OpenArm Driver

A Python library for controlling OpenArm, using OpenArm CAN.

Quick start

TODO

Install

pip install openarm-driver

Sample usage

import openarm_driver

arm = openarm_driver.SingleArmDriver("right_arm")
# You can also use your own config file as well.
# config = openarm_driver.Config("/path/to/config.yaml")
# arm = openarm_driver.SingleArmDriver("right_arm", config)

try:
    arm.start()
    while True:
        cur_position = arm.fetch_position()
        # Some process to calculate the next steps.
        next_positions = inference(cur_position)
        for next_postion in next_positions:
            arm.smooth_move(next_postion, hz=50, duration=1)
            # you can use simple command as well (Please be careful not to move the arm too much).
            # arm.send_position(next_postion)
finally:
    arm.stop()

Config

Please refer to the default configuration.

Bundled configurations

The package bundles several configurations. Pass a bundled name to Config() to select one, or pass a path to use your own file:

import openarm_driver

openarm_driver.available_configs()
# ['openarm_cell', 'openarm_cell_higher_pd', 'openarm_pedestal']

config = openarm_driver.Config("openarm_pedestal")
arm = openarm_driver.SingleArmDriver("right_arm", config)

# Or make it the default for every driver created afterwards.
openarm_driver.set_default_config(config)

Name	Description
openarm_cell	Default. OpenArm mounted on the cell frame.
openarm_cell_higher_pd	Same as openarm_cell with higher PD gains.
openarm_pedestal	OpenArm mounted on the pedestal (zero joint offsets).

The default safety checks run in this order:

1. JointPosChecker clips commands to joint position limits.
2. JointDeltaPosChecker rejects excessive single-command jumps.
3. JointVelocityChecker limits the remaining command using the elapsed time.

joint_velocity_limits is specified in rad/s. send_position() measures the elapsed command time automatically, so callers do not need to provide the node control frequency. Custom configurations may omit this field to disable command velocity limiting.

Elapsed command time is capped at 40 ms. This bounds the position increment allowed by the velocity limiter after a scheduling pause or command gap. At 250 Hz, a normal 4 ms interval still uses 4 ms in the calculation.

Safety stops and recovery

send_position() returns True after dispatching the checked target, including any safety clamping. A force-stop safety rejection returns False and latches the reason in the read-only arm.safety_stop_reason property. The rejected target is never dispatched. Further position commands return False, with warnings at most once every two seconds while commands are attempted. This replaces the previous RuntimeError for force-stop safety rejections.

The latch stops new position commands and leaves the last dispatched target in place. It does not automatically disable motors or periodically resend that target; actual holding behavior depends on the motor and communication state. An explicit stop() skips the return trajectory after a latch, logs the reason, and calls disable_all(). If a safety rejection interrupts a normal stop trajectory, stop() still proceeds to disable the motors.

After inspecting and resolving the cause, recover with stop() followed by start(). Starting clears the latch and synchronizes the command baseline to the position read from the motors before sending the startup trajectory. safety_stop_reason is None when no safety stop is latched. The existing get_health() return structure remains (motor_status, bus).

smooth_move(), move_to_start_position(), move_to_stop_position(), and start() return False when their trajectory is rejected and True when it finishes dispatching. Rejection stops the remaining trajectory steps. A failed start leaves started=False, retains the reason, and blocks subsequent position commands until recovery. Motors may still be enabled until stop() is called. Successful dispatch does not verify physical arrival at the target.

Existing callers can continue to ignore these return values. Custom trajectory hooks returning None remain supported; an explicit False or a latched safety stop prevents successful startup. Configuration errors and CAN exceptions retain their exception behavior. This change requires no additional node inputs or metadata. It adds no fresh-feedback startup gate: cached feedback can still be stale when motors are not responding. Health diagnostics remain observational.

Development

Test

uv sync
uv run pytest

Release

git clone git@github.com:enactic/openarm_driver.git
cd openarm_driver
dev/release.sh ${VERSION} # e.g. dev/release.sh 1.0.0

Related links

• 📚 Read the documentation
• 💬 Join the community on Discord
• 📬 Contact us through openarm@enactic.ai

License

Licensed under the Apache License 2.0. See LICENSE.txt for details.

Copyright 2026 Enactic, Inc.

Code of Conduct

All participation in the OpenArm project is governed by our Code of Conduct.