Design of Compliant Mechanisms for Minimizing Input Power in Dynamic Applications

Abstract

In this paper, we investigate power flow in compliant mechanisms that are employed in dynamic applications. More specifically, we identify various elements of the energy storage and transfer between the input, external load, and the strain energy stored within the compliant transmission. The goal is to design complaint mechanisms for dynamic applications by exploiting the inherent energy storage capability of compliant mechanisms in the most effective manner. We present a detailed case study on a flapping mechanism in which we compare the peak input power requirement in a rigid-body mechanism with attached springs versus a distributed compliant mechanism. Through this case study, we present two different approaches, (1) generative-load exploitation and (2) reactance cancellation, to describe the role of stored elastic energy in reducing the required input power. In contrast to a conventional mechanism with a spring, stress and strain in a compliant mechanism are more uniformly distributed. The entire mechanism stores energy rather than just a spring, providing more energy storage per unit mass. We propose a compliant flapping mechanism and its evaluation using nonlinear transient analysis. The input power requirement of the proposed compliant flapping mechanism is found to be 48% and 10% less than those of the four-bar flapping mechanism without and with a spring, respectively. The results show that a compliant mechanism can be a better alternative to a rigid-body mechanism with attached springs.