Modern Control Engineering

(Chris Devlin) #1
842 Chapter 10 / Control Systems Design in State Space

MATLAB Program 10–31


% Obtaining Ke ---- minimum-order observer


Aab = [1];


Abb = [-2];


LL = [-8];


Ke = acker(Abb',Aab',LL)'


Ke =


6


MATLAB Program 10–30


% Determination of transfer function of observer controller ---- full-order observer


A = [0 1;0 -2];


B = [0;4];


C = [1 0];


K = [4 0.5];


Ke = [14;36];


[num,den] = ss2tf(A-KeC-BK, Ke,K,0)


num =


0 74.0000 256.0000


den =


1 18 108


To obtain the transfer function of the observer controller, we use MATLAB. MATLAB
Program 10–30 produces this transfer function. The result is

num
den

=

74 s+ 256
s^2 + 18 s+ 108

=

74 (s+3.4595)
(s+ 9 +j5.1962)(s+ 9 - j5.1962)

Next, we obtain the observer gain matrix Kefor the minimum-order observer. MATLAB
Program 10–31 produces Ke.The result is

Ke= 6

The response of the system with minimum-order observer to the initial condition can be ob-
tained as follows: By substituting u=-Kxinto the plant equation given by Equation (10–79)

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