primitive-agilex-piper-description-rbnx

Robonix package wrapping the AgileX Piper arm URDF + robot_state_publisher. Stand-in for system.soma (URDF + RSP), which is on robonix’s v0.2 roadmap. Until soma ships that responsibility natively, this package owns the joint-driven TF tree for the Piper arm.

Catalog name: robonix.primitive.agilex.piper.description.

What this package publishes

base_link → link1 → link2 → link3 → link4 → link5 → link6 (→ gripper links)

driven from /arm/joint_states_single via robot_state_publisher.

This package does not publish camera hand-eye calibration. In the current vertical-grasp deploy, grasp_pose consumes rbnx-boot/hand-eye-data/2d_homography.npy to map RGB bbox pixels directly into arm/base_link XY, then combines that with the configured desktop height.

Boot ordering

This package needs to boot after piper_ctl (which publishes /arm/joint_states_single). Without joint feedback, RSP stays quiet on /tf and the arm appears “frozen at zero” in RViz. The deploy manifest enforces this by listing piper_ctl before piper_description under primitive:.

Independent of orbbec_camera; the camera stream is consumed later by llm_detect and grasp_pose, while this package only publishes the arm TF subtree.

Capability surface

Empty on purpose:

capabilities: []

The package registers a provider on atlas (so rbnx boot proceeds through the primitive block) but declares no routed contracts.

TF is a global ROS 2 side-channel — every tf2-aware node joins /tf + /tf_static automatically — so atlas-routing it would only add indirection. With capabilities: [], rbnx boot‘s spawn_and_init walks wait_for_registration → finds driver_contract=None → marks the package ACTIVE without trying to drive INIT / ACTIVATE.

Driver-init lifecycle

There is no Driver(CMD_INIT) handler — the package skips CMD_INIT entirely and is considered “up” the moment it registers on atlas. start.sh launches robot_state_publisher directly with the vendored Piper URDF, remapping joint_states → /arm/joint_states_single.

It is independent of primitive-agilex-piper-handeye-rbnx and primitive-orbbec-dabai_dcw-camera-rbnx; those publish disjoint data or TF subtrees.

Frame names — NOT prefixed with `arm/`

The vendored upstream URDF uses bare names (base_link, link1… link6). We keep the upstream names verbatim — that matches what primitive-agilex-piper-arm-rbnx actually publishes in JointState.name = ['joint1', 'joint2', ..., 'joint6', 'gripper'].

⚠️ Future moving-platform conflict: if the Piper ever sits on a Ranger Mini / mobile chassis whose own URDF also defines base_link, the two TF roots collide. Resolution then will be to fork the URDF and add a tf_prefix (e.g. arm/) to all link/joint names, AND update primitive-agilex-piper-arm-rbnx‘s JointState.name accordingly. For the current fixed-arm grasp deploy no chassis is involved, so collision is impossible.

Layout

primitive-agilex-piper-description-rbnx/
├── package_manifest.yaml        # capabilities: []
├── launch/
│   └── piper_urdf.launch.py     # robot_state_publisher + remap
├── scripts/
│   ├── build.sh                 # rbnx codegen + colcon build
│   ├── start.sh                 # source ROS, exec atlas_register_and_launch.py
│   └── atlas_register_and_launch.py
└── src/
    └── piper_description/       # vendored upstream (URDF + meshes only;
                                 # launch/, rviz/, mujoco_model/ stripped)
        ├── package.xml
        ├── CMakeLists.txt
        ├── meshes/              # *.STL (~9 MB)
        └── urdf/                # piper_description.urdf (with-gripper, default)
                                 # piper_no_gripper_description.urdf (override via env)

Build

scripts/build.sh does two things, both fast:

rbnx codegen — generates atlas_pb2 / atlas_pb2_grpc Python stubs for scripts/atlas_register_and_launch.py.
colcon build --packages-select piper_description — installs URDF + meshes under rbnx-build/ws/install/piper_description/share/ so the URDF’s package://piper_description/meshes/... references resolve at RViz / MoveIt time. RSP itself does not need this for TF computation, but downstream visualisers do.

Config

This package has no Driver(CMD_INIT) handler, so the per-package config: block in the deploy manifest is ignored. Configuration comes from the top-level env: block instead:

Env	Meaning
`PIPER_URDF_PATH`	Absolute path to the URDF variant to use. Defaults to the vendored with-gripper URDF.
`ROBONIX_ATLAS`	Atlas gRPC endpoint. Defaults to `127.0.0.1:50051`.

Example override to switch to the no-gripper variant:

env:
  PIPER_URDF_PATH: ${RBNX_INVOCATION_CWD}/../packages/piper_description/src/piper_description/urdf/piper_no_gripper_description.urdf

Choosing the URDF variant

Variant	Joints	When to use
`piper_description.urdf` (default)	joint1..joint8	`gripper_exist: true` in piper_ctl config (`skill-pick-rbnx` uses gripper)
`piper_no_gripper_description.urdf`	joint1..joint6	`gripper_exist: false` (rare; manual EE swap)

Override via PIPER_URDF_PATH, or by editing atlas_register_and_launch.py::_resolve_urdf_path.

Run standalone

bash scripts/build.sh
ROBONIX_ATLAS=127.0.0.1:50051 \
    bash scripts/start.sh

The script exits if atlas is unreachable (5s RPC timeout). Once the launch is running, /tf should carry base_link → link6 iff primitive-agilex-piper-arm-rbnx is also up and publishing JointState.

Verification

rbnx caps | grep piper_description
# Expected: piper_description provider, no caps

ros2 run tf2_ros tf2_echo base_link link6
# Should report a transform that moves when you ros2 topic pub to
# /arm/pos_command or wiggle the arm by hand.

# Optional: if primitive-agilex-piper-handeye-rbnx is up too, the chain
# base_link → link6 → camera_color_optical_frame should resolve:
ros2 run tf2_ros tf2_echo base_link camera_color_optical_frame

Vendor / upstream

src/piper_description/ is a verbatim subset of agilexrobotics/piper_ros src/piper_description/, with the following stripped (none needed for TF publishing in a robonix deploy):

launch/ — upstream launches add joint_state_publisher_gui + RViz, both inappropriate for a headless deploy.
rviz/ — display config; users who want RViz should write their own outside this package.
mujoco_model/ — sim-only; not in pipeline.

License

This package: MulanPSL-2.0. Vendored URDF + meshes inherit upstream piper_ros‘s licensing (upstream package.xml declares “TODO”; the practical assumption is the non-commercial Solidworks export defaults — consult AgileX before redistribution).