Patent Publication Number: US-2022224255-A1

Title: Transport system, processing system, and article manufacturing method

Description:
BACKGROUND 
     Field 
     The present disclosure relates to a transport system, a processing system, and a method of manufacturing an article. 
     Description of the Related Art 
     In general, a transport system is used in a production line used for assembling industry products, a semiconductor exposure apparatus, or the like. In particular, a transport system in a production line transports workpieces such as components by a plurality of movers between a plurality of stations within a factory-automated production line or between factory-automated production lines. Further, such a transport system may be used as a transport apparatus within a process apparatus. As transport systems, a transport system using a linear motor and a magnetic levitation transport system have already been proposed. 
     In these transport systems, a plurality of movers transport workpieces such as components, and each of the movers has movement machine difference, which is a position error at the time of its movement due to a machining error or an assembly error of the reading surface of the sensor. 
     Accordingly, Japanese Patent No. 5753060 discloses a method of controlling the current flow of electromagnets so as to stop a carriage at a target stop position by using data for correcting the position of each carriage, which is determined based on a movement machine difference of each carriage, which is measured in advance using a common measuring jig, in a transport system using a linear motor. 
     SUMMARY 
     According to an aspect of the present disclosure, a transport system includes a mover configured to be movable in a first direction, a stator having a plurality of coils arranged in the first direction and configured to apply force to transport the mover in the first direction while using a plurality of coils, to which current is applied, to levitate the mover in a second direction intersecting the first direction, and a control unit configured to control the current applied to the plurality of coils to control operation of the mover, wherein the control unit is configured to control the current applied to the plurality of coils using machine difference information of the mover to control an attitude of the mover while the mover is being levitated. 
     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. 1  is a schematic diagram illustrating a configuration of a transport system according to a first embodiment of the present disclosure. 
         FIG. 2  is a schematic diagram illustrating the configuration of the transport system according to the first embodiment of the present disclosure. 
         FIG. 3  is a schematic diagram illustrating a coil and coil related configuration in the transport system according to the first embodiment of the present disclosure. 
         FIG. 4  is a schematic diagram illustrating a control system for controlling the transport system according to the first embodiment of the present disclosure. 
         FIG. 5A  is a schematic diagram illustrating a method of acquiring a correction value for correcting a movement machine difference of a mover in the transport system according to the first embodiment of the present disclosure. 
         FIG. 5B  is a schematic diagram illustrating the method of acquiring the correction value for correcting the movement machine difference in the transport system according to the first embodiment of the present disclosure. 
         FIG. 6  is a schematic diagram illustrating an example of data acquired in the method of acquiring the correction value for correcting the movement machine difference of the mover in the first embodiment transport system of the present disclosure. 
         FIG. 7  is a schematic diagram illustrating an attitude control method of the mover in the transport system according to the first embodiment of the present disclosure. 
         FIG. 8  is a schematic diagram illustrating an example of a control block used for controlling the position and the attitude of the mover in the transport system according to the first embodiment of the present disclosure. 
         FIG. 9A  is a schematic diagram illustrating processing by a mover position calculation function in the transport system according to the first embodiment of the present disclosure. 
         FIG. 9B  is a schematic diagram illustrating the processing by the mover position calculation function in the transport system according to the first embodiment of the present disclosure. 
         FIG. 10  is a schematic diagram illustrating processing by a mover attitude calculation function in the transport system according to the first embodiment of the present disclosure. 
         FIG. 11A  is a schematic diagram illustrating the processing by the mover attitude calculation function in the transport system according to the first embodiment of the present disclosure. 
         FIG. 11B  is a schematic diagram illustrating the processing by the mover attitude calculation function in the transport system according to the first embodiment of the present disclosure. 
         FIG. 12  is a schematic diagram illustrating a relationship between a force acting on a yoke plate attached to the mover and a force component and a torque component acting on the mover in the transport system according to the first embodiment of the present disclosure. 
         FIG. 13  is a graph schematically illustrating a thrust constant profile in the Z-direction in the transport system according to the first embodiment of the present disclosure. 
         FIG. 14A  is a schematic diagram illustrating a stator coil in the transport system according to the first embodiment of the present disclosure. 
         FIG. 14B  is a schematic diagram illustrating the stator coil in the transport system according to the first embodiment of the present disclosure. 
         FIG. 15  is a graph schematically illustrating a relationship between the amount of current applied to the coil and the magnitude of an attractive force acting between the coil and the yoke plate in the transport system according to the first embodiment of the present disclosure. 
         FIG. 16  is a schematic diagram of the mover viewed from top to bottom along the Z-direction in the transport system according to the first embodiment of the present disclosure. 
         FIG. 17  is a graph schematically illustrating an attractive force profile in the Y-direction in the transport system according to the first embodiment of the present disclosure. 
         FIG. 18A  is a schematic diagram illustrating a method for acquiring machine difference in a position of a mover in the X direction over the entire linear scale in a transport system according to a second embodiment of the present disclosure. 
         FIG. 18B  is a schematic diagram illustrating the method for acquiring the machine difference in the position of the mover in the X direction over the entire linear scale in the transport system according to the second embodiment of the present disclosure. 
         FIG. 19  is a graph showing difference between a laser interferometer measurement and a linear encoder measurement when the mover is slid to be moved in the X direction on a plurality of Z-axis rollers in the transport system according to the second embodiment of the present disclosure. 
         FIG. 20  is a schematic diagram illustrating an example of a control block for controlling the position and attitude of a mover in a transport system according to a third embodiment of the present disclosure. 
         FIG. 21A  is a schematic diagram illustrating a method of measuring the weight of a mover in a transport system according to a fourth embodiment of the present disclosure. 
         FIG. 21B  is a schematic diagram illustrating the method of measuring the weight of the mover in the transport system according to the fourth embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present disclosure will be described below with reference to  FIG. 1  to  FIG. 17 . 
     First, a configuration of a transport system  1  according to the present embodiment will be described with reference to  FIG. 1  to  FIG. 3 .  FIG. 1  and  FIG. 2  are schematic diagrams illustrating the configuration of the transport system  1  including movers  101  and stators  201  according to the present embodiment. Note that  FIG. 1  and  FIG. 2  are views of extracted main portions of each mover  101  and each stator  201 , respectively. Further,  FIG. 1  is a diagram of the mover  101  when viewed from a diagonally upper side, and  FIG. 2  is a diagram of the mover  101  and the stator  201  when viewed from the X direction described later.  FIG. 3  is a schematic diagram illustrating coils  202 ,  207 , and  208  and a configuration related to the coils  202 ,  207 , and  208  in the transport system  1 . 
     As illustrated in  FIG. 1  and  FIG. 2 , the transport system  1  according to the present embodiment has the mover  101  forming a carrier, a carriage, or a slider and the stator  201  forming a transport path. Further, the transport system  1  has an integration controller  301 , coil controllers  302 , coil unit controllers  303 , and a sensor controller  304 . Note that  FIG. 1  illustrates three movers  101   a ,  101   b , and  101   c  as the mover  101  and two stators  201   a  and  201   b  as the stator  201 . In the following description, a reference including only the numeral common to others is used when it is not particularly required to distinguish components that may be present as multiple components, such as the mover  101  and the stator  201 , and a lowercase alphabet is appended to a numeral reference to distinguish the individuals if necessary. Further, when a component of the mover  101  on the R side and a component on the L side of the mover  101  are distinguished from each other, “R” indicating the R side or “L” indicating the L side is appended to the lowercase alphabet. 
     The transport system  1  according to the present embodiment is a transport system with an inductive type linear motor that generates electromagnetic force between the coil  207  of the stator  201  and a conductive plate  107  of the mover  101  and applies the thrust in the X direction to the mover  101 . Further, the transport system  1  according to the present embodiment is a magnetic levitation type transport system that causes the mover  101  to levitate and transports the mover  101  in a contactless manner. The transport system  1  according to the present embodiment forms a part of a processing system having a process apparatus together that performs processing on a workpiece  102  transported by the mover  101 . 
     The transport system  1  transports the workpiece  102  held by the mover  101  to a process apparatus that performs a processing operation on the workpiece  102  by transporting the mover  101  by the stator  201 , for example. The process apparatus is not particularly limited and may be, for example, a film forming apparatus such as a vapor deposition apparatus, a sputtering apparatus, or the like to form a film on a glass substrate that is the workpiece  102 . Note that, although  FIG. 1  illustrates three movers  101  for two stators  201 , the number is not limited thereto. In the transport system  1 , one or a plurality of movers  101  may be transported on one or a plurality of stators  201 . 
     Herein, coordinate axes, directions, and the like used in the following description are defined. First, the X-axis is taken along the horizontal direction that is the transport direction of the mover  101 , and the transport direction of the mover  101  is defined as the X direction. Further, a Z-axis is taken along the perpendicular direction that is a direction orthogonal to the X direction, and the perpendicular direction is defined as a Z direction. The perpendicular direction corresponds to a direction of the gravity (mg direction). Further, a Y-axis is taken is taken along a direction orthogonal to the X direction and the Z direction, and the direction orthogonal to the X direction and the Z direction is defined as a Y direction. Furthermore, a rotation direction around the X-axis is defined as a Wx direction, a rotation direction around the Y-axis is defined as a Wy direction, and a rotation direction around the Z-axis is defined as a Wz direction. Further, “*” is used as a multiplication symbol. Further, the center of the mover  101  is defined as origin Oc, the Y+ side is denoted as R side, and the Y− side is denoted as L side. Note that, although the transport direction of the mover  101  is not necessarily required to be a horizontal direction, the Y direction and the Z direction can be similarly defined also in such a case with the transport direction being defined as the X direction. Note that the X direction, the Y direction, and the Z direction are not necessarily limited to directions orthogonal to each other and can be defined as directions intersecting each other. Further, the displacement in the transport direction is defined as the position, the displacement in other directions as the attitude, and the position and the attitude are together defined as the state. 
     Further, symbols used in the following description are as follows. Note that each symbol is used for respective cases of the coils  202 ,  207 , and  208  in a duplicated manner. 
     Oc: the origin of the mover  101   
     Os: the origin of the linear scale  104   
     Oe: the origin of stator  201   
     j: index for identifying a coil 
     (Note that j is an integer satisfying 1≤j≤N, where N is an integer greater than or equal to two.) 
     N: the number of installed coils 
     Ij: current amount applied to the j-th coil 
     P: state including the position and the attitude of the mover  101  (X, Y, Z, Wx, Wy, Wz) 
     X(j, P): X-coordinate of the j-th coil when viewed from the center of the mover  101  in a state P 
     Y(j, P): Y-coordinate of the j-th coil when viewed from the center of the mover  101  in a state P 
     Z(j, P): Z-coordinate of the j-th coil when viewed from the center of the mover  101  in a state P 
     T: force applied to mover  101   
     Tx: force component in the X direction of force T 
     Ty: force component in the Y direction of force T 
     Tz: force component in the Z direction of force T 
     Twx: torque component in the Wx direction of force T 
     Twy: torque component in the Wy direction of force T 
     Twz: torque component in the Wz direction of force T 
     Ex(j, P): force in the X direction working on the mover  101  in the state P when unit current is applied to the j-th coil 
     Ey(j, P): force in the Y direction working on the mover  101  in the state P when unit current is applied to the j-th coil 
     Ez(j, P): force in the Z direction working on the mover  101  in the state P when unit current is applied to the j-th coil 
     Σ: sum when index j is changed from  1  to N 
     *: product of matrix or vector 
     M: torque contribution matrix 
     K: pseudo-current vector (column vector) 
     Tq: torque vector (column vector) 
     Is: coil current vector (column vector) 
     Fs: coil force vector (column vector) 
     M(a, b): element on the a-th row and on the b-th column of the matrix M 
     Inv( ) inverse matrix 
     Tr( ) transpose matrix 
     Tr(element  1 , element  2 , . . . ): column vector whose elements are element  1 , element  2 , . . . 
     As indicated by arrows in  FIG. 1 , the mover  101  is configured to be movable in the X direction that is the transport direction. The mover  101  has yoke plates  103  and a conductive plate  107 . Further, the mover  101  has a linear scale  104 , a Y-target  105 , and Z-targets  106 . The mover  101  further includes an RFID (Radio Frequency Identification) tag  512 , which is an information medium in which identification information for identifying each mover  101  is registered. 
     A plurality of yoke plates  103  are attached and installed on a plurality of portions of the mover  101 . Specifically, the yoke plates  103  are attached and installed along the X direction at respective ends on the R side and the L side on the top face of the mover  101 . Further, the yoke plates  103  are attached and installed along the X direction at respective side faces on the R side and the L side of the mover  101 . Each yoke plate  103  is an iron plate made of a substance having a large magnetic permeability, for example, iron. 
     The conductive plate  107  is attached and installed along the X direction at the center part on the top face of the mover  101 . The conductive plate  107  is not particularly limited as long as it has conductivity, such as a conductive metal plate, and an aluminum plate or the like having a small electric resistance is preferable. 
     Note that the installation places of yoke plates  103  and conductive plate  107  and the number thereof are not limited to the example described above and may be changed as appropriate. 
     The linear scale  104 , the Y-target  105 , and the Z-target  106  are attached and installed in the mover  101  at positions that can be read by the linear encoder  204 , the Y-sensor  205 , and the Z-sensor  206  installed on the stator  201 , respectively. 
     The RFID tag  512  is attached to the mover  101  to be installed in the mover  101  at a position readable by a RFID reader  513 . The RFID reader  513  is installed at a specific position of a transport path of the mover  101  in the transport system  1 . An individual ID (Identification) as identification information is registered in the RFID tag  512  so as to identify the mover  101  to which the RFID tag  512  is attached. Instead of the RFID tag  512 , the mover  101  may be provided with an information medium such as a QR code (registered trademark) indicating an individual ID of the mover  101 . In this case, instead of the RFID reader  513 , a reader such as a scanner that reads the individual ID from the information medium can be used according to the information medium. 
     The stator  201  has the coils  202 ,  207 , and  208 , the linear encoder  204 , the Y-sensor  205 , and the Z-sensor  206 . 
     A plurality of coils  202  are attached and installed along the X direction on the stator  201  so as to be able to face, along the Z direction, the yoke plate  103  installed on the top face of the mover  101 . Specifically, the plurality of coils  202  are arranged and installed in two lines parallel to the X direction so as to be able to face, from the top in the Z direction, the two yoke plates  103  installed at respective ends on the R side and the L side on the top face of the mover  101 . 
     A plurality of coils  208  are attached and installed along the X direction to the stator  201  so as to be able to face, along the Y direction, the yoke plates  103  installed on the side face of the mover  101 . Specifically, the plurality of coils  208  are arranged and installed in two lines parallel to the X direction so as to be able to face, from the side in the Y direction, the two yoke plates  103  installed on respective side faces on the R side and the L side of the mover  101 . 
     A plurality of coils  207  are attached and installed along the X direction on the stator  201  so as to be able to face, along the Z direction, the conductive plate  107  installed on the top face of the mover  101 . Specifically, the plurality of coils  207  are arranged and installed in a single line parallel to the X direction so as to be able to face, from the top in the Z direction, the conductive plate  107  installed at the center part on the top face of the mover  101 . 
     The stator  201  applies force to the mover  101  that is movable in the transport direction by respective coils  202 ,  207 , and  208  to which current is applied. Thereby, the mover  101  is transported in the transport direction while the position and the attitude thereof are controlled. 
     Note that the installation places of the coils  202 ,  207 , and  208  are not limited to the examples described above and may be changed as appropriate. Further, the number of installed coils  202 ,  207 , and  208  may be changed as appropriate. 
     The linear encoder  204 , the Y-sensor  205 , and the Z-sensor  206  function as a detection unit that detects the position and the attitude of the mover  101  that moves in the transport direction. 
     The linear encoder  204  is attached and installed on the stator  201  so as to be able to read the linear scale  104  installed on the mover  101 . The linear encoder  204  detects the relative position to the linear encoder  204  of the mover  101  by reading the linear scale  104 . 
     The Y− sensor  205  is attached and installed on the stator  201  so as to be able to detect the distance in the Y direction to the Y-target  105  installed on the mover  101 . The Z-sensor  206  is attached and installed on the stator  201  so as to be able to detect the distance in the Z direction to the Z-target  106  installed on the mover  101 . 
     The mover  101  is configured to be transported with the workpiece  102  attached or held above or under the mover  101 , for example. Note that  FIG. 2  illustrates a state where the workpiece  102  is attached under the mover  101 . Note that the mechanism used for attaching or holding the workpiece  102  to the mover  101  is not particularly limited, and a general attaching mechanism, a general holding mechanism, or the like such as a mechanical hook, an electrostatic chuck, or the like may be used. 
     Note that  FIG. 2  illustrates a case where the mover  101  and the stator  201  are embedded inside a chamber of a vapor deposition apparatus  701  that is an example of the process apparatus that performs a processing operation on the workpiece  102 . The vapor deposition apparatus  701  has a vapor deposition source  702  that performs deposition on the workpiece  102  attached to the mover  101 . The vapor deposition source  702  is installed on a lower part inside the chamber of the vapor deposition apparatus  701  so that the vapor deposition source  702  can face the workpiece  102  attached under the mover  101 . With vapor deposition using the vapor deposition source  702 , a thin film of a metal, an oxide, or the like is formed on a substrate that is the workpiece  102  attached under the mover  101  transported to an installation place of the vapor deposition source  702 . In such a way, the workpiece  102  together with the mover  101  is transported, processing is performed on the transported workpiece  102  by the process apparatus, and an article is manufactured. 
     Further,  FIG. 1  illustrates a region including a place where a structure  100  such as a gate valve, for example, is present between the stator  201   a  and the stator  201   b . The place where the structure  100  is present is a place which is located between a plurality of stations within a production line or between production lines and where continuous arrangement of electromagnets or coils is not possible. 
     A control system  3  that controls the transport system  1  is provided to the transport system  1 . Note that the control system  3  may form a part of the transport system  1 . The control system  3  has the integration controller  301 , the coil controllers  302 , the coil unit controllers  303 , and the sensor controller  304 . The coil controllers  302  and the sensor controller  304  are connected to the integration controller  301  in a communicable manner. The plurality of coil unit controllers  303  are connected to the coil controller  302  in a communicable manner. The plurality of linear encoders  204 , the plurality of Y-sensors  205 , and the plurality of Z-sensors  206  are connected to the sensor controller  304  in a communicable manner. The coils  202 ,  207 , and  208  are connected to each coil unit controller  303  (see  FIG. 3 ). 
     The integration controller  301  determines current instruction values to be applied to the plurality of coils  202 ,  207 , and  208  based on the output from the linear encoder  204 , the Y-sensor  205 , and the Z-sensor  206  transmitted from the sensor controller  304 . The integration controller  301  transmits the determined current instruction values to the coil controllers  302 . The coil controller  302  transmits the current instruction values received from the integration controller  301  to respective coil unit controllers  303 . The coil unit controller  303  controls the current amounts of the connected coils  202 ,  207 , and  208  based on the current instruction values received from the coil controller  302 . 
     The RFID reader  513  is connected to the integration controller  301  in a communicable manner. The RFID reader  513  acquires the individual ID of the mover  101  by reading the RFID tag  512  of the mover  101 . The RFID reader  513  transmits the acquired individual ID to the integration controller  301 . The integration controller  301  can receive and recognize the individual ID of the mover  101  transmitted from the RFID reader  513  to identify the mover  101 . The RFID reader  513  is installed at one or a plurality of positions in the transport path constituted by the stator  201 . 
     As illustrated in  FIG. 3 , one or a plurality of coils  202 ,  207 , and  208  are connected to each coil unit controller  303 . A current sensor  312  and a current controller  313  are connected to each of the coils  202 ,  207 , and  208 . The current sensor  312  detects the current value flowing in the connected coils  202 ,  207 , and  208 . The current controller  313  controls the current amount flowing in the connected coils  202 ,  207 , and  208 . 
     The coil unit controller  303  instructs the current controller  313  for a desired current amount and a timing for flowing the current based on the current instruction value received from the coil controller  302 . The current controller  313  detects the current value detected by the current sensor  312  and controls the current amount so that current of a desired current amount flows in individual coils  202 ,  207 , and  208 . 
     Next, the control system  3  that controls the transport system  1  according to the present embodiment will be further described with reference to  FIG. 4 .  FIG. 4  is a schematic diagram illustrating the control system  3  that controls the transport system  1  according to the present embodiment. 
     As illustrated in  FIG. 4 , the control system  3  has the integration controller  301 , the coil controller  302 , the coil unit controllers  303 , and the sensor controller  304 . The control system  3  functions as a control unit that controls the transport system  1  including the mover  101  and the stator  201 . The coil controller  302 , the sensor controller  304 , and the RFID reader  513  are connected to the integration controller  301  in a communicable manner. 
     The plurality of coil unit controllers  303  are connected to the coil controller  302  in a communicable manner. The coil controller  302  and the plurality of coil unit controllers  303  connected thereto are provided in association with respective columns of the coils  202 ,  207 , and  208 . The coils  202 ,  207 , and  208  are connected to each coil unit controller  303 . The coil unit controller  303  can control the level of the current of the connected coils  202 ,  207 , and  208 . 
     The coil controller  302  instructs target current values to each of the connected coil unit controllers  303 . The coil unit controller  303  controls the current amount of the connected coils  202 ,  207 , and  208 . 
     The plurality of linear encoders  204 , the plurality of Y-sensors  205 , and the plurality of Z-sensors  206  are connected to the sensor controller  304  in a communicable manner. 
     The plurality of linear encoders  204  are attached to the stator  201  at intervals such that one of the linear encoders  204  can always measure the position of one mover  101  even during transportation of the mover  101 . Further, the plurality of Y-sensors  205  are attached to the stator  201  at intervals such that two of the Y-sensors  205  can always measure the Y-target  105  of one mover  101 . Further, the plurality of Z-sensors  206  are attached to the stator  201  at intervals such that three of the two lines of Z-sensors  206  can always measure the Z-target  106  of one mover  101  and so as to form a plane. 
     The integration controller  301  determines current instruction values to be applied to the plurality of coils  202  based on the output from the linear encoders  204 , the Y-sensors  205 , and the Z-sensors  206  and transmits the current instruction values to the coil controllers  302 . The coil controller  302  instructs the coil unit controllers  303  for the current value and the timing for flowing the current based on the current instruction values from the integration controller  301  as described above. Accordingly, the integration controller  301  functions as a control unit to transport the mover  101  in a contactless manner along the stator  201  and control the attitude of the transported mover  101  in six axes. 
     The integration controller  301  can identify the mover  101  by the individual ID of the mover  101  received from the RFID reader  513  that has read the RFID tag  512  attached to the mover  101 . Thus, the integration controller  301  can control the operation of the movers  101  by applying individual parameters to the respective movers  101 . 
     Next, a method of acquiring a correction value for correcting the movement machine difference of the moving devices of the mover  101  according to the present embodiment will be described with reference to  FIG. 5A  and  FIG. 5B .  FIG. 5A  and  FIG. 5B  are schematic diagrams illustrating the method of acquiring the correction value for correcting the movement machine difference in the transport system  1  according to the present embodiment, and illustrate a common measuring jig  500  commonly used for a plurality of the movers  101  in acquiring the correction value.  FIG. 5A  illustrates a common measuring jig  500  viewed in the −X direction.  FIG. 5B  illustrates a common measuring jig  500  viewed in the −Z direction. 
     The common measuring jig  500  has a linear encoder  204  similar to that of the stator  201  and a laser displacement meter  502  as a distance measuring means. The linear encoder  204  is mounted on a common measuring jig  500  so that a linear scale  104  of the mover  101  installed on the common measuring jig  500  can be read. The laser displacement meter  502  is installed on a common measuring jig  500  so as to detect the position of the mover  101  in the X direction installed on the common measuring jig  500 . The common measuring jig  500  is used to acquire machine difference information which is information on a movement machine difference of the mover  101  for each of the plurality of movers  101 . The machine difference of the mover  101  for which the machine difference information is acquired includes the machine difference in each of the X, Y and Z directions. 
     In the common measuring jig  500 , by reading the linear scale  104  of the mover  101  by the linear encoder  204 , the position in the X direction of the mover  101  installed in the common measuring jig  500  can be detected. The position in the X direction of the mover  101 , which is also installed in the common measuring jig  500 , can be detected by measurement using the laser displacement meter  502 . 
     The mover  101  can be identified by reading the RFID tag  512  of the mover  101  installed in the common measuring jig  500  by using the RFID reader  513 . 
     The mover  101  is installed in the common measuring jig  500  so as to simulate the levitation state of the mover  101 . In this case, the mover  101  may be supported at the Bessel points  501 , or an abutment (not illustrated) may be used as a reference. In the common measuring jig  500 , it is important to perform a common installation with good reproduction for the plurality of movers  101 . 
     Here, among the Z-targets  106  of the mover  101 , the Z-target  106  arranged on the +Y direction side, which is the right side toward the +X direction that is the advancing direction, is defined as a Z-target  106 R. Among the Z-targets  106  of the mover  101 , the Z-target  106  arranged on the −Y direction side, which is the left side toward the +X direction that is the advancing direction, is defined as a Z-target  106 L. 
     When acquiring the correction value for correcting the movement machine difference, the mover  101  installed in the common measuring jig  500  is measured by a three-dimensional measuring machine  503  and the laser displacement meter  502 . Specifically, the three-dimensional measuring machine  503  measures, along the X direction, the position of the Y-target  105  in the Y direction, the position of the Z-target  106 R in the Z direction, and the position of the Z-target  106 L in the Z direction. In the measurement, in order to reduce the amount of correction data, measurement may be performed in increments of 1 mm in the X direction, for example. The position of the mover  101  in the X direction is measured by the laser displacement meter  502 . 
     Similarly, with respect to the plurality of movers  101 , the position in the Y direction of the Y-target  105 , the position in the Z direction of the Z-target  106 R and the position in the Z direction of the Z-target  106 L are measured along the X direction by the three-dimensional measuring machine  503 . Similarly, the positions of the plurality of  101  movers  101  in the X direction are measured by the laser displacement meter  502 . 
       FIG. 6  shows an example of data measured as described above for the Y-target  105 , the Z-target  106 R, and the Z-target  106 L of the mover  101 . 
     In  FIG. 6 , the upper part illustrates the Y-target  105 , the Z-target  106 R and the Z-target  106 L to be measured, and the lower part shows a graph of the measured data. In the graph shown in the lower part, the horizontal axis indicates the position of the X-axis of the measurement point. The vertical axis indicates, as an error Err, a value obtained by subtracting the measured value from the design value when the mover  101  is installed in the common measuring jig  500 . In the graph, Err 105  represents the error Err for the Y-target  105 , Err 106 R represents the error Err for the Z-target  106 R, and Err 106 L represents the error Err for the Z-target  106 L. 
     The error Err is a deviation of the target surface of each target read by the sensor from the design value. That is, when the Y-sensor  205  reads the Y-target  105 , Err 105  becomes a reading error unique to each mover  101 . When the Z-sensor  206  reads the Z-target  106 R, Err 106 R becomes a reading error unique to each mover  101 . When the Z-sensor  206  reads the Z-target  106 L, Err 106 L becomes a reading error unique to each mover  101 . 
     The reading error of the Y-sensor  205  and the reading error of the Z-sensor  206  become movement machine differences in the attitude of each mover  101  at the time of levitation. Hereinafter, the reading error of the Y-sensor  205  is denoted as Cy, and the reading error of the Z-sensor  206  is denoted as Cz. The reading error Cy is the movement machine difference of the mover  101  in the Y direction. The reading error Cz is the movement machine difference of mover  101  in the Z direction. The reading errors Cy and Cz are used as correction values for correcting the movement machine difference of the mover  101  in the transport control of the mover  101 . 
     Note that when the measured data is used as the correction value, data between the measurement points can be interpolated from a plurality of measurement points by using a method such as Lagrange interpolation. 
     These reading errors Cy and Cz are associated with the individual ID of the mover  101  registered in the RFID tag  512  by the integration controller  301 , and are stored in a storage unit such as a semiconductor storage device, a magnetic storage device or the like as machine difference information  521  of the sensor (see  FIG. 7 ). Note that the reading errors Cy and Cz may be stored in an external storage device which can be referenced by the integration controller  301 . 
     On the other hand, the machine difference Cx of the position of the mover  101  in the X direction can be calculated by the following Equation (X1) based on the measurement result by the laser displacement meter  502 . 
         Cx =(Ref_ Lx−Lx )−(Ref_ Ex−Ex )  Equation (X1)
 
     Herein, Ex, Lx, Ref_Lx, and Ref_Ex represent the following, respectively. 
     Ex: the measured value of the linear encoder  204  mounted on the common measuring jig  500   
     Lx: the measured value of the laser displacement meter  502   
     Ref_Lx: the design value of the position in the X direction from the laser displacement meter  502  to the mover  101   
     Ref_Ex: the design value of the attached position of the linear encoder  204   
     Thus, the machine difference Cx which is the movement machine difference of the mover  101  in the X direction is acquired. This machine difference Cx in the position in the X direction is associated with the individual ID of the mover  101  registered in the RFID tag  512  by the integration controller  301 , and is stored as difference information  520  (see  FIG. 7 ) in the X direction in a storage unit such as a semiconductor storage device, a magnetic storage device or the like. Note that the machine difference Cx may be stored in an external storage device that can be referenced by the integration controller  301 . 
     Hereinafter, the attitude control method of the mover  101  performed by the integration controller  301  will be described below with reference to  FIG. 7 .  FIG. 7  is a schematic diagram illustrating the attitude control method of the mover  101  in the transport system  1  according to the present embodiment.  FIG. 7  illustrates the overview of the attitude control method of the mover  101  by mainly focusing on the data flow. The integration controller  301  performs a process using a mover position calculation function  401 , a mover attitude calculation function  402 , a mover attitude control function  403 , and a coil current calculation function  404  as described below. Accordingly, the integration controller  301  controls transportation of the mover  101  while controlling the attitude of the mover  101  in six axes. Note that, instead of the integration controller  301 , the coil controller  302  can perform the same process as the integration controller  301 . 
     First, the mover position calculation function  401  calculates the number and position of the movers  101  on the stator  201  constituting the transport path from the measured values from the plurality of linear encoders  204 , information on the attached positions thereof, and the machine difference information  520  of the movers  101  in the X direction. At this time, the mover position calculation function  401  can correct the movement machine difference for each of the movers  101  by using the machine difference information  520  in the X direction stored in association with the individual ID registered in the RFID tag  512  of the mover  101 . 
     According to the above calculation, the mover position calculation function  401  updates the mover position information (X) and the number of units information in mover information  406 , which is information about the mover  101 . The mover position information (X) indicates the position of the mover  101  in the X direction that is the transport direction of the mover  101  on the stator  201 . The mover information  406  is prepared for each mover  101  on the stator  201  as indicated by POS- 1 , POS- 2 , . . . in  FIG. 7 , for example. 
     Next, the mover attitude calculation function  402  specifies the Y-sensor  205  and the Z-sensor  206  capable of measuring each mover  101  from the mover position information (X) in the mover information  406  updated by the mover position calculation function  401 . 
     Next, the mover attitude calculation function  402  calculates attitude information (Y, Z, Wx, Wy, Wz) which is information on the attitude of each mover  101 , and updates the mover information  406 . The mover attitude calculation function  402  calculates an attitude (Y, Z, Wx, Wy, Wz) based on the values outputted from the specified Y-sensor  205  and Z-sensor  206  and the machine difference information  521  of the sensors of the Y-target  105 , the Z-target  106 R and the Z-target  106 L. At this time, the mover attitude calculation function  402  can correct the machine difference of the individual mover  101  by using the machine difference information  521  of the sensors stored in association with the individual ID registered in the RFID tag  512  of the mover  101 . The mover information  406  updated by the mover attitude calculation function  402  includes the mover position information (X) and the attitude information (Y, Z, Wx, Wy, Wz). 
     Next, the mover attitude control function  403  calculates the application force information  408  for each mover  101  from the current mover information  406  including the mover position information (X) and the attitude information (Y, Z, Wx, Wy, Wz) and the attitude target value. The application force information  408  is information relating to the magnitude of the force to be applied to each mover  101 . The application force information  408  includes information on the three-axis components of force (Tx, Ty, Tz) of the force T to be applied and the three-axis components of torque (Twx, Twy, Twz) of the force T. The application force information  408  is prepared for each mover  101  on the stator  201  as indicated as TRQ- 1 , TRQ- 2 , . . . in  FIG. 7 , for example. 
     Herein, Tx, Ty, and Tz, which are three-axis components of force, are an X direction component, a Y direction component, and a Z direction component of force, respectively. Further, Twx, Twy, and Twz, which are three-axis components of torque, are a component around the X-axis, a component around the Y-axis, and a component around the Z-axis of torque, respectively. The transport system  1  according to the present embodiment controls transportation of the mover  101  while controlling the attitude of the mover  101  in six axes by controlling these six-axis components (Tx, Ty, Tz, Twx, Twy, Twz) of the force T. 
     Next, the coil current calculation function  404  determines a current instruction value  409  applied to respective coils  202 ,  207 , and  208  based on the application force information  408  and the mover information  406 . 
     In such a way, the integration controller  301  determines the current instruction value  409  by performing a process using the mover position calculation function  401 , the mover attitude calculation function  402 , the mover attitude control function  403 , and the coil current calculation function  404 . The integration controller  301  transmits the determined current instruction value  409  to the coil controller  302 . 
     Control of the position and the attitude of the mover  101  will be further described in detail with reference to  FIG. 8 .  FIG. 8  is a schematic diagram illustrating an example of a control block used for controlling the position and the attitude of the mover  101 . 
     In  FIG. 8 , the symbol P denotes the position and the attitude (also referred to as a position and attitude or a state) of the mover  101  and has components (X, Y, Z, Wx, Wy, Wz). The symbol ref denotes a target value of (X, Y, Z, Wx, Wy, Wz). The symbol err denotes a deviation between the target value ref and the position and the attitude P. 
     The mover attitude control function  403  calculates force T to be applied to the mover  101  for achieving the target value ref based on the magnitude of the deviation err, the change of the deviation err, an accumulation value of the deviation err, or the like. 
     The coil current calculation function  404  calculates coil current I to be applied to the coils  202 ,  207 , and  208  for applying the force T to the mover  101  based on the force T to be applied and the position and the attitude P. The coil current I calculated in such a way is applied to the coils  202 ,  207 , and  208 , and thereby the force T works on the mover  101 , and the position and the attitude P changes to the target value ref. 
     By configuring the control block in such a way, it is possible to control the position and the attitude P of the mover  101  to a desired target value ref. 
     The process in accordance with the mover position calculation function  401  will now be described with reference to  FIG. 9A  and  FIG. 9B .  FIG. 9A  and  FIG. 9B  are schematic diagrams illustrating the process in accordance with the mover position calculation function. 
     In  FIG. 9A , the reference point Oe corresponds to a position reference of the stator  201  to which the linear encoder  204  is attached. Further, the reference point Os corresponds to a position reference of the linear scale  104  attached to the mover  101 .  FIG. 9A  illustrates a case where two movers  101   a  and  101   b  are transported as the mover  101 , and three linear encoders  204   a ,  204   b , and  204   c  are arranged as the linear encoder  204 . Note that the linear scales  104  are attached to the same positions of respective movers  101   a  and  101   b  along the X direction. 
     For example, the single linear encoder  204   c  faces the linear scale  104  of the mover  101   b  illustrated in  FIG. 9A . The linear encoder  204   c  reads the linear scale  104  of the mover  101   b  and outputs a distance Pc. Further, the position of the linear encoder  204   c  on the X-axis whose origin is the reference point Oe is Sc. Therefore, the position Pos( 101   b ) of the mover  101   b  can be calculated by the following Equation (1). 
       Pos(101 b )= Sc−Pc   Equation (1)
 
     For example, two linear encoders  204   a  and  204   b  face the linear scale  104  of the mover  101   a  illustrated in  FIG. 9A . The linear encoder  204   a  reads the linear scale  104  of the mover  101   a  and outputs the distance Pa. Further, the position of the linear encoder  204   a  on the X-axis whose origin is the reference point Oe is Sa. Therefore, the position Pos( 101   a ) on the X-axis of the mover  101   a  based on the output of the linear encoder  204   a  can be calculated by the following Equation (2). 
       Pos(101 a )= Sa−Pa   Equation (2)
 
     Further, the linear encoder  204   b  reads the linear scale  104  of the mover  101   a  and outputs the distance Pb. Further, the position of the linear encoder  204   b  on the X-axis whose origin is the reference point Oe is Sb. Therefore, the position Pos( 101   a )′ on the X-axis of the mover  101   a  based on the output of the linear encoder  204   b  can be calculated by the following Equation (3). 
       Pos(101 a )′= Sb−Pb   Equation (3)
 
     Herein, since respective positions of the linear encoders  204   a  and  204   b  have been measured accurately in advance, the difference of two values Pos( 101   a ) and Pos( 101   a )′ is sufficiently small. When the difference of the positions of the mover  101  on the X-axis based on the output of the two linear encoders  204  is sufficiently small in such a way, it can be determined that these two linear encoders  204  are observing the linear scale  104  of the same mover  101 . 
     Note that, when a plurality of linear encoders  204  face the same mover  101 , it is possible to uniquely determine the position of the observed mover  101  by calculating the average value of the positions based on the output of the plurality of linear encoders  204  or the like. 
     Further, the mover  101  may rotate around the Z-axis by a rotation amount Wz. A case where correction of the position of the mover  101  using the displacement of this rotation amount Wz is required will be described with  FIG. 9B .  FIG. 9B  illustrates a case where the linear scale  104  is attached to one of the side faces in the Y direction of the mover  101   b . The position Os is the origin of the linear scale  104 , and the position Oc is the origin of the mover  101   b . When the distance from the center Oc of the mover  101  to the linear scale  104  is D, more accurate position Pos( 101   b ) of the mover  101   b  can be obtained by calculating the position Pos( 101   b ) of the mover  101   b  by using the following Equation (1b). 
       Pos(101 b )= Sc−Pc−Wz*D   Equation (1b)
 
     Further, in consideration of the machine difference Cx ( 101   b ) which is the movement machine difference in the position of the mover  101   b  in the X direction, the position Pos ( 101   b ) of the mover  101   b  can be calculated by using the following Equation (1c) to obtain a more accurate position of the mover  101   b.    
       Pos(101 b )= Sc−Pc−Wz*D+Cx (101 b )  Equation (1c)
 
     The mover position calculation function  401  calculates and determines the position X in the X direction of the mover  101  as the mover position information based on the output of the linear encoder  204  as described above. When calculating the position X, the mover position calculation function  401  can correct the movement machine differences of the respective movers  101  by taking into account the machine differences Cx of the positions of the movers  101  in the X direction. 
     Next, the process by using the mover attitude calculation function  402  will be described with reference to  FIG. 10 ,  FIG. 11A  and  FIG. 11B . 
       FIG. 10  illustrates a case where a mover  101   c  is transported as the mover  101 , and Y-sensors  205   a  and  205   b  are arranged as the Y-sensor  205 . The two Y-sensors  205   a  and  205   b  face the Y-target  105  of the mover  101   c  illustrated in  FIG. 10 . The rotation amount Wz around the Z-axis of the mover  101   c  is calculated by the following Equation (4), where the values of relative distances output by the two Y-sensors  205   a  and  205   b  are Ya and Yb, respectively, and the spacing between the Y-sensors  205   a  and  205   b  is Ly. 
         Wz =( Ya−Yb )/ Ly   Equation (4)
 
     Herein, the reading errors Cy of the Y-sensors  205   a  and  205   b  are represented by reading errors Cy( 205   a ,  101   c ) and Cy( 205   b ,  101   c ), respectively. Then, the values Ya and Yb of the outputs of the Y-sensors  205   a  and  205   b  can be corrected in consideration of the reading errors Cy( 205   a ,  101   c ) and Cy( 205   b ,  101   c ), respectively. The output values Ya′ and Yb′ of the Y-sensors  205   a  and  205   b  after correction taking into account the reading errors Cy( 205   a ,  101   c ) and Cy( 205   b ,  101   c ), respectively, are represented by the following Equations (4a) and (4b), respectively. 
         Ya′=Ya+Cy (205 a, 101 c )  Equation (4a)
 
         Yb′=Yb+Cy (205 b, 101 c )  Equation (4b)
 
     The corrected rotation amount Wz′ of the mover  101   c  around the Z-axis in consideration of the reading errors Cy( 205   a ,  101   c ) and Cy ( 205   b ,  101   c ) of the Y-sensors  205   a  and  205   b  is calculated by the following Equation (4c). 
         Wz ′=( Ya′−Yb ′)/ Ly   Equation (4c)
 
     Note that, depending on the position of the mover  101 , three or more Y-sensors  205  may face the Y-target  105  of the mover  101 . In this case, the inclination of the Y-target  105 , that is, the rotation amount Wz′ around the Z-axis can be calculated using the least squares method or the like. 
       FIG. 11A  and  FIG. 11B  illustrate a case where a mover  101   d  is transported as the mover  101 , and Z-sensors  206   a ,  206   b , and  206   c  are arranged as the Z-sensor  206 . The three Z-sensors  206   a ,  206   b , and  206   c  face the Z-target  106  of the mover  101   d  illustrated in  FIG. 11A  and  FIG. 11B . Herein, the values of relative distances output by the three Z-sensors  206   a ,  206   b , and  206   c  are Za, Zb, and Zc, respectively. Further, the distance between sensors in the X direction, that is, the distance between the Z-sensors  206   a  and  206   b  is Lz 1 . Further, the distance between sensors in the Y direction, that is, the distance between the Z-sensors  206   a  and  206   c  is Lz 2 . Then, the rotation amount Wy around the Y-axis and the rotation amount Wx around the X-axis can be calculated by the following Equations (5a) and (5b), respectively. 
         Wy =( Zb−Za )/ Lz 1  Equation (5a)
 
         Wx =( Zc−Za )/ Lz 2  Equation (5b)
 
     The reading errors Cz of the Z-sensors  206   a ,  206   b , and  206   c  are represented by Cz( 206   a ,  101   d ), Cz( 206   b ,  101   d ), and Cz( 206   c ,  101   d ), respectively. Then, the values Za, Zb, and Zc of the outputs of the Z-sensors  206   a ,  206   b , and  206   c  can be corrected in consideration of the reading errors Cz( 206   a ,  101   d ), Cz( 206   b ,  101   d ), and Cz( 206   c ,  101   d ), respectively. The corrected output values Za′, Zb′, and Zc′ of the Z-sensors  206   a ,  206   b , and  206   c  considering the reading errors Cz( 206   a ,  101   d ), Cz( 206   b ,  101   d ), and Cz( 206   c ,  101   d ) are represented by the following Equations (5c), (5d), and (5e), respectively. 
         Za′=Za+Cz (206 a, 101 d )  Equation (5c)
 
         Zb′=Zb+Cz (206 b, 101 d )  Equation (5d)
 
         Zc′=Zc+Cz (206 c, 101 d )  Equation (5e)
 
     The corrected rotation amount Wy′ of the mover  101   d  around the Y-axis in consideration of the reading errors Cz( 206   a ,  101   d ) and Cz( 206   b ,  101   d ) of the Z-sensors  206   a  and  206   b  can be calculated by the following Equation (5f). 
         Wy ′=( Zb′−Za ′)/ Lz 1  Equation (5f)
 
     The corrected rotation amount Wx′ of the mover  101   d  around the X-axis in consideration of the reading errors Cz( 206   a ,  101   d ) and Cz( 206   c ,  101   d ) of the Z-sensors  206   a  and  206   c  can be calculated by the following Equation (5g). 
         Wx ′=( Zc′−Za ′)/ Lz 2  Equation (5g)
 
     The mover attitude calculation function  402  can calculate the rotation amounts Wx′, Wy′, and Wz′ around the respective axes as the attitude information of the mover  101  by performing correction in consideration of the reading errors Cy of the Y-sensors  205  and the reading errors Cz of the Z-sensors  206  as described above. 
     Further, with the mover attitude calculation function  402 , it is possible to calculate the position Y in the Y direction and the position Z in the Z direction of the mover  101  as attitude information on the mover  101  as follows. 
     First, calculation of the position Y in the Y direction of the mover  101  will be described with reference to  FIG. 10 . In  FIG. 10 , two Y-sensors  205  faced by the mover  101   c  are Y-sensors  205   a  and  205   b , respectively. Further, the measured values of the Y-sensors  205   a  and  205   b  are Ya and Yb, respectively. Further, the middle point of the position of the Y-sensor  205   a  and the position of the Y-sensor  205   b  is denoted as Oe′. Furthermore, the position of the mover  101   c  obtained by Equations (1) to (3) is denoted as Os′, and the distance from Oe′ to Os&#39; is denoted as dX′. At this time, the position Yin the Y direction of the mover  101   c  can be calculated by approximate calculation with the following Equation (6). 
         Y =( Ya+Yb )/2− Wz*dX′   Equation (6)
 
     The position Y of the mover  101   c  in the Y direction can be corrected in consideration of the reading errors Cy( 205   a ,  101   c ) and Cy( 205   b ,  101   c ) of the Y-sensors  205   a  and  205   b . The position Y′ of the mover  101   c  in the Y direction corrected in consideration of the reading errors Cy( 205   a ,  101   c ) and Cy ( 205   b ,  101   c ) can be approximately calculated by the following Equation (6a). 
         Y ′=( Ya′+Yb ′)/2− Wz′*dX′   Equation (6a)
 
     Next, calculation of the position Z in the Z direction of the mover  101  will be described with reference to  FIG. 11A  and  FIG. 11B . Three Z-sensors  206  faced by the mover  101   d  are Z-sensors  206   a ,  206   b , and  206   c , respectively. Further, the measured values of the Z-sensors  206   a ,  206   b , and  206   c  are Za Zb, and Zc, respectively. Further, the X-coordinate of the Z sensor  206   a  and the X-coordinate of the Z-sensor  206   c  are the same. Further, the linear encoder  204  is located in the middle position between the Z-sensor  206   a  and the Z-sensor  206   c . Further, the position X of the Z− sensor  206   a  and the Z-sensor  206   c  is denoted as Oe″. Furthermore, the distance from Oe″ to the center Os″ of the mover  101   d  is denoted as dX″. At this time, the position Z in the Z direction of the mover  101   d  can be calculated by approximate calculation with the following Equation (7). 
         Z =( Za+Zb )/2+ Wy*dX″   Equation (7)
 
     The position Z of the mover  101   d  in the Z direction can be corrected in consideration of the reading errors Cz( 206   a ,  101   d ), Cz( 206   b ,  101   d ), and Cz( 206   c ,  101   d ) of the Z-sensors  206   a ,  206   b , and  206   c . The position Z′ of the mover  101   d  in the Z direction corrected in consideration of the reading errors Cz( 206   a ,  101   d ), Cz ( 206   b ,  101   d ) and Cz( 206   c ,  101   d ) can be approximately calculated by the following Equation (7a). 
         Z ′=( Za′+Zb ′)/2+ Wy′*dX″   Equation (7a)
 
     Note that, when both the rotation amounts of Wz and Wy are large for the position Y and the position Z, calculation can be performed at higher approximation accuracy. 
     Thus, the integration controller  301  performs processing using the mover position calculation function  401  and the mover attitude calculation function  402  to function as an acquisition unit for acquiring the position and the attitude of the mover  101 . When acquiring the position and the attitude of the mover  101 , the integration controller  301  can correct the position and attitude of the mover  101  in consideration of the machine difference Cx of the position of the mover  101  in the X direction, the reading error Cy of the Y− sensor  205 , and the reading error Cz of the Z− sensor  206 . 
     Next, a method of determining current values to be applied to the coils  202 ,  207 , and  208  used for applying desired force T to the mover  101  will be described. The force T applied to the mover  101  includes Tx, Ty, and Tz, which are three-axis components of force, and Twx, Twy, and Twz, which are three-axis components of torque, as described above. The integration controller  301  that performs a process using the coil current calculation function  404  can determine current values to be applied to the coils  202 ,  207 , and  208  in accordance with the method of determining current values described below. 
     Note that, out of the force components and the torque components applied by the coils  202 ,  207 , and  208 , influence from one force component or torque component caused to the other force components or torque components may be sufficiently negligible for some cases. Specifically, the force and torque applied by the coils  202 ,  207 , and  208  is formed of the force in X direction applied by the coil  207 , the force in the Y direction and the torque in the Wz direction applied by the coil  208 , and the force in the Z direction, the torque in the Wx direction, and the torque in the Wy direction applied by the coil  202 . The force in the Y direction and the torque in the Wz direction applied by the coil  208  work in the horizontal direction. The force in the Z direction, the torque in the Wx direction, and the torque in the Wy direction applied by the coil  202  work in the levitation direction. When the influence is sufficiently negligible, the current values can be calculated taking into consideration of only the force in the X direction for the coil  207 , the force in the Y direction and the torque in the Wz direction for the coil  208 , and the force in the Z direction, the torque in the Wx direction, and the torque in the Wy direction for the coil  202 . A case where the influence can be sufficiently neglected will be described below. 
     First, current applied to each coil  202  for applying the force component Tz in the Z direction, the torque component Twx in the Wx direction, and the torque component Twy in the Wy direction to the mover  101  will be described with reference to  FIG. 12  to  FIG. 14B . 
       FIG. 12  is a schematic diagram illustrating a relationship between the force working on the yoke plate  103  attached to the mover  101  and the force component Tz and the torque components Twx and Twy working on the mover  101 . 
     In  FIG. 12 , Fzj denotes force applied to the yoke plate  103  by the j-th coil  202 . Note that j is an integer satisfying 1≤j≤N, where the number N of installed coils  202  is an integer greater than or equal to two. The torque applied by each force Fzj contributes to the torque components Twx and Twy. The torque applied by each force Fzj is determined in accordance with the force Fzj and the distance between the point of action and the center Oc of the mover  101 . 
       FIG. 13  is a graph schematically illustrating a thrust constant profile  601  in the Z direction. The thrust constant profile  601  schematically illustrates attractive force working on the yoke plate  103  when unit current is applied to the coil  202  used for levitation that faces the yoke plate  103 . The magnitude of the attractive force continuously changes with respect to the motion in the X direction. 
     An example of the configuration of the coil  202  will be described with reference to  FIG. 14A  and  FIG. 14B .  FIG. 14A  and  FIG. 14B  are schematic diagrams illustrating the coil  202 .  FIG. 14A  is a diagram of the coil  202  when viewed from the Z direction, and  FIG. 14B  is a diagram of the coil  202  when viewed from the X direction. 
     As illustrated in  FIG. 14A  and  FIG. 14B , the coil  202  has a winding  210  and a core  211 . Current is applied to the winding  210  by the current controller  313 . In response to application of current to the winding  210 , a magnetic path  212  that is a path of a magnetic flux is formed. Attractive force works between the coil  202  and the yoke plate  103  due to the magnetic flux in the magnetic path  212  formed in such a way. 
     The relationship between the current applied to the coil  202  and the magnitude of the attractive force working between the coil  202  and the yoke plate  103  will be described in more detail with reference to  FIG. 14A  to  FIG. 15 .  FIG. 15  is a graph schematically illustrating the relationship between the current applied to the coil  202  and the magnitude of the attractive force working between the coil  202  and the yoke plate  103 . In the graph illustrated in  FIG. 15 , the horizontal axis represents the current amount I applied to the coil  202 , and the vertical axis represents the magnitude of attractive force Fz working between the coil  202  and the yoke plate  103 . The graph illustrated in  FIG. 15  indicates an attractive force profile  604  indicating the magnitude of attractive force Fz to the current amount I. 
     When the spacing in the Z direction between the coil  202  and the yoke plate  103  is constant, the attractive force Fz is approximately proportional to the square of the current amount I. Herein, in the graph illustrated in  FIG. 15 , F0 represents an average magnitude of force working on each coil  202  required for compensating the gravity mg working on the mover  101 . 
     Herein, numeric values and symbols are set as follows. 
     Bottom area of the core  211  of one coil  202 : S=0.01 [m 2 ] 
     A part of the mass of the mover  101  compensated by one coil  202 : F0=100 [N] (around 10 [kg]) 
     Vacuum magnetic permeability: μ0=4π×10 −7    
     Airgap: gap [m] 
     Number of turns of the winding  210  of the coil  202 : n [turn] 
     Coil current: I [A] 
     Magnetic flux density between the core  211  and the yoke plate  103 : B [T] 
     If the magnetic permeability of the core  211  and the yoke plate  103  is sufficiently large relative to the vacuum magnetic permeability, Fz and B can be approximately calculated by the following Equation (8a) and (8b), respectively. 
         Fz=S*B   2 /(2*μ0)  Equation (8a)
 
         B=N*I*μ 0/(2*gap)  Equation (8b)
 
     Herein, when the number of turns is 500 [turn] and the coil current I0 is 1.0 [A], the airgap “gap” can be calculated to be 0.006266 [m] by Equation (8a) and Equation (8b). 
     Herein, in the attractive force profile  604 , a point where I=I0 leading to Fz=F0 is Q. A part around this point Q will be described. 
     If the “gap” changes in the expansion direction by 0.25 [mm] from 0.006266 [m], it is necessary to generate larger magneto-motive force in the coil  202  in order to compensate the expanding “gap”. If the “gap” is 0.006516 [m] and Equations (8a) and (8b) are calculated so as to generate the same Fz, the coil current I is calculated to be 1.0399 [A]. Because of such a level of current value, the variation in the current value of the coil current during transportation of the mover  101  is sufficiently small compared to the coil current I0 that is a reference. 
     Therefore, around the point Q, the relationship expressed in the following Equation (8c) is met between current dI applied in addition to the current I0 and the magnitude of force dF additionally generated in the Z-axis direction by application of current dI. Note that the relationship expressed by Equation (8c) is not met around the origin O. 
         dF∝dI   Equation (8c)
 
     Herein, the ratio of dF and dI is defined by the following Equation (8d). 
         dF/dI=Ez   Equation (8d)
 
     In the thrust constant profile  601  illustrated in  FIG. 13 , Ez(j, P) is indicated. Ez(j, P) has a ratio indicated by Equation (8d). That is, Ez(j, P) represents the ratio of the magnitude of force dF additionally generated in the Z-axis direction to the current Id when the additional current dI is applied to the current I0 being applied on average to the j-th coil  202  when the mover  101  is in the position and attitude P. 
     Description is provided with reference to  FIG. 12  in accordance with the denotation described above, where j is the index identifying the coil  202 . In the following, for simplified illustration, additional force dFzj in the Z direction is simply denoted as Fzj, and the additional current dIj is denoted as Ij. 
     The additional force Fzj generated in the Z direction by the j-th coil  202  is expressed by the following Equation (9a), where Ij represents additional current applied to the j-th coil  202 . 
         Fzj=Ez ( j,P )* Ij   Equation (9a)
 
     Furthermore, X(j, P) is defined as the relative position in the X direction of the j-th coil  202  when viewed from the origin Oc of the mover  101 , and Y(j, P) is defined as the relative position in the Y direction of the j-th coil  202  when viewed from the origin Oc of the mover  101 . Then, the force component Tz in the Z direction, the torque component Twx in the Wx direction, and the torque component Twy in the Wy direction are expressed by the following Equations (9b), (9c), and (9d), respectively. 
         Tz =Σ( Ez ( j,P )* Ij )  Equation (9b)
 
         Twx =Σ(− Ez ( j,P )* Y ( j,P )* Ij )  Equation (9c)
 
         Twy =Σ( Ez ( j,P )* X ( j,P )* Ij )  Equation (9d)
 
     If the current Ij satisfying the above Equations (9b), (9c), and (9d) is applied to each coil  202 , desired force component and torque component (Tz, Twx, Twy) can be obtained. 
     The torque contribution matrix M is defined here. The torque contribution matrix M is a matrix indicating the magnitude of contribution to each force component and torque component (Tz, Twx, Twy) when unit current is applied to each of the first to j-th coils  202  when the mover  101  is in the position and attitude P. In such a way, the torque contribution matrix M is used and information related to contribution to each component of the force component and the torque component (Tz, Twx, Twy) caused by unit current applied to each coil  202  is used to determine the current value applied to each coil  202 . 
     In the torque contribution matrix M, the first row is associated with the Z direction, the second row is associated with the Wx direction, and the third row is associated with the Wy direction. Then, respective elements M(1, j), M(2, j), and M(3, j) on the first row on the j-th column, the second row on the j-th column, and the third row on the j-th column of the torque contribution matrix M are expressed by the following Equations (10a), (10b), and (10c), respectively. The torque contribution matrix M is a matrix of three rows by N columns. Note that respective rows of the torque contribution matrix M are linearly independent of each other. 
         M (1, j )= Ez ( j,P )  Equation (10a)
 
         M (2, j )=− Ez ( j,P )* Y ( j,P )  Equation (10b)
 
         M (3, j )= Ez ( j,P )* X ( j,P )  Equation (10c)
 
     On the other hand, a column vector whose elements are current amounts I1 to IN to be applied to the first to N-th coils  202  is introduced with a coil current vector Is. The coil current vector Is is a column vector on the N-th row on the first column expressed by the following Equation (10d). 
         Is=Tr ( I 1, I 2, . . . , Ij, . . . ,IN )  Equation (10d)
 
     The torque vector Tq is defined here as the following Equation (11). 
         Tq=Tr ( Tz,Twx,Twy )  Equation (11)
 
     Then, the following Equation (12) is obtained from Equations (9b) to (9d), (10a) to (10d), and (11). 
         Tq=M*Is   Equation (12)
 
     The pseudo current vector K is introduced here. The pseudo current vector K is a column vector having three rows by one column and is a vector satisfying the following Equation (13) when Tr(M) is a transpose matrix of the torque contribution matrix M. 
         Tr ( M )* K=Is   Equation (13)
 
     Since it is possible to apply a larger current value to the coil  202  which more contributes to Tz, Twx, and Twy by defining the coil current vector Is as a vector expressed by Equation (13), it is possible to apply current efficiently. 
     Equation (12) can be transformed into the following Equation (14) by using Equation (13). 
         Tq=M*Tr ( M )* K   Equation (14)
 
     In Equation (14), M*Tr(M) is a product of a matrix of three rows by N columns and a matrix of N rows and three columns and thus is a square matrix of three rows by three columns. Further, respective rows of the torque contribution matrix M are linearly independent of each other. Therefore, an inverse matrix can be obtained from M*Tr(M) in any cases. Thus, Equation (14) can be transformed into the following Equation (15). 
         K=Inv ( M*Tr ( M ))* Tq   Equation (15)
 
     The coil current vector Is expressed by the following Equation (16) is finally obtained from Equations (13) and (15). In such a way, the coil current vector Is can be uniquely found. 
         Tr ( M )* Inv ( M*Tr ( M ))* Tq=Is   Equation (16)
 
     By calculating the coil current vector Is as described above, it is possible to determine current to be applied to each coil  202 . Accordingly, since it is possible to independently apply the force component Tz in Z direction, the torque component Twx in the Wx direction, and the torque component Twy in the Wy direction to the mover  101 , it is possible to stabilize the attitude of the mover  101  in the Z direction, the Wx direction, and the Wy direction. 
     Next, current applied to the coil  208  for applying the force component Ty in the Y direction and the torque component Twz in the Wz direction to the mover  101  will be described with reference to  FIG. 16  and  FIG. 17 . The force component Ty and the torque component Twz work in the horizontal direction, respectively.  FIG. 16  is a schematic diagram of the mover  101  when viewed from the top to the bottom in the Z direction.  FIG. 17  is a graph schematically illustrating an attractive force profile  605  in the Y direction. In the graph illustrated in  FIG. 17 , the horizontal axis represents current applied to the coil  208 , and the vertical axis represents force working on the mover  101 . 
     Note that, for simplified illustration,  FIG. 16  illustrates a case where, as the coils  208  installed on the stator  201 , four coils  208   a R,  208   b R,  208   a L, and  208   b L face the mover  101 . Further, the coil  208   a L and the coil  208   a R are paired to operate as one coil  208   a . Further, the coil  208   b L and the coil  208   b R are paired to operate as one coil  208   b . In such a way, the j-th paired coil  208   j R and coil  208   j L are paired to operate as one coil  208   j.    
     The attractive force profile  605  illustrated in  FIG. 17  indicates the relationship between the level of current IL and IR applied to the j-th pair of coils  208   j  and the magnitude of the force Fy working on the mover  101 . No repulsive force works and only the attractive force works between the coil  208  and the yoke plate  103 . Thus, when force is applied in Y+ direction to the mover  101 , current is applied to the coil  208   j R on the R side in a range  605   a  of the attractive force profile  605 . Further, when force is applied in Y− direction to the mover  101 , current is applied to the coil  208   j L on the L side in a range  605   b  of the attractive force profile  605 . 
     For example, when force Fa in the Y+ direction is applied, current Ia can be applied to the coil  208   j R on the R side. Further, for example, when force Fb in the Y− direction is applied, current Ib can be applied to the coil  208   j L on the L side. 
     The index j is defined as an index identifying a pair of coils  208 . Further, X(j, P) is defined as the relative position in the X direction of the j-th pair of coils  208  when viewed from the origin Oc of the mover  101 . Further, force in the Y direction applied by the j-th pair of coils  208  is denoted as Fyj. Then, the force component Ty in the Y direction and the torque component Twz in the Wz direction that correspond to the horizontal direction are expressed by the following Equations (17a) and (17b), respectively. 
         Ty=ΣFyj   Equation (17a)
 
         Twz =Σ(− Fyj*X ( j,P ))  Equation (17b)
 
     A Y direction force vector Fys having elements of force Fy 1 , Fy 2 , . . . , FyN in the Y direction applied by the first to N-th coils  208  is defined here by the following Equation (17c). 
         Fys=Tr ( Fy 1, Fy 2, . . . , Fyj, . . . ,FyN )  Equation (17c)
 
     Furthermore, the torque vector Tq is defined by the following Equation (17d). 
         Tq=Tr ( Ty,Twz )  Equation (17d)
 
     In the torque contribution matrix M, the first row is associated with the Y direction, and the second row is associated with the Wz direction. Then, respective elements M(1, j) and M(2, j) on the first row on the j-th column and the second row on the j-th column of the torque contribution matrix M are expressed by the following Equations (17e) and (17f), respectively. 
         M (1, j )=1  Equation (17e)
 
         M (2, j )= X ( j,P )  Equation (17f)
 
     To calculate current to be applied to the coil  208 , first, the Y direction force vector Fys satisfying the following Equation (17g) is determined. 
         Tq=M*Fys   Equation (17g)
 
     Since Tq is a vector of two rows by one column and M is a matrix of two rows by N columns, there are innumerable combinations of elements of the Y direction force vector Fys satisfying Equation (17g), however, the combination can be calculated uniquely in accordance with the following method. 
     Herein, the pseudo current vector K of two rows by one column is introduced. The pseudo current vector K is a vector satisfying the following Equation (17h), where Tr(M) is a transpose matrix of the torque contribution matrix M. 
         Tr ( M )* K=Fys   Equation (17h)
 
     Equation (17g) can be transformed into the following Equation (17i) by using Equation (17h). 
         Tq=M*Tr ( M )* K   Equation (17i)
 
     The item M*Tr(M) is a product of a matrix of two rows by N columns and a matrix of N rows by two columns and thus is a square matrix of two rows by two columns. Further, respective rows of the torque contribution matrix M are linearly independent of each other. Therefore, an inverse matrix can be obtained from M*Tr(M) in any cases. Thus, Equation (17i) can be transformed into the following Equation (17j). 
         K=Inv ( M*Tr ( M ))* Tq   Equation (17j)
 
     The Y direction force vector Fys expressed by the following Equation (17k) is finally obtained from Equations (17h) and (17j). Accordingly, the Y direction force vector Fys can be uniquely calculated. 
         Tr ( M )* Inv ( M*Tr ( M ))* Tq=Fys   Equation (17k)
 
     After the Y direction force vector Fys is obtained, current to be applied to each coil  208  can be calculated by counting backward from the attractive force profile  605  calculated or measured in advance. 
     As described above, the current to be applied to each coil  208  can be determined. Accordingly, since the force component Ty in the Y direction and the torque component Twz in the Wz direction can be independently applied to the mover  101 , the attitude of the mover  101  can be stabilized in the Y direction and the Wz direction. For example, current can be applied to the coil  208  so that the torque in the Wz direction is always 0. 
     In this way, in the present embodiment, the movement machine difference of the mover  101  in the Z direction and the movement machine difference of the mover  101  in the Y direction of the mover  101  are corrected to thereby control the currents applied to the plurality of coils  202  and  208 . Thus, the movement of the mover  101  is controlled so as to be in the target attitude (Y, Z, Wx, Wy, Wz). Therefore, the respective attitudes of the plurality of movers  101  can be controlled with higher accuracy. For example, the operation of the mover  101  is controlled so as to be at the target position in the Z direction by correcting the movement machine difference of the mover  101  in the Z direction and controlling the current values applied to the plurality of coils  202 . Thus, the attitude of the mover  101  during being levitated is controlled. Therefore, the position of each of the plurality of movers  101  at the time of levitation can be controlled with higher accuracy. 
     Next, a control method of the coil  207  that applies thrust in the X direction, which is the transport direction, to the mover  101  will be described. The transport system  1  according to the present embodiment is a transport system with an induction type linear motor. The coil  207  generates electromagnetic force between the coil  207  and the conductive plate  107  of the mover  101  and applies thrust in the X direction, that is, the force component Tx in the X direction to the mover  101 . The conductive plate  107  is not particularly limited, and a plate whose electric resistance is relatively small, for example, an aluminum plate is used. 
     When current is applied, each coil  207  generates a moving magnetic field in the X direction, which is the transport direction, to generate electromagnetic force between the coil  207  and the conductive plate  107 . Thereby, each coil  207  causes the mover  101  to generate the force component Tx as the thrust in the X direction, which is the transport direction. When the speed of the mover  101  is insufficient, it is possible to increase the current to be applied to each coil  207  or change the timing of application of current to each coil  207  so that the speed at which the moving magnetic field moves becomes higher. 
     In the present embodiment, the movement of the movers  101  is controlled to achieve the target transport speed by controlling the current value and/or timing of currents applied to the plurality of coils  207  by correcting for the movement machine difference in the X direction of the movers  101 . Thus, the transport speed of each of the plurality of movers  101  can be controlled with higher accuracy. 
     As described above, the integration controller  301  determines and controls the current instruction values of current to be applied to respective coils  202 ,  207 , and  208 . Accordingly, the integration controller  301  controls transportation of the mover  101  on the stator  201  in a contactless manner while controlling in six axes the attitude of the mover  101  being transported by the stator  201 . Note that all or a part of the function of the integration controller  301  as the control apparatus may be replaced with the coil controller  302  as well as other control apparatuses. 
     Note that, although the case where the current of the coil  207  is controlled in the same manner as the current of the coil  202  and the coil  208  has been described in the present embodiment, the embodiment is not limited thereto. For example, in a simpler configuration, an induction motor controller may be connected to the integration controller  301 , and the current of each coil  207  may be controlled by the induction motor controller so that a constant moving magnetic field is generated. 
     As described above, according to the present embodiment, it is possible to apply the force component and the torque component in the six axes (Tx, Ty, Tz, Twx, Twy, Twz) independently to the mover  101 . Thus, according to the present embodiment, it is possible to transport the mover  101  in a contactless manner stably in the X direction while stabilizing the attitude of the mover  101  in the Y direction, the Z direction, the Wx direction, the Wy direction, and the Wz direction. 
     Further, according to the present embodiment, the position and the attitude of the mover  101  can be controlled in consideration of the machine difference Cx of the position of the mover  101  in the X direction, the reading error Cy of the Y-sensor  205 , and the reading error Cz of the Z-sensor  206 . Thus, it is possible to reduce or avoid the influence of machine differences that may exist for each of the plurality of movers  101 . Therefore, according to present embodiment, in the magnetic levitation type transport system  1 , the plurality of movers  101  can be transported with higher accuracy. 
     It should be noted that, although the above description has been made on the case of correcting the movement machine difference in the X direction, the movement machine difference in the Y direction, and the movement machine difference in the Z direction of the mover  101 , any one or two of these may be corrected. 
     Second Embodiment 
     A second embodiment of the present disclosure will be described with reference to  FIG. 18A  to  FIG. 19 . Note that the same components as those in the above first embodiment are labeled with the same references, and the description thereof will be omitted or simplified. Note that the correction of the movement machine difference by the present embodiment can be executed in combination with the correction of the movement machine difference by the first embodiment. 
     In the present embodiment, when acquiring a correction value for correcting the movement machine difference of the mover  101 , the machine difference of the position of the mover  101  in the X direction is acquired over the entire area of the linear scale  104 . Hereinafter, a method of acquiring the mechanical difference of the position of the mover  101  in the X direction over the entire area of the linear scale  104  will be described with reference to  FIG. 18A  and  FIG. 18B .  FIG. 18A  and  FIG. 18B  are schematic diagrams illustrating the method of acquiring the mechanical difference of the position of the mover  101  in the X direction over the entire area of the linear scale  104 , and illustrates a common measuring jig  510  commonly used for the plurality of movers  101  when the correction value is acquired.  FIG. 18A  illustrates the common measuring jig  510  as viewed in the −X direction.  FIG. 18B  illustrates the common measuring jig  510  viewed in the −Z direction. 
     The common measuring jig  510  has a linear encoder  204  similar to that of the stator  201  and a laser interferometer  504  as a distance measuring means. The linear encoder  204  is attached and installed on the common measuring jig  510  so as to read the linear scale  104  of the mover  101  which is slid in the X direction in the common measuring jig  510 . The laser interferometer  504  is attached and installed on the common measuring jig  510  so as to detect the position of the mover  101  in the X direction slid in the X direction in the common measuring jig  500 . 
     The common measuring jig  510  has a plurality of Z-axis rollers  505 . The plurality of Z-axis rollers  505  are arranged in two or more lines along the X direction. The Z-axis roller  505  is, for example, a ball roller. The mover  101  is placed on a plurality of lines of the Z-axis rollers  505 . The Z-axis rollers  505  can slide the placed mover  101  in the X direction. The common measuring jig  510  may be provided with a Y-axis roller (not illustrated) for regulating the mover  101  in the Y direction when the mover  101  is slid in the X direction. 
     In the common measuring jig  510 , by reading the linear scale  104  of the mover  101  by the linear encoder  204 , the position of the mover  101  in the X direction sliding in the X direction in the common measuring jig  510  can be detected. The position of the mover  101  in the X direction sliding in the X direction in the common measuring jig  500  can also be detected by measurement by the laser interferometer  504 . 
       FIG. 19  is a graph showing, as Err, the difference between the measured value of the laser interferometer  504  and the measured value of the linear encoder  204  when the mover  101  is moved in the X direction by sliding on the plurality of Z-axis rollers  505 . Note that, when measuring with the laser interferometer  504 , measurement in increments of 1 mm in the X direction may be performed in order to reduce the amount of correction data, for example. When the measured data is used as a correction value, the data between the measurement points can be interpolated from a plurality of measurement points by using a method such as Lagrange interpolation. 
     The machine difference Cx′ of the position of the mover  101  in the X direction can be calculated by the following Equation (X1)′. 
         Cx ′=(Ref_ Lx′−Lx ′)−(Ref_ Ex′−Ex ′)  Equation (X1)′
 
     Here, Ex′, Lx′, Ref_Lx′, and Ref_Ex′ represent the following, respectively. Ex′: measured value of the linear encoder  204  attached to the common measuring jig  510   
     Lx′: measured value of the laser interferometer  504   
     Ref_Lx′: design value of the position in the X direction from the laser interferometer  504  to the mover  101   
     Ref_Ex′: design value of the attached position of the linear encoder  204 . 
     The machine difference Cx′ can be acquired over the entire area of the linear scale  104  based on the measurement result obtained when the mover  101  is slid by the Z-axis rollers  505  and moved in the X direction. Note that the machine difference Cx′ does not necessarily have to be acquired in the entire area of the linear scale  104 , but may be acquired in a portion of the linear scale  104 . 
     The machine difference Cx′ in the X direction is stored by the integration controller  301  as machine difference information  520  in the X direction in association with the individual ID of the mover  101  registered in the RFID tag  512 . In calculating the position X of the mover  101  in the X direction, the machine difference Cx′ associated with the individual ID of the mover  101  is considered. 
     In the mover position calculation function  401 , when the machine difference Cx( 101   b )′ which is the machine difference Cx′ of the position of the mover  101   b  in the X direction is considered, the position Pos( 101   b )′ of the mover  101   b  can be calculated by the following Equation (1c)′ instead of the Equation (1c). The machine difference Cx( 101   b )′ may be a value corresponding to the position of the linear scale  104  read by the linear encoder  204   c , out of values acquired over the entire area of the linear scale  104 . 
       Pos(101 b )′= Sc−Pc−Wz*D+Cx (101 b )′  Equation (1c)′
 
     The more accurate position of the mover  101   b  can be acquired by calculating using the equation (1c)′ considering the machine difference Cx′. 
     Thus, in present embodiment, when calculating the position X of the mover  101  in the X direction in the mover position calculation function  401 , the machine difference Cx′ of the position of the mover  101  in the X direction acquired over the entire area of the linear scale  104  is taken into account. The machine difference Cx′ is associated with an individual ID registered in the RFID tag  512  of the mover  101 . This makes it possible to correct the machine difference of the individual mover  101 . Therefore, in present embodiment, a more accurate current position can be acquired regardless of the position of the mover  101 . 
     Based on the position of the mover  101  obtained as described above, the integration controller  301  can control the transport speed of the mover  101  by maintaining a constant speed, decelerating or accelerating the speed. 
     In the present embodiment, since the more accurate current position can be acquired regardless of the position of the mover  101 , when the mover  101  is transferred at the target transport speed, the mover  101  can be made to follow the target transport speed more accurately. Therefore, the speed ripple which is the speed unevenness with respect to the target transport speed of the mover  101  can be suppressed to be small. Therefore, according to the present embodiment, in the magnetic levitation type transport system  1 , the plurality of movers  101  can be conveyed with higher accuracy. 
     Third Embodiment 
     A third embodiment of the present disclosure will be described with reference to  FIG. 5A ,  FIG. 5B  and  FIG. 20 . Note that the same components as those in the above first and second embodiments are labeled with the same references, and the description thereof will be omitted or simplified. 
     In the present embodiment, a method of controlling the position and attitude of the mover  101  using the machine difference information of the natural frequency of the mover  101  will be described. Note that the correction of the movement machine difference by the present embodiment can be executed in combination with the correction of the movement machine difference by the first or second embodiment. 
     First, the natural frequency of each mover  101  is measured. In the measurement of the natural frequency, as illustrated in  FIG. 5A  and  FIG. 5B , the mover  101  for measuring the natural frequency is supported at the Bessel points  501 . With the mover  101  thus supported, an acceleration sensor (not illustrated) is attached to the mover  101  to perform impact excitation using, for example, hammering, and the natural frequency of the mover  101  is measured from the measurement result of the acceleration sensor at that time. 
     Next, the coefficient of a filter for removing the natural frequency is determined from the measured natural frequency of the mover  101 . As the filter for removing the natural frequency, for example, a band-stop filter having a narrow stopband such as a notch filter can be used. 
     The machine difference of the natural frequency is stored in the storage device as machine difference information  522  (see  FIG. 20 ) of the natural frequency in association with the individual ID of the mover  101  registered in the RFID tag  512  by the integration controller  301 . The machine difference of the natural frequency may be stored in an external storage device that can be referenced by the integration controller  301 . 
     An operation correction using the machine difference information of the natural frequency measured as described above will be described in detail with reference to  FIG. 20 .  FIG. 20  is a schematic diagram illustrating an example of a control block for controlling the position and attitude of the mover  101  in the case of correcting the operation using the machine difference information of the natural frequency. 
     In  FIG. 20 , the symbol P denotes the position and the attitude of the mover  101  having (X, Y, Z, Wx, Wy, Wz) as components, the symbol ref denotes a target value of (X, Y, Z, Wx, Wy, Wz), and the symbol err denotes a deviation between the target value ref and the position and the attitude P. 
     Similar to the case illustrated in  FIG. 8 , the mover attitude control function  403  calculates force T to be applied to the mover  101  for achieving the target value ref based on the magnitude of the deviation err, the change in the deviation err, the accumulation value of the deviation err, or the like. In present embodiment, the integration controller  301  executes processing using a filter function  514 . The filter function  514  applies the filter for removing the natural frequency to the force T to calculate the filtered force T′. When applying the filter for removing the natural frequency, the integration controller  301  determines the filter coefficient of the filter for removing the natural frequency by the filter function  514  from the machine difference information  522  of the natural frequency stored in association with an individual ID registered in an RFID tag  512  of the mover  101 . 
     The coil current calculation function  404  calculates coil current I to be applied to the coils  202 ,  207 , and  208  in order to apply the filtered force T′ to the mover  101  based on the filtered force T′ and the position and the attitude P. When the coil current I thus calculated are applied to the coils  202 ,  207 , and  208 , the filtered force T′ works on the mover  101  to change the position and the attitude P to the target value ref. 
     By configuring the control block in such a way, it is possible to control the position and the attitude P of the mover  101  to a desired target value ref by using the machine difference information of the natural frequency of the mover  101 . 
     In the present embodiment, as described above, in the filter function  514 , the filter for removing the natural frequency is applied to the force T to be applied to the mover  101  to calculate the filtered force T′. The filter coefficient of the filter for removing the natural frequency is determined from the machine difference information of the natural frequency stored in association with the individual ID registered in the RFID tag  512  of the mover  101 . Thus, the position and the attitude of the individual mover  101  can be controlled. Therefore, according to the present embodiment, the plurality of movers  101  can be transferred with high accuracy. 
     Fourth Embodiment 
     A fourth embodiment of the present disclosure will be described with reference to  FIG. 21A  and  FIG. 21B . Note that the same components as those in the above first to third embodiments are labeled with the same references, and the description thereof will be omitted or simplified. 
     In present embodiment, a case where the weight of the mover  101  is measured will be described with reference to  FIG. 21A  and  FIG. 21B .  FIG. 21A  and  FIG. 21B  are schematic diagrams illustrating the method of measuring the weight of the mover  101 .  FIG. 21A  illustrates a common measuring jig  500  viewed in the −X direction.  FIG. 21B  illustrates the common measuring jig  500  viewed in the −Z direction. 
     When the weight of the mover  101  is measured, the mover  101  is supported by Bessel points  501  of the mover  101  in the common measuring jig  500  in the same manner as the first embodiment. In present embodiment, a weight sensor  511  for measuring the weight of the mover  101  is installed on a support part for supporting the mover  101  of the common measuring jig  500 . 
     For each of the plurality of movers  101 , the mover  101  is installed in the common measuring jig  500 , and the weight can be measured by a weight sensor  511 . The weight sensor  511  is not particularly limited as long as it can measure the weight of the mover  101 , but a load cell or the like can be used. 
     When the plurality of movers  101  are manufactured, variations in the weight of the plurality of movers  101  may occur due to manufacturing errors or assembly errors of components. From the viewpoint of transporting the plurality of movers  101  with high accuracy, it is preferable that the plurality of movers  101  have small or no variation in weight. 
     In order to correct the variation in the weight of the mover  101 , first, the weight of each of the plurality of movers  101  is measured by the weight sensor  511  as described above. Then, based on the measurement result of the weight, the weight of the plurality of movers  101  is adjusted so that the weights of the plurality of movers  101  are the same by, for example, a method of installing a weight on a part or all of the plurality of movers  101 , a method of changing components, or the like. Thus, the variation in the weight of the plurality of movers  101  can be reduced or eliminated. By correcting the variation in the weight in this way, the plurality of movers  101  can be transferred with high accuracy. 
     Even when the plurality of movers  101  have variation in weight, the plurality of movers  101  can be transferred with high accuracy by correcting the machine difference of the movers  101  as in the first to third embodiment described above. 
     MODIFIED EMBODIMENTS 
     The present disclosure is not limited to the embodiments described above, and various modifications are possible. 
     For example, although the cases where the position and the attitude of the mover  101  are controlled in the X direction, the Y direction, the Z direction, the Wx direction, the Wy direction, and the Wz direction have been described as examples in the above embodiments, the embodiment is not limited thereto. The displacement may be acquired in at least any one of directions of the X direction, the Y direction, the Z direction, the Wx direction, the Wy direction, or the Wz direction to control the position and the attitude. 
     Further, although the magnetic floating type transport system  1  that causes the mover  101  to float and transport the mover  101  in a contactless manner has been described in the above embodiments, the embodiment is not limited thereto. For example, when the mass of the mover  101  or the mass of the workpiece  102  placed on the mover  101  is large and the levitation force to be applied in the vertical direction is large, a static pressure by a fluid such as air may be separately used for levitation to assist the levitation force. The transport system  1  can also be configured as a levitation type transport system for levitating the mover  101  by utilizing static pressure or the like by a fluid instead of electromagnetic force as a levitation force. 
     Further, although the cases where a predetermined number of lines of a plurality of coils  202 ,  207 , or  208  are arranged have been described as examples in the above embodiments, the embodiment is not limited thereto. A predetermined number of lines of each coil can be arranged in accordance with the yoke plate  103 , the conductive plate  107  arranged in the mover  101 . 
     Further, although the case where the mover  101  is provided with the yoke plates  103  and the conductive plate  107  have been described as examples in the above embodiments, the embodiment is not limited thereto. The mover  101  may have a magnet group including a plurality of permanent magnets instead of the yoke plate  103  and the conductive plate  107 . The magnet group may include, for example, a plurality of permanent magnets arranged along the X direction. 
     Further, the transport system according to the present disclosure can be used as a transport system that transports a workpiece together with a mover to an operation area of each process apparatus such as a machine tool that performs each operation process on the workpiece that is an article in a manufacturing system that manufactures an article such as an electronic device. The process apparatus that performs the operation process may be any apparatus such as an apparatus that performs assembly of a component to a workpiece, an apparatus that performs painting, or the like. Further, the article to be manufactured is not limited to a particular article and may be any component. 
     As described above, the transport system according to the present disclosure can be used to transport a workpiece to an operation area, perform an operation process on the workpiece transported in the operation area, and manufacture an article. Further, the transport object to be transported by the transport system according to the present disclosure may be other than a workpiece. For example, an article other than a workpiece, a living body such as a person or an animal may be the transport object. 
     According to the present disclosure, a plurality of movers can be transferred with higher accuracy in a levitation type transport 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 comprise 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. 2021-003049, filed Jan. 12, 2021, and Japanese Patent Application No. 2021-190122, filed Nov. 24, 2021, which are hereby incorporated by reference herein in their entirety.