System identification and PID controller tuning using band‐pass filters

An online recursive system identification technique using band‐pass filters has been developed to estimate the continuous‐time frequency response of any process control system at a number of discrete frequencies. Tuning of PID controllers employs a gradient optimization technique, based on the estimated discrete frequency response of the process rather than a transfer function model of the process. The performances of the identification technique and controller tuning algorithm are demonstrated by a simulation and by experimental results on a distillation column composition control.