China Civil UAV Theory Questions — Questions 296–305

A multi-axis aircraft performs its maneuvers by adjusting each rotor's speed. A fuel engine would need a gearbox to change speed, which responds slowly. An electric system only needs to adjust current to change motor speed quickly, with a simple structure and fast response.

Receiving ground control signals is the function of the onboard remote receiver.

The ESC's full name is electronic speed controller (Electronic Speed Control), abbreviated ESC. Depending on the drive motor, ESCs are brushed or brushless. The ESC regulates motor speed according to the control signal. The flight controller sends control signals to the ESC, controlling motor speed indirectly; the device that controls speed directly is the ESC.

Wind turbines and helicopter rotors can change pitch; fixed-wing airplane and multi-axis propellers use fixed-pitch propellers.

One ESC connects to one motor.

Study note: receiver first, then flight controller. The onboard remote receiver receives the signal and passes the command to the flight controller for processing; the flight controller then sends the processed commands to each ESC, and each ESC controls its motor's speed.

The link antenna frequently receives and sends information, so to avoid interfering with the flight controller and GPS it must be kept away from the flight controller and GPS antennas.

ESCs are brushed or brushless. Motors are classified as DC/AC, brushed/brushless, and outrunner/inrunner/stepper. Multi-rotor UAVs typically use a brushless ESC driving a three-phase AC outrunner brushless motor.

A brushless ESC is an electronic device that controls a brushless motor's speed and direction. Multi-axis aircraft motors are generally brushless, so brushless ESCs are used.

Li-polymer batteries have high energy density: for the same capacity, a lithium battery is the lightest in weight.