CocoNuts Humanoid
B✓ Links verified May 19, 2026
Guides and BOM only — orobot firmware does not yet support this hardware.
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23 stars on GitHub.
CocoNuts is an open-source humanoid robotics research platform designed around a key mechanical insight: minimizing leg inertia by concentrating actuator mass near the root of the limbs. By relocating the heavy knee and ankle pitch actuators near the hip joint using timing belt transmissions, the swinging portion of each leg becomes significantly lighter — reducing the energy cost of locomotion.
Source: https://github.com/MarcDcls/coconuts
The lower leg uses a four-bar parallel linkage mechanism to transmit ankle pitch motion from the proximally-mounted actuator. The hip and knee use RMD-X6 quasi-direct drive (QDD) actuators, while the ankle uses TD30-40 and TD40-52 harmonic drive actuators for precise position control.
A single-leg benchmark prototype was built and tested to validate the design. Three configurations were evaluated (ankle only, knee only, knee+ankle), revealing key tradeoffs: the RMD-X6 motors are oversized for the current structural scale (favorable power-to-weight would require either a larger frame or lighter actuators), and the timing belt + parallel linkage system introduces compliance that makes precise control more challenging. These findings led to a design pivot, and the repository is now maintained as an open technical reference.
The full humanoid CAD is available on OnShape (linked in repository). The GitHub repo contains all 3D-printable structural parts for the one-leg benchmark prototype. Hardware uses a CANalyst-II interface for motor communication via Python software.
License: hardware CERN-OHL-S v2, software Apache 2.0. Published with DOI via Zenodo.
🖨 Print Files (49)
aluminum_profile.stl
ankle_alu.stl
ankle_bearing_cover.stl
ankle_shaft.stl
ankle_mirror.stl
bearing_cover_1.stl
Required Hardware
| Item | Qty | Unit Cost (USD) | Total (USD) | Notes |
|---|---|---|---|---|
| MyActuator RMD-X6 QDD actuator (CAN, integrated driver) | 4 | $550 | $2,200 | Hip/thigh joints — "oversized for scale" per repo, can substitute X4-24 (~$300) — MyActuator shop |
| HarmonicDrive TD30-40 actuator (with motor + driver) | 4 | $700 | $2,800 | Knee/ankle joints — HarmonicDrive TD series |
| HarmonicDrive TD40-52 actuator | 2 | $850 | $1,700 | Larger torque joints — HarmonicDrive TD series |
| CANalyst-II USB-CAN interface | 1 | $90 | $90 | Required for motor comms — Amazon search |
| Mini-PC / NUC running Linux (Intel i5+ class) | 1 | $400 | $400 | Realtime control host — Amazon search |
| 6S 5000 mAh LiPo battery (22.2V) | 2 | $80 | $160 | One pack + spare — Amazon search |
| 24V → 5V/12V step-down DC-DC buck converter | 2 | $15 | $30 | Aux rails — Amazon search |
| GT2 timing belt + pulley assortment (5mm bore) | 1 | $25 | $25 | Knee parallel linkage — Amazon search |
| BNO055 IMU module (or VectorNav VN-100) | 1 | $25 | $25 | Body orientation — Amazon search |
| Foot contact / FSR pressure sensors | 4 | $10 | $40 | Ground contact detection — Amazon search |
| 16 AWG silicone hookup wire (red/black, 10 ft each) | 1 | $20 | $20 | High-current motor power — Amazon search |
| XT60 / XT90 connector pairs | 6 | $2 | $12 | Battery / motor power — Amazon search |
| CAN-bus DB9 cable + 120Ω terminator pair | 2 | $10 | $20 | Daisy-chain wiring — Amazon search |
| M3 / M4 / M5 socket-head screw assortment (stainless) | 1 | $30 | $30 | Frame fasteners — Amazon search |
| Heat-set threaded inserts M3 + M4 (200-pack) | 1 | $20 | $20 | Amazon search |
| Aluminum 20×20 V-slot extrusion + brackets | 1 | $50 | $50 | Test stand for one-leg benchmark — Amazon search |
| 3D-printer filament (PA-CF or PETG-CF, 2 kg) | 2 | $50 | $100 | Structural printed parts (CAD on OnShape) — Amazon search |
| E-stop button (panel-mount, normally-closed) | 1 | $15 | $15 | Safety — Amazon search |