Multivariable QFT robust control of a heat exchanger

This paper presents the multivariable robust control of a laboratory-scale heat exchange process. After theoretical and experimental identification of its non-linear equations, 2×2 linear models with uncertainty and significant coupling are obtained. Using Horowitz's non-sequential multivariable method (within QFT) diagonal matrices of controllers and prefilters are designed to guarantee certain robust specifications of tracking and stability. The overdesign in the controllers, implicit in the multivariable method, is reduced by applying an iterative methodology that reduces the bandwidth of the controllers of each loop, guaranteeing original control specifications without losing sight of feedback principles.