Fuzzy Control of Induction Motor
Using concepts of direct torque control, a fuzzy controller has
been designed with a cascaded final state selector, which reduced rule base and
gave birth to a new control technique of induction motor.In this text, an Application Specific Fuzzy Switching (ASFS) has been designed for direct torque control of squirrel cage induction motor, so space vector modulation for direct torque control shall be dealt subsequently. Control is generated by
maintaining constant volts per hertz output; used to drive a pulse width
modulated (PWM) circuit.
Direct Torque Control with Space Vector Modulation:
Direct torque control (DTC) combines field-oriented control, digital signal processing
and application specific integrated circuit.The mathematical model of induction motor observer estimates actual torque and flux of the motor from current and voltage feedback. If actual torque is below its differential hysteresis limit, the torque status goes high and if it is above its differential limit the torque status goes low.
Induction Motor control technique with Fuzzy Logic
The torque error, flux error and flux angle are given as the input parameters for the fuzzy controller. Defuzzification technique used here is mean of median and
output denotes a switching state. Actual torque, flux and flux angle are determined from current and voltage feedbacks.
Encoding Fuzzy Controller Output:
The fuzzy controller selects optimal switching state,and then it is
encoded for subsequent processing. The fuzzy controller is defuzzified to generate a crisp value, which is
rounded off to the nearest integer value.
Results:
The fuzzy controller developed here along-with the final state selector has been
used to control an induction motor. Simulation model has been used to operate the motor at desired speed of 1500 r.p.m. In order to eliminate continuous maintained speed error, an integrator has
been introduced after speed error is calculated. Accordingly, torque error and
flux error are calculated and fed to fuzzy controller.
Full details in this report:
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For motor control using PID, visit this link:
http://www.eurojournals.com/ejsr_35_2_05.pdf