On The 2R Pseudo-Rigid-Body Model Of Compliant Mechanisms

The compliant mechanism is a kind of new type mechanism that uses the elastic deformation of component itself to accomplish the transmission of motion and force. Compared with conventional rigid-body mechanisms, compliant mechanisms have many advantages in cost-reduction and performance-improvement such as part-count reduction, reduced assembly time, simplified manufacturing processes, reduced friction, wear and noise. Therefore, compliant mechanisms attract many scholars and become a worldwide advanced topic.In the study of compliant mechanisms, compliant links often under large deflections which introduce geometry nonlinearities make the analysis of compliant mechanisms much too complex. Therefore, an appropriate model lays the foundation for the research of compliant mechanisms. The classic Pseudo-Rigid-Body Model (PRBM) can simulate the tip locus of compliant link accurately in a certain extent, but can not simulate the tip deflection angle of the flexible link. Focused on the deficiency of the PRBMs existed, a new two DOF (Degree Of Freedom) PRBM is proposed in this study. Some researches in the modeling of PRBM, the optimization of model parameters and the characteristic analysis of PRBM are carried out as follows.In the modeling of PRBM, classic PRBM is a single DOF system included two rigid links and one torsional spring which can be called 1R PRBM. A two DOF PRBM included three rigid links and two torsional springs, i.e. 2R PRBM is proposed in this study. The kinematic equations of 2R PRBM are also deduced. Compared with 1R PRBM and 3R PRBM, the new 2R PRBM indicates its superiority over simulating the tip character of compliant links.In the optimization of model parameters, a new parametric approximation method based on simulating the tip locus and tip deflection angle of the compliant link simultaneously is proposed. With this optimization technique, the optimal characteristic radius factors of the 2R PRBM is obtained for the two different external loads (force and moment). A linear regression for the spring stiffness coefficient of the 2R PRBM is presented. For the combination of external force and moment lord, the parameters of 2R PRBM for the complex loads is obtained by limiting the spring stiffness coefficient.In the characteristic of PRBM, the expression of strain energy of compliant link and that of PRBMs with different DOF under three kinds of loads are derived. The ability of strain energy storage of PRBM is investigated through a comparison study in strain energy among PRBMs with different DOF. Some conclusions are drawn which may be useful to the dynamics of compliant mechanisms.