JPH08233643A - Measuring device - Google Patents

Abstract

PURPOSE: To remove measuring error caused by low frequency vibration components on a floor on which cells are installed, by compensating a filter frequency characteristics based on an output sensitivity ratio of a measuring cell and a floor vibration measuring cell to a floor vibration and setting the ratio of the output level almost stable irrelevant to the floor vibration frequency. CONSTITUTION: A measuring signal and a floor vibration detection signal which are detected respectively by a measuring cell 2 and a floor vibration detecting cell 4 installed on a same floor (F) are amplified 5, filtered 6, A/D converted 8, removed 10, 12 mechanical vibration, and output a filtered measurement signal W(t) and a filtered floor vibration as detection signals A(t) respectively. A sensitivity compensation means 18 calculates 14 output sensitivity rate caused by differences in spring constant and load weight of the cells 2, 4 based on the signals W(t), A(t) and a sensitivity compensated signals α.A(t) is outputted 16 based thereon. And subtraction 20 of the signal α.A(t) from the signal W(t) can provide a floor vibration compensated signal O(t) which is formed by compensating error of a measuring signal caused by floor vibration on the floor (F) when the cell 2 is installed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weighing device for removing a weighing error from a weighing signal from a weighing cell due to a low-frequency vibration component of a floor on which the weighing cell is installed.

[0002]

2. Description of the Related Art Generally, in a factory production line, when weighing an object to be weighed, mechanical vibration occurs when the object to be weighed is placed on the weighing device, and the ground, building, floor, or pedestal is installed at the place where the weighing device is installed. Floor vibration occurs due to such environment, and these vibration components are superimposed on the weighing signal. The superposed weighing signal is digitally converted by the A / D converter at a predetermined sampling frequency and filtered by a digital filter to remove the mechanical vibration component. However, if the frequency of the floor vibration is lower than the frequency of the mechanical vibration, it is necessary to set the cutoff frequency of the digital filter low in order to remove it with one digital filter, which increases the filtering time. Will slow down the weighing speed.

In this case, a weighing device having a floor vibration compensation (AFV) function for separately removing the floor vibration by correction is used. In this weighing device, a floor vibration detection cell that outputs a floor vibration detection signal is installed on the same floor as the weighing cell near the weighing cell that weighs the object to be weighed and outputs a weighing signal corresponding to the weight. To do. Then, two digital filters having the same filter frequency characteristic are provided, both signals are respectively filtered to remove mechanical vibration, and then the floor vibration signal is subtracted from the measurement signal to remove the floor vibration component from the measurement signal. Floor vibration compensation is performed. As a result, the cutoff frequency of the digital filter can be set high, and high-speed weighing is realized.

At this time, as shown in FIG. 14, the weighing cell side and the floor vibration detecting cell side differ in how the output signal gain and phase are delayed with respect to the input signal, and the floor vibration can be accurately removed as they are. May not be. This difference in gain and the occurrence of phase difference occur between the weighing cell and the floor vibration detection cell.
This is due to the difference in spring constant and load weight (including tare). Therefore, regarding the difference in gain, it is necessary to perform sensitivity correction for matching the output sensitivity of one of the cells with the other so as to match the gains of the outputs of both cells. The phase difference is relatively small and can be ignored.
The sensitivity correction will be described below.

In the vibration model of FIG. 15, the equations of motion of the weighing cell and the floor vibration detecting cell are as shown in equations (1) and (2). In both equations (1) and (2), M0 is the load (mass) at the free end of the floor vibration detection cell, M
1 is the load (mass) at the free end of the weighing cell when no object is placed, m is the mass of the object, k0, k1
The spring constant of the floor vibration detecting cell weighing cell, x0, x1 is the displacement of the free end of both cells, x _B is the displacement of the floor F.

[0006]

[Equation 1]

Since the relative displacement between the floor side and the load side becomes the output of each cell, the above equations (1) and (2) should be transformed into equations (3) and (4). You can

[0008]

[Equation 2]

The above equations (3) and (4) are used to obtain the transfer function, which is the input / output relationship, with the displacement of the floor as the input of the system and the output of the cell as the output of the system. G
When 1 (jω) and Go (jω) are obtained, equations (5) and (6) are obtained. In equations (5) and (6), ω
Is the frequency of the floor vibration to be corrected, ω ₁ is the natural frequency of the weighing cell, and ω ₀ is the natural frequency of the floor vibration detection cell.

[0010]

(Equation 3)

Therefore, the output sensitivity ratio α between the metering cell side and the floor vibration detecting cell side is given by the following equation (7).

[0012]

[Equation 4]

Where 1 >> (ω / ω _o ) ² , 1 >> (ω / ω
₁ ) ² , that is, for the floor vibration frequency to be corrected,
When the natural frequency is at a sufficiently high frequency on both the weighing cell side and the floor vibration detection cell side, equation (8) is obtained.

[0014]

(Equation 5)

In the equation (8), the part of is m =
0, that is, the output sensitivity ratio of both cells in the state where the object to be weighed is not placed, and the portion of represents the output sensitivity ratio of both cells in the state where the object to be weighed is placed. ing.
These sensitivity ratios show how much the sensitivity of the weighing cell changes depending on whether or not the object to be weighed is placed. Therefore, for example, the sensitivity of the weighing cell is corrected on the basis of the output sensitivity ratio calculated by the above-described simple formula, and the gains of the outputs of both cells are matched to perform highly accurate floor vibration compensation.

[0016]

However, the conventional device has the following problems. As mentioned above, the conventional _{apparatus, 1 »(ω / ω o} ) 2, 1» (ω / ω 1) 2
Since it was used under the condition of, the output sensitivity ratio α was assumed to be constant regardless of the floor vibration frequency ω. However, in order to improve productivity, the number of input samples to the digital filter decreases, and the cutoff frequency of the digital filter rises depending on the frequency domain, resulting in an increase in the natural frequency of both cells. Approach. FIG. 16 shows the frequency characteristic of floor vibration with respect to the output sensitivity of each cell at this time. In this case, the horizontal axis represents the floor vibration frequency (Hz), and the vertical axis represents the output sensitivity (gf / μm).

When the floor vibration frequency ω becomes large as shown in this figure, the frequency ω in the equation (7) cannot be ignored, and therefore the equation (8) does not hold, and the output sensitivity ratio α becomes as shown in the equation (7). It does not become constant. Therefore, when the sensitivity is corrected with the output sensitivity ratio α kept constant as in the conventional case, the sensitivity is corrected with a sensitivity ratio different from the actual one in the frequency range other than the floor vibration frequency where the sensitivity ratios match. There was a problem that it could not achieve high precision weighing due to lack of property.

An object of the present invention is to solve the above problems and to provide a weighing device capable of easily performing high-speed and highly accurate weighing regardless of changes in the floor vibration frequency.

[0019]

In order to achieve the above object, the invention of claim 1 is a weighing cell which weighs an object to be weighed and outputs a weighing signal corresponding to the weight thereof. A floor vibration detection cell that detects a vibration of the installed floor and outputs a floor vibration detection signal, a first digital filtering unit that filters the weighing signal, and a second digital filter that filters the floor vibration detection signal. Filtering means, sensitivity calculation means for calculating an output sensitivity ratio between the weighing cell and the floor vibration detection cell, and an output sensitivity corrected signal by correcting at least one of the weighing signal and the floor vibration detection signal with the output sensitivity ratio. And a floor vibration compensator for compensating the error of the weighing signal due to the floor vibration by subtracting the floor vibration signal from the weighing signal in which the output sensitivity ratio between the signals is corrected. A floor vibration compensating means for outputting a completed signal, and at least one of the first and second digital filtering means has an output sensitivity ratio calculated from a frequency characteristic of sensitivity of the weighing cell and the floor vibration detecting cell to floor vibration. Based on the above, the filter frequency characteristic is corrected so that the ratio of the output levels of the first and second digital filtering means is set to be substantially constant regardless of the floor vibration frequency. According to the above configuration, the first
Alternatively, at least one of the second digital filtering means corrects the filter frequency characteristic based on the output sensitivity ratio calculated from the frequency characteristic of the sensitivity of the weighing cell and the floor vibration detecting cell to the floor vibration, and The output level ratio of the second digital filtering means is set to a filter characteristic that is substantially constant regardless of the floor vibration frequency. Therefore, accurate floor vibration compensation can be performed regardless of the floor vibration frequency.

According to a second aspect of the present invention, a plurality of weighing cells for weighing the respective objects to be weighed into a plurality of weighing hoppers and outputting a weighing signal corresponding to the weight, and the weighing cells are installed. A plurality of floor vibration detection cells that detect the floor vibration and output a floor vibration detection signal, a first digital filtering unit that filters the weighing signals, and a second digital filtering unit that filters the floor vibration detection signals. Digital filtering means, floor vibration calculation means for detecting the vibration mode of the floor based on the floor vibration detection signals, and calculating the vertical displacement of the floor at the position where each weighing cell is installed; A sensitivity calculation means for obtaining an output sensitivity ratio between the floor vibration detection cell and the vibration mode component forming the vibration mode, and a small amount of the weighing signal or the floor vibration detection signal. Both are caused by the floor vibration by subtracting the floor vibration signal from the sensitivity correction means for correcting one of them with the output sensitivity ratio to generate an output sensitivity corrected signal and the weighing signal in which the output sensitivity ratio between the signals is corrected. The floor vibration compensating means for outputting the floor vibration corrected signal that compensates the error of the weighing signal, and the floor vibration corrected signal indicating the weight of the object to be weighed in each weighing hopper. And a combination calculation means for calculating a combination close to a target value within a certain permissible range, and at least one of the first or second digital filtering means comprises a weighing cell and a floor vibration detection cell. The filter frequency characteristic is corrected based on the output sensitivity ratio calculated from the frequency characteristic of the sensitivity to floor vibration, and the ratio of the output levels of the first and second digital filtering means is adjusted to the floor vibration circumference. Regardless of the number are set to the filter characteristics to be substantially constant. According to the above configuration, in the combination weighing device, at least one of the first and second digital filtering means is based on the output sensitivity ratio calculated from the frequency characteristic of the sensitivity of each weighing cell and the floor vibration detection cell to the floor vibration. Then, the filter frequency characteristic is corrected so that the ratio of the output levels of the first and second digital filtering means becomes substantially constant regardless of the floor vibration frequency.
Therefore, accurate floor vibration compensation can be performed for each weighing cell regardless of the floor vibration frequency.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a weighing device according to an embodiment of the present invention. This weighing device consists of a weighing cell (load cell) 2, floor vibration detection cell (load cell) 4,
Amplifier 5, low-pass filter 6, A / D converter 8, first
The digital filtering means 10, the second digital filtering means 12, the sensitivity compensating means 18 including the sensitivity calculating means 14 and the sensitivity correcting means 16, and the floor vibration compensating means 20. The first and second digital filtering means 10 and 12, the sensitivity compensating means 18, and the floor vibration compensating means 20 are built in the CPU 9. The operation of this device will be described below.

First, the weighing signal of the article M detected by the weighing cell 2 and the floor vibration detection signal detected by the floor vibration detection cell 4 installed on the same floor F as the weighing cell 2 are respectively detected by the amplifier 5. The signal is amplified and removed by the low-pass filter 6 above a certain frequency, and is digitally converted by the A / D converter 8 at a predetermined sampling frequency.
In this case, the low-pass filter 6 is used for the purpose of removing (anti-aliasing) a certain frequency or more in relation to the sampling frequency of the A / D converter 8. Mechanical vibration corresponding to the weight is superimposed on the weighing signal and the floor vibration detection signal. Then, the weighing signal is filtered by the first digital filtering means 10, the mechanical vibration is removed, and the filtered weighing signal W (t) is output. Further, the floor vibration detection signal is filtered by the second digital filtering means 12, the mechanical vibration is removed, and the filtered floor vibration detection signal A (t) is output.

Next, the filtered weighing signal W (t) and the filtered floor vibration detection signal A (t) are sent to the sensitivity compensating means 18.
Is input to The sensitivity compensating unit 18 includes a sensitivity calculating unit 14 and a sensitivity correcting unit 16. The sensitivity calculation means 14 calculates the output sensitivity ratio α between the weighing cell 2 and the floor vibration detection cell 4 due to the difference in spring constant and load weight (including tare) between the weighing cell 2 and the floor vibration detection cell 4. . The sensitivity correction means 16 corrects the filtered floor vibration detection signal A (t) from the floor vibration detection cell 4, for example, based on the calculated output sensitivity ratio α, and the sensitivity corrected signal α · A.
(T) is output. The filtered weighing signal W (t)
May be corrected.

Next, the filtered signal W of the weighing cell 2
(T) and the sensitivity-corrected weighing signal α · A of the floor vibration detection cell 4
The floor vibration compensating means 20 performs a subtraction process on (t) and W (t) −α · A (t) = O (t) to calculate the vertical displacement of the position where the weighing cell 2 is installed. A floor vibration corrected signal O (t) in which a certain floor vibration is corrected is output. Thereby, the floor vibration corrected signal O (t) in which the error of the weighing signal due to the floor vibration is compensated is obtained.

At least one of the first and second digital filtering means 10 and 12 used here is to obtain the second-stage filter characteristic by correcting the first-stage filter characteristic as follows. . For this digital filtering means, for example, a linear phase FIR digital filter is used.

First, in the first stage, the filter characteristics are set based on the filtering delay time determined by the weighing capacity of the weighing device and the damping effect of damping the natural frequency of the vibration system. In this example, as shown in FIG.
A main filter having a stepped filter frequency characteristic F0 (ω) and a pre-filter are used in combination in two stages.

FIG. 3 shows a frequency characteristic obtained by multiplying the filter of the first stage and the frequency characteristic of the sensitivity of the weighing cell to the floor vibration, and FIG. 4 shows the frequency characteristic of the filter of the first stage and the floor vibration detecting cell. The frequency characteristic obtained by multiplying the frequency characteristic of sensitivity to floor vibration is shown. In this first stage, floor vibration compensation (AFV) is performed when the floor vibration frequency is around 15 Hz.
The sensitivity ratio α at 15 Hz is used so that the attenuation effect of is maximized. When the floor vibration frequency is 15 Hz, the sensitivity of the weighing cell to floor vibration is S1, and the sensitivity of the floor vibration detection cell to floor vibration is S2, so the sensitivity ratio α is α =
It is represented by S1 / S2 (constant). FIG. 5 shows frequency characteristics showing the damping effect of floor vibration compensation in that case. In this graph, the damping effect of floor vibration compensation is minus infinity (d
B) is large, and the damping effect is small as it approaches 0 (dB).

Here, when the metric is further speeded up, the number of input samples to each digital filtering means decreases, and the cutoff frequency of each digital filtering means increases in the frequency domain, so that the output sensitivity ratio α becomes , Α
= F (ω) as a function of the floor vibration frequency ω. This sensitivity ratio frequency characteristic is shown in FIG. As shown in this figure, when the floor vibration frequency ω increases, the sensitivity ratio α changes rapidly. Therefore, in the first stage filter as described above, when the floor vibration frequency is 15 Hz, the sensitivity ratios match and a desired filter frequency characteristic is obtained, but in other frequencies, the sensitivity ratios differ. Since the desired filter frequency characteristic cannot be obtained, the effect of floor vibration compensation cannot be exhibited.

Therefore, in this apparatus, the first stage filter is corrected to the following second stage filter characteristic. That is, at least one of the first digital filtering means 10 and the second digital filtering means 12 has the weighing cell 2 calculated from the frequency characteristic of the sensitivity of the weighing cell and the floor vibration detecting cell to floor vibration (transfer function to floor vibration). Of the output sensitivity ratio α between the floor vibration detection cell 4 and the floor vibration detection cell 4, that is, α expressed in the following equation (9).
= F (ω) is compensated, and the filter characteristics are set such that the ratio of the output levels of the first and second digital filtering means 10 and 12 becomes substantially constant regardless of the floor vibration frequency ω. It should be noted that the output sensitivity ratio α of the equation (9) is obtained by multiplying by and represents the output sensitivity ratio irrelevant to the floor vibration frequency, which is mainly due to the load weight, and is mainly related to the floor vibration frequency. The output sensitivity ratio resulting from the load weight is shown.

[0030]

(Equation 6)

An example of setting the filter characteristic in the second stage will be described below. Now, let the frequency characteristic of the amplitude on the metering cell side be G1 (ω), the filter frequency characteristic of the second stage of the first digital filtering means 10 be F1 (ω), and the frequency characteristic of the amplitude on the floor vibration detection cell side be G2 (ω).
(Ω), assuming that the second-stage filter frequency characteristic of the second digital filtering means 12 is F2 (ω), the first and second digital filtering means 10, shown on the left side of the following equation (10), The ratio of the 12 output levels is C
Filter frequency characteristic F1
(Ω) and F2 (ω) are set. This F1 (ω), F
2 (ω) is α = f (ω) = F1 in the equation (9).
There is a relationship of (ω) / F2 (ω).

[0032]

(Equation 7)

This second stage filter frequency characteristic F1
(Ω) or F2 (ω) is obtained by multiplying the first stage filter frequency characteristic F0 (ω) of FIG. 2 by the sensitivity ratio α = f (ω) of FIG. In this case, both the filter frequency characteristics F1 (ω) and F2 (ω) are obtained, but either one may be obtained. An example of this desired second stage filter frequency characteristic is shown in FIG. The filter frequency characteristic of FIG. 7 is obtained by correcting the filter frequency characteristic of the first stage main filter of FIG. 2 to the second stage.

Since the digital filtering means 10 and 12 shown in FIG. 1 perform so-called superposition integration processing in which time-series data are multiplied by weighting factors and added,
Convert the obtained frequency domain characteristics to time domain characteristics,
That is, the weighting factor has to be obtained, which can be easily obtained by inverse Fourier transform. Also,
Remez, a well-known digital filter design method
Design method using desired algorithm (desired frequency characteristics,
The weighting coefficient may be obtained by using a method of obtaining the weighting coefficient by giving the sampling frequency and the number of weighting coefficients. In this way, the first and second digital filtering means 10 and 12 are set to have filter characteristics such that the ratio of their output levels becomes substantially constant regardless of the floor vibration frequency ω.

Although it is possible to design these filters by the sensitivity calculating means 14 of FIG. 1, when it is difficult to design them in real time in practice, a plurality of filters with different load weights m are preset. May be prepared, and the most suitable filter may be selected from the obtained sensitivities.

FIG. 8 shows floor vibration compensation (A
It is shown in the attenuation effect frequency characteristic of FV). As shown in this figure,
Compared to before the output level correction in FIG. 5, after the output level correction, the damping effect is large and the sensitivity to floor vibration is 1/10 to 10
It can be reduced to 1/100. Also, 30Hz
It is sufficiently attenuated even at the above high frequencies and exhibits the effect of floor vibration compensation even in the relatively high frequency range.

FIG. 9 shows the floor vibration sensitivity characteristic of the weighing cell with respect to the floor vibration frequency. In this figure, the curve before the output level correction is a product of the filter effect of FIG. 4 and the damping effect frequency characteristic of the floor vibration compensation before the output level correction of FIG. 8, and the curve after the output level correction is 4 is a product of the damping effect frequency characteristics of floor vibration compensation after the filtering of FIG. 4 and before the output level correction of FIG. As shown in this figure, compared to the floor vibration sensitivity characteristics before output level correction when the same level floor vibration detection signal is input in all frequency regions, after the output level correction, the floor vibration compensation floor vibration The influence of sensitivity is further reduced, and the weighing performance is improved regardless of changes in the floor vibration frequency ω.

As described above, even if the output level ratio is corrected to be constant, the damping effect of floor vibration compensation does not completely become 0 (minus infinity (dB)). This is because the weighing signal W (t) and the floor vibration detection signal A are expressed by the following equation.
This is because there is a sensitivity ratio error and a phase difference θ between (t). Now, the measurement signal W (t) = βsinωt, and the floor vibration detection signal α · A (t) = γβsin (ω, whose sensitivity has been corrected.
When the floor vibration corrected signal O (t) is calculated as t + θ), O (t) = W (t) −α · A (t) = βsin ωt−γβsin (ωt + θ) = β√ (1 + γ ² −2γ cosθ) · sin (Ωt +
φ) φ = tan ⁻¹ {γsin θ / (1-γ cosθ)}, and the damping effect of floor vibration compensation is E = √ (1 + γ ² −
2 γ cos θ). However, in actual operation, the phase difference θ is small and does not pose a problem in the damping effect of floor vibration compensation.

Next, the description of the second embodiment will be continued. Figure 10
11 and 12 show schematic configuration diagrams of the combination weighing device according to the second embodiment. In this device, in order to remove a weighing error due to floor vibration from the weighing result of the object to be weighed M, as shown in FIG. 10, a plurality of weighing cells 2-1 to 2-n and a weighing cell via a frame FR are provided. A plurality (three or more) of floor vibration detection cells 4-1 to 4-m are installed on the same floor F as 2-1 to 2-n. In addition, this device, as shown in FIG.
In the CPU 9, the first digital filtering means 1 is respectively associated with the plurality of weighing cells 2-1 to 2-n.
0-1 to 10-n, sensitivity calculating means 14-1 to 14-n, sensitivity correcting means 16-1 to 16-n and floor vibration compensating means 20-1 to 20.
-n is provided. In addition, a plurality of floor vibration detection cells 4-1
Corresponding to 4 to 4-m, second digital filtering means 12-1 to 12-m and floor vibration calculating means 34 are provided.

In this case, in order to reduce the size and cost of the apparatus, the weighing cells 2-1 to 2-n and the floor vibration detecting cell 4-1 are used.
~ 4-m is not one to one, but is usually a floor vibration detection cell 4-1
~ 4-m is a smaller number than the weighing cells 2-1 to 2-n (n>
m). Therefore, the floor vibration calculation means 34
The floor vibration mode is surface-calculated from the outputs of the floor vibration detection cells 4-1 to 4-m, and the floor vibration component at the installation position of each weighing cell 2-1 to 2-n is calculated from the vibration mode.

In FIG. 10, a plurality of weighing cells 2-1 to 2-1 are provided.
-n and weighing signals of the objects M to be weighed, which are respectively input into the weighing hoppers 28-1 to 28-n, and the floor vibration detection cell 4
-The floor vibration detection signals detected from 1 to 4-m are
Each is amplified by the amplifier 5, and the low-pass filter 6
Is input to the multiplexer 7 via. Each signal is
The multiplexer 7 selectively outputs the signal to the A / D converter 8 by the switching signal c from the CPU 9, converts it into a digital signal, and inputs it to the CPU 9.

In FIG. 11, the weighing signal is the first digital filtering means 10-1 built in the CPU 9.
Filtered by .about.10-n to remove mechanical vibrations and become filtered weighing signals W1 (t) to Wn (t). Also,
The floor vibration detection signal is filtered by the second digital filtering means 12-1 to 12-m to remove the mechanical vibration and the filtered floor vibration detection signal A1 (t) to Am (t).
Becomes Each filtered signal has sensitivity means 14-1 to 14-
The floor vibration is corrected by n, the sensitivity correcting means 16-1 to 16-n and the floor vibration compensating means 20-1 to 20-n. The combination calculating means 36 combines the weights of the objects M to be weighed based on the floor vibration compensation signals O1 (t) to On (t) so that the combination is close to the target value within a certain allowable range. , And outputs an opening signal OS for selectively opening the weighing hoppers 28-1 to 28-n corresponding to the weighing cells 2-1 to 2-n.

FIG. 12 shows a side view of this combination weighing device. In this apparatus, the objects to be weighed M are supplied and fed onto the dispersion table 22 via a supply chute 21 from a supply conveyor (not shown). The objects to be weighed M supplied to the dispersion table 22 are dispersed in the surroundings, and the radiation troughs 24-1 to 24-n.
Is supplied to the pool hoppers 26-1 to 26-n via the hoppers and temporarily pooled there, and then each of the weighing hoppers 28-1 to 28-28.
-n is supplied. The objects M to be weighed in the weighing hoppers 28-1 to 28-n are weighed by the weighing cells 2-1 to 2-n attached to the weighing hoppers 28-1 to 28-n, and the combination calculation is performed based on the weighing values. Then, the weighing hopper 2 is operated by the opening signal OS.
Gates 8-1 to 28-n are selectively opened and discharged to the collecting chute 30. The discharged article M is packed in the packaging machine 32.
Will be packed into a bag with the target weight.

Here, at least one of the first digital filtering means 10-1 to 10-n and the second digital filtering means 12-1 to 12-m is similar to the first embodiment, and each weighing cell 2 is provided. The filter frequency characteristic is corrected based on the output sensitivity ratio calculated from the frequency characteristic of the sensitivity of the floor vibration detecting cell 4 to the floor vibration,
And the ratio of the output levels of the second digital filtering means 10 and 12 is set to a filter characteristic that becomes substantially constant regardless of the floor vibration frequency. In this embodiment, it is assumed that the first digital filtering means 10-1 to 10-n are set to the above filter characteristics. The setting operation will be described below with reference to FIG. In this case, the floor vibration calculation means 34 obtains the vibration mode of the floor, and then the sensitivity calculation means 14 causes the weighing cells 2-1 ...
The output sensitivity ratio between 2-n and the virtual floor vibration detection cell at the installation position obtained corresponding to the vibration mode component forming the floor vibration mode is obtained.

First, the floor vibration calculation means 34 calculates the vibration mode of the floor. XY plane (horizontal plane) shown in FIG.
In the output of floor vibration detection cells 4-1 to 4-m fixed at the position of point P (x, y), the floor vibration component Vp (t) (t is By expressing the time) as Vp (t) = A (t) .x + B (t) .y + C (t) (11), the vibration of the floor at the installation position of each weighing cell 2-1 to 2-n Calculate the ingredients. In this case, the floor vibration detection cells 4-1 to 4-m have vertical (2-axis) direction components generated by rotational movement around the X-axis and vertical (2-axis) generated due to rotation around the Y-axis in the behavior on the XY plane. ) Direction component and the motion in the axis (Z) direction perpendicular to the XY plane are detected, and the other motions are not detected. Therefore, the motion of the vertical (Z axis) direction component generated by the rotational motion around the X axis is represented by B ( t), the vertical (Z-axis) direction movement caused by the rotational movement about the Y-axis is A (t), and the Z-axis direction movement is C (t), and the combination of these movements represents the floor vibration.

The vibration mode of the floor is A in equation (11).
It is obtained by obtaining (t), B (t) and C (t). That is, the equation (11) in which the values of A (t), B (t), and C (t) are known values is used as the arbitrary position P on the XY plane.
The output resulting from the vibration of (x, y) is represented. A (t), B
The values of (t) and C (t) are, for example, the outputs Vp (t) of three floor vibration detection cells 4 fixed on the XY plane and the position coordinates (x, y) of each floor vibration detection cell 4. Can be obtained by applying the equation (11) to solve the three-dimensional simultaneous simultaneous equations. However, since there is an error in the output of each floor vibration detection cell 4, the floor vibration at three or more points is actually present. Detection cell 4
Therefore, using the method of least squares, the above A (t), B
It is preferable to obtain the values of (t) and C (t).

In this way, the installation positions P1 (x1, y1) to Pn of the respective weighing cells 2-1 to 2-n calculated by the floor vibration calculating means.
The floor vibration components V1 (t) to Vn (t) at (xn, yn) are output to the sensitivity calculating means 14 and the sensitivity correcting means 16. Then, the sensitivity calculating means 14 causes the respective weighing cells 2-1 to 2-n.
And the output sensitivity ratio α1 calculated from the frequency characteristics of the floor vibration detection cell and the floor vibration
~ Αn is required. Similar to the first embodiment, the first digital filtering means 10-1 to 10-n correct their filter frequency characteristics on the basis of the output sensitivity ratios α1 to αn, respectively, to obtain the first and second values. The ratio of the output levels of the digital filtering means 10 and 12 is set to a filter characteristic that becomes substantially constant regardless of the floor vibration frequency. As a result, in the combination weighing device, accurate floor vibration compensation can be performed on the weighing signals from the weighing hoppers 28-1 to 28-n regardless of the floor vibration frequency.

[0048]

As described above, according to the present invention, the first
Alternatively, at least one of the second digital filtering means corrects the filter frequency characteristic based on the output sensitivity ratio calculated from the frequency characteristic of the sensitivity of the weighing cell and the floor vibration detecting cell to the floor vibration, and The output level ratio of the second digital filtering means is set to a filter characteristic that is substantially constant regardless of the floor vibration frequency. Therefore, accurate floor vibration compensation can be performed regardless of the floor vibration frequency. As a result, it is possible to provide a weighing device that can easily perform high-speed and highly-accurate weighing regardless of changes in the floor vibration frequency.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a weighing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a first stage filter frequency characteristic.

FIG. 3 is a diagram showing a floor-to-floor vibration sensitivity frequency characteristic of the first-stage weighing cell.

FIG. 4 is a diagram showing a floor vibration sensitivity frequency characteristic of the floor vibration detection cell in the first stage.

FIG. 5 is a diagram showing a damping effect frequency characteristic of the first stage floor vibration compensation (AFV).

FIG. 6 is a diagram showing a sensitivity ratio frequency characteristic.

FIG. 7 is a diagram showing a second-stage filter frequency characteristic.

FIG. 8 is a diagram showing a damping effect frequency characteristic of the second stage floor vibration compensation (AFV).

FIG. 9 is a diagram showing the vibration sensitivity frequency characteristic with respect to floor of the second-stage weighing cell.

FIG. 10 is a part of a schematic configuration diagram showing a combination weighing device according to another embodiment.

FIG. 11 is a part of a schematic configuration diagram showing the combination weighing device.

FIG. 12 is a side view showing the combination weighing device.

FIG. 13 is an explanatory diagram showing the principle of surface calculation for calculating a floor vibration mode.

FIG. 14 is a diagram showing a state of an output signal with respect to an input signal of a digital filter.

FIG. 15 is a diagram showing a vibration model.

FIG. 16 is a diagram showing a conventional frequency sensitivity characteristic to floor vibration.

[Explanation of symbols]

2 ... Metering cell, 4 ... Floor vibration detecting cell, 10 ... First digital filtering means, 12 ... Second digital filtering means, 14 ... Sensitivity calculating means, 16 ... Sensitivity correcting means, 18 ... Sensitivity compensating means, 20 ... Floor vibration compensation means,
34 ... Floor vibration calculation means, 36 ... Combination calculation means.

Claims (2)

[Claims] 1. A weighing cell which weighs an object to be weighed and outputs a weighing signal corresponding to the weight, and a floor which detects a vibration of a floor on which the weighing cell is installed and outputs a floor vibration detection signal. A vibration detecting cell, a first digital filtering means for filtering the weighing signal, a second digital filtering means for filtering the floor vibration detecting signal, and an output sensitivity ratio between the weighing cell and the floor vibration detecting cell. Sensitivity calculating means for calculating, sensitivity correcting means for correcting at least one of the weighing signal and the floor vibration detection signal with the above output sensitivity ratio to generate an output sensitivity corrected signal, and the weighing for which the output sensitivity ratio between the signals is corrected. A floor vibration compensating means for subtracting the floor vibration signal from the signal and outputting a floor vibration corrected signal that compensates for an error in the weighing signal caused by the floor vibration. At least one of the second digital filtering means corrects its filter frequency characteristic based on the output sensitivity ratio calculated from the frequency characteristic of the sensitivity of the weighing cell and the floor vibration detecting cell to the floor vibration, and the first and the second digital filtering means correct the filter frequency characteristic. 2. A weighing device in which the ratio of the output levels of the digital filtering means of 2 is set to a filter characteristic that becomes substantially constant regardless of the floor vibration frequency. 2. A plurality of weighing cells for weighing respective objects to be weighed into a plurality of weighing hoppers and outputting a weighing signal corresponding to the weights, and vibrations of the floor on which these weighing cells are installed. A plurality of floor vibration detection cells that detect and output a floor vibration detection signal; a first digital filtering unit that filters the weighing signals; and a second digital filtering unit that filters the floor vibration detection signals. , Floor vibration calculation means for detecting the vibration mode of the floor based on the floor vibration detection signals, and calculating the vertical displacement of the floor at the position where each weighing cell is installed; a weighing cell and a floor vibration detecting cell; Output sensitivity ratio between the above-mentioned vibration modes corresponding to the vibration mode component forming the vibration mode, and at least one of the weighing signal or the floor vibration detection signal. The sensitivity correction unit that corrects the output sensitivity ratio to generate an output sensitivity corrected signal, and subtracts the floor vibration signal from the weighing signal in which the output sensitivity ratio between the signals is corrected, and Floor vibration compensating means for outputting a floor vibration corrected signal that compensates for an error, and each of the objects to be weighed is selectively combined based on the floor vibration corrected signal weighing signal indicating the weight of the object to be weighed in each weighing hopper. And a combination calculation means for calculating a combination close to a target value within a certain allowable range, and at least one of the first or second digital filtering means is provided for floor vibration of the weighing cell and the floor vibration detection cell. The filter frequency characteristic is corrected based on the output sensitivity ratio calculated from the frequency characteristic of sensitivity so that the ratio of the output levels of the first and second digital filtering means is independent of the floor vibration frequency. The combination weighing device that is set in the filter characteristic almost constant.