Flame Wheel 550 × Navio2 × Raspberry Pi 4B (Copter)
Continuously estimates local air density ρ in flight and retunes ArduPilot’s cruise-speed parameters so that forward-flight power ≈ hover power. Runs entirely on the companion computer; the ArduPilot firmware remains stock.
How it works:
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Producer obtains baro pressure + temperature from MAVLink SCALED_PRESSURE, calculates air density and target cruise speed, signs two 27-byte UDP frames (AIRDENS and CRSPEED) each second, and writes “RHO_LAST / V_TARGET_LAST” to /opt/airsense/.env every 60 s.
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Consumer verifies HMAC + sequence, low-pass filters CRSPEED, and, when change ≥2 % or 60 s elapsed, writes WPNAV_SPEED and LOIT_SPEED via PARAM_SET (clamped 250–1200 cm s⁻¹). If no CRSPEED arrives for 15 s it loads the last .env value, pushes it, and warns the operator.
sudo apt update sudo apt install python3-pip python3-venv git make git clone https://github.com/fitoori/atmosense.git cd atmosense python3 -m venv venv && . venv/bin/activate pip3 install -r requirements.txt export AIRSENSE_HMAC_KEY=$(openssl rand -hex 16) sudo make deploy sudo systemctl status airsense.service ctrlbridge.service
- Density-aware speed set-point — recalculates
WPNAV_SPEED/LOIT_SPEEDonce per second (default) so the multirotor flies at its power sweet-spot. - Signed telemetry link — 27-byte UDP frames with truncated HMAC-SHA-256.
- Low-pass smoothing & rate clamp — prevents parameter chatter; ≤ 1 Hz writes, 2 % dead-band.
- Fail-safe fallback — if sensor data stalls for 15 s, reloads last speed
from
/opt/airsense/.env, pushes it, and warns the pilot. - Systemd-native — self-restarting services, clean SIGTERM/SIGINT shutdown.
- Unit-tested — ≥ 90 % coverage on math, framing, filtering, fallback paths.
Key environment variables
AIRSENSE_HMAC_KEY 32-char hex, shared by both services AIRSENSE_RATE 1 sensor sample rate (Hz) AIRSENSE_UDP_PORT 14560 producer → consumer port FLIGHTCTL_ALPHA 0.15 low-pass weighting factor FLIGHTCTL_FORCE_SEC 60 unconditional parameter refresh period
Default config assumes: • ArduPilot MAVLink on udp:127.0.0.1:14550 • Companion UDP loopback port 14560 for Airsense frames.
Override via environment variables in the .service files.