Stable running velocity change of biped robot based on virtual torque

Abstract

This paper proposes a method to generate a stable running trajectory for a biped robot based on virtual torque at the stepping foot for velocity changes. For a velocity change, an external force is necessary, which is generated by moving the ZMP (Zero Moment Point). Moving the ZMP has the same effect as applying a virtual torque at the foot on the ground. By using this method, the velocity of a biped robot can be changed. When a running trajectory for a biped robot is generated based on its model modeled with a single particle, the dynamics of the real robot which has relatively large mass of the swing legs could make the biped robot motion unstable. Based on the gravity-compensated inverted pendulum model with the virtual torque at the stepping foot, a trajectory resulting in stable velocity changes is generated. The effectiveness and the improvements in the performance of the proposed method were shown in computer simulations with a 2D biped robot.