Gait generation and transition for bipedal locomotion system using Morris-Lecar model of central pattern generator

Abstract

In this paper, we intend to improve the CPG network presented by Pinto et al. based on 4-cell model for bipedal locomotion systems. This model is composed of four coupled identical cells and internal dynamics of each one is described by the Morris-Lecar nonlinear differential equation; also, the couplings between the cells follow the synaptic type. We exploited an elitist Non-dominated Sorting Genetic Algorithm (NSGA II) to find the best set of coupling weights by which the phase differences became optimally close to the ones required for a primary bipedal gait. Thus, we achieved the rhythmic signals associated with four primary bipedal gaits of walk, run, two-legged jump, and two-legged hop. Also, we successfully obtained all secondary gaits corresponding to the bipedal locomotion identified by Pinto et al. from the 4-cell model by symmetry breaking bifurcations of primary gaits. Particularly, we were able to produce the secondary gait, called "hesitation walk," through transition from primary gaits of run and two-legged jump.