Study On The Key Technologies Of Rotary Ultrasonic Maching Based On Contactless Energy Transfer

Rotary ultrasonic machining is a precision and efficient processing method of hard and brittle materials and composites. The development of high speed, high efficiency, and high power rotary ultrasonic machining equipment has become a hot topic at present. Compared to the traditional non-rotating ultrasonic machining, the rotary motion of rotary ultrasonic machining makes ultrasonic energy transfer more complicated and difficult, which greatly limits the application of the rotary ultrasonic machining techniques. Contactless energy transfer(CET) based on electromagnetic induction can be replaced with the traditional slip ring brushes for providing electrical power to the ultrasonic transducer. This contactless energy transfer(CET) is security, stability, and no restrictions of speed. However, due to the air gap existing in primary and secondary side, rotary transformer has larger leakage inductance, poorer coupling capacity compared to the tightly coupled transformer. Its transmission efficiency and transmission power is limited. Secondly, amplitude decay caused by the change cutting force of ultrasonic machining affects the machining results.To solve the above problems, following aspects were studied in this paper:1) Based reluctance model, leakage inductance model and mutual inductance model, the coupling mechanism and energy transfer characteristics of rotary transformer was analyzed. Its loss types and loss reasons were analyzed also to optimize the core and coil structure of rotary transformer.2) Considering the real electrical properties of ultrasound vibrator, circuit compensation topology, mathematical model to characterize the transmission efficiency and power transfer capability, calculation of circuit compensation components to achieve maximum transmission efficiency were established. The effect rules and mechanisms of compensation component values and equivalent series resistance(ESR) on the energy transfer properties were theoretically and experimentally studied.3) Based on circuit compensation of the maximum transmission efficiency, relationship mode between transmission efficiency, transmission power, power load impedance, voltage across the compensation element and coil turns were established. The effect rules of coil turns on power transmission performance were analyzed to establish the coil turns optimization method for controlling the power load impedance and the voltage across the compensation element. On the premise of taking into account transmission efficiency, maximum power output capacity and power transmission security of rotary ultrasonic vibration system were achieved.4) Against the amplitude decay caused by instable cutting force during rotary ultrasonic machining, the effect rules of cutting force on electrical parameters of ultrasonic vibrator were studied, the effect rules and internal mechanisms of cutting force on transmission efficiency, transmission power and power factor were studied. Circuit compensation topologies and compensation components debugging methods were given for the output powers adaptively increasing with cutting forces increasing. After the coil turns of rotary transformer was optimized, the effects of axial cutting forces on energy transfer properties were experimentally studied.5) Temperature rise tests of different power limit piezoelectric ultrasonic vibrator and rotary transformer under different compensation state were conducted. New special ultrasonic machining tool collet was designed for effective transmission of ultrasonic energy and flexible replacement of tool. Accessory contactless energy transmfer(CET) rotary ultrasonic machining tool is developed.