An induction machine operated with a direct self controller (DSC) show
s a sluggish response during startup and under changes of torque comma
nd. Fuzzy logic is used in conjunction with direct self control to min
imize these problems. A fuzzy logic controller chooses the switching s
tates based on a set of fuzzy variables. Flux position, error in flux
magnitude and error in torque are used as fuzzy state variables. Fuzzy
rules are determined by observing the-vector diagram of flux and curr
ents. The operation of the direct self controller becomes difficult at
low speeds due to the effect of change in stator resistance on the fl
ux measurements. To improve the system performance at low speeds a fuz
zy resistance estimator is proposed to eliminate the error due to the
change in stator resistance. At constant flux and torque commands any
change in stator resistance of the induction machines causes an error
in stator current. This error is utilized by the fuzzy resistance esti
mator to correct the stator resistance used by the controller to match
the machine resistance. Both fuzzy controller and fuzzy resistance es
timator are simulated for a 3 hp induction motor. The simulation resul
ts demonstrate a good performance.