Parallel force/position controller with observer for robot manipulators

Parallel force/position control constitutes an effective framework to handle interaction of a robot manipulator with a compliant surface. Typically, contact force and joint position and velocity measurements are needed. However, industrial robots are often endowed with joint position sensors only, and velocity has to be reconstructed. This work is aimed at proposing a parallel controller with a model-based velocity observer. Tracking of end-effector position along the unconstrained directions and regulation of contact force along the constrained direction is ensured. Semiglobal exponential stability of the closed-loop system is proved by resorting to a Lyapunov argument. The scheme is tested in simulation for a robot manipulator and the numerical results are illustrated.