**Genetic Algorithm Optimized PI and Fuzzy Sliding Mode**

**Speed Control for DTC Drives**

Abstract— This paper presents a detailed comparison between

a conventional PI controller and a variable structure controller

based on a fuzzy sliding mode strategy used for speed control

in direct torque control induction motor drive. Genetic algorithms

are used to tune the PI controller gains to ensure optimal

performance. The performance of the two controllers are

investigated and compared for different dynamic operating

conditions such as of reference speed and for load torque step

changes at nominal parameters and in the presence of parameter

variation and imprecision. Results show that the PI controller has

better performance for nominal operating conditions while the

fuzzy sliding mode is more robust against parameter variation

and uncertainty, and is less sensitive to external load torque

disturbances with a fast dynamic response.

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**DIRECT TORQUE CONTROL OF INDUCTION MOTOR**

WITH FUZZY MINIMIZATION TORQUE RIPPLE

WITH FUZZY MINIMIZATION TORQUE RIPPLE

Direct torque control (DTC) is receiving wide atten-

tion in the recent literature [1, 2]. DTC minimizes the use

of machine parameters [3, 4]. This type of control is es-

sentially a sliding mode stator flux-oriented control. The

DTC uses the hysteresis band to directly control the flux

and torque of the machine. When the stator flux falls out-

side the hysteresis band, the inverter switching stator is

changed so that the flux takes an optimal path toward

the desired value [3, 4].

The name direct torque control is derived from the

fact that on the basis of the errors between the reference

and the estimated values of torque and flux it is possible

to directly control the inverter states in order to reduce

the torque and flux errors within the prefixed band limits

[5, 6].

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**IMPROVED DTC OF INDUCTION MOTOR WITH FUZZY****RESISTANCE ESTIMATOR**

Abstract- The aim of the work is to study the

feasibility of stator resistance estimator in DTC

scheme. Fuzzy logic is used to estimate the stator

resistance. DTC with fuzzy estimator is characterized

by fast torque and flux response in very-low speed

operation.

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controller for speed control of a simplified direct torque neuro

fuzzy controlled (DTNFC) induction motor drive. First, a

simplified direct torque neuro fuzzy control (DTNFC) for a voltage

source PWM inverter fed induction motor drive is presented.

This control scheme uses the stator flux amplitude and the

electromagnetic torque errors through a four rules adaptive NF

inference system (ANFIS) to generate a voltage space vector

(reference voltage). This voltage is used by a space vector

modulator to generate the inverter switching states. Then a VGPI

controller is designed in order to be used as the speed controller

in the simplified DTNFC induction motor drive. Simulation

of the simplified DTNFC induction motor drive using VGPI for

speed control shows promising results. The motor reaches

the reference speed rapidly and without overshoot, load

disturbances are rapidly rejected and the detuning problem

caused by the stator resistance variation is fairly well dealt with.

**DIRECT TORQUE NEURO FUZZY SPEED CONTROL**

OF AN INDUCTION MACHINE DRIVE BASED

ON A NEW VARIABLE GAIN PI CONTROLLER

This paper presents an original variable gain PI (VGPI)OF AN INDUCTION MACHINE DRIVE BASED

ON A NEW VARIABLE GAIN PI CONTROLLER

controller for speed control of a simplified direct torque neuro

fuzzy controlled (DTNFC) induction motor drive. First, a

simplified direct torque neuro fuzzy control (DTNFC) for a voltage

source PWM inverter fed induction motor drive is presented.

This control scheme uses the stator flux amplitude and the

electromagnetic torque errors through a four rules adaptive NF

inference system (ANFIS) to generate a voltage space vector

(reference voltage). This voltage is used by a space vector

modulator to generate the inverter switching states. Then a VGPI

controller is designed in order to be used as the speed controller

in the simplified DTNFC induction motor drive. Simulation

of the simplified DTNFC induction motor drive using VGPI for

speed control shows promising results. The motor reaches

the reference speed rapidly and without overshoot, load

disturbances are rapidly rejected and the detuning problem

caused by the stator resistance variation is fairly well dealt with.