Meeting Abstract
Legged animals are often challenged to change gaits to negotiate destabilizing substrates. In our previous study of branch running (Hunt et. al. 2014), we found that the American cockroach (Periplaneta americana) transitioned from an upright to an inverted running gait on smaller diameter rods. The probability of transitioning to an inverted gait increased gradually as an inverse sigmoidal function of rod diameter. To investigate differences in leg coordination between upright and inverted running, we elicited fast escape responses (47.16±11.67cm/s) on an intermediate diameter rod (19.1 mm) where both gaits are employed. We quantified the timing of touchdown and liftoff gait events for all six legs using close-up high speed video. We found that running velocity and duty factor remained comparable across gaits. In addition to similar running performance, we also found no significant difference in the distribution of relative foot touchdown times within the stride. Kinematic data suggests inter-leg coordination changes may be unnecessary to maintain performance on destabilizing substrates, and that an alternating tripod gait is sufficient for both upright and inverted rod running. Examination of tarsal structure contacts during running showed cockroaches used their euplantulae equally often, but used their claws less on inverted compared to upright running. Given the simple control, we are presently exploring the design of a feed forward robot that could traverse branches, pipes and wires.
