Hybrid Dual-mode Gait Planning of Wearable Extra Robotic Legs based on Multi-level Inverted Pendulum Model

This paper is written according to the wearable extra robotic legs named Extra Assistant Robotic Legs (EARL). The EARL consists of one upper base and two robotic legs. The upper base is worn through a backpack around the upper body and the robotic legs are distributed around the lower body. In this paper, the research subject is the robotic legs of the EARL. In order to ensure that the human body can have better movements matching under the state of wearing the EARL, and realize efficient, flexible and stable coordinated movements, a planning algorithm of hybrid dual-mode gait includes walking and running for movements of the robotic legs is proposed. The gait planning is an important means and a foundation of the development and design of the robotic legs. The algorithm is set up according to the dynamic model of the EARL. The dynamic model is established by using the multi-level inverted pendulum with the joint deformation when the robotic legs hit the ground. The desired joint trajectories of the EARL are planned by the piecewise function and the gait cycle is determined by an experiment. Ultimately the prototype simulation is set up to verify the tracking performance of the EARL. The proposed validity is ensured by the simulation. The simulation results show the planned trajectories are continuous curves. The angular velocity of joints minus to 0 is to call for an end or to start another cycle. It can ensure the continuity and stability of the EARL. 6 sudden changes of each figure represent 6 selected gait phases. In a word, the robotic legs of the EARL can achieve efficient and stable moving by tracking the planned trajectories. The hybrid dual-mode gait planning algorithm is not only a supplement of the gait planning theory, but the improvement of the cooperative control strategy between the robotic legs and the wearer's legs as well. (Abstract)