Dynamic Compliant Force Control Strategy for Suppressing Vibrations and Over-Grinding of Robotic Belt Grinding System

This work develops a dynamic compliant force control (DCFC) strategy for the robotic belt grinding system to suppress the vibrations and over-grinding phenomenon. First, the vibration mechanism is investigated, and the corresponding vibration models before and after contact are constructed, both of which can decompose the vibrations into three components: free, accompanying and forced vibrations. Next, the extra compliant hardware is equipped to the grinder to realize the dynamic adjustment of equivalent damping. The DCFC strategy considering mechanical compliance accompanied by the dynamic closed-loop control of the grinder damping is presented based on the empirical wavelet transform and multi-scale permutation entropy. Moreover, the cutting fluctuation ratio index is proposed to evaluate the severity of the over-grinding together with overgrinding time. Experiments demonstrate that compared with the general force control, the DCFC strategy can reduce the vibration amplitude from 3.01 mm/s(2) to 0.97 mm/s(2), and the over-grinding time/cutting fluctuation ratio from 1.05 s/24.71% to 0.54 s/13.18%, consequently enhancing the grinding stability and quality.