Novel Back EMF Zero Difference Point Detection Based Sensorless Technique for BLDC Motor

2017, IEEE

ABSTRACT: In this paper a novel position sensorless scheme named Back EMF Zero Difference Point (ZDP) detection has been proposed for six-switch VSI converter fed permanent magnet BLDC motor. This technique is based on the comparison of back EMFs and detection of the points in the back EMF waveforms where they cross each other or in other words they are equal. Commutation point is achieved exactly at the same instant when the difference of back EMFs of any two phases becomes zero. The simulation study has been carried out for the proposed sensorless scheme. The proposed sensorless scheme has the excellent performance from zero to the extra high speed. The method needs no additional delay circuit as used for calculation of commutation point from back EMF ZCP and involves less calculation burden. The method is fault tolerant and accurate even in the case of noise in measurement (or estimation) of phase back EMFs. A nonzero threshold value proportional to input voltage (or reference speed) is used for overcoming the problem due to quantization and sampling for digital implementation. This method proves to be excellent substitute of hall sensing scheme as it also senses at zero speed.

KEYWORDS:

  1. BLDC motor
  2. Back EMF ZDP
  3. Commutation
  4. Sensorless control
  5. Zero difference point.

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1 VSI fed BLDC motor with indirect Back EMF detection scheme

EXPECTED SIMULATION RESULTS:

Fig.2. Phase Back EMF ZDPs, switching signals, counter output and triggering sequence signals.

Fig.3. Steady state operation at the low speed of 600 rpm.

Fig.4. performance of proposed sensorless scheme at 17000 rpm

Fig.5. Noise immune performance during steady state operation for reference speed of 17000rpm.

Fig.6. sensing fault occurs at 0.5 second in the measurement of phase-B back EMF.

Fig.7. speed increases when sensing fault occurs (here phase-B sensing fault

CONCLUSION:

In the proposed Back EMF Zero Difference Point (ZDP) detection method, the very first commutation signal is achieved at starting itself i.e. one step before the ZCP method, which proves the superiority of the method. The back EMF for the proposed scheme can be applied to various existing back EMF detection or estimation techniques. This technique is insensitive to the inherent noise in measurement (or estimation) of back EMF. This method does not need extra

Circuitry as needed for delay after ZCP for getting commutation point, thereby less computational complexity is involved. The speed (or input voltage) proportional threshold used for avoiding uncertainty in the zero difference of back EMF, sets its scope of wide usability in precise operation from zero to extra high speed. Operation at initial zero back EMF is the main strength of this method and it doesn’t necessitate separate starting techniques. Speed response at transient period is 0.15 ms faster than previous methods for identical motor parameters.

REFERENCES:

[1] M.V.Kesava Rao, Department of Electrical technology, IISc Bangalore, ‘‘Brush Contact Drops in DC machines’’, Accepted 25-6-1934, Bangalore Press.

[2] Y.S. Jeon, H.S. Mok, G.H. Choe, D.K. Kim, J.S. Ryu, “A New Simulation Model of BLDC Motor with Real Back EMF waveform”, 7 th workshop on Computers in power Electronics , 2000 (COMPEL 2000), page 217- 220.

[3] Padmaja yedmale, “Brushless DC (BLDC) Motor Fundamentals”, AN885, 2003 Microchip Technology.

[4] S. Tara , Syfullah Khan Md “Simulation of sensorless operation of BLDC motor based on the zero cross detection from the line voltage” International Journal of Advanced Research in Electrical Electronics and Instrumentation Engineering, vol 2, issue 12 , December 2013, ISSN 2320-3765.

[5] J. R. Frus and B. C. Kuo, “Closed-loop control of step motors using waveform detection,” in Proc. Int. Conf. Stepping Motors and Systems, Leeds, U.K., 1976, pp. 77–84.

 

Compensation of torque ripple in high performance BLDC motor drives

 

ABSTRACT:

Brushless DC motor drives (BLDC) are finding expanded use in high performance applications where torque smoothness is essential. The nature of the square-wave current excitation waveforms in BLDC motor drives permits some important system simplifications compared to sinusoidal permanent magnet AC (PMAC) machines. However, it is the simplicity of the BLDC motor drive that is responsible for causing an additional source of ripple torque commonly known as commutation torque to develop. In this paper, a compensation technique for reducing the commutation torque ripple is proposed. With the experimental results, the proposed method demonstrates the effectiveness for a control system using the BLDC motors that requires high speed and accuracy.

KEYWORDS:

  1. Brushless DC motor drives
  2. Commutation
  3. Torque ripple
  4. Trapezoidal back EMF

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. The block diagram of the speed controller.

EXPECTED SIMULATION RESULTS:

Fig. 2. Experimental result in low-speed range (without compensation).

Fig. 3. Experimental result in low-speed range (with compensation).

Fig. 4. Experimental result in the high-speed range (without compensation).

Fig. 5. Experimental result in the high-speed range (with compensation).

Fig. 6. Experimental result in the high-speed range (with compensation).

Fig. 7. Sine wave response for the proposed speed controller.

CONCLUSION:

This paper has proposed a compensation technique for reducing the commutation torque ripple in high-performance BLDC motor drives. The idea is to equalize the mismatched times of two commutated phase currents during the commutation intervals. In low-speed operation, a method to slow down the rising time of the on-going phase current can be a desirable technique. In high-speed operation, a method to slow down the falling time of the off-going phase current becomes a desirable strategy. However, it is not easy to implement the proposed strategies by using cost-effective one-chip microprocessors because it is needed to calculate the commutation time intervals within the sampling period in low and high speed operation. Instead of calculating the commutation time intervals, two dimensional lookup tables that describe the relation of the commutation time interval and the motor parameters such as the back EMF and the initial motor current, are used. For the experiments, a 16-bit microprocessor was used for the controller. Additionally a CPLD (1600 gates) was used to generate gate signals of the inverter and the commutation time signals. To verify the feasibility of the propose method, it is applied to the spindle motor drive control for the industrial sewing machines. The effects of torque ripple are particularly undesirable in the industrial sewing machines. They lead to speed oscillations which cause deterioration in the performance. In addition, the torque ripple may excite resonances in the mechanical portion of the drive system, produce acoustic noise. With the experimental results, the proposed method demonstrates the effectiveness for a high-performance control system using the BLDC motors that requires high speed and accuracy.

REFERENCES:

 

Berendesen, C., Champenois, G., & Bolopion, A. (1993). Commutation strategies for brushless DC motor: influence on instant torque. IEEE Transactions on Power Electronics, 8(2), 231–236. Carlson, R., Lajoie-Mazenc, M., & Fagundes, J. C. S. (1992). Analysis of torque ripple due to phase commutation in brushless DC machines. IEEE Transactions on Industry Applications, 28(3), 632–638.

Chung, K., Zhu, Y., Lee, I., Lee, K., & Cho, Y. (2007). Simulation of the reduction of force ripples of the permanent magnet linear synchronous motor. Journal of E. E. T, 2(2), 208–215. Holtz, J., & Springob, L. (1996). Identification and compensation of torque ripple in high-precision permanent magnet motor drives. IEEE Transactions on Industrial Electronics, 43(2), 309–320.

Jahns, T. M., & Soong, W. L. (1996). Pulsating torque minimization techniques for permanent magnet AC motor drives—a review. IEEE Transactions on Industrial Electronics, 43(2), 321–330.

A New Approach of Minimizing Commutation Torque Ripple for Brushless DC Motor Based on DC–DC Converter

 

ABSTRACT:

Brushless dc motor still suffers from commutation torque ripple, which mainly depends on speed and transient line current in the commutation interval. This paper presents a novel circuit topology and a dc link voltage control strategy to keep incoming and outgoing phase currents changing at the same rate during commutation. A dc–dc single-ended primary inductor converter (SEPIC) and a switch selection circuit are employed in front of the inverter. The desired commutation voltage is accomplished by the SEPIC converter. The dc link voltage control strategy is carried out by the switch selection circuit to separate two procedures, adjusting the SEPIC converter and regulating speed. The cause of commutation ripple is analyzed, and the way to obtain the desired dc link voltage is introduced in detail. Finally, simulation and experimental results show that, compared with the dc–dc converter, the proposed method can obtain the desired voltage much faster and minimize commutation torque ripple more efficiently at both high and low speeds.

KEYWORDS:

  1. Brushless dc motor (BLDCM)
  2. Commutation,
  3. Dc link voltage control
  4. Single-ended primary inductor converter (SEPIC)
  5. Torque ripple

 SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Configuration of BLDCM driving system with a SEPIC converter

EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulated phase currents at n = 1000 r/min. (a) Without dc link voltage control. (b) With dc link voltage control by a SEPIC converter.

Fig. 3. Simulated phase currents at n = 2500 r/min. (a) Without dc link voltage control. (b) With dc link voltage control by a SEPIC converter.

Fig. 4. Simulated electromagnetic torque at n = 1000 r/min. (a) Without DC link voltage control. (b)With DC link voltage control by a SEPIC converter.

Fig. 5. Simulated electromagnetic torque at n = 2500 r/min. (a) Without dc link voltage control. (b) With dc link voltage control by a SEPIC converter.

 CONCLUSION:

A new circuit topology and control strategy has been proposed to suppress commutation torque ripple of BLDCM in this paper. A SEPIC converter is placed at the input of the inverter, and the desired dc link voltage can be achieved by appropriate voltage switch control. The switch control separates the two procedures, adjustment of SEPIC converter, and regulation of speed so that torque can respond immediately during transient commutation and robustness can be improved. Furthermore, no exact value of the commutation interval T is required, and the proposed method can reduce commutation torque ripple effectively within a wide speed range. Finally, the simulated and measured results show an improved performance of the proposed method.

REFERENCES:

[1] Y.-C. Son, K.-Y. Jang, and B.-S. Suh, “Integrated MOSFET inverter module of low-power drive system,” IEEE Trans. Ind. Appl., vol. 44, no. 3, pp. 878–886, May/Jun. 2008.

[2] A. Sathyan, N. Milivojevic, Y.-J. Lee, M. Krishnamurthy, and A. Emadi, “An FPGA-based novel digital PWM control scheme for BLDC motor drives,” IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 3040–3049, Aug. 2009.

[3] G. J. Su and J. W. Mckeever, “Low-cost sensorless control of brushless DC motors with improved speed range,” IEEE Trans. Power Electron., vol. 19, no. 2, pp. 296–302, Mar. 2004.

[4] C.-T. Pan and E. Fang, “A phase-locked-loop-assisted internal model adjustable-speed controller for BLDC motors,” IEEE Trans. Ind. Electron., vol. 55, no. 9, pp. 3415–3425, Sep. 2008.

[5] C. Xia, Z. Li, and T. Shi, “A control strategy for four-switch threephase brushless dc motor using single current sensor,” IEEE Trans. Ind. Electron., vol. 56, no. 6, pp. 2058–2066, Jun. 2009.