On-line trajectory generation for a humanoid robot based on combination of off-line patterns

When a humanoid robot moves in an actual working environment, it is necessary for the robot to generate appropriate locomotion trajectory in real-time to ensure its stability. But it is difficult to solve nonlinear differential equations of stability constraints in real-time to get stable locomotion trajectory. This paper proposed a method to generate stable and smooth locomotion trajectory through linking basic off-line patterns together considering stability constraints. These basic locomotion patterns include forward walk, turn-about, standstill, mark time, etc. In order to move and adapt to different route circumstance, the robot makes a selection of one basic pattern which can be link with the current locomotion pattern according to stability constraints and route requirements. We adopt spline interpolation to link current pattern and newly selected pattern for generating smooth trajectory. The effectiveness of the proposed method was confirmed by experiments on our newly developed humanoid robot.