Novel Optimization Approach in Ultrasonic Machining: Unilateral Compensation for Resonant Vibration in Primary Side

Resonant frequency and impedance matching have great significance for the vibration performance and online monitoring of the rotary ultrasonic machining. Network compensation is a typical solution to match the resonant frequency and the impedance between the rotary ultrasonic holder (RUH) and the ultrasonic transducer. However, the traditional bilateral compensation method could adversely affect the rotary dynamic balance of the RUH. Currently, the existing unilateral compensation methods can only realize the resonant frequency matching. A novel unilateral compensation method that satisfies both the resonant frequency and the impedance matching is proposed. First, the impedance model of the RUH vibrating system is established according to its equivalent circuit. It is found that, without any compensation methods, the resonant frequency and the impedance between the RUH and the transducer have deviated. Second, the primary-series and primary-parallel compensation topologies are applied to the RUH system, and the expressions of compensation capacitance value, voltage gain, power transfer efficiency, and output active power are derived. The deviations of the resonant frequency and the impedance are eliminated with primary-series compensation topology; and as a result, the voltage gain is increased from 0.267 to 0.90, the output active power is 11.3 times than that without compensation. Third, the state-space model of primary-series topology is constructed. Finally, the above theoretical results are verified by the experimental results.