Simulink doubt -not have enough information to determine output sizes for this block

Please find attached the simulink diagram. The code in the main function block is as follows :

    function [xdot,xcapdot,dbar_dot,xdotr,ut] =fcn(x,xcap,dbar,xr,A,B,C,L,Kp,Kr,r,d,tau)
    y=C*x

    ycap=C*xcap

    dbar_dot=((B'/(B'*B))*L*(y-ycap))/(tau)

    xdotr=r-y

    k=Kp*xcap

    uf=-(k+Kr*xr)

    ut=-uf-dbar

    xdot=(A*x+B*ut+B*d)

   xcapdot=(A*xcap)+(B*uf)+(L*(y-ycap));

On running this simulink program, I am getting the following error

Simulink does not have enough information to determine output sizes for this block. If you think the errors below are inaccurate, try specifying types for the block inputs and/or sizes for the block outputs.
Inner matrix dimensions must agree. Function 'MATLAB Function' (#35.196.200), line 16, column 11: "B*ut"
Function 'MATLAB Function' (#29.235.239), line 18, column 19:
"B*uf"
Errors occurred during parsing of MATLAB function 'MATLAB Function'

The problem lies in the fact that simulink (Refer to attached pic) is considering x and xcap and xdot as 1*1 but they are actually (3*1). How should I correct this

What error am I doing? How should I correct them.

[Swarooph]

Reading the error, the first part clearly says

Undefined function or variable 'uf'

Where is this variable? It is neither computed inside the function nor an input to the function. It is in line 8 of the code pasted above.

Also, I don't think you have pasted the full function code. The second part of the error is pointing to line 12 but your code has only 8 lines?

[Rakesh Jain]

Actually I have given one line space. after every line of code for clarity. I have edited it above now. It is a full function code

[Rakesh Jain]

The problem lies in the fact that simulink (Refer to attached pic) is considering x and xcap and xdot as 1*1 but they are actually (3*1). How should I correct this

[Swarooph]

One thing you can try is to explicitly specify the sizes for these input variables in MATLAB function block editor's Edit Data option. Take a look at the documentation example here to see how to do this and then set the size appropriately.

Answer 1

[Souarv De]

Assign these values at the starting of your function

x = zeros(3,1);

xcap = zeros(3,1);

xdot = zeros(3,1);

[tret retret]

what is the correct way for assigning?

For example the output data is a vector [x1;x2], but the data are written to a file as [x1 x2].

If the program read out the file with

value = sscanf(file, '%g', [1,2])

and then makes a following assignment:

x1 = value(1,1)
x2 = value(1,2)
value=double([x1;x2])

I got the same error massage.

If the program makes an assignmnet as a scalar

x1 = value(1,1)
x2 = value(1,2)
value=0;

there is no error massage. But schould value be declared as a scalar?