Field-oriented control (FOC)
also: vector control
A motor-control technique that regulates torque and magnetic field of AC and brushless motors independently, giving smooth, efficient, quiet operation.
Brushless and permanent-magnet synchronous motors make torque most effectively when the stator's magnetic field is held at the right angle to the rotor's. FOC measures the motor phase currents, uses the rotor angle (from a sensor, or estimated in "sensorless" designs) to transform them into a rotating reference frame (the Clarke and Park transforms), and runs fast current loops on the torque-producing and field-producing components separately.
Compared with simpler six-step (trapezoidal) commutation, the payoff is smoother torque, lower acoustic noise and vibration, better efficiency across the speed range and precise torque control. That is valuable in pumps, fans, compressors, e-bikes, drones and robots.
Where it bites: FOC needs a microcontroller with fast ADC and PWM peripherals, accurate current sensing, known motor parameters and careful tuning. Sensorless FOC can struggle at very low speed and when starting under load, which matters for products that must always start reliably.
Founder takeaway
If your motor must be quiet, efficient or precisely torque-controlled, ask whether FOC is planned and how low-speed startup under load is handled.
engineer review pending