JPH06160360A - Foreign matter detection - Google Patents

Abstract

PURPOSE:To improve foreign matter detection ability by applying fractal theory to the output waveform of a foreign matter detecting sensor to quantity complexity of output signal waveform. CONSTITUTION:The chemical flowing from a chemical tank 1 to a piping 2 passes through a foreign matter detecting sensor 3, and the analogue signal outputted from the sensor 3 is converted into digital signal (4), then sent to a calculator 5. The calculator 5 performs arithmetic processing with discrete data series (herein after referred to as time series). In short, an averaging part 5-1, for improved S/N in the time series and also for maintained fractal characteristics, performs integration averaging process, to calculate fractal dimension, for a fractal analyzing part 5-2 to make quantitative review. A decision part 5-3 comparison-calculates the fractal dimension with that pre-calculated for each chemical containing no foreign matter, for deciding presence of foreign matter. If it is decided that foreign matter is present, a printer 6 records chemical, kinds of foreign matter, detection time, etc., so that an alarm device 7 reports mingled foreign matter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting a foreign substance by a foreign substance detection sensor installed in a pipe from a chemical liquid tank.

[0002]

2. Description of the Related Art Conventionally, the presence or absence of foreign matter is determined by setting a certain threshold value on the output waveform of the foreign matter detection sensor. In the conventional method, information about a foreign substance is obtained from amplitude information of a waveform, and the amplitude value of a signal having a low S / N ratio, for example, a signal having information about a foreign substance to be detected is smaller than that of noise. If it is small, it is difficult to detect the presence or absence of foreign matter.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite signal processing method for detecting a minute foreign substance that cannot be detected by threshold value judgment and for specifying the type of foreign substance. The foreign matter in the present invention refers to air bubbles, gelatin, etc. that have not been completely dissolved, undissolved solid chemicals, aggregates due to poor dispersion, etc. (hereinafter referred to as foreign matter etc.).

[0004]

Means for Solving the Problems The above problem is to apply the fractal theory to the output waveform of the foreign matter detection sensor when the foreign matter is detected by the foreign matter detection sensor installed in the pipe from the chemical liquid tank. It is solved by a method characterized by improving the foreign matter detection ability by quantifying the complexity of.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing an embodiment of the present invention. In the present invention, in the pipe from the chemical liquid tank 1, 2
It is composed of a foreign matter detection sensor 3, an A / D converter 4, a computer 5, a printer 6, and an alarm device 7. Further, inside the computer 5, it is divided into an averaging processing section 5-1, a fractal analysis executing section 5-2, and a judging section 5-3.

The chemical liquid flowing from the chemical liquid tank 1 through the pipe 2 passes through the foreign matter detection sensor 3 installed in the middle of the pipe 2. Although the ultrasonic type foreign matter detection sensor is used in the present embodiment, the detection method by other means can also be used in the following method. An analog signal is always output from the foreign matter detection sensor 3 while the chemical solution is passing. A
The / D converter 4 is a device for converting an analog output signal from the foreign matter detection sensor 3 into a digital signal for processing by the computer 5, and a data series discretized by this (hereinafter referred to as a time series). ), The following arithmetic processing is performed inside the computer 5.

The obtained time series is subjected to averaging processing in the averaging processing section 5-1 which is one of the constituent processing elements of the computer 5. In the signal processing as in the present case, signal averaging processing is generally performed for the purpose of improving the S / N ratio. In the present embodiment, the averaging process 5-1 is a process performed to improve the S / N ratio and not reduce the fractal property (self-similarity). The averaging process includes a moving average and an integrating averaging process. In this embodiment, the integrating averaging process is adopted.

The time series subjected to the integration and averaging processing in the averaging processing section 5-1 is passed to the fractal analysis section 5-2. The fractal analysis unit 5-2 (details of the analysis method will be described later) is a process performed to calculate a fractal dimension, which is one of the feature amounts for performing quantitative evaluation. The fractal dimension calculated by the fractal analysis unit 5-2 is passed to the determination unit 5-3. The determination unit 5-3 determines the presence / absence of foreign matter by comparing and calculating the fractal dimension obtained by fractal analysis and the fractal dimension calculated in advance for each chemical liquid that does not contain foreign matter (hereinafter referred to as the reference dimension). Is a processing unit for.

When the determination unit 5-3 determines that there is a foreign substance, a signal indicating an abnormality is transmitted to the printer 6 and the alarm device 7 from the determination unit 5-3.
The printer 6 is a device for recording information such as the type of liquid medicine, the type of foreign matter, and the foreign matter detection time when receiving the abnormal signal from the determination unit 5-3. The alarm device 7 is a device for notifying the mixture of foreign matter by a buzzer and a lamp when receiving an abnormal signal from the determination unit 5-3.

FIG. 2 is a diagram showing a procedure of fractal analysis. The analysis window setting 20 is set so as to cut out a time series of finite length from the time series obtained in real time when executing the fractal analysis.

FIG. 3 is a diagram showing the concept of the analysis window.
In the time series 30 of 1024 points, the horizontal axis represents time and the vertical axis represents amplitude value. The amplitude value is maximum and dimensionless. 1
An analysis window 31 of 256 points is set for the time series 30 of 024 points. The time series displayed in the analysis window 31 is a part of the time series 30 of 1024 points, that is, the analysis window width 3
Only 0-1 is cut out, and the amplitude value on the vertical axis of the analysis window 31 is enlarged and displayed to show the concept of the analysis window 31. The analysis window width 30-1 is not limited to 256 points and is usually determined according to the type of foreign matter. For example, if it is something like a bubble, the time series corresponding to it shows pulse-like behavior, so the analysis window width 30-1 should be small.
The analysis window width 30-1 needs to be large for a time series that exhibits a relatively gradual behavior including low frequency components such as foreign matter.

In this embodiment, the analysis window width is 3 for bubbles.
0-1 was set to 64 points, and foreign matters were set to 128 points.
Further, when setting the analysis window 31, one analysis window 31 is set in FIG. 3, but it is also possible to set a plurality of analysis windows at the same time, and this embodiment also adopts the method of setting a plurality of windows. Inclusive. In this way, by setting a plurality of analysis windows 31 having a width according to the type of foreign matter in the same time series, it is possible to detect each foreign matter with high accuracy.

In FIG. 2, an analysis domain transform 21 is a process performed for transforming the time series cut out by the analysis window setting 20 into the frequency domain, and is a fast Fourier transform as a technique for transforming from the time domain into the frequency domain. (FF
T) was adopted.

The fractal dimension calculation 22 is performed on the data string transformed into the frequency domain by the analysis domain transformation.
This is a process performed to quantify the complexity of the data string.

The movement 23 of the analysis window is performed immediately after the calculation 22 of the fractal dimension, and in order to obtain a new time series, the movement amount 30-2 of the analysis window in the time axis direction 30-3 in FIG.
This is a process for moving the analysis window 31 by an amount. The analysis window movement amount 30-2 is determined in consideration of the resolution and the processing time enough to capture the fractal dimension sudden change portion 41 in FIG. In this embodiment, the analysis window movement amount 30-2 is empirically set to about 1/10 of the analysis window width 30-1. In the determination unit 5-3 of the computer 5, the presence / absence of foreign matter is determined by comparing and calculating the fractal dimension obtained by the fractal dimension calculation 22 and the reference dimension. When it is determined that there is a foreign substance as a result of the comparison calculation, an abnormal signal is transmitted to the alarm device 7, and then the analysis area conversion 21 is executed again. When it is determined that there is no foreign matter, the analysis area conversion 21 is executed without operating the alarm device 7.

In this way, a new time series is extracted by moving the analysis window 23, the analysis time domain conversion 21 process is performed on the extracted time series, and the fractal dimension calculation 22 is performed after conversion into the frequency domain. By repeating the series of procedures, the fractal dimension corresponding to each analysis window 31 is obtained, and the presence / absence of foreign matter is determined in real time by the value of each fractal dimension.

FIG. 4 is a diagram showing a time series of 1024 points including information such as foreign matter. It exists at the position 40 of 50 μsec. In such a time series, it is extremely difficult to detect a foreign substance or the like by threshold determination.

FIG. 5 is a diagram showing the transition of the fractal dimension obtained by the above procedure. The horizontal axis is time,
The vertical axis represents the fractal dimension. In FIG. 5, a sudden change 41 in the fractal dimension is recognized near 50 μsec, which is the position where foreign matter or the like exists.

In the time series of FIG. 4, the fractal dimension of the chemical solution, that is, the reference dimension when there is no foreign substance is known (1.5
To 1.6), the presence of foreign matter can be easily determined. In this embodiment, 50% of the fluctuation width of the reference dimension
When the above changes occur, the determination unit 5-3 of the computer 5 is set to determine that there is a foreign substance. Such a criterion is an empirically determined value, and it must be individually determined according to the types of chemicals and foreign substances, required detection accuracy, etc. Usually, the optimum value is selected by preliminary experiments. In the present embodiment, the same criterion is set for foreign matters such as bubbles and foreign matters, which is 50% or more of the fluctuation width of the reference dimension. It was

[0020]

According to the present invention, it is possible to improve the ability to detect minute foreign matter such as bubbles and foreign matter which are difficult to detect by threshold determination.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

[Fig.2] Flow chart of fractal analysis procedure

FIG. 3 is a conceptual diagram of a method of setting an analysis window.

[Figure 4] Time-series data including information such as foreign matter

[Fig. 5] Fractal analysis result (transition of fractal dimension)

[Explanation of symbols]

 1 Chemical Solution Tank 2 Piping 3 Foreign Object Detection Sensor 4 A / D Converter 5 Computer 5-1 Averaging Processing Section 5-2 Fractal Analysis Section 5-3 Judgment Section 6 Printer 7 Alarm Device 20 Analysis Window Setting 21 Analysis Area Conversion 22 Fractal Dimension calculation 23 Movement of analysis window 24 Comparison calculation with reference dimension 25 Alarm activation 30 Time series of 1024 points 30-1 Analysis window width 30-2 Analysis window movement amount 30-3 Analysis window movement direction 31 Analysis window 40 Foreign matter Occurrence position of 41 etc. Fractal dimension sudden change part

Claims (1)

[Claims] 1. When a foreign substance is detected by a foreign substance detection sensor installed in a pipe from a chemical liquid tank, a fractal theory is applied to the output waveform of the foreign substance sensor to quantify the complexity of the output signal waveform. A foreign matter detecting method characterized by improving foreign matter detecting ability.