Flight Controller (FC for short) receives pre-saved flight routes and real-time remote control commands to maintain stable flight. Apart from external control signals, the FC also needs to accurately determine the aircraft's attitude, heading, position, velocity and altitude. These data are collected by various sensors, whose readings vary across locations, so on-site calibration is required. Detailed instructions are as follows.
GPS provides data on the aircraft's position, velocity and altitude. Position can also be calculated via inertial navigation when GPS is unavailable, such as for submarines. GPS modules are usually mounted at a high position and integrated with a magnetometer to avoid interference from other components and conductive airframe structures, hence calibration is also needed.
The transmitter controls aircraft movements such as pitch and roll. Each movement corresponds to a channel with a specific signal range, which varies among different transmitters. The FC calibrates to acquire the maximum channel range of the transmitter for precise control.
For example, if the maximum pitch angle is 30 degrees, the FC’s maximum PWM output is 2000μs while the transmitter’s maximum output is 1900μs. The FC will convert the received 1900μs maximum signal to 2000μs accordingly.
In summary, three items need calibration: the flight controller’s accelerometer, built-in magnetometer, GPS magnetometer, and transmitter channel range.