Control of underactuated undulatory locomotor exploiting anti-resonance: A case study

Rhythmic movements in animal locomotion appear to exploit a resonance of the body-environment dynamics to maintain high efficiency. To gain insights into the locomotion mechanism, this paper studies a simple three-link undulatory locomotor model that swims through a single joint torque actuator. We have found that, when the locomotor is driven by a sinusoidal input of a given amplitude, the resulting locomotion speed is maximum when the driving frequency is close to the anti-resonance of the link chain. We then show how the anti-resonance can be exploited in the feedback control based on central pattern generators.