CN101936863B - Device and method for detecting grain pile density by using mechanical wave propagation process in grain pile - Google Patents

Abstract

The present invention relates to a device and a measuring method for detecting the density of a grain pile by utilizing the mechanical wave propagation process in the grain pile, comprising: a microphone or/and a vibration sensor group, distributed in the grain pile, and used to detect the fluctuation process of the excitation signal in the grain pile; The channel signal acquisition and processing analysis device is connected to the microphone or/and vibration sensor group, and is used to measure the time between sound waves passing through every two microphones or/and vibration sensors; the signal excitation device is connected to the multiple The channel signal acquisition, processing and analysis device is used to generate the required audio frequency vibration signal; the sound generating device is connected to the signal excitation device and is used to generate effectively propagated sound waves in the grain pile. The present invention adopts the statistical test method to establish a regression model, and the accuracy of the model will be further improved with the increase of the number of effective samples, and the test is easy.

Description

Device and method for detecting grain heap density by using mechanical wave propagation process in grain heap

technical field

The invention relates to a device and a measuring method for measuring the density of granular materials, in particular to a device and a method for detecting the density of grain piles by using the mechanical wave propagation process in the grain piles.

Background technique

The propagation of sound and vibration depends on the mass distribution of the medium, and the wave process is propagated in the medium by the mechanical motion of the particle. Therefore, there are various applications for obtaining the properties of the medium by means of the measurement of the mechanical fluctuation parameters. At present, acoustic detection technology has been applied in many fields, such as ultrasonic medical detection, ultrasonic flaw detection of metal materials, acoustic pile measurement of building foundations, and geophysical seismic exploration. In geological exploration, excitation and measurement of the propagation process of elastic waves in the stratum are used to detect information such as the composition and boundaries of different stratum structures; in medical testing, the difference in absorption and reflection of ultrasonic waves in different tissues of the human body is used to detect the internal organs of the human body and the position and size of the tissue; in the detection of metals, ceramics and multi-layer materials, by measuring the propagation parameters of ultrasonic waves in solid samples, data analysis results such as defects inside the material and the thickness of thin-layer materials can be obtained.

In the detection of grain density in grain piles, the usual method is to measure the density of the sample by weighing method, such as the widely used bulk density measurement method, microwave method and capacitance method based on the measurement of grain dielectric coefficient, and nuclear ray method. However, the method of directly measuring the bulk density destroys the shape of the grain heap during the sampling process, and the measurement based on the sample density cannot obtain the actual density of the grain heap, and non-destructive testing technology should be used. Since the measurement of the correlation between the dielectric constant and density of grain piles requires the exclusion of other factors, such as the influence of water content on the dielectric constant; Factors of measurement, the method has capacitance method and microwave absorption method. Although the capacitance method can accurately measure the dielectric constant of the medium around the electrode, it needs to have enough sampling points in the granary to judge that the sample point value represents the average value of the entire granary. Nuclear radiation density measurement requires professional training for operators and strict management of radioactive sources.

At present, in practice, "sampling is used to measure the density of grain, such as a volumetric container, or a large container of 0.25 to 1 cubic meter, carefully fill the grain to weigh the net weight, and then divide it by the volume of the container to obtain the sample density; multiply the sample density by the correction factor Calculate the average density of grain piles; the correction coefficient is the ratio of the sample density to the calculated density of the standard bin with the same storage conditions and known volume and weight as the standard bin, which is an analogous estimation method for sampling measurement. Since the standard warehouse must store the same kind of grain under the same conditions, but in practice it can only be approximated, so the category benchmark is generally selected based on experience. The accuracy of this measurement method is difficult to determine, and the operation is complicated and laborious.

Contents of the invention

The present invention avoids the above-mentioned shortcomings in the prior art and provides a device and method for detecting the density of grain piles by using the mechanical wave propagation process in the grain piles, which reduces the workload of conventional methods for measuring the density of grain piles, and also reduces errors.

By the following formulas (1), (2)

P-wave velocity: $\mathrm{Vp}=\sqrt{\frac{\mathrm{\λ}+2\mathrm{\μ}}{\mathrm{\ρ}}}---\left(1\right)$

其中：ρ-介质密度，c-波速Shear wave velocity:

Among them: ρ-medium density, c-wave velocity

It can be seen that the density of the medium is related to parameters such as the propagation speed of mechanical waves.

Technical scheme of the present invention is:

A device for detecting the density of grain piles by using the mechanical wave propagation process in the grain piles, including:

The microphone or/and vibration sensor group is connected to the multi-channel signal acquisition and processing analysis device of the microphone or/and vibration sensor group, the signal excitation device connected to the multi-channel signal acquisition and processing analysis device is connected to the The sounding device of the above-mentioned signal excitation device.

The microphone or/and vibration sensor group is used to detect the fluctuation process of the excitation signal in the grain pile, and transmit it to a multi-channel signal acquisition, processing and analysis device;

The multi-channel signal acquisition, processing and analysis device is used to measure the time between sound waves passing through every two microphones or/and vibration sensors;

The signal excitation device is used to generate the required audio frequency vibration signal;

The sound generating device is used to generate effectively propagated sound waves in grain piles.

The sound generating device is a loudspeaker or an exciter.

The method for measuring grain bulk density by the above-mentioned device comprises the following steps:

Distributing the sounding device, microphone or/and vibration sensor group in the grain pile, and measuring the distance D between each microphone or/and vibration sensor in the microphone or/and vibration sensor group,

The signal excitation device receives the signal given by the multi-channel signal acquisition and processing analysis device and generates a signal with a certain frequency and amplitude,

The sounding device is driven by the signal excitation device to generate vibration of a given frequency and radiate into the grain pile,

The microphone or/and vibration sensor group collects the fluctuation signal excited by the sound generating device in the grain pile and transmits it to the multi-channel signal acquisition and processing analysis device, and the multi-channel signal acquisition, processing and analysis device performs analysis and processing, and measures Acoustic wave passes through the time T between every two sensors, and two sensor signal strengths S1, S2, calculates the wave velocity V=D/T in the grain heap, and the attenuation Att=(S2-S1)/D of fluctuation;

Obtain the grain accumulation parameters that need to be measured, including moisture, bulk density, grain size, grain density, hardness, thousand-grain weight, and porosity;

Establish the grain bulk density regression model ρ=f(V, Att, grain stacking parameters) with respect to the grain stacking parameters, V and Att, and calculate the grain bulk density at each measurement location.

Advantages of the present invention:

The invention adopts the method of exciting and measuring sound waves in the grain pile, obtains the sound propagation parameters associated with the grain pile density, and establishes the phenomenological model of the grain pile density and the sound propagation parameters. The actual density of the grain heap can be measured with little disturbance to the state of the grain heap, which reduces the workload required for estimating the density of the grain heap by the bulk density correction method; and can directly measure the required grain bin, reducing the need for estimation by the sample bin. Other granary density errors; at the same time, since the measured grain heap density is the overall average of the grain heaps on the sound propagation path, the representative error of sampling points caused by single-point density measurement is avoided. The regression model is established by the statistical test method, the accuracy of the model will be further improved with the increase of the number of effective samples, and it is easy to test. It avoids the complexity of establishing the grain heap elastic wave constitutive model due to the uncertainties of grain grain characteristics, such as water content, surface friction coefficient, and grain density.

Description of drawings

Fig. 1 is a schematic diagram of the working principle of the present invention;

Fig. 2 is the schematic diagram of the structure of the grain bulk density calibration and verification device;

Figure 3 is a comparison chart of the wheat density estimation method obtained by the sound velocity, attenuation, and accumulation parameters and the actual density.

Detailed ways:

As shown in FIG. 1 , the device for detecting grain bulk density of the present invention includes a microphone or/and a vibration sensor group 1 , a multi-channel signal acquisition conditioning and processing analysis device 2 , a signal excitation device 3 , and a sounding device 4 . The microphone or/and vibration sensor group 1 is distributed in the grain pile, and is used to detect the fluctuation process of the excitation signal in the grain pile; the multi-channel signal acquisition conditioning and processing analysis device 2 is connected to the microphone or/and The vibration sensor group 1 is used to measure the time between the sound waves passing through every two sensors; the signal excitation device 3 is connected to the multi-channel signal acquisition conditioning and processing analysis device 2, which is used to provide a certain frequency, amplitude signal and drive the sounding device 4; the sounding device 4 is connected to the signal excitation device 3, and distributed in the grain pile, for generating effectively propagated acoustic vibrations in the grain pile.

The multi-channel signal acquisition, processing and analysis device 2 has no less than two high-speed analog signal acquisition channels, and can simultaneously identify, process and analyze the collected composite signals. The sampling system rate may not be greater than 200kHz/s, and the number of digits for digital-to-analog conversion may not be greater than 24Bit. The repetition error of the wave velocity measured by this device should not be greater than 1.5%.

The microphone or/and vibration sensor group can simultaneously pick up sound or vibration signals from no less than two positions in the grain pile. The signal excitation device is an acoustic vibration generating device capable of effectively propagating in the grain pile, and may be an electrical signal source or a power amplifier. The frequency response range of the sounding device is 30-1500Hz.

The sound generating device and the microphone or/and vibration sensor group are properly arranged to generate and obtain sound waves in the grain pile, or simultaneously obtain propagation signals of sound waves and elastic waves. The sound generating device can be a loudspeaker or an exciter. When the sound generating device is a loudspeaker, the sound generating device is electrically connected to the signal excitation device, and the signal excitation device gives it an excitation signal of a certain frequency and amplitude. When the sound generating device is an exciter, the sound generating device may not be connected to the signal excitation device at this time, and the excitation signal is one or more timing signals that emit impact sounds generated by the signal acquisition, processing and analysis device.

The method for measuring grain bulk density by the above-mentioned device comprises the following steps:

1) Distribute the sounding device 4, the microphone or/and the vibration sensor group 1 in the grain pile, and measure the distance D between every two microphones or/and the vibration sensor in the microphone or/and the vibration sensor group 1,

2) The multi-channel signal acquisition conditioning and processing analysis device 2 gives the signal,

3) The signal excitation device 3 receives the signal provided by the multi-channel signal acquisition conditioning and processing analysis device 2 and generates a signal of a certain frequency and amplitude,

4) The sounding device 4 is driven by the signal excitation device 3 to generate a vibration source of a certain frequency,

5) The microphone or/and vibration sensor group 1 collects the fluctuation signal of the vibration source and transmits it to the multi-channel signal acquisition conditioning and processing analysis device 2, and is analyzed and processed by the multi-channel signal acquisition conditioning and processing analysis device 2 to obtain The sound wave passes through the time T between every two sensors, and the signal strengths S1 and S2 of the two sensors, and calculates V=D/T, and the attenuation Att=(S2-S1)/D of the fluctuation;

6) Establish a regression model ρ=f(V, Att, grain accumulation parameters) about V, Att(D, T) and grain accumulation parameters in the grain heap, and calculate the grain heap density at each measurement position.

The following takes wheat as an example to illustrate how to measure the density of wheat in the grain pile:

First, the value of the sound velocity in the grain pile is measured by the time difference method: on the path of sound propagation in the grain pile, sensors are arranged at two points with an adjacent distance D, and the time difference between the sound waves passing through the two points is measured by a multi-channel signal acquisition and processing analysis device T, the wave velocity V=D/T can be calculated; from the two sensor signal strengths S1, S2, the wave attenuation Att=(S2-S1)/D can be calculated.

From the theory of mechanical waves, it can be known that the propagation speed of fluctuations in a medium is related to the density of the medium and its elastic parameters. However, it is difficult to measure the elastic parameters of actual grain piles accurately, and the relationship between the elastic parameters and the density of grain piles can be established by measuring the fluctuation velocity.

A common measurement method is adopted to obtain grain accumulation parameters representing the grain pile under test. The parameters of the grain pile and the measured fluctuation parameters are taken as the independent variables, and the density of the grain pile is taken as the dependent variable. For example, the multiple linear regression equation established for wheat is as follows:

Wheat density=A+B*wave velocity+C*attenuation+D*grain accumulation parameter; (1)

Among them, A is a constant, and B, C, and D are the coefficients of wave velocity, attenuation, and grain accumulation parameters respectively.

Estimates of wheat density obtained from regression equation (1) for a given measurement method. Figure 3 is a comparison chart of the estimated wheat density and the actual density obtained by the sound velocity, attenuation, and grain accumulation parameters.

Verification of grain bulk density, and calibration of the instruments used, can be performed in the laboratory as described. According to the principle that when the wavelength of the sound wave is much larger than the width of the pipe section, only plane waves will exist in the pipe, the speaker box 21, the air pipe section 22, the sample pipe section 23, the matching pipe section 24, the sensor installation hole 25, and the multi-channel signal acquisition, conditioning and analysis are produced. The grain pile sound propagation parameter calibration and verification device constituted by the processing device 26 is shown in FIG. 2 . The air pipe section 22 is to ensure that the sound wave at the end face of the sample section is a plane wave, and the food to be measured is loaded into the sample pipe section 23 and the matching pipe section 24 . The length of the sample tube section 23 and the installation spacing of the sensors therein are based on the fact that the signal acquisition and processing device 26 can measure and meet the measurement accuracy; The sensor signal is not affected.

The accumulation parameters of the grain are measured, and the grain with known parameters is loaded in the sample section and the matching section according to a series of set densities, and the relationship between the grain bulk density and the fluctuation parameter is obtained through the above steps. After variance analysis, multiple regression, statistical testing and other steps, the regression model of sample density and fluctuation parameters and grain accumulation parameters can be established, and the model can be tested and verified through new experiments.

Claims (4)

1. utilize the device of mechanical wave communication process detection bulk density of grain in the grain heap, it is characterized in that, comprising:

Microphone is or/and the vibration transducer group, multi-channel signal acquiring conditioning and Treatment Analysis device, signal excitation device, sound-producing device; Said microphone is or/and the vibration transducer group connects described multi-channel signal acquiring conditioning and Treatment Analysis device, signal excitation device, sound-producing device successively; Described multi-channel signal acquiring conditioning is handled microphone or/and the signal that the vibration transducer group transmits with the Treatment Analysis device analysis; Measurement of sound is through the time T between per two sensors; With two sensor signal strength S 1; S2, decay Att=(the S2-S1)/D that calculates the velocity of wave V=D/T in the grain heap and fluctuate.

2. the device that utilizes mechanical wave communication process detection bulk density of grain in the grain heap as claimed in claim 1 is characterized in that:

Described microphone is or/and the vibration transducer group is used for detecting the wave process that grain is piled pumping signal;

Described signal excitation device is used to produce required acoustic frequency vibration signal;

Described sound-producing device is used for producing the sound wave that effect spread is arranged at the grain heap.

3. according to claim 1 or claim 2 the mechanical wave communication process in the grain heap utilized detects the device of bulk density of grain, it is characterized in that comprise: described sound-producing device is loudspeaker or vibrator.

4. a method of utilizing claim 1 or 2 said measurement device bulk density of grain is characterized in that, comprises the steps:

With sound-producing device, microphone or/and the vibration transducer component be distributed on the path of acoustic propagation in the grain heap, and measure said microphone or/and in the vibration transducer group each microphone or/and the distance B between the vibration transducer,

The signal excitation device receives said multi-channel signal acquiring and nurses one's health signal that provides with the Treatment Analysis device and the signal that produces certain frequency, amplitude,

Sound-producing device receives the driving of said signal excitation device, and produce the vibration of given frequency and be radiated in the grain heap,

Microphone or/and the vibration transducer group gather the fluctuation signal that said sound-producing device excites and pass to multi-channel signal acquiring conditioning and Treatment Analysis device in grain heap; And carry out analyzing and processing with the Treatment Analysis device by the conditioning of described multi-channel signal acquiring; Measurement of sound through each microphone or/and the time T between the vibration transducer and two sensor signal strength S 1, S2; Decay Att=(the S2-S1)/D that calculates the velocity of wave V=D/T in the grain heap and fluctuate;

Obtain the grain of required measurement and pile up parameter, wherein grain accumulation parameter comprises moisture, unit weight, seed yardstick, seed density, hardness, mass of 1000 kernel, factor of porosity;

Foundation is piled up the regression model ρ=f (V, Att, grain are piled up parameter) of parameter about grain heap V and Att, grain, and calculates the bulk density of grain of each measuring point.

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