Hybrid force/velocity robot contour tracking: an experimental analysis of friction compensation strategies

In this paper we experimentally analyze the performances of an hybrid force/velocity controller for the automatic edge following of 2D unknown planar contours performed by a robot manipulator. In this work we show that joint friction effects have to be taken into account in the controller design in order to achieve reasonable performances in terms of normal force and tangential velocities errors. For this reason we compare two model-based methods for coping with friction: a static one based on a previously identified model and an adaptive one recursively updating joint friction parameters. The proposed controllers are compared through an extensive experimental activity on a 2-DOF SCARA robot tracking an high stiffness aluminium-bar over a wide range of operative conditions.