Multivariable Robust Control of an Approach Flow System

The objective of this paper is to design a robust controller for the multivariable system having five inputs such as reel speed (U-1), thick stock flow rate (U-2), ash flow rate(U-3), flow rate of retention aid(U-4), and ash fraction in thick stock(U-5) and two outputs Y-1 (bone dry weight) and Y-2(bone dry ash weight). The controlled variables are chosen as an ash flow rate (U-3) and flow rate of retention Aid (U-4) for the approach flow system of a paper making process. The paper includes a mathematical model and presents Linear Quadratic Gaussian (LQG) controller design for the system. The paper concludes that the LQG robust control strategy provides better stability & performance objectives compare to the PID controller in the presence of uncertainty & disturbances.