Parallel nonlinear decoupling for process control — A NARMAX approach

The contribution of this paper is twofold. First, we focus on the application of a particular NARMAX (nonlinear ARMAX) model representation based on local models for adaptive decoupling. Second, in order to improve the robustness of the adaptive control algorithm we introduce a diagonal PI-controller in parallel with the adaptive decoupler. These controllers are separated in the frequency domain, such that the decoupler and PI-controller takes care of control actions at higher and lower frequencies, respectively. The parallel control structure supports incremental control design, in the sense that improved process knowledge is used to successively upgrade control performance. The concept is illustrated by a semi-realistic simulation example.