State derivatives returned by S-function 'BUCKchap3_6plant' in 'BUCKchap3_6/S-Function' during flag=1 call must be a real vector of length 2

error：State derivatives returned by S-function 'BUCKchap3_6plant' in 'BUCKchap3_6/S-Function' during flag=1 call must be a real vector of length 2。

function [sys,x0,str,ts]=BUCKchap3_6plant(t,x,u,flag) switch flag, case 0 [sys,x0,str,ts]=mdlInitializeSizes; case 1 sys=mdlDerivatives(t,x,u); case 3 sys=mdlOutputs(t,x,u); case {2, 4, 9 } sys = []; otherwise error(['Unhandled flag = ',num2str(flag)]); end

function [sys,x0,str,ts]=mdlInitializeSizes sizes = simsizes; sizes.NumContStates = 2; sizes.NumDiscStates = 0; sizes.NumOutputs = 2; sizes.NumInputs = 1; sizes.DirFeedthrough = 1; sizes.NumSampleTimes = 0; sys=simsizes(sizes); x0=[0 0]; str=[]; ts=[];

function sys=mdlDerivatives(t,x,u) L=1e-3; R=20; C=1000e-6; Vin=50;

sys(1)=(-x(2)+Vin*u(1))/L; sys(2)=x(1)/C-x(2)/C/R;

function sys=mdlOutputs(t,x,u) sys(1)=x(1); sys(2)=x(2);

[Walter Roberson]

Just before

sys(1)=(-x(2)+Vin*u(1))/L; sys(2)=x(1)/C-x(2)/C/R;

Add

assert(all(imag(u)==0), 'u is imaginary or nan')

Answer 1

[FUN S]

Thank you very much

Answer 2

[FUN S]

By adding assert(all(imag(u)==0), 'u is imaginary or nan'); before sys(1)=(-x(2)+Vin*u(1))/L; sys(2)=x(1)/C-x(2)/C/R;, but the problem remains the same. The following I gives a control model (BUCKchap3_6ctrl) and control object(BUCKchap3_6plant) code.

function [sys,x0,str,ts]=BUCKchap3_6plant(t,x,u,flag)
switch flag,
    case 0
        [sys,x0,str,ts]=mdlInitializeSizes;
    case 1
        sys=mdlDerivatives(t,x,u);
    case 3
        sys=mdlOutputs(t,x,u);
    case {2, 4, 9 }
        sys = [];
    otherwise
        error(['Unhandled flag = ',num2str(flag)]);
end

function [sys,x0,str,ts]=mdlInitializeSizes
sizes = simsizes;
sizes.NumContStates = 2;
sizes.NumDiscStates = 0;
sizes.NumOutputs = 2;
sizes.NumInputs = 1;
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 0;
sys=simsizes(sizes);
x0=[0 0];
str=[];
ts=[];

function sys=mdlDerivatives(t,x,u)
L=1e-3;
R=20;
C=1000e-6;
Vin=50;
% ut = u(1);
assert(all(imag(u)==0), 'u is imaginary or nan');
sys(1) = -x(2)/L + Vin / L * u(1);
sys(2) = x(1)/C - x(2) /C / R;
% sys(1)=(-x(2)+Vin*u(1))/L; % sys(2)=x(1)/C-x(2)/C/R;

function sys=mdlOutputs(t,x,u)
sys(1)=x(1);
sys(2)=x(2);

function [sys,x0,str,ts]=BUCKchap3_6ctrl(t,x,u,flag)
switch flag,
    case 0,
        [sys,x0,str,ts]=mdlInitializeSizes;
    case 3,
        sys=mdlOutputs(t,x,u);
    case {1, 2, 4, 9 }
        sys = [];
    otherwise error(['Unhandled flag = ',num2str(flag)]);
end

function [sys,x0,str,ts]=mdlInitializeSizes
sizes = simsizes;
sizes.NumDiscStates = 0;
sizes.NumOutputs = 1;
sizes.NumInputs = 5;
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 0;
sys=simsizes(sizes);
x0=[];
str=[];
ts=[];

function sys=mdlOutputs(t,x,u)
L=1e-3;
R=20;
C=1000e-6;
Vin=50;
wn=210;
k21=wn;
k22=wn;
Vref=u(1);
e=u(2);
de=u(3);
x1=u(4);
x2=u(5);
Q=-k22*e-k21*de;
f=L*x1/C/R;
ut=(f+(1-L/C/R/R)*x2+C*L*Q)/Vin;
sys(1)=ut;

[Aliff Ashraff]

hello can u solve the problem?

[Walter Roberson]

"Fun S": I reformatted your code to make it readable. Please check it to ensure that I correctly interpreted the comment positions.