The FOC control variants are established as the most popular used in high performance industrial applications.
The goal of FOC is to maintain the amplitude of the rotor flux linkage Ψ at a fixed value, except for field-weakening
operation or flux optimization, and only modify a torqueproducing current component in order to control the torque
of the ac motor [6]. FOC control operates by measuring and adjusting the stator currents in order to keep the angle
between the stator flux and rotor flux as close to 90r as possible. Instead of attempting to control the three phases
that power the stator independently, FOC maps them as a single space vector and runs that quantity through several
mathematical transforms (Park, Clarke and inverse Parktransform). These real time mathematical transformations
must be carried out very quickly by high performance processing capability of computer engines (e.g. modern
DSPs, FPGAs). The FOC speed control technique, in a sense, imitates the DC motor’s operation because its goal is
to be able to separately control the torque producing and magnetizing flux components. The knowing of motor
parameters, especially rotor time constant, is very importantin order to achieve the FOC control.