# Yertle — A 3D Printed Quadrupedal Robot for Locomotion Research Yertle is a 12-DOF quadruped robot designed for locomotion research. It fuses the leg geometry of the [Kangal](https://grabcad.com/library/diy-quadruped-robot-1) quadruped with the body geometry of [SpotMicro](https://spotmicroai.readthedocs.io/), making most parts cross-compatible with the SpotMicro ecosystem. **Source:** https://github.com/Jerome-Graves/yertle **Creator:** Jerome Alexander Graves **License:** MIT **Status:** Work-in-progress (functional; ROS2 integration pending) This Program is a learning entry point. The original firmware is C++ on an ESP32 with a Python GUI master controller — the orobot Program here exposes a stubbed JavaScript interface so you can explore the gait/command surface in-browser. To run on real hardware, follow the upstream build and flash instructions. ## Mechanical - 4 legs × 3 DOF (hip yaw + hip pitch + knee) = **12 servos total** - Leg extension: ~20 cm - Mass: ~1.8 kg - Frame: PLA or ABS, printable on a 150 × 150 mm bed (Ender 3 Pro tested) - Print time: ~2 weeks (5–10 h/day on a single Ender 3 Pro) ## Electronics | Role | Component | |---|---| | Microcontroller (master of servos/sensors) | **ESP32s** | | Optional onboard SBC (vision/ROS) | Raspberry Pi 4B | | Servo driver | PCA9685 (16-channel PWM) | | Servos × 12 | SPT5435LV-180W, 35 kg·cm waterproof digital (≥ 15 kg·cm required) | | IMU (optional) | MPU9250 9-axis | | Battery | 7.4 V 2S 5000 mAh LiPo (~30 min runtime) | | Power | SBEC 6 V 20 A | The robot can run headless from the ESP32 alone (UDP-over-WiFi to a Python GUI on a laptop/phone) or with a Pi4 onboard for vision and ROS. ## Software architecture Master/slave over **serial or UDP/WiFi**: - **Slave (ESP32, C++/Arduino):** servo control, sensor read, inverse kinematics, safety limits. - **Master (Python 3 GUI):** gait generation, sensor fusion, ROS2 (todo). Runs on anything with WiFi + screen + Python 3. - **Simulation:** Python-based built-in simulator; URDF available for Gazebo/Unity. ## Build cost ~**£250** total (servos dominate at ~£162). See full BOM in the upstream [Design/README](https://github.com/Jerome-Graves/yertle/blob/main/Design/README.md). ## 3D printed parts (21 STLs) - **Shell (4):** Top, Bottom, Front, Back - **Frame (9):** Inner/Outer/Upper/Lower Shoulder Frame, Left/Right Servo Mount, Servo Mount Top Bracket, Side Body Beam, Electronics Mounting Plate - **Legs (8):** Inner/Outer Tibia, Femur, Femur Servo Connector, Left/Right Shoulder, Short Link, Long Link All STLs: https://github.com/Jerome-Graves/yertle/tree/main/Design/STL ## Hardware compatibility (BYOD) Yertle is **not** an orobot-firmware-native build. It uses a custom ESP32 firmware. Running the orobot Program against real hardware requires bridging the orobot WebSocket protocol to Yertle's UDP master/slave protocol — a custom integration tracked under the orobot ESP32 BYOD effort. ## Inspirations - [Kangal](https://grabcad.com/library/diy-quadruped-robot-1) (leg design) - [SpotMicro](https://spotmicroai.readthedocs.io/) (body geometry, parts compatibility) - [Open Quadruped](https://github.com/adham-elarabawy/open-quadruped) --- *Extracted from commit `99c1f98` on 2026-04-27.*
Category: Mobile Robots
| Qty | Part | Notes | |-----|------|-------| | 12 | SPT5435LV-180W 35kg·cm waterproof digital servo | ≥15 kg·cm required | | 1 | M3 screw, nut & washer assortment (x100) | — | | 1 | MPU9250 9-axis IMU | optional | | 1 | ESP32s microcontroller | — | | 1 | Raspberry Pi 4B | optional, for vision/ROS | | 1 | PCA9685 16-channel PWM servo driver | — | | 1 | 7.4V 2S 5000mAh LiPo battery | ~30 min runtime | | 1 | SBEC 6V 20A voltage regulator | — | | 4 | Miniature ball bearings 5×16×5mm | — | | 4 | Deep groove ball bearings 25×37×7mm | — | | 8 | RS PRO miniature ball bearing 3×13×5mm | — | | 4 | 25T metal servo circular horn | — | | 4 | 25T metal servo arm horn | — | | 32 | Sleeve bearing 3mm bore × 5mm OD × 5mm | — | | 1 | PLA filament 1kg | or ABS/PETG |