Preliminary Experiment of Gait Synchronization Control in Human-Supernumerary Robotic Leg System Based on Phase Variables

This paper presents the experimental validation of a novel control strategy that considers the human gait cycle as a continuous periodic process rather than several sequences of discrete events. The current control methodology separates the gait cycle into independent states with corresponding switching rules, which takes time to tune control parameters in different states. While based on the proposed strategy, The entire gait cycle is parameterized by a monotonical signal (i.e., phase variables), which assists the Supernumerary Robotic Leg (SRL) to synchronize with the human wearer's gait cycle without tuning extra parameters. Then, the Discrete Fourier Transformation (DFT) is implemented in the control law to design a virtual constraint that helps to characterize the desired waking speed as a function of phase variables by the virtual constraint. Thus, a Proportional-Derivative (PD) controller is applied in the SRL to achieve the desired waking pattern. Finally, we implemented the proposed control strategy to the custom SRL and conducted preliminary verification experiments.