Providing process values in a process system having a real-time requirement

Abstract

In automation-engineering installations, there is a need to exchange process information between different devices. For this, OPC Unified Architecture (OPC UA) from OPC Foundation has become established as a standard protocol. However, rather than transmit requested OPC-UA subscriptions via the conventional OPC-UA session channel, the invention sets up a separate TSN data communication by means of which that subscription information is transmitted.

Claims

1. A method for operating a server device in a system for controlling at least one process, said method comprising: determining respective current process values for at least one process parameter of one of the processes controlled by the system at different transmission times; sending the respective determined current process value of the at least one process parameter to a respective client device using a data network, the server device forming a group including the at least one current process parameter that must be sent to said client device, said server device consolidating said group including said current process value of the at least one process parameter into a respective TSN (Time Sensitive Network) telegram at a respective transmission time using the TSN standard; and sending the TSN telegram into the data network for transmission via the data network to the respective client device which is adapted to read an information group that includes the current process value of the at least one process parameter from the TSN telegram.

2. The method of claim 1, further comprising the server device receiving a TSN request telegram from at least one client device in a configuration phase via a network connection during a OPC-UA (Open Platform Communications Unified Architecture) session in accordance with the OPC-UA standard.

3. The method of claim 1, wherein the request TSN telegram contains information specifying in what form or how often updated information will be provided by the server for the requested process values.

4. The method of claim 1, further comprising sending a keep-alive message from the server device when the current process value of at least one process parameter of the group has not changed in comparison to the last message, at the next transmission time.

5. The method of claim 1, further comprising forming a group for a request, said group including at least one process parameter that must be sent by the server device to at least one client device in accordance with at least one property of the request.

6. The method of claim 5, wherein the property of the request in accordance with which the group must be sent by the server device is the frequency of sending the group or the quality of service used for sending the group.

7. The method of claim 1, further comprising: the server device receiving a request telegram from at least one client device; and the server determining whether the request is a request for an existing group or a new group must be formed.

8. The method of claim 1, further comprising reserving an appropriate path in the data network for each group using the TSN standard.

9. A system to control a process, said system having a data network, said system comprising: at least one server device connected to the data network, said server device using machine code that is fixed in a machine-readable medium, said machine code comprising: a) a routine determining respective current process values for at least one process parameter of one of the processes controlled by the system at different transmission times, b) a routine forming a group including the at least one current process parameter that must be sent to a respective client device, said server device consolidating said group including said current process value of the at least one process parameter into a respective TSN (Time Sensitive Network) telegram at a respective transmission time using the TSN standard, and c) a routine sending the respective TSN telegram to a respective client device using the data network; and at least one client device connected to data network, said client device being adapted to send out a request telegram to the server device, said request telegram indicating process values of at least one process parameter that must be sent to the client device, said client device being adapted to receive a TSN telegram from the server device addressed to the client device via the data network at various transmission times, said TSN telegram having information groups that include the at least one process value, said client device being adapted to read an information group that includes the at least one process value from the TSN telegram.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is described below with reference to the following figures:

(2) FIG. 1 a schematic representation of the information stored on the server with regard to a subscription.

(3) FIG. 2 an exemplary network with a server and a plurality of client devices, and

(4) FIG. 3 a flow chart for an embodiment of the method according to the invention, which can be carried out in the system of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

(5) In the case of the exemplary embodiment described in the following, it has to do with a preferred embodiment of the invention. However, in the case of the exemplary embodiment, the described components of the embodiment each represent individual features of the invention that are independent of each other, which also further develop the invention independently of each other, thereby also being considered an integral component of the invention on an individual basis or in another combination than the one shown. Furthermore, other features of the invention, which have already been described, can also be added to the described embodiment.

(6) A client requests one or a plurality of subscriptions with one or a plurality of elements (monitored items) and characteristics (e.g. publishing rate) from the server.

(7) In FIG. 1, five servers are indicated as an example, which request information as follows:

(8) Client A

(9) Items: z, y Proxy: Redundant
Client B Items: z, x, v
Client C Items: y, w
Client D Items: v, u, s, t Client E
Items: s, t

(10) Two groups are formed from this as follows:

(11) Entity group 1:

(12) Client: A, B, C Items: v, x, y, z Proxy: Redundant
Entity group 2: Client: D, E Items: v, u, s, t

(13) The server itself forms (or supplements) these groups, E1, E2. These groups form the basis for the management of subscriptions in the server. One group consolidates a plurality of process parameters to be monitored v, w, x, y, z (monitored items) from potentially different clients, Client A, Client B, . . . , using the characteristics. Characteristics can, for example, be the publishing rate or the requested quality (guarantee) of the transmission etc.

(14) Thereby, groups are not a 1:1 representation of the subscription request of an individual client, but rather an optimized consolidation/splitting of various subscription requests of various clients.

(15) When forming groups it can be determined that no new groups are required for the new subscription. In this case, the client will only be informed which groups are relevant for it. The server also informs the network of the new communication request (TSN path extension and reservation).

(16) New groups are created in this step, so the server also initiates a path and a bandwidth reservation for this new entity group. The client is also addressed by the path. The client is informed of this (the new group). In FIG. 2, such a network is illustrated, which consists of a server device and five client devices, Client A etc. Data paths E1-Data and E2-Data are each reserved for both groups, E1 and E2.

(17) The advantage of the UDP subscription is fully achieved by using TSN according to the invention in order to form an OPC-UA subscription (1:n communication), but without having the UDP disadvantages mentioned in the above.

(18) Furthermore, OPC-UA acquires new characteristics by means of TSN, that are not possible in OPC-UA nor can they be added via the UDP mechanism:

(19) Now, for example, it becomes possible to use media redundancy in OPC-UA without further complexity, which results in a considerable increase in availability.

(20) Now, determinism (guaranteed latency/real-time) and loss-free transmission also exists for OPC-UA by means of the quality of service of TSN.

(21) In particular, this is considered an advantage since OPC-UA does so explicitly without determinism due to the event-based communication, thereby ruling out the use in certain real-time environments.

(22) By using the claimed method, it is possible for OPC-UA to be used in fields where use has been ruled out up until this point.

(23) Due to the use of TSN mechanisms to form OPC-UA subscriptions, additional mechanisms to protect against attacks on OPC-UA communication from TSN are available.

(24) Calculated paths and reservation ensures that the flooding of the network cannot disturb productive communication. This does not require any other management effort in the OPC-UA client or server.

(25) In FIG. 3, communication between client and server is still illustrated as an example; this receives the requested process values, Send1, Send2 . . . , after the subscription of the client at the server.