Cooperative massive object transportation by two humanoid robots

In this paper, a motion generation method for transportation of a massive object by multiple humanoid robots is proposed. A joint trajectory (acceleration level) of the whole-body is determined by solving a quadratic programming problem with inequality/equality constraints. The proposed method was varified by performing dynamic simulations using a dynamic simulator OpenHRP. Frictional constraints between the supporting foot and the ground has generally been formulated by inequality equations approximating a friction cone by an inverted pyramid. However the inequality constraint cause high computational cost. Therefore, in this paper frictional force is estimated by assuming virtual large masses at the tip of the limbs. The motion generated by the proposed method satisfies the constraints such as prevention of slip of the feet of the robots and avoidance of excessive joint torque, and it was possible to move an object of 200 kg. The simulation results with the proposed method were compared with the results with a conventional PD controller in order to show the effectiveness of the proposed method.