Files
AR-Autopilot/firmware/ar_autopilot_v1/src/pid/pid_inner_task.h
T
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

46 lines
1.7 KiB
C++

// =============================================================================
// pid_inner_task.h -- 50 Hz inner-loop control task (Sprint 2)
// =============================================================================
//
// Wraps the header-only PidInner controller in a FreeRTOS task pinned to
// Core 1 (real-time core). Reads the rudder position from hal::rudder_sensor,
// consumes the setpoint that the outer loop / Modbus client wrote, and
// commands hal::rudder_actuator. Refuses to act in STANDBY or with master
// power off (those interlocks live in hal::rudder_command itself).
// =============================================================================
#pragma once
#include "pid_inner.h"
namespace arautopilot::pid {
/// Initialise the controller with the seed gains. Must be called from
/// setup() once.
void pid_inner_task_init();
/// Spawn the FreeRTOS task. Must be called after pid_inner_task_init().
void pid_inner_task_start();
/// Update the setpoint that the inner loop pursues. Called by the Modbus
/// slave (when an operator writes a holding register) and, later, by the
/// outer loop task. Units: degrees, signed.
void pid_inner_set_setpoint_deg(float setpoint_deg);
/// Read the current setpoint (thread-safe).
float pid_inner_setpoint_deg();
/// Read the latest PID output command (signed PWM percent).
float pid_inner_last_output_pct();
/// Read the latest error (deg) the controller saw.
float pid_inner_last_error_deg();
/// Hot-swap gains at runtime (thread-safe).
void pid_inner_update_gains(float kp, float ki, float kd);
/// Read the gains currently in use.
void pid_inner_get_gains(float& kp, float& ki, float& kd);
} // namespace arautopilot::pid