Online whole-stage gait planning method for biped robots based on improved Variable Spring-Loaded Inverted Pendulum with Finite-sized Foot (VSLIP-FF) model.

Environmental adaptability and real-time control are significant to the actual application of biped robots. The current Spring-Loaded Inverted Pendulum (SLIP) walking exhibits the compliant interaction with environments. However, the movability and controllability of this model is limited owing to the lack of ankles. Moreover, complicated nonlinear optimization problems in gait generation bring difficulties to real-time control. To overcome these problems, this study proposes an online whole-stage gait planning method to enhance the bipedal walking performance. Firstly, considering the role of ankles, this study applies the proposed template model called Variable Spring-Loaded Inverted Pendulum with Finite-sized Foot (VSLIP-FF) model. Then a Finite State Machine (FSM)-based gait pattern including the corresponding bio-inspired gait strategies is established, which extends the single cyclic gait to the whole-stage gait. Secondly, to realize real-time gait planning, an online gait generator based on a neural network is applied to reduce the calculational burden. Finally, the method is applied on the simulation prototype and real robot platform for verification. Experimental results validate that the proposed method can achieve an autonomous gait with the online planning time of 0.01s, and the step length range is expanded by 37.52% compared with the traditional SLIP model.