We developed an energy landscape to understand the physical principles of probabilistic locomotor transitions in complex 3D terrain. For a model system of cockroaches traversing beam-like obstacles, using animal experiments and robotic physical modelling, we demonstrated that locomotor transitions of animals and robots on complex 3-D terrain correspond to barrier-crossing transitions on a potential energy landscape. We discovered that locomotor modes are attracted to energy basins on landscape separated by potential energy barriers. Kinetic energy fluctuation from oscillatory self-propulsion helps the system stochastically escape from one basin and reach another to make transitions. We also found that escape is more likely toward lower barrier direction. Our energy landscape approach from first principles helps understand how multipathway transitions across locomotor modes statistically emerge from physical interaction with the complex terrain.
We developed a snake robot with a partitioned gait and snake-like anisotropic friction and used it as a physical model to understand stability principles. The robot traversed steps as high as a third of its body length rapidly and stably. However, on higher steps, it was more likely to fail due to more frequent rolling and flipping over, which was absent in the snake with a compliant body. Adding body compliance reduced the robot’s roll instability by statistically improving surface contact, without reducing speed. Besides advancing understanding of snake locomotion, our robot achieved high traversal speed surpassing most previous snake robots and approaching snakes, while maintaining high traversal probability.
Qihan Xuan, Ratan Othayoth, Chen Li, Qiyuan Fu, Yaqing Wang
Othayoth R, Thoms G, *Li C (2020), Animals and robots transition from more challenging to easier locomotor modes to traverse obstacles, Integrative and Comparative Biology 60Abstract
Xuan Q, *Li C (2020), Template model reveals mechanism of wing and leg coordination during self-righting of a cockroach-inspired robot, Integrative and Comparative Biology 60Abstract
Wang Y, Othayoth R, *Li C (2020), Cockroaches bend head and use legs differentially to traverse grass-like beam obstacles, Integrative and Comparative Biology 60Abstract
Fu Q, Gart SW, Mitchel TW, Kim JS, Chirikjian GS, *Li C (2020), Body lateral deformation and compliance help snakes and snake robots stably traverse large steps, Integrative and Comparative Biology 60 Abstract
We discovered that snakes partition their body to traverse large 3-D terrain like steps. By doing so, their can maintain near-perfect static stability while generating thrusts to overcome drag. This body partitioning strategy is conserved when terrain properties like surface friction and step height changes. We also observed similar partitioning for other types of 3-D terrain. These results suggest that this may be a strategy generally useful for traversing complex 3-D terrain.
Ratan Othayoth was selected for the second time in two consecutive years as a finalist for Best Student Paper Award of Division of Comparative Biomechanics at Society for Integrative & Comparative Biology 2019.
Sean, Ratan, and Rick presented research at Society for Integrative & Comparative Biology (SICB) 2017 Meeting in New Orleans, LA on January 4-8, in the session on Locomotion: Obstacles and Perturbations
Gart SW, *Li C (2017), Dynamic traversal of large gaps and high bumps by cockroaches, Integrative and Comparative Biology 57Abstract
Othayoth R, Xuan Q, *Li C (2017), Leg vibrations help cockroaches self-right using wings, Integrative and Comparative Biology 57Abstract
Han Y, Luo Y, Bi J, *Li C (2017) Body shape affects yaw and pitch motions of insects traversing complex 3-D terrains, Integrative and Comparative Biology 57Abstract
Photo with Prof. Bob Full (Prof. Chen Li’s postdoctoral advisor)