Design On Control System Of Ultrasonic Motor Based On Low-Frequency PWM And Single Neuron Adaptive Strategy

Ultrasonic motor is a special motor which works based on the inverse piezoelectric effect of piezoceramic materials.It has various advantages,such as,low running noise,no electromagnetic interference,small inertia,rapid response and power self-locking.So it is widely used in precision motion control fields.However,the piezoelectric energy conversion and the friction energy transfer both are contained in the interior of ultrasonic motor,which makes its nonlinearity and the multivariable coupling become serious.So,putting forward an effective control strategy is urgent,what’s more,designning a specialized drive and control system is also in need.The main research content is as follows:First of all,the thought of low-frequency PWM had been proposed in this paper.The strategy named intermittent PWM,positive inversion PWM,positive inversion and breakoff PWM were expounded clearly.At the same time,the comparisions had been conducted in these aspects,such as,the travelling wave vibration of stator,the open loop speed characteristics and the input power.Meanwhile,the application field of them was also given.Secondly,the strategy named low-frequency PWM and single neuron adaptive strategy was proposed. Specifically,the duty cycle of low-frequency PWM was adjusted by the single neuron adaptive strategy.Four symmetrical high-frequency PWM signals based on the DDS technology had a logical operation with low-frequency PWM signal by the TTL AND gate circuit. So the intermittent PWM control method was constructed,which could reply to the challenge caused by the nonlinearity and time-varying characteristics of ultrasonic motor.The most important work aimed at calculating the parameters of PID controller and the weighting coefficients.Thirdly,the system architecture of ultrasonic motor control system based on low-frequency PWM and single neuron adaptive strategy was constructed.Meanwhile, Several units were designed,such as,the circuit of signal generator for producing four symmetrical PWM signals based on the DDS technology,the double push-pull and power magnify circuit,the feedback circuit of isolated voltage located on the stator surface,the signal conditioning circuit,the optocoupler isolation circuit,the relay protection circuit,the supply circuit and the upper-position computer interface based on Visual Basic software.Finally,the ultrasonic motor with two phase wave had been selected as the experimental motor.The performance testing was conducted by using DSP,CPLD and the ultrasonic motor simulation software.Of course,the speed curve and the position curve were analyzed deeply.Simulation results showed that control system of ultrasonic motor based on low-frequency PWM and single neuron adaptive strategy had an excellent adaptivity when it was compared with the fixed PID parameters control system.