A variable stiffness PZT cellular actuator with tunable resonance for cyclic motion tasks

A simple and efficient approach for varying the inherent stiffness and impedance of a muscle-like actuator is presented. The basic architecture of PZT cellular actuators has already achieved a large effective strain (10-20%). This architecture is modified and extended so that each cellular unit can be switched between a zero compliance state and constant compliance state. The effective stiffness of the cellular actuator is varied by changing the distribution of cellular units in the rigid versus compliant state. Furthermore, by placing a multitude of these cellular units in series or parallel, the stiffness can vary within a large set of discrete values. This paper also demonstrates the viability of the variable stiffness cellular actuator for cyclic tasks such as running and flapping. The basic principle and design concept for the actuator is described, followed by force-displacement analysis. A dynamic model is then constructed to demonstrate the variable resonance properties of the actuator under load.