Dynamics of Tensegrity Robots With Negative Stiffness Elements

Abstract

Tensegrity structures have unique features such as low mass to payload ratio, strength, and robustness. Therefore, they present great potential in robotics, aerospace, and civil engineering. The dynamics of tensegrity robots is highly nonlinear and constrained. As a result, their modeling, simulation, state estimation, and control are non-trivial. Strings in tensegrity structures are usually modeled as linear springs. Utilization of nonlinear elastic/damping elements in tensegrities would further enrich their dynamics and endow them with additional properties, such as multiple equilibrium configurations. In this paper, our preliminary work on the dynamics of actuated tensegrities with strings containing nonlinear elastic and/or damping elements is presented. At first, the formulation of tensegrity dynamics with general nonlinear elastic/damping elements is explored. Later dynamics of tensegrities with negative stiffness honeycombs incorporated into strings are considered. Simulations are performed on three tensegrity systems: two-bar, three-bar, and six-bar structures. Results demonstrate that negative stiffness honeycombs result in nonlinear steady-state response to constant external force, reduced force magnitudes in strings and bars, and increased range of motion.INDEX TERMS negative stiffness beam, nonlinear stiffness element, nonlinear damping element, tensegrity, tensegrity dynamics with negative stiffness honeycomb.

Elastostatic Modeling of Multi-Link Flexible Manipulator Based on Two-Dimensional Dual-Triangle Tensegrity Mechanism

“…Many research groups dealing with designing an appropriate model and control [23,24], using deep reinforcement learning [25,26], model predictive control [27], and convex optimization [28]. Some researchers design models with negative stiffness components [29]; that idea is a promising approach for system property optimization. Another attractive property of tensegrity structures is the presence of multiple equilibria and the ability to switch between them in order to reach higher power capabilities [30].…”