Robust control under variable flow and volume

Models of continuous flow processes with variable parameters are studied and methods developed for their robust control. New, composite variables have been introduced recently and such processes have proven invariant under variable flow and volume, if they are modelled as functions of the new variables and if their flow patterns do not change. The processes can be identified as functions of these variables by estimating a set of successive, equidistant values of the finite impulse response. This is considered a high-order model, which is subsequently reduced to a low-order state-space model by means of the optimal Hankel-norm approximation. The robust feedback control is developed in terms of the same variable on the basis of the low-order model. The study extends to the case of a flow pattern which changes independently of and in addition to the simultaneous variation of the total flow and volume. The controls of simulated processes prove the approach superior to methods which have the regular time as their independent variable under unsteady flow and volume