A Study Of Ultrasonic Toolholder Integrated System With Loosely Coupled Power Transfer

With the widely used of hard and brittle materials in the field of aerospace, medical, machinery, vehicles and electronics, the traditional processing methods have been unable to meet their processing requirements. Rotary ultrasonic machining(RUM) has been proved to be a very effective machining method for hard and brittle materials. Loosely coupled rotating transformer can overcome various defects of carbon brushes and slip rings. In order to promote the using of rotary ultrasonic machining, an ultrasonic toolholder integrated system with loosely coupled rotating transformer is designed, which can be expediently install and remove on general NC milling machine. Its main contents and results are as follows:(1) The whole construction of toolholder integrated system is proposed. Based on the structure and size of spindle of NC milling machine, structure of toolholder integrated system is designed. Based on the design theory of sandwich piezoelectric transducer and using modal analysis by simulation, a half-wavelength 28 KHz ultrasonic transducer vibrator is designed and manufactured. Integrating the loosely coupled rotating transformer and ultrasonic transducer vibrator in the toolholder, then it is installed on the NC milling machine, so contactless coaxial rotation between primary and secondary of loosely coupled rotating transformer is realized.(2) The equivalent circuit of loosely coupled rotating transformer is derived according to the principle of electromagnetic. A mathematical model of loosely coupled rotating transformer with pot-core and adjacent winding is built and analyzed by simulation. Formulas of magnetizing inductance and leakage inductance are derived based on parameters of the cores and the coils. A flowchart of design is summarized, and according to the flowchart, a loosely coupled rotating transformer is designed and manufactured.(3) Loosely coupled rotating transformer has big leakage inductance, and the ultrasonic power supply circuit is designed based on this characteristic: Taking microcontroller ATmega16 A as the controller and output two PWM signals to control the driver chip IR2114 SS, so IR2114 SS can drive the two IGBTs in asymmetric half bridge inverter circuit. Using the secondary leakage inductance of loosely coupled rotating transformer as the matching inductance to match the piezoelectric transducer. The perimary leakage inductance and parasitic capacitances of switches resonance to realize ZVS, and each state in a complete switching cycle of asymmetrical half bridge has been studied in details, so the conditions of ZVS are given. The experimental results show that the ultrasonic power source realized ZVS; the amplitude of ultrasonic transducer vibrator is added with the increase of the supply voltage in a certain range.