Cockroach-inspired winged robot reveals principles of ground-based dynamic self-righting

Animals and robots alike face challenges of flipping-over as they move in complex terrain. Small insects like cockroaches can rapidly right themselves when upside down, yet small fast-running legged robots are much less capable of ground-based self-righting. Inspired by the discoid cockroach that opens its wings to push against the ground to self-right, we designed actuated wings for robot self-righting based on recently-developed rounded shells for obstacle traversal [1]. We measured the self-righting performance of a robot using these actuated wings, and systematically studied the effects and trade-offs of wing opening magnitude, speed, symmetry, and wing geometry. Our study provided a proof-of-concept that robots can take advantage of an existing body structure (rounded shell) in novel ways (as actuated wings) to serve new locomotor functions, analogous to biological exaptations [2]. Our results demonstrated that the robot self-rights dynamically, with active wing pushing followed by passive falling, and benefits from increasing kinetic energy by pushing faster and longer. Our experiments also showed that opening both wings asymmetrically increases righting probability at low wing opening magnitudes.