A generalized 3D inverted pendulum model to represent human normal walking

International audienceThis paper compares different inverted pendulum models to represent the stance phase of human normal walking. We have developed a model which takes into account the mechanism of the foot during the single support phase, by defining a pivot point under the ground level. Similarly to other models, the pivot point as well as the rod length remain constant during the complete single support phase. Lowering the position of the pivot point allows reducing the vertical amplitude of the center of mass (CoM) trajectory and therefore approaching the real CoM trajectory. Another big advantage of this model is that it can be easily adapted to pathological walking as the walking symmetry hypothesis -needed to build classical inverted pendulum models, is not used. We have measured the whole body kinematics of 5 healthy male subjects and set a reference CoM trajectory based on multibody modeling of the human body (16 segments). Then, we have determined a common mathematical definition of three inverted pendulum models extended in the three dimensional space: the classical IP-3D, the EIP-3D and our GIP-3D model. To insure continuity of the approached trajectories, a double support phase is represented by a simple pendulum which is a homothetic transformation of the inverted pendulum defining the previous single support phase, except for our GIP-3D model