Gait Planning of Omnidirectional Walk on Inclined Ground for Biped Robots

When a biped robot moves about in a physical environment, it may encounter inclined ground. Biped walking on inclined ground still remains challenging for biped robots. Previous studies have discussed biped walking on inclined ground along specific directions. However, omnidirectional walk on inclined ground has rarely been investigated. In this paper, we propose a gait pattern generation method for omnidirectional biped walking on inclined ground. First, a model that describes the motion of biped walking on inclined ground uniformly with two angle parameters is proposed. A mathematical relationship between motions in the sagittal and coronal planes of the biped robot are presented. Then, based on nonorthogonal motion decoupling, a method that generates gait patterns for omnidirectional walking with a double support phase for biped robots is proposed. The trajectories of each foot are designated by the walking speed, step length, and walking direction. The motion trajectory of the center of mass (CoM) of the robot is planned using a linear inverted pendulum model in the sagittal and coronal planes. The motion of CoM in the sagittal and coronal planes is constrained in parallel to the gradient vector of the inclined ground and the horizontal plane, respectively. Finally, the effectiveness of the proposed gait planning method for biped walking on is validated by simulations and experiments with an actual biped robot.