JPH06149776A - Simulation device based upon petri net - Google Patents

Abstract

PURPOSE:To store a pattern icon, generated corresponding to a pattern model of a Petri net graph, in pair with the pattern model so that it can be utilized as a component as to the simulation device based upon the Petri net for simulating a production system, etc. CONSTITUTION:In the simulation device based upon the Petri net, a component control means 2-1 which saves a pair of the pattern model of the Petri net and the pattern icon generated corresponding to it in a storage device as the component and reads them out at a request is provided. Consequently, the pattern icon manually generated for the pattern model can be saved as the component and then utilized afterward.

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 for simulating a production system or the like.

[0002]

2. Description of the Related Art Flowing various parts and materials into a production line,
A discrete event system such as a production system in which a process is performed in several process steps to produce a certain product is simulated using a graph drawn by a Petri net. Parts that flow through the system are represented by tokens that move in the Petri net graph.

By performing this simulation,
You can get hints for constructing a system that can perform production as quickly as possible without causing excessive or insufficient parts in the production line. Such hints include information regarding the number of devices to be installed, information regarding the location and capacity of the intermediate buffer, and the like.

The Petri net is a kind of model proposed by C. Petri that expresses a discrete event system composed of a plurality of processes simultaneously proceeding in parallel. The components of a discrete event system are divided into conditions and events, "conditions" are represented by "places", "events" are represented by nodes called "transitions," and causal relationships between conditions and events are represented by "arcs" that connect the two. By modeling the system.

A graphical representation of the system elements such as "place", "transition", and "arc" by using simple figures (icons),
It is called Petri net graph. At present, such a Petri net graph is drawn and simulated on a display device of a workstation or a high-performance personal computer.

FIG. 2 shows the hardware structure of a conventional Petri net-based simulation apparatus. In FIG.
1 is a central processing unit, 2 is a control unit, 3 is a main storage unit, 4 is a display device (eg, CRT display), 5 is a data input device (eg, keyboard), 6 is a pointing input device (eg, mouse), Reference numeral 7 is an auxiliary storage device (eg, magnetic disk). The auxiliary storage device 7 is provided as needed. As a whole, it has a computer configuration.

To create a model of the system by the Petri net graph, the operator uses the data input device 5
Alternatively, the pointing input device 6 is operated to place and create icons such as places and transitions on the screen of the display device 4. This operation can be performed interactively with the screen. The control unit 2 converts the created model data into computer internal data and saves it in the main storage unit 3 or the auxiliary storage device 7.

FIG. 11 is a diagram for explaining the basic operation of the Petri net graph. In FIG. 11, 8-10 are places, 11-13 are tokens, 14 are transitions, and 15-17 are arcs. In general, a transition can be fired if there are more tokens than the number of arcs connecting the places with the transition in each place on the input side.

FIG. 11A shows a Petri net graph in a state before ignition. Place 8 has two tokens 11 and place 9 has one token 12. Places 8 and 9 and transitions 14
Since there are only one arc connecting each and, the transition 14 is ready to be fired.

When fired, as many tokens as the number of arcs connected to the transition are removed from each input place, and one token is given to the place on the output side. In addition, the method of putting in and out multiple tokens in the input place is so-called "first in first out",
The one that comes in first is taken out first. Figure 11
(B) shows the state after ignition.

FIG. 7 is a diagram for explaining the Petri net graph created by the simulation apparatus and the hierarchy. Figure 7
In the figure, 20 to 27 are places, 28 to 31 are transitions, 32 is a pattern model, and 33 is a pattern icon. FIG. 7A shows the following simulation model of the production system. The material is taken out from the warehouse (place 20), processed in the processing step A, then sent to the intermediate buffer (place 24), and transferred in the transfer step B.
And send it to the product storage (place 27). Then, in the first stage of the processing step A and the transfer step B, the worker (place 21) makes a setup.

The processing step A will be described in more detail. The transition 28 represents “setup”, but it is fired when a token exists in the place 20 (warehouse), the place 21 (worker), and the place 23 (processing machine). The presence of tokens in these places means that materials can be removed from the warehouse, workers can work, and processing machines can be used. At this time, the transition 28 representing “setup” is ignited, and after a predetermined setup time (ignition duration time) elapses,
The token is sent to the place 22 representing “waiting for processing” and the place 21 representing the worker. Next, transition 2
9 (machining) is ignited, and after a lapse of a predetermined machining time (ignition duration), a token is sent to a place 24 representing "intermediate buffer" and a place 23 representing "machining machine".

Similarly, the transition 30 constituting the transfer process B is "setup", the place 25 is "waiting for transfer",
The transition 31 represents “conveyance” and the place 26 represents “conveyance tool”. Then, when it becomes possible to carry out the setup, the setup is carried out and the conveyance is executed.

FIG. 7A shows only two steps and is not so complicated because the number of elements is small. But,
Depending on the production system, the number of elements and the number of processes are so large that they cannot be displayed at one time on the display surface, and scroll display or split display is required, which is difficult to see. If you try to force it to be displayed at one time and then reduce it, it will be hard to see.

Therefore, in order to simplify the Petri net graph, when there are a plurality of parts having the same arrangement and connection relation of the elements, the parts are regarded as one pattern,
Instead of that, one icon is displayed instead. This is what is called the layering of the Petri net graph.

For example, looking at the processing step A and the transfer step B of the Petri net graph of FIG. 7A, the placement of the places and transitions and the way of connecting by arcs are exactly the same. Therefore, this is captured as one pattern model. FIG. 7B shows the pattern model 32 thus captured. 1 when creating a Petri net graph using this pattern model 32
Two parts are defined (registered), and the auxiliary storage device 7 (see FIG.
Refer to)). Then, this is represented by a pattern icon 33 as shown in FIG.

FIG. 8 is a Petri net graph simplified by implementing layering. Reference numerals correspond to those in FIG. 7, and 33A and 33B are pattern icons. The pattern icon 33A represents the processing step A, and the pattern icon 33B represents the carrying step B. In contrast to the Petri net graph of FIG. 8 drawn using the pattern icons 33 (33A, 33B), the graph of the pattern model 32 of FIG.

The process of making FIG. 8 is as follows. If you want to place the machining process in the next stage of place 20,
The parts management window is opened at that position, the parts (pattern models) registered one after another are displayed, and when it is found that the pattern model 32 is available, it is decided to use it. Then, the pattern icon 33 is incorporated at a position where the processing step A is desired to be arranged. Even when it is desired to arrange the transfer process B in the next stage of the place 24, if the adoption of the pattern model 32 is determined in the same manner, the pattern icon 33 is incorporated.

Thus, the system having the same contents as that of FIG. 7A is represented as shown in FIG. 8 which is much simpler than that. The attribute variables (eg, firing duration) of each element of the processing process and the transportation process are opened by clicking the pattern icons 33A and 33B of FIG. 8 with the mouse (the pattern model 32 of FIG. 7B). Set for each element.

Conventionally, as the pattern icon 33 that replaces the pattern model 32, a ready-made icon (default shape icon) that has been created in advance is used, and regardless of the process contents of the pattern model 32,
The same thing was being displayed. In FIG. 8, as long as the same pattern model 32 is used, the same pattern icon 33 is displayed in both the working process and the carrying process.

Although the graph is simplified by this,
Since there is a drawback that it is difficult to distinguish the process contents, a shape that reflects the process contents is devised and an icon of that shape is created. Icon creation is shown in Figure 2.
The data input device 5 (or the pointing input device 6) is operated.

FIG. 9 shows an example of a pattern icon devised for a pattern model. 9A is a pattern icon 34 for the pattern icon 33 representing the processing step A of FIG. 8, and FIG. 9B is a pattern icon 35 for the pattern icon 33 representing the transfer step B of FIG. is there.

FIG. 10 shows the Petri net graph of FIG.
It is the figure represented using the pattern icon of FIG. If expressed in this way, the process contents can be displayed more easily than in FIG.

FIG. 6 is a diagram showing functional blocks of the simulation apparatus that operates as described above. Reference numeral 60 is a Petri net graph creation unit, 61 is a Petri net graph hierarchy management unit, 62 is a parts management unit, and 63 is a Petri net graph storage unit. The Petri net graph creation unit 60 represents a function of creating a Petri net graph by arranging places and transitions by the data input device 5 (or the pointing input device 6). This also creates the pattern icon.

The Petri net graph hierarchy management unit 61 manages the hierarchical relationship when the Petri net graph is hierarchized. For example, in the pattern icon 34 of FIG.
When the pattern model 32 of (b) is represented, the relationship is recorded. The parts management unit 62 manages the parts used to create the Petri net graph. When it is determined that the pattern model 32 is to be used as a component, this is registered as one component and managed so that it can be taken out when a request is made. The Petri net graph storage unit 63 stores the created Petri net graph.

As a conventional document concerning simulation based on Petri net, for example, “Measurement and Control” magazine September 1969 issue (Vol. 28, No. 9), P1-4.
3 and Japanese Patent Laid-Open No. 4-130953.

[0027]

[Problems to be Solved by the Invention]

(Problem) In the above-described conventional Petri net-based simulation device, since the pattern icon that has been created is not saved, there is a problem that it cannot be used even if it is used at a later opportunity.

(Explanation of Problems) Even if icons such as the pattern icon 34 and the pattern icon 35 are created for the pattern model 32 to create a Petri net graph as shown in FIG. The pattern icon 35 has not been saved as a part. Therefore, when creating another Petri net graph at a later opportunity, even if the pattern model 32 registered as a part is selected in an attempt to arrange the transfer process,
Appearing is the pattern icon 33 given as default, not the pattern icon 35.

Therefore, if it is desired to display the pattern icon 35, the data input device 5 (pointing input device 6) must be used again to recreate this icon. An object of the present invention is to solve such a problem.

[0030]

In order to solve the above problems, according to the present invention, a display device for displaying a Petri net graph, an input device for performing an operation for creating and editing a Petri net graph, and a storage device. And a petri net-based simulation device having a central processing unit that is connected to the display device, the input device, and the storage device and performs a process of creating and editing a Petri net graph, and creates the pattern model of the Petri net graph and the corresponding model. The pattern icon is stored as a part in the storage device as a part, and a part managing means for reading out the part when the request is made is provided.

[0031]

[Operation] In a simulation device based on a Petri net, a pattern model of a Petri net graph and a pattern icon created corresponding to the pattern model are paired and stored as parts in the storage device, and are stored when requested. A component management means for reading is provided. As a result, the pattern icon created by hand for the pattern model can be saved as a component and can be used at a later opportunity.

[0032]

【Example】

(Structure) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a hardware configuration of a simulation device based on the Petri net of the present invention. Reference numerals correspond to those in FIG. 2, and 2-1 is a parts management means. Since the parts having the same reference numerals as those in FIG. 2 operate in the same manner as the conventional one, the description thereof is omitted.

A feature of the present invention is that the control unit 2 is provided with a component management means 2-1 for managing a pattern model and a pattern icon devised corresponding to the pattern model as a pair. This means is implemented as software, for example. When a pattern icon is newly created by the component management means 2-1, it is paired with the corresponding pattern model and registered as a component in the auxiliary storage device 7.

FIG. 5 is a diagram showing a screen of the display device 4 when a component management operation is performed. 50 is a parts management window, 51 is a setting completion button, 52 is an edit stop button, 5
3 is a read button, 54 is a model name column, 55 is a comment column, 56 is an image column, and 57 is a pattern icon display column.

In the middle of creating a Petri net graph by arranging places and transitions one after another, the parts management window 50 is opened to check whether or not the process to be arranged is registered as a part. In the model name column 54, the names of pattern models registered as parts (eg, “machining process”, “conveying process”, “timer”, etc.) are written. Look there and choose what you need.

It is assumed that a Petri net graph including a timer T as shown in FIG. 3 is being created.
Note that 36 to 42 are places and 43 to 47 are transitions. Here, the operation of the timer T will be described. If the token exists in the place 41, the transition 44 fires. The firing duration here is 0, and tokens are immediately sent to places 38 and 39. When the token arrives at the place 38, the transition 43 can be fired (the operation is permitted) when the token exists at the place 36.

On the other hand, when the token comes to the place 39,
Transition 45 fires. If the duration of the transition 45 is set to be 10 seconds, the token is sent to the place 40 after 10 seconds. Place 3 at this point
Since there are tokens at 8 and 40, the transition 46 is fired. The token of the place 38 is lost, and the transition 43 cannot be fired (operation is not permitted). The firing duration here is 0, the token is immediately sent to the place 42, and the transition 4
7 ignites.

If the firing duration of the transition 47 is set to 5 seconds, the token is sent to the place 41 after 5 seconds. Then, the operation as described above is followed again, and the operation is permitted. In this way, an intermittent timer is realized in which after operating for 10 seconds, there is a rest of 5 seconds.

(Reading of Parts) Now, in drawing the above-mentioned timer part, the part management window 50 is opened when searching for whether or not a timer having an element structure as shown in the drawing is registered as a part. Model name field 5
When “Timer” is selected in 4, the comment as shown in the comment column 55 is displayed and the image column 56
The specific element configuration is displayed in. "1" described in the four corners means the number of connection terminals of this graph and other elements.

When looking at this and recognizing that it can be used, the read button 53 is pressed. Then, the pattern icon 48 registered as a part in a pair with the graph in the image column 56 is displayed in the pattern icon display column 57. Next, when the setting completion button 51 is pressed, the pattern icon 48 is incorporated at the position of the timer T, and the Petri net graph as shown in FIG. 4 can be created. If it is desired to cancel the incorporation, the edit cancel button 52 may be pressed.

(Registration of Parts) After creating the pattern icon 48 of FIG. 5 and replacing it with the pattern model of the configuration of the timer T of FIG. 3 for the first time, register the parts by pairing them as follows. Like Click the pattern icon 48 in the Petri net graph with the mouse,
The parts management window 50 is displayed. Image column 56
The graph of the timer T is fetched in, and the pattern icon 48 is fetched in the pattern icon display field 57. After performing necessary editing work such as entering the part name "timer" in the model name field 54, the setting complete button 5
Press 1. Then, the two are stored in the auxiliary storage device 7 (see FIG. 1) in a form associated with each other.

Although the present invention has been described by taking a part of a Petri net graph as an example, the present invention can also be applied to part management in a graph (eg, flowchart, PERT diagram) incorporating a hierarchical relationship.

[0043]

As described above, in the present invention, a pattern model of a Petri net graph and a pattern icon created corresponding to the pattern model are paired in the storage device as a part in the Petri net-based simulation device. A component management means was provided for saving and reading them when requested.

Therefore, it is possible to save the pattern icon, which has been created with difficulty once for the pattern model, as a component, and anyone can use it again and again at a later opportunity.

[Brief description of drawings]

FIG. 1 is a diagram showing a hardware configuration of a simulation device based on a Petri net of the present invention.

FIG. 2 is a diagram showing a hardware configuration of a conventional Petri net-based simulation apparatus.

FIG. 3 Petri net graph including a pattern model

FIG. 4 is a diagram of the Petri net graph of FIG. 3 drawn using a pattern icon.

FIG. 5 is a diagram showing a screen of a display device when a component management operation is performed.

FIG. 6 is a diagram showing functional blocks of a simulation device.

FIG. 7 is a diagram for explaining a Petri net graph created by a simulation device and hierarchical structure.

FIG. 8: Petri net graph simplified by implementing layering

FIG. 9: Pattern icons devised for the pattern model

FIG. 10: Petri net graph represented using pattern icons

FIG. 11 is a diagram illustrating the basic operation of a Petri net graph.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Central processing unit, 2 ... Control part, 2-1 ... Plural simulation condition setting means, 2-2 ... Icon changing means, 3
... Main storage unit, 4 ... Display device, 5 ... Data input device, 6 ...
Pointing input device, 7 ... Auxiliary storage device, 8 to 10
… Places 11 to 13… Tokens, 14… Transitions, 15 to 17… Arc, 20 to 27… Places, 2
8 to 31 ... Transitionon, 32 ... Pattern model,
33, 33A, 33B ... Pattern icons, 34, 3
5 ... Pattern icon, 36-42 ... Place, 43-
47 ... transition, 48 ... pattern icon, 50
... Parts management window, 51 ... Setting completion button, 52 ...
Edit cancel button, 53 ... Read button, 54 ... Model name column, 55 ... Comment column, 56 ... Image column, 57 ... Pattern icon display column, 60 ... Petri net graph creation unit, 61 ... Petri net graph hierarchy management unit, 62 ... Parts management unit, 63 ... Petri net graph storage unit

Claims (1)

[Claims] 1. A display device for displaying a Petri netgraph, an input device for performing an operation for creating and editing a Petri netgraph, a storage device, and the display device, the input device, and the storage device, In a Petri net-based simulation apparatus having a central processing unit that performs processing for creating and editing a Petri net graph, a pattern model of a Petri net graph and a pattern icon created corresponding thereto are paired as a part in the storage device. A petri net-based simulation device, characterized in that it comprises a component management means for storing and reading them when requested.