Kinematic Analysis of Planar Biomechanical Models using Mixed Coordinates

Kinematic analysis (KA) is a powerful tool used in the study of biomechanical systems, since it allows for the computation of the orientation of the model segments, trajectory of specific points, angular displacement of joints, among other variables of interest. Two approaches can be used to perform the kinematic analysis of multibody systems, namely, forward (FK) or inverse kinematics (IK). In the first case, the model is guided using linear and angular drivers calculated in a previous step. Afterwards, the consistent generalized coordinates are obtained by imposing the kinematic constraints that define the model. On the other hand, in IK the position and orientation of each segment is computed by minimizing the difference between the experimental data and a set of points belonging to the model, namely the coordinates of the system or other points of interest. This procedure allows for the fitting of the computational model to the experimental data.