Displacement-enforced mode transitions in rotary metamorphic flexure bearings

Bearings play a critical role in mechanical and mechatronic systems. Flexure bearings enable high-precision rotational motion, and their wear-free properties have the potential to enable substantially more longevity than conventional bearings. However, flexure bearings are typically only able to operate over a limited range of motion, precluding their use in applications requiring larger displacements. To address this, we previously introduced the metamorphic flexure bearing (MFB), which primarily operates as a flexure bearing but transitions automatically to a conventional bearing to accommodate greater displacement. The transition between bearing modes is enforced mechanically by a retention mechanism, which produces a displacement-dependent resistive force to selectively activate one bearing at a time. Herein, we present a rotary-motion MFB and demonstrate key performance characteristics during quasi-static operation for two types of retention mechanisms (retention-handoff and constant-stiffness). We also investigate the occurrence of a “combined mode”, in which both bearings are simultaneously engaged during dynamic operation, and define the acceleration thresholds that govern this behavior. Our results provide a starting point for design and implementation of rotary MFBs across applications.