Friction compensation and robustness issues in force/position controlled manipulators

When a manipulator interacts with the external environment, it is important to take into account the presence of friction between the end-effector and the contact surface, as this can cause coupling effects between force and position controlled degrees of freedom and compromise the system stability. In this paper, friction is described by a `complete´ model, and a fixed friction compensation function is proposed as an alternative strategy to compensation through high-gain controllers or by means of adaptive algorithms. A force/position controlled planar manipulator is considered to study the friction effects and the effectiveness of the proposed solutions. Simulation results are reported and discussed