No feedback for drive state from DifferentialBase_REB

Autonomous Machines Isaac Omniverse Isaac Sim
#1

Hi, i’m checking how differential base actually works on flat simulation ( Plane mesh with 2 degree angle ), i put there robot so it moves down on this downhill, but when i start navsim and create application - drive state that received in Isaac SDK side is 0 for both linear and angular velocities.

DifferentialBase_REB have relationship to main robot usd, and connected to left and right revolute joints accordingly, joints have articulation and Drive API there. TargetType is set to velocity , damping is 10000.

#2

Also one thing i mentioned - Differential base Simulator always provides different value for wheel base, and if for carter change is tiny like 0.000002 for value 0.62840X, mine is unpredictable.

#3

One of the things that changed in Isaac Sim 2020.2 was that differential base doesn’t automatically compute the wheel base and wheel radius anymore and requires the user to provide it.

If you create a new REB differential base component it should have those two values under the details panel that can be set. I am curious if this resolves your issue.

#4

@Hammad_M, Hmm, interesting, i don’t see those fields.
I’m using isaac-sim-headless version 2020.2.28133, but this fields not present in Details.

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From this point it looks like UI is lacking this fields, so probably it’s similar to topic i created about DriveAPI Omni.physx.ui extension lacking TypeAttribute in DriveAPI

#5

Also according to API documentation there is no methods to create this attributes for Differential base https://docs.omniverse.nvidia.com/py/isaac/source/extensions/omni.isaac/robot_engine_bridge/docs/index.html#omni.isaac.RobotEngineBridgeSchema.RobotEngineDifferentialBase
Only Holonomic one contains CreateWheelBaseAttr and CreateWheelRadiusAttr
https://docs.omniverse.nvidia.com/py/isaac/source/extensions/omni.isaac/robot_engine_bridge/docs/index.html#omni.isaac.RobotEngineBridgeSchema.RobotEngineHolonomicBase

When i try to manually add same to differential base it says: “object has no attribute…”

And actually WheelBase will add only response in terms of angular stuff.

#6

I have solved this problem.
Issue was that i have manually created Plane mesh, then applied collision API there. For some reason this is not sufficient to have differential base state feedback - it returns 0, like nothing is connected.

Solution was to create “Ground Plane” through Physics menu and set correct solvers in physics scene.

#7

Sorry about that @asakhon-AITHEON I was two days too early :)
We released isaac sim 2020.2.2 today which should allow you to set the wheel base and radius for that component.