Step function returning NaN values.

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Pulkit Sharma 2018-3-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/387470-step-function-returning-nan-values

关闭： Stephen23 2018-3-10

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   T = A(i,1);
K = A(i,2);
if T==0
    T=0.001;
end
s = tf('s');
X= ((-1*s^3)+(-1.533*10e-17*s^2)+(0.0001996*s)+9.227*10e-22)/((s^5)+(-2.602*10e-18*s^4)+(0.00378*s^3)+(6.935*10e-21*s^2)+(1.267*10e-6*s));
Y= 0;
Z= ((-0.01994*s^2)+(-3.174*10e-5))/((s^5)+(-2.602*10e-18*s^4)+(0.00378*s^3)+(6.935*10e-21*s^2)+(1.267*10-6*s));
num=[(0.6*(T^2)*K) 4.8*K*T 9.6*K];
den=[8*T 0];
tfPID=tf(num,den);
itf=X+Y+Z;
jtf=itf*tfPID;
ftf=jtf/(1+jtf);
step(ftf);
dt = 20;
t = 0:dt:800;
e = 1 - step(ftf,t);
H = sum(t'.*abs(e)*dt);

My step function, for varying values of T and K, is giving nan values.I made sure that denominator does not become zero. This is affecting my values in H. How to avoid this? Please help.