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Institute for Robotics and Intelligent Machines (IRIM)
Institute for Robotics and Intelligent Machines (IRIM)
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ItemDecentralized Adaptive Control of a Two Degree of Freedom Flexible Arm(Georgia Institute of Technology, 1989-12) Yuan, Bau-San ; Book, Wayne J. ; Huggins, J. D.A robust adaptive control is derived by signal-synthesis methods for a light, flexible two degree-of-freedom manipulator. The controller for each joint is decentralized, using measurements of one joint's position as well as one link's strain. The coupling to other dynamics is treated as a bounded uncertainty in the model. A stability proof has been developed and is outlined. Performance of the advanced controller is compared to a Linear Quadratic Regulator (LOR) and to an independent joint control. Both simulations and experiments are presented. The cases of payload variations are considered at this point.
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ItemSmall 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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ItemA 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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ItemEfficient 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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ItemDirect Adaptive Control of a One-Link Flexible Arm with Tracking(Georgia Institute of Technology, 1989) Yuan, Bau-San ; Book, Wayne J. ; Siciliano, BrunoA robust tracking controller for a one-link flexible arm based on a model reference adaptive control approach is proposed. In order to satisfy the model matching conditions, the reference model is chosen to be the optimally controlled linearized model of the system. The resulting controller overcomes the fundamental limitation in previously published research on direct adaptive control of flexible robots that required additional actuators solely to control the flexible degrees of freedom. The nominal trajectory is commanded by means of a tracking control. Simulation results for the prototype in the laboratory show improvements obtained with the outer adaptive feedback loop compared to a pure optimal regulator control. Robustness is tested by varying the payload mass.
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ItemSymbolic Modeling and Dynamic Simulation of Robotic Manipulators with Compliant Links and Joints(Georgia Institute of Technology, 1989) Cetinkunt, Sabri ; Book, Wayne J.The explicit, non-recursive symbolic form of the dynamic model of robotic manipulators with compliant links and joints are developed based on a Lagrangian-assumed mode of formulation. This form of dynamic model is suitable for controller synthesis, as well as accurate simulations of robotic applications. The final form of the equations is organized in a form similar to rigid manipulator equations. This allows one to identify the differences between rigid and flexible manipulator dynamics explicitly. Therefore, current knowledge on control of rigid manipulators is likely to be utilized in a maximum way in developing new control algorithms for flexible manipulators. Computer automated symbolic expansion of the dynamic model equations for any desired manipulator is accomplished with programs written based on commercial symbolic manipulation programs (SMP, MACSYMA, REDUCE). A two-link manipulator is used as an example. Computational complexity involved in real-time control, using the explicit, non-recursive form of equations, is studied on single CPU and multi-CPU parallel computation processors.
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ItemTowards the Unification of Navigational Planning and Reactive Control(Georgia Institute of Technology, 1989) Arkin, Ronald C.The illusion that reactive and hierarchical planning methods are at odds with each other needs to be dropped. By exploiting each method's strengths, a synthesis of hierarchical and reactive paradigms can yield robust, flexible, and generalizable navigation. Psychological and neuroscientific studies support this claim.
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ItemTechnology 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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ItemModeling, 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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ItemWorkstation Recognition Using a Constrained Edge Based Hough Transform for Mobile Robot Navigation(Georgia Institute of Technology, 1989) Arkin, Ronald C. ; Vaughn, David L.Landmark recognition is a task required of many robotic systems. In this work, we examine the use of a constrained Hough transform used by a mobile robot to locate a docking workstation. This algorithm deals with the uncertainty inherent in a mobile robot by making use of a spatial uncertainty map maintained by the robot. Several iterations of the Hough transform are run with transformed models of the dock. Votes are accumulated in a collapsed Hough space which, although unable to recover range and orientation information, simplifies locating the dock within the image.