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# Autonomous Zero-Turn Retrofit Kit
[](LICENSE)
[](#status--honest-limitations)
[](software/tests)
[](https://ardupilot.org/rover)
[](https://github.com/zohebzma2-cmyk/autonomous-mower/discussions)
> **Most open-source mowers convert a toy robot-mower. This retrofits a 615 lb commercial gas zero-turn.**
*Parametric CAD, spec-matched to the full published envelope (1968 × 1610 × 1039 mm · deck 1321 mm · tyres 508/279 mm) — [still renders](gallery.html) · [carrier PCB](hardware/pcb/)*
Turn a seated zero-turn mower into a self-driving, iPad-controlled robot — **RTK GPS + LiDAR + cameras + on-device AI** — weatherproofed to live outdoors, and **reproducible on any ZTR** by re-measuring a handful of dimensions.
> **Status: 🔧 in active build.** Design, CAD, firmware, control software, and docs are complete and verified (69/69 tests). The machine is currently being built in person — parts on order, brackets printing, wiring the kill-chain first. This is a multi-month, safety-gated build, documented as it happens — not a plug-and-play kit.
**Confirmed reference machine:** Gravely **ZT X 52** · ~2021 · **Kohler 7000** (24 hp, 725 cc) · electric PTO clutch.
> 🏁 **New here? Start with [`docs/00-BUILD-MANUAL.md`](docs/00-BUILD-MANUAL.md)** — the end-to-end build sequence.
>
> 🕹️ **Already RC-controlled (tracked / slope mower)?** [`docs/ADAPT-RC-MOWER.md`](docs/ADAPT-RC-MOWER.md). The Pixhawk drops in front of the stock drive controller, so you skip the actuators and ESP32.
>
> 🚜 **Phase 3 — the whole rig:** [`docs/ATTACHMENTS.md`](docs/ATTACHMENTS.md) — self-dumping power bagger, rotating blower/trimmer boom, FIMCO tow sprayer with speed-proportional dosing, TPMS, self-start ignition + choke, and the no-rut 3-point turn planner (physics inside).
>
> 📓 **How it evolved:** [`docs/DESIGN-LOG.md`](docs/DESIGN-LOG.md) — every iteration, every wrong turn, constraints A–Z.
> **What's next:** [`docs/ROADMAP-75.md`](docs/ROADMAP-75.md) — 75 planned upgrades.
> **Ordering:** [`cart/ORDER.md`](cart/ORDER.md) + machine-readable [`cart/ORDER-SHEET.csv`](cart/ORDER-SHEET.csv).
> **Building:** [`docs/MEASURE.md`](docs/MEASURE.md) (the 10-minute caliper session — do this first) · [`docs/PRINT-QUEUE.md`](docs/PRINT-QUEUE.md) (40 parts, grams + hours) · [`docs/TOOLS.md`](docs/TOOLS.md) · [`docs/SUBSTITUTIONS.md`](docs/SUBSTITUTIONS.md) · [`docs/CHANGELOG.md`](docs/CHANGELOG.md).
>
> 🌐 **Interactive writeup:** [zohebalvi.com/projects/autonomous-mower](https://zohebalvi.com/projects/autonomous-mower.html) — 3D model, live control-UI demo, architecture, and the full parts list with order links.
> ⚠️ **A 52″ mower deck can kill.** Read [`docs/BUILD.md` §0 Safety](docs/BUILD.md) before powering anything. **Blades stay disconnected until drive + navigation + every failsafe is proven.**
---
## The architecture in one line
**ArduPilot Rover** on a Pixhawk 6C owns drive + RTK navigation + the failsafe chain (skid-steer fits a ZTR natively); a **Raspberry Pi 5 + Hailo-8L** (13 TOPS) rides shotgun for LiDAR obstacle-stop and camera AI, talking to the FC over MAVLink; an **ESP32** closes the lap-bar position loop the autopilot can't drive directly. One web UI serves both an iPad over WiFi and an on-unit touchscreen.
```
┌───────────── SENSE ─────────────┐ ┌────── THINK ──────┐ ┌──── ACT ────┐
Dual RTK GPS (±2 cm, ~0.4° heading) ─────┼──► Pixhawk 6C ────────┼──► lap-bar L/R
360° LiDAR ──────────────┐ │ (ArduPilot Rover) │ (via ESP32)
Front + rear cameras ────┼──► Pi 5 + Hailo├── MAVLink ───────────┤
Overhead ultrasonic ─────┘ (vision/UI) │ ESP32 (lap-bar PID) ├──► PTO relay
└───────────────────────┘ (blades)
```
---
## The machine — down to the millimetre
| | Gravely ZT X 52 (Kohler 915256) |
|---|---|
| Overall | **1968 × 1610 × 1039 mm** (L×W×H) |
| Curb weight | 615 lb (279 kg) |
| Cutting deck | **1321 mm** (52″), 11-ga fabricated |
| Rear drive wheels | 20×10-8 → **Ø 508 mm**, 254 mm wide |
| Front casters | 11×6-5 → **Ø 279 mm** |
| Seat pan height | 580 mm off ground (**no factory ROPS**) |
| Frame rail | 50.8 mm square tube |
| Lap-bar tube | **Ø 25.4 mm** round steel (MIC to confirm), 560 mm spacing, ~90 mm throw |
| Powertrain | 24 hp Kohler 7000 (725 cc) · Hydro-Gear ZT-2200 · 7 mph · **electric PTO** |
Retrofit parts are modeled to their datasheets — e.g. the **PA-14P actuator** (retracted 241.6 mm, Ø38.1 mm body, 6.35 mm clevis pin), **simpleRTK2B** (68.58 × 53.34 mm, Arduino-Uno footprint), **RPLidar A1M8** (teardrop 96.74 × 70.28 mm base). See [`cad/params.scad`](cad/params.scad).
---
## What's in the repo
```
autonomous-mower/
├── docs/
│ ├── 00-BUILD-MANUAL.md ← START HERE — Phase 0–6 build sequence
│ ├── BUILD.md ← full build & SAFETY spec (architecture, training, go/no-go)
│ ├── WIRING.md ← power distribution, kill-chain, per-module pinouts
│ ├── PRINT_GUIDE.md ← per-part orientation, brim, supports, plate batching
│ └── wiring-diagram.svg
├── cad/ ← parametric OpenSCAD — 40 print-ready parts
│ ├── params.scad ← ★ MASTER PARAMETERS — edit SECTION 1 to fit any ZTR
│ ├── assembly.scad ← whole machine; SHOW=all|body|black|retro for multi-material export
│ ├── mower.scad ← parametric mower mock (context)
│ ├── {enclosure,actuator_brackets,gps_mast,lidar_mount,camera_mount,controls_bracket,badge,attachments_brackets,sensor_mounts}.scad
│ ├── export_stl.sh ← export every PRINT_* part + bed-fit gate (rejects > 145 mm)
│ ├── bake_brims.sh ← welds a bed-adhesion brim onto every part
│ ├── render_gallery.sh · render_hero.py ← gallery stills · README orbit GIF + social card
│ └── stl/ · renders/ · vendor/
├── software/
│ ├── companion/ ← Python: app.py (HTTP+SSE), safety.py, vision.py, missions.py, mav.py
│ ├── ui/ ← the control UI (iPad + on-unit kiosk)
│ ├── tests/ ← 69 stdlib tests (safety, geofence, attachments, turns, coverage, keep-outs, vision, mission encoding)
│ └── deploy/ ← systemd service + Chromium kiosk autostart
├── firmware/
│ ├── lapbar_controller/ ← ESP32: FC-PWM → pot → BTS7960 position loop, fail-to-neutral
│ └── ardupilot/ ← rover_params.parm (skid-steer, RTK, geofence, moving-baseline)
├── hardware/pcb/ ← ★ MowerCarrier: power + kill-chain + ESP32 carrier board
│ └── kicad/ ← generated KiCad 9 project (ERC/DRC clean) + Gerbers — read REVIEW.md before fab
│ ├── schematic.svg · layout.svg · render-*.png ← exported from the KiCad project
│ └── README.md · netlist.md · BOM.md · FABRICATION.md
└── cart/ ← ORDER.md (real BOM + links), order.html
```
---
## Quickstart
### CAD → STL
```bash
cd cad
# 1. Edit params.scad SECTION 1 to your machine — start from a profile in cad/profiles/
# (zt-x-52.scad = the reference build; generic-60in.scad = commercial-class starting point)
# or generate your block interactively: zohebalvi.com/mower → "Adapt it to YOUR mower"
openscad assembly.scad # see the whole machine
./export_stl.sh # export all printable parts + bed-fit check
./bake_brims.sh # weld brims for adhesion
./render_gallery.sh # machine stills; python3 render_hero.py re-shoots the orbit GIF (needs Pillow)
# slice cad/stl/brim/*.stl in FlashPrint for the Adventurer 3 (ASA or PETG)
```
### Dev setup (once — user-level, no sudo/Homebrew)
```bash
./scripts/setup-dev.sh # uv + Python 3.12 .venv + OpenSCAD (+ --kicad: KiCad, Freerouting, arduino-cli)
./scripts/check.sh --full --sitl # every gate: tests, mypy, CAD asserts, renders, docs, SITL end-to-end
```
### Control software (runs today, no hardware)
```bash
python3 software/companion/app.py --sim --port 8080
# open http://localhost:8080 — arm, draw a zone, run a coverage mission in simulation
python3 software/tests/test_backend.py # 69/69
./scripts/sitl.sh # the REAL ArduPilot Rover 4.7.1 firmware (SITL) behind the same UI
```
### Firmware
- **ESP32:** flash `firmware/lapbar_controller/lapbar_controller.ino` (Arduino IDE / arduino-cli).
- **ArduPilot:** load `firmware/ardupilot/rover_params.parm` in Mission Planner (skid-steer + RTK + failsafes; moving-baseline block commented for the dual-antenna heading upgrade).
---
## Training — all three, built in order
1. **Teach-and-repeat** — drive the path once, it repeats the RTK track.
2. **Boundary → auto-coverage** — drive the perimeter, the planner fills it with rows and uploads them as an ArduPilot AUTO mission. It handles real yards: L/U shapes (cell decomposition, routed transits), rows along the direction with the fewest turns, **keep-outs** (beds, trees, the shed — or spots the sonar keeps hitting), no-rut turns with **perimeter laps** for the headland, and shows m², minutes and % covered before it moves.
3. **AI learns the yard** — the camera/LiDAR model refines a semantic map over runs (Hailo).
---
## Precision
The upgrade that matters is **dual-antenna moving-baseline heading**. One RTK antenna gives a great position but a noisy heading at a standstill; a second antenna on a ≥ 500 mm baseline fixes heading geometrically (~0.4°), turning ~10 cm cross-track into a few cm. Config in `firmware/ardupilot/rover_params.parm`.
| | |
|---|---|
| Position | **±2 cm** RTK-fixed (u-blox ZED-F9P) |
| Heading | **~0.4°** moving-baseline (dual antenna) |
| Cross-track | few cm, row to row |
| On-device AI | **13 TOPS** (Hailo-8L), INT8, < 30 ms, no cloud |
---
## Safety — a layered kill chain (wire & test this FIRST)
No single failure leaves the machine moving. Blades stay disconnected until every layer is proven.
1. **Physical e-stop** (normally-closed) — in series with the drive relay + PTO relay; cuts power independent of any code.
2. **RC kill** — an independent FlySky channel → ArduPilot RC failsafe → HOLD + disarm.
3. **Software interlock** (`safety.py`) — evaluates incline (15° cutoff), overhead (1.6 m), and obstacle every cycle; priority `e-stop > slope > overhead > obstacle`.
4. **Fail-to-neutral** — on e-stop or signal loss the ESP32 drives the lap bars to center, then coasts; ArduPilot failsafes (GPS loss, geofence, low battery) hold.
Full pinout + kill-chain wiring in [`docs/WIRING.md`](docs/WIRING.md).
---
## Bill of materials
Real, in-stock parts — verified against live listings, no fabricated SKUs. Two tiers: **functional ≈ $1,644**, or **precision ≈ $1,812** with the dual-antenna heading kit. Full itemized sheet with links in [`cart/ORDER.md`](cart/ORDER.md).
- **Navigation / compute:** Pixhawk 6C ([Holybro](https://holybro.com/products/pixhawk-6c)) · simpleRTK2B + ANN-MB-00 ([ArduSimple](https://www.ardusimple.com/product/simplertk2b/)) · Pi 5 + Hailo AI HAT+ ([PiShop](https://www.pishop.us/product/raspberry-pi-ai-hat-13-tops/))
- **Perception:** RPLidar A1M8 · 2× Pi Camera 3 · JSN-SR04T ultrasonic
- **Steering / drive:** 2× Progressive Automations PA-14P · 2× BTS7960 · ESP32
- **Safety / power:** IP65 NC e-stop · 40 A relays · PM02 power module · fuse block · bucks
---
## Adapting to another zero-turn
Open [`cad/params.scad`](cad/params.scad) → **SECTION 1**, re-measure the lap bars / frame / seat, re-render, re-slice. That's the whole port — the mounts, brackets, and masts regenerate around your numbers. Toro, Bad Boy, Spartan, Ferris, Scag, etc.
---
## Status & honest limitations
Design + CAD + firmware + control software + docs are complete and verified (49/49 tests). The build is **in progress in person**. Remaining work is hardware-gated: SITL/on-FC validation of the MAVLink handshake, training the Hailo `.hef` model, and the future fleet/RaaS layer. See [`docs/BUILD.md §12`](docs/BUILD.md).
## Related open-source mowers & rovers
This project stands on the shoulders of a great open community — go star these too:
- **[OpenMower](https://github.com/ClemensElflein/OpenMower)** (Clemens Elflein) — the flagship: retrofits *consumer* robot mowers with a custom mainboard + RTK + ROS. Same RTK/Pi/vision philosophy; we take it to a full-size gas ZTR.
- **[Ardumower / Sunray](https://github.com/Ardumower/Sunray)** — the original DIY-mower ecosystem; Sunray pioneered RTK-without-a-perimeter-wire.
- **[ArduPilot Rover](https://ardupilot.org/rover)** — the autopilot this build runs. The [robot-mower threads](https://discuss.ardupilot.org/t/robot-mower-based-on-ardurover/61999) on their Discourse are the best place to talk shop.
- **[Twisted Fields — Acorn](https://github.com/Twisted-Fields/acorn-precision-farming-rover)** & **[FarmBot](https://github.com/farmbot)** — adjacent open outdoor-autonomy / ag-robotics done well.
## Community & contributing
- 💬 **[GitHub Discussions](https://github.com/zohebzma2-cmyk/autonomous-mower/discussions)** — *Show & Tell* your ZTR build, ask in *Q&A*, propose *Ideas*, follow *Build logs*.
- 🔧 **Adapting to a different zero-turn?** That's the whole point — a new machine profile is the most valuable contribution you can make. See [`Adapting to another zero-turn`](#adapting-to-another-zero-turn) and open a PR with your `params.scad` SECTION 1.
- 🛠️ **Custom carrier PCB** — the power/kill-chain/ESP32 board lives in [`hardware/pcb/`](hardware/pcb/): a routed, ERC/DRC-clean KiCad 9 project generated from one Python file, with Gerbers ready for review ([`REVIEW.md`](hardware/pcb/kicad/REVIEW.md) first). Remix it for your machine.
- See [`CONTRIBUTING.md`](CONTRIBUTING.md) for the safety-gated workflow. Good first issues are labeled `good first issue`.
## License & safety
Open source under the [MIT License](LICENSE). ⚠️ **This drives a machine with large blades that can kill** — it's released for education/research; you are solely responsible for safe construction, testing, supervision, and local-law compliance. Keep blades disconnected until every failsafe is proven.
*A personal robotics project by [Zoheb Alvi](https://zohebalvi.com).*
b1b1ea139This file is pinned to the selected release. Download the original to open it in your design tool.