FLEXIBLE LINK ROBOT:

The flexible robot system consists of a single lightweight flexible arm counterbalanced with a rigid appendage. The arm is actuated by a DC motor located at the base. A servo amplifier is used to control the DC motor; this amplifier accepts control inputs from the computer through the DAS20 D/A converter in the range [-5,5] Volts. An optical encoder attached to the shaft of the DC motor is used to measure the angular position of the shaft at each sampling instant. The optical encoder's outputs are passed through a signal conditioning circuit before being acquired by the computer. The signal conditioning circuit outputs pulses which are counted by two counter/timers on a data acquisition board which resides in the computer. The signal conditioning circuit is used to double the encoder's effective resolution, as well as to determine the direction of rotation. An accelerometer mounted at the endpoint of the flexible arm is used to measure the linear acceleration at the endpoint. The accelerometer system consists of the accelerometer and accelerometer interface, a Kistler Piezotron Coupler. The accelerometer interface output is passed through a Butterworth low-pass filter before being acquired by the PC via one of theDAS20's A/D converters. A small incandescent light bulb is also mounted at the robot arm endpoint. The light is used in conjunction with a linear array line scan camera to record the movement of the endpoint; the camera is interfaced with another computer. Note that while the camera is used to record and evaluate the performance of the flexible arm system, the camera signal is not used for controller feedback. The modes of vibration of the flexible arm system may be changed by attaching a small weight near the endpoint of the flexible link. The position of the weight along the link has a significant effect on the system dynamics. The weight will later be used to test the controllers behavior in the presence of plant parameter variations. We desire to minimize endpoint vibrations while the robot arm is slewed through a user-defined angle via a position step input. The slew rate should be as fast as is possible.

For a more complete description of this experimental set-up for both the single link and two link versions (the two link version has been studied extensively at OSU but is not currently used in this laboratory) see:

Single link flexible robot:

A. P. Tzes and S. Yurkovich, "An Adaptive Input Shaping Control Scheme for Vibration Suppression in Slewing Flexible Structures," IEEE Transactions on Control Systems Technology, Vol. 1, No. 2, pp. 114-121, June 1993.

S. Yurkovich and A. P. Tzes, "Experiments in Identification and Control of Flexible-Link Manipulators," IEEE Control Systems, pp. 41-47, February 1990.

S. Yurkovich and F. E. Pacheco, "On Controller Tuning for a Flexible-Link Manipulator with Varying Payload," Jour. of Robotic Systems, Vol. 6, No. 3, pp. 233-254, 1989.

S. Yurkovich, F. E. Pacheco and A. P. Tzes, "On-Line Frequency Domain Information for Control of a Flexible-Link Robot with Varying Payload," IEEE Transactions on Automatic Control, Vol. 34, No. 12, pp. 1300-1304, December 1989.

A. P. Tzes and S. Yurkovich, "Application and Comparison of On-Line Identification Methods for Flexible Manipulator Control," The International Journal of Robotics Research, Vol. 10, No. 5, pp. 515-527, October 1991.

A. P. Tzes and S. Yurkovich, "A Frequency Domain Identification Scheme for Flexible Structure Control," ASME Journal of Dynamic Systems, Measurement, and Control, Vol. 112, pp. 427-434, September 1990.

S. Yurkovich, F. E. Pacheco and A. P. Tzes, "On-Line Frequency Domain Information for Control of a Flexible-Link Robot with Varying Payload," IEEE Transactions on Automatic Control, Vol. 34, No. 12, pp. 1300-1304, December 1989.

P. Kotnik, S. Yurkovich and U. Ozguner, "Acceleration Feedback for Control of a Flexible Manipulator Arm," Journal of Robotic Systems, Vol. 5.3, June 1988.



Two link flexible robot:

V. G. Moudgal, K. M. Passino, and S. Yurkovich, "Rule-Based Control for a Flexible-Link Robot," IEEE Transactions on Control Systems Technology, Vol. 2, No. 4, Dec. 1994.

V. G. Moudgal, W. A. Kwong, K. M. Passino, and S. Yurkovich, "Fuzzy Learning Control for a Flexible-Link Robot," IEEE Transactions on Fuzzy Systems, Vol. 3, No. 2, May 1995.

E. R. Garcia-Benitez, J. M. Watkins and S. Yurkovich, "Nonlinear Control with Acceleration Feedback for a Two-Link Flexible Robot," IFAC Control Engineering Practice, Vol. 1, no. 6, pp. 989-997, 1993.

K. L. Hillsley and S. Yurkovich, "Vibration Control of a Two-Link Flexible Robot Arm," Dynamics and Control, Vol. 3, pp. 261-280, 1993.

E. R. Garcia-Benitez, S. Yurkovich and K. Passino, "Rule-Based Supervisory Control of a Two-Link Flexible Manipulator," Journal of Intelligent and Robotic Systems, Vol. 7, pp. 195-213, 1993.