An Intelligent Fuzzy Sliding Mode Controller for aBLDC Motor

ABSTRACT:  

Brushless DC (BLDC) motors are one of the most widely used motors, not only because of their efficiency, and torque characteristics, but also because they have the advantages of being a direct current (DC) supplied, eliminating the disadvantages of using Brushes. BLDC motors have a very wide range of speed, so speed control is a very important issue for it. Sliding mode control (SMC) is one of the popular strategies to deal with uncertain control systems. The Fuzzy Sliding Mode Controller (FSMC) combines the intelligence of a fuzzy inference system with the sliding mode controller. In this paper, an intelligent Fuzzy Sliding Mode controller for the speed control of BLDC motor is proposed. The mathematical model of the BLDC motor is developed and it is used to examine the performance of this controller. Conventionally PI controllers are used for the speed control of the BLDC motor. When Fuzzy SMC is used for the speed control of BLDC motor, the peak overshoot is completely eliminated which is 3% with PI controller. Also the rise time is reduced from 23 ms to 4 ms and the settling time is reduced from 46 ms to 4 ms by applying FMSMC. This paper emphasizes on the effectiveness of speed control of BLDC motor with Fuzzy Sliding Mode Controller and its merit over conventional PI controller.

KEYWORDS:

  1. BLDC motors
  2. Sliding Mode Control
  3. Fuzzy Sliding Mode controller
  4. PI Controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig 1 Block diagram of BLDC speed control.

EXPECTED SIMULATION RESULTS:

 

Fig 2 Step response with Fuzzy SMC and Fuzzy PI and PI Controllers

Fig 3 Current in the three phases

 

CONCLUSION:

 Fuzzy sliding mode controller for the speed control of BLDC motor is designed and its performance comparison with PI controller is carried out in this paper. Conventionally PI controllers are used for the speed control of BLDC motor and they give moderate performance under undisturbed conditions even though they are very simple to design and easy to implement. But their performance is poor under disturbed condition like sudden changes in reference speed and sudden change in load. The BLDC motor with PI controller shows large overshoot, high settling time and comparatively large  speed variation under loaded condition.

The Fuzzy Sliding Mode Controller combines the intelligence of fuzzy logic with the Sliding Mode technique. The peak overshoot is completely eliminated and the rise time and settling time are improved when Fuzzy SMC is applied for the speed control of BLDC motor. The fluctuation in speed of the motor under loaded condition is also reduced when fuzzy SMC is applied. Thus this controller becomes an ideal choice for applications where very precise and fine control is required.

REFERENCES:

[1] Neethu U., Jisha V. R., “Speed Control of Brushless DC Motor : A Comparative Study”, IEEE International Conference on Power  Electronics, Drives and Energy Systems, Vol. 8, No. 12, 16-19 December 2012, Bengaluru India.

[2] Chee W. Lu, “T orque Controller for Brushless DC Motors”, IEEE Transactions on Industrial Electronics, Vol. 46, No. 2, April 1999.

[3] Tony Mathew, Caroline Ann Sam, ”Closed Loop Control of BLDC Motor Using a Fuzzy Logic Controller and Single Current Sensor”, International Conference on Advanced Computing and Communication Systems (ICACCS), Vol. 2, No. 13, 19-21 December 2013, Coimbatore India.

[4] T . Raghu, S. Chandra Sekhar, J. Srinivas Rao,“SEPIC Converter based – Drive for Unipolar BLDC Motor”, International Journal of Electrical  and Computer Engineering (IJECE), Vol.2, No.2, April 2012, pp. 159- 165.

[5] M. A. Jabbar, Hla Nu Phyu, Zhejie Liu, Chao Bi, “Modelling and Numerical Simulation of a Brushless Permanent – Magnet DC Motor in Dynamic Conditions by Time – Stepping T echnique”, IEEE Transactions on Industry Applications, Vol. 40, no. 3, MAY/JUNE 2004.

Unknown Input Observer for a Novel Sensorless Drive of Brushless DC Motors

 

ABSTRACT:

In this paper, a novel motor control method is proposed to improve the performance of sensorless drive of BLDC motors. In the terminal voltage sensing method, which is a great portion of sensorless control, a precise rotor position cannot be obtained when excessive input is applied to the drive during synchronous operation mode. Especially in the transient state, the response characteristic decreases. To cope with this problem, the unknown input (back-EMF) is modeled as the additional state of system in this paper. Taking into account the disturbance adopted by the back-EMF, the observer can be obtained by an equation of the augmented system. An algorithm to detect the back-EMF of a BLDC motor using the state observer is constructed. As a result, a novel sensorless drive of BLDC motors that can strictly estimate rotor position and speed is proposed.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of BLDC motor drive

EXPECTED SIMULATION RESULTS:

Fig. 2. Speed response for the start and transient state. (a) In the proposed sensorless scheme. (b) In the conventional scheme use sensor.

Fig. 3. Simulation results of the proposed sensorless scheme at 2000 (rpm). (a) Rotor speed. (b) Rotor position. (c) Phase current. (d) Line-to-line back-EMF. (e) Commutation function. (f) Commutation signal.

Fig. 4. Simulation results of the proposed sensorless scheme at 100 (rpm). (a) Rotor speed. (b) Rotor position. (c) Phase current. (d) Line-to-line back-EMF. (e) Commutation function. (f) Commutation signal.

CONCLUSION:

In this paper, the unknown input (back-EMF) is modeled as the additional state of system. Considering disturbance that is adopted by back-EMF, the observer can be obtained effectively using the equation of augmented system and estimating back-EMF. As a result, an effective algorithm to estimate rotor position and speed of motor using the state observer is proposed. Use of sensorless control method can remove problem on manufacture that is happened in circuit to detect rotor position and speed. Moreover the production of inexpensive motor controller may be possible because the additional circuit such as encoder is not necessity. In cases using the proposed sensorless control method, the start-up performance has an almost analogous transient state characteristic after forced alignment, compared with the conventional method. This method also provides useful motor control because it is possible to analyze about transient state as well as steady state unlike various sensorless control methods that have been recently proposed. In addition, it can be easily applied in industry applications requiring the low-cost style drive of BLDC motor because actual realization is very simple.

REFERENCES:

[l] T. J. E Miller, “Brushless Permanent-Magnet and Reluctance Motor Drives,” Clarendon

Press, Oxford 1989.

[2] S. Ogasawara and H. Akagi, “An Approach to Position Sensorless Drive for Brushless DC

Motors,” IEEE Trans. Ind. Appl., vol. 27, no. 5, pp. 928-933, Sep./Oct. 1991.

[3] J. C. Moreira, “Indirect Sensing for Rotor Flux Position of Permanent Magnet AC Motors

Operating Over a Wide Speed Range,” IEEE Trans. Ind. Appl., vol. 32, no. 6, pp. 1392-1401,

Nov./Dec. 1996.

[4] H. R. Andersen and J. K. Pedersen, “Sensorless ELBERFELD Control of Brushless DC Motors for Energy-Optimized Variable-Speed Household Refrigerators,” EPE Conf. Rec., vol. 1,

  1. 314-318, Sep. 1997.

[5] Hyeong-Gee Yee, Chang-Seok Hong, Ji-Yoon Yoo, Hyeon-Gil Jang, Yeong-Don Bae and Yoon-Seo Park, “Sensorless Drive for Interior Permanent Magnet Brushless DC Motors,” Electric Machines and Drives Conf. Record, 1997, IEEE International 18-21 pp. TD1/3.1-

TD1/3.3, May 1997.