Simultaneous closed-loop automatic tuning method for cascade controllers

A new automatic tuning method for cascade control systems is presented. The technique consists in estimating the parameters of the primary and secondary process simultaneously by evaluating a closed-loop set-point step response. Then, based on the estimated model, the two proportional-integral-derivative controllers are tuned by applying an internal model control strategy. A performance assessment strategy can also be implemented in this context. Both self-regulating and nonself-regulating processes are considered. Simulation results show the effectiveness of the methodology.