Design of Compliant Straight-line Mechanisms Using Flexural Joints

Straight-line compliant mechanisms are important building blocks to design a linear-motion stage,which is very useful in precision applications.However,only a few configurations of straight-line compliant mechanisms are applicable.To construct more kinds of them,an approach to design large-displacement straight-line flexural mechanisms with rotational flexural joints is proposed,which is based on a viewpoint that the straight-line motion is regarded as a compromise of rigid and compliant parasitic motion of a rotational flexural joint.An analytical design method based on the Taylor series expansion is proposed to quickly obtain an approximate solution.To illustrate and verify the proposed method,two kinds of flexural joints,cross-axis hinge and leaf-type isosceles-trapezoidal flexural(LITF)pivot are used to reconstruct straight-line flexural mechanisms.Their performances are obtained by analytic and FEA method respectively.The comparisons of the results show the accuracy of the approach.Both examples show that the proposed approach can convert a large-deflection flexural joint into approximate straight-line mechanism with a high linearity that is higher than 5 000within 5 mm displacement.This can lead to a new way to design,analyze or optimize straight-line flexure mechanisms.