Design of Robust Process Controllers

Abstract The task of designing a robust process controller consists of determining the control algorithm that meets the system performance requirements across a broad range of operating conditions while recognizing the compromises demanded by the available implementation vehicles. This design task generally involves an iterative procedure wherein the compromises forced on the designer and the performance demanded represent an infeasible set that must be negotiated upon until a resolution is achieved. In the chemical and refining industries this task is particularly challenging for two reasons. On the one hand, there is little freedom to change the basic process design in order to achieve feasibility. On the other hand, large levels of research and/or engineering effort to mathematically represent the process is normally not justifiable because of the fact that the number of processes of a given genre is small and so the cost is not distributed across a large number. The needs of our industry have forced a unified approach to control theory wherein the economy is incorporated in the fact that a single design procedure is utilized. In this paper we describe our work in developing such a unified approach to process control. Because of its generality, it is proposed as a potential solution to many of the current control problems encountered not only in our industry but across a broad class of industrial needs. In addition, we outline our current research efforts which will lead to the development of highly versatile and robust controllers whose structure changes to meet the performance requirements on-line in real time.