Abstract: The identification and compensation methods of torque ripple based on steady state error analysis are presented in order to reduce the fluctuation of steady-state error of servo system and create environment for the accurate identification of the friction model. The relationship between steady state errors and input and interference of signals in servo system is determined. On this basis, the composition of steady state error for the uniform motion is researched. The steady state error induced by system disturbance including torque ripple, friction moment and others is obtained. The function form of torque ripple is obtained by using methods such as spectrum analysis and least squares criterion. The compensation of ripple can be achieved by programmable multi-axis controller (PMAC). The experimental results show that the fluctuation of steady state error decreases to different degrees. It has obvious effect at low speed; the peak-to-peak value reduces from 10 μm to 3.3 μm after compensation. At high speed, the peak-to-peak value also decreases to 3.2 μm after compensation. Besides, the Stribeck curve can be apparently acquired. Therefore, the method proposed can effective compensate the torque ripple and lay the foundation for precise compensation of friction disturbance and improvement of dynamic performance of servo system.

Key words: Steady state error, System analysis, Torque ripple