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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 1

EXPERT SYSTEMS AND SOLUTIONS

Email: expertsyssol@gmail.com

expertsyssol@yahoo.com

Cell: 9952749533www.researchprojects.info

PAIYANOOR, OMR, CHENNAI

Call For Research Projects Final

 year students of B.E in EEE, ECE, EI,

M.E (Power Systems), M.E (Applied

Electronics), M.E (Power Electronics)

Ph.D Electrical and Electronics.

Students can assemble their hardware in our 

Research labs. Experts will be guiding the projects.

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Elektrical Machines and Drives

Wuppertal University

Tutorial 2

Sensor less Motor Drives

Ralph M. Kennel

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 3

Reasons for Industrial Applications

of Drives with Encoderless Control:

� Cost

� Reliability

� Robustness

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 4

Industrial Drives with Sensorless Control

since several years / decades sensorless control is investigated

and published on conferences and magazines

- acceptance in industry, however, is rather low

Why ?new ideas and concepts are interesting for industry,

only if they do not result in higher cost or higher effort!!!

What does that meanf or industrial drives with sensorless control ?

no additional or more powerful processors / controllers no additional hardware or additional sensors (e. g. voltage sensors)

no increased installation effort with respect to parameter adjustments

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 5

introduction

� f undamental model methods

� high f requency injection methods

sensorless control of electrical machines

� machine response on high f requency injection voltages

� tracking of  magnetic saliencies / anisotropies

practical results

� experiences with industrial drives

conclusions

Sensor less (Encoder less) Motor Drives

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 6

Categories of Machine Models for ÄSensorless³ Control

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Basic Principlesof  Encoder less Control

high f requency injectionfundamental model

� simple realisation

� does not work at frequency 0

� parameter dependencies

current injection voltage injection

� measuring voltage is high enough

� additional voltage sensors

stationary current response

� standard microcontroller sufficient

� very small measuring current

transient current response

� no additional hardware

� very short measuring time

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 8

stator rotor  

mechanicswhen knowing voltage uS

as well as current i S

it should be possible

calculate speed [

Fundamental Model of an Induction Machine

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 9

Calculation of Speed by Fundamental Model

is not Practicable for Very Low Speeds

... because

� the voltage signal becomes very small

� errors between real voltage and values used f or calculation

cannot be avoided and become more signif icant

� DC components of  these errors

let the integrators f or f lux calculation drif t away

the calculated speed gets more and more incorrect

is an encoder/resolver the only feasable solution ??

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 10

� this is basically a current injection method

voltage sensors are necessary !!!

� it is possible to use current derivativesinstead of  motor voltages

measuring current derivatives, however ,

by standard current transducers is not really possible

� but, industrial current transducershave a current derivative available internally

can this be made avail abl e for c ustomer s ???

Signal Injection Methodaccording to J. Holtz, H.Pan, etc.

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 11

INFORM method

according to M. Schroedl(Technical University of  Vienna, Austria)

� this is basically a transient voltage injection method

currents have to be sensed at specif ic times !!!

� when using standard current transducers

these cannot be synchronized with PWM

the hardware of  a standard industrial drive

has to be changed

neverthel ess this method comes c l ose to i nd ustr i al need s ! 

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 12

Stationary Signal Injection Methodsaccording to R. Lorenz, S.-K. Sul, R. Kennel, etc.

� the basic idea is

to use the electrical machine itself  as a resolver !!!

� a resolver is nothing else but an electrical machine

can we operate the motor itself  like a resolver ?

� if  the machine itself  is a resolver (encoder)

is that really an Äencoder less³ control ???

g ood i dea ± but does i t work ???

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 13

R esolver

Stator u

e

Rotor u

R

Stator u2

Stator u

1

R1

R2

S1 S3

S4

S2

u2(K

K

TT0

u1(K

K

TT0

Tamagawa

injection of a

stationary (sinusoidal)

high f requency signal

sensing of  a two-dimensional

stationary (sinusoidal)

signal response

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 14

Stationary Signal Injection Methodsaccording to R. Lorenz, S.-K. Sul, R. Kennel, etc.

� the basic idea is

to use the electrical machine itself  as a resolver !!!

� a resolver is nothing else but an electrical machine

can we operate the motor itself  like a resolver ?

� if  the machine itself  is a resolver (encoder)

is that really an Äencoder less³ control ???

now we do the same w i th an el ectr i cal AC machi ne

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 15

Fundamental Frequency Excitation

(in E- F coordinates)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 16

High Frequency Excitation

(in E- F coordinates)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 17

(F)c

(F)sa

(F)c(F)

s(F)

cs(F)c i l 

i l i u [ j

dt 

d r  ! ¼

½

»¬«

!qs

ds( )s 0

0

l 

l l 

Machine Model for High Frequency Signals

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 18

High Frequency Behaviour of the Machine Model

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 19

injection of  high f requency voltages

f undamental voltage phasor/vector 

f undamental current phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 20

injection of  high f requency voltages

f undamental voltage phasor/vector 

f undamental current phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 21

injection of  high f requency voltages

f undamental voltage phasor/vector 

f undamental current phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 22

injection of  high f requency voltages

f undamental voltage phasor/vector 

f undamental current phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 23

Injection of High Frequency Rotating Phasors

rotating voltage phasor uc elliptic current response i c

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 24

elliptic current response i c (rotating)

� machine responds

on a rotating voltage phasor 

with an elliptic current response

� ellipse is correlated

with the geometric anisotropy

of  the rotor 

� rotor position inf ormation

is included

in the high f requency current

Position Information of Salient Rotors

in High Frequency Rotating Phasors

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 25

Saturation Anisotropy

of a Permanent Magnet Synchronous Machine

rotor f lux saturation of  a

permanent magnet synchronous machine

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 26

Position Information of non-salient rotors

in High Frequency Rotating Phasors

� machine responds

on a rotating voltage phasor with an elliptic current response

� ellipse is correlated

with the saturation anisotropy

� rotor position inf ormation

is included

in the high f requency current elliptic current response i c (rotating)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 27

Injection of High Frequency

 Al ternating (Pu lsating) Voltage Phasors

composing an alternating (pulsating) voltage phasor 

by two phasors rotating in opposite direction

advantage :

no rotational (HF) f ield

no additional torque

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 28

High Frequency Current Response

of  a Synchronous Machine

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 29

Current Response

of  a Misoriented System

voltage and current

show diff erent orientation !!

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 30

Current Response

under a Misorientation of  90°

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 32

Tracking the estimated angle of  the rotor f lux by controlling i cq to 0

Tracking Scheme for Magnetic Anisotropies

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 33

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 34

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 35

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 36

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 37

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 38

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 39

step response of  the PLL;

PLL is locked af ter ca. 10 -15 ms

Encoderless Control Structure

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 40

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 41

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 42

tracking control of  injection voltage

f undamental current phasor/vector 

f undamental voltage phasor/vector 

injected high f requency

voltage phasor/vector 

high f requency

current phasor/vector (response)

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 43

the estimated angle can be used

f or f i el d or i entat i on as well as f or 

speed or  posi t i on control

of  synchronous machines

control structureof an encoder less control

with alternating high f requency

signal injection

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 44

Stator Admittance in Complex Plane

trajectory of  stator admittance(SMPMSM, carrier f requency f  c = 0.5 kHz)

a) theoretisch b) experimentell

north and south polecan be distinguished

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 45

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Tracking Control

tracking of  estimated rotor f lux angle by adjusting/controlling i cq to zero

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 51

Stator Admittance in Complex Plane

trajectory of  stator admittance(SMPMSM, carrier f requency f  c = 0.5 kHz)

a) theoretisch b) experimentell

north and south pol

ecan be distinguished

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 52

the concept of  encoder less control as presented hereworks similar to radio broadcasting :

the inf ormation of  rotor position

is modulated by a high f requency signal

the inf ormation is demodulated / extracted

f rom motor currents

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 53

� Synchronous Machines

Trager..

Position

Synchron–maschine

AM / FM Position

Demodulator

Trager..

PositionLaufer

Asynchron–maschine

?Position

Feld

..

PositionFeld

PositionLaufer..

Modulation of Carrier Signals by Electrcial Machines

� Induction Machinesworks f ine !!

f urther research to be done !!

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal University Page 54

Combination of 

Field Oriented Control

and Encoderless Detection

of Rotor Position

� the estimated angle can be used

for f ield orientation as well as

for speed and/or  position control 

of synchronous machines

� high frequency test signals are superposed to

the fundamental stator voltage(s)

� drive control structure remains as before

� no additional sensors required

� the scheme is parameter independant

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal UniversityPage 55

Drive with Speed Control

Sprungantwort der Drehzahlregelung

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Step Response of Encoderless Position Control

Sprungantwort der Lageregelung

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal UniversityPage 57

Results

� the tracking control scheme presented heresynchronizes on the saturation anisotropyof a synchronous machine.

� the tracking control schemeis not de pend i ng on any machi ne  parameter .

� the size of  additional software f or the tracking control is com parabl e to the software of a rotor model  f or the f ield oriented control of  an induction machine.

� the hi g h frequency c urrent si g nal can be measuredtog ether w i th the f undamental c urrent by the standard c urrent transd ucer s of a standard drive inverter.

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Prof. Dr. -Ing. Ralph M. Kennel Wuppertal UniversityPage 58

Practical Experience with an Industrial Servo Drive

� training of  a development engineer 2 x 1 week in our laboratory

Implementation of  a sensor less control

into a servo drive of  

� programming of  additional sof twarein manuf acturerµs f actory

� delivery of  prototypeaf ter ca. 3 months

� presentation on Hanover Fair in April 2006

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