Analysis of decentralized control structures for nonlinear systems

✍ Scribed by V. Manousiouthakis; M. Nikolaou

• Publisher: American Institute of Chemical Engineers
• Year: 1989
• Tongue: English
• Weight: 702 KB
• Volume: 35
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690350405

✦ Synopsis

Configuration of feedback loops between input and output variables of a given plant constitutes a subtask of control system synthesis. In the past, this subtask has been tackled through direct decomposition of either the process or the set of input-output variables. Linear interaction analysis has been used in both approaches to assess and minimize subsystem interactions. Since most chemical processes exhibit nonlinear behavior, it is evident that a measure is needed for assessment of interactions in the presence of system nonlinearities. In this paper we focus on input-output variable set decomposition and introduce the notion of nonlinear block relative gain (NBRG) as a nonlinear interaction measure. Both the statistic and dynamic versions of NBRG are discussed, and a computational procedure is presented for their evaluation. Direct simulations on a CSTR verify the interactions predicted by NBRG for different feedback configurations. Moreover, nonsymmetry of the effect of one loop on another, a fact not captured by the linear BRG, is accurately predicted by NBRG.