440 Chapter 7 / Control Systems Analysis and Design by the Frequency-Response MethodDrawing Nyquist Plots of a System Defined in State Space. Consider the
system defined by
where state vector (n-vector)
output vector (m-vector)
control vector (r-vector)
state matrix (n*nmatrix)
control matrix (n*rmatrix)
output matrix (m*nmatrix)
D= direct transmission matrix (m*rmatrix)
C=
B=
A=
u=
y=
x=
y=Cx+Du
x# =Ax+Bu
MATLAB Program 7–8
% ---------- Nyquist plot----------
num = [1];
den = [1 1 0];
w = 0.1:0.1:100;
[re,im,w] = nyquist(num,den,w);
plot(re,im)
v = [-2 2 -5 5]; axis(v)
grid
title('Nyquist Plot of G(s) = 1/[s(s + 1)]')
xlabel('Real Axis')
ylabel('Imag Axis')
Real Axis- 21 – 1.5 – 1 – 0.5 0 0.5 1.5 2
Imag Axis- 2
1- 5
5- 1
2- 3
- 4
034Nyquist Plot of G(s)=1/[s(s+1)]Figure 7–40
Nyquist plot offorv 7 0.G(s)=1
s(s+ 1 )A MATLAB program using this nyquistcommand is shown in MATLAB Program 7–8. The
resulting Nyquist plot is presented in Figure 7–40.Openmirrors.com