On the equivalence between PD plus DOB and PID controllers applied to servo drives

This work shows that a Proportional Derivative controller with weighted Derivative action plus a Disturbance Observer, is equivalent to a Proportional Integral Derivative (PID) controller with weighted Proportional and Derivative actions, when they are applied to servo drives. A byproduct of this equivalence is a tuning rule for the PID controller, called the DOB tuning, which is expressed in terms of the cutoff frequency of the filter employed in the DOB. Experiments in a laboratory testbed allow assessing the performance of a PID controller under the resulting tuning formulae. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.