A Versatile Design Framework for Stable Reconfigurable Structures with Efficient Actuation
Maria Redoutey · Deep Blue (University of Michigan) · 2023
Structures that move, deploy, and reconfigure offer many advantages, such as advanced functionality, the ability to stow and transport, and adaptability. Despite these advantages, traditional civil engineering structures such as bridges, shelters, and domes are not typically designed to reconfigure, due to several challenges that arise when designing at a civil engineering scale. These challenges include that the effect of gravity can hinder the actuation of a reconfigurable structure, the inherent flexibility of structures with multiple degrees of freedom (DOFs), and the difficulty of ensuring stability and stiffness in the final deployed state. This dissertation explores the design of reconfigurable structures to address these challenges and make the structures feasible for use at a civil engineering scale. First, an open-source design framework for reconfigurable structures that are stable under gravity at any global orientation is established. Optimization is used to design springs that offset the potential energy due to gravity and transform reconfigurable structures into systems with textit{continuous equilibrium}. One set of springs can be designed to maintain continuous equilibrium, even when the structure is reoriented with respect to a global reference frame. Next, the design framework is extended to systems with more than one DOF. The spring properties are computed such that the multi-DOF system follows a specific motion path while remaining globally stable and in continuous equilibrium. Next, the practical implementation of continuous equilibrium structures in real-world applications is discussed. Mechanical models and physical prototypes are used to investigate the behavior of continuous equilibrium structures, and a reduction in actuation forces is observed when springs are used to counteract gravity. Finally, a novel dome-like reconfigurable structure is introduced. Despite having multiple DOFs, this structure has a unique infinitesimal mechanism which allows it to deform into a dome-like shape with high out-of-plane stiffness. The optimization framework is used to design the dome-like structure to have continuous equilibrium, making it stable under gravity and reducing the forces needed for deployment. This dissertation presents methods for designing reconfigurable structures to have lower actuation forces, inherent stability, and robust stiffness. These methods are of importance in scenarios where gravity cannot be neglected, and in particular to the realization of large deployable and reconfigurable structures at the civil engineering scale.