Control of grinding circuits using phenomenological models

Abstract Dynamic models are obtained as combinations of phenomenological models of the grinding system components, and the tuning of multivariable controllers for new operating conditions of such systems is discussed by means of models. The total model is first reduced to the steady state and its parameters evaluated by experimental and computational techniques. By means of known dependences of the parameters on operating conditions, any new steady state, following e.g. a change in feed or grain size distribution is then reproduced by simulation with the model. Without further experimentation, the original model is next adjusted to agree with the new point of operation, and the number of its grain size classes is reduced to two, in order to obtain its dynamic responses by simulation. These are converted to frequency responses, and appropriate multivariable controllers are designed by means of Nyquist arrays.