Despite the great efforts devoted to induction motor control,
many of the theoretical results cannot be directly applied to
practical systems. Intelligent control techniques are generally
classified as expert system control, fuzzy-logic control, neuralnetwork
control and genetic algorithm. Various artificial
intelligent controllers are as follows:-
(a) Fuzzy Logic Controller: The speed of induction motor is
adjusted by the fuzzy controller. In Table-I, the fuzzy rules
decision implemented into the controller are given. The
conventional simulated induction motor model as shown in
Fig. 2 is modified by adding Fuzzy controller and is shown in
Fig. 4 . Speed output terminal of induction motor is applied as
an input to fuzzy controller, and in the initial start of induction
motor the error is maximum, so according to fuzzy rules FC
produces a crisp value. Then this value will change the
frequency of sine wave in the speed controller. The sine wave
is then compared with triangular waveform to generate the
firing signals of IGBTs in the PWM inverters. The frequency
of these firing signals also gradually changes, thus increasing
the frequency of applied voltage to Induction Motor [12,14].
As discussed earlier, the crisp value obtained from Fuzzy
Logic Controller is used to change the frequency of gating
signals of PWM inverter. Thus the output AC signals obtained
will be variable frequency sine waves. The sine wave is
generated with amplitude, phase and frequency which are
supplied through a GUI. Then the clock signal which is
sampling time of simulation is divided by crisp value which is
obtained from FLC. So by placing three sine waves with
different phases, one can compare them with triangular
waveform and generate necessary gating signals of PWM
inverter. So at the first sampling point the speed is zero and
error is maximum. Then whatever the speed rises, the error
will decrease, and the crisp value obtained from FLC will
increase. So, the frequency of sine wave will decrease which
will cause IGBTs switched ON and OFF faster. It will increase
the AC supply frequency, and the motor will speed up. The
inputs to these blocks are the gating signals which are
produced in speed controller block. The firing signals are
applied to IGBT gates that will turn ON and OFF the IGBTs.