Abstract: Owing to excellent performances such as large movement range and high precision, the generalized triple-cross-spring flexure pivots (GTCSFP) can be widely used in precision instruments. Based on the strain energy formulation of a beam flexure, a rotational stiffness model of GTCSFP is derived, and the applicable scope and error estimation method are given. In the process of establishing the simplified model, zero axis drift is assumed and trigonometric functions are approximately treated. The following conclusions can be drawn. When the intersection point locates at 12.73% length of the spring ,the moment-rotation relationship of GTCSFP is linear. Bending moment and tangential force are the driving loads, while the radial force affects the rotational stiffness of GTCSFP. In the applicable scope, the rotational stiffness model is accurate. The accuracy of the analytical model is verified by finite element analysis and the rotational stiffness test of GTCSFP. The model has guiding significance and reference value to the design and optimization of GTCSFP.

Key words: flexure bearing, flexure pivots, large stroke, stiffness model, triple cross-spring