function J= GA_PID(kpid,opt) Error: Function definition not supported in this context. Create functions in code file.

% GA03.m
% kpid: pid 參數
% opt=1: 畫出系統響應圖
function J= GA_PID(kpid,opt)
% 將受控體轉為數位模型
ts=0.01;
sys=tf(39,[1,74,0]);
dsys=c2d(sys,ts,'z');
[num,den]=tfdata(dsys,'v');
% 初值設定
u_1=0.0;u_2=0.0;
y_1=0.0;y_2=0.0;
e_1=0;e_2=0;
x=[0,0,0];
w1=0.9;
w2=0.01;
w3=200;
w4=2;
J=0;
s=0;
tu=0;
for k=1:1:100
    time(k)=k*ts;
    r(k)=1;
    u(k)=kpid(1)*x(1)+kpid(2)*x(2)+kpid(3)*x(3);
    % u 限定在 -10 ~ 10
    if u(k) >= 10
        u(k)=10;
    end
    if u(k) <= -10
        u(k)=-10;
    end
    y(k)=-den(2)*y_1-den(3)*y_2+num(2)*u_1+num(3)*u_2;
    e(k)=r(k)-y(k);
    % 算目標函數
    J=J+w1*abs(e(k))+w2*u(k)*u(k);
    ey(k)=y(k)-y_1;
    if ey(k) < 0
        J=J+w3*abs(ey(k));
    end
    % 算上升時間
    if y(k) > 0.95 & y(k) < 1.05 & s==0
        tu=time(k);
        s=1;
    end
    % 增量式數位 PID
    %x(1)=e(k)-e_1;
    %x(2)=e(k);
    %x(3)=e(k)-2*e_1+e_2;
    % 一般數位 PID
    x(1)=e(k);
    x(2)=x(2)+e(k)*ts;
    x(3)=(e(k)-e_1)/ts;
    % 更新 u(k-2),u(k-1)
    u_2=u_1;u_1=u(k);
    % 更新 y(k-2),y(k-1)
    y_2=y_1;y_1=y(k);
    % 更新 e(k-2),e(k-1)
    e_2=e_1;e_1=e(k);    
end
% 算目標函數
J=J+w4*tu;
% 畫出響應圖
if opt==1
    figure(1);
    plot(time,r,'r',time,y,'b');
    xlabel('Time(s)');ylabel('r,y');
end

Answer 1

[Geoff Hayes]

Lin - I observe that same error message if I copy your code and paste it into the MATLAB command window. The error message is telling you that you need to create a file named GA_PID.m and save the above code to that file. You would then call this function from the command line, passing in the correct inputs. See Declare function name, inputs, and outputs for more details.

[Lin Bo Yang]

how to passing in the correct input

i create a file named GA_PID.m and save the above code to that file but appear same error message

[Geoff Hayes]

how are you calling this function? what are you passing as inputs. please show the line of code that you have written to do this.

[Lin Bo Yang]

[Lin Bo Yang]

i call function J= GA_PID(kpid,opt) Convert a controlled body to a digital model

[Geoff Hayes]

It looks like you are copying and pasting the code from the m file into the command prompt/window. You just need to call the function and pass in the correct inputs. i.e.

>> J= GA_PID(kpid,opt) ;

where you have already defined the variables kpid and opt.

[Lin Bo Yang]

ok but it appear new error

Undefined function or variable 'opt'. this opt have to define?

sry I'm beginning in matlab haha:)

[Geoff Hayes]

yes you need to define the input parameters to this function. Look at the signature and initial comments:

% GA03.m
% kpid: pid 參數
% opt=1: 畫出系統響應圖
function J= GA_PID(kpid,opt)

Presumably, it is telling you what kpid and opt should be...they need to be passed into your function so that it can make use of them. You may want to contact the author of the code to see how they should be defined.