JPH06176003A - Simulation device based upon petri net - Google Patents

Abstract

PURPOSE:To easily represent an object which can be represented with neither a basic Petri net nor an extended Petri net and an object which requires complicated logical constitution for the representation and to evade the complication of a Petri net diagram. CONSTITUTION:Transition data 101 consist of a transition main body 102 and a user description part 103. A Petri net processing part 104 is provided newly with an evaluation part 105 and a data setting part 106 in addition to the constitution of a simulation model generation part 105, a simulation execution part 108, etc. The user description part 103 which holds order, a rule, a function or a procedure that a user should describe is provided corresponding to the transition body 102 and the Petri net processing part 104 passes the information of the user description part 103 to the evaluation part 105 when the firing of transition ends. The evaluation part 105 determines a place where a token is sent out according to the description of the user description part 103.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Petri net-based simulation apparatus realized by a workstation, a personal computer or the like.

[0002]

2. Description of the Related Art When designing a discrete event system such as a processing machine, an assembly machine, a production system composed of workers and transfer equipment, etc., individual constituent equipment necessary for achieving a target production capacity. It is necessary to fully consider the number of items, the arrangement of intermediate buffers and their capacity.

In such a case, conventionally, a simulation model is created using a general-purpose language or a simulation-dedicated language, and simulation is performed to evaluate various design plans. However, it was difficult for ordinary designers to learn how to use those languages, and it was difficult to use them.

In order to solve this problem, recently, JP-A-63-136249 and JP-A-63-317805 have been recently used.
As disclosed in Japanese Unexamined Patent Publication No. 2003-242242, many methods have been proposed that can easily create a simulation model visually by using a graph representation of a Petri net.

The Petri net graph is a model in which elements in the system are divided into conditions and events, conditions are placed, events are represented by nodes called transitions, and a relationship between conditions and events is represented by an arc. And
The establishment of a condition is represented by placing a token in a place, and the transition is fired according to the moving state of this token to verify the system dynamics. The above place is represented by place data consisting of a list of arcs to be input to the place, a list of arcs to be output, the number of tokens placed in the place, etc. The transition is also a list of arcs to be input to the transition and output It is represented by transition data consisting of data such as a list of arcs
Further, the arc is represented by arc data composed of data such as a start point node and an end point node.

FIG. 10 shows an example of a Petri net. When tokens are present in all the input places 51 and 52, the transition 54 connected by the arcs 55 and 56 can be fired (see FIG. 10A). After the firing ends, the tokens are removed from the input places 51 and 52 one by one, and the tokens are output to the output place 53 connected by the arc 57 (see FIG. 7B). By using the graph representation of this Petri net, simulation models of various systems can be visually represented and complicated programming can be eliminated.

[0007]

Problems to be Solved by the Invention JP-A-63-3178
In the conventional Petri net-based simulation method as seen in Japanese Patent Publication No. 05, tokens are sent to all output places after the transition is fired. In addition, an extended Petri net called a colored Petri net is proposed in which the tokens and arcs are colored and the processing is switched according to the color as an extension of the Petri net function. , After the transition finished firing, tokens were being sent to all output places connected to the arc with the specified color.

For this reason, it is extremely difficult to describe the control such that after the transition has finished firing, the place which holds the least number of tokens among all the output places is selected and the tokens are sent only to that place. . It should be noted that such control is necessary in the following situations.

In the process of making a certain product, when the process 1 is performed using the machine A and then the process 2 is performed using the machine B, the time t required for the process 2 is longer than the time t ₁ required for the process 1. ₂
Is much longer, add machine B for processing 2 and t ₂
/ T By preparing ₁ unit, the product flow can be made smooth. At this time, there may be a difference in processing capability between the existing machine and the machine to which the machine B group is newly added. In such a case, when the product that has undergone the process A is sent to the machine with the least waiting in the next process, it can be processed efficiently both spatially and temporally. When performing such processing, the control as described above is required.

Even if such control can be expressed well, the Petri net diagram is extremely difficult for not only the creator but also a third party to understand. Therefore, when expressing a production line with complicated control by a conventional Petri net, it requires considerable skill and skill to express the control logic of the production machine with the Petri net, or in some cases, the expression is It had the drawback of being impossible.

Therefore, according to the present invention, by further expanding the function of the Petri net, it is possible to easily express an object that cannot be expressed by a conventional basic Petri net or an extended Petri net, or an object that requires a complicated logical structure for expression. In addition, the purpose is to prevent the Petri net diagram from becoming complicated.

[0012]

In order to achieve the above-mentioned object, the present invention carries out a simulation based on a means for creating a Petri net, a means for displaying the created Petri net, and the created Petri net. In a simulation device based on Petri net with means,
Means for setting the function of the transition with respect to the transition in the Petri net, means for storing the set function, means for evaluating the stored function,
Upon execution of the simulation, a means for sending out the token only to the place determined according to the evaluation result after the firing of the transition is provided.

[0013]

In the present invention, the transition in the Petri net is preset by the user to which place the token is to be sent after firing. When running the simulation, after the transition fires, tokens are not always sent to all output places, but rather the order, rules, functions, etc. given by the user.
Tokens are sent out only to the places determined by the procedure.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below based on embodiments with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The input unit 11 is composed of a keyboard and a mouse, and inputs the positions of places, transitions, arcs, etc. that make up the Petri net, or
It is used to instruct the execution of simulation. The processing unit 12 stores various data input from the input unit 11 in the storage unit 13, and based on these data, the place generation unit 14 generates the place data and the transition generation unit 15 generates the transition data. Then, the arc generation unit 16 generates arc data. Furthermore, the processing unit 12 performs a simulation based on these data.

The generated data of places, transitions, arcs, etc. is supplied to the display unit 17 such as a CRT display and the Petri net diagram is displayed.

Tables 1, 2 and 3 show examples of the data structures of the above-mentioned place data, transition data and arc data. The meaning of the user description in the transition data will be described later.

[0018]

[Table 1]

[Table 2]

[Table 3] FIG. 2 is a block diagram schematically showing a portion for processing transition data in the Petri net-based simulation apparatus shown in FIG.

In the present invention, the transition data 101 is composed of a transition body 102 and a user description portion 103 as shown in FIG. The Petri net processing unit 104 includes a simulation model creation unit 10
In addition to the conventional configuration such as 7 and the simulation execution unit 108, an evaluation unit 105 and a data setting unit 106 are newly provided. Corresponding to the transition body 102, a user description portion 103 that holds the order, rules, functions or procedures to be described by the user is provided, and the petri net processing unit 104 provides the user description when the transition firing ends. Information of the portion 103 is passed to the evaluation unit 105. If the order, rule, function or procedure is described in the user description portion 103, the evaluation unit 105 determines the place to send the token according to the description. The operation of setting data in the user description portion 103 of the transition is performed by the data setting unit 106 using a means such as a dialog panel. The transition data 101 is included in the storage unit 13 shown in FIG. 1, and the Petri net processing unit 104 is included in the processing unit 12.

Next, the operation of the above-mentioned Petri net-based simulation apparatus will be described.

Data of Petri net elements such as places, transitions and arcs are input from the input unit 11 according to the event to be modeled, and the simulation model creating unit 107 creates a Petri net diagram of the event to be simulated. It is displayed on the display unit 17.

In FIG. 3, when the transition firing ends and the tokens are sent to the output place of the transition, the transition evaluation unit 105 of the present invention has a function of sending the tokens in a predetermined order. It is a Petri net figure in the case. For the sake of convenience, the transition having the function of sending out the tokens in such a predetermined order will be referred to as a destination-specified transition.

The place 201 and the place 202 are connected to the destination designated transition 203 by the arc 207 and the arc 208, respectively, and the destination designated transition 203 is made by the arc 209, the arc 210 and the arc 211 to the place 204 and the place 205.
And the place 206.

The order of sending out the tokens in the above-mentioned destination designated transition is set, for example, by the following procedure (see FIG. 4). The destination designated transition 203 is designated by the mouse provided in the input section 11.
(Step 101), by pressing the mouse button
(Step 102), the data setting unit 106 is activated,
An order designation panel P as shown in FIG. 5 is displayed on the display unit 17 (step 103). In the order designation panel P, an input frame P for setting the order of sending the tokens
1 is provided. When the data setting unit 106 is activated for the first time, the destination field of the input frame P1 is blank. Now, the place 204 is named "line1", the place 205 is named "line2", the place 206 is named "line3", and the tokens are sent in the order of the places 204, 205, and 206. In this case, first, specify the destination field corresponding to the firing order "1" in the input frame P1 with the mouse (step 104) and select the destination "l" from the keyboard.
"ine1" is input (step 105). Similarly, "l
ine2 ”and“ line3 ”are also firing order“ 2 ”,“ 3 ”
Enter in the destination field corresponding to. Repeat this input operation until all destinations are specified (Step 10
6). After the setting is completed, it is confirmed whether or not the setting should be canceled (step 107). If the setting is canceled, the processing is terminated as it is, and if the setting is not canceled,
The input data is stored in the user description portion 103 of the transition data 101 (step 108), and then the process ends.

When executing the simulation, the user instructs the simulation start from the input unit 11 to activate the simulation executing unit 108,
Based on the Petri net diagram created earlier, transitions that satisfy the firing conditions are fired in sequence.

When a transition is fired, the transition data 1 is calculated by the evaluation unit of the Petri net processing unit 104.
The user description part 103 of 01 is evaluated, and the tokens are sent from the transition to each place at each firing in the order based on the evaluation result.

In the above example, the place 204, the place 205, and the place 2 are set in the destination designated transition 203.
Since the tokens are designated to be sent in the order of 06, the destination designated transition 203 is only in the place 204 at the end of the first firing, only in the place 205 at the end of the next firing, and in the place 206 at the end of the next firing. Only send out tokens.

FIG. 6 is a flow chart for explaining the operation of the evaluation section at the time of executing the above-mentioned simulation. The figure (a) shows the schematic flow chart, and the figure (b) shows the flow chart of the destination designation processing.

The destination designation transition has a "next destination place" as a local variable described by the user, in addition to the order data for sending the tokens. This variable is set to the pointer of the place to send the token at the end of the next firing. Immediately after setting the data, nil
The data is set.

When the simulation is started, the ignition process (step 151) and the ignition end process (step 15)
After step 2), destination designation processing (step 153) is performed.

In the destination designation process, the user description data is read (step 154), and it is checked whether or not the next destination place is designated in the user description data (step 155). The token is sent to the next destination place described in the description data (step 157). If not specified, the first place specified by the user description data is set as the next destination place (step 156), and the process proceeds to step 157. Next, the next destination place is set (step 158), and the process ends.

As a result, tokens can be sent from the same transition to different places at each firing, and a complicated process can be expressed with a small number of Petri net elements.

FIG. 7 shows a case in which the transition evaluation unit of the present invention has a function of determining the place to which the token is to be sent depending on the state of the place when the token is sent to the output place of the transition after the firing is completed. It is a Petri net diagram of. For the sake of convenience, the transition having the function of determining the place to which the token is to be sent according to the state of such a place will be referred to as a destination evaluation transition.

The structure of the Petri net diagram when this destination evaluation transition is used is the same as that of FIG.
The destination designated transition 203 is changed to a destination evaluation transition 403.

The evaluation method for sending out the token in the above-mentioned destination evaluation transition is set by the following procedure (see FIG. 8), for example. Input unit 11
Destination transition transition 403 with the mouse provided in
Is designated (step 201) and the mouse button is pressed (step 202), the data setting unit 106 is activated, and the evaluation method setting panel Q as shown in FIG. 9 is displayed on the display unit 17 (step 203). On the evaluation method setting panel Q, there are several selection frames Q1 to Q4 for selecting an evaluation method, such as “select minimum value”, “select maximum value”, “randomly select”, and “user description”. It is provided.

Among these selection frames, “select minimum value”, “select maximum value”, and “randomly select” are evaluation functions prepared in advance, and any of these evaluation functions can be selected by the mouse. If is selected (Step 2
04), the data corresponding to the evaluation function is stored in the user description portion 103 (steps 205 to 208).
“Choose the minimum value” is to set the token to be sent only to the place having the smallest token amount among the output places. "Choose maximum value", "Choose randomly"
Is also the same.

When "user description" is selected, it becomes possible to input in the user description frame Q5, and the conditional expression desired by the user is input in a predetermined simple language from the keyboard into the user description frame Q5. . For example, "line1"
Sum of the token amount of "line2" and the token amount of "line2"
Only when it is less than the token amount of "ine3"
When sending a token to "e3", IF ((line1
+ Line2) <line3) THEN (line2)
Is entered as a user description (step 20
7), written in the user description portion 103.

When executing the simulation, the user instructs the start of the simulation from the input unit 11 to activate the simulation executing unit 108,
Based on the Petri net diagram created earlier, transitions that satisfy the firing conditions are fired in sequence.

When the transition is fired, the transition data 1 is calculated by the evaluation unit of the Petri net processing unit 104.
The user description portion 103 of 01 is evaluated, and the place to which the token is sent is determined according to the state of the place based on the evaluation result.

Now, the destination evaluation transition 403
In the state of FIG. 7, the destination evaluation transition 403 shows that the token amount is minimum, that is, “2”, after the firing in the state of FIG. Send tokens only to place 204. Place 204
When the token amount becomes 4, the token destination is randomly selected if the token amount is the same, so at the end of the next firing, one of the places with the same token amount One is randomly selected and the token is sent to that place.

In the above description, the destination designation transition and the destination evaluation transition are different embodiments, but it is possible to designate which one of the destination designation transition and the destination evaluation transition is selected in the menu at the start of the apparatus. You may Further, the type may be designated after the transition is designated.

In the above embodiment, the tokens and arcs are not colored, but the same color as the token to be output is sent to all output places connected by the specified arc. The present invention can also be applied to such a colored Petri net.

In the above embodiment, the evaluation section is set for each transition. However, a destination designation transition, a destination evaluation transition, etc. are defined in advance, and then only some parameters are set. Can be used as a transition with a special function.

[0044]

As described above, according to the present invention, it is possible to set the order, rules, functions and procedures in the transition. Therefore, after the transition is fired, tokens are not always sent to all output places, and are determined by the order, rules, functions, and procedures set in the transition processing part. You can

(1) It is possible to describe a process that cannot be expressed only by a basic Petri net or a conventional extended Petri net.

(2) It is possible to easily express a complicated logical structure.

(3) The scale of the Petri net diagram can be reduced.

(4) It is possible to quickly create a simulation model.

(5) The Petri net diagram can be prevented from becoming complicated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

2 is a block diagram schematically showing a portion for processing transition data in the simulation device based on the Petri net shown in FIG. 1. FIG.

FIG. 3 is an explanatory diagram showing an example of a Petri net diagram using a destination-specified transition.

FIG. 4 is a flowchart showing a flow of setting processing when a destination designated transition is used.

FIG. 5 is an explanatory diagram showing an example of an order designation panel used when setting a destination designation transition.

FIG. 6 is a flowchart for explaining the operation of the evaluation unit when executing a simulation.

FIG. 7 is an explanatory diagram showing an example of a Petri net diagram using a destination evaluation transition.

FIG. 8 is a flowchart showing a flow of a setting process when a destination evaluation transition is used.

FIG. 9 is an explanatory diagram showing an example of an evaluation method setting panel used when setting a destination evaluation transition.

FIG. 10 is an explanatory diagram showing the principle of a Petri net.

[Explanation of symbols]

11: input unit, 12: processing unit, 13: storage unit, 14: place generation unit, 15: transition generation unit, 16: arc generation unit, 17: display unit, 101: transition data, 102: transition body, 103: User description part, 104: Petri net processing part, 105: evaluation part, 106: data setting part, 107: simulation model creation part, 108: simulation execution part, 20
1,202,204-206: Place, 203,40
3: transition, 207 to 211: arc

Claims (3)

[Claims] 1. A Petri net-based simulation apparatus comprising: a unit for creating a Petri net; a unit for displaying the created Petri net; and a unit for performing a simulation based on the created Petri net. Means for setting a transition function for the transition in, a means for storing the set function, a means for evaluating the stored function, and the evaluation after the completion of firing of the transition during simulation execution. A simulation device based on a Petri net, characterized in that: means for sending a token only to a place determined according to the result, and. 2. The petri net-based simulation apparatus according to claim 1, wherein the means for setting the transition function specifies an order of sending out tokens each time the transition is fired. 3. The means for setting the function of the transition sets the place to which the token should be sent next according to the token amount of a plurality of places to which the token should be sent. Simulation device based on Petri net.