Meeting Abstract

98-4  Saturday, Jan. 7 14:15 - 14:30  Leg vibrations help cockroaches self-right using wings OTHAYOTH, RS*; XUAN, QH; LI, C; Johns Hopkins University ratan@jhu.edu http://li.me.jhu.edu/

When flipped over, cockroaches can use their wings to push against the ground to self-right dynamically. In this process, it often takes an animal multiple failed maneuvers before it eventually rights. However, it is not clear what governs this seemingly random locomotor transition. Here, we hypothesize that vibrations induced by leg flailing help achieve successful righting. To test this hypothesis, we directly modified leg vibrations in the discoid cockroach (Blaberus discoidalis) by attaching weights (1.5 times leg mass) to hind legs and challenged the animal to self-right on a flat, rigid surface. We discovered that an increase in leg vibrations increased righting probability from 45 ± 8 % (N = 30 animals, n = 150 trials) to 75 ± 7 % (N = 30, n = 150) (P < 0.0001, repeated-measures ANOVA) and reduced righting time from 4.0 ± 3.5 s to 2.8 ± 2.8 s (P = 0.0049). Upon removal of added leg mass (N = 30, n = 150), righting probability and righting time recovered to 28 ± 7 % and 4.4 ± 3.5 s. To further confirm our hypothesis, we created and tested a cockroach-inspired winged self-righting robot with continuously variable vibrations, and made similar observations over a broad range of wing opening magnitudes. To begin to understand our observations, we developed a locomotion energy landscape model, and found that the energy fluctuations due to vibrations were comparable to the potential energy barriers required to transition from a metastable overturned orientation to an upright orientation. Our study supports the plausibility of locomotion energy landscapes for understanding locomotor transitions, and highlights the need for further stochastic modeling to capture the uncertain nature of when maneuvers result in successful righting. Our study also provides inspirations for legged robots to co-opt leg oscillations to assist locomotor transitions.