Why vehicle floating in the sky?

[Tong Xu]

Hello, I have compiled chrono version 8 from source code by Ubuntu20.04. I also created terrain which consisted by rigid and deformable terrain according to multiple concatenating patches. But why sometimes vehicle floats in the sky. Is this because of the chrono code?

Thanks a lot

[Luning Bakke]

Hello,

Does your vehicle still float in the sky if you use only one type of terrain? Either rigid or deformable? 

Also, what you mean by "sometimes vehicle floats in the sky"? Does that mean it drives fine for a while, then it floats? Or it means, you initialize the problem differently, sometimes it drives fine on the ground, but sometimes it floats? 

Thank you,

Luning

[Tong Xu]

Thanks for asking. When I am only using one deformable terrain or different combined rigid terrain, it will be ok. If I combine several different types of deformable textures or deformable textures with rigid textures by multiple patches, It will definately floating in the sky. I doubt that it because of the AddMovingPatch() function? And I compile by this source code from gym-chrono repo: https://github.com/zzhou292/chrono/tree/feature/robot_model. Thanks a lot.

Best regards,

Tong 

[dr.ratz...@gmail.com]

Does this problem persist with the current version of chrono?

[Tong Xu]

Sry, I don't test now. It seems that provided conda packages version 8.0 or 9.0 are working on Ubuntu22.04. I only have Ubuntu20.04 now. 

[Radu Serban]

Hi Tong,

 

The reason for vehicles “floating” in certain areas is most likely due to the fact that they are actually interacting with the virtual SCM grid from a nearby deformable terrain patch. See the following discussion for details: https://groups.google.com/g/projectchrono/c/KfVffIkvfRs. As I mentioned there, I intend to provide support in Chrono for the type of mixed terrain you are interested in, but that may not be available for a while (I don’t have the bandwidth to work on this right now). In the meantime, I pushed an intermediate fix which allows the user to restrict the computational domain of an SCM terrain patch. See the new function SCMTerrain::SetBoundary and, as an illustration of its use, uncomment line 260 in demo_VEH_SCMTerrain_WheeledVehicle .

 

Of course, to use this new feature, you would need to start using the latest Chrono code.

Note that there is no direct limitation based on the Ubuntu distro version. All that matters is the version of the compiler. Assuming you use GCC, the version included with Ubuntu 20.04 is GCC v. 9.3. That should be good enough to build the latest Chrono code and, and if it is not, it’s possible to upgrade your compiler version in Ubuntu 20.04.

 

Regardless, I strongly encourage you to start using a newer version of Chrono (ideally, the latest in the ‘main’ git branch) as there were quite a few changes, improvements, and bug fixes since Chrono v. 8.

 

--Radu

Thanks a lot

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[Tong Xu]

Hi Radu,

Thanks for reply! The default glibc version for Ubuntu20.04 is 2.31. However instead of installing pychrono from source, now I install it from conda and I met the error as following and my GCC version is 9.4. Any way to solve it and I think upgrading glibc version is likely to break os?

Python 3.9.21 | packaged by conda-forge | (main, Dec  5 2024, 13:51:40)
[GCC 13.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pychrono
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/tong/miniconda3/envs/chrono/lib/python3.9/site-packages/pychrono/__init__.py", line 54, in <module>
    from .core import *
  File "/home/tong/miniconda3/envs/chrono/lib/python3.9/site-packages/pychrono/core.py", line 10, in <module>
    from . import _core
ImportError: cannot import name '_core' from partially initialized module 'pychrono' (most likely due to a circular import) (/home/tong/miniconda3/envs/chrono/lib/python3.9/site-packages/pychrono/__init__.py)
>>> import _core
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.32' not found (required by /home/tong/miniconda3/envs/chrono/lib/python3.9/site-packages/_core.so)