Design And Implementation Of Portable Ultrasonic Therapy Instrument Based On Frequency Tracking

Medical research shows that ultrasound has good penetrability.Ultrasound has a significant effect in the treatment of chronic soft tissue diseases such as neuralgia,spondylopathy,Meniere’s disease and amyotrophic sclerosis.The frequency range of medical ultrasonic physiotherapy instruments on the market is 0.7MHz～1.2MHz.Medical ultrasonic physiotherapy instruments on the market generally have problems such as low sound-to-electric conversion efficiency,large size,high price,and complex functions.Ultrasonic transducers are sensitive devices.When the ultrasonic transducer is worn and hot,the ultrasonic power supply cannot change the resonance frequency of the ultrasonic transducer in time,which will cause the frequency of the ultrasonic power supply system to be detuned.Therefore,it is necessary to study a frequency tracking method to constantly monitor and adjust the resonant frequency.According to electrical knowledge,when the ultrasonic transducer exhibits a capacitive load characteristic as a whole,the overall power loss of the ultrasonic physiotherapy apparatus will be large,and the acoustic-electric conversion efficiency will be low.This thesis develops a household ultrasonic physiotherapy instrument with high efficiency,low cost and easy to carry.A 12V rechargeable lithium battery is used to power the physiotherapy instrument.A low-power STM32L151 microcontroller combined with a signal generator is used to generate the excitation signal.The signal is amplified by a drive circuit and a class E power amplifier with good high-frequency performance.Finally,the ultrasonic transducer is driven to generate ultrasonic waves with an output center frequency of 1 MHz and an intensity of 150m W/cm~2,200m W/cm~2,250m W/cm~2and 500m W/cm~2.Since the parameters of the conventional static impedance matching network are not easy to adjust,a dynamic LC-type impedance matching network is designed for dynamic impedance matching.Aiming at the problem of transducer resonance frequency drift,the feedback regulation system designs a compound frequency tracking method combining PID algorithm and phase-locked loop.An oscilloscope and an ultrasonic power meter are used to verify the feasibility of the composite frequency automatic tracking method.This thesis develops a prototype of an ultrasonic physical therapy instrument and uses an oscilloscope to verify the rationality of the entire system design.Test the ultrasonic intensity of each gear ultrasonic physiotherapy instrument.Calculate and analyze the output efficiency and acoustic-electric conversion efficiency of the ultrasonic physical therapy instrument.Finally,the ultrasonic physiotherapy instrument was tested by 8 volunteers.The test results show that the output center frequency of the ultrasonic physical therapy instrument is 1MHz,and the error range is±10%.The ultrasonic output intensity is adjustable,the acoustic-electric conversion efficiency can reach 44.6%,and the overall conversion efficiency can reach 42.5%.The physiotherapy instrument has high acoustic-electric conversion efficiency,stable output power,and dynamically adjustable output sound intensity.It is a portable ultrasonic physiotherapy instrument suitable for home use.