Research On The High-precision Position Control Of Ultrasonic Motor Based On Transient Response

Ultrasonic motor has the advantages of fast response speed,high torque-to-mass ratio,no electromagnetic interference during operation,with power-off self-locking ability,low torque operation in the absence of variable speed device,etc.,making the ultrasonic motor has been widely used.In this paper,the ultrasonic motor is applied to the high precision pointing mechanism,the traditional position control strategy positioning accuracy is low,can not fully meet the high precision positioning requirements.Therefore,it is very important to study the application of high precision position control strategy for ultrasonic motor to further expand the application range of ultrasonic motor.Aiming at the shortcomings of the traditional ultrasonic motor controller performance,this paper designs the digital ultrasonic motor controller with the DSP(Chips number: TMS320F28335)as the control core.The pulse width modulation function of the chip can accurately adjust the frequency,phase difference and duty cycle of the drive signal.The accurate measurement of the motor operating parameters is realized by the differential signal processing circuit and the low-pass filter circuit.The controller has the characteristics of fast running speed and high precision.While the use of serial communication makes the controller has a good human-computer interaction performance.In order to realize the accurate measurement of transient response of ultrasonic motor,the ultrasonic characteristic test system of ultrasonic motor is built by using high precision orthogonal rotary encoder,digital ultrasonic motor controller and LabVIEW computer.The system was validated using the fixed frequency method and the oscilloscope method to ensure the reliability of the test system.The influence of the motor body factor,the measuring device factor and the motor driving parameter factors on the start and stop characteristics are obtained by measuring and analyzing the starting and stopping characteristics of the ultrasonic motor by using the verified test system.Aiming at the shortcomings of traditional control algorithm,the stepping position control method of ultrasonic motor based on transient response is studied.In order to verify the running step and the running stability of the step angle,a high precision displacement detection test bed is built by using the high precision absolute rotary encoder,the digital ultrasonic motor controller and the LabVIEW program.On this basis,The experimental results show that the stepping angle of the ultrasonic motor is less than 1 "and has better stability.In order to realize the fast and high precision positioning control,the traditional PID position control algorithm is combined with the step control algorithm,the experimental results show that the control algorithm has the characteristics of short adjustment time and high positioning accuracy.