A Gain Scheduling Controller for Friction Compensation

Friction in mechanical systems can show a very complex behaviour. In addition to its non-linear dependence on the velocity, friction is also function of the position. In the vicinity of motion reversal points, i.e. in the prerolling/pre-sliding regime, the position dependence dominates and appears in the form of a rate-independent hysteresis with nonlocal memory. One of the ways of treating this complex behaviour is through the use of the Describing Function (D.F.) method. This approach yields equivalent dynamic parameters, which are function of the amplitude of motion.