5.1.1 DIRECT TORQUE CONTROL
These control, was purposed to be the most controllers for driving motor. Its method of operation have been explained in detailed. It is also shown in this work that it allows the free and separated control of motor torque and motor stator flux. It is clear that its strategy is easier to handle than the flux vector control because voltage modulators and coordinate transformation are not needed, although it introduced some drawback being the high magnitude of torque ripple.
5.1.2 Direct torque control with duty ratio fuzzy controller
After all the demonstration, it focused on introducing a modulation in the DTC while fuzzy logic controller is in charge of controlling modulation between the active selected state and a null one.
Therefore it has been recommended and deeply explained that fuzzy logic with DTC can create the fuzzy logic DTC controller. The theoretical claim that duty ratio control can reduce torque ripple in the control gave acceptable results and reduces the computation burden by skipping unnecessary complex mathematical modeling of the nonlinear systems. By using duty ratio control, a particular motor performance can be achieved at a lower switching frequency compared to the ordinary DTC, which in turn improves the performance of the drive by minimizing the flux harmonics.
All recommendation is summarized schematically in the following ideas:
• Design a fuzzy controller that will enhance better performance, this fuzzy controllers should take into consideration the following ideas:
1. Design completely an automatic acceptable controller.
2. The controller must be used to any motor.
3. Minimize the electrical noises, which appear in any power drive.
• Design the torque ripple reduction with fuzzy logic with duty ratio controllers and also with multilevel converters.
Design fuzzy logic with duty ratio DTC without sensor implementation that will be sensing two currents, the DC voltage and by means ofobservers.
• Design and apply different fuzzy logic, not only to induction motors as it has been done in the present work, but also to any electrical motor.