OpenArm

OpenArm is an open-source, seven-degree-of-freedom humanoid robot arm developed by Enactic, Inc., a Tokyo robotics company. The project publishes the arm's CAD files, bill of materials, firmware, control libraries, simulation assets and teleoperation code so that research groups can build or buy the hardware and reproduce each other's experiments. Its stated purpose is physical AI research and deployment in contact-rich environments: most joints use backdrivable quasi-direct-drive motors chosen for compliance and safe human-robot interaction (the middle joints use a 40:1 Damiao motor that Enactic says is not QDD), while keeping a nominal payload of 4.1 kg per arm.^[1][2] The software repositories are licensed under the Apache License 2.0 and the hardware repository under CERN-OHL-S-2.0.^[1]

The current generation, OpenArm 2.0, launched in May 2026 and widened the project from a single arm into a three-part platform: the arm, a standardized evaluation enclosure called OpenArm Cell, and a motorless leader arm called OpenArm KER for teleoperation.^[3][4] Several unrelated GitHub projects also use the name OpenArm; this article covers only the Enactic project at github.com/enactic/openarm and openarm.dev.

Origin and maintainer

The main repository was created on 29 September 2024 under the GitHub organization reazon-research, and its early release notes still point at reazon-research/OpenArm pull requests; that path now redirects to enactic/openarm.^[5][6] Enactic, Inc. was founded in July 2025 with its headquarters in Yotsuya, Shinjuku, Tokyo, and a lab in Akihabara. Its own description of the business is "humanoids that care": the company is building a humanoid care robot named Ena, targeted at Japanese nursing-care facilities and scheduled for a beta launch in late 2026, and treats OpenArm as its open-source research line.^[3] Press releases issued in March and June 2026 name Hiroto Yamamoto (山本泰豊) as representative director; the company website in September 2026 lists Daijiro Mori as representative.^[3][7][8] Enactic's June 2026 release says the company has partnered with more than 90 care providers.^[8]

Enactic also hosts English and Japanese documentation for the Damiao motors used in the arm at damiao.enactic.ai, and the OpenArm motor page links to those datasheets.^[9][10]

Version history

The March 2026 GTC press release said OpenArm 2.0 was planned for April 2026 and that the repository had passed 1,700 GitHub stars as of February 2026; the launch slipped to May, and by mid-September 2026 the repository had about 3,360 stars and 366 forks.^[5][7] Note that GitHub's tag list jumps from 0.3 to 1.1; the July 2025 "OpenArm 01" launch was announced on X and on enactic.ai rather than as a tagged release.^[6][11]

OpenArm 2.0 hardware

Specifications

Enactic's documentation defines the payload figures precisely. Nominal payload is the weight that can be held for one minute in the worst posture (arm fully extended); peak payload is the weight that can be moved from arms-down into the worst posture over three seconds, held for one second, and returned. Both figures include the end effector, so an arm carrying a 1.5 kg gripper has 2.6 kg nominal and 4.5 kg peak capacity left for the object.^[2]

The reach, per-arm weight and 1 kHz figures appear only in the summary graphic at the top of the hardware page and not in the mechanical text; the equivalent OpenArm 1.0 graphic listed a 633 mm reach; Enactic has not explained the difference, which may reflect the redesigned, more compact 2.0 gripper.^[2][20] The docs describe the arm as "scaled for a person around 160-165 cm tall" to balance reach against inertia.^[17] The complete 3D CAD and bill of materials are distributed through a Google Drive folder linked from the hardware page, alongside the openarm_hardware GitHub repository of STL, STEP and Fusion 360 files.^[1][2]

Motors and transmission

OpenArm uses three Damiao motor families, chosen joint by joint to trade payload against bulk: the small DM-J4310 at the wrist, the DM4340 series in the middle of the chain, and the 98 mm DM-J8009P at the shoulder. Motors with cross-roller bearings are used where a joint is supported on one side only. The documentation is candid that the DM4340 series, with its 40:1 reduction, "is not a QDD motor" and was chosen "to balance high payload capacity with a clean, compact appearance"; the 4310 (10:1) and 8009P (9:1) are the low-ratio, backdrivable actuators.^[10] The docs also note that the linked 8009 datasheet is for the DM8009 rather than the DM8009P actually fitted, and describe the two as nearly identical.^[10] This is the opposite choice from joints built on high-reduction harmonic drive gearing, which resists being pushed by hand.

Gripper

The 2.0 end effector replaced the 1.0 linkage-driven parallel gripper with a simpler actuation mechanism to shrink the envelope for work in confined spaces. A camera sits inside the gripper case so in-hand vision is captured during grasping, and the finger geometry was shaped to keep that view unobstructed. Fingers are designed to be swapped so that users can test task-specific geometries without redesigning the gripper.^[19][21] The 1.0 gripper, by comparison, opened to a maximum jaw gap of 88 mm with a 60-degree rotor travel and used ball-bearing slider rails to stay smooth for force feedback; its J8_B interface part was the documented point for mounting a custom end effector.^[22]

Backdrivability and bilateral control

The design argument runs through every OpenArm document: a quasi-direct-drive joint with a low gear ratio can be pushed by hand and gives way on contact instead of fighting it. Enactic's overview lists "QDD backdrivable motors and high compliance" under a "safety-first architecture" and describes "bilateral force feedback for contact-rich teleoperation and high-fidelity data collection, beyond what unilateral leader-follower setups can capture."^[17] The same property is a hazard the safety guide flags explicitly: because the arm is so backdrivable, a load will "fall rapidly" if an emergency stop cuts power.^[23]

The teleoperation stack offers two modes. Unilateral control sends the leader arm's joint positions to the follower with no feedback, which the docs recommend for free-space motion and warn is easy to overload during contact. Bilateral control closes a two-way loop so the operator feels what the follower touches. The openarm_teleop implementation runs leader, follower and admin threads on a periodic timer, tunes per-joint position and velocity gains, and applies a tanh-based friction model (tau_f = Fc * tanh(k * dq) + Fv * dq + Fo) to compensate Coulomb and viscous friction. Bilateral control requires a control rate of at least 500 Hz, and the docs warn that bad gains produce oscillation.^[24][25] All motor commands go through the Damiao MIT control mode, which takes a {kp, kd, q, dq, tau} tuple per motor and returns position, velocity, torque and temperature.^[9]

Software stack

Sources: README repository table and GitHub organization listing.^[1][5]

The description package supports both hardware generations through an arm_type argument; v2.0 uses named presets such as default_bimanual, right_arm and left_arm_with_pinch_gripper.^[26] The ROS 2 bringup exposes the arm as a position, velocity and torque command interface, launches either fake or real hardware, and takes separate CAN interfaces for the left and right arms; the docs flag the hardware bridge and gripper bridging as still under active development.^[27] MuJoCo support is a set of MJCF files with torque-controlled actuators and separate visual and collision geometry groups, maintained for the MuJoCo engine.^[28] The Isaac Lab repository is pinned to Isaac Sim 5.1.0 and Isaac Lab 2.3.0 at the time of writing, and Enactic states the model is officially integrated into NVIDIA's Isaac ecosystem.^[13][29]

Outside Enactic's own code, Hugging Face's LeRobot added openarm_follower, openarm_leader, bi_openarm_follower and bi_openarm_leader classes in v0.4.4 (27 February 2026), plus an "OpenArm Mini" teleoperator; later releases fixed OpenArm Mini feature compatibility (v0.6.0) and stopped zeroing positions on connect (v0.6.1).^[14] LeRobot's OpenArm page notes that the CAN adapter has no macOS driver and the integration is Linux-only.^[30]

The dataset format stores per-episode action and obs trees of Parquet files (joint position, velocity and torque per arm, plus a lifter elevation channel) alongside timestamped JPEG frames from ceiling, head and wrist cameras, with a metadata.yaml describing tasks and success flags; it installs with pip install openarm_dataset and requires Python 3.10 or newer.^[31] Tutorials cover data collection with KER, with a VR headset, and over WebXR, followed by training and inference.^[32]

OpenArm Cell and OpenArm KER

OpenArm Cell is the evaluation enclosure introduced with 2.0. Its premise is that a claim like "Model A outperforms Model B" is only meaningful when both were run under identical conditions, so the Cell fixes background, lighting, camera placement and arm mounting position. The enclosure and power system are built from MISUMI off-the-shelf parts, a vertically adjustable Z-axis lifts both arms to suit workpiece height, an area-sensor "reach-in stop" cuts power if someone enters the workspace, and a calibration jig mechanically constrains the gripper to its CAD-defined zero angles so assembly tolerances do not leak into datasets. Each Cell weighs roughly 100 kg and draws roughly 480 W before the PC is counted.^[21][33] WowRobo's kit lists the frame at 1100 x 926 x 1883 mm with a 300 mm Z-axis.^[34] At GTC 2026 Enactic ran two policies in one Cell with success judged automatically and scores displayed live.^[7]

OpenArm KER, the Kinematic Equivalent Replica, is a leader arm with no motors: every joint has a magnetic encoder and bearings, the joint structure matches OpenArm 2.0 exactly, and the link lengths are scaled to 70 percent, so joint angles map one-to-one to the follower without retargeting. The whole device weighs 1.7 kg (CFRP tubes, machined aluminum and resin), mounts on the shoulders like a backpack in about 30 seconds, and folds into a travel case. All axes share a common encoder module that daisy-chains with individually assigned IDs, which is enough for a 7-plus-1 DoF controller.^[35][36] WowRobo's listing specifies 16 Infineon TLE5012B 15-bit absolute encoders across a bimanual KER.^[34] The "What's New in 2.0" page still carries a note that KER "has not been released yet"; Enactic announced its release on 26 June 2026 and the firmware repository was created on 24 June 2026.^[4][5][21]

Cost and availability

OpenArm can be built from the public files or bought assembled. The README quotes $6,500 for a complete bimanual system, and the same figure is labelled "Bill of Materials" on the hardware graphic.^[1][2] Enactic's purchase page, which the project says "updates regularly as we certify vendors", lists two official partners and eight other vendors as of September 2026.^[34]

The purchase page marks unevaluated vendors as "not guaranteed to work with official OpenArm software" and warns that the "OpenArmX Pro Max" sold by one vendor is not affiliated with or compatible with the project.^[34] The Enactic announcement of worldwide availability on 30 October 2025 quoted a starting price of $5,000 for OpenArm 1.x.^[12]

Research and deployment use

The project fine-tuned and deployed NVIDIA's GR00T N1 foundation model on OpenArm hardware by May 2025, while the repository still lived under Reazon Research; the 0.3 release notes point to a reazon-research/Isaac-GR00T fork.^[6] In June 2026 it began what it described as Japan's first practical validation of NVIDIA Isaac GR00T N1.7 in nursing care, using OpenArm 2.0 as the evaluation platform and listing Isaac Sim, Isaac Lab, Cosmos, DGX H100 training and Jetson Thor edge inference as the stack.^[8] The March 2026 press release described the project as used for research by "domestic and international research institutions and companies", without naming them.^[7]

The openarm_dataset layout, the Cell lifter channel, and the dora-rs evaluation nodes are all built around the AutoEval idea Enactic credited in its March 2026 announcement to Zhiyuan Zhou's work on continuous real-world policy evaluation: run policies around the clock with minimal human intervention and compare them side by side.^[15] Whether the Cell yields comparable numbers across labs is a claim the project is making about its own design; no independent cross-lab study had been published as of September 2026.

Comparison with other open-source arms

Payload definitions differ between vendors (Enactic's "nominal" is a one-minute hold at full extension; Trossen's "working payload" comes with an extension caveat), so the column is not a like-for-like ranking.

References

1. ^1 ^2 ^3 ^4 ^5 ^6 ^7Enactic. "enactic/openarm" README. GitHub. Accessed 16 September 2026. github.com/...openarm
2. ^1 ^2 ^3 ^4 ^5 ^6 ^7 ^8 ^9 ^10 ^11 ^12 ^13 ^14 ^15Enactic. "OpenArm 2.0: General" (dimensions, payload definitions, key-features graphic). docs.openarm.dev. Source file website/docs/hardware/openarm-2.0/general.mdx, accessed 16 September 2026. docs.openarm.dev/...general
3. ^1 ^2 ^3 ^4 ^5Enactic, Inc. Company website (news list, company profile, OpenArm 2.0 "Launched May 2026"). Accessed 16 September 2026. enactic.ai
4. ^1 ^2 ^3Enactic (@enactic_ai). "We are excited to announce the release of a new OpenArm teleoperation device: KER..." X, 26 June 2026. x.com/...2070582925998117068
5. ^1 ^2 ^3 ^4 ^5GitHub REST API. Repository metadata for enactic/openarm (created 2024-09-29, stars, forks) and organization listing for enactic (Enactic, Inc., Japan, org created 2025-05-16). Accessed 16 September 2026. api.github.com/...openarm
6. ^1 ^2 ^3 ^4 ^5 ^6 ^7 ^8Enactic. "Releases: enactic/openarm" (0.1, 0.2, 0.3, 1.1). GitHub. github.com/...releases
7. ^1 ^2 ^3 ^4 ^5Enactic, Inc. "【株式会社Enactic】NVIDIA 主催のGTC 2026 に出展" (GTC 2026 exhibition, OpenArm Cell first showing, 1,700+ stars as of February 2026, 2.0 planned for April 2026). PR TIMES, 12 March 2026. prtimes.jp/...000000004.000166268
8. ^1 ^2 ^3Enactic, Inc. "株式会社Enactic、NVIDIA GR00T N1.7の介護領域における日本初の実用性検証を開始" (GR00T N1.7 nursing-care validation; 90+ care providers; company profile). PR TIMES, 2 June 2026. prtimes.jp/...000000006.000166268
9. ^1 ^2Enactic. "OpenArm CAN Library" (three-layer architecture, Damiao MIT control mode). docs.openarm.dev. docs.openarm.dev/...can
10. ^1 ^2 ^3 ^4 ^5 ^6 ^7 ^8Enactic. "OpenArm 2.0: Motor" (motor selection, DM-J4310-2EC V1.1 / DM4340 series / DM-J8009P-2EC specification table, links to damiao.enactic.ai datasheets). docs.openarm.dev. docs.openarm.dev/...motor
11. ^1 ^2Enactic (@enactic_ai). "We just open-sourced #OpenArm 01..." X, 24 July 2025. x.com/...1948215999427219771
12. ^1 ^2Enactic (@enactic_ai). "Fully assembled OpenArm is now available worldwide, starting at $5,000!" X, 30 October 2025. x.com/...1983800630675435926
13. ^1 ^2Enactic (@enactic_ai). "The official #OpenArm model is integrated into NVIDIA #IsaacLab." X, 25 December 2025. x.com/...2004126742873813413
14. ^1 ^2Hugging Face. "Releases: huggingface/lerobot" (v0.4.4, 27 February 2026: "add OpenArm robot & teleoperator", "add bi manual openarm follower and leader", "add OpenArm Mini teleoperator"; v0.6.0; v0.6.1). GitHub. github.com/...releases
15. ^1 ^2Enactic (@enactic_ai). "How do we make robot policy evaluation reproducible across labs? Announcing OpenArm 02..." X, 3 March 2026. x.com/...2028934873516544235
16. ^GitHub. Commit history for website/docs/hardware/openarm-2.0/general.mdx and website/docs/overview/whats-new-in-2.0.mdx in enactic/openarm (commits dated 15-20 May 2026). github.com/...general.mdx
17. ^1 ^2 ^3 ^4Enactic. "Project Overview" (What's Unique, Specifications at a Glance, ecosystem). docs.openarm.dev. docs.openarm.dev
18. ^1 ^2Enactic. "Step 2: Setup SocketCAN Interface" and "OpenArm Setup Guide" (CAN-FD 5 Mbps recommended, CAN 2.0 at 1 Mbps, 24 V supply, Ubuntu 22.04/24.04). docs.openarm.dev. docs.openarm.dev/...can-setup
19. ^1 ^2Enactic. "OpenArm 2.0: Gripper." docs.openarm.dev. docs.openarm.dev/...gripper
20. ^Enactic. "General Specifications" (OpenArm 1.0 documentation, key-features graphic with 633 mm reach). docs.openarm.dev, version 1.0. docs.openarm.dev/...hardware
21. ^1 ^2 ^3Enactic. "What's New in 2.0." docs.openarm.dev. docs.openarm.dev/...whats-new-in-2.0
22. ^Enactic. "Gripper Specifications" (OpenArm 1.0 documentation: 88 mm jaw gap, 60-degree rotor travel, J8_B interface). docs.openarm.dev, version 1.0. docs.openarm.dev/...gripper
23. ^Enactic. "Safety Guide." docs.openarm.dev. docs.openarm.dev/...safety-guide
24. ^Enactic. "Leader-Follower Teleoperation" (unilateral vs bilateral). docs.openarm.dev. docs.openarm.dev/teleop
25. ^Enactic. "Bilateral Force Feedback Control" (thread architecture, gain and friction parameters, 500 Hz requirement). docs.openarm.dev. docs.openarm.dev/...bilateral-control
26. ^Enactic. "OpenArm Description Package" (v1.0 and v2.0 arm_type values, robot presets). docs.openarm.dev. docs.openarm.dev/...description
27. ^Enactic. "ROS2 Control" (openarm_bringup, fake and real hardware launch, hardware bridge status). docs.openarm.dev. docs.openarm.dev/...control
28. ^Enactic. "MuJoCo" (MJCF files, torque-controlled actuators). docs.openarm.dev. docs.openarm.dev/...mujoco
29. ^Enactic. "Isaac Lab Simulation" (four RL environments, official Isaac integration). docs.openarm.dev. docs.openarm.dev/simulation ; and Enactic, "enactic/openarm_isaac_lab" README (Isaac Sim 5.1.0 and Isaac Lab 2.3.0 badges). github.com/...openarm_isaac_lab
30. ^Hugging Face. "OpenArm" page in LeRobot documentation (Linux-only note, payload figures). github.com/...openarm.mdx
31. ^Enactic. "OpenArm Dataset" (directory layout, Python API, Python 3.10+). docs.openarm.dev. docs.openarm.dev/dataset
32. ^Enactic. Tutorial section (data-collection-ker, data-collection-vr, data-collection-webxr, training, inference) in enactic/openarm website/docs/tutorial. github.com/...tutorial
33. ^Enactic. "OpenArm Cell: General" (design rationale, ~100 kg, ~480 W, reach-in stop, zero-position jig). docs.openarm.dev. docs.openarm.dev/...general
34. ^1 ^2 ^3 ^4Enactic. "Buying OpenArm" (official partners, vendor table, prices, OpenArmX warning, WowRobo Cell and KER descriptions). docs.openarm.dev. Accessed 16 September 2026. docs.openarm.dev/purchase
35. ^Enactic. "OpenArm KER: General" (motorless leader arm, 70 percent link lengths, 1.7 kg, backpack mount). docs.openarm.dev. docs.openarm.dev/...general
36. ^Enactic. "OpenArm KER: Encoder Module" (common module, daisy-chain, 7+1 DoF). docs.openarm.dev. docs.openarm.dev/...encoder-module
37. ^1 ^2 ^3Seeed Studio. "Seeed-Projects/reBot-DevArm" README (B601-RS: 6 DoF + 1 gripper, 2.5 kg payload, 754 mm max reach, DC 48 V, CERN-OHL-W-2.0 hardware, Apache-2.0 software). GitHub. Accessed 16 September 2026. github.com/...reBot-DevArm
38. ^1 ^2 ^3TheRobotStudio. "Standard Open SO-100 & SO-101 Arms" README (follower bill of materials with six STS3215 7.4 V servos; Apache-2.0 repository license). GitHub. Accessed 16 September 2026. github.com/...SO-ARM100
39. ^1 ^2Trossen Robotics. "ViperX-300 6DOF" specifications (6 DoF, 750 mm reach, 750 g working payload, XM540-W270 and XM430-W350 servos). Interbotix X-Series Arms Documentation. docs.trossenrobotics.com/...vx300s