Dynamics modeling and stable gait planning of a quadruped robot in walking over uneven terrains

Quadruped robots have unique capabilities for motion over uneven natural environments. This article presents a stable gait for a quadruped robot in such motions and discusses the inverse-dynamics control scheme to follow the planned gait. First, an explicit dynamics model will be developed using a novel constraint elimination method for an 18-DOF quadruped robot. Thereafter, an inverse-dynamics control will be introduced using this model. Next, a dynamically stable condition under sufficient friction assumption for the motion of the robot on uneven terrains will be obtained. Satisfaction of this condition assures that the robot does not tip over all the support polygon edges. Based on this stability condition, a constrained optimization problem is defined to compute a stable and smooth center of gravity (COG) path. The main feature of the COG path is that the height of the robot can be adjusted to follow the terrain. Then, a path generation algorithm for tip of the swing legs will be developed. This smooth path is planned so that any collision with the environment is avoided. Finally, the effectiveness of the proposed method will be verified.