A precise rotational flexure pivot for airborne equipment

Current joints used for airborne equipment suffer from problems of friction, wear, and thermal gradients. Flexure pivots, on the other hand, achieve their motion by the deflection of their flexible members, so the performance increases and the cost reduces. At present, the cross-spring pivot cannot satisfy the positioning requirements for some ultra-precision airborne equipment. Consequently, the intersection point is generalized to arbitrary position in order to improve the performance. Firstly, considering the mechanical interface, a model for the generalized cross-spring pivot is developed. The relationships between stiffness/accuracy and design parameters are analyzed, and the influence is evaluated of two different length leaves resulting from manufacturing errors on its performance. Therefore, a flexure pivot with constant stiffness or small center shift is obtained. Furthermore, the characteristics revealed by the analysis model are verified by finite element analysis (FEA). Finally, taking the advantage of building block method, a complex flexure pivot with higher precision is proposed. When the rotational angle is up to 15° and a vertical load is applied, the center shift of the complex flexure pivot is less than 3 μm, and its precision is even better than the butterfly pivot, which is extensively utilized abroad.