Field-oriented control or vector control

Vector control (motor)

Vector control is one method used in variable frequency drives to control the torque of three-phase AC electric motors by controlling the current fed to the machine.-Method:...

 is "a math-intensive technique for controlling brushless dc and ac induction motors" that "reduces motor size, cost and power consumption" and "is a a cousin of flux vector control

Vector control (motor)

Vector control is one method used in variable frequency drives to control the torque of three-phase AC electric motors by controlling the current fed to the machine.-Method:...

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Field-oriented control (FOC) is very common in induction motor control due to its ability to control the motor speed more efficiently compared to other control systems, and because the cost to build a FOC system is cheap.

Indirect field-oriented control (IFOC) is a variant of FOC that measures the field position within the induction motor indirectly via slip calculations using a mathematical model of the motor (rather than measuring the field directly).

Overview

The stator current of an induction motor can be broken down into the torque and field component currents. When decoupled, this means the torque and field of a motor can be controlled independently using these current components. Using the stators' axis as a point of origin, the torque and field currents can be related to the stator in a way allowing for control algorithm development.

For DC motors, the field and torque currents are equivalent to the field and armature

Armature (electrical engineering)

In electrical engineering, an armature generally refers to one of the two principal electrical components of an electromechanical machine–generally in a motor or generator, but it may also mean the pole piece of a permanent magnet or electromagnet, or the moving iron part of a solenoid or relay....

currents and can be controlled that way, while AC motors require a microprocessor to calculate the corresponding currents.

Because FOC relies on current manipulation, it requires no additional sensors to be attached to the motor, instead needing the impedance of the motor for calculations.