EC Motor: Closed Loop Speed Control
A Control Circuitry can be added to the Driver Circuitry.
Hall sensors (or an additional optical encoder) are used to measure the actual speed of the rotor. This signal is the actual value input for a Control Circuitry, usually based on PI control algorithm.
The voltage level to the motor is adjusted by implementing an additional feature inside the driver circuitry:
Pulse Wave Modulation PWM.
The average voltage to the 3 windings can be varied by switching supply voltage ON/OFF.
The switching frequency is very high (10 kHz or higher).
Speed can be held on a constant level, independent from load torque.
That must be considered when designing the PC for closed loop operation.
Motor manufacturing tolerance should be considered too