Models of central pattern generators for quadruped locomotion - II. Secondary gaits

We continue the analysis of the network of symmetrically coupled cells mode ling central pattern generators (CPG) for quadruped locomotion proposed by Golubitshy-Stewart, Buono and Collins by studying secondary gaits. Secondar y gaits are modeled by output signals from the CPG where each cell emits on e of two different output signals along with exact phase shifts. Examples o f secondary gaits are transverse gallop, rotary gallop, and canter. We clas sify secondary gaits that bifurcate when the Poincare map of a primary gait has a real eigenvalue crossing the unit circle. in particular, we show tha t periodic solutions modeling transverse gallop and rotary gallop bifurcate from primary gaits. Moreover, we find gaits from period-doubling bifurcati ons and analyze plausible footfall patterns. Numerical simulations are perf ormed using the Morris-Lecar equations as cell dynamics.