Multiband Resonance Frequency Tracking Circuit for Ultrasonic Machining
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Solution Overview
Problem
Existing ultrasonic machining systems face challenges in quickly and accurately tracking the resonance frequency of piezoelectric transducers due to limitations in existing resonance frequency tracking methods, such as poor flexibility, slow tracking, and inability to distinguish between forward and reverse resonance frequencies, especially under changing load conditions.
Innovation Solution
A multiband resonance frequency tracking circuit and method using an output current-voltage phase difference direction detection circuit and a PWM control chip to quickly determine the resonance frequency tracking direction and degree, allowing for fast and accurate tracking of the forward resonance frequency by adjusting the driving frequency based on detuning states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase-locked loop technology is used for resonance frequency tracking, then frequency tracking can be implemented, but the adjustment range is limited and hardware parameters must be changed for different transducers, resulting in poor flexibility and high costs
Solution Approach 1:
The patent changes the control parameter from hardware parameters to software parameters (PWM duty cycle). The PWM control chip can output frequencies from 15kHz to 100kHz by software configuration, eliminating the need to change hardware parameters when switching between different piezoelectric transducers with different resonance frequencies.
2Speed
If complex frequency tracking method is used, then tracking speed is improved, but the method cannot distinguish between forward and reverse resonance frequencies
Solution Approach 1:
The patent uses feedback from the phase difference detection circuit to determine whether the current frequency is forward or reverse resonance. When the phase difference is zero, the system identifies forward resonance frequency; when the phase difference is 180 degrees, it identifies reverse resonance frequency. This feedback mechanism enables both fast tracking and accurate frequency direction identification.
3Device complexity
If maximum current method is used for resonance frequency tracking, then implementation is simple, but tracking is slow and cannot keep up with sudden load changes
Solution Approach 1:
The patent replaces the slow maximum current detection method with a phase difference detection circuit that provides real-time feedback. The phase difference between voltage and current signals is detected and immediately used to adjust the driving frequency, enabling fast response to load changes while maintaining implementation simplicity.
4Adaptability or versatility
If fuzzy PI control strategy is used, then tracking can be implemented, but the method cannot distinguish forward from reverse resonance frequency when impedance characteristics change greatly
Solution Approach 1:
The patent introduces a phase difference detection circuit as an intermediary between the driving signal and the piezoelectric transducer. This intermediary provides accurate information about the resonance state through phase difference measurement, enabling the system to distinguish forward from reverse resonance frequency even when impedance characteristics change significantly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly reduces the time to determine resonance frequency loss and improves the capability to quickly and accurately track the forward resonance frequency, ensuring stable operation under varying load conditions.
Implementation Method 1
A piezoelectric transducer is a core component of an entire ultrasonic system. Under the excitation of an external high-frequency driving signal, the piezoelectric transducer produces vibration with a same frequency.
Implementation Method 2
When the driving signal has a frequency the same as an inherent frequency of the piezoelectric transducer, the piezoelectric transducer has a maximum output vibration amplitude.
Data Source
AI summary
The present invention discloses a multiband resonance frequency tracking circuit applied to ultrasonic machining, including an output current-voltage phase difference direction detection circuit and a multiband resonance frequency tracking circuit, where a detection signal output end of the output current-voltage phase difference direction detection circuit is connected to a signal input end of the multiband resonance frequency tracking circuit. Through the foregoing technical solutions, in the present invention, a system detuning state is quickly determined by using a current-voltage phase difference direction detection signal outputted by a D flip-flop in a chip SN74HC74D, and a dead-time resistor between a 5th pin and a 7th pin in a chip EG3525 can be changed in a timely manner based on a detuning degree of a piezoelectric transducer, so as to change a system driving frequency to track a resonance frequency of the piezoelectric transducer and implement fast and accurate tracking.