Stiffness and Stress Analysis of a Class of Bridge-Type Direct CouplingCompliant Mechanism

Accurate stiffness and stress models of a class of bridge-type direct coupling compliant mechanism have been studied.First,the analytical stiffness equations for this compliant mechanism were formulated based on pseudo-rigid-body model and Castigliano's displacement theorem.Then,the effect of parasitic stiffness equations and the accuracy of rotational stiffness equations of flexure hinges on the overall analytical stiffness equations were comprehensively studied by the orthographic experimental method based on the comparison between the two analytical stiffness equations and the finite element analysis(FEA) results with the design parameters arranged.The results show that parasitic stiffness equations have less than 3% influence with the error,while accuracy of rotation stiffness equations has great effect and thus the accurate stiffness model can be obtained with the choice of the most accurate rotation stiffness equations.Compared with FEA results,the error of the derived stiffness model is less than 8% for t/r0.65.Finally,an experimental configuration was used to verify the overall stiffness equations and the errors compared with experimental and FEA results are 4% and 3.96% respectively.In addition,the analytical stress equations for this compliant mechanism were formulated based on the overall stiffness equations and the error compared with FEA results is less than 4%,which verifies their accuracy.