Introducing a nonlinear coupling for central pattern generator: Improvement on robustness by expanding basin of attraction and performance by decreasing the transient time

Abstract

Different types of models have been introduced for central pattern generators mostly based on coupled nonlinear oscillators. One of the most important responsibilities of a central pattern generators is to make an acceptable phase for each limb to make a stable motion. In nonlinear oscillators, the phase difference is made by means of commensurate coupling between them. Linear coupling between oscillators has been widely used in the literature. It is used to make a suitable phase difference between oscillators appropriate to the kind of motion (e.g. walking and running). In this research, it is shown that there are some coexisting attractors in the same coupling, in which phases between oscillators are not ideal to generate rhythms of motion. Consequently, there will be some undesired oscillator states, in which their functionality is significantly decreased. In this article, a novel nonlinear coupling is introduced as a solution for this problem to have a more robust central pattern generators by tackling inappropriate attractors and expanding the basin of attraction of the suitable attractor. In addition, this nonlinear coupling for central pattern generators cues arrived their steady state 2.8 times faster than central pattern generators with linear ones.