Dynamic simulation of a humanoid robot with four DOFs torso

In this paper, we present the 3D dynamic simulation of walking gait of biped Robian II virtual manikin. The biped has 16 degrees of freedom (DOFs). Initially, a biomimetic approach is used to model a humanoid biped having 25-DOFs based on common European male (75 kg, 1.78 m). Using human being motion recording, foot/ground contact model and inverse kinematics, a 3D dynamic simulation of this humanoid is carried out. Scale factorization is used in order to reach Robian II weight and height. A 3D dynamic simulation of the Robian size humanoid gives the effort wrench exerted by the torso on the lower limbs. An analysis of the six components of this wrench shows the existence of two coupling relations. A study of four DOFs mechanisms based on the general state equation formalism leads us to an interesting result. Indeed, four DOFs are necessary and sufficient to emulate the dynamic effects. A RPPP mechanism is presented in order to replace Robian´s upper part. Results of 3D simulation of the 16-DOFs resulting biped are presented. The ZMP control algorithm is used to ensure dynamic stability of the biped during walking gait.