Tesis doctoral de Rosa PÁ mies VilÁ
This thesis presents the kinematic and dynamic study of human motion by means of multibody system dynamics techniques. For this purpose, two biomechanical models are used: a 2d model formed by 11 segments with 14 degrees of freedom, and a 3d model that consists of 18 segments with 57 degrees of freedom. The movement of the subject is recorded in the laboratory using a motion capture system that provides the position along time of 37 markers attached on the body of the subject. Position data are filtered using an algorithm based on singular spectrum analysis (ssa) and the natural coordinates of the model are calculated using algebraic relations between the marker positions. Afterwards, a kinematic procedure ensures the kinematic consistency and the data processing continues with the approximation of the position histories using b-spline curves and obtaining, by analytical derivation, the velocity and acceleration values. This information is used as input of an inverse dynamic analysis. Differing to most published works, in this thesis the force plates measurements are not used directly as inputs of the analysis. When both feet contact the ground, kinematic measurements are insufficient to determine the individual wrench at each foot. One of the contributions of the thesis is a new strategy that is proposed to solve the this indeterminacy (called corrected force plate sharing, cfp) based on force plates data. Using this method, a set of two contact wrenches dynamically consistent with the movement are obtained with no need neither to add residual wrenches nor to modify the original motion. Also in the ida field, the sensitivity of the joint torques to errors in the anthropometric parameters, in the force plate measurements and to errors committed during the kinematic data processing is studied. The analysis shows that the results are very sensitive to errors in force measurements and in the kinematic processing, being the errors in the body segment parameters less influential. A new 3d foot-ground contact model is presented and its parameters are estimated using optimization techniques. The model is used as an alternative method to solve the mentioned sharing problem during the double support phase and it is also used, in a forward dynamic analysis, to estimate the contact forces between the biomechanical model and its environment. The forward dynamic simulation requires the implementation of a controller that is based, in this case, on the extended kalman filter. The most important contributions of the thesis in ida are focused on the cfp sharing method and regarding the analysis of the influence of errors in input data on the inverse dynamics results, the statistical modelling of the uncertainties together with the perturbation of more than one parameter at same time (remaining height and weight as a constant parameters) is also new in the literature. Moreover, the presented foot-ground contact model is also original. In the current state of the art, there are no models that use real data captured in the laboratory to solve the contact wrench sharing problem during the double support phase. Furthermore, there are few studies simulating the foot-ground interaction in a forward dynamic analysis using a continuous foot-ground contact model. Finally, developing a model that is used for both forward and inverse dynamic analysis is a relevant aspect of the methodology used. Although the two approaches separately are common research topics in the field of biomechanics, a small number of studies prove the validity of the obtained results. In this thesis, the results of the inverse dynamics are used as input data for the forward dynamic analysis, and the results of the latter (the motion) have been compared with the motion capture in the laboratory (input of the inverse dynamics analysis). Thus, the circle has been closed which allows us to validate the accuracy of both the models and the obtained results.
Datos académicos de la tesis doctoral «Application of multibody dynamics techniques to the analysis of human gait«
- Título de la tesis: Application of multibody dynamics techniques to the analysis of human gait
- Autor: Rosa PÁ mies VilÁ
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 21/12/2012
Dirección y tribunal
- Director de la tesis
- Josep María Font Llagunes
- Tribunal
- Presidente del tribunal: jí¶zsef Kí¶vecses
- Miguel Tavares silva (vocal)
- (vocal)
- (vocal)