How to configure the articulated vehicle JSON file ? Including coordinates, units and other issues.

kyrie James

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Dec 27, 2022, 10:47:02 PM12/27/22

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Dear all,

First of all at this time to disturb you, I am sorry !

Happy New Year to you and the Chrono team !

I tried to import my own vehicle parameters by modifying the official JSON file ( articulated _ chassis ), but I encountered some problems :
( 1 ) When I import my own frame OBJ file, because my frame is the actual size, I need to reset the coordinates and related parameters, I do not know how to start, even do not know what the unit is. I hope to provide some explanations or comments. This really makes me a headache.

The powerful function of Chrono cannot be separated from the efforts of everyone in the team, and I am very interested in Chrono.

Thank you !

JC Denton

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Dec 29, 2022, 1:11:03 PM12/29/22

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There are some example obj files for vehicles in the chrono project such as the truck_chassis.obj or sedan_chassis_col.obj

If you open these up to compare to your obj file you should be able to apply the same scale and orientation when you export. You can also change the world up direction using ChWorldFrame::SetYUP for Y up, or ChWorldFrame::Set() to set the coordinate system to whatever you need.

Radu Serban

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Dec 30, 2022, 3:46:23 AM12/30/22

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I am not sure I understood your question exactly, but I assume you want to modify the sample articulated chassis vehicle model to represent your own vehicle.

Assuming you understand how vehicle modeling works in Chrono::Vehicle and what a subsystem template is (a parameterized generic model of a particular topology), you will need to adjust the various hard-point locations to match the geometry of your vehicle.

See https://api.projectchrono.org/manual_vehicle.html

In particular, you will need to properly set the locations of the suspension subsystems relative to the chassis reference frames (properly set “Suspension Location” in ACV_Vehicle.json). Similarly, you will need to properly adjust “Rear Connector Location” in ACV_FrontChassis and “Front Connector Location” in ACV_RearChassis. Together, these parameters should match the actual wheelbase of your vehicle. Then, you need to properly position the spindle in ACV_RigidSuspension.json to obtain the actual wheel track (track width) of your vehicle.

In general, you must go through all JSON specification files and change *all* parameters to match the geometry, mass properties, and other settings to correspond to the measurements of the vehicle you are trying to model.

--Radu

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kyrie James

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Dec 30, 2022, 7:55:06 AM12/30/22

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Thank you and the team busy in reply to me ! I will follow your advice to see the relevant examples, and continue to ask you for advice.