Extreme High Step Climbing: Nonlinear Analysis of a Highly-Deformable- Tracked Robot

The mobility on rough terrain is a crucial factor in designing rescue robots. Rubbles scattered across disaster site obstruct the robots, which may limit search areas and disturb rapid rescue. To improve mobility in such situations, we proposed a novel mobile mechanism, called mono-wheel track (MW-track), which is an elastic track driven by a single wheel without passive wheels. This mechanism demonstrated high mobility on step-shaped obstacles by using a self-adaptive track. However, the principle underlying this mechanism is still unclear. Herein, we provide a model of track deformation that estimates step-climbing capability, based on large-deformation analysis of the nonlinear beam. The model was evaluated by comparing 1) the curve geometry of the theoretical track with the actual leaf spring and 2) the theoretical value of the climbable height with the actual value measured by step-climbing tests using a mobile robot with the MW-track mechanism. Furthermore, several tests were conducted under various ground friction and track stiffness conditions to investigate their effect on climbable step height. The mechanism for target step height was determined through the model and tests. The model affords a mechanical procedure to determine design parameters for target obstacles.