JP2013153267A - Process control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process control system that can continuously obtain latest measurement data during a maximum response waiting time.SOLUTION: A process control system in which a communication path between a radio field device and a control system is made redundant by a gateway to which a maximum response waiting time Ta to detect abnormality is set comprises: response waiting time monitoring means for monitoring a prescribed response waiting time Tb for a data acquisition request to the gateway; communication path disconnection means for disconnecting a communication path if there is no reply from the gateway during the prescribed response waiting time Tb; communication path establishment request means for requesting establishment of a communication path again regarding the disconnected communication path; reestablishment response waiting time monitoring means for monitoring a prescribed reestablishment response waiting time Tc for the communication path reestablishment request; and abnormality determination means for determining that it is abnormal if there is no reply from the gateway during the prescribed reestablishment response waiting time Tc and outputting an alarm.

Description

  The present invention relates to a process control system, and more particularly, to an improvement of a process control system configured to perform wireless communication between a field device and a control system.

  Communication between the field device and the control system in the process control system is 4 to 20 mA analog communication using a two-wire signal line → hybrid communication such as HART (registered trademark) in which a digital signal is superimposed on 4 to 20 mA analog communication. → For industrial automation, which was formulated by the ISA100 Committee of the International Society of Automation (ISA) and issued in September 2009 via digital communications such as FOUNDATION Fieldbus (registered trademark) and PROFIBUS (registered trademark) It has evolved into radio represented by the wireless communication standard ISA100.11a.

  As a result of the dramatic increase in the amount of information that can be used in plant operations through hybrid communication and digital communication, a variety of information such as multiple process amounts and diagnostic results transmitted by equipment can be obtained using DCS (Distributed Control System) It is now possible to communicate to a higher-level system such as a device management system, enabling facility management and predictive maintenance.

  In addition to these, field wireless technology that wirelessly communicates between field devices and control systems can reduce wiring and engineering costs, enable devices to be installed in places where wiring is difficult, and add or delete devices. Since it has many merits such as being easy, it can be expected to realize instrumentation that would have been impossible until now by utilizing these merits.

  FIG. 4 is a block diagram showing an example of a system configuration conforming to ISA100.11a. The wireless network 1 is composed of, for example, four wireless field devices 2a to 2d. These wireless field devices 2a to 2d are obtained by adding a wireless communication function to field devices such as transmitters and operation terminals conventionally used in process control systems.

  The backbone router 3 has a function for connecting the wireless field devices 2a to 2d to each other and the wireless field devices 2a to 2d and the gateway 5. For example, three backbone routers 3a to 3c are connected to the backbone network. 4 is connected. These backbone routers 3a to 3c are access point functions for connecting the field wireless devices 2a to 2d to the backbone network 4, interface functions for connecting to the gateway 5, and field wireless devices 2a to 2d via the backbone network 4. Has a routing function for communication.

  As a communication protocol of the backbone network 4, for example, IP (Internet Protocol) is used.

  The gateway 5 has a function of interfacing between a host system such as the DCS 10 and the wireless network 1 based on ISA100.11a. In the example of FIG. 4, two gateways 5 a and 5 b are connected between the backbone network 4 and the control network 9, and processing depending on the application of the higher system is performed.

  Modbus servers 6a and 6b are mounted on the gateways 5a and 5b, respectively. The measurement data of the field wireless devices 2a to 2d are notified to the gateways 5a and 5b via the backbone routers 3a to 3c, and transferred and stored in the Modbus servers 6a and 6b installed in the gateways 5a and 5b. The measurement data transferred and stored in these Modbus servers 6a and 6b is transferred and output to the DCS 10 in response to a data acquisition request from the DCS 10 which is a Modbus client.

  The gateways 5a and 5b and the host system such as the DCS 10 are connected by Ethernet (registered trademark) 100BASE-TX, 100BASE-FX, or the like corresponding to metal or optical media. By using optical media, stable communication can be performed even in an environment with large electromagnetic noise.

  As a communication protocol between the gateways 5a and 5b and the DCS 10, for example, Modbus / TCP (Modbus / Transmission Control Protocol) is used. Modbus / TCP is an implementation of the Modbus protocol on top of the Ethernet TCP / IP protocol, and is widely used in industry.

  A system manager 7 and a security manager 8 are also connected to the backbone network 4.

  The system manager 7 has a function of controlling the operation of the wireless network 1 based on ISA100.11a, such as the communication period of the wireless field devices 2a to 2d and communication error processing.

  The security manager 8 has a function of ensuring the security of field wireless communication in cooperation with the system manager 7 and manages security key distribution and update, device authentication, and the like.

  Note that an integrated gateway in which four functions including the gateway, system manager, security manager, and backbone router defined in ISA100.11a are integrated has been put into practical use.

  According to the configuration of FIG. 4, the communication path between the field wireless devices 2a to 2d and the DCS 10 is made redundant by the three backbone routers 3a to 3c, and the field wireless devices 2a to 2d and the backbone router 3a are made redundant. The wireless communication path between ˜3c is also made redundant. It can be said that ISA100.11a defines various basic functions for improving communication reliability.

  Although not shown in FIG. 4, the VIPS (Virtual IP) function is provided in the redundant gateways 5a and 5b, so that the DCS 10 as the Modbus client can switch the control right of the gateways 5a and 5b. It is possible to construct a communication environment in which communication is always performed for one IP address without being aware of whether the gateway 5 has a single configuration or redundancy, and the implementation of the DCS 10 can be simplified.

  Non-Patent Document 1 describes a field wireless solution concept based on ISA100.11a and a field wireless system concept centered on DCS.

  Non-Patent Document 2 describes a technique related to a field wireless device and a field wireless system compliant with ISA100.11a.

  Patent Document 1 describes a technique for simplifying connection establishment in a system that accesses another system via an addressable redundant gateway.

  Patent Document 2 describes a technique for detecting a failure of a duplexed gateway at an early stage by alternately using duplexed gateways.

Shuji Yamamoto and two others, “ISA100.11a compliant field wireless solution to innovate instrumentation”, Yokogawa Technical Journal, Yokogawa Electric Corporation, 2010, Vol. 53 No. 2 (2010) p. 7-p. 12 Shuji Yamamoto, three others, “The world's first ISA100.11a-compliant wireless field device”, Yokogawa Technical Report, Yokogawa Electric Corporation, 2010, Vol. 53 No. 2 (2010) p. 13-p. 16

Special table 2008-502216 Japanese Patent Laid-Open No. 10-285202

  FIG. 5 is a diagram for explaining the operation of each part in FIG. In FIG. 5, it is assumed that one gateway 5a currently has the control right and is in a control state, and the other gateway 5b is in a standby state.

  The DCS 10 that is a Modbus client transmits a VIP address to the gateway 5a on the control side, and requests establishment of a communication path (S1). If there is no problem with the communication path establishment request from the DCS 10, the gateway 5a returns a communication path establishment request OK (S2). When the DCS 10 confirms the reply of the communication path establishment request OK from the gateway 5a, the DCS 10 transmits a data acquisition request to the gateway 5a (S3). If there is no problem in response to the data acquisition request from the DCS 10, the gateway 5a returns a data acquisition request OK and also transmits measurement data (S4). Thereafter, when the DCS 10 and the gateway 5a are operating normally, the data acquisition request, the communication path establishment request OK, and the measurement data exchange are repeated (S5, S6).

  However, if a failure occurs in the gateway 5a, the data acquisition request OK cannot be returned to the data acquisition request from the DCS 10 (S7). The standby-side gateway 5b constantly monitors the state of the control-side gateway 5a. If the standby-side gateway 5b recognizes that the control-side gateway 5a has failed, the control-side connection is switched to obtain control (S8). Thereby, the other gateway 5b will be in a control state. Note that the response times of these gateways 5 are designed to be sufficiently shorter (for example, less than 25 msec) than the maximum response waiting time (for example, 4 sec). In addition, the switching time of the gateway 5 is, for example, a maximum of 1 sec.

  On the other hand, when the DCS 10 does not respond from the gateway 5a beyond the maximum response waiting time, the DCS 10 recognizes that the gateway 5a has failed, and notifies the user of an alarm indicating that the measurement data cannot be acquired correctly (S9). ).

  In this way, in the process of switching the control right from the gateway 5a to 5b, the communication path between the ModS client DCS 10 and the gateway 5a is disconnected (S10). Therefore, the DCS 10 transmits a VIP address to the gateway 5b newly in the control state, and requests establishment of a communication path (S11). If there is no problem with the communication path establishment request from the DCS 10, the gateway 5b returns a communication path establishment request OK (S12). When the DCS 10 confirms the return of the communication path establishment request OK from the gateway 5b, the DCS 10 transmits a data acquisition request to the gateway 5b (S13). If there is no problem in response to the data acquisition request from the DCS 10, the gateway 5b returns a data acquisition request OK and also transmits measurement data (S14). The alarm notification to the user is continuously performed until the measurement data acquisition from the gateway 5b newly in the control state is completed (S15).

  However, in a system with redundant gateways as shown in Fig. 4, the Modbus client is unaware of whether the gateway is redundant, so if the control gateway fails, the standby gateway will be updated. Although it becomes the control side, an abnormality of the gateway on the control side is detected based on the maximum response waiting time, and the latest measurement data during the maximum response waiting time cannot be acquired.

  Further, when the field wireless device 2 is an operation terminal such as a valve driven by an operation signal output from the DCS 10, the operation signal output is interrupted.

  The present invention pays attention to such a conventional problem, and its purpose is that even when one of the redundant gateways fails and is switched to the other, the wireless field device and the control system are not connected. It is to provide a process control system that can continuously send and receive signals.

The invention of claim 1 which achieves such a problem,
In the process control system in which the communication path between the field wireless device and the control system is made redundant by the gateway in which the maximum response waiting time Ta for detecting an abnormality is set,
The control system includes:
Response waiting time monitoring means for monitoring a predetermined response waiting time Tb for the data acquisition request to the gateway;
A communication path cutting means for cutting the communication path when there is no response from the gateway at the time when the predetermined response waiting time Tb has passed;
Communication path establishment request means for requesting establishment of a communication path again for the disconnected communication path;
Re-establishment response waiting time monitoring means for monitoring a predetermined re-establishment response waiting time Tc for the communication path re-establishment request;
An abnormality determining means for determining an abnormality and outputting an alarm when there is no response from the gateway when the predetermined re-establishment response waiting time Tc has elapsed;
Is provided.

The invention of claim 2 is the process control system according to claim 1,
The maximum response waiting time Ta, the response waiting time Tb, and the re-establishment response waiting time Tc are in a relationship represented by the following equation.
Maximum response waiting time Ta ≧ response waiting time Tb + re-establishment response waiting time Tc

The invention according to claim 3 is the process control system according to claim 1 or 2,
The wireless field device is a transmitter that transmits measurement data to the control system.

The invention according to claim 4 is the process control system according to claim 1 or 2,
The wireless field device is an operation terminal driven by an operation signal output from the control system.

  As a result, even if the control right is switched between the redundant gateways, the measurement data of the field wireless device can be continuously acquired and the operation signal to the field wireless device can be continuously transmitted. If both gateways are out of order, an alarm indicating the failure of the gateway can be output to the user after the maximum response waiting time has elapsed, as in the prior art.

It is a block diagram which shows one Example of this invention. It is operation | movement explanatory drawing of each part in FIG. It is a flowchart explaining the flow of operation | movement of FIG. It is a block diagram which shows an example of the conventional system configuration. It is operation | movement explanatory drawing of each part in FIG.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and the same reference numerals are given to portions common to FIG. The difference between FIG. 1 and FIG. 4 is that the DCS 10 operating as the control system of FIG. 1 is provided with predetermined functional blocks based on the present invention.

  In FIG. 1, the DCS 10 is provided with a response waiting time monitoring unit 11, a communication path disconnection unit 12, a communication path re-establishment request unit 13, a re-establishment response waiting time monitoring unit 14, and an abnormality determination unit 15. Yes.

  FIG. 2 is a diagram for explaining the operation of each part in FIG. In FIG. 2, it is assumed that one gateway 5a currently has a control right and is in a control state, and the other gateway 5b is in a standby state.

  The DCS 10 that operates as a control system and is also a Modbus client transmits a VIP address to the gateway 5a on the control side and requests establishment of a communication path (S1). If there is no problem with the communication path establishment request from the DCS 10, the gateway 5a returns a communication path establishment request OK (S2). When the DCS 10 confirms the reply of the communication path establishment request OK from the gateway 5a, the DCS 10 transmits a data acquisition request to the gateway 5a (S3). If there is no problem in response to the data acquisition request from the DCS 10, the gateway 5a returns a data acquisition request OK and also transmits measurement data (S4). Thereafter, when the DCS 10 and the gateway 5a are operating normally, the data acquisition request, the communication path establishment request OK, and the measurement data exchange are repeated (S5, S6).

  However, if a failure occurs in the gateway 5a, the data acquisition request OK cannot be returned to the data acquisition request from the DCS 10 (S7). The standby-side gateway 5b constantly monitors the state of the control-side gateway 5a. If the standby-side gateway 5b recognizes that the control-side gateway 5a has failed, the control-side connection is switched to obtain control (S8). Thereby, the other gateway 5b will be in a control state. The response times of these gateways 5 are designed to be sufficiently shorter (for example, less than 25 msec) than the maximum response waiting time Ta (for example, 4 sec). In addition, the switching time of the gateway 5 is, for example, a maximum of 1 sec.

  The response waiting time monitoring unit 11 of the DCS 10 monitors the elapse of a predetermined response waiting time Tb for a data acquisition request to the gateway 5a. The communication path disconnecting unit 12 confirms that there is no response from the gateway 5a when the predetermined response waiting time Tb monitored by the response waiting time monitoring unit 11 has elapsed, and disconnects the communication path (S10).

  The communication path establishment request unit 13 transmits a VIP address to the gateway 5b newly in the control state, and requests re-establishment of the communication path (S11). If there is no problem in response to the communication path re-establishment request from the DCS 10, the gateway 5b returns a communication path establishment request OK (S12).

  The re-establishment response waiting time monitoring unit 14 monitors the progress of a predetermined re-establishment response waiting time Tc for the communication path re-establishment request. The abnormality determination unit 15 determines that there is no response from the gateway 5b when a predetermined re-establishment response waiting time Tc monitored by the re-establishment response waiting time monitoring unit 14 has elapsed, and determines that an abnormality has occurred and outputs an alarm. However, the alarm output is not shown in FIG.

The maximum response waiting time Ta, the response waiting time Tb, and the re-establishment response waiting time Tc are set so that the relationship represented by the following equation is established.
Maximum response waiting time Ta ≧ response waiting time Tb + re-establishment response waiting time Tc

  When the DCS 10 confirms the return of the communication path establishment request OK from the gateway 5b, the DCS 10 transmits a data acquisition request to the gateway 5b (S13). If there is no problem in response to the data acquisition request from the DCS 10, the gateway 5b returns a data acquisition request OK and also transmits measurement data (S14).

  FIG. 3 is a flowchart for explaining the flow of the operation of FIG. The DCS 10 transmits a data acquisition request to the gateway 5 having the control right (S1), and then confirms whether a response is received from the gateway 5 for the data acquisition request (S2). If the response from the gateway 5 can be received, it means that the gateway 5 is operating normally regardless of the response content, so the data acquisition request is continuously executed.

  If the response reception from the gateway 5 to the data acquisition request cannot be confirmed, it is checked whether or not the waiting time after sending the data acquisition request exceeds a predetermined response waiting time Tb (S3). (S4).

  After the communication path is disconnected, a communication path establishment request is again made to the gateway 5 having the control right (S5), and whether or not a response is received from the gateway 5 for the communication path re-establishment request is confirmed (S6).

  When the response reception from the gateway 5 to the communication path re-establishment request is confirmed, it is confirmed whether or not the response is normal (S7). If it is confirmed as normal, it is determined that the switching of the gateway 5 is completed and a communication path with the new gateway has been established, and a series of processes after step S1 are executed to receive measurement data from the new gateway 5. If the response reception from the gateway 5 to the communication path re-establishment request is confirmed to be abnormal, the user is notified of the abnormality (S8).

  When the response reception from the gateway 5 to the communication path re-establishment request cannot be confirmed, it is confirmed whether or not the waiting time after transmitting the communication path re-establishment request exceeds a predetermined re-establishment time Tc (S9). If the predetermined re-establishment time Tc is exceeded, it is determined that the gateway 5 is abnormal, and the user is notified of an abnormality meaning that data could not be acquired (S8).

  In this way, by executing the loop processing of steps S1, S2, S3, S4, S5, S6, S7, S1,... In FIG. Measurement data can be continuously captured via the other.

  When both of the redundant gateways 5 are out of order or in the case of a single configuration, the processing of steps S1, S2, S3, S4, S5, S6, S9, and S8 is executed by executing the conventional processing. Similarly, the user can be notified of an abnormality after the maximum response waiting time Ta (≧ response waiting time Tb + re-establishment response waiting time Tc) has elapsed.

  In the above embodiment, an example of a transmitter in which the field wireless device 2 transmits measurement data to the DCS 10 that is a control system has been described. However, the transmitter is not limited to the transmitter, and is output from the DCS 10 that is a Modbus client. Even an operation terminal such as a valve driven by an operation signal can transmit an operation signal according to the same processing procedure when a redundant gateway is switched.

  As described above, according to the present invention, even when one of the redundant gateways fails and is switched to the other, the process control can continuously transmit and receive signals between the field wireless device and the control system. A system can be realized and the process control system can be driven stably.

DESCRIPTION OF SYMBOLS 1 Wireless network 2 Wireless field device 3 Backbone router 4 Backbone network 5 Gateway 6 Modbus server 7 System manager 8 Security manager 9 Control network 10 DCS
DESCRIPTION OF SYMBOLS 11 Response waiting time monitoring part 12 Communication path cutting part 13 Communication path re-establishment request part 14 Re-establishment response waiting time monitoring part 15 Abnormality judgment part

Claims (4)

In the process control system in which the communication path between the field wireless device and the control system is made redundant by the gateway in which the maximum response waiting time Ta for detecting an abnormality is set,
The control system includes:
Response waiting time monitoring means for monitoring a predetermined response waiting time Tb for the data acquisition request to the gateway;
A communication path cutting means for cutting the communication path when there is no response from the gateway at the time when the predetermined response waiting time Tb has passed;
Communication path establishment request means for requesting establishment of a communication path again for the disconnected communication path;
Re-establishment response waiting time monitoring means for monitoring a predetermined re-establishment response waiting time Tc for the communication path re-establishment request;
An abnormality determining means for determining an abnormality and outputting an alarm when there is no response from the gateway when the predetermined re-establishment response waiting time Tc has elapsed;
A process control system characterized by comprising: 2. The process control system according to claim 1, wherein the maximum response waiting time Ta, the response waiting time Tb, and the re-establishment response waiting time Tc have a relationship represented by the following expression.
Maximum response waiting time Ta ≧ response waiting time Tb + re-establishment response waiting time Tc   The process control system according to claim 1, wherein the wireless field device is a transmitter that transmits measurement data to the control system.   The process control system according to claim 1, wherein the wireless field device is an operation terminal driven by an operation signal output from the control system.

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