A deployable tensegrity footbridge that connects at mid-span

This paper describes a near full-scale deployable tensegrity footbridge that deploys from both sides and connects at mid-span. Tensegrity structures are pre-stressed structures composed of tension elements (cables) surrounded by compression elements (struts) in equilibrium. The deployment of each bridge half is control by five active continuous cables and is assisted by the release of energy in spring elements that are longer when the bridge is folded. Two topologies (uniform and symmetric) that differ in terms of symmetry of elements are compared with respect to serviceability performance and deployed shape prior to mid-span connection. While both topologies have similar performance, the deployed shape of the symmetric topology results in much smaller pre-control distances between mid-span nodes than the uniform topology. This paper presents a two-stage control methodology for determining control commands for mid-span connection of the two bridge halves. The control methodology determines active cable-length changes based on computational control using a simplified analytical model and then, through measurement of the structural response to cable-length changes. Both halves are successfully connected at the end of deployment. Active control strategies provide effective solutions for completing deployment of multi-degree-of-freedom structures.