Dynamic-stability criteria are crucial for robot’s motion planning and balance recovery. Nevertheless, few studies focus on the motion stability of quadruped robots with dynamic gait, none of which have accurately evaluated the robots’ stability. To fill the gaps in this field, this paper presents a new stability criterion for the motion of quadruped robots with dynamic gaits running over irregular terrain. The traditional zero-moment point (ZMP) is improved to analyze the motion on irregular terrain precisely for dynamic gaits. A dynamic-stability criterion and measurement are proposed to determine the stability state of the robot and to evaluate its stability. The simulation results show the limitations of the existing stability criteria for dynamic gaits and indicate that the criterion proposed in this paper can accurately and efficiently evaluate the stability of a quadruped robot using such gaits.

A kind of crawler-type robot with variable structure based on four-bar linkage was designed to solve the obstacle clearance problem. Firstly, the design scheme of the variable structure tracked robot was proposed, and the virtual prototype was designed. Then the mathematical model between the deformation of the four-bar linkage and the total length of the track was established. the numerical analysis shows that the total length of the track is 0.91% in the deformation process, which is smaller than the elongation of the general rubber track. The feasibility of the scheme was verified theoretically. Finally, a physical prototype experiments were carried out and experiments show that the variable structure crawler could achieve good obstacle performance through deformation.