Wing opening and leg flailing together facilitates strenuous self-righting on the ground

Self-righting when flipped over on the ground is strenuous for many terrestrial animals and robots. During self-righting, the discoid cockroach repeatedly opened and pushed its wings against the ground to attempt a somersault but rarely succeeded; instead, it often eventually rolled to the side to self-right. Its legs flailed in this process. Here, we studied whether simultaneous wing opening and leg flailing is beneficial. We developed a robot with two wings and a leg to emulate the animal’s strenuous self-righting. As wing opening and leg flailing amplitudes increased, self-righting probability increased. A potential energy landscape model to measure the potential energy barriers to self-right revealed the mechanism. Without leg flailing, the pitch kinetic energy from pushing wings was too small to overcome the high barrier to somersault. Without wing opening, the rolling kinetic energy fluctuation from the flailing leg was too small to overcome the low barrier to roll. However, when used together, wing opening reduced the roll barrier and enabled probabilistic crossing of the reduced roll barriers using kinetic energy fluctuation from leg flailing. Our study showed that animals and robots can modify their potential energy landscapes to better elicit locomotor transitions.