Kristine has received some questions regarding how to run this case. Improve the readme file.

Gunnerus DP should have a plot config file

Update configuration to use OSP-IS

The DP controller is unstable for the construction vessel example case. The solver is using too big time steps.

XML files should be updated to:

<OspModelDescription xmlns="https://open-simulation-platform.com/OspModelDescription/1.0.0" version="1.0">

The current PlotConfig.json for DPShip has the following variable:

{
"simulator": "Room2",
"variable": "q[1]"
}

which is not valid, as Room2 is not part of the DPShip config. When loading in the demo-app, a warning/notification is displayed in the terminal.

The documentation for the gunnerus-dp case in gunnerus-dp/doc/documentation.pdf has several invalid cross references. The text

Error! Reference source not found.

is shown instead of the actual cross references

There seems to be some behavior of the tutorial FMUs (mass-spring-damper system) that is not according to how the corresponding physical system would behave. It is very noticeable for some parameter settings, but I think it also slightly influences many other simulations where it is not as noticeable. This happens both when I download the FMUs on this repo and using the ones that are on STC. I think this is because the implementation of the damper is wrong.

This happens when the damperCoefficient is set high and the springStiffness is set to a low value. This makes it so the dominating force in the system is the damping force. In the physical system this would just make the mass slowly move toward the steady state position.

The figure below is what is simulated by STC with the parameters listed at the bottom. The green function is the x position of the mass. In this simulation the mass moves 6 kilometers in under 15 seconds! This must be unrealistic with the parameters described at the bottom.

As mentioned I think this is because the damper is implemented wrong. In the plot the x velocity of the mass is in blue and the damper force in the x direction is in orange. In the beginning of the simulation the damper force is in the same direction as the velocity (both positive). This cases the velocity to increase with again increases the damper force and causes a positive feedback loop. This causes the mass to accelerate incredibly fast in the positive x direction. This positive feedback loop is only stopped when the mass is far enough from the starting position that the spring force is stronger than the damper force causing the x velocity to decrease.

The problem with the damper force calculation is that it makes it possible for the damper force to be in the same direction as the velocity.

I have an idea of what might be wrong with the implementation, but I do not know exactly what the correct implementation would be.

Parameters used in simulation:

• springStiffness: 1
• damperCoefficient: 10
• initialPositionX: -10
• initialPositionY: -10
• initialVelocity: 10
• initialVelocity: 10
• The rest are just the default values (I don't think they matter much for showing the problem)

Several of the _OspModelDescription.xml files contain a unit definition like the following:

<Unit name="m">
    <BaseUnit kg="1" m="1" s="0" A="0" K="0" mol="0" cd="0" rad="0" factor="1.0" offset="0.0"/>
</Unit>

Here, the correct thing would be to set kg="0".

This definition is used in the following cases, as far as I can tell:

• dp-ship
• gunnerus-dp
• open-modelica-thruster

The configuration files for the Gunnerus DP demo case should follow the official OSP-IS standard and pass the OSP IS validator.

Hello,

me and my colleagues are trying to simulate the Gunnerus ship for research purposes and wanted to simulate the waypoint-following demo case. We already simulated other demo cases succesfully, for example "gunnerus-dp" or "construction-vessel". But when loading the waypoint-following demo case we all get the same error:

Cosim Demo App:
Could not create execution from OspSystemStructure.xml file: No resolvers available to handle URI: fmu-proxy://localhost:9090?guid=b71f76f7-b51e-40d5-affb-f63905622e2b

Cosim App:
error: No resolvers available to handle URI: fmu-proxy://localhost:9090?guid=b71f76f7-b51e-40d5-affb-f63905622e2b

As can be seen we tried to simulate it with the demo app and also with the cosim command line interface. We also neither changed the demo case after downloading it nor the cosim demo app or the cosim app.

Maybe someone had the same issue or can direct us towards where the cause of this issue may be? We would really appreciate a response as we are really grasping at straws with this error code.