64-1 Saturday, Jan. 5 13:30 - 13:45 In silico experiments reveal the importance of randomness of motions in cockroach’s winged self-righting XUAN, Q*; OTHAYOTH, R; LI, C; Johns Hopkins University email@example.com http://li.me.jhu.edu
Terrestrial animals must self-right when overturned to survive. The discoid cockroach Blaberus discoidalis can dynamically self-right by opening its wings to push against the ground while flailing its legs to induce body vibration. Interestingly, although wing and leg motions are oscillatory, they both have a substantial degree of randomness. Here, we test the hypothesis that randomness in these motions is useful for self-righting. We developed a multi-body dynamics simulation of a cockroach-inspired self-righting robot, with simplified body morphology and controlled, modifiable motions. The robot repeatedly opened and closed its wings and oscillated an appendage mimicking flailing legs to induce body vibration. We first validated the simulation against robot experiments and then used it to perform experiments in silico to study the effect of randomness. With strictly periotic wing and appendage oscillations (no randomness), the robot self-righted at a modest probability (62 ± 11 %) within 5.0 ± 0.8 seconds. After randomness was introduced, however, the robot almost always self-righted (99 ± 4 %) within 3.6 ± 0.7 seconds. By systematic parameter variation, we discovered that an appropriate phase offset between wing and appendage oscillations when the body pitched up was critical to self-righting. Strictly periotic wing and appendage oscillations limited the coupled oscillator system to visit only a small number of phase offsets, often causing it to be trapped near failure limit cycles. Added randomness in wing and appendage oscillations allowed the system to explore a diversity of phase offsets, increasing its probability to escape failure limit cycles and self-right. Our study reveals the importance of coordination between body parts and the usefulness of randomness of motions in self-righting.