One of the main goals of robotics is to articulate objects. To do this, it is very common to use electric motors. In the case of a flying robot, like drones, the actuators need high rotational speed to turn the propellers and allow flight. In this case, brushless motors are often used. The particularity of the brushless motor is that it can reach very high speed compared to other types of motor with less torque, of course.
Brushless motors are motors with three windings called three-phase motors. That is to say, it generates a continuous rotation when the currents on these coils are shifted. The generation of the current profiles on each coil, in order to obtain the desired speed, requires the use of a speed controller (called ESC, Electronic Speed Controller) in order to transform a PWM command into rotational speed.
The motor requires a high current to function properly, so the ESC will be powered by a power source external to the microcontroller. The ESC control is connected to a PWM pin of the microcontroller.