Session: 16-01-01: Poster Session: NSF-Funded Research (Grad & Undergrad)

Paper Number: 99764

99764 - The Effect of Kinematics on the Design of Continuous Equilibrium Structures 

Reconfigurable structures are systems with components that move along a prescribed kinematic path, such as robotic arms, adaptable building facades, micro-grippers, and retractable roofs. A fundamental challenge in designing reconfigurable structures is actuating them efficiently while preserving stiffness and stability. In many designs, a large input of energy is required for actuation, resulting in inefficient, over-designed, and costly structures. Continuous equilibrium systems are a subset of reconfigurable structures with a kinematic mode that allows them to reconfigure with a negligible input of energy; they are characterized by a flat potential energy curve. Advantages of systems with continuous equilibrium include low energy required for actuation and an inherently stable reconfiguration path. Incorporating continuous equilibrium design principles can lead to more viable reconfigurable structures, especially for large structures where the effect of gravity is significant. 

Under gravity, most reconfigurable structures do not have continuous equilibrium with a constant potential energy curve; rather, the potential energy due to gravity changes as the structure moves through its kinematic path. There is currently no comprehensive framework to transform structures into systems with continuous equilibrium while considering gravity. Additionally, previous studies only consider structures at one static orientation. In many applications such as robotics, functionality needs to be preserved as the structure reorients, or rotates in space.

Our work presents a design framework that transforms reconfigurable structures into systems with continuous equilibrium. We use optimization to find the properties of springs that, when added to a structure, minimize the fluctuation of potential energy along the kinematic path. The framework can account for a structure at multiple orientations and computes spring properties that will maintain continuous equilibrium as the structure rotates. In this poster, we explore how the kinematics of a structure affect which spring types are most effective at attaining continuous equilibrium. We consider torsional springs, extensional springs, internal springs (which are fully attached to the structure) and external springs (which are attached to the structure on one end and anchored to an external support on the other). To explore the effect of kinematics, we compare three linkages that have been optimized to have continuous equilibrium: the Watt’s linkage, a Scissor Mechanism, and a Double Rocker linkage. Each structure has unique features that result in different springs being most effective. For example, the symmetry in the kinematics of the Scissor Mechanism leads to internal springs being less effective than external springs, especially when optimizing for multiple orientations. In addition to the types of springs, we also explore which spring locations are the most critical for minimizing the fluctuation in potential energy for each system.

This work offers insight into which spring types and locations are most effective at transforming a reconfigurable structure into a system with continuous equilibrium. This is useful because while our computational methods represent an ideal model of a continuous equilibrium structure, real-world designs will have constraints such as cost, time to build, and availability of materials that will limit the types of springs that can be used, their locations, and their properties. Knowing which springs are going to reduce the fluctuation in the potential energy curve the most will be critical for the practical application of this optimization framework.

Presenting Author: Maria Redoutey University of Michigan

Presenting Author Biography: Maria Redoutey is a PhD Candidate in Civil Engineering at the University of Michigan. She is a member of the Deployable and Reconfigurable Structures Lab (DRSL) led by Prof. Evgueni Filipov. A fundamental challenge for reconfigurable structures, especially for large-scale applications, is their actuation. Maria’s research responds to this challenge through the creation of computational models and optimization tools for the design of reconfigurable structures with safe, stable, and efficient deployment paths.

Authors:

Maria Redoutey University of Michigan
Evgueni Filipov University of Michigan