Research On Drive And Precise Servo Of Traveling Wave Ultrasonic Motor

This dissertation focuses on the traveling wave type ultrasonic motor.The main research contents are as follows:research on the driving mechanism and the driving power of the motor;the speed control and the position-speed servo control of the motor under continuous operation;the precise position control and the ultra-low speed control of the motor with the microstep driving technique;research on the multipled ultrasonic motor with high torque as well as its driving device.The history,classification,application and research status of the ultrasonic motor were firstly introduced.The domestic and international research achievements on driving and controlling the ultrasonic motor were overviewed.The significance and contents of the research in this dissertation were illustrated based on the development trend of ultrasonic motor.For the operation and control mechanism of the traveling wave type ultrasonic motor,the construction was analyzed,which mainly concentrated on the piezoceramics,the elastic resonator of the stator,and the rotor.When it came to the piezoceramics,the piezoelectric effect of the lead zirconate titanate(PZT)was illustrated.As the vibration sources,the polarized PZT plays a vital role in the formation of the travelling wave,through whose ring structure the vibration travels.To the elastic resonator of the stator,the equivalent circuit model of the stator was established according to the electromechanical analogy method.The relationship between the impedance characteristic and the vibration of the stator were also analyzed.Once activating the PZT,the travelling speed of the teeth of the stator was derived by analyzing its motion trail.For the rotator,the contact and friction between the rotator and the teeth of the stator were analyzed by incremental hypotheses of the precompression between the stator and the rotator based on the motion balance.The stable state of the speed and the speed control of the motor under steady excitations were also summarized.For the drive of the traveling wave type ultrasonic motor,three driving circuits were designed.These driving circuits adopted low-pass filter based on square wave inversion,resonance booster,and direct frequency synthesis respectively.In the push-pull drive circuit,higher harmonics in the square wave was eliminated by the low-pass filter composed of the leakage inductance of the boosting transformer and the clamped capacitance of the motor.For the resonance booster,the secondary side of the low-ratio boosting transformer was in series with a resonant inductor,forming a resonance circuit with the clamped capacitor of the motor.Since the circuit was operated in the vicinity of the resonance frequency,the driving voltage could be improved by the frequency selectivity of the resonance circuit to drive the motor.To the direct frequency synthesis,the sine-wave supply was composed of connecting DDS chip and linear power amplifier.The corresponding drive circuits were manufactured.Their performance of drive circuits was tested and compared.For speed control,a H? robust controller for the ultrasonic motor was designed using the S/T mixed-sensitivity method.The nonlinear speed model and the parameter variation range were obtained by the identification method based on the Hammerstein model.The corresponding nominal speed model and the perturbations were computed to obtain the constraints of the stability(the complementary sensitivity)of the controller.The tracking performance index of the speed was analyzed and transformed into the constraints of the system performance(the sensitivity).Based on the S/T mixed-sensitivity method,the tracking control was transformed into the standard H? robust control,which was solved by MATLAB.The simulation and experiment results verified the good control effect of the controller.In the precise position-speed servo control system for ultrasonic motor by 2D platform,the system adopted a time-sharing control structure with a position closed-loop control circuit and a speed closed-loop control circuit,which switched reference to the input signal of speed.The position tracking was achieved by piecewise and proportional regulations in the position loop,the speed control was achieved using the H? control strategy in the speed loop.Meanwhile,the host link system and the position signal collection by the lower computers were designed with frequency interference suppressed and overcurrent protected.The position error of the platform is less than 3 ?m,which proves that it has good tracking ability.For the research on the precise position control and the ultra-low speed control of the ultrasonic motor,taking the advantage of the fast start and stop of the motor,a micro-stepping controller was designed based on the high accurate position feedback.The position accuracy of the rotational angle was reaching at 0.1".Based on the stepwise model of the ultrasonic motor,the double variables and change-velocity integral controller was designed.With the integral coefficient modified dynamically according to the reference model,the ultra-low speed closed-loop was built based on the speed observer using the moving average method.The error rate of speed was below 10%with the target speed at 0.05deg/s.The high-power ultrasonic motor as well as its driving circuit was designed.Based on the impedance characteristic of the stator,the stators with same properties were coaxial and parallel assembled to improve the mechanical behavior of the motor.The drive circuit of the high-power ultrasonic motor was manufactured based on the push-pull square wave inverter circuit and the impedance matching of the booster transformer.The stalling torque reached 6Nm and the no-load speed reached 50r/min.In the end of the dissertation,the whole work was concluded,and the potential of the ultrasonic motor on further research was pointed out.