franka-node-client

Python client for franka-node, the Zenoh node in front of franka-rs's target control. Drive a node-served Franka arm from a laptop, a workstation or a notebook, on Linux, macOS or Windows, without a byte offset, a sequence number, a timestamp or a lease token in your own code.

python -m pip install franka-node-client     # the same version as the node

From a checkout of the node's revision: python -m pip install ./crates/franka-node/python.

import franka_node

node = franka_node.Node("tcp/<node-host>:7447")         # or Node(session=my_zenoh_session)
with node.arm("fr3") as arm:                              # lease token + acquire, release on exit
    with arm.cartesian_targets() as t:                    # enable; stop on exit
        t.move_by([0.0, 0.0, 0.05])                       # +5 cm z, relative to the goal
        state = t.wait(timeout=5.0)                       # until the arm is there
        print(state.position, state.quaternion, state.refused)
    arm.gripper.move(0.04)

The verbs and conventions are those of the franka Python bindings: quaternions (x, y, z, w), rotation vectors in the base frame, O_T_EE as a (4, 4) matrix, robot mode names such as "move" and "user_stopped".

API

• Node(connect=None, *, session=None): close(), context manager, client_id, status(name=None, timeout=2.0) -> dict, arm(name) -> Arm. A borrowed session is used as it is configured and never closed.
• Arm: state(timeout=1.0) -> ArmState, on_state(callback) -> Subscription, acquire(timeout=3.0), release(), context manager, home(speed=0.2, *, episode=None, timeout=90.0), stop(timeout=10.0), recover(timeout=10.0), gripper, cartesian_targets(*, episode=None, max_velocity=0.1, max_angular_velocity=0.3, lead=0.03, angular_lead=0.15, rate=50.0) and joint_targets(*, episode=None, max_velocity=0.5, lead=0.15, rate=50.0).
• CartesianTargets / JointTargets: move_to, move_by, follow(chunk, dt), target(), state(), wait(timeout=None, ...), stop(), context manager.
• Gripper: move(width, *, wait=True, timeout=10.0), grasp(width, force, *, wait=True, timeout=10.0), homing(timeout=40.0), stop(), state(timeout=1.0) -> GripperState.
• franka_node.rotated(quaternion, rotation_vector).
• Errors: NodeError, and under it Refused (the node's reason verbatim), NodeTimeout, SessionEnded and ProtocolError.

What the client does for you (the lease, the keepalive, pacing under the node's max_step and max_lead, the anchor flag, wait, SessionEnded) is described on the book page Serve arms over Zenoh.

Tuning panel

The client installs franka-tuning-panel, a browser page for the live parameters of a running Cartesian impedance session: franka-tuning-panel --connect tcp/<node-host>:7447. It opens a Zenoh client session (--mode peer if you need a peer, which --listen requires), queries it with a --timeout of 1.0 s by default, and binds to loopback, reachable from another machine through an ssh tunnel. --expose-to-network (with --host 0.0.0.0) serves it on the network instead, which has no authentication of any kind: anyone who can reach the port can change any live parameter of a moving robot. See Tune a running controller for the tunnel, exposure, presets and limits.

The package version is the franka-rs workspace version. Apache-2.0.