Straight-Line Contouring Control of Fully Actuated 3-D Bipedal Robotic Walking

Satisfactory tracking of a planned path on the walking surface is an important requirement for bipedal robotic walking in many applications. In this paper, a model-based feedback control strategy is proposed for fully actuated three-dimensional (3-D) bipedal robots to realize exponential tracking of a straight-line contour on the walking surface as well as the desired periodic or aperiodic motion along the contour. First, the full-order dynamic model of bipedal robotic walking is presented. Second, a state feedback control law is synthesized based on input-output linearization with the output function designed as the tracking errors of a straight-line contour on the walking surface, the desired position trajectory along the contour, and the desired walking pattern. Sufficient conditions for the exponential stability of the hybrid time-varying closed-loop system are then established based on formal stability analysis. Finally, simulation results had validated the proposed contouring control strategy on a 3-D bipedal robot with nine revolute joints.