A High Robustness PS/N Compensation and Characteristic Analysis Under Variation Load for Rotary Ultrasonic Machining

Contactless energy transfer (CET) is widely applied in the power transfer of rotary ultrasonic machining (RUM). However, the compensation mismatch caused by variation load leads to low transfer efficiency, poor frequency accuracy, narrow bandwidth, and vibration attenuation for RUM. To address this issue, a new parallel–series/none (PS/N) with primary compensation was proposed, which achieves the performance of lower frequency deviation, high bandwidth, and constant current gain under variation load. Based on equivalent circuit model of ultrasonic vibration tool holder (UVTH), the impedance characteristics were investigated to clarify the defects of current compensation method. Then the model of PS/N compensation was established. The numerical calculation shows that the compensation capacitance of PS/N hardly changes with the load. The impedance characteristics, frequency deviation, bandwidth, and current gain ratio were analyzed compared with series/none (S/N) under fixed compensation strategy. The experimental results are in good agreement with the calculated results. The proposed PS/N with fixed compensation can limit the frequency deviation within 1.4 Hz, increase the bandwidth of frequency chasing by 8.75 times, and control the amplitude fluctuation within 3.3% under high load. This significantly improves reliability, stability, and consistency of machining quality of RUM.