Plantwide control - A review and a new design procedure

Most (if not all) available control theories assume that a control structur e is given at the outset. They therefore fail to answer some basic question s that a control engineer regularly meets in practice (Foss 1973): 'Which v ariables should be controlled, which variables should be measured, which in puts should be manipulated, and which links should be made between them?' T hese are the questions that plantwide control tries to answer. There are two main approaches to the problem, a mathematically oriented app roach (control structure design) and a process oriented approach. Both appr oaches are reviewed in the paper. We also provide some definitions of terms used within the area of plantwide control.