Research On High Precision Driving Characteristics Of Ultrasonic Motor

Ultrasonic motors have the advantages of low speed,large torque,self-locking after power failure,high control accuracy,and no external electromagnetic interference.Ultrasonic motors are widely used in aerospace,precision manufacturing,robotics,optical equipment and other fields.In this paper,based on the control strategy of PID continuous operation and step operation,the transient response and high-precision driving characteristics of the ultrasonic motor are studied,and these performances are applied to the positioning control.And designed a flexible shaft with adaptive contact performance,optimized the flexible shaft structure parameters and tested the performance of the flexible shaft ultrasonic motor,so as to improve the precise positioning of the ultrasonic motor.Research on transient response of ultrasonic motor under different loads and preloads.A test system for the transient characteristics of the ultrasonic motor was built.The test system can accurately adjust the preload and load of the motor,so that the ultrasonic motor can meet the operation under different working conditions.A motion equation describing the transient response of the motor is established,and the effect of load and preload on the start-stop time of the ultrasonic motor is theoretically analyzed.The built-in test system was used to test the start-stop characteristics of the ultrasonic motor under different loads and preloads,and the change rule of the ultrasonic motor start time and stop time with the preload and load was obtained.The results show that the starting time decreases with increasing load and increases with increasing pre-pressure.As the load and pre-pressure increase,the stopping time shows a decreasing trend.Research on the positioning characteristics of ultrasonic motors.In order to achieve the high-precision positioning characteristics of the motor,a position control method was developed,which includes two operating modes,a continuous operating mode and a stepping mode.In the continuous mode,the PID control method is used to control the speed of the motor.Through the parameter tuning method,the positioning curves of the ultrasonic motor at different Kp,Ki,Kd values are tested to determine the PID control parameters.The stepping mode mainly uses absolute encoders and digital controllers to detect and feed back positioning data during the stepping process.The stepping characteristics under different loads and preloads were studied to obtain the operating frequency and step length with the smallest step angle.The results show that under different load and preload conditions and different target operating angles,the positioning error of the control process is less than 3.7 ″,and the total adjustment time is less than 1.4 s.The effect of flexible shaft on the positioning characteristics of ultrasonic motor was studied.In order to improve the motion stability of the motor,a flexible shaft with adaptive contact is designed and manufactured.The flexible shaft adopts ANSYS software to simulate the bending moment and torque of the flexible shaft to obtain the preliminary structural parameter range of the flexible shaft.In order to optimize the structural parameters of the flexible shaft,when the radius of the flexible shaft is 1 mm and the minimum shaft diameter is 1.5 mm,the stability of the ultrasonic motor is the best.The speed stability,transient characteristics and stepping characteristics of flexible shafts with different structural parameters were tested.Experiments show that the flexible shaft improves the stability and positioning accuracy of the ultrasonic motor,and the final positioning accuracy is within 2.4 ″.