id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
4455	Unreasonable high deviation between imported FMU and original model	Bernhard Thiele	Lennart Ochel	"I wrote an exercise for exporting and importing model-exchange FMUs using OpenModelica and observed rather large deviations between the original model and the imported FMU which I can't explain. Exercise and underlying model are attached to this ticket.

The model below feeds the original PI controller with the same input as the FMU wrapped PI controller.

[[Image(screenshot1.png)]]

If I simulate that using standard settings (dassl, tolerance 1e-6) and plot the respective outputs, I get following result:

[[Image(plot1.png)]]

It is possible to get closer if one manually sets the step size and makes it very small (e.g., Euler with step size 0.0001s). The strange thing is, that the FMU is rather sensitive to changing the step size, e.g., for 0.001s it will be significantly different than for 0.0001s, while the result for the Modelica PI will not change significantly when doing this change."	defect	closed	high	Future	FMI		fixed		Lennart Ochel Adrian Pop