Organizational Unit:
Institute for Robotics and Intelligent Machines (IRIM)

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Publication Search Results

Now showing 1 - 10 of 36
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    Small Motion Experiments on a Large Flexible Arm with Strain Feedback
    (Georgia Institute of Technology, 1989-06) Yuan, B. S. ; Huggins, J. D. ; Book, Wayne J.
    Initial experiments on state space feedback control of a large flexible manipulator with a parallel linkage drive are described. A linear controller using joint angle and strain measurements was designed to minimize a quadratic performance index with a prescribed stability margin. It is based on a simplified model that accounts for the constraints of the parallel linkage kinematically rather than through constraint forces. The results show substantial improvement over a simple P.O. joint control.
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    A Reduced Order Model Derivation for Lightweight Arms with A Parallel Mechanism
    (Georgia Institute of Technology, 1989-05) Tsujisawa, Takahiko ; Book, Wayne J.
    RALF (Robotic Arm, Large and Flexible) with a parallel link mechanism has been developed at School of Mechanical Engineering at Georgia Institute of Technology. The structure consists of two ten foot long links and an actuator link which is parallel to the first link and drives the second link. In this paper, a derivation of a reduced order model for RALF by the modal cost analysis methods is shown. The original models are based on the first 5 component modes of each link. Two sets of mode shapes are considered which result from different boundary conditions on the components (links). The reduced order model which consists of the first 2 modes of each link is optimal from the control point of view. The evaluation of the reduced order model is made by the comparison between the frequency responses and the modal cost analysis results.
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    Efficient Dynamic Models for Flexible Robots
    (Georgia Institute of Technology, 1989-05) Lee, Jeh Won ; Book, Wayne J.
    Dynamic equations of motion of flexible manipulators are more complicated than those of rigid manipulators. The number of equations of motion increases as the number of modes to be included increases. It is difficult to understand the effect of flexible motion on rigid motion via recursive forms of the equations of motion for multi-link arm even if it were efficient. On the other hand, the closed form of the equations of motion is useful in understanding the characteristics of model parameters. However, the equations resulting from existing closed forms are too complex to serve this purpose. Therefore, a method which is structurally well organized and computationally efficient is developed.
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    Technology and Task Parameters Relating to the Effectiveness of the Bracing Strategy
    (Georgia Institute of Technology, 1989) Book, Wayne J. ; Wang, J. J.
    The bracing strategy has been proposed in various forms as a way to improve robot performance. One version of the strategy employs independent stages of motion. The first stage, refered to here as the large or bracing arm, carries the second stage of motion. After the first stage has completed its motion it is braced to provide a more rigid base of motion with a more accurate relationship to the parts to be manipulated. The hypothesis of this research is that more rapid completion of certain tasks is possible with lighter arms using the bracing strategy. While it is easy to make conceptual arguments why this should be so, it is less easy to specify even approximately when this will be true for some reasonably generic situation. There is no relevant experience base with bracing arms to be compared to non-bracing arms. Furthermore, if one were interested in obtaining such practical, or at least relevant, experience, there would be no methodical guidance on the selection of an interesting case. An "interesting case" is one in which the unproven approach, bracing in this paper, can show its superiority. If one such case exists, only the extent of applicability of the new approach is in question. One set of "interesting cases" is likely to be applications in which a large workspace must be covered, but where a series of small accurate moves will remain within a smaller region of the total workspace. A prototype application with these characteristics will be set up and a skeleton design of arms using the competing strategies will be compared.
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    Modeling, Design, and Control of Flexible Manipulator Arms: Status and Trends
    (Georgia Institute of Technology, 1989) Book, Wayne J.
    The desire for higher performance manipulators has lead to dynamic behavior in which the flexibility is an essential aspect. This paper first examines the mathematical representations commonly used in modeling flexible arms and arms with flexible drives. Then design considerations directly arising from the flexible nature of the arm are discussed. Finally, controls of joints for general and tip motion are discussed.
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    Dynamic Analysis and Control of Lightweight Arms with a Parallel Mechanism
    (Georgia Institute of Technology, 1988-07) Yuan, B. S. ; Lee, J. W. ; Book, Wayne J.
    A parallelogram drive enables lightweight arms to have a higher rigidity and to reduce the actuator weight moved. Analysis of the flexible closed kinematic chain dynamics and design of the control are described in this paper. The system dynamics is derived by the Lagrangian formula via the assumed mode method. Holonomic constraints due to the geometry of the parallelogram mechanism must be imposed on the dynamics. An orthonormal basis has been. computed from the singular value decomposition of the constraint Jacobian matrix in order to eliminate the constraint force in the equations of motion. The comparatively large workspace and fast motion make motion control with flexibility in each link computationally demanding. The general rigid control (GRC) is implemented to overcome these problems. The solution algorithm checks the constraint violations. Numerical simulation illustrates the results under feedback control.
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    Performance of Lightweight Manipulators Under Joint Variable Feedback Control: Analytical Study of Limitations
    (Georgia Institute of Technology, 1988-06) Cetinkunt, Sabri ; Book, Wayne J.
    The performance limitations of joint variable feedback controlled manipulators due to manipulator flexibility are studied in fine and gross motions. A finite dimensional time-domain manipulator model is used in the study. Fine motion analysis results agree very well with the previously reported results based on infinite dimensional frequency domain models. The limitations of a class of adaptive controllers in high speed gross motion control are studied. Manipulation speeds are quantified as low, medium, or high with reference to the arm flexibility and dynamic nonlinearities.
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    Experimental Verification of a Large Flexible Manipulator
    (Georgia Institute of Technology, 1988-06) Lee, Jae Won ; Huggins, James D.
    A large experimental lightweight manipulator would be useful for material handling, for welding, or for ultrasonic inspection of a large structure such as an airframe. The flexible parallel link mechanism is designed for high rigidity without increasing weight. This constrained system is analyzed by singular value decomposition of the constraint Jacobian matrix. This paper presents a verification of the modeling using the assumed mode method. Eigenvalues and eigenvectors of the linearized model are compared to the measured system natural frequencies and their associated mode shapes. The modeling results for large motions are compared to the time response data from the experiments. The hydraulic actuator are also verified.
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    Decentralized Adaptive Control of Robot Manipulators with Robust Stabilization Design
    (Georgia Institute of Technology, 1988-06) Yuan, Bau-San ; Book, Wayne J.
    Due to geometric nonlinearities and complex dynamics, a decentralized technique for adaptive control for multilink robot arms is attractive. Lyapunov-function theory for stability analysis provides an approach to robust stabilization. Each joint of the arm is treated as a component subsystem. The adaptive controller is made locally stable with servo signals including proportional and integral gains. This results in the bound on the dynamical interactions with other subsystems. A nonlinear controller which stabilizes the system with uniform boundedness is used to improve the robustness properties of the overall system. As a result, the robot tracks the reference trajectories with convergence. This strategy makes computation simple and therefore facilitates real-time implementation.
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    A Framework for Analysis of a Bracing Manipulator with Staged Positioning
    (Georgia Institute of Technology, 1988) Kwon, Dong-Soo ; Book, Wayne J.
    The concepts of staging and bracing arc introduced with the specific example of a bracing manipulator. Staging describes the operational strategy which divides the positioning procedure into two or more levels to maximize the efficiency of the total positioning system. A bracing manipulator can be operated like a two-stage motion system. The bracing effect is evaluated from the view point of reduction of positioning uncertainty. Uncertainty sources in the manipulator, and the reduction of the positioning uncertainty by geometric bracing constraints arc analyzed. The framework of controlling a bracing manipulator will be discussed with the hybrid position and force control.