A Novel Fuzzy Dynamic Observer for High Speed BLDC Motor


In this paper, a high performance brushless DC (BLDC) motor drive based on a fuzzy dynamic observer (FDO) is investigated. The FDO acts on the motor current and its gains are corrected by estimating current, rotor position and speed by fuzzy logic control (FLC). FLC is correcting gain’s FDO via real time. A PI speed control was chosen due to its low processing time and fast control. In order to reduce the model complexity, the back-EMF is assumed as being trapezoidal in a simplified machine model. The presented drive has been simulated by the MATLAB/SIMULINK software on the high speed BLDC motor model. Simulation results show that the proposed drive is able to estimate the rotor position and speed with high precision when high speeds are considered. Simulation results also show the reliability, fast computation and excellent dynamic performance with using fuzzy logic for high speed BLDC motor.


  1. BLDC motor
  2. Fuzzy dynamic observer
  3. Fuzzy logic



Fig. 1. Block diagram of speed control of a three-phase BLDC motor.


Fig. 2. Speed of rotor (N=30,000 rpm).

 Fig. 3. Back EMF three-phases (N=30,000 rpm).

Fig. 4. Total torque (N=30,000 rpm).

Fig. 5. Speed and estimated speed with FDO (N=30,000 rpm).

Fig. 6. Rotor position and estimated position with FDO (N=30,000 rpm).

Fig. 7. Speed estimated error with FDO (N=5,000 rpm, N=10,000 rpm and N=30,000 rpm).


In this study, a fuzzy dynamic observer (FDO) scheme for a high speed BLDC motor drive is investigated. FDO micro gains are regulation by using fuzzy logic control (FLC) via real time. This approach has been simulated on a high speed BLDC motor nonlinear model. The FDO acts on the phase currents and also the micro gains will be quickly regulated real time according to error values by FLC. Also, the use of PI speed control accelerates the calculations of the rotor position estimation and speed. In this study, simulation results show that FDO are suitable for high speed BLDC motors and torque ripple is one of the indirect factors affecting the errors estimation. Nevertheless, these results show that the FDO is suitable for high speeds. In addition, as torque ripple is one of the main estimation error this parameter can be decrease by the torque ripple optimization.


[1] Lei Hao, H. A. Toliat, “BLDC Motor Full-Speed Operating Using hybrid Sliding Mode Observer “Applied Power Electronics Conference and Exposition, APEC ’03. Eighteenth Annual IEEE, vol. 1, pp. 286 – 293, February 2003.

[2] S. M. M. Mirtalaei, J. S. Moghani, K. Malekian, B. Abdi, “A Novel Sensorless Control Strategy for BLDC Motor Drives Using a Fuzzy Logic-based Neural Network Observer “International Symposium on Power Electronics, Electrical Drives, Automation and Motion, SPEEDAM 2008. IEEE, vol. 1, pp. 1491 – 1496, July 2008.

[3] Li Qiang, W. Ruixia, “Study on Rotor Position Detection Error in Sensorless BLDC Motor Drives “5th International Conference Power Electronics and Motion Control, IPEMC 2006. IEEE, vol. 3, pp. 1-5, August 2006.

[4] J. Lee, S. Sathiakumar, Y. Shrivastava, “A novel speed and position estimation of the brushless DC motor at low speed “Power Engineering Conference, AUPEC 2008. IEEE, vol. 3, pp. 1-6, December 2008.

[5] M. Divandari. R. Brazamini, A. Dadpour, M. Jazaeri, “A Novel Dynamic Observer and Torque Ripple Minimization via Fuzzy Logic for SRM Drives “International Symposium on Industrial Electronics, ISIE 2009. IEEE, vol. 1, pp. 847 – 852, July 2009.

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