What is the role of the initial positions of the segments?
The initial positions, only serves as the initial guess on the segments positions. This means that if the model assembles correctly one can be satisfied with the initial positions. They will have no influence on any analysis results. If the model is a closed chain mechanism then there might be several kinematic solutions that will fulfill the kinematic constraints on the model. In such a case the initial position can be used to ensure that the model chooses the correct solution, simply by providing initial positions which are close to the correct one.
