Coordination between oscillators: An important feature for robust bipedal walking

Biological inspired control approaches based on central pattern generator (CPG) have been used to generate human-like rhythmic locomotion for bipedal robots. CPG consists of several oscillators with coupled mutual inhibition. In the application of CPG to bipedal walking, one of the important problem is how to coordinate oscillators so as to achieve stable walking, since without proper coordination the rhythmic trajectory generated by CPG may fail to control the walking. To solve this problem, this paper presents a method of coordination between two oscillators using phase information. In the method, approximated phase values of the oscillators are derived and used as the feedback to coordinate two oscillators. Furthermore, coordination between multiple oscillators with different frequencies and phases has also been explored. This method is verified with a 2D robust walking controlled by four oscillators. Several walking scenarios are tested: adding external force, change walking frequency and step length during walking. Robust walking is achieved in our simulation.