Hello, I have problem with my s-function

The errors are:

Error in 'Quad4/s-function' while executing MATLAB S-function 'quadrotor_sfcn', flag = 1 (derivatives), at time 0.0.

Dimensions of arrays being concatenated are not consistent.

And this is my s-function:

function [sys,x0,str,ts] = quadrotor_sfcn(t,x,u,flag)

switch flag

% Initialization %

case 0

sizes = simsizes;

sizes.NumContStates = 6;

sizes.NumDiscStates = 0;

sizes.NumOutputs = 3;

sizes.NumInputs = 3;

sizes.DirFeedthrough = 0;

sizes.NumSampleTimes = 1; % at least one sample time is needed

sys = simsizes(sizes);

%

% initialize the initial conditions

%

x0 = [30 0 -20 0 10 0];

%

% str is always an empty matrix

%

str = [];

%

% initialize the array of sample times

%

ts = [0 0];

%%%%%%%%%%%%%%%

% Derivatives %

%%%%%%%%%%%%%%%

case 1

sys=quadrotor(t,x,u);

%%%%%%%%%%%

% Outputs %

%%%%%%%%%%%

case 3

sys = [x(1) x(3) x(5)];

case{2,4,9}

sys=[];

otherwise

error(['unhandledFlag=', num2str(flag)]);

end

% systems details

function xdot=quadrotor(t,x,u)

Jx=4.856*10^-3;

Jy=Jx;

Jz=8.801*10^-3;

Jr=3.357*10^-5;

m=0.468;l=0.225;

g=9.81;a1=(Jy-Jz)/Jx;

a2=Jr/Jx;a3=(Jz-Jx)/Jy;

a4=Jr/Jy;a5=(Jx-Jy)/Jz;

b1=l/Jx;b2=l/Jy;b3=1/Jz;

x1dot=x(2);

x2dot=x(4)*x(6)*a1-x(4)*a2*g+u;

x3dot=x(4);

x4dot=x(2)*x(6)*a3+x(2)*a4*g+u;

x5dot=x(6);

x6dot=x(4)*x(2)*a5+u;

xdot = [x1dot x2dot x3dot x4dot x5dot x6dot];

Answer 1

[Chunru]

Try the following:

xdot = [x1dot x2dot x3dot x4dot x5dot x6dot]';