Research On Optimization Compensation Method Of Ultrasonic Motor Drive Temperature Drift Characteristics

Ultrasonic motor is a new type of special motor.It works differently than traditional motors.The stator vibrates with high frequency vibration driven by piezoelectric ceramics and the rotor’s movement is driven through the friction between the stator and rotor during the motor works.And the movement of piezoelectric ceramics is the result of input voltage.Ultrasonic motor features distinctive,as a result,it is superior in many respects than electromagnet motors.It has the advantages of lower speed than electromagnet motors,larger torque in unit volume,short response time,breakpoint self-locking and so on.Because of the above advantages,ultrasonic motor has become a research hot spot of science and technology industry.A lot of loss is produced when ultrasonic motor is running.On one hand,it comes from the piezoelectric ceramic internal;on the other hand,it is generated by the friction between the stator and rotor contact film.The accumulation of the loss causes the temperature rising of the motor.As a result,the admittance characteristic of the motor changes.Compensation of the motor temperature drift characteristics need to start from the source,so need to study how to reduce system wear and tear.In this paper,the temperature drift characteristics of ultrasonic motor are studied,and a temperature compensation method based on frequency tracking principle is proposed.Finally,an optimal frequency tracking system is constructed.The main contents and achievements of this paper are as follows:In this paper,we first construct a mathematical model of ultrasonic motor which can reflect the characteristics of temperature drift.The modeling process is based on the energy conversion process inside the ultrasonic motor.The loss of the ultrasonic motor is calculated quantitatively.The influence of the loss on the parameters of the piezoelectric ceramic is pointed out.Finally,the equivalent circuit model of the ultrasonic motor is established.Through the simulation of the model,it is found that the ultrasonic motor admittance spectrum and the phase spectrum are shifted to the left,and the minimum admittance phase is found in the ultrasonic motor.This paper designs an optimal frequency tracking principle for ultrasonic motors for temperature drift compensation.Optimal frequency tracking principle set the mechanical quality factor as the performance indicators.The system ensures that the ultrasonic motor running in the occasion when mechanical quality factor is largest by adjusting the drive frequency.It can be shown that the frequency of the mechanical quality factor is approximately equal to the minimum frequency of the admittance phase.So the core of the optimal frequency tracking principle is transformed into the tracking of the minimum admittance phase.The optimal frequency tracking system is a combination of hardware and software which is based on the optimal frequency tracking principle.This paper introduces the realization of the system.The system consists of two parts: ultrasonic motor driver and software system.The optimal frequency tracking system has the compensation function of ultrasonic motor temperature drift.