A Family of Butterfly Flexural Joints: Q-LITF Pivots

The typical leaf-type isosceles-trapezoidal flexural (LITF) pivot consists of two flexural beams and two rigid-bodies. The single LITF pivot has the small range of motion and relatively large center shift. However, the vacancy in the pivot point makes LITF pivots much easier to be cascaded than other commonly used flexure joints. The performances of LITF pivots will be greatly improved by connecting them together in series. This paper presents an innovative design of LITF pivots. The single LITF pivot is regarded as a basic configurable module, and four of them can be used to construct new types of flexure joint, which are referred to here as quadri-LITF (Q-LITF) pivot. Ten types of Q-LITF pivots are synthesized in this paper. Compared with a single LIFT pivot, the stroke of a Q-LITF pivot is larger, and stiffness of the mechanism becomes smaller. The center-shift of the Q-LIFT pivot can be optimized by tuning geometric parameters of its single LITF modules. Based on the pseudorigid-body (PRB) model of the single LITF pivot, the method for analyzing the Q-LITF pivots is proposed. One type of the Q-LITF pivots is selected as an example to demonstrate the proposed method for the Q-LITF pivot analysis. The comparison between the results of PRB model analysis and the finite element analysis (FEA) shows the feasibility and efficiency of the analysis procedure.