KR20110012342A - Method of designing programmable logic controller ladder logic and generating ladder code - Google Patents

Abstract

PURPOSE: A method of designing a programmable logic controller ladder logic and a generating ladder code is provided to verify the logic error of a ladder code by simulating the change of state of an output coil according to the change of state of a specific input contact point. CONSTITUTION: An active diagram editor(110) designs an PLC control logic. A ladder diagram generator(120) reads an AD-XML. The ladder diagram generator generates XML format. A ladder diagram editor(130) visualizes the generated LD-XML format. An I/O port simulator(140) detects the logical error of a ladder code.

Description

PCL Ladder Logic Design and Ladder Code Generation Method {METHOD OF DESIGNING PROGRAMMABLE LOGIC CONTROLLER LADDER LOGIC AND GENERATING LADDER CODE}

The present invention relates to a programmable logic controller (PLC) ladder logic design and ladder code generation method, and more particularly, to design control logic of a manufacturing system through a UML (Unified Modeling Language) activity diagram, and to control the designed control logic. After generating a ladder code (Ladder Code) based on the PLC ladder logic design to verify the logic error of the ladder code by simulating the state change of the output coil according to the state change of the specific input contact of the generated ladder code and It relates to a ladder code generation method.

With the rapid globalization of the corporate environment, most companies are striving to change their organizational structures from cost to time, product to customer, and scale to agility for survival. It is a key means of survival strategy.

Recently, as the level of automation in the enterprise is advanced, the process control method and the logistics flow become more complicated. Therefore, the reliability and productivity of the controller logic programming that controls the entire system are emerging as important tasks. Currently, PLC (Programmable Logic Controller) is adopted as most automated manufacturing system controller, and control logic is mainly written using ladder diagram (LD).

PLC ladder code writing process, which is widely used in production, has two problems. First, there is a lack of systematic program design and development process methodologies, and there is a strong tendency to rely heavily on programmer experience. In other words, it is common to refer to mechanical drawings, engineering drawings, and equipment specifications including general layout, pneumatic circuit diagrams, time tables, etc. in a way that only the author can understand, or write the code directly without documentation. .

Second, the PLC ladder diagram has a structure that is difficult to verify the logical error that occurs when programming. PLC ladder diagrams provide only a partial view of the entire system, which makes it difficult to see the interactions between components at a glance. Specifically, ladder diagrams have a structure that makes it difficult to see how changes in state of inputs and outputs in one rung affect other rungs, which can occur when new code or code changes are made. Logic errors are difficult to verify.

Among these issues, in order to settle the systematic development process, it is essential to introduce an appropriate control logic design tool that can be used in the ladder code development process. And in order to solve the logical errors that may occur when writing new code, it is desirable to automatically generate ladder code based on the designed control logic rather than coding. You can also reduce the likelihood of logic errors by modifying the designed control logic instead of directly modifying the ladder code when process control methods or logistics flows change.

Accordingly, for the systematic design of control logic, the design tool that extends the activity diagram (AD) of UML (Unified Modeling Language), an object-oriented modeling tool, is used and the ladder code is automatically generated based on the designed control logic. By developing a method and a tool for generating, there is a demand for the development of a technology that can solve the problems of the conventional PLC ladder programming process.

SUMMARY OF THE INVENTION The present invention has been made to improve the prior art as described above. The control logic of a manufacturing system is designed through a Unified Modeling Language (UML) activity diagram, and a ladder code is generated based on the designed control logic. Programmable logic controller (PLC) ladder logic design and ladder code generation method for generating a logic error of the ladder code by simulating a state change of an output coil according to a state change of a specific input contact of the generated ladder code after generating The purpose is to provide.

In order to achieve the above object and to solve the problems of the prior art, a programmable logic controller (PLC) ladder logic design and ladder code generation method according to an embodiment of the present invention, a manufacturing system through a UML (Unified Modeling Language) activity diagram Designing the control logic of the; Generating a ladder code based on the designed control logic; And verifying a logic error of the ladder code by simulating a state change of an output coil according to a state change of a specific input contact of the generated ladder code.

According to the PLC ladder logic design and ladder code generation method of the present invention, by automatically generating ladder code that is difficult to program through an easy-to-use UML activity diagram, it is possible to minimize the possibility of occurrence of logical errors in the ladder program. Can be.

In addition, according to the PLC ladder logic design and ladder code generation method of the present invention, by automatically generating the ladder code after changing the design, to minimize the logical errors that can occur when the code changes directly, to shorten the verification time and systematic The effect of enabling change management can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a PLC ladder code generation tool according to an embodiment of the present invention.

PLC ladder code generating apparatus 100 according to an embodiment of the present invention includes an activity diagram editor 110, ladder diagram generator 120, ladder diagram editor 130, and input and output port simulator 140.

Activity diagram editor 110 designs the PLC control logic. Activity diagram editor 110 analyzes the process flow of an automated manufacturing system to design control logic. Control logic written in the form of activity diagrams can be stored in an XML format called AD-XML.

The ladder diagram generator 120 reads AD-XML and generates an XML format called LD-XML, which is a ladder code representation format. LD-XML extends the TC-6XML format of the PLCopen group, which is a standard storage method for IEC 61131-3PLC codes. That is, in order to express the exact coordinates of the graphic ladder code, information representing the rows and columns of the ladder line may be added to the attribute of the existing position element. The generated LD-XML format may be visualized as a graphic ladder diagram through the ladder diagram editor 130. The input / output port simulator 140 may perform input / output port simulation to detect a logical error of the created ladder code.

2 is a flow chart showing the flow of the PLC ladder logic design and PLC ladder code generation method according to an embodiment of the present invention.

PLC ladder logic design and PLC ladder code generation method according to an embodiment of the present invention, step (210) of designing the control logic of the manufacturing system using a Unified Modeling Language (UML) Activity Diagram (AD), Automatically generating a ladder code based on a design result of the control logic (220), and verifying a logic error of the generated ladder code by simulating a state change of an output coil due to a state change of a specific input contact point 230.

Among the UML diagrams, an activity diagram (AD) has a structure similar to a flowchart and can represent various control flows including a parallel control flow, which is suitable as a ladder logic design tool. In other words, among various design tools for modeling an automated manufacturing system, the flowchart method can express sequential logic well and is easy to understand intuitively, but the general flowchart cannot express control flow such as parallel confluence or branching. On the other hand, the Activity Diagram (AD) has an advantage that it can express various control logic flows including parallel control flows while having a structure similar to a flowchart.

The ladder diagram consists of a combination of AND, OR, and NOT logic. AND can be subdivided into AND-Join and AND-Split, OR into OR-Join, and NOT into normally closed contact and negative coil.

As shown in FIG. 3, the activity diagram may represent AND logic and OR logic among logics required by ladder logic, but not logic. Therefore, in order to use the activity diagram as a design tool for generating ladder code, it is necessary to extend the modeling function to express the NOT logic.

According to an embodiment of the present invention, a transition, which is one of the components of the activity diagram, may be extended to three types as shown in FIG. 4 to express NOT logic. In other words, the transition of the activity diagram includes a normal transition representing a general logic flow, a non-transition transition representing a closed contact point, and a not output transition representing a reverse coil. OUT).

5 is a diagram illustrating control logic designed with an activity diagram according to an embodiment of the present invention. FIG. 6 is a diagram of FIG. 5 converted to a ladder diagram.

The control logic of FIG. 5 is equivalent to "IF (A = on.AND.B = on) .OR. (C = NOT on), THEN (D- = on)." That is, according to an embodiment of the present invention, the condition that A and B are simultaneously turned on may be represented by AND-Join (AJ), and the condition that D is turned on when AND-Join or C is OFF is OR It can be expressed as Join (OJ). If C is OFF, the ON of D may be expressed through a reverse input transition in the case of a closed contact.

In order to automatically generate ladder code through UML activity diagrams, the mapping relationship between each component must be defined in advance. The components of the ladder diagram defined in the IEC 61131-3 standard are contacts, coils, power flow, power rails, and function blocks.

The contact includes a normally open and a closed contact, the coil includes a general coil and an inverted coil, and the power flow includes a horizontal power flow and a vertical power flow. The power rail includes a left power rail and a right power rail.

The ladder diagram may be implemented in a somewhat different configuration for each PLC manufacturer, the present invention will be described by taking an example in which the components of the ladder diagram is implemented by only the components defined in the IEC 61131-3 standard. The graphical representation of each component of the ladder diagram is as shown in FIG.

Components of the activity diagram may be divided into activity elements and transition elements. The activity element may consist of start activity, stop activity, general activity, special activity, and block activity. The general activity and the special activity may be composed of inputs and outputs depending on the state used. The special activity may be further defined to easily use counters and timers which are mainly used for automation control, and the block activities are intended to express logic hierarchically.

The transition element may be composed of a general transition, a NOT transition, and a logic flow transition to express control logic. The NOT transition may include a reverse input transition and a reverse output transition representing a closed contact and a reverse coil. The logic flow transition may be composed of OR-Join, AND-Join, and AND-Split depending on whether the logic flow is parallel / sequential and joined / branched. The graphical representation of each element of the activity diagram is as shown in FIG. 5.

7 is a diagram illustrating a mapping relationship between activity diagram and ladder diagram elements according to an embodiment of the present invention.

In order to automatically read the activity diagram through the mapping relationship defined in FIG. 7 and convert the activity diagram into a ladder diagram, it is necessary to decompose the activity diagram into units corresponding to rungs of the ladder diagram. The rung is a basic unit of a ladder program including an input unit and an output unit combined by AND, OR, and NOT logic. As such, the basic unit of the activity diagram corresponding to the rung for converting the ladder diagram is referred to as an input output unit (IOU), and may be used as a conversion unit that can be exchanged with the rung one to one. The procedure for automatically generating ladder code through an activity diagram can be divided into four steps.

In the first step, you can graphically create an activity diagram and then save it as an XML structure. The XML schema for this is called AD-XML. In the second step, the activity diagram expressed in AD-XML is decomposed into IOU units and stored in a two-dimensional table structure called an IOU-table. The IOU-table consists of input activity columns, transition columns and output activity columns. In the third step, IOUs are classified into five types of IOUs for conversion, and the direction of membership can be determined for each identified IOU by reading the IOU-table. In the fourth step, ladder code can be automatically generated through conversion rules provided for each type and predefined mapping relationships. Hereinafter, the first to fourth steps will be described in detail.

The first step is the creation and storage of the activity diagram. For the automatic generation of ladder code, it is necessary to convert and store graphically represented activity diagrams into computer-processable data structures. AD-XML consists of two elements: activity elements and transition elements. All activity elements have a name attribute in common, and special activity elements additionally have function and initial value attributes. Block activities have no attributes and have other elements as child elements. All transition elements have start and destination attributes in common, and logic flow transition elements additionally have logic flow type attributes.

The second step is to break down the activity diagram into IOUs. The IOU corresponds to the rung, the basic unit of the ladder diagram, which consists of a combination of input and output activities and their relationships. The way to decompose an activity diagram into units of IOUs is to find subsets within the diagram that have only activity as input and output. In other words, IOU is a unit that finds and binds activities to be started / arrived based on a specific transition in AD-XML. 8 is a diagram illustrating an example of an activity diagram broken down into IOUs in accordance with one embodiment of the present invention. According to one embodiment of the invention, one activity diagram may be broken down into five IOUs.

A method of generating an IOU-table according to an embodiment of the present invention is as follows. First, in each transition of the activity diagram stored in AD-XML, we identify a single transition with only the activity element as the start and destination attribute values. Subsequently, when the transition element is included as the start and arrival attribute values of a specific transition in the identification process, the two transitions are collectively referred to as a grouping transition. Thereafter, an IOU-table can be created that consists of three components: a single transition (or a grouping transition) and the input and output activities connected to it.

Table 1 shows the result of generating an IOU based on the activity diagram of FIG. 8 in the ⓐ-ⓕ transition. For example, row 4 may be grouped as a case where the logic flow transitions ⓓ-OJ and another logic flow transition ⓔ-AJ are contiguous, where B, E, and D may be input activities and E may be an output activity. .

The third step is the determination of the type of IOU. Each identified IOU is classified into five types according to the characteristics of the corresponding rung as shown in FIG. 9. IOUs can be broadly divided into a single type consisting of the basic components of the ladder diagram and a complex type that can be expressed as a combination of a single type.

A single type can be differentiated from type-1 to type-4 depending on the rung structure being mapped. Type 1 can be converted to the left / right power rails of the ladder diagram as an IOU with start or stop activity. Type 2 is the most basic IOU and can be converted to a rung consisting of a single point of contact and a single coil. Type-3 is an IOU that contains logic flow transitions. Type-3-1 (OR-Join), Type-3-2 (AND-Join), Type depending on the nature of the logic flow in parallel / sequential, confluence / branch. Can be subdivided into -3-3 (AND-Split). Type-4 is an IOU that contains functional blocks such as timers and counters, which can be converted to normal contacts when used as inputs and block types when used as outputs.

Complex types are cases where multiple logic flow transitions are contiguous, in which case it is difficult to know the preceding and succeeding activities for one activity at a time, requiring a multi-step transformation process. First, I / O activities are grouped together based on logic flow transitions, and then defined as a block activity to implement the mapping process. Then, each element in the block activity is mapped back to a single type. In the case of a complex type, the grouping method is different depending on the case where Join is preceded and when Split is preceded, and thus it can be divided into 5-1 type (Join leading) and 5-2 type (Split leading).

As shown in FIG. 10, after the IOU-table is created, the type of each IOU may be determined as follows.

Retrieve the number of transitions belonging to the transition column of each row of the IOU-table. If the number of transitions of the search result is two or more, it may be determined as a complex type and the type of IOU may be determined as <type 5>. It also searches for a function block in the input and output activity columns. If the search result includes the functional block, the type of IOU may be determined as <type 4>. In addition, if the I / O activity column contains start / stop activity, you can determine the type of IOU as <type 1>.

In addition, when the number of input activities is greater than the number of output activities, it is determined by the joining logic and branches to condition (7) shown in FIG. If the number of input and output activities is the same, branch to condition (6), otherwise determine to branch logic to determine the type of IOU as <type 3-3>. In addition, if there is only one number of input and output activities, it may be determined as a basic IOU and determined as <type 2>. Otherwise, it may be determined as a complex type and the type of an IOU may be determined as <type 5>. In addition, if the join logic flow transition is OR logic, the type of the IOU may be determined as <type 3-1>. Otherwise, the type of the IOU may be determined as <type 3-2>.

The fourth step is automatic ladder code generation. The automatic generation of the ladder code can be converted through the mapping relationship between the components shown in FIG. 7 and the five types of ladder pattern conversion methods for each row of the IOU-table shown in FIG. 9. For a single type, ladder code can be generated by converting the input activity of the IOU-table into the input of the rung, the output activity into the output, and the transition into logic between the input and the output.

However, complex types require additional conversion steps. In other words, a hierarchical conversion method may be used in which a complex type is changed to a single type through grouping, automatic generation of ladder code, and then degrouped to convert elements in the group into basic ladder elements.

Among the complex types, Join preceding type <5-1> is a case where a logic flow transition AND-Join or OR-Join is used as a preceding transition and connected to another logic flow transition. In this case, you can create a group that contains all the activities linked to the preceding transition once to form the IOU for the trailing transition.

11 is a diagram illustrating a grouping method of a join preceding complex type according to an embodiment of the present invention. The example activity diagram of FIG. 11 consists of three consecutive logic flow transitions (AJ, OJ, AS) and six activities. Grouping targets two consecutive logic flow transitions. AJ and OJ, and OJ and AS may be the grouping targets as shown in FIG. 11. In other words, two grouping processes are required. First, in the case of AJ and OJ, AJ is the leading transition and OJ is the trailing transition. Activities A and B connected to the preceding transition AJ may be grouped as GR1 of FIG. 11.

However, secondary grouping is needed because the primary grouping result still contains complex types. Transitions subject to secondary grouping are OJ and AS. All activities connected to the OJ are grouped as GR2 in ⓑ of FIG. Through the two-step grouping process, a complex type may be converted into a type <type-3-3> as shown in ⓒ of FIG. 11. The IOU expressed as a single type generates a rung whose inputs are grouped into GR2, the outputs are coils E and F, and their connection relationship is AND-Split, as shown in ⓓ of FIG. The grouped components of the generated rungs are released in stages as shown in ⓔ, ⓕ in FIG. 11 to complete the ladder code.

Split preceding type <5-2> is a case in which a logic flow transition AND-Split is connected to another logic flow transition as an input, as shown in FIG. 12. In this case, as shown in ⓐ of FIG. 12, a group including all activities connected to the subsequent transition is created to form an IOU for the preceding transition. Through the grouping process, the complex type is converted into a single type <type 3-3> as shown in ⓑ of FIG. 12. Thereafter, as in the case of join joining, it is possible to complete the ladder code step by step by generating a rung and releasing grouping as shown in ⓒ and ⓓ of FIG. 11.

FIG. 13 illustrates a structure of a conveyor-based logistics handling system for performing identification / extraction of defective items and classification of non-defective products (metal products / non-metal products) and counting as a case object system according to an embodiment of the present invention.

If we take a closer look at the defect extraction function, the product flows along the conveyor at regular intervals, and when it arrives at the position for identifying good or bad, two light sensors identify the bad. Good or bad products are classified according to the height of the product. Products lower or higher than the specified standard will be defective.

That is, a product that detects only the 'low position sensor' among the 'high position sensor' and 'low position sensor' installed at the same point is determined as good. In other cases, it is determined to be defective. The product determined to be defective is extracted by the extraction cylinder Extract_Cyd. In order to determine the defective product, the state of the two position sensors must be managed, so the variables of 'High_Memory' and 'Low_Memory' are used. In this case, we use 'Extract_Sensor' to extract the defective product and 'Ok_Limit Switch' to initialize the memory variable. The control logic representing the reject extraction scenario is as follows:

1) IF (((High_Sensor = on) .or. (High_Memory = set)) .and. (Extract_Cyd = NOT on)) THEN (High_ Memory = set).

2) IF (((Low_Sensor = on) .or. (Low_Memory = set)) .and. (Extract_Cyd = NOT on) .and. (OK_LimitSwitch = NOT on)) THEN (Low_Memory = set).

3) IF (Extract_Cyd = on) .and. ((High_Memory = set .and. Low_Memory = set) .or. (High_Memory = NOT set .and. Low_Memory = NOT set)) THEN (Extract_Cyd = on).

14 is a diagram illustrating an activity diagram of control logic of a defective article extraction scenario according to an embodiment of the present invention. Using the automatic generation function based on the control logic designed in this way, ladder logic as shown in FIG. 15 may be generated.

Simulation is required to verify that the generated ladder diagram accurately represents the reject extraction scenario and that there are no logical errors. The developed system provides a simulation function for changes in output coil values for input contacts commonly used in commercial PLC code generation programs such as "GM-Win".

FIG. 15 illustrates a simulation process through change of output ports to ON-OFF state change of a specific input port for the generated code. In the simulation process, the ON of the input port is represented by a square point, and the ON of the output port is represented by a circular point. Ladder code generated automatically as a result of the input / output port simulation for the case system can be verified to produce error-free code similar to the way the practitioner writes in the field.

PLC ladder logic design and ladder code generation method according to the present invention can be implemented in the form of program instructions that can be executed by various computer means can be recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal line, a wave guide, or the like, including a carrier wave for transmitting a signal designating a program command, a data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above-described embodiments, which can be variously modified and modified by those skilled in the art to which the present invention pertains. Modifications are possible. Accordingly, the spirit of the present invention should be understood only by the claims set forth below, and all equivalent or equivalent modifications thereof will belong to the scope of the present invention.

1 is a block diagram showing the configuration of a PLC ladder code generation tool according to an embodiment of the present invention.

2 is a flow chart showing the flow of the PLC ladder logic design and PLC ladder code generation method according to an embodiment of the present invention.

3 is a comparison of a ladder diagram and an activity diagram for a control flow in accordance with one embodiment of the present invention.

4 illustrates the types of transitions in an activity diagram in accordance with one embodiment of the present invention.

FIG. 5 illustrates control logic designed with activity diagrams in accordance with one embodiment of the present invention. FIG.

FIG. 6 is a diagram of FIG. 5 converted to a ladder diagram. FIG.

FIG. 7 illustrates a mapping relationship between activity diagram and ladder diagram components in accordance with one embodiment of the present invention. FIG.

8 shows an example of an activity diagram broken down into IOUs in accordance with one embodiment of the present invention.

9 illustrates the types of IOUs in accordance with an embodiment of the present invention.

10 is a flowchart illustrating a flow of a method of determining an IOU type according to an embodiment of the present invention.

FIG. 11 is a diagram illustrating a grouping method of a join preceding complex type according to an embodiment of the present invention. FIG.

12 illustrates a grouping method of Split preceding complex types according to an embodiment of the present invention.

FIG. 13 is a view illustrating a structure of a handling system with a conveyor-based water that performs identification / extraction of defective items and classification of non-defective products (metal products / non-metal products) and counting as a case object system according to an embodiment of the present invention.

14 is a diagram illustrating an activity diagram of control logic of a defective article extraction scenario according to an embodiment of the present invention.

FIG. 15 is a diagram illustrating a simulation process through change of output ports for ON-OFF state change of a specific input port for a code generated according to one embodiment of the present invention. FIG.

<Explanation of symbols for the main parts of the drawings>

100: ladder code generator

110: Activity Diagram Editor

120: ladder diagram generator

130: ladder diagram editor

140: I / O port simulator

Claims (7)

Designing control logic of the manufacturing system via a Unified Modeling Language (UML) activity diagram; Generating a ladder code based on the designed control logic; And Verifying a logic error of the ladder code by simulating a state change of an output coil according to a state change of a specific input contact of the generated ladder code Programmable Logic Controller (PLC) ladder logic design and ladder code generation method comprising a. The method of claim 1, The transition of the UML activity diagram includes a normal transition, a NOT transition, and a logic flow transition, wherein the NOT transition represents a Not Transition-IN representing a closed contact, and a reverse coil. And a Not-Transition-OUT, wherein the logic flow transition includes OR-Join, AND-Join, and AND-Split classified according to parallel / sequential and confluence / branch of logic flow. PLC ladder logic design and ladder code generation method. The method of claim 1, Generating a ladder code (Ladder Code) based on the designed control logic, Storing the activity diagram represented graphically as an XML structure through AD-XML; Decomposing the activity diagram expressed in the AD-XML into an input output unit (IOU) unit and storing the IOU in which the activity diagram is decomposed through an IOU-table implemented as a two-dimensional table; Determining the type of each IOU stored through the IOU-table according to the characteristics of a corresponding rung; And Generating a ladder code according to the type of each IOU PLC ladder logic design and ladder code generation method comprising a. The method of claim 3, The type of IOU includes a single type and a complex type, wherein the single type is converted into a rung consisting of a first single type, a single point of contact and a single code including start or stop activities. A second single type, a third single type including a logic flow transition, a fourth single type including a functional block such as a timer or a counter, wherein the complex type is preceded by a first complex type and a Split preceded by a Join PLC ladder logic design and ladder code generation method comprising a second complex type. The method of claim 3, Generating ladder code according to the type of each IOU, Generating the ladder code by converting the input activity of the IOU-table into an input unit of a rung, an output activity to an output unit, and a transition to logic between the input unit and the output unit when the type of the IOU is a single type PLC ladder logic design and ladder code generation method comprising a. The method of claim 3, Generating ladder code according to the type of each IOU, If the type of the IOU is a complex type, converting the complex type into a single type through grouping; And After generating the ladder code, ungrouping to convert the elements in the group to the default ladder element. PLC ladder logic design and ladder code generation method comprising a. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 6.

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