U.S. patent application number 16/916780 was filed with the patent office on 2020-10-15 for electric linear motor.
This patent application is currently assigned to Kone Corporation. The applicant listed for this patent is Kone Corporation. Invention is credited to Tero HAKALA, Marko HINKKANEN, Reza HOSSEINZADEH, Tuukka KORHONEN, Pasi RAASSINA, Seppo SAARAKKALA, Maksim SOKOLOV, Seppo SUUR-ASKOLA.
Application Number | 20200325003 16/916780 |
Document ID | / |
Family ID | 1000004985793 |
Filed Date | 2020-10-15 |
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United States Patent
Application |
20200325003 |
Kind Code |
A1 |
KORHONEN; Tuukka ; et
al. |
October 15, 2020 |
ELECTRIC LINEAR MOTOR
Abstract
The invention refers to an electric linear motor comprising a
longitudinal stator beam; at least one mover adapted to move along
the stator beam; which stator beam comprises at least two side
faces located at opposite sides of the stator beam, each of the
side faces carrying ferromagnetic poles spaced apart by a pitch,
and which mover comprises at least two counter-faces facing the
respective side faces of the stator beam, wherein the at least two
side faces, as well as the at least two counter-faces facing the
respective side faces, are inclined or offset with respect to each
other.
Inventors: |
KORHONEN; Tuukka; (Helsinki,
FI) ; HAKALA; Tero; (Helsinki, FI) ; RAASSINA;
Pasi; (Helsinki, FI) ; SUUR-ASKOLA; Seppo;
(Helsinki, FI) ; HINKKANEN; Marko; (Helsinki,
FI) ; SAARAKKALA; Seppo; (Helsinki, FI) ;
SOKOLOV; Maksim; (Helsinki, FI) ; HOSSEINZADEH;
Reza; (Helsinki, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kone Corporation |
Helsinki |
|
FI |
|
|
Assignee: |
Kone Corporation
Helsinki
FI
|
Family ID: |
1000004985793 |
Appl. No.: |
16/916780 |
Filed: |
June 30, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/FI2018/050763 |
Oct 18, 2018 |
|
|
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16916780 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B66B 7/044 20130101;
H02K 41/033 20130101; H02K 7/09 20130101; H02K 2201/03 20130101;
H02P 6/006 20130101; B66B 11/0407 20130101 |
International
Class: |
B66B 11/04 20060101
B66B011/04; B66B 7/04 20060101 B66B007/04; H02K 41/03 20060101
H02K041/03; H02P 6/00 20060101 H02P006/00; H02K 7/09 20060101
H02K007/09 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2018 |
EP |
18164721.5 |
Apr 24, 2018 |
EP |
18168990.2 |
Claims
1. An electric linear motor, comprising a longitudinal stator beam;
at least one mover adapted to move along the stator beam; which
stator beam comprises at least two side faces located at opposite
sides of the stator beam, each of the side faces carrying
ferromagnetic poles spaced apart by a pitch, and which mover
comprises at least two counter-faces facing the respective side
faces of the stator beam, wherein the at least two side faces, as
well as the at least two counter-faces facing the respective side
faces, are inclined or offset with respect to each other.
2. The electric linear motor according to claim 1, wherein the
mover has in at least one of said counter-faces at least one rotor
unit having at least one winding and at least one permanent magnet,
which are arranged to co-act with the ferromagnetic poles of the
respective side face of the stator beam.
3. The electric linear motor according to claim 1, wherein the
mover has in each of said counter-faces at least one rotor unit
having at least one winding and at least one permanent magnet,
which are arranged to co-act with the ferromagnetic poles of the
respective side face of the stator beam.
4. The electric linear motor according to claim 1, wherein the
stator beam comprises at least four side faces located two by two
at opposite sides of the stator beam, such that the four side faces
substantially cover circumference of the stator beam, and wherein
the mover comprises at least four counter-faces facing the
respective side faces of the stator beam, and wherein the side
faces located at opposite sides of the stator beam, as well as the
counter-faces facing said side faces, are inclined or offset with
respect to each other.
5. The electric linear motor according to claim 4, wherein each of
the side faces carries ferromagnetic poles spaced apart by a pitch,
and wherein the mover has in each of said counter-faces at least
one rotor unit having at least one winding and at least one
permanent magnet, which are arranged to co-act with the
ferromagnetic poles of the respective side face of the stator
beam.
6. The electric linear motor according to claim 1, wherein the
ferromagnetic poles are teeth provided on a side face of a
ferromagnetic stator rod, which teeth which are spaced apart by
teeth gaps.
7. The electric linear motor according to claim 1, wherein the
side-faces carrying ferromagnetic poles of the stator beam do not
have any permanent magnets as well as no windings either.
8. The electric linear motor according to claim 1, wherein each of
said rotor units comprises permanent magnets as well as motor
winding, preferably three-phase motor winding.
9. The electric linear motor according to claim 1, wherein the
mover has in each of said counter-faces at least two rotor units
arranged consecutively in the travelling direction, each of said
rotor units having at least one winding and at least one permanent
magnet, which are arranged to co-act with the ferromagnetic poles
of the respective side face of the stator beam.
10. The electric linear motor according to claim 1, wherein each of
said rotor units contains at least two rotors having windings
connected in series or in parallel.
11. A control apparatus of an electric linear motor according to
claim 1, wherein the control apparatus comprises at least one drive
unit configured to supply electrical power to the respective at
least one rotor unit of the mover.
12. The control apparatus of claim 11, wherein the control
apparatus comprises drive units configured to supply electrical
power separately to the respective rotor units of the mover such
that each rotor unit is supplied by a separate drive unit.
13. A transport system comprising an electric linear motor and a
control apparatus according to claim 11, the transport system
further comprising: a mobile load-receiving part coupled to the
mover and arranged to travel along a trajectory defined by the
stator beam by means of the propulsion force of the mover.
14. A method of controlling the electric linear motor with a
control apparatus according to claim 11, the method comprising
obtaining position information of the mutual position of the
ferromagnetic poles and the at least one rotor unit facing said
ferromagnetic poles, the position information being obtained in the
travelling direction of the rotor unit representing d, q-coordinate
system of said at least one rotor unit by means of the position
information such that the d-axis of said rotor unit is in the
direction of the ferromagnetic poles facing the rotor unit and the
q-axis is orthogonal to the d-axis obtaining information of length
of air gap between the ferromagnetic poles and the at least one
rotor unit facing said ferromagnetic poles supplying, by means of
the at least one drive unit a d-axis current component to the at
least one winding of the at least one rotor unit to adjust the
length of air gap towards given reference value wherein the d-axis
current component is established based on the difference between
air gap reference value and obtained air gap length
information.
15. The method according to claim 14, comprising: obtaining
position information of mutual position of ferromagnetic poles
located at opposite sides of the stator beam and the rotor units
facing said ferromagnetic poles, the position information being
obtained in the travelling direction of the rotor unit representing
d, q-coordinate systems of said rotor units by means of the
position information such that the d-axis of each said rotor unit
is in the direction of the ferromagnetic poles facing the rotor
unit and the q-axis is orthogonal to the d-axis obtaining
information of length of air gap between the ferromagnetic poles
and the rotor units facing said ferromagnetic poles supplying, by
means of the drive units separate d-axis current components to the
windings of the rotor units at opposite sides of the stator beam to
adjust the length of air gaps towards given reference values,
wherein the separate d-axis current components are established
based on the difference between air gap reference value and
obtained air gap length information.
16. The method according to claim 14, wherein the mover has in at
least one of said counter-faces at least two rotor units arranged
consecutively in the travelling direction, each of said rotor units
having at least one winding and at least one permanent magnet,
which are arranged to co-act with the ferromagnetic poles of the
respective side face of the stator beam, and wherein the control
apparatus comprises drive units configured to supply electrical
power separately to the respective rotor units of the same
counter-face, the method comprising: supplying by means of the
drive units separate d-axis current components to the windings of
rotor units of the same counter-face to straighten tilt of the air
gap, the separate d-axis current components being established based
on difference between air gap reference value and air gap length
information.
17. The method according to claim 14, comprising: obtaining travel
position information and/or travel speed information of the mover
feeding with the at least one drive unit to the at least one
winding of the at least one rotor unit a q-axis current component
based on the difference between travel position reference and
obtained travel position information and/or travel speed reference
and obtained travel speed information to adjust the travel position
and/or speed towards said position and/or speed reference.
18. The method according to claim 17, comprising: feeding with the
drive units to the windings of rotor units separate q-axis current
components based on the difference between travel position
reference and obtained travel position information and/or travel
speed reference and obtained travel speed information to adjust the
travel position and/or speed towards said position and/or speed
reference.
19. The method according to claim 14, comprising: changing at least
one of d-axis current component and q-axis current component of a
rotor unit responsive to change of at least one of travel position
information, travel speed information and air gap length
information when changing the at least one of d-axis current
component and q-axis current component, providing at the same time
a correction term to the other of the d-axis current component and
the q-axis current component to compensate the effect of change to
the attraction force and/or propulsion force of the mover.
20. The method according to claim 14, comprising: calculating a
propulsion force reference value based on difference between travel
position reference and obtained travel position information and/or
between travel speed reference and obtained travel speed
information of the mover calculating an attraction force reference
value based at least on difference between air gap reference value
and air gap length information changing at least one of d-axis
current component and q-axis current component of a rotor unit
responsive to change in at least one of propulsion force reference
value, attraction force reference value and air gap length
information of the rotor unit.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of PCT International
Application No. PCT/FI2018/050763 which has an International filing
date of Oct. 18, 2018, and which claims priority to European patent
application number 18164721.5 filed Mar. 28, 2018, and 18168990.2
filed Apr. 24, 2018, the entire contents of each of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an electric linear motor
having a linear longitudinal stator with ferromagnetic poles. The
motor has a mover which comprises the rotor components of the
electric motor e.g. in case of the current invention windings and
permanent magnets. Thus, the mover travelling with a load-receiving
part to be moved along the linear stator form a linear motor. In
prior art linear motors, stator typically comprises motor windings
and/or permanent magnets. A disadvantage of these motors is caused
by the fact that the linear stator comprising windings and/or
permanent magnets are quite expensive, particularly if longer
trajectories, such as higher elevator shafts are considered with a
length of e.g. 50 m or more. Furthermore, the weight of such a
linear stator adds up considerably when used already for a mid-rise
elevator. Also the power electronics required in the shaft to drive
said linear motor may be complicated and expensive.
SUMMARY OF THE INVENTION
[0003] It is therefore object of the present invention to provide
an electric linear motor which is comparably cheap to manufacture
and which is well adapted also for long movement paths.
Accordingly, a solution for controlling the motor is also provided
to reduce friction between stator and mover(s) without additional
components. This means that also more effective (e.g. due to
reduced friction losses), simple and reliable linear motor and/or
linear motor control apparatus is provided.
[0004] This object is solved with an electric linear motor
according to claim 1, a control apparatus according to claim 11, a
transport system according to claim 13 and a method according to
claim 14. Preferred embodiments of the invention are subject-matter
of the dependent claims. Embodiments of the invention are also
shown in the description and in the drawings. The inventive content
may also consist of several separate inventions, especially if the
invention is considered in the light of explicit or implicit
subtasks or with respect to advantages achieved. In this case, some
of the attributes contained in the claims below may be superfluous
from the point of view of separate inventive concepts. The features
of different embodiments of the invention can be applied in
connection with other embodiments within the scope of the basic
inventive concept.
[0005] A first aspect of the invention is an electric linear motor,
comprising a longitudinal stator beam and at least one mover
adapted to move along the stator beam. The stator beam comprises at
least two side faces located at opposite sides of the stator beam,
each of the side faces carrying ferromagnetic spaced apart by a
pitch. The mover comprises at least two counter-faces facing the
respective side faces of the stator beam. The at least two side
faces, as well as the at least two counter-faces facing the
respective side faces, are inclined or offset with respect to each
other.
[0006] The inclined or offset side faces/counter-faces of the
electric linear motor makes it possible to control turning of the
mover around the longitudinal axis of the stator beam.
[0007] According to a preferred embodiment, the mover has in each
of said counter-faces at least one rotor unit having at least one
winding and at least one permanent magnet, which are arranged to
co-act with the ferromagnetic poles of the respective side face of
the stator beam.
[0008] According to a preferred embodiment, the stator beam
comprises at least four side faces located two by two at opposite
sides of the stator beam, such that the four side faces
substantially cover circumference of the stator beam. The mover
comprises at least four counter-faces facing the respective side
faces of the stator beam. The side faces located at opposite sides
of the stator beam, as well as the counter-faces facing said side
faces, are inclined or offset with respect to each other.
[0009] According to a preferred embodiment, the at least four side
faces and the respective counter faces form a parallelogram.
[0010] According to a preferred embodiment, each of the side faces
carries ferromagnetic poles spaced apart by a pitch, and the mover
has in each of said counter-faces at least one rotor unit having at
least one winding and at least one permanent magnet, which are
arranged to co-act with the ferromagnetic poles of the respective
side face of the stator beam.
[0011] According to an embodiment, the mover has in the other
counter face permanent magnets but with no windings. Counter face
with permanent magnets only is not considered as a "rotor unit" as
no propulsion force may be generated in the travelling direction of
the mover.
[0012] The term "rotor unit" means independently controllable rotor
entity. Thus the winding(s) of said rotor unit is/are configured to
be supplied, with a separate controllable drive unit like inverter
such that independent control of current of the winding(s) is
possible. The linear motor is configured according to the invention
to enable air gap control interlinked with movement control in the
travelling direction, with windings of the rotor units, such that
mover may be levitated around the stator beam while travelling
along the stator beam.
[0013] The feature "at least two side faces located at opposite
sides of the stator beam" can mean that surface normals of said at
least two side faces both have a vector component such that said
vector components are in opposite directions. Therefore, attraction
force components in opposite directions may be generated between
the at least two rotor units and the ferromagnetic poles of the
respective side faces of the stator beam, to enable air gap control
of the mover in relation to the stator beam.
[0014] According to the invention, the at least one rotor unit
comprises at least one winding and at least one permanent magnet.
Preferably, the at least one rotor unit comprises permanent magnets
and a three-phase winding. Additionally or alternatively, the at
least one rotor unit may comprise a one-phase winding. According to
an embodiment, each rotor unit comprises at least one permanent
magnet and at least one winding. In a preferred embodiment each
rotor unit comprises permanent magnets and motor winding, most
preferably three-phase motor winding. The side-faces carrying
ferromagnetic poles of the stator beam do not have any permanent
magnets as well as no windings either.
[0015] Therefore each of said rotor units may be controlled
independently as regards to controlling d-axis and q-axis current
components.
[0016] This kind of motor type may be a stator-mounted permanent
magnet (SM PM) motor wherein permanent magnet(s) and winding(s)
is/are mounted to the mover. One suitable motor type is a
flux-switching permanent magnet (FSPM) motor. Other suitable motor
types may be, for example, doubly salient permanent magnet (DSPM)
motor and flux reversal permanent magnet (FRPM) motor.
[0017] In an alternative embodiment motor may be a hybrid
excitation (HE) synchronous machine.
[0018] A second aspect of the invention is a control apparatus of
an electric linear motor according to the first aspect of the
invention. The control apparatus comprises at least one drive unit
configured to supply electrical power to the respective at least
one rotor unit of the mover.
[0019] According to a preferred embodiment, the control apparatus
comprises drive units configured to supply electrical power
separately to the respective rotor units of the mover such that
each rotor unit is supplied by a separate (at least one) drive
unit. This can mean that independently adjustable control currents
may be provided to the windings of the rotor units at opposite
sides of the stator beam, thus enabling air gap control of the
motor. According to an embodiment, the drive units may have a
common DC link to share regenerative power (e.g. braking power)
between the rotor units.
[0020] A third aspect of the invention is a transport system
comprising an electric linear motor according to the first aspect
of the invention and a control apparatus according to the second
aspect of the invention. The transport system further comprises a
mobile load-receiving part coupled to the mover and arranged to
travel along a trajectory defined by the stator beam by means of
the propulsion force of the mover.
[0021] The transport system may be an elevator system, in which
case the load-receiving part may be an elevator car, an elevator
car sling or corresponding. The load receiving part may be
configured to transfer passengers and/or cargo. The transport
system may alternatively be an escalator, in which case the
load-receiving part may an escalator step band or portion of the
step band. The transport system may alternatively be a moving walk,
in which case the load-receiving part may be the moving band or
portion of the moving band. The transport system may alternatively
be a belt conveyor, in which case the load receiving part may be
belt of the belt conveyor. The transport system may alternatively
be a vehicle or a train, in which case the load-receiving part may
be mobile body or consist.
[0022] A fourth aspect of the invention is a method of controlling
the electric linear motor according to the first aspect of the
invention with a control apparatus according to the second aspect
of the invention. The method comprises obtaining position
information (X.sub.act) of the mutual position of the ferromagnetic
poles and the at least one rotor unit facing said ferromagnetic
poles, the position information being obtained in the travelling
direction (x) of the rotor unit, representing d, q-coordinate
system of said at least one rotor unit by means of the position
information (X.sub.act) such that the d-axis of said rotor unit is
in the direction of the ferromagnetic poles facing the rotor unit
and the q-axis is orthogonal to the d-axis, obtaining information
of length of air gap (Y.sub.act) between the ferromagnetic poles
and the at least one rotor unit facing said ferromagnetic poles,
and supplying, by means of the at least one drive unit a d-axis
current component to the at least one winding of the at least one
rotor unit to adjust the length of air gap towards given reference
value (Y.sub.ref), wherein the d-axis current component is
established based on the difference between air gap reference value
(Y.sub.ref) and obtained air gap length information
(Y.sub.act).
[0023] In a preferred embodiment the at least one rotor unit has
winding and permanent magnets. The method comprises supplying, by
means of the at least one drive unit a d-axis current component to
the winding of the at least one rotor unit to adjust the length of
air gap towards given reference value (Y.sub.ref).
[0024] According to a preferred embodiment, the method comprises
obtaining position information of the mutual position of the
ferromagnetic poles and the rotor unit facing said ferromagnetic
poles, the position information being obtained in the travelling
direction of the rotor unit, representing d, q-coordinate systems
of said rotor units by means of the position information such that
the d-axis of each rotor unit is in the direction of the
ferromagnetic poles facing the rotor unit and the q-axis is
orthogonal (i.e. 90 degrees in the electrical angle of the motor)
to the d-axis, obtaining information of length of air gap between
the ferromagnetic poles and the rotor unit(s) facing the
ferromagnetic poles, and supplying, by means of the drive units
separate d-axis current components to the rotor units at the
opposite sides of the stator beam to adjust the length of the air
gaps towards given reference values, wherein the separate d-axis
current components are established based on the difference between
air gap reference value and obtained air gap length
information.
[0025] The phrase "obtaining position information of the mutual
position of the ferromagnetic poles and the rotor unit facing said
ferromagnetic poles" means that said position may be measured with
a suitable sensor or, alternatively or additionally, said position
may be estimated, for example, from currents and voltages of the
winding of a rotor unit, to get the position of the ferromagnetic
pole(s) relative to the winding.
[0026] The phrase "mutual position between the ferromagnetic poles
and the facing rotor unit(s) in the travelling direction of the
respective rotor unit(s)" means the mutual position as measured in
the intended travelling direction of the rotor unit, i.e. in the
longitudinal direction in which the counter-face of the rotor unit
travels along the side-face of the stator beam.
[0027] According to an embodiment, the mover has in at least one
counter-face at least two rotor units arranged consecutively in the
travelling direction, each of said rotor units having at least one
winding and at least one permanent magnet, which are arranged to
co-act with the ferromagnetic poles of the side face facing said
rotor units.
[0028] According to a refinement, the ferromagnetic poles as well
as the rotor units at the opposite sides of the stator beam are
arranged symmetrically at the same level in the transverse
direction of the stator beam such that the attractive force
components between the rotor units and stator beam exist at the
same level in the transverse direction of the stator beam.
[0029] According to an embodiment, stator beam comprises at least
four side faces located two by two at opposite sides of the stator
beam, such that the four side faces substantially cover
circumference of the stator beam, each of the side faces carrying
ferromagnetic poles spaced apart by a pitch. The mover comprises at
least four counter-faces facing the respective side faces of the
stator beam. The mover has in each of said counter-faces at least
one, preferably at least two rotor units having at least one
winding and at least one permanent magnet, which are arranged to
co-act with the ferromagnetic poles of the respective side face of
the stator beam. This can mean that an increased propulsion force
may be provided while levitating with the linear motor.
[0030] According to an embodiment, the ferromagnetic poles are
teeth provided on a side face of a ferromagnetic stator rod, which
teeth are spaced apart by teeth gaps. The side-faces carrying
ferromagnetic poles of the stator beam do not have any permanent
magnets as well as no windings either. Therefore the stator is
cheap and easy to manufacture, install and maintain.
[0031] According to an embodiment, the mover has in at least one,
preferably in each of said counter-faces at least two rotor units
arranged consecutively in the travelling direction, each of said
rotor units having at least one winding and at least one permanent
magnet, which are arranged to co-act with the ferromagnetic poles
of the respective side face of the stator beam. This can mean that
at least two separate force components may be provided at different
locations by means of the rotor units such that tilting of air gap
may be straightened to keep stator beam and mover separated when
simultaneously levitating and driving with the linear motor.
[0032] According to an embodiment, at least one of said rotor units
contains at least two rotors having windings connected in series or
in parallel. This can mean that, within an rotor unit more uniform
force distribution may be provided, both in direction of air gap
(attraction force for levitation control of the mover) and in the
travelling direction (propulsion force for speed control of the
mover). In a refinement, each of said rotor units contains at least
two rotors having windings connected in series or in parallel to
provide even more uniform force distribution.
[0033] According to an embodiment, the electric linear motor
comprises at least two movers adapted to move along the same stator
beam, and the transport system comprises at least two independently
movable load-receiving parts, each coupled to a different mover.
This can mean that several independently movable load receiving
parts may be moved along the same trajectory, such as several cars
of a multicar elevator system.
[0034] According to an embodiment, the transport system comprises
two parallel stator beams and at least two movers adapted to move
along different stator beams, and wherein each of the
load-receiving parts is coupled to said at least two movers.
Therefore propulsion force of the transport system may be increased
and load capacity of the load-receiving part may be increased as
well.
[0035] According to an embodiment, at least two movers of the same
stator beam are coupled to a same load-receiving part. This can
also mean that propulsion force/load capacity of load-receiving
part and thus the transport system may be increased. When combining
this embodiment with the previous one, propulsion force and/or load
capacity may be even further increased.
[0036] According to an embodiment, the mover has in each of said
counter-faces at least two rotor units arranged consecutively in
the travelling direction, each of said rotor units having at least
one winding and at least one permanent magnet, which are arranged
to co-act with the ferromagnetic poles of the respective side face
of the stator beam. The control apparatus comprises drive units
configured to supply electrical power separately to the respective
rotor units of the same counter-face. The method comprises:
supplying by means of the drive units separate d-axis current
components to the rotor units of the same counter-face to
straighten tilt of the air gap, the separate d-axis current
components being established based on difference between air gap
reference value and air gap length information. This can mean that
at least two separate attraction force components may be provided
at different locations on the same side of the stator beam by means
of the rotor units such that tilting of air gap may be straightened
to keep stator beam and mover separated when levitating and
simultaneously driving with the linear motor.
[0037] According to an embodiment, the method comprises: obtaining
travel position information and/or travel speed information of the
mover, and feeding with the drive unit(s) to the winding(s) of the
rotor unit(s) separate q-axis current components based on the
difference between travel position reference and obtained travel
position information and/or between travel speed reference and
obtained travel speed information to adjust the travel position
and/or speed towards said position and/or speed reference. The term
"travel position information of the mover" means position
information in the travel direction of the mover, in which
direction the mover travels along the stator beam. Consequently,
the term "travel speed information of the mover" means speed
information in the travel direction of the mover, in which
direction the mover travels along the stator beam. Contrary to
prior art control systems, wherein common q-axis current components
based on common current reference have been used to adjust
propulsion force/speed, by using separate q-axis current
components/current references for separate drive units according to
the embodiment it is possible to better adapt to different physical
conditions of separate drive units (for example different air gaps
lengths) to maintain more even propulsion force between different
drive units and thus more accurate and comfortable speed control of
the mover.
[0038] According to an embodiment, the method comprises calculating
the travel speed reference based on difference between travel
position reference and travel position of the mover.
[0039] According to a refinement, the method comprises: when
changing at least one of d-axis current component and q-axis
current component of an rotor unit responsive to change of at least
one of air gap length, travel position information and travel speed
information, providing at the same time a correction term to the
other of d-axis current component and q-axis current component to
compensate the effect of change to the attraction force and/or
propulsion force of the mover.
[0040] According to a refinement, the method comprises calculating
a propulsion force reference value based at least on difference
between travel position reference and obtained travel position
information and/or between travel speed reference and obtained
travel speed information of the mover, calculating an attraction
force reference value based at least on difference between air gap
reference value and air gap length information, and changing at
least one of d-axis current component and q-axis current component
of a rotor unit responsive to change in at least one of propulsion
force reference value, attraction force reference value and air gap
length information of the rotor unit.
[0041] The inventive motor, apparatus and control method has the
advantage of reduced losses due to optimized current consumption as
well as minimized friction due to levitation. Further advantage is
improved ride comfort due to reduction of propulsion force ripple.
Therefore the linear motor is well suitable e.g. for high
elevators, particularly for elevators with a height of more than 50
m, preferably of more than 100 m. This linear motor concept is
therefore adapted for any high-rise applications as this solution
does not need any elevator ropes or counterweight which are an
obstacle in the design of high-rise elevators because of the
correlated weight. Of course the linear motor can also be used for
other applications with long movement tracks as e.g. escalators,
moving sidewalks moving ramps, trains and inclined elevators.
[0042] Preferably, the mover also has a power source as for example
a battery or an accumulator, which is preferably also configured as
back-up power source for the mover. The power back up is preferably
designed for the electro-magnetic power elements of the motor
connected with the mover as e.g. windings or permanent magnets.
Thus, with this power source, all electric loads of the mover can
be fed. These loads are in case of an elevator car also the
lightings, ventilation, door drives and of any 10 devices of the
elevator car as for example car display panels, loudspeakers,
displays, etc. Furthermore, the power of a wireless data connection
with any kind of conveyor control can be supplied with the power
source. According to an embodiment, the battery/accumulator may be
connected to a common DC link of all the drive units associated
with the same load-receiving part (e.g. elevator car). The battery
may be coupled directly or via a power-interrupting switch to the
DC link, and/or there may be a voltage converter between battery
and DC link to enable voltage difference between battery/DC
link.
[0043] Preferably, the power supply from the shaft to mover is
implemented wirelessly with coupled coils principle, whereby a
primary coil being mounted to the environment or stator beam
whereas a secondary coil is moving with the car. When the mover
arrives at a certain position, primary and secondary are coupled
and power is fed from primary to secondary to a battery mounted to
the mover. The primary coil may be located in every stopping
floor.
[0044] The term "levitation" in connection with the invention means
that an air gap between side-face and respective counter-face is
maintained with current adjustment of the rotor unit(s). However,
within the scope of the invention it may also be possible to use
some additional guide elements to provide assisting guidance for
the mover relative to the stator beam. On the other hand, in many
embodiments the levitation may be implemented without any
additional guide elements.
[0045] Following expressions are used as a synonym:
element--element to be moved--elevator car; environment--elevator
shaft-escalator track; stator poles--stator teeth;
[0046] in an embodiment winding of a rotor unit may be in the form
of one coil only.
[0047] For the skilled person it is obvious that components
mentioned in connection with the present invention can be provided
one one-fold or multi-fold according to the needs. For example, one
stator beam can co-act with three movers located above each other
at the element to be moved. Furthermore, two stator beams may be
located at a wall of the environment or even more than two stator
beams as e.g. three or four stator beams.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] The invention is now described hereinafter with respect to
the enclosed drawing. In this drawing
[0049] FIG. 1 shows a side view of an electric linear motor
according to an embodiment
[0050] FIG. 2A shows a cross-section through a stator beam and a
mover of FIG. 1,
[0051] FIG. 2B shows a cross-section through a stator beam and a
mover of FIG. 1 of an alternative modification,
[0052] FIG. 2C shows a cross-section through a stator beam and a
mover according to an embodiment of the invention,
[0053] FIG. 2D shows a detail of a cross-section through a stator
beam and a mover according to an embodiment of the invention.
[0054] FIG. 3 shows a schematic drawing of the function of a
switching permanent magnet motor (FSPM) according to an
embodiment,
[0055] FIG. 4 illustrates schematically the control system
according to an embodiment
[0056] FIG. 5 shows a side view of a multi-car elevator system
according to an embodiment,
[0057] FIG. 6 shows a horizontal cross-section of the parts of the
elevator motor and the guide rails in the area between the elevator
car and the shaft wall of FIG. 5.
[0058] FIG. 7 shows a side view of an electric linear motor
according to an embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] It is emphasized that identical parts or parts with the same
functionality are designated by the same reference numbers in all
figures.
[0060] FIG. 1 shows a side view of an electric linear motor. To
facilitate understanding of the matter, only two opposite side
faces 6A, 6B and respective counterfaces 7A, 7B of the motor are
illustrated in FIG. 1. The linear motor comprises a longitudinal
stator beam 1 and a mover 24, 26, which surrounds the stator beam
1. The stator beam 1 has four side faces 6A, 6B, 6C, 6D as
illustrated in FIG. 2A and FIG. 2B. The side faces are located two
by two at opposite sides of the stator beam 1, such that the four
side faces 6A, 6B; 6C, 6D substantially cover circumference of the
stator beam 1. Each of the side faces carries ferromagnetic poles
8, i.e. ferromagnetic teeth, spaced apart by a pitch 8', e.g. a gap
or slot between the teeth 8.
[0061] The mover 24, 26 comprises four counter-faces 7A, 7B; 7C, 7D
facing the respective side faces 6A, 6B; 6C, 6D of the stator beam
1.
[0062] The mover has in each of said counter-faces 7A, 7B; 7C, 7D
rotor units 2,3,4,5; 2',3',4',5'. The motor may be a flux-switching
permanent magnet motor as depicted in FIG. 3. All the permanent
magnets and three-phase motor windings are in the rotor units 2, 3,
4, 5. 3. In the embodiment of FIG. 3, the ferromagnetic poles 8 are
teeth provided on a side face 6A, 6B; 6C, 6D of a ferromagnetic
stator rod 50, which stator rod 50 is embedded into respective
side-face of the stator beam.
[0063] The stator side of the motor is very simple, as the
side-faces 6A, 6B; 6C, 6D of the stator beam carrying ferromagnetic
poles 8 do not have any permanent magnets as well as no windings
either. This simplicity is cumulative when the stator beam 1
becomes long to extend moving range of the mover 24, 26. When mover
24, 26 travels along the stator beam 1, there is an air gap 15
between the side faces 6A, 6B, 6C, 6D and the counter-faces 7A, 7B,
7C, 7D. This air gap 15 is maintained in a noncontact manner with
levitation. The windings 74, 76 and permanent magnets 71 of the
rotor units are arranged to co-act with the ferromagnetic poles 8
of the respective side faces 6A, 6B; 6C, 6D of the stator beam 1 to
generate force components needed to levitate and drive the mover
24, 26 along the trajectory defined by the stator beam 1.
[0064] The expression "at least two side faces 6A, 6B, 6C, 6D
located at opposite sides of the stator beam 1" means that surface
normals of said at least two side faces (n.sub.1, n.sub.2, n.sub.3,
see FIG. 2C) both have a vector component such that said vector
components are in opposite directions. Therefore, when attraction
force is generated between said rotor units 2, 3, 4, 5 and the
respective side faces 6A, 6B; 6C, 6D, the generated attraction
forces have vector components in opposite directions relative to
each other to enable adjustment of air gap length parallel to
y-direction of FIG. 1 and therefore levitation of the mover.
[0065] Further, in some embodiments it may be necessary to control
turning of the mover 24, 26 around the longitudinal axis (parallel
to direction x of FIG. 1) of the stator beam. To enable this,
stator and mover may be designed such that rotating torque is
generated around the stator beam 1. Thus, as illustrated in FIG.
2D, at least some of the opposite side faces 6A, 6B may be inclined
with respect to each other, that is, angled from parallel direction
around the longitudinal axis of the stator beam. Of course the
respective counter faces 7A, 7B of the mover have to be inclined in
the same manner to face the side faces 6A, 6B.
[0066] As illustrated in FIG. 2C, at least some of the side faces
6A, 6B, 6C and the respective counter faces 7A, 7B, 7C may be
curved.
[0067] As illustrated in modification of FIG. 2B, at least some of
the opposite side faces (and the respective counter faces 7A, 7B,
7C, 7D) may be offset with respect to each other. The side faces
6A, 6B, 6C, 6D (and the respective counter faces 7A, 7B, 7C, 7D)
may form a parallelogram. Also this modification may enable
generation of rotating torque around the stator beam 1.
[0068] The mover frame 25 may be made of any suitable rigid,
preferably light-weight material, such as glassfiber composite,
carbon fibre composite or aluminium.
[0069] As FIG. 1 shows, the mover 24, 26 has in each counter-face
7A, 7B two rotor units 2, 3; 4, 5 arranged consecutively in the
travelling direction, which is parallel to direction x in FIG. 1.
Two consecutive, rotor units are needed to straighten tilt of air
gap 15. Each rotor unit is supplied with its own inverter 9, 10,
11, 12. In an alternative embodiment the mover 24, 26 has in each
counter-face 7A, 7B three rotor units arranged consecutively in the
travelling direction, and each rotor unit is supplied with its own
inverter. In some other embodiments there may be even more than
three rotor units per counter-face/inverters for supplying the
same. Still in another embodiment, as illustrated in FIG. 7, the
mover 24, 26 has in one counter-face 7A two rotor units 2, 3
arranged consecutively in the travelling direction, whereas the
other counter-face 7B at opposite side of the stator beam 1 has
only one, longer rotor unit 4. Each rotor unit 2, 3, 4 has an
inverter 9, 10, 11. Also this kind of solution may be adequate to
straighten tilt of air gap 15 with control of the rotor units.
Further, to achieve uniform force distribution, each rotor unit has
two (or even more than two) commonly controlled rotors 2A, 2B; 3A,
3B; 4A, 4B; 5A, 5B with windings. To achieve common control,
windings of the different rotors of same rotor unit are connected
in series or in parallel to be supplied with the same inverter 9,
10, 11, 12.
[0070] FIG. 4 depicts a control architecture used to control
levitation and travel of the linear motor of FIG. 1. The control
architecture shows control elements which are implemented in the
control software of the processing units of each inverter 9, 10,
11, 12.
[0071] According to FIG. 4, each inverter 9, 10, 11, 12 receives
position information X.sub.act of the mutual position of the
three-phase windings of the rotor unit controlled with
corresponding inverter, and the ferromagnetic poles
facing/co-acting with said three-phase windings. The mutual
position X.sub.act is measured in the travelling direction,
parallel to direction x in FIG. 1, by means of one or more position
sensors 16A, 16B, 16C, 16D, which may be hall sensors or inductive
proximity sensors, for example. Each inverter 9, 10, 11, 12
controls current supply of the rotor windings in a d, q-coordinate
system of its own. The d, q coordinate system is synchronized by
means of the position information X.sub.act to the position of
ferromagnetic poles of the stator beam facing the rotor windings.
The d-axis is referenced to the direction of the ferromagnetic
poles 8 such that it is in the direction of the center line of the
co-acting ferromagnetic pole. This direction may be the same as
center line of the stator teeth (see FIG. 3); on the other hand it
may also differ from that, e.g. due to saturation of the stator
teeth. d-axis direction may also be defined otherwise: for example,
to be in position wherein flux linkage of R-phase of the rotor unit
has its maximum.
[0072] Each inverter 9, 10, 11, 12 receives also information of
length of air gap (Y.sub.act) between side-face 6A, 6B carrying the
ferromagnetic poles 8 and the counterface 7A, 7B containing the
rotor unit 2, 3, 4, 5. Air gap length information (Y.sub.act) may
be received from sensors 16A, 16B, 16C, 16D or, additionally or
alternatively, from separate air gap sensors, such as eddy current
sensors, which may be disposed at same locations as sensors 16A,
16B, 16C, 16D or which may replace one or more of the sensors 16A,
16B, 16C, 16D. To measure air gap length as well as air gap tilt in
longitudinal direction of stator beam 1, at least two sensors are
needed for example at opposite ends at opposite sides of the mover,
for example at sensor positions 16A and 16D of FIG. 1.
[0073] Further, to measure turning of the mover 24, 26 around the
longitudinal axis of the stator beam, two parallel air gap sensors
16, 16' may be disposed in transverse direction of air gap 15, as
illustrated in FIG. 2D.
[0074] A reference value for the air gap Y.sub.ref is memorized in
the processing unit of the inverter 9, 10, 11, 12. Air gap
controller 40 calculates a difference between the air gap reference
value Y.sub.ref and the air gap length information Y.sub.act and
generates a reference value for the attraction force F.sub.yref,
e.g. the force component parallel to the y-direction of FIG. 1, to
adjust the length of air gap Y.sub.act towards the reference value
Y.sub.ref. Air gap controller 40 is a state controller which uses
observer 42 to obtain simulated position y and velocity y' (in the
y-axis direction of FIG. 1) of the mover 24, 26 mass under the
effect of the attraction force estimate F.sub.yref.
[0075] In a first embodiment air gap controllers 40 of inverters
controlling rotor units at both opposite sides of the stator beam
are used to adjust air gap length. In a second alternative
embodiment, on one side of the stator beam the reference value for
the attraction force F.sub.yref, is kept constant and air gap
controller is used only in connection with rotor units of the other
side of the stator beam to adjust attraction force reference value
F.sub.yref. This means the one or more rotor units of one side
provide a constant attraction force against which the air gap
controllers act at the other side of the stator beam. In a further
alternative, no inverter/motor windings are used to generate a
constant attraction force F.sub.yref, Instead, at one side of the
stator beam the rotor units of the counter face are replaced with
permanent magnets only, which permanent magnets generate an
attraction force towards the side face of the stator beam. On the
other side of the stator beam rotor units with windings are
controlled with air gap controllers of the inverters to act against
the attraction force of said permanent magnets. With this solution
no motor windings/inverters are needed for those counter faces with
permanent magnets only.
[0076] Further, at least one of the inverters 9, 10, 11, 12 of a
common mover receives travel position information x.sub.act and
travel speed information v.sub.act of the mover. In this connection
travel position information x.sub.act and travel speed information
refers to position/speed information of the mover in the direction
parallel to the x-axis direction of FIG. 1. In the current
embodiment the same position information x.sub.act is used to
define mutual position between rotor unit and respective
ferromagnetic poles to synchronize d, q-axis of the drive
unit/inverter to said ferromagnetic poles 8. This information is
also used to control position x.sub.act/speed v.sub.act of the
mover along the stator beam 1. In this embodiment the travel
position information x.sub.act is be received from the one or more
sensors 16A, 16B, 16C, 16D but alternatively a separate sensor may
be used. The travel speed information v.sub.ea may be received from
a separate speed sensor, such as an encoder or tachometer, or it
may be obtained from timely variation of the travel position
information x.sub.act (e.g. time derivative of the travel position
information) which is the case in this embodiment. One of the
inverters of a common mover acts as a master which performs
position/speed control in the travelling direction of the mover and
outputs a propulsion force reference value F.sub.xref (i.e.
reference force component parallel to the x-axis direction of FIG.
1) to the other inverters 9, 10, 11, 12. Other inverters of the
common mover then act as slaves, which do not perform
position/speed control but propulsion force control only. If two or
more movers are coupled to a common load-receiving means, such as
to a common elevator car, it is also possible that only one
inverter of only one mover acts as a master and all the other
inverters/movers act as slaves to avoid interference of
position/speed controllers.
[0077] Going back to FIG. 4, processing unit of the master inverter
9, 10, 11, 12 calculates travel position reference value x.sub.ref
to establish an intended motion profile for the controlled
mover(s). Position controller 44 calculates travel speed reference
value v.sub.ref from the difference between travel position
reference x.sub.ref and travel position of the mover x.sub.act in
the travelling direction x of the mover. Speed controller 45
calculates a propulsion force reference value F.sub.xref from the
difference between the travel speed reference v.sub.ref and the
travel speed information v.sub.act.
[0078] Propulsion force reference value F.sub.xref, attraction
force reference value F.sub.yref and air gap length information
Y.sub.act are inputted into magnetic model 43, which calculates
d-axis and q-axis current reference components I.sub.dref,
I.sub.qref for the rotor windings. In case of slave inverters, each
slave inverter calculates its own attraction force reference value
F.sub.yref by means of the air gap length information Y.sub.act,
but receives propulsion force reference value F.sub.xref from the
master inverter. With these reference values as well as the air gap
length information from air gap sensor 16A, 16B slave inverter
calculates the d-axis and q-axis current component reference values
with the magnetic model 43.
[0079] The magnetic model may consist of algorithms, which
represent how attraction force and propulsion force of the motor
depend on d-axis and q-axis currents as well as air gap length.
This representation may be based on the following motor
equations:
i d = ( a d0 - b dm y ) ( .psi. d - .psi. r ) + ( b d y + a dd
.psi. d S + .differential. dq V + 2 .psi. d U .psi. q V + 2 ) .psi.
d ( 1 ) i q = ( a qo + b q y + a qq .psi. q T + .differential. dq U
+ 2 .psi. d U + 2 .psi. q V ) .psi. q ( 2 ) F x = 3 .pi. r ( .psi.
d i q - .psi. d i d ) ( 3 ) F y = - 3 2 [ b d .psi. d 2 + b q .psi.
q 2 - b dm ( .psi. d - .psi. r ) 2 ] - f .sigma. ( 1 + c .sigma. y
) 2 ( 4 ) ##EQU00001##
wherein i.sub.d and i.sub.q represent current components in d, q
coordinate system, a.sub.d0, a.sub.dd, a.sub.dq, a.sub.q0,
a.sub.qq, a.sub.dq, b.sub.dm, b.sub.d, b.sub.q, c.sub..sigma.,
f.sub..sigma., .psi..sub.r, S, T, U, V are motor-specific
constants. They are derived based on reluctances, which depend on
motor geometry. .psi..sub.d and .psi..sub.q are d and q-axis
components of the motor flux linkage, .tau. is pole pitch of the
motor (2.pi.), y is air gap length between rotor and stator, and
F.sub.x is propulsion force reference value and F.sub.y is
attraction force reference value.
[0080] in view of the above equations, F.sub.x may be represented
to be dependent only on magnetic flux linkage and air gap length
y:
F.sub.x(.psi..sub.d,.psi..sub.q,y)
also F.sub.y may be represented to be dependent only on magnetic
flux linkage and air gap length y:
F.sub.y(.psi..sub.d,.psi..sub.q,y)
[0081] Thus magnetic flux linkage components .psi..sub.d and
.psi..sub.q may be solved by means of the representations (3) and
(4) when the (reference) values of propulsion force F.sub.xref and
attraction force F.sub.yref are received from the speed controller
45 and the air gap controller 40. Reference current values
I.sub.dref, I.sub.qref may then be calculated with the equations
(1) and (2) by means of the magnetic flux linkage components
.psi..sub.d and .psi..sub.q.
[0082] Alternatively or additionally, the magnetic model 43 may
comprise a table, having d-axis and q-axis current components
memorized and indexed by means of propulsion force reference values
F.sub.xref, attraction force reference values F.sub.yref, and air
gap length information Y.sub.act. To get more accurate values for
the d, q-axis current reference components, it is possible to use
interpolation between the memorized values of the table. Table
values may also be determined with simulation, for example by using
Finite Element Method (FEM).
[0083] In the magnetic model 43 at least one of d-axis current
reference component I.sub.dref and q-axis current reference
component I.sub.qref of the motor windings is changed when a change
in at least one of the propulsion force reference value F.sub.xref,
attraction force reference value F.sub.yref and air gap length
information Y.sub.act of the rotor unit 2, 3, 4, 5 takes place.
Therefore magnetic model 43 may speed up adaptation of the rotor
units and thus the mover to variable operation conditions, making
operation of the mover 24, 26 more stable and responsive.
[0084] d-axis and q-axis current component reference values
I.sub.dref, I.sub.qref are communicated to current controller 41,
which calculates d-axis and q-axis voltage references U.sub.d,
U.sub.q for the windings of the rotor unit based on the difference
between d- and q-axis current reference values I.sub.dref,
I.sub.qref and measured d-axis and q-axis current components
I.sub.d, I.sub.q. Transformation from d, q coordination system to
three phase voltage components U.sub.R, U.sub.S, U.sub.T, as well
as transformation from three-phase current measurements i.sub.R,
i.sub.S, i.sub.T to d, q-axis component values I.sub.d, I.sub.q
takes place with Park and Clarke transformations, which
transformations as such are known in the art. For the
synchronization of the d, q coordinate system travel position
information X.sub.act is used as disclosed above.
[0085] The three-phase voltage components of the rotor unit
U.sub.R, U.sub.S, U.sub.T are communicated to state vector PWM
modulator 46 (pulse width modulator) of the inverter, which creates
the control pulses for controlling the solid state switches of the
inverter power stage to introduce modulated three-phase voltage
components to the windings of the rotor unit. These solid state
switches may be, for example, igbt-transistors, mosfet-transistors,
silicon carbide transistors and/or gallium nitride transistors.
[0086] In an alternative embodiment, an adequate performance level
may be achieved with a simplified control architecture, wherein the
speed controller 45 of the master inverter outputs directly q-axis
current reference components I.sub.qref to the slave inverters.
Each slave inverter generates d-axis current reference component
I.sub.dref of its own, by means of the air gap controller 40. These
d, q-current reference components I.sub.dref, I.sub.qref are then
directly communicated to current controller 41, thus avoiding use
of magnetic model 43, i.e. bypassing it. This may reduce processing
power needed for levitation/speed control of the mover 24, 26.
[0087] Instead of one inverter 9, 10, 11, 12 acting as a master, it
is possible to use a separate master control unit which may perform
function of at least one of air gap controller 40, position
controller 44 and speed controller 45 for one or more of the
inverters 9, 10, 11, 12 and output the required reference values to
the inverters 9, 10, 11, 12 to control current supply to the rotor
units.
[0088] FIG. 5 shows a multicar elevator system according to an
embodiment of the third aspect of the invention. Elevator system
comprises plurality of elevator cars 16 each coupled to parallel
stator beams 1, 1' (see FIG. 6) by means of the movers 24, 26. The
cars are in a circular motion within two parallel elevator shafts
17. To each car four movers 24, 26 are installed, 2 per stator beam
1, 1''. The linear motors are similar to those disclosed in the
embodiments above, thus there are 32 rotor units per car and 32
inverters per car. All the inverters of the same car 16 are
connected to common DC link, such that regenerative energy
returning from one inverter back to DC link may be shared
with/supplied to the other inverters. Each car 16 has a battery,
which is connected to the common DC link.
[0089] The invention can be carried out within the scope of the
appended patent claims. Thus, the above-mentioned embodiments
should not be understood as delimiting the invention.
* * * * *