Patent Publication Number: US-11025186-B2

Title: Electric linear motor, elevator and method for controlling rotation of a mover with respect to a stator beam of an electric linear motor

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to electric linear motors. In particular, however not exclusively, the present invention concerns controlling of the operation of electric linear motors. 
     BACKGROUND 
     Electric linear motors can be utilized in a variety of applications, such as in elevators to move the elevator car in the elevator shaft. Some typical electric linear motors are such that they have a long linear stator beam equipped with controllable electromagnetic components such as coils for generating magnetic field. The rotor, or “mover”, typically comprises permanent magnets, magnetic fields of which, when being in electromagnetic engagement with the “traveling” magnetic field of the stator, causes the rotor to move along the linear stator. 
     However, some electric linear motors can be operated by feeding current to the windings in the mover in order to control the movement of the mover along the stator beam. In such motors, there may not be windings in the stator beam at all. In addition to the control of the movement along the stator beam, the current fed into the windings can be controlled such as to generate an air gap between the stator and the mover, that is, to magnetically levitate the mover with respect to the stator beam. 
     However, in the known solutions, there are challenges with controlling of the levitation in that the mover tends to rotate with respect to the stator beam, that is around the stator beam, thus in many cases causing mechanical contact between the mover and the stator beam. Therefore, there is still a need to develop electric linear motors utilizing magnetic levitation to generate the air gap of the motor. 
     SUMMARY 
     An objective of the present invention is to provide an electric linear motor, an elevator, and a method for controlling rotation of a mover with respect to a stator beam of an electric linear motor. Another objective of the present invention is that the electric linear motor, the elevator, and the method facilitate the controlling of the rotation of the mover with respect to the stator beam. 
     The objectives of the invention are reached by an electric linear motor, an elevator and a method as defined by the respective independent claims. 
     According to a first aspect, an electric linear motor is provided. The electric linear motor comprises at least one stator beam, wherein the at least one, preferably each one, stator beam comprises a plurality of stators, such as two or four, extending in a longitudinal direction of the stator beam. The electric linear motor further comprises at least one mover, wherein the at least one, preferably each one, mover comprises a plurality of armatures, such as comprising windings or three-phase windings into which current(s) may be injected. Furthermore, each one of the plurality of armatures is adapted for establishing an electromagnetic coupling or engagement with a corresponding one of the stators for moving the mover along said stator. At least one of the plurality of armatures is arranged to be offset from the aligned position with respect to the corresponding one of the stators in a perpendicular direction relative to the longitudinal direction. Said perpendicular direction may, preferably, be also in parallel with respect to a width of the corresponding stator, thus meaning that said armature and/or stator facing said armature is moved sideways from the aligned position. 
     The stator(s) may have a longitudinal direction, such as parallel relative to the longitudinal direction of the stator beam(s), a direction of the width of the stator, and a direction of the thickness of the stator, therefore, defining substantially three dimensions of the stator(s). 
     The aligned position refers herein to an arrangement in which the at least one of the plurality of armatures would be arranged to directly face, that is aligned with, the corresponding stator. 
     In an embodiment, the armature may comprise a winding. 
     In an embodiment, additionally or alternatively, the armature may comprise a permanent magnet. In a preferred embodiment, the armature may comprise a magnetic core, a winding and a permanent magnet. 
     The term “along said stator” refers herein to movement of the mover relative to said stator while having an air gap of the electric linear motor therebetween, that is, being near to and, preferably, in electromagnetic coupling or engagement with each other. Thus, there may, preferably, not be a mechanical contact between the mover and said stator at least during the movement. In some embodiments of the present invention, there may, however, be other components or elements, such as surfaces, of the mover and the stator beam, or components between the mover and the stator beam, which may be in mechanical contact with one another, such as guiding elements, even during the movement. 
     In preferable embodiments, the at least one of the plurality of armatures may be arranged offset from the aligned position, for example asymmetrically with respect to the corresponding stator, such that a torque component or components for rotating the mover in a first direction with respect to the stator beam, that is around a rotating axis oriented in the direction of the stator beam, is/are being generated when current(s) is/are injected to winding(s) therein. The torque component(s), therefore, allow the rotation of the mover to be controlled by controlling said current(s). 
     In various embodiments, at least one additional armature, preferably also comprising a winding, of the plurality of armatures may be arranged offset from the aligned position with respect to its corresponding one of the stators for generating a torque component for rotating the mover in a second direction with respect to the stator beam. The second direction may, preferable, be opposite with respect to the first direction. 
     In various embodiments, two of the plurality of armatures may be arranged at opposite sides of the stator beam. In some embodiments, said two of the plurality of armatures may be arranged offset with respect to the corresponding stators for generating torque components for rotating the mover with respect to the stator beam in same direction. 
     In various embodiments, the plurality of stators may comprise at least four stators and the plurality of armatures at least four armatures. In some embodiments, there may be four stators arranged on four sides of the stator beam. In such embodiments, the stator beam may have a cross-sectional shape of a polygon, a quadrangle, a square, or a parallelogram, for instance, thus, defining four sides of which specific two sides are opposite with respect to each other and specific other two sides are opposite with respect to each other. 
     In some embodiments, the stator beam may have a rounding shape in corners of the stator beam, such as, a substantially tubular shape. 
     Furthermore, the plurality of stators and the plurality of armatures may, preferably, be arranged with respect to each other for enabling a control of an air gap, that is a length of the air gap at at least one or several different positions, between the stator beam and the mover, for example, preferably, by magnetic levitation. 
     In various embodiments, two consecutive armatures of the plurality of armatures may be arranged offset to opposite directions with respect to their corresponding stator. 
     In various embodiments, the electric linear motor may comprise air gap regulation means for regulating movement of the mover in at least one of the following: a first direction with respect to the stator beam, a second direction with respect to the stator beam. 
     In addition or alternatively, the electric linear motor may comprise air gap regulation means that comprise a number of guide elements arranged for limiting rotation of the mover with respect to the stator beam at least in one direction while, preferably, allowing movement in a direction of the air gap, such as, a portion of the mover moving in a direction of a length of the air gap at the position of said portion. Thus, the mover may be allowed to move such that the length of the air gap changes. According to various embodiments, the number of guide elements may comprise at least one of the following: a guide surface, such as a low friction surface, a roller, a permanent magnet, an electromagnet. 
     According to a second aspect, an elevator is provided. The elevator comprises an electric linear motor comprising at least one stator beam, wherein the at least one, preferably each one, stator beam comprises a plurality of stators, such as two or four, extending in a longitudinal direction of the stator beam. The electric linear motor further comprises at least one mover, wherein at least one, preferably each one, mover comprises a plurality of armatures, such as comprising windings or three-phase windings. Furthermore, each one of the plurality of armatures is adapted for establishing an electromagnetic coupling or engagement with a corresponding one of the stators for moving the mover along said stator. At least one of the plurality of armatures is arranged to be offset from an aligned position with respect to the corresponding one of the stators in a perpendicular direction relative to the longitudinal direction. The elevator further comprises a number of elevator cars, and an elevator shaft, wherein the at least one stator beam is arranged to extend along the elevator shaft. Furthermore, the at least one mover is coupled to each one of the number of elevator cars, respectively, for moving the elevator car in the elevator shaft. 
     The electric linear motor of the elevator according to the second aspect may be in accordance with any embodiment of the electric linear motor according to the first aspect. 
     In various embodiments of the elevator, the electric linear motor may comprise a plurality of stator beams and a plurality of movers. In some embodiments, at least two, preferably four, of the movers may be coupled to same elevator car, that is, one elevator car may be coupled to more than one of the movers. 
     Alternatively or in addition, at least two of the movers may be arranged to be moved along different stator beams. 
     In various embodiments, the elevator may comprise a plurality of elevator cars, wherein each elevator car may have at least one of the movers being coupled to said elevator car for moving said elevator car in the elevator shaft. 
     According to a third aspect, a method for controlling rotation of a mover with respect to a stator beam of an electric linear motor is provided. The electric linear motor comprises a number of stator beams, wherein at least one of the number of stator beams comprises a plurality of stators extending in a longitudinal direction of the stator beam. The electric linear motor further comprises a number of movers, wherein at least one of the number of movers comprises a plurality of armatures. Each one of the plurality of armatures is adapted for establishing an electromagnetic coupling with a corresponding one of the stators for moving the mover along said stator. Furthermore, at least one of the plurality of armatures is arranged to be offset from an aligned position with respect to the corresponding one of the stators in a perpendicular direction relative to the longitudinal direction, such as also in parallel with respect to a width of the corresponding stator. The armature comprises a winding. The method comprises
         controlling currents of the at least one of the plurality of armatures, such as of the winding(s) thereof, by current controlling means for controlling the rotation of the mover with respect to the stator beam.       

     In some embodiments, the electric linear motor may comprise the at least one of the plurality of armatures arranged offset from the aligned position with respect to its corresponding one of the stators for generating a torque component for rotating the mover in a first direction with respect to the stator beam, and at least one additional armature, preferably comprising a winding, of the plurality of armatures is arranged offset with respect to its corresponding one of the stators for generating a torque component for rotating the mover in a second direction with respect to the stator beam. In such embodiments, the method may comprise controlling currents of windings of said one and said at least one additional armature by the current controlling means for controlling the rotation of the mover in the first and second directions. 
     In various embodiments, the electric linear motor may comprise two of the plurality of armatures arranged at opposite sides of the stator beam and offset from aligned positions for generating torque components for rotating the mover in same direction with respect to the stator beam. In such embodiments, the method may comprise
         controlling currents of windings of said two of the plurality of armatures by the current controlling means for controlling the rotation of the mover in the first or in the second direction.       

     Alternatively or in addition, the method may comprise controlling a direct component of the currents of windings for controlling the rotation of the mover, that is, the direct (d) axis component of the currents. 
     The present invention provides an electric linear motor, an elevator, and a method for controlling rotation of a mover with respect to a stator beam of an electric linear motor. The present invention provides advantages over known solutions such that by utilizing the electric linear motor according to an embodiment of the present invention it is possible to generate a rotational force or a torque component which can be controlled by controlling the current of the mover windings. 
     Various other advantages will become clear to a skilled person based on the following detailed description. 
     The expression “a number of” refers herein to any positive integer starting from one (1), that is, being at least one. 
     The expression “a plurality of” refers herein to any positive integer starting from two (2), that is, being at least two. 
     The terms “first”, “second” and “third” are herein used to distinguish one element from other element, and not to specially prioritize or order them, if not otherwise explicitly stated. 
     The exemplary embodiments of the present invention presented herein are not to be interpreted to pose limitations to the applicability of the appended claims. The verb “to comprise” is used herein as an open limitation that does not exclude the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. 
     The novel features which are considered as characteristic of the present invention are set forth in particular in the appended claims. The present invention itself, however, both as to its construction and its method of operation, together with additional objectives and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       Some embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. 
         FIG. 1  illustrates schematically an elevator according to an embodiment of the present invention. 
         FIG. 2  illustrates schematically an elevator according to an embodiment of the present invention. 
         FIG. 3  illustrates schematically an elevator according to an embodiment of the present invention. 
         FIGS. 4A and 4B  illustrate schematically electric linear motors according to some embodiments of the present invention. 
         FIG. 5  illustrate schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 6  illustrate schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 7  illustrate schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 8  illustrates schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 9  illustrates schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 10  illustrates schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 11  illustrates a flow diagram of a method according to an embodiment of the present invention. 
         FIG. 12  illustrates schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 13  illustrates schematically an electric linear motor according to an embodiment of the present invention. 
         FIG. 14  illustrates schematically an electric linear motor according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SOME EMBODIMENTS 
       FIG. 1  illustrates schematically an elevator  100  according to an embodiment of the present invention. The elevator  100  may comprise at least one or a plurality of elevator cars  10  moving in the elevator shaft  13  or the elevator car pathway  13 . 
     According to various embodiments, the elevator car(s)  10  may comprise a first electrical drive  12  or a drive unit  12 , such as a frequency converter or an inverter, and/or a first energy storage  14  such as a battery or batteries, which are shown with dashed lines indicating the optionality of the feature. 
     The first electrical drive  12  may be utilized for operating a mover (not shown in  FIG. 1 ) arranged to the elevator car  10  for moving the car  10  within the elevator shaft  13 . There may also be other electrically operated equipment in the elevator car  10  such as lighting, doors, user interface, emergency rescue equipment, etc. The first electrical drive  12  or a further electrical drive, such as an inverter or a rectifier, may be utilized for operating one or several of said other equipment of the elevator car  10 . The first energy storage  14  may, preferably, be electrically coupled to the first electrical drive  12 , for example, to the intermediate circuit of the drive, for providing electrical power to the first electrical drive  12  and/or for storing electrical energy provided by the first electrical drive  12  or a further electrical drive or other electrical power source. 
     There may preferably be at least two landing floors, having landing floor doors  19  or openings  19 , comprised in the elevator  100 . There may also be doors comprised in the elevator car  10 . Although in  FIG. 1  it is shown that there are two horizontally separated sets, or “columns”, of vertically aligned landing floors, there could as well be only one column as in conventional elevators or more than two, for example, three. 
     Regarding the elevator shaft  13 , it may be such as defining substantially closed volume in which the elevator car  10  is adapted and configured to be moved. The walls may be, for example, of concrete, metal or at least partly of glass, or any combination thereof. The elevator shaft  13  herein refers basically to any structure or pathway along which the elevator car  10  or cars  10  are configured to be moved. 
     As can be seen in  FIG. 1  with respect to the elevator  100 , the elevator car  10  or cars  10  may be moved within the elevator shaft  13  along a stator beam  16  or beams  16  vertically and/or horizontally depending on the direction of the stator beams  16 . According to various embodiments, the elevator car  10  or cars  10  may be configured to be moved along a number of vertical  16  and/or horizontal  16  and/or inclined stator beams, for example, two beams such as in  FIG. 1 . The stator beams  16  may be part of an electric linear motor of the elevator  100  utilized to move the elevator car  10  or cars  10  in the elevator shaft  13 . The stator beams  16  may, preferably, be arranged in fixed manner, that is, stationary with respect to the elevator shaft  13 , for example, to a wall of the shaft by fastening portions. 
     The elevator  100  may comprise an elevator control unit  1100  for controlling the operation of the elevator  100 . The elevator control unit  1100  may be a separate device or may be comprised in the other components of the elevator  100  such as in or as a part of the first electrical drive  12 . The elevator control unit  1100  may also be implemented in a distributed manner so that, e.g., one portion of the elevator control unit  1100  may be comprised in the first electrical drive  12  and another portion in the elevator car  10 . The elevator control unit  1100  may also be arranged in distributed manner at more than two locations or in more than two devices. 
     The elevator control unit  1100  may comprise one or more processors, one or more memories being volatile or non-volatile for storing portions of computer program code and any data values and possibly one or more user interface units. The mentioned elements may be communicatively coupled to each other with e.g. an internal bus. 
     The processor may be configured to execute at least some portion of computer program code stored in the memory causing the processor, and thus the elevator control unit  1100 , to perform desired tasks. The processor may thus be arranged to access the memory and retrieve and store any information therefrom and thereto. For sake of clarity, the processor herein refers to any unit suitable for processing information and control the operation of the elevator control unit  1100 , among other tasks. The operations may also be implemented with a microcontroller solution with embedded software. Similarly, the memory is not limited to a certain type of memory only, but any memory type suitable for storing the described pieces of information may be applied in the context of the present invention. 
     According to an embodiment, the elevator shaft  13  may comprise electrical power means for providing electrical power to the elevator car  10 . For example, a bus bar with vertically running connector rails. The connector rails may be connected to three phases of an AC mains network and one of the vertical connector rails may be a control connector connecting the elevator car  10  with the elevator control unit  1100 , for instance. The elevator car  10  may comprise a contactor which may be pressed via a connector against the elevator car  10 . Via the contactor, the elevator car  10  may be provided with electric power for the operation of the mover  20  as well as for all further car components needing electric power, as e.g. doors, input/output (I/O), lighting, etc. Alternatively, electrical power to elevator car  10  may be provided wirelessly, through split coils, based on inductive coupling. For example, the primary coil may be disposed in elevator shaft  13  and the secondary coil may be disposed on the elevator car  10 . 
       FIG. 2  illustrates schematically a part of an elevator  100  according to an embodiment of the present invention. There are two elevator cars  10  configured to be moved in the elevator shaft  13  by an electric linear motor. The electric linear motor may comprise a plurality of stators  17  comprised in a stator beam  16  or beams  16 , in this case two. The stator beam  16  or beams  16  may be arranged vertically or horizontally, for example, in  FIGS. 1 and 2  the elevator  100  comprises vertical stator beams  16  and horizontal stator beams  16 . However, the stator beam  16  or beams  16  may also be arranged to any direction(s) in which the elevator car  10  is desired to be moved, that is, in an inclined direction. One stator beam  16  may comprise a plurality of stator beam parts arranged one after another to yield the desired length for the stator beam  16  in whole. 
     The mover  20  may, preferably, be a C-shaped or U-shaped (not shown). The mover  20  may, preferably, comprise at least one or several permanent magnets and/or magnetic core element(s) or ferromagnetic material, and optionally, a plurality of windings. The windings may, preferably, be comprised in the armature  22  of the mover  20  and adapted to face the stators  17  of the stator beam  16 . However, in some embodiments, the mover  20  may comprise only one or several permanent magnets and/or magnetic core element(s) or ferromagnetic material, while the windings may reside in the stators  17  of the stator beam  16 . The windings of the stator may thus enable forming of the controllable magnetic field for moving the mover  20  in electromagnetic engagement with the stator  17 . 
     The windings, when comprised in the mover  20 , may, preferably, be arranged to be in electromagnetic engagement with the stators  17  for moving the mover  20  along the stator beam  16 . The mover  20  may be attached or coupled to the elevator car  10 , for example, to the back wall of the car  10  such as shown in FIG.  2 . The mover  20  may be shaped and designed in such a way as to enable the movement of the mover  20  along the stator beam  16  without interference from the fastening or support portions therein. 
     According to some embodiments, the stator beam  16  may comprise stators  17  on opposite sides of the stator beam  16 . Said stators  17  may be, for example, two of the four stators  17 . In a preferably embodiment, the stator beam  16  may comprise four stators  17  on each four side of the stator beam  16 , the cross-sectional shape of which may, preferably, be a polygon, a quadrangle, a square, or a parallelogram, or the like, for instance, thus, defining four sides of which specific two sides are opposite with respect to each other and specific other two sides are opposite with respect to each other. 
     The movement of the mover  20  along the stator beam  16  may be implemented by known control methods, such as, field-oriented or vector control or the like. The basic idea is to produce an alternating magnetic field, for example by an electrical drive  12 , by injecting current to the windings of the mover or the stator  17 . The windings facing the mover  20  or the stator  17  then co-acts with the mover  20  or the stator  17 , respectively, through the electromagnetic engagement or coupling, and produces a force which moves the mover  20  and thus the elevator car  10  along the stator beam  16 . 
     The stator beam  16  or beams  16  may comprise a plurality of stators  17  extending substantially along the whole stator beam  16 . There may, advantageously, be four stators  17  arranged at all four sides of the stator beam  16 . There may also be a fastening portion or portions by which said part  16  may be attached in fixed manner to the structures, such as a wall, of the elevator shaft  13 . The fastening portion  35  may also be a separate fastening portion which may then be attached to the stator beam  16  for arranging the stator beam  16  into the elevator shaft  13  or the fastening portion may be an integrated part of the stator beam  16  or a part thereof. The stators  17  may, preferably, be of ferromagnetic material and comprise teeth on their outer surface for providing a suitable magnetic circuit for co-acting with the mover  20 , that is, magnetic teeth. According to a preferable embodiment of the present invention, the stator beam  16  or beams  16  are passive in the sense that they do not comprise controllable elements or components, such as coils, for controlling the movement of the mover  20  along the stator beam  16 . 
     In  FIG. 2 , the stator beams  16  are arranged to the back wall  31  of the elevator shaft  13 . It should be noted, however, that the elevator shaft  13  refers herein to the any elevator car pathway  13  which, as described above, may include vertical parts, horizontal parts, and/or parts having a third direction different with respect to vertical and horizontal directions, that is, an inclined direction. For example, the part of the elevator shaft  13  depicted in  FIG. 2  comprises two vertical parts and one horizontal part. 
     In  FIG. 2 , the elevator shaft  13  or the elevator car pathway  13  may further comprise a front wall  32 . The front wall  32  may, preferably, comprise an opening  19  for entering into the elevator car  10  or cars  10 . Although shown in  FIG. 2  that the opening  19  for entering the elevator cars  10  is arranged only at vertical parts of the elevator shaft  13 , the opening  19  may as well be arranged to the horizontal part or any part of the elevator shaft  13 . It should be noted, however, that the elevator shaft  13  may in some cases comprise only one wall or a structure arranged to accommodate the necessary equipment such as the stator beam  16 . Thus, the elevator shaft  13  or the elevator car pathway  13  does not necessarily have to define a substantially closed volume, that is, surrounded by wall elements or glass or any other structures as long as there is at least a support structure to support the stator beam(s)  16 . 
     The elevator  100 , or particularly the elevator shaft  13  or shafts  13  thereof, according to the various embodiments of the present invention may comprise at least one, however, preferably more than one, positions for changing the direction of movement of the elevator car  10  at which the direction of movement of an elevator car  10  may be changed from one direction to another, which said another is un-parallel relative to said one direction, for example, such as when changing the direction between the vertical and horizontal directions. In  FIG. 2 , there are shown two such positions. The changing of the direction at these positions may be implemented, for example, by rotatable stator beam parts and/or rotatable movers  20  coupled to the elevator car  10 . 
     The mover  20  may, preferably, comprise armatures comprising winding(s) that may be arranged around, for example, magnetic teeth arranged to the armature of the mover  20 , for example, for three-phase current injection by an electrical drive  12 , and may, optionally, also comprise permanent magnets and/or ferromagnetic material or mover irons. The windings may be controlled, for example, by injecting three-phase current having a phase shift of 120 degrees between two phases. The current in the windings may be controlled, as stated hereinbefore, by an electrical drive  12  such as a frequency converter or an inverter. If an electrical energy storage  14 , such as a battery, coupled to the elevator car  10  is being utilized, the electrical drive  12 , such as a frequency converter, may draw electrical power from the storage to convert the direct current (DC) of the battery to suitable alternating current (AC) for the mover  20  to be moved along the stator beam  16 . 
       FIG. 3  illustrates an elevator  100  according to an embodiment of the present invention. The elevator  100  may comprise two stator beams  16 , advantageously, arranged parallel to each other, however, it is clear that there could be three or four or even more stator beams  16 . The same applies to the number of movers  20  configured to be moved relative to a corresponding stator beam  16  as described hereinabove. 
     In  FIG. 3 , the mover  20  has a C-shape. The mover  20  may, preferably, comprise a plurality of armatures comprising windings, and, optionally, at least one or several permanent magnets and/or magnetic core element(s) or ferromagnetic material. The armatures may, preferably, be comprised in the mover  20  and adapted to face the stators  17  of the stator beam  16 . 
     The operation of the linear electric motor  5  may be controlled by an electrical drive  12  or a plurality of electrical drives  12 , such as a frequency converter or converters or an inverter or inverters. There may be a separate elevator control unit  1100  or it may be comprised, at least partly, in the electrical drive  12 . There may be one electrical drive  12  for controlling one mover or several drives  12  controlling one mover depending on the structure and configuration of the mover  20  in question, for example, a mover  20  comprising one or several controllable electromagnetic components such as windings. In addition, electrical power for operating the electrical drive  12  or drives  12  may be drawn from the electrical energy storage  14  of the elevator car  10 . 
       FIGS. 4A and 4B  illustrate schematically electric linear motors  5  according to some embodiments of the present invention. The electric linear motors  5  may comprise a number of stator beams  16 , such as one or two or more, wherein at least one of the number of stator beams  16  comprises a plurality of stators  17 , such as two or four, extending in a longitudinal direction  18  of the stator beam  16 . The longitudinal direction has been marked in  FIGS. 4A-5  with a number  18  and the direction away or towards the viewer. The direction  18 B of the width of the stator  17  is also shown in  FIGS. 4A and 5 . This applies also in  FIGS. 4B, 6-10 and 12-14  although not explicitly mentioned herein in connection with said figures. Furthermore, the electric linear motor  5  may comprise a number of movers  20 , such as from one to more than ten or even twenty, wherein at least one of the number of movers  20  comprises a plurality of armatures  22 . The armature(s)  22 ,  22 A- 22 D may, preferably, comprise a winding or windings, such as a three-phase winding, and, optionally, a magnetic core of the armature  22 ,  22 A- 22 D. Still further, the armature  22 ,  22 A- 22 D may additionally comprise a permanent magnet or magnets. 
     Furthermore, each one of the plurality of armatures  22  may be adapted for establishing an electromagnetic coupling or engagement with a corresponding one of the stators  17  for moving the mover  20  along said stator  17 . In addition, at least one of the plurality of armatures  22  is arranged to be offset  25  from aligned position with respect to the corresponding one of the stators  17  in a perpendicular direction relative to the longitudinal direction  18 . In addition, the plurality of stators and the plurality of armatures may preferably be arranged with respect to each other for enabling a control of an air gap between the stator beam and the mover, for example, preferably, by magnetic levitation. 
     In  FIG. 4A , one of the plurality of armatures, marked with reference number  22 , has been arranged into the aligned position with respect to the corresponding one of the stator  17 . 
       FIG. 4A  illustrates an electric linear motor  5  comprising one armature  22  arranged to be offset  25  with respect to its corresponding stator  17 . The at least one of the plurality of armatures  22  may be arranged offset such that a torque component for rotating the mover in a first direction  101  with respect to the stator beam  17  is being generated when current is injected to said offset armature  22 . 
       FIG. 4B  illustrates an electric linear motor  5  comprising two armatures  22  arranged to be offset  25  from aligned position with respect to their corresponding stators  17 . In  FIG. 4B , at least one additional armature of the plurality of armatures  22  is arranged offset with respect to its corresponding one of the stators  17  for generating a torque component for rotating the mover in a second direction  102  with respect to the stator beam  16 . 
     According to various embodiments, two of the plurality of armatures  22  may be arranged at opposite sides of the stator beam  16 , such as illustrated in  FIGS. 4A and 4B . 
     According to various embodiments, the two of the plurality of armatures  22  may be arranged offset for generating torque components for rotating the mover with respect to the stator beam in opposite directions, such as armatures  22 A and  22 B shown in  FIG. 4B . 
       FIG. 5  illustrates schematically an electric linear motor  5  according to an embodiment of the present invention. The electric linear motor  5  may comprise a number of stator beams  16 , such as one or two or more, wherein at least one of the number of stator beams  16  comprises a plurality of stators  17 , such as four as shown in  FIG. 5 , extending in a longitudinal direction  18  of the stator beam  16 . Furthermore, the electric linear motor  5  may comprise a number of movers  20 , such as from one to more than ten or even twenty, wherein at least one of the number of movers  20  comprises a plurality of armatures  22 , such as four as shown in  FIG. 5 . Furthermore, each one of the plurality of armatures  22  may be adapted for establishing an electromagnetic coupling or engagement with a corresponding one of the stators  17  for moving the mover  20  along said stator  17 . In addition, at least one of the plurality of armatures  22  is arranged to be offset  25  with respect to the corresponding one of the stators  17  in a perpendicular direction relative to the longitudinal direction  18 . In addition, the plurality of stators and the plurality of armatures may preferably be arranged with respect to each other for enabling a control of an air gap between the stator beam and the mover, for example, preferably, by magnetic levitation. 
     According to various embodiments, the two of the plurality of armatures  22  may be arranged offset  25  for generating torque components for rotating the mover with respect to the stator beam in same direction, such as armatures  22 A and  22 C, and armatures  22 B and  22 D, respectively, shown in  FIG. 5 . 
     According to various embodiments, two consecutive armatures  22 , such as  22 A and  22 B, or  22 A and  22 D, or  22 D and  22 C, of the plurality of armatures  22  may be arranged offset  25  to opposite directions with respect to their corresponding stator, as shown in  FIGS. 4B and 5 . 
       FIG. 6  illustrates schematically an electric linear motor  5  according to an embodiment of the present invention. The electric linear motor  5  in  FIG. 6  is substantially similar to one shown in  FIG. 5 , however, in  FIG. 6  the stator  17  or stators  17  have a reduced width of the stator  17  or stators  17 . This is emphasized in  FIG. 6  by the dashed line in the air gap  15  indicating that the edges of the armatures  22 A- 22 D and the stators  17  align at the other end. The offsetting  25  may still be provided similarly as in  FIG. 5 . However, the edge of the armatures  22 A- 22 D (or armatures in  FIGS. 13 and 14 ) does not have to align with the edge of the stator(s)  17  having the reduced width. 
     Stator  17  or stators  17  having the reduced width, such as shown in  FIG. 6 , may be utilized in connection with various embodiments of the present invention, for example, in connection with ones illustrated in  FIGS. 7-10  and  FIGS. 12-14 . 
       FIG. 7  illustrates schematically an electric linear motor  5  according to an embodiment of the present invention. The electric linear motor  5  in  FIG. 7  is substantially similar to one shown in  FIG. 5 , however,  FIG. 7  additionally illustrates means for determining position of the mover  20  with respect to the stator beam  16 . In the embodiment shown in  FIG. 7 , the means comprise proximity sensors  51 , such as an inductive proximity sensor. The electric linear motor  5  may comprise one or several sensors arranged for determining the position, such as at various positions of the mover  20  and/or stator beam  16 . Furthermore, in some embodiments, the means may comprise only one element, such as a distance sensor for measuring the distance between the sensor and a surface, for example, a surface of the stator beam  16  when the sensor is arranged to the mover  20 . The means may in some embodiments comprise two elements, such as transmitting element and a receiving element of the means. The sensor for measuring the position of the mover  20  with respect to the stator beam  16  from the rotation point of view may be arranged as in  FIG. 7 , that is outside the air gap  15 , or alternatively into the air gap  15 . 
     In various embodiments, the elevator  100  and/or the elevator car  10  may be configured to control the current fed into the armatures  22 ;  22 A- 22 D, that is winding(s) therein, based on the signal received from the means for determining position of the mover  20  with respect to the stator beam  16 . Preferably, the current may be controlled, such as by the first electrical drive  12 , to affect the magnitude of the torque(s) generated by the offset armature(s), such as for rotating the mover  20  in the first  101  and/or the second  102  direction. In preferable embodiments, the controlling the current(s) comprises controlling a direct component of the current(s) for controlling the rotation of the mover  20 , that is, the direct (d) axis component of the currents. 
       FIG. 8  illustrates schematically an electric linear motor  5  according to an embodiment of the present invention. The electric linear motor  5  in  FIG. 8  is substantially similar to one shown in  FIG. 5 , however, the stator beam  16  has a rounding shape in corners of the stator beam  16 , such as a substantially tubular shape. The tubular shape allows more rotation of the mover  20  with respect to the stator beam  16  without the two coming in contact with one another in the air gap  15 . In various embodiments, the mover  20  may also include rounding shapes on the surface facing the stator beam  16 . 
     According to various embodiments, the electric linear motor  5  may comprise air gap regulation means for regulating movement of the mover  20  in at least one of the following: a first direction with respect to the stator beam, a second direction with respect to the stator beam. In various embodiments, the air gap regulation means may include means which limit the rotation in one of the directions, that is, such means remain passive during times when the rotation of mover  20  is within some predefined range, such as less than five or ten degrees, for instance, relative to the intended or unrotated position of the mover  20  with respect to the stator beam  16 , such as shown in  FIGS. 4A-8 . Alternatively or in addition, the air gap regulation means may include means which fix the mover  20  relative to the stator beam  16  at one position. 
     In some embodiments, the air gap regulation means may comprise a number of guide elements arranged for regulating rotation of the mover with respect to the stator beam at least in one direction. The number of guide elements  71  may comprise at least one of the following: a guide surface  72 , such as a low friction surface, a roller  73 , a permanent magnet  81 , an electromagnet  81 . 
       FIG. 9  illustrates schematically an electric linear motor  5  according to an embodiment of the present invention. The electric linear motor  5  in  FIG. 9  is substantially similar to one shown in  FIG. 5 , however, the motor  5  further comprises guide elements  71  arranged to limit or regulate the rotation of the mover  20  at least in one direction or in two directions. The motor  5  in  FIG. 9  comprises guide surfaces  72  and/or a rollers  73  arranged between the edge of the mover  20  and the fastening portion or the edge of the stator beam  16 . The tubular shape allows more rotation of the mover  20  with respect to the stator beam  16  without the two coming in contact with one another. In various embodiments, the mover  20  may also include rounding shapes on the surface facing the stator beam  16 . 
       FIG. 10  illustrates schematically an electric linear motor  5  according to an embodiment of the present invention. The electric linear motor  5  in  FIG. 10  is substantially similar to one shown in  FIG. 5 , however, the motor  5  further comprises guide elements arranged to limit or regulate the rotation of the mover  20  at least in one direction or in two directions. The motor  5  in  FIG. 10  comprises a permanent magnet(s)  81 , such as a permanent magnet array, or an electromagnet(s)  81  arranged between the edge of the mover  20  and the fastening portion or the edge of the stator beam  16 . In various embodiments, the permanent magnets  81  may, preferably, be arranged both on to the mover side and on to the stator beam side such that poles of the facing magnets are in opposite directions in order to achieve passive guidance for limiting or regulating the movement of the mover  20  with respect to the stator beam  16 . 
       FIG. 11  illustrates a flow diagram of a method according to an embodiment of the present invention. 
     Step  90  refers to a start-up phase of the method. Suitable equipment and components may be obtained and systems assembled and configured for operation. For example, an electric linear motor  5  may be obtained and assembled for use. The motor  5  may comprise a number of stator beams  16 , wherein at least one of the number of stator beams  16  comprises a plurality of stators  17  extending in a longitudinal direction  18  of the stator beam, and a number of movers  20 , wherein at least one of the number of movers comprises a plurality of armatures  22 , wherein each one of the plurality of armatures  22  is adapted for establishing an electromagnetic coupling with a corresponding one of the stators  17  for moving the mover  20  along the corresponding one of the stators. The motor  5  may further comprise at least one of the plurality of armatures  22 A- 22 D that may be arranged to be offset  25  from aligned position with respect to the corresponding one of the stators  17  in a perpendicular direction relative to the longitudinal direction  18 . 
     Step  91  refers to controlling currents of winding(s) of the at least one of the plurality of armatures, that is the offset armature(s), by current controlling means, such as by the first electrical drive  12 , for controlling the rotation of the mover  20  with respect to the stator beam  16 . 
     According to an embodiment, the electric linear motor  5  may comprise one of the plurality of armatures  22 ;  22 A- 22 D arranged offset  25  with respect to its corresponding one of the stators  17  for generating a torque component for rotating the mover in a first direction  101  with respect to the stator beam  16 , and at least one additional armature  22 A- 22 D of the plurality of armatures  22  is arranged offset  25  with respect to its corresponding one of the stators for generating a torque component for rotating the mover  20  in a second direction  102  with respect to the stator beam  16 , wherein the method the comprises controlling currents of said one  22 A- 22 D and said at least one additional armature  22 A- 22 D by the current controlling means, such as the first electrical drive  12 , for controlling the rotation of the mover  20  in the first  101  and second  102  directions. 
     In some embodiments, the electric linear motor  5  may comprise two of the plurality of armatures arranged at opposite sides of the stator beam  16  and offset  25  for generating torque components for rotating the mover  20  in same direction with respect to the stator beam  16 , and wherein the method may comprise controlling currents of said two  22 A- 22 D of the plurality of armatures  22  by the current controlling means for controlling the rotation of the mover in the first  101  or in the second  102  direction. 
     In various embodiments, the method may comprise controlling a direct component of the currents for controlling the rotation of the mover  20 . 
     Method execution is stopped at step  99 . The method may be performed continuously, intermittently, or when needed, for instance. 
     According to various embodiments, such as shown in  FIG. 12 , the electric linear motor  5  may comprise a number of stator beams  16 , wherein at least one of the number of stator beams  16  comprises a plurality of stators  17  extending in a longitudinal direction  18  of the stator beam  16 , and a number of movers  20 , wherein at least one of the number of movers  20  comprises a plurality of armatures  22 . Furthermore, each one of the plurality of stators  17  may be adapted for establishing an electromagnetic coupling with a corresponding one of the armatures  22  for moving the mover  20  along said stator  17 . Still further, alternatively with respect to embodiments in  FIGS. 4A-9 , at least one of the plurality of stators  17  may be arranged to be offset  25  with respect to the corresponding one of the armatures  22  in a perpendicular direction relative to the longitudinal direction  18 . Thus, the at least one stator  17  or several stators  17  may be arranged to the stator beam  16  by displacing them from the center points while the armatures  22  of the mover  20  may be substantially at the center points of the mover  20 . Moreover, the mover  20  may thus be substantially symmetrical from the point of view of the armature positions while the stator beam  16  may be asymmetrical with respect to the stator position(s). 
     According to still other embodiments, such as shown in  FIG. 13 , the electric linear motor  5  may comprise a number of stator beams  16 , wherein at least one of the number of stator beams  16  comprises a plurality of stators  17  extending in a longitudinal direction  18  of the stator beam  16 . The stators  17  may comprise stator windings. Furthermore, the electric linear motor  5  may comprise a number of movers  20 , comprising armatures, wherein each armature may comprise a magnetic core and, optionally, a permanent magnet or magnets for defining magnetic teeth. Furthermore, each one of the plurality of stators  17  may be adapted for establishing an electromagnetic coupling with a corresponding one of the armatures for moving the mover  20  along said stator  17 . Still further, at least one of the plurality of stators  17  comprising stator winding may be arranged to be offset  25  with respect to the corresponding one of the armatures in a perpendicular direction relative to the longitudinal direction  18 . Thus, the at least one stator  17  or several stators  17  may be arranged to the stator beam  16  by displacing them from the center points while the armatures of the mover  20  may be substantially at the center points of the mover  20 . Moreover, the mover  20  may thus be substantially symmetrical from the point of view of the armature positions while the stator beam  16  may be asymmetrical with respect to the stator position(s). In these embodiments, the rotation of the mover  20  with respect to the stator beam  16  may be controlled by controlling currents of the at least one of the plurality of stator windings by current controlling means for controlling the rotation of the mover  20  with respect to the stator beam  16 . 
     According to still other embodiments, such as shown in  FIG. 14 , the electric linear motor  5  may comprise a number of stator beams  16 , wherein at least one of the number of stator beams  16  comprises a plurality of stators  17  extending in a longitudinal direction  18  of the stator beam  16 . The stators  17  may comprise stator windings. Furthermore, the electric linear motor  5  may comprise a number of movers  20 , comprising armatures, wherein each armature may comprise a magnetic core and, optionally, a permanent magnet or magnets for defining magnetic teeth. Furthermore, each one of the plurality of stators  17  may be adapted for establishing an electromagnetic coupling with a corresponding one of the armatures for moving the mover  20  along said stator  17 . Still further, at least one of the plurality of armatures may be arranged to be offset  25  with respect to the corresponding one of the stators  17  in a perpendicular direction relative to the longitudinal direction  18 . Thus, at least one armature may be arranged to be offset  25  from aligned position with respect to the corresponding stator  17  in similar manner as shown in  FIGS. 4A-10  with respect to the at least one of the plurality of armatures  22 A- 22 D. In these embodiments, the rotation of the mover  20  with respect to the stator beam  16  may be controlled by controlling currents of the at least one of the plurality of stator windings by current controlling means for controlling the rotation of the mover  20  with respect to the stator beam  16 . 
     In various embodiments comprising stator windings, such as in  FIGS. 13 and 14 , the electric linear motor  5  may otherwise be substantially similar to ones illustrated and described in connection with  FIGS. 4A-10 , however, the current controlling means, such as electrical drives, may be comprised in connection with the stator windings, such as arranged to the elevator shaft  13 , instead of being arranged to the elevator car(s)  10 . 
     The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.