JP2010034809A - Field bus system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field bus system capable of reducing network loads without having a display device connected to a field bus consume network resources and preventing the setting error of a control loop. <P>SOLUTION: In the field bus system, a plurality of display devices 110-130 and a plurality of field devices 40, 50 are connected through a common field bus 80. Each display device has a data reception exclusive function not for transmitting data to other devices, and the setting of each display device is performed in an exclusive device for setting to which a network address is allocated and which is connected to the field bus temporarily only during setting. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fieldbus system, and more particularly to a display connected to a fieldbus.

  In recent plant control systems, Foundation Fieldbus FF-H1 (registered trademark), PROFIBUS-PA (registered trademark), etc., which have various field devices such as differential pressure gauges, flow meters, thermometers, actuators, and controllers installed in the plant, are available. In many cases, these field devices are connected to a line bus power supply type field bus and are configured to perform data communication with each other via the field bus.

  As a prior art document regarding the display in such a fieldbus system, there is the following Patent Document 1. This Patent Document 1 describes a technique related to a display that allows a signal processing state to be easily confirmed even in a field device installed at a position where the display unit is difficult to see.

JP 2003-28674 A

  FIG. 7 is a block diagram showing an example of a conventional fieldbus system. In FIG. 7, the displays 10 to 30, the field devices 40 and 50, and the controller 60 are connected to a common field bus 80, and these devices can communicate with each other via the field bus 80.

  Each of these devices is assigned a unique address. Specifically, as shown in FIG. 7, for example, the display 10 is “10”, the display 20 is “20”, the display 30 is “30”, the field device 40 is “40”, and the field device 50 is “50”. The controller 60 is assigned “60”, and the address is displayed as “Addr” in FIG.

  The display devices 10 to 30 do not have sensors, communicate with the field devices 40 and 50 connected to the field bus 80, and display the measured values of the field devices 40 and 50 on the internal display unit.

  The field devices 40 and 50 have sensors such as a differential pressure gauge, a flow meter, and a thermometer, and have a function of transmitting measurement data to other devices connected to the field bus 80. Note that the field devices 40 and 50 include actuators, controllers and the like in addition to those having these sensors.

  The controller 60 performs connection setting for each device connected to the fieldbus 80.

  FIG. 8 is a functional block diagram showing a configuration example of the display 20 of FIG. 7, and the displays 10 and 30 are similarly configured. The transmission / reception I / F 21 is a communication interface of the display device 20 and can communicate with other devices connected to the field bus 80.

  The field communication unit 22 stores field bus protocol information for communicating with other devices connected to the field bus 80. Based on this protocol information, the field communication unit 22 transmits and receives via the transmission / reception I / F 21. The data is converted into fieldbus data or data in a format that can be processed by the setting holding unit 23 and the display unit 24.

  The setting holding unit 23 holds various setting data for the display device 20. The change of the setting data is processed by a setting change request from another device connected to the fieldbus 80.

  The display unit 24 displays the measurement data acquired by the field communication unit 22 communicating with the field devices 40 and 50 based on the contents of the setting data held in the setting holding unit 23.

  FIG. 9 is a sequence diagram illustrating an operation in which the display 20 acquires data from the field device 40. The data acquisition method includes a data acquisition method A in which a data read request is sent from the display device 20 to the field device 40 at regular intervals, and a request from the controller 60 to the field device 40 to issue data to the display device 20 at regular intervals. When the issuance request is sent from the controller 60 as an issuance trigger, the field device 40 receives the issuance request and issues data. The display unit 20 receives the data issued from the field device 40 and displays it on the display unit 24. There is data acquisition method B. In any of these methods, communication with the display device 20 occurs to acquire display data.

  FIG. 10 is an explanatory diagram of a setting method of the display device 20 and is a view (in other words, a setting screen example) of the display device 20 viewed from the application of the controller 60. Since the display devices 10 to 30 are assigned with unique addresses on the fieldbus 80 and are recognized as individual devices, they can transmit and receive data.

  Therefore, the controller 60 is provided with a data block for individually performing display settings of these indicators 10 to 30 (in the case of the indicator 20, the data block DB2 for the indicator 20). In changing the display setting, the controller 60 changes the setting value of the data block of the corresponding display. (For example, on the setting screen provided by the application of the controller 60, the data block for the display 20 to be changed is selected and the setting value is changed. At this time, the controller 60 displays the data for changing the setting. (The display 120 changes the setting for display based on the data for changing the setting received via the field bus.)

  However, in the conventional fieldbus system, a unique address is assigned to each display unit, so installing multiple displays consumes network resources for the number of units and connects many devices. It will not be possible.

  In addition, the conventional fieldbus system transmits the data request packet to the field device for each display unit to acquire the measurement data, so if many display units are connected to the fieldbus, the communication volume for data acquisition increases. As a result, a large network bandwidth is used, and a load for data acquisition is applied to the network. Since the display is a secondary position in the control system, it is not preferable that the display uses a large network bandwidth.

  Furthermore, since a unique address is also assigned to the display device, a display device that is not related to control is displayed on the network when the control loop is set. As a result, the output value of the field device must be used as the input of another field device, but there is a risk that an error in setting the control loop occurs, for example, the input of the display device is mistaken.

  The present invention solves these problems, and an object of the present invention is to reduce the network load without causing the display connected to the fieldbus to consume network resources, and to prevent a control loop setting error from occurring. To realize the system.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
A fieldbus system in which a plurality of display units and a plurality of field devices are connected via a common fieldbus,
Each display unit has a data reception dedicated function that does not transmit data to other devices, and each display unit is assigned a network address and is dedicated to being temporarily connected to the fieldbus only at the time of setting. It is performed by a setting device.

The invention according to claim 2 is the fieldbus system according to claim 1,
Each display device receives communication data for control by each field device via the field bus, extracts data to be displayed from these data, and converts the extracted data into display data. It is characterized by being displayed.

The invention according to claim 3 is the fieldbus system according to claim 1 or 2,
The field bus is instructed to issue data to each field device connected to the field bus, and setting data for changing the display setting of each display device is transmitted to the setting device as a transmission destination. The controller to be connected is connected.

The invention according to claim 4 is the display system for field communication according to any one of claims 1 to 3,
The arithmetic control unit is
It is determined whether or not the received data is setting data that requests a setting change to the own device. If it is determined that the received data is setting data that requests a setting change to the own device, the received data is based on the setting data. The setting information stored in the storage unit is updated and changed.

Invention of Claim 5 is the fieldbus system in any one of Claims 1-4,
The setting device is provided with a data block including a database having a content equivalent to a setting content of a corresponding display.

The invention according to claim 6 is the fieldbus system according to any one of claims 1 to 5,
The display device and the setting device have the same setting update determination means.

  With the fieldbus system according to the present invention, it is possible to reduce the amount of communication required for data acquisition, reduce the network load, and improve the connection possibility of many field devices.

  FIG. 1 is a block diagram showing an embodiment of a fieldbus system according to the present invention. The same reference numerals are given to the parts common to FIG. In FIG. 1, field devices 40 and 50, a controller 60, and displays 110 to 130 are always connected to a common field bus 80, and these devices can communicate with each other via the field bus 80. The setting device 70 is temporarily connected to the field bus 80 only when the displays 110 to 130 are set.

  A unique address is assigned to each of these devices except the displays 110 to 130. Specifically, for example, as shown in FIG. 1, the field device 40 is assigned “40”, the field device 50 is assigned “50”, the controller 60 is assigned “60”, and the setting device 70 is assigned “70”. In FIG. 1, the address is also displayed as “Addr”. In the case of conforming to FF-H1, a 16-bit address is assigned and is often indicated by a hexadecimal number.

  The field devices 40 and 50 have sensors such as a differential pressure gauge, a flow meter, and a thermometer, as in the past, and have a function of transmitting measurement data to other devices connected to the field bus 80. . Note that the field devices 40 and 50 include actuators, controllers and the like in addition to those having these sensors.

  The controller 60 performs connection setting of each device connected to the fieldbus 80 as in the conventional case.

  As described above, the setting device 70 is temporarily connected to the field bus 80 only when the displays 110 to 130 are set. While connected to the fieldbus 80, it can be recognized as a field device on the network and can communicate with other devices.

  The displays 110 to 130 do not have sensors as in the conventional case, receive data from the field devices 40 and 50 connected to the field bus 80, and store the measured values of these field devices 40 and 50 in the inside. Display on the display. A difference from the conventional displays 10 to 30 is that a unique address is not assigned, so that the displays 110 to 130 do not participate in the network even when they are connected to the fieldbus 80, and therefore cannot be recognized from the network. .

  FIG. 2 is a specific functional block diagram of the display device 120 and the setting device 70 in FIG. 1, and the display devices 110 and 130 are configured in the same manner as the display device 120.

  As compared with the configuration example of the display 20 in FIG. 7, the internal configuration of the display device 120 is changed from the transmission / reception I / F 21 to the reception I / F 121 and the field communication unit 22 to the communication analysis unit 122.

  In the reception I / F 121, the data transmission function is deleted as compared with the conventional transmission / reception I / F 21. Data that flows through the fieldbus 80 is received, but data transmission to the fieldbus 80 is not performed.

  The communication analysis unit 122 receives and analyzes data flowing through the field bus 80 via the reception I / F 121. A difference from the conventional field communication unit 22 is that data transmission to other devices connected to the field bus 80 is not performed. In displaying data, the data to be displayed is analyzed and extracted from the data flowing through the fieldbus 80 and used. Further, in order to make a setting, if it is a setting value change request to the data block of the setting device 70 corresponding to the own device (the data block DB2 for the display 120 in FIG. 4), the setting holding unit 123 performs the setting according to the request. Update the setting value.

  The setting holding unit 123 holds various setting data for the display device 120. Compared with the conventional setting holding unit 23, the internal data is different, but it has an equivalent function. Also, it has information for newly identifying the setting device 70. This information is basically set when the device is shipped.

  Further, the display device 120 is used when executing, for example, a display unit 124 that uses liquid crystal to display data such as measurement values acquired from each field device, a program or application for operating as a display device, and these programs. A storage unit (not shown) such as a RAM or ROM for storing data, display operation setting information, address information, various information, and the like is also provided.

  In the setting device 70, a transmission / reception I / F 71 is a communication interface of the setting device 70 and can communicate with other devices connected to the field bus 80.

  The field communication unit 72 stores a fieldbus protocol for communicating with other devices connected to the fieldbus 80 via the transmission / reception I / F 71. Based on this protocol information, the transmission / reception I / F is stored. Data to be transmitted / received via F21 is converted into fieldbus data or data in a format that can be processed by the setting holding unit 23 and the display unit 24.

  The setting holding unit 73 holds setting information of the setting device 70 and settings of display devices that can be set. The setting information of the display includes information equivalent to that of the corresponding display, and can be referred to and updated from other devices. If an invalid setting value is specified at the time of update, it also has a function of rejecting the update.

  Furthermore, the setting device 70 stores programs and applications for operating as the setting device, data used when executing these programs, address information, various information, and the like, and further, identification information of each of the displays 110 to 130. And a storage unit such as a RAM or a ROM that stores the setting information for setting the display operation of each display unit in association with each other.

  FIG. 3 is a sequence diagram illustrating an operation in which the display device 120 acquires data from the field device 40. Data acquisition methods include a data acquisition method A ′ and a data acquisition method B ′ described below.

  In the data acquisition method A ′, the display device 120 receives and displays the content returned by the field device 40 in response to a data read request from another device participating in the field bus 80.

  In the data acquisition method B ′, the controller 60 requests the field device 40 to issue data to other devices at a predetermined interval in advance, and when the issuance request is transmitted from the controller 60 as an issuance trigger, the field device 40 Receive and issue data. The issued data is destined for other devices, but can be received by the display device 120, so the display device 120 receives this data and displays it on the display unit 124.

  In any of these data acquisition methods, communication with the display device 120 does not occur when acquiring display data. In addition, other equipment, may be any, including if the controller 60 devices participating in the field bus 80. Both data acquisition methods use the feature of the field bus that “communication flowing on the bus can be received by all devices”.

  FIG. 4 is an explanatory diagram of a setting method of the display device 120, and is a view of the display device 120 as viewed from the application of the controller 60 (in other words, a setting screen example). The data block for each of the displays 110 to 130 is branched and displayed from the setting device 70, which is different from the conventional one. The displays 110 to 130 are not assigned unique addresses on the fieldbus 80.

  On the other hand, the setting device 70 has a data block including a database having contents equivalent to the setting contents of the displays 110 to 130 inside. The data block DB1 corresponds to the setting content of the display unit 110, the data block DB2 corresponds to the setting content of the display unit 120, and the data block DB3 corresponds to the setting content of the display unit 130. The correspondence relationship between the data blocks DB1 to DB3 and the displays 110 to 130 is held by the displays 110 to 130.

  For example, when changing the setting of the display 120, the setting value of the data block DB2 for the display 120 is changed on the application. (In other words, on the setting screen provided by the application of the controller 60, the data block for the display 120 to be changed is selected and the setting value is changed. At this time, the controller 60 sets the setting change data. Is transmitted to the setting device 70. Since the setting change data reaches not only the setting device 70 but also each device connected to the field bus 80, the display unit 120 displays the setting change data. The display setting is changed based on the above (described later).

  FIG. 5 is an operation explanatory diagram when the setting of the display 120 is changed from the controller 60. When the display device 120 is set, the setting device 70 is temporarily connected to the field bus 80. As a result, the setting device 70 participates in the network and can be recognized from other devices connected to the fieldbus 80.

  When changing the setting of the display device 120, the controller 60 accesses the data block DB2 for the display device 120 in the setting device 70 to change the internal setting data. The change request from the controller 60 reaches not only the setting device 70 but also each device connected to the fieldbus 80. The setting device 70 attempts to change the data in the setting holding unit 73 including the setting data of the data block DB2 for the display device 120. If the request is correct, the data in the setting holding unit 73 is updated. If the request is incorrect, the data is not updated and an error is notified. Note that the same request determination algorithm for determining whether to update or change the setting is used for the display device 120 and the setting device 70.

  When the display 120 receives the data update request made to the data block DB2 for the display 120 by the communication analysis unit 122 via the reception I / F 121, the display 120 tries to change the data in the setting holding unit 123. If the request is correct, the data in the setting holding unit 123 is updated. If the request is incorrect, the data is not updated. Since the same request determination algorithm is used for the display device 120 and the setting device 70, data mismatch does not occur between the two devices.

  The display 120 displays data with the updated setting contents. When the setting of the display device 120 is completed, the setting device 70 may be disconnected from the field bus 80. As a result, the setting device 70 cannot be recognized from the network.

The reason why the setting of the display device 120 can be changed by a setting change request to the setting device 70 is as follows.
1) The display device 120 can receive all data communication with the setting device 70.
2) Information capable of recognizing the setting device 70 is set in the setting holding unit 123 of the display device 120 in advance. Thereby, communication to data block DB2 for indicator 120 can be recognized.

3) The setting update algorithm of the setting device 70 and the display device 120 is the same. Since the display device 120 cannot transmit data, it cannot know the operation result of the setting change, but the operation result can be known by the setting device 70 performing the same process and transmitting the result.
4) The data of the setting holding unit 73 in the setting device 70 and the setting holding unit 123 of the display device 120 are the same.

  As a result, the fieldbus system of the present invention obtains data by transmitting the setting data transmitted from the controller toward the setting device to each display device connected to the fieldbus and not having an address. Communication volume can be reduced, and the network load can be reduced.

  Further, according to the configuration of the present invention, the display device does not transmit data and does not have an address, so that it does not consume extra network resources such as an address. For example, when 10 display units are connected to the fieldbus, it has been necessary to assign 10 addresses in the past. However, in the method of the present invention, only one setting device address needs to be assigned, and the number of display units is increased. If so, there is no need to assign more addresses. As a result, as long as hardware restrictions such as fieldbus current allow, an additional display can be added as necessary.

  In addition, since the display device does not have an address and does not participate in the network, the display device is not recognized on the network when the control system is set, and a control loop setting error caused by the display device does not occur. While the setting of the display unit is being changed, the setting device can be recognized from the network. However, if the setting device is disconnected from the network after the setting is completed, the output value of the field device must be input to another field device when setting the control loop. Incorrect settings such as accidental input to the display unit can be prevented.

  In addition, since the display device acquires and displays data that is not addressed to the device itself, the influence on the network load due to the connection of the display device is small.

  Further, the setting of a plurality of display devices can be changed with a single setting device. The setting device address only needs to be used when the display unit is set, and when there is no need to change the setting (for example, during steady operation other than when the display unit is set), the setting device is disconnected. By doing so, no extra address is consumed, in other words, no extra network resources are consumed.

  In the above-described embodiment, since the display device does not have an address, it is not possible to display data other than data that flows on the fieldbus due to communication with other devices. However, these data can also be displayed by the following method. .

  FIG. 6A is an explanatory diagram of a method of periodically reading from the setting device 70. This is a method in which the setting device 70 is continuously connected to the field bus 80 after the display is set, and a parameter read request is continuously transmitted to the field device at a constant cycle. Data can be read by the following procedure. it can.

1) The setting device 70 reads parameters from the field device.
2) The field device returns reply data based on the Read request. The setting device 70 may discard the reply data.
3) The display device receives a reply to the setting device 70, analyzes the received reply data addressed to the setting device, and displays a value.

  FIG. 6B is an explanatory diagram of a method for periodically issuing and setting parameters to be displayed. In this method, a dummy functional block is created in the setting device 70, and parameter issuance is set for the dummy functional block when the control loop is set. In operation, even if the setting device 70 is removed, data issuance is continued, so that data can be continuously read from the display. Data can be read by the following procedure.

1) The master device (or controller) transmits a data issue instruction to the field device according to the setting information.
2) The field device issues the held data to the functional block of the setting device based on the data issue instruction. At this time, the setting device 70 does not need to participate in the network.
3) The display device receives the issuance data for the field device, analyzes the received issuance data addressed to the setting device, and displays the value.

  Moreover, you may provide a communication state diagnostic function in the indicator used by this invention as needed. As a result, it can be used as a cause investigation material when some trouble occurs on the field bus, and improvement in maintainability can be expected.

  In addition, the display device used in the present invention is provided with an external communication port, and the data received by the device and the analysis result data of the communication analysis unit in the display device are transmitted to the dedicated or general-purpose device via the external communication port. , Fieldbus diagnosis becomes possible.

  It is also possible to add a security function to the setting device 70 so that the setting cannot be changed when a device other than the correct setting device is used. For example, the setting device 70 periodically transmits specific data on the field bus 80. The specific data is data known in advance by the display, and the correct setting device 70 is recognized using this data as a key. By executing this process, the setting device 70 with different specific data cannot be updated.

  In the system of the present invention, the setting update result cannot be transmitted from the display. Basically, since the same update algorithm is used for the setting device 70 and the display device, data inconsistency does not occur between these devices, but there is a possibility that data inconsistency may occur for some reason. There is. In order to synchronize these data, for example, the following configuration can be considered.

  When the setting device 70 joins the network by setting, the setting device 70 transmits a specific data frame to the field bus 80. The display device that has received a specific frame operates as a field device by participating in the network only for a certain period. Within this period, the setting device 70 and the display unit synchronize setting data. The display unit leaves the network after a certain period of time, and thereafter operates based on information set synchronously.

  In the above-described embodiment, the display 120 is described as having the communication analysis unit 122 and the setting holding unit 123. However, the communication analysis unit 122 and the setting holding unit 123 are arithmetic controls that control various functions and operations of the respective units. It may be provided by a unit (for example, CPU).

  For example, the arithmetic control unit of the display unit converts the data acquired via the reception I / F 121 for display, and determines whether or not the received measurement / control data is data to be displayed. And a setting holding unit 123 that determines whether or not the received setting data is a request for setting change to the own device, and updates and sets the display operation based on the determination result and the received data. .

  In this case, the arithmetic control unit of the display device 120 starts up an OS or the like stored in a storage unit (not shown), reads out and executes a program stored on the OS, and thereby displays the entire display device 120 (for example, The communication analysis unit, the setting holding unit, the display unit, and the like may be controlled to perform unique operations.

  In the fieldbus system according to the present invention, the controller has a LAS (Link Active Scheduler) function, and a data request message (hereinafter referred to as CD (Compel Data)) for transmitting various data from the field device. A data request schedule that is arbitrarily set as to which device is to be transmitted at the timing may be stored, and a CD may be transmitted based on this schedule. The CD schedule may include a communication execution list based on one period so that the controller periodically transmits a CD to each field device.

  As described above, according to the present invention, a display device connected to a field bus can reduce network load without consuming network resources, and can realize a field bus system that does not cause a control loop setting error. Can contribute to the optimal operation and control of the controlled object through the field control loop.

It is a block diagram which shows one Example of the fieldbus system which concerns on this invention. It is a functional block specific example figure of the indicator 120 and the setting apparatus 70 of FIG. FIG. 11 is a sequence diagram for the display device 120 to acquire data from the field device 40. FIG. 11 is an explanatory diagram of a setting method of the display device 120 It is operation | movement explanatory drawing in the case of changing the setting of the indicator 120 from the controller 60. FIG. It is operation | movement explanatory drawing of the display system which displays communication data other than control communication. It is a block diagram which shows an example of the conventional fieldbus system. It is a functional block diagram which shows the structural example of the indicator 20 of FIG. FIG. 10 is a sequence diagram for the display device 20 to acquire data from the field device 40. It is explanatory drawing of the setting method of the indicator.

Explanation of symbols

40, 50 Field device 60 Controller 70 Setting device 71 Transmission / reception I / F
72 Field Communication Unit 73 Setting Holding Unit 80 Fieldbus 110-130 Display 121 Reception I / F
122 Communication Analysis Unit 123 Setting Holding Unit 124 Display Unit

Claims (6)

A fieldbus system in which a plurality of display units and a plurality of field devices are connected via a common fieldbus,
Each display unit has a data reception dedicated function that does not transmit data to other devices, and each display unit is assigned a network address and is dedicated to being temporarily connected to the fieldbus only at the time of setting. A fieldbus system characterized by being performed by a setting device.   Each display device receives communication data for control by each field device via the field bus, extracts data to be displayed from these data, and converts the extracted data into display data. The fieldbus system according to claim 1, wherein the fieldbus system is displayed.   The field bus is instructed to issue data to each field device connected to the field bus, and setting data for changing the display setting of each display device is transmitted to the setting device as a transmission destination. The fieldbus system according to claim 1, wherein a controller is connected.   4. Each display device according to claim 1, wherein if the setting data received via the field bus is data addressed to the display device, the display device changes display settings based on the setting data. A fieldbus system according to any one of the above.   The fieldbus system according to any one of claims 1 to 4, wherein the setting device is provided with a data block including a database having a content equivalent to a setting content of a corresponding display.   6. The fieldbus system according to claim 1, wherein the display device and the setting device have the same setting update determination unit.

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