Friction compensation methods in position and speed control systems

Friction appears in the bearings and reduction gear of controlled electrical drives and affects the quality of the position, speed or force control. The servosystem performance can be improved by implementation of acceleration feedback. For the reason that acceleration measurement is often either not possible or practical, the implementation of acceleration estimation by an observer or differentiation of speed is proposed. Another approach to friction influence compensation is based on the disturbance observer. Its advantage is that it can be applied generally to the estimation of various disturbances. This paper deals with these friction compensation methods which are not based on friction model, but on the compensation of friction as a disturbance. The efficiency of these methods in a servodrive with Stribeck friction is compared by computer simulation and experimentally on a servosystem laboratory model.