Organizational Unit:

Institute for Robotics and Intelligent Machines (IRIM)

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https://hdl.handle.net/1853/70657

Includes Organization(s)

Organizational Unit

Biorobotics and Human Modeling Lab

Organizational Unit

Humanoid Robotics Laboratory

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Publication Search Results

Now showing 1 - 10 of 23

Combining a multirate repetitive learning controller with command shaping for improved flexible manipulator control

(Georgia Institute of Technology, 1999-11) Rhim, Sungsoo ; Hu, Ai-Ping ; Sadegh, Nader ; Book, Wayne J.

Command shaping, a feedforward approach used to control flexible manipulators, performs most effectively when applied to a linear system. In practice, various nonlinearities are present in a given system that will deteriorate the performance of command shaping. In this work, a multirate repetitive learning controller (MRLC) is used in conjunction with a command shaping method known as the optimal arbitrary time-delay filter (OATF) for discrete-time joint control of a single flexible link manipulator containing nonlinearities. With very little a priori knowledge of the given system, a MRLC is able to cancel the nonlinearities at select frequencies and achieve near-perfect tracking of a periodic desired trajectory. By doing this, a MRLC controls the joint to follow a given shaped command more closely, thus allowing the OATF to more effectively attenuate residual tip vibrations. It is shown both analytically and experimentally that this controller is more effective than a conventional PID and OATF controller at attenuating residual tip vibrations.
Inverse dynamics for commanding micromanipulator inertial forces to damp macromanipulator vibration

(Georgia Institute of Technology, 1999-10) Loper, Jeffery Cameron ; Book, Wayne J.

A multi degree of freedom manipulator can be commanded to generate base forces by utilization of the dynamic equations relating joint torques or joint accelerations to base forces. This can be extended to a full order case with three base moments and three base forces. In the experiments described two forces were sufficient to damp the fundamental modes. With a force command capability a variety of damping algorithms can be used to determine the desired force. A simple acceleration feedback algorithm was used which approximates a two degree of freedom dynamic vibration absorber where the damping coefficient can be adjusted by the acceleration feedback gain. The resulting damping ratio of the fundamental mode was increased by factors of between 18 and 191.
Adaptive Command Shaping Using Adaptive Filter Approach in Time Domain

(Georgia Institute of Technology, 1999-06) Rhim, Sungsoo ; Book, Wayne J.

Since its introduction, the command shaping method has been applied to the control of many different types of flexible manipulators. A properly designed command shaper cancels the resonance poles of the system regardless of the given reference input to the system. However, designing an effective command shaper requires a priori knowledge about the system parameters. Recently, some efforts have been made to make the command shaper less sensitive to the uncertainty of the system parameters and to make the command shaper adapt to the unknown system parameters. This research is an effort to develop an effective adaptive command-shaping algorithm in the time domain. In the paper, the authors propose an adaptive command-shaping algorithm using an adaptive filtering technique in the time domain and verify the effectiveness of the proposed algorithm with proper experiments.
Optimal filtering to minimize the elastic behavior in serial link manipulators

(Georgia Institute of Technology, 1998-06) Magee, David P. ; Book, Wayne J.

This paper presents a new optimal filtering algorithm called the Optimal Arbitrary Time-delay (OAT) filter that has been designed to minimize the elastic behavior in serial link manipulators. However, as the analysis will show, the filtering algorithm can reduce the level of vibration in any system whose elastic motion can be modeled as a set of linear, ordinary differential equations with proportional damping. After analyzing some of the filter properties, experimental results demonstrate just how well the optimal filtering algorithm can minimize vibration.
Vibration cancellation in complex support structures for precision robots

(Georgia Institute of Technology, 1997-11) Rhim, Sungsoo ; Book, Wayne J.

This paper examined the effectiveness of the Optimal Arbitrary Time-delay filter applied to cancel the undesired elastic modes of vibration in complex supporting structures for precision robot which is under development. To achieve the desired positioning precision, suppressing the structure vibration is essential. For this to be done OAT filter method was chosen. Modeling of the system has been performed and using this model, simulations were done without and with OAT filter. The ability of OAT filter in canceling the vibration of the structure was demonstrated in the simulation results. And to verify this results, experiment involving OAT filter within the robot control system has been done on the current version of the precision robot. Even though the dynamics response of supporting structure in the precision robot system has an inherent characteristics of small magnitude and high value of natural frequencies, response due to the filtered command showed that the filter successfully reduced vibration in magnitude and got rid of the residual vibrations faster than the response with unfiltered command.
Control approaches for a dissipative passive trajectory enhancing robot

(Georgia Institute of Technology, 1997-06) Gomes, Mario Waldorff ; Book, Wayne J.

A mechanically passive device is described which, when controlled by an appropriate algorithm, restricts the user to move the tip of the device along a specified but arbitrary path. One advantage of such a device is safety from malfunctions of the controlling actuators. A novel approach for controlling such a device is presented, along with some results of the control algorithms that were implemented on the testbed device.
Torque control of a redundantly actuated passive manipulator

(Georgia Institute of Technology, 1997-06) Davis, Hurley T. ; Book, Wayne J.

The study of passivity in the robotics domain has been motivated by safety and stability concerns in applications such as haptic displays, surgical robots, teleoperation, and manufacl1u·ing. This paper describes a passive manipulator with a redundant actuation scheme which allows for enhanced control capabilities and greater overall utility. An algorithm for determining passive actuator excitations from generally active control laws is presented. The torque translation algorithm is a graphical method based upon using knowledge of the specific passivity-induced constraints to select a subset of the available actuators to provide an acceptable output torque. The algorithm successfully provides a set of passive actuator torques for all manipulator states, and experimental results are given.
Combined Command Shaping and Inertial Damping for Flexure Control

(Georgia Institute of Technology, 1997-06) Magee, David P. ; Cannon, David W. ; Book, Wayne J.

This paper describes a new control approach that combines command shaping and inertial damping to control small robots that are attached to the end of a flexible manipulator. The command shaping guarantees that the level of vibration will be minimized during the robot motion and the inertial damping removes any residual effects after the motion is complete. Experimental results from two different test beds verifY the effectiveness of the combined approach for minimizing vibration in elastic systems.
The Concept and Implementation of a Passive Trajectory Enhancing Robot

(Georgia Institute of Technology, 1996-11) Book, Wayne J. ; Charles, Robert ; Davis, Hurley T. ; Gomes, Mario Waldorff

A novel controlled passive device is described which allows its end effector to be pushed only along a specified but arbitrary path. The force to move the end effector must be provided by an external source such as a human, gravity, or fluid flow. Possible applications include computer assisted surgery, haptic displays, exercise machines, and teleoperator masters. Advantages of the passive approach taken include safety from run away motors and freedom from supplying substantial amounts of energy to the device. This paper describes the concept and how it has been implemented and shows feasibility through initial experiments with simple control of a prototype system.
Neural network control of non minimum phase systems based on a noncausal inverse

(Georgia Institute of Technology, 1996-11) Register, Andrew H. ; Book, Wayne J. ; Alford, Cecil O.

A new approach for feedforward ANN control of nonminimum phase mechanical systems is proposed. A standard backpropagation-of-errors ANN is used to form an inverse model controller which is applied to simulated nonminimum phase systems. Learning in the new approach is based on the convolution between a noncausal impulse response and a desired tip trajectory. Selection of the proper input set, input scaling and the ANN structure are investigated. Once the input and structure are specified, the ANN is trained over a single trajectory. After training, the ANN is used to drive the system in an open-loop configuration. Plots of the system states resulting from the ideal excitation and from ANN excitation are compared. The results obtained by varying both the number of units and the input set are presented. The results demonstrate the effectiveness of the proposed ANN inverse model approach.