[!WARNING] ⚠️ CHARGING SAFETY — POWER SWITCH OFF

Always turn the power switch OFF before charging.
Keep it OFF throughout charging.

If the adapter indicator turns green but the system will not power on:

If, after extended charging, the adapter indicator turns green but the system will not power on after the adapter is unplugged and the power switch is turned ON, check the battery pack's output with a multimeter.

The recovery procedure below applies only to a 2-series-cell lithium-ion pack rated 7.4 V nominal / 8.4 V maximum. Do not use this procedure for deeply discharged or damaged cells.

1. Turn the power switch OFF, unplug the adapter, and disconnect the battery pack from the PCB.
2. Use a regulated, current-limited external supply at 7.4 V or 8.4 V, with a 1 A or 2 A current limit that does not exceed the pack's specified charging current. Alternatively, use an adjustable DC bench supply with the voltage limit set to 7.4 V and the current limit set to 1 A. These are voltage and current limits, not a requirement to force a constant 1 A into the battery. An adapter's nameplate current rating alone is not a controlled charging current.
3. With the recovery supply switched OFF, connect its positive and negative leads to the battery pack's matching protected charging terminals, checking polarity carefully. Do not bypass the protection board or connect directly to bare cells. Enable the supply for 10–20 seconds while monitoring the pack to attempt to release the protection cutoff. Then switch the supply OFF and disconnect it. Stop if there is abnormal heating or any other abnormal behavior. Confirm that the pack output has recovered; if it remains at 0 V, stop and contact the battery supplier or [email protected] rather than repeating the attempt.
4. Once the output has recovered and the pack is operating normally, reconnect the battery to the PCB and reconnect the compatible charging adapter to resume normal charging. Keep the power switch OFF throughout charging.

[!WARNING] When testing and tuning servos, avoid stalling them as much as possible.

Meet XGO-Duck

XGO-Duck is a duck-shaped biped robot adapted by Luwu Dynamics from Pollen Robotics' Microduck. It combines a printable structure, fifteen Feetech 1910 servos, an Arduino UNO Q, and a custom expansion board with an IMU and servo interfaces.

This repository is the hardware starting point: print the parts, prepare the electronics, and assemble the robot. Companion repositories provide the onboard runtime and reinforcement-learning tools, connecting a physical build with motion experiments.

Build	Run	Experiment
Print the body, legs, neck, head and soft parts. Assemble with the illustrated guide.	Configure and calibrate the robot through the companion runtime's browser interface.	Study the simulation, train policies and explore your own motions.
Hardware files	Onboard runtime	RL tools

A closer look

XGO-Duck prototype — printed parts, articulated legs, and a movable head and beak.

A movable head and beak Four neck/head joints and a separate mouth servo.

Electronics you can inspect Rear-mounted controller stack and accessible wiring.

The photos show project prototypes. Follow the assembly guide and matching board files for your build revision.

Hardware at a glance

Subsystem	What it uses	Role
Controller	Arduino UNO Q	Linux host for policy inference and web UI; STM32 MCU for servo and sensor communication
Actuation	15 Feetech 1910 serial servos	10 leg joints, 4 neck/head joints, and 1 mouth joint
Expansion board	Luwu UNO Q expansion board	Power distribution, servo connections and IMU integration
Motion sensing	QMI8658A 6-axis IMU	Acceleration and angular-velocity feedback
Structure	STL parts	Body, leg, neck and head components
Soft parts	TPU-designated STL files	Foot soles and mouth parts

The motion policy outputs targets for 14 joints; the mouth servo is controlled separately. Component details and purchasing checks are collected in the BOM notes.

How the system connects

flowchart TD
    UI[Browser: setup, calibration and control] <--> HOST[UNO Q Linux: ONNX policy and web UI]
    RL[Training computer: simulation and RL] -->|Export ONNX policy| HOST
    HOST <-->|Arduino Bridge| MCU[UNO Q STM32: servo and IMU loop]
    MCU <-->|Serial bus| SERVOS[15 Feetech 1910 servos]
    IMU[QMI8658A IMU] -->|Sensor feedback| MCU
    BOARD[Custom expansion board] --- SERVOS
    BOARD --- IMU

This is a functional overview; use the board design and assembly documentation for electrical connections.

Start your build

Current board version: V1.1 (2026-10-26). Use the V1.1 design and production files. Previous files and wiring instructions are archived separately.

1. Prepare parts and electronics

Open the bill of materials for the robot purchasing list, supplier links and battery requirements, and PCBA/ for the expansion-board files. The robot BOM and PCB manufacturing BOM serve different purposes: a finished expansion board already includes its board-level components.

Part	Quantity
Arduino UNO Q (2 GB / 4 GB)	1
Robot expansion board — Luwu Dynamics Store	1
Feetech 1910 servo with AMP 3-pin cable	15
Battery pack, listed as “18650 battery 8.4V”	1
8.4 V Li-ion battery charger with 5.5 × 2.1 mm DC barrel plug (DC5521)	1
M2 × 6 countersunk, flat-end self-tapping screw	204 (200+4 for roller)
M2.3 × 8 flat-top round-head, flat-end self-tapping screw	6
M3 × 16 round-head machine screw	4
10 × 15 × 3 mm bearing	11 (3+8 for roller)
16 × 22 × 4 mm bearing	11

Quantities include the optional roller skates: 4 additional M2 × 6 screws and 8 additional 10 × 15 × 3 mm bearings. Confirm the pack, charger, connector polarity and power requirements using the component notes before sourcing or powering the build.

The expansion-board store page also offers a separate battery-and-charger option. Select Only Robot Driver Board for Arduino UNO Q for the board above; the bundle has not been verified against the battery and charger specifications in this list. See the purchasing notes.

For easier purchasing, Luwu Dynamics offers an official XGO-Duck electronics kit containing all components in the BOM except the Arduino UNO Q.

Identify the three fasteners before ordering. Items 7 and 8 are self-tapping screws with flat ends. Items 8 and 9 share the same rounded side profile; item 8 has a flat top, while item 9 has the gently domed top shown in the photo below and a machine thread. The following shape guide is illustrative. See the product photo and size references in the BOM.

Item 9 has the domed top shown here. Item 8 has the same rounded sides but a flat top. The photo is a head-style reference, not a size or thread specification.

2. Print the structure

Download the models from structure/. The filenames carry useful assembly information:

Filename pattern	Meaning	Example
2x_	Print two copies	2x_shank.stl
4x_	Print four copies	4x_tire.STL, 4x_tire_axis.STL
left_ / right_	Separate left and right parts	left_foot.stl, right_foot.stl
tpu	Flexible part	2x_foot_bottom_tpu.stl, mouth_up_tpu.stl

Use the print inventory to track parts. Test a servo mount and bearing fit before printing the full set; a complete validated print profile is still to be documented.

For the optional roller skates, print 2x_tire_support.STL × 2, 4x_tire.STL × 4 and 4x_tire_axis.STL × 4.

Print orientation matters: place the part as shown before slicing — lay it flat with the open channel facing up and the two end tabs resting firmly on the build plate. Use 4 walls and 13% Gyroid infill. Do not stand it upright, lay it on its side, or flip it over, and do not rely on the slicer's auto-arrange. Otherwise the holes may deform and the ends may break. After slicing, check the preview against the reference image before printing.

3. Configure servos and assemble

Prepare each servo's ID and center position using the runtime setup instructions, then follow Assembly_Guide.pdf.

Assembly reference	Focus
Page 1	Servo ID placement
Pages 2–5	Shaft preparation, initial structure and cable routing
Pages 6–15	Legs, feet and soles
Pages 16–23	Head and neck mechanisms
Pages 24–25	Final assembly

The build guide adds preparation and inspection checkpoints. Configure one servo at a time, label its ID, and leave cable clearance through each joint's movement.

4. Calibrate and bring it to life

Install the onboard runtime, verify servo and IMU feedback, and complete calibration with the robot supported. Start with the default pose before motion trials.

The runtime includes walk, get-up and pick policies, plus separate mouth control. Their behavior depends on the assembled hardware, calibration and test conditions. Using the bundled policies does not require training a new model.

Hardware files

Path	Contents
Assembly_Guide.pdf	25-page illustrated assembly reference
BOM.md	Whole-robot purchasing list, supplier links and battery reference image
structure/	Printable STL models
V1.1 schematic	Altium schematic source
V1.1 BOM · Placement data	Board materials and placement coordinates
V1.1 production files	Fabrication notes, Gerber and drill files
V1.1 silkscreen layout	PDF reference
V1.1 DWG · STEP model	Drawing and 3D model
Previous version archive	Complete previous files and historical instructions
docs/	Build, printing, BOM and troubleshooting notes

From hardware to your own behavior

Repository	Purpose
xgoduck_hardware	Mechanical parts, electronics, BOM and assembly
xgoduck_runtime_arduino	UNO Q firmware, policy execution, browser setup and control
xgoduck_rl	Simulation, reinforcement-learning training and policy export

Keep the hardware, runtime and policy revisions together in your build record. This makes it easier to reproduce a working configuration and diagnose changes.

Origins and contributions

XGO-Duck builds on Microduck and microduck_rl by Pollen Robotics. The duck form, 15-servo arrangement and policy joint order originate in that work. Luwu Dynamics' adaptation focuses on Arduino UNO Q, Feetech 1910 servos, the custom expansion board, and the matching software/model integration. See origins and adaptations.

Build reports, tested print settings, clearer assembly photos and reproducible fixes are welcome. Read CONTRIBUTING.md or open an issue.

For reuse terms, consult LICENSING.md and the applicable file-level notices. Contact: [email protected].