C++ autopilot Projects

ardupilot

72 9,830 10.0 C++

ArduPlane, ArduCopter, ArduRover, ArduSub source

Project mention: Reading Sensor Data From Flight Controller Mateksys F405-TE - Integrated IMU - No Documentation | /r/stm32f4 | 2023-12-07

PX4-Autopilot

26 7,589 9.9 C++

PX4 Autopilot Software

Project mention: Kalman Filter Tutorial: Kalman Filter from the Ground Up | news.ycombinator.com | 2023-10-14

They are widely used in narrow circles :)
Two of (arguably the best) open source RC aircraft flight controllers (ArduPilot and PX4) are using extended Kalman filters in their state estimators (essentially sensor fusion that provides attitude/position estimate):
https://github.com/ArduPilot/ardupilot/tree/master/libraries...
https://github.com/PX4/PX4-Autopilot/blob/main/src/modules/e...
I'm not that familiar with cleanflight/betaflight/inav scene to know what the FPV racer flight controllers use.

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NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020).