Analysis of Uncertainty Influence in the Design of Interval Type‐3 Fuzzy Controllers With Type‐3 Fuzzy Harmony Search: The Case of the Water Tank

ABSTRACT Nonlinear control systems are an integral part of complex engineering systems. The main difference from linear systems is their ability to adapt to changes and unpredictable conditions. These systems exhibit behaviors that cannot be predicted by simple linear equations, making them essential for applications requiring precise control over a range of operating conditions and are widely used in industry, engineering, and technology. In this article, we focus on the water level in a tank. Based on the nonlinear control model of the water tank, a type‐3 fuzzy interval controller was designed with the objective of maintaining the water level in a tank at a desired value. To evaluate the controller's performance, different interval type‐3 fuzzy control systems (IT3‐FLS) were designed by varying the lower scale and lower lag parameters, which represent the uncertainty domain (DOU) of the IT3‐FLS, to achieve the best parameterization for handling the uncertainty of the problem. Once the optimal parameterization of the lower scale and lower lag parameters of the controller was obtained, the interval type‐3 fuzzy harmony search algorithm (IT3‐FHS) optimized the controller antecedent parameters. The results of simulations performed under different conditions are presented: with and without noise applied to the IT3‐FLS controller.