The nonlinear characteristics of large deflection multi-section flexure-based compliant mechanisms

As compact deformable structures, flexure-based compliant mechanisms (FCMs) can be used in multibody systems to eliminate the uncertain tribological effects associated with traditional revolute joints. This is due to their simple monolithic structure, leading to predictable behaviour. However, large deformation FCM deformation is difficult to predict accurately due to nonlinear characteristics. This paper focuses on the assessment of five nonlinear multi-section FCM designs and the prediction of their deflected shape. The FCM designs have increasing complexity; a single-section FCM, two double-section FCMs and two triple-section FCMs. For each design, a mathematical representation is derived, based on large deflection Euler-Bernoulli theory, which is then combined with a multi-step optimisation scheme. Predictions of the FCM deformed shape under loading are compared to experimental results achieved using corresponding prototypes constructed from spring steel sections. The resulting FCM deformed structures were measured using a laser scanner, showing that the predictions give an excellent representation of the deflected shapes. The potential is, therefore, to predict the response of FCMs with guaranteed accuracy for precise system design.