Self-tuning of Fuzzy Logic Controllers in Cascade Loops

Cascade control is a multi-loop control scheme commonly used in chemical plants. But, as the involved processes are in general complex, with delays and non-linearities, conventional control methods are not able to guarantee the final control aims. Fuzzy Control (FLC) has been successful applied to these applications. However, controller parameters adjustment is a critical point and in Fuzzy Control there is no systematic procedure for tuning. We propose a simple tuning strategy for these FLC based on the Relay method that allows to apply it to more complicated FLC configurations, like cascade loops.