2d Spatial Model of the Human Gait Single Support Phase Based on Predict Ive Dynamics

Abstract

The simulation of human body movement is a valuable tool for different fields such as robotics and biomechanics. Even with the growing number of researches, there are still few groups in Brazil that work on developing models of human movement.Such simulation has been a challenging problem from a modeling and computational point of view. This dissertation brings a bibliographical review of concepts of structural dynamics and the main determinants of the dynamics of human walking. Four twodimensional models of increasing complexity found in the literature are initially analyzed to understand the influence of the various elements and degrees of freedom on the quality of the obtained results. Before introducing these models, an investigation of some kinematic variables, known as determinants of walking, is performed for the simple support phase. The simpler model considers an inverted pendulum, and then joints are added to simulate the hip, knee, ankle/foot, and finally the entire leg mechanism is replaced by a spring. The effects of successive additions of degrees of freedom are analyzed and the results are compared with Winter's experimental results for torques and reaction forces. Based on these analyzes, this work proposes a twodimensional model of human walking during the simple support phase (SSP) with seven degrees of freedom. The forces resulting from muscular actions are represented by torques at each joint. All masses of upper body segments are grouped. The model is based on inverse dynamics, with angular displacements being interpolated by 5th degree B-splines and the body kinematics is calculated using the Denavit-Hartenberg (DH) robotic formulation. The equations of motion are obtained based on a recursive Lagrangian formulation, due to its computational efficiency. An optimization problem is established to obtain the B-splines control points, where the objective function is defined by the dynamic effort. The constraints imposed on movement are of two types: the time-dependent constraints (torque/angle limits and dynamic stability defined by the PUC-Rio -Certificação Digital Nº 1712766/CA Zero Moment Point criterion) and the independent time constraints (initial and final state). The results of the model are favorably compared with Winter's experimental data, in particular the ground reaction forces.