Turned off Characteristics of Linear Ultrasonic Motor

The high controllability and high resolution control of linear ultrasonic motors depend on effective control of driving signals. For a good control characteristic, step control which the driver output turned off and on was used. Therefore, a novel dual PWM topology structure ultrasonic motor driver was designed and analyzed. According to the characteristics of the circuits, two kinds of hardware turned off methods named methods A and B were discussed. The differences of the voltage applied on motor by different methods were figured out. Finally, a series of experiments were carried out in the clean room to study the influence of step characteristic by different turn off methods. The experimental results show that the steplength was 230 nm by method A and 125 nm by method B, while cycles of driving signals were 6. The method B has a smaller steplength when cycles are 6. The average steplength varies in non-linear while driving cycles changing. The steplength varies approximately in linear while voltage amplitude changing. Therefore, method B is better to implement step control, because it gets a better control in positioning system.