Analysis and evaluation of a near-zero stiffness rotational flexural pivot

Abstract

Compared with conventional rigid joints, flexural pivots store strain energy and therefore increase power requirement, posing some design challenges in several fields. A given flexural pivot can be approximately balanced with other compliant components such as springs, but inappropriate parameters and installing positions may lead to a high remaining stiffness induced by external forces. The objective of this paper is to analyze a near-zero stiffness rotational flexural pivot (NZSRFP) via balancing a generalized cross-spring pivot and to evaluate the effect of forces so as to offer useful qualitative and quantitative design insights. Taking advantage of the law of conservation of energy, a mathematical model is developed to determine the stiffness of balancing springs, and thus three special cases are presented to simplify physical models. Meanwhile, the stiffness relation between flexural pivot and balancing springs is analyzed, and the force is evaluated to attenuate its effect on the resulting stiffness. Finally, the analytical model is verified by finite element analysis (FEA) and experiments. Compared with unbalanced flexural pivot, the NZSRFP allows the rotational stiffness to be reduced to 0.55% by appropriately selecting design parameters.