Biologically Inspired Adaptive Dynamic Walking of a Quadruped on Irregular Terrain-Proposal of the Design of Coupled Neuro-Mechanical System and Evaluation of the Mutual Entrainment among Pitching Motion, CPG and Rolling Motion-

Abstract

We have been trying to induce a quadruped robot to walk with medium walking speed on irregular terrain based on biological concepts. In this paper, we define adaptive walking based on biological concepts as “coupled-dynamics-based motion generation”, in which a neural system and a mechanical system are coupled and generate motion by interacting with the environment emergently and adaptively. We design the mechanical system and the neural system consisting of a central pattern generator (CPG), responses and reflexes. A CPG receives sensory input and changes the period of its own active phase as responses. Especially, we propose that the rolling motion should be input to CPGs in order to synchronize the pitching and rolling motions. PD-controller at joints as the stretch reflex constructs the virtual spring-damper system as the visco-elasticity model of a muscle. The desired angle and P-gain of each joint in the virtual spring-damper system is switched based on the phase signal of the CPG. CPGs, the motion of the virtual spring-damper system of each leg and the rolling motion of the body are mutually entrained through the rolling motion feedback to CPGs, and can generate adaptive walking on irregular terrain. The mutually entrained system closely couples the representative indices such as walking speed, gaits, stability and energy consumption . We report our experimental results of dynamic walking on terrains of medium degrees of irregularity in order to verify the effectiveness of the designed neuro-mechanical system.