JPH079379B2 - Weight detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is designed to place an object to be weighed on a weight weighing device (herein, simply referred to as a weighing device) and to perform a DC steady state (stationary state). ) Under a stable vibration condition before becoming a).

(Prior Art) Generally, as shown in FIG. 1, a measuring unit having an elastic body 1 such as a spring and a load cell is used in a weighing device such as a scale, and the lower end of this elastic body 1 is a machine base 2 or the like. On the fixed side, and the object to be weighed 4 is placed on the upper end of the tray 3 via the tray 3.

By the way, in the weighing device configured in this way, when the object to be weighed is placed on the tray and the weight of the object to be weighed is to be freely vibrated, as shown by the solid line in FIG. 15,
The peak of the impact occurs during mounting and vibration is superimposed, and the central displacement of the vibration reaches a constant value (stable vibration state) only after the mounting is completed, but the vibration continues. The detected value that exhibits such a vibration state is amplified and A / D
Even if the value was converted, the obtained value had an oscillatory component and was not stable, so that an accurate weight could not be obtained.

For this reason, conventionally, in the above-described weighing device, a damper for damping is attached between the tray on which the object to be weighed is placed and the machine base side, and a signal circuit or an amplifier for removing low-frequency harmful vibrations is added. It was common to have a filter in series with the circuit.

Thus, if a damper or filter is provided in the weighing device and a filter is provided in series with the signal circuit or amplification circuit, a detection value having a time response as shown by the alternate long and short dash line in FIG. After a lapse of time, the detected value becomes a DC steady state, and accurate superposition can be obtained.

(Problems to be Solved by the Invention) However, even if the weighing device is provided with the damper and the filter as described above, in general, there is a relatively long response delay until the detected value reaches a DC steady state. , For example,
Even if a strong damper and a filter effective against low-frequency harmful vibration are provided in order to obtain a highly accurate and highly sensitive weighing device, it is generally 0.
It took about 6 to 1 second.

The present invention has been made in view of the above-described current situation, and the vibration is stable after the object to be weighed is placed on the tray and the object to be weighed is relatively stationary with respect to the tray (after the placement is completed). An object of the present invention is to provide a method for detecting the weight of an object to be weighed in an extremely short time by using the vibration data under the above condition (under the condition after T _{1 in} FIG. 15).

(Means for Solving the Problem) In the weight detecting method of the present invention, the object to be weighed is placed on the placing portion on the elastic body of the weighing device, and the detected value of the detector exhibits a stable vibration state. In this case, this vibration is regarded as the vibration composed of the linear component due to the true value of the object to be weighed and the harmonic vibration component due to the impact motion at the time of placement, and the same displacement of the vibration displacement obtained by the detector Among the values obtained by integrating the absolute value of the displacement velocity at each point for each displacement point, the displacement point having the largest value is used as the value of the DC component to obtain the weight of the object to be weighed.

(Operation) However, under such a stable vibration state,
If the absolute value of the displacement temperature at the same displacement point of the vibration displacement is integrated for each displacement point, the integrated value will be passed at the displacement point of the DC component because it will pass at the fastest speed due to the elastic energy of the elastic body and the speed. It will be the maximum. Therefore, the displacement point having the largest value among the values obtained by integrating the absolute value of the displacement velocity at the same displacement point of the vibration displacement for each displacement point becomes the DC component. In this way, the weight of the object to be weighed can be accurately obtained even when the detection value of the detector of the weighing device is in a vibrating state. In addition, as for the data for obtaining the weight of the object to be weighed, many data can be obtained within an extremely short time (for example, if the vibration frequency of the weighing device is 20 to 40 cycles, 10 to 0.25 seconds to 0.5 seconds). Vibration occurs once, and it is possible to collect data about 20 times during this period, so accurate measurement can be performed in a short time.

(Example) Hereinafter, the weight detection method of the present invention will be described in more detail, and then an example of the case where the weight detection method is applied to a load cell type and an optical type weighing device will be described.

As shown in FIG. 1, when the x-coordinate having the positive direction of the weight is given and the time from the weighing start time is t, in the weighing device having the elastic body 1 such as a modeled load cell, the weighing device is placed on the tray 3. The displacement X (t) ⊂x of the vibration when the object to be weighed 4 is placed and the impact load is applied to the elastic body 1 is expressed by the following equation (1).

X (t) = Acos ωt + Bsin ωt + P (1) In the equation (1), Here, A and B are integration constants, K is the equivalent spring constant of the load cell 1, M is the equivalent mass of the pan 3, m is the equivalent mass of the object 4, and g is the gravitational acceleration.

By the way, the above P is a direct current component obtained when this vibration is attenuated and becomes a direct current steady state, “Acos ωt + Bsin
ωt ”is the harmonic vibration component, and ω is the natural frequency of the vibration system determined by the device.

Now, within the vibration state shown by the solid line in FIG. 15, a predetermined time range [T1, T2] (T1, T2ε
t), when measured in a predetermined displacement range [X1, X2] (X1, X2εx), the vibration X (t) represented by the above formula (1) shows a certain displacement point x ₁ (x ₁ ε [X1, X2]) multiple times. Now, suppose that the time when the vibration passes the displacement point x ₁ within [T1, T2] n times and passes the displacement point x ₁ at the i-th time is t (x ₁ ,
If i), i = 1, ..., N (x ₁ ), the following expression (2) is given.

xi = X (t (xi, 1)) = X (t (xi, 2)) = ... = X (t (xi, i)) = ... = X (t (xi, n (xi)) )) (2) Further, the vibration speed at the displacement point xi is expressed by the following equation (3).

Therefore, (here Is a monotonic function that depends on the system. ) Vi represented by the above equation (4) is taken as a function of x, and Vi is integrated at each displacement point as shown in FIG.
The following expression (5) is obtained.

When X (t) = P in the above equation (1), the displacement speed Vi is determined by the relationship between elastic energy and the displacement speed, and in the case of damped vibration, the number of passing times is the maximum.
Since the integrated value of (V _{1 to} Vn ₍ x ₎ ) has an extreme value (the maximum value in FIG. 2 (b); F (x) _MAX ), the following formula (6) for finding the extreme value is satisfied. The value of x (= xp) becomes the DC component (see FIG. 2 (b)).

From this DC component xp, weigh the object Is required.

As described above, the weight detection method according to the present invention can detect the accurate weight of the object to be weighed even under a vibrating state.

The extreme value may be obtained by differentiating the function F (x) representing the integrated value of the displacement velocity with x as described above, or by simply comparing the integrated values of the respective displacement points. You may ask.

Next, an embodiment in which the present weight detection method is applied to an actual load cell type weighing device will be described with reference to FIG.

FIG. 3 is a configuration diagram showing a schematic configuration of a detection unit of the load cell type weighing device according to the present embodiment, and FIG. 4 is a block diagram showing a schematic configuration of the entire weighing device.

As shown in FIG. 3, in the detection unit 10 of the weighing device according to the present embodiment, the fixed end side of the load cell 11 is attached to the load cell support base 15 protruding from the machine base 12, and the free end side of the load cell 11 is attached. Is constructed by attaching the support frame 16. In addition, a saucer 13 is attached to the upper end of this support frame,
The load cell 11 is configured so that its free end side is displaced by the weight of the object 14 to be weighed on the tray 13.

The detection unit 10 is electrically connected to an amplifier 21 as shown in FIG. 4, and the amplifier 21 is connected to an arithmetic unit 30 via an A / D (analog / digital) converter 22. There is. The arithmetic unit 30 has a subtractor 31, an integration memory 32, and an extreme value determiner 33. In the present embodiment, the arithmetic unit 30 has each of these functions, and a series of units as shown in the flowchart of FIG. It is composed of a Wackip microcomputer that performs processing.

In this weighing device, in order to amplify the detection value detected by the detection unit, the amplifier 21 is interposed between the detection unit and the arithmetic unit 30 that performs arithmetic processing. P in the above equation (1) is Becomes Incidentally, G is the gain of the amplifier 21.

Then, the detected value (displacement) X _S (t) (where X _S is A /
The detected value on the detector side of the D converter) is amplified by the amplifier 21 to become the detected value X (t), converted into a digital signal by the A / D converter 22, and transmitted to the arithmetic unit 30. It That is, the detected value X (t), which is an analog value that changes continuously
Becomes a quantized time series, so in the arithmetic unit, X (t) is an integer value and t is a positive integer value. Now, the detected value digitized in this way is X
_{Let D} (t).

The differential processing of the expressions (3) and (4) is the differential processing of the detected value X _D (t) in the differentiator 31 (X _D (t) -X (t-1)).
Has been substituted in. Further, the speed is processed so as to have an absolute value, and the negative speed is also used as the absolute value.

The momentary displacement velocity (absolute value) thus obtained by the subtractor 31 is within the predetermined time range [T1, T2] and the predetermined displacement range [X1, X2] and is integrated for each displacement point. It is cumulatively stored at a predetermined address (ADD (X1) to ADD (X2)) of the memory 32 (see FIG. 5). Within a predetermined time range (T1 to T2
Up to). The extreme value determiner 33 determines the displacement point Xp indicating the extreme value (the maximum value in the present device) of the values (integrated value) stored in the address of the data in the cumulative storage device 32. This integration storage unit 32 executes the above-mentioned expression (5), and the extreme value determiner 33 executes the above-mentioned expression (6).

Then, the displacement point Xp indicating the extreme value obtained by the above determination is the direct current component, and the weight of the object to be weighed from the direct current component Xp. Can be detected. This is because the speed at which the direct current component passes through the displacement point becomes the highest due to the relationship between elastic energy and speed.

As described above, the present measuring device has a relatively simple structure and can detect the accurate weight of the object to be weighed in a short time and easily even in a vibrating state.

Further, in the above embodiment, the vibration is detected by the load cell, but instead of this, as shown in FIG.
A speedometer 11 'for detecting the speed of the above is attached to the elastic body 1', and as shown in FIG. 8, it is obtained from the speedometer (included in the detecting section 10 'in FIG. 8). The detected values (position and velocity of each displacement point) are amplified and sampled by amplifiers 21A ', 21B' and A / D converters 22A ', 22B', and predetermined processing is performed by the arithmetic unit 30 '. That is, the absolute value of the displacement velocity at each displacement point may be calculated, and this value may be integrated and stored to determine the extreme value.

Next, an example in which the weight detection method according to the present invention is used in an optical weighing device will be described. FIG. 9 is a configuration diagram showing an overall configuration of the weighing device according to the present embodiment, FIG.
The figure is a configuration diagram showing an amplification mechanism and an integration storage mechanism of the present apparatus.

As shown in FIG. 9, the optical weighing device according to the present embodiment has a light source having a wavelength component that can be sensed by an image sensor (multi-element charge storage photoelectric converter) 62 (in the case of the present embodiment). , A semiconductor laser oscillator) 55, and a collimator 56 that is configured integrally with this light source to form a light beam from the light source 55 into a parallel light flux that is sufficiently thinner than the light receiving area (light receiving width l ₀ ) of the light receiving bit 62a of the image sensor 62. , Bend the light flux parallel to the optical axis of the lens so that it passes through the focal point of the lens, and elastic body 59
Displacement magnifying lens system that magnifies the amount of displacement (in this embodiment, a convex lens that is a resolution optical system is used) 57
The displacement magnifying lens system 57 is mounted on a support frame 58 that supports the tray 53. The support frame 58 is attached to the free end side of the elastic body 59, the fixed end side of the elastic body 59 is attached to the support base 60 protruding from the machine base side, and the free end side of the elastic body 59 is a tray. It is configured to be displaced by the weight of the object to be weighed 65 on 53. The optical path of the parallel light flux is corrected so that the light flux emitted from the light source 55 passes through the collimator 56 and the displacement magnifying lens system 57 in front of the line L to irradiate the parallel light flux on the surface of the image sensor 62. A cylinder lens 61 for correcting the optical path is disposed, and a sensor (light receiving element) that senses a parallel light flux and stores the integrated light amount in front of the cylinder lens 61.
As 62a), an image sensor 62 having a photodiode array is provided via a space. 10 As shown, the distance G · f from principal point O ₁ of the displacement magnifying lens system 57 to the light receiving surface 62b of the image sensor 62, the image space focal point F from the main point O ₁ of the displacement enlarging lens system 57 is set to G times the distance to ₁ (image space focal length) f. This is a configuration for amplifying displacement, like the amplifier in the load cell type weighing device described above. Further, the image sensor 62 is formed by a light receiving element array in which m light receiving elements 62a are arranged in the vibration direction (vertical direction), and each light receiving element 62a constituting this light receiving element array has an end (an upper end in this embodiment). ), A signal (referred to as a light receiving bit number) is sequentially added, and as shown in FIG. 11, the displacement (X1 ≦ X ≦ X2) to be measured and the above light receiving bit number j (j = 0,1,2, ..., m). -1) is configured to correspond. For this reason, in this configuration, the received light bit number is immediately quantized displacement. Therefore, in order to obtain sufficient resolution, the light receiving element 62a
The width l _{0 in} the vibration direction of must be sufficiently small.

Further, as shown in FIG. 9, the image sensor 62 is connected to an extreme value determiner 64 of an arithmetic unit 65 via an A / D converter 63. In this embodiment, the arithmetic unit 65 is composed of a one-chip microcomputer, and the extreme value determiner 64 is realized in this microcomputer as shown in the flow chart of FIG.

Thus, the present weighing device weighs an object to be weighed in a stable vibration state as follows.

That is, the light emitted from the light source 55 is converted into a sufficiently thin parallel light beam by the collimator 56, passes through the displacement magnifying lens system 57, passes through the focal point F ₁ thereof, and the cylinder lens 61.
The optical path is corrected so that the light-receiving surface of the front image sensor 62 is illuminated, and the light-receiving surface of the image sensor 62 is illuminated. In this state, when the object 65 to be weighed is placed on the tray 53 and the elastic body 59 is in a vibrating state, the displacement magnifying lens system 57 is vertically displaced (vibrated) and the passing light of the image sensor 62 is transmitted. Shake up and down on the light receiving surface. Here, the displacement X _S (t) of the elastic body 59 (in other words, the displacement magnifying lens system 57) that is in a stable vibration state, by passing through the displacement magnifying lens system 57 as shown in FIG. The light is amplified on the light receiving surface 62b of the image sensor 62, and is transmitted as a displacement X (t) at the light arrival point of the parallel light flux. Therefore, in this device, P in the above equation (1) is Is used. Here, G is a gain.

The light-receiving point of each light-receiving surface 62b of the image sensor 62, to which the amplified displacement is transmitted as described above, has the light-receiving point of the elastic body 5b.
Since it constantly moves by the vibration of 9, it receives light in an amount that is inversely proportional to its moving speed (in other words, proportional to the time during which the light-receiving point of the parallel light flux remains on each light-receiving element).

That is, if these are expressed by mathematical expressions, now, when the light-arriving point of the parallel light flux passes through the light receiving element 62a (light receiving bit number j) for the Sth time, a minute time [ _0] for passing through the width l ₀ in the vibration direction of the light receiving element [ t (j, s), t (j, s) + Δt
(J, s)], Therefore, when passing through the Sth time, the light receiving amount Is (j) of this light receiving element is expressed by the following equation (8).

However, in the equation (8), L is a proportional constant. Therefore, within the predetermined time range [T1, T2] to be measured, the light-receiving point of the parallel light flux is n when the light receiving element 62a (light receiving bit number j) is arbitrary.
(J) Total received light amount I of the light receiving element 62a when passing through the light receiving element 62a
(J) is expressed by the following equation (9).

The above equation (8) corresponds to the above equation (5), and the equation (9) corresponds to the above equation (6).

Therefore, each light receiving bit 62 that constitutes the image sensor 62
The light a receives a parallel light flux of an amount represented by the above equation (9) within a predetermined time range [T1, T2].

The received light amount (irradiation amount) I (j) (j = 0,1,2, ..., m-1) stored in each light receiving element in this image sensor is A / D.
It is converted into a digital value I _D (j) by the converter 63 and transmitted to the extreme value determiner 64 formed in the arithmetic unit 65.

This extreme value determiner 64 determines the light receiving element showing the lowest light receiving amount from the light receiving amount of each light receiving element 62a of the image sensor 62, and the displacement point Xp corresponding to the light receiving bit number jp of this light receiving element is determined. It becomes a DC component. And the value of this DC component
The weight value of the object to be weighed from Xp Can be detected. This is because the speed at which the DC component passes through the light receiving bit where the DC component is located becomes the highest due to the relationship between the elastic energy and the speed.

In the calculation device according to the present embodiment, the calculation of each of the above formulas is optically processed except for the extreme value determination / output. That is, in the optical weighing device as in the present embodiment, the velocity value at each displacement point is input to the predetermined address of the integrating storage device like the load cell type weighing device, but such a process is unnecessary. Then, as shown in FIG. 11, each light receiving element of the light receiving element array arranged in the vibration direction becomes each displacement point as it is, and each light receiving element receives the light receiving amount which is inversely proportional to the speed and stores (stores) the total amount. To do. Then, as shown in the flowchart of FIG. 12, only the extreme value determination is performed by the extreme value determiner 64 in the arithmetic unit 65 composed of a microcomputer.

Therefore, the configuration is extremely simple, and high-speed processing (measurement) can be performed by an arithmetic unit having a small capacity.

Further, in the case of the optical type, the weight detection method described above can be implemented with a simple configuration, and thus high reliability can be expected.

In the case of this optical metering device, the location where the amount of received light is the minimum is the true value, so the predetermined time range for measurement [T1, T2] and the predetermined displacement range [X1, X2] , It is necessary to set it appropriately considering the weighing device and the object to be weighed or the state of weighing.

For example, in the measurement showing the vibration state as shown in FIG.
It is necessary to set the range as shown in FIG. 2 (a) as the predetermined time range and the predetermined displacement range.

Further, the displacement magnifying lens system portion of the above optical embodiment may be configured as a displacement magnifying lens by using a concave mirror 57 'as shown in FIG. 13, or a prism as shown in FIG. 57a "and the convex lens 57b" may be used together.

(Effects of the Invention) According to the weight detection method of the present invention, accurate weighing is possible even under stable vibration conditions, which has been impossible in the past with accurate weighing. Moreover, a short time (2 to 3 of the conventional
Double speed). Therefore, unlike the conventional case, it is not necessary to wait until the elastic body reaches a steady state, so that a large amount of objects on a line transferred by a conveyor or the like can be measured accurately and quickly. That is, when it is necessary to weigh an object being transferred in the transfer step, a considerable amount of time has been conventionally required in the measuring step, and the transfer speed is restricted by the time of the weighing process. If the method is used, the transfer speed can be significantly improved.

Moreover, since the information obtained from the displacement signal is integrated to detect the mass of the object to be weighed, a weighing error is less likely to occur with respect to a disturbance having an average value of zero. Further, since it has a relatively simple configuration, it is easy to implement, and the time required for the weight detection process is short, and high reliability can be expected.

Further, according to the weight detecting method according to the present invention, when it is carried out, it is not necessary to use a damper for damping like a conventional weight measuring device, so that the production cost can be significantly reduced,
Moreover, since the viscous resistance element is eliminated, it is possible to obtain the effect that the impact generated when the objects to be weighed are suddenly loaded is not left as a weighing error.

As described above, the weight detection method according to the present invention is an epoch-making invention that opens up a new area that is not in the conventional concept of weighing.

[Brief description of drawings]

FIG. 1 is a configuration diagram modeling a schematic configuration of a weighing device, and FIGS. 2 (a) and 2 (b) show the relationship between displacement and time and displacement and displacement speed in the weighing device having the configuration of FIG. Diagram, FIG. 3 is a configuration diagram showing a schematic configuration of a detection unit of the load cell type weighing device according to the present embodiment, FIG. 4 is a block diagram showing a schematic configuration of the entire weighing device, and FIG. 5 is each displacement. FIG. 6 is a diagram showing a relationship between points and addresses of an integration storage device, FIG. 6 is a flow chart showing a processing process in an arithmetic unit, FIG. 7 is a configuration diagram of a detecting portion showing another embodiment, and FIG. FIG. 7 is a block diagram showing the overall configuration of the embodiment shown in FIG. 7, FIG. 9 is a configuration diagram showing the overall configuration of the optical weighing device according to the present embodiment, and FIG. 10 shows the amplification mechanism and integrated storage mechanism. Configuration diagram, Fig. 11 is an enlarged view of the light receiving bit part of the image sensor in Fig. 10. FIG. 12 is a flow chart showing the processing process in the arithmetic unit, FIG. 13 is a plan view showing another embodiment of the displacement magnifying lens system, and FIG. 14 is another embodiment of the displacement magnifying lens system. FIG. 15 is a side view, and FIG. 15 is a diagram showing various vibration states when a loose object is dropped. 1,11,59 …… Elastic body, 10 …… Detector, 30,65 …… Computing unit, 31 …… Differentiator (displacement speed calculator), 32 …… Integration memory, 33,64 …… Extreme value Judge.

Claims (1)

[Claims] 1. When an object to be weighed is placed on a mounting portion on an elastic body of a weighing device and a detected value of a detector exhibits a stable vibration state, this vibration is a true value of the object to be weighed. It is considered that the vibration is composed of the linear component caused by the vibration and the harmonic vibration component caused by the impact motion during mounting, and the absolute value of the displacement velocity at the same displacement point of the vibration displacement obtained by the detector is calculated for each displacement point. A weight detection method, wherein the displacement point having the largest value among the values obtained by integration is used as the value of the DC component to obtain the weight of the object to be weighed.