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Novel Back-EMF Detection
Technique of Brushless DC Motor
Drives for Wide Range Control Without
Using Current and Position Sensors
IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 23,
NO. 2, p.934~940,MARCH 2008
Yen-Shin Lai, Senior Member, IEEE, and Yong-Kai Lin
Adviser : Ming-Shyan Wang
Student :Jin-Mu Lin
Outline
Abstract
 Introduction
 PWM control and problem description
 Proposed technique
 Experimental results
 Conclusion
 Appendix
 References

Abstract

本文提供一個新的反電動勢檢測技術，可以廣範圍的控制。
特點:
1.解決以前只能控制high or low duty的情況。
2.不需要使用任何hall or position sensor=用未激磁相量測到
的端電壓來計算反電動勢的零交越點，產生正確的換相控制。
3.容易使用數位系統來實現=使用FPGA架構來實現BLDC Driver
System。
Introduction

與感應馬達比較，優點：沒有轉子側的銅損。

減少BLDC控制成本的做法=無感測器控制。


這些參考論文使用的方式都使用從量測與dc-link串聯
的 “電阻”產生的資料，重建中性點電壓和終端點電壓。
各參考論文提及:
So…..

為了解決以上的問題，本論文提出一個新的方式
來計算在高速與低速時的反電動勢的零交越點。
PWM control and problem description
The
high-side power device
is controlled by chopper
signal every consecutive
120° in a fundamental period.
The
associated low-side
control signal is shifted by
180° ,as compared to its highside one, to clamp the related
inverter output to the
negative dc-link rail.
Defines the terminal voltages of
three-phase windings

“
” denotes the terminal voltage for the phase connected to the
positive dc-link rail during PWM control period.

“
” indicates the terminal voltage for the phase connected to the
negative dc-link rail.

“
” is the terminal voltage for the
floating phase.
The back-EMF voltage is detected
via the terminal voltage of floating phase.

非激磁相的端電壓公式(1/2)
非激磁相的端電壓公式(2/2)
檢測零交越點在上升、下降的端電壓(1/1)


As shown in Fig. 3, the
terminal voltage of the
floating phase has either
rising edge or
falling edge.
For both, when the
terminal voltage
becomes zero,
the zero-crossing point
occurs.
上升邊緣的端電壓
當PWM ON時
 未激磁相的端電壓可以用(6)導出寫成

(7)
這情況下的零交越點端電壓
(8)
當PWM OFF時
 未激磁相的端電壓就是
(9)
Fig.4
下降邊緣的端電壓
當PWM ON時
 未激磁相的端電壓可以用(6)導出寫成

(10)
這情況下的零交越點端電壓
(11)
當PWM OFF時
 未激磁相的端電壓就是
(12)
Fig.4
低工作率控制下的端電壓理想的波形
Proposed technique
計算:零交越點時間點(>50%)
V

Duty ratio > 50%

By (13), the time instant of
zero-crossing point can be
determined as follows:
計算:零交越點時間點(<50%)

Duty ratio < 50%

By (15), the time instant of
zero-crossing point can be
determined as follows:
Experimental results
Experimental results Duty = 95%
Ch1=voltage;
Ch2 =current.
Experimental results Duty = 95%
Ch1 = voltage;
commutation
signals:
Ch2 = by calculation;
Ch3 = by Hall sensor.
Experimental results Duty = 55%
Ch1=voltage;
Ch2 =current.
Experimental results Duty = 55%
Ch1 = voltage;
commutation
signals:
Ch2 = by calculation;
Ch3 = by Hall sensor.
Experimental results Duty = 45%
Ch1=voltage;
Ch2 =current.
Experimental results Duty = 45%
Ch1 = voltage;
commutation
signals:
Ch2 = by calculation;
Ch3 = by Hall sensor.
Experimental results Duty = 5%
Ch1=voltage;
Ch2 =current.
Experimental results Duty = 5%
Ch1 = voltage;
commutation
signals:
Ch2 = by calculation;
Ch3 = by Hall sensor.
Current waveform from standstill to closed-loop
operation.
Experimental results, speed versus duty, rated
speed = 2500 rpm.
Conclusion




1. the duty can be smoothly controlled from 5% to
95%;
2.讓BLDC無感測控制的想法注入新的ideal。
3.Present a novel back-EMF detection technique to
provide wide duty-ratio range control for BLDCM
drives while not requiring position and current
sensors.
4.Confirm the performance of the presented
technique derived from an FPGA-based system.
APPENDIX

MOTOR SPECIFICATIONS
1.No.of poles=8,
2.rated power=70w,
3.Vdc=24v,
4.Rated=2500rpm
References 1/2

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
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




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Thanks for listening!!!