On-line tuning strategy for PI control algorithms

On-line model-based tuning of the parameters of conventional PI control algorithms is considered. This is accomplished by requiring satisfaction of the performance specifications. The specifications are defined as time domain response envelopes, which are appealing to the practitioner. The parameters adaptation at each sampling point is accomplished by using a linear relationship between the process output and the PI tuning parameters. Thus the adaptation strategy directly uses the sensitivity of the closed-loop response to the parameters. Nominal stability condition is also developed for the algorithm and used only as an indicator of the stability of the closed loop response. The efficiency of the method is presented through implementation on a 8180 time delayed integrator process and on a MIMO non-linear C8TR process. Robustness of the method is also examined by considering modeling error in the MIMO example