Discritization of transfer function

uttam gavand

2019 6 5

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Namaste,

I want to implement higher order transfer function in microcontroller. I have used 'c2d' command with all available options but not getting satisfactory results.

So I want to use Al-alaoui transform (s=[8(1-z^-1)]/[7*T(1+(1/(7*z)))] where T is 0.1sec in my program) into my program. I have used symbolic toolbox but not getting simplified results.

Can anyone help me

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David Wilson 2019-6-5

在 MATLAB Online 中打开

Here's my take on your problem: I've invented an arbitrary continuous TF (since you neglected to tell us what you are dealing with), and then discretised it in a variety of ways, including your "AA" method. Results are relatively poor, except at small sample times.

tau = 2; zeta = 0.5; 
Gc = tf([5 2],conv([6 5 4],[tau^2 2*tau*zeta 1])) % continuous TF 
Ts = 1; % sampling time [s] 
B = cell2mat(Gc.Numerator);
A = cell2mat(Gc.Denominator); 
G = poly2sym(B,s)/poly2sym(A,s); 
syms s z T
Gd = subs(G,s,8*(1-1/z)/(7*T*(1+1/7/z))) 
Gd = subs(Gd,T,Ts); [N,D] = numden(Gd); Gd1 = tf(sym2poly(N), sym2poly(D),Ts);
%Gd = subs(Gd2,T,Ts); [N,D] = numden(Gd); Gd2 = tf(sym2poly(N), sym2poly(D),Ts);
Gd2 = c2d(Gc,Ts,'zoh'); 
Gd3 = c2d(Gc,Ts,'foh'); 
Gd4 = c2d(Gc,Ts,'tustin'); 
step(Gc, Gd1, Gd2, Gd3, Gd4)
legend('G_c','AA')