Quaddle — a 4-servo open-source robot dog for Makers, Robotics Hobbyists and Education

[Kai Mai]

Hi everyone,

This is Kai Mai.  I am based in the Bay Area and have been lurking around since Ed Katz invited me to this group a few years ago.

My company Petoi just launched our newest robot: Quaddle, on Kickstarter now. https://www.kickstarter.com/projects/petoi/quaddle-open-source-desktop-robot-kit. We're targeting early December shipment.

It's built to actually be used, not just watched: teach it a trick by hand and it replays it, write your own gaits from scratch, drop its URDF into whatever sim you already train in, or reconfigure the same 4 servos into five different mechanical forms. If you've wanted a cheap, real robot to test physical AI or gait ideas on instead of just simulating them, Quaddle is for you.

OpenCat, the platform underneath Quaddle, has been open source since 2016: https://github.com/PetoiCamp/OpenCatEsp32-Quadruped-Robot/. The OpenCat-based Bittle dogs and Nybble cats have been used in K-12 classrooms and university robotics labs, with 20+ academic papers citing them. Quaddle's own code follows the same path Bittle and Nybble took — it opens before delivery as we are refining it, so it's not public yet.

Here are the specs:
- Starting at $99 with gyroscope & PIR sensors. The most advanced model, Quaddle Scout, starts at $179 with gesture, light & infrared sensors.
- ESP32-S3 microcontroller
- Supports block coding, Python, MicroPython, and Arduino C++
- 4 servos, 90+ built-in moves. On the Buddy and Scout tiers, every joint is a position-feedback servo, so you can physically hand-guide a motion and it's captured directly — teach-and-replay, not an RL loop.
- URDF is public now: https://huggingface.co/petoi/quaddle — imports into Gazebo, PyBullet, Isaac Sim, and other standard tools. There's also an early, rough web-based simulator if you want to poke at it with nothing installed: https://www.petoi.com/pages/quaddle-robot-simulator
- It can be transformed into a biped, a tricycle, a bar-spinning gymnast, a 4WD car, and a water-paddler, just by swapping the attachment: https://www.youtube.com/watch?v=YfREsyasRe8&list=PLLNT_w5z-uR4&index=14
- Supports ROS/ROS2 integration, Raspberry Pi Zero, and additional Arduino modules

Mechanically, the interesting constraint is the actuator budget — one hip servo per leg, but still enabling lifelike movements.

I'd love to get this group's feedback on the product itself — what stands out, what looks off, anything you'd want to see done differently, and how it can be used for STEM/Physical AI/robotics education.

Best,
Kai Mai