A Practical Method for Determining the Pseudo-rigid-body Parameters of Spatial Compliant Mechanisms via CAE Tools

Compliant Mechanisms (CMs) are employed in several applications requiring high precision and reduced number of parts. For a given topology, CM analysis and synthesis may be developed resorting to the Pseudo-Rigid Body (PRB) approximation, where flexible members are modelled via a series of spring-loaded revolute joints, thus reducing computational costs during CM simulation. Owing to these considerations, this paper reports about a practical method to determine accurate PRB models of CMs comprising out-of-plane displacements and distributed compliance. The method leverages on the optimization capabilities of modern CAE tools, which provide built-in functions for modelling the motion of flexible members. After the validation of the method on an elementary case study, an industrial CM consisting of a crank mechanism connected to a fully-compliant four-bar linkage is considered. The resulting PRB model, which comprises four spherical joints with generalized springs mounted in parallel, shows performance comparable with the deformable system.