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MATLAB draws the polar coordinate diagram of the control system
Polar coordinate drawing function nyquist diagram
Function usage
nyquist(sys)
nyquist(sys,w)
[re,im,w]= nyquist(sys) The
first method of use: Given the model object sys of the open loop system, automatically select the drawing frequency of w.
The second method of use: Given the model object sys of the open-loop system, manually select the drawing frequency of w. The
third method of use: return the parameter vector of the polar coordinate graph without drawing.
re is the real part vector of the complex function G(jw), im is the virtual Part vector
Draw the polar coordinate graph of the following function
G open (s) = 10 s 2 + 2 s + 5 G_{open} (s) = \frac{10}{s^{2}+2s+5}Gopen(s)=s2+2s+510
The MATLAB code is as follows:
num=[0 0 10]%分子，作多项式模型
den=[1 2 5]%分母
sys=tf(num,den)%构建系统对象
nyquist(sys)
Output:
num = 1 × 3
0 0 10
den = 1 × 3
1 2 5
sys =
10 s 2 + 2 s + 5 \frac{10}{s^{2}+2s+5 } s2+2s+510
Continuous-time transfer function.
image:
Improving methods for unsatisfactory rendering
1. Use axis() to change the coordinate display range,
such as axis([-1,1.5,-2,2])
2. The specified range of the given angular frequency
w=0:0.1:100;
nyquist(sys,w)