Patent Publication Number: US-2021175787-A1

Title: Conveyance system, movable element, control apparatus, control method, and method of manufacturing articles

Description:
BACKGROUND 
     Field 
     The present disclosure relates to a conveyance system, a movable element, a control apparatus, a control method, and a method of manufacturing article. 
     Description of the Related Art 
     Conveyance systems are commonly used in production lines for industrial product assembly and in semiconductor exposure apparatuses, for example. Especially, a conveyance system in a production line conveys works, such as parts, between a plurality of stations in an automated production line or between production lines in a factory. A conveyance system is also used as a conveyance apparatus in a processing apparatus. Among those, conveyance systems using a movable magnet type linear motor have been discussed. 
     Conveyance systems using a linear motor include a guide apparatus, such as a linear guide, that involves mechanical contact. The conveyance systems using a guide apparatus, such as a linear guide, have an issue in decrease of productivity due to contaminants, such as wear fragments of rails and bearings, lubricants, and volatilized lubricants, from a sliding portion of the linear guide. There is also another issue in decrease of the lifetime of the linear guide due to increase in friction of the sliding portion during high-speed conveyance. 
     Japanese Patent Laid-Open No. 2005-079368 discusses a magnetic levitation conveyance apparatus that realizes contactless conveyance of a conveyance tray. According to Japanese Patent Laid-Open No. 2005-079368, two rows of permanent magnets for control in a conveyance direction (hereinafter, “X-direction”) and for control in a levitation direction (hereinafter, “Z-direction”) are disposed under a chamber along the conveyance direction of the conveyance tray. Furthermore, a row of permanent magnets for a horizontal direction (hereinafter, “Y-direction”) perpendicular to the conveyance direction is disposed. On the conveyance tray, three sets of coils are disposed correspondingly to the permanent magnets. 
     SUMMARY 
     According to an aspect of the present disclosure, a conveyance system includes a movable element including a first coil group and a second coil group, wherein the first coil group includes a plurality of first coils disposed along a first direction, and the second coil group includes a plurality of second coils disposed along a second direction intersecting with the first direction, and a stator including a plurality of magnetic bodies disposed along the first direction so that the plurality of magnetic bodies are capable of facing the first coil group and the second coil group, wherein, in a case where electric current is applied to the first coil group or the second coil group, a force is generated between the movable element and the plurality of magnetic bodies; and wherein the movable element is capable of moving in the first direction along the plurality of magnetic bodies while an orientation of the movable element is controlled by the generated force. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic view illustrating a movable element of a conveyance system according to a first exemplary embodiment of the present disclosure.  FIG. 1B  is a schematic view illustrating a stator of the conveyance system according to the first exemplary embodiment of the present disclosure. 
         FIG. 2  is a schematic view illustrating an entire configuration of the conveyance system according to the first exemplary embodiment of the present disclosure. 
         FIGS. 3A and 3B  are schematic views illustrating coil groups in the conveyance system according to the first exemplary embodiment of the present disclosure.  FIG. 3C  illustrates magnitudes of forces generated by application of an electric current to the coil groups in the conveyance system according to the first exemplary embodiment of the present disclosure. 
         FIG. 4A  is a schematic view illustrating a control system that controls the conveyance system according to the first exemplary embodiment of the present disclosure.  FIG. 4B  is a schematic view illustrating a control system that controls a conveyance system according to a second exemplary embodiment of the present disclosure. 
         FIG. 5  illustrates a movable element controller in the conveyance system according to the first exemplary embodiment of the present disclosure. 
         FIG. 6  illustrates actions of coils in the conveyance system according to the first exemplary embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure is directed to a conveyance system that conveys a movable element without physical contact while controlling an orientation of the movable element and not requiring upsizing of a system configuration, a movable element, a control apparatus, a control method, and a method of manufacturing an article. 
     An apparatus discussed in Japanese Patent Laid-Open No. 2005-079368 includes at least three rows of coil arrays and has a large and complicated structure. If a coil for X and a coil for Y are disposed nearby with each other to reduce the structure size, the coil for Y that is supposed to face a permanent magnet for Y turns to facing the coil for X in consequence of a movable element displaced toward Y, for example, and therefore orientation control of the movable element becomes difficult. 
     First Exemplary Embodiment 
     A first exemplary embodiment of the present disclosure will be described below with reference to  FIGS. 1A and 1B to 6 . 
     First, an entire configuration of a conveyance system  1  according to the present exemplary embodiment will be described below with reference to  FIGS. 1A and 1B .  FIGS. 1A and 1B  are schematic views illustrating a movable element  101  and a stator  201  according to the present exemplary embodiment.  FIG. 1A  illustrates an extracted main portion of the movable element  101 , and  FIG. 1B  illustrates an extracted main portion of the stator  201 . Further,  FIG. 1A  is a view illustrating the movable element  101  viewed in a Z-direction, and  FIG. 1B  is a view illustrating the stator  201  viewed in a Y-direction. The Z- and Y-directions will be described below. 
     As illustrated in  FIGS. 1A and 1B , the conveyance system  1  according to the present exemplary embodiment includes the movable element  101  and the stator  201 . The movable element  101  is configured as a cart, slider, or carriage. The stator  201  is configured as a conveyance path. The conveyance system  1  is a conveyance system that includes a movable coil type linear motor. Further, the conveyance system  1  is a magnetic levitation type conveyance system that does not include a guide, such as a linear guide, and conveys the movable element  101  on the stator  201  without physical contact with the movable element  101 . 
     The conveyance system  1 , for example, conveys the movable element  101  using the stator  201  and conveys a work  102  on the movable element  101  to a processing apparatus for processing the work  102 . While  FIGS. 1A and 1B  illustrate one movable element  101  with respect to the stator  201 , the present exemplary embodiment is not limited to the illustrations. The conveyance system  1  can convey a plurality of movable elements  101  on the stator  201 . 
     Coordinate axes and directions used herein will be defined as follows. First, an X-axis is defined along a horizontal direction that is a conveyance direction of the movable element  101 , and the conveyance direction of the movable element  101  is defined as “X-direction”. In the present specification, the X-direction is sometimes referred to as “first direction”. A Z-axis is defined along a vertical direction that is a direction perpendicular to the X-direction, and the vertical direction is defined as “Z-direction”. A Y-axis is defined along a direction perpendicular to the X- and Z-directions, and the direction perpendicular to the X- and Z-directions is defined as “Y-direction”. Rotations about the X-, Y-, and X-axes will be denoted by Wx, Wy, and Wz, respectively. The symbol “*” will be used as a multiplication sign. A center of the movable element  101  will be referred to as “origin O”, and a positive Y-side and a negative Y-side from the origin O will be referred to as “R-side” and “L-side”, respectively. The conveyance direction of the movable element  101  does not always have to be the horizontal direction, and in a case where the conveyance direction is not the horizontal direction, the conveyance direction can yet be defined as the X-direction, and the Y- and Z-directions can yet be defined as described above. 
     Next, the movable element  101  as a conveyance target of the conveyance system  1  according to the present exemplary embodiment will be described below with reference to  FIGS. 1A and 2 .  FIG. 2  is a schematic view illustrating an entire structure of the conveyance system  1  according to the present exemplary embodiment.  FIG. 2  illustrates the movable element  101  and the stator  201  viewed in the X-direction. In  FIG. 2 , the L-side is a cross section A along a line A-A′ specified in  FIG. 1A , and the R-side is a cross section B along line B-B′ specified in  FIG. 1A . 
     As illustrated in  FIGS. 1A and 2 , the movable element  101  has an upper surface  101   a , a side surface  101   b , and a lower surface  101   c . Further, the movable element  101  includes coil arrays  103 R and  103 L each including a plurality of coils  103 . While the movable element  101  provided with two coil arrays including the one on the L-side of the upper surface  101   a  of the movable element  101  and the other on the R-side of the upper surface  101   a  is described in the present exemplary embodiment, the movable element  101  is not limited to the arrangement and can include one coil array or three or more coil arrays. In the present specification, the upper surface  101   a  of the movable element  101  faces upward (a surface facing in a positive Z-direction) among surfaces that are parallel to the X-direction, which is the conveyance direction, and perpendicular to the vertical direction (Z-direction) that is at right angles to the X-direction. The lower surface  101   c  of the movable element  101  faces downward (a surface that faces a negative Z-direction) among the surfaces that are parallel to the X-direction, which is the conveyance direction, and perpendicular to the vertical direction (Z-direction) that is at right angles to the X-direction. The side surface  101   b  of the movable element  101  faces the stator  201  among surfaces that are parallel to the X-direction, which is the conveyance direction, and parallel to the vertical direction (Z-direction) that is at right angles to the X-direction. 
     As illustrated in  FIG. 1A , coils  103   a   1 R to  103   a   3 R,  103   b   1 R to  103   b   6 R, and  103   c   1 R to  103   c   3 R are in the R-side of the upper surface  101   a  of the movable element  101 . Each center of the coils  103   a   1 R to  103   a   3 R and  103   c   1 R to  103   c   3 R is at a distance rx 3  from an origin Om, which is the center of the movable element  101 , in the Y-direction to the R-side. Each midpoint between the coils  103   b   1 R and  103   b   4 R, between the coils  103   b   2 R and  103   b   5 R, and between the coils  103   b   3 R and  103   b   6 R is at the distance rx 3  from the origin Om, which is the center of the movable element  101 , in the Y-direction to the R-side. 
     Coils  103   a   1 L to  103   a   3 L,  103   b   1 L to  103   b   6 L, and  103   c   1 L to  103   c   3 L are in the L-side of the upper surface  101   a  of the movable element  101 . Each center of the coils  103   a   1 L to  103   a   3 L and  103   c   1 L to  103   c   3 L is at the distance rx 3  from the origin Om, which is the center of the movable element  101 , in the Y-direction to the L-side. Each midpoint between the coils  103   b   1 L and  103   b   4 L, between the coils  103   b   2 L and  103   b   5 L, and between the coils  103   b   3 L and  103   b   6 L is at the distance rx 3  from the origin Om, which is the center of the movable element  101 , in the Y-direction to the L-side. 
     An area of the upper surface  101   a  of the movable element  101  between areas where the coils  103  are disposed in the R-side and L-side is an area where the work  102  to be conveyed is placed. 
     The coil arrays  103 R and  103 L are disposed in the upper surface  101   a  of the movable element  101  along the X-direction. Specifically, the coil array  103 R is disposed on the R-side of the upper surface  101   a  of the movable element  101 . The coil array  103 L is disposed in the L-side of the upper surface  101   a  of the movable element  101 . Hereinafter, unless discrimination is necessary, each coil of the movable element  101  will be referred to as “coil  103 ”. In a case where discrimination between the R- and L-sides is unnecessary but each coil  103  needs to be, or at least should be, identified individually, the coil  103  is identified individually using the identifier using the lowercase letter and the number and without the letter “R” or “L” at the end of the reference numeral. In a case of  FIG. 1A , the coils  103  are individually identified as “coils  103   a   1  to  103   a   3 ”, “coils  103   b   1  to  103   b   6 ”, or “coils  103   c   1  to  103   c   3 ”. 
     The coil  103   a   1 R is disposed on one end of the R-side of the upper surface  101   a  of the movable element  101  in the X-direction, and the coil  103   c   3 R is disposed on the other end in the X-direction. The coils  103   b   1 R to  103   b   6 R are disposed on the R-side of the upper surface  101   a  of the movable element  101  between the coils  103   a   3 R and  103   c   1 R. The coils  103   a   1 R to  103   a   3 R, for example, are aligned on a line R-R along the X-direction at equal distances in the X-direction. Further, the coils  103   c   1 R to  103   c   3 R, for example, are aligned on the line R-R along the X-direction at equal distances in the X-direction. The coils  103   b   1 R to  103   b   3 R and the coils  103   b   4 R to  103   b   6 R are disposed in two rows on opposite sides across the line R-R and at equal distances along the X-direction. 
     The coil  103   a   1 L is disposed on one end of the L-side of the upper surface  101   a  of the movable element  101  in the X-direction, and  103   c   3 L is disposed on the other end in the X-direction. The coils  103   b   1 L to  103   b   6 L are disposed on the L-side of the upper surface  101   a  of the movable element  101  between the coils  103   a   3 L and  103   c   1 L. The coils  103   a   1 L to  103   a   3 L, for example, are aligned on a line L-L along the X-direction at equal distances in the X-direction. The coils  103   c   1 L to  103   c   3 L, for example, are aligned on the line L-L along the X-direction at equal distances in the X-direction. The coils  103   b   1 L to  103   b   3 L and the coils  103   b   4 L to  103   b   6 L are disposed in two rows on opposite sides across the line L-L and at equal distances along the X-direction. 
     The coils  103   a   1 L to  103   a   3 L and  103   c   1 L to  103   c   3 L are disposed at corresponding positions to the coils  103   a   1 R to  103   a   3 R and  103   c   1 R to  103   c   3 R 1 , respectively, in the X-direction. The coils  103   b   1 R and  103   b   4 R are disposed at corresponding positions to the coils  103   b   1 L and  103   b   4 L, respectively, in the X-direction. The coils  103   b   2 R and  103   b   5 R are disposed at corresponding positions to the coils  103   b   2 L and  103   b   5 L, respectively, in the X-direction. The coils  103   b   3 R and  103   b   6 R are disposed at corresponding positions to the coils  103   b   3 L and  103   b   6 L, respectively, in the X-direction. 
     The center of the coil  103   a   2 R and the center of the coil  103   c   2 R are at a distance ry 3  away toward one side and the other side of the movable element  101  in the X-direction, respectively, from where a line extended from the origin Om (the center of the movable element  101 ) in the Y-direction intersects at right angles with the line R-R. The center of the coil  103   a   2 L and the center of the coil  103   c   2 L are at the distance ry 3  away toward one side and the other side of the movable element  101  in the X-direction, respectively, from where the line extended from the origin Om in the Y-direction intersects at right angles with the line L-L. The centers of the coils  103   a   1  to  103   a   3  and  103   c   1  to  103   c   3  are at the distance rx 3  away from where a line extended from the respective centers in the Y-direction intersects at right angles with a line extended from the origin Om in the X-direction. While the coils  103   b  are disposed so that an intermediate line between a line connecting the centers of the coils  103   b   1  to  103   b   3  and a line connecting the centers of the coils  103   b   4  to  103   b   6  is at the distance rx 3  away from the origin O in the Y-direction are described above as an example, the coils  103   b  are not limited to the example. 
     Three sets of two coils  103 , i.e., the coils  103   b   1 R and  103   b   4 R,  103   b   2 R and  103   b   5 R, and  103   b   3 R and  103   b   6 R are included in a coil group and the two coils  103  of each set are disposed along the Y-direction. Three sets of two coils  103 , i.e., the coils  103   b   1 L and  103   b   4 L,  103   b   2 L and  103   b   5 L, and  103   b   3 L and  103   b   6 L are included in a coil group and the two coils  103  of each set are disposed along the Y-direction. The number of coils  103   b  that are disposed along the Y-direction is not limited to two. Further, an arrangement direction of the coils  103   b  does not always have to be perpendicular to the X-direction, which is the conveyance direction, and can be any direction that intersects with the X-direction. 
     The coils  103   a R are a group of three coils  103  disposed along the X-direction, and so are the coils  103   c R, the coils  103   a L, and the coils  103   c L. The number of coils  103   a  that are disposed along the X-direction is not limited to three and can be any number greater than one, and the number of coils  103   c  that are disposed along the X-direction is not limited to three and can be any number greater than one. 
     In the present exemplary embodiment, a group of coils  103  disposed along the X-direction is sometimes referred to as “first coil group”. A group of a plurality of sets of two coils  103  disposed along a direction that intersects with the X-direction is sometimes referred to as “second coil group”. Specifically, the second coil group according to the present exemplary embodiment are the group of the sets of coils  103   b   1 L and  103   b   4 L,  103   b   2 L and  103   b   5 L, and  103   b   3 L and  103   b   6 L and the group of the sets of coils  103   b   1 R and  103   b   4 R,  103   b   2 R and  103   b   5 R, and  103   b   3 R and  103   b   6 R. In the present exemplary embodiment, the coils  103   b   1 L and  103   b   4 L, the coils  103   b   2 L and  103   b   5 L, and the coils  103   b   3 L and  103   b   6 L are sometimes referred to as “ 103   b   1 ⋅ 4 L”, “ 103   b   2 ⋅ 5 L”, and “ 103   b   3 ⋅ 6 L”, respectively. Further, the coils  103   b   1 R and  103   b   4 R, the coils  103   b   2 R and  103   b   5 R, and the coils  103   b   3 R and  103   b   6 R are sometimes referred to as “ 103   b   1 ⋅ 4 R”, “ 103   b   2 ⋅ 5 R”, and “ 103   b   3 ⋅ 6 R”, respectively. 
     Each coil  103  can be a coil with a core or a coreless coil. In the present exemplary embodiment, each coil  103  is a coil with a magnetic iron-core (core) in a magnetic circuit. Therefore, a strong magnetic attractive force is generated between the core of the coil  103  and a permanent magnet  203 , and this contributes to the levitation of the movable element  101 . The coil  103  with the core is suitable especially in a case where the movable element  101  or the work  102  placed on the movable element  101  has a large mass. The core of the coil  103  can be any core with which a magnetic attractive force is generated between the core and at least one permanent magnet  203 . Desirably, the core of the coil  103  is disposed to face the plurality of permanent magnets  203 . 
     The movable element  101  includes the plurality of coils  103  disposed symmetrically on the R- and L-sides across a central axis of the upper surface  101   a  of the movable element  101  along the X-axis as an axis of symmetry. Electric currents of the plurality of coils  103  are controlled, for example, in units of three coils  103 . The unit of electric current application control on the coils  103  will be referred to as “coil unit”. When an electric current is applied to the plurality of coils  103 , an electromagnetic force is generated between the plurality of coils  103  and the plurality of permanent magnets  203  of the stator  201  and acts on the movable element  101 . The movable element  101  with the plurality of coils  103  is moved while the orientation of the movable element  101  is controlled in six axes by the electromagnetic force received by the plurality of permanent magnets  203  of the stator  201 . 
     The movable element  101  is movable in the X-direction along the plurality of permanent magnets  203  disposed in two rows along the X-direction. The movable element  101  is conveyed with the work  102 , which is a conveyance target, held by the upper surface  101   a  or the lower surface  101   c  of the movable element  101 . The movable element  101  can include, for example, a holding mechanism that holds the work  102 , such as a work holder. 
     Next, the stator  201  of the conveyance system  1  according to the present exemplary embodiment will be described below with reference to  FIGS. 1B and 2 .  FIG. 1B  illustrates the permanent magnets  203  viewed in the Z-direction. 
     The stator  201  includes the plurality of permanent magnets  203  disposed in two rows along the X-direction, which is the conveyance direction of the movable element  101 . The plurality of permanent magnets  203  is disposed on the stator  201  to face the coils  103  of the upper surface  101   a  of the movable element  101 . The stator  201  extends in the X-direction, which is the conveyance direction of the movable element  101 , and forms the conveyance path of the movable element  101 . The plurality of permanent magnets  203  is disposed on the stator  201  with a yoke  221  therebetween and faces toward a lower part of the stator  201 . The yoke  221  is made of a high-permeability material such as iron. The plurality of permanent magnets  203  is disposed at predetermined intervals along the conveyance direction of the movable element  101  and is alternately magnetized. A reference position of the stator  201  in the X-direction will be denoted by Of. 
     The movable element  101  to be conveyed on the stator  201  includes an encoder  111 , a Y-sensor  112 , a Z-sensor  113 , a movable element controller  302 , and a cable  130 . The stator  201  includes a scale  211 , a Y-target  212 , and a Z-target  213 . The encoder  111  is disposed on, for example, a bottom portion of the movable element  101 . The scale  211  is disposed on the stator  201  along the X-direction to face the encoder  111  of the movable element  101 . The encoder  111  detects a pattern of the scale  211  and detects the distance of the movable element  101  in the X-direction from a reference position of the scale  211 . The Y-target  212  is, for example, disposed along the X-direction to face the Y-sensor  112  disposed on the side surface  101   b  of the movable element  101 . The Y-sensor  112  measures the distance between the Y-sensor  112  and the Y-target  212  in the Y-direction. The Z-target  213  is, for example, disposed along the X-direction to face the Z-sensor  113  disposed on the bottom portion of the movable element  101 . The Z-sensor  113  measures the distance between the Z-sensor  113  and the Z-target  213  in the Z-direction. Desirably, three Z-sensors  113  ( 113   b L,  113   f L,  113   c R) are disposed, i.e., two are disposed in the L-side and one is disposed in the R-side. The encoder  111 , the Y-sensor  112 , the Z-sensor  113 , the coil  103 , and the cable  130  are connected to the movable element controller  302 . The cable  130  is connected to, for example, an integrated controller  301 , which will be described below, of the stator  201 . Further, the cable  130  is desirably guided by a cable carrier system such as a Cableveyor® so that the movable element  101  is not stressed by the cable  130 . 
     The plurality of permanent magnets  203  is disposed in two rows along the X-direction and disposed in the stator  201  to face the coils  103  on the R-side and the L-side of the upper surface  101   a  of the movable element  101 . The plurality of permanent magnets  203  in one row on the R-side is disposed along the X-direction to face the coils  103   a R,  103   b R, and  103   c R on the R-side of the movable element  101 . Further, the plurality of permanent magnets  203  in the other row on the L-side is disposed along the X-direction to face the coils  103   a L,  103   b L, and  103   c L on the L-side of the movable element  101 . 
     A guide member  108  is disposed on the movable element  101 . Desirably, the guide member  108  is disposed on the side surface  101   b  of the movable element  101  along the X-direction. Further, a Z-roller  262  and a Y-roller  261  are disposed on the stator  201 . The guide member  108  desirably has, for example, a C- or U-shaped cross section. With the C- or U-shaped cross section, the guide member  108  can surround the Z-roller  262  and the Y-roller  261 . 
     The plurality of Z- and Y-rollers  262  and  261  is disposed on the stator  201  along the conveyance direction (first direction (X-direction)). While the Z-roller  262  is disposed on the R-side and the Y-roller  261  on the L-side in  FIG. 2  as an example, the Z-roller  262  and the Y-roller  261  can be disposed on the R-side and on the L-side, respectively. 
     With the guide member  108 , an amount of movement of the movable element  101  is regulated. Specifically, in a case where the movable element  101  is moved by a predetermined amount or more in the Z-direction, the Z-roller  262  comes into contact with the inside of the guide member  108  and prevents the movable element  101  from moving further. Similarly, in a case where the movable element  101  is moved by a predetermined amount or more in the Y-direction, the Y-roller  261  comes into contact with the inside of the guide member  108  and prevents the movable element  101  from moving further. 
     While the guide member  108  is disposed on the movable element  101  and the Z-roller  262  and the Y-roller  261  are disposed on the stator  201  in the present exemplary embodiment as an example, the guide member  108  can be disposed on the stator  201 . In this case, the Z-roller  262  and the Y-roller  261  are disposed on the side surface  101   b  of the movable element  101  along the X-direction (first direction). 
     Next, the coil unit will be described below with reference to  FIGS. 3A to 3C . 
     In the present exemplary embodiment, the coil unit includes the first coil group including six coils  103  disposed along the first direction. Further, the coil unit  1031  includes the second coil group including three coil sets each including two coils  103  disposed along a second direction intersecting with the first direction. Specifically, the coil unit  1031  including the six coils  103  of the first coil group and the six coils  103  of the second coil group is taken as an example, but the coil unit  1031  is not limited to the above-described example.  FIG. 3A  illustrates a coil unit  103 R viewed from the positive Z-direction. The coil unit  103 R includes twelve coils  103   a   1 R to  103   a   3 R,  103   b   1 R to  103   b   6 R, and  103   c   1 R to  103   c   3 R. The permanent magnet  203  is a permanent magnet on the stator  201 . 
     Each coil  103  is connected to the movable element controller  302 , and the amounts of electric current of the six coils  103   a   1 R to  103   a   3 R and  103   c   1 R to  103   c   3 R are controlled independently of each other. 
     Electric currents having the same magnitude are applied to the coils  103   b   1 R and  103   b   4 R, respectively, in different directions from each other. Similarly, electric currents having the same magnitude are applied to the coils  103   b   2 R and  103   b   5 R, respectively, in different directions from each other, and electric currents having the same magnitude are applied to the coil  103   b   3 R and  103   b   6 R, respectively, in different directions from each other. 
     Actions of the coils  103   b   1 R and  103   b   4 R will be described below with reference to  FIG. 6 . 
     Desirably, the coils  103   b   1 R and  103   b   4 R in  FIG. 6  are wire-wound coils and the wire winding direction of the coils  103   b   1 R and  103   b   4 R is determined such that the magnetic poles of the coils  103   b   1 R and  103   b   4 R proximate to the permanent magnet  203  are opposite from each other. The present exemplary embodiment is not limited to those described above, and each of the coils  103  can be controlled so that electric currents of the same amplitude are applied in different directions between the coils  103 . 
     For example, as in  FIG. 6 , an electric current is applied to the coils  103   b   1 R and  103   b   4 R so that the magnetic pole of the coil  103   b   4 R proximate to the permanent magnet  203  is a south pole and the magnetic pole of the coil  103   b   1 R proximate to the permanent magnet  203  is a north pole. In a case where the magnetic pole of the permanent magnet  203  proximate to the coils  103  is magnetized in a south pole, forces Fyn and Fyp act on the coils  103   b   1 R and  103   b   4 R toward the positive Y side, and therefore the movable element  101  is moved in the positive Y direction. 
     Meanwhile, forces Fzn and Fzp in the Z-direction act to cancel each other. 
     As described above, the coil units  103 R and  103 L each include the six coils  103  for each of which an electric current is controlled independently and the three coil sets each including two coils  103  to which electric currents of the same amplitude are applied in different directions from each other. The six coils  103  for each of which an electric current is controlled independently are the coils  103   a   1  to  103   a   3  and  103   c   1  to  103   c   3 . The three coil sets each including two coils  103  to which electric currents of the same amplitude are applied in different directions from each other are the coils  103   b   1  and  103   b   4 , the coils  103   b   2  and  103   b   5 , and the coils  103   b   3  and  103   b   6 . 
       FIG. 3B  illustrates the coil unit  103 R viewed from the positive Y direction. Each arrow in the permanent magnets  203  schematically indicates a magnetization direction in the permanent magnets  203 . 
       FIG. 3C  is a thrust constant profile schematically illustrating the magnitudes of a force Fx in the X-direction, a force Fy in the Y-direction, and a force Fz in the Z-direction that are generated when a unit electric current is applied to the coils  103  of the coil unit  103 R. 
     A distance to the origin Om, which is a reference position of the movable element  101 , viewed from the reference position Of of the stator  201  is denoted by X. 
     In response to an electric current applied to the coils  103   a   1 R to  103   a   3 R and  103   c   1 R to  103   c   3 R, forces are generated mainly in the X- and Z-directions. A force generated in the Y-direction is small enough to be ignored. 
     In response to an electric current applied to the coils  103   b   1 R and  103   b   4 R, the coils  103   b   2 R and  103   b   5 R, and the coils  103   b   3 R and  103   b   6 R, forces are generated mainly in the Y-direction as illustrated in  FIG. 6 . Forces are also generated slightly in the-X and Z-directions but are small enough to be ignored. 
     In  FIGS. 3A and 3C , for example, Fx(a 1 R, x) schematically indicates the magnitude of a force in the X-direction that is generated in response to a unit electric current applied to the coil  103   a   1 R in a case where the position of the movable element  101  in the X-direction is a position x. The first and second parameters in the parentheses of Fx are a coil index and the position of the movable element  101  in the X-direction, respectively. 
     Similarly, in  FIGS. 3B and 3C , Fz(a 3 R, x) indicates the magnitude of a force in the Z-direction that is generated in response to a unit electric current applied to the coil  103   a   3 R in a case where the position of the movable element  101  in the X-direction is the position x. 
     Similarly, in  FIGS. 3A and 3C , Fy(b 1 R⋅b 4 R, X) indicates the magnitude of a force in the Y-direction that is generated in response to a unit electric current applied to the coils  103   b   1 R and  103   b   4 R in a case where the position of the movable element  101  in the X-direction is the position x. 
     Desirably, in regard to the sizes of the permanent magnets  203  and the coils  103 , the size of three coils  103  matches with the size of two permanent magnets  203 . The same applies to the coil unit  103 L. 
     Next, a control system that controls the conveyance system  1  according to the present exemplary embodiment will be described below with reference to  FIG. 4A .  FIG. 4A  is a schematic view illustrating a control system that controls the conveyance system  1  according to the present exemplary embodiment. 
     As illustrated in  FIG. 4A , the control system includes the integrated controller  301  and the movable element controller  302  and functions as a control apparatus that controls the conveyance system  1  including the movable element  101  and the stator  201 . 
     The coil  103 , the encoder  111 , the Y-sensor  112 , and the Z-sensor  113  are connected to the movable element controller  302  to communicate with each other. The movable element controller  302  is connected to the integrated controller  301  via the cable  130  and receives a conveyance instruction and power supply from the integrated controller  301 . The movable element controller  302  controls the amount of electric current of each connected coil  103  individually. 
     The movable element controller  302  calculates the position and orientation of the movable element  101  based on outputs from the encoder  111 , the Y-sensor  112 , and the Z-sensor  113 . 
     Further, the movable element controller  302  determines an electric current instruction value to be applied to the plurality of coils  103  based on the position of the movable element  101  and changes in the position. 
     As described above, the integrated controller  301  and the movable element controller  302  function as a control apparatus, convey the movable element  101  along the stator  201  without physical contact, and control the orientation of the movable element  101  to be conveyed in six axes. 
     A method of detecting an X-coordinate of the position of the movable element  101  will be described below with reference to  FIG. 2 . 
     In  FIG. 2 , the encoder  111  on the movable element  101  reads the pattern of the scale  211  on the stator  201  and acquires the X-coordinate of the movable element  101  in the conveyance direction. 
     The encoder  111  and the scale  211  can be of an absolute position detection type or a combination of an incremental encoder and an appropriate reset signal. 
     A method of detecting a Y-coordinate of the position of the movable element  101  will be described below with reference to  FIGS. 1 and 2 . 
     The Y-sensor  112  is a sensor that detects the distance between the Y-sensor  112  and the Y-target  212 . The Y-target  212  is disposed continuously along the conveyance path. 
     Detection values of the movable element  101  that are detected by the Y-sensors  112   b R and  112   f R are respectively denoted by Y 112   b R and Y 112   f R. 
     In a case where the coordinates of the Y-sensors  112   b R and  112   f R are expressed as (a2, b) and (−a2, b), respectively, a Y-position of the movable element  101  and the rotation amount Wz about the Z-axis are calculated by the following formulas 1a and 1b: 
         Y =( Y 112 bR+Y 112 fR )/2  (1a), and
 
         Wz =( Y 112 bR−Y 112 fR )/(2* a 2)  (1b).
 
     A method of detecting a Z-position of the movable element  101  will be described below with reference to  FIGS. 1A and 2 . 
     The Z-sensor  113  is a sensor that detects the distance between the Z-sensor  113  and the Z-target  213 . The Z-target  213  is disposed continuously along the conveyance path. 
     The Z-sensor  113  is provided at three or more positions on the movable element  101 . 
     For example, the XY coordinates of the positions  113   b L,  113   f L, and  113   c R of the Z-sensors  113  at the three positions as illustrated in  FIG. 1A  are respectively expressed as (−a, −b), (a, −b), and (0, b). An orientation and Z-position Z of the movable element  101 , the rotation amount Wy about the Y-axis, and the rotation amount Wx about the X-axis are calculated by the following formulas 1c, 1d, and 1e: 
         Z =( Z 113 bL+Z 113 fL+Z 113 cR )/3  (1c),
 
         Wx =( Z 113 cR −( Z 113 bL+Z 113 fL )/2)/(2* b )  (1d), and
 
         Wy =( Z 113 bL−Z 113 fL )/(2* a )  (1e),
 
     where Z 113   b L, Z 113   f L, and Z 113   c R are detection values of the Z-sensors  113 , respectively. 
     Next, a method of controlling the orientation of the movable element  101  by the movable element controller  302  will be described below with reference to  FIG. 5 .  FIG. 5  schematically illustrates a control loop for calculating the magnitude of a force to be applied to the movable element  101 . 
     A target value ref is a target value of the orientation of the movable element  101  that is specified by the integrated controller  301 , and a current position pos is orientation information about the movable element  101  that is acquired from the Y- and Z-sensors  112  and  113 . An orientation controller  501  calculates a torque T to be applied to the movable element  101  based on a difference err between the target value ref and the current position pos. 
     An electric current I to be applied to the coil unit  103  is determined based on the calculated torque T, and in response to output of a desired electric current, the output acts as a force F on the movable element  101  and is eventually detected as a current position pos. 
     The orientation controller  501  can be, for example, a proportional-integral-derivative (PID) controller. Alternatively, a filter can be placed as needed in accordance with a characteristic of the movable element  101  to stabilize the orientation of the movable element  101 . 
     A torque T to be applied to the movable element  101  is expressed by formula 2 below. Components Tx, Ty, and Tz are three-axis components of the torque T and are an X-direction component, a Y-direction component, and a Z-direction component of the torque T, respectively. Further, components Twx, Twy, and Twz are three-axis components of a moment and are a component of the moment about the X-axis, a component of the moment about the Y-axis, and a component of the moment about the Z-axis, respectively. By controlling the six-axis components Tx, Ty, Tz, Twx, Twy, and Twz of the torque T, the conveyance system  1  according to the present exemplary embodiment controls conveyance of the movable element  101  while controlling the orientation of the movable element  101  in six axes. 
         T =( Tx,Ty,Tz,Twx,Twy,Twz )  (2).
 
     First, a general formula to be satisfied by a desired torque T will be specified. 
     A coil number index of the six coils  103  and the three sets of two coils  103  on the right side of the movable element  101  will be denoted by j. The coil number index is, for example,  103   a   1 R,  103   a   2 R,  103   a   3 R,  103   b   1 ⋅ 4 R,  103   b   2 ⋅ 5 R,  103   b   3 ⋅ 6 R,  103   c   1 R,  103   c   2 R, and  103   c   3 R. 
     Further, coil number indexes  103   a   1 L,  103   a   2 L,  103   a   3 L,  103   b   1 ⋅ 4 L,  103   b   2 ⋅ 5 L,  103   b   3 ⋅ 6 L,  103   c   1 L,  103   c   2 L, and  103   c   3 L of the six coils  103  and the three sets of two coils  103  on the left side of the movable element  101  will also be denoted by j. 
         Tx=ΣIj*Fx ( j,x )  (3a),
 
         Ty=ΣIj*Fy ( j,x )  (3b),
 
         Tz=ΣIj*Fz ( j,x )  (3c),
 
         Twx=−Σj*Fz ( j,x )* Yj   (3d),
 
         Twy=ΣIj*Fz ( j,x )* Xj   (3e), and
 
         Twz=ΣIj*Fx ( j,x )* Yj−/Ij*Fy ( j,x )* Xj   (3f),
 
     where Ij is the magnitude of an electric current to be applied to the jth coil, (Xj, Yj) are the coordinates of the jth coil, and Σ is a sum in a case where j is changed from 1 to 18. 
     Thus, in a case where an electric current value Ij that satisfies formulas 3a to 3f is determined, a desired torque T is applied. 
     The above-described electric current value Ij has eighteen degrees of freedom (the six coils  103  and the two sets (R- and L-sides) of the three sets of two coils  103 ) whereas the torque T has six degrees of freedom, so that there are numerous solutions of the electric current value Ij. Thus, an appropriate constraint condition is set to obtain a solution of the electric current value Ij. 
     Next, a method of uniquely determining the coil electric current value Ij will be described below. In expressions of forces described below, forces that respectively act in the X-, Y-, and Z-directions are denoted by x, y, and z, respectively, and the R-side on the positive Y-side, the negative Y-side, a positive X side, a negative X-side, and a center in  FIG. 1A  are denoted by R, L, F, b, and c, respectively. 
     In  FIG. 1A , force vectors F that act on the coils  103  on the R- and L-sides, respectively, are expressed as follows. Each force F that acts on the corresponding coil  103  is an electromagnetic force generated between the permanent magnets  203  and the plurality of coils  103  to which an electric current is applied. The permanent magnets  203  and the plurality of coils  103  to which the electric current is applied generate an electromagnetic force in the X-direction, which is the conveyance direction of the movable element  101 , as well as electromagnetic forces in the Y- and Z-directions different from the X-direction. 
     The forces F generated from the coils  103  in  FIGS. 1A and 3A  are as follows: 
     FxbL: a force in the X-direction that is generated from the coils  103   a   1 L,  103   a   2 L, and  103   a   3 L,
 
FzbL: a force in the Z-direction that is generated from the coils  103   a   1 L,  103   a   2 L, and  103   a   3 L,
 
FycL: a force in the Y-direction that is generated from the coils  103   b   1 ⋅ 4 L (coils  103   b   1 L and  103   b   4 L),  103   b   2 ⋅ 5 L (coils  103   b   2 L and  103   b   5 L), and  103   b   3 ⋅ 6 L (coils  103   b   3 L and  103   b   3 L),
 
FxfL: a force in the X-direction that is generated from the coils  103   c   1 L,  103   c   2 L, and  103   c   3 L,
 
FzfL: a force in the Z-direction that is generated from the coils  103   c   1 L,  103   c   2 L, and  103   c   3 L,
 
FxbR: a force in the X-direction that is generated from the coils  103   a   1 R,  103   a   2 R, and  103   a   3 R,
 
FzbR: a force in the Z-direction that is generated from the coils  103   a   1 R,  103   a   2 R, and  103   a   3 R,
 
FycR: a force in the Y-direction that is generated from the coils  103   b   1 ⋅ 4 R (coils  103   b   1 R and  103   b   4 R),  103   b   2 ⋅ 5 R (coils R 103   b   2 R and  103   b   5 R), and  103   b   3 ⋅ 6 R (coils  103   b   3 R and  103   b   6 R),
 
FxfR: a force in the X-direction that is generated from the coils  103   c   1 R,  103   c   2 R, and  103   c   3 R, and
 
FzfR: a force in the Z-direction that is generated from the coils  103   c   1 R,  103   c   2 R, and  103   c   3 R.
 
A force F is defined as
 
         F =( FxbL,FzbL,FycL,FxfL,FzfL,FxbR,FzbR,FycR,FxfR,FzfR ). 
     The f torques T (Tx, Ty, Tz, Twx, Twy, Twz) are respectively calculated by the following formulas 4a, 4b, 4c, 4d, 4e, and 4f: 
         Tx=FxfR+FxbR+FxfL+FxbL   (4a),
 
         Ty=FycL+FycR   (4b),
 
         Tz=FzbR+FzbL+FzfR+FzfL   (4c),
 
         Twx ={( FzfL+FzbL )−( FzfR+FzbR )}*2* rx 3  (4d),
 
         Twy ={( FzfL+FzfR )−( FzbL+FzbR )}*2* ry 3  (4e), and
 
         Twz ={( FxfL+FxbL )−( FxfR+FxbR )}*2* rx 3  (4f).
 
     Since the force F has ten degrees of freedom, in order to calculate the force F from the torque T having six degrees of freedom, four constraints are further introduced. 
     In order to equally distribute the forces F that act on the same axis, constraints of the following three formulas are introduced: 
         FxfR=FxbR   (4g),
 
         FxfL=FxbL   (4h), and
 
         FycL=FycR   (4i).
 
     Further, in order to equally distribute rotation forces about the Y-axis to the L- and R-sides, the following constraint is introduced: 
         FzfR−FzbR=FzfL−FzbL   (4j).
 
     Once the torque T is determined from the ten formulas 4a to 4j, the force F is determined. 
     Up to this point, ten force vectors F are uniquely determined. 
     A method of uniquely determining an electric current value of the coils  103  from this point will be described below. 
     FxbL and FzbL are expressed as follows using electric current values Ia 1 L, Ia 2 L, and Ia 3 L of the coils  103   a   1 L,  103   a   2 L, and  103   a   3 L and the magnitudes of the thrust constant profile: 
         FxbL=Fx ( a 1 L,x )* IL 1+ Fx ( a 2 L,x )* Ia 1 L+Fx ( a 3 L,x )* Ia 3 L   (5a), and
 
         FzbL=Fz ( a 1 L,x )* Ia 1 L+Fz ( a 2 L,x )* Ia 2 L+Fz ( a 3 L,x )* Ia 3 L   (5b).
 
     Then, the following constraint 
         Ia 1 L+Ia 2 L+Ia 3 L= 0  (5c)
 
     is introduced, and therefore three independent conditions are acquired with respect to the unknown numbers Ia 1 L, Ia 2 L, and Ia 3 L, so that the electric current values Ia 1 L, Ia 2 L, and Ia 3 L are uniquely determined. 
     By a similar method, electric current values Ic 1 L, Ic 2 L, and Ic 3 L are determined from FxfL and FzfL: 
         FxfL=Fx ( c 1 L,x )* Ic 1 L+Fx ( c 2 L,x )* Ic 2 L+Fx ( c 3 L,x )* Ic 3 L   (6a),
 
         FzbL=Fz ( c 1 L,x )* Ic 1 L+Fz ( c 2 L,x )* Ic 2 L+Fz ( c 3 L,x )* Ic 3 L   (6b), and
 
         Ic 1 L+Ic 2 L+Ic 3 L= 0  (6c).
 
     By a similar method, electric current values Ia 1 R, Ia 2 R, and Ia 3 R are determined from FxbR and FzbR: 
         FxbR=Fx ( a 1 R,x )* Ia 1 R+Fx ( a 2 R,x )* Ia 2 R+Fx ( a 3 R,x )* Ia 3 R   (7a),
 
         FzbR=Fz ( a 1 R,x )* Ia 1 R+Fz ( a 2 R,x )* Ia 2 R+Fz ( a 3 R,x )* Ia 3 R   (7b),
 
       and 
         Ia 1 R+Ia 2 R+Ia 3 R= 0  (7c).
 
     By a similar method, electric current values Ic 1 R, Ic 2 R, and Ic 3 R are determined from FxfR and FzfR: 
         FxfR=Fx ( c 1 R,x )* Ic 1 R+Fx ( c 2 R,x )* Ic 2 R+Fx ( c 3 R,x )* Ic 3 R   (8a),
 
         FzbR=Fz ( c 1 R,x )* Ic 1 R+Fz ( c 2 R,x )* Ic 2 R+Fz ( c 3 R,x )* Ic 3 R   (8b),
 
       and 
         Ic 1 R+Ic 2 R+Ic 3 R= 0  (8c).
 
     Next, a method of determining electric current values I(b 1 ⋅ 4 L), I(b 2 ⋅ 5 L), I(b 3 ⋅ 6 L), I(b 1 ⋅ 4 R), I(b 2 ⋅ 5 R), and I(b 3 ⋅ 6 R) from FycL and FycR will be described below. 
     The electric current values I(b 1 ⋅ 4 L), I(b 2 ⋅ 5 L), and I(b 3 ⋅ 6 L) are uniquely determined from, in addition to 
         FycL=Fy (( b 1⋅4 L ), x )* I ( b 1⋅4 L )+ Fy (( b 2⋅5 L ), x )* I ( b 2⋅5 L )+ Fy (( b 3⋅6 L ), x )* I ( b 3⋅6 L )  (9a),
 
         I ( b 1⋅4 L )+ I ( b 2⋅5 L )+ I ( b 3⋅6 L )=0  (9b), and
 
         I ( b 1⋅4 L ): I ( b 2⋅5 L ): I ( b 3⋅6 L )= Fy (( b 1.3 L ), x ): Fy (( b 2⋅5 L ), x ): Fy (( b 3⋅6 L ), x ),
 
       i.e., 
         I ( b 3⋅6 L )* Fy (( b 1⋅4 L ), x )= I ( b 2⋅5 L )* Fy (( b 2⋅5 L ), x )= I ( b 1⋅4 L )* Fy (( b 3⋅6 L ), x )   (9c).
 
     Similarly, electric current values I(b 1 ⋅ 4 R), I(b 2 ⋅ 5 R), and I(b 3 ⋅ 6 R) are uniquely determined from, in addition to 
         FycR=Fy (( b 1⋅4 R ), x )* I ( b 1⋅4 R )+ Fy (( b 2⋅5 R ), x )* I ( b 2⋅5 R )+ Fy (( b 3⋅6 R ), x )* I ( b 3⋅6 R )  (9d),
 
         I ( b 1⋅4 R )+ I ( b 2⋅5 R )+ I ( b 3⋅6 R )=0  (9e), and
 
         I ( b 1⋅4 R ): I ( b 2⋅5 R ): I ( b 3⋅6 R )= Fy (( b 1⋅4 R ), x ): Fy (( b 2⋅5 R ), x ): Fy (( b 3⋅6 R ), x ),
 
       i.e., 
         I ( b 3⋅6 R )* Fy (( b 1⋅4 R ), x )= I ( b 2⋅5 R )* Fy (( b 2⋅5 R ), x )= I ( b 1⋅4 R )* Fy (( b 3⋅6 R ), x )  (9f).
 
     By controlling the electric currents to be applied to the plurality of coils  103  as described above, the movable element controller  302  controls each of the six-axis components of the force to be applied to the movable element  101 . 
     By determining and controlling the electric current instruction values of the electric currents to be applied to the plurality of coils  103  as described above, the movable element controller  302  controls contactless conveyance of the movable element  101  on the stator  201  while controlling the orientation of the movable element  101  on the stator  201  in six axes. Specifically, the movable element controller  302  functions as a conveyance control unit that controls conveyance of the movable element  101 , and controls contactless conveyance of the movable element  101  on the stator  201  by controlling the electromagnetic forces that the permanent magnets  203  receive from the plurality of coils  103 . Further, the movable element controller  302  functions as an orientation control unit that controls the orientation of the movable element  101 , and controls the orientation of the movable element  101  on the stator  201  in six axes. 
     As described above, according to the present exemplary embodiment, the plurality of coils  103  in two rows applies a six-axis force of the three-axis force components Tx, Ty, and Tz and the three-axis moment components Twx, Twy, and Twz to the movable element  101 . In this way, conveyance of the movable element  101  is controlled while the orientation of the movable element  101  is controlled in six axes. According to the present exemplary embodiment, by using the coils  103  in two rows, which is less than the number of six-axis components of the force that are variable numbers to be controlled, conveyance of the movable element  101  can be controlled while the orientation of the movable element  101  is controlled in six axes. 
     Thus, according to the present exemplary embodiment, since the number of rows of coils  103  is reduced contactless conveyance of the movable element  101  of which orientation of the movable element  101  is controlled can be realized without an increase in system size or complication of the system. Furthermore, according to the present exemplary embodiment, since the number of rows of coils  103  is reduced, a downsized and inexpensive magnetic levitation type conveyance system can be realized. 
     While the permanent magnets  203  are disposed in the stator  201  in the present exemplary embodiment, not a permanent magnet but a soft magnetic material can be used, and an electric current is applied to the coils  103  of the movable element  101  to generate a force between the soft magnetic material of the stator  201  and the coils  103  of the movable element  101 . This realizes contactless conveyance or rotation of the movable element  101  by a simple structure while the orientation of the movable element  101  is controlled. In the present specification, a hard magnetic material, such as a permanent magnet, or a soft magnetic material are referred to as “magnetic body”. 
     Second Exemplary Embodiment 
     A second exemplary embodiment will be described below with reference to  FIG. 4B .  FIG. 4B  is a schematic view illustrating a control system that controls the conveyance system  1  according to the present exemplary embodiment. A component that is the same as or similar to a component in the first exemplary embodiment is given the same reference numeral, and redundant descriptions of the component are omitted or simplified. 
     A basic structure of the movable element  101  according to the present exemplary embodiment is substantially the same as that in the first exemplary embodiment. In the first exemplary embodiment, the movable element controller  302  and the integrated controller  301  are connected via the cable  130 . 
     The movable element controller  302  according to the present exemplary embodiment receives conveyance instructions wirelessly from the integrated controller  301 . 
     In  FIG. 4B , a wireless unit  601  of the stator  201 , a wireless unit  602  of the movable element  101 , and a battery  603  are added in place of the cable  130  in  FIG. 4A . The wireless units  601  and  602  are desirably a 5G wireless unit because the latency is low. 
     According to the present exemplary embodiment, since the movable element  101  is cableless, a more precise contactless state is realized. Thus, the present exemplary embodiment is suitable for a deposition apparatus that moves in a high vacuum. [Modified Examples] 
     The present disclosure is not limited to the above-described exemplary embodiments, and various modifications can be made. 
     For example, in a case of a use in a vacuum environment or underwater environment, organic substances may be released or leak from a plastic member used around the coils  103  or in a core material. Similarly, an adhesive for insulation may partially leak or deteriorate. 
     Thus, especially in an environment without much dust, such as a vacuum environment, underwater environment, or a clean room, it is desirable to cover the coils  103  and parts near the coils  103  with a component for insulation from an ambient environment. 
     While there are various insulation methods, it is suitable to cover a single or plurality of coils with a metal box and fill the inside with gas. 
     Further, in order to exhaust and release heat generated by the coils  103  to the outside, the gas is desirably a gas with high thermal conductivity. For example, helium gas is desirable, or hydrogen gas can be used. 
     Nitrogen gas, carbon dioxide gas, and atmosphere are also adequate enough to protect the parts near the coils  103 . 
     Further, a coil array including a plurality of coil box units each including a single or plurality of coils that is collectively arranged and disposed in box shape can be employed. 
     While, in the exemplary embodiment, only the electromagnetic forces are used as a levitation force that the coils  103  receive from the permanent magnets  203  to levitate the movable element  101 , the present disclosure is not limited to those described above. For example, in a case where the mass of the movable element  101  or the mass of the work  102  held on the upper surface  101   a  or the lower surface  101   c  of the movable element  101  is so large that a great levitation force is to be applied in the vertical direction, a static pressure generated by a fluid, such as air, can additionally be used for levitation to supplement the levitation force. 
     While, in the present exemplary embodiment, the first coil group  103  is disposed in two rows, the present disclosure is not limited to those described above. For example, the first coil group  103  can be disposed in three, four, or five rows. The present disclosure realizes six-axis control of the orientation of the movable element  101  using a smaller number of rows of coils  103  than the number of variable numbers, i.e., six, in the six-axis control of the orientation of the movable element  101 . 
     A conveyance system according to an exemplary embodiment of the present disclosure can be used as a conveyance system that conveys a work together with a movable element to a working area of processing apparatuses, such as machine tools, that perform processing on the work to be processed into an article, in a system of manufacturing an article such as an electronic device. The processing apparatuses that perform processing can be any apparatuses such as an apparatus that assembles parts and a work, a coating apparatus, and a deposition apparatus. An article to be manufactured is not limited to a particular article and can be any parts. 
     As described above, an article is manufactured by conveying a work to the working area using the conveyance system according to the exemplary embodiment of the present disclosure and processing the work conveyed to the working area. With the conveyance system according to the exemplary embodiment of the present disclosure, an increase in system size and complication of the system are avoided as described above. Thus, in the system of manufacturing an article using the conveyance system according to the exemplary embodiment of the present disclosure in conveying a work, the apparatuses that perform processing are arranged with a high degree of freedom without an increase in system size or complication of the system. 
     Other Embodiments 
     Embodiment(s) of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may include one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-221444, filed Dec. 6, 2019, which is hereby incorporated by reference herein in its entirety.