Research On Dual Frequency Ultrasonicpower Supply With Fast Frequency Trackingfunction

With the development of ultrasonic power technology,single-frequency ultrasonic power is far from being able to meet the needs of the industrial field,so this thesis has developed a dual-frequency ultrasonic power source with frequency tracking function.The ultrasonic power source uses 16 dual-frequency ultrasonic waves of 28KHz/40 KHz.To clean the transducer,the ultrasonic power supply supports 28 KHz single-frequency cleaning mode,40 KHz single-frequency cleaning mode and dual-frequency cleaning mode with 28KHz/40 KHz automatic switching frequency.According to the problems found in the process of searching domestic and foreign documents and testing,this thesis makes in-depth research in the following aspects:1.Analyze the sound field distribution and energy transfer process of dual-frequency ultrasound,and calculate according to related formulas.In theory,the working mode of dual-frequency switching can effectively eliminate the influence of standing waves.High-frequency ultrasound can deeply clean the pollution in the gap of the object.The low-frequency ultrasonic can clean the contaminants on the surface of the object.The dual-frequency cleaning method is more efficient and lower in cost.2.Aiming at the matching problem of dual-frequency ultrasonic power supply,this thesis analyzes the impedance characteristics of the dual-frequency transducer,designs two matching circuits according to the test parameters,uses electromagnetic relays for matching circuit switching,and describes the parameters of the transducer matching circuit Calculation method.3.Regarding the speed and accuracy of ultrasonic power supply,this thesis uses DDS digital synthesis frequency technology to achieve frequency output,and uses AD9833 chip and UCC3895 chip to achieve a PWM signal with an output accuracy of0.1Hz,which improves the control accuracy of ultrasonic power supply.The HZ6686 frequency tracking chip independently developed by the laboratory team realizes fast frequency tracking.Compared with the frequency tracking scheme implemented by traditional software algorithms,the integrated frequency tracking chip is used to assist the MCU to complete the frequency tracking.The MCU can perform frequency tracking judgment in each acquisition cycle.Furthermore,the frequency tracking speed is greatly improved,and the average frequency tracking speed can reach35.7us/Hz.4.Through experiments,this thesis explores the factors that cause the piezoelectric sheet of the ultrasonic transducer to heat up,and designs the PI constant power control function and the segmented power soft start function.Excessive power is a factor that causes the piezoelectric sheet of the transducer to continue to heat up.Frequent start and stop of the transducer will also cause the temperature of the piezoelectric sheet of the transducer.Research has found that if a segmented power soft start method is adopted,The temperature rise of the piezoelectric sheet of the transducer can be effectively suppressed.5.In terms of cleaning effect,this thesis compares the single-frequency cleaning mode and the dual-frequency cleaning mode.The experimental study found that the dual-frequency cleaning mode is better than the single-frequency cleaning mode for objects with more complex structures.More uniform,higher cleaning efficiency.