Modeling the critical drop height of tensegrity robots

Mobile tensegrity robots are an attractive technology for the next generation of adaptive, multi-terrain robots due to their light weight, versatility, and impact resistance. However, few researchers characterize the impact resistance of their tensegrity robots, and predicting the maximum height from which a given tensegrity robot can survive a drop remains a complex challenge. This critical drop height can be determined experimentally, but that strategy requires producing, dropping, and breaking many tensegrity robots, costing time and resources. In this paper, we present a method for predicting the critical drop height of a tensegrity robot using finite element analysis (FEA). First, we experimentally measure the material properties for the robot’s components. Next, we perform preliminary drop tests from low heights to determine general parameters for the simulation without breaking the robot. Finally, we simulate drops from different heights to enable the prediction of the critical drop height: the lowest drop height where the critical stress is exceeded in one of the components. The simulation is used to predict the critical drop height of a 3-bar tensegrity robot in three different orientations. Drop experiments confirm the simulation’s predictions, as plastic deformation is observed after drops exceeding the critical drop height. We further demonstrate the model’s utility by using it to make a design change to the 3-bar tensegrity robot; the model predicts that changing the material of the tensegrity’s rods from aluminum to titanium increases the critical drop height from 0.5 m to 1.5 m, and experiments confirm this increased impact resilience. The modeling strategy presented in this study paves the way for improved tensegrity robot designs with enhanced impact resistance.