EKF FAILSAFES
Critical safety mechanisms. Understanding Extended Kalman Filter variance, lane switching, and emergency behaviors.
Safety Mechanisms
The EKF Core: Fusion Architecture
The **Extended Kalman Filter (EKF)** is the mathematical brain of the autopilot. Its job is to calculate a single, trusted "Truth" (Attitude, Posit...
EKF Lane Switching & Redundancy
Modern flight controllers (like the Cube Orange) have multiple redundant IMUs (Accelerometers/Gyros). ArduPilot leverages this by running **Multipl...
EKF Variance & Innovations
When the GCS screams **"EKF Variance"** or **"Velocity Variance"**, it means the autopilot is confused. Specifically, it means the sensor data (GPS...
GPS Glitch Protection
GPS is imperfect. Multipath errors (signals bouncing off buildings) can cause the GPS reported position to jump 10 meters instantly. If the flight ...
Compass Fusion & Magnetic Interference
Magnetometers (Compasses) are the most fragile sensors on a drone. They are easily corrupted by power lines, metal bridges, or even the drone's own...
Wind Estimation & Drag Fusion
Knowing the wind speed is critical for accurate navigation, especially for Return-to-Launch calculations ("Do I have enough battery to fight this h...
Optical Flow Fusion
Optical Flow is the primary method for non-GPS navigation (FlowHold) and precision landing. The sensor reports the "angular velocity" of the ground...
Terrain Estimation (EKF)
For precision landing and optical flow, the drone must know its height above the ground (AGL), not just its height above sea level (ASL). The EKF m...
Vibration Failsafe & Clipping
Vibration is the #1 enemy of the EKF. If the frame vibrates too much, the accelerometers produce "Aliased" data—high-frequency shaking that the E...
The Crash Checker
The **Crash Check** is a software safety mechanism designed to detect if the vehicle is out of control and impacting the ground. If a crash is conf...