Digital control system design for a unique nonlinear MIMO process using QFT technique

A 19-input, 106-output thermal process is closed-loop-stabilised to meet time- and frequency-domain performance criteria. A unique nonlinear process modelling technique is used to transform several nonmeasurable process parameters into two `state-dependent linear variables´ (gain and dominant pole location) with quantified uncertainty. A linear equivalent model set with quantified uncertainty is amenable to the quantitative feedback theory (QFT) design technique, and the analogue multiloop compensation was developed using QFT. Because the system primarily functions as a regulator, a simplified MIMO system decoupling method, specific to this type of process, was developed and demonstrated. The resulting digital control system is in operation on the Uranium Atomic Vapor Laser Isotope Separation Demonstration System at the Lawrence Livermore National Laboratory