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modelica / ModelicaStandardLibrary

Free (standard conforming) library to model mechanical (1D/3D), electrical (analog, digital, machines), magnetic, thermal, fluid, control systems and hierarchical state machines. Also numerical functions and functions for strings, files and streams are included.
https://doc.modelica.org
BSD 3-Clause "New" or "Revised" License
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ContinuousClock has insufficient smoothness for many models in ModelicaTest.Tables #4295

Closed henrikt-ma closed 4 months ago

henrikt-ma commented 5 months ago

This affects many models, but let's talk about Modelica-4.1.0/regression/Tables/CombiTable1Ds/Test3 to make things concrete.

After Modelica.Blocks.Sources.ContinuousClock was modified in https://github.com/modelica/ModelicaStandardLibrary/pull/4150, the model no longer builds in System Modeler, since the input to the table isn't consider sufficiently differentiable to compute the second order derivative of the output.

Before the change to ContinuousClock, the input to the block was a piecewise smooth signal, and by not switching between the if-equation during continuous-time integration, there was no lack of smoothness.

Would it make sense to replace the ContinuousClock source blocks with something more differentiable?

beutlich commented 4 months ago

Would it make sense to replace the ContinuousClock source blocks with something more differentiable?

Would Modelica.Blocks.Sources.RealExpression(y=time) be of rescue?

henrikt-ma commented 4 months ago

Would it make sense to replace the ContinuousClock source blocks with something more differentiable?

Would Modelica.Blocks.Sources.RealExpression(y=time) be of rescue?

It would save System Modeler, but let's not worry about that; we'll fix that on the tool side, as decided (but still not noted) in the last MAP-Lib release preparation meeting.

henrikt-ma commented 4 months ago

Closing, as it was concluded that this is a tool issue. I'll open another issue (#4325) regarding the lack of excitation in the second order derivative.