Position/force control of robot manipulators without velocity/force measurements

In this paper, we consider the problem of designing a position/force controller for robot manipulators during constrained motion. The proposed controllers are based on exact knowledge of the system dynamics and do not require measurements of link velocity and end-effector force. The elimination of velocity measurements is accomplished by two different methods: 1) a model-based velocity observer, and 2) a high-pass filtering technique. Both of the controllers also include an open-loop force control strategy to achieve semi-global exponential end-effector position/velocity/force tracking.