Architecture:Field Controller Layer

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

• System Architecture Overview
• Farm Controller Layer (Local / Federated)
• Hydraulic & Water Systems
• Electrical & Control Interfaces
• Measuring, Monitoring & Documentation Systems