Sensorless Control of Permanent Magnet Brushless DC Motors

Sensorless Control of Permanent

Magnet Brushless DC Motors

Satishbabu Bhogineni

DEPARTMENT OF ELECTRICAL ENGINEERINGINDIAN INSTITUTE OF TECHNOLOGY DELHI

OCTOBER 2016

©Indian Institute of Technology Delhi (IITD), New Delhi, 2016

Sensorless Control of Permanent

Magnet Brushless DC Motors

by


Department of Electrical Engineering

submitted

in fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI

OCTOBER 2016

CERTIFICATE

This is to certify that the thesis entitled, “Sensorless Control of Permanent

Magnet Brushless DC Motors” being submitted by Mr. SATISHBABU

BHOGINENI for the award of the degree of Doctor of Philosophy is a record

of bonafide research work carried out by him under my guidance and supervision in

the Department of Electrical Engineering of Indian Institute of Technology Delhi.

Mr. Satishbabu Bhogineni has fulfilled the requirements for the submission of

this thesis, which to my knowledge has reached the requisite standard. The results

obtained here in have not been submitted to any other University or Institute for

the award of any degree.

Date:

Place:

Prof. K. R. Rajagopal

Department of Electrical Engineering

Indian Institute of Technology Delhi

Hauz Khas, New Delhi – 110016, India

i

ACKNOWLEDGEMENTS

It is my pleasure to record sincere gratitude to my supervisor, Prof. K. R.

Rajagopal for providing me the opportunity to work under his supervision. I am

heartily thankful to him for his constant encouragement, counsel, direction and

involvement. His valuable suggestions and guidelines kept me focused in my re-

search. His mentorship, co-operation and support have been of utmost importance

for the completion of this dissertation.

I am thankful to IIT Delhi authorities for providing me the necessary facilities for

the completion of my research work.

I am grateful to my SRC committee members, Prof. Balasubramanian, Prof. I. N.

Kar, Dr. A. R. Abhayankar and Prof. Viresh Dutta for their valuable suggestions

and feedback during the course of my research.

I would like to express my gratitude to my teachers Prof. Bhim Singh, Prof. G.

Bhuvaneswari, Prof. M. Veerachary, Prof. S. S. Murthy and Prof. J. K. Chaterjee

for their support during my course work.

I would also like to thank Phaneendra Babu Bobba and Gaurang. I. Vakil for

invaluable support and assistance. I am thankful to my fellow research scholars

and M.Tech students with whom I discussed and shared the lab facilities.

My sincere thanks to the PG Machines Lab staff, Mr. Srichand, Mr. Puran Singh,

and Mr. Jagbeer Singh for providing facilities and equipment required for my work.

I am greatly indebted to Dhirendra Yadav, Surajbhan Sevda and other friends for

iii

making my stay enjoyable and memorable at Vindyachal house. I am greatly

thankful to my friends Prasad Yanamadala, Raja Shekar, Sudhakar, Sarvesh and

Satish for their support and guidance. This list is still not complete and I apologize

to those not listed by name as you all contributed to my experience.

Most importantly, I would like to express my heart-felt gratitude to my parents,

grand parents, uncles and aunts. None of this would have been possible without

the love and patience of my family. I am also thankful to all who have directly

or indirectly helped me during my Ph.D. Finally, my greatest regards to the Lord

for the love, opportunity and ability face the complexities of life and complete this

dissertation successfully.


IIT Delhi

ABSTRACT

Permanent magnet brushless DC (BLDC) motor drives are increasingly used

in a variety of applications starting with the most critical ones in aerospace to

high quality toys. As on today, almost all two-wheeler and three-wheeler electric

vehicles are driven by these motors. Apart from its wide acceptance in industry

and also for agricultural pumps, energy efficient domestic appliances such as refrig-

erators, air conditioners, washing machines and ceiling fans are being increasingly

driven by these BLDC motors.

These motors are equipped with hall sensors for the rotor position feedback

which is essential in switching currents to the appropriate stator windings in syn-

chronism with the obtained rotor position. Typically, in a three-phase BLDC

motor, apart from the three main power cables, five extra wires are needed for

the rotor position sensors, two for supplying power to these sensor units and the

remaining three for the position signals. These sensor units will occupy some space

anyway and are also sensitive to temperature variations. Use of hall sensors re-

duces the reliability and at the same time increases the cost. Coupled to this with

the problems associated with the assembly and accuracy, it’s always advantageous

to have a position sensor free system for driving this BLDC motor.

The back EMF based sensorless control is widely used in BLDC motors nowa-

days owing to its easy implementation and cost effectiveness. In this method, the

zero crossing point (ZCP) of the back EMF is estimated by detecting the ZCPs of

v

either the phase or the line voltages given to the motor. Among these two voltage

detection based methods, the line voltage ZCP based sensorless control method

uses simple circuits compared to the phase voltage ZCP based method. Moreover,

the line voltage ZCPs can be obtained directly from motor terminals. The investi-

gations carried out in this work on the line voltage ZCP method had brought out

more information on the errors associated with this method and remedial solu-

tions are successfully implemented. The available current in sensorless control can

be advantageously used to improve the line voltage ZCP based sensorless control

method. By using current in addition to terminal voltages, a novel line back EMF

based sensorless control technique is proposed in this work which improved the

performance of the drive. This has been done without using any costly processors

and hence is very economical which is one of the prime concerns addressed in

this work so as to make these sensorless schemes viable for low cost and medium

performance applications like majority of the domestic appliances and automotive

components. Hardware implementation of this proposed scheme is done and the

test results are in agreement with designed and simulated ones. Further studies are

carried out to improve these techniques and some improvements are also suggested

to eliminate the delay caused by the filter used for voltage sensing.

In a three phase BLDC motor, six power devices are usually used in an inverter

configuration. So as to decrease the cost of the drive, reduced parts converters

are being used with induction and permanent magnet synchronous motors. These

are also used in BLDC motors, but with a penalty of having an additional current

sensor. The use of four switches three phase inverter (FSTPI) with BLDC motor

necessitates extra high side current sensing. Addition of extra sensor nullifies

the benefit of having reduced number of switches. In this work, by appropriate

logic, the requirement of this additional current sensor is eliminated thus bringing

back the cost advantage of the reduced number of switches and that too on the

sensorless control mode.

To eliminate high side current sensing, a current reconstruction method is

proposed with a simple low side resistive current sensing which reduces the cost

of the drive. By using the reconstructed current, two direct current control tech-

niques are proposed. The first one is the constant ON/OFF control, where the

current is sensed during lower switch conduction period by fixing the upper switch

conduction time. The second method is the fixed frequency sensing control. Here,

a current sensing state is inserted at fixed intervals in to the operation of motor.

The same logic is extended to PWM control and proposed a modified symmetric

PWM for inserting the sensing states in to the operation. The hardware imple-

mentation of the single resistive current sensing with modified symmetric PWM is

carried out and the test results are again in agreement with the designed and sim-

ulated ones which definitely is a step ahead in having economic sensorless control

of BLDC motors.

Contents

Certificate i

Acknowledgements iii

Abstract v

Contents ix

List of Figures xv

List of Tables xxi

Abbreviations xxii

Symbols xxv

1 INTRODUCTION 1

1.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 PERMANENT MAGNET BRUSHLESS MOTORS . . . . . . . . . 3

1.2.1 Permanent Magnet Synchronous Motor . . . . . . . . . . . . 6

1.2.2 Brushless DC Motor . . . . . . . . . . . . . . . . . . . . . . 7

1.2.3 Construction and Operation of BLDC Motor . . . . . . . . . 10

1.3 FOUR SWITCH THREE PHASE INVERTER . . . . . . . . . . . 13

1.4 SENSORLESS CONTROL OF BLDC MOTOR . . . . . . . . . . . 14

1.5 MOTIVATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.6 LITERATURE SURVEY . . . . . . . . . . . . . . . . . . . . . . . . 18

1.6.1 BLDC Motor . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.6.2 Modeling and Control . . . . . . . . . . . . . . . . . . . . . 20

1.6.3 Sensorless Control . . . . . . . . . . . . . . . . . . . . . . . 21

ix

1.6.4 Starting Mechanism . . . . . . . . . . . . . . . . . . . . . . 25

1.6.5 Four Switch Three Phase Inverter . . . . . . . . . . . . . . . 26

1.7 SCOPE OF THE WORK . . . . . . . . . . . . . . . . . . . . . . . 27

1.8 ORGANISATION OF THE THESIS . . . . . . . . . . . . . . . . . 28

2 MODELING AND CONTROL OF BLDC

MOTOR 31

2.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.2 MODELING OF BLDC MOTOR . . . . . . . . . . . . . . . . . . . 32

2.2.1 Development of Simulation Model . . . . . . . . . . . . . . . 36

2.2.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . 38

2.3 CONTROL OF BLDC MOTOR . . . . . . . . . . . . . . . . . . . . 38

2.3.1 Voltage/Speed control . . . . . . . . . . . . . . . . . . . . . 41

2.3.2 Current/Torque control . . . . . . . . . . . . . . . . . . . . . 41

2.3.3 Pulse Amplitude Modulation Control . . . . . . . . . . . . . 42

2.3.4 Pulse width Modulation Control . . . . . . . . . . . . . . . . 43

2.3.4.1 Bipolar PWM Techniques . . . . . . . . . . . . . . 43

2.3.4.2 Simple Bipolar PWM Technique . . . . . . . . . . 44

2.3.4.3 Complementary PWM Technique . . . . . . . . . . 44

2.3.4.4 Unipolar PWM Technique . . . . . . . . . . . . . . 45

2.3.5 Hysteresis Current Control . . . . . . . . . . . . . . . . . . . 46

2.4 SENSORLESS CONTROL . . . . . . . . . . . . . . . . . . . . . . . 48

2.4.1 Back EMF based Methods . . . . . . . . . . . . . . . . . . . 49

2.4.1.1 Filtered Voltage Methods . . . . . . . . . . . . . . 50

2.4.1.2 Unfiltered Voltage Methods . . . . . . . . . . . . . 52

2.4.2 Machine Equations based Methods . . . . . . . . . . . . . . 54

2.4.3 Model based Methods . . . . . . . . . . . . . . . . . . . . . 55

2.4.4 Inductance based Methods . . . . . . . . . . . . . . . . . . . 56

x

2.5 SENSING CURRENTS AND VOLTAGES . . . . . . . . . . . . . . 57

2.5.1 Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . 57

2.5.2 Voltage Sensing . . . . . . . . . . . . . . . . . . . . . . . . . 59

2.6 HARDWARE SETUP DESCRIPTION . . . . . . . . . . . . . . . . 59

2.6.1 Experimental Results from DSO . . . . . . . . . . . . . . . . 63

2.6.2 Existing Hall Signals . . . . . . . . . . . . . . . . . . . . . . 63

2.7 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

3 LINE VOLTAGE ZCP BASED SENSORLESS CONTROL 69

3.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

3.2 COMMUTATION INSTANT DETECTION . . . . . . . . . . . . . 72

3.3 VIRTUAL HALL SIGNAL GENERATION CIRCUIT . . . . . . . . 74

3.4 EFFECT OF WINDING RESISTANCE DROP . . . . . . . . . . . 75

3.5 ERRORS IN LV-ZCP BASED SENSORLESS CONTROL . . . . . 78

3.5.1 Error due to Low Pass Filter Used in Voltage Sensing . . . . 79

3.5.2 Error due to Winding Impedance . . . . . . . . . . . . . . . 79

3.5.3 Error due to Winding Resistance Drop . . . . . . . . . . . . 80

3.5.4 Error due to Measurement and Signal Processing . . . . . . 80

3.5.4.1 Measurement Errors . . . . . . . . . . . . . . . . . 80

3.5.4.2 Signal Processing Errors . . . . . . . . . . . . . . . 80

3.5.5 Effect of Voltage Spikes due to Residual Current . . . . . . . 81

3.6 SIMULATION RESULTS . . . . . . . . . . . . . . . . . . . . . . . 82

3.7 HARDWARE IMPLEMENTATION . . . . . . . . . . . . . . . . . 88

3.7.1 Hardware Results . . . . . . . . . . . . . . . . . . . . . . . . 89

3.8 EFFECT OF DELAY ON PERFORMANCE . . . . . . . . . . . . 89

3.9 EFFECT OF PARAMETERS ON ERROR . . . . . . . . . . . . . 95

3.9.1 Winding Resistance . . . . . . . . . . . . . . . . . . . . . . . 95

3.9.2 Winding Inductance . . . . . . . . . . . . . . . . . . . . . . 96

xi

3.9.3 Filter Capacitance . . . . . . . . . . . . . . . . . . . . . . . 96

3.9.4 Inertia of System . . . . . . . . . . . . . . . . . . . . . . . . 97

3.10 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

4 LV-ZCP BASED SENSORLESS CONTROL WITH UNIPO-

LAR PWM TECHNIQUES 99

4.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

4.2 UNIPOLAR PULSE WIDTH MODULATION TECHNIQUES . . . 99

4.3 ERROR IN COMMUTATION INSTANT DETECTION . . . . . . 103


4.5 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

5 LINE BACK EMF BASED SENSORLESS CONTROL 111

5.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

5.2 PROPOSED COMMUTATION INSTANT DETECTION SCHEME 112

5.3 COMMUTATION INSTANT DETECTION . . . . . . . . . . . . . 113

5.4 VIRTUAL HALL SIGNAL GENERATION . . . . . . . . . . . . . 115


5.5.1 Voltage Drop Estimation Circuit . . . . . . . . . . . . . . . 117

5.5.2 Commutation Signals Generation . . . . . . . . . . . . . . . 118


5.7 COMPENSATION FOR FILTER DELAY . . . . . . . . . . . . . . 119

5.8 HARDWARE RESULTS . . . . . . . . . . . . . . . . . . . . . . . . 122

5.9 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

6 FOUR SWITCH THREE PHASE INVERTER BASED BLDC

MOTOR DRIVE 127

6.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

6.2 FOUR SWITCH THREE PHASE INVERTER . . . . . . . . . . . 129

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6.3 FSTPI BASED BLDC MOTOR CONTROL . . . . . . . . . . . . . 132

6.4 HYSTERESIS CURRENT CONTROL . . . . . . . . . . . . . . . . 137

6.4.1 C–Phase Conduction in Sector II and V . . . . . . . . . . . 139

6.5 VOLTAGE CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . 143

6.5.1 C–Phase Conduction in Sector II and V . . . . . . . . . . . 145

6.6 CURRENT SENSING . . . . . . . . . . . . . . . . . . . . . . . . . 146

6.7 LOW SIDE CURRENT SENSING . . . . . . . . . . . . . . . . . . 147

6.8 HYSTERESIS CURRENT CONTROL USING LOWER SWITCH

CURRENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

6.8.1 Constant ON/OFF Time Control . . . . . . . . . . . . . . . 150

6.8.2 Fixed Time Sensing Control . . . . . . . . . . . . . . . . . . 153

6.9 VOLTAGE CONTROL USING LOWER SWITCH CURRENT . . 155

6.10 PROPOSED CURRENT SENSING IN VOLTAGE CONTROL . . 157

6.10.1 PWM Control Using Lower Switch Currents . . . . . . . . . 158

6.10.2 PWM Control Using Lower Side DC Bus Current . . . . . . 159

6.10.3 Control Strategy . . . . . . . . . . . . . . . . . . . . . . . . 161

6.11 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

7 SENSORLESS CONTROL OF FSTPI BASED BLDC MOTOR 167

7.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

7.2 LINE BACK EMF BASED SENSORLESS CONTROL . . . . . . . 168


7.3.1 Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . 169

7.3.2 Voltage Sensing . . . . . . . . . . . . . . . . . . . . . . . . . 171

7.3.3 Control Strategy . . . . . . . . . . . . . . . . . . . . . . . . 172

7.3.4 Hardware Results . . . . . . . . . . . . . . . . . . . . . . . . 173

7.4 STARTING MECHANISM . . . . . . . . . . . . . . . . . . . . . . . 174

7.5 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

xiii

8 MAJOR CONCLUSIONS AND SUGGESTIONS FOR FUTURE

WORK 177

8.1 MAJOR CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . 177

8.2 MAIN CONTRIBUTIONS OF THIS RESEARCH WORK . . . . . 181

8.3 SUGGESTIONS FOR FUTURE WORK . . . . . . . . . . . . . . . 182

REFERENCES 185

Appendix-I 199

Appendix-II 201

Appendix-III 203

Authorbiodata 207

xiv

List of Figures

1.1 Voltage, current waveforms and position information required in

PMSM and BLDC motor . . . . . . . . . . . . . . . . . . . . . . . . 5

1.2 Different rotor structures used in PMBL motors . . . . . . . . . . . 7

1.3 Vector controlled three phase PMSM motor drive . . . . . . . . . . 8

1.4 Control structure of BLDC motor drive . . . . . . . . . . . . . . . . 10

1.5 BLDC motor construction details . . . . . . . . . . . . . . . . . . . 11

1.6 Phase back EMF, current, hall signal and torque waveforms of

BLDC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.7 Basic BLDC motor drive structure . . . . . . . . . . . . . . . . . . 12

2.1 Electrical circuit model . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.2 Flux function realisation by IFFT . . . . . . . . . . . . . . . . . . . 37

2.3 Coupled circuit model . . . . . . . . . . . . . . . . . . . . . . . . . 37

2.4 Simulation results using developed model with sinusoidal and trape-

zoidal back EMFs at noload . . . . . . . . . . . . . . . . . . . . . . 39

2.5 Simulation results using developed model with different back EMF

shapes with load . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.6 Different PWM techniques used in BLDC motor control . . . . . . . 47

2.7 Principle of commutation instant detection by phase back EMF zero

crossing point and back EMF integration . . . . . . . . . . . . . . . 50

2.8 Principle of commutation points generation from 3rd harmonic back

EMF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

2.9 High side and low side current sensing using resistance element . . . 58

2.10 Hardware implementation block diagram . . . . . . . . . . . . . . . 61

2.11 Experimental setup showing all components . . . . . . . . . . . . . 62

xv

2.12 Three phase current waveforms from DSO with normal mode and

precision mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

2.13 Sensed three phase voltage waveforms from DSO with normal mode

and precision mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

2.14 Measured time periods of existing hall signals . . . . . . . . . . . . 66

2.15 Measured sector widths of existing hall signals . . . . . . . . . . . . 67

3.1 Relation between line back EMF zero crossing point and hall signal 70

3.2 Relation between line voltage zero crossing point and hall signals

when running with sensors . . . . . . . . . . . . . . . . . . . . . . . 74

3.3 Virtual hall signals generation circuit . . . . . . . . . . . . . . . . . 75

3.4 Error due to winding drop in line voltage zero crossing points . . . 77

3.5 Effect of voltage spikes due to residual current. . . . . . . . . . . . . 81

3.6 Waveforms of BLDC motor running with hall sensors with current

at three different speeds . . . . . . . . . . . . . . . . . . . . . . . . 83

3.7 Waveforms of LV-ZCP based sensorless control at 5000rpm and

2500rpm with hysteresis current control . . . . . . . . . . . . . . . . 84

3.8 Waveforms of LV-ZCP based sensorless control at 1000rpm with

hysteresis current control . . . . . . . . . . . . . . . . . . . . . . . . 85

3.9 Failure mode waveforms at at 1000rpm speed and 1.0A current . . . 85

3.10 Waveforms of LV-ZCP based sensorless control at with PWM con-

trol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

3.11 Implementation of line voltage ZCP based sensorless control . . . . 88

3.12 Waveforms of with hall sensor with PWM control . . . . . . . . . . 90

3.13 Waveforms of with and LV-ZCP based sensorless control with PWM

control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

3.14 Waveforms of LV-ZCP based sensorless control with current control 92

3.15 Power developed with delay in commutation . . . . . . . . . . . . . 92

xvi

3.16 Variation power and current with delay angle . . . . . . . . . . . . 93

3.17 Deviation of current in LV-ZCP method form ideal commutation . . 94

4.1 BLDC motor conduction states with unipolar PWM . . . . . . . . . 100

4.2 Floating phase voltages (a) and (b) Upper switch PWM before turn

ON and after turn OFF, (c) and (d) Lower switch PWM before turn

ON and after turn OFF of corresponding phase. . . . . . . . . . . . 101

4.3 Actual average voltage of floating phase. . . . . . . . . . . . . . . . 103

4.4 Average terminal voltage upper switch PWM. . . . . . . . . . . . . 103

4.5 Waveforms of LV-ZCP based sensorless control with H-PWM-L-

PWM technique at 2500rpm . . . . . . . . . . . . . . . . . . . . . . 107

4.6 Waveforms of LV-ZCP based sensorless control with H-PWM-L-ON

and H-ON-L-PWM techniques at 2500rpm . . . . . . . . . . . . . . 108

4.7 Waveforms of LV-ZCP based sensorless control with PWM-ON and

ON-PWM techniques at 2500rpm . . . . . . . . . . . . . . . . . . . 109

5.1 Principle of the commutation instant detection . . . . . . . . . . . . 114

5.2 Comparison virtual hall signals with actual hall signal . . . . . . . . 115

5.3 Generation of switching signals from virtual hall signals . . . . . . . 116

5.4 Schematic diagram of proposed line back EMF based sensorless con-

trol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

5.5 Voltage drop estimation Circuit . . . . . . . . . . . . . . . . . . . . 118

5.6 Commutation Instant Detection Circuit . . . . . . . . . . . . . . . 118

5.7 Waveforms with the proposed line back EMF ZCP method with

different loads and speeds (1) . . . . . . . . . . . . . . . . . . . . . 120


different loads and speeds (2) . . . . . . . . . . . . . . . . . . . . . 121

5.9 Compensation circuit for filter delay . . . . . . . . . . . . . . . . . . 121

xvii

5.10 Waveforms with the proposed line back EMF ZCP method and with

improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123


current PI control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

6.1 Four switch three phase inverter based 3- phase motor drive . . . . 129

6.2 Switching states of four switch three phase inverter . . . . . . . . . 130

6.3 State voltages of four switch three phase inverter . . . . . . . . . . 132

6.4 Four switch three phase inverter based BLDC motor drive . . . . . 133

6.5 FSTPI BLDC states . . . . . . . . . . . . . . . . . . . . . . . . . . 134

6.6 FSTPI BLDC Three Phase Conduction . . . . . . . . . . . . . . . . 135

6.7 SSTPI based BLDC Hysteresis Control . . . . . . . . . . . . . . . . 136

6.8 FSTPI based BLDC Hysteresis Control . . . . . . . . . . . . . . . . 136

6.9 FSTPI based BLDC motor hysteresis current control using (a) four

states and (b) eight states . . . . . . . . . . . . . . . . . . . . . . . 137

6.10 Hysteresis Control using Eight States . . . . . . . . . . . . . . . . . 138

6.11 Experimental results (a) Independent control of two phase currents

and (b) maximum DC current is controlled by hysteresis control . . 139

6.12 C-phase conduction (a) Average model and (b) Equivalent circuit . 142

6.13 Experimental waveforms for voltage controlled PWM (a) without

C phase current control and (b) with C phase current control . . . . 146

6.14 current sensor positions in FSTPI-BLDCM . . . . . . . . . . . . . . 147

6.15 Resistive Current sensing positions . . . . . . . . . . . . . . . . . . 147

6.16 Constant ON time control . . . . . . . . . . . . . . . . . . . . . . . 151

6.17 Constant OFF time control . . . . . . . . . . . . . . . . . . . . . . 151

6.18 Phase A current waveform with constant ON/OFF control . . . . . 152

6.19 Waveforms with constant ON/OFF control (a) Three phase currents

and switching signals and (b) Magnified phase currents . . . . . . . 153

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6.20 Principle of current sensing in constant frequency sampling control . 155

6.21 Waveforms with constant frequency sampling control at 2000rpm

(a) 0.3A (b) 0.5A loads . . . . . . . . . . . . . . . . . . . . . . . . . 156

6.22 Waveforms with constant frequency sampling control at 1900rpm

(a) 0.3A (b) 0.5A loads . . . . . . . . . . . . . . . . . . . . . . . . . 156

6.23 Different PWM techniques used in sector II and V . . . . . . . . . . 159

6.24 Simulation results with PWM control . . . . . . . . . . . . . . . . . 161

6.25 Hardware results with PWM control at 1900rpm (a) Uncontrolled

C phase current at no load, (b) Controlled C phase current at no

load, (c) Uncontrolled C phase current with load and (d) Controlled

C phase current with load . . . . . . . . . . . . . . . . . . . . . . . 162

6.26 Hardware results with PWM control (a) Lower side switch cur-

rents sensing at 1250rpm, (b) Lower side DC bus current sensing at

1250rpm and (d) Lower side DC bus current sensing at 1900rpm . . 163

6.27 PWM control logic . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

7.1 Block diagram of FSTPI based sensorless control . . . . . . . . . . 169

7.2 Current sensing with single low side current sense resistor . . . . . . 170

7.3 Simulation results explaining principle of current sensing with single

low side current sense resistor . . . . . . . . . . . . . . . . . . . . . 171

7.4 Commutation instant detection logic . . . . . . . . . . . . . . . . . 173

7.5 Experimental waveforms of FSTPI based sensorless control with

single resistive current sensing (a) With IR drop compensation (b)

With complete compensation . . . . . . . . . . . . . . . . . . . . . 174

7.6 Experimental waveforms of FSTPI based sensorless control with

single resistive current sensing with phase advancing . . . . . . . . . 174

7.7 Starting mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

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List of Tables

3.1 Delay variation with speed and load . . . . . . . . . . . . . . . . . . 86

4.1 Unipolar PWM commutation instants . . . . . . . . . . . . . . . . . 106

5.1 The Commutation Instant Detection Logic . . . . . . . . . . . . . . 114

5.2 Decoding of Switching Signals . . . . . . . . . . . . . . . . . . . . . 115

5.3 Virtual Hall Signal Generation . . . . . . . . . . . . . . . . . . . . . 116

6.1 Switching states and corresponding voltages of FSTPI . . . . . . . . 131

6.2 States used and corresponding voltage . . . . . . . . . . . . . . . . 148

6.3 Currents sensed in different sectors of operation . . . . . . . . . . . 149

6.4 Current sensing in constant ON/OFF time control . . . . . . . . . . 153

6.5 Current sensing in constant frequency sampling control . . . . . . . 156

6.6 Current sensing in PWM control . . . . . . . . . . . . . . . . . . . 159

6.7 Current sensing in DC bus in different sectors of operation . . . . . 160

xxi

Abbreviations

AC Alternating Current

ACP Actual Commutation Point

ADC Analog to Digital Converter

ALV Average Line Voltage

AlNiCo Alluminium Niclel Cobalt

ANN Artificial Neural Networks

ASIC Application Specific Integrated Circuit

BLDC BrushLess DC

BLDCM BrushLess DC Motor

DC Direct Current

DSP Digital Signal Processor

EMF Electro Motive Force

EMI Electro Magnetic Interference

EV Electrc Vehicle

FSTPI Four Switch Three Phase Inverter

H Hall Signal

IC Integrated Circuit

ICP Ideal Commutation Point

IGBT Insulated Gate Bipolar Transistor

IM Induction Motor

IPM Intellignet Power Module

LPF Low Pass Filter

MMF Magneto Motive Force

MOSFET Metal Oxide Semiconductor Feild Effect Transistor

NdFeB Neodymium Ferrous Boran

PAM Pulse Amplitude Modulation

PCB Printed Circuit Board

PI Proportional Integral

PID Proportional Integral Derivative

PM Permanent Magnetxxiii

PM BLDC Permanent Magnet BrushLess DC

PMDC Permanent Magnet DC

PMSM Permanent Magnet Synchronous Motor

PMBL Permanent Magnet BrushLess

PSO Particle Swam Optimisation

PWM Pulse Width Modulation

RMS Root Mean Square

RTOS Real Time Operating System

RTW Real Time Workshop

SmCo Samarium Cobalt

SPM Smart Power Module

SSTPI Six Switch Three Phase Inverter

SVM Space Vector Modulation

TI Texas Instruments

VH Virtual Hall Signal

VLSI Very Large Scale Integration

VSI Voltage Source Inverter

ZCP Zero Crossing Point

xxiv

Symbols

D Duty ratio

KE EMF constant

KT Torque constant

Kp Proportional gain

Ki Integral gain

p Time derivative operator

Te Electromagnetic torque developed

TL Applied load torque

X Any switch state

Z High impedance state/ leg both switches are off

ω Angular rotor speed

ωe Electrical rotor speed

ωr Rotor speed

ωm mechnical rotor speed

N Rotor speed in rpm

Ts Sampling time

F Frequency

t Time

Fs Switching frequency

d− axis Direct axis

q − axis Quadrature axis

Vd d− axis voltage

Vd q− axis voltage

Id d− axis current

Iq q− axis current

τx Time constant

Pag Air gap power

Pave Average power

Pcap Power capability

xxv

Ploss Power loss

Idc DC-link current

Sx Switch x

emax Phase back EMF maximum value

Sx − Sy Switch x to y in numerical order

yx∗ Reference value of that variable yx

Idm Maximum DC-link current

Vdc DC-link voltage

Ra, Rb, Rc Phase resistances

La, Lb, Lc Phase inductances

ea, eb, ec Phase back-EMFs

eab, ebc, eca Line back-EMFs

ia, ib, ic Phase currents

va, vb, vc Terminal voltages of the

A, B and C phases respectively

van, vbn, vcn Terminal voltages of the

A, B and C with respect to neutral

Ha, Hb, Hc Hall signals

corresponding to A, B, C phases

θ Angular position

φ Difference angle

J Rotor inertia

B Friction factor

xxvi

Documents

Sensorless Control of Permanent Magnet Brushless DC Motors