Deployment of a Tensegrity Footbridge

Abstract

Deployable structures are structures that transform their shape from a compact state to an extended in-service position. Structures composed of tension elements that surround compression elements in equilibrium are called tensegrity structures. Tensegrities are good candidates for deployable structures since shape transformations occur by changing lengths of elements at low energy costs. Although the tensegrity concept was first introduced in 1948, few full-scale tensegrity-based structures have been built. Previous work has demonstrated that a tensegrity-ring topology is potentially a viable system for a deployable footbridge. This paper describes a study of a near-full-scale deployable tensegrity footbridge. The study has been carried out both numerically and experimentally. The deployment of two modules (one half of the footbridge) is achieved through changing the length of five active cables. Deployment is aided by energy stored in low stiffness spring elements. Self-weight significantly influences deployment, and deployment is not reproducible using the same sequence of cable-length changes. Active control is thus required for accurate positioning of front nodes in order to complete deployment through joining both sides at center span. Additionally, testing and numerical analyses have revealed that the deployment behavior of the structure is non-linear with respect to cable-length changes. Finally, modelling the behavior of the structure cannot be done accurately using friction-free and dimensionless joints. Similar deployable tensegrity structures of class two and higher are expected to require simulation models that include joint dimensions for accurate prediction of nodal positions.

Synthesis of minimum energy adaptive structures

“…Applications of this concept have been suggested for space cranes, scaffolding and large structural rings for antennas (Miura and Furuya 1988;Campanile 2003;Subramaniam and Kramer 1992). Active tensegrity structures, structures whose stability depends on self-stress, have been used for deployable systems (Tibert 2002) as well as for control of displacements (Fest et al 2003;Veuve and Smith 2015) and of the structure fundamental frequency (Santos and Micheletti 2015;Bel Hadj Ali and Smith 2010). Active compliant structures, which can be thought of as structures working as monolithic mechanisms (Hasse and Campanile 2009) have been investigated for shape control of antenna reflectors (Jenkins 2005), for shape morphing of aircraft wings to improve on manoeuvrability (Previtali and Ermanni 2012;Kota et al 2003) as well as for the control of direct daylight in buildings (Lienhard et al 2011).…”

Dialectic Form Finding of Structurally Integrated Adaptive Structures

“…Elements are combined in a self-equilibrated pre-stressed state that provides stability and stiffness to the structure. The tensegrity concept exists for almost 60 years now and has received significant interest from scientists and engineers (Munghan and Abel, 2011;Rhode-Barbarigos et al, 2012a;Ingber et al, 2014;Kim et al, 2014) especially for adaptive/shape-changing applications as actuators and structural elements can be combined (structurally integrated actuation) (Adam and Smith, 2008;Veuve et al, 2015). Tensegrity structures have been traditionally developed and analyzed using formfinding methods in which bilateral rigidity elements are modeled as truss elements (elements experiencing tension or compression).…”

Control‐oriented modeling and deployment of tensegrity–membrane systems

“…A comprehensive survey of works in this area can be found in [15]. More recent contributions include the deployment of a tensegrity-ring module [56] and the deployment of a tensegrity footbridge [57]. Also very recently Sultan [50] presented a deployment strategy based on infinitesimal mechanisms for tensegrity systems and accurate path tracking was achieved by implementing a robust nonlinear feedback controller.Control design, including deployment control, for tensegrity-membrane systems is a much more difficult task than that for tensegrity systems.…”