EP1430458A2

EP1430458A2 - Method for monitoring an automation unit

Info

Publication number: EP1430458A2
Application number: EP02774423A
Authority: EP
Inventors: Peter Becker
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2001-09-26
Filing date: 2002-09-26
Publication date: 2004-06-23
Anticipated expiration: 2022-09-26
Also published as: DE10147490A1; WO2003027984A3; US20050027372A1; ES2248612T3; CN1561510A; US6895369B2; DE10294374D2; EP1430458B1; CN100407240C; WO2003027984A2; DE50203983D1; ATE302452T1

Abstract

A method for monitoring an automation unit with a controller and several terminals is disclosed, whereby the terminal can adopt at least two status values. Measures are provided with which some of the previous status changes can be subsequently reconstructed.

Description

description

Process for monitoring an automation system

The invention relates to a method for monitoring an automation system with a control device and several terminals. In particular, the invention relates to the reliable detection of several signal changes in a message telegram between the terminal and the control device in an automation system according to the preamble of claim 1.

In automation systems with several end devices (also called automation devices) and control devices (also called operator control and monitoring stations or "operator station"), events are mapped to binary signals.

Signal changes (level-triggered changes) are recorded by the end devices and reported to one or more control devices by means of a message telegram, where the reported signal level is displayed and processed.

In the prior art, a second message, for example with the content that the signal has changed again in the meantime, can only be sent again when the control device has confirmed the receipt of the first message to the terminal. This confirmation is made with an acknowledgment message.

If a single signal is reported in a message telegram, the last two signal changes are recognized in the prior art. The general conditions for this are: a) Additional information "overflow" is provided in the message telegram, which indicates that one or more signal changes could not be reported; b) a message was received with the same signal state as the signal last reported and stored in the control unit. In order to increase the performance of the message protocol and to use system resources more effectively, message telegrams are used that contain more than one signal, namely eight signals, for example. The additional information in the form of the "overflow flag" in the message telegram and the fact that a message telegram was received represents a one-to-many relationship for several signals. An assignment of the additional information in the "overflow flag" and the event "reception" a message telegram "for a single one of the several signals is no longer possible. This makes it unusable for general signal tracking. The information available in the message telegram is rather reduced to the respective signal state; an interim change from the original to a second state and back is not recognized.

The object of the present invention is to provide a method by means of which at least some of the previous changes of state can also be subsequently reconstructed.

This object is achieved by a method according to claim 1. Preferred embodiments of the invention are the subject of the dependent claims.

According to the invention, the message telegram is expanded in order to inform the control unit, if necessary, that a further transition has taken place beyond the transitions readable from the message telegram. For this, one or two further binary information items are provided per signal. If the signaling telegram also transmits the current state of the terminal, it can be concluded from the comparison of the previous with the current state of the terminal that further transitions or a plausibility check of the information transmitted by the signaling telegram can be carried out. The method according to the invention for monitoring an automation system, which comprises at least one terminal device that can assume at least two status values and that outputs a message telegram that depends on the at least two status values, and a control device that reads the message message from the at least one terminal device, wherein the at least one terminal only outputs a further message telegram after it has received an acknowledgment signal from the control device, is characterized in that the message telegram has at least one first transition component which indicates a transition from a first state value to a second state value of the at least two state values, and contains at least one second transition component, which indicates a transition from the second state value to the first state value of the at least two state values.

The message telegram preferably has at least one status component that indicates a current one of the at least two status values of the terminal, the control device compares the current status value of the terminal with a previous status value of the same terminal and is dependent on the comparison result and the first and / or second transition component, state transitions of the respective terminal are determined before the current state value is reached.

In a further preferred embodiment of the invention, at least one associated value information component is provided for associated value information in the message telegram, which component creates an association of at least one of the transition components and the associated value information.

All components of the at least one message telegram are preferably represented in binary form.

One advantage of the invention is that the control device can be used on the basis of the received signal state S1 and the event Information EOl and ElO can simulate the signal curve of the last two signal changes.

Further features and advantages of the invention will become apparent from the following description of a preferred exemplary embodiment, in which reference is made to the accompanying drawings.

FIG. 1 shows the sequence of changes in state and the associated representation during a state transition according to the prior art.

FIG. 2 shows the sequence of state changes and the associated representation in the case of several state transitions according to the prior art.

FIG. 3 shows the sequence of changes in state and the associated representation in the case of a plurality of message telegrams and a number of state transitions according to the prior art.

FIG. 4 shows the sequence of changes in state and the associated representation in the case of a plurality of message telegrams and a plurality of state transitions in accordance with the invention.

In Figure 1, an automation system with two terminals 1 and 2 and a control device 3 is shown. The control unit comprises an input keyboard 4 and a screen for displaying signals and status information of the terminals 1, 2 connected to it and, depending on the scope of the automation system, further terminals, not shown.

Each of the terminals 1 and 2, which generally perform special tasks in the automation system, can assume at least two different status values. These status values are communicated to control unit 3 as status information or as a notification of a transition between status values. divided, the communication between terminal 1 or 2 and control device 3 is indicated in the figures as a double arrow. The control unit 3 reads in the different, asynchronous messages from the individual terminals, so that the personnel for monitoring the system have an overview of the overall state of the system and can intervene in a regulating manner via the control unit 3, if necessary. (Here and in the following "reading" means the recognition, recording and processing of messages from the end devices in the control device, without these messages first having to be called up at the respective end device, which is also possible, however.)

The control unit should always display the current state of the terminal - with a time delay - and also at least the last transition cycle of the terminal ("0" -> "1"; "1" -> "0" or "1" -> "0"; "0" -> "1"). In certain applications, the second aspect is of particular importance. In the case of status messages (so-called "events"), it is important to determine whether an event has occurred or not. B. whether a flap in the system was opened and closed again. How often this happens is of minor importance and, if necessary, is determined in the end device and is then available as additional information.

The right part of FIG. 1 shows the sequence of several changes in the state of the terminal 1, the content of messages exchanged between the terminal 1 and the control unit 3 and the associated representation in the control unit 3 according to the prior art.

At a point in time t0, the terminal is in a logic state which is denoted by “0”. This status value can, for example, when the

Automation system is present or it may have been reached at a later time. In the first case it is Control device 3, the status value of the terminal 1 is not immediately known, and the original status value is only recognized by notifying the control device 3 of a change in the status of the terminal 1.

At a time t1, the terminal 1 changes from a logic status value "0" to a logic status value "1". This transition triggers the output of a message telegram by the terminal 1. The message telegram u contains a state component S1, which is an identical image of the state value of the terminal 1. (For the sake of simplicity, a system is assumed here in which a signal can only assume two state values, but the invention is not restricted to this and the state component S1 can generally assume several state values.) The message telegram is read in by the control unit 3. The reading takes place over a certain period of time; it is indicated by an oblique arrow from a lower to an upper level in FIG. 1. In addition to the arrow, the content of the message telegram is specified, which in this case only consists of the state component S1, the content of which is "1", ie. H. is the new status value that the terminal 3 has now assumed. Reading is ended at a time after tl.

When the reading of the message telegram by the control device 3 has ended, a signal D1 in the control device 3, which corresponds to a representation of the status value S1 of the terminal 1, is set from a logic status value "0" to a logic status value "1". (For the sake of simplicity, it is assumed here that a state value transition of the terminal in one direction corresponds to a transition of the signal Dl in the same direction. However, this is not a prerequisite for the implementation of the invention and it is clear to the person skilled in the art that the relationship between state S1 and representation - Dl signal can also be selected complementary.) After the complete transmission of the message telegram from the terminal 1 to the control unit 3, further processing steps follow in the control unit 3. The duration of the processing steps is indicated by the horizontal arrow at the upper level. Only after completion of the processing steps does the control unit 3 send an acknowledgment signal to the sender terminal 1, with which it notifies the terminal 1 that the message telegram from the terminal 1 has been successfully read in by the control unit 3. The transmission of the acknowledgment signal also has a certain period of time, which is shown by an oblique arrow Q from the upper level to the lower level. The subsequent idle state of communication between terminal 1 and control unit 3 is indicated by a horizontal arrow at the lower level. During this time, the terminal 1 processes the

Notification by the control unit 3. Only then can the terminal 1 send a message to the control unit 3 that a further transition has taken place. In the example shown, such a transition took place at time t2, shortly after the first message was sent from the terminal 1 to the control unit 3. During the transition at time t2, the communication between the terminal 1 and the control unit 3 and the processing took place in the Terminal 1 or in the control unit 3 instead. The second state value transition from the logical "1" to the logical "0" was therefore temporarily stored by the terminal 1 and is only now being sent to the control unit 3. The display signal Dl is set to "0", and in this case the control unit 3 does not miss a transition.

FIG. 2 shows an expanded message telegram which enables communication between the terminal 1 and the control unit 3 at a higher rate of changes in the state value of the terminal 1. If signals change very quickly, there can be a very high reporting load. This places a load on the automation system and considerably limits the system's ability to communicate. To prevent this, a method known in the art as "acknowledgment-triggered reporting" (QTM) is introduced, with which messages are interactively influenced. The terminal only reports a message if this signal has been enabled by the control device using a telegram. If a signal is activated in the terminal, the terminal reports a signal change and deletes the activation in the terminal. Further signal changes can no longer be reported due to the deleted activation. If a signal change is lost, this signal can no longer be activated in order to deactivate this self-blocking ("deadlock"), it is imperative that at least the last two signal changes are recognized.

For this purpose, in the method according to FIG. 2, a further component is included in the message telegram, which is designated by OV ("overflow"). In addition to the transitions of the terminal 1 shown in FIG. 1 from "0" to "1" at t1 and from "1" to "0" at t2, there is a further transition from "0" to "1" at t3. The transition from "1" to "0" at t2 cannot be reported immediately by the terminal 1 to the control unit 3 for the reasons mentioned above and would therefore be lost, since at the time when the terminal 1 sent another message to the Control unit 3 can set, its state value - again - is "1". The state value "1" of the

Terminal 1 thus corresponds to the last reported one, and control unit 3 would not recognize a - already completed - state value transition of terminal 1. However, in order to document the transition that has already been completed, the component OV is set to "1" in the next message telegram, which indicates to the control unit 3 that, in addition to the notified transitions, a "hidden" transition has also taken place. Upon receipt of the second message telegram, which notifies the transition from "1" to "0" of the terminal 1, the display signal is therefore set from "1" to "0". However, since the component OV of the message telegram is also set to "1", the display signal D1 is immediately turned on again Set "1" to account for the "hidden" transition. The resulting display signal D1 is shown in FIG. 2 at the top right.

As shown in FIG. 3, this information is not sufficient if the terminal 1 can assume several independent states and therefore more than one state component must be reported to the control unit 3. FIG. 3 shows an example with a state component S1 and a state component S2 of the message telegram.

In the example in FIG. 3, the same sequence of state value transitions of the state component S1 as in FIG. 2 takes place. H. a first state value transition from "0" to "1" at t1, a second state value transition from "1" to "0" at t2 and a third state value transition from "0" to "1" at t4. In addition, a state value transition of a second state component S2 takes place from "0" to "1" at t3 between t2 and t4. The first message telegram m, which is sent from the terminal 1 to the control unit 3 at tl, therefore contains as

Values for components S1 and S2 "1" or "0". The second message telegram, which is sent from the terminal 1 to the control unit 3 after t4, contains "1" and "1" as values for the components S1 and S2, since at this point in time both S1 and S2 have the value "1" to have. The "hidden" transition from S1 at t2 and t4 is thus lost to the system. This would not change even with an additional component OV of the message telegram, since the system could no longer clearly assign this component OV to one of the status values S1 and S2.

FIG. 4 shows an embodiment for the reliable detection of state value transitions in the case of several possible states of the terminal in QTM processes by expanding the message telegram. Under the condition that the control unit has saved the signaling state, further binary information is in principle necessary for each signal signaled. loading is the control unit not in the signaling state or is this information difficult to determine, e.g. B. in the start-up situation of the control unit, in addition to the respective status component, at least two further binary information items are required for each status component. In other words, the message telegram contains at least a first transition component EOl, which indicates a transition from a first state value to a second state value, and a second transition component ElO, which indicates a transition from the second state value to the first state value.

In FIG. 4, the additional binary information EOl (status value changes from "0" to "1") and ElO (status value changes from "1" to "0") are assigned to each signal. If a state value transition takes place, this is done in the corresponding

Event bit EOl or ElO recorded. (The components Sl, EOl, ElO, S2, ... are listed at the bottom right of the figure.) After sending the message after the time tl, this event information is deleted. The subsequent events at t2 and thereafter are collected and reported to the control unit when the acknowledgment signal Q arrives. The control unit can emulate the signal curve of the last two signal changes on the basis of the received signal state S1 and the event information EOL and ElO.

If further state value transitions still take place after t4 without a message being able to be sent, the event information EOl and ElO remain unchanged (the events EOl and ElO have taken place); only the state component S1 assumes the current signal state.

In FIG. 4, the components S1, EOL and ElO of the first state are therefore all at "0" at the time t0, as are the components S2, EOL and ElO of the second state of the terminal 1. At the time t1, the state value of S1 changes from "0" to "1", so that Sl and EOl each take the value "1", all other variables keep the value "0" at. Immediately after the transition, the value of EOl is reset to "0" because the transition has already been reported with the last message telegram, so that components S1, EOl and ElO have the value "1", "0" and "0" accept.

At time t2, the transition from S1 from "1" to "0" takes place. The values of Sl, EOl and ElO are therefore "0", "0" and "1". Since this transition cannot be reported immediately by the terminal 1 to the control unit 3, these values are maintained until the time t4. At t4 there is a further transition from S1 from "0" to "1". However, the previous transition from Sl could still not be reported, so the value of Sl, EOl and ElO is now "1", "1" and "1". These values remain until the next message telegram, which is sent to the control unit at t5 in the example shown. The values in the message telegram at t5 indicate to the control unit 3 that the current status value Sl is "1" and that two transitions have taken place since the last message telegram. The display signal D1 for the first state of the terminal 1, as shown in FIG. 4 at the top right, can (qualitatively) reconstruct the course of the transitions, namely through the transitions "0" to "1", "1" to "0 "and" 0 "to" 1 ". This corresponds to the transitions from S1. At t5, the transition components EOl and ElO to Sl are reset to "0".

In the meantime, a transition from S2 from "0" to "1" has also taken place at t3. This sets S2 to "1" and EOl to "1". These values remain until they are communicated to the control unit in a message telegram. This takes place at time t5. Only then are the transition components EOl and ElO to S2 reset to "0".

In addition to the transitions, FIG. 4 shows the values from Sl, S2, EOl to Sl, ElO to Sl, EOl to S2 and E10 to S2 together with the respective values of the other components. The system according to the invention can be expanded if the status component S1 or S2 of the message telegram indicates a current status value of the terminal 1 and the control unit 3 compares the current status value of the terminal 1 with a previous status value of the same terminal 1. Depending on the comparison result and the respective transition component EOl or ElO, state value transitions of the respective terminal 1 or 2 can be determined before the current state value is reached.

In the case of some message telegrams according to the prior art, accompanying information is provided which communicates further information to the control device. For example, the accompanying information can contain a time that tells the control unit when the state change occurs at one

Terminal was detected. In a preferred embodiment of the invention, at least one associated value information component is provided in the message telegram for such associated value information, which ensures the assignment of the corresponding transition components and the associated associated value information. For example, the associated value information component for Sn is set to "1" if the time specification in the associated value information relates to a state transition of Sn. If other state transitions are also recognized in the terminal at the same time, further associated value information components are correspondingly set to "1". If the transition from Sn is the only state transition that was recognized at the time and only time information is output from the terminal to the control unit, only one associated value information component is set to "1", all others remain at "0". Modifications to the expansion of the message telegram by means of associated value information components are obvious to the person skilled in the art and will not be explained further.

The invention is not limited to the examples above. It was assumed that all components S1, S2, EOl and ElO of the message telegram are shown in binary form. However, this is not absolutely necessary, but some or all of the components can also be available as analog values.

Claims

claims

1. A method for monitoring an automation system, which comprises: at least one terminal (1, 2) that can assume at least two status values and that outputs a message telegram that depends on the at least two status values, and a control device (3) that the message telegram Reads in from the at least one terminal (1, 2), the at least one terminal (1, 2) only issuing a further message telegram after it has received an acknowledgment signal (Q) from the control device (3), characterized in that the message telegram at least one first transition component (EOl), which indicates a transition from a first state value to a second state value of the at least two state values, and at least one second transition component (ElO), which indicates a transition from the second state value to the first state value of the at least two state values - shows, contains.

2. The method according to claim 1, wherein the message telegram has at least one status component (S1, S2), characterized in that the at least one status component (S1, S2) of the message telegram indicates a current one of the at least two status values of the terminal (1, 2) , the control unit (3) compares the current state value of the terminal (1, 2) with a previous state value of the same terminal (1, 2) and, depending on the comparison result and the first and / or second transition component (EOl, ElO), state transitions of the respective end devices (1, 2) are determined before the current state value is reached.

3. The method as claimed in one of the preceding claims, in which the message telegram has associated value information, characterized in that the message telegram has at least one associated value information component which establishes an assignment of at least one of the transition components and the associated value information.

4. The method according to any one of the preceding claims, characterized in that all components (Sl, S2, EOl, ElO) of the at least one message telegram are shown in binary form.