Abstract
This paper presents a case study in which several multivariable control strategies were tested for a reactor-flasher system of an industrial chemical process. This reactor-flasher system which has three manipulated variables and three controlled variables is open loop unstable. Since the system variables interact severely, controlling the system is very difficult with the traditional PID control. We examined various control strategies such as multiloop single variable control, modified single variable control with compensators, and PI control combined with Linear Quadratic Regulator (LQR), Linear Quadratic Gaussian(LQG)/Loop Transfer Recovery(LTR) and Dynamic Matrix Control (DMC) combined with LQR. DMC combined with LQR showed better control performance than the others while remaining robust in the face of modeling errors.
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Abbreviations
- A, B, C, D:
-
matrices used in the state space model
- ADD:
-
summation block
- E:
-
matrix to select the controlled variables
- FC:
-
flow controller
- G:
-
control gain matrix
- II:
-
filter gain matrix
- LT:
-
level transmitter
- TT:
-
temperature transmitter
- Ki :
-
proportional control gain, i = 1, 2, 3
- LC:
-
level controller
- s:
-
Laplace variable
- ul :
-
flow rate of the reactor product
- u2 :
-
flow rate of recycle 1
- u3 :
-
flow rate of recycle 2
- u10 :
-
a steady state condition of u1
- u20 :
-
a steady state condition of u2
- u30 :
-
a steady state condition of u3
- x:
-
state vector
- X1 :
-
mass of liquid in the reactor
- x2 :
-
mass of liquid in the flasher
- x3 :
-
reactor temperature
- y m :
-
measured output vector
- y:
-
selected output vector
- τ i :
-
reset time, i=l, 2, 3
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Lee, J.K., Park, S.W. Control of a reactor-flasher system. Korean J. Chem. Eng. 8, 156–163 (1991). https://doi.org/10.1007/BF02706677
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DOI: https://doi.org/10.1007/BF02706677