A compliant 5-bar tristable mechanism utilizing metamorphic transformation

Compliant multistable mechanisms, which are capable of steadily staying at multiple distinct positions without power input, have many potential applications in switches, valves, closures, relays, statically-balanced mechanisms, reconfigurable robots, and large-displacement micro actuators. In this paper, we propose a new idea of utilizing metamorphic transformations to develop compliant multistable mechanisms. By distributing the prescribed stable equilibrium positions into different metamorphic working phases, the design of a compliant multistable mechanism can be greatly simplified. The idea is demonstrated by a tristable mechanism that can metamorphically transform from a compliant 5-bar mechanism into a compliant 4-bar mechanism in a certain range of motion. The kinetostatic solution of this tristable mechanism is formulated and the kinetostatic results confirm that the mechanism has two deflected stable equilibrium positions besides its initial assembly position, with one occuring in the 4-bar working phase and the other in the 5-bar working phase. Although the discussion is limited to a planar 5-bar mechanism, the idea of utilizing metamorphic transformations to achieve multistable behivors can surely be extended to other types of linkages.