Generalised proportional integral torque control for single-link flexible manipulators

In this study, a generalised proportional integral (GPI) output feedback control scheme is proposed to control the torque of a single-link flexible arm for free and constrained motion. The control is based on the properties of differential flat systems. The control is also found to be robust with respect to the motor static friction. The only variable to measure is the torque in the hub by means of only one sensor, which in this case, is constituted by a pair of strain gauges. An hybrid control law is presented to control the manipulator in collision with an object (constrained motion) and when it can freely move (free motion) commanded by an on-line impact detection algorithm. Experiments are presented to verify the goodness of the proposed control law.