Frequency control technology for ultrasonic motor based on correlation phase extraction method

Abstract

In order to solve the problems that the speed of ultrasonic motor is usually affected by the changes of temperature and load, and that due to installation volume and cost of the speed sensor, the closed-loop control based on speed feedback is often limited in some special applications, a frequency closed-loop control method based on phase difference feedback is introduced. Firstly, the type of phase difference feedback quantity is optimally selected according to the sensitivity of different motor phase differences to the temperature and load change; secondly, aiming to the interference of mechanical and harmonic noises on phase difference calculating result, the correlation phase extraction method is proposed to improve the accuracy of phase difference between driving voltage and monitor electrode voltage; lastly, the corresponding frequency closed-loop control scheme is given according to the changes of temperature and load change, respectively. Experiment results indicate that this method can reduce the speed fluctuations caused by the changes of temperature and load, and improve the speed stability of motor system. Because only two voltage signals are needed to be recorded, this method is easy for implementation.

Keywords

• electric machinery
• ultrasonic motor
• phase difference
• closed-loop control
• correlation analysis