Toward development of a biomimetic tensegrity footbridge

Biomimetic structures interact with their environment, change their properties, learn and self-repair, thereby providing properties that are similar to living organisms. Interactions with the environment involve unique challenges in the field of computational control, algorithms, damage tolerance, and structural analysis. Tensegrity structures are pin-jointed structures of cables and struts in a self-stress state. Tensegrity structures are suitable for active control since the shape of the structure can be changed by changing the length of the elements. Consequently, they are good candidates for biomimetic structures. This paper describes research that is moving toward a case study of biomimetic behaviour of a deployable tensegrity footbridge. This footbridge is made of four modules. Each module is composed of pentagonal circuit-pattern including interconnected struts in a ring configuration that can be folded if cable lengths are changed. Various actuator combinations can be selected for deployment. This property is particularly interesting for biomimetic structures since a single shape change can be achieved many ways. Methodologies for deployment and folding of tensegrity footbridge via combinations of spring and cable clustered actuation are described. Analytical predictions are compared with test results of a near-full-scale tensegrity footbridge. Strategies for folding and deployment are different. A continuous cable and spring configuration is feasible for deployment of tensegrity footbridge. Since the deployment behaviour is non-linear and since deformed geometry as well as joint friction influences the deployment pattern, pre-defined control commands cannot provide the desired deployed position. Active deployment control is thus justified.