Specifications

Time Delays
2-47
Thegoalistomaximize byadjustingtherefluxflowrate andthesteam
flow rate in the reboiler.
To obtain a linearized model around the steady-state operating conditions, the
transient responses to pulses in steam and reflux flow are fitted by first-order
plus delay models. The resulting transfer function model is
Note the different time delays for each input/output pair.
You can specify this MIMO transfer function by typing
H = tf({12.8 –18.9;6.6 –19.4},...
{[16.7 1] [21 1];[10.9 1] [14.4 1]},...
'iodelay',[1 3;7 3],...
'inputname',{'R' , 'S'},...
'outputname',{'Xd' , 'Xb'})
The resulting TF model is displayed as
Transfer function from input "R" to output...
12.8
Xd: exp(–1*s) * ----------
16.7 s + 1
6.6
Xb: exp(–7*s) * ----------
10.9 s + 1
Transfer function from input "S" to output...
–18.9
Xd: exp(–3*s) * --------
21 s + 1
–19.4
Xb: exp(–3*s) * ----------
14.4 s + 1
X
D
R
S
X
D
s
()
X
B
s
()
12.8e
1s–
16.7e 1+
------------------------
18.9e
3s–
–
21.0s 1+
-------------------------
6.6e
7s–
10.9s 1+
------------------------
19.4e
3s–
–
14.4s 1+
-------------------------
Rs
()
Ss
()
=