How schould the matlab function be to hold an signal between two values?

I have a rising signal of a temperature. As long as the value has not reached a limit, e.g. 90%, "0" is to be displayed. If the value is reached, 1 is displayed. After that, the value can drop to e.g. 30% until "0" is output again. This is to achieve that the value remains between the two limits by the output of 0 and 1.

It is about a Simulink model and the code for it should be in a matlab-fct block.

I tried a lot with if-functions but i dont get it.

Answer 1

[Les Beckham]

Perhaps something like this in a MATLAB Function block?

function out = determineStatus(in)

persistent out
if isempty(out)
    out = 0;  % initial output value
end

% implement the hysteresis
if out = 0 && in > 90
    out = 1;
elseif out = 1 && in < 30
    out = 0;
end

end

[AF]

Thanks for your quick reply. I have tried it now but unfortunately it does not work (I can not garantee that it is me -.-). I will try to explain the problem again:

I have two inputs. One is a constant (A), the second increases with the time (B).

If B/A >0.9 then "1" should be output. Before "0".

If the once was reached, B/A can sink up to B/A=0.3. Then again "0" is to be outputed.

This is to control an engine, which then turns on and off and controls B.

[Fangjun Jiang]

Should be "if out == 0 && in > 90", "elseif out == 1 && in < 30"

With that in consideration, it is better to define "out" as true or false.

[Les Beckham]

@Fangjun Jiang

Of course you are right (== instead of =). Thanks for pointing that out. I thought about true/false vs. 1/0 but since OP specifically asked for 0 and 1, I went with that.

Also, good call on the relay block. I knew there was a simpler way to do this with a built-in block but I don't currently have Simulink to browse through the library.

@AF

Then feed B/A into the function and change 90 and 30 to 0.9 and 0.3.

[AF]

Thanks @Les Beckham,

it's working.

Answer 2

[Fangjun Jiang]

The Relay block does exactly that.

[AF]

Thanks!!!

Excactly what i was looking for