Research On Ultrasonic Motor And Antifriction Technique Based On Bolt-Clamped Transducer

Since frictional vibration damages a mechanical system's performances when the system works at a low velocity, efficient antifriction techniques are the key tasks that have been seeking after all along. Ultrasonic motors are a new kind of solid actuators that come into being since 1980's, which use inverse piezoelectric effect of PZT to excite stator's elliptical vibration and produce driving power by frictional coupling. In order to realize smooth movement of mechanical system at a low velocity, the following work investigates new types of linear ultrasonic motors and antifriction technique by superposing the motor's elliptical vibrating motion at the friction interface to change frictional characteristics, produce ultrasonic lubricant effect and realize active control of friction force.The ultrasonic dynamic contact of bolt-clamped transducer and rigid plane are modeled using Hertzian contact theory, and the analyzing results reveal that the nodal plane of the bolt-clamped transducer is levitated in normal direction by the ultrasonic dynamic contact action, and the real area of contact of bolt-clamped transducer and rigid plane decreases in the same time. The established contact model has provided good explanation for the phenomena of the reduction of frictional coefficient induced by longitudinal ultrasonic vibration and has great academic significance in proposing friction reduction technology based on elliptical ultrasonic vibration. The normal levitation of nodal plane tested under ultrasonic dynamic contact action validates the normal dynamic contact model.In order to increase output power of conventional standing wave ultrasonic motors to satisfy the antifriction technique, this dissertation presents a new linear transducer-metallic plate type ultrasonic motor based on the conventional standing wave ultrasonic motor's structure. The stator of this motor is composed of a bolt-clamped transducer and a metallic plate in which legs are machined. Through acoustic coupling of the transducer and the elastic plate, energy is transferred to the metallic plate, thus, the metallic plate's flexural vibrating mode comes into being and driving force is produced by the legs'rectilinear motion.