How to use max inside Simulink Fcn block?

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?

[Ankit]

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]

> 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.

Answer 1

[Walter Roberson]

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.