Driving Mechanism and Control of Ultrasonic Motor

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The estimated driving torque is compared with the actual load torque. The estimation is based on a primitive driving model. The detailed studies, considering warp of both surfaces of rotor and stator, have not been developed yet. Moreover, it is well known that a squealing sound occurs while the motor is driving.Elastic deformation of the rotor, vertical and horizontal vibrations of teeth and rotary speed were measured precisely by using a newly developed measuring system. The experiment shows the followings :(a) Each tooth of the stator comes into contact with the rotor in order of proximity as the preloaded force becomes larger.(b) The elastic deformation measured on the teeth near the rotor, is greater than it is away from the rotor.(c) The circumferential speeds of thye teeth are almost the same.(d) The squeal vibration with a frequency of 4.9 kHz is measured on the specific teeth.USM has two problems for constant speed drive, one is the influence of temperature rise during operation, and the other is the influence of initial deformations of the stator and the rotor. The adaptive control method has been applied to achieve constant speed drive, however, it is difficult to design a controller systematically.In this study H_* repetitive control method is applied as follows :(a) H_* speed control system is designed for robust stability against the influence of the temperature fluctuation.(b) A repetitive compensator is attached to improve the characteristic of disturbance rejection.The efficiency of the repetitive compensator is also confirmed by the control experiment.