Force sensing facilitates traversal in cluttered beams with interaction

Robots often struggle in traversing cluttered obstacles, while animals are good at it. For example, the discoid cockroach can traverse cluttered grass-like beams with physical interaction in various ways (Othayoth, Thoms, Li, 2020, PNAS). The animal pushes across flimsy beams, but it usually rolls its body to traverse stiff beams, which overcomes a lower potential energy barrier. To make this transition, besides using kinetic energy fluctuation from self-propulsion, the animal also adjusts its head, abdomen, and legs (Wang, Othayoth, Li, 2021, J. Exp. Biol., in review). This suggests that the animal can sense resistive forces and actively switch to the less costly roll mode. To test this hypothesis, we developed a physics model of a robot capable of environmental force sensing propelled forward to traverse beams. The stiffness of beams was accurately estimated from the noisy sensed force using the model, with higher accuracy for smaller noise. Then, the model predicted contact forces and mechanical energetic cost to plan and control the simulation robot to traverse beams with a lower cost. The simulation robot pushed cross flimsy beams and rolled through stiff beams just like cockroaches do. At last, we demonstrated this sensing and estimation in a robotic physical model.