A unified geometric model for designing elastic pivots

Elastic pivots are commonly used in precision machines and instruments as bearings for guiding small displacements or rotations. They provide accurate and frictionless motion with little hysteresis. Elastic pivots are frequently designed with either straight beams or notches shaped as conic sections with circular, elliptical, parabolic, or hyperbolic profiles. The compliance of a pivot is typically predicted by analytical expressions derived from implicit equations for the pivot’s profile. This article describes a more general geometric model suited to representing the entire family of conic section shapes using quadratic rational Bézier curves. This general representation of the geometry is suitable for computer aided design and analysis, especially with finite element methods that yield compliances and stress distributions. The utility of this formulation is demonstrated by optimizing an elastic pivot to meet compliance and stress requirements.