Trajectory planning for smooth transition of a biped robot

This paper presents a third-order spline interpolation based trajectory planning method which is aiming to achieve smooth biped swing leg trajectory by reducing the instant velocity change which occurs at the time of collision of the biped swing leg with the ground. We first characterize the bipedal walking cycle and point out some major issues that need to be addressed to plan a continuous swing leg trajectory by using the concept of the spline interpolation and zero moment points (ZMP). We demonstrate that the impact effects can be avoided at the time of the swing foot's heel touching with the ground. The proposed biped trajectory planning method has been tested on our soccer-playing humanoid robot, Robo-Erectus, which got Second Place at the 2002 RoboCup Humanoid Walk competition.