The authors have studied applicability of the H∞ control to bilinear plants, which can be encountered in different control plants of resources processing. Those plants are characterized by the model dynamics depending on the change of manipulated variable. The nominal transfer function was determined for the one concentration set point and the other concentration values except for the set point were regarded as factors inducing model deviations. Time variations of the manipulated variable and inverse responses of the controlled variables were also considered in the designing stage. The results shows that stable control can be achieved over a wide range of concentration value, i. e. controlled variable. The results were also compared with those from the fuzzy control applied to the process under the same conditions. The fuzzy control shows that the rise time is shorter than that in the H∞ control, but a big overshoot appeared when another rule table was used. It is considered that the H∞ control has a conservative tendency caused by establishing robust stability. However, it has an advantage of the systematic and routine design which can hardly be conducted in the fuzzy control.
