Brushless dc (BLDC) motors are very popular and are replacing brush motors in numerous applications due to its superior electrical and mechanical characteristics owing to its trouble free construction. This paper presents the BLDC motor sensorless speed control system with fuzzy logic implementation. The sensorless techniques based on the back EMF sensing and the rotor position detection with a high starting torque is suggested. The rotor position is aligned at standstill for without an additional sensor. Also, the stator current can be easily adjusted by modulating the pulse width of the switching devices during alignment which will be helpful to reduce cost and complexity of the drive system without compromising the performance. The design analysis and simulation of the proposed system is done using MATLAB version 2010a and the simulation results of sensored drive using PI controller and sensorless drive using proposed methods are analyzed.
1. Brushless dc motor
2. Hall sensored drive
3. PI controller
4. Back EMF sensorless drive
5. Fuzzy controller
Fig. 1.Proposed block diagram of sensorless speed control of BLDC motor.
EXPECTED SIMULATION RESULTS:
Fig. 2(a) Variation of Back EMF signal with reference set at 1400 rpm
Fig. 2(b) Variation of stator current with reference set at 1400 rpm.
Fig. 3.Generated pulse from fuzzy logic controller.
Fig. 4(a) Speed response of sensored drive technique using PI controller.
Fig. 4(b) Speed response of sensorless drive technique using PI controller.
Fig. 4(c) Speed response of sensorless drive technique using fuzzy logic controller.
Fig. 5(a) Variation of Electromagnetic torque with reference set at 1400 rpm under sensorless drive using PI controller.
Fig. 5(b) Variation of Electromagnetic torque with reference set at 1400rpm under sensorless drive using fuzzy logic controller.
Sensorless speed control of BLDC motor drive with fuzzy logic implementation based on comparator with zero crossing detection have been experimented using MATLAB and evaluation of results are observed. The simulation results have shown that speed response of the BLDC motor can be controlled without sensors and also reduces the torque ripple. The results obtained from sensorless speed control of BLDC motor demonstrates that the system is less cost compared to sensored control and also good dynamic performance is obtained. This makes the motor suitable in application such as fuel pump, robotics and industrial automation. The proposed speed control scheme is robust, efficient and easy to implement in place of sensored applications.
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