FOC (Field Orientated Control)

Field-Oriented Control (FOC) is an advanced motor control method used to precisely control the magnetic field inside a motor. It is the primary control method used by VESC controllers for PMSM and many BLDC motors.

Unlike traditional BLDC control, which energizes the motor phases in discrete steps, FOC generates smooth sinusoidal current waveforms that continuously rotate with the motor’s magnetic field. For this reason, FOC is often referred to as sine wave motor control.

Compared to traditional BLDC control, FOC provides:

• Smoother motor operation
• Lower electrical noise
• Improved efficiency
• Better low-speed performance
• More accurate torque control
• Reduced motor heating

FOC uses mathematical transformations to separate motor current into two components:

• D-Axis Current – controls magnetic field strength
• Q-Axis Current – produces torque

In most applications, torque is controlled by regulating the Q-axis current while minimizing D-axis current.

FOC requires accurate motor parameters such as motor resistance, inductance, and flux linkage. These values are typically measured using the Motor Detection Wizard in VESC Tool.

Example

A motor operating under FOC control can run smoothly across a wide speed range while maintaining precise torque control and high efficiency.

In simple terms: FOC is a sine wave motor control method that continuously controls the motor’s magnetic field to produce smooth, efficient, and precise motor control.