Parameter Estimation for Biomechanical Models Based on a Special Form of Natural Coordinates

Abstract

We present parameter estimation results for a full three-dimensional model of the human body with nearly 100 degrees of freedom. This task could only be achieved by the use of sophisticated numerical techniques not only for optimization but also for the model setup. We have developed an object-oriented biomechanical modeling library based on a special form of natural coordinates that does not only serve to establish the full set of equations of motion of highly complex biome-chanical systems, but also to efficiently compute all the derivative information that is required in the parameter estimation context. Our parameter estimation algorithm is based on a multiple shooting state discretization and uses a generalized Gauss–Newton method. Eight experiments are combined in a multiple experiment setting. Inconsistent initial values are treated by a special form of non-stiff Baumgarte relaxation.