On the controller effect in closed-loop identification for DC servomechanisms under PD control

This paper adresses the effect that a controller has on the parameter estimates for a closed-loop identification methodology with a DC servomechanism. Closed-loop identification is performed with a direct method, where a PD controller, which stabilizes the system without knowledge about its parameters, closes the loop. It is shown that when the perturbation signal is absent, exponential convergence can be claimed, making the identification algorithm robust. However, when there exists a perturbation signal it can be established a region where the parameter estimates belong to, and it is shown how this region is affected by the PD controller gains.