A novel traveling wave ultrasonic motor using sandwich-type ring stator

This paper intends to present and verify a new idea for constructing traveling wave ultrasonic motors that may utilize the advantages of sandwich-type transducer-higher efficiency PZT working mode of d₃₃ than d₃₃ easy fabrication and minimization of the adhesive layer fatigue problem under harsh environment. A traveling wave ultrasonic motor using a composite sandwich-type ring stator was proposed in this paper. The proposed stator contains a ring-like stator and a pair of rotors. We implement the stator by cutting a duralumin alloy ringlike beam into four parts. And the PZT elements were sandwiched and bolted in the ring beam in accordance with 90 degree rotational symmetry. Two disk type rotors are pressed in contact to the teeth on both end surfaces of the stator, and the pre-pressure between the stator and the rotors is applied by a spring and a nut system. The working principle of the proposed motor was analyzed. The FEM modal analysis method was used to design the stator and the FEM transient analysis was used to simulate the establishment of traveling wave on the ring-like stator. A prototype motor was manufactured and experimentally characterized. The working mode shapes of prototype stator were tested by a laser Doppler scanner to verify the theoretical analysis. The maximal no-load speed and torque of the prototype are tested to be 2.23rpm and maximum torque of 15gf-cm at an exciting voltage of 100V. Possible variations of the present design aimed to increase output torque should be adjusting the dimensions of PZT element, increasing the depth of parallelism of the composite sandwich-type stator in fabrication.