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 (U₁), thick stock flow rate (U₂), ash flow rate(U₃), flow rate of retention aid(U₄), and ash fraction in thick stock(U₅) and two outputs Y₁ (bone dry weight) and Y₂(bone dry ash weight). The controlled variables are chosen as an ash flow rate (U₃) and flow rate of retention Aid (U₄) 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.