In order to synthesize a robust system of control over technological units, an analysis of appropriate mathematical models was performed. The uncertainty of models of technological iron ore processing units was accounted for by connecting a diagonal block at the top using a fractional linear transformation. To study robust control systems of technological units, we applied the following types of robust controllers: suboptimal H ∞ -controller, a controller that was synthesized using the method of circuit formation, and µ-controller. We performed an analysis of results of the study into indicators of robust quality and stability of control, created on the basis of these types of controllers. The best results were obtained using μ-controller, which ensures a minimal overshoot value of 2 %. Reducing the order of the selected μ-controller to the fourth order was performed by approximation using the Hankel norm. Under such a condition, a root-mean-square error relative to the base controller is 0.027. Results of present research could be used in the synthesis of control over technological iron ore processing units under conditions of uncertainty in parameters.