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S. Skogestad, M. Hovd and P. Lundström, ``Towards integrating design and control: Use of frequency-dependent tools for controllability analysis'', Proc. Process Systems Engineering (PSE) 91, III.3.1-III.3.15, Canada, Aug. 1991.

Abstract.
By controllability (dynamic resilience) we generally mean the best closed-loop performance achievable using any controller. Since the controllability can not be altered by change of the control algorithm, but only by design modifications, it follows that the term controllability provides a link between process design and process control. In this paper we focus on two aspects of controllability: The plants sensitivity to disturbances and the limitations imposed by interactions when using decentralized control. We use simple tools such as the RGA, the PRGA (Performance RGA) and the closely related Closed Loop Disturbance Gain (CLDG). For example, if k'th column of the CLDG is large, then this indicates that disturbance k will be difficult to reject. This may pinpoint the need for modifying the process. The PRGA provides a measure of interaction which also includes one-way coupling. In the paper we apply these measures to distillation column control and fluid catalytic cracker (FCC) control.