Electromagnetic motors can have problems when operating in extreme environments. In addition, if one needs to do mechanical work outside a structure, electrical feedthroughs are required to transport the electric power to drive the motor. Piezoelectric motors can be designed directly with high torques and lower speeds without the need for gears. One can also actuate piezoelectric, electrostrictive, or magnetostrictive materials in a benign environment and transmit the power in acoustic form as a stress wave and actuate external to the benign environment. This technology removes the need to perforate a structure and allows work to be done directly on the other side of a structure without the use of electrical feedthroughs, which can weaken the structure, pipe, or vessel.

The solution is to design a matching actuator and workpiece that can be bolted/fastened into a barrier on either side, and tuned to transmit acoustic power across the barrier. In the working end, the acoustic power is converted to rotary or linear motion at the end effectors to do useful work.

Designs were developed for producing rotary and linear motion on the exterior of a structure without a conventional electrical or mechanical feed-through. Acoustic energy is pumped at a set frequency or range of frequencies to produce resonance motion in a structure that can be converted into rotary or linear motion. The unique feature of these motors is that they can be designed to produce work across a structure without perforating the structure mechanically. In addition, since the device comes in two parts, one could design the actuator for a given frequency and switch in the end effectors to produce rotary or linear work.

This method of transferring useful mechanical work across solid barriers by pumping acoustic energy through a resonant structure features the ability to transfer work (rotary or linear motion) across pressure or thermal barriers, or in a sterile environment, without generating contaminants. Reflectors in the wall of barriers enhance the efficiency of the energy/power transmission. The method features the ability to produce a bi-directional driving mechanism using higher-mode resonances. The approach can be used to develop actuators that operate at the same frequency of the driving actuator or produce rotary or linear motion at lower frequencies.

There are a variety of applications where the presence of a motor is complicated by thermal or chemical environments that would be hostile to the motor components and reduce life and, in some instances, not be feasible.

This work was done by Stewart Sherrit, Xiaoqi Bao, and Yoseph Bar-Cohen of Caltech for NASA’s Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Refer to NPO-48422.