Micro Walking Machines Using Piezoelectric Actuators

A large number of attempts have been made in recent years to apply piezoelectric ceramics to actuators for movable systems. In effect, piezoelectric ceramics have been placed under the category of precision positioners.i> In this paper, the future of micro travelling systems is reviewed mainly on the basis of studies conducted by the author et al. Piezoelectric/electrostrictive actuators can roughly be classified according to their driving principles into the following two types: one type is designed to utilize the displacement created rigidly under an electric field applied; the other type is designed to utilize the displacement created by an alternating electric field as a result of mechanical resonance. The elements of both types, called inchworm and ultrasonic motor respectively, differ considerably in driving principle, though they are very similar in appearance. In addition, a third type known as photostrictive actuator has been developed. This type is designed to be driven by irradiated light.