alro65 295efa2d83 sprint-2: PID inner loop + Python rudder simulator
End-to-end implementation per docs/sprint-2-plan.md.

Builds: pio run -e esp32-dev SUCCESS, RAM 6.8%, Flash 26.8% (351 KB).
Tests: pytest 129/129 green (110 Sprint 1 + 19 Sprint 2).

Python (arautopilot/studio/simulator/):

- rudder_dynamics.py: marine-realistic physical model of a hydraulic
  rudder actuator. Defaults tuned so 100 % PWM produces steady-state
  v_max ~5 deg/s, matching the brief's "typical 3-6 dps" for a 30 m
  yacht. Includes deadband, min-useful PWM snap, port/stbd asymmetry,
  end-stops, optional external torque, RunRecorder helper.
- pid_inner.py: pure-Python reference PID. Anti-windup via back-
  calculation, setpoint rate limit, setpoint deadband, derivative LPF,
  actuator non-linearity compensation. This module is the algorithmic
  source of truth; C++ firmware is a line-by-line port.

Firmware (firmware/ar_autopilot_v1/src/pid/):

- pid_inner.h: header-only C++17 controller, byte-equivalent port of
  pid_inner.py. Compiles on ESP32 toolchain AND on host g++/clang/MSVC
  (no Arduino dependencies) -- ready for native Unity cross-validation
  once a host compiler is installed.
- pid_inner_task.{h,cpp}: FreeRTOS task wrapper. 50 Hz on Core 1
  (real-time core). Subscribes to TWDT, bleeds integrator during
  STANDBY, surfaces telemetry + tunables via the Modbus slave.

Modbus map (regenerated from YAML):

- 6 new INPUT registers (40-45): setpoint, output, error, kp/ki/kd live
- 4 new HOLDING registers (16-19): writable setpoint + kp/ki/kd req
  (writes propagate atomically; zero kp rejected as ILLEGAL_DATA_VALUE)

Tests:

- test_rudder_simulator.py: 9 tests (zero-input rest, full deflection,
  end-stop saturation, deadband, min-useful snap, asymmetry, recorder
  API, invalid dt, end-stop velocity zeroing).
- test_pid_inner_python.py: 10 tests (positive/negative step response,
  setpoint deadband holds, anti-windup bounds under saturation,
  allowed=false bleeds integrator, actuator deadband + asymmetry
  compensation, output saturation, rate limit, disturbance rejection).

NOT in Sprint 2 (intentional per brief sec. 12):
  - Outer heading PID, gain scheduling by SOG, ROT feed-forward
    (those land in Sprint 3)
  - Cross-validation tests via ctypes (need host C++ compiler that
    this Windows machine lacks; algorithmic parity enforced by review)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-18 15:27:45 -04:00

AR-Autopilot

Professional marine autopilot for vessels in the 30-40 m range (motor yachts, motor sailboats, fishing vessels, small ferries, coastal patrol boats).

Part of the AR Suite alongside AR-ECDIS, VMS-Sailor, AR-ShipDesign, AR-ElecArrangement, and AR-StabCol. Sold standalone or bundled with AR-ECDIS.

NOT Dynamic Positioning. NOT joystick docking. This is a classic heading-and-track autopilot with intelligent drift compensation, controlling rudder actuators (hydraulic or electric).


Status

Sprint 0 — Foundations (in progress).

This sprint delivers the repository structure, core data model, seed library, and a passing test suite. No functional firmware, Studio GUI, or display yet — those start in Sprint 1.

See docs/AR_Autopilot_brief.md for the complete project brief, scope, and roadmap.


Components

Component Tech Purpose
Studio (arautopilot/studio/) Python 3.11 + PySide6 Project configurator (integrator-side, not shipped to customers). Generates per-vessel .appack packages
Firmware (firmware/ar_autopilot_v1/) C++ on ESP32 via PlatformIO Real-time PID control, NMEA 2000 + Modbus, safety logic. Runs on the AR-NMEA-IO v1.0 board (shared with VMS-Sailor)
Display (display/) Flutter Desktop (Win + Linux) Dedicated bridge cockpit-feel touch display with rotary knob input
Core models (arautopilot/core/) Pydantic v2 Shared data model (vessel config, PID config, actuator config, alarms, modes, knob state)
Library (arautopilot/library/) YAML + JSON Curated seed: actuator profiles, default tunings per vessel type

Requirements

  • Python 3.11 or newer
  • Git
  • (Later sprints) PlatformIO, Flutter SDK, WiX Toolset

Quick start (Sprint 0)

# Create venv and install
python -m venv .venv
.\.venv\Scripts\Activate.ps1
python -m pip install -U pip
pip install -e ".[dev]"

# Run tests
pytest

# Run the Sprint 0 demo (creates, saves, reloads a project config)
python examples/sprint0_demo.py

Repository layout

AR-Autopilot/
├── arautopilot/          # Python package (core models, library, studio stubs, tests)
├── firmware/             # ESP32 firmware (Sprint 1+; only pinout.h in Sprint 0)
├── display/              # Flutter dedicated display (Sprint 4+)
├── examples/             # Runnable demos
├── docs/                 # Brief + per-sprint design docs
├── installer/            # WiX MSI scripts (later)
└── tools/                # Helper scripts (later)

See docs/architecture.md for a one-page architecture overview.


Sprint roadmap

Sprint Focus
0 Foundations: repo structure, core data model, seed library, tests
1 Firmware base (I/O, Modbus, NMEA 2000 read, STANDBY mode)
2 PID inner loop (rudder position control)
3 PID outer loop + Heading Hold (with ROT feed-forward & gain scheduling)
4 Studio + basic dedicated display
5 True Course + Track Keeping (smooth XTE correction)
6 Safety, alarms, NMEA 2000 publish, VMS alarm consumption
7 Knob + commissioning + offline auto-tuning
8 EKF + adaptive tuning + telemetry + VPN
9 Hardening + integrated testing
10+ Phase 2 (wind modes for sailboats) and beyond

Full detail in the brief.


License

Proprietary. All rights reserved. See LICENSE.txt.

Commercial deployment requires a per-vessel license bound to the installation HWID. Contact alro65@gmail.com for licensing.

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