root-joint-pinned#

Code

RC.009

Validator

CheckStage

Compatibility

Tags

Summary#

The root joint (the first target of isaac:physics:robotJoints) must be pinned for robot types that require a fixed base (e.g. Manipulator, End Effector) and must not be pinned for other robot types.

Description#

The root joint is the first joint in the isaac:physics:robotJoints relationship. A joint is considered pinned when one of its two bodies is not a rigid body (e.g. body is the world or a non-physics prim). For types such as Manipulator and End Effector, the root joint must be pinned (fixed base). For all other valid robot types, the root joint must not be pinned.

Why is it required?#

  • To match simulation expectations for fixed-base vs mobile robots

  • To prevent incorrect physics behavior (e.g. floating manipulators or incorrectly fixed mobile bases)

  • To keep asset configuration consistent with the declared robot type

Examples#

# Valid: Manipulator with pinned root (body0 or body1 is non-rigid / world)
over "Robot" (
    prepend apiSchemas = ["IsaacRobotAPI"]
)
{
    token isaac:robotType = "Manipulator"
    rel isaac:physics:robotJoints = [ </joints/root>, </joints/joint_1> ]
    rel isaac:physics:robotLinks = [ </links/base>, </links/link_1> ]
}
# Root joint: body0 = world (or non-rigid), body1 = base link -> pinned

# Invalid: Manipulator with root joint not pinned (both bodies are rigid)
# Root joint must have one body that is world or non-rigid for Manipulator/End Effector

# Invalid: Non-manipulator type with root joint pinned
# For robot types other than Manipulator and End Effector, root must not be pinned

How to comply#

  • Ensure the default prim has isaac:robotType and isaac:physics:robotJoints (see robot-type and robot-schema).

  • For Manipulator and End Effector: make the root joint pinned by having one of its physics:body0 or physics:body1 targets be the world or a prim without RigidBodyAPI.

  • For all other robot types: ensure both bodies of the root joint are rigid bodies (root joint not pinned).

For More Information#