Kuka Omnirob creeps when initial velocities are zero.

[Ashton2024]

I am using the physics engine bullet 2.78. I placed the kuka Omnirob in an empty scene and removed the code that sets initial velocities so in theory it shouldn't move. However when the simulation is started it slowly creeps forward. I noticed that other physics engines such as ODE doesn't have this creep. Also increasing the mass of the robot slows the creep.

I am just wondering if this is a just a short coming with using the bullet 2.78 physics engine or is there a way to prevent this creeping issue?

[coppelia]

Hello,

there are several causes for this:

• some joints are free, and due to the engine's way they compute things, there could be tiny imprecisions that creep up. Try to set e.g. a velocity mode for those joints, with target velocity 0 and a large torque (that will act as joint friction)
• have a look at design considerations 7 and 8 in particular: instability can arise from linked masses/inertias that differ too much

Cheers