Mechanical self-stabilization, a working hypothesis for the study of the evolution of body proportions in terrestrial mammals

Locomotion is a behaviour resulting from the interaction of the nervous and muculo-skeletal systems and the environment. However the musculo skeletal systems of some terrestrial mammals present an intrinsic ability to realize a dynamic stable locomotion. Actual anthropomorphic passive walkers demonstrate that a pure mechanical system with leg and arms is able to walk down an inclined plane. Numerical simulations confirm that self-stabilization of the mechanics is acting in running too. The necessity to ensure the dynamic stability of a cyclic locomotion set physical constraints to the musculo-skeletal system. A description of the locomotor apparatus with neuromechanical variables like the stiffness accessible to the experimentationenables for maintaining the number of degrees of freedom of biomechanical models as low as possible. The maximization of the robustness of the mechanical self-stabilization of the models with regard to the body proportions represents for future simulations an optimization criterion which should bring a new light to the comprehension of the body proportions. Keyword s: stability locomotion body proportion running quadruped mammals.