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Position Sensorless Control Based on Coordinate
Transformation for Brushless DC Motor Drives
Yuanyuan Wu, Zhiquan Deng, Xiaolin Wang, Xing Ling, and Xin Cao
IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 25, NO. 9, SEPTEMBER 2010 2365-2371
學生:王沼奇
教授:王明賢
目錄
 I. INTRODUCTION
 II . PROPOSED ARITHMETIC FOR SENSORLESS BLDC
DRIVES
– A. Constructed Position Signals Based on Coordinate
Transformation
– B. Implementation of the New Scheme
– C. Review of the Error Compensation Methods
目錄
 III. PROPOSED ARITHMETIC FOR SENSORLESS BLDC
DRIVES
– A. Constructed Position Signals Based on Coordinate
Transformation
– B. Implementation of the New Scheme
 IV. CONCLUSION
INTRODUCTION
 However, the rotor position sensors show some disadvantages
from the standpoint of total system cost, size, and reliability .
 Consequently, for eliminating these sensors from the motor,
many research workers have attempted to control the speed of
BLDC motors without rotor position sensors or speed sensors
Traditional
Sensorless-Control Methods

which is expressed as Sa in Fig. 1. At
the rising edge of Sa, the MOSFET T1
should be ON, and theMOSFET T5
should be OFF.

At the falling edge of Sa , the MOSFET
T2 should be ON, and
the MOSFET T6 should be OFF.

Similarly, according to the rising
and falling edges of Sb and Sc , other
commutation instants could be obtained.
Consequently, the BLDC motor could
worknormally on the rated state.
 In the TVM, for obtaining the commutation sequences, it
compares Ua , Ub , and Uc to Ud/2 that is different from the
PVM as shown in Fig. 1(b), and there is no resistance divider for
the filter. Its operation process is the same as PVM.
Analysis of the RotorPosition-Detection Error
 In a PM BLDC motor, the transient value of flux linkage in each
phase winding is directly related to the rotor position.
 However, the back EMF is due to the rate of change of flux
linkages, hence, the back EMF can be indirectly related to the
rotor position, and used for position sensorless control.
 EMF due to the armature
reaction field, which is
usually only around 10%–
20% of the magnitude of the
open-circuit field [21] and
may distort the motor air-gap
agnetic field excited by PM.
 2) Error Caused by the LowPass Filters: Usually, the
terminal or phase voltages are
used instead for sensorless
control,as the back EMF is
difficult to be detected
directly.
Review of the Error
Compensation Methods
 Sensorless commutation IC
for BLDC motors based on
the frequency-independent
phase shifter, in which the
position error could be
compensated by decreasing
the slew rate γd, the period
Td was calculated which
depended strongly
Constructed Position Signals Based on
Coordinate Transformation
Implementation of the New Scheme
 1) Hardware Implementation: The proposed sensorless BLDC
motor drive system could be designed as shown in Fig. 4.
 In comparison with Fig. 1, the back EMF zero-crossing detection
circuit is substituted by the back EMF sampling circuit,which
includes the low-pass filters,
 2) Program Implementation: The program flow of the proposed
arithmetic is presented in Fig. 5(a). Since the back EMF is not
generated at standstill, a proper starting procedure is necessary.
 In this paper, an open loop ramping control scheme is adopted to
accelerate the motor to a certain speed level.
 Once the motor reaches the speed at which the back EMF can be
reliably
 detected, the control mode will be changed from the open loop
ramping control to the proposed sensorless control.
CONCLUSION