Design of Compliant Parallel Kinematic Machines

Abstract

Conventional Parallel Kinematic Machines (PKMs) suffer from poor repeatability due to backlash in various joints. Use of flexures to overcome this limitation has also been reported in the published literature. However, conventional flexures suffer from axis drift, limited range of motion and stress concentrations. We present a new method of design of Compliant PKMs (CPKMs) and using a new type of compliant joints. We employ large displacement compliant joints to construct PKMs, which exhibit sub-micron accuracy. The methodology presented in this paper allows us to synthesize a PKM for any desired number and type of kinematic degrees of freedom by employing modular construction elements. A library of constraining legs synthesized from compliant joints is used for construction of any CPKM. The paper presents a systematic approach to transforming an arbitrary 3D motions specification into a set of motions along orthogonal axes using dual vector. The method enables construction of any CPKM by using the library of standard constraining legs and active legs. The methodology is illustrated with a design example.