UAV Emergency Communication - Secondary Channel

Python-based secondary safety channel for UAV emergency communication experiments using MAVLink and ArduPilot SITL.

The project validates how a separate software channel can monitor a UAV link, detect loss of communication and trigger emergency actions in simulation.

What It Does

• Monitors MAVLink heartbeat and telemetry over a dedicated UDP endpoint
• Detects primary-link loss using timeout-based monitoring
• Sends emergency actions through a separate command path
• Supports RTL, LAND, GUIDED HOLD, ARM/DISARM, TAKEOFF and altitude-change workflows
• Logs operational events, command acknowledgements and observed vehicle state
• Includes optional MAVLink 2 signing configuration for security-oriented testing
• Provides a PySide6 desktop orchestrator for Windows-based lab runs

Architecture

ArduPilot SITL / MAVProxy
        |
        | UDP 14550
        v
Mission Planner

ArduPilot SITL / MAVProxy
        |
        | UDP 14560
        v
Secondary monitor path

Secondary channel script
        |
        | TCP command path
        v
ArduPilot command interface

The desktop application starts and supervises the main lab components:

• ArduPilot SITL through WSL
• secondary_channel_v4.py on Windows
• PowerShell failover and restore commands
• optional Mission Planner launch
• live stdout/stderr panels and parsed status values

Repository Structure

app.py                    # PySide6 application entry point
main_window.py            # desktop UI
process_manager.py        # QProcess orchestration and log parsing
commands.py               # command builders for SITL, failover and secondary script
config.py                 # environment-based configuration
secondary_channel_v4.py   # current main secondary-channel implementation
secondary_channel_v*.py   # incremental experiment versions
widgets/                  # UI panels
docs/                     # architecture and validation notes

Requirements

• Windows
• Python 3
• WSL with ArduPilot SITL configured
• Mission Planner, optional but recommended for visual validation
• Python packages:
  • pymavlink
  • PySide6

Install dependencies:

pip install -r requirements.txt

Quick Start

Start the desktop orchestrator:

py app.py

Run the current secondary-channel script directly:

py secondary_channel_v4.py

Example SITL command:

sim_vehicle.py -w -v ArduCopter -f quad --map --console --out=<WINDOWS_HOST_IP>:14550 --out=<WINDOWS_HOST_IP>:14560 -A "--serial2=tcp:5782"

Configuration

The application reads configuration from environment variables through config.py.

Variable	Purpose	Default
ARDUPILOT_WSL_PATH	ArduPilot path inside WSL	~/ardupilot/ArduCopter
SECONDARY_WINDOWS_HOST_IP	Windows host IP used by SITL outputs	172.30.208.1
SECONDARY_MONITOR_UDP_PORT	UDP port for monitor link	14560
MISSION_PLANNER_UDP_PORT	UDP port for Mission Planner	14550
SECONDARY_COMMAND_HOST	host for command path	127.0.0.1
SECONDARY_COMMAND_TCP_PORT	TCP command port	5782
SECONDARY_CHANNEL_SIGNING_ENABLED	enables MAVLink signing config	false in script
SECONDARY_CHANNEL_COMMAND_UNSIGNED_POLICY	command unsigned-message policy	reject

Do not commit real signing keys or operational secrets.

Test Scenario

1. Start ArduPilot SITL.
2. Connect Mission Planner to UDP 14550.
3. Start the secondary-channel script or desktop orchestrator.
4. Arm the vehicle in simulation and take off to a safe test altitude.
5. Simulate monitor-link failure by blocking UDP 14560.
6. Confirm that the secondary channel detects link loss.
7. Select or trigger an emergency action: RTL, LAND or HOLD.
8. Validate the result through command acknowledgements, logs and Mission Planner state.

Current Limitations

• Simulation-only project; no real RF or LoRa hardware is integrated
• Not flight-certified and not intended for real aircraft operation
• Failover is validated in ArduPilot SITL, not in a physical UAV environment
• Some status parsing is based on process output and should be replaced with structured telemetry for a production-grade tool

Roadmap

• Add a clean architecture diagram under docs/
• Add repeatable test logs and screenshots
• Move older experiment versions into a dedicated experiments/ directory
• Add basic lint/compile checks
• Document MAVLink signing test cases more explicitly