Random field estimation approach to robot dynamics (1990)
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    Publication Date: 2011-08-19
    Description: The difference equations of Kalman filtering and smoothing recursively factor and invert the covariance of the output of a linear state-space system driven by a white-noise process. Here it is shown that similar recursive techniques factor and invert the inertia matrix of a multibody robot system. The random field models 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. They are easier to describe than the models based on classical mechanics, which typically require extensive derivation and manipulation of equations of motion for complex mechanical systems. With the spatially random models, more primitive locally specified computations result in a global collective system behavior equivalent to that obtained with deterministic models. The primary goal of applying random field estimation is to provide a concise analytical foundation for solving robot control and motion planning problems.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Systems, Man, and Cybernetics (ISSN 0018-9472); 20; 1081-109
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  • 9
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    Magnetically suspended flywheel system study (1984)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A program to study the application of a graphite/epoxy, magnetically suspended, pierced disk flywheel for the combined function of spacecraft attitude control and energy storage (ACES) is described. Past achievements of the program include design and analysis computer codes for the flywheel rotor, a magnetically suspended flywheel model, and graphite/epoxy rotor rings that were successfully prestressed via interference assembly. All hardware successfully demonstrated operation of the necessary subsystems which form a complete ACES design. Areas of future work include additional rotor design research, system definition and control strategies, prototype development, and design/construction of a UM/GSFC spin test facility. The results of applying design and analysis computer codes to a magnetically suspended interference assembled rotor show specific energy densities of 42 Wh/lb (92.4 Wh/kg) are obtained for a 1.6 kWh system.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Langley Research Center An Assessment of Integrated Flywheel System Technol.; p 307-328
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  • 10
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    GSFC Flywheel Status (1983)
    In:  CASI
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    Publication Date: 2014-09-10
    Description: The assessment of flywheel energy storage for spacecraft power system is based on the conceptual flywheel design. This conceptual design of an integrated flywheel is based on the Mechanical Capacitor which evolved from development of magnetic bearings and permanent magnet ironless-brushless DC motors. The mechanical capacitor is based on three key technologies: (1) a composite rotor with a low ID to OD ratio for high energy density (weight and volume); (2) magnetic suspension close to the geometric center of the rotating mass to minimize loads normally encountered on the ends of a shaft, a no-wear mechanism in a vacuum environment, and to minimize losses at high rotational speeds; (3) permanent magnet ironless-brushless DC motor/generator for high efficiency of conversion and low losses at high rotational speeds. The complete system would include the necessary electronics for the motor/generator, containment, and counterrotating wheels for attitude control compatibility.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Langley Research Center Integrated Flywheel Technol., 1983; p 23-34
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