Dynamic stability analysis of a trotting quadruped robot on unknown rough terrains

This paper presents a dynamic stability analysis method for a trotting quadruped robot on unknown rough terrains based on Lyapunov theory of switching system. The dynamic model of a trotting quadruped robot is built as a nonlinear switching system. In a single stance phase, the dynamic model is approximated as a 3D seven-link mechanism and a linear inverted pendulum, and a contact force distribution/control strategy is proposed based on sliding mode to guarantee the position and orientation of seven-link mechanism asymptotic stable. Considering the switching process, the trotting quadruped robot becomes a non-autonomous system. A common Lyapunov function is designed to prove the uniform asymptotic stability of the height and torque angles. And Landing position of swing legs are calculated to make sagittal position error of robot converging to 0. Finally, a trotting experiment is performed on a rough terrain to validate the effectiveness of the proposed method.