Robust PI controller design with respect to fuzzy sensitivity margins

The paper deals with PI controller design for linear systems with parametric uncertainty with respect to sensitivity margin. The plant is considered as possibility distribution on a plant space and the closed loop specifications are given in terms of the peak of sensitivity function described by fuzzy numbers. The controller design is understood as the inclusion of respective α-cuts. Such consideration makes it possible to degrade the closed loop specifications towards the uncertainty that occurs very rarely. The proposed procedure is applied on the speed control of a hydraulic turbine – a non-minimum phase system.

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► We characterized both model of plant and closed-loop specifications by fuzzy numbers.
► We proposed a method for PI controller design for interval sensitivity margin specifications.
► Simulations proved an improvement of control performance.