David P. Magee

Filtering micro-manipulator wrist commands to prevent flexible base motion

This paper examines control issues related to positioning a small articulating robot attached to a much larger, flexible manipulator. By shaping the joint position error with a finite impulse response filter actuation torques can be found to maneuver the small robot with minimal residual vibration of its base. This paper develops a new filter form with the advantage of shorter delay times than current input shaping methods. Experimental results show the effectiveness of the new filtering technique to prevent vibration when used as part of a feedback control system.

Experimental study on micro/macro manipulator vibration control

This work investigates issues related to vibration control in a micro/macro manipulator. This paper provides experimental results obtained by the combination of two dissimilar flexible control techniques to a micro/macro flexible link testbed. Inertial damping and command filtering techniques are implemented simultaneously to form a robust controller that results in minimal residual vibration due to commanded movements or external excitations. Experimental results show the effectiveness of both control techniques in their individual state as well as the improved performance resulting from their combination. The experimental results of the combined controller clearly show the advantages of each technique.

Eliminating multiple modes of vibration in a flexible manipulator

Vibration suppression is often difficult to achieve in systems whose parameters are a function of configuration. A modified command filtering technique is proposed that eliminates the first two modes of vibration in a large, flexible manipulator with position-dependent parameters. The elimination of residual vibration is demonstrated using a circular trajectory located in the workspace of the manipulator so that a change in system properties occurs. The modified command filtering technique is compared to previous control methods in order to demonstrate its effectiveness in eliminating residual vibration.<<ETX>>

Filtering Schilling manipulator commands to prevent flexible structure vibration

The remediation and management of various nuclear sites will require inspection, removal and surveillance operations within many waste storage tanks. Due to the large dimensions, many tasks will be performed with a small articulated robot mounted on a long reach manipulator. However, the motion of the small arm tends to excite the vibrational modes of the larger structure. This paper presents several applications of a finite impulse response (FIR) compensation filter within the micromanipulators joint feedback control structure to suppress the structures flexible behavior. Simulation results of filtering a Schilling manipulators azimuth joint commands while mounted on the tip of a long slender beam verify the effectiveness of the proposed control strategies.

A novel teleoperated long-reach manipulator testbed and its remote capabilities via the Internet

During the 1995 DOE Robotics Forum at Albuquerque, New Mexico, Georgia Techs Intelligent Machine Dynamics Laboratory demonstrated remote display capabilities of its telemanipulated long-reach manipulator testbed through the Internet. This paper describes the testbed and addresses the methods, limitations, and capabilities of remote operations.

A comparison of joint control algorithms for teleoperated pick and place tasks using a flexible manipulator

This paper presents initial results of an on going study of robot control algorithms used for teleoperation of long reach manipulators. The focus of the paper is the effect of the slave robot control algorithm on the performance of a teleoperation schemes that uses long reach, flexible manipulators. This study investigates the influence of PD, PD with input shaping, and PD with modified command filtering on pick and place teleoperation tasks. Data from 90 trials using 6 operators is used in an attempt to identify any increase in performance resulting from the use of any of the above control schemes. The results of this investigation indicate an increase in performance, based upon a combination of interaction forces and task execution time, of teleoperated pick and place tasks when a flexible robot uses either PD with input shaping or PD with modified command filtering.<<ETX>>

Command filtering and path planning for remote manipulation of a long reach flexible robot

We focus on the fusion of autonomous and teleoperated commands. This combination provides full use of the robots workspace without requiring large motion amplification between a master and slave robot. Combining autonomous and teleoperated commands provides the potential for large variations in the commanded momentum of the flexible robot. These variations excite the lightly damped, low resonant frequencies associated with these manipulators. Two techniques are proposed to reduce the vibration during sudden stops in the commanded motion of a flexible manipulator. First a new command filtering approach that permits shorter delay times than standard input shaping methods is presented. Next, we propose dynamic alteration of the desired trajectory. Our investigation shows that filtering techniques exhibit an oscillatory response, more so than standard PD control algorithms, during hard stopping conditions. However the shorter time delay filtering algorithm has less vibration than standard input shaping techniques. Furthermore, any vibration may be eliminated by commanding the robot to decelerate instead of immediately stopping the motion.

Structural vibration control of micro/macro-manipulator using feedforward and feedback approaches

Pacific Northwest Laboratory (PDL) researchers investigated the combined use of two control approaches to minimize micro/macro-manipulator structural vibration: (1) modified input shaping and (2) inertial force active damping control. Modified input shaping (MIS) is used as a feedforward controller to modify reference input by canceling the vibratory motion. Inertial force active damping (IFAD) is applied as a feedback controller to increase the system damping and robustness to unexpected disturbances. Researchers implemented both control schemes in the PNL micro/macro flexible-link manipulator testbed collaborating with Georgia Institute of Technology. The experiments successfully demonstrated the effectiveness of two control approaches in reducing structural vibration. Based on the results of the experiments, the combined use of two controllers is recommended for a micro/macro manipulator to achieve the fastest response to commands while canceling disturbances from unexpected forces.

Comparison of dynamic analysis of a Schilling hydraulic manipulator with experimental results

Two independent models of the dynamics of a Schilling Titan II hydraulic manipulator were developed and compared in order to obtain an accurate model of the manipulator dynamics. These models will be used in the development of feedback control laws and active damping algorithms. One of the model is an analytical model which was developed {open_quotes}by hand{close_quotes} with the assistance of computer symbolic manipulation. The other is a numerical model developed using a commercially available dynamics code. The data from these models were then compared with experimental data from an actual Titan II manipulator.