| With its increasing use in many areas of industry, the ultrasonic metal welding process is becoming a promising type of manufacturing technology. High-quality ultrasonic power supply is necessary for realizing high-quality and high-efficiency ultrasonic metal welding, and moreover, frequency self-tracking is a decisive unit to a excellent ultrasonic power supply.Based on thorough study of CJHJ-2000 ultrasonic welding power supply, by applying computer measuring and control technology , ultrasonic frequency self-tracking in the resonance system is worked out. The purpose is to develop a new type of ultrasonic power supply in which the frequency self-tracking control is credibly and exactly realized. Work in the paper are as follows.(1) Investigating the electrical impedance and working characteristic of the ultrasonic transducer. Based on the equivalent theory of mechanics and electricity, amplitude of ultrasonic vibration system can be obtained by measuring the electrical current value in the equivalent circuit. At the same time, the resonance situation of ultrasonic vibration system can be obtained by measuring phase difference between voltage and current.(2) After thorough analysis of CJHJ-2000 the ultrasonic metal welding power supply, the article concludes that the power supply can't effectively track frequency of maximum resonance amplitude.(3) On the basis of discussing a frequency self-tracking control strategy for ultrasonic power supply in details, the hardware and software of a microcomputer measuring and control system are set up. In the hardware, there are measuring circuit, magnifying circuit and filter, signal adjusting circuit, D/A inverter, singlechip system and sine wave signal generator. The software includes full-range natural frequency searching module, frequency self-tracking module and phase difference measure and control module.(4) Testing results of all the hardware circuit show that all the hardware circuit...
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