An ultrasonic linear motor using ridge mode traveling waves

A new type of ultrasonic linear motor is presented using traveling waves excited along a ridge atop a substrate. The ridge cross-section was designed to permit only the fundamental mode to be excited during operation of the motor, with the source of vibration a Langevin transducer in this study. The ridge waveguide was first made of lossy media to avoid reflecting vibration energy back toward the vibration source, forming a traveling wave. A 5-mm wide, 15-mm tall PMMA ridge was used to move a slider placed upon it toward the vibration source, in opposition to the direction of the traveling wave transmitted along the waveguide ridge. Using a low-loss aluminum ridge combined with a rubber damper clamped onto the far end of the waveguide, similar results were obtained. To obtain bi-directional operation, the damper was replaced with a second Langevin transducer, giving a pair of transducers located perpendicularly to the ends of the ridge and driven with an appropriate phase difference. The moving direction of the slider was reversed by shifting this phase difference by 180 degrees. With this simple configuration, it is possible to fabricate a linear micromotor system on a silicon substrate or other semiconductor wafer adjacent to other electronic and optoelectric devices.