Novel Double Compensation for Impedance-Frequency Characteristics of Rotary Ultrasonic Machining via Multiobjective Genetic Algorithm

Rotary ultrasonic machining (RUM) is a superior technology to machine hard and brittle materials. Traditionally, the compensation optimization for the RUM system is limited to a single resonant frequency. This article presents a novel double compensation approach for the impedance and frequency regulations of RUM via multiobjective genetic algorithm (MOGA) aiming to achieve the system resonance and monitor the machining process in real time. For this, we first establish the impedance model of the rotary ultrasonic holder (RUH) by adopting the T-type circuit that includes the comprehensive electromagnetic parameters. The obtained impedance model reveals that both frequency mismatch and impedance mismatch exist in the RUM system, causing the low voltage gain and low vibration transmission. To obtain the optimal compensation to match both the frequency and impedance, an optimization model-based MOGA is developed to intelligently search the accurate capacitance values, where the Pareto frontier is employed to visualize the capacitance solution distribution. Moreover, the response feature of the RUH system is attained by using the state-space equation. Detailed comparisons of four compensation topologies show that the series-series (SS) topology offers the optimal performance, which can match both of the frequency and the impedance well, improving the output active power 7.634 times compared to the conventional one. Finally, the validity of the proposed optimization method is confirmed by using both simulations and experiments.