Field-Oriented Control (FOC)

Field-Oriented Control (FOC), also known as vector control, is a technique used to control Permanent Magnet Synchronous Motor (PMSM) and Brushless-DC Motor (BLDC). FOC provides good control capability over the full torque and speed ranges. The FOC implementation requires the transformation of stator currents from the stationary reference frame to the rotor flux reference frame (also known as the d-q reference frame).

Speed control and torque control are the most commonly used control modes of FOC. The position control mode is less common. Most traction applications use the torque control mode in which the motor control system follows a reference torque value. In the speed control mode, the motor controller follows a reference speed value and generates a torque reference for the torque control that forms an inner subsystem. In the position control mode, the speed controller forms the inner subsystem.

FOC algorithm implementation requires real-time feedback of the currents and rotor position angle. Measure the current and position by using sensors. The sensorless techniques can be used to estimate feedback values (using motor hall sensors and phase angles) instead of the actual sensor-based measurements. This technique is called Sliding-mode based rotor estimation.

More detailed information about FOC can be found at the Field-Oriented Control or Field Oriented Control (FOC) - A Deep Dive.