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Intermediate build

How to build Upkie

6-DoF wheel-legged balancer · Intermediate

Upkie is an open-source wheel-legged biped that balances on two wheels: four mjbots qdd100 servos, two moteus wheel drives, a Raspberry Pi 4 with pi3hat, and RYOBI power.

Start the buildProject files
Difficulty
Intermediate

Some soldering, calibration and Linux comfort needed.

Build time
2–4 weekends

Our estimate, part-time

Parts cost
Not published

No total is published

Degrees of freedom
6

Apache-2.0

What is Upkie?

Upkie, by Stéphane Caron, is a wheeled biped that balances on two wheels and bends its hips and knees like legs.

Four mjbots qdd100 quasi-direct-drive servos run the legs and two moteus developer-kit actuators drive the RC wheels. A Raspberry Pi 4 with a pi3hat provides CAN-FD and the IMU, and power comes from RYOBI-compatible 18 V tool batteries.

The main repo has the balancing agents and docs, and upkie_description has the URDF. The BOM lists suppliers but no total.

Upkie specifications

DoF
6 (4 hip/knee, 2 wheel)
Leg servos
mjbots qdd100
Wheel drives
moteus dev kit
Compute
Raspberry Pi 4 + pi3hat
Battery
RYOBI 18 V

Figures as published by the project. See Sources below.

Bill of materials

PartQtyNotes
mjbots qdd100 servo4
moteus developer kit2
mjbots pi3hat1
mjbots power_dist1
Raspberry Pi 41
RYOBI-compatible battery + contacts1
Where's the full bill of materials?

The full BOM, with exact quantities and vendors, lives in the project's own files. Prices change often, so treat Not published as a ballpark. Start at the project repository.

Tools you'll need

  • FDM printer
  • Hex drivers
  • Soldering iron

Step-by-step build overview

Electronics & wiring overview

All six actuators sit on the pi3hat's CAN-FD buses, with power from the RYOBI pack through power_dist.

Battery packpower sourceLaptop / PChigh-level controlIMUsensingRaspberry Pireal-time controllermoteus controllersdrivers / bushobby/smart servos6 joints / motors
PowerData / commandsSensor feedbackOverview only. Follow the project's own schematic for pinouts and voltages.

Software

URDF model

Upkie agents and spines (Apache-2.0), with the URDF in upkie_description.

Tips from the bench

  • ☕ Use a tether or stand for the first balancing tests.

Upkie FAQ

Is Upkie a legged or wheeled robot?

It's both: a biped that balances on wheels.

Sources

Written by Bots n' Beans from the project's own documentation. Check the sources for the latest revision before you buy parts.

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