DE4134811A1 - Actuator control method w.r.t. fixed commands - has several function elements assigned to various signals, and other function elements to define operational steps - Google Patents

Abstract

The control method assigns differing function elements (6,8,10,14,19) to the various signals to be outputted by associated devices and to their respective input signals. These function elements are controlled by further elements which define a fixed series of control steps. By carrying out these control steps data is exchanged by the function elements. The control steps are divided into three groups, bit-commands which operate on boolean variables, block-commands which operate on block building blocks, and loading commands to enter data into memory. USE/ADVANTAGE - E.g. for turbines. Consistent and reliable control, easy to determine faults.

Description

The invention relates to a method for sequencing of various actuators (actuators) according to specified commands to be carried out.

Sequential control systems have long been used to control industrial Processes used. In the past, industrial controls were big Part of standardized hardware components with a Functional range per component composed, like him today relatively simple software elementary building blocks such as AND, OR, counters, Memory etc. of the programmable programmable controllers. Extensive control tasks required voluminous design Controls that are difficult for the operations and maintenance personnel manageable and therefore difficult to look after.

Because in very many processes at least some shares never parallel but run sequentially (eg start turbine, turbine operation, Departing turbine), offered the construction of controls to the sequential order principle. This was z. B. in case of failure makes it relatively easy to recognize by a first rough selection, in which of the possible operating states the plant was located, d. H. it could be targeted in one particular part of the overall system possibly errors are searched and the rest of the whole system needed not included.  

The division was made in cycles or in steps. Depending on the technologically possible fineness of gradation in such steps could thus the troubleshooting on a smaller portion of the overall system be concentrated.

The flow control measures also provide virtually one for the Diagnosis of the control is a suitable process description for each single step indicates what feedback is expected from the process after a certain command is given to the process. When additional process description is known to the controller, in which Time the feedback must come (monitoring time). After expiration This monitoring time is a disturbance of the process process, if until then the expected process result is not reached. The disorder is then located on the step in which the controller "Hangs", and their cause is in the missing step-on conditions to search.

Later, programmable logic controllers for the Implementation of sequential control systems used. When using programmable logic controllers have created new problems due to the principle slow (sequential) operation of this programmable units over conventional technology, in the case of each module a completely independent active at any time Processing performance. These could be defused Problems in that the control programs were built so that only ever the currently current portion of the overall program was passed through what is particularly well supported by sequential control. Another Defusing the time problem is by modern techniques, such. B. the Multiprocessor technology, achievable.

The advantages of an Alaufsteuerung are
- Distribution of the automation task into the task components relevant at any time
- Step-by-step commissioning options
- good basis for diagnostic procedures
- shorter program run times, ie performance increase
- meaningful, because technology-oriented, program structuring
- technology-oriented program control
- fast and safe localization of the cause of accidents.

Efforts are underway for sequencers to users unified tools for creating programs available to you put. The following are some for the understanding of Sequential control important terms explained in more detail.

The flow control practically represents state control comparable to the principle of Petri nets. To move from a state in To get another, transitions are needed.

States are referred to in the flow control as "steps" that (State) transitions are referred to as "transitions". The Description of the relation between steps and transitions by means of "active compounds".

Step and subsequent transition are considered as a unit. The Linking several steps and transitions results in a structure which is referred to as a chain part. The effect of the flow control on the process is followed by commands with optionally downstream Command recipients defined while the transitions the Describe input influences. As long as a step is processed, the commands assigned to it are executed. At the same time, the Step assigned transition then checked whether the Stepping conditions for the following step are met.

The invention is based on the problem, one for a method of initially described genus for a variety of processes appropriate, consistent, complete and workable supply of Provide functional elements for the flow control to always carry out the configuration according to a uniform scheme can. These tasks are performed with those currently in place or in Working guidelines are not fully met.

The problem is inventively achieved in that the implementation the method according to three types of functional elements the first of which is based on the sequence of steps second to the transitions associated with each step and the third refer to the instructions to be executed in steps corresponding to the respective step by an indication of another functional part  are assigned in which the respective command with further device and / or plant-specific conditions before outputting a signal one or more process components can be linked.

Due to the division described above, it is possible that the device- and / or plant-specific command receiver for itself, Specify in particular in the form of software blocks, by the Notes in the instructions associated with these steps are controlled by them become. The steps with the associated commands can also individually, d. H. without detailed consideration of the device or plant-specific conditions. This is one great flexibility in terms of type and number of steps and their Assignment to more or less extensive software blocks possible. Subsequent changes to the control process can be relatively easy in the flow control program will be inserted. Leave the software blocks to adapt to the particular circumstances of the process control element. Also in this case, a subsequent change in a simple manner possible.

In a preferred embodiment, exactly four types of Structural elements for connecting steps within a framework Sequence control provided, of which a kind to the sequence of Steps, the second type on steps with alternative branching, the third kind on steps with parallel branching and the fourth kind on Refer to steps with branching in a loop. The Structural elements determine the connection of steps and enable the structure of flow control structures. With the above Structural elements described can be that of sequential control actions to be carried out in conjunction with the orders and the possibly disconnect downstream command receivers. At the sequence the transitions assigned to the respective step are processed, in case of a flawless processing on the next step is passed. In the alternative branching are the one Processed step associated transitions, of which at least two must exist and the different branches are assigned. The branch whose transition conditions are met first becomes then go through. If several transitions at the same time are fulfilled, the procedure is according to a defined priority rule.  

Parallel branching involves the steps of two or more Go through chain branches in parallel. This chain branches is a Associated with a merge transition, which is then processed when the last steps of all assigned parallel branches are active.

This means that the faster passing chain branches so long wait until the slowest chain branch completes its last step. With the loop will be on one in the chain further forward Step over. There is a strong similarity to that Alternative branch, but with one branch on one further forward lying step is returned. Each of the mentioned Substructures should be separated and individually numberable. This is possible by providing an "offset" at the initial term of each substructure Specification is projectable, which is practically the beginning of a counting sequence represents.

Transitions, especially in the form of transition blocks, give the Conditions by which a state transition of one or more Steps takes place. Transition blocks break out Function blocks together. The transition blocks can be separated from the chain structure and then the appropriate steps be assigned. This is another advantage through which the Flexibility in setting up the scheduling program and at subsequent changes is facilitated. The transition blocks process input signals only combinatorial.

In a preferred embodiment, the respective Assigned commands a format with at least two fields of which each of the first field refers to the marking of the Behavior of a command size and the second field in the name of a Obtain command size associated with a command receiver the possibly conditional effects on the process are definable. Commands are generally the link between one defining the procedure and one in the context of the expiration in the Process acting part.  

Commands have their main meaning in the flow control as Connection between the sequence controlling chain part and the Command receivers. They practically transfer orders to the Command receiver, d. H. to variables, block modules, etc. Please note is that a command can only be edited as long as that with him connected step is active (and possibly one more time if he becomes inactive).

Another field in the format of a command is expediently for Feedback is provided, based on the command size.

The identification of the first field relates in particular to the Behavior of the command size and includes the properties stored, delayed, time-limited or pulsed.

Preferably, exactly five mutually different types of commands provided, depending on bit commands, block commands, load commands, Get image control commands and action commands.

The bit instructions act on Boolean variables, which are used as command variables are declared and contain labels. The block commands work on actuators in the process and are processed by block building blocks, which are described in more detail below. The block modules act on the actuators taking into account device or process-specific variables. Block commands must be with the Labels are provided, with feedback also given can be.

A block command, like the other commands, is handled when the associated step is set. If the associated step is deleted, either the state-influenced command size must be in the state return that she had before putting the stride, or hers Maintain state. In the second case, the command is stored. A Effect of this kind only returns to its original state back when through one of the following steps with a corresponding command is actively reset.  

With the load command any data types can be "downloaded". Markings must be indicated.

Image control commands control the editing of on a monitor or Recording means displayable images with programs.

The action commands call networks. The network will be executed as long as the command is being edited be called by several action commands.

The commands activate command receivers that carry the commands execute a program part independently of the sequencer form. You can activate commands from several steps become a separate processing mechanism. in the In the simplest case, a command receiver is a Boolean variable that is set and reset. In the more complex case is the Command Recipient is a block module that demonstrates the behavior of a Plant component controls or regulates, receives orders and confirms emits.

Block modules preferably process input quantities sequentially and / or combinatorial in conjunction with the respective instruction issued by various points of the flow structures can be output. Block blocks are thus used for the closed representation of technological functions triggered by commands and usually act on an actuator. With block modules becomes a Decoupling between chain and command output achieved. The effect that is to be achieved in the chain regardless of the respective Properties of the actuator can be specified. The adaptation to the respective Actuator happens exclusively in block block.

Actions are networks and are only edited if at least one Action command calls the respective network. The main objective of actions is to realize subchains. Actions are by a name defined by action commands and include a Summary of logical building blocks. Only if an action command is processed, actions are processed. All data, which are valid in the context of the calling instruction, in the respective one Network can be used.  

Action commands are preferably used in conjunction with chains. Actions can be used to insert subchains into existing chains. Functions and procedures that should only occur if a certain Chain state exists are configured using actions.

Command receivers can be divided into those that are in another Processing context as the chain itself are (block modules and Networks), and those that work depending on the chain position become (actions).

For controlling an actuator belonging links, the equally be needed in several ways (eg is in a executed plant a particular amplifier or engine type multiple times used) are configured as a block block (ie as a type). For special actuators that in an executed plant only once occur, the belonging to the control links as Networks configured.

The functional elements of the flow control and their connections are to facilitate program creation and monitoring during operation certain symbols are assigned graphically on a screen can be represented. For example, the symbol for a Step a square or rectangle. The active compounds between the Steps can be represented by dashes. The assignment of Transitions to steps are indicated by dashes, by the Step symbols starting, marked.

Transition blocks are represented by a circuit diagram with building blocks of combinatorial logic and their active compounds in a rectangular Frame shown, from which a dash to the associated bar runs in the chain. For the representation of the commands are rectangles determined, divided according to the format and with each other are arranged. Command receivers (networks) are activated by a Schematic with logical components and their active connections as well as represented with the processes and command sizes as inputs. The the same representation can be used for the contents of block modules In addition, in the block modules themselves hints in Rectangles on the steps that issue the commands are.  

With extensive sequencers, the chains, steps and Transitions into several, individually representable parts of description divided up. To facilitate the creation of scheduling programs will name the steps and transitions used in a chain assigned, with reference to the position of the steps and Transitions are stored in the flowchart of the chain. The names are for each step and each transition identifiers, at the same time as a reference for the partial images of the individual steps with associated Commands and the fields are used with transition blocks. The identifiers are also used for technological numbering used, d. H. with the identifiers can during the Process steps are selected and monitored. The Name structuring can be done automatically when creating the workflow structure or by hand. Transition blocks are z. B. as Instruction list, ladder diagram or function diagram configured. The Steps and transition blocks together with their names or Labels displayed on a monitor. Steps and Transition blocks are displayed with graphic symbols, especially with rectangles and crossbeams.

Sequential control systems often have different operating modes. The behavior of a flow control therefore depends not only on the steps, commands and transitions, but also on the operating mode requirements in the respective application. It is in most cases a circuit, for. B. a user-specific project-specific function block for the preprocessing of the operating modes (input) signals, the automatic, hand, start, stop, etc. created. The resulting signals are linked to the chain device and in part to the command receivers ( FIG. 8).

Depending on their status, the mode input signals of a chain block cause different effects on the sequence behavior of the chain, ie on the functionality of the chain block. The mode input signals ( FIG. 8 K ON) of a chain module and the output signals (K OUT) are therefore advantageously combined to form a particular data type. These composite data types consist of individual signals, the so-called original chain signals.

These are signals that have specific selective effects on the inner Have runtime behavior of the chain. The chain input signals can be in Release signals and Schrittanwahlsignale be divided.

Depending on the industry and task, z. As the mode input signals, such as manual, automatic or jog mode, very different effects on the chain sequence behavior. In some applications, z. B. the manual operation a similar behavior as the set-up, ie the actuators can be moved with minimal safety interlocks by hand, in other applications, even the chain position must be tracked in manual mode. This shows that for signals such as start, automatic, manual, etc., therefore, no fixed rules for a general sequence control are processed. From these operating mode input signals, which come, for example, from the control console, the original chain signals must be derived in a preprocessing of the operating mode module ( FIG. 8).

One of a series of steps, transitions and commands Chain block behaves outwardly like a normal one Function block with memory function, d. H. its output variables depend on both its inputs and its respective Condition mainly due to the active steps of the chain part is marked.

To predict a predictable behavior of a chain also complex receive, it is necessary to the chain building block after one below still more detailed specification to edit.

The duration of the steps can be monitored.

Structured sequencers have the following advantages:
- Clean and easy-to-read program structures are created, similar to the use of structured programming languages or the use of tools for the structured implementation draft.

To clear structures leads above all the renouncement of uncontrollable jumps:
- alternative branches end in principle with an alternative merger,
- a trailing jump is only allowed in connection with the loop construct,
- The processing sequence of each step is much easier to survey than when using free jumps.

It is a syntax-driven editor used, so that only syntactically correct sequences can be entered. The following rules are B. automatically monitored:
a sequencer can have at most one initial step and at most one final step,
- parallel branches must synchronize themselves again at a parallel merge,
- Jumps out of parallel branches or into parallel branches are not permitted and also not possible when using a structured grammar.

The invention will be described below with reference to a drawing illustrated embodiment, from which give more details, features and benefits.

It shows

Fig. 1 is a flow chart of a gas burner control;

Fig. 2 is an unstructured step chain for the sequence control of the gem in the flow chart. Fig. 1 illustrated gas burner operation;

Fig. 3 shows a structured sequencer for the flow control of the gas burner operation according to. Fig. 1;

Fig. 4a, b, c another structured sequencer for the sequence control of the gas burner control gem. Fig. 1 with part structures;

Figure 5 is a functional block diagram of a block.

Figure 6 is a simplified functional block diagram of a block.

Fig. 7a, b functional diagrams for valves;

Fig. 8 is a rough structure of a process control;

Fig. 9 is a schematic diagram of the interaction of a chain device with chain input and output signals;

Fig. 10 is an illustration of various parts of the description.

A flow control for a gas burner known per se in the problem area from the field of chemical process engineering has a first ground state purging, which is denoted by 1 in FIG. 1 and to which a specific time is assigned. The ground state 1 is followed by a second ground state ignition, at which reference numeral 2 is designated in FIG. 1 and is initiated after the expiration of a purge time, which is monitored. The basic state 2 is assigned a safety time. After ignition, the sequence control goes into a third basic state operation, which is designated in Fig. 1 with 3 . The operation is followed by the ground state Aus indicated at 4 in FIG. 1, when the regular switch-off conditions are present.

If there are pre-conditions for purging after switching off, the system switches to state 1 . Another, in Fig. 1 denoted by 5 state fault-off is reached when the purge time has expired and an interference off condition or the safety time after ignition without ignition has expired or the flame is not burning and repetitions have expired in vain attempt at ignition be carried out first. If it is switched off due to a fault, the operation 3 is followed by the state 5 , which causes the switch-off and changes to state 4 only after unlocking. During rinsing unburned gas residues are flushed out of the combustion chamber with air. During ignition, gas flowing out of a nozzle is ignited. The allowable transitions from one state to another are in Fig. 1 with unspecified arrows Darge presents, with each transition whose requirements are specified.

For the method illustrated in the flow chart in Fig. 1, a sequence of flow control is established which is in the form of a chain of steps as shown in Fig. 2. It is a restructured step sequence. The step sequence begins with the initial step 6 , which is assigned to the ground state Aus. The initial step 6 indicates the initial state of the block comprising the step sequence.

The initial step is graphically represented by a rectangle with double border on a monitor. Under the initial step 6 , a transition 7 is shown, which are the preconditions that are processed by a transition block, which is not shown in detail. If the transition conditions are present, the step 8 is skipped, the state Rinse, with a subsequent alternative branching. If the transition designated by 9 in FIG. 2 is fulfilled, which relates to the proper execution of the purging, then step 10 is passed, which relates to the ignition. The presence of disturbance conditions results from a transition 11 , in the fulfillment of which a transition is made to a step 12 which corresponds to the disturbance off state. Step 10 again has the property of alternative branching.

A transition 13 which checks the end of a time set for the ignition allows, if the test result is positive, the transition to a step 14 , which is a blank step. If the transition 15 of the alternative branching indicates that the interference conditions are fulfilled, step 12 follows.

From Fig. 1 it can be seen that the conditions "time expired" and "flame does not burn" are sequentially testable conditions. To make this possible, the empty step 14 is provided. The empty step 14 includes an alternative branch with three transitions. The one transition 16 checks whether the flame has not burned and less than a predetermined number of ignitions has been initiated. If this transition is fulfilled, an idle step 17 is entered , followed by the transition 7 .

The condition "flame burns" is assigned to the transition 18 , with its positive test result on the step 19 , which is assigned to the operation. With the further transition 20 can be determined whether the flame is not burning and the predetermined number of ignitions has been initiated. If the transition is positive, step 12 follows.

Step 19 also includes an alternative branch. The transition 21 associated with step 19 determines the turn-off followed by step 6 . Another transition 21 following step 21 determines the presence of noise conditions, followed by step 12 , which is a sequence step, ie associated with only one transition 22 relating to the acknowledgment of a fault message associated with step 12 . FIG. 2 schematically shows the steps necessary for carrying out the method of the firing control with the associated transitions without the commands to be executed in connection with the steps.

FIG. 3 schematically shows a structured sequencer with the steps, the associated transitions including transition blocks and the commands associated with the steps, for the sequential control of the method shown in FIG. 1. The structuring refers to the four structural elements explained further above. In addition, a distinction of the different interference conditions is made possible here.

The same steps and transitions of the processes shown in FIGS. 2 and 3 have been given the same reference numerals. The order of steps 6 , 8 , 10 , 14 and 19 is the same as in the method of FIG. Fig. 2. The transition 7 depends on a transition block 23 , by which the conditions are checked by which the transition from step 6 to step 8 is released. The transition 9 is associated with a transition block 24 , which performs combinatorial combinations of input variables that must be present when properly carried out flushing. The transition block is used to process those input variables that allow the ignition.

The transition 13 is associated with a transition block 26 , with which it is determined whether the predetermined time for the ignition step has expired. The transition 15 is associated with a transition block 26 a. Transitions 16 , 18 , 20 are each assigned the transition blocks 27 , 28 , 30 . Transition block 27 handles the inputs that occur when the torch is not operating and a number of firing attempts has occurred that is less than a predetermined number.

The transition block 28 processes those input variables which occur when the flame is burning. Transition block 30 processes those inputs that occur when the flame is not burning and the predetermined number of firing attempts have been made.

During an idle step 17 is provided as an alternative after the step 14 according to the example shown in Fig. 2 procedure, 16 of the step 6 follows in FIG. 3 on the step 14 in the presence of the conditions of the transition. The alternative branches, which are formed by the transitions 11 , 15 and 20 , are each followed by steps 31 , 32 , 33 which relate to a disturbance of the purging, the ignition or the exceeding of the predetermined number of ignition attempts. Transitions 21 , 21 a of the alternative branching of step 19 are each assigned transition blocks 34 , 35 . Transitions block 34 monitors inputs indicating the off state of the gas burner. The transition block 35 monitors input variables that indicate faults. If this transition 34 is fulfilled, step 6 follows. If, on the other hand, the transition 35 is fulfilled, a step 36 , which reports a malfunction, closes.

All steps 31 , 32 , 33 , 36 are followed by a similar transition 37 , with which the presence of an acknowledgment is checked. If this is fulfilled, then go to step 6 .

In FIG. 3, commands to act as a link between the functional elements indicating the sequence steps and the functional elements to be controlled are schematically illustrated to show the power of the structural possibilities of a sequence control. Step 8 is associated with an instruction 38 which, like all instructions, has a three-field format.

A first field 39 is provided for specifying a command qualifier: e.g. B. S stored, D delayed, L time-limited and P-shaped. These command qualifiers refer to the temporal execution of the respective command. A second field 40 is provided for receiving a particular symbolic name of a command variable. Instead of a command variable, a program part to be executed can also be addressed. A field 4 is provided for feedback, but this is not always necessary for all commands.

If there is no entry in field 39 , then the command has no effect. An intended, but not yet specified, command can thus be displayed. An entry N does not mean saving. When the chain is switched further, the command is processed again with a negative command effect. An indication S is intended for the storing setting of the instruction. The entry R means store reset. The specification L means time-limited, ie a shortened processing time is specified. The command is processed as long as the associated step is active and acts for at least one program run. With D, the command is time-delayed, but processed as long as the associated step is set. The delay is at least one program cycle and must be specified. The indication P causes the corresponding instruction to process a program cycle after setting the associated step. There are also combinations, for. B. DS and DR possible and permissible.

The instruction sizes in instructions represent break points, d. H. Commands have a long-range effect in a defined area. they seem z. B. out of the chain in other parts of the description.

Command sizes have multi-assignment behavior. Ie. they may have multiple origins but only one goal.

The message indicator for the confirmation in field 41 consists of the sequential number of the command (since usually several commands are configured per step) and one of the following letters.

Examples:
A (command) output,
R command effect is reached (response control)
X Fault message, command effect not reached.

The following different types of commands are possible: Assignment commands and execution commands. Assignment commands include bit commands, Network control commands and load commands. To the execution commands include bit control commands and action commands. Give bit commands Effects on Boolean variables declared as command sizes are and which are usually resumed in networks that are still described below.  

Block commands are intended to exert effects on actuators. Specify the command qualifiers. Feedback is possible.

With the command 38 z. B. a block module 42 is activated, which is assigned to a pump which is intended for the flushing of the combustion chamber of the gas burner. The block module is shown in FIG . The block module 42 defines a closed technological function which can be triggered by commands from various locations (typically from flow structures). The block module 42 acts on an actuator, namely the pump, via the operation of a contactor 43 in the power supply of the pump. The block module 42 is supplied with a plurality of input signals coming from actuators or from the process. The block module 42 has an input 44 for a signal prescribing automatic mode and an input 45 for a manual mode signal. Furthermore, an input 46 is provided for an enable signal. An input 47 is intended for switching off the pump. Another input 48 is provided for inputting a pulse shaping signal.

The pending at the inputs 44 to 48 signals are combinatorially processed in block block in the manner shown in the diagram by means of AND gates 49 , 50 , 51 and OR gates 52 , 53 . Each of the AND gates 49 and 50 and the AND gate 51 and the input 47 downstream OR gates 52 , 53 respectively control the inputs of an SR flip-flop 54 , which acts on the contactor 43 . The AND gates 49 to 51 , the OR gates 52 , 53 and the flip-flop 54 are preferably realized by software chips in a memory-programmed controller.

The realization of additional links, z. B. from Operating mode influences or protective interlocks are included Software blocks can be configured in the graphics section of the block blocks. It Thus, a separation between the initiation of the function and its Achieve realization. Ie. when changing the actuator, only the Adaptation made in the block module, the "calling" program stays unchanged.  

The instruction size "pump 1 on " acts on one input of the AND gate 49 , while the instruction size "pump 1 off" acts on the input of the AND gate 51 .

A block module is shown in the manner shown in Fig. 6 on the monitor by a rectangle, in the first line is the name of the block block. The following two lines show the command values under consecutive numbering (counting numbers). If there are several command values, the "block" of the block block is extended according to the number of command values.

A simplified functional image without the internal circuit details shown in FIG. 5 is shown in FIG . The function picture gem. FIG. 5 may be shown multiple times in a more comprehensive representation of a start-up control on a monitor. In many controllers, certain drives, contactors, etc. are used multiple times. Each of these elements has z. B. the same control logic, which is configured as a command block type. The connections, ie the current parameters, must be configured according to the application.

By means of the block modules, decoupling between the sequence controlling sequence and the command output can be achieved. The effect to be achieved is determined by the instructions for the chain. The properties of the respective actuator are taken into account independently of the block modules. The adaptation to the special actuator is therefore done exclusively in block block. The command 38 is z. B. "open valve". The nature of this valve is shown in the block module. Fig. 7a shows the block module for a control valve, in which the control properties are in the valve itself.

Fig. 7b shows the block block for a control valve, which is controlled by open / close signals and whose control must be configured using the block. However, the sequencer is not affected by whether a valve with control behavior or a valve is used whose control behavior is determined by the configuration of the block module. The actuator should acc. Fig. 7a, b between (= 0) and on (= percent max) are operated.

The commands "Close Valve" and "Open Valve" work according to. Fig. 7a and b respectively to a memory 55, 56 with the characteristics of an RS flip-flop. The valve with control properties is controlled via a setpoint adjuster 57 connected downstream of the accumulator 55 . According to the block diagram 7 b, in addition to the setpoint adjuster 57 , a control block 58 controlled by the latter is also necessary, which outputs a control signal to the contactor of the valve.

The step 10 gem. FIG. 3 is associated with two instructions 58 , 59 which act on block modules, not shown, which have the basic structure described above. The step 19 is associated with a plurality of instructions 61 , 62 , 63 . Steps 31 , 32 , 33 and 36 are each assigned a command 64 , 65 , 66 , 67 , each of which relates to a block module with which a message characterizing the type of disturbance is produced at the sequence control device.

The sequencer acc. Fig. 3 consists of four nested alternative branches (for processing the accidents) and a loop (for the return).

Since the transition 7 "preconditions" must also be run through, this solution means that the off-step is active only one processing cycle, if the preconditions are met, and thus switches the chain in the next processing cycle in the state "Rinse". This measure represents a decentralized treatment of an exceptional case. Exceptions here are the various incidents.

The decentralized handling of exceptional cases increases the information gain for the user, who can immediately recognize the type of disturbance by which step representing a state of emergency is active. Gem. Fig. 3 is z. B. immediately apparent whether a purging, ignition or operational fault of the gas burner is present, since every possible state of emergency is represented by a separate step.

Decentralized program parts for the treatment of incidents have the Another advantage that they form starting points for action by the the system becomes "fault tolerant" (i.e., automatic elimination or Bypassing the error), or by following a manual intervention can restart without interrupting the higher-level sequence must become.

FIG. 4 a shows a structured sequencer for the gas burner control according to FIG. Fig. 1. In Fig. 4a, no transition blocks and function blocks are shown. The gem. Figs. 2, 3 and 4a, corresponding steps and transitions have been given the same reference numerals. In the step chain gem. Fig. 4a, the exceptional cases, the various incidents, summarized centrally. Steps 6 , 8 , 10 and 14 change with respect to the sequencer in accordance with FIG. Fig. 3 not. Likewise, the step sequences shown in FIGS. 3 and 4a are identical in transitions 7 , 9 , 11 , 13 , 15 and 18 . Transitions 11 and 15 are followed by a blank step 70 . On the empty step 14 follows gem. Fig. 4a shows an alternative branching with the transition 18 and a transition 68 , which refers to the disturbance "does not burn". The transition 68 is followed by the second empty step 70 . The transition 69 associated with step 19 involves checking for "off" or "interference conditions".

Step 19 is followed by the empty step 70 , which includes an alternative branch with the transitions 71 , 72 . The transition 71 checks the conditions "off" or "does not burn" with a number of ignition attempts that falls below the specified number. The transition 72 checks the conditions "interference conditions" and "does not burn" for a given number of ignition attempts. Transition 72 reaches step 12 . Both steps 12 and 70 are followed by step 6 .

The above-described process sequences are in particular using programmable logic controllers, which have an input, Output elements are connected to the devices of the respective process.

Networks as command receivers can be used from multiple locations Stepping out can be achieved.  

The variables that z. B. cause the activation of an actuator and thus practically represent a command indication, can from the Step sequence will be recorded. Networks can become actions which are building blocks that are only be edited when editing a command calling the actions becomes. In the action, all data in the context of the calling Command are valid. The essential purpose of Actions is the realization of subchains.

In the coarse structure shown in Fig. 8, there is shown a preprocessing module 73 called modes which processes a series of input signals necessary for the respective conditions of a scheduler.

The behavior of a flow control depends not only on their Steps, commands and transitions, but also from the Operating mode requirements in the respective application. It is in the In most cases, a circuit for the preprocessing of the operating modes (input) signals, such as automatic, hand, start, stop, etc. makes sense. The Resulting signals are with the KETTE building block and partly with the command recipients, eg. As the block modules, linked.

The input signals of the respective CHAIN block (as composite data type with "K ON") depend on their status have different effects on the runnability of the chain, d. H. on the functionality of the CHAIN module. In addition to the data type "K A "there is still a data type" K AUS ", with which the zusammengeformten Output signals of the respective chain to be designated.

The composite data types "K-IN" (chain input signals) and "K-OFF" (chain output signals) consist of single signals, the so-called original chain signals.

These are signals that have specific selective effects on the inner Have runtime behavior of the chain. The chain input signals can be in Release signals and Schrittanwahlsignale be divided.  

The chain input signals are in a chain block ( 74 ) z. B. processed in the manner shown in Fig. 9. The processing module ( 73 ) generates for the chain z. B. the following control signals:

HE Reset the chain to I-step (s) UZEIT Release of the monitoring time TMT Tap with transitions TRANS-FREE transition release DEAD Typing without transitions BEF-FREE sharing command STURGEON QUIT Fault

Furthermore, the processing module ( 73 ) z. B. generates the following step selection signals or data:

PRESET Transfer of the step number DESIRED STEP Input step number

The chain block itself generates the following signals or data:

TIME STOE Monitoring time expired IS-STEP Query possibility of the current step number

Depending on the industry and task, z. B. the Operating mode input signals, such as manual, automatic or jog mode, very different effects on the chain drainage behavior. In some Use cases means z. B. the manual operation a similar behavior like the set-up operation, d. H. the actuators can with minimal Security locks are moved by hand, in others In manual applications, even the chain position must be used be tracked. This example alone shows that signals like Start, automatic, hand, etc. therefore no original chain signals for can be a generally valid flow control.

From these mode input signals z. B. come from the control panel, the original chain signals must be derived in a preprocessing. Output signals of the chain, denoted by IST-STEP and ZEIT-STOE in FIG. 9 ( 75 ), can be further processed for diagnostic purposes.

A CHAIN block, z. B. the KETTE module shown in FIGS . 8 and 9 ( 74 ) behaves outwardly like a normal function block with memory function, ie its output variables depend both on its input variables as well as on its respective state, mainly by the active Steps of the chain part is marked.

In order to obtain a predictable behavior of a chain which is also complexly branched, it is expedient to process the KETTE block according to the following rule, each time it comes to processing (like other blocks):
- Phase 1 The commands of all active steps of the chain are processed;
- Phase 2 All valid transitions designated by ( 76 ) in FIG. 8 are processed. When a transition is triggered, the previous deactivation steps and their follow-up steps are marked for activation;
- Phase 3 The steps to be deactivated are deactivated and their commands are processed (step flag value "0");
- Phase 4 The steps to be activated are activated and their commands are processed (step memory value "1").

When a step begins to expire, a waiting time begins during the active phase of a step. The next Step will not be active until the waiting time has expired, provided it is in the transition block is mitgeschaltet accordingly and possibly more Transition conditions are met.

Furthermore, with the beginning of the active phase of a step, a Monitor side triggered, which is slightly larger. If the Monitoring time has elapsed without the respective step being completed is, there is a fault.

In Fig. 4a, the steps S0, S1, S2, S3, S4, S5 and the transitions T1, T2, T3, T4, T5, T11, T21, T31 and T 51 are used, which are used as identifiers for the steps which are also displayed on a screen together with the geometric structure of the chain.

The identifiers are used simultaneously as a reference for the steps and transitions in partial images of FIGS. 4 b, 4 c. In addition to the identifiers is a z. B. technology-related name.

For illustrative purposes, the projected sequence control, as shown in FIG. 3 for better understanding, is not shown completely on a screen. The sequence control is then shown with the substructures shown in FIGS. 4a, b and c, of which FIG. 4a is the step chain with the identifiers, FIG. 4a is a step S1 with the associated commands, and FIG. 4b is a transition T1 refers.

The identifiers simultaneously represent the technological numbering This means that the identifier z. B. also for display in the ongoing process events can be used. Ie. the Operating personnel can recognize, for. If a fault has occurred, in which state (step) the process is located.

The concept and the handling of the numbering are therefore of great importance Meaning. There are several methods of identifier formation that during configuration are available:

a) Automatic numbering (default)

When editing, z. For example, an additional step with transition will appear in inserted a sequence of existing steps and transitions, this step (and the transition) gets the next possible number of the entire sequence, regardless of whether the insertion is at the beginning or the End of the sequence is done. During the saving is a continuous generated linear numbering. All references become automatic customized. Analogously, the substitution of a step works.

b) Hand numbering

All numbers remain as they are projected. With every change must immediately, d. H. before the next possible, the referencing be automatically adjusted with. When adding an item becomes The system generates a proposal that can be changed. When deleting remain corresponding gaps.  

c) offset numbering

This setting practically means "hand numbering", but only affecting parts of the chain structure. For some areas of the chain structure (such as branches and macro steps), information can be specified for the beginning of a counting area. When switching to "automatic numbering", these configured counting spaces are taken into account. The offset information is specially marked. Fig. 4a ( 72 ) shows an example. For labeling square brackets were used.

For example, the numbering takes place in the decimal system. The transitions Substructures are made by appending another decade characterized.

The chain structure, the transitions, the commands, the actions, etc. are each assigned their own description parts. This is shown in FIG . A division into such parts of the description supports readability and reusability. For a chain structure is z. B. a designated 80 in Fig. 10 Description part provided. The description of parts for commands, transitions and actions are designated in FIG. 10 with 81, 82 and 83.

Claims (19)

1. A method for sequencing the work to be performed by different actuators according to predetermined instructions, characterized in that the signals to be output to the devices and the signals generated by the devices to be processed are associated with different functional elements whose interaction is determined by further functional elements by the determining a sequence of steps associated with instructions to be executed by the devices, in the course of which the data exchange with the other command portions is handled on the basis of indications. 2. The method according to claim 1, characterized, that exactly four structural elements for the connection of steps in Frame of a step chain are provided, of which a kind on the sequence of steps, the second kind on steps with Alternative branch, the third kind on steps with Parallel branching and the fourth kind on steps with Looping to a subsequent step in the sequence refers.   3. The method according to claim 1 or 2, characterized, that for the action on the command quantities exactly three Various types of commands are provided, each one refer to bit instructions, block instructions and load instructions. 4. The method according to one or more of the preceding claims, characterized, that for the control of program parts exactly two different Types of commands are provided that focus on image or Obtain network commands and the action commands. 5. The method according to claim 3, characterized, that the bit instructions affect stored Boolean variables. 6. The method according to claim 3, characterized, that the block commands act on block blocks, the Process input quantities sequentially and / or combinatorially and output control signals in accordance with the respective command. 7. The method according to claim 3, characterized, that the load commands enter data in memory. 8. The method according to claim 4, characterized, that the network commands each have a name defined by a name Calling network of logical building blocks, said editing takes place as long as the calling step is active. 9. The method according to claim 4, characterized, that the action commands each have a name defined by a name Call up a network of logical building blocks that have a type character has, where the processing is done, as long as the calling step is active.   10. The method according to claim 9, characterized, that each defined by a name as actions logical building blocks during the execution of the calling action Command associated with states of a chain Data is processed. 11. The method according to one or more of the preceding claims, characterized, that through logical building blocks feasible, technological Functions by itself as a block under a name with input and Outputs set and commands that follow the steps are assigned, are abuttable. 12. The method according to one or more of the preceding claims, characterized, that the steps and transition blocks are assigned names that associated with the steps and transition blocks graphical representations can be displayed on a monitor. 13. The method according to one or more of the preceding claims, characterized, that in a separate mode part each for the Case of a flow control typical operating mode signals in normalized chain signals adapted for steps of the chain being transformed. 14. The method according to claim 12 or 13, characterized, that the mode signals in with the steps of the chain and with Block blocks linked step selection signals and enable signals divided into preprocessing data types.   15. The method according to one or more of the preceding claims, characterized, that in a chain defined by a series of steps Block after the call the commands of the active steps and the Transitions are processed and that at one by one fulfilled transition continued step the previous steps as inactive and marked the follow-up steps for activation become. 16. The method according to claim 15, characterized, that the deactivated steps after editing their commands be marked. 17. The method according to claim 15, characterized, that the steps to be activated are marked. 18. The method according to one or more of the preceding claims, characterized, that the respective chain part is divided into counting spaces and that the transition from one counting room to another through a marking is given. 19. The method according to one or more of the preceding claims, characterized, that at least the chain structure, the transitions, the commands (step-oriented), the actions each have their own is assigned descriptive description part.