Invariant Control of Variable Flow Processes

An integrated flow variable is introduced. It is shown that the residence distributions and weighting functions of many continuous flow processes which are time-variable under unsteady flow conditions, are invariant with regard to this new variable. Constant parameter controllers may be designed for time-variable processes on the basis of models which are written in terms of this variable, and then methods can be applied which are analogous to the conventional design methods. Assuming the volumetric process flow is measured, the operation of such controller is synchronized to the integrated flow variable instead of the time-base of the conventional controller. The control coefficients of both types of controllers have a simple mutual relationship.