Tip-trajectory tracking control of single-link flexible robots by output re-definition

Output re-definition techniques are proposed so that the transfer function of the system with the new output is minimum phase and this facilitates the design of trajectory tracking controllers. There are various output functions suggested in the literature. The authors show that the zero dynamics of a single-link flexible robot is exponentially stable with the newly defined output function. Asymptotic tracking of step input, linear and second-order polynomial trajectories are achieved using controllers designed based on this new technique and the link vibrations are damped out significantly. The unique feature of the controller design technique is that the poles of the zero dynamics can be placed at any desired locations in the left half of the s-plane. This enables the suppression of undesirable vibrations while the robot tip is tracking a prescribed tip-trajectory