Selective-actuation micro-positioning systems based on flexure parallel mechanisms

Abstract

This thesis focuses on the design and modeling methods of selective-actuation flexure parallel mechanisms that can be used as a micro-positioning system. The design of SA FPMs is realized through synthesis of macro-scale SA parallel mechanisms, conversion of the macro-scale SA parallel mechanisms into SA FPMs, and optimization of FPM parameters for resolution and stiffness. The premise of SA parallel mechanism synthesis is to obtain the Jacobian matrix of the mechanism in diagonal form based on screw theory. The optimization is carried out based on a number of performance indices including global resolution transmission scale, resolution uniformity and stiffness of the FPM. An improved pseudo rigid-body (PRB) model is proposed to give more precise estimation of FPM movement. In this improved version of PRB model, deformations of the flexure members are first computed using PRB method. Then these computed deformations are substituted back to the PRB model as second order effect for compensation. To illustrate the feasibility of the proposed design method, an SA FPM having three translational degrees of freedom is developed. Experimental results show that the prototype FPM can provide accurate decoupled linear motions and the resolution and stiffness performances of the FPM are very close to the designed values. As a generic FPM design method, this approach is also applied to the design of a 6-DOF dexterous SA FPM. Preliminary study of this mechanism has also carried out.