Multi-band resonant frequency tracking circuit and method applied to ultrasonic machining

Abstract

The invention discloses a multi-band resonant frequency tracking circuit applied to ultrasonic machining, which comprises an output current and voltage phase difference direction detection circuit and a multi-band resonant frequency tracking circuit, wherein the detection signal output end of the output current and voltage phase difference direction detection circuit is connected with the signal input end of the multi-band resonant frequency tracking circuit. By adopting the technical scheme, the system detuning condition is quickly judged through the current and voltage phase difference direction detection signal output by a D trigger in the SN74HC74D chip, and the dead zone resistance between a pin 5 and a pin 7 in the EG3525 chip can be changed in time according to the detuning degree of a piezoelectric transducer, so that the system driving frequency is changed to track the resonant frequency of the piezoelectric transducer, and rapid and accurate tracking is realized. The realization process of the circuit function is simple and rapid, and the capability of rapidly and accurately tracking the forward resonant frequency point of the piezoelectric transducer is improved.

Description

technical field [0001] The invention relates to the technical field of ultrasonic machine tools, in particular to a multi-band resonant frequency tracking circuit and method applied to ultrasonic processing. Background technique [0002] The piezoelectric transducer is the core component of the entire ultrasonic system. Under the excitation of the external high-frequency drive signal, the piezoelectric transducer produces vibrations at the same frequency. When the frequency of the driving signal is the same as the natural frequency of the piezoelectric transducer , the output vibration amplitude of the piezoelectric transducer is the largest. However, during the ultrasonic machining process, the resonance frequency of the piezoelectric transducer drifts due to the change of the external load force. Therefore, in the process of ultrasonic machining, it is necessary to continuously adjust the frequency of the driving signal to track the resonance frequency of the piezoelectri...

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Problems solved by technology

[0004]However, there is a limitation in the frequency adjustment range of PLL technology. For different types of piezoelectric transducers with different resonant frequencies, it is necessary to adjust the hardware parameters of PLL to Change the range of output frequency, so the use of phase-locked loop technology to achieve resonance frequency tracking has disadvantages such as poor flexibility, poor structure, and high cost; the composite frequency tracking method can speed up the resonance frequency tracking to a certain extent, but the composite frequency tracking method also exists A certain defect, that is, it only uses the phase difference of zero to judge whether to track the resonance frequency, but the piezoelectric transducer actually has positive and negative resonance frequencies, at the positive resonance frequency point Fs and the reverse resonant frequency point Fp, their phases are both zero, at this time the composite resonant frequency tracking strategy will not be able to distinguish whether the tracked resonant frequency is forward resonant frequency or reverse resonant frequency; the maximum current The biggest disadvantage of the method of tracking the resonant frequency is that the tracking is slow. When the load changes suddenly, the resonant frequency tracking often cannot keep up with the change of the load. Therefore, the maximum current method to track the resonant frequency is not suitable for application scenarios with severe load changes; the fuzzy PI strategy The disadvantage of the resonant frequency tracking method is that under load conditions, when the impedance characteristics of the piezoelectric transducer vary greatly, since the fuzzy PI only uses the phase difference as the control signal, the fuzzy PI cannot distinguish the resonant frequency being tracked as a positive resonance frequency or anti-resonant frequency

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