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Industry Application of Zero-Speed Sensorless
Control Techniques for PM Synchronous Motors
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 37, NO. 2, MARCH/APRIL 2001
Alfio Consoli, Fellow, IEEE, Giuseppe Scarcella, Member, IEEE, and Antonio Testa, Member, IEEE
Student: Jia-Je Tsai
Adviser: Ming-Shyan Wang
Date : 10th-Dec-2008
Department of Electrical Engineering
Southern Taiwan University
Outline
Abstract
I. INTRODUCTION
II. SENSORLESS CONTROL OF PMSM DRIVES
III. A SIMPLE SENSORLESS TECHNIQUE
IV. ROTOR POSITION DETECTION AT STANDSTILL
V. EXPERIMENTAL RESULTS
VI. CONCLUSIONS
VII. REFERENCES
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Abstract
This paper presents the state of the art in the area of industrial applications of
sensorless control for permanent-magnet synchronous motor (PMSM) drives.
Based on high-frequency signal injection, it is possible to achieve zero-speed
operation without increasing the complexity and the cost of the system.
The paper focuses on the practical implementation of one of the previously
described high-frequency injection techniques in both salient and nonsalient
PM machines.
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INTRODUCTION
PMSM drives are today gradually replacing classic dc drives in a large number
of industrial applications, taking full advantage of key features of PM motors,
such as compactness, efficiency, robustness, reliability, and shape adaptation
to working environment.
PMSM drives need a relatively expensive position transducer to correctly align
the current vector.
Sensorless techniques generally estimate the rotor position by processing
electrical motor variables, such as phase currents or stator voltages.
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INTRODUCTION
The simplest PMSM sensorless techniques are based on rotor-flux-position
estimation, by integration of the back EMF, but it fails at low and zero speed.
A simple sensorless technique following such an approach is presented in this
paper. It properly works at any speed, ranging from zero to the rated value, and
can be applied to both salient and nonsalient machines.
It does not require the knowledge of any motor parameter, while it allows lowcost implementation, requiring only current sensors already included in
standard drives.
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SENSORLESS CONTROL OF PMSM DRIVES
By neglecting hysteresis and eddy-current losses, the model of a cageless
interior PMSM (IPMSM),written in a d-q rotor reference frame, with the d axis
aligned with the direction of the PM flux m , as shown in Fig. 1, is
vqs  rs iqs 
d qs
 r ds
dt
d ds
vds  rs ids 
 r qs
dt
d r
pp

(Te  Tl )
dt
J
qs  Lq iqs  ( Lls  Lmq )iqs
ds  Ld ids  PM  ( Lls  Lmq )ids  PM
Te 
3
sin(2 )
pp (PM I s sin( )  ( Ld  Lq ) I s2
)
2
2
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(1)
(2)
(3)
(4)
(5)
(6)
6
SENSORLESS CONTROL OF PMSM DRIVES
q
Is

d
r
s
Fig. 1. Vector diagram of a PMSM.
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SENSORLESS CONTROL OF PMSM DRIVES
It is assumed that Lq  Ld in an IPMSM owning a salient magnetic
structure, Lq  Ld while in a surface-mounted PMSM (SPMSM) owning a
nonsalient magnetic structure.
As it is possible to observe from (6), in a PMSM the torque depends on
both the amplitude of the stator current vector I s and by the torque angle,
defined as the angular displacement  of the current vector from the d
axis.
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A SIMPLE SENSORLESS TECHNIQUE
In this paper, a simple but effective zero-speed sensorless technique for PMSM
drives is presented. Compared with other techniques based on high-frequency
signal injection, the proposed sensing shows lower sensitivity to noise, higher
resolution.
A high-frequency ( f h  600Hz) stator voltage component Vsh and on a suitable
demodulation of the generated stator current component I sh .
In IPMSMs a maximum of the current amplitude occurs when the voltage vector
is aligned with the maximum inductance axis and a minimum occurs when the
voltage vector is aligned with the minimum inductance axis.
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A SIMPLE SENSORLESS TECHNIQUE
Assuming an IPMSM supplied only with the 600-Hz additional voltage
component , the mathematical model of the machine gives
Vsh sin( h   r )  rs iqsh  r ( Ld idsh  PM )  Lq
diqsh
dt
didsh
Vsh cos( h   r )  rs idsh  r Lq iqsh  Ld
dt
(7)
(8)
where
t
t
0
0
r   r dt  r 0 , h   h dt  h 0
expressed in electrical radians are respectively, the angular position of the d
axis and of the additional 600-Hz voltage vector.
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A SIMPLE SENSORLESS TECHNIQUE
From the previous equations at zero rotor speed it is possible to obtain the
following steady-state expression:
2
2
I sh  idsh
 iqsh
 R1 (t )  R2 (t )  R3 (t )
2
(9)
where

R1 (t )  



R2 (t )  



R3 (t )  




 cos 2    

h
r
2
2
2
2 2
2
2 2

rs  h Ld
rs  h Lq 
Vsh2h2 L2q  2
Vsh2 rs2

sin  h   r 
2
2
2
2 2
2
2 2

rs  h Lq
rs  h Ld 
Vsh2 rs h Lq 
Vsh2 rs h Ld

sin 2  h   r 
2
2
2
2 2
2
2 2

rs  h Ld
rs  h Lq 
Vsh2 rs2
 
Vsh2h2 L2q


 


 

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A SIMPLE SENSORLESS TECHNIQUE
Substituting in (9) the parameters of an actual IPMSM, as reported in Table I.
At frequencies higher than 400 Hz, (9) can be reduced to I sh 2  R2 (t )
(10)
TABLE I
PMSM PARAMETERS
IPMSM
SPMSM
3
3
Back EMF[V/Krpm]
45
45
Rated Power[kW]
.75
.69
Pole Pairs
3
3
Rs
.7
1.3
Ld[mH]
5.4
3.3
Lq[mH]
9.2
3.3
Max speed[rpm]
3000
3000
N  of Phases
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A SIMPLE SENSORLESS TECHNIQUE
According to such an hypothesis, as shown in Fig. 2, minimum points of I sh
occur at  h  k   r (k  0,1, 2,...n) and maximum points at
2
h   / 2  k  r (k  0,1, 2,...n)
The position  r of the d axis can be easily obtained from
known.

The sampling time Ts 
(11)
 h , which is
2 h  r
Fig. 2. Proposed rotor position estimation technique in a IPMSM
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A SIMPLE SENSORLESS TECHNIQUE
TABLE II
ROTOR POSITION SAMPLING TIME
Rotor speed
Ts(pp=2)
Ts(pp=3)
0rpm
416  s
416  s
1000rpm
441  s
454  s
2000rpm
469  s
500  s
-1000rpm
395  s
385  s
-2000rpm
375  s
357  s
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A SIMPLE SENSORLESS TECHNIQUE
Vsh has been settled to 15 V by trials, obtaining an experimentally
evaluated efficiency reduction of less than 1% at rated power.
High Frequency
Voltage
Generator
*
* a
b *
+
v
v
vc
+
+
+
PWM
Inverter
+
PMSM
+
ias
Bandpass
Filter
iash
ibs
Notch
Filter
ibsh
2
I sh
Calculation
Current
Control
d/dt
d/dt
Maximum
Detection
h
Minimum
Detection
Position
Estimation
Algorithm
r
Fig. 3. Implementation of the proposed technique
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A SIMPLE SENSORLESS TECHNIQUE
The approximation introduced in (10) causes a small constant phase errore
2
between I sh and R2 (t )
Fig. 4. e as a function of Ld / Lq
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ROTOR POSITION DETECTION AT STANDSTILL
According to the proposed technique, the estimated position shows an
uncertainty of electric  degrees.
In order to solve such uncertainty, the rotor can be initially placed in a
known position by injecting a dc current.
A dc current pulse is injected along the d axis, zero torque is generated,
avoiding any shaft motion.
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ROTOR POSITION DETECTION AT STANDSTILL
The injected current and the magnet flux own the same sign, the saturation
level will increase, as well as the saliency and the amplitude of the highfrequency current component as the Fig. 5.
Fig. 5. I sh
2
envelope as afunction of Ld
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ROTOR POSITION DETECTION AT STANDSTILL
I sh
2
Fig. 6. and 7. show the envelope of
experimentally recorded when a
current test signal is injected, having, respectively, the same and the opposite
sign of the rotor flux.
Fig. 6. Time = 50 ms/div; 1: I sh
2
evenlope 500 mA 2 / div; 2 : test current 10 A/div
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ROTOR POSITION DETECTION AT STANDSTILL
Fig. 7. Time = 50 ms/div; 1: I sh
2
evenlope 500 mA 2 / div; 2 : test current 10 A/div
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EXPERIMENTAL RESULTS
The first is based on a 0.75-kW six-pole IPMSM, whose parameters are
reported in Table I. (Figs. 8-13)
The second prototype is based on a 0.69-kW six-pole SPMSM, whose
parameters are also reported in Table I.
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EXPERIMENTAL RESULTS
the output of a 1024-pulses-per-round encoder.
Fig. 8. Time = 20 ms/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed 90 rad/s.
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EXPERIMENTAL RESULTS
Fig. 9. Time = 2 s/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed 0.6 rad/s.
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EXPERIMENTAL RESULTS
Fig. 10. Time = 2 s/div; speed 50 (rad/s)/div;1: measured r ; 2 : estimated r .
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EXPERIMENTAL RESULTS
Fig. 11. Time = 0.5 s/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed -4 to 4 rad/s.
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EXPERIMENTAL RESULTS
Fig. 12. Time = 0.5 s/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed 0 to 4 rad/s.
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EXPERIMENTAL RESULTS
According to Table II, at zero speed in Fig. 13 we have a rotor position
sampling time of 416  s , thus allowing good accuracy.
Fig. 13. Time = 1 s/div; current 1 A/div;speed 50 (rad/s)/div;
1: estimated r ; 2 : phase current.
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EXPERIMENTAL RESULTS
Fig. 14 shows a shaft position control test in which the reference is changed
from 0 to 2 rad and back to 0.
Fig. 14. Time = 100 ms/div; position 5 rad/div;speed 50 (rad/s)/div;
1: reference and shaft position ; 2 : r .
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EXPERIMENTAL RESULTS
Fig. 15. Time = 50 ms/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed 50 rad/s.
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EXPERIMENTAL RESULTS
Fig. 16. Time = 2 s/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed 0.5 rad/s.
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EXPERIMENTAL RESULTS
Fig. 17. Time = 0.5 s/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed -5 to 5 rad/s.
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EXPERIMENTAL RESULTS
Fig. 18. Time = 0.5 s/div; position 5 rad/div;1: measured  r ;
2 : estimated  r . Mechanical rotor speed 0 to 5 rad/s.
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CONCLUSIONS
It has been shown that the proposed technique can be used either in IPMSMs,
owning a salient magnetic structure, or in SPMSMs and dc brushless motors,
that own a nonsalient structure.
The proposed technique features wide speed operating range, from zero up to
the rated speed, wide position estimation bandwidth, that allows for either
speed and position control, and good accuracy.
Although sufficient for vector and speed control, the resolution obtained at the
present is not sufficient for servo applications.
However, no theoretical limits prevent to reach higher resolutions by
improving the practical implementation of the proposed sensorless technique,
which, in this paper, has been mainly oriented to low-cost applications.
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REFERENCES
[1] E. K. Kenneth, A. C. Liew, and T. A. Lipo, “New observer-based DFO
scheme for speed sensorless field-oriented drives for low-zero-speed
operation,” IEEE Trans. Power Electron., vol. 13, pp. 959–968, Sept. 1998.
[2] A. Consoli, A. Musumeci, S. Raciti, and A. Testa, “Sensorless vector and
speed control of brushless motor drive,” IEEE Trans. Ind. Electron., vol. 41,
pp. 91–96, Feb. 1994.
[3] R. Dhaouadi, N. Mohan, and L. Norum, “Design and implementation of an
extended Kalman filter for the state estimation of a permanent magnet
synchronous motor,” IEEE Trans. Power Electron., vol. 6, pp. 491–497,
Sept./Oct. 1994.
[4] M. Schroedl and T. Stefan, “New rotor position detector for permanent
magnet synchronous machines using the “INFORM” method,” Eur. Trans.
Elect. Power Eng., vol. 1, no. 1, pp. 47–53, 1991.
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Thanks for your attention
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