[
 {
  "name": "Diablo",
  "maker": "Direct Drive Tech (DDT)",
  "open_source": "partial",
  "license": "SDK/ROS2: Apache-2.0; STL/SDF and RL URDF repos: no licence file (all rights reserved)",
  "url": "https://www.robotshop.com/products/diablo-worlds-first-direct-drive-self-balancing-wheeled-leg-robot",
  "height_mm": 491,
  "mass_kg": 22.9,
  "payload_kg": 4,
  "wheel_diameter_mm": 200,
  "leg_topology": "Per leg: hip and knee-drive motors coaxial at the body, with a four-bar (parallelogram-style) linkage carrying the knee drive. 3 DOF per leg (hip, knee, wheel). No hip abduction. Crouched height 270 mm.",
  "leg_motors": "4x DDT M1502D direct drive (24 V, 9.6 Nm rated, >=17 Nm stall, 115 rpm rated, >=200 rpm no-load)",
  "wheel_motors": "2x DDT M1502D direct drive",
  "battery": "Li-ion 32 V 6 Ah (~192 Wh derived); ~3 h standing, ~4 h creeping travel, ~15 min squatting",
  "price_usd": 4399,
  "cad_or_urdf_url": "https://github.com/DDTRobot/DiabloSTLSDF",
  "sources": [
   "https://www.robotshop.com/products/diablo-worlds-first-direct-drive-self-balancing-wheeled-leg-robot",
   "https://top3dshop.com/product/direct-drive-diablo-wheeled-bipedal-robot",
   "https://aifitlab.com/products/direct-drive-tech-m1502d_133-directdrive-motor",
   "https://github.com/DDTRobot/DiabloSTLSDF",
   "https://github.com/DDTRobot/Col_DIABLO_Issac_RL",
   "https://www.docs.mybotshop.de/diablo.html",
   "https://diablo-sdk-docs.readthedocs.io/en/latest/",
   "https://github.com/DDTRobot/diablo_ros2"
  ],
  "notes": "Wheel diameter is 200 mm from the simplified RL URDF (wheel radius 0.1 m, thigh/shank 0.14 m each, efforts 27 Nm, 26 rad/s). The SDF has the real linkage. Speed 2 m/s, jump 8 cm. M1502D sells separately for $310 (backorder). Compute is a Raspberry Pi in the MYBOTSHOP integration. ROS 2 is recommended."
 },
 {
  "name": "TITA",
  "maker": "Direct Drive Tech (DDT)",
  "open_source": "partial",
  "license": "tita_rl: MIT; TITA_Description URDF and DDT_Lab: no licence file",
  "url": "https://top3dshop.com/product/direct-drive-tita",
  "height_mm": 490,
  "mass_kg": 24.1,
  "payload_kg": 10,
  "wheel_diameter_mm": 185,
  "leg_topology": "Serial leg with hip abduction (+/-45 deg), hip pitch, knee and wheel: 4 DOF per leg, 8 total. Reconfigurable to quadruped modes.",
  "leg_motors": "Quasi-direct-drive joint modules, 120 Nm peak (model unknown)",
  "wheel_motors": "QDD module (part of the 8 DOF; model unknown)",
  "battery": "43.2 V nominal; 1 h per pack; 2 hot-swappable packs",
  "price_usd": 12999,
  "cad_or_urdf_url": "https://github.com/DDTRobot/TITA_Description",
  "sources": [
   "https://top3dshop.com/product/direct-drive-tita",
   "https://github.com/DDTRobot/TITA_Description",
   "https://github.com/DDTRobot/tita_rl",
   "https://github.com/DDTRobot/DDT_Lab"
  ],
  "notes": "Mass 24.1 kg is without battery; the URDF sums to ~27.7 kg (derived). Wheel radius 0.0925 m from the URDF. Speed 3 m/s, jump 30 cm (another listing says 20 cm). Jetson Orin NX 16GB, ROS 2 + Zenoh. Richest public RL tooling (Isaac Gym MIT; Isaac Lab DDT_Lab unlicensed)."
 },
 {
  "name": "Ascento (ICRA 2019 research robot)",
  "maker": "ETH Zurich (later Ascento Robotics)",
  "open_source": false,
  "license": null,
  "url": "https://arxiv.org/abs/2005.11435",
  "height_mm": 660,
  "mass_kg": 10.4,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "One hip motor per leg driving an optimised three-bar linkage that approximates vertical wheel travel. Torsion springs for gravity compensation and jumping. No knee motor, no abduction.",
  "leg_motors": "2x ANYbotics ANYdrive series-elastic actuators, 40 Nm peak",
  "wheel_motors": "2x Maxon EC90 frameless direct-drive hub motors, 3.5 Nm max, EPOS4 controllers",
  "battery": "4x 3S LiPo 5000 mAh in series (motors) + 4S 2200 mAh LiPo (compute); ~1.5 h",
  "price_usd": null,
  "cad_or_urdf_url": null,
  "sources": [
   "https://arxiv.org/abs/2005.11435",
   "https://newatlas.com/robotics/ascento-wheeled-legged-robot",
   "https://arxiv.org/html/2402.06143v1"
  ],
  "notes": "Height adjustable 310-660 mm. SLS PA12 topology-optimised parts. Intel NUC i7, LQR control. Jump ~0.4 m (New Atlas). RL stair-climbing follow-up in Isaac Gym needed 20 ms delay simulation. Commercial Ascento Pro/Guard specs differ."
 },
 {
  "name": "Upkie",
  "maker": "Stéphane Caron and contributors (open-source community)",
  "open_source": true,
  "license": "Apache-2.0 (wheel tyre mesh CC BY 4.0)",
  "url": "https://github.com/upkie/upkie",
  "height_mm": null,
  "mass_kg": 5.3,
  "payload_kg": null,
  "wheel_diameter_mm": 112,
  "leg_topology": "Serial 2-link leg: hip motor at torso, knee motor carried on the femur, wheel motor at foot. No abduction. 6 actuators.",
  "leg_motors": "4x mjbots qdd100 beta 2 (16 Nm peak <1 s, 28.8 rad/s)",
  "wheel_motors": "2x mjbots moteus developer kit (direct drive), 1.7 Nm, 111 rad/s",
  "battery": "RYOBI 18 V tool battery",
  "price_usd": 3000,
  "cad_or_urdf_url": "https://github.com/upkie/upkie_description",
  "sources": [
   "https://github.com/upkie/upkie",
   "https://upkie.github.io/upkie/bill-of-materials.html",
   "https://upkie.github.io/upkie/kinematics.html",
   "https://github.com/upkie/upkie_description",
   "https://github.com/upkie/parts",
   "https://archive.fosdem.org/2026/schedule/event/8PUMMD-open-source-robotics-practice-upkie-wheeled-bipeds/",
   "https://ftp.fau.de/fosdem/2026/ub2147/8PUMMD-open-source-robotics-practice-upkie-wheeled-bipeds.vtt"
  ],
  "notes": "Mass is summed from the URDF (derived). Cost is 'around $3,000' per the FOSDEM 2026 abstract. Raspberry Pi 4 + mjbots pi3hat. FDM-printed parts in FreeCAD. v2 (2026) uses a stiffer fork lower leg after printed tibias and femurs broke. PPO balancer (ground-velocity action) and mjlab policies."
 },
 {
  "name": "TRON 1 (wheeled-foot configuration)",
  "maker": "LimX Dynamics",
  "open_source": "partial",
  "license": "tron1-rl-isaaclab and tron1-mujoco-sim: Apache-2.0; tron1-rl-isaacgym: BSD-3-Clause",
  "url": "https://limxdynamics.com/en/tron1/spec",
  "height_mm": 845,
  "mass_kg": 20,
  "payload_kg": 10,
  "wheel_diameter_mm": null,
  "leg_topology": "unknown from spec page; multi-modal biped with interchangeable point-foot, sole and wheel feet",
  "leg_motors": "48 V joint actuators, 30 Nm rated, 60 Nm peak, 15 rad/s",
  "wheel_motors": "unknown",
  "battery": "46.8 V 4.5 Ah ternary Li, <=2 h, swappable",
  "price_usd": 25000,
  "cad_or_urdf_url": "https://github.com/limxdynamics/tron1-rl-isaaclab",
  "sources": [
   "https://limxdynamics.com/en/tron1/spec",
   "https://www.robotshop.com/products/limx-dynamics-tron-1-multi-modal-biped-robot-edu",
   "https://github.com/limxdynamics/tron1-rl-isaaclab",
   "https://github.com/limxdynamics/tron1-mujoco-sim"
  ],
  "notes": "Height and mass are upper bounds (<=845 mm size, <=20 kg). Wheeled speed <=3 m/s. Intel i3 12th gen. The Isaac Lab repo ships a USD and is the best permissively licensed Isaac Lab wheel-legged starting point."
 },
 {
  "name": "foc-wheel-legged-robot",
  "maker": "Skythinker616 (hobby, Bilibili)",
  "open_source": true,
  "license": "GPL-3.0",
  "url": "https://github.com/Skythinker616/foc-wheel-legged-robot",
  "height_mm": null,
  "mass_kg": null,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "Closed linkage, 2 body-mounted motors per leg, controlled as a virtual leg (VMC) with LQR gains fitted against leg length",
  "leg_motors": "4x 4010 gimbal BLDC (12 V, 0.22 Nm stall, 125 g, CNY 50)",
  "wheel_motors": "2x 2804 gimbal BLDC direct drive (0.04 Nm stall, CNY 13)",
  "battery": "3S 800 mAh LiPo, 20-30 min",
  "price_usd": null,
  "cad_or_urdf_url": "https://github.com/Skythinker616/foc-wheel-legged-robot/tree/main/solidworks",
  "sources": [
   "https://github.com/Skythinker616/foc-wheel-legged-robot",
   "https://github.com/Skythinker616/foc-wheel-legged-robot/tree/main/solidworks",
   "https://github.com/Skythinker616/foc-wheel-legged-robot/tree/main/matlab"
  ],
  "notes": "BOM CNY 549 without FPV (~USD 75 at an assumed ~7.2 CNY/USD; conversion not sourced, so price_usd is left null). Mostly 3D printed + acrylic. STM32 CAN FOC drivers, ESP32 + MPU6050, Simscape sim. ~1.8k stars."
 },
 {
  "name": "Micro-Wheeled_leg-Robot",
  "maker": "MuShibo / Li Yufeng (hobby)",
  "open_source": true,
  "license": null,
  "url": "https://github.com/MuShibo/Micro-Wheeled_leg-Robot",
  "height_mm": null,
  "mass_kg": null,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "Desktop-scale linkage leg driven by Feetech bus servos",
  "leg_motors": "2x Feetech bus servos (model unknown)",
  "wheel_motors": "2x gimbal BLDC via SimpleFOC (L6234 driver, AS5600 encoders)",
  "battery": "unknown",
  "price_usd": null,
  "cad_or_urdf_url": "https://github.com/MuShibo/Micro-Wheeled_leg-Robot",
  "sources": [
   "https://github.com/MuShibo/Micro-Wheeled_leg-Robot"
  ],
  "notes": "No licence file (all rights reserved). ESP32 + MPU6050, web joystick. ~3.8k stars."
 },
 {
  "name": "Venus-1 four-link wheel-legged robot",
  "maker": "track-tech (undergraduate thesis)",
  "open_source": true,
  "license": "GPL-3.0",
  "url": "https://github.com/track-tech/Venus-1__Four-link-wheel-legged-robot",
  "height_mm": null,
  "mass_kg": null,
  "payload_kg": null,
  "wheel_diameter_mm": 90,
  "leg_topology": "Four-bar linkage leg (fitted with Pyslvs)",
  "leg_motors": "2x Xiaomi CyberGear (CNY 499 each)",
  "wheel_motors": "2x DJI M2006 P36 geared + C610 ESC",
  "battery": "24 V 35C LiPo",
  "price_usd": null,
  "cad_or_urdf_url": "https://github.com/track-tech/Venus-1__Four-link-wheel-legged-robot",
  "sources": [
   "https://github.com/track-tech/Venus-1__Four-link-wheel-legged-robot"
  ],
  "notes": "Cost ~CNY 2,576 without RC. Structure is 3 mm 3240 epoxy (FR4-like) plate; electronics bay printed. Author's defects: geared M2006 backlash causes jitter at the balance point (use direct-drive gimbal wheels); CyberGear must be re-zeroed every power-up; PU wheels came loose; yaw drift."
 },
 {
  "name": "Wheel-legged robot (Multivac11)",
  "maker": "Multivac11 (solo hobby/student build)",
  "open_source": true,
  "license": null,
  "url": "https://github.com/Multivac11/Wheel-legged-robot--Main_Code",
  "height_mm": null,
  "mass_kg": 12.9,
  "payload_kg": null,
  "wheel_diameter_mm": 150,
  "leg_topology": "Five-bar: joint motor spacing 150 mm, thigh 150 mm, shank 270 mm, virtual leg 95.5-398 mm",
  "leg_motors": "4x Unitree A1 (RS-485, one UART per motor, run at 500 Hz)",
  "wheel_motors": "2x DJI M3508 (modified gearbox)",
  "battery": "unknown",
  "price_usd": null,
  "cad_or_urdf_url": null,
  "sources": [
   "https://github.com/Multivac11/Wheel-legged-robot--Main_Code"
  ],
  "notes": "No licence file. Body 9.5 kg, each leg linkage 1.626 kg excluding wheel, wheel radius 75 mm."
 },
 {
  "name": "Open Duck Mini v2",
  "maker": "Antoine Pirrone (apirrone) and community; sponsored by Hugging Face / Pollen Robotics",
  "open_source": true,
  "license": "Apache-2.0 (main repo); Runtime, Playground and reference-motion repos have no licence file",
  "url": "https://github.com/apirrone/Open_Duck_Mini",
  "height_mm": 420,
  "mass_kg": 2.1,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "Walking biped (no wheels): 5 DOF per leg (hip yaw, roll, pitch, knee, ankle) + 4 DOF neck/head + 2 hobby-servo antennas",
  "leg_motors": "14x Feetech STS3215 7.4 V '19 kg.cm' bus servos (~EUR 14 each; ~3.35 Nm cap in identified model)",
  "wheel_motors": null,
  "battery": "2S 2x18650 (Molicel P30B) + BMS + 5 V UBEC",
  "price_usd": 400,
  "cad_or_urdf_url": "https://cad.onshape.com/documents/64074dfcfa379b37d8a47762/w/3650ab4221e215a4f65eb7fe/e/0505c262d882183a25049d05",
  "sources": [
   "https://github.com/apirrone/Open_Duck_Mini",
   "https://github.com/apirrone/Open_Duck_Mini/blob/main/docs/print_guide.md",
   "https://github.com/apirrone/Open_Duck_Mini/blob/main/docs/sim2real.md",
   "https://docs.google.com/spreadsheets/d/1gq4iWWHEJVgAA_eemkTEsshXqrYlFxXAPwO515KpCJc",
   "https://github.com/apirrone/Open_Duck_Playground",
   "https://github.com/apirrone/Open_Duck_Mini_Runtime",
   "https://github.com/apirrone/Open_Duck_reference_motion_generator",
   "https://github.com/Rhoban/bam",
   "https://arxiv.org/html/2501.05204v1",
   "https://tnkr.ai/explore/docs/open-duck-mini/open-duck-mini-v2"
  ],
  "notes": "price_usd is the README's 'under $400' bound; the BOM sheet totals EUR 398.10 (EUR 432.34 with expression package) and the Tnkr kit is $600. Mass is summed from MJCF body masses (derived). Fully printed in PLA at 15% infill, TPU soles. Pi Zero 2W, BNO055. Trained in MuJoCo Playground/MJX at 50 Hz with Placo reference motions, imitation reward, BAM actuator models, backlash and 0-3 step delay randomization."
 },
 {
  "name": "Microduck",
  "maker": "Pollen Robotics / Hugging Face",
  "open_source": "partial",
  "license": "Code Apache-2.0; STL meshes in microduck_rl CC BY-NC-SA 4.0; vendor asks it not be called open-source hardware",
  "url": "https://github.com/pollen-robotics/microduck",
  "height_mm": 250,
  "mass_kg": 0.8,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "Small walking biped (15 servos) with passive roller-skate wheel attachments ('roller mode')",
  "leg_motors": "15 servos (modelled as BAM XL330 models in microduck_rl)",
  "wheel_motors": "passive wheels (unpowered)",
  "battery": "NP-F550 2600 mAh, ~1 h",
  "price_usd": 399,
  "cad_or_urdf_url": "https://github.com/pollen-robotics/microduck_rl",
  "sources": [
   "https://github.com/pollen-robotics/microduck",
   "https://pollen-robotics.com/microduck",
   "https://techcrunch.com/2026/08/27/hugging-face-is-selling-a-cute-399-open-source-duck-robot-microduck/",
   "https://cnx-software.com/2026/08/28/microduck-a-duck-like-biped-robot-designed-for-physical-ai-experimentation-and-fun",
   "https://github.com/pollen-robotics/microduck_rl",
   "https://github.com/pollen-robotics/microduck_rl/blob/develop/AGENTS.md"
  ],
  "notes": "Rockchip RK3566, 50 Hz. Pre-orders opened 2026-08-27. mjlab PPO, 1-2 h to a usable gait at 4096 envs. Models voltage sag and backlash as a passive hinge. Character features: seeded per-robot voice, petting detection, Tamagotchi-style app. Head is 38% of mass."
 },
 {
  "name": "Go2-W (wheeled quadruped, technique reference only)",
  "maker": "Unitree",
  "open_source": false,
  "license": null,
  "url": "https://www.robotshop.com/products/unitree-go2-w-wheeled-robotic-dog-us",
  "height_mm": null,
  "mass_kg": 18,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "Quadruped, 3 joints per leg + powered wheel per leg",
  "leg_motors": "Unitree joint motors (~45 Nm knee per reseller)",
  "wheel_motors": "unknown",
  "battery": "15000 mAh per one reseller (figures conflict)",
  "price_usd": null,
  "cad_or_urdf_url": null,
  "sources": [
   "https://www.robotshop.com/products/unitree-go2-w-wheeled-robotic-dog-us"
  ],
  "notes": "Not a biped; listed because Unitree has no wheel-legged biped. Reseller specs conflict."
 },
 {
  "name": "Beni",
  "maker": "Mondo Robotics (Shenzhen)",
  "open_source": false,
  "license": null,
  "url": "https://www.notebookcheck.net/4K-without-the-flight-This-jumping-robot-could-replace-your-drone.1356616.0.html",
  "height_mm": null,
  "mass_kg": 1.75,
  "payload_kg": null,
  "wheel_diameter_mm": null,
  "leg_topology": "two wheel-legs (self-balancing)",
  "leg_motors": null,
  "wheel_motors": null,
  "battery": "swappable pack, about 90 min (reports vary)",
  "price_usd": 549,
  "cad_or_urdf_url": null,
  "sources": [
   "https://www.notebookcheck.net/4K-without-the-flight-This-jumping-robot-could-replace-your-drone.1356616.0.html",
   "https://www.diyphotography.net/?p=321790",
   "https://www.photoworkout.com/?p=223335",
   "https://www.tomsguide.com/cameras-photography/i-cant-fly-drones-in-nyc-so-i-let-this-camera-robot-follow-me-around-instead-and-came-away-impressed"
  ],
  "notes": "Consumer follow-and-film camera robot (Kickstarter, >$2.5 M). 3.86 lb, 17.9 mph top speed, jumps obstacles (10 cm in some reports, 10 in in another), rights itself after falls, climbs stairs by hopping, onboard tracking with no internet, 4K30 camera. Hands-on reviews: tracking still unreliable, not waterproof. Inspiration for Gyropup's character and tricks; Gyropup is ten times heavier and built to be tougher."
 }
]