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Architecture:Field Controller Layer

From AOWIS

Principles:Field Controller Layer

See overview: System Architecture Overview

The Field Controller Layer is the on-site, safety-authoritative AOWIS controller. It is responsible for executing irrigation schedules, monitoring sensors, enforcing fail-safes, and ensuring reliable operation even without network connectivity.

All AOWIS deployments must include a Field Controller for each irrigation site or zone.

1. Purpose

The Field Controller:

  • Executes irrigation schedules in real time.
  • Reads all field sensors and enforces safety logic.
  • Operates autonomously offline; cannot be bypassed by Farm or HQ Controllers.
  • Provides local operator monitoring for non-critical functions only.
  • Logs all events, including safety triggers, irrigation actions, and manual operator inputs.

2. Core Responsibilities

  • Irrigation Execution
    • Opens and closes valves according to schedules.
    • Controls pumps based on tank levels, flow, and pressure.
    • Stops irrigation when safety thresholds are exceeded.
  • Sensor Monitoring
    • Soil moisture per zone
    • Water tank levels (FULL / LOW floats)
    • Flow meters and pressure sensors
    • Battery voltage / current
    • Rain detection (e.g., tipping bucket)
    • Optional: Optical / camera data for local analytics
  • Fail-Safe Enforcement
    • Prevent over-irrigation, flooding, and pump damage.
    • Stop pumps when tank is LOW or battery voltage below minimum.
    • Stop irrigation during rain lockout or safety-triggered conditions.
    • Operates independently of software updates or network availability.
  • Local Operator Interaction
    • Embedded interface (small touchscreen, local web UI, or buttons + display).
    • Operators may view data, acknowledge alerts, or trigger non-critical overrides only.
    • Critical irrigation decisions cannot be overridden by the operator.
  • Event Logging & Auditability
    • All irrigation events, sensor readings, alerts, and operator interactions must be logged with timestamps.
    • Logs are persisted locally and later transmitted to Farm/HQ Controllers during sync.

3. Offline Operation Requirements

  • The Field Controller must operate independently of LAN, WiFi, or cellular connections.
  • Irrigation, safety enforcement, and data collection must continue uninterrupted.
  • Any local operator interface functions must not compromise safety-critical rules.

4. Optional Weather-Aware Control

  • Field Controllers operate fully offline by default using local sensors, operational logic, and historical data.
  • When internet connectivity is available, controllers may fetch local or global weather forecasts:
    • High wind, storm, or extreme precipitation warnings trigger automated alerts to operators.
    • Controllers can temporarily maintain minimum water levels in tanks, suspend irrigation, or adjust equipment operation to prevent structural damage.
    • Forecasts may also inform reservoir management, overflow routing, irrigation sequencing, and protective actions for farm structures.
  • Local wind measurement devices are recommended at every farm to provide real-time, farm-wide risk assessment:
    • Controllers evaluate wind conditions continuously for all critical infrastructure.
    • Immediate actions are triggered if an asset is at risk (e.g., tanks, greenhouses, solar panels, or lightweight structures).
    • Actions may include maintaining minimum ballast, suspending irrigation, adjusting movable structures, or sending operator alerts.
  • All forecast- and wind-informed actions are non-normative and optional; offline/manual operation remains fully functional.
  • Actions based on wind measurements or forecasts must never override core safety-critical rules.
  • All such preventive actions and alerts are logged for auditability.

5. Authority Rules

  • Field Controller is fully authoritative for all safety-critical operations.
  • No remote controller or operator input can bypass Field Controller fail-safes.
  • Farm or HQ Controllers may suggest configuration or irrigation adjustments, but Field Controller rules take precedence.

6. Human Interface

  • Minimal embedded UI for operators:
    • View irrigation status per zone
    • See safety alerts (tank LOW/FULL, battery low, rain lockout)
    • Acknowledge alerts
  • Operators cannot override critical safety logic.
  • Operator actions are logged for audit purposes.

7. Hardware & Integration

  • Embedded microcontrollers (ESP32, Arduino, or industrial equivalent).
  • Interfaces:
    • PIO/relay control for pumps and valves
    • Analog/digital inputs for sensors
    • Optional serial / I2C / SPI for additional modules
  • Power: must tolerate brownouts, low-voltage conditions, and recover automatically.
  • Optional backup: small local battery or UPS to maintain control during power interruptions.

8. Compliance Notes

  • AOWIS compliance requires each field site to have a Field Controller.
  • All safety and irrigation decisions must be logged locally.
  • Any attempt to bypass Field Controller logic by higher-layer controllers invalidates AOWIS compliance.
  • Field Controller must remain fully functional even if disconnected from Farm or HQ controllers.

9. References

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