System and method for transmitting real-time-critical and non-real-time-critical data in a distributed, industrial automation system

• US 8,064,482 B2
• Filed: 10/01/2008
• Issued: 11/22/2011
• Est. Priority Date: 11/24/2000
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Krause, Karl-Heinz
• Primary Examiner(s): Yao; Kwang B
• Assistant Examiner(s): Duda; Adam
• Application Number:
  US12/243,906
• Publication Number:
  US 20090034524A1
• Time in Patent Office: 1,147 Days
• Field of Search: 395/200, 395/275, 395/325, 364/940.81, 364/942, 364/942.03, 364/942.1, 370/468, 370/493, 370/474, 370/476, 370/352, 370/445, 370/353
• US Class Current: 370/468
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/6454 Random, e.g. Ethernet
• CPC Class Codes: H04L 2012/6462 Movable boundaries in packets or frames

Abstract

A system and a method provides both for a real-time-critical communication and a non-real-time-critical communication in a switched data network consisting of users and switching units, for example a distributed automation system, by means of a cyclic operation. In a so-called transmission cycle (12), there exists for all users and switching units of the switched data network in each case at least one section (13) for transmitting real-time-critical data and at least one section (14) for transmitting non-real-time-critical data, as a result of which the real-time-critical communication is separated from the non-real-time-critical communication. Since all users and switching units are always synchronized to a common time base, the respective sections for transmitting data in each case take place at the same time for all users and switching units, i.e. the real-time-critical communication takes place independently in time from the non-real-time-critical communication and is, therefore, not influenced by the latter.

Claims

1. A control system for a distributed, industrial automation system, comprising:

a plurality of Ethernet switching units in a switched data network operating via a common synchronous time base among the Ethernet switching units, each Ethernet switching unit comprising a processor and an associated memory and being connected to a user device or a plurality of user devices or another Ethernet switching unit in a distributed, industrial automation system,

wherein a communication between the user devices is effected in transmission cycles via data packets forwarded across the switched data network, wherein each transmission cycle is subdivided into a first section for transmission of real-time-critical data over the switched data network and a second section for transmission of non-real-time-critical data over the switched data network,

wherein the Ethernet switching units are configured to have a length of the transmission cycle before a time of data transmission, including a length of the transmission cycle comprising the first section intended for transmission of the real-time critical data and a remaining length of the transmission cycle comprising the second section intended for transmission of the non-real-time-critical data; and

wherein non-real-time-critical data occurring during the first section of the transmission cycle is temporarily stored in the memory and later forwarded across the switched data network during the second section of a current or subsequent transmission cycle.

2. The system of claim 1, wherein the memory is configured to be accessed by the processor and the user device.

3. The system of claim 1, wherein the Ethernet switching units are configured to schedule data transmissions for each output port and are configured to temporarily store data received at an input port and later retrieve the stored data to transmit it during a corresponding section of the transmission cycle.

4. The system of claim 1, wherein the Ethernet switching units each comprise a plurality of output ports.

5. The system of claim 1, wherein the Ethernet switching units are integrated in the plurality of user devices.

6. The system of claim 1, further comprising:

at least one user device without an Ethernet switching unit connected to the switched data network via a direct Ethernet connection, wherein the at least one user device participates in non-real-time communication without disturbing the real-time-critical communication by having its non-real-time communication forwarded across the switched data network during the second section of the current or subsequent transmission cycle by at least one Ethernet switching unit configured to receive data from the at least one user device.

7. The system of claim 1, wherein the user devices comprise engineering drivers operating under real-time control for the distributed, industrial automation system.

8. The system of claim 1, wherein connections between the Ethernet switching units are point-to-point connections.

9. The system of claim 1, wherein scheduling of real-time-critical data transmissions and non-real-time-critical data transmissions occurs in a processor of the Ethernet switching units, the processor being disposed between a memory coupled to the user device which is local to the Ethernet switching unit and a physical data network layer.

10. The system of claim 1, wherein all real-time-critical communications, including data and links, are known before their actual data transmission.

11. The system of claim 1, wherein the Ethernet switching units comprise a physical communication channel configured to convey data in both directions.

12. The system of claim 1, wherein real-time-critical data is immediately forwarded across the switched data network by the processor upon arrival at an Ethernet switching unit since real-time-critical data is planned in advance to coincide with the first section.

13. A control system for a distributed, industrial automation system, comprising:

a plurality of Ethernet switching units in a switched data network operating via a common synchronous time base among the Ethernet switching units, each Ethernet switching unit comprising a processor and an associated memory and being connected to a user device or a plurality of user devices or another Ethernet switching unit, wherein connections between the Ethernet switching units are point-to-point connections and a communication between the user devices is effected in transmission cycles via data packets forwarded across the switched data network, wherein timing of real-time-critical data is planned in advance;

wherein each transmission cycle is subdivided into a first section for transmission of real-time-critical data over the switched data network and a second section for transmission of non-real-time-critical data over the switched data network,

wherein the Ethernet switching units are configured to have a length of the transmission cycle before a time of data transmission, including a length of the transmission cycle comprising the first section intended for transmission of the real-time critical data and a remaining length of the transmission cycle comprising the second section intended for transmission of the non-real-time-critical data,

wherein at least one Ethernet switching unit is configured to receive non-real-time-critical data from an additional user device without an Ethernet switching unit connected to the switched data network via a direct Ethernet connection at an arbitrary time and to schedule communication of the non-real-time-critical data on the switched data network without disturbing transmission of the real-time-critical data.

14. The system of claim 13, wherein all Ethernet switching units in the switched data network operate according to the transmission cycle and the common time base.

15. The system of claim 14, wherein the Ethernet switching units are configured to schedule data transmissions for each output port and are configured to temporarily store data received at an input port and later retrieve the stored data to transmit it during a corresponding section of the transmission cycle.

16. The system of claim 13, wherein real-time-critical data is immediately forwarded across the switched data network by the processor upon arrival at an Ethernet switching unit since real-time-critical data is planned in advance to coincide with the first section.

17. The system of claim 13, wherein non-real-time-critical data occurring during the first section of the transmission cycle is temporarily stored in the memory and later forwarded across the switched data network during the second section of a current or subsequent transmission cycle.