JPH04130957A - Simulation method based upon petri net graph - Google Patents

Abstract

PURPOSE:To provide a transition with an arithmetic function by including a program to be started at the time of igniting the transition in transition data indicating the attribute of the transition. CONSTITUTION:A transition tr2 is provided with an arithmetic function for applying an OK or NG identifier(ID) to a token with prescribed probability. When token exists in an inspection waiting product arranging place pl2, the inspection specifying transition tr2 is ignited. The transition tr2 is programmed so as to produce non-defective units of 80% probability and defective units of 20% probability by the program started at the time of igniting the transition tr2. A token to which an OK ID for a non-defective product or an NG ID for a defective unit is added is newly formed and outputted to the place pl3 after the lapse of a given ignition continuing time. A token having the OK or NG ID based upon the prescribed probability is added to a temporarily stored token by the program started at the time of igniting the transition tr2.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for simulating a design proposal for a discrete event system such as a production system on a workstation or a high-performance personal computer using a Petri net graph. It is.

[Conventional technology]

For example, when designing a production system consisting of processing machines, assembly machines, workers, transport equipment, etc., the number of individual components necessary to achieve the target production capacity, the arrangement of intermediate buffers, etc. It is necessary to carefully consider its capacity, etc.

In such cases, it has traditionally been the practice to create a simulation model using a general-purpose language or a language specific to Siminiregion, and perform simulations to evaluate various design proposals. However, it has been difficult for ordinary production line designers to learn how to use these languages, making it difficult for them to master them.

In order to solve the problem 3 above, many methods have recently been proposed that use graph representations of Petri nets to visually and easily create models of simini-regions. (“
Measurement and Control J, VOl, 28. Nα9, p74
5 to P787, etc.) A Petri net graph is a model that divides elements in a system into conditions and events, represents conditions with nodes called places, and events with nodes called transitions, and expresses a model with a graph that connects the relationships between conditions and events with arcs. It is. Then, the establishment of the condition is expressed by placing a token in a place, and the system's Guinamitics is verified by firing a transition according to the movement state of this token. The above places, transitions and arcs are the first
It is represented by place data, transition data, and arc data as shown in Tables 3 to 3.

Table 1, Table 2, Table 3, and Figure 6 (a), et al. are examples of Petri net graphs.
When there is a token in all manual braces PLI and PL2, the transition TR can be fired (see figure (
(See a)), turn-on brace PLI, PL2 after firing ends
Remove tokens one by one from output brace PL3
This shows how the token is output (see (b) in the same figure). By using the graph representation of this Petri net, it is possible to visually represent a simulation model of a discrete event system such as a production system, and it is possible to eliminate the need for complicated programming.

However, in the traditional basic Petri net graph (a) Unable to express the concept of time.

) It is not possible to express arithmetic processing.

(C) Tokens cannot be identified and unique control cannot be performed for each token.

(6) Logic other than AND cannot be expressed.

There is a problem.

Therefore, for (a), we use a temporal Petri net that introduces the concept of time, for (C), we use a colored Petri net that has different attributes for each token, and for (d), we use a time Petri net that introduces the concept of time, and for (d), we use , switches, forbidden arcs, etc. have been proposed (see the above-mentioned document ``Measurement and Control'').

[Problem to be solved by the invention]

However, although it is possible to deal with (a) by devising the representation of the graph, the scale of the net used to express the calculation process becomes large, which impairs visibility, which is an advantage of Petri nets. There's a problem.

The present invention solves the above-mentioned problems and makes it possible to easily express arithmetic processing in a system modeled by a Petri net.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a program that is started based on the firing of the transition in transition data representing attributes of the transition, and when the transition is fired, the program that is started based on the conditions specified by the program is It is characterized by changing the attributes of the token that passes through the transition.

[Effect]

The effects of the present invention will be explained by giving specific examples.

FIG. 1 is a functional block diagram showing an outline of the present invention.

In the figure, in addition to conventional basic Petri net graph elements such as places, transitions, and arcs, a Petri net graph creation unit 101 generates a transition firing duration, a startup program when a transition fires, a token and an arc identifier, an inhibiting arc, and an enabling arc. It creates, displays, and manages Petri net graphs with extensions such as

Tables 4 to 7 show examples of the structure of Petri net data in the present invention. Table 4 is place data, Table 5
The table shows transition data, the 6th table shows arc data, and the 7th table shows token data.

Table 4 Table 5 (hereinafter referred to as margin) Table 6 Table 7 Note that the attributes of the token data include, for example, the number of repairs.

The created Petri net graph is stored in the Petri net graph storage unit 102.

Based on the Petri net graph stored in the Petri net graph storage unit 102 , the simulation execution unit 103 determines that all input braces have tokens with the same identifiers as the input arcs, and all the places connected by inhibition arcs have tokens. fires a transition that satisfies the transition firing condition that does not exist and tokens exist in places connected by all permission arcs,
It executes the transition firing startup program written in the transition, outputs tokens with matching identifiers to all output arcs after the transition firing duration time has elapsed, and at the same time outputs tokens with matching identifiers to all output arcs.
4 to memorize the execution process. This operation is repeated in sequence and ends when there are no more transitions that satisfy the transition firing conditions.

The flow of the above processing is shown in FIG. FIG. 2(a) is a flowchart showing the overall flow;
C) is a routine showing the process of inquiring whether arc ignition is possible;
(6) in the same figure is a routine showing processing for transition ignition, (e) in the same figure is a routine showing processing for starting arc ignition,
FIG. 5(f) shows a routine showing the process of ending arc ignition, and the mark (marked in the same figure) shows a routine showing the process of the start-up program at the time of ignition.

The stain corrosion result evaluation unit 105 processes and edits the data stored in the simulation execution process storage unit 104 to obtain evaluation indicators for the production system design plan.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 is an overall configuration diagram of a workstation for implementing the present invention. In this figure, 200 is a central processing unit equipped with a control device f201 and a main memory device 202, 203 is a display device such as a bitmap display, 204 is a data input device such as a keyboard, and 205 is a data input device such as a mouse. Bointing manually made lid, 206 auxiliary storage device such as a magnetic disk, 20
7 is a printing/drawing device such as a laser printer.

Here, the correspondence between FIG. 1 and the embodiment of the present invention will be shown. b) The IJ net graph creation unit 101 is the control device 201,
Display device 203. Data input device 204. In the Bointink human power system W2O5, the simulation execution unit 103 and the simulation result evaluation unit 105 are connected to the control device 20.
1, the Petri net graph storage unit 102 is a main memory bag! 202, the siminilation execution process storage unit 104
corresponds to the auxiliary storage device 206.

In this example, the Petri net is
It has the structure shown in Table 7, and as shown in Table 5,
By introducing a time element into the transition data, it is possible to express the firing duration of the transition, and a token is output after this time has elapsed. The time is given either by a fixed method or by a random variable. Furthermore, by adding a program called an action to the transition data that is started when the transition fires,
It is possible to perform processing according to the token identifier, such as changing the firing duration and determining the attribute setting of the output token according to the state of the place.

In addition, as shown in Tables 6 and 7, by assigning identifiers to token data and arc data and allowing tokens to pass through only arcs with matching identifiers, control according to the type of token can be performed. It becomes possible.

Furthermore, as shown in Table 6, an inhibition arc and a permission arc are provided in the arc from place to transition, and the inhibition arc prohibits firing when a token exists in the place, and the permission arc only fires when a token exists in the place. By allowing firing, NOT logic can be easily expressed.

FIG. 4 is a model of the product inspection and adjustment process using the method of the present invention. The inspection and adjustment process has a storage area for products waiting for inspection with a capacity of 5, from which products are taken out one by one and inspected. Products pass inspection 80% of the time and are sent to the packing area. The 20% that are defective are adjusted in the adjustment process and then sent back to the product storage area awaiting inspection. In addition, pH ~ p+4 in the figure
indicates a place, trl to tr4 indicate a transition, and acl to aclo indicate an arc. In this embodiment, the transition tr2 is equipped with an arithmetic function that assigns an OK or NG identifier to a token with a predetermined probability. Further, it is assumed that an OK identifier is assigned to the arc ac7, and an NG identifier is assigned to the arc ac9.

In Figure 4, the product has arrived at the place pH and has a volume of 5
If there is space in the inspection waiting product storage place 1112, the transition tri is fired and the inspection waiting product storage place p12 is entered. When five products accumulate in the inspection waiting product storage area, the firing of the transition trl is prohibited by the inhibition arc ac3 from the place p12 to the transition tri.

If a token exists in the inspection waiting product storage area place p12, the inspection process transition tr2 is fired. In this embodiment, this inspection process transition tr2
is programmed to generate a non-defective product with an 80% probability and a defective product with a 20% probability by the program (see Table 5 and Figure 2 ((to)) that is activated when a fire occurs.
Generate a new token (see Table 7) with an identifier of OK for a good product and NG for a defective product, and place p after the given firing duration time (see Table 5) has elapsed.
Output to +3. Specifically, in the transition firing flow shown in Figure 2 (6), a token whose identifier is OK or NG is added to the -time storage token with a predetermined probability by the trigger-on-fire program shown in Figure 2 (Figure 2). If the output token is OK, use the token identifier and the transition t from place p+3.
The identifiers of the arcs to r4 (see Table 6) match, the transport transition tr4 to the packaging area is fired, and a token is output to the packaging place p14 after the firing duration time has elapsed. If the output token is NG, the token identifier and the identifier of the arc from place p13 to transition tr3 match, and the adjustment process transition tr
3 is fired, and the token with the NG identifier erased by the action program activated at the time of firing is output to the inspection waiting product storage place p12 after the firing duration time has elapsed.

This operation is repeated in sequence and ends when there are no more transitions that satisfy the firing conditions. At the same time, this process of execution is
It is stored in the simulation execution process storage unit 104.

The simulation result evaluation unit 105 processes the data stored in the simulation execution process storage unit 104,
Edit and obtain evaluation indicators for production system design proposals.

When trying to express the Petri net shown in FIG. 4 with a conventional V)IJ net, as shown in FIG. 5, eight transitions tri, tr3. tr4. tr21~t
r25 and 7 place pH, I)12. p14~
p16. p131°p132 are required, making it very complicated.

Furthermore, in the conventional Petri net shown in Fig. 5, 1
4 transitions trl vs. 4 transitions t
r22 to tr25 correspond to a ratio of defective products to non-defective products of 1:4, and if this ratio were 1=8, tr26 to tr29 would be required following tr25, making the configuration even more complicated.

In the above-described embodiment, the action program is started at the same time as the action is fired, but it may be started a certain period of time after the action is fired.

Furthermore, in the above-mentioned embodiment, the production system is expressed using a Petri net, but the present embodiment is not limited to this, and a simulation of a system that can be expressed using a Petri net is performed. It can be applied in any case, and the same effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, by providing the transition data indicating the attributes of the transition, which is a Petri net element, with a program that is activated when the transition is fired, it is possible to provide the transition with a calculation function. .

This makes it possible to use a simple graph representation to perform processing according to the identified copy of the token, such as changing the firing duration, setting the attributes of the token to be output, and making decisions according to the state of other places. becomes.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of the present invention, FIG. 2 is a flowchart showing the processing at the time of siminilation of a Petri net graph according to the present invention, and FIG. 3 is a configuration diagram of a workstation for implementing the present invention. Figure 4 is an explanatory diagram of the Petri net graph of the product inspection process expressed according to the present invention;
The figure is an explanatory diagram of the Petri net graph of the product inspection process expressed by the conventional example corresponding to the Petri net graph of Figure 4, No. 61! 1 is an explanatory diagram showing the basic representation of a Petri net graph. 101: Vetri Net Graph Creation Diagram 102: Vetri Net Graph Storage Unit 103: Simulation Execution Unit 104: Simulation Execution Process Storage Unit 105 Niji Mini Region Result n Value m 200: Central Processing Unit 201: Control Unit 202:
Main storage device 203: Display device 204: Data input device 205: Pointing input device 206: Auxiliary storage device 207: Printing/drawing device a
cl ~ aclO: arc pH ~ p14 nibrace trl ~ tr4: ) transition

Claims (1)

[Claims] 1. A program that is activated based on firing of the transition is included in transition data representing attributes of the transition, and when the transition is fired, the attributes of a token passing through the transition are changed based on conditions specified by the program. A simulation method based on Petri net graphs.