This thesis is carried out in collaboration with Comau S.p.A. The experimentation of state observers for the reconstruction of the angular velocity of the links of a flexible industrial manipulator has been performed, in the presence of unmodeled or uncertain parts. In a particular simplified condition in which there is only one axis moving at a time, a study was done to understand how faithfully the dynamics of the machine can be reconstructed using simple single axis models, extending them to take into account the multi-variable dynamics of the system and trying to reconstruct the action of non-linear friction as well.