CN107246901B - Coal bunker material level detection system and method based on string vibration - Google Patents
Coal bunker material level detection system and method based on string vibration Download PDFInfo
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- CN107246901B CN107246901B CN201710557618.1A CN201710557618A CN107246901B CN 107246901 B CN107246901 B CN 107246901B CN 201710557618 A CN201710557618 A CN 201710557618A CN 107246901 B CN107246901 B CN 107246901B
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- 239000000463 material Substances 0.000 title claims abstract description 57
- 239000003245 coal Substances 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000001514 detection method Methods 0.000 title claims abstract description 23
- 238000005259 measurement Methods 0.000 claims abstract description 25
- 229910000831 Steel Inorganic materials 0.000 claims description 6
- 239000010959 steel Substances 0.000 claims description 6
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- 238000000611 regression analysis Methods 0.000 claims description 3
- 238000010304 firing Methods 0.000 claims description 2
- 239000000428 dust Substances 0.000 abstract description 8
- 238000000691 measurement method Methods 0.000 abstract description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Abstract
The invention relates to material height detection, in particular to a coal bunker material level detection system and method based on string vibration. The technical problems of low measurement speed and inaccurate measurement result existing in the detection of the height of the material level in the existing coal bunker are solved. A coal bunker material level detection system based on string vibration comprises a string vertically connected between the top end and the bottom end of the interior of a silo for containing materials, a mechanical string striking device for striking the string, a sound wave spectrometer for collecting the string vibration frequency and a computer system; the signal output end of the computer system is connected with the signal input end of the mechanical string striking device; the signal input end of the acoustic wave spectrometer is connected with the signal input end of the computer system. The detection system provided by the invention solves the problems that the measurement precision and the measurement speed of the current common measurement method cannot be considered and are easily interfered by dust and suspended matters, realizes continuous and accurate detection of the material level height of the coal bunker, and is not influenced by the dust and the suspended matters in the silo.
Description
Technical Field
The invention relates to material height detection, in particular to a coal bunker material level detection system and method based on string vibration.
Background
For coal mines, coal washery, power plants and the like, the material level detection of the coal bunker is an important index for detecting the stock quantity and the quality of coal, and the automatic and continuous monitoring of the material level is an important embodiment for improving the degree of automation. Because of the characteristics of complex site working conditions, large dust, easy adhesion, easy hanging and the like, accurate and continuous measurement of the material level becomes a great difficulty in the material level measurement technology. The most common methods for automatically measuring the material level of the coal bunker at present mainly comprise a heavy hammer method, an ultrasonic ranging method and a laser ranging method. The weight method converts the material level height according to the descending distance of the weight, has simple and reliable principle, can avoid the interference of dust and suspended objects, has high measurement precision, but has slower measurement speed, needs the weight to reciprocate up and down for one-time measurement, and is not beneficial to continuous monitoring; the ultrasonic method measures the time taken from sending out to returning to the whole process of an ultrasonic pulse, but because dust in a coal bunker is serious and false echoes can be generated under the action of various suspended objects to influence the measurement result, meanwhile, the ultrasonic divergence angle is large, the power is limited, long-distance measurement is difficult to realize, and the range is limited; the laser method measures the time from sending to returning of laser pulse, and also can generate false echo under the action of dust and various suspended matters in the coal bunker, meanwhile, the propagation time is small because of extremely high propagation speed of laser, the relative error of time measurement is large, in addition, for the coal bunker, coal is black, the absorption effect on light wave is very strong, the reflected light intensity is very low, and the measurement is unfavorable.
Disclosure of Invention
The invention provides a coal bin material level detection system and method based on string vibration, which are used for solving the technical problems of low measurement speed and inaccurate measurement result in the existing detection of the material level height in a coal bin.
The coal bunker material level detection system based on string vibration is realized by adopting the following technical scheme: a coal bunker material level detection system based on string vibration comprises a string vertically connected between the top end and the bottom end of the interior of a silo for containing materials, a mechanical string striking device for striking the string, a sound wave spectrometer for collecting the string vibration frequency and a computer system; the signal output end of the computer system is connected with the signal input end of the mechanical string striking device; the signal output end of the acoustic wave spectrometer is connected with the signal input end of the computer system.
Based on the string vibration theory, the system measures the sound frequency emitted by string vibration, a calibration model of the string length and the vibration frequency is obtained by utilizing polynomial fitting, and the string length is accurately calculated, so that the material level height is determined. The whole measuring process comprises the steps of string striking, sound spectrum measurement and data analysis processing.
The coal bunker material level detection method based on string vibration is realized by adopting the following technical scheme: a coal bunker material level detection method based on string vibration comprises the following steps:
(a) The silo height is set asHThe material level is as followshThe chord length, i.e. the length of free vibration of the string, islWhen the material level in the bin changes, the chordLength of free vibration of wirelChanges occur; the relationship between chord length and level height ish=H-l；
(b) Fill level calibration
Length of free vibration of string when silo level changeslAlso changes, and at the same time, the change of the material level can also lead the tension of the string to change slightly, and the vibration frequency of the stringfCorresponding changes may occur; for this, a polynomial fit is used to build the chord lengthlSum frequencyfObtaining a calibration model by regression analysis; will chord lengthlSum frequencyfThe relation of (2) is expressed as follows by a higher order polynomial:
l=a 0 +a 1 f + a 2 f 2 +…+ a n f n
in the middle ofa 0 、a 1 、…，a n Regression coefficients of each order, the specific ordernDetermined by the amount of data used for scaling; under different material level heights, a computer system controls a motor to drive a linkage lever to strike strings, and a sound wave spectrometer collects the vibration frequency of the strings to further measure the material level heights as followsl 1 、l 2 、…、l m Vibration frequency of corresponding stringf 1 、f 2 、…、f m Wherein, the method comprises the steps of, wherein,m>nthe regression equation can be obtained:
after the mathematical model is established, the computer system performs fitting by combining the related data under the support of corresponding software to obtain regression equation coefficientsa 0 、a 1 、…，a n Is to establish the chord lengthlSum frequencyfQuantitative relationship between the two;
(c) The motor is controlled by the computer system to drive the linkage lever to strike the string and the string is struck by soundAfter the vibration frequency of the string is measured by the wave spectrometerl=a 0 +a 1 f + a 2 f 2 +…+ a n f n Calculating free vibration chord lengthlIs brought intoh=H-lThe actual material level height in the silo can be obtained by the formula.
For a specific material, calibration is needed before measurement, namely materials with different heights are filled in a silo, then vibration frequencies of chord lines at each height under the action of external force with the same frequency are measured respectively, corresponding polynomials are listed, and regression coefficients of various orders are fitted according to the polynomials to finish calibration; the actual measurement can then be made.
The detection system provided by the invention solves the problems that the measurement precision and the measurement speed of the current common measurement method cannot be considered and are easily interfered by dust and suspended matters, realizes continuous and accurate detection of the material level height of the coal bunker, and is not influenced by the dust and the suspended matters in the bunker. The method has accurate measurement and high processing speed, and can meet the requirements of the existing coal mines, power plants and coal washery; the method can be used for measuring coal and measuring the material level of other ores and chemical raw materials. The whole system has simple structure and low cost.
Drawings
FIG. 1 is a schematic diagram of a coal bunker level detection system according to the present invention.
1-silo, 2-string, 3-sonic spectrometer, 4-computer system, 5-motor, 6-linkage lever.
Detailed Description
The mechanical string striking device comprises a motor 5 and a linkage lever 6; the signal input end of the motor 5 is connected with the signal output end of the computer system 4, and the power output end of the motor 5 is connected with a linkage lever 6 for firing the string 2.
The sonic spectrometer 3, the motor 5 and the linkage lever 6 are all positioned at the position of the chord line 2 near the top end of the silo 1. The string 2 is a steel wire rope.
Examples
1. Device structure
The system architecture is shown in fig. 1. The system comprises: string 2, mechanical striking device, sonic spectrometer 3, computer system 4. The string 2 is a steel wire rope which is vertically arranged, has the diameter of about 3-5 cm and the length of the steel wire rope is equal to the height of the silo 1, and the upper end and the lower end of the steel wire rope are respectively fixed with the top end and the bottom end of the silo 1; the mechanical string striking device consists of a motor 5 and a linkage lever 6, and the rotating speed and the torque of the mechanical string striking device are controlled by a computer system 4, so that the string striking frequency and the string striking force can be adjusted in a certain range; the computer system 4 receives the measured data of the acoustic wave spectrometer 3, processes and analyzes the measured data to obtain the material level height, and simultaneously, the computer system 4 also performs time sequence control of the processes of string striking, acoustic spectrum measurement and data analysis.
2. Principle of measurement
According to the theory of string vibration, when a continuous uniform string with two fixed ends vibrates, the motion of the string can be expressed as superposition of a plurality of standing waves. For the firstnThe amplitude and the frequency of the harmonic vibration of each point of the chord line are respectively as follows:
amplitude of vibration
（1）
Frequency of
（2）
In the method, in the process of the invention,lfor the chord length of the material to be measured,Tfor the string tension,ρis the string density. Wherein,,nthe corresponding vibration frequency is the fundamental frequency when=1,nat other values, harmonics are each time. From the above equation, it can be seen that the vibration of the string includes a variety of frequencies, but the fundamental frequency is much stronger than the other harmonics, so it determines the frequency of the string, so the present invention calculates the string length by measuring the fundamental frequency of the string vibration. According to equation (2), the fundamental frequency of string vibration is related to the chord length, the tension of the string, and the density of the string, which is a constant for a given string.
When the material level in the bin changes, the string 2 freely vibrates in lengthlChanges, as shown in the figure1, the height of the silo is set asHThe material level is as followshThe chord length and the level height relationship is:
h=H-l （3）
3. fill level calibration
Length of free vibration of string when the material level of the silo 1 is changedlThe change is also carried out, meanwhile, the change of the material level can also lead to the tiny change of the tension of the steel wire string, and if the measured vibration frequency directly calculates the chord length according to the formula (2), calculation errors can be caused. The change rule of tension to the material level height is not easy to be quantitatively described by a mathematical formula, and based on the change rule, the invention establishes the chord length by using polynomial fittinglSum frequencyfAnd a calibration model is obtained by regression analysis. Will chord lengthlSum frequencyfThe relation of (2) is expressed as follows by a higher order polynomial:
l=a 0 +a 1 f + a 2 f 2 +…+ a n f n （4）
in the middle ofa 0 、a 1 、…，a n Regression coefficients of each order, the specific ordernDepending on the amount of data used for scaling. The material level heights are respectively measured by a weight methodl 1 、l 2 、…、l m Corresponding vibration frequencyf 1 、f 2 、…、f m (wherein,m>n) Multiple groups of structural forms (regression equations) can be obtained:
after the mathematical model is established, relevant parameters can be fitted by software such as MATLAB, SPSS and the like to obtain regression equation coefficientsa 0 、a 1 、…，a n Is to establish the chord lengthlSum frequencyfQuantitative relationship between the above.
After the string vibration frequency is measured, the free vibration string length is calculated by the method (4)lThe material level height can be obtained by carrying the formula (3).
The rotation speed of the motor is controlled by a computer, and strings are continuously struck at the frequency of 5-20 Hz, so that the continuous measurement of the material level height can be realized.
Claims (4)
1. The coal bunker material level detection method based on string vibration is realized by adopting a coal bunker material level detection system based on string vibration, and comprises a string (2) vertically connected between the top end and the bottom end inside a silo (1) for containing materials, a mechanical string striking device for striking strings, an acoustic wave spectrometer (3) for collecting the vibration frequency of the string (2) and a computer system (4); the signal output end of the computer system (4) is connected with the signal input end of the mechanical string striking device; the signal output end of the acoustic wave spectrometer (3) is connected with the signal input end of the computer system (4);
the mechanical string striking device comprises a motor (5) and a linkage lever (6) connected to the power output end of the motor (5) and used for firing the string (2); the signal input end of the motor (5) is connected with the signal output end of the computer system (4);
the acoustic wave spectrometer (3), the motor (5) and the linkage lever (6) are all positioned at the position of the chord line (2) close to the top end of the silo (1);
the string (2) adopts a steel wire rope; frequency of vibration of string (2)fLength of free vibration with string (2)lThe relation is:
，Tfor the tension of the string (2),ρfor the density of the strings (2), the frequencies of the strings are determined taking into account the fundamental frequency, taken heren =1；
The method is characterized by comprising the following steps of:
(a) The height of the silo (1) is set asHThe material level is as followshThe chord length, i.e. the length of the free vibration of the string (2), islWhen (when)When the material level in the silo (1) changes, the string (2) freely vibrates in lengthlChanges occur; the relationship between chord length and level height ish=H-l；
(b) Fill level calibration
When the material level of the silo (1) changes, the string (2) freely vibrates in lengthlAlso changes, and at the same time, the change of the material level can also cause the tension of the string (2) to change slightly, and the vibration frequency of the string (2)fCorresponding changes may occur; for this, a polynomial fit is used to build the chord lengthlSum frequencyfObtaining a calibration model by regression analysis; will chord lengthlSum frequencyfThe relation of (2) is expressed as follows by a higher order polynomial:
l=a 0 +a 1 f+a 2 f 2 +…+a n f n
in the middle ofa 0 、a 1 、…，a n Regression coefficients of each order, the specific ordernDetermined by the amount of data used for scaling; under different material level heights, a motor (5) is controlled by a computer system (4) to drive a linkage lever (6) to strike strings, and the vibration frequency of the strings (2) is collected by a sound wave spectrometer (3), so that the material level heights are measured respectivelyl 1 、l 2 、…、l m Vibration frequency of corresponding string (2)f 1 、f 2 、…、f m Wherein, the method comprises the steps of, wherein,m>nthe regression equation can be obtained:
the method comprises the steps of carrying out a first treatment on the surface of the After the mathematical model is established, the computer system (4) combines the related data to perform fitting under the support of the corresponding software to obtain the regression equation coefficienta 0 、a 1 、…，a n Is to establish the chord lengthlSum frequencyfQuantitative relationship between the two;
(c) The motor (5) is controlled by the computer system (4) to drive the linkage lever (6) to strike the string, and the string is passed throughAfter the vibration frequency of the string (2) is measured by the ultrasonic spectrometer (3), the ultrasonic spectrometer usesl=a 0 +a 1 f+a 2 f 2 +…+a n f n Calculating free vibration chord lengthlIs brought intoh=H-lThe actual material level height in the silo (1) can be obtained by the formula.
2. The method for detecting the level of a coal bunker based on string vibration according to claim 1, further comprising the step of (d): the computer system (4) is used for controlling the rotating speed of the motor (5) and continuously striking strings at the frequency of 5-20 Hz, so that the real-time continuous measurement of the material level height can be realized.
3. The method for detecting the material level of the coal bunker based on the string vibration according to claim 1, wherein in the step (b), different material level heights are detected by adopting a weight method.
4. A coal bunker level detection method based on string vibration as claimed in any one of claims 1 to 3, wherein the computer system (4) uses MATLAB or SPSS software to fit a regression equation to obtain regression coefficientsa 0 、a 1 、…，a n Is a value of (2).
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| CN108182776A (en) * | 2017-12-28 | 2018-06-19 | 无锡联河光子技术有限公司 | A kind of alarm mode analysis method of distributed optical fiber fence safety pre-warning system |
| CN112113636A (en) * | 2020-08-26 | 2020-12-22 | 上海大学 | Coal bunker material level intelligent detection system and method based on frequency modulation continuous wave radar |
| CN114964416B (en) * | 2021-02-25 | 2024-05-28 | 中国科学院声学研究所 | Measuring system and method for reserves of coal bunker cylinder |
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