Bipedal Locomotion Control via CPGs with Coupled Nonlinear Oscillators

Abstract

This paper describes the design and analysis of a biologically inspired central pattern generator (CPG) using a network of mutually coupled nonlinear oscillators to generate rhythmic walking pattern for biped robots. The paper examines the characteristics of a CPG model composed of a network of nonlinear oscillators, and the effect of assigning symmetrical and asymmetrical coupling mechanism among oscillators within the network structure under different possibilities of inhibitions and excitations. The paper highlights the necessity to understand the targeted physical system and its functionalities before concluding the design parameters of the CPG. In addition, the paper considers the way in which the sensory feedback contributes to generate adaptive walking trajectory and enhance gait stability, and how the driving input and external perturbation affect the speed of locomotion and change the period of its own active phase. Modeling of bipedal robot using a CPG based controller and a musculo-skeletal system has been achieved for the purpose to realize the interaction with each other and to study the necessary conditions for stable dynamic walking on dynamic terrain that lead to stable and sustained response from the network. The kinematics and dynamics of a five-link biped robot has been modeled and its joints are actuated through simulation by the proportional torques output from the CPG to generate the trajectories for hip, knee, and ankle joints. The CPG based bipedal locomotion is carried out and evaluated through simulations using MATLAB.