JPH102843A - Production process control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To check production processes and perform judgment for grasping quality of a product easily and securely and also setting criterion according to change of condition easily and securely. SOLUTION: Comparison with an allowable range curve and power spectral obtained as required on a frequency shaft and when the power spectrum is within the allowable range curve, it is determined as normal and when the power spectrum is out of the allowable range curve, it is determined as abnormal. As the allowable area curve is displayed in the display 40 and also the power spectrum is superposed displayed in it, the normal and the abnormal states are easily determined visibly. The allowable range curve is decided by an average value and standard deviation of the power spectrum and also the average value and the standard deviation of the power spectrum are calculated as required with the lapse of time and the obtained value is updated, so that the allowable range curve adapted to present condition can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing process management system for managing a manufacturing process that directly or indirectly affects the quality of a product manufactured by a continuous or batch process.

[0002]

2. Description of the Related Art In a manufacturing process for manufacturing a predetermined product by a driving force from a motor or the like, a load signal (load power) from the motor or the like is used in order to check the manufacturing process and to grasp the quality of the product. Or load current, etc.)
2. Description of the Related Art A method of expressing a power spectrum, which is a frequency characteristic obtained by analysis by (fast Fourier transform), is widely known.

[0003] By such a method, it is possible to detect a subtle state change of a product in a manufacturing process having a periodicity such as an electric motor.

That is, a load characteristic that changes with time is represented by its magnitude (Amplitude) and change tendency (Trend).
), The method of decomposing into vibration components (Vibration) is extremely orthodox. Each of these characteristics is a load level (power level), level change (overall time-dependent change), power spectrum distribution ( Qualitative characteristics observed through the vibration of the contents), and complement each other to capture the overall process characteristics.

Among them, the monitoring of the manufacturing process based on the power spectrum, which is a frequency characteristic, is used as a method for grasping the transition of the qualitative state of the content product. (Regardless of time series or cross section) to determine appropriateness / abnormality, and to detect or identify a specific state.

[0006]

However, in the case of such a power spectrum, unlike a general criterion represented by a single scalar quantity, a two-dimensional space composed of a frequency axis and a power axis is used. Because it is represented by the upper curve,
When setting a criterion (criterion pattern) for determination, it is necessary to have abundant knowledge of an object to be determined and a high level of judgment ability based on experience.

In other words, in monitoring a manufacturing process using a power spectrum, a power spectrum at a certain point in time of a specific process is registered on a screen as a reference pattern, but only a single power spectrum curve is registered. However, even if the comparison can be performed as a criterion, it is not a criterion for determining whether the state of the power spectrum in each measurement is appropriate or abnormal. Therefore, a method has been proposed in which a rough upper limit curve is additionally set to determine whether or not the curve exceeds the upper limit curve.However, the setting method must be arbitrarily determined, and the standard pattern must be determined. There is also a drawback that a check is not made for a downward shift.

Further, it is necessary to reset the reference pattern so as to follow a change in the situation so that the obtained reference pattern can always maintain its validity with respect to the change with time of the target process.

That is, it is general that the following of such a situation change is reset by manual judgment, and a reasonable standard for the timing and the correction method has not been established.

[0010] The present invention has been made in view of such circumstances, and it is possible to easily and reliably perform a check of a manufacturing process and a determination for grasping the quality of a product, and to respond to a change in a situation. It is an object of the present invention to provide a manufacturing process management system capable of easily and surely setting a judgment environment.

[0011]

According to the first aspect of the present invention,
In a manufacturing process management system that manages a manufacturing process for continuously or batch-producing various products by a driving force from a driving source, an FFT (high speed) is performed on sampling data of load information from the driving source. Fourier transform)
A power spectrum calculating means for performing a process to obtain a power spectrum of a frequency of a predetermined band as needed, and an allowable range curve calculating for obtaining an allowable range curve having a predetermined width from the power spectrum of the frequency obtained by the power spectrum calculating means Means, comparing means for comparing the allowable range curve obtained by the allowable range curve calculating means with the power spectrum of the frequency obtained at any time by the power spectrum calculating means, and a result of the comparison by the comparing means, If the power spectrum of the frequency obtained at any time by the spectrum calculation means falls within the allowable range curve, it is determined to be normal, and if the power spectrum is out of the allowable range curve, it is abnormal. Determination means for determining And it features.

According to the first aspect of the present invention, the allowable range curve calculated by the allowable range curve calculating unit is compared with the power spectrum of the frequency obtained by the power spectrum calculating unit as needed, and the power spectrum of the frequency is calculated by the determining unit. If the power spectrum of the frequency is within the allowable range curve, it is determined to be normal, and if the power spectrum is out of the allowable range curve, it is determined to be abnormal.

[0013] Since the allowable range curve is calculated and updated as needed based on the new power spectrum, even if there is a qualitative change in the system due to aging, it is possible to set the allowable range curve corresponding to the change. In addition, it is easy and reliable to check the manufacturing process and determine the quality of the product.

According to a second aspect of the present invention, the allowable range curve calculated by the allowable range curve calculating means is displayed, and the power spectrum of the frequency determined by the power spectrum calculating means with respect to the allowable range curve is displayed. Display means for superimposing is displayed.

According to the second aspect of the present invention, the allowable range curve calculated by the allowable range curve calculating means is displayed on the display means, and the power spectrum of the frequency calculated by the power spectrum calculating means is superimposed and displayed. Therefore, it is easy to visually confirm the normal or abnormal judgment.

According to a third aspect of the present invention, the allowable range curve calculated by the allowable range curve calculating means is determined by an average value and a standard deviation of the power spectrum calculated by the power spectrum calculating means. It is characterized by.

According to the third aspect of the present invention, the allowable range curve is determined by the average value and the standard deviation of the power spectrum obtained by the power spectrum calculating means. Even if there is a significant change, it is possible to set an allowable range curve corresponding to the change.

The invention according to claim 4 is characterized in that the average value and the standard deviation of the power spectrum are calculated at any time following the passage of time, and the obtained values are updated.

According to the fourth aspect of the present invention, the allowable range curve determined by the average value and the standard deviation of the power spectrum is updated as needed, so that it is possible to set the allowable range curve that fits the current situation. .

According to a fifth aspect of the present invention, the allowable range curve calculated by the allowable range curve calculating means is stored in a storage means.

According to the fifth aspect of the present invention, since the allowable range curve obtained by the allowable range curve calculating means is stored in the storage means, the latest allowable range curve can be used.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a process management system according to the present invention.

As shown in FIG. 1, the manufacturing apparatus 10 of the process control system is for manufacturing, for example, a product accompanied by kneading, and performs a kneading operation by obtaining a driving force from a motor 20. Has become. Further, the manufacturing apparatus 10 is separately prepared in advance for performing batch processing and for performing continuous processing, and the start timing of the batch processing or continuous processing is given by operating the operation start switch 11. It has become.

The processing in the manufacturing apparatus 10 is not limited to kneading, but can be processing such as stirring and kneading.

Here, when the batch processing or the continuous processing is started by the operation start switch 11, a signal indicating the start is sent to the DI (digital input board) of the personal computer main body 30 side.
The operation start timing is given to the CPU 31 via the CPU 32.

An analog signal indicating a load characteristic (load power or the like) of the motor 20 is converted into a digital signal by an A / D converter 33 of the personal computer 30. Here, it is considered that the load characteristics of the motor 20 include characteristics representing the inner surface of the product (in other words, characteristics representing the quality of the product).

Also, the CPU 31 of the personal computer main body 30 side
Calculates an allowable range curve (representing the upper and lower limits of the power spectrum) and a power spectrum as shown in FIG. 2 by an operation based on an FFT calculation program stored in a memory (not shown). ing.
Further, the hard disk 34 of the personal computer body 30 includes
The above-mentioned allowable range curve and the like are recorded, and when the manufacturing process is checked or the judgment for grasping the quality of the product is performed, it is displayed on the display 40 which is a peripheral device of the personal computer body 30. It is supposed to be.

Further, the display 40 has a CPU
31 is superimposed on the permissible range curve, and if the power spectrum deviates from the permissible range curve, the manufacturing apparatus 10 and / or the motor 20 have some abnormality. Is easily estimated.

Here, the data of the permissible range curve recorded on the hard disk 34 is updated by a key input of the keyboard 50, so that if the power spectrum is normal, the permissible curve is determined based on the data. By updating the range curve, it is possible to always maintain the latest allowable range curve according to the change of the situation. Incidentally, the data of the power spectrum obtained by the CPU 31 is also recorded on the hard disk 34.

Next, the operation of the manufacturing process management system having the above configuration will be described with reference to FIGS.

First, the operation of the batch processing will be described with reference to the flow of FIG. That is, when kneading of the manufacturing apparatus 10 is started (step 301), an allowable range curve after t seconds is displayed on the display 40 (step 30).
2). Next, after the information obtained in (Steps 303 and 304) is A / D converted, a power spectrum is obtained by an FFT operation (Steps 306 and 307).

Here, how to obtain the power spectrum and the allowable range curve will be described.

That is, information on the load characteristics of the motor 20 for applying a driving force to the manufacturing apparatus 10 is obtained from a certain time t.
M pieces are collected at a sampling interval ΔT. Here, the load characteristics include not only the load power described above but also information such as a vibration or an audio signal.

Then, the CPU 31 of the personal computer main body 30 side
Performs the arithmetic processing of the sampling data based on the FFT calculation program.

That is, when the data is decomposed into frequency components according to the FFT calculation program, power spectra of m frequency components are obtained. At this time, the power spectrum of the frequency fi at the time t is described as P (t, fi) (i = 1, 2,... M).

When the power spectrum at each time point of t1, t2, t3,... Tn is obtained, t1 to t1
Average value S for each frequency based on n data up to n
1 (fi) and the standard deviation σ (fi) are obtained. Before obtaining these, the average value S2 (fi) of the sum of squares is obtained.

That is, the average values S1 (fi), S2 (f
i) and the standard deviation σ (fi) are obtained by the following equations.

(Equation 1)

The allowable range curve H (fi) can be obtained by the following equation.

(Equation 2)

Here, α is statistically known to be 95.5% when the observed value falls within the allowable range curve if α = 2. Therefore, when the power spectrum obtained by the FFT deviates from this allowable range curve, it can be considered that some abnormality has occurred in the manufacturing apparatus 10 and / or the motor 20.

By the way, when α = 1, 63.8%, α
In the case of = 3, it can be managed by the 99.7% management standard.

Here, in order to display the allowable range curve with high accuracy , the number of data n is increased and H (fi
) May be obtained, but if n is too large, the effect of new data will be diminished by being dragged more than necessary to past data. Conversely, if n is too small, it is difficult to establish a statistical basis (by the way, it should be noted that when peculiar data or the like is used, the allowable range curve becomes distorted).

It is considered that this n has an appropriate value depending on the target system. However, in the existing system, it is assumed that a proper n is used and (n +
1) When the data P (tn + 1, fi) is obtained,
The average value S1 when updating the tolerance curve with this
(Fi) and the mean square value S2 (fi) are obtained as follows.

[0043]

(Equation 3)

In other words, S1 (fi) and S2 (fi) have a meaning that one average value is lost and one new data is added. By using this result, the allowable range curve H (fi) updated from the above equation is obtained.

Then, the allowable range curve H (fi) thus obtained is displayed on the frequency axis, and
The power spectrum obtained from the current data is superimposed and displayed (step 307). In this state, it is determined whether or not the power spectrum is out of the allowable range curve. As shown in FIG. 5, when the power spectrum is within the allowable range curve, it is determined that the power spectrum is normal, and as shown in FIG. If the power spectrum deviates from the allowable range curve, it is determined that the power spectrum is abnormal (steps 308 to 3).
10).

After the determination of whether the power spectrum is normal or abnormal is repeated several times, when the batch processing is completed, it is determined whether or not the allowable range curve has been updated (steps 311 to 313).

Here, when the allowable range curve is updated, the data of the allowable range curve recorded on the hard disk 34 is updated by the key input of the keyboard 50 as described above, and the obtained value is obtained by the CPU 31. The power spectrum data is also recorded on the hard disk 34 (steps 314 and 315).

As described above, the renewal of the data of the allowable range curve and the repetition of the recording of the data of the power spectrum make it possible to construct an appropriate allowable range curve that fits the present condition, thereby enabling more appropriate management. In addition, since the data of the allowable range curve is recorded on the hard disk 34, the optimum allowable range curve can always be used.

On the other hand, when the manufacturing apparatus 10 is a continuous processing step, it follows the flow shown in FIG.

That is, in (Step 401),
The allowable range curve of the hard disk 34 optimized by updating as described above is displayed on the display 40. Then, (Step 402) to (Step 410)
The flow proceeds according to the above-described procedure, and the allowable range curve is updated in (Step 411), and (Step 412)
In, the collected data is recorded.

As described above, in this embodiment, the allowable range curve and the power spectrum calculating means (for example, (Step 306)) obtained by the CPU 31 as the allowable range curve calculating means by the comparing means (for example, (Step 308)). Is compared with the power spectrum of the frequency obtained as needed, and when the power spectrum of the frequency falls within the allowable range curve by the determining means (for example, (steps 309 and 310)), it is determined that the frequency is normal. If the power spectrum deviates from the allowable range curve, it is determined that the power spectrum is abnormal.

The permissible range curve is calculated as shown in FIG.
In 4), the system can always be constructed based on the latest data, so even if there is a qualitative change in the system due to aging, check the manufacturing process corresponding to the change and grasp the quality of the product. Is easy and reliable.

A display 40 as display means is provided.
Is displayed, and the power spectrum of the frequency determined by the power spectrum calculation means (for example, (step 306)) is superimposed and displayed, so that it is easy to visually confirm the normal or abnormal judgment. .

Further, since the allowable range curve is determined by the average value and the standard deviation of the power spectrum obtained by the power spectrum calculating means (for example, (step 306)), the qualitative characteristics of the system accompanying the aging change are determined. Even if there is a significant change, the setting of the allowable range curve corresponding to the change becomes possible in the same manner as described above.

Further, the average value and the standard deviation of the power spectrum are calculated at any time according to the passage of time, and the obtained values are updated. can get.

Further, C as an allowable range curve calculating means is used.
Since the allowable range curve obtained by the PU 31 is stored in the hard disk 34 as a storage unit, the latest allowable range curve can be used. In the above-described embodiment, a case has been described where the FFT is employed to perform the arithmetic processing of the sampling data. However, the present invention is not limited to this example, and wave red analysis may be used.

[0057]

As described above, according to the manufacturing process control system of the present invention, the frequency axis of the allowable range curve obtained by the allowable range curve calculating means and the power spectrum obtained by the power spectrum calculating means as needed. By the above comparison, it can be determined that the power spectrum is normal if the power spectrum falls within the allowable range curve, and it can be determined that the power spectrum is abnormal if the power spectrum is out of the allowable range curve. Further, since the allowable range curve can be updated with a power spectrum obtained from normal measured data, even if there is a qualitative change in the system due to a change with time, it is possible to make a determination corresponding to the change.

Further, the permissible range curve calculated by the permissible range curve calculating means is displayed on the display means, and the power spectrum calculated by the power spectrum calculating means is superimposed and displayed on the frequency axis. Or, it becomes easy to determine the abnormality.

Further, since the allowable range curve is determined by the average value and the standard deviation of the power spectrum obtained by the power spectrum calculating means, even if there is a qualitative change of the system due to a change over time, It becomes possible to update the allowable range curve corresponding to the change.

Further, the allowable range curve determined by the average value and the standard deviation of the power spectrum is updated at any time, so that the setting fits the present condition.

The allowable range curve calculated by the allowable range curve calculating means is stored in the storage means.
The latest tolerance curve can be used.

Accordingly, it is possible to easily and reliably perform a check of the manufacturing process and a determination for grasping the quality of the product, and easily and reliably set a determination environment according to a change in the situation. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a process management system according to the present invention.

FIG. 2 is a diagram showing a relationship between an allowable range curve and a measured power spectrum in the process management system of FIG.

FIG. 3 is a flowchart showing an operation of batch processing in the process management system of FIG. 1;

FIG. 4 is a flowchart showing an operation of a continuous process in the process management system of FIG. 1;

FIG. 5 is a diagram showing a determination result of an operation state in the process management system of FIG. 1;

FIG. 6 is a diagram showing a determination result of an operation state in the process management system of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 11 Operation start switch 20 Motor 30 Personal computer main body 33 A / D converter 34 Hard disk 40 Display 50 Keyboard

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 11, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

That is, the average values S1 (fi), S2 (f
i) and the standard deviation σ (fi) are obtained by the following equations.

(Equation 1)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

The allowable range curve H (fi) can be obtained by the following equation.

(Equation 2)

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction contents]

Here, in order to display the allowable range curve with high accuracy, the number of data n is increased and H (fi
) May be obtained, but if n is too large, the effect of new data will be diminished by being dragged more than necessary to past data. Conversely, if n is too small, it is difficult to establish a statistical basis (by the way, it should be noted that when peculiar data or the like is used, the allowable range curve becomes distorted).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction contents]

[0043]

(Equation 3)

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (5)

[Claims] 1. A manufacturing process management system for managing a manufacturing process for continuously or batch-producing various products by a driving force from a driving source, wherein a sampling data of load information from the driving source is On the other hand, a power spectrum calculating means for performing a FFT (Fast Fourier Transform) process to obtain a power spectrum of a frequency in a predetermined band as needed, and an allowance having a predetermined width from the power spectrum of the frequency obtained by the power spectrum calculating means. An allowable range curve calculating means for obtaining a range curve; a comparing means for comparing the allowable range curve obtained by the allowable range curve calculating means with a power spectrum of a frequency obtained at any time by the power spectrum calculating means; As a result of the comparison by the means, When the power spectrum of the frequency obtained as needed falls within the allowable range curve, it is determined that the power spectrum is normal, and when the power spectrum is out of the allowable range curve, it is determined that the power spectrum is abnormal. And a means for controlling the manufacturing process. 2. A display for displaying the allowable range curve calculated by the allowable range curve calculating means and superimposing and displaying a power spectrum of the frequency calculated by the power spectrum calculating means on the allowable range curve. 2. The manufacturing process management system according to claim 1, further comprising means. 3. The power supply apparatus according to claim 3, wherein the allowable range curve calculated by the allowable range curve calculating means is determined by an average value and a standard deviation of the power spectrum calculated by the power spectrum calculating means. Item 3. The manufacturing process management system according to item 1 or 2. 4. The power spectrum according to claim 1, wherein the average value and the standard deviation of the power spectrum are calculated as needed over time, and the obtained values are updated. 3. The manufacturing process management system according to 3. 5. A manufacturing process control system of claim 1, 2, 3 or 4, wherein the tolerance curve tolerance curve obtained by the calculation means, characterized in that it is stored in the storage means.