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Book,
Wayne J.
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Wayne J.
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ItemSteerability in Planar Dissipative Passive Robots(Georgia Institute of Technology, 2009) Gao, Dalong ; Book, Wayne J.Steerability is intuitively the ability to change directions. In this paper, a formal definition is given for the steerability of a robot achieved either passively or actively. A dissipative passive robot uses only passive actuators such as brakes and clutches (a clutch is essentially a brake plus a gearbox) to redirect or steer operator-imposed motion by dissipating energy. While it has safety and ergonomic advantages, which are essential for human interactions, it also has difficulties in redirecting certain motions since passive actuators cannot add energy. The force generated from a passive actuator is used to measure the steerability. A steerability theorem was then developed for a manipulator with generalized passive actuators. The steerability analysis for an example diamond-shaped manipulator shows the difference in steerability when using only brakes or a combination of brakes and clutches. Further analyses show the difference comes from the ability of a clutch to change the direction of the generated force in the subject robot by altering the effective gear ratios
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ItemTransfer functions of flexible beams and implication of flexibilty on controller performance(Georgia Institute of Technology, 1994) Cetinkunt, Sabri ; Book, Wayne J.Dynamic behavior of many mechanical motion systems having distributed flexibility are described by linear partial differential equations, i.e. flexible beams, satellite appendages, plates. Understanding the open loop transfer function (poles, zeros, d.c. gain) is a prerequisite for a successful controller design. The open loop pole-zero patterns of a flexible beam (using its infinite dimensional model) are studied as a function of actuator and sensor locations. The physics of the flexible beam dynamics is discussed in order to explain the physical source and the meaning of zeros, and its implications in terms, of the limitations imposed on the maximum closed loop bandwidth achievable. Although the actual system dynamics involve an infinite number of modes, finite dimensional models are needed for the design of a real time controller. The accuracy of finite dimensional models using different mode shapes are compared from a controller design point of view.
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ItemContact Control for Advanced Applications of Light Weight Arms(Georgia Institute of Technology, 1992) Book, Wayne J. ; Kwon, Dong-SooMany applications of robotic and teleoperated manipulator arms require operation in contact and noncontact regimes. This paper deals with both regimes and the transition between them with special attention given to problems of flexibility in the links and drives. This is referred to as contact control. Inverse dynamics is used to plan the tip motion of the flexible link so that the free motion can stop very near the contact surface without collision due to overshoot. Contact mus occur at a very low speed since the high frequency impact forces are too sudden to be affected by any feedback generated torques applied to a joint at the other end of the link. The effects of approach velocity and surface properties are discussed. Force tracking is implemented by commands to the deflection states of the link and the contact force. This enable a natural transition between tip position and tip force control that is not possible when the arm is treated as rigid. The effects of feedback gain, force trajectory, and desired final force level are of particular interest and are studied. Experimental results are presented on a one-link arm and the system performance in the overall contact task is analyzed. Extension to multi-link cases with potential applications are discussed.
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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.