Published: CABEQ 18 (4) (2004) 345–352
Paper type: Original Scientific Paper

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The Higher Order Multilevel Fuzzy Logic Controller

J. Savković-Stevanović

The higher order multilevel fuzzy controller was used to achieve an improvement of the performance of the auto controller tuning. A tuning method with higher order multilevel membership function is incorporated in a tuning formula based on the gain/phase margins. The higher order fuzzy multilevel controller was made to vary with respect to the plant's normalized dead time and system state error. The multilevel tuning actually has made the fuzzy logic controller able to improve adaptation of the control environment. The higher order multilevel controller was settled faster by the first order multilevel fuzzy logic controller in conjunction with less overshoot in set point control. As a case study the two coupled chemical stirred tanks were used. Numerical solutions showed validity of the proposed tuning methods. The obtained results were: illustrated feasibility of using the higher order multilevel fuzzy controller to represent tuning formula on the gain/phase margin for unstable zeros. The higher order multilevel controller was improved robustness and sharpness to determine gain/phase margin. This work is the first report in the literature showing the third order membership functions theory.

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Controller tuning, fuzzy logic, higher order fuzzy controller, nonlinear systems