(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.
(Georgia Institute of Technology, 1992)
Book, Wayne J.; Kwon, Dong-Soo
Many 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.