Weak DC Motors Generate Earthworm Locomotion Without a Brain

In this paper, we develop an extremely simple earthworm-like robot as a minimal model of the wave generation principle of earthworms. The major contribution of this work is to show that autonomous and distributed peristaltic wave generation is possible without a sensor, controller, or microprocessor. The key idea behind this brainless robot is to exploit the passivity intrinsic to the low-torque DC motor in each linear joint as a control law of a rhythmic oscillator. To reproduce an earthworm-like body structure that allows body contraction and expansion, the proposed robot is composed of multiple body segments that are mutually connected by linear joints. Inflation of the body segment was reproduced by a flexible plate that connects two adjacent segments. The experiments show that the brainless robot generates peristaltic locomotion similar to that of real earthworms.