The development of a small size ultrasonic motor for precise and high-speed positioning control

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The purpose of this research is to apply a Hybrid Transducer-Type Ultrasonic Motor (HTUSM) which we have proposed to presice positioning control. In this work, the improvement of the characteristics of HTUSMs and the development of the control system for a HTUSM have been done. We have obtained the following results.1.Trial-made HTUSMs The HTUSMs were made and the characteristics of these motors were measured. The minimum diameter of the motor was 5mm and the maximum diameter was 80mm. The driving frequency is between 20kHz and 30kHz. In the 5mm HTUSM,the maximum torque, no-load speed and the maximum efficiency are 50gf・cm, 800rpm and 20%, respectively.In the 80mm HTUSM,these characteristics are 160kgf・cm, 3rpm and 2%, respectively. The maximum torque of these HTUSMs was more than one hundred times as large as that of the same size of electro-magnetic motors.2.Improvement of the efficiency We proved theoretically that the efficiency of HTUSMs could be improved by adding odd harmonic co … More mponents to the fundamental harmonic driving signal. In order to realize this driving system, we devised the shape of a stator transducer. The resonance frequency of 3rd torsional mode could be adjusted to three times that of the fundamental mode in this transducer. Using this method, the efficieny of HTUSMs increased about 20%3.Investigation of the frictional characteristics and the frictional material We proposed a new evaluation method for frictional material using conventional wear test to determine the most suitable frictional material for HTUSMs. This method can be used for life prediction of HTUSMs.4.Development of control system 1)Positioning control : The small angular displacement of the rotor in proportion to the applied DC voltage to torsional vibrator can be obtained. Making use of this motion and the rotary operation, we developed the new precise angular positioning control system. The resolution of the proposed system was 4.85*10^<-2>rad, the same as that of rotary encoder. 2)Speed control : We pointed out that the revolution speed was propotional to the current in the torsional vibration element. We proposed the speed control system of HTUSMs by means of this feature. Additionaly, we indicated that series connection was suitable for synchronous operation of HTUSMs. Less