JP2510313B2 - Assembly sequence planning expert system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention plans an assembly sequence of products to be produced on that day in order to implement a mixed production system in which product groups to which different options are added are assembled on the same line. For the system.

[Prior Art] In the production method as described above, the daily production model number, that is, the production number of each option to be added, is fixed on one regular day before assembly, for example, on the previous day. The work that determines the order in which the production models for one day are sent to the assembly line is called the assembly sequence plan. The most basic idea in this assembly sequence plan is leveling, and the man-hour load in each process It is important to stabilize the process by minimizing the fluctuation of

In the planning process, the defective parts that cause the concentration of load are corrected by trial and error by manually judging the quality of the plan, and for the purpose of speeding up the planning process and the dispersion of the planning accuracy among planners. To avoid this, automation using a computer has been considered.

For example, there is an OR-like modeling method that calculates the line balance using standard man-hours in order to obtain the optimum solution of the assembly sequence plan. However, the problem of the assembly sequence planning has complicated constraints, and the conditional expression of the model can be solved only by calculating the combination of all the sequences and determining the optimum solution. This method is not practical because the number of combinations explosively increases and even if a high-speed computer is used, this calculation is impossible in a realistic time.

[Problems to be Solved by the Invention] An assembly sequence planning system that is automated by using a computer, determines a satisfactory assembly sequence plan within a practical time, and easily responds to changes in conditions such as a production plan. Is to provide.

[Means for Solving the Problems] In order to solve the above problems, the assembly sequence planning system according to the present invention includes: 1) an input unit for inputting the number of products to be assembled; 2) sequentially from a plurality of options in accordance with priority. A rearrangement processing unit for selecting a notable option and rearranging the assembling order of products to be assembled, 3) Corresponding to a distribution state in the assembling order of products having the notable option selected by the rearranging processing unit An evaluation value calculation unit for calculating an evaluation value, 4) a comparison unit for comparing the evaluation value with a set reference value, 5) evaluation knowledge for evaluating a production sequence of a product having an option to be noted, and attention to Knowledge base with rearrangement knowledge for rearranging the production sequence of products with options, 6) Evaluate the evaluation value above the standard value for all sequentially selected options. In order to determine the satisfactory assembly sequence, a control unit that activates the rearrangement processing unit, the evaluation value calculation unit, and the comparison unit using the knowledge base, 7) an output unit that outputs the satisfactory assembly sequence, The sorting knowledge is sorted by focusing on the selected option with lower priority under the constraint that the order of products having the high priority option already used for sorting is not changed. When the evaluation value of the order regarding the option being rearranged is below the reference value due to the constraint of the high priority option already used for rearrangement, with the first rule for performing rearrangement. In order to alleviate the restrictions of the first rule, the order of products having high priority options already used for sorting does not fall below the reference value. It is characterized in that it comprises a second rule again rearranged in.

[Operation] This system is an expert system constructed by a so-called knowledge engineering approach, which analyzes the thinking process of skilled persons in the assembly sequence planning work and expresses it on a computer.

The procedure for deciding the plan is as follows: When the number of assembled products of each additional option within a certain period, for example, for one day, is taken in via the input unit, a predetermined option (for example, high priority is given). (In order from option)
Paying attention to, the rearrangement is performed in the assembling order having the evaluation value exceeding the preset reference value. By performing this operation while paying attention to each option, a finally satisfying assembly order is determined. At that time, as a result of rearranging a certain option, when the load level evaluation value falls below the reference value set for that option, the level evaluation value has already exceeded the reference value. Relax the constraint of the option array with a high degree within the standard value of each option, rearrange the array of options with a higher priority than itself, and rearrange them to determine the product launch order solution. .

Here, when the terms are defined, "option" is a specification that can be selected by the orderer's will as to whether or not to add it separately from the basic specifications of the product. The term "is a distribution situation in which, when attention is paid to a specific option having an assembly order, products that should be equipped with the option and products that are not equipped with the option are lined up on the manufacturing line. Also, from the viewpoint of the load on the manufacturing line, the priorities are determined in the order of relatively high leveling demand among multiple types of options, but the option with a higher leveling priority than a certain option. Is called "priority option". further,
In the sorting process in which the options to be focused on are sequentially selected from a plurality of options according to the priority and the sorting is performed, in the sorting focused on the option A,
An option having a higher priority that has already been used for rearrangement, that is, a priority higher than A is expressed as a high-order option.

[Effects of the Invention] Unlike a system that obtains an optimal solution using an OR method such as linear programming, a preset criterion is set based on knowledge built on a computer using a knowledge engineering approach. Since this is a system that seeks a satisfying solution that selects a higher equal order, the assembly order is determined within a practical time, and the desired leveling of all the multiple options to be noted is guaranteed with quantitative accuracy. It will be realized under. Further, it is possible to easily and promptly respond to a change in the production plan or the like by changing the setting of the reference value or modifying the knowledge base for evaluation and rearrangement as necessary.

[Embodiment] The overall configuration of an assembly sequence planning expert system according to the present invention is shown in FIG. The input unit 1 which receives the model of the product to be assembled for one day and the presence / absence of various options and the number of them from the host computer through the communication means or the magnetic or optical storage means receives the data from the I / O interface. Send to 2. The interface 2 has a function of converting this data into a format readable by the main body of the expert system. On the contrary, it also has a function of sending the result derived by the main body of the expert system to the output unit 3 such as a printer or a CRT. The main body of the expert system comprises a knowledge base 4 and a control unit 5 as an inference engine.

The knowledge base 4 includes rearrangement knowledge 41, evaluation knowledge 42, and reference value 43 for each option. Sorting knowledge 41
Is basically the knowledge of the rearrangement that is necessary to evenly distribute the products to which the option with a large number of man-hours is added to the assembly line without continuing, and pay attention to the option with a higher priority first. After the rearrangement is performed, there is a rule for rearranging by paying attention to the option with the next priority under the constraint that the order of products having this option is not changed. Furthermore, due to the constraint condition of the prioritized option that has been noticed earlier and has already been sorted, the evaluation value of the order for the option with a lower priority than the prioritized option during the sorting process is lower than the reference value. In this case, a rule is included in which the rearrangement is performed again as long as the order of the higher-order options for which the rearrangement has been completed does not fall below a reference value described later. The evaluation knowledge 42 includes rules and the like for calculating the evaluation value by evaluating the average arrangement of the worst arrangement part or the whole regarding the rearranged assembly order. In other words, when paying attention to an option, the method of using the place where the products with the option are most concentrated in a line as the point of evaluation, and the product with the option added from the entire assembling sequence in one day In this method, the point of evaluation is whether or not the distribution is uniform. The reference value 43 stores a reference value for each option, but this value may be input when the system is started or may be stored in advance as a database.

The control unit 5 includes a rearrangement processing unit 51, an evaluation value calculation unit 52, a comparison unit 53, and a reference value changing unit 54. The rearrangement processing unit 51 rearranges the assembly order by using the rearrangement knowledge 41, and the evaluation value calculation unit 52 calculates an evaluation value by using the evaluation knowledge 42 for the rearranged assembly order, and compares them. The unit 53 compares the reference value of the option obtained from the reference value 43 with the calculated evaluation value and determines whether the rearranged order is satisfactory. Further, the reference value changing means 54 is used in a special case, but due to mutual interference of each option,
If the rearrangement does not succeed, it has a function of lowering the reference value of a specific option based on the input through the input unit 1.

Next, the process flow of the assembly sequence planning expert system according to the present invention will be described with reference to the flowchart shown in FIG.

In step 10 (hereinafter referred to as # 10), data indicating the products to be assembled for one day, which are sent via the input unit 1, are loaded into the work area of the expert system. In step # 15, the option reference value 43 is accessed for each option given to the input product to be assembled, and the corresponding reference value is set. In # 20, it is determined whether or not there is a noticeable option for rearranging the ranking, and if YES, the process proceeds to # 25. In # 25, based on the rearrangement knowledge 41, rearrangement is performed on options that should be noted at this point. The knowledge of sorting here is
For example, there is a rearrangement constraint condition such that the already defined order of prioritized options is not changed. # 30
In, the evaluation knowledge for the order sorted by # 25
The evaluation value calculation unit 52 calculates the evaluation value based on 42.
In # 35, the evaluation value and the reference value are compared, and if the evaluation value exceeds the reference value, the process jumps to # 20 to check the option to be noted for the next sorting. If the evaluation value is less than or equal to the reference value, proceed to # 40. In # 40, we re-focus on the higher priority options that were noticed earlier than the options we are currently looking at, that is, relax the constraints, but the range where the evaluation value exceeds the corresponding reference value. The rearrangement is performed in. In # 45 and # 50, the evaluation value is calculated in the same way as in # 30 and # 35, and the evaluation value is compared with the reference value. If the evaluation value exceeds the reference value # 20
Jump to, and if the evaluation value is less than or equal to the reference value, proceed to # 60, inquire whether to change the reference point and rearrange, and if YES, jump to # 15 and set the reference value again. . If no, jump to # 20. #
In the case of NO in 20, that is, when there are no more notable options, the final result is output in # 65 and the process ends.

Next, the rearrangement procedure of the present system will be described with a specific example.

FIG. 3 (a) shows the initial state of the assembly sequence. Here, it is assumed that the options added to the basic specifications of the product have higher priority in the order of A, B, and C options. First, the rearrangement is performed by paying attention to the highest-order (highest priority) A option. That is, in the fifth and sixth products, since the products to which the A option has been added are continuous and thus the evaluation points are bad, the sixth and ninth products are replaced. By this replacement, the new order becomes the order shown in FIG. 3 (b). Next, the B option is rearranged, and the rearrangement is performed. However, since there is a constraint condition that the order of products having the A option is not changed, the 10th and 12th are interchanged. As a result, the assembly order is as shown in FIG. Next, the C option is focused on and the rearrangement is performed. At that time, there is a constraint condition that the order of the products having the A option and the B option is not changed. The rearrangement such as exchanging the 9th and 9th is impossible, and when the evaluation value of the order of the C option exceeds the reference value of the C option, the assembling order shown in FIG. 3C is the final result. .

However, when the standard value of the C option is high and the evaluation value of the order of the C option is lower than the standard value of the C option, the constraint condition of the upper option is relaxed, and the evaluation value of the order of the A and B options is the standard value. The rearrangement is performed so as to increase the evaluation of the C option, at the expense of a certain decrease in the range above. For example, if the reference value is set such that the interval of the B option arrangement should be 1 or more, it becomes possible to interchange the 6th and 7th, and the final result of the assembly sequence is shown in FIG. The order is as shown in d).

So far, in order to explain the assembly sequence planning expert system according to the present invention, the assembly sequence of products to which various options are added to a common basic specification has been taken up, but instead of this, products of different types are assembled. Assuming a line in which such a product flows, the basic man-hours of those products are regarded as the above-mentioned basic specifications, and the man-hours added to the basic man-hours of each product are considered as the above-mentioned option, so that an assembly line in such an assembly line is considered. The planning expert system according to the present invention can also be applied to sequence planning.

[Brief description of drawings]

FIG. 1 shows an embodiment of an assembly sequence planning expert system according to the present invention. FIG. 1 is an overall configuration diagram, FIG. 2 is a flow chart showing a processing procedure, and FIGS. 3 (a) to 3 (d) are rearranged. It is explanatory drawing which shows a mode. (1) …… Input section, (3) …… Output section, (4) …… Knowledge base, (5) …… Control section, (51) …… Sort processing section, (52) …… Evaluation value calculation Department, (53) …… Comparison department.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Fukunaga No. 10 Sakano Nitta, Taniwahara Village, Tsukuba-gun, Ibaraki Prefecture Kubota Iron Works Co., Ltd. Tsukuba Plant (72) Kyoichi Tsukamura 1 Shikizu Higashi, Naniwa-ku, Osaka-shi, Osaka 2-47, Kubota System Development Co., Ltd. (72) Inventor Naozumi Imai 1-2-47, Shikitsuhigashi, Naniwa-ku, Osaka City, Osaka Prefecture (56) In Kubota System Development Co., Ltd. (56) Reference JP-A-1-234142 (JP, A) JP-A-1-159143 (JP, A) JP-A-63-298568 (JP, A) JP-A-60-20844 (JP, A)

Claims (2)

(57) [Claims] 1. A system for planning the order of the model types to be put into an assembly line of a mixed-flow production system for assembling a product group to which various options are added, wherein: 1) an input unit for inputting the number of assembled products of the product; 2) A rearrangement processing unit that sequentially selects an attentionable option from a plurality of options according to priority, and rearranges the assembly order of products to be assembled, 3) The attentional process selected by the rearrangement processing unit An evaluation value calculation unit that calculates an evaluation value corresponding to the distribution state in the assembly order of products that have options, 4) a comparison unit that compares the evaluation values with reference values that have been set, and 5) a product that has notable options. Knowledge base with evaluation knowledge to evaluate production sequence and rearrangement knowledge to rearrange production sequence of products with notable options, 6) Selected sequentially A control unit that activates the rearrangement processing unit, the evaluation value calculation unit, and the comparison unit by using a knowledge base in order to determine a satisfying assembly order having an evaluation value equal to or higher than a reference value for all options, 7). An output unit that outputs the satisfactory assembly order, and the sorting knowledge is prioritized under the constraint that the order of products having a high priority option already used for sorting is not changed. A first rule for rearranging the selected options having a low degree of reordering is provided, and regarding the option being rearranged due to the constraint condition of the high-priority option already used for reordering, If the evaluation value of the order is lower than the reference value, it has the high priority option already used for the rearrangement in order to relax the constraint of the first rule. Assembly Sequence Planning expert system characterized in that it comprises a second rule to perform again rearranging the extent that even the order of the goods does not fall below the reference value. 2. The knowledge comprises, for the selected notable option, a rule for evaluating the spacing of the parts in the worst row of products having this notable option, and an overall average of this notable option. The assembly sequence planning expert system according to claim 1, further comprising: a rule for evaluating a specific distribution state.