Design of compliant mechanisms based on compliant building elements. Part I: Principles

Abstract

In this paper, we present a new design method and principle, i.e., Compliant Building Elements (CBE), for compliant mechanisms that adopts a systematic and synthetic approach to generate practicable flexure designs. The CBE is unique in that it encodes a compliant system's quantitative information, including elasticity, geometry, location, and orientation, in a parametric matrix. Based on the matrix, a degree-of-freedom (DOF) concept is defined to describe permitted motions of a flexure; next, the screw theory is used to guide the design and synthesis of compliant mechanisms from DOF decomposition to actuator layout selection. In CBE, a compliant system consists of three types of compliant elements, i.e., compliant elements formed by serial or parallel connections and basic compliant elements. The synthesis procedure is a top-down and iterative process, starting from laying out the stage topology to finally optimizing the compliant connection elements and types (i.e., serial or parallel), where the iteration stops when the stage characteristics meet the design requirements. A library of various compliant elements is provided to help the designers quickly generate the initial stage topological designs and optimize the performance with reduced design iterations. The matrix-based design method for compliant mechanisms, i.e., CBE, which is analogous to the screw-based type synthesis for rigid parallel mechanisms, enables early-stage flexure system design via building compliant blocks just like building LEGO® bricks.