Research On The Frequency Trackingand Control Method Of Ultrasound Transducer System

Ultrasound transducer systems are widely used in industrial production, such as electronic packaging industry and ultrasonic processing industry. Ultrasound transducer systems mainly consist of two parts: ultrasonic generator and transducer. When the drive signal’s output frequency equals to the resonant frequency of the transducer, the transducer outputs the maximum power. So the whole work is aimed for improving the efficiency of frequency tracking, in which the theoretical of selecting phase as a controlled amount, phase response characteristics, Zero Phase Error Tracking Controller design for transducer are discussed.The impedance model is established based on the equivalent circuit method. The relationship between the resonant frequency and the parameters of the dynamic branch is achieved and the law is verified by simulation. Based on the law, the theoretical of selecting phase as a controlled amount is proposed.Mathematical models of the various parts of the ultrasound transducer system are established and the simulation model is built by MATLAB/Simulink. By using different frequencies to drive the transducer, the phase difference response of the voltage and current across the transducer is obtained. It provides a reference amount for the algorithm of resonant frequency searching and the design of Zero Phase Error Tracking Controller.A new resonant frequency searching algorithm is proposed, which combined crude with precision search. The new algorithm satisfies the requirements of fast frequency tracking. The transducer is driven by the resonant frequency searched by the novel algorithm. In order to make the input signal be accurately tracked, a zero phase error tracking controller is designed. The rationality and validity of the designer are verified by simulation.The phase difference response characteristics of this transducer system is got by the experiment. Then the theory mathematical modeling of each part of the ultrasound transducer system is validated to be correct by comparing with the theoretical simulation. The feasibility of this design can be illustrated by comparing the frequency tracking ability of the pure transducer system, the transducer system that be joined the impedance matching and the transducer system that be joined the coarse searching resonance frequency difference algorithm and the controller. The search algorithm and controller are verified, which make the responding time cut down 4ms, the stable value achieve 0°in the static drive and the dynamic drive fluctuate between 0°and 0.2°.All above research contexts, methods meets the stability, accuracy and rapidity for the frequency tracking of ultrasound transducer, and help to improve the efficiency of the transducer.