Abstract: A new method based on the “virtual leg” is presented which can realize the running of the humanoid running
robot in the sagittal plane. Firstly, the trajectory of the center of mass (COM) of the robot is planned by solving the two
dimensional dynamic equation of “virtual leg” in the stance phase and the COM of the robot moves like a projectile in the
air in the flight phase. Then the trajectories of two feet and two arms are planned which are followed by the kinematic
parameters calculated by solving the nonlinear equations with the Newton-Raphson algorithm. Finally, the torque of each joint
is achieved according to the dynamic equations. The simulation results show that the angle of each articulation and the
torque of each joint change smoothly and that the stability margin is high. The running robot can run at the speed of 1.2m/s
in the horizontal direction.

Key words: humanoid robot, running robot, kinematics, motion planning