Pseudo-Rigid-Body Modeling For Energy-Storing Foot

Compliant mechanisms is an important field of mechanisms. In recent years,the research on compliant mechanisms is arousing more and more interests and attentions. The pseudo-rigid-body modeling method is simple and effective to compliant mechanisms research. The existing researches of pseudo-rigid body model are mostly focus on the lumped compliant mechanisms and distributed compliant mechanisms with constant cross section and linear material. However, there is little research to curve type, variable cross-section distributed compliant mechanisms. This provides the motivation to develop an efficient method to analysis these new mechanisms. Taking compliant energy-storing foot as an example, this paper investigates the pseudo-rigid-body modeling for distributed compliant mechanisms.Firstly, The paper classifies distributed compliant mechanisms in its geometric configuration, section feature and closed form. Taking S-type energy-storing foot as an example, this paper give the mathematical description of curve type, variable cross-section distributed compliant mechanisms, which has a general significance of the research on distributed compliant mechanisms.Secondly, the definition of pseudo-rigid-segments is provided. The two dividing principles of pseudo-rigid-segments are improved in this paper. The constraint condition of curve segment is provided and the approximation error between pseudo-rigid-segment and compliant mechanism is calculated. The selection method of curve segment coefficient is provided.Thirdly, based on the result of pseudo-rigid-segments dividing, the pseudo-rigid-body model of the S-foot is established. Using the provided calculation method, the influence of various factors, such as dividing method, segment number and torsional spring constant, on the accuracy of pseudo-rigid-body model the analyze. The selection method of torsional constant modified coefficient is provided. Finally, taking the design basis of composite spring plate, the deflection curve equation of compliant energy-storing foot is deduced. The deflection curve equations are also obtained through finite element method and pseudo-rigid body model. The displacement of the joints on the pseudo-rigid body model is calculated. Based on the deflection curves obtained by the three methods, the modeling method is confirmed to be available by analyze the error of the deflection curves and contrast the displacement of the mechanism.