Four DOF TORSO dynamic effects on biped walking gait

In this paper, a study of the upper part dynamic effects on locomotion system allows us to identify the kinematic structure of a new prototype called ROBIAN II. The biped has 16 degrees of freedom (dofs). Initially, a bio-mimetic approach is used to model a virtual manikin biped having 25 dofs based on common European male (75 kg, 1.78 m). Using, human being motion recording, foot/ground contact model, inverse kinematics and Newton-Euler equations, a 3D dynamic simulation of this virtual manikin is carried out. Scale factorization is used to get a new manikin which weight and height are those of ROBIAN 11 prototype. A 3D dynamic simulation of the obtained virtual manikin is carried out in order to identify the effort wrench exerted by its 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 General State Equation (GSE) formalism leads us to an interesting result. Indeed, four dofs are necessary and sufficient to emulate the dynamic effects. An RPPP mechanism is presented in order to replace the virtual manikin upper part. Results of 3D simulation of the 16 dofs resulting biped are then presented. A control method is used to ensure dynamic stability of this biped during walking gait.