Regarding Gazebo RTF becoming low after increasing joints in the simulation

I am working on a simulator environment in Gazebo 9.0.0 which have multiple joints in the sdf world. This causes RTF to drop down a huge number. I observed reducing the joints improves RTF I tried tweaking gazebo physics parameter: step size, update rate and iters to improve RTF but this causes instability in the simulation world, All the models starts vibrating a lot and also behaves weird in different pc. How can i improve the RTF without instability, Is there a limitation that Gazebo sim highly depends on joint numbers?

Asked by Saail on 2021-07-07 09:01:54 UTC

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Answers

Hello. I also had troubles with a low RTF with a lot of joints (actually, I think that the real issue is more the number of links/models in the world than the number of joints).

You could try to remove some unecessary collision checks (for example if you know that two given links won't collide anyway, or if a given collision is not relevant for your use case) with a collision bitmask tag, or the selfCollide tag for example. Also, try to use simple geometries for collision (such as sphere, box, cylinder) instead of meshes.

Finally, for the stability issue, you can try to add a bit of damping in the unstable joints, and enable the implicitSpringDamper tag in joints, wich is a more stable implementation of damping (see here in " Elements For Joints" part for implicitSpringDamper tag).

Asked by Clément Rolinat on 2021-07-12 03:05:27 UTC

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Thanks for your reply. RTF dropping is due to more number of joints. I verified the issue by reducing the joints and making link static.

In the simulation environment, I have made all collision simple (by using simple geometry: cuboid, sphere and cylinder). Well I ll try bitmask tag once.

Instability occurs when i change physics parameter to increase RTF.Also implicitSpringDamper tag is used along with continuous joints.Most of the joints in my simulation is fixed j

Asked by Saail on 2021-07-13 00:00:26 UTC

out of curiosity, what are you trying to simulate that requires a lot of fixed joints ? Maybe you could represents with a single link some group of links with fixed joints ?

Asked by Clément Rolinat on 2021-07-13 02:46:14 UTC