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Institute for Robotics and Intelligent Machines (IRIM)
Institute for Robotics and Intelligent Machines (IRIM)
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32 results
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ItemCooperative Exploration of Level Surfaces of Three Dimensional Scalar Fields(Georgia Institute of Technology, 2011) Wu, W. ; Zhang, Fumin
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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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ItemForce reflecting teleoperation with adaptive impedance control(Georgia Institute of Technology, 2004-02) Love, Lonnie J. ; Book, Wayne J.Experimentation and a survey of the literature clearly show that contact stability in a force reflecting teleoperation system requires high levels of damping on the master robot. However, excessive damping increases the energy required by an operator for commanding motion. The objective of this paper is to describe a new force reflecting teleoperation methodology that reduces operator energy requirements without sacrificing stability. We begin by describing a new approach to modeling and identifying the remote environment bf the teleoperation system. We combine a conventional Multi-Input, Multi-Output Recursive Least Squares (MIMO-RLS) system identification, identifying in real-time the remote environment impedance, with a discretized representation 'of the remote environment. This methodology generates a time-varying, position dependent representation of the remote environment dynamics. Next, we adapt the target impedance of the master robot with respect to the dynamic model of the remote environment. The environment estimation and impedance adaptation are execute simultaneously and in real time. We demonstrate, through experimentation, that this approach significantly reduces the energy required by an operator to execute remote tasks while simultaneously providing sufficient damping to ensure contact stability.
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ItemControl Techniques and Programming Issues for Time Delayed Internet Based Teleoperation(Georgia Institute of Technology, 2003-06) Munir, Saghir ; Book, Wayne J.This article focuses on Internet-based real time control, such as remote bilateral teleoperation. In such applications it is required that the control loop be closed around a time delayed network. Although various researchers have worked on this problem, this paper focuses on two control strategies (based on wave variables and a time forward observer), bandwidth issues, and some related programming details. Experimental results of bilateral teleoperation via the Ethernet between Atlanta and Tokyo are given. The system used was a two degree of freedom haptic interface, bilaterally coupled to simulation (implemented on a windows NT based computer) of a similar system.
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ItemInertial Vibration Damping of a Flexible Base Manipulator(Georgia Institute of Technology, 2003) George, Lynnane E. ; Book, Wayne J.A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) manipulator is often used to increase reach capability, but flexibility in the macromanipulator can make it susceptible to vibration. A rigid manipulator attached to a flexible but unactuated base was used to study a scheme to achieve positioning of the micromanipulator combined with enhanced vibration damping of the base. . The interaction forces and torques acting between the robot and its flexible base were modeled and studied. Simulated and measured interactions generated at the base of a three degree of freedom rigid robot are compared. Simulated and experimental results are included that demonstrate with the proper control of these interactions, damping can be added to the base.
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ItemInternet Based Teleoperation using Wave Variables with Prediction(Georgia Institute of Technology, 2002-06) Munir, Saghir ; Book, Wayne J.Wave-based teleoperation has been previously attempted over the Internet, however, performance rapidly deteriorates with increasing delay. This paper focuses on the use of a modified Smith predictor, a Kalman filter and an energy regulator to improve the performance of a wave-based teleoperator. This technique is further extended for use over the Internet, where the time delay is varying and unpredictable. It is shown that the resulting system is stable even if there are large uncertainties in the model of the remote system (used in prediction). Successful experimental results using this technique for teleoperation in a master-slave arrangement over the Internet, where the control signal is streamed between Atlanta (Georgia) and Tokyo (Japan), are also given
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ItemNoise effect on adaptive command shaping methods for flexible manipulator control(Georgia Institute of Technology, 2001-01) Rhim, Sungsoo ; Book, Wayne J.Since its introduction, the command shaping method to design command shapers as robust as possible based on the has been applied to the control of many types of flexible manipu- available infonnation on a given system (e.g., expected varialators and sthe effectiveness in the vibration suppression has been tion range of the natural frequency) [11]. Unfortunately, the roverified. However, designing an effective command shaper requires a priori knowledge about the system parameters. Recently, some bustness of the shaper comes at the expense of the command efforts have been made to make the command shaper adapt to the shaper length, which means more delay in the response. Morechanges in the system parameters. In this paper, the indirect and _. over, this approach still requires a fair amount of a priori knowlthe direct adaptive command shaping methods in the time domain edge about the system parameters for proper design. The second are compared, especially in terms of the noise effect on the per- approach is to make the command shaper adapt to uncertain formance. Analysis shows that the direct approach is less sensitive . to the noise and this analytic result is verified by the proper simu- or varying system parameters. The indirect adaptive command lation. Finally, experimental results using the direct approach are shaping method has focused on the system identification either included. in the frequency domain [3], [14] or in the time domain [2], [8].
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ItemAlternatives in the generation of time domain models of fluid lines using frequency domain techniques(Georgia Institute of Technology, 2000-10) Watson, Cody ; Book, Wayne J.By converting from frequency domain models to time domain models, nonlinear behavior and linear distributed behavior can both be effectively represented. Three methods are presented to convert fluid line models from the frequency domain to the time domain. Comparison shows that combining components in the frequency domain has advantages in accuracy and efficiency in many practical cases. Methods of finding model poles and residues and ways to avoid numerical difficulties with poles at the origin are discussed.
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ItemModeling Mechanisms with Nonholonomic Joints Using the Boltzmann-Hamel Equations(Georgia Institute of Technology, 1997-02) Obergfell, Klaus ; Book, Wayne J.This article describes a new technique for deriving dynamic equations of motion for serial chain and tree topology mech anisms with common nonholonomic constraints. For each type of nonholonomic constraint, the Boltzmann-Hamel equations produce a concise set of dynamic equations. These equations are similar to Lagrange's equations and can be applied to mechanisms that incorporate that type of constraint. A small library of these equations can be used to efficiently analyze many different types of mechanisms. Nonholonomic constraints are usually included in a La grangian setting by adding Lagrange multipliers and then eliminating them from the final set of equations. The ap proach described in this article automatically produces a minimum set of equations of motion that do not include La grange multipliers.
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ItemA Time-Domain Inverse Dynamic Tracking Control of a Single-Link Flexible Manipulator(Georgia Institute of Technology, 1994-06) Kwon, Dong-Soo ; Book, Wayne J.A manipulator system with a large workspace volume and high payload capacity has greater link flexibility than do typical industrial robots and teleoperators. If link flexibility is significant, position control of the manipulator's end-effector exhibits nonminimum-phase, noncollocated, and flexible-structure system control problems. This paper addresses inverse dynamic trajectory planning issues of a single-link flexible manipulator. The inverse dynamic equation of a single-link flexible manipulator was solved in the time-domain. By dividing the inverse system equation into its causal part and anticausal part, the inverse dynamic method calculates the feed-forward torque and the trajectories of all state variables that do not excite structural vibrations for a given end-point trajectory. Through simulation and experiment with a single-link manipulator, the effectiveness of the inverse dynamic method in producing fast and vibration-free motion has been demonstrated.