WO2015142908A1

WO2015142908A1 - Field instrument concentrator for interconnecting a local fieldbus network and one or more remote fieldbus networks

Info

Publication number: WO2015142908A1
Application number: PCT/US2015/021048
Authority: WO
Inventors: David Katz; Aaron Richard Kreider; Davis Mathews; Lonnel J. Swarr
Original assignee: David Katz; Aaron Richard Kreider; Davis Mathews; Swarr Lonnel J
Priority date: 2014-03-17
Filing date: 2015-03-17
Publication date: 2015-09-24
Also published as: WO2015142908A4

Abstract

A fieldbus networks interconnecting device for interconnecting a local fieldbus network and at least one remote fieldbus network includes a ring topology communications network and gateway devices attachable to the ring topology network. The system provides both self-healing system redundancy and self-healing media redundancy.

Description

Field Instrument Concentrator for Interconnecting a Local Fieldbus Network and One or More Remote Fieldbus Networks RELATED APPLICATIONS

This application claims priority to US Provisional Patent Application Serial No. 61/953,967 filed March 17, 2014 at Attorney Docket No. 14-1318-P-l and to US Provisional Patent Application Serial No. 62/075,959 filed November 6, 2014 at Attorney Docket No. 14-1319-P2, each provisional patent application incorporated fully by reference herein.

FIELD OF THE DISCLOSURE

The disclosure related to fieldbus technology for controlling industrial processes, and more specifically, to fieldbus technology in which one or more remote fieldbus networks or devices are connected to one or more local fieldbus networks.

BACKGROUND OF THE DISCLOSURE

A fieldbus is a network used in process automation in which field devices form some of the nodes on the network and a head station or host process controller forms one of the nodes on the network. The function of the fieldbus network is to transmit data to and from the nodes in a reliable and timely manner.

Redundancy is often used in fieldbus networks to increase reliability and minimize downtime. System redundancy utilizes redundant hardware that enables continued operation of the fieldbus despite a hardware failure. Examples of system redundancy include the use of redundant power supplies, redundant controller boards, and redundant field devices to minimize the risk of a non-recoverable network fault.

Media redundancy utilizes multiple pathways to enable communication of the data between nodes even if there is a fault along the network. Many fieldbus protocols are designed for a linear topology where the end nodes of the network are connected to an adjacent node and the interior nodes are attached to pairs of adjacent nodes. A fault along the network may isolate nodes downstream from the fault. Some fieldbus implementations in practice run duplicate wires to the field devices to provide alternative data pathways in the case of a fault.

Other communications networks utilize network topologies that provide redundant data pathways . A ring topology for example has each node on the network connected to two adjacent nodes. A media redundancy protocol is used to "linearize" the ring and form a logical linear network for communications along the network. A fault in the network converts the ring network to a physical linear network, and the media redundancy protocol handles the resulting change in the physical topology of the network.

In addition to redundancy, there is an increasing need to connect remote fieldbus networks to a local fieldbus network. A "local fieldbus network" as used herein is a fieldbus network that includes a host process controller connected to the network for making process control decisions. A number of persons skilled in the fieldbus art prefer to limit the field devices attached to a local fieldbus network to actuators and the like to minimize communications on the network, and prefer that 10 devices (including sensors and the like) and other field devices be attached to a different ("remote") fieldbus network .

There is a need to provide a device that can reliably interconnect one or more remote fieldbus networks to a local fieldbus network while providing both system and media redundancy .

BRIEF SUMMARY OF THE DISCLOSURE

Disclosed is a fieldbus networks interconnecting device for interconnecting a local fieldbus network and at least one remote fieldbus network. The interconnecting device includes a ring topology communications network and a first gateway device attachable to the ring topology network. The first gateway device is capable of two-way communications between the ring topology network and the local fieldbus network when the first gateway device is also connected to the local fieldbus network.

Attachable to the ring topology network is at least one second gateway device, each second gateway device capable of two-way communication between the ring topology network and a respective one of the remote fieldbus networks when such second gateway device is also connected to the respective one of the remote fieldbus networks. The first gateway device and each second gateway device are capable of communicating with the ring topology network utilizing a ring redundancy protocol supporting the ring topology network.

In an embodiment of the networks attachment device the ring topology network uses an Ethernet protocol, and may use the Profinet protocol or other Ethernet-based fieldbus protocols. The ring topology network includes a backplane that mounts the gateway devices to the ring network. The ring topology network may be the Media Redundancy Protocol .

A gateway device may include redundant power supplies that provide power to a fieldbus attached to the device.

The gateway device may include redundant processors or process controllers that are each independently capable of acting as a proxy between the fieldbus protocol and the ring network protocol. One processor is active, the other one or more processors are standby processors.

The gateway device may include redundant linking modules, each linking module housing a processor or a processor and power supply. The linking modules may removably plug into a base that in turn is attachable to the ring network. During normal operation one linking module is an active module and the other one or more linking modules are standby modules. A standby module automatically becomes an active module in the event of a fault or failure of the active module.

A redundant linking module may also be removable from the base without creating a fault on the ring network.

The redundant processors or redundant processors and power supplies provide self-healing system redundancy, while the ring network topology provides self-healing media redundancy. The modular nature of the system enables a great deal of flexibility in attaching different types of remote fieldbuses or remote fieldbus devices to a local fieldbus network .

Other objects and features of the disclosure will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing sheets illustrating one or more embodiments of the teachings made herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates two local fieldbus networks connected to multiple remote fieldbus networks utilizing the disclosed fieldbus networks interconnecting device;

Figure 2 illustrates a downstream interconnection device forming part of the interconnecting device;

Figure 3 illustrates a switching arrangement interconnecting two processing boards of the device shown in Figure 2 ;

Figure 4 illustrates the switching arrangement after one of the processing boards is removed;

Figure 5 illustrates the switching arrangement after the other of the processing boards is removed.

Detailed Description

Figure 1 illustrates a first local Profinet fieldbus network 10 and a second local Profinet fieldbus network 12. The Profinet fieldbus networks 10, 12 include a redundant DCS controller 14, 16 respectfully that each communicate with a redundant Ethernet LAN 18. A system workstation 20 is attached to the Ethernet LAN 18.

Also connected to the local Profinet networks 10, 12 is a field instrument concentrator or fieldbus networks interconnecting device 22. The fieldbus networks interconnecting device 22 connects one or more local fieldbus networks with one or more remote fieldbus networks.

In the illustrated embodiment the fieldbus networks interconnecting device 22 interconnects each local fieldbus network 10, 12 with a remote Profibus PA fieldbus network 24, a Foundation Fieldbus HI fieldbus network 26, an I/O fieldbus network 28, and an Ethernet-based fieldbus network 30. The Profibus network 24 includes Profibus fieldbus devices 24d. The Foundation Fieldbus network 26 includes HI fieldbus devices 26d. The I/O network 28 includes a digital output 28a, a digital input 28b, an analog output 28c, and an analog input 28d. The Ethernet network 30 includes Ethernet field devices 30d.

The fieldbus networks interconnecting device 22 utilizes one or more bus couplers 32 and one or more downstream interconnection devices 34. The bus couplers 32 and the downstream interconnection devices 34 are connected to a ring topology network 36 that carries communications between the bus couplers 32 and the downstream devices 34.

The ring topology network 36 provides a redundant communications network interconnecting the bus couplers 32 and the downstream interconnection devices 34. The ring topology network 36 utilizes a ring redundancy protocol to provide media redundancy along the network.

Each bus coupler 32 acts as gateway device between the DCS controller 14, 16 attached to the bus coupler and the downstream interconnection devices 34. The bus coupler 32 acts as a proxy between the local fieldbus protocol and the ring network protocol, enabling two-way communication between the local fieldbus network and the ring network 36. The bus coupler 32 also provides power to the ring network 36.

Each downstream interconnection device 34 acts as a gateway device between the fieldbus network connected to the device 34 and the ring network 36. A downstream device 34 is adapted to connect to a specific remote fieldbus network and enables two-way communications between the devices on the remote network and the ring network 35. The downstream device 34 acts as a proxy between the remote fieldbus protocol and the ring network protocol, acts as an 10 device for the ring network protocol, or acts as a managed or unmanaged switch if connected to remote Ethernet devices. A downstream device 34 may also provide power to the fieldbus attached to the device.

The illustrated ring topology network 36 is an Ethernet ring network utilizing the Profinet protocol. The Ethernet ring network 36 includes a backplane 38 and terminators 40, 42 on the ends of the backplane that create a loop-back to close the ring. The Ethernet ring network 36 utilizes the Media Redundancy Protocol (MRP) formalized at IEC 62439-2 for media redundancy .

The backplane 38 provides the logical and physical communication layers between the bus couplers 32 and the downstream interconnection devices 34. The backplane 38 acts as a VPN (Virtual Private Network) that handles the systems communications (both synchronous and asynchronous) between the bus couplers 32 and the downstream interconnection devices 34.

The backplane 38 modifies layer 1 of the physical OSI model to allow for the transmission of Ethernet data over PCB traces on the backplane instead of normal Ethernet cable. The backplane protocol may be implemented at application layer 7 of the OSI protocol as SMNP .

The backplane 38 also provides mechanical fixturing of the bus couplers 32 and the downstream interconnection devices 34. The backplane 38 may also carry power to the downstream interconnection devices 34for internal operations of the devices .

Figure 2 illustrates a downstream interconnecting device 32 adapted to connect the ring network 36 with a remote Profibus PA fieldbus network. A Profibus PA fieldbus is a two- wire fieldbus in which power and communications signals are carried over the same wires as set out in IEC 61158-2.

The interconnecting device 32 includes a pair of like linking modules 44a, 44b that plug into a base or base module 46. The pair of linking modules 44 provide redundant power supplies and processing or controller boards for operation of the Profibus fieldbus. The base 46 mounts the interconnecting device 32 to the backplane 38 and interfaces the linking modules 44 to the backplane 38. A power line 47 extends through the base 46 to each processing and supplies power from the Ethernet ring 36 for internal operation of the processing board .

A linking module 44 is housed within a housing 48. The linking module 44 includes a power supply module 50 and a processor or processing board 52. The power supply module 50 provides and conditions the power provided to the Profibus fieldbus. The processing board 52 runs the firmware that implements the gateway between the backplane 38 and the Profibus fieldbus segment attached to the device 32.

An output line 54 from each power supply 50 extends to a terminal output 56 on the block 44. The block 44 also includes a bulk power input terminal 58 for connecting an external bulk power supply. The power input terminal 58 is connected to the bulk power input line 60 of each power supply 50. Each power supply 50 isolates the bulk power and supplies low noise power with current limiting to the terminal output 56. The power supply conditioning circuitry includes an isolated DC/DC switching converter, a foldback function, load sharing, and diagnostics. The foldback function provides current limiting in the case of a short circuit or other fault condition. Diagnostic LEDs (not shown) provide status information regarding the operation of the power supply.

During normal operation the two power supplies 50 share the power load, the load sharing balancing the current load between the two power supplies. Current sharing is accomplished by connecting together the output voltage error amplifier signals of each supply 50. The currents from the error amplifiers sum together and create an error voltage that represents the threshold for the primary currents of the two DC/DC converters. This causes the two power supplies to have the same transformer primary current which results in both converters sourcing equal currents to the applied load. Load sharing provides the advantage of spreading out the heat between the two power supplies, which leads to improved performance and reliability. If one power supply fails, the other power supply will immediately take over and supply the entire current load for the fieldbus segment.

During normal operation one processing board 52 is an active board and the other processing board 52 is a standby board. The two processing boards 52 communicate with one another via a local, internal bus (not shown) . In the event the backup processing board detects the failure of the active processing board, the backup processing board takes over the role of the active processor board.

Each processing board 52 of the device 32 shown in Figure 2 runs a Profinet device stack 58 and a Profibus device stack 60. The Profinet device stack 58 manages communications with the backplane 38 and includes a Profinet client, a TCP/IP stack, and an MRP client.

The Profinet device stack 58 communicates with the backplane 38 through a 3 -port Ethernet switch 62 that ties the MAC of the processing board 52 to the network ring 36. The device stack 58 communicates through one port of the switch 62. The two other ports of the switch 62 connect the processing board 62 with each neighboring device on the ring network 36.

As shown in Figure 2, the processing board 52 of the linking module 42a is considered adjacent an upstream device on the ring network 36 and the processing board 52 of the linking module 42b is considered adjacent a downstream device on the ring network 36. Ethernet line 64 extends from the backplane 38, through the base 46, and into one port of the switch 62 of the board 42a. Ethernet line 66 extends from one port of the switch 62 of the board 42b, through the base 44, and to the backplane 38. The two Ethernet lines 64, 66 connect the device 32 to the neighboring upstream and downstream devices on the ring network 36.

The remaining port of each switch 62 are daisy-chained together by an Ethernet line 68. The two processing boards 62 can be considered as separate, adjacent devices on the ring network 36. Each processing board 62 is connected to the adjacent board 62 by the daisy-chain line 68, and is connected to an adjacent device 32 or bus controller 34 by the Ethernet line 64 or Ethernet line 66. Because only one processing board 62 is active on the network, the switch 62 of the standby processing board acts as a through- switch to transfer communications to and from the active processing board 62.

In embodiments in which there are additional redundant linking modules 44 between the most upstream and downstream linking modules 44a, 44b, the switch 62 of each additional linking module would also be daisy-chained with the switches 62 of the adjacent processing boards.

Figures 3-5 illustrate an alternative switching arrangement between the linking modules 44 that enables a linking module 44 to be removed from the base 46 without causing a break in the network ring 36. This enables a redundant linking module 44 to be removed from the system without disrupting the normal ring topology of the network ring 36.

Each processing board 52 includes a two-position multiplexer or switch 70 that is connected to the port of the Ethernet switch 62 that was otherwise daisy-chained to the switch of the adjacent processing board. One terminal of the muxes 70 is connected by an Ethernet line 68 for daisy- chaining the two processing boards 52 together as previously described .

The other terminal of the mux 70 of the processing board connected to the Ethernet line 64 is connected to a "Y" branch 72 added to the Ethernet line 66. The other terminal of the mux 70 of the processing board connected to the Ethernet line 66 is connected to a "Y" branch 74 added to the Ethernet line 64.

The state of the muxes 70 is controlled by a respective control line 76 connected to each mux 70. The control line 76 extends from the mux 70 to a ground 80 carried on the other processing board. A voltage source 82 obtained through the network ring is connected to each control line 76.

In normal operation the control lines 76 are pulled low and the muxes 70 connect the ports of the Ethernet switches 62 to the Ethernet line 68 as shown in Figure 3. The processing boards 52 are effectively daisy-chained together as was previously described with respect to Figure 2.

Figure 4 illustrates removal of the downstream linking module 44b. The remaining active linking module is connected to the upstream Ethernet line 64. The control line 76 connected to the remaining active linking module 44 is pulled high, connecting the port of the active three-port switch 62 to the Y-branch 72 and, from the Y-branch 72, to the downstream Ethernet line 66. Figure 5 illustrates removal of the upstream linking module 44a. The remaining active linking module is connected to the downstream Ethernet line 66. The control line 76 connected to the remaining active linking module 44 is pulled high, connecting the port of the active three-port switch 62 to the Y-branch 74 and, from the Y-branch 74, to the upstream Ethernet line 64.

Returning to Figure 2, Profibus device stack 60 manages communications with the Profibus fieldbus segment and generates Manchester-encoding and decoding as defined by IEC 61158-2 for data communications to and from the Profibus fieldbus. The Manchester data is injected from the Profibus device stack 60 with a Medium Access Unit 76 and onto the power line by a communications input/output line 78 that extends through the base 46 to inject the communications signal on the power line.

In use, an end of the Profibus segment 24 is connected to the base terminal 56 and a bulk power supply for powering the Profibus segment is connected to the input power terminal 58.

Some fieldbus physical protocols transmit power and communications simultaneously over the bus but do so using separate wires extending along the bus. The base 46 is adapted to connect the power line and the communications input/output line to separate terminals.

Each bus coupler 32 is constructed in a similar manner as the downstream interconnecting device 34 shown in Figures 2-5, with redundant linking modules mounted on a base connected to the backplane 38. A bus coupler 32 can be provided without power supplies if the bus coupler can draw power from the local fieldbus, that is, each linking module can be provided with just a processing board.

A downstream interconnecting device 34 adapted for connecting remote digital and/or analog 10 devices to the local fieldbus will include a base that acts as a gateway between the Ethernet backplane 38 and the 10 devices, and contains the hardware and firmware to implement a Profinet-to- 10 proxy. Digital, analog, and HART 10 devices can plug into a base. Power for the 10 devices can come from the Ethernet ring 36 or can be provided by a separate low-voltage power supply. In possible embodiments the base can include a backplane for connecting 10 devices, the backplane in essence defining an 10 fieldbus interconnecting the remote 10 devices.

A downstream interconnecting device 34 adapted for connecting a remote Ethernet fieldbus may include Ethernet switches that will plug directly into the Ethernet backplane 38.

Furthermore, Ethernet switches attached directly to the backplane 38 will provide the ability of extending the network 36 further downstream to either additional modular based systems such as the device 22 or directly to other devices in the field. An Ethernet switch or module extends the VPN running on the backplane (including the local Profinet, TCP/IP, and MRP communications that are running on the Ethernet backplane. Power Over Ethernet (POE) may also be injected onto downstream Ethernet connections from the backplane 38. The POE is preferably implemented in accordance with appropriate industry or government standards . such as IEEE 802.3af and 802.3at. In addition, intrinsically safe POE options can be made available that can support POE running into hazardous environments, including Zones 2, 1, and 0 in accordance with the European ATEX directive.

While this disclosure includes one or more illustrative embodiments described in detail, it is understood that the one or more embodiments are each capable of modification and that the scope of this disclosure is not limited to the precise details set forth herein but include such modifications that would be obvious to a person of ordinary skill in the relevant art and fall within the purview of the following claims.

Claims

1. A fieldbus network interconnecting device for interconnecting a local fieldbus network and at least one remote fieldbus network, the interconnecting device comprising: a ring topology communications network;

a first gateway device attachable to the ring topology network for communications along the network, the first gateway device capable of two-way communications between the ring topology network and the local fieldbus network when the first gateway device is also connected to the local fieldbus network;

at least one second gateway device attachable to the ring topology network, each second gateway device capable of two- way communication between the ring topology network and a respective one of the remote fieldbus networks when such second gateway device is also connected to the respective one of the remote fieldbus networks; and

the first gateway device and each second gateway device each capable of communicating with the ring topology network utilizing a ring redundancy protocol supporting the ring topology network.

2. The networks interconnecting device of claim 1 wherein the ring topology network comprises a backplane forming at least a portion of the ring topology network, the first gateway device and each second gateway device attachable to the backplane.

3. The networks interconnecting device of claim 1 wherein the ring typology network is adapted to communicate using a first communications protocol and each at least one second gateway device is configured to act as a gateway between the ring topology network and a fieldbus network in which the fieldbus network uses a second communications protocol different from the first communications protocol.

4. The networks interconnecting device of claim 3 wherein the first communications protocol is an Ethernet protocol and the second communications protocol is a fieldbus protocol that enables communications and power to be transferred over the same wires of a wired fieldbus network.

5. The networks interconnecting device of claim 4 wherein the second communications protocol is an Ethernet protocol that is different from the first communications protocol .

6. The networks interconnecting device of claim 4 wherein the second communications protocol is an 10 protocol.

7. The networks interconnecting device of claim 1 wherein each at least one second gateway device comprises a redundant power supply arrangement for powering a remote fieldbus connected to such second gateway device.

8. The networks interconnecting device of claim 7 wherein the redundant power supply arrangement is adapted to share the electrical load between two or more power supplies during normal operations.

9. The networks interconnecting device of claim 1 wherein the first gateway device provides power to the ring topology network.

10. The networks interconnecting device of claim 1 wherein each gateway device comprises a redundant controller arrangement that provides two-way communication between the fieldbus attached to the gateway device and the ring topology network .

11. The networks interconnecting device of any one of the claims 1-10 wherein the ring topology network is a Profinet network.

12. The networks interconnecting device of any one of the claims 1-10 wherein the ring redundancy protocol is the Media Redundancy Protocol .

13. A gateway device for enabling two-way communications between a first non-Ethernet process control communications network and a second Ethernet process control communications network, the gateway device comprising:

a first processor and a second processor, each processor adapted to be a gateway between the first and second networks, the first processor connected to a first communications line, the first communications line being adapted to be connected to a first location on the Ethernet network, the second processor connected to a second communications line, the second communications line being adapted to be connected to a second location on the Ethernet network, and the first and second processors are connected by a third communications line extending from the first processor to the second processor.

14. The gateway device of claim 13 wherein the one processor is connected to the first communications line and to the third communications line by first three-port Ethernet switch, and the second processor is connected to the second communications line and to the third communications line by a second three-port Ethernet switch.

15. The gateway device of claim 14 wherein the third communications line is connected to the first Ethernet switch by a first two-position multiplexer and the third communications line is connected to the second Ethernet switch by a second two-position multiplexer, each multiplexer having a first state connecting the third connection line to the Ethernet switch and a second state disconnecting the third connection line from the Ethernet switch.

16. The gateway device of claim 15 wherein each multiplexer includes a first terminal connected to the third communications line and a second terminal;

the second terminal of the first multiplexer is connected to a fourth communications line extending from the second terminal to the first communications line; the second terminal of the second multiplexer is connected to a fifth communications line extending from the second terminal to the second communications line.

17. The gateway device of claim 16 wherein each control circuit connects the first terminal of the multiplexer connected to the control circuit to the three-way port and disconnects the second terminal of the multiplexer from the three-way port when the multiplexer is in the first state and connects the second terminal of the multiplexer to the three- way port and disconnects the first terminal of the multiplexer from the three-way port when the multiplexer is in the second state .

18. The gateway device of claim 17 wherein each processor is pluggable into a base, the processors connected to the control circuits when plugged into the base, each control circuit responsive to the presence of the processor in the control circuit to place the multiplexer connected to the control circuit in the first state, each control circuit responsive to the removal of the processor from the control circuit to place the multiplexer connected to the control circuit in the second state.

19. The gateway device of claim 18 wherein each processor forms a portion of a linking module pluggable into the base, each linking module including a power supply adapted to power a fieldbus segment attached to the gateway device.

20. The gateway device of claim 12 wherein each processor is a Media Redundancy Protocol client.