Page 181 - MATLAB an introduction with applications

166 ——— MATLAB: An Introduction with Applications

Response to input r1=exp (–0.7t)
1.2

1
Input r = exp (–0.7t)
0.8

output 0.6

and
Input 0.4

0.2
Output
0

–0.2
0 2 4 6 8 10 12
t Sec

Fig. E3.17(b) Response curve for input r= e –0.7t

Example E3.18: A unity-feedback control system is defined by the following feedforward transfer function
K
() =
Gs
2
( ss + 7s + 9)
(a) determine the location of the closed-loop poles, if the value of gain is equal to 3
(b) plot the root loci for the system using MATLAB.

Solution:
>> % MATLAB Program to find the closed-loop poles
>> p=[1 7 9 3];
>> roots(p)
ans =
–5.4495
–1.0000
–0.5505

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