On the rectification of vibratory motion

The author establishes a theoretical framework for analyzing and classifying actuators which generate their output by rectifying small-amplitude mechanical vibrations such as might be generated by piezoelectric elements. These ideas are of interest when designing for microfabrication because motors based on these principles: (1) can generate translational output directly without use of rotary bearings; (2) appear to be scalable over several orders of magnitude of the length scale; and (3) appear to be capable of generating mechanical power proportional to driving frequency over several orders of magnitude of frequency. Achieving this performance is dependent on being able to fabricate features, or at least control surface irregularities, on the scale v/w where v is the velocity of the actuator and w is the operating frequency.<>