A transformable tensegrity-ring footbridge

Tensegrity structures are spatial reticulated structures composed of cables and struts. A tensioncompression equilibrium leads to lightweight systems that change shape through length changes in their members. Active members thus control several degrees of freedom simultaneously. Tensegrityring modules are transformable circuit-pattern modules. The linear combination of tensegrity rings has been shown to be viable for a footbridge application. Shape transformations of a 1⁄4 scale fourring-module tensegrity-footbridge system are studied in this paper. Transformations are obtained employing active continuous cables and springs in the tensegrity system to reduce the number of active elements. Obtaining a desired shape may involve independent actuation in several active elements. Independent actuation steps are found with the combination of a dynamic relaxation algorithm and a stochastic search algorithm.