Development Of Ultrasonic Motor Drive Circuit Based On FPGA

Ultrasonic motor,as a new type of motor,has the advantages of fast starting response speed,large starting torque,large output torque and no step loss when running at low speed,self-locking at shutdown,and less electromagnetic interference.The ultrasonic motor uses the inverse piezoelectric effect of piezoelectric material to realize the conversion of electrical energy and mechanical energy,and realizes the rotation of the rotor through the elliptical movement of the stator and the friction between the stator and the rotor.However,heat will quickly accumulate during the movement of the ultrasonic motor,which leads to changes in the motion state of the ultrasonic motor,which increases the control complexity.Nowadays,ultrasonic motor drives generally adopt a combination of push-pull topology and series inductance matching.It is necessary to add a DC power supply and a transformer step-up link in the drive circuit,which increases the development cost.Aiming at the problem that the most commonly used push-pull topology of ultrasonic motors today requires DC power supply and transformer step-up links to significantly increase the cost,this paper tries the mains grid power supply scheme.First,according to the research requirements of the topology scheme,the ultrasonic motor is modeled on the equivalent circuit,and the ultrasonic motor is used for frequency sweep analysis with the impedance analyzer,and the parameters of the ultrasonic motor’s equivalent circuit model are determined.Based on the equivalent circuit model after determining the parameters,this article uses a combination of formula calculation and simulation analysis,starting from the actual application requirements,from the perspectives of circuit size,development cost,and application scenarios,the full bridge topology,half bridge topology and push-pull topology are analyzed.The circuit structure and matching circuit structures such as series inductance matching,T-type matching and LLCC matching are compared and analyzed,and an ultrasonic motor drive scheme based on half-bridge topology and LLCC matching circuit is designed.After that,based on the designed ultrasonic motor power drive scheme,the control and feedback module of the ultrasonic motor driver was designed and the construction of the ultrasonic motor drive platform was realized.Under the driving platform,the ultrasonic motor frequency modulation-speed regulation characteristics,amplitude modulation-speed regulation characteristics,temperature drift characteristics and isolated pole voltage change characteristics under the frequency and amplitude modulation conditions are carried out.Based on the test results,a speed regulation strategy of ultrasonic motor based on amplitude modulation and speed regulation is designed,and a temperature drift compensation scheme of ultrasonic motor based on the phase difference between isolated pole voltage and phase voltage is proposed.This article solves the problem that the push-pull topology circuit requires a DC power supply module to provide DC voltage and the transformer boost link increases the cost and inconvenience,and proposes a power drive structure with more application potential.