JP4327648B2 - Computer program, inventory management apparatus and method - Google Patents

Description

The present invention relates to a computer program, an inventory management apparatus, and a method for calculating a safe stock quantity based on a demand forecast value and a demand actual value in the past.

  2. Description of the Related Art Conventionally, an inventory management method of an ordering point method in which a certain amount is ordered when the inventory amount of a product is cut off the ordering point inventory is known. Here, the “order point inventory” is an inventory quantity obtained by adding a safety inventory quantity to a demand forecast value within a procurement period of the product predicted based on a past demand actual value. Then, as a method for calculating the safety stock amount, the method of obtaining the equation (1) has been common (see, for example, Non-Patent Document 1).

  Here, the “safety factor” is determined by the allowable shortage rate. The larger the safety factor, the smaller the shortage probability. In addition, the “procurement period” is a period from when an order is placed until the product arrives.

  On the other hand, when an appropriate demand forecast is possible, the variation in the forecast error between the demand forecast value and the actual demand value is smaller than the variation in the actual demand value itself. It is known that the product rate can be realized (for example, see Patent Document 1). In this case, the safety stock quantity is calculated as shown in Equation (2).

Here, as a unit of the procurement period, a forecast unit period (demand forecast cycle) of demand forecast is used. That is, when demand forecast is performed on a daily basis, the unit is a day. When the demand forecast is performed on a weekly basis, the unit is a week.
Japanese Patent No. 3260333 By Takao Suguro, “Appropriate Inventory Approach / How to Find”, Nikkan Kogyo Shimbun

  However, in the method described in Patent Document 1, when the procurement period is longer than the forecast unit period of the demand forecast, it is difficult to obtain an appropriate safety stock quantity. For example, when the demand forecast of a certain product is performed on a weekly basis (demand forecast cycle: one week) and the procurement period of the product is four weeks, the safety stock quantity can be calculated by the equation (3).

  In the above formula (3), the “variation degree of prediction error” from the first week to the fourth week is the same, and is independent (refers to the state where the results at each time point are not dependent on each other, the same applies hereinafter). For example, the “prediction error variation degree” for four weeks is based on the property that the route is four times (= 2 times) the “prediction error variation degree” for each week.

  However, in reality, it is unlikely that the “degree of variation in prediction error” in each week is the same. For example, it is considered that the earlier the demand is predicted, the more difficult it is, and the “degree of variation in prediction error” will increase as the future increases. In addition, the “degree of variation in prediction error” for each week may not be independent. For example, when the actual demand value increases or decreases in a certain cycle (for example, every other week), if the prediction error for a certain week is positive, the prediction error for the next week is likely to be negative. . Even if it is difficult to accurately predict the demand amount one week ahead, a product having such demand characteristics may be predicted with relatively high accuracy if it is collected for four weeks.

  As described above, in general, the “degree of prediction error variation” is not constant every week and is not independent. Therefore, in the conventional safety inventory calculation as shown in Patent Document 1, the safety inventory quantity is too small. May be excessive.

The present invention has been made in consideration of such circumstances, and even when the procurement period is longer than the forecast unit period of demand forecast, accurately estimate the degree of variation in prediction error within the procurement period, It is an object of the present invention to provide a computer program, an inventory management device, and a method thereof capable of appropriately calculating a safety stock quantity.

In order to solve the above problems, a computer program according to the present invention provides:
Computer
A first setting means for setting a procurement period of the product for each product for which a safety stock quantity is to be calculated;
Second setting means for setting a cumulative period, which is a period for calculating a prediction error of the product, from a procurement period set for the product for which the safety stock quantity is calculated by the first setting unit;
Of the demand actual value of the product stored in the storage device and the demand predicted value of the product calculated for each prediction unit period using the demand actual value, the second for each demand forecast time of the product. obtaining means for obtaining forecast value definitive period determined by the set accumulated period setting means and the actual demand value,
First calculation means for calculating a cumulative error indicating a sum of differences between the demand prediction value and the demand actual value for each prediction unit period in the period from the demand prediction value and the demand actual value acquired by the acquisition means;
Based on the accumulated error at the plurality of demand prediction points calculated by the first calculation unit, the product functions as a second calculation unit that calculates a safety stock amount of the product.

In addition, the inventory management device according to the present invention,
A first setting means for setting a procurement period of the product for each product for which a safety stock quantity is to be calculated;
Second setting means for setting a cumulative period, which is a period for calculating a prediction error of the product, from a procurement period set for the product for which the safety stock quantity is to be calculated by the first setting unit;
Of the demand actual value of the product stored in the storage device and the demand predicted value of the product calculated for each prediction unit period using the demand actual value, the second for each demand forecast time of the product. a forecast value and the actual demand value definitive the period determined by the cumulative period set by the setting means and acquisition means for acquiring,
First calculation means for calculating a cumulative error indicating a sum of differences between the demand prediction value and the demand actual value for each prediction unit period in the period from the demand prediction value and the demand actual value acquired by the acquisition means;
And second calculating means for calculating a safety stock quantity of the product based on the accumulated error at the plurality of demand forecast points calculated by the first calculating means.

Furthermore, the inventory management method according to the present invention includes:
An inventory management method performed by an information processing device that calculates a safety stock quantity based on an error between a demand actual value of a product and a demand forecast value of the product,
For the products respectively to be calculated subject to the safety stock quantity, a first setting step of setting the lead time of the product,
A second setting step for setting a cumulative period, which is a period for calculating a prediction error of the product, from a procurement period set for the product for which the safety stock quantity is calculated in the first setting step;
Of the demand actual value of the product stored in the storage device and the demand predicted value of the product calculated for each prediction unit period using the demand actual value, the second for each demand forecast time of the product. an acquisition step of acquiring the forecast value and the actual demand value definitive the period determined by the cumulative period set by the setting step of,
A first calculation step of calculating a cumulative error indicating a sum of differences between the demand prediction value and the demand actual value for each prediction unit period in the period from the demand prediction value and the demand actual value acquired in the acquisition step;
And a second calculation step of calculating a safety stock amount of the product based on the accumulated errors at the plurality of demand prediction points calculated in the first calculation step.

  According to the present invention, even if the procurement period is longer than the forecast unit period of the demand forecast, it is possible to accurately estimate the degree of variation in the prediction error within the procurement period and appropriately calculate the safety stock amount.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of an inventory management apparatus according to an embodiment of the present invention. As shown in FIG. 1, the inventory management apparatus according to the present embodiment includes a database 100, a demand prediction unit 110, and a safe stock quantity calculation unit 120.

  The demand forecasting unit 110 calculates future demand forecast values based on demand record values in a demand record DB 101 described later and information of various masters 103, and stores the results in a demand forecast history DB 102 described later. Further, the safety stock quantity calculation unit 120 calculates a safety stock quantity from the demand forecast value stored in the demand forecast history DB 102 and the demand actual value stored in the demand performance DB 101, and this is calculated as a safety stock quantity DB 104 described later. To store. The DB 100 includes the demand record DB 101, the demand forecast history DB 102, the various masters 103, and the safety stock DB 104. The demand record DB 101 stores demand record values for each past product and each period.

  FIG. 2 is a diagram illustrating an example of data stored in the demand record DB 101 of the inventory management apparatus according to the present embodiment. The data in the first row of FIG. 2 indicates that the actual demand value of the product with the product code AAAA in January 2003 was 105.

  FIG. 3 is a diagram illustrating an example of data stored in the demand prediction history DB 102 of the inventory management apparatus according to the present embodiment. The demand forecast history DB 102 stores demand forecast results for each period for each product-based forecast start time. The data in the first row of FIG. 3 indicates that the result of predicting the demand amount in January 2003 based on the results until December 2002 is 97 for the product with the product code AAAA. Further, the data in the second row of FIG. 3 indicates that the result for the product for which the demand amount in February 2003 is predicted based on the results until December 2002 was 84.

  Various masters 103 shown in FIG. 1 are masters necessary for the operation of each unit of the apparatus, and include, for example, a product master. FIG. 4 is a diagram illustrating an example of a product master provided in the inventory management apparatus according to the present embodiment. The data on the first line in FIG. 4 is information on the product code AAAA, and the product name is product 1, the allowable shortage rate is 0.05, the procurement period is 4 months, and the evaluation period is 12 months. Show.

  FIG. 5 is a diagram illustrating an example of data (safety stock amount of each product) accumulated in the safe stock amount DB 104 of the stock management apparatus according to the present embodiment, and the data on the first line in FIG. It shows that the safety stock quantity of the code AAAA is 50.

  FIG. 6 is a block diagram illustrating a detailed configuration of an information processing apparatus (computer) that implements the inventory management apparatus according to the present embodiment. In FIG. 6, the CPU 201 comprehensively controls each device connected to the system bus 212. The RAM 202 functions as a main memory, work area, temporary save area, and the like for the CPU 201. Further, the ROM 203 stores a boot program.

  The input control unit 204 controls input from the input unit 205 realized by a pointing device such as a keyboard or a mouse. The display control unit 206 controls display by the display unit 207 realized by a CRT monitor, a liquid crystal monitor, or the like. Furthermore, the external memory control unit 208 is an operating system (OS) that is a control program of the CPU 201, a program for realizing various functions to be described later of the inventory management apparatus, various master files, various databases, user files, editing Controls access to the external memory 209 that stores various data such as files.

  The external memory 209 further stores various tables for realizing various functions of the information processing apparatus. Examples of the external memory 209 include a hard disk (HD), a flexible disk (FD), a compact flash (registered trademark) that can be connected to a PCMCIA card slot via an adapter, smart media, and the like. In the present embodiment, it is assumed that the program recorded in the external memory 209 is executed by being loaded into the RAM 202 as necessary.

  In addition, the communication I / F control unit 210 executes communication control processing with an external device via a network 211 such as a LAN or the Internet.

  Next, detailed processing of the safe inventory quantity calculation unit 120 of the inventory management apparatus according to the present embodiment will be described. FIG. 7 is a flowchart for explaining a detailed processing procedure of the safe stock quantity calculation unit 120 of the inventory management apparatus according to the present embodiment. Note that the inventory management apparatus according to the present embodiment repeatedly executes the series of processes shown in FIG. 7 as many as the number registered in the product master for each product.

  In explaining the safety stock quantity calculation process, the demand forecast unit period is one month, and the current time is the end of December 2003, and the demand quantity after January 2004 is calculated from the demand data until the end of December 2003. Assume that the safety stock quantity as of January is calculated and calculated. The product master is as shown in FIG.

  First, the safety stock amount calculation unit 120 acquires data related to the product (step S71). The data acquired here includes at least a demand actual value, a demand forecast value, and an allowable shortage rate of the product. The allowable shortage rate is the maximum value of the probability that there is no help for the shortage of the product.

  FIG. 8 is a flowchart for explaining details of the data acquisition process in step S71 of FIG. First, the target product is set from the product master shown in FIG. 4 (step S71a). For example, the product 1 with the product code AAAA is set as a target. Next, the current date (current time) is extracted and set (step S71b). The allowable shortage rate, the procurement period, and the evaluation period of the set product are extracted from the product master shown in FIG. 4 and set (step S71c). For example, the allowable shortage rate 0.05 of the product 1, the procurement period 4.0 months, and the evaluation period 12.0 months are extracted and set. Note that the allowable shortage rate, the procurement period, and the evaluation period can be arbitrarily set.

  Then, the safety factor corresponding to the extracted allowable shortage rate is extracted and set from the safety factor table shown in FIG. 12 (step S71d). The safety factor is a constant determined by the allowable shortage rate. For example, the allowable shortage rate is 1.65 at 5%, 2.33 at 1%, 2.58 at 0.5%, etc. Yes. Further, a safety factor may be calculated and set from the allowable shortage rate. Next, an accumulation period is calculated and set based on the procurement period (step S71e). Thereafter, the demand forecast value is extracted from the demand forecast history DB 102 in which the data shown in FIG. 3 is stored, and the demand record value is extracted from the demand record DB 101 in which the data shown in FIG. 2 is stored (step S71f).

  After the above-described data acquisition process in step S71 is completed, a cumulative error at each past time point is calculated based on the demand prediction value and the actual demand value (step S72). Here, the cumulative error is calculated based on the following equation (4).

  FIGS. 9-11 is a figure which shows each accumulated error of each time of goods 1-3 calculated based on the said Formula (4). In the calculation, since the procurement periods of the products 1, 2, and 3 are April, 0.5, and 3.5 months, respectively, the minimum integer that does not fall below the accumulation period. 4 months, 1 month, and 4 months defined by the above, and the evaluation period was 12 months.

  Next, the degree of variation in accumulated error is calculated based on equation (5) (step S73).

  As shown in FIG. 9, the degree of variation in the cumulative error of the product 1 as of January 2004 is as shown in Expression (6).

  Similarly, the degree of variation in the accumulated error between the products 2 and 3 as of January 2004 is 10 and 139, respectively.

  Next, the safety stock quantity is calculated based on the equation (7) (step S74).

  Here, the allowable shortage rate is 0.05 for all products, and the safety factor in this case is 1.65 (allowable shortage rate: 5%) from the safety factor table shown in FIG. The safety stock quantity of each product is as follows.

  In actual operation, the procurement period of each product changes. For example, in the case of producing a product in its own factory, the manufacturing period (lead time) may be shortened by improving the process, or the procurement period (lead time) may be shortened by changing the supplier. In such a case, an appropriate safety stock quantity can be calculated simply by changing the procurement period of the product master.

  In the above description, the method for obtaining the safety stock quantity by obtaining the degree of variation of the accumulated error and multiplying it by the equation (9) has been described.

  On the other hand, the safety stock quantity may be obtained by obtaining the degree of variation of the cumulative error rate represented by Expression (10) and multiplying it by Expression (11).

  When the degree of variation in the accumulated error is proportional to the demand forecast value, it is possible to calculate a more appropriate safety stock quantity using the accumulated error rate.

  Finally, the calculated safety stock quantity is stored in the safety stock quantity DB 104 (step S75).

  It should be noted that the above-described method for calculating the safe stock quantity can be applied to all stock management systems that require the calculation of the safe stock quantity, such as a regular order method and a quantitative order method. In addition to the above-described model, a model as shown in the following equation may be used as the safety inventory quantity calculation formula.

The model shown in Expression (12) determines the amount of safety stock based on the amount of accumulated demand actual value exceeding the accumulated demand predicted value (maximum accumulated excess amount). In the case of the product 1 shown in FIG.
The safety stock quantity calculation formula can be anything as long as it includes the procurement period and forecast error, and replaces the “procurement period” with “procurement period / cumulative period”. The safety stock quantity may be calculated by replacing the “error” part with the “cumulative error”.

  As described above, by calculating the safety stock quantity based on the cumulative error rate of the demand forecast value and the actual demand value within the procurement period, it is possible to accurately estimate the “prediction error variation degree” within the procurement period. . Therefore, an appropriate safety stock quantity can be calculated even for a product whose procurement period is longer than the forecast unit period of demand forecast. In addition, when the present invention is applied to a product whose procurement period is shorter than the forecast unit period of the demand forecast, the cumulative period = 1, and the formula for calculating the safety stock quantity is as shown in Expression (13).

This is synonymous with the formula for calculating the safety stock in the prior art. That is, according to the method proposed in the present invention, when the procurement period is longer than the forecast unit period of the demand forecast, the safe stock quantity can be calculated more appropriately than in the past, and there is no problem with the conventional method. In some cases, it is possible to achieve the same effect as the conventional method.
As described above, the embodiment has been described in detail. However, the present invention can take an embodiment as a system, apparatus, method, program, storage medium, or the like, and specifically includes a plurality of devices. The present invention may be applied to a system that is configured, or may be applied to an apparatus that includes a single device.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowchart shown in the figure) that realizes the functions of the above-described embodiment is directly or remotely supplied to the system or apparatus, and the computer of the system or apparatus Is also achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  As a recording medium for supplying the program, for example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card ROM, DVD (DVD-ROM, DVD-R) and the like.

  As another program supply method, a client computer browser is used to connect to an Internet homepage, and the computer program of the present invention itself or a compressed file including an automatic installation function is downloaded from the homepage to a recording medium such as a hard disk. Can also be supplied. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  In addition to the functions of the above-described embodiments being realized by the computer executing the read program, the OS running on the computer based on the instruction of the program is a part of the actual processing. Alternatively, the functions of the above-described embodiment can be realized by performing all of them and performing the processing.

  Furthermore, after the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion board or The CPU or the like provided in the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

It is a block diagram of the inventory management apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the data accumulate | stored in the demand performance DB101 of the inventory management apparatus which concerns on this embodiment. It is a figure which shows an example of the data accumulate | stored in the demand prediction log | history DB102 of the inventory management apparatus which concerns on this embodiment. It is a figure which shows an example of the goods master with which the inventory management apparatus which concerns on this embodiment is equipped. It is a figure which shows an example of the data (safety stock quantity of each goods) accumulate | stored in safe stock quantity DB104 of the inventory management apparatus which concerns on this embodiment. It is a block diagram which shows the detailed structure of the information processing apparatus (computer) which implement | achieves the inventory management apparatus which concerns on this embodiment. It is a flowchart for demonstrating the detailed process sequence of the safe stock quantity calculation part 120 of the inventory management apparatus which concerns on this embodiment. It is a flowchart for demonstrating the detail of the data acquisition process of FIG.7 S71. It is a figure which shows each accumulation error of each time of the goods 1 calculated based on Formula (4). It is a figure which shows each accumulation error of each time of the goods 2 calculated based on Formula (4). It is a figure which shows each accumulation error of each time of the goods 3 calculated based on Formula (4). It is a figure which shows an example of the safety coefficient table with which the inventory management apparatus which concerns on this embodiment is equipped.

Explanation of symbols

100 database (DB)
101 Demand results DB
102 Demand forecast history DB
103 Various masters 104 Safety stock DB
110 Demand forecasting section 120 Safety inventory calculation section

Claims (10)

Computer
A first setting means for setting a procurement period of the product for each product for which a safety stock quantity is to be calculated;
Second setting means for setting a cumulative period, which is a period for calculating a prediction error of the product, from a procurement period set for the product for which the safety stock quantity is calculated by the first setting unit;
Of the demand actual value of the product stored in the storage device and the demand predicted value of the product calculated for each prediction unit period using the demand actual value, the second for each demand forecast time of the product. obtaining means for obtaining forecast value definitive period determined by the set accumulated period setting means and the actual demand value,
First calculation means for calculating a cumulative error indicating a sum of differences between the demand prediction value and the demand actual value for each prediction unit period in the period from the demand prediction value and the demand actual value acquired by the acquisition means;
A computer program for functioning as second calculation means for calculating a safety stock amount of the product based on the accumulated errors at the plurality of demand forecast points calculated by the first calculation means. The computer program according to claim 1, wherein the second calculation unit further calculates a degree of variation of the cumulative error, and calculates a safety stock quantity based on the degree of variation of the cumulative error.   The computer program product according to claim 2, wherein the second calculation unit calculates a safety stock quantity by multiplying the degree of variation by a square root of a ratio of the procurement period to the accumulation period.   4. The computer program according to claim 2, wherein the second calculation unit calculates a square root of an average value of a sum of squares of differences between the demand forecast value and the actual demand value as the degree of variation. .   5. The computer program according to claim 1, wherein the first calculation unit calculates the cumulative error as a cumulative error rate. 6. Further causing the computer to function as a third setting means for setting an allowable shortage rate of the product,
The said 2nd calculation means calculates the safety stock quantity of the said goods by further using the safety factor determined by the allowable shortage rate of the said goods, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. A computer program described in 1.   The computer program according to any one of claims 1 to 6, wherein the second setting unit sets the cumulative period to a minimum integer prediction unit period that is not less than the procurement period. The computer further
Prediction means for calculating a demand predicted value of a product based on the actual demand value stored in the storage device,
Storage means for storing the demand prediction value calculated by the prediction means in the storage device
The computer program according to claim 1, wherein the computer program is caused to function as a computer program. A first setting means for setting a procurement period of the product for each product for which a safety stock quantity is to be calculated;
Second setting means for setting a cumulative period, which is a period for calculating a prediction error of the product, from a procurement period set for the product for which the safety stock quantity is to be calculated by the first setting unit;
Of the demand actual value of the product stored in the storage device and the demand predicted value of the product calculated for each prediction unit period using the demand actual value, the second for each demand forecast time of the product. a forecast value and the actual demand value definitive the period determined by the cumulative period set by the setting means and acquisition means for acquiring,
First calculation means for calculating a cumulative error indicating a sum of differences between the demand prediction value and the demand actual value for each prediction unit period in the period from the demand prediction value and the demand actual value acquired by the acquisition means;
An inventory management apparatus comprising: a second calculation unit configured to calculate a safety stock quantity of the product based on the cumulative error at the plurality of demand prediction points calculated by the first calculation unit. . An inventory management method performed by an information processing device that calculates a safety stock quantity based on an error between a demand actual value of a product and a demand forecast value of the product,
For the products respectively to be calculated subject to the safety stock quantity, a first setting step of setting the lead time of the product,
A second setting step for setting a cumulative period, which is a period for calculating a prediction error of the product, from a procurement period set for the product for which the safety stock quantity is calculated in the first setting step;
Of the demand actual value of the product stored in the storage device and the demand predicted value of the product calculated for each prediction unit period using the demand actual value, the second for each demand forecast time of the product. an acquisition step of acquiring the forecast value and the actual demand value definitive the period determined by the cumulative period set by the setting step of,
A first calculation step of calculating a cumulative error indicating a sum of differences between the demand prediction value and the demand actual value for each prediction unit period in the period from the demand prediction value and the demand actual value acquired in the acquisition step;
An inventory management method comprising: a second calculation step of calculating a safety stock quantity of the product based on the accumulated errors at the plurality of demand prediction points calculated in the first calculation step. .

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