Redundant devices in a process control system

• US 20020083364A1
• Filed: 12/05/2000
• Published: 06/27/2002
• Est. Priority Date: 12/05/2000
• Status: Active Grant

• Current Assignee: Fisher-Rosemount Systems Incorporated (Emerson Electric Company)
• Original Assignee: Fisher-Rosemount Systems Incorporated (Emerson Electric Company)
• Inventors: Bonwell, Steve D., Christensen, Dan Dean
• Granted Patent: US 6,742,136 B2
• Time in Patent Office: Days
• US Class Current: 714/13
• CPC Class Codes: G05B 2219/24174 One channel is used for communication while other is tested, in redundant I-O
• CPC Class Codes: G06F 11/2005 using redundant communication controllers

Abstract

A method of and a device for implementing redundancy in a process control network using a pair of redundant devices, such as redundant I/O devices, communicatively connected to a segment of the bus in parallel to each other and in series between the controller and field devices on the segment. The redundant devices are assigned a virtual publishing address, which may be the unique address of one of the redundant devices, that is used in communicating over the bus. At all times, one of the redundant devices is operating in an active mode and communicating with the devices in process control network, and the other redundant device is operating in a backup mode wherein the redundant device maintains a communication connection with the devices and listens for messages transmitted by the devices and intended for the redundant devices, but does not respond to messages from the other devices until the device switches to the active mode.

Claims

1. A process control system for communications in a process control network having a plurality of devices each having a unique address, the process control system comprising:

a bus;

a primary redundant device having a first unique address communicatively linked to the bus and programmed to publish messages on the bus including a virtual publishing address;

a secondary redundant device having a second unique address communicatively linked to the bus and programmed to publish messages on the bus including the virtual publishing address; and

at least one receiving device communicatively linked to the bus and programmed to process messages published on the bus containing the virtual publishing address;

wherein the primary redundant device operates in an active mode whereby the primary redundant device transmits messages on the bus for the at least one receiving device, and the secondary redundant device operates in a backup mode whereby the secondary device does not transmit messages on the bus.

2. A process control system according to claim 1, wherein the secondary redundant device operates in the active mode when the primary redundant device is disabled.

3. A process control system according to claim 2, wherein the secondary redundant device determines that the primary redundant device is disabled based on the failure of the primary redundant device to transmit messages containing the virtual publishing address on the bus.

4. A process control system according to claim 2, further comprising a controller communicatively linked to the primary and secondary redundant devices and programmed to receive status information from the primary and secondary redundant devices and, upon receiving status information indicating that the primary redundant device is or is about to become disabled, causes the primary redundant device to operate in the backup mode and the secondary redundant device to operate in the active mode.

5. A process control system according to claim 2, wherein the primary and secondary redundant devices are communicatively connected by a communication link external to the bus and the primary redundant device is programmed to transmit status information indicating that the primary redundant device is or is about to become disabled to the secondary redundant device via the communication link.

6. A process control system according to claim 1, wherein the primary and secondary redundant devices each have a publishing buffer for storing messages to be transmitted by the primary and secondary redundant devices on the bus, and a subscribing buffer for storing messages received over the bus, and wherein the secondary redundant device is programmed to process messages containing the virtual publishing address, to receive the messages transmitted on the bus by the primary redundant device and containing the virtual publishing address, and to store the received messages in the publishing buffer of the secondary redundant device.

7. A process control system according to claim 1, wherein the primary and secondary redundant devices are programmed to process messages containing the unique address of at least one device, and the primary and secondary redundant devices receive and process messages containing the unique address of the at least one device while operating in the active mode and in the backup mode.

8. A process control system according to claim 1, wherein the bus includes a first portion and a second portion, each of the first and second portions having at least one device communicatively linked thereto, wherein the primary and secondary redundant devices are communicatively linked in parallel to each other and in series between the first portion and the second portion of the bus.

9. A process control system according to claim 1, wherein the primary and secondary redundant devices are communicatively connected by a communication link external to the bus.

10. A process control system according to claim 1, wherein the primary and secondary redundant devices are configured to detect the presence of the other of the primary and secondary redundant devices and to determine which of the primary and secondary redundant devices will operate in the active mode and which will operate in the backup mode.

11. A process control system according to claim 1, wherein the devices are communicatively linked to the bus via slots, the system further comprising:

a first slot communicatively connecting the primary redundant device to the bus; and

a second slot communicatively connecting the secondary redundant device to the bus;

wherein the primary and secondary redundant devices are configured to determine that the primary redundant device is connected to the first slot and to operate in the active mode based upon the determination that the primary redundant device is connected to the first slot, and to determine that the secondary redundant device is connected to the second slot and to operate in the backup mode based upon the determination that the secondary redundant device is connected to the second slot.

12. A process control system according to claim 11, wherein the first and second slots each include a plurality of pins connecting the first and second redundant devices to the first and second slots respectively, and each pin having an associated voltage level, whereby the primary and secondary redundant devices determine that the primary redundant device is connected to the first slot and the secondary redundant device is connected to the second slot based on the voltage levels of the pins.

13. A process control system according to claim 1, further comprising a host device having a display communicatively linked to the bus, the host device being configured to detect the presence of the primary and secondary redundant devices, to detect the operation of the primary redundant device in the active mode and the operation of the secondary redundant device in the backup mode, and to display on the display of the host device the presence of the primary and secondary redundant devices, the operation of the primary redundant device in the active mode, and the operation of the secondary device in the backup mode.

14. A process control system according to claim 1, wherein the virtual publishing address is one of the first unique address and the second unique address.

15. A process control system according to claim 1, wherein the primary and secondary redundant devices are I/O devices.

17. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising the step of configuring the secondary redundant device to operate in the active mode when the primary redundant device is disabled.

18. A method of implementing redundant devices within a process control system in a process control network according to claim 17, further comprising the step of configuring the secondary redundant device to determine that the primary redundant device is disabled based on the failure of the primary redundant device to transmit messages containing the virtual publishing address on the bus.

19. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising:

transmitting on the bus status information indicating that the primary redundant device is or is about to become disabled from the primary redundant device in a message containing the virtual publishing address while the primary redundant device is operating in the active mode;

configuring the secondary redundant devices to process messages containing the virtual publishing address; and

causing the secondary redundant device to operate in the active mode upon receiving the message containing the virtual publishing address and the status information.

20. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising:

communicatively connecting the primary and secondary redundant devices by a communication link external to the bus; and

transmitting status information indicating that the one of the primary and secondary redundant devices operating in the active mode is or is about to become disabled from the one of the primary and secondary redundant devices operating in the active mode to the other of the primary and secondary redundant devices via the communication link.

21. A method of implementing redundant devices within a process control system in a process control network according to claim 16, wherein the primary and secondary redundant devices each have a publishing buffer for storing messages to be transmitted by the primary and secondary redundant devices on the bus, and a subscribing buffer for storing messages received over the bus, the method further comprising:

configuring the primary and secondary redundant devices to detect messages containing the virtual publishing address;

transmitting messages containing the virtual publishing address on the bus from the primary redundant device;

detecting at the primary redundant device messages containing the virtual publishing address; and

storing the detected messages containing the virtual publishing address in the publishing buffer of the secondary redundant device.

22. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising:

configuring the primary and secondary redundant devices to process messages containing the unique address of at least one device;

receiving messages containing the unique address of the at least one device; and

processing the messages containing the unique address of the at least one device at the primary and secondary redundant devices while operating in the active mode and in the backup mode.

23. A method of implementing redundant devices within a process control system in a process control network according to claim 16, wherein the bus has a first portion and a second portion each having at least one device communicatively linked to the bus, the method further comprising communicatively linking the primary and secondary redundant devices in parallel to each other and in series between the first portion and the second portion of the bus.

24. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising communicatively connecting the primary and secondary redundant devices by a communication link external to the bus.

25. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising:

configuring the primary and secondary redundant devices to detect the connection of the other of the primary and secondary redundant devices;

detecting at the primary redundant device the connection of the secondary redundant device, and at the secondary redundant device the connection of the primary redundant device;

causing the primary redundant device to operate in the active mode based on the connection of the secondary redundant device; and

causing the secondary redundant device to operate in the backup mode based on the connection of the primary redundant device.

26. A method of implementing redundant devices within a process control system in a process control network according to claim 16, wherein the devices are communicatively linked to the bus via slots, the method further comprising:

communicatively connecting the primary redundant devices to the bus via a first slot;

communicatively connecting the secondary redundant devices to the bus via a second slot;

causing the primary redundant device to determine the connection to the bus via the first slot and to operate in the active mode based upon the determination that the primary redundant device is connected to the bus via the first slot; and

causing the secondary redundant device to determine the connection to the bus via the second slot and to operate in the backup mode based upon the determination that the secondary redundant device is connected to the bus via the second slot.

27. A method of implementing redundant devices within a process control system in a process control network according to claim 26, wherein the first and second slots each include a plurality of pins connecting the first and second redundant devices to the first and second slots, respectively, and each pin having an associated voltage level, the method further comprising:

determining that the primary redundant device is connected to the bus via the first slot based on the voltage levels of the pins of the first slot; and

determining that the secondary redundant device is connected to the bus via the second slot based on the voltage levels of the pins of the second slot.

28. A method of implementing redundant devices within a process control system in a process control network according to claim 16, wherein a host device having a display is communicatively linked to the bus, the method further comprising:

detecting at the host device the presence of the primary and secondary redundant devices, the operation of the primary redundant device in the active mode, and the operation of the secondary redundant device in the backup mode; and

displaying on the display of the host device indicia of the presence of the primary and secondary redundant devices, the operation of the primary redundant device in the active mode, and the operation of the secondary redundant device in the backup mode.

29. A method of implementing redundant devices within a process control system in a process control network according to claim 16, wherein the virtual publishing address is one of the first unique address and the second unique address.

30. A method of implementing redundant devices within a process control system in a process control network according to claim 16, wherein the primary and secondary redundant devices are I/O devices.

16. A method of implementing redundant devices within a process control system for communications in a process control network having a plurality of devices communicatively linked over a bus, wherein each of the devices has a unique address and is capable of communicating on the bus, the method comprising:

configuring a primary redundant device having a first unique address and a secondary redundant device having a second unique address to transmit messages containing a virtual publishing address on the bus;

operating the primary redundant device in an active mode whereby the primary redundant device transmits messages containing the virtual publishing address on the bus;

operating the secondary redundant device in a backup mode whereby the secondary redundant device does not transmit messages on the bus; and

receiving messages containing the virtual publishing address at least one receiving device configured to process messages containing the virtual publishing address.

31. A redundant pair of devices in a process control network having a plurality of devices communicatively linked over a bus, wherein each of the devices has a unique address and is capable of communicating on the bus, at least one device being programmed to process messages published on the bus containing a virtual publishing address, the redundant pair of devices comprising:

a primary redundant device having a first unique address communicatively linked to the bus and programmed to publish messages on the bus including the virtual publishing address; and

a secondary redundant device having a second unique address communicatively linked to the bus and programmed to publish messages on the bus including the virtual publishing address;

wherein the primary redundant device operates in an active mode whereby the primary redundant device transmits messages on the bus for the at least one receiving device, and the secondary redundant device operates in a backup mode whereby the secondary device does not transmit messages on the bus.

32. A redundant pair of devices according to claim 31, wherein the secondary redundant device operates in the active mode when the primary redundant device is disabled.

33. A redundant pair of devices according to claim 32, wherein the secondary redundant device determines that the primary redundant device is disabled based on the failure of the primary redundant device to transmit messages containing the virtual publishing address on the bus.

34. A redundant pair of devices according to claim 32, further comprising a controller communicatively linked to the primary and secondary redundant devices and programmed to receive status information from the primary and secondary redundant devices and, upon receiving status information indicating that the primary redundant device is or is about to become disabled, causes the primary redundant device to operate in the backup mode and the secondary redundant device to operate in the active mode.

35. A redundant pair of devices according to claim 32, wherein the primary and secondary redundant devices are communicatively connected by a communication link external to the bus and the primary redundant device is programmed to transmit status information indicating that the primary redundant device is or is about to become disabled to the secondary redundant device via the communication link.

36. A redundant pair of devices according to claim 31, wherein the primary and secondary redundant devices each have a publishing buffer for storing messages to be transmitted by the primary and secondary redundant devices on the bus, and a subscribing buffer for storing messages received over the bus, and wherein the secondary redundant device is programmed to process messages containing the virtual publishing address, to receive the messages transmitted on the bus by the primary redundant device and containing the virtual publishing address, and to store the received messages in the publishing buffer of the secondary redundant device.

37. A redundant pair of devices according to claim 31, wherein the primary and secondary redundant devices are programmed to process messages containing the unique address of at least one device, and the primary and secondary redundant devices receive and process messages containing the unique address of the at least one device while operating in the active mode and in the backup mode.

38. A redundant pair of devices according to claim 31, wherein the bus includes a first portion and a second portion, each of the first and second portions having at least one device communicatively linked thereto, wherein the primary and secondary redundant devices are communicatively linked in parallel to each other and in series between the first portion and the second portion of the bus.

39. A redundant pair of devices according to claim 31, wherein the primary and secondary redundant devices are communicatively connected by a communication link external to the bus.

40. A redundant pair of devices according to claim 31, wherein the primary and secondary redundant devices are configured to detect the presence of the other of the primary and secondary redundant devices and to determine which of the primary and secondary redundant devices will operate in the active mode and which will operate in the backup mode.

41. A redundant pair of devices according to claim 31, wherein the primary redundant device is communicatively linked to the bus via a first slot and the secondary redundant device is communicatively linked to the bus via a second slot, and wherein the primary and secondary redundant devices are configured to determine that the primary redundant device is connected to the first slot and to operate in the active mode based upon the determination that the primary redundant device is connected to the first slot, and to determine that the secondary redundant device is connected to the second slot and to operate in the backup mode based upon the determination that the secondary redundant device is connected to the second slot.

42. A redundant pair of devices according to claim 41, wherein the first and second slots each include a plurality of pins connecting the first and second redundant devices to the first and second slots respectively, and each pin having an associated voltage level, whereby the primary and secondary redundant devices determine that the primary redundant device is connected to the first slot and the secondary redundant device is connected to the second slot based on the voltage levels of the pins.

43. A redundant pair of devices according to claim 31, wherein the virtual publishing address is one of the first unique address and the second unique address.

44. A redundant pair of devices according to claim 31, wherein the primary and secondary redundant devices are I/O devices.