Dynamic output feedback passification with application to an elastic joint robot

Output feedback passification problem is studied when the given system is not minimum-phase or does not have relative degree one. Using a parallel connection with an additional dynamics, the authors provide a dynamic output feedback control law which renders the composite system passive. For linear time-invariant systems, a necessary and sufficient condition for designing an input-dimensional additional system is presented. Motivated by the dynamic passification scheme, a point-to-point control law for an elastic joint robot is presented when only the position measurements are available. This provides an alternative way of replacing the role of the velocity measurements for the proportional-derivative (PD) feedback law. The performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.