A Buffering Strategy for Quadrupedal Robots Based on Virtual Model Control

A buffering strategy for quadrupedal robots based on virtual model control is presented. According to the contact status of legs and the vertical velocity of the torso, the whole landing process is divided into three phases, that is, the falling phase, the buffering phase and the recovering phase. During falling phase, virtual spring-damper sections are implemented for flight toes to track the planned trajectories. For the buffering phase and the recovering phase, the mathematical relation between the virtual forces applied on the COM (center of mass) of the torso and the supporting legs is established according to the number of the supporting legs. And the torso's COM is controlled by the virtual forces through active variable stiffness control. To reduce the impact in landing process, reasonable stiffness and damping are determined according to which phase the robot is in. The simulation shows that the buffering strategy is effective.