getlinio command returns empty array

I am trying to find the analysis points for existing simulink model 'rct_CSTR_OL'. However the following command returns an empty array

>> sys = 'rct_CSTR_OL'

sys =

rct_CSTR_OL

>> open_system(sys)
>> getlinio(sys)

ans =

       []

However the gain scheduling example uses the analysis point with the following command

% Linearize process dynamics at trim conditions
G = linearize('rct_CSTR_OL', 'rct_CSTR_OL/CSTR', op);

where op is the operating point created with operspec command.

I do not understand the effect of using the subsystem name 'rct_CSTR_OL/CSTR' in the above command because all examples of linearize command use linio to create analysis point.

When I try to replace the second argument in linearize with the following code

io(1)= linio('rct_CSTR_OL/CSTR',3, 'input');
io(2)= linio('rct_CSTR_OL/CSTR', 1, 'output');
io(3)= linio('rct_CSTR_OL/CSTR', 2, 'output');
G = linearize('rct_CSTR_OL', io, op)

it throws the following error

For linear analysis, the specified I/Os must map to a valid set of ports of a Simulink block. Port 3 on the "rct_CSTR_OL/CSTR" block
is no longer valid.

My questions:

1. What analysis points are being used in the first code fragment

2. How can I create a linio object to achieve the same effect as done by the first fragment

Kindly let me know. Thanks.

[I-Tsun Wang]

I had the same error

Answer 1

[Valentina Bugueño Olivos]

Is it is a Simulink block you must identify the lines as inputs or outputs.

You can do it by clicking right in the line --> click linear analysis points ---> select the type of signal (input perturbation/output measurement)

Now when you use getlinio it won't give yoy an empty array

:)