KR100348196B1 - Sequence control method - Google Patents

Abstract

PURPOSE: A method for controlling sequence is provided to improve the suitability by allowing each step of an SFC(Sequence Flow Control) to control the whole flow without using a separate scheduler. CONSTITUTION: A step of an SFC is made as an independent task which is multi-processed by a multiprocessing operating system(300). The task comprises a routine for receiving a token, a routine for performing a transition according to an input transient condition, a routine for performing a corresponding internal step operation, and a routine for transferring a token to a task corresponding to an output transient condition. Input/output transient information of each step and input/output step information of each transition are set(310). A task generated according to the input/output transient information and the input/output step information is performed(320).

Description

Sequence control method

The present invention relates to a sequence control method, and more particularly, to a method for controlling a flow of a program represented by SFC of IEC 1131-3, which is an international standard of programming language for PLC, in designing and implementing a sequence flow controller.

In general, each unit element in the control system has its own sequence flow control. Typical functions of general control software include sequencing tasks, monitoring the state of the system, and determining the dynamic state of the system in real time. Conventional Ladder Logic Diagrams (LLDs) have been used to organize the workflow of these systems. They have specified the input and output procedures of a programmable logic controller (PLC), and have done their work repeatedly. However, as the size of the system increases, the complexity of the LLD becomes much more severe. Therefore, when a problem occurs, it is difficult to find the problem, and when the specifications of the system change, most of the contents have to be changed.

To overcome this limitation of LLD, PLC companies have developed several programming languages. The International Electrotechnical Commission (IEC) created IEC 1131 for compatibility and harmonization of these various languages, and one of the languages that represents the flow of the entire system is the Soquential Function Chart: Hereinafter referred to as SFC). However, when the internal structure of the SFC is complicated or branches having different characteristics overlap, it is difficult to continue the entire flow, and there is a need to manage a work step by having a separate controller such as a scheduler. In addition, as the number of work steps increases, the load of the scheduler increases as well, resulting in insufficient work efficiency due to insufficient time to execute each step necessary due to the load of the scheduler.

The present invention was created to solve the above-mentioned problems, and in order to perform each step of the SFC without having a separate scheduler in executing the sequential program labeled as SFC to control the entire flow itself, It is an object of the present invention to provide a sequence control method for generating steps as a separate task and controlling the entire flow itself while exchanging information for performing a program between the tasks.

Figure 1 shows an example of a program labeled SFC, which is one of the programming languages for PLC presented in IEC 1131-3.

2 illustrates an example of a task corresponding to a step of an SFC.

3 is a flowchart illustrating a large flow for the sequence control method according to the present invention.

Sequence control method of the SFC according to the present invention for achieving the above object

Making the steps in the SFC into independent tasks that are multiprocessed by a multiprocessing operating system;

Setting input / output transition information of each step and input / output step information of each transition: and

And executing the generated task according to the input / output transition condition information of each set step and the input / output step information of each transition.

And the task is a routine for receiving a token and performing a transition according to an input transition condition. It is preferable to include a routine for performing an operation in the corresponding step and a routine for transmitting a token to a task corresponding to an output transition condition.

The token of the routine for receiving the token includes information about a task unique number, and the routine for performing the transition according to the input transition condition checks the number of input transitions. When the number of input transitions is one, the routine performs a transition according to an input transition condition, and when the number of input transitions is two or more, a routine for checking only an output transition of a task corresponding to a unique number of a task that has passed a token. . In addition, the routine for passing the token to the task corresponding to the output transition condition is a routine for checking the number of output transitions. If the number of output transitions is one, if the output transition condition is true, the token is passed to the task connected to all output transitions of the task, and if the output transition is false, the routine and the number of output transitions waiting for the output are two or more. It includes a routine that checks the transition conditions in a predetermined order, finds the first participating condition, and passes the token to the output step task of the transition.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Figure 1 shows an example of a program labeled SFC, which is one of the programming languages for PLC presented in IEC 1131-3. Referring to FIG. 1, the SFCs are described as square boxes (S1, S2, S3,...) In the SFC and are referred to as "steps", and the bars T1, T2, T3, ...) and connecting the step with the step is referred to as "transition". Each step describes the operation of the system in different languages, as specified in IEC 1131, and the transition examines a given "transition condition", denoted by C1, C2, C3, ... in FIG. While connecting the flow to the next step. At this time, the flow can proceed to the next step only when the transition condition is "true", and when it is "false", it stays there until it is "true". This condition is represented by a boolean expression.

In addition, there are three types of flows provided by the SFC. Firstly, when one step S1 is completed as shown in FIG. 1, the transition to the next step is performed. The condition C1 is checked and if the transition condition C1 is true, the process proceeds to the next step. Referring to FIG. 1 as a second flow, one step is completed as 'S2-> T2-> S3', 'S2-> T2-> S4', and 'S2-> T2-> S5'. After that, the next transition condition is checked, and when the transition condition is true, several steps are performed at the same time. This case is referred to as a "Simultaneous Branch", and this corresponds to the horizontal line 100 shown in FIG. At this time, there is no restriction such as separate priority between the steps performed at the same time and is performed independently at the same time. In case of the last third flow, when only one operation is performed, such as 'S5-> T4-> S7' or 'S5-> T5-> S8' or 'S5-> T6-> S9' of FIG. to be. Such a case is referred to as a "selection branch", and the display feather 110 corresponds to a horizontal line in FIG. 1. At this time, the flow is connected after the execution of the step S5.

The concept of the present invention is to continue the flow by making each step a separate task for the SFC as described above, and multitasking the tasks on a multi-tasking operating system. In addition, the steps are made of tasks having a structure as shown in FIG. 2 to construct the entire flow through information exchange between tasks without separate flow control.

Based on the above concept, when the steps constituting the SFC for the above-described SFC are to be configured as separate tasks, the structure of the task will be described.

2 illustrates a preferred embodiment of the structure of the task, wherein the task includes a token receiving routine 200 for receiving a token according to an input transition condition and a transition routine 210 for performing a transition according to an input transition condition. It comprises a step operation routine 220 for performing the operation inside the step and a token delivery routine 230 for transferring the token to the task corresponding to the output transition conditions. The token of the token receiving routine 200 includes information on the task unique number that sent the token, and the transition routine 210 is a routine for checking the number of input transitions and the number of input transitions is two or more, It consists of a routine that checks only the output transition of the task corresponding to the unique number of the task that delivered the token. In addition, the token transfer routine 230 checks the number of output transitions. If the number of output transitions is one, if the output transition condition is true, the token passes to the task connected to all output transitions of the task. If the output transition is false, the routine and the number of output transitions to wait for the output are true. It consists of a routine that checks the transition conditions in a predetermined order and finds the first true condition and passes the token to the output step task of the transition.

Referring to the internal operation of the task, the token receiving routine 200 first waits for a token including information on the task unique number and receives the token when it comes. Then, the number of input transitions is checked through the transition routine 210. If the number of input transitions is one, the input transition condition is checked and passed if 'TRUE', and if 'FALSE', Wait for it to be true. If the number of input streams is two or more, only the output transition of the corresponding task is examined using the unique number (id) of the task that delivered the token. Wait until Then the operation inside the step is performed.

After the above, the number of output transitions is checked. If the number of output transitions is one, the output transition condition is examined and passed if the output transition condition is 'true' and waited until it is true. If true, the token is passed to the tasks connected to all transitions of this task. If the output transition token contains the unique number (id) of the task that sends the token. If the number of output transitions is more than one, the first step is to find the condition that becomes 'true' first from the leftmost output transition condition, and transfer the token to the output step task of the transition. At this time, the token contains the unique number of the task that sends the token.

Meanwhile, a method of controlling a sequence by exchanging information between tasks without separate flow control based on the IEC 1131-3 SFC using a task having the structure as described above will be described.

3 is a flowchart illustrating a large flow of a sequence control method according to the present invention. The sequence control method includes a step 300 of making the steps in the SFC into independent tasks that are multi-processed by a multiprocessing operating system. A task 310 for setting input / output transition information of steps and input / output step information of each transition, and the generated task according to the input / output transition condition information of each set step and input / output step information of each transition. A process 320 is executed.

This will be described in more detail. As shown in FIG. 2, once a task is created, a token is waited for in the token receiving routine of the task. The token is provided by a general multi-tasking operating system as a tool for synchronizing tasks and conveying information. The name 'token' does not refer to a particular object, but is a general term for those used for this purpose. The task of sending the token may send arbitrary information inside the token.

The task receiving the token checks the number of its own transitions. If the number is "1" as in the case of T1-> S2 or T2-> S3 shown in FIG. 1, the task checks the corresponding transition condition. If true, proceed to the next. In this case, as in the case of [S3 and S10 and S11-> T11-> S12 in FIG. 1, if there is one input transition but there are a plurality of step tasks connected to the transition, the token corresponding to the number is received. That is, after receiving the number of tokens, the transition condition is checked. This is the case of the "simultaneous branching" described above, which satisfies SFC's specification of checking the transition condition and proceeding to the next step task after all three step tasks S3, S10 and S11 are completed.

Next, in the case of [T8 or T9 or T10]-> S11 of FIG. 1, the number of input transitions of the S11 task is '3'. Find out which task sent the token. Thus, only the output transition condition of the task is checked, and if the condition is "TRUE", it proceeds to the next. This is the case of the "selective branch" above, where the flow of work flows into only one of several branches, so we only need to check the transition condition of the branch that sent the token.

Once the input transition has been checked, the task inside the step is performed, and when this task is completed, the next step is to determine which step to proceed with the flow, this time checking the number of output transitions for this task. . As in the case of S3-> T11 or S10-> T11 of FIG. 1, if the number is "1", the transition condition is checked and if the condition is "true", the token is transmitted to the task connected to the transition. Here, the token contains the unique number of the sending task. In this case, as in the case of T2-> [S3 and S4 and S5] of FIG. 1, the number of tasks connected to the output transition may be one or more. In such a case, the same token is transmitted to all of the tasks. This corresponds to the "concurrent branch" described above.

When the number of output transitions is plural, it is the same as S5-> [T4 or T5 or T6] of FIG. 1, in this case, a task connected to the first transition to the first "true" by sequentially checking from the leftmost transition condition. Send a token to. This also corresponds to the "selective branch" described above, the flow is to proceed according to the specification. The token contains a unique number of the sending task can be confirmed by the receiving task.

As described above, according to the present invention, by providing a method of progressing the work in the SFC itself without a separate controller, the entire flow continues even if the structure of the SFC becomes complicated or branches of different characteristics overlap. There is no problem.

In addition, since it does not require any additional work due to the internal structure of the SFC, it is very flexible, extensible, and once identified, the program is composed of one unit and can be used by other programs, making it easy to reuse and modular. Have

In addition, tracking the flow of tokens makes it easy to grasp the flow of the whole, it is easy to test each part separately in the development stage of the application, and it is easy to grasp the entire structure by directly converting the displayed contents into one-to-one.

Claims (5)

In the sequence control method using the IEC 1131-3 SFC, Making the steps of the SFC into independent tasks that are multiprocessed by a multiprocessing operating system: Setting input / output transition information of each step and input / output step information of each transition: and And executing the generated task according to the input / output transition condition information of each set step and the input / output step information of each transition. The method of claim 1, wherein the task is Routine to receive tokens: Routines that perform transitions based on input transition conditions: Routines that perform actions inside that step: and And a routine for transmitting the token to the task corresponding to the output transition condition. 3. The token of claim 2 wherein the token of the routine for receiving the token is Contains information about the task's unique number, The routine for performing the transition according to the input transition condition is The number of input transition routines; A routine for performing a transition according to an input transition condition when the number of input transitions is one; And If the number of the input stream is two or more, the control method comprising a routine for checking only the output transition of the task corresponding to the unique number of the task passing the token. The routine of claim 2 or 3, wherein the routine for transferring a token to a task corresponding to an output transition condition is Routines to check the number of output transitions: If the number of output transitions is one, the routine passes if the output transition condition is true, passes the token to the task connected to all the output transitions of the task, and if it is false, waits for it to be true: and If the number of output transitions is more than one, the sequence control method comprising a routine for checking the output transition conditions in a predetermined order to find the first true condition and passing the token to the output step task of the transition. 5. The method of claim 4, wherein the token delivered to the output step task includes information about the task unique number.