control system bode plot

how to plot this two equatio and the resutant output is shown in the figure

Answer 1

[Birdman]

Try this:

alpha=1;Wcr=10;
syms w
Mag(w)=piecewise(w<Wcr,20,w>=Wcr,-26.144+20*alpha*log(w));
w=logspace(-1,3,1000);
semilogx(w,Mag(w));grid on;xlabel('Frequency');ylabel('dB')

[Irshad Baruah]

its showing error in

Error in matlab_program (line 5)

Mag(w)=piecewise(w<Wcr,20,w>=Wcr,-26.144+20*alpha*log(w));

[Irshad Baruah]

this is the paper , i want to find the fractional zero part i.e figure 1

[Birdman]

which version of MATLAB are you using?

[Irshad Baruah]

Matlab R2013a

[Birdman]

ok then, try this:

hold off;
alpha=1;Wcr=10;
w1=logspace(-1,log10(Wcr),1000);w2=logspace(log10(Wcr),3,1000); 
Mag1=20*ones(1,numel(w1));Mag2=@(w2) 20*alpha*log10(w2);
semilogx(w1,Mag1);hold on;semilogx(w2,Mag2(w2));grid on;xlabel('Frequency');ylabel('dB')

[Irshad Baruah]

Thank you Birdman it's working if I face any problem I let you know again thanks for helping me out

[Birdman]

You are welcome. You can accept the answer if it helped.

[Irshad Baruah]

alpha value should be fractional,in this code if i chang the alpha value the graph got cut

[Birdman]

Hello Irshad,

Sorry for the late reply. There has been something in the code that I missed, so the following code is working:

hold off;
alpha=0.09;Wcr=10;
w1=logspace(-1,log10(Wcr),1000);w2=logspace(log10(Wcr),3,1000); 
Mag1=20*alpha*ones(1,numel(w1));Mag2=@(w2) 20*alpha*log10(w2);
semilogx(w1,Mag1);hold on;semilogx(w2,Mag2(w2));grid on;xlabel('Frequency');ylabel('dB')