MATLAB: How to plot multiple curves in the same graph window

MATLAB and Simulink Student Suiteplottinggraphs

I want to plot graphs for multiple Kp values for a proportional controller. I tried using for loop to perform this. But I didn't get the output.Below, I attach the code which I have written for your reference. Please guide me on this. If you can tell me if there's any other way to do it, then that would be great.
Kindly reply asap.
Thank you.

Best Answer

Try this: 
J=20.48*10e-6;
b=0.702;
kt=14.70;
kb=0.48;
R=1.6;
L=0.02*0.001;
num=kt;
den=[(J*L) ((J*R)+(L*b)) ((b*R)+(kb*kt))];
kp=0:50:300; %plotting graph for P controller with Kp values in steps of 50
for k = 1:numel(kp)
    ki=0;
    kd=0;
    numc=[kd,kp(k),ki];
    denc=[0 1];
    numa=conv(num,numc);
    dena=conv(den,denc);
    [numac,denac]=cloop(numa,dena);
    sys = tf(numac,denac)
    [y{k},t{k}] = step(sys);
%     QL(k,:) = [min(y{k}), max(y{k})]                    % Information
end
figure
hold on
for k = 2:numel(y)
    plot(t{k}, y{k})
end
hold off
xlabel('time(sec)'), ylabel('velocity(rad/sec)')
title ('pid control');
grid
It is necessary to create a system object to use the step funciton. The first step output is uniformly zero, and that causes problems with the plot. Start with the second one instead.
Also, use feedback rather than cloop (that has been deprecated).
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