Micro Geared Ultrasonic Motor

We propose a micro geared ultrasonic motor, the smallest set of a micro ultrasonic motor and micro planetary gear. Our micro ultrasonic motor is one of the most powerful motors in one-millimeter-scale motors. The use of a micro planetary gear amplifies the motor torque to several tens of times and the geared motor enables a high torque density that was unachievable by existing miniature motors. The goal of this paper is to analyze the dynamic characteristic of the micro geared ultrasonic motor with a mathematical model and confirm the torque amplification experimentally using a micro planetary gear prototype. To build the microgear components, we employ a micro-injection molding process using metallic glass, a relatively new material, with a low melting temperature. The micro planetary gear assembly with a diameter of 2 mm, a length of 5.9 mm, and a gear ratio of 256 is built and connected to the micro ultrasonic motor. The micro geared ultrasonic motor demonstrates a continuous torque of 0.4 mN·m and a peak torque of 1 mN·m in the load lifting experiments.