Patent Publication Number: US-2023142815-A1

Title: A linear conveyor system, a control method for a linear conveyor system, a control program for a linear conveyor system and a recording medium

Description:
TECHNICAL FIELD 
     This invention relates to a linear conveyor system with a mechanism for driving a slider by linear modules. 
     BACKGROUND 
     Patent literature 1 discloses a linear drive conveyor system in which a plurality of tracks for driving a moving body in a predetermined driving direction are arranged in parallel. This system is provided with a junction track for transferring the moving body between the plurality of tracks. This junction track can receive the moving body from one track while facing the one track or perform a reverse operation thereof. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] US2016/0159585A1 
       
    
     SUMMARY 
     Technical Problem 
     As just described, the system described in patent literature 1 uses a movable linear module for transferring a slider (moving body) between a plurality of fixed linear modules (track) arranged in parallel. In such a system, the following problem has occurred in some cases in performing a transfer operation of moving the slider between the fixed linear module and the movable linear module. 
     That is, the transfer operation of the slider can be performed by a position control for the slider driven by the fixed linear modules and the movable linear module. Such a position control is executed based on coordinate axes set for the respective fixed linear modules and movable linear module. However, there have been cases where the position control cannot be executed based on these coordinate axes and the transfer operation of the slider cannot be performed since the coordinate axes set for the respective linear modules relating to the transfer operation are not continuous. 
     This invention was developed in view of the above problem and aims to provide a technique capable of suppressing the occurrence of a situation where a transfer operation of moving a slider between a fixed linear module and a movable linear module cannot be performed due to the discontinuity of coordinate axes set for the respective fixed linear module and movable linear module. 
     Solution to Problem 
     A linear conveyor system according to the invention, comprises: a slider to be driven in a first direction; a plurality of fixed linear modules arrayed in a second direction intersecting the first direction; a movable linear module moving between a plurality of facing ranges arranged in the second direction while facing toward the plurality of fixed linear modules from the first direction, the movable linear module driving the slider in the first direction; a slider transfer mechanism conveying the movable linear module between the plurality of facing ranges; and a controller which sets a coordinate axis representing positions in the first direction by coordinate values, the coordinate value changing according to a position change in the first direction, for each of the plurality of fixed linear module and the movable linear module and executes a position control based on the coordinate axes for the slider driven by the fixed linear module and the movable linear module, wherein: the slider is engageable with and disengageable from one end of each of the fixed linear modules and the movable linear module in the first direction and the fixed linear modules and the movable linear module drive the engaged slider in the first direction, a transfer operation of moving the slider between the fixed linear module and the movable linear module is performed, and the controller controls drive of the slider in the transfer operation by a speed control to control a speed of the slider based on a speed command value instead of by the position control if it is judged before the transfer operation that one coordinate axis and an other coordinate axis are not continuous as a result of performing a judgment process of judging whether or not the one coordinate axis, the one coordinate axis being the coordinate axis of the fixed linear module, and the other coordinate axis, the other coordinate axis being the coordinate axis of the movable linear module, are continuous in the first direction. 
     A control method for a linear conveyor system according to the invention is a control method for a linear conveyor system with a slider to be driven in a first direction, a plurality of fixed linear modules arrayed in a second direction intersecting the first direction, a movable linear module moving between a plurality of facing ranges arranged in the second direction while facing toward the plurality of fixed linear modules from the first direction, the movable linear module driving the slider in the first direction, and a slider transfer mechanism conveying the movable linear module between the plurality of facing ranges, the control method comprising: setting a coordinate axis for each of the plurality of fixed linear module and the movable linear module, the coordinate axis representing positions in the first direction by coordinate values, the coordinate value changing according to a position change in the first direction; performing a judgment process of judging whether or not one coordinate axis, the one coordinate axis being the coordinate axis of the fixed linear module, and an other coordinate axis, the other coordinate axis being the coordinate axis of the movable linear module, are continuous in the first direction; and performing a transfer operation of moving the slider between the fixed linear module and the movable linear module by a speed control for controlling a speed of the slider based on a speed command value if it is judged that the one coordinate axis and the other coordinate axis are not continuous as a result of the judgment process. 
     A control program according to the invention is a control program for a linear conveyor system with a slider to be driven in a first direction, a plurality of fixed linear modules arrayed in a second direction intersecting the first direction, a movable linear module moving between a plurality of facing ranges arranged in the second direction while facing toward the plurality of fixed linear modules from the first direction, the movable linear module driving the slider in the first direction, and a slider transfer mechanism conveying the movable linear module between the plurality of facing ranges, the control program causing a computer to: set a coordinate axis for each of the plurality of fixed linear module and the movable linear module, the coordinate axis representing positions in the first direction by coordinate values, the coordinate value changing according to a position change in the first direction; perform a judgment process of judging whether or not one coordinate axis, the one coordinate axis being the coordinate axis of the fixed linear module, and an other coordinate axis, the other coordinate axis being the coordinate axis of the movable linear module, are continuous in the first direction; and perform a transfer operation of moving the slider between the fixed linear module and the movable linear module by a speed control for controlling a speed of the slider based on a speed command value if it is judged that the one coordinate axis and the other coordinate axis are not continuous as a result of the judgment process. 
     A recording medium according to the invention computer-readably records the above linear conveyor system control program according. 
     In the invention thus configured (linear conveyor system, linear conveyor system control method, linear conveyor system control program and recording medium), the transfer operation of moving the slider between the fixed linear module and the movable linear module is performed. At this time, the judgment process of judging whether or not the one coordinate axis, which is the coordinate axis of the fixed linear module, and the other coordinate axis, which is the coordinate axis of the movable linear module, are continuous is performed. If it is judged in the judgment process before the transfer operation that the one coordinate axis and the other coordinate axis are not continuous, the transfer operation is performed while the speed control (not the position control) for controlling the speed of the slider based on the speed command value is executed. Thus, it is possible to suppress the occurrence of a situation where the transfer operation of moving the slider between the fixed linear module and the movable linear module cannot be performed due to the discontinuity of the coordinate axes set for the respective fixed linear module and movable linear module. 
     Specifically, the linear conveyor system may be configured so that the controller drives the slider by a feedback control based on a deviation between a position command value generated based on a position profile representing a change of a position of the slider over time and a position detection value indicating the detected position of the slider in the position control and drives the slider by a feedback control based on a deviation between a speed command value generated based on a speed profile representing a change of the speed of the slider over time and a speed detection value indicating the detected speed of the slider in the speed control. In this way, the position control and the speed control of the slider can be precisely executed by the position profile and the speed profile. 
     The linear conveyor system may be configured so that the controller moves the slider from a stop position where the slider stops when the speed control is completed to a movement target position by the position control when the speed control is completed in the transfer operation of moving the slider from a movement start position toward the movement target position. In such a configuration, a steady-state deviation (i.e. difference between the stop position and the movement target position) remaining when the speed control is completed can be solved by the position control and the slider can be reliably moved to the movement target position. 
     The linear conveyor system may be configured so that the controller controls the drive of the slider in the transfer operation by the position control if it is judged before the transfer operation that the one coordinate axis and the other coordinate axis are continuous as a result of performing the judgment process. In such a configuration, the transfer operation of the slider is performed by the position control if it is judged in the judgment process that the coordinate axes are continuous, and the transfer operation of the slider is performed by the speed control if it is judged in the judgment process that the coordinate axes are discontinuous. Thus, it is possible to suppress the occurrence of the situation where the transfer operation of moving the slider between the fixed linear module and the movable linear module cannot be performed due to the discontinuity of the coordinate axes set for the respective fixed linear module and movable linear module. 
     The linear conveyor system may be configured so that the controller sets the coordinate axes such that the coordinate values represented by the respective coordinate axes of the plurality of fixed linear modules and the movable linear module do not overlap each other. In such a configuration, a control for the slider can be precisely executed based on the coordinate axes not overlapping each other, in other words, the coordinate axes uniquely representing the positions in the first direction. 
     The linear conveyor system may be configured so that the coordinate axis represents the positions in the first direction by the coordinate values that linearly change with a predetermined gradient according to the position change in the first direction. Further the linear conveyor system may be configured so that the controller judges that the one coordinate axis and the other coordinate axis are not continuous if a gradient between the coordinate value of an end of the one coordinate axis on the side of the other coordinate axis and the coordinate value of an end of the other coordinate axis on the side of the one coordinate axis is different from the predetermined gradient. In this way, the continuity of the coordinate axes can be easily judged. 
     Advantageous Effects of Invention 
     According to the invention, it is possible to suppress the occurrence of a situation where the transfer operation of moving the slider between the fixed linear module and the movable linear module cannot be performed due to the discontinuity of the coordinate axes set for the respective fixed linear module and movable linear module. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view showing an example of a linear module provided in a linear conveyor system according to the invention. 
         FIG.  2    is a perspective view showing the linear module of  FIG.  1    with the inside of the linear module partially exposed. 
         FIG.  3    is a diagram schematically showing an example of the linear conveyor system according to the invention. 
         FIG.  4    is a block diagram showing an example of an electrical configuration of the linear conveyor system of  FIG.  3   . 
         FIG.  5    is a flow chart showing an example of a drive control for the transfer operation performed in the linear conveyor system shown in  FIG.  3   . 
         FIG.  6    is diagram schematically showing an example of initial setting made by the drive control shown in  FIG.  5   . 
         FIG.  7    is diagram schematically showing an example of initial setting made by the drive control shown in  FIG.  5   . 
         FIG.  8    is a chart schematically showing an example of the transfer operation performed by the drive control shown in  FIG.  5   . 
         FIG.  9    is a graph schematically showing examples of position and speed profiles used in the drive control of  FIG.  5   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG.  1    is a perspective view showing an example of a linear module provided in a linear conveyor system according to the invention, and  FIG.  2    is a perspective view showing the linear module of  FIG.  1    with the inside of the linear module partially exposed. In  FIGS.  1  and  2   , XYZ orthogonal coordinate axes including an X direction parallel to a horizontal direction, a Y direction parallel to the horizontal direction while being orthogonal to the X direction and a Z direction parallel to a vertical direction are shown. Further, an oblique right-upper side along the X direction in  FIGS.  1  and  2    is written as an X 1  side and an oblique left-lower side along the X direction in  FIGS.  1  and  2    is written as an X 2  side. Similar notations are also used as appropriate in the following drawings. This linear module has a basic configuration similar to, for example, that of a module of a linear conveyor device described in WO2018/055709A1. Here, the entire linear conveyor system is described after the linear module is described. 
     A linear module M extending in the X direction, base members  3  supporting the linear module M from below and a slider  4  engaged with the linear module M are shown in  FIGS.  1  and  2   . The linear module M is mounted on the upper ends of three base members  3  arranged at equal intervals in the X direction and drives the slider  4  in the X direction by a magnetic force. In this example, the linear module M is composed of two module units  20  arrayed in the X direction. However, the number of the module units  20  constituting the linear module M is not limited to two, and may be one, three or more. 
     The module unit  20  includes a base plate  21  extending in the X direction. The base plate  21  is a flat plate having a rectangular shape in a plan view from the Z direction. Two guide rails  22  parallel to the X direction are arranged on the upper surface of the base plate  21  while being spaced apart in the Y direction. Further, a plurality of linear motor stators  23  arranged in a row in the X direction at a predetermined arrangement pitch P 23  and a plurality of magnetic sensors  24  arranged in a row in the X direction at a predetermined arrangement pitch P 24  are mounted on the upper surface of the base plate  21 . Here, the arrangement pitch P 24  of the magnetic sensors  24  is longer than the arrangement pitch P 23  of the linear motor stators  23 . In the Y direction, the plurality of linear motor stators  23  are arranged between the two guide rails  22  and the plurality of magnetic sensors  24  are arranged between the linear motor stators  23  and one guide rail  22 . 
     The linear motor stator  23  is an electromagnet including a coil and a core inserted in the coil. On the other hand, the slider  4  is provided with a mover including a permanent magnet and a back yoke for holding the permanent magnet. The linear motor stators  23  drive the slider  4  in the X direction by giving a magnetic thrust to the mover of the slider  4  by generating a magnetic flux corresponding to an applied current. Further, a magnetic scale indicating positions in the X direction is mounted on the slider  4 , and the magnetic sensor  24  detects the position of the slider  4  in the X direction by reading the magnetic scale. The slider  4  is driven in the X direction by feedback-controlling the current applied to the linear motor stators  23  based on the position of the slider  4  detected by the magnetic sensors  24  as described later. 
     Further, the module unit  20  includes a cover member  25  having a rectangular shape in a plan view which covers these guide rails  22 , linear motor stators  23  and magnetic sensors  24  from above. The cover member  25  includes a support leg  251  projecting downward in a center in the Y direction, and the support leg  251  is mounted on the upper surface of the base plate  21 . Clearances are formed between the cover member  25  and the base plate  21  on both ends in the Y direction, and both end parts of the slider  4  inserted between the cover member  25  and the base plate  21  through these clearances are respectively engaged with the two guide rails  22 . 
     The liner module M includes a plurality of (two) module units  20  arrayed in the X direction. Such a linear module M has a rectangular shape in a plan view. The module unit  20  on the X 1  side, out of the two module units  20  of the linear module M, is laid between the base member  3  on the X 1  side end and a central base member  3 , out of the three base members  3 , and the module unit  20  on the X 2  side is laid between the base member  3  on the X 2  side end and the central base member  3 , out of the three base members  3 . 
     The slider  4  can be engaged with the guide rails  22  of the linear module M by approaching form an end of the linear module M toward a central side of the linear module M in the X direction. The slider  4  engaged with the guide rails  22  in this way is driven in the X direction by the linear module M. Further, the slider  4  can be separated from the guide rails  22  of the linear module M by exiting to outside from an end of the linear module M in the X direction. 
       FIG.  3    is a diagram schematically showing an example of the linear conveyor system according to the invention. The linear conveyor system  1  includes five linear modules M. Note that mutually different signs M 1 , M 2 , M 3 , M 4  and M 5  are given to the five linear modules M in  FIG.  3   . 
     The linear modules M 2 , M 3  and M 4  are fixed linear modules fixed to an installation surface of the linear conveyor system  1 , and the linear modules M 1 , M 5  are movable linear modules movable in the Y direction with respect to the installation surface. The fixed linear modules M 2 , M 3  and M 4  and the movable linear modules M 1 , M 5  have different lengths in the X direction while having the same width in the Y direction. However, these have the common basic configuration shown in  FIGS.  1  and  2    except the lengths in the X direction. 
     The three fixed linear modules M 2 , M 3  and M 4  are arranged in parallel to the X direction while being spaced apart in the Y direction. The fixed linear modules M 2 , M 3  and M 4  arranged in parallel to the X direction in this way have the same length in the X direction. On the other hand, the movable linear modules M 1 , M 5  have the same length shorter than the fixed linear modules M 2 , M 3  and M 4  in the X direction. However, a dimensional relationship of the movable linear modules M 1 , M 5  and the fixed linear modules M 2 , M 3  and M 4  is not limited to this example. 
     Such a linear conveyor system  1  includes two actuators  5   a ,  5   b  which drives the movable linear modules M 1 , M 5  in the Y direction. The actuator  5   a  is arranged in parallel to the Y direction on the X 2  sides of the fixed linear modules M 2 , M 3  and M 4  in the X direction. The actuator  5   b  is arranged in parallel to the Y direction on the X 1  sides of the fixed linear modules M 2 , M 3  and M 4  in the X direction. In this way, the two actuators  5   a ,  5   b  are arranged to sandwich three fixed linear modules M 2 , M 3  and M 4  in the X direction. 
     The actuator  5   a  is, for example, a single-axis robot including a ball screw parallel to the Y direction, and the movable linear module M 1  is attached to a nut of the ball screw of the actuator  5   a . This actuator  5   a  drives the movable linear module M 1  in the Y direction along a movable region Ra. Here, the movable region Ra is a region extending in the Y direction and including a facing range Fa 2  facing toward an end on the X 2  side of the fixed linear module M 2  from the X 2  side in the X direction, a facing range Fa 3  facing toward an end on the X 2  side of the fixed linear module M 3  from the X 2  side in the X direction and a facing range Fa 4  facing toward an end on the X 2  side of the fixed linear module M 4  from the X 2  side in the X direction. The facing range Fa 2  is equivalent to a presence range (including a tolerance of the movable linear module M 1 ) of the movable linear module M 1  arranged in a row with the fixed linear module M 2  in the X direction, the facing range Fa 3  is equivalent to a presence range (including the tolerance of the fixed linear module M 1 ) of the movable linear module M 1  arranged in a row with the fixed linear module M 3  in the X direction, and the facing range Fa 4  is equivalent to a presence range (including the tolerance of the fixed linear module M 1 ) of the movable linear module M 1  arranged in a row with the fixed linear module M 4  in the X direction. 
     The actuator  5   b  is, for example, a single-axis robot including a ball screw parallel to the Y direction, and the movable linear module M 5  is attached to a nut of the ball screw of the actuator  5   b . This actuator  5   b  drives the movable linear module M 5  in the Y direction along a movable region Rb. Here, the movable region Rb is a region extending in the Y direction and including a facing range Fb 2  facing toward an end on the X 2  side of the fixed linear module M 2  from the X 1  side in the X direction, a facing range Fb 3  facing toward an end on the X 1  side of the fixed linear module M 3  from the X 1  side in the X direction and a facing range Fb 4  facing toward an end on the X 1  side of the fixed linear module M 4  from the X 1  side in the X direction. The facing range Fb 2  is equivalent to a presence range (including a tolerance of the movable linear module M 5 ) of the movable linear module M 5  arranged in a row with the fixed linear module M 2  in the X direction, the facing range Fb 3  is equivalent to a presence range (including the tolerance of the fixed linear module M 5 ) of the movable linear module M 5  arranged in a row with the fixed linear module M 3  in the X direction and the facing range Fb 4  is equivalent to a presence range (including the tolerance of the fixed linear module M 5 ) of the movable linear module M 5  arranged in a row with the fixed linear module M 4  in the X direction. 
     In such a linear conveyor system  1 , the slider  4  can be circularly driven. For example, the fixed linear module M 2  drives the slider  4  engaged therewith toward the X 1  side in the X direction with the movable linear module M 5  located in the facing range Fb 2 , whereby the slider  4  can be moved from the fixed linear module M 2  to the movable linear module M 5 . Then, the movable linear module M 5  located in the facing range Fb 4  drives the slider  4  engaged therewith toward the X 2  side in the X direction after the actuator  5   b  moves the movable linear module M 5  from the facing range Fb 2  to the facing range Fb 4 , whereby the slider  4  can be moved from the movable linear module M 5  to the fixed linear module M 4 . 
     Further, the fixed linear module M 4  drives the slider  4  engaged therewith toward the X 2  side in the X direction with the movable linear module M 1  located in the facing range Fa 4 , whereby the slider  4  can be moved from the fixed linear module M 4  to the movable linear module M 1 . Then, the movable linear module M 1  located in the facing range Fa 2  drives the slider  4  engaged therewith toward the X 1  side in the X direction after the actuator  5   a  moves the movable linear module M 1  from the facing range Fa 4  to the facing range Fa 2 , whereby the slider  4  can be moved from the movable linear module M 1  to the fixed linear module M 2 . 
     In this way, the slider  4  can be circularly driven clockwise. Further, the slider  4  can be circularly driven counterclockwise by performing an operation opposite to the above one. Such a circular drive is not limited to the one between the fixed linear modules M 2  and M 4 , and can be similarly performed between the fixed linear modules M 2  and M 3  and between the fixed linear modules M 3  and M 4 . Further, the circular drive is merely an example of a drive mode of the slider  4  executable by the linear conveyor system  1  and the slider  4  can be driven in various other modes. 
       FIG.  4    is a block diagram showing an example of an electrical configuration of the linear conveyor system of  FIG.  3   . The linear conveyor system  1  includes a control device  11  which controls the position of each slider  4  while monitoring the entire system. This control device  11  is a computer such as a personal computer. 
     The control device  11  includes a controller  12 , a storage  13  and a display  14 . The controller  12  is, for example, a processor configured by a CPU (Central Processing Unit) and performs computation in the control device  11 . The storage  13  is, for example, configured by an HDD (Hard Disk Drive) and stores data and programs used in computation in the control device  2 . Particularly, the storage  13  stores a program  18  for causing the controller  12  of the control device  11  to execute a drive control of  FIG.  5    to be described later. This program  18  may be installed in the storage  13  by being provided in a state readable by the control device  11  by means of a recording medium  19  such as a USB (Universal Serial Bus) memory or may be installed in the storage  13  by being downloaded from an Internet server. The display  14  is, for example, a touch panel display and functions as a UI (User Interface) for not only showing displays to a user, but also receiving input operations from the user. 
     The controller  12  of such a control device  11  causes each of the linear modules M 1  to M 5  to drive the slider  4  by feedback-controlling the linear motor stators  23  based on the position of the slider  4  detected by the magnetic sensors  24 . Further, each of the actuators  5   a ,  5   b  includes a servo motor  51  which rotates the ball screw and an encoder  52  which detects the rotational position of the servo motor  51 . The controller  12  causes the respective actuators  5   a ,  5   b  to drive the movable linear modules M 1 , M 5  by feedback-controlling the servo motors  51  based on the rotational positions detected by the encoders  52 . 
     Such a controller  12  controls the drive of the slider  4  by selectively executing a position control and a speed control for each slider  4 . Specifically, the controller  12  controls the position of the slider  4  (position control) by executing a feedback control of controlling a current to be supplied to the linear motor stators  23  of the movable linear modules M 1  to M 5  based on a deviation between a position detection value Dp indicating the position of the slider  4  detected by the magnetic sensors  24  of the linear modules M 1  to M 5  and a position command value Ip ( FIG.  9   ). Further, the controller  12  controls a speed of the slider  4  (speed control) by executing a feedback control of controlling the current to be supplied to the linear motor stators  23  of the movable linear modules M 1  to M 5  based on a deviation between a speed detection value Dv indicating the speed of the slider  4  detected by the magnetic sensors  24  of the linear modules M 1  to M 5  and a speed command value Iv ( FIG.  9   ). 
     Particularly, a transfer operation of moving the slider  4  between one fixed linear module and the movable linear module M 1 , M 5  while locating the movable linear module M 1 , M 5  in the facing range facing the one fixed linear module, out of the plurality of fixed linear modules M 2 , M 3  and M 4  arranged in parallel can be performed in this embodiment. Such a transfer operation is controlled as follows. 
       FIG.  5    is a flow chart showing an example of a drive control for the transfer operation performed in the linear conveyor system shown in  FIG.  3   ,  FIGS.  6  and  7    are diagrams schematically showing an example of initial setting made by the drive control shown in  FIG.  5   ,  FIG.  8    is a chart schematically showing an example of the transfer operation performed by the drive control shown in  FIG.  5   , and  FIG.  9    is a graph schematically showing examples of position and speed profiles used in the drive control of  FIG.  5   . The flow chart of  FIG.  5    is performed in accordance with the program  18  by the controller  12 . 
     In Step S 101 , coordinate axes A 1  to A 5  are set for the respective linear modules M 1  to M 5  (initial setting of coordinate axes). The coordinate axes A 1  to A 5  have position coordinate values P which linearly (i.e. with a certain gradient SL) increase according to position changes from the X 1  side toward the X 2  side in the X direction and are individually set for the liner modules M 1  to M 5 . Specifically, as shown in  FIG.  6   , the movable linear modules M 1  to M 5  are connected in series in this order by a wiring W, and a coordinate setting command is transmitted from the control device  11  to the linear module M 1  on the most upstream side of a signal path, out of these linear modules M 1  to M 5 . The linear module M 1  having received the coordinate setting command sets, in itself, the coordinate axis A 1  having position coordinate values P of “0 to 20” which linearly increase with the gradient SL from an end on the X 1  side toward an end on the X 2  side in the X direction. When the setting of the coordinate axis A 1  is completed, the linear module M 1  transmits the coordinate setting command, together with a maximum value (=20) of the position coordinate values P, to the linear module M 2 . The linear module M 2  having received the coordinate setting command sets, in itself, the coordinate axis A 2  having position coordinate values P of “21 to 120” which linearly increase with the gradient SL from an end on the X 1  side toward an end on the X 2  side in the X direction. Note that a minimum value (i.e. the first value) of the position coordinate values P set for the linear module M 2  is a value consecutively following the maximum value of the position coordinate values P received from the linear module M 1  on an upstream side. When the setting of the coordinate axis A 2  is completed, the linear module M 2  transmits the coordinate setting command, together with a maximum value (=120) of the position coordinate values P, to the linear module M 3 . 
     By Repeating this, 
     The coordinate axis A 1  having the position coordinate values P of “0 to 20” is set for the linear module M 1 , 
     The coordinate axis A 2  having the position coordinate values P of “21 to 120” is set for the linear module M 2 , 
     The coordinate axis A 3  having the position coordinate values P of “121 to 220” is set for the linear module M 3 , 
     The coordinate axis A 4  having the position coordinate values P of “221 to 320” is set for the linear module M 4 , and 
     The coordinate axis A 5  having the position coordinate values P of “321 to 340” is set for the linear module M 5 . 
     Note that a change rate of changing the position coordinate value P with respect to a position change in the X direction, i.e. the gradient, is the same among the coordinate axes A 1  to A 5 . 
     In this way, the drive control of the slider  4  can be executed in an initial set state Si where the coordinate axes A 1  to A 5  are so set that the position coordinate values P represented by the respective coordinate axes A 1  to A 5  of the plurality of linear modules M do not overlap each other. When the initial setting of the coordinate axes is completed in this way, whether or not to drive the slider  4  for the transfer operation is confirmed (Step S 102 ). If it is judged in Step S 102  to drive the slider  4  (YES), the linear module M having the coordinate axis A, to which a movement start position Ls (i.e. current position) of the slider  4  belongs (in other words, the linear module M engaged with the slider  4  stopped at the movement start position Ls) is specified (Step S 103 ). Further, the linear module M having the coordinate axis A, to which a movement target position Ld of the slider  4  belongs (in other words, the linear module M engaged with the slider  4  having reached the movement target position Ld) is specified (Step S 104 ). 
     Then, the continuity of the coordinate axis A of the linear module M specified in Step S 103 , to which the movement start position Ls belongs, and the coordinate axis A of the linear module M specified in Step S 104 , to which the movement target position Ld belongs, is judged (Step S 105 ). Specifically, if a gradient SLb of a straight line connecting the position coordinate value P of an end of the coordinate axis A of the linear module M, to which the movement start position Ls belongs, on the side of the movement target position Ld and the position coordinate value P of an end of the coordinate axis A of the linear module M, to which the movement target position Ld belongs, on the side of the movement start position Ls matches the gradient SL indicating the change rate of the position coordinate values P on the coordinate axes A (A 1  to A 5 ), continuity is judged. Unless otherwise, discontinuity is judged. 
     For example, in the case of moving the slider  4  from the fixed linear module M 4  to the movable linear module M 5  facing the fixed linear module M 4  (i.e. movable linear module M 5  located in the facing position Fb 4 ), the coordinate axis A 4  of the fixed linear module M 4  and the coordinate axis A 5  of the movable linear module M 5  are continuous. Thus, in Step S 105 , the continuity (YES) of the coordinate axes A 4 , A 5  is judged and the position control of the slider  4  is executed in Step S 106 . 
     In Step S 106 , a position profile Fp of  FIG.  9    is generated based on the coordinate axes A 4 , A 5  having the consecutive position coordinate values P of “220 to 340”. In the graph of  FIG.  9   , a horizontal axis represents time and a left vertical axis represents the position of the slider  4  on the coordinate axis. As shown in  FIG.  9   , the position profile Fp shows a change of the position (in other words, position command value Ip) of the slider  4  moving from the movement start position Ls to the movement target position Ld over time. The position of the slider  4  is feedback-controlled based on a deviation (=Ip-Dp) between the position command value Ip at each time t represented by this position profile Fp and the position detection value Dp by the magnetic sensors  24  for detecting the position of the slider  4 . In this way, a servo control is executed to cause the position of the slider  4  to follow the position command value Ip. When the slider  4  reaches the movement target position Ld, whether or not to finish the drive control is judged (Step S 110 ). 
     On the other hand, in a drive mode shown in a field “Transfer Operation C” of  FIG.  8   , the slider  4  is driven from the movement start position Ls belonging to the coordinate axis A 2  of the fixed linear module M 2  to the movement target position Ld belonging to the coordinate axis A 5  of the movable linear module M 5  facing the fixed linear module M 2  (i.e. the movable linear module M 5  located in the facing position Fb 2 ). In this case, as shown in a field “Coordinate Axes” of  FIG.  8   , the coordinate axis A 2  of the fixed linear module M 2  and the coordinate axis A 5  of the movable linear module M 5  are discontinuous, and a gap G is present between the position coordinate value P of an end E 2  of the coordinate axis A 2  on the side of the coordinate axis A 5  and the position coordinate value P of an end E 5  of the coordinate axis A 5  on the side of the coordinate axis A 2 . Thus, it is judged in Step S 105  that the coordinate axes A 2 , A 5  are not continuous (NO) and advance is made to Step S 107 . 
     Specifically, in the example of the transfer operation C, a gradient SLb (=(y 5 -y 2 )/(x 5 -x 2 )) between the coordinate value P 2  (x 2 , y 2 ) of the end E 2  of the coordinate axis A 2  (one coordinate axis) on the side of the coordinate axis A 5  (other coordinate axis) and the coordinate value P 5  (x 5 , y 5 ) of the end E 5  of the coordinate axis A 5  (other coordinate axis) on the side of the coordinate axis A 2  (one coordinate axis) is calculated. Then, whether the gradient SLb is equal to or different from the above gradient SL of each coordinate axis A 2 , A 5  is judged. Since the gradient SLb and the gradient SL are different in this example, it is judged that the coordinate axes A 2 , A 5  are not continuous. 
     In Step S 107 , a speed profile Fv of  FIG.  9    is generated. In the graph of  FIG.  9   , the horizontal axis represents time and a right vertical axis represents the speed of the slider  4  on the coordinate axis. As shown in  FIG.  9   , the speed profile Fv shows a change of the speed (in other words, speed command value Iv) of the slider  4  moving from the movement start position Ls to the movement target position Ld over time. However, this speed control has a steady-state deviation and the slider  4  stops at a stop position La near the movement target position Ld when the speed control is completed. The speed of the slider  4  is feedback-controlled based on a deviation (=Iv-Dv) between the speed command value Iv at each time t represented by this speed profile Fv and the speed detection value Dv by the magnetic sensors  24  for detecting the speed of the slider  4 . In this way, a servo control is executed to cause the speed of the slider  4  to follow the speed command value Iv. 
     In Step S 108 , whether or not the speed control of the slider  4  has been completed, in other words, whether the slider  4  has stopped is judged. When it is judged that the slider  4  has stopped and the speed control of the slider  4  has been completed (“YES” in Step S 108 ), the position control is executed for this slider  4  (Step S 109 ). That is, as described above, the steady-state deviation remains between the stop position La of the slider  4  moved by the speed control and the movement target position Ld. Accordingly, the controller  12  moves the slider  4  from the stop position La where the slider  4  stops when the speed control in the transfer operation C is completed to the movement target position Ld by the position control. Note that the position of the slider  4  is moved from the fixed linear module M 2  to the movable linear module M 5  by the speed control associated with the transfer operation. That is, the position control of the slider  4  is executed singly by the movable linear module M 5  as a movement destination of the slider  4  by the transfer operation, out of the fixed linear module M 2  and the movable linear module M 5  used for the transfer operation. Thus, the discontinuity of the coordinate axes A 2 , A 5  is not problematic in this position control. When the position control is completed and the slider  4  reaches the movement target position Ld, whether or not to finish the drive control is judged (Step S 110 ). 
     Return is made to Step S 102  unless the drive control is finished (“NO” in Step S 110 ), whereas the flow chart of  FIG.  5    is finished if the drive control is finished (“YES” in Step S 110 ). 
     As just described, the controller  12  selectively uses the position control and the speed control according to the continuity of the coordinate axes. Specifically, the controller  12  drives the slider  4  by the feedback control based on the deviation between the position command value Ip generated based on the position profile Fp representing the change of the position of the slider  4  over time and the position detection value Dp indicating the detected position of the slider  4  in the position control (Step S 106 ). On the other hand, the controller  12  drives the slider  4  by the feedback control based on the deviation between the speed command value Iv generated based on the speed profile Fv representing the change of the speed of the slider  4  over time and the speed detection value Dv indicating the detected speed of the slider  4  in the speed control (Step S 107 ). 
     In the example described above, the transfer operation C of moving the slider between one fixed linear module M 2  and the movable linear module M 5  while locating the movable linear module M 5  in the facing range Fb 2  facing toward the one fixed linear module M 2 , out of the plurality of linear modules M 1  to M 5  arranged in parallel, is performed. At this time, a judgement process (Step S 105 ) of judging whether or not the coordinate axis A 2  (one coordinate axis) of the one fixed linear module M 2  and the coordinate axis A 5  (other coordinate axis) of the movable linear module M 5  are continuous is performed (Step S 105 ). If it is judged in the judgment process before the transfer operation C that the coordinate axes A 2 , A 5  are not continuous, the transfer operation C is performed (Step S 107 ) while the speed control (not the position control) is executed for the slider  4 . Thus, it is possible to suppress the occurrence of a situation where the transfer operation C of moving the slider  4  between the movable linear module M 1  and the movable linear module M 5  cannot be performed due to the discontinuity of the coordinate axes A 2 , A 5  respectively set for the movable linear module M 1  and the movable linear module M 5 . 
     Further, the control device  11  moves the slider  4  from the stop position La where the slider  4  stops when the speed control is completed to the movement target position Ld by the position control (Step S 109 ) when the speed control (Steps S 107 , S 108 ) is completed in the transfer operation of moving the slider  4  from the movement start position Ls toward the movement target position Ld. In such a configuration, the steady-state deviation (i.e. difference between the stop position La and the movement target position Ld) remaining when the speed control is completed can be solved by the position control and the slider  4  can be reliably moved to the movement target position Ld. 
     Further, if it is judged before the transfer operation C that the coordinate axis A 4  (one coordinate axis) and the coordinate axis A 5  (other coordinate axis) are continuous (“YES” in Step S 105 ) as a result of performing the judgment process (Step S 105 ), the control device  11  performs the transfer operation C while controlling the drive of the slider  4  in the transfer operation C by the position control (Step S 106 ). That is, the transfer operation of the slider  4  is performed by the position control if it is judged in the judgment process (Step S 105 ) that the coordinate axes, to which the movement start position Ls and the movement target position Ld respectively belong, are continuous, and the transfer operation of the slider  4  is performed by the speed control if it is judged in the judgment process (Step S 105 ) that these coordinate axes are not continuous. Thus, it is possible to suppress the occurrence of a situation where the transfer operation of moving the slider  4  between the fixed linear module and the movable linear module cannot be performed due to the discontinuity of the coordinate axis A 2 , A 3 , A 4  and the coordinate axis A 1 , A 5  respectively set for the fixed linear module M 2 , M 3 , M 4  and the movable linear module M 1 , M 5 . 
     Further, the control device  11  sets the position coordinate values P such that the position coordinate values P represented by the respective coordinate axes A 2 , A 3 , A 4 , A 1  and A 5  of the plurality of fixed linear modules M 2 , M 3 , M 4  and the movable linear modules M 1 , M 5  do not overlap each other. In such a configuration, a control for the slider  4  can be precisely performed based on the coordinate axes A 2 , A 3 , A 4 , A 1  and A 5  not overlapping each other, in other words, the coordinate axes A 2 , A 3 , A 4 , A 1  and A 5  uniquely representing the positions in the X direction. 
     Further, the coordinate axes A 1  to A 5  represent the positions in the X direction by the position coordinate values P that linearly change with the predetermined gradient according to the position changes in the X direction. In the above example, the control device  11  judges that the coordinate axes A 2  and A 5  are not continuous if the gradient between the position coordinate value P of the end E 2  of the coordinate axis A 2  on the side of the coordinate axis A 5  and the position coordinate value P of the end E 5  of the coordinate axis A 5  on the side of the coordinate axis A 2  is different from the gradient of the position coordinate values P on each coordinate axis A 1  to A 5 . In this way, the continuity of the coordinate axes A 2 , A 5  can be easily judged. 
     As just described, in this embodiment, the linear conveyor system  1  corresponds to an example of a “linear conveyor system” of the invention, the control device  11  corresponds to an example of a “controller” of the invention, the program  18  corresponds to an example of a “linear conveyor system control program” of the invention, the recording medium  19  corresponds to an example of a “recording medium” of the invention, the slider  4  corresponds to an example of a “slider” of the invention, the coordinate axes A 1  to A 5  correspond to an example of “coordinate axes” of the invention, the coordinate axis A 2  corresponds to an example of “one coordinate axis” of the invention, the coordinate axis A 5  corresponds to examples of an “other coordinate axis” of the invention, the position coordinate value P corresponds to an example of a “coordinate value” of the invention, the transfer operation C corresponds to an example of a “transfer operation” of the invention, the facing ranges Fa 2  to Fa 4 , Fb 2  to Fb 4  correspond to examples of a “facing range” of the invention, the fixed linear modules M 2 , M 3  and M 4  correspond to an example of “fixed linear modules” of the invention, the fixed linear module M 2  corresponds to an example of “one fixed linear module” of the invention, the movable linear modules M 1 , M 5  correspond to examples of a “movable linear module” of the invention, each of a slider transfer mechanism Ta constituted by the movable linear module M 1  and the actuator  5   a  and a slider transfer mechanism Tb constituted by the movable linear module M 5  and the actuator  5   b  corresponds to an example of a “slider transfer mechanism” of the invention, the movement start position Ls corresponds to an example of a “movement start position” of the invention, the movement target position Ld corresponds to an example of a “movement target position” of the invention, the X direction corresponds to an example of a “first direction” of the invention, the Y direction corresponds to an example of a “second direction” of the invention, the position profile Fp corresponds to an example of a “position profile” of the invention, the position command value Ip corresponds to an example of a “position command value” of the invention, the position detection value Dp corresponds to an example of a “position detection value” of the invention, the speed profile Fv corresponds to an example of a “speed profile” of the invention, the speed command value Iv corresponds to an example of a “speed command value” of the invention, and the speed detection value Dv corresponds to an example of a “speed detection value” of the invention. 
     Note that the invention is not limited to the above embodiment and various changes other than the aforementioned ones can be made without departing from the gist of the invention. For example, a combination of the movable linear module and the fixed linear module, to which the speed control is applied in the transfer operation, is not limited to the above example. The speed control may be executed in performing the transfer operation in a combination of the movable linear module M 1  and the fixed linear module M 3 , a combination of the movable linear module M 1  and the fixed linear module M 4 , a combination of the movable linear module M 5  and the fixed linear module M 2  and a combination of the movable linear module M 5  and the fixed linear module M 3 . Further, a moving direction of the slider  4  in the transfer operation may be from the movable linear module M 1  to the fixed linear module M 3 . The same applies also to the other combinations. 
     Further, the set mode of the coordinate axes A 1  to A 5  in the initial set state Si is not limited to the above example. For example, the position coordinate values P may be set to increase in order of the coordinate axes A 5 , A 4 , A 3 , A 2  and A 1 . 
     Further, an array direction of the fixed linear modules M 2 , M 3  and M 4  is not limited to the Y direction (horizontal direction) and may be the Z direction (vertical direction). In this case, the actuators  5   a ,  5   b  elevate and lower the movable linear modules M 1 , M 5  in the Z direction. 
     Further, the number and arrangement of the fixed linear modules or movable linear modules may be changed as appropriate. Accordingly, the fixed linear module M 3  may be omitted. Further, the linear conveyor system  1  may be configured to move the slider  4  along an L-shaped path composed of one fixed linear module M 2  and one actuator  5   a  for driving the movable linear module M 1 . Alternatively, the fixed linear module M 4  may be moved in parallel to the X direction from the state of  FIG.  3    and arranged on a side opposite to the fixed linear modules M 2 , M 3  with respect to the actuator  5   b.    
     Further, driving directions of the slider  4  by the fixed linear modules Ma,  2   b  and driving directions of the slider  4  by the actuators  5   c ,  5   d  need not necessarily be orthogonal and may be oblique to each other. 
     REFERENCE SIGNS LIST 
     
         
           1  . . . linear conveyor system 
           11  . . . linear conveyor system (controller) 
           18  . . . program (control program for a linear conveyor system) 
           19  . . . recording medium 
           4  . . . slider 
         A 1  . . . coordinate axes 
         A 2  . . . coordinate axes (one coordinate axis) 
         A 3  . . . coordinate axes 
         A 4  . . . coordinate axes 
         A 5  . . . coordinate axes (other coordinate axis) 
         P . . . one coordinate axis 
         E 2  . . . end of the other coordinate axis 
         P 2  . . . coordinate value of end of the other coordinate axis 
         E 5  . . . end of the one coordinate axis 
         P 5  . . . coordinate value of end of the one coordinate axis 
         SL . . . predetermined gradient 
         SLb . . . gradient between the coordinate value of end of the other coordinate axis and the coordinate value of end of the one coordinate axis 
         C . . . transfer operation 
         Fa 2 -Fa 4 , Fb 2 -Fb 4  . . . facing range 
         M 1  . . . movable liner module 
         M 2  . . . fixed linear module (one fixed linear module) 
         M 3  . . . fixed linear module 
         M 4  . . . fixed linear module 
         M 5  . . . movable linear module 
         Ta, Tb . . . slider transfer mechanism 
         La . . . stop position 
         Ls . . . movement start position 
         Ld . . . movement target position 
         X . . . X direction (first direction) 
         Y . . . Y direction (second direction) 
         Fp . . . position profile 
         Ip . . . position command value 
         Dp . . . position detection value 
         Fv . . . speed profile 
         Iv . . . speed command value 
         Dv . . . speed detection value