Device, method for accessing field device, and program

Abstract

To perform input / output to / from a field equipment by an appropriate method irrespective of the position of a control application.SOLUTION: A device of the present disclosure is a device to which field equipment for performing at least one of acquisition of data for control of a plant and operation of the plant is connected, and the device includes an access path control unit. The access path control unit acquires position information of the field equipment. When the field equipment is connected to the device, the access path control unit performs input / output to / from the field equipment, based on the position information of the field equipment; and when the field equipment is connected to other device, the access path control unit performs input / output to / from the field equipment via an access path control unit of the other device to which the field equipment is connected, based on the position information of the field equipment.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an apparatus, a method for accessing field devices, and a program.

Background Art

[0002] In a process control system in a plant or factory, etc., a configuration in which field devices such as sensors and actuators are directly connected to a controller is common. In the present disclosure, a controller to which field devices are directly connected and which functions as an interface with other controllers is called an IO node.

[0003] A control application operating on a controller performs a control operation using process data read from a sensor, and outputs the operation result to an actuator to control the plant. Conventionally, a field device or an IO node is logically connected to a control application installed on a determined controller, and it is not possible to change and operate a combination of a field device, an IO node, a controller, and a control application. However, in this method, when replacing the hardware of a controller during operation of a control application, it is necessary to stop the system. For this reason, a method for replacing the hardware of a controller without stopping the system has been proposed (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, there are points to be improved in the prior art. The present disclosure aims to provide an apparatus, a method for accessing a field device, and a program that can perform input / output to the field device in an appropriate manner regardless of the position of the control application.

Means for Solving the Problems

[0006] The present disclosure relates to a control device having an access path control unit that operates in cooperation with each other, a control system including the control device, a method for accessing a field device, an apparatus, and a program.

[0007] Some embodiments of the control system include one or more field devices that perform at least one of acquisition of data for plant control and operation of the plant, a first control application directly connected to a first field device included in the one or more field devices and capable of controlling the first field device, and a first control device including a first access path control unit, a second control application capable of controlling the first field device, and at least one second control device including a second access path control unit, and a network that communicably connects the first control device and the second control device. The first access path control unit and the second access path control unit are configured to cooperate to control the input / output path to the first field device from each of the first control application and the second control application. In this way, by providing the first and second access path control units and controlling the input / output path to the first field device from each of the first control application and the second control application, input / output can be performed on the field device in an appropriate manner regardless of the position of the control application.

[0008] In one embodiment, the first access path control unit and the second access path control unit may be configured to be able to switch between a first state in which the first control application inputs and outputs to the first field device and a second state in which the second control application inputs and outputs to the first field device. In this way, if the first state and the second state can be switched, the control application can be switched between the first control device and the second control device without stopping the system.

[0009] In one embodiment, the first access path control unit and the second access path control unit may be configured such that a method by which the first control application specifies an input / output unit of the first field device is the same as a method by which the second control application specifies the input / output unit of the first field device. In this way, if the first access path control unit and the second access path control unit are configured such that the first control application and the second control application specify the input / output unit of the first field device in the same way, the same control application can be swapped between the first control device and the second control device without changing the settings.

[0010] In one embodiment, the first control application and the second control application may be configured to specify the input / output unit of the first field device by a unique name. In this way, by specifying the input / output unit of the first field device by a unique name in the first control application and the second control application, it becomes possible to identify the field device regardless of the physical location of the control application.

[0011] In one embodiment, the input / output unit of the first field device is allocated to the memory area of the first control device, and the first access path control unit may be configured to execute input / output instructions from the first control application and the second control application to the first field device by specifying an address in the memory area. In this way, if the first access path control unit executes input / output instructions from the first and second control applications to the first field device by specifying an address in the memory area, input / output instructions from the second control application can also be processed efficiently.

[0012] In one embodiment, the second access path control unit may be configured to transfer the input / output instruction from the second control application to the first field device to the first access path control unit via the network. In this way, since the input instruction from the second control application to the first field device is transferred to the first access path control unit, even for input / output instructions from the second control application, the first access path control unit specifies the address of the memory area to which the input / output of the field device is allocated and executes it, so that the processing can be performed efficiently without causing an extra processing load or communication load.

[0013] In one embodiment, when replacing the first field device, the first access path control unit may be configured to fix the input / output data stored in the memory area. When replacing the first field device, if the first access path control unit fixes the input / output data stored in the memory area, it becomes possible to replace the first field device without stopping the first control device and the second control device.

[0014] In one embodiment, the control system further includes a second field device directly connected to the network and included in the one or more field devices, and at least one of the first access path control unit and the second access path control unit is configured to be inputtable / outputtable to the second field device, and the first access path control unit and the second access path control unit may be configured to be able to control the input / output path to the second field device from the first control application and the second control application. In this way, if at least one of the first access path control unit and the second access path control unit is configured to be inputtable / outputtable to a second field device directly connected to the network, and the first access path control unit and the second access path control unit are configured to be able to control the input / output path to the second field device from the first control application and the second control application, then in addition to the first field device, it becomes possible to incorporate and control the second field device into the control system.

[0015] In one embodiment, the first control device includes a determination unit, and a plurality of control applications including at least one of the first control application and the second control application perform the same control operation based on the output value from the first field device to calculate the input value to the first field device, and the determination unit may be configured to determine the input value to the first field device based on the plurality of input values calculated by the plurality of control applications. In this way, if the first control device includes a determination unit and determines the input value to the first field device based on the plurality of input values calculated by the plurality of control applications, the reliability of the control of the control system can be improved.

[0016] A control device according to some embodiments is a control device to which field devices that perform at least one of acquisition of data for control of a plant and operation of the plant are directly connected, and includes a control application capable of controlling the field devices, and an access path control unit configured to cooperate with another access path control unit included in another control device different from the control device to control an input / output path from the control application and the control application of the other control device to the field devices. In this way, by providing an access path control unit and controlling the input / output path from the own device and other control devices to the first field device, it is possible to perform input / output to the field device in an appropriate manner regardless of the position of the control application.

[0017] An access method to a field device according to some embodiments is an access method to a field device for performing at least one of acquisition of data for control of a plant and input / output from a control device to the field device for operation of the plant, wherein the control application of the control device designates an input / output unit of the field device and instructs input / output, and the access path control unit of the control device acquires position information of the designated field device, and based on the position information, when the field device is connected to another control device, performs input / output to the field device via the access path control unit of the other control device to which the field device is connected. In this way, by acquiring the position information of the designated field device and performing input / output to the field device via the access path control unit of the other control device to which the field device is connected based on the position information, it is possible to perform input / output to the field device in the same access method regardless of the physical position of the field device.

[0018] An apparatus according to some embodiments is an apparatus to which field devices for performing at least one of acquisition of data for control of a plant and operation of the plant are connected, and includes an access path control unit. The access path control unit acquires position information of the field device, and when the field device is connected to the apparatus, performs input / output to the field device based on the position information of the field device. When the field device is connected to another apparatus, input / output to the field device is performed via the access path control unit of the other apparatus to which the field device is connected, based on the position information of the field device.

[0019] In one embodiment, when the access path control unit of the apparatus receives an input / output instruction to the field device together with a unique name of an input / output unit of the field device, the access path control unit refers to a conversion table indicating a correspondence relationship between the unique name of the input / output unit of the field device and the position information of the field device, and can acquire the position information of the field device based on the unique name of the input / output unit of the field device.

[0020] In one embodiment, the conversion table is stored in a server arranged on a network to which the apparatus and the other apparatus are connected. The access path control unit of the apparatus makes an inquiry to the server and can acquire the position information of the field device based on the unique name of the input / output unit of the field device.

[0021] In one embodiment, the apparatus stores the conversion table.

[0022] An access method according to some embodiments is an access method to a field device for performing at least one of acquisition of data for plant control and input / output to and from the field device for performing operations of the plant from a device, wherein an access path control unit of the device acquires position information of the field device, and based on the position information, when the field device is connected to the device, input / output is performed to the field device via the access path control unit of the device, and based on the position information, when the field device is connected to another device, input / output is performed to the field device via the access path control unit of the other device to which the field device is connected.

[0023] A program according to some embodiments is an access method to a field device for performing at least one of acquisition of data for plant control and input / output to and from the field device for performing operations of the plant from a device, wherein an access path control unit of the device acquires position information of the field device, and based on the position information, when the field device is connected to the device, input / output is performed to the field device via the access path control unit of the device, and based on the position information, when the field device is connected to another device, input / output is performed to the field device via the access path control unit of the other device to which the field device is connected.

Advantages of the Invention

[0024] According to the present disclosure, input / output can be performed on a field device in an appropriate manner regardless of the position of the control application.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0026] Before describing the embodiments according to the present disclosure, a comparative example based on the prior art will be described.

[0027] [Comparative Example] Patent Document 1 proposes a process control system in which a control application operates on virtual hardware on a controller to which field devices are not connected, and a redundant IO node to which field devices are connected and the controller are connected via a network. According to this process control system, the redundant IO node converts signals input and output by field devices and signals communicated with the controller via the network. Thereby, the control application can operate on any controller and can be connected to any field device. According to this process control system, by temporarily changing the combination of the control application and the controller, the hardware of the controller can be replaced without stopping the system. However, in the control system of Patent Document 1, the redundant IO node does not carry a control application, and the field device is controlled only by the controller. For this reason, there was room for improvement in the method of accessing the field device.

[0028] Patent Document 2 discloses a control system in which an IO node to which field devices are connected and a controller are connected via a network, similar to Patent Document 1. The IO node described in Patent Document 2 is configured to be operable with a control application that controls field devices connected to the IO node. Further, a control application on a controller to which field devices are not connected in Patent Document 2 is configured to be able to access field devices connected to the IO node via the network. For communication between the controller and the IO node, a communication protocol such as OPC UA (OPC Unified Architecture) is used, for example. In the control system of Patent Document 2, even if the control application of the controller moves to another controller, the control application can access the same field device via the network.

[0029] In a control system as disclosed in Patent Document 2, in order to access field devices connected to an IO node, a control application running on a controller executes procedures for accessing field devices via a network. A control application running on an IO node that controls field devices connected to its own device directly accesses a specific memory address assigned for input / output of the field devices to perform input / output of information. Therefore, if the control application running on the controller is installed on the IO node, access to the field devices becomes network-based access. In this case, compared with the case of directly specifying a memory address for input / output to the field devices, an extra communication load or processing load occurs. Also, since the control application running on the IO node does not assume network-based access to the field devices, it cannot be installed on the controller. In order to perform hardware replacement or software update without stopping the system, it is preferable that the control application perform input / output to the field devices in an appropriate manner regardless of whether it is on the controller or on the IO node.

[0030] Therefore, the present disclosure proposes a control system, a control device, and a method for accessing a field device that can perform input / output to the field device in an appropriate manner regardless of the position of the control application. The present disclosure also proposes a control system that can easily perform replacement of the control device and load distribution. Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0031] [First Embodiment] FIG. 1 is a schematic diagram showing an example of a control system 1 according to the first embodiment. The control system 1 includes one or more field devices 10, an IO node 20, a controller 30, and a network 40, respectively. The control system 1 may further include a monitoring device 45. The field device 10 is a first field device. The IO node 20 is a first control device. The controller 30 is a second control device.

[0032] The field device 10 performs at least one of acquisition of data for control of the plant and operation of the plant. The field device 10 is, for example, a sensor 11 such as a temperature sensor or a flow meter, or an actuator 12 such as a valve device, a fan, or a motor.

[0033] The IO node 20 is a device to which the field device 10 is directly connected and in which the control application 21 (see FIG. 2) operates. The IO node 20 is also used as an interface between the field device 10 and the controller 30. In the following description, when there are a plurality of IO nodes 20, they may all be referred to as the IO node 20. When necessary for the description, one of the plurality of IO nodes 20 may be specified as the IO node 20A to distinguish it from a specific IO node 20. Also, the field device connected to the IO node 20A may be referred to as the field device 10A (sensor 11A and actuator 12A).

[0034] The controller 30 of the present embodiment is a device in which the field device 10 is not directly connected and in which the control application 31 (see FIG. 2) operates. In the present embodiment, the device to which the field device 10 is directly connected to the controller is the IO node 20. The controller 30 is configured to be communicable with the IO node 20 via the network 40. The controller 30 can access the field device 10 via the IO node 20 according to the control application 31. The controller 30 can input and output to and from a plurality of field devices 10 connected to the IO node 20.

[0035] The network 40 is a dedicated communication network within the plant that can connect information devices such as the IO nodes 20, the controller 30, and the monitoring device 45 within the plant. The network 40 may include a wired or wireless in-plant communication network (LAN: Local Area Network). The wired in-plant communication network may include, for example, Ethernet. The wireless in-plant communication network includes wireless networks compliant with wireless communication standards such as Wi-Fi (registered trademark) and WiMAX (registered trademark). Furthermore, a communication network using a standardized protocol such as OPC UA or PROFINET may also be used.

[0036] The monitoring device 45 is a device used to monitor the operating status of the entire plant. The operating status of the application may be transmitted to the monitoring device 45 from each of the IO nodes 20 and the controller 30. The operating status of the application includes operation, stop, idle, error, etc. The monitoring device 45 has display means and input means. The monitoring device 45 controls the IO nodes 20 and the controller 30 according to the instructions of the operator or according to a programmed procedure. The monitoring device 45 is used to stop the control applications 21, 31 or to adjust the operation of the application.

[0037] Next, with reference to FIG. 2, a configuration example of the main part of the control system 1 will be further described.

[0038] The IO node 20 may be configured to include a control application 21, an IO access routing unit 22, an IO access unit 23, and a communication unit 24. The control application 21 is the first control application. The IO access routing unit 22 is the first access path control unit. Note that the IO node 20A shown in FIG. 1 also has components similar to those of the IO node 20. In the following, the components of the IO node 20A may be described with the same reference numerals as the components of the IO node 20.

[0039] The control application 21 can control the field device 10 connected to the IO node 20. The control application 21 may also control the field device 10A connected to another IO node 20A. The control application 21 may operate on an operating system. The control application 21 performs control of the field device 10 necessary for process control (for example, collection of measurement data from the field device 10 and transmission of control data to the field device 10, etc.).

[0040] The IO access routing unit 22 provides an IO access method abstracted for the control application 21. The IO access routing unit 22 adaptively changes the access method according to the physical relationship between the IO node 20 equipped with the IO access routing unit 22 and the field device 10. In order to abstract the hardware, the IO access routing unit 22 may be included in the virtualization unit 25 within the IO node 20. The virtualization unit 25 virtually operates on the hardware of the IO node 20 as a substitute for the hardware. The virtualization unit 25 is provided to enable replacement of the hardware of the IO node 20 without changing the control application 21. However, the virtualization unit 25 is not essential for providing the function of the IO access routing unit 22. It is possible to implement the IO access routing unit 22 even without the virtualization unit 25.

[0041] The IO access unit 23 performs input / output processing of data with the field device 10 connected to the IO node 20. The IO access unit 23 may include ports and circuits for IO access, etc.

[0042] The communication unit 24 communicates with other IO nodes 20A and the controller 30 via the network 40. The communication unit 24 performs necessary communication processing according to the type of the network 40. The communication unit 24 may include a physical interface for connecting to the network 40 and circuits for performing protocol processing, etc.

[0043] The controller 30 is configured to include a control application 31, an IO access routing unit 32, and a communication unit 33. The control application 31 is a second control application. The IO access routing unit 32 is a second access path control unit. Since the control application 31, the IO access routing unit 32, and the communication unit 33 each have the same or similar functions as the control application 21, the IO access routing unit 22, and the communication unit 24 of the IO node 20, the description thereof will be omitted.

[0044] The IO access routing unit 22 and the IO access routing unit 32 are configured to cooperate to control the input / output paths to the field device 10 from the control application 21 and the control application 31, respectively. In the present disclosure, "cooperate" means, for example, that the IO access routing units of each device know the existence and notification destination of each other, and the presence or absence of the control application connected to itself (if present, its information, status, etc.), and the presence or absence of the field device connected to itself (if present, its information, status, etc.) can be exchanged with the IO access routing unit of other devices as appropriate. Therefore, when an instruction is received from a monitoring device or the like, it is possible to execute or request execution of processing for an appropriate counterpart (the IO access routing unit of another device). The IO access routing unit 22 and the IO access routing unit 32 determine the access method as follows, for example, according to the physical positional relationship with the field device 10. The functions provided by the IO access routing unit 22 and the IO access routing unit 32 are referred to as the IO access routing function.

[0045] (1) Memory address specification: The input / output unit of the field device 10 is usually allocated to the memory area of the IO node 20. When the control application 21 of the IO node 20 accesses the field device 10 directly connected to the IO node 20, the IO access routing unit 22 specifies the address of the memory area corresponding to the input / output unit of the field device 10 indicated by the control application 21 with the I / O name, and accesses the field device 10.

[0046] (2) Via network: When the control application 31 of the controller 30 accesses the field device 10 connected to the IO node 20 connected by the network 40, the IO access routing unit 32 transfers the input / output instruction indicated together with the I / O name from the control application 31 to the IO node 20 via the network 40. The IO access routing unit 22 of the IO node 20 that has received the input / output instruction from the controller 30 specifies the memory address corresponding to the input / output of the field device 10 and accesses the field device 10. When the control application 21 of the IO node 20 accesses the field device 10A connected to another IO node 20A connected by the network 40, the IO access routing unit 22 also transfers the input / output instruction from the control application 21 to the IO node 20A via the network.

[0047] The input / output unit means a unit for performing data input / output to the field device 10 at one time. For example, in the case where the field device 10 is a sensor 11 for measuring temperature, the temperature information output from the field device 10 can be the input / output unit. For example, when the field device 10 is a heater (actuator 12) and an instruction to raise the temperature to a predetermined set value is transmitted to the field device 10, the operation instruction of the heater and the information indicating the set temperature output to the field device 10 can be the input / output unit. The field device 10 can be accessed by one or more input / output units. The input / output destination of the information of each input / output unit of the field device 10 is called I / O. The I / O is, for example, a memory address.

[0048] (Processing of the IO access routing unit) Referring to FIGS. 3 and 4, an example of the processing executed by the IO access routing units 22 and 32 will be described. FIG. 3 shows the processing executed by the IO access routing units 22 and 32 in response to instructions from the control applications 21 and 31. FIG. 4 shows the processing executed by the IO access routing unit 22 in response to an input / output instruction received from another IO node 20A or the controller 30 via the network 40 by the communication unit 24 of the IO node 20 and received from the communication unit 24.

[0049] First, in FIG. 3, the IO access routing units 22 and 32 receive an input / output instruction to the field device 10 together with a unique name that abstracts the I / O of the field device 10 from the control applications 21 and 31 (step S101). As the unique name, a name defined to be unique within the system can be used. The unique name of the I / O is hereinafter referred to as the I / O name. The control applications 21 and 31 access by specifying the I / O name assigned to the I / O, rather than specifying the physical location of the field device 10 or the IP address of the IO node 20 to which the field device 10 is connected. Thereby, the control applications 21 and 31 can identify the I / O of the field device 10 for input / output in the same way regardless of the physical location relationship or connection relationship with the field device 10.

[0050] Next, the IO access routing units 22 and 32 identify the location information of the corresponding field device 10 based on the I / O name received from the control applications 21 and 31 (step S102). The location information of the field device 10 can be paraphrased as the path connected to the field device 10. The location information of the field device 10 includes information on the IO node 20 to which the field device 10 is connected. The identification of the field device 10 corresponding to the I / O name and its location information can be performed by various methods. For example, each IO access routing unit 22 and 32 can be provided with a conversion table showing the correspondence between the I / O name and the field device 10 and its location information. Alternatively, a management server for storing the correspondence between the I / O name and the field device 10 and its location information can be provided on the network 40. The management server can return the location information of the field device 10 in response to an inquiry from the IO access routing units 22 and 32 using the I / O name.

[0051] When the IO access routing units 22 and 32 identify the location information of the corresponding field device 10 based on the I / O name, they determine whether the field device 10 is connected to its own device (step S103).

[0052] In step S103, when the field device 10 corresponding to the I / O name is connected to its own device (step S103: Yes), the IO access routing units 22 and 32 proceed to step S104. In this case, the own device is the IO node 20. The IO access routing unit 22 accesses the I / O by specifying the memory address corresponding to the I / O name and performs data input / output (step S104).

[0053] In step S103, if the field device 10 corresponding to the I / O name is not connected to the own device (step S103: No), the IO access routing units 22 and 32 proceed to step S105. Hereinafter, it is assumed that the field device 10 corresponding to the I / O name is the field device 10A in FIG. 1. In this case, the IO access routing units 22 and 32 transfer the input / output instruction of data from the control applications 21 and 31 to the IO access routing unit 22 of the other IO node 20A to which the field device 10A corresponding to the I / O name is connected (step S105). In other words, the IO access routing units 22 and 32 control the path so as to direct the input / output from the control applications 21 and 31 to the IO node 20A to which the field device 10A corresponding to the I / O name is connected.

[0054] The access to the I / O is executed by the IO access routing unit 22 according to the instruction received from the communication unit 24 in the other IO node 20A that has received the input / output instruction (see FIG. 4). The IO access routing units 22 and 32 of the IO node 20 or the controller 30 which is the own device acquire the input / output result of the data from the IO access routing unit 22 of the other IO node 20A to which the field device 10A corresponding to the I / O name is connected (step S106).

[0055] After step S104 or step S106 is completed, the IO access routing units 22 and 32 transmit the input / output result of the data to the control applications 21 and 31 (step S107).

[0056] Next, based on FIG. 4, the processing executed by the IO access routing unit 22 according to the instruction received from the communication unit 24 will be described. When the communication unit 24 of the IO node 20 receives an input / output instruction from another IO node 20 or the controller 30, the IO access routing unit 22 of the IO node 20 receives a data input / output instruction from the communication unit 24 (step S201). The IO access routing unit 22 that has received the input / output instruction from the communication unit 24 confirms that the input / output instruction is an input / output instruction to the field device 10 connected to its own device (step S202).

[0057] Next, the IO access routing unit 22 that has received the input / output instruction from the communication unit 24 accesses the I / O by specifying a memory address to perform data input / output (step S203). After step S203, the IO access routing unit 22 transmits the data input / output result to the IO access routing units 22 and 32 of the controller 30 or the IO node 20 that has transmitted the input / output instruction via the communication unit 24 (step S204).

[0058] For example, corresponding to step S105 in FIG. 3, when the IO node 20A in FIG. 1 receives an input / output instruction for the field device 10A from the IO node 20, the IO access routing unit 22 of the IO node 20A performs data input / output by specifying a memory address according to the instruction received from the communication unit 24 of the IO node 20A. The IO access routing unit 22 of the IO node 20A transmits the data input / output result to the IO access routing unit 22 of the IO node 20 that has transmitted the input / output instruction via the communication unit 24 of the IO node 20A.

[0059] By doing the above, the control applications 21 and 31 can access the I / O with an abstracted I / O name without specifying the location information of the field device 10 or the connected IO node 20. As a result, the control application can access the I / O in the same way regardless of the physical positional relationship between the mounted IO node 20 or the controller 30 and the field device 10.

[0060] (Transfer of Control Application) Next, with reference to the flowchart of FIG. 5, the processing when moving the control application 21 from the IO node 20 to which the field device 10 to be controlled is connected to the controller 30 will be described. In this case, the method of accessing the I / O is changed from memory address specification to via the network. The transfer itself of the control application 21 can utilize a general live migration mechanism. The transfer target is only the control application 21. The virtualization unit 25 and the IO access routing unit 22 do not move.

[0061] First, the control application 21 on the IO node 20 is instructed to move (step S301). The instruction to move includes cases where the operator of the control system 1 instructs from the monitoring device 45, or cases where an instruction is automatically issued from the monitoring device 45 triggered by some operation of any device in the control system 1. The instruction to move is issued, for example, to the virtualization unit 25 of the IO node 20. The processing of each of the following devices may be performed under the control of the monitoring device 45.

[0062] The virtualization unit 25 of the IO node 20 that has received the transfer instruction temporarily stops the operation of the control application 21 and copies the data necessary to resume operation to the destination controller 30 (step S302).

[0063] The IO access routing unit 22 of the IO node 20 sets the position of the control application 31 that accesses the field device 10 to the destination controller 30 so that it can be accessed via the network (step S303). The control application 31 executes the same processing as the control application 21 on the controller 30. Step S303 may be executed in parallel with step S302.

[0064] When the necessary data is copied to the destination controller 30, the control application 31 resumes processing (step S304). The control application 31 issues an input / output instruction indicated together with the I / O name to the I / O access routing unit 32.

[0065] The I / O access routing unit 32 automatically determines an access destination for controlling the field device 10 based on the I / O name specified by the control application 31 (step S305). For example, the correspondence between the I / O name and the position information of the field device 10 is stored in advance in the I / O access routing unit 32 by a conversion table. Therefore, in step S305, there is no need to make setting changes or the like manually or by a dedicated program.

[0066] Next, with reference to the flowchart of FIG. 6, the processing when the control application 31 is moved from the controller 30 to the IO node 20 to which the field device 10 to be controlled is connected will be described. In this case, the access method to the I / O is changed from via the network to specifying the memory address. In the following description, points common to the description of the flowchart of FIG. 5 will be omitted.

[0067] First, a movement is instructed to the control application 31 on the controller 30 (step S401).

[0068] The virtualization unit 34 of the controller 30 that has received the movement instruction temporarily stops the operation of the control application 31 and copies the data necessary to resume operation to the destination IO node 20 (step S402).

[0069] When the necessary data is copied to the destination IO node 20, the control application 21 that executes the same processing as the control application 31 at the IO node 20 resumes processing (step S403).

[0070] When the control application 21 of the IO node 20 resumes processing, the IO access routing unit 22 of the IO node 20 determines that the access destination is the field device 10 connected to the own device based on the I / O name specified by the control application 21. The IO access routing unit 22 sets the access destination of the control application 21 to the field device 10 connected to the own device (step S404). After that, the IO access routing unit 22 performs input / output on the memory address connected to the field device 10 with the input / output instruction received from the control application 21 together with the I / O name.

[0071] In this way, in the control system 1, the control application 21 can switch between the state of accessing the field device 10 (the first state) and the state of the control application 31 accessing the field device 10 (the second state). By doing so, it becomes possible to switch the control applications 21 and 31 between different IO nodes 20 and controllers 30 without being aware of the change in the positions of the control applications 21 and 31. Also, the switching of the control application is not limited to between the IO node 20 and the controller 30. The operating control applications can be switched between different IO nodes 20 or between different controllers 30.

[0072] (Forcing) Generally, when replacing a field device, since it becomes impossible to access the information of the target input / output unit from the IO node, a function is known that rewrites and fixes the value of the information acquired by the I / O in the IO node to a specified value and disconnects it from the value of the information of the input / output unit corresponding to the actual I / O. Such a function is called forcing or I / O lock, etc. The control application continues to operate as if it is accessing the I / O even during the replacement of the field device.

[0073] In the control system 1, by providing this forcing function to the IO access routing unit 22 of the IO node 20, the same function can be realized even in a system configuration where the controller 30 and the IO node 20 are connected by the network 40. Specifically, when replacing the field device 10, the IO access routing unit 22 fixes the input / output data stored in the I / O memory area of the IO node 20 corresponding to the input / output unit of the field device 10.

[0074] As described above, according to the present embodiment, the control applications 21 and 31 can access the I / O in an appropriate manner by instructing the I / O name without caring about the positions of the control applications 21 and 31 themselves and the access method to the field device 10. Further, the control applications 21 and 31 that control the field device 10 can continue to access the field device 10 even if they are moved or switched to any controller 30 or another IO node 20A. Furthermore, by the cooperation of the IO access routing units 22 and 32, an optimal method for accessing the I / O is selected. As a result, unnecessary processing load or communication load is not generated due to the movement of the control applications 21 and 31 or the like.

[0075] [Second Embodiment] The control system 1A according to the second embodiment includes, in addition to the configuration of the control system 1 of the first embodiment, a cache server 50 connected to the network 40 as shown in FIG. 7. The cache server 50 has a cache function for input / output data accessed in the past. The controller 30 connected to the network 40 can access the field device 10 via the cache server 50.

[0076] FIG. 8 shows a configuration example of the main part of the control system 1A. Since the IO node 20 and the controller 30 are the same as the IO node 20 and the controller 30 of the first embodiment shown in FIG. 2, the same reference numerals as those in the first embodiment are given and the description is omitted.

[0077] The cache server 50 includes a cache database 51, an IO access routing unit 52, and a communication unit 53. The IO access routing unit 52 may be included in the virtualization unit 54. The cache database 51 is a storage unit. The IO access routing unit 52 is a third access path control unit.

[0078] The cache database 51 can store input / output data for I / O corresponding to the input / output units of one or more field devices 10. The input / output data may include current and past data. The cache database 51 may include a semiconductor memory, a magnetic storage device, a magneto-optical storage device, etc., which can store a large amount of data.

[0079] The IO access routing unit 52 cooperates with the IO access routing units 22 and 32 of other devices to control the input / output path for I / O so as to direct all or part of the access to the IO node 20 to the cache server 50. For example, the IO access routing unit 22 transmits input / output data for the field device 10 to the IO access routing unit 52. The IO access routing unit 52 stores the input / output data received from the IO access routing unit 22 in the cache database 51. The IO access routing units 22, 32, and 52 cooperate to transfer the input / output instruction from the control application 31 to the field device 10 to the cache server 50.

[0080] The field device 10 or the IO node 20 may not have a higher processing capacity than the controller 30. Therefore, it may not be able to handle a large number of accesses from a plurality of control applications 21 and 31. In such a case, the IO access routing unit 22 of the IO node 20 exchanges data only with the cache server 50. Also, other controllers 30 perform input / output with respect to the cache server 50. The cache server 50 can adopt hardware that has a high processing capacity and can handle a large number of accesses without problems.

[0081] The communication unit 53 is configured to be the same as or similar to the communication units 24 and 33.

[0082] The cache server 50 is used, for example, in the following manner.

[0083] 1. Use of the cache server based on the I / O access load The IO access routing unit 22 of the IO node 20 monitors the input / output load to the connected field device 10. When the load of the IO node 20 satisfies a predetermined condition, the IO access routing unit 22 of the IO node 20 may direct the input / output instruction to the field device 10 to the cache server 50. When the input / output from a plurality of control applications 21 and 31 concentrates on a specific IO node 20, the IO node 20 may have a high processing load and may not be able to respond in real time. In such a case, the IO access routing unit 22 instructs other IO nodes 20A and the controller 30 to change the access method via the cache server 50. In subsequent processing, the IO node 20 transfers the input / output data to the cache server 50 and does not communicate with other IO nodes 20A and the controller 30.

[0084] The IO node 20 communicates only with the cache server 50 and can maintain a real-time response without increasing the processing load to handle within the range that the IO node 20 can handle. Although accesses from each control application 21 and 31 concentrate on the cache server 50, the communication load between the IO node 20 and the cache server 50 can be reduced by using the cached data. When storing data in the cache data server, the IO node 20 may be configured to fetch data in descending order of a predetermined priority.

[0085] 2. Distribution of access based on the I / O access purpose The IO access routing unit 22 of the IO node 20 can distribute the input and output based on the access purpose of the input and output to the I / O. For example, when using the I / O for control, the control applications 21, 31 can be set to directly perform input and output to the field device 10 via the connected IO node 20 of the field device 10. When using the I / O for monitoring purposes, the control applications 21, 31 can be set to refer to the data stored in the cache server 50.

[0086] When using the I / O for control, especially when performing data input or rewriting to the I / O for operation, real-time performance is required while the access is not overly concentrated. For this reason, it is preferable that the control applications 21, 31 can directly access the IO node 20 without going through the cache server 50. When using the output data of the I / O for monitoring by a monitoring device 45 or the like, real-time performance is not overly required while access from many devices may concentrate on the same IO node 20. For this reason, it is preferable that the control applications 21, 31 can access the output data of the I / O via the cache server 50.

[0087] (Forcing) In the control system 1A according to the present embodiment, the forcing function when replacing the IO node 20 can be provided to the cache server 50. Referring to FIG. 9, the procedure for replacing the IO node 20 in the control system 1A will be described.

[0088] First, the IO access routing unit 22 of the IO node 20 to be replaced notifies other IO access routing units to change the access method to the I / O of the field device 10 connected to the IO node 20 to be replaced from the controller 30 or the monitoring device 45 via the cache server 50 (step S501). The IO access routing unit 22 of the IO node 20 sequentially transfers the value of the information of the input / output unit obtained from the I / O to the cache server 50. As a result, the access from the control application 31 to the I / O is redirected to the cache server 50. The control application 31 accesses the I / O of the field device 10 of the IO node 20 via the cache database 51 of the cache server 50.

[0089] Next, on the cache server 50, the value of the information of the input / output unit of the field device 10 connected to the IO node 20 to be replaced is locked (step S502). That is, the value of the information of the input / output unit (input / output data) on the cache server 50 is separated from the value of the actual input / output unit of information obtained from the I / O, and a fixed value is provided to the control application 31 until the lock is released.

[0090] The driver of the control system 1A or another operator replaces the IO node 20 to be replaced (step S503).

[0091] When the replacement of the IO node 20 is completed, the lock of the I / O on the cache server 50 is released by the input of the driver or the operator, or when the control system 1A detects the completion of the replacement work (step S504).

[0092] After the lock of the I / O on the cache server 50 is released, in the IO access routing unit 32, the access method to the I / O corresponding to the input / output unit of the field device 10 is restored to the original state (step S505). As a result, the control application 31 of the controller 30 can access the IO node 20 via the network 40.

[0093] By doing so, in the control system 1A according to the second embodiment, the processing load of the IO node 20 to which the field device 10 is connected can be dispersed temporally and / or according to the access purpose. Also, in the control system 1A according to the second embodiment, the IO node 20 can be replaced without stopping the entire system.

[0094] [Third Embodiment] FIG. 10 shows a control system 1B according to the third embodiment. In this control system 1B, in addition to the components of the control system 1 according to the first embodiment, field devices 10B (sensors 11B, actuators 12B) are directly connected to the network 40. Further, the control system 1B may include a cache server 50 as in the second embodiment. The field device 10B is a second field device. As the field device 10B, an IoT (Internet of Things) sensor or the like is assumed. In this case, since it is conceivable to use inexpensive general-purpose devices, it is assumed that the field device 10B itself cannot have an IO access routing function.

[0095] In such a case, either the IO access routing unit 22 on the IO node 20 or the IO access routing unit 32 on the controller 30 may be configured to be accessible to the field device 10B in a communication protocol that the field device 10B can communicate with and to enable input / output. The communication protocols that the field device 10B can communicate with include, for example, OPC UA, PROFINET, Modbus / TCP, MQTT, and HTTP, etc. Further, the IO access routing units 22 and 32 are configured to be able to control the input / output path so that input / output can be performed from the control applications 21 and 31 to the field device 10B. For example, the IO access routing unit 32 of the controller 30 that cannot perform input / output to / from the field device 10 may transfer an input / output instruction from the control application 31 to the IO access routing unit 22 of the IO node 20 that can perform input / output to / from the field device 10B. By doing so, it becomes possible to incorporate and control the field device 10B such as an IoT device directly connected to the network 40 into the control system 1B of the present disclosure.

[0096] When the control system 1B includes the cache server 50, the IO access routing unit 55 of the cache server 50 may access the field device 10B. The IO node 20 or the controller 30 performs input / output to / from the field device 10B via the cache server 50. In this case, since communication only needs to be performed between the field device 10B and the cache server 50 using the above communication protocol, processing such as protocol conversion does not need to be performed at each of the IO nodes 20 and the controller 30.

[0097] [Fourth Embodiment] As shown in FIG. 11, in the control system 1C according to the fourth embodiment, the IO access routing units 22, 32, and 52 of each device are constructed on the application frameworks 26, 35, and 55. The control system 1C is different from the configuration in which the virtualization units 25, 34, and 54 included the IO access routing units 22, 32, and 52 in the control system 1A according to the second embodiment.

[0098] The application frameworks 26, 35, 55 are a collection of libraries used to implement the standard structure of an application. The control applications 21, 31 and the cache database 51 can perform input / output operations on the abstracted I / O by using the APIs provided by the application frameworks 26, 35, 55. The application frameworks 26, 35, 55 change the access method according to the location information of the actual field device 10. The control applications 21, 31 do not need to be aware of the access method to the field device 10.

[0099] Instead of using the virtualization units 25, 34, 54, by using the application frameworks 26, 35, 55, the same effects as when using the virtualization units can be obtained. Also, since the application frameworks 26, 35, 55 are libraries, it is easy to modify and change the system.

[0100] (Determination of output value based on multiple calculation results) In each of the above embodiments, the IO access routing units 22, 32, 52 cooperate with each other to control the input / output path and direct it to an appropriate device in response to the input / output instruction to the I / O from the control applications 21, 31. The IO access routing units 22, 32, 52 can also be provided with a function of determining the control content for the field device 10 based on the calculation results from the multiple control applications 21, 31.

[0101] For example, in each of the above-described embodiments, as shown in FIG. 12, a determination unit 27 can be provided in the IO access routing unit 22 of the IO node 20. For example, based on the output of the sensor 11, it is assumed that a plurality of control applications including at least one of the control applications 21 and 31 instruct an input to the actuator 12 with an input value calculated by performing the same control operation. The determination unit 27 compares the plurality of input values calculated by the plurality of control applications, or statistically processes the plurality of input values to determine a final input value. For example, the determination unit 27 may determine the average value of the plurality of output values as the input value. Alternatively, when there are three or more control applications, the determination unit 27 may adopt the input value that appears most frequently from the plurality of input values.

[0102] By doing so, the reliability of the control by the control systems 1, 1A, and 1B can be enhanced.

[0103] Note that the determination unit 27 may be located not in the IO access routing unit 22 but between the IO access routing unit 22 and the field device 10.

[0104] Although the embodiments according to the present disclosure have been described based on the drawings and examples, those skilled in the art can easily make various modifications or corrections based on the present disclosure. Therefore, it should be noted that the specific configuration of the present invention is not limited to the embodiments of the present disclosure, and includes various modifications or corrections without departing from the spirit of the present invention.

Description of Reference Numerals

[0105] 1, 1A, 1B, 1C Control systems 10, 10A Field devices (first field devices) 10B Field device (second field device) 11, 11A, 11B Sensors 12, 12A, 12B Actuators 20, 20A IO nodes (first control devices) 21 Control Application (First Control Application) 22 IO Access Routing Unit (First Access Path Control Unit) 23 IO Access Unit 24 Communication Unit 25 Virtualization Unit 26 Application Framework 27 Judgment Unit 30 Controller (Second Control Device) 31 Control Application (Second Control Application) 32 IO Access Routing Unit (Second Access Path Control Unit) 33 Communication Unit 34 Virtualization Unit 35 Application Framework 40 Network 45 Monitoring Device 50 Cache Server 51 Cache Database (Storage Unit) 52 IO Access Routing Unit (Third Access Path Control Unit) 53 Communication Unit 54 Virtualization Unit 55 Application Framework

Claims

1. An apparatus to which a first field device for acquiring data for controlling a plant and / or performing at least one of operations of the plant is connected, comprising an access path control unit , wherein the access path control unit , when receiving an input / output instruction to a second field device that is the same as or different from the first field device, together with a unique name of an input / output unit of the second field device, acquires position information of the second field device based on the unique name of the second field device; , when the second field device is the same device as the first field device connected to the apparatus, performs input / output to the second field device based on the position information of the second field device; , when the second field device is a device different from the first field device connected to another apparatus, performs input / output to the second field device via an access path control unit of the other apparatus to which the second field device is connected, based on the position information of the second field device; the apparatus has an application for controlling the second field device, and the access path control unit can switch the application between a state of performing input / output to the second field device and a state of not performing input / output to the second field device.

2. The apparatus according to claim 1, wherein the access path control unit of the apparatus refers to a conversion table showing a correspondence relationship between the unique name of the second field device and the position information of the second field device, and acquires the position information of the second field device based on the unique name of the second field device.

3. The conversion table is stored in a server arranged on a network to which the apparatus and the other apparatus are connected, and the access path control unit of the apparatus inquires the server and acquires the position information of the field device based on the unique name of the field device. The apparatus according to claim 2.

4. The apparatus according to claim 2, which stores the conversion table.

5. A method for accessing a field device for performing at least one of data acquisition for plant control and operation of the plant, from a device to which a first field device is connected, to perform input / output to a second field device that is the same as or different from the first field device, comprising: The access path control unit of the device acquires position information of the second field device; Based on the position information, when the second field device is the same device as the first field device connected to the device, input / output is performed to the second field device via the access path control unit of the device; Based on the position information, when the second field device is a device different from the first field device connected to another device, input / output is performed to the second field device via the access path control unit of the other device to which the second field device is connected; including that; The device has an application for controlling the second field device, and the access path control unit can switch the application between a state of performing input / output to the second field device and a state of not performing input / output to the second field device; Access method.

6. A method for accessing a field device for performing at least one of data acquisition for plant control and operation of the plant, from a device to which a first field device is connected, to perform input / output to a second field device that is the same as or different from the first field device, comprising: The access path control unit of the device acquires position information of the second field device; Based on the position information, when the second field device is the same device as the first field device connected to the device, input / output is performed to the second field device via the access path control unit of the device; Based on the position information, when the second field device is a device different from the first field device connected to another device, performing input / output to the second field device via the access path control unit of the other device to which the second field device is connected; The device has an application for controlling the second field device, and the access path control unit causes a computer to execute an access method by which the application can switch between a state of inputting / outputting to / from the second field device and a state of not inputting / outputting to / from the second field device. A program that causes a computer to execute.

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