JPH06149773A - Simulation device based upon petri net - Google Patents

Abstract

PURPOSE:To easily represent complex logic constitution and evade a state wherein the Petri net diagram becomes complex by enabling a user to give the individual function to an arc. CONSTITUTION:The simulation device 1 based upon the Petri net is equipped with an arc function definition part 2 which allows the user to specify an arc in the Petri net and define a function for the arc and an arc function execution part 3 which executes the function of the arc on the basis of the function that the user defines when simulation is performed.

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 production line designers to learn how to use these 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. 8 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. 8A). After the completion of firing, 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, the simulation model of the production system can be represented visually, and complicated programming can be eliminated.

[0007]

However, in the conventional simulation apparatus based on the Petri net as disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-317805,
The arc has only the function of sending a token to the node at its end point, which is insufficient to simulate the process of the actual production system. Therefore, a so-called extended Petri net has been proposed in order to expand the function of the Petri net. In this extended Petri net, arcs can control the flow of tokens by the color and logical expression of tokens and can notify other nodes of the state of one node by using permit arcs or inhibition arcs. It was not possible to change the attribute of the token when passing. For this reason, it is difficult to express a complicated logical structure by a Petri net, and even if it is expressed, the number of nodes increases remarkably, which makes the Petri net diagram complicated and it takes time to create a simulation model. . In addition, such a Petri net diagram is extremely difficult for not only the creator but also a third party to understand. For this reason, in order to simulate a production line with complicated control using a conventional Petri net-based simulation device, considerable skill is required to express the control logic of a production machine in a Petri net, and many Was accompanied by difficulties.

Therefore, the present invention enables a user to give a unique function to an arc, thereby easily expressing a complicated logical structure and avoiding a complicated Petri net diagram. The purpose is to

[0009]

In order to achieve the above-mentioned object, the present invention specifies a petri net, a means for displaying the created petri net, and an arc in the petri net by designating the arc. It is provided with a means for the user to define a function for the arc, a means for storing the defined function, and a means for executing the function of the arc based on the function defined by the user when executing the simulation. Is characterized by.

[0010]

The operation of the present invention will be described with reference to the principle diagram shown in FIG.

According to the present invention, in addition to the simulation device 1 having the same structure as that of the prior art including the display unit 1a, the input unit 1b, the processing unit 1c, and the storage unit 1d as shown in FIG. Arc function definition part 2 for defining
And an arc function execution unit 3 that executes the defined function at the time of simulation. Correspondingly, in addition to the area 4 (see FIG. 2 (a)) for storing the data of the conventional arc consisting of the start point node, the end point node, the multiplicity, the graphic information, etc., the function data is added to the arc user A data area 5 for holding the function is newly provided. The arc function definition unit 2 has means such as a user function setting panel and means for starting this, and the arc function execution unit 3 executes the function set or described in the arc function definition unit 2. Have the means to do. The data area 5 newly added to the arc is given to the arc that called the arc function definition unit 2.

When the simulation is executed, the token from the input place passes through the arc and reaches the output place, but when the token passes through the arc, the arc function defined by the arc function definition unit 2 The arc function execution unit 3 controls the passage of the token according to the function.
For example, if an arc is defined so that a token cannot pass within a predetermined time, the token is suspended from passing within that time, and after that time the token passes and the process proceeds. To do.

[0013]

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. 3 is a block diagram showing the configuration of the embodiment of the present invention. The input unit 11 is composed of a keyboard and a mouse, and a place forming a Petri net,
It is used for inputting positions of transitions, arcs, etc., for inputting arc functions, or for instructing 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.

Tables 1, 2 and 3 show examples of data structures of place data, transition data and arc data.

[0016]

[Table 1]

[Table 2]

[Table 3] The data of places, transitions, arcs, etc. generated as described above is supplied to the display unit 17 such as a CRT display, and the Petri net is displayed.

In the present embodiment, in addition to the above-mentioned configuration, an arc function defining section 18 for the user to define the arc function and an arc function executing section 19 for executing the defined arc function. Is provided.

Next, with reference to the flow chart of FIG. 4, the operation of the above-described simulation apparatus when the user defines the arc function will be described.

Now, place 5 as shown in FIG.
1, 52, 53, transition 54, arc 55, 5
A case will be described in which a Petri net graph composed of 6, 57 is displayed on the display unit 17, and a user function is defined for the arc 56.

First, the mouse provided on the input section 11 is used to move the mouse cursor C to the position of the arc 56, and the mouse button is pressed to specify the arc 56 (step 101). Then, by pressing the selection item menu display button provided on the mouse (step 10
2) The arc function defining unit 18 is activated via the processing unit 12, and the selection item menu M as shown in FIG. 5 is displayed on the display unit 17 (step 103). The selection item menu M includes, for example, three items of “attribute setting”, “edit”, and “user function setting”. Here, when "user function setting" is selected from the menu with the mouse (step 104), the display unit 17 displays a user function setting panel P for user definition as shown in FIG.

On the user function setting panel P, some functions are prepared in advance in the form of buttons. It should be noted that the button here means a small rectangular area displayed on the display unit 17, which is designated by the mouse cursor C and is not actually physically pressed. In the example of FIG.
There is a color conversion button P1 for converting the color of the token in the colored Petri net, a variable button P2 for accessing the variable held by the token, and a user-described button P3 for defining the function of the arc with an expression or the like. To do.
When the color conversion button P1 is pressed, it becomes possible to input the input color and the output color, and the color of the token having the color specified by the input color when the token passes through the arc during the simulation execution becomes the output color. To be converted. When the variable button P2 is pressed, the variable name and data can be input, and when the token passes through the arc during simulation, the value of the token variable specified by the variable name is specified by the data. It will be a value. Further, when the user description button P3 is pressed, it becomes possible to input a conditional expression in the description field P4, and it becomes possible to describe complicated processing as necessary. This description is, for example, "Sma
lltalk (registered trademark of Xerox, Inc., USA).

Here, an example of user description will be described. For example, when the manufacturing process of a product is represented by a Petri net graph, the product flow is represented by a token flow. In the transition, if the condition of the input place is satisfied, it is fired and changes to the next state, but in the actual manufacturing process, the work may not be progressed just by satisfying the input condition.
For example, during the lunch break at the manufacturing plant, even if the raw materials and materials are available and the manufacturing machines are in operation,
No work is actually done. Therefore, when expressing the manufacturing process of a product by a Petri net graph, it is necessary to be able to express such a time limitation. For example, assume that the lunch break is from 12:00 to 13:00 and the time required to complete the process is 30 minutes.
In this case, no new work can be accepted from 11:30 to 13:00. This condition is described above in "S
It is as follows when described by "malltalk (registered trademark)".

(TIME> 11:30) & (TIME <13:00) if True: [↑ false] This formula is False from the current time TIME from 11:30 to 13:00. It indicates to return. Note that TIME is a global variable that holds the simulation time.

The above various data input using the user function setting panel P is stored in the storage unit 13 via the processing unit 12.

If "attribute setting" or "edit" is selected in the menu selection in step 104, the corresponding processing is performed (step 10).
7, 108). That is, by selecting the attribute setting, it is possible to set the multiplicity of the arc and the arc settings such as normal, permit, and inhibit, and by selecting the edit, it is easy to see the shape of the arc on the screen. It can be transformed by operating the mouse.

Next, the operation at the time of executing the simulation will be described with reference to the flowchart of FIG.

When the start of the simulation is instructed from the input unit 11, the simulation time is set (step 201) and it is determined whether or not all the transitions can be fired at that time. The details of the determination of whether or not the transition is fired are as follows. First, a transition is selected (step 202), an input arc of the transition is selected (step 203), and whether or not there are tokens of multiplicity indicated by each arc in the input place ahead of the input arc. Is determined (step 204). When the token exists, True is returned as the determination result. If the token does not exist, False is returned and the process moves to the next transition (step 205). Next, in the arc function execution unit 19, if there is a user description of the arc, it is executed (step 206), and the execution result is Tru.
If it is e, True is returned (step 207). If the execution result of the user description is False, False is returned, and the process moves to the next transition (step 20).
5). The same processing is performed for all input arcs (steps 208 and 209), and when the determination result is true for all input arcs (step 210),
The transition is set as an ignition candidate in the array (step 211).

Next, a transition that can be fired is checked from among all the transitions (steps 212, 21).
3) At random, one transition is extracted and ignition work is performed (step 214).

The above process is repeated until there are no transitions that can be fired.

Next, the transition whose firing ends at the earliest time is taken out from the fired transitions,
Carry out the work to end the ignition. That is, the token is set in the output place of the transition (step 215) and the simulation time is advanced (step 216).

In the same manner, transition firing and token output are repeated in the same manner to sequentially represent the movement of the production system.

The simulation is executed as described above, and the design plan of the production system is evaluated based on the obtained result. The simulation itself using the Petri net is described in the above-mentioned JP-A-62-27725.
Since it is disclosed in Japanese Patent Publication No. 0, etc., it will not be described in detail here.

In the present embodiment, the arc function executing section is called by the simulation executing section existing in the processing section 12, but it can be incorporated in the simulation executing section.

[0034]

As described above, according to the present invention, the arc function defining portion for the user to define a certain function in the arc and the arc function executing portion for executing the defined function during the simulation are provided. Therefore, when the token passes through the arc, it becomes possible to change the attribute of the token. For this reason, it is easy to express a complicated logical structure by using a Petri net with a complicated logical structure, and the number of nodes in the expressed Petri net can be reduced, so that the Petri net diagram is simplified and the simulation model can be created in a short time. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of the present invention.

FIG. 2 is an explanatory diagram showing a storage state of arc data according to the present invention.

FIG. 3 is a block diagram showing an example of this embodiment.

FIG. 4 is a flowchart for explaining a user function setting process in this embodiment.

FIG. 5 is an explanatory diagram showing a selection item menu displayed when a user function is set.

FIG. 6 is an explanatory diagram showing a user function setting panel displayed when performing user function setting.

FIG. 7 is a flowchart for explaining a process at the time of executing a simulation.

FIG. 8 is an explanatory diagram showing the principle of a Petri net.

[Explanation of symbols]

1: Simulation device, 2: Arc function definition unit,
3: arc function execution unit, 4, 5: data area, 11: input unit, 12: processing unit, 13: storage unit, 14: place generation unit, 15: transition generation unit, 16: arc generation unit, 17: display Part, 18: arc function definition part, 19: arc function execution part

Claims (1)

[Claims] 1. A means for creating a petri net, a means for displaying the created petri net, and means for designating a function for a user by designating an arc in the petri net. And a means for storing the function, and a means for executing the arc function based on the function defined by the user when executing the simulation.