Tip-trajectory tracking control of single-link flexible robots via output redefinition

Output redefinition is proposed for a flexible-link robot so that the transfer function of the system is minimum phase and this facilitates the design of trajectory tracking controllers. We show that the zero-dynamics is exponentially stable with the newly defined output function. Asymptotic tracking of step, 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 us to suppress undesirable link vibrations well while the robot tip tracks a prescribed tip-trajectory