An Exponentially Stable Adaptive Force/Position Control for Robot Manipulators

Abstract The problem of controlling a robot manipulator while the end effector is in contact with an environment of finite but unknown stiffness is considered in this paper. An exponentially stable control law is derived starting from a Slotine and Li position control algorithm. The original position trajectory is scaled so as to fulfill the force control objective. A passivity-based adaptive observer is designed to compute the time-varying scaling factor, which depends on the unknown stiffness constant of the environment. The paper is an extension of a previous work where the one-degree-of-freedom linear case is analyzed.