Transcript Adviser ： 龔應時 Student ： 王德智

Initial Rotor Position Estimation
for Sensorless
Brushless DC Drives
IEEE TRANSACTIONS ON INDUSTRY APPLICAT IONS, VOL. 45, NO. 4, JULY/AUGUST 2009
Prasit Champa, Pakasit Somsiri, Pongpit Wipasuramonton, and Paiboon Nakmahachalasint,pp.1318-1324
Adviser ： 龔應時
Student ： 王德智
Outline
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Abstract
Introduction
Proposed Initial Rotor Position Estimation Method
Inductance Comparison Process
Polarity Determination Process
Conclusion
Reference
Abstract(1/2)
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This paper presents a method for determining the initial rotor
position of a brushless dc machine at standstill without a position
sensor.
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The key principle of the rotor position estimation is based on the
simple detection and comparison of phase voltage and current
responses relating to the stator inductance varied with the position
of the rotor magnet.
Abstract(2/2)
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In the proposed method, only three voltage-pulse injections are
applied, and a 30°resolution can be achieved. Moreover, no
knowledge of machine parameters is required.
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The effectiveness of the proposed method is validated by
experimental results.
Introduction(1/3)
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BRUSHLESS dc (BLDC) motors
are widely used in a number of
industrial applications such as
compressors, electric vehicles,
and hard disk drives because of
their high power density,
durability, high efficiency, silent
operation, and high starting
torque, thus making their drives a
much more attractive solution in
recent years.
Introduction(2/3)
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This information is generally available by using position sensors such as
Hall devices or encoders, which make the drive system unfavorable in terms
of cost and reliability.
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Therefore, sensorless control techniques have been developed for reliable
and low-cost sensorless control of BLDC motors in recent years.
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Startup is one of the major problems in sensorless BLDC drives, which are
mostly based on back-electromotive-force (EMF) estimation techniques.
Introduction(3/3)
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The main reason is that the back-EMF voltage disappears at
standstill.
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However, a temporary reverse rotation or even a startup failure may
occur due to unknown load characteristics and no initial rotor
position information.
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In this paper, the rotor position estimation is based on a simple
detection-and-comparison technique of phase voltages and current
responses, resulting from an applied sequence of only three voltagepulse injections.
Sensorless BLDC Drive System
Configuration
Actual Experimental BLDC
Drive
θ0 = 43◦
θ0 = 125◦
θ0 = 305◦
Conclusion(1/2)
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A simple initial rotor position estimation method at standstill has
been introduced in this paper.
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It is based on the stator inductance variation due to the influences of
the saturation of the stator iron and the flux due to the position of the
rotor magnets.
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In the proposed method, only three narrow voltage pulses have
been applied to the phase windings to determine the rotor position,
and a 30°resolution has been achieved.
Conclusion(2/2)
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Additionally, only one sensing resistor has been added into a typical
BLDC drive.
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It is particularly suitable for sensorless BLDC drive applications in
which low cost is the major requirement.
References
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[1] STMicroelectronics, Application Note AN1276 BLDC Motor Start Routine for the ST72141
Microcontroller. [Online]. Available: www.st.com
[2] S. Ogasawara and H. Agaki, “An approach to position sensorless drives for brushless DC
motors,” IEEE Trans. Ind. Appl., vol. 27, no. 5, pp. 928–933,Sep./Oct. 1991.
[3] P. B. Schmidt, M. L. Gasperi, G. Ray, and A. H. Wijenayake, “Initial rotor angle detection of a
non-salient pole permanent magnet synchronous machine,” in Conf. Rec. IEEE IAS Annu.
Meeting, New Orleans, LA, 1997, pp.459–463.
[4] G. H. Jang, J. H. Park, and J. H. Chang, “Position detection and startup algorithm of a rotor in
a sensorless BLDC motor utilizing inductance variation,” Proc. Inst. Elect. Eng.—Elect. Power
Appl., vol. 149, no. 2,pp. 137–142, Mar. 2002.
[5] W.-J. Lee and S.-K. Sul, “A new starting method of BLDC motors without position sensor,”
IEEE Trans. Ind. Appl., vol. 42, no. 6, pp. 1532–1538, Nov./Dec. 2006.
[6] Y.-S. Lai, F.-S. Shyu, and S. S. Tseng, “New initial position detection for three-phase brushless
DC motor without position and current sensors,” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 485–
491, Mar./Apr. 2003.
[7] J. Sugawara, T. Kaimori, and S. Nichikata, “A novel and simple initial rotor position detecting
method for PMSMs,” in Proc. IEEE PEDS, 2005, pp. 612–617.
Thank You
For Your Attention