If the element of the bus is put as an input to the matlab function

We designed simulink as shown in the picture above.

Matlab function wrote the following code, but it doesn't work.

How can we solve this error?

function y = fcn(u)

element.u1 = u.x;
element.u2 = u.y;
element.u3 = u.dy/dt;

y = 4 * element.u1 - 4 * element.u2 - 4 * element.u3;
end


Error 
Property 'x' is not recognized as valid.

Function 'MATLAB Function' (#36.34.37), line 3, column 14:
"u.x"

Answer 1

[Yash Sharma]

Hi 가은 최,

I understand that you have elements in a bus, and you want to access these elements inside a MATLAB function block.

The DOT(.) notation you are currently using to access elements inside MATLAB function block only works with non-virtual busses and by default the Bus Creator block outputs virtual bus. To access elements from virtual bus you can use indexing. Change your code as follows:

function y = fcn(u) 
    element.u1 = u(1);   % x 
    element.u2 = u(2);   % y  
    element.u3 = u(3);   % dy/dt 
    y = 4 * element.u1 - 4 * element.u2 - 4 * element.u3; 
end 

You can also convert your virtual bus to non-virtual bus by using “signal conversion” block, you will have to create Simulink bus object first.

Refer to the documentation below to get more information on how to convert virtual bus to nonvirtual bus.

• Signal Conversion: https://www.mathworks.com/help/simulink/slref/signalconversion.html
• Simulink.Bus.createObject: https://www.mathworks.com/help/simulink/slref/simulink.bus.createobject.html