Tuning of Smith predictor based generalized ADRC for time-delayed processes via IMC

A control strategy combining generalized active disturbance rejection control (GADRC) with Smith predictor (SP) is investigated for time-delayed systems. It takes all available model information into consideration, including the plant dynamic and the time delay, thus inherits the advantages of both SP-ADRC and GADRC. Since SP-GADRC can be transformed into a two-degree-of-freedom (TDF) feedback control structure, it is simply interpreted and tuned through the equivalent TDF internal model control (TDF-IMC) by using the delay-free part of the system as the nominal model for the IMC design and selecting the bandwidths of controller and extended state observer (ESO) for SP-GADRC as the inverse of the time constants of the setpoint filter and the disturbance-rejection filter in IMC, respectively. The analysis and tuning is of tutorial value for practitioners and engineers, and the effectiveness is validated by a few comparative simulations.