How can I use the Matlab function ziegler() in m-file?

I have run the given program which include a function named ziegler(key,vars) as shown below-

s=tf('s');

G=10/(s+1)/(s+2)/(s+3)/(s+4)

step(G);

k=dcgain(G)

L=0.76; T=2.72-L;

[Gc1,Kp1]=ziegler(1,[k,L,T,10])

G_c1=feedback(G*Gc1,1);

As I try to run this program an error is showing as-

??? Undefined function or method 'ziegler' for input arguments of type 'double'.

Can anyone solve this problem...

Thanks!

Answer 1

[Wayne King]

You need to save that file, zeigler.m, in a folder that is on the MATLAB path, or just add the folder you have the M-file saved in to the path.

For example, assume you have the file saved in c:\mfiles, then use

   >>addpath 'c:\mfiles'

to add that to the MATLAB path, or use

   >>pathtool

Once you have added it, you should be able to enter

>>which ziegler

and see that MATLAB recognizes where the M-file is.

[ALOKE]

I have this method but it is still showing error as

*??? Attempt to execute SCRIPT ziegler as a function:

C:\Users\Aloke\Documents\MATLAB\ziegler.m*

can you please tell me that ziegler() belongs to which toolbox?

[Wayne King]

ziegler.m is not a MathWorks' function. How are you trying to call it from the command line?? Make sure it is on the path as you have done and then call it as you have done above

 >>[Gc1,Kp1]=ziegler(1,[k,L,T,10]);

[Walter Roberson]

Where did you obtain your ziegler.m from ?

[ALOKE]

I understand the your solution. Thanks

Answer 2

[Walter Roberson]

ziegler appears to be a routine in the File Exchange contribution http://www.mathworks.com/matlabcentral/fileexchange/2302-feedback-control-systems

Answer 3

[Shahzeb Awan]

add following two function in your path:-

function [Gc,Kp,Ti,Td,H]=ziegler(key,vars)
Ti=[]; Td=[]; H=1;
if length(vars)==4,
    K=vars(1); L=vars(2); T=vars(3); N=vars(4); a=K*L/T;
    if key==1, Kp=1/a;
    elseif key==2, Kp=0.9/a; Ti=3.33*L;
    elseif key==3 || key==4, Kp=1.2/a; Ti=2*L; Td=L/2; end
elseif length(vars)==3,
    K=vars(1); Tc=vars(2); N=vars(3);
    if key==1, Kp=0.5*K;
    elseif key==2, Kp=0.4*K; Ti=0.8*Tc;
    elseif key==3 || key==4, Kp=0.6*K; Ti=0.5*Tc; Td=0.12*Tc; 
    end
elseif length(vars)==5,
    K=vars(1); Tc=vars(2); rb=vars(3); N=vars(5);
    pb=pi*vars(4)/180; Kp=K*rb*cos(pb);
    if key==2, Ti=-Tc/(2*pi*tan(pb));
    elseif key==3||key==4, Ti=Tc*(1+sin(pb))/(pi*cos(pb)); Td=Ti/4; 
    end
end
[Gc,H]=writepid(Kp,Ti,Td,N,key);
end




function [Gc,H]=writepid(Kp,Ti,Td,N,key)
switch key
    case 1, Gc=Kp;
    case 2, Gc=tf(Kp*[Ti,1],[Ti,0]); H=1;
    case 3, nn=[Kp*Ti*Td*(N+1)/N,Kp*(Ti+Td/N),Kp];
        dd=Ti*[Td/N,1,0]; Gc=tf(nn,dd); H=1;
    case 4, d0=sqrt(Ti*(Ti-4*Td)); Ti0=Ti; Kp=0.5*(Ti+d0)*Kp/Ti;
        Ti=0.5*(Ti+d0); Td=Ti0-Ti; Gc=tf(Kp*[Ti,1],[Ti,0]);
        nH=[(1+Kp/N)*Ti*Td, Kp*(Ti+Td/N), Kp];
        H=tf(nH,Kp*conv([Ti,1],[Td/N,1]));
    case 5, Gc=tf(Kp*[Td*(N+1)/N,1],[Td/N,1]); H=1;
end
end