A Novel Friction Compensation Method Based on Stribeck Model With Fuzzy Filter for PMSM Servo Systems

Friction deteriorates speed and position control accuracy of high-precision machine tools and causes distortion phenomenon when the speed crosses zero. In this paper, a new compensation method based on static Stribeck model (SB) combined with fuzzy low-pass filter (SBFF) is studied for friction compensation of permanent magnet synchronous motor (PMSM) servo systems. First, models of the servo system, the Stribeck, and the LuGre are established. Then, it is theoretically derived that the hysteresis effect of the LuGre model (LG) can be equivalent to a low-pass filter term compared to the SB. Based on this, the relationship between the filter time constant and the motor reference speed can be derived. To further improve the friction compensation effect near zero speed and to weaken the delay generated by the filter during the non-zero-speed range, fuzzy logic is introduced to adjust the filter time constant according to the reference speed variation. Through simulations and experiments, compensation strategies based on the LG feedforward, SB feedforward, SBFF feedforward and SBFF feedback are compared, and the robustness of the proposed SBFF feedforward compensation method over entire speed range is verified as well.