electromagnetic propulsion, suspension and levitation new ......electromagnetic propulsion,...

• )

Electromagnetic Propulsion, Suspension and Levitation –

New Concepts of Bearingless Systems for High-Precision

Industry

Prof.dr. Elena Lomonova

Swiss Chapter of IEEE Power Electronics Society – 21.02.2020, ETH

2Swiss Chapter of IEEE Power Electronics Society

Research areas • High-tech systems

– Linear and planar motors, magnetic

levitation

– Ultra-high precision power amplifiers

– Field modeling, materials, parasitic effects

– Wireless energy transfer

• Health– Power amplifiers for MRI and X-ray

– Medical robotics

– High-speed motors

• Sustainable energy– Smart grids

– Energy management, chargers, storage

– In-wheel motors and active suspension


Planar motors• Planar motor is an xy-positioning device

• Mover could be magnetically levitated

• First concept: Sawyer motor (1968)

– Stepper motor with air bearings

• Permanent magnet planar motors

– Semiconductor equipment

– Integrated magnetic bearings

(waferscanners)

– Air bearings (wafer dicing)

http://www.google.nl/url?sa=i&source=images&cd=&cad=rja&docid=713HxNJxXpyldM&tbnid=U0ECAvG_55NGbM:&ved=0CAgQjRwwAA&url=http://www.asml.com/asml/show.do?lang=EN&ctx=46772&dfp_product_id=822&ei=HIMsUu1JxazRBebRgJAP&psig=AFQjCNGWSkvo8GKS66ScNRVNwHxtmkb5aQ&ust=1378735260050886



Planar motors• Planar motor is an xy-positioning device

• Mover could be magnetically levitated

• First concept: Sawyer motor (1968)

– Stepper motor with air bearings

• Permanent magnet planar motors

– Semiconductor equipment

– Integrated magnetic bearings

(waferscanners)

– Air bearings (wafer dicing)




Application of planar stages



light source



lens

light source



reticle

lens

light source



reticle

lens

light source

lens



reticle

wafer

lens

light source

lens


Application of planar stagesSemiconductor lithography

planar

motor



• Process in the production of integrated

circuits (micro-processors)

wafer

short

stroke

long

stroke

planar

motor

integrated

circuit



lens

mask

light

source



• Accurate and fast positioning of the

wafer is crucial

Acceleration > 50 m/s2 (5 g)

Positioning accuracy < 1 nm



lens

mask

light

source



• Accurate and fast positioning of the

wafer is crucial

Acceleration > 50 m/s2 (5 g)

Positioning accuracy < 1 nm

• Typically dual-stage topology for 6-

DoF positioning of the wafer


Levitated and suspended planar stages

Contents

• Application

• Working principle

• Commutation

• Over-actuation

– Power minimization

– Heat distribution

– Force distribution


Moving coils –planar motor

courtesy of Philips


Moving-magnet planar motor

courtesy of TU/E


Magnetically levitated planar motor

• Production of force in x,y,z-directions

• Flux linkage variation in x,y,z-directions

A+ A- B+ B- C+ C-x

z





• Instead of double sided actuator

A+ A- B+ B- C+ C-x

z





• Single sided actuator

A+ A- B+ B- C+ C-x

z


Single-sided coreless motor (periodical section)

• Magnetic

flux φ

• Magnetic flux

density B

A+ A- B+ B- C+ C-

x

z


Single-sided coreless actuator

Levitation and propulsion force

can be decoupled

sin

4sin

3

8sin

3

a pm

b pm

c pm

z

z

z

x

x

ex

e

e

0

0

0

sin

4sin

3

8sin

3

a

b

c

xI I

xI I

xI I

0

, ,

0

, ,

3sin

2

3cos

2

z

nx n pm

n a b c

z

nz n pm

n a b c

F i Iex

F i Iez

A+ A- B+ B- C+ C-

x

z


Moving coil vs moving magnet


Moving-magnet vs moving-coil planar motor

• Magnet array is finite, increases modeling complexity

• Force is acting on coil volumes, torque arm is larger and

position dependent for moving-magnet planar motors

• Modeling and control is more complex in moving-magnet

case, however, the levitated structure is less complex

xz

xz


Halbach magnet array• Halbach magnet array

– Increased flux density near coils

– Intrinsic shielding of own fields

– Back-iron is unnecessary (magnetically no function)


Linear magnet array

Coil shape

• Rectangular


Planar Magnet array


Planar Magnet array

Coil shape

• Round


Planar Magnet array

Coil shape

• Rectangular

(45 degrees)


Round coils

• Flux density alternating in x,y,z

directions

• Round coils can be applied

which are limited in size

τ

x

y


Round coils


directions



τ

x

y


Rectangular coils

• Long coils can be applied

• Forces in x and y directions

can be physically decoupled

x

y

τn

Fx=0

Fy=0

τn


Rectangular coils

• Long coils can be applied

• Forces in x and y directions

can be physically decoupled

x

y

τn

Coil length: 2nτn

τn


Decoupling/Commutation• Each coils produces a Lorentz force and torque due to

each magnet in the magnet array

22 2 sin 2 sin

40

4

4 cos

z z

n n

z

n

p p

y cx c

x z x z c y xy

n n

xy

y y z x c x z x

z

p

x c

z xy z x y c

n

p yp xF B i e T F y p B i e

BF T F p x F p F

B

p xF B i e T F p y


Decoupling/Commutation• Each coils produces a Lorentz force and torque due to each magnet

in the magnet array

• The interaction (forces and torque components) can be described on

the level of the

– Magnet array (rigid body approach)

– Individual magnets (force and torque distribution)

1, 2, ,

1, 2, ,

1, 2, ,

1, 2, ,

1, 2, ,

1, 2, ,

( ) ( ) ( )

( ) ( ) ( )

( ) ( ) ( )

( ) ( ) ( )

( ) ( ) ( )

( ) ( ) ( )

x x x n x

y y y n y

z z n zz

x x n xx

y y n yy

z z n zz

F F p F p F p

F F p F p F p

F p F p F pFw

T p T p T pT

T p T p T pT

T p T p T pT

1

2

..( )

..

..

n

i

i

p i

i

Γ


Decoupling/Commutation

• Commutation algorithm contains real-time model of all

interactions in the planar motor

• Model implemented in look-up tables

• Inverse is based on minimization of losses

• Outer-loop provides stability

Planar motor

Power amplifiers

Feedback/ Feedforward

controller

Commutation x

1( )i p w Γ

1

-

22, ( )min

pp i wP i R p w R

ΔΓΓ


Multi-physical model

Electromagnetic model

force and torque

Commutation

current




force and torque

Commutation

current

Mechanical model

shape




force and torque

Commutation

current

Mechanical model

shape

Thermal model

temperature

Over-actuation


Mechanical model1 3

2 4


Thermal model

Vertical Heat flux

OFF ON OFF

RzRzRz

Ry Ry

Ry Ry

RzRzRz

y

z

coil

cooling block

epoxy

Lateral Heat flux


Multi-physical framework

Electromagnetic modelforce and torque

Mechanical modelshape

Thermal modeltemperature

Commutationcurrent


Multi-physical framework


Electromagnetic model• Electromagnetic interactions between coils and magnets

x

z

y



• Commutation defines currents from electromagnetic model

x

z

y


Electromagnetic model• Force and torque distribution on the magnet plate is

obtained from electromagnetic model

• Force and torque distribution, and currents are highly

position dependent

x

z

y


Mechanical model• Mechanical model coupled to electromagnetic model to

predict deformation

• Over-actuation allows reducing deformation

x

z

y


Thermal model• Temperature distribution is calculated from current

distribution

• Over-actuation allows reducing maximum temperature,

increasing maximum acceleration

x

z

y



• Commutation defines currents from electromagnetic model

x

z

y


Electromagnetic model• Force and torque distribution on the magnet plate is

obtained from electromagnetic model

• Force and torque distribution, and currents are highly

position dependent

x

z

y



predict deformation


x

z

y



distribution



x

z

y


TopologiesSeveral moving-magnet planar motor topologies have been

manufactured and studied

HPPA (TU/e) EPM (Philips) COPAM (TU/e)


Comparison

Acceleration

Accuracy

Deformation

Goal: Combine advantages in a new design

x

x

x

x

topology

criterion


Double layer design

• Two layers of coils

• Height of the coils

optimized such that

dissipation per unit of

force is equal

• Phase shift in each layer

to reduce force ripples

Patent application filed


Power dissipation

Lowest mean

Dissipated power during full acceleration (50 m/s2):

Min [kW] Max [kW] Mean [kW]

HPPA 2.26 3.34 2.86

COPAM 3.22 4.44 3.80

EPM 3.33 4.12 3.65

DLPM 2.44 3.30 2.85


Trajectory - Temperature

Lowest temperature rise

Power dissipation [kW] Maximum temperature [oC]

HPPA 0.97 48

COPAM 1.4 57

EPM 1.2 59

DLPM 1.1 47


What limits the performance of a

single-stage planar motor?

cooling plates




Eddy currents

• Induced in electrically conducting

materials

• Create a parasitic force




Eddy currents

• Induced in electrically conducting

materials


Flexible behavior of the mover

• Excited by the force acting on the

permanent magnets

• Cause spatial deformation of the

mechanical structure


What limits the performance of a single-stage planar motor?

Eddy currents

• Induced in electrically

conducting materials


Flexible behavior of the mover

• Excited by the force acting on

the permanent magnets

• Cause spatial deformation of

the mechanical structure

cooling plates


Magnetically suspended, iron-core, planar motors

• Planar motor suspended from ceiling

• Moving-coils, stationary magnets

• Based on the same principles as a coreless levitated

planar motor

• Levitation without power consumption

Ceiling

Mover


Structure

• 4 iron-core linear motors

• 45 degrees rotated wrt

magnets

• Propulsion in x, and y

• Passive attraction force

Bottom view Side view


Principles

• Controlled as three-phase motor

• Small force ripples

• Only considerable torque Ty

Laminated iron yoke

Permanent magnets

Coils

Nonferromagnetic plate

Fx

FzZero current


Principles




Laminated iron yoke

Permanent magnets

Coils


Fx

Fzd-axis current


Principles




Laminated iron yoke

Permanent magnets

Coils


Fx

Fzq-axis current


Magnetic loading

• Fz,r is proportional to magnetic flux density B

• Motor constant k is proportional to B

• Magnet with low remanence, limited acceleration

k >

Magnetic suspension Acceleration Torque compensation


Contactless power supply

• Power supply through resonant inductive coupling with

low position variation

• Plastic bonded magnets required (with low remanence Br)

to reduce eddy current losses

Switched

primary coil array

(yellow coils active)

Secondary coil


Realization• planar stroke: 200x200 mm2

• nominal acceleration: 5 ms-2

• power transfer: 335 W

• variation power transfer: 15%

• Mover size: 37x37 cm2

• moving mass: 9 kg


Conclusions• Planar stages could be levitated or suspended

• 45 degrees rotated coil cannot only be used in coreless,

but also iron-core planar motors

• Balance between acceleration, suspension force and

mass in multi-physical design

• Integration of energy transfer system in the airgap

requires magnets with a low electric conductivity (and

hence, with a low magnetic loading)

• Superconducting motors are the next generation of planar

stages


Thank you for your attention

Acknowledgements:

dr. J. Jansen, dr. T. Overboom, dr. J. Smeets,

dr. J. de Boeij, dr. H. Rovers, dr. C. Custers

• )

Electromagnetic Propulsion, Suspension and Levitation –

New Concepts of Bearingless Systems for High-Precision

Industry

Prof.dr. Elena Lomonova

Swiss Chapter of IEEE Power Electronics Society – 21.02.2020, ETH

electromagnetic propulsion, suspension and levitation new ......electromagnetic propulsion,...

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