[Show abstract][Hide abstract] ABSTRACT: The complexity of nonlinear differential equations of dynamics makes it practically impossible to obtain the walk pattern on-line through computing the whole dynamics. This paper proposed a method of online trajectory generation based on key parameters of off-line typical walk patterns for a biped humanoid. The key parameters include hip parameters, step length, walking cycle and so on. The walking pattern can be obtained according to these parameters. In order to generate walking patterns online, first the key parameters of the on-line walking pattern are computed based on the parameters of off-line typical patterns, then stability optimization has been done on-line and on-line trajectories are derived. The effectiveness of the proposed method is confirmed by simulations and experiments with our developed humanoid robot with 33 DOF.