Frequency domain tuning approach for adaptive feedforward control using lead–lag compensators

Abstract

AbstractThe tuning of lead–lag compensators to be used as feedforward controllers for measured disturbances is performed in the frequency domain. The identification of process Gu and disturbance dynamics Gd uses extended recursive least squares, and the frequency responses are calculated from the least squares coefficients. A lead–lag compensator Gll is designed which minimises the function $G_{{\rm ll}} (j\omega ) + (G_{{\rm d}} (j\omega ))/(G_{{\rm u}} (j\omega ))$ over a finite number of frequencies, using the Nelder–Mead simplex method. The effectiveness of the frequency domain tuning strategy is compared by simulation to established tuning rules for first‐order plus delay processes. The tuning method is experimentally verified on a pilot scale methanol–water distillation column. © 2011 Canadian Society for Chemical Engineering