vectorcontrole

Vector control, also known as field-oriented control (FOC), is a method for controlling AC motors that decouples stator flux and torque to achieve fast, predictable dynamic response similar to a DC motor. It enables precise torque regulation over a wide speed range by controlling motor currents in a rotating reference frame.

It achieves this by transforming three-phase stator currents into a two-axis coordinate system rotating with the rotor, typically the dq frame, using Clarke and Park transforms. In this frame, the stator current components correspond to flux-producing (d axis) and torque-producing (q axis) components. Two current controllers regulate the dq currents, usually with proportional–integral controllers, while a high-frequency inverter (three-phase bridge) synthesizes the required stator voltages. A rotor position or speed estimate is used to compute the correct rotating frame angle; this can be provided by sensors (encoders or resolvers) or obtained sensorlessly through motor models and observers.

Indirect FOC estimates rotor angle from motor constants and measurements, while direct FOC attempts to control the flux vector directly without speed estimation. Compared with scalar control, vector control provides decoupled control of flux and torque, enabling accurate torque regulation, fast transients, and smooth operation across a wide speed range.

Challenges include sensitivity to motor parameter variations (resistance, inductances), temperature effects, and higher computational demand. These require accurate modeling, parameter identification, and robust estimation. Sensor-based implementations rely on precise position feedback, while sensorless approaches use observers to estimate rotor state. Applications include servo drives, robotics, CNC machines, and electric vehicles, where high performance motor drive capabilities are essential.