| Summary: | 博士 === 國立清華大學 === 動力機械工程學系 === 92 === A thin-disc ultrasonic actuator using a piezoelectric buzzer is proposed as the actuating component for the novel shaft-driving type ultrasonic actuator. By placed the screw constraints on the metal sheet of a buzzer, a 3-phase reflected wave was constituted and propagated based on the purpose locations of constraints. This wave configuration could convert electrical energy to actuate the kinematical power for rotating the rotor. In mechanical design, the benefits of this novel ultrasonic actuator are the separated design in both of rotors and stators, convenient arrangement in mechanism, manufacturing cost in cheap, and simple structures in thin. Since the high rotary speed is closed to 4000 rpm, the motor keeps the potential and developed commercialization in future.
The input and output signals were acquisition according to the single-frequency exciting of system resonant frequencies and the multiple-frequency exciting of pseudo random binary sequences (PRBS), respectively. The dynamic transfer function of a stator was obtained via the system identification technique, and, therefore, one model of a three order equivalent circuit was built in which the dynamic features and electromechanical characteristics were considered based on material oscillating behaviors. Because of the admittance transfer function derived from measured method, it is more representative than that of past issues through the theoretical deduction in materials, physics, and mechanics.
By calculating the parameters of an equivalent circuit model, the quality factor of the ultrasonic actuating system is about 17.71 and the electromechanical coupling coefficient approaches 0.56. Both of these factors could be as the reference to suppress temperature levitation, launch the stability, either an improvement of the mechanism. An implementation of a single-axis piezoelectric actuating platform confirms the practical value for the ultrasonic actuator.
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