Abstract: Compliant mechanism is a kind of new type mechanism and its analysis is very complex because compliant links often under large deflections which introduce geometry nonlinearities. Pseudo-rigid-body model (PRBM) can simplify large- deflection analysis of compliant links. Based on PRBM, a 2R model is proposed for the compliant mechanisms with compliant links and a parametric approximation is made to the deflection angle of a compliant link. This model comprises three rigid links of different length which are connected by two torsional springs of different stiffness coefficient. The characteristic radius factor is used to indicate the length of the rigid links and the stiffness coefficient is used to indicate the torsion capability of torsion springs. A two-dimensional optimization for the optimal characteristic radius factors and a linear regression for the spring stiffness coefficient are presented. This model can simulate accurately both the deflection path and angle of the compliant link. Finally, the expression of strain energy of compliant link and that of PRBMs are derived. The ability of strain energy storage of PRBM is investigated through a comparison study in strain energy among PRBMs.

Key words: Compliant mechanism, Parametric approximation, Pseudo-rigid-body model, Strain energy