Multi-objective optimisation of deployable bistable scissor structures

Abstract

Lightweight bistable deployable structures can be designed to be transportable and reusable. They instantaneously achieve some structural stability when transformed from the compact to the deployed state through a controlled snap-through, as a result of intended geometric incompatibilities between the beams. Due to their transformable bistable nature their design requires assessing both their non-linear transformation behaviour, as well as their service state in the deployed configuration. The requirement of a low peak force during transformation can be shown to oppose the high stiffness requirement in the deployed state; their design can therefore be formulated as a multi-objective non-linear optimisation problem. In this contribution, a size and shape optimisation method is elaborated by choosing the best material combinations, the optimal geometry of the structure and beam cross-sections. The originality of this contribution is the use of a multi-objective evolutionary algorithm to structurally optimise bistable scissor structures taking into account the deployed state as well as the transformation phase. First, the method is applied to optimise a single bistable scissor module. Next, a multi-module bistable scissor structure is optimised and the single module and full structure based approaches are critically compared.