FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
PROGRAMMABLE LOGIC CONTROLLER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

DESCRIPTION
Field
[0001] The present invention relates to a programmable logic controller that serves as a client when connected to a server.
Background
[0002] A programmable logic controller that controls a device to be controlled (hereinafter, "control target device") that is represented by an industrial machine retains files of a production quantity, an amount of energy consumption, and quality data of manufactured products with regard to a manufacturing line, for example. The files retained in the programmable logic controller are transmitted to a high-order server by using a protocol unique to a manufacturer of the programmable logic controller or a general protocol, and are used for purposes, such as preparation of a production plan or a quality analysis. An example of the general protocol is an FTP (file transfer protocol). A specific example of the high-order server that is a transmission destination of the files is a server forming a manufacturing execution system (MES).
[0003] An example of a method for preventing a file in the server from being updated with incomplete data that is being received because of cable disconnection during reception of the file is a method that does not overwrite the file with received data while the server is receiving the file, and performs overwriting after completion of the reception.

[0004] Patent Literature 1 discloses a process controller that stores a program transmitted from a maintenance terminal in a second storage region that is a volatile memory and, after completion of the reception of the program, rewrites the program in a first storage region that is a non-volatile memory. A motion controller disclosed in Patent Literature 1 does not rewrite the program in the first storage region until completion of transfer of the program, when the program is transferred from the maintenance terminal that is a server side. Therefore, in a case where transfer of the program is not completed normally, the controller can continue the operation using the program in the first storage region.
[0005] Patent Literature 2 discloses a high-order control device that reads out data in a sensor-setting information memory of a network unit through message communication.
Citation List Patent Literatures
[0006] Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 2006-338304
Patent Literature 2: Japanese Patent Application Laid-Open Publication No. 2011-28525
Summary
Technical Problem
[0007] A program design of a programmable logic controller that controls an industrial machine and a program design of a server that analyzes and studies data received from the programmable logic controller are greatly different in required techniques. Therefore, a program designer of the programmable logic controller and a program

designer of the server are often different.
[0008] For this reason, in a case where it is unclear whether the server has a function of preventing a file from being updated with incomplete data that is being transmitted or a case where it is known that the server does not have the aforementioned function, the program designer of the programmable logic controller needs to request the program designer of the server to provide the server with the function of preventing the file from being updated with the incomplete data.
[0009] When the techniques in Patent Literatures 1 and 2 are combined, there is obtained a configuration in which a server-side device reads out data in a client-side device through message communication. However, in a case where the function of preventing the file in the server from being updated with the incomplete data is achieved by an operation at the initiative of the server side, the program designer of the programmable logic controller needs to request the program designer of the server to provide the server with a function of reading out the data in the client-side device through message communication. [0010] If the program designer of the server refuses to provide the server with the function of preventing the file from being updated with the incomplete data, the program designer of the programmable logic controller cannot prevent the file in the server from being updated with the incomplete data. If the file in the server is updated with the incomplete data, the server cannot prepare a production plan or perform a quality analysis correctly. This leads to reduction in a factory operation ratio or deterioration of the product quality.
[0011] The present invention has been achieved in view of the above problems, and an object of the present

invention is to provide a programmable logic controller that can prevent a file in a server from being updated with incomplete data, irrespective of whether the server is provided with a function of preventing the file from being updated with the incomplete data.
Solution to Problem
[0012] To solve the above problem and achieve the object, the present invention provides A programmable logic controller to control a control target device according to a sequence program to thereby acquire information from the control target device, the programmable controller serving as a client when the programmable logic controller is connected to a server, the programmable logic controller comprising: a storage device to store therein a data file created on a basis of the information from the control target device; and a file transfer processing unit to, when transferring to the server the data file stored in the storage device, request the server to delete a pre-update data file in the server after completion of transfer of the data file.
Advantageous Effects of Invention
[0013] According to the programmable logic controller of the present invention, an effect is obtained where it is possible to prevent a file in a server from being updated with incomplete data, irrespective of whether the server is provided with a function of preventing the file from being updated with the incomplete data.
Brief Description of Drawings
[0014] FIG. 1 is a block diagram illustrating a
configuration of a system to which a programmable logic

controller according to an embodiment of the present invention is applied.
FIG. 2 is a flowchart illustrating an operation flow of the system to which the programmable logic controller according to the present embodiment is applied.
FIG. 3 is a sequence diagram at a time of file transmission in the system to which the programmable logic controller according to the present embodiment is applied.
FIG. 4 is a flowchart illustrating another example of the operation flow of the system to which the programmable logic controller according to the present embodiment is applied.
Description of Embodiments
[0015] A programmable logic controller according to an embodiment of the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiment.
[0016] Embodiment.
FIG. 1 is a block diagram illustrating a configuration of a system to which a programmable logic controller according to an embodiment of the present invention is applied. The system to which the programmable logic controller according to the present embodiment is applied includes a programmable logic controller 1 that controls a control target device 9, and a server 6 that prepares a production plan and performs a quality analysis. A personal computer can be applied to the server 6. However, the server 6 is not limited thereto.
[0017] The programmable logic controller 1 includes an arithmetic processing unit 2 that performs a determination process according to a user's operation, an internal device 3 to be used by the arithmetic processing unit 2, a file

transfer processing unit 5 that performs file transfer by an FTP in response to a request from the arithmetic processing unit 2, a communication processing unit 4 that performs communication with the server 6 in response to a request from the file transfer processing unit 5, and an external storage device 7 that retains therein a file to be transferred. An external storage medium 8 can be inserted into the external storage device 7. The file to be transferred is stored in the external storage medium 8. That is, the external storage device 7 and the external storage medium 8 are a storage device that stores therein a data file created on the basis of information from a control target device. An example of the external storage device 7 is an SD memory card reader/writer. An example of the external storage medium 8 is an SD memory card. The external storage medium 8 may not be removable from the external storage device 7.
[0018] The arithmetic processing unit 2 executes a sequence program to control the control target device 9, and stores information acquired from the control target device 9 in the internal device 3. The arithmetic processing unit 2 creates a data file from the information stored in the internal device 3 and stores the data file in the external storage medium 8 inserted into the external storage device 7. That is, the external storage device 7 stores in the external storage medium 8 the data file created on the basis of the information from the control target device 9.
[0019] The file transfer processing unit 5 is implemented in the programmable logic controller 1 by a firmware process. Therefore, a user of the programmable logic controller 1 is not required to create and implement a sequence program.

[0020] FIG. 2 is a flowchart illustrating an operation flow of a system to which the programmable logic controller according to the present embodiment is applied. At Step SI, with a user's operation as a trigger, the arithmetic processing 2 requests the file transfer processing 5 to perform file transfer by the FTP. When the file transfer by the FTP is requested from the arithmetic processor 2, the file transfer processing unit 5 reads out a file to be transferred from the external storage medium 8, issues to the communication processing unit 4 an instruction to transmit the file to the sever 6 with another name, together with a file-transmission start message, and starts file transmission. The operation at Step SI is a first operation of transmitting a data file stored in the external storage medium 8 to the server 6 with another file name.
[0021] At Step S2, the file transfer processing unit 5 confirms whether a file-reception completion response has been received from the server 6 through the communication processing unit 4. When the file-reception completion response has not been received (NO at Step S2), the file transfer processing 5 confirms at Step S4 whether timeout has been done. When the timeout has been done (YES at Step S4), the file transfer processing unit 5 determines that the file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S4), the operation proceeds to Step S2, and the file transfer processing unit 5 confirms again whether the file-reception completion response has been received.
[0022] When the file-reception completion response has been received (YES at Step S2), the operation proceeds to Step S3, and the file transfer processing unit 5 transmits a message requesting deletion of a pre-update file in the

server 6, to the server 6 through the communication processing unit 4. The operation at Step S3 is a second operation of requesting the server 6 to delete a data file having the same file name as that of a data file stored in the external storage medium 8.
[0023] At Step S5, the file transfer processing unit 5 confirms whether a file-deletion completion response has been received from the server 6 through the communication processing unit 4. When the file-deletion completion response has not been received (NO at Step S5), the file transfer processing unit 5 confirms at Step S7 whether the timeout has been done. When the timeout has been done (YES at Step S7), the file transfer processing unit 5 determines that the file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S7), the operation proceeds to Step S5, and the file transfer processing unit 5 confirms again whether the file-deletion completion response has been received.
[0024] When the file-deletion completion response has been received (YES at Step S5), the operation proceeds to Step S6, and the file transfer processing unit 5 transmits a message specifying a file name to be changed, to the server 6 through the communication processing unit 4. [0025] At Step S8, the file transfer processing unit 5 confirms whether a file-name-specification completion response has been received from the server 6 through the communication processing unit 4. When the file-name-specification completion response has not been received (NO at Step S8), the file transfer processing unit 5 confirms at Step S10 whether the timeout has been done. When the timeout has been done (YES at Step S10) , the file transfer processing unit 5 determines that the file transmission has failed, and ends the process abnormally. When the timeout

is not done (NO at Step S10), the operation proceeds to Step S8, and the file transfer processing unit 5 confirms again whether the file-name-specification completion response has been received.
[0026] When the file-name-specification completion response has been received (YES at Step S8), the operation proceeds to Step S9, and the file transfer processing unit 5 transmits a message requesting a file name change, to the server 6 through the communication processing unit 4. The operations at Steps S6 and S9 are a third operation of requesting the server 6 to change a file name of a data file transmitted with another file name to the same file name as that of a data file stored in the external storage medium 8.
[0027] At Step Sll, the file transfer processing unit 5 confirms whether a file-name-change completion response has been received from the server 6 through the communication processing unit 4. When the file-name-change completion response has not been received (NO at Step Sll), the file transfer processing unit 5 confirms at Step S12 whether the timeout has been done. When the timeout has been done (YES at Step S12), the file transfer processing unit 5 determines that file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S12), the operation proceeds to Step Sll, and the file transfer processing unit 5 confirms again whether the file-name-change completion response has been received. [0028] When the file-name-change completion response has been received (YES at Step Sll), the file transfer processing unit 5 determines that file transmission has been performed successfully, and ends the process normally. [0029] FIG. 3 is a sequence diagram at a time of file transmission in a system to which the programmable logic

controller according to the present embodiment is applied. The programmable logic controller 1 transmits to the server 6 a file-transmission start message Ml together with a file to be transferred. The server 6 having received the file-transmission start message Ml returns a file-reception completion response M2 to the programmable logic controller 1.
[0030] The programmable logic controller 1 having received the file-reception completion response M2 from the server 6 transmits to the server 6 a message M3 requesting deletion of a pre-update file. The server 6 having received the message M3 requesting deletion of the pre-update file deletes the pre-update file, and thereafter returns a file-deletion completion response M4 to the programmable logic controller 1.
[0031] The programmable logic controller 1 having received the file-deletion completion response M4 from the server 6 transmits a file-name specification message M5 to the server 6. The server 6 having received the file-name specification message M5 returns a file-name-specification completion response M6 to the programmable logic controller 1.
[0032] The programmable logic controller 1 having received the file-name-specification completion response M6 from the server 6 transmits a file-name-change request message M7 to the server 6. The server 6 having received the file-name-change request message M7 changes a file name specified by the file-name specification message M5 to a file name specified by the file-name-change request message M7, and thereafter returns a file-name-change completion. response M8 to the programmable logic controller 1. Upon reception of the file-name-change completion response M8 from the server 6, the programmable logic controller 1

completes file transfer.
[0033] With a user's operation as a trigger, the file transfer processing unit 5 performs the first operation of transmitting a data file stored in the external storage medium 8 to the server 6 with another file name, the second operation of requesting the server 6 to delete a data file having the same file name as that of the data file stored in the external storage medium 8, and the third operation of requesting the server 6 to change the file name of the data file transmitted with the other file name to the same file name as that of the data file stored in the external storage medium 8. Therefore, it is not necessary for a user to consciously perform a special operation in order to prevent a file in the server 6 from being updated with incomplete data. As a result, the update of a file in the server 6 with incomplete data can be surely prevented. [0034] FIG. 4 is a flowchart illustrating another example of the operation flow of the system to which the programmable logic controller according to the present embodiment is applied. At Step S51, with a user's operation as a trigger, the arithmetic processing unit 2 requests the file transfer processing unit 5 to perform file transfer by the FTP. Upon reception of the request for the file transfer by the FTP from the arithmetic processing unit 2, the file transfer processing unit 5 specifies a file to be transferred, and transmits a message specifying a file name to be changed, to the server 6 through the communication processor 4.
[0035] At Step S52, the file transfer processing unit 5 confirms whether a file-name-specification completion response has been received from the server 6 through the communication processing unit 4. When the file-name-specification completion response has not been received (NO

at Step S52), the file transfer processing unit 5 confirms at Step S54 whether the timeout has been done. When the timeout has been done (YES at Step S54), the file transfer processing unit 5 determines that file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S54), the operation proceeds to Step S52, and the file transfer processing unit 5 confirms again whether the file-name-specification completion response has been received.
[0036] When the file-name-specification completion response has been received (YES at Step S52), the operation proceeds to Step S53, and the file transfer processing unit 5 transmits a file-name-change request message to the server 6 through the communication processing unit 4. The operations at Steps S51 and S53 are a fourth operation of requesting the server 6 to change a file name of a pre-update data file in the server 6 to another file name. [0037] At Step S55, the file transfer processing unit 5 confirms whether a file-name-change completion response has been received from the server 6 through the communication processing unit 4. When the file-name-change completion response has not been received (NO at Step S55), the file transfer processing unit 5 confirms at Step S57 whether the timeout has been done. When the timeout has been done (YES at Step S57), the file transfer processing unit 5 determines that file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S57), the operation proceeds to Step S55, and the file transfer processing unit 5 confirms again whether the file¬name-change completion response has been received. [0038] When the file-name-change completion response has been received (YES at Step S55), the operation proceeds to Step S56, and the file transfer processing unit 5 reads out

from the external storage medium 8 a file to be transferred, issues to the communication processing unit 4 a file-transmission start message and an instruction to transmit the file to the server 6, and starts file transmission. The operation at Step S56 is a fifth operation of transmitting to the server 6 a data file stored in the external storage medium 8.
[0039] At Step S58, the file transfer processing unit 5 confirms whether a file-reception completion response has been received from the server 6 through the communication processing unit 4. When the file-reception completion response has not been received (NO at Step S58), the file transfer processing unit 5 confirms at Step S60 whether the timeout has been done. When the timeout has been done (YES at Step S60), the file transfer processing unit 5 determines that file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S60), the operation proceeds to Step S58, and the file transfer processing unit 5 confirms again whether the file-reception completion response has been received. [0040] When the file-reception completion response has been received (YES at Step S58), the operation proceeds to Step S59, and the file transfer processing unit 5 transmits a message requesting deletion of the file having the file name changed in the server 6, to the server 6 through the communication processing unit 4. The operation at Step S59 is a sixth operation of requesting the server 6 to delete a pre-update data file having the file name changed to another file name.
[0041] At Step S61, the file transfer processing unit 5 confirms whether a file-deletion completion response has been received from the server 6 through the communication processor 4. When the file-deletion completion response

has not been received (NO at Step S61), the file transfer processing unit 5 confirms at Step S62 whether the timeout has been done. When the timeout has been done (YES at Step S62), the file transfer processing unit 5 determines that the file transmission has failed, and ends the process abnormally. When the timeout is not done (NO at Step S62), the operation proceeds to Step S61, and the file transfer processing unit 5 confirms again whether the file-deletion completion response has been received.
[0042] When the file-deletion completion response has been received (YES at Step S61), the file transfer processing unit 5 determines that the file transmission has been performed successfully, and ends the process normally. [0043] As described above, it is also possible to change the file name of a file in the server 6 prior to transfer of a file that is to be transferred. In a case where the file name of a file in the server 6 is changed prior to file transfer, the changed file name of the file to be transferred in the server 6 prior to the file transfer is changed back to the original file name when file transfer from the programmable logic controller 1 to the server 6 becomes incomplete. This enables the server 6 to prepare a production plan or perform a quality analysis, using the pre-update file.
[0044] With a user's operation as a trigger, the file transfer processing unit 5 performs the fourth operation of requesting the server 6 to change the file name of a pre-update data file in the server 6 to another file name, the fifth operation of transmitting to the server 6 a data file stored in the external storage medium 8, and the sixth operation of requesting the server 6 to delete the pre-update data file having the file name changed to the other file name. Therefore, in order to prevent update of the

file in the server 6 with incomplete data, a user is not required to consciously perform a special operation. As a result, it is possible to surely prevent a file in the server 6 from being updated with incomplete data. [0045] In the above descriptions, the file transfer processor 5 performs the file transfer by the FTP. However, a communication protocol is not limited to the FTP. File transfer can be performed by other communication protocols. [0046] The programmable logic controller 1 according to the present embodiment includes the file transfer processing unit 5 that, at the time of transfer of a data file stored in the external storage medium 8 to the server 6, requests the server 6 to delete a pre-update data file in the server 6 after completion of the transfer of the data file. Therefore, in a system using the programmable logic controller 1 according to the present embodiment, it is possible to prevent a file in the server 6 from being updated with incomplete data that is being transmitted, when the file in the server 6 is updated with a file transmitted from the programmable logic controller 1, even in a case where a function of preventing file update with incomplete data is not provided in the server 6. [0047] The configuration described in the above embodiment represents an example of the contents of the present invention. The configuration can be combined with other known techniques and a part of the configuration can be omitted or modified without departing from the scope of the present invention.
Reference Signs List
[0048] 1 programmable logic controller, 2 arithmetic processing unit, 3 internal device, 4 communication processing unit, 5 file transfer processing unit, 6

server, 7 external storage device, 8 external storage medium, 9 control target device.

We Claim :
1. A programmable logic controller to control a control target device according to a sequence program to thereby acquire information from the control target device, the programmable controller serving as a client when the programmable logic controller is connected to a server, the programmable logic controller comprising:
a storage device to store therein a data file created on a basis of the information from the control target device; and
a file transfer processing unit to, when transferring to the server the data file stored in the storage device, request the server to delete a pre-update data file in the server after completion of transfer of the data file.
2. The programmable logic controller according to claim 1,
wherein
the file transfer processing unit performs
a first operation of transmitting the data file stored in the storage device, to the server with another file name,
a second operation of requesting the server to delete a data file having a same file name as that of the data file stored in the storage device, and
a third operation of requesting the server to change a file name of the data file transmitted with the other file name, to a same file name as that of the data file stored in the storage device.
3. The programmable logic controller according to claim 2,
wherein with a user's operation as a trigger, the file
transfer processing unit performs the first operation, the
second operation, and the third operation in order.

4. The programmable logic controller according to claim 1,
wherein
the file transfer processing unit performs
a fourth operation of requesting the server to change a file name of the pre-update data file in the server, to another file name,
a fifth operation of transmitting the data file stored in the storage device, to the server, and
a sixth operation of requesting the server to delete the pre-update data file having the file name changed to the other file name.
5. The programmable logic controller according to claim 4,
wherein with a user’s operation as a trigger, the file
transfer processing unit performs the fourth operation, the
fifth operation, and the sixth operation in order.