Analysis of quasi-static and dynamic motion mechanisms for piezoelectric miniature robots

Piezoceramic actuators are often used when there is a need for high precision translation and are therefore of particular interest in the development of miniature robotic systems. In this paper the effect of miniaturisation on two dynamic and two quasi-static motion mechanisms has been experimentally evaluated using a miniature piezoceramic drive unit. The actuator design, comprising six piezoceramic multilayer bimorphs, and the rapid prototype process used to fabricate the monolithic multilayer structure, are described. Experiments show that for a mass of 1–10 g, corresponding to the miniature robot considered, it is possible to use both dynamic and quasi-static motion mechanisms. With the present drive unit at low loads, the dynamic motion mechanisms are less demanding and work closer to the ideal case than quasi-static motion mechanisms. At higher loads the opposite will in general be true. Artefacts due to vibrations and bouncing in the vertical direction are the main reason for non-ideal behaviour when a small movable mass is used. In particular, movements generated by mechanisms utilizing a vertical velocity component are sensitive to a low mass. The design parameters to avoid or reduce these artefacts are identified and discussed.