Friction Models and Friction Compensation

Karl Astrom, Department of Automatic Control, Lund Institute of Technology

Friction appears in all mechanical systems and has a significant impact on control. Successful design of mechatronic systems requires an understanding of the effects of friction as well as techniques for compensation. Friction phenomena are complicated because they are caused by many different physical mechanisms. Friction can cause a substantial deterioration of the performance of a control system. Typical effects are steady state errors and oscillations. Many attempts have been made to compensate for friction. Early efforts include introduction of dither signals. Other ideas are based on model based control. This talk reviews several models for friction that have been useful to model friction in motion control systems and to compensate for effects of friction. Results from experiments with friction compensation are also presented.