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Flight Controller

The Flight Controller is the heart of the Air System and is responsible for -

  1. Controlling and stabilizing the UAV.
  2. Communicating with the various components on the UAV, the GCS, and the RC.
  3. Logging data & events.

Composition​

The Flight Controller consists of hardware and software working together to accomplish its goal. Its primary constituents are -

Hardware​

  • Microcontroller (MCU)
  • Blackbox
  • Indicator LEDs
  • Sensors (IMU, Magnetometer, Barometer and Temperature).
  • Communication Interfaces (USB, ESCs, Rc Receiver, Telemetry, Battery and GPS/GNSS).
  • Power regulator, oscillator, ESD/EMI protection ICs etc.

Software​

  • Firmware
  • Bootloader

Interfaces​

To connect with other components of the Air System, the Flight Controller exposes the following interfaces -

  • USB Interface: Receives firmware upgrades and also used for debugging.
  • Blackbox Interface: Stores FC Logs persistently.
  • ESC Interface: Communicates with ESCs using PWM to control motor speed.
  • Radio Control Interface: Receives uni-directional control signals from the RC.
  • Telemetry Radio Interface: Communicates bidirectionally with the GCS.
  • GPS Interface: Receives position and timing data for navigation.
  • Peripheral/Payload Interfaces (I2C, SPI, UART, CAN): Connects with external peripherals and payloads to enrich UAV operations.

Firmware​

The firmware executes on the MCU and is responsible for carrying out the functions of the flight controller. The firmware has the following responsibilities -

  1. System State Management -
    1. Ensuring only valid System State transitions are performed, only after checking guards.
    2. Enforcing the behavior of the 3 aspects of the System State - Activity, Error and Flight Control Mode.
  2. Component Management -
    1. Initializing, reading sensors and processing raw data into pose.
    2. Managing indicator LEDs.
    3. Receive and parse data from RC Receiver and Telemetry Radio.
  3. Flight Stabilization & Control -
    1. Stabilize UAV based on raw and filtered sensor data.
    2. Calculate setpoints from RC values based on Flight Control Mode; calculate errors based on current pose and setpoints.
    3. Calculate motor speed commands from errors and send to ESCs.
  4. GCS Communication -
    1. Discover and establish connection with GCS.
    2. Send/Receive telemetry data from GCS (including RC values, pose, battery level, position etc).