How to use max inside Simulink Fcn block?

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winkmal
winkmal 2019-9-24
评论： winkmal 2019-9-24
In my Simulink sheet, I have a Fcn block which does a very simple calculation from its input:
u(36)/u(38)*u(39)
Since the input can sometimes assume (unphysical) negative values, I wanted to exlude them:
max(0, u(36)/u(38)*u(39))
But as soon as I call the simulation, I get
The expression: max(0, u(36)/u(38)*u(39))
in '.../.../...'
has a syntax error
So does that mean that max is undefined inside Fcn blocks? If so, what could I use instead?
  2 个评论
Ankit
Ankit 2019-9-24
Fcn Block allows following mathematical function
Mathematical functions — abs, acos, asin, atan, atan2, ceil, cos, cosh, exp, floor, hypot, log, log10, power, rem, sgn (equivalent to sign in MATLAB®), sin, sinh, sqrt, tan, and tanh.
Just to confirm are you referring this block?: Fcn
winkmal
winkmal 2019-9-24
> Just to confirm are you referring this block?: Fcn
Yes, indeed. I also noticed that the max function is not part of the list of available (mathematical) functions.

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采纳的回答

Walter Roberson
Walter Roberson 2019-9-24
Math Function Blocks https://www.mathworks.com/help/simulink/slref/mathfunction.html do not accept expressions: they only accept keywords.
You can build max() against a constant with https://www.mathworks.com/help/simulink/slref/minmax.html or with Saturate blocks.

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