JPH07333045A - Weighing apparatus - Google Patents

Abstract

PURPOSE:To allow high-speed weighing even if a range to be weighed in weight and shape is wide by selecting the signal which has stabilized most rapidly among weighing signals which are filtered by a plurality of filters having different filtering characteristics. CONSTITUTION:In order to remove a natural frequency of a weighing apparatus in respective weights and shapes most effectively, filtering characteristics different from one another are set for digital filters 18-1 to 18-8. Weighing signals A0 to A8 sampled at predetermined sampling cycles and digitized by an ADD- converter 6 are stored in a RAM 26 of the corresponding filters 18-1 to 18-8, and filtered weighing signals (analyzed data) B1 to B8 calculated by each calculator 24 based on the weighing signals A0 to A8 are output to respective stabilization determiners 20-1 to 20-8. The determiners 20-1 to 20-8 determine, based on the analyzed data B1 to B8, the data which has stabilized most rapidly, and a data selection means 22 selects the analyzed data which is determined to have stabilized most rapidly to output it as weighing data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weighing device, and more particularly to speeding up the weighing.

[0002]

2. Description of the Related Art Generally, when measuring the weight of an object to be weighed by a weighing device, the characteristic vibration of the weighing device superimposed on the weighing signal is filtered and the filtered weighing signal is taken in as weighing data at a stable stage. . In this case, the natural vibration of the weighing device is in a constant frequency band depending on the weight and shape of the object to be weighed, so considering the response of the weighing signal,
By using a filter that effectively removes the band, the delay of the weighing signal is minimized to increase the speed.

FIG. 3 shows the configuration of a conventional weighing device using a digital filter. Weight detector (load cell) 2
The weighing signal of the object to be weighed detected from is amplified by the amplifier 4, digitized by the A / D converter 6, and filtered by the digital filter 8. Then, the weighing data determined to be stable by the stability determiner 10 that performs a moving average calculation or the like is output. On the other hand, when the analog filter of FIG. 4 is used, it is filtered by the analog filter 5 and digitized by the A / D converter 6, and then stable determination is performed.

[0004]

However, the conventional device has the following problems. When the above-mentioned weighing device is used for a weight checker that determines whether it is a positive quantity product or a non-quantity goods, the measurement range of the object to be measured is limited to some extent, so a filter with a constant removal band should be used. By using it, speeding up can be achieved. On the other hand, in the case of an automatic weight sorter that performs pricing according to the weight of the object to be weighed or sorts the weight of the object to be weighed, the object to be weighed has various shapes and weights. Since it has to measure the objects to be weighed in these wide measuring ranges at random,
It is necessary to use a filter that covers a wide range of frequency bands. However, a filter having such a wide elimination band has a slow response and thus cannot improve the weighing speed.

An object of the present invention is to solve the above problems and to provide a weighing device capable of high-speed weighing even if the weight and shape of the object to be weighed are in a wide range.

[0006]

In order to achieve the above object, the weighing apparatus of the present invention comprises a plurality of filters having different filtering characteristics for processing weighing signals from a weight detector, and output signals of these filters. It is provided with a discriminating means for discriminating stabilization and a data selecting means for selecting a filtered weighing signal which is the earliest determined discrimination.

[0007]

According to the present invention, the data selecting means selects the earliest stabilized signal among the filtered weighing signals filtered by the plurality of filters. Therefore,
A filter is automatically selected according to the weight and shape of the object to be weighed.

[0008]

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 apparatus is an automatic weight sorter that weighs the objects M to be weighed using the weighing conveyor 1 and sorts into multiple ranks. The weighing conveyor (load cell) 2, the amplifier 4, the amplifier 4, A / D converter 6, digital filter 18 (8 types in this example, 18-1 to 18-
8), the stability determiner 20 (in this example, 8)
20-1 to 20-8) and a data selection means 22. Digital filters 18-1 to 18-8 are A /
It is connected in parallel to the D converter 6, and each of the arithmetic units 2
4, RAM 26.

The digital filters 18-1 to 18-8 are, for example, 200 g to 300 g and 300 g to 400 when the weight range of the object M to be weighed is 200 to 1000 g.
g, 400 g to 500 g, 500 g to 600 g,
600g-700g, 700g-800g, 800
With respect to the eight stages of g to 900 g and 900 g to 1000 g, the filtering characteristics are set to be different from each other so as to most effectively remove the natural frequency of the weighing device in the weight and shape. The number of the digital filters is increased or decreased according to the width of the object M to be weighed.

Hereinafter, the digital filters 18-1 to 18-1 will be described.
An example of setting 8-8 will be described. First, the weighing signal of the object to be weighed detected by the weight detector 2 is amplified by the amplifier 4 and sampled by the A / D converter 6 at a predetermined sampling cycle (for example, 50 to 100 times / sec). Digitized. This digitized weighing signal A0 (current data), A1 (previous data), A2
(2nd previous data), ... A8 (8th previous data) are stored in the RAM 26 of the corresponding digital filters 18-1 to 18-8. Based on the weighing signals A0 to A8, each computing unit 24 carries out a computation according to the following computing equations (1) to (8), respectively, to obtain a filtered weighing signal (solution data) B1.
Output ~ B8.

Operational expression (1) of the digital filter 18-1: (A0 + A1 + A2 + ... A8) / 9 Operational expression (2) of the digital filter 18-2: (A0 + A
1 + A2 + ... A7) / 8 Digital filter 18-3 operation formula (3): (A0 + A
1 + A2 + ... A6) / 7 Digital filter 18-4 operation formula (4): (A0 + A
1 + ... A5) / 6 Digital filter 18-5 operation formula (5): (A0 + A
1 + ... A4) / 5 Digital filter 18-6 operation formula (6): (A0 + A
1 + ... A3) / 4 Digital filter 18-7 operation formula (7): (A0 + A
1 + A2) / 3 Digital filter 18-8 operation formula (8): (A0 + A
1) / 2 For example, from the digital filter 18-1, the solution data B
Outputs 1.

That is, the digital filters 18-1 to 18-1
8-8 are set to eight stages of low frequency band to high frequency band elimination filters having different filtering characteristics depending on the weight range of the object to be weighed. These solution data B1 to B8 and weighing signals A0 to
The solution data C1 (previous solution data of B1) to C8 (previous solution data of B8) obtained by taking in the previous weighing signal of A8 and performing the same calculation are stored in the RAM 26. In addition to the arithmetic expressions (1) to (8) for obtaining the average value described above, expressions such as a convolution operation and a thinning operation can be used.

Next, the digital filters 18-1 to 18-8
The solution data output from each is the stability determiner 20-1.
Given to ~ 20-8. The stability determiners 20-1 to 20-8 are
Based on these solution data, the fastest and stable data is determined. The data selection means 22 selects the filtered weighing signal (solution data) which is determined to be stabilized the fastest and outputs it as weighing data.

The operation of this weighing device will be described below with reference to the flow chart of FIG. First, a weighing signal is taken in from the weight detector 2, and the weighing signals A0 to A8 digitized by the A / D converter 6 via the amplifier 4 are converted into R
It is stored in the AM 26 (step S1). Each digital filter 1 is based on the data stored in the RAM 26.
The arithmetic units 24 of 8-1 to 18-8 correspond to the arithmetic expressions (1) to
Calculation is performed according to (8), and each solution data B1 to B
8 is output (step S2). Then, in each of the digital filters 18-1 to 18-8, the solution data B
1 to B8 and its previous solution data C1 to C8 are RAM
It is stored in step 26 (step S3).

Based on the solution data stored in the RAM 26, the stability discriminators 20-1 to 20-8 perform stability discrimination.

First, the solution data B1 and the previous solution data C1
It is confirmed whether or not match (step S4). If they match, the data output from the digital filter 18-1 is output.
Data is initially determined to be stable, and the output at this time is selected as the weighing data. If they do not match, it is then confirmed whether the solution data B2 and the previous solution data C2 match (step S5). If they match, it is considered that the data output from the digital filter 18-2 is stable first, and the output at this time is selected as the weighing data.
If they do not match, then it is confirmed whether or not the solution data B3 and the previous solution data C3 match (step S6).
Thereafter, similarly, it is confirmed whether or not the data match with each other (steps S7 to S11), and one of the digital filters 18-1 to 18-8 outputs the earliest and stable data. When none of the digital filters 18-1 to 18-8 outputs (step S11), step S1
Then, the measurement signal is captured again.

For example, if the weight of the object to be weighed is 250 g, the data output from the digital filter 18-1 is first judged to be stable, and the output of this filter is selected as the weighing data. Similarly, if the object is 720 g, the data output from the digital filter 18-6 is selected.

As described above, this weighing device is provided with a plurality of digital filters for eliminating the natural vibration of the weighing device corresponding to a wide range of weights and shapes of the object to be weighed, and the signal that converges earliest is used as the weighing data. I will import it,
It is possible to speed up weighing. In addition, when this weighing device is used for static weighing in which the object to be weighed is not moved, it is possible to achieve high-speed weighing and high accuracy.

In this embodiment, the digital filter, the stability determiner and the data selecting means are separately constructed, but they are constructed in a single arithmetic element such as a DSP (digital signal processor). Good.

In this embodiment, the weighing device is used for the automatic weight sorter, but it may be used for the combination weighing device or the semi-automatic weighing device.

Although a plurality of digital filters are used for a plurality of filters in this embodiment, a plurality of analog filters may be used.

[0022]

As described above, according to the present invention, the data selecting means selects the earliest stabilized signal among the filtered weighing signals filtered by the plurality of filters, so that the weight of the object to be weighed is selected. , The filter according to the shape is automatically selected. This makes it possible to provide a weighing device capable of high-speed weighing even if the weight and shape of the object to be weighed are in a wide range.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the above-mentioned weighing device.

FIG. 3 is a block diagram showing a conventional weighing device.

FIG. 4 is a block diagram showing a conventional weighing device.

[Explanation of symbols]

2 ... Weight detector (load cell), 6 ... A / D converter, 1
8-1 to 18-8 ... Digital filter, 20-1 to 20-8 ...
Judgment means (stability judgment device), 22 ... Data selection means.

Claims (1)

[Claims] 1. A plurality of filters having different filtering characteristics for processing a weighing signal from a weight detector, a discriminating means for discriminating the stabilization of an output signal of these filters, and a discriminated filter having the earliest stabilization. A weighing device, comprising: a data selection means for selecting a weighing signal.