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.