| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 95 === This study proposes the conceptual design of a ring-type vibrator with double layer piezo films for a rotary traveling wave ultrasonic motor to achieve the larger displacement and faster speed compared with a single layer piezo film. When the vibrator is excited, it generates the traveling wave to rotate the rotor. The vibratory model of the vibrator is generated by utilizing the classic plate theory and the electroelastic theory to obtain the analytical solution of the vibrator displacement. A contact model of the vibrator and the rotor is generated by using the equivalent system and the Coulomb’s friction law to calculate the normal force and the friction torque on the contact surfaces of the vibrator and the rotor. The axial displacement of the vibrator affected by the rotor and the base of the vibrator, the rotational speed, the torque and the power of the rotor are calculated. The random jumping method is used for optimization of the dimensions and the input parameters of the ultrasonic motor. The objective function is the energy conversion efficiency between the vibrator and the rotor. The 4th order Runge-Kutta method is used and a computer program is generated to obtain the rotational speed, the torque and the power in the transient state and the steady state. The calculated results show that the amplitude of the traveling wave is proportional the the input voltage. As the preload increases, the amplitude of the traveling wave and the effect are decreased. The friction torque increases when the contact area between the vibrator and the friction coat increases. When the tangential speed of the vibrator is slower than that of the rotor, the friction torque will be inversed to reduce the speed of the rotor. The wear of the rotor increases and the efficiency is decreased. The calculated optimal results show that the input voltage is 110 V, the preload is 127 N, and the rotational speed is 1.24 rad/s, the maximum impedance torque is 0.56 Nm, the energy conversion efficiency is 100 %.
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