Contact Aided Compliant Mechanisms: Concept and Preliminaries

Abstract

Compliant mechanisms (CMs) are the focus of active research because of the scalability, robustness and ease of manufacture endowed by their unitized construction. However, despite significant advances in development of systematic design techniques for these mechanisms, currently CMs are not capable of performing certain kinematic tasks that rigid body mechanisms can readily perform. This paper explores the use of contact interactions to enhance the functionality of CMs and thus widen their scope of application. Unlike CM designs without contact interactions, contact aided compliant mechanisms (CCMs) can be designed to generate non-smooth output port trajectories with a single continuous input. CCMs can also be designed to generate non-smooth force-deflection characteristics within the small deformation bounds imposed by linear elasticity. A wide variety of contact interactions, from the simple case involving a single point contact of a CM with a rigid external body to the more complex case of multiple contacts between different parts of the CM itself, can be used creatively to bridge the gap between the capabilities of CMs and conventional rigid body mechanisms. Several novel CCM designs that demonstrate useful non-smooth output trajectories are fabricated and tested. This paper also explores the use of optimization as a tool for systematic synthesis of CCMs. A simple one dimensional example is used to illustrate the use of topology optimization for systematic synthesis of a CCM for non-smooth force-deflection characteristics.