Design, characterization and stability test of a multistable composite compliant actuator for exoskeletons

A novel actuator is presented that merges traditional electromechanical motors and multistable composite structures. Previously, it has been shown that these structures are able to arrange themselves in multiple stable configurations corresponding to local minima of their strain energy. When coupled with an electromechanical motor as proposed in this article, the resulting actuator shows significant benefits. These are in terms of safety, energy saving and control implementation using the compliance of the overall structure, the particular shape of the strain energy landscape, and the accurately predictable non-linear behavior. Hence the proposed actuator is well-suited for robotics applications. The parameters characterizing the design of the transmission are analyzed, and a physical model is developed. A case study is presented in which the performance for a particular configuration of the system is evaluated and reported. A conceptual application of the proposed actuator is discussed for assistive robotics, where new perspectives on the use of non-rigid transmission elements might become beneficial in terms of safety and energy harvesting.