Modeling and Synthesis of Multi-Stable Equilibria Devices

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This research addresses the concept of using multi-stable equilibria (MSE) devices as a type of adaptive system. MSE systems are those that have more than one configuration at which their potential energy is at a minimum such that no power is required to maintain the equilibrium position. As opposed to adaptive structures that use active materials such as piezoelectrics and shape memory alloys, the adaptive states of MSE systems are passive and need only actuation to move among the stable states. Because of this focus on passive and nondissipative aspects of energetic systems, the impact of MSE systems is in improving system performance in terms of operating range, accuracy, reliability, and energy efficiency. The approach of the research is to synthesize MSE systems for specific engineering tasks such as designing devices to have specific stable geometrical configurations and/or natural frequencies at each equilibrium position. Although some analysis has been done on a few bistable structures, the significance of this research is in providing insight into the MSE design process by creating a synthetic, rather than analytic, approach to a more general class of systems. Some areas of application for MSE devices are those in which single operating points limit system efficiency, actuator characteristics inhibit a large range of adaptability, and where the minimization of dissipative effects are important. Fully compliant structures when combined with magnetic actuation lead to smooth nonlinear systems, which are amenable to accurate modeling. They also possess ultra-high precision and repeatability, and long system life due to wear-free operation. Such systems also have several advantages when scaled down to the micro-systems domain. The results of the proposed research should have broad impact on design and analysis of multi-state precision mechanical systems, adaptive transducers, passive human augmentation systems, and adaptive structures.