RESULTS AND DISCUSSION
Table 4.1 simulated data for torque error.
TORQUE ERROR (Nm) WITHDIRECT TORQUE CONTROL TORQUE ERROR (Nm) WITH FUZZY TIME (S)
0 0 0
0.2 0.025 1
0.15 0.018 2
0.16 0.02 3
0.15 0.0195 4
0.15 0.0195 10
Figure 4.1 Result for torque error using DTC and fuzzy logic with duty ratio.
From the graph, the data in the table were used. The torque behavior of the motor using ordinary DTC and fuzzy logic with duty ratio control for a torque command of 0.15Nm with the output drive updated at a rate of 5kHz were used. The flux ripple regained was 0.05wb (0.2-0.15)N-m greater and lesser values with the only DTC while infuzzy logic with duty ratio control, the ripple was reduced further to 0.0055Nm(0.025-0.00195)Nm greaterand lesser value, assumed under shoot in the torque value at the starting voltage vector were neglected.
Table 4.2 Data for flux linkage error
ERROR IN FLUX LINKAGE (Wb) WITH DTC ERROR IN FLUX LINKAGE (Wb) WITH FUZZY TIME
0 0 0
18 2.4 1
12 1.5 2
14 1.7 3
13.33 1.733 4
13.33 1.733 10
Figure 4.2 Result for flux linkage in fuzzy logic with duty ratio and DTC
From the illustration, data in table were used. torque response of the motor in the control for a step torque in fuzzy logic with duty ratio control and DTC for a torque command of 2.4Wb with the motor drive output updated at a rate of 5kHz were used, the ripple generated was 4.67Wb (18-13.33)Wb greater and lesser values with ordinary DTC, while in fuzzy logic with duty ratio control, ripples was reduced further to 0.667b (2.4-1.733)Wb upper and lower values, assumed order response in flux value at starting voltage sector were neglected.
Table 4.3 Data for position of the stator flux linkage.
ERROR IN THE POSITION OF FLUX LINKAGE WITH DTC ERROR IN THE POSITION OF FLUX LINKAGE WITH FUZZY TIME
0 0 0
3.3 0.9 1
2.2 0.06 2
2.5 0.07 3
2.45 0.0643 4
Figure 43 Result for position of stator flux linkage using DTC and fuzzy logic with duty ratio.
In the analysis, the data in the tablewere used. The position where the stator flux linkage of the motor using ordinary DTC and fuzzy logic with duty ratio control respectively for a step angular command of 3.3 degree with the drive output updated at a rate of 5kHz were used, the position where the flux linkage ripple was reduced to 0.85degree (3.3-2.45) greater and lesser values with the ordinary DTC while in fuzzy logic with duty ratio control, the ripple wasreduced to 0.857 degree (0.9-0.0643)degreegreater and lesser values, assumed the under shoot in the flux value at the starting of each voltage sector were neglected.
In the analysis, the data in the tables were used. The torque, flux, and the position of the stator flux linkage responsesof the motor using ordinary DTC and fuzzy logic with duty ratio control respectively for a step torque, flux and angular command of 0.15N¬-m, 2.4wb and 3.3 degree with the drive output updated at a rate of 5KHZ were used. The torque, flux and the position of the flux linkage space vector ripples generated were 0.09N-m, 4.67wb and 0.85 degree approximately, while in fuzzy logic control with duty ratio, the ripples were reduced to 0.0055N-m, 0.44wb and 0.04 degree respectively, neglecting the both under shoot at the beginning of each voltage vector. With these, we observed that the ripples were reduced drastically and able to achieve 95% of improvement.
CONCLUSION S AND RECOMMENDATIONS
These controller, was purposed as the most controllers for driving induction 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 deeply explanation, it has be known to 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:
• To design a fuzzy controller that will enhance better performance. This fuzzy controllers should take into consideration the following ideas:
1. To design completely an automatic adaptive controller.
2. The controller must be used to any electrical motor.
3. To 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.