A Low Cost Speed Estimation Technique for Closed Loop Control of BLDC Motor Drive



This paper proposes a sensorless speed control technique for Brushless DC Motor (BLDC) drives by estimating speed from the hall sensor signals. Conventionally, the speed is measured using precision speed encoders. Since these encoders cost almost half of the entire drive system, there arises the need for a low cost speed estimation technique. This is proposed by measuring the frequency of the in-built-hall sensor signals. Here, a closed loop speed control of BLDC motor is proposed using a current controlled pulse width modulation (PWM) technique. Since BLDC motor is an electronically commutated machine, the commutation period is determined by a switching table that shows the hall signals’ status. The entire system was simulated in MATLAB/Simulink and the performance of the system was analyzed for different speed and torque references.


  1. Brushless DC Motor (BLDC)
  2. Speed estimation
  3. Hall sensors
  4. Current controlled PWM
  5. Inverter



Fig.1. Proposed Block Diagram



Fig. 2. Speed and Torque response of the BLDC drive for reference speed of 3000rpm; (a) Speed; (b) Electromagnetic torque developed


Fig. 3. Speed and Torque response of the BLDC drive for reference speed of 2000rpm; (a) Speed; (b) Electromagnetic torque developed

Fig. 4. Stator current measured for speed (reference) of 3000rpm and applied torque 0.5Nm

Fig. 5. Back EMF measured for speed (reference) of 3000rpm and applied torque 0.5Nm

Fig. 6. Speed and Torque response in sensored and sensorless mode for a reference speed of 2500rpm; (a) Speed response in sensored mode; (b) Speed response in sensorless mode; (c) Change in applied torques


This paper proposes a low cost speed estimation technique for BLDC motor drive. This method was found to be working for the entire range of speeds below the rated speed. The performance of the system was comparable with that of the conventional speed encoder based control technique. Actual speed was found to maintain the reference speed for different values of load torques. This was verified successfully by using MATLAB/Simulink. Since the proposed speed estimation technique does not require the motor parameters like resistance, inductance etc., the system is suitable for robust applications, especially in industries.

The future scope of the work can be extended as explained below:

  • Although the work emphasizes on speed encoder-less control technique, the cost of the system can be further reduced by replacing the hall sensors with a suitable low cost counterpart.
  • Since the torque-ripples are found to be appreciably high, novel techniques for its reduction can be studied.


[1] Hsiu-Ping Wang and Yen-Tsan Liu, “Integrated Design of Speed- Sensorless and Adaptive Speed Controller for a Brushless DC Motor,” IEEE Transactions on Power Electronics, Vol. 21, No. 2, March 2006.

[2] K.S.Rama Rao, Nagadeven and Soib Taib, “Sensorless Control of a BLDC Motor with Back EMF Detection Method using DSPIC,” 2nd IEEE International Conference on Power and Energy, pp. 243-248, December 1-3, 2008.

[3] W. Hong, W. Lee and B. K. Lee, “Dynamic Simulation of Brushless DC Motor Drives Considering Phase Commutation for Automotive Applications,” Electric Machines & Drives Conference,2007 lEMDC’07 IEEE International, , pp. 1377-1383, May 2007.

[4] B. Tibor, V. Fedak and F. Durovsky, “Modeling and Simulation of the BLDC motor in MATLAB GUI,” Industrial Electronics (lSIE), 2011 IEEE International Symposium on Industrial Electronics, Gdansk, pp. 1403-1407, June 2011.

[5] V. P. Sidharthan, P. Suyampulingam and K. Vijith, “Brushless DC motor driven plug in electric vehicle,” International Journal of Applied Engineering Research, vol. 10, pp. 3420-3424, 2015.

Diode Clamped Three Level Inverter Using Sinusoidal PWM



An inverter is a circuit which converts dc power into ac power at desired output voltage and frequency. The ac output voltage can be fixed at a fixed or variable frequency. This conversion can be achieved by controlled turn ON & turn OFF or by forced commutated thyristors depending on applications. The output voltage waveform of a practical inverter is non sinusoidal but for high power applications low distorted sinusoidal waveforms are required. The filtering of harmonics is not feasible when the output voltage frequency varies over a wide range. There is need for alternatives. Three level Neutral Point Clamped inverter is a step towards it.


  1. Harmonics
  2. Inverter
  3. THD
  4. PWM



Figure1.Diode clamped three level inverter



 Figure2. Upper triangular pulse width modulation

Figure3. lower triangular pulse width modulation

Figure4. three level voltage waveform

Figure5.Matlab model of three level inverter feeding induction motor

 Figure 6. stator waveform of three level inverter


In normal inverters odd harmonics are present which causes distortion of the output waveform. By using the “THREE LEVEL DIODECLAMPED INVERTER” we can eliminate some number of harmonics hence increasing the efficiency of the inverter.


[1] A.Mwinyiwiwa, Zbigneiw Wolanski, ‘Microprocessor Implemented SPWM for Multiconverters with Phase-Shifted Triangle Carriers’ IEEE Trans. On Ind. Appl., Vol. 34, no. 3, pp 1542-1549, 1998.

[2] J. Rodriguez, J.S. Lai, F. Z. Peng, ’ Multilevel Inverters: A Survey of Topologies, Controls and Applications’, IEEE Trans. On Ind. Electronics, VOL. 49, NO. 4, pp. 724-738, AUGUST 2002

[3] D. Soto, T. C. Green, ‘A Comparison of High Power Converter Topologies for the Implementation of FACTS Controller’, IEEE Trans. On Ind. Electronics, VOL. 49, NO. 5, pp. 1072-1080, OCTOBER 2002.

[4] Muhammad H. Rashid, Power Electronics: Circuits, Devices and Applications, Third edition, Prentice Hall of India, New Delhi, 2004.

[5] Dr. P. S. Bimbhra, Power Electronics, Khanna Publishers, Third Edition, Hindustan Offset Press, New Delhi-28, 2004.

Simulation Analysis of SVPWM Inverter Fed Induction Motor Drives


In this paper represent the simulation analysis ofspace vector pulse width modulated(SVPWM) inverter fedInduction motor drives. The main objective of this paper isanalysis of Induction motor with SVPWM fed inverter and harmonic analysis of voltages & current. for control of IMnumber of Pulse width modulation (PWM) schemes are used tofor variable voltage and frequency supply. The most commonlyused PWM schemes for three-phase voltage source inverters(VSI) are sinusoidal PWM (SPWM) and space vector PWM(SVPWM). There is an increasing trend of using space vectorPWM (SVPWM) because of it reduces harmonic content involtage, Increase fundamental output voltage by 15% & smoothcontrol of IM. So, here present Modeling & Simulation ofSVPWM inverter fed Induction motor drive inMATLAB/SIMULINK software. The results of Total HarmonicDistortion (THD), Fast Fourier Transform (FFT) of current areobtained in MATLAB/Simulink software.


  1. Inverter
  2. VSI
  3. SPWM
  4. SVPWM
  5. IM drive



  Figure 1.Simulation Block Diag. of SVPWM Three level inverter with IM load



Figure 2 Inverter Line voltage

Figure 3 Inverter Line currents

Figure 4 Stator Current

Figure 5 Rotor Current

Figure 6 Mechanical Speed

Figure 7 Torque

Figure 8 Harmonic (FFT) Analysis of Line current


The SVPWM Inverter fed induction motor driveModeling & then simulation is done in MATLAB/SIMULINK 12. From simulation results of THD & FFT analysis concluded that SVPWM technique is better overall PWM techniques which gives less THD in Inverter current 4.89%., which under the permissible limit.


[1] A. R. Bakhshai H. R. Saligheh Rad G. Joos, space vectormodulation based on classification method in three-phasemulti-level voltage source inverters, IEEE 2001

[2] Bimal K Bose, modern power electronics and ac drives © 2002Prentice hall ptr.

[3] Dorin O. Neacsu, space vector modulation –An introductiontutorial at IECON2001 IEEE 2001

[4] Fei Wang, Senior Member, “Sine-Triangle versus Space-VectorModulation for Three-Level PWM Voltage-Source Inverters”,IEEE transactions on industry applications, vol. 38, no. 2,March/April 2002. The 27th Annual Conference of the IEEEIndustrial Electronics Society

[5] F. Wang, Senior, Sine-Triangle vs. space vector modulation forthree-level voltage source inverters ,IEEE 2000