Experimentation of Humanoid Walking Allowing Immediate Modification of Foot Place Based on Analytical Solution

This paper proposes a method of a real-time gait planning for humanoid robots which can change stride immediately at every step. Based on an analytical solution of an inverted pendulum model, the trajectories of the COG (center of gravity) and the ZMP (zero-moment point) are parameterized by polynomials. Since their coefficients can be efficiently computed with given boundary conditions, this framework can provide a real-time walking pattern generator for humanoid robots. To handle the unexpected result caused by immediate changes of foot placement, we made single support periods as an additional trajectory parameter and the ZMP fluctuation was suppressed by mixing the opposite phase of the ZMP error. The effectiveness of our method is shown by experiments of the humanoid robot HRP-2.