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Modelica annotation derivative: noDerivative versus zeroDerivative

I have successfully used annotation(derivative) in Modelica functions. Now I have reached a point where I think I need to use zeroDerivative or noDerivative, but from the specification I just do not understand what is the difference, and when to use what.
https://specification.modelica.org/v3.4/Ch12.html#declaring-derivatives-of-functions
It seems zeroDerivative is for time-constant parameters??
Does somebody have a simple example?

Solution

  • Use zeroDerivative to refer to inputs that are non-varying, i.e. parameters or constant values.

    Use noDerivative for signals that do not have a derivative value. For example if an input signal comes from an external function.