WO2023026337A1

WO2023026337A1 - Weighing device and weighing method using three-axis acceleration sensor

Info

Publication number: WO2023026337A1
Application number: PCT/JP2021/030859
Authority: WO
Inventors: 健井原; 剛松田; 吉一長根
Original assignee: 株式会社エー・アンド・デイ
Priority date: 2021-08-23
Filing date: 2021-08-23
Publication date: 2023-03-02

Abstract

Provided is a weighing device and a weighing method that enable automatic solution of a problem caused by changes in three-axis directions by using a three-axis acceleration sensor. A weighing device (1) comprises: a weighing tray (11); a weight sensor (12) connected to the weighing tray; a three-axis acceleration sensor (20) that sets x and y on a plane parallel to the horizontal of the weight sensor and z in a direction perpendicular to the horizontal of the weight sensor, and detects acceleration changes in the three axes of x, y, and z; a storage unit (14) that stores reference outputs of the three-axis acceleration sensor along the three axes when the weight sensor is horizontally situated; and an arithmetic operation unit (13). The arithmetic operation unit compares currently-obtained outputs of the three-axis acceleration sensor in along the three axes with the reference outputs, detects existence of inclination when an output along x and/or y has been changed and existence of an installation place change when an output along z has been changed, and notifies of a user of the change.

Description

Weighing device and weighing method using triaxial acceleration sensor

The present invention relates to a weighing device and weighing method using a triaxial acceleration sensor.

A balance, which is a weighing device, uses a weight sensor to measure the component Wv of a load perpendicular to the weighing pan, and uses the gravitational acceleration g at the location where the balance is installed to determine the mass m of the object placed on the weighing pan as follows: It is obtained from the formula (1).

As shown in FIG. 10A, when the direction in which the gravitational acceleration g acts coincides with the direction perpendicular to the weighing pan, the mass measured by the balance, that is, the measured value m can be said to be a true value. On the other hand, as shown in FIG. 10(B), when the direction in which the gravitational acceleration g acts does not match the direction perpendicular to the weighing pan, a component Wh that cannot be detected by the balance is generated, and the weight value m is lighter than the true value.

Due to the circumstances of the balance described above, it can be said that the weighed value contains an error when the following two occur.
(i) When the balance tilts and the load component Wv perpendicular to the weighing pan decreases (ii) When the location where the balance is installed changes and the gravitational acceleration g changes A typical balance is equipped with a level (bubble bubble) to detect the tilt of the balance. For example, Japanese Laid-Open Patent Publication No. 2002-100000 discloses a technique for more accurately controlling the level of a balance by detecting air bubbles in a level with an optical sensor.

JP 2016-038377 A

For the above (i), although there is a technique such as Patent Document 1, it is necessary to mount a plurality of optical sensors around the bubble, which makes the configuration complicated.

Regarding (ii) above, we ask the user to adjust the sensitivity using a weight when the installation location of the balance is changed. There is

With respect to these problems, the inventors believe that the balance itself can detect the above problems (i) and (ii) by detecting the acceleration of the balance in three axial directions, and the balance itself can solve them. I wondered.

The present invention has been made based on the above-mentioned conventional problems and the above-mentioned knowledge of the inventors. It is an object of the present invention to provide a weighing device and a weighing method that automatically solves

In order to solve the above problems, a weighing device according to one aspect of the present invention includes a weighing pan, a weight sensor connected to the weighing pan, x and y on a plane parallel to the horizontal of the weight sensor, and the weight sensor. a three-axis acceleration sensor for detecting acceleration changes in the three axes of x, y, and z by setting z in a direction perpendicular to the horizontal of the weight sensor; A storage unit for storing three-axis reference outputs, and an arithmetic processing unit, wherein the arithmetic processing unit compares the three-axis current outputs of the three-axis acceleration sensor with the reference outputs to determine x and/or Alternatively, if the output of y has changed, it detects that there is a tilt, and if the output of z has changed, it detects that there is a change in the installation location and notifies the user.

In the above aspect, if the output of x and/or y of the three-axis acceleration sensor has changed, the arithmetic processing unit uses equation (14) to calculate the measured value m detected by the weight sensor as It is also preferable to correct to the corrected metric value m'.

In the above aspect, when only the output of z of the three-axis acceleration sensor has changed, the arithmetic processing unit changes the value of gravitational acceleration used for calculating the weight value m detected by the weight sensor to the three-axis acceleration sensor. It is also preferable to change the local gravitational acceleration value glocal obtained using the z-axis output of the axial acceleration sensor to obtain the corrected metric value m'.

In the above aspect, if the outputs of z and x and/or y of the three-axis acceleration sensor have changed, the arithmetic processing unit changes the value of the gravitational acceleration used in the equation (14) to the three-axis acceleration sensor. It is also preferable to correct the measured value m detected by the weight sensor to a corrected measured value m' by changing the local gravitational acceleration glocal obtained using the three-axis outputs of the acceleration sensor.

In the above aspect, when the corrected weight value m' of the object to be weighed exceeds the range of the allowable threshold for the reference mass of the object to be weighed, the arithmetic processing unit warns the user that the error cannot be eliminated by correction. is also preferred.

In order to solve the above problems, a weighing method according to an aspect of the present invention includes a weighing pan, a weight sensor connected to the weighing pan, x and y on a plane parallel to the horizontal plane of the weight sensor, and (A) using a weighing device equipped with a three-axis acceleration sensor that detects acceleration changes in the three-axis directions of x, y, and z by setting z in the direction perpendicular to the horizontal direction of the weight sensor; (B) comparing said current output with said three-axis reference output when the weight sensor is horizontal; (C) said (B) ) if the output of x and/or y has changed in step (D) if the output of z has changed in step (B) is characterized by notifying the user that there is a change in the installation location.

In the above aspect, (E) if the output of x and/or y has changed in step (B), the weight value m detected by the weight sensor is corrected using equation (14). and (F) if only the output of z has changed in step (B), the gravitational acceleration value used to calculate the weighing value m detected by the weight sensor is changed. , changing the local gravitational acceleration value glocal obtained using the z-axis output of the three-axis acceleration sensor to obtain a corrected metric value m'; and x and/or y outputs have changed, the value of the gravitational acceleration used in the above equation (14) is replaced by the local gravitational acceleration glocal and correcting the measured value m detected by the weight sensor to a corrected measured value m'.

In the above aspect, (H) weighing an object, and if the corrected weight value m' of the object exceeds the allowable threshold range for the reference mass of the object, the error cannot be eliminated by correction, and the user It is also preferred to have the step of alerting the

According to the present invention, it is possible to provide a weighing device and a weighing method that automatically detect changes in acceleration in three axial directions and automatically solve problems caused by the changes.

It is a figure which shows the relationship of each component of a triaxial acceleration sensor. FIG. 10 is a diagram showing results of correction using a triaxial acceleration sensor; 1 is a configuration block diagram of a weighing device according to a first embodiment of the present invention; FIG. It is a schematic perspective view of the same weighing device. It is a flowchart of the weighing method using the same weighing device. FIG. 4 is a configuration block diagram of a weighing device according to a second embodiment of the present invention; It is a flowchart of the weighing method using the same weighing device. FIG. 4 is a diagram showing a preferred mounting form of an acceleration sensor in the embodiments; FIG. 4 is a diagram showing a preferred mounting form of an acceleration sensor in the embodiments; It is a figure showing consideration about the weighing value of a balance.

First, the inventor's considerations up to the point of conceiving the preferred embodiment of the present invention will be described based on the drawings.

1. Consideration by the inventor 1-1. Problems with Balances As described above with reference to FIG. 10, a balance generally includes a weighing pan and a weight sensor connected to the weighing pan to measure the load component Wv perpendicular to the weighing pan, Using the gravitational acceleration g at the place where the balance is installed, the mass m (weighing value) of the object to be weighed is obtained from equation (1).

Therefore, when the following two occur, the weight value m measured by the balance contains an error.
(i) When the balance tilts and the load component Wv perpendicular to the weighing pan decreases (ii) When the location where the balance is installed changes and the gravitational acceleration g changes

1-2. Considerations for Solving Problems To solve this problem, the inventors have proposed that the tilt and gravitational acceleration of the balance can be detected by mounting a triaxial acceleration sensor on the balance. ii) both were considered to be auto-detectable by the balance. Secondly, the inventors have found that by using the value of the triaxial acceleration sensor, the balance can detect the change in the weight value resulting from the decrease in the load component Wv perpendicular to the weighing pan and the change in the gravitational acceleration g. I thought that it would be possible to automatically correct it after identifying it.

FIG. 1 is a diagram showing the relationship between the tilt angle and each component of gravitational acceleration when a triaxial acceleration sensor is mounted on a certain virtual plane vp. This three-axis acceleration sensor (hereinafter referred to as an acceleration sensor) detects acceleration of the virtual plane vp in orthogonal three-axis directions. The x and y of the acceleration sensor are on the virtual plane vp, and the z is in the direction perpendicular to the virtual plane vp. Each component of gravitational acceleration g for this three-axis acceleration sensor is expressed as "gx, gy, gz". The gx and gy components are on the virtual plane vp, and the gz component is in the direction perpendicular to the virtual plane vp. The tilt angle θ is the angle between the direction of the gravitational acceleration g and the direction of the gz component.

Let each component output by the acceleration sensor at the tilt angle θ be "Xout(θ), Yout(θ), and Zout(θ)". When the gravitational acceleration g detected by the acceleration sensor is g={gx(θ), gy(θ), gz(θ)}, gx(θ), gy(θ), and gz(θ) are the inclination Using the outputs "Xout(0), Yout(0), Zout(0)" when the angle .theta.=0, the equations (2), (3) and (4) can be expressed. However, Ax, Ay, and Az are proportional coefficients, and g=|g|.

The relationship between the tilt angle θ of the acceleration sensor and the gravitational acceleration g is shown in FIG.

becomes.

1-3. Correction for Balance Tilt Consider the correction of the weight value for balance tilt, ie a decrease in the load component Wv perpendicular to the weighing pan. The tilt of the balance can be detected by monitoring the x and y outputs of the acceleration sensor. Let m(0) be the mass of the weighing object when the tilt angle of the balance is θ=0, and m(θ) be the mass of the weighing object when the tilt angle is θ. Let W be the load on the weighing pan of the balance, and Wv be the load component perpendicular to the weighing pan. Here, if the aforementioned virtual plane vp is set parallel to the horizontal plane of the weight sensor, when the tilt angle θ=0, W=m(0) and gravitational acceleration g=Wv. A relationship is formed.

However, when the tilt angle θ≠0, the gravitational acceleration gz(θ) perpendicular to the weighing pan is given by Equation (8) from Equation (6), so the load component Wv perpendicular to the weighing pan is given by Equation (8) (9) becomes

From this, formula transformations of formulas (10) to (13) hold.

The balance acquires the mass m(θ) as a weighing value. From equations (12) and (13), when the balance has an inclination angle θ, the weighing value m(0) when the inclination angle θ=0 is multiplied by a correction term including θ. It turns out that you underestimate the mass. Therefore, when there is an inclination angle θ, in order to obtain the correct mass (measurement value), it is necessary to divide the mass m(θ) when there is an inclination angle θ by the correction term including θ, cosθ or √1-sin2θ. There is

Regarding the correction term, theoretically, the value will be the same regardless of which formula (12) or (13) is used. However, in reality, it is assumed that an extremely small tilt (0.1° or less) of θ≃0 is detected, so a small angle change cannot be detected using the cosine component of Equation (12). . Therefore, it is preferable to use the sine component of equation (13) as the correction term.

Therefore, when the acceleration sensor detects the tilt angle θ, the balance calculates the weight value m (mass m(θ)) measured by the balance based on the equations (13) and (5) by the following equation: (14) is performed to calculate a corrected measured value m'.

FIG. 2 is a diagram showing the results of verification of correction using a triaxial acceleration sensor. In the verification, a balance with a weighing capacity of 10 kg and a minimum display of 0.01 g was used, and the weighing object placed on the weighing pan was 10000 g. Here, the tilt angle from the installation surface (horizontal) of the balance is changed from 0° to 0.5°. , a corrected metric value m' was obtained. As shown in FIG. 2, a corrected weight value m' of 10000 g was obtained at any tilt angle.

1-4. Correction for changes in the location of the balance Consider the correction of weighing values for changes in the gravitational acceleration g due to changes in the location where the balance is installed due to shipment from the factory or movement of facilities. A change in the gravitational acceleration g can be detected by monitoring the gravitational acceleration gz(θ) in the direction perpendicular to the horizontal direction of the weight sensor. As described above, in the balance, the weight value m is obtained by Equation (1) using the component Wv of the load perpendicular to the weighing pan. Therefore, if the value of "g" used in equation (1) is changed from the value before movement of the balance to the value after movement of the balance (hereinafter referred to as "local gravitational acceleration "glocal"), Errors due to changes in the location where the balance is installed can be eliminated.

Here, the local gravitational acceleration glocal is obtained using the output value of the acceleration sensor. From equation (6), glocal is equation (15).

When the acceleration sensor detects a change in the gravitational acceleration g, the balance replaces the value of the gravitational acceleration g used to calculate the weighing value m detected by the weight sensor in Equation (1) with the acceleration obtained in Equation (15). The measured value is obtained by changing the value of the local gravitational acceleration glocal obtained using the output of the sensor. Here, in this consideration, since the case where the installation location of the balance changes, that is, the case where only the z component of the acceleration sensor changes, in equation (15), the tilt angle θ is zero and glocal = gz(θ=0). In other words, when the acceleration sensor detects a change in gravitational acceleration g, the balance converts the load component Wv perpendicular to the weighing pan measured by the weight sensor to the local gravitational acceleration glocal (where θ=0). The divided value is taken as the corrected metric value m' (equation (16)).

In the conventional technology, the local gravitational acceleration glocal is stored in (1) the numerical value of the gravitational acceleration at the representative point in the storage unit of the balance (for example, Ibaraki 9.79952 [m/s2], Sapporo 9.80478 [ m/s2], Osaka 9.79703 [m/s2], etc.), select the point closest to the place where the balance is installed (on-site), or (2) adjust using a weight at the place where the balance is installed (on-site). Therefore, it was sought after. On the other hand, if the above consideration using the acceleration sensor is used, the local gravitational acceleration glocal of the balance using the output value of the acceleration sensor can be reflected, so the weighing accuracy is improved more than the conventional technique, and This has the advantage of eliminating the need for on-site adjustments using weights each time the balance is installed in a different location.

1-5. Correction when both the tilt of the balance and the change in the installation location occur Consider the correction of the weighing value when both a decrease in the load component Wv perpendicular to the weighing pan and a change in the gravitational acceleration g occur. If both occur, based on considerations 1-3 and 1-4 above, both errors can be corrected by changing the value of "g" used in equation (14) for inclination to the local gravitational acceleration glocal. can be resolved. glocal is Eq. (15), and a further transformation to Eq. (17) holds.

The sine term of equation (17) is obtained from equation (5) including gx(θ) and gy(θ) detected by the acceleration sensor. Therefore, the local gravitational acceleration glocal can be obtained from equation (17) by substituting the output values of x, y, and z of the acceleration sensor. In other words, the balance uses the local gravitational acceleration glocal (θ≠0) to replace the weight value m (mass m(θ)) measured by the balance when both tilting of the balance and changes in gravitational acceleration occur. Then, the corrected measurement value m' is calculated by the following equation (18).

1-6. Weighing method using a three-axis acceleration sensor Based on the above considerations, the inventors first proposed that a three-axis acceleration sensor be mounted on the balance, and the reference output "Xout By comparing (0), Yout(0), Zout(0)” with the current output “Xout(1), Yout(1), Zout(1)”, (i) the tilt of the balance and (ii) ) It was thought that the balance itself could detect changes caused by the installation location after distinguishing them. Furthermore, the inventors secondly found that the weight value when the balance is tilted can be corrected based on the consideration of 1-3 above, and the weight value when the installation location of the balance is changed can be corrected based on the consideration of 1-4 above. , and the metric value when both occur can be corrected based on considerations 1-5 above.

Therefore, by equipping the balance with a 3-axis acceleration sensor and detecting the following three acceleration change patterns, the balance can automatically detect changes in the tilt of the balance and changes in the installation location, and reduce weighing error caused by changes. can be automatically corrected.
Pattern (1) z only changes Pattern (2) x and/or y changes (i.e. x and y change, x change, or y change)
Pattern (3) z and x and/or y change (i.e. x, y, z all change, x and z change, or y and z change)

When pattern (1) occurs: the balance detects that the installation location has changed and notifies the user. Then, the weight value is corrected by the equation (16). The gravitational acceleration g uses the local gravitational acceleration glocal.
If pattern (2) occurs: the balance detects that a tilt has occurred and notifies the user. Then, the weight value is corrected using equation (14). For the gravitational acceleration g, the value used last time is used as it is.
If pattern (3) occurs: the balance detects changes in both tilt and gravitational acceleration and notifies the user. Then, the weight value is corrected by the equation (18). The gravitational acceleration g uses the local gravitational acceleration glocal.

Based on the above considerations, preferred embodiments of the present invention will be described with reference to the drawings.

2. First Embodiment 2-1. Configuration of Weighing Apparatus (Balance) FIG. 3 is a configuration block diagram of the weighing apparatus according to the first embodiment of the present invention, and FIG. 4 is a schematic perspective view of the weighing apparatus. The weighing device is an electronic scale (hereinafter referred to as balance 1). The balance 1 has a main body case 10 , a weighing pan 11 , a weight sensor 12 , an arithmetic processing section 13 , a storage section 14 , an operation section 15 , a display section 16 and a triaxial acceleration sensor 20 .

As shown in FIG. 4, the body case 10 houses a Roberval mechanism 12' that connects the weighing pan 11 and the weight sensor 12. As shown in FIG. The Roberval mechanism 12' is a structure for transmitting the load received by the weighing pan 11 to the weight sensor 12, and is formed of a rectangular metal block. It is a well-known one comprising a fixed portion to be fixed, upper and lower secondary rods connecting the floating portion and the fixed portion, and a load transmission portion for transmitting the load acting on the floating portion to the weight sensor 12 . The weighing pan 11 is supported by a Roberval mechanism 12 ′ and placed on the body case 10 . The weighing pan 11 has a horizontal surface 11' on which an object to be weighed is placed. For the weight sensor 12, an electromagnetic balance type, strain gauge type, capacitance type, or the like is used. The load detected by the weight sensor 12 is A/D converted and input to the arithmetic processing unit 13, where it is converted into a weight value.

As described above, a balance generally measures the load component Wv perpendicular to the weighing pan, and uses the gravitational acceleration g at the location where the balance is installed to calculate the weight of the weighing object from equation (1). We are looking for the value m. In order to utilize this principle, it is assumed that the weight sensor 12 is placed on a horizontally leveled table while the main body case 10 is being held while using, for example, a level. 12 is mounted so as to keep horizontal (for example, it is mounted so that the plane provided by Roberval mechanism 12' keeps horizontal). The weighing pan 11 is supported downward in a direction perpendicular to the horizontal plane of the weight sensor 12 by a pan boss (not shown) protruding from the Roberval mechanism 12', and the horizontal plane 11' of the weighing pan 11 coincides with the horizontal plane of the weight sensor. installed to do so.

The three-axis acceleration sensor 20 (hereinafter referred to as the acceleration sensor 20) is an IC module equipped with a sensor that integrates a spring and a weight and an element that detects displacement when acceleration is applied to the sensor. The acceleration sensor 20 is arranged on a virtual plane vp parallel to the horizontal of the weight sensor 12, and the x and y of the acceleration sensor 20 are arranged in the virtual plane vp, and the z is arranged in a direction perpendicular to the virtual plane vp. Thus, in the acceleration sensor 20, x and y are set parallel to the horizontal of the weight sensor 12, z is set in the direction perpendicular to the horizontal of the weight sensor 12, and orthogonal three-axis directions (x, y, Detect the acceleration of z). That is, the acceleration sensor 20 is attached so that the horizontal plane of the acceleration sensor 20 and the horizontal plane of the weight sensor 12 are aligned. In this embodiment, since the purpose of this embodiment is to detect and correct the change due to the inclination of the load received by the weight sensor 12, by attaching the acceleration sensor 20 and the weight sensor 12 so that they are horizontally aligned, both can be corrected. The origin of the tilt angle is the same, and the error can be reduced. The virtual plane vp on which the acceleration sensor 20 is arranged may be set at any position within the main body case 10 as long as it does not interfere with the weight sensor 12 . A suitable setting of the virtual plane vp on which the acceleration sensor 20 is mounted, that is, the mounting position of the acceleration sensor 20 will be described later. Note that the x-axis and y-axis settings in FIG. 4 may be reversed.

After the acceleration sensor 20 is attached to the balance 1 and before the balance 1 is shipped from the factory, the reference output "Xout ( 0), Yout(0), and Zout(0)'' are measured and stored in the storage unit 14, which will be described later.

The operation unit 15 and the display unit 16 are provided on the front side surface of the body case 10 of the balance 1. From the operation unit 15, a weighing operation, which will be described later, can be performed. The display unit 16 displays a screen associated with weighing, which will be described later.

The arithmetic processing unit 13 is a microcontroller in which, for example, a CPU, ROM, RAM, etc. are mounted on an integrated circuit. The arithmetic processing unit 13 has an acceleration change detection unit 131 and a change notification unit 132 for detecting changes in acceleration using the acceleration sensor 20 . Further, the arithmetic processing unit 13 has a tilt correcting unit 133 and a gravity correcting unit 134 in order to perform correction accompanying changes in acceleration. The functions of the

functional units

131, 132, 133, and 134 are implemented by, for example, reading and executing programs stored in the storage unit 14 by the CPU. The details of the function of each functional unit will be described later in "2-2. Weighing Method".

The storage unit 14 is a semiconductor memory device such as RAM, flash memory, or a storage medium such as a memory card. The storage unit 14 stores various programs for calculation of the calculation processing unit 13 . Further, the storage unit 14 stores reference outputs “Xout(0), Yout(0), Zout(0)” of the acceleration sensor 20 for detecting changes using the acceleration sensor 20 .

The above is the configuration of the balance 1 using the acceleration sensor 20 according to the first embodiment. Next, a weighing method using the balance 1 will be described.

2-2. Weighing Method FIG. 5 is a flowchart of a weighing method using the weighing device according to the first embodiment. This flow is automatically started before the balance 1 shifts to weighing mode, such as when the power of the balance 1 is turned on or when the balance 1 has not been used for a certain period of time.

When the flow starts, first, in step S101, the acceleration change detection unit 131 functions to acquire the current outputs "Xout(1), Yout(1), Zout(1)" of the acceleration sensor 20.

Next, in step S102, the acceleration change detection unit 131 reads out the reference outputs "Xout(0), Yout(0), Zout(0)" and the current outputs "Xout(1), Yout(1)". ), Zout(1)".

Next, in step S103, the acceleration change detection unit 131 determines which change in the next pattern corresponds.
Pattern (1): Only z is changed Pattern (2): x and/or y are changed Pattern (3): z and x and/or y are changed

If there is no change in any of patterns (1) to (3), the process proceeds to step S104, and the change notification unit 132 functions to notify the user that there is no change in acceleration. The change notification unit 132 displays, on the display unit 16, for example, a message that there is no change in acceleration, or in other words, a message that there is no abnormality in the tilt of the balance or gravitational acceleration. After the notification by the change notification unit 132 ends, the balance 1 shifts to the weighing mode.

On the other hand, if pattern (1) is detected in step S103, the flow moves to steps S105 and S106. In step S106, the change notification unit 132 notifies the user that pattern (1) has changed. The change notification unit 132 displays, on the display unit 16, for example, a message indicating that there is a change in the acceleration in the z direction, or in other words, that a change in the installation location will affect the measured value.

Next, the flow moves to step S107, and the gravity correction unit 134 functions. The gravity correction unit 134 applies the current outputs "Xout(1), Yout(1), and Zout(1) of the acceleration sensor 20 to Equation (15) to determine the local gravitational acceleration glocal, and in Equation (16) , to determine the weight value.When the setting of the correction by the gravity correction unit 134 is completed, the balance 1 shifts to the weighing mode.At this time, the gravity correction unit 134 detects changes in the installation location (acceleration in the z direction It is also preferable to notify the user that the correction corresponding to the change) has been set.In subsequent weighings, the balance 1 uses the correction weighing value m' obtained by equation (16) as the true value for correction. The measured value m' is displayed on the display unit 16 and recorded in the storage unit 14 or a designated storage device.

If pattern (2) is detected in step S103, the flow moves to steps S108 and S109. In step S109, the change notification unit 132 notifies the user that pattern (2) has changed. The change notification unit 132 displays a message on the display unit 16, for example, that there is a change in the acceleration in the x and y directions, or in other words that the tilt of the balance affects the weighing value.

Next, the flow moves to step S110, and the tilt correction section 133 functions. The inclination correction unit 133 makes settings so as to correct the measurement value by Equation (14). When the setting of the correction by the tilt correction section 133 is completed, the balance 1 shifts to the weighing mode. At this time, the tilt correction unit 133 preferably notifies the user that correction corresponding to the tilt of the balance (change in acceleration in the x and y directions) has been set. Then, in subsequent weighing, the balance 1 displays the corrected weighed value m′ on the display unit 16 as the corrected weighed value m′ corrected by the equation (14) as the true value, and displays it on the storage unit 14 or the specified Record to an external storage device.

If pattern (3) is detected in step S103, the flow moves to steps S111 and S112. In step S112, the change notification unit 132 notifies the user that pattern (3) has changed. The change notification unit 132 displays, for example, a message on the display unit 16 that there is a change in the acceleration in the x, y and z directions, or in other words, that the tilt of the balance and the change in the installation location will affect the weighing value. indicate.

Next, the flow moves to step S113, and both the gravity correction section 134 and the tilt correction section 133 function. First, the gravity correction unit 134 functions to obtain the local gravitational acceleration glocal from the current outputs "Xout(1), Yout(1), and Zout(1) of the acceleration sensor 20 by Equation (17). Next, The tilt correction unit 133 functions to set the weighing value to be obtained by the formula (18), which is obtained by applying the local gravitational acceleration glocal to the formula (14).When this setting is completed, the balance 1 enters the weighing mode. At this time, the tilt correction unit 133 and the gravity correction unit 134 notify the user that corrections corresponding to both the tilt of the balance and changes in the installation location (changes in acceleration in the x, y, and z directions) have been set. In subsequent weighing, the balance 1 obtains the corrected weighing value m' using the formula (18), displays it on the display unit 16, and stores it in the storage unit 14 or a designated external storage device. Record.

2-3. Effect As described above, according to the balance 1 of the present embodiment, by mounting the triaxial acceleration sensor 20 on the balance 1,
(i) when the balance is tilted and the load component Wv perpendicular to the weighing pan decreases, and (ii) when the location where the balance is installed changes and the gravitational acceleration g changes. can be detected by

In particular, by simultaneously monitoring changes in x, y, and z outputs with the three-axis acceleration sensor 20, it is possible to identify which of the above problems (i) and (ii) is caused, and It is possible to appropriately correct the metric value in response to the problem.

Also, with regard to (i) above, it is only necessary to attach the triaxial acceleration sensor 20, so the configuration does not become complicated. Regarding the above (ii), while it was left up to the user to deal with changes in the installation location, the balance itself can detect and automatically correct it.

3. Second Embodiment In the second embodiment, the weighing method in the first embodiment is combined with daily inspection. The same reference numerals are used for the elements described in the first embodiment, and the description is omitted.

3-1. Configuration of Weighing Apparatus (Balance) FIG. 6 is a configuration block diagram of a weighing apparatus according to a second embodiment of the present invention. The balance 1 includes a main body case 10, a weighing pan 11, a weight sensor 12, an arithmetic processing unit 13, a storage unit 14, an operation unit 15, a display unit 16, a triaxial acceleration sensor 20, a built-in weight 17, a weight adjustment unit 18, It has a level 19 .

The built-in weight 17 and the weight addition/removal unit 18 are known in balances with an automatic calibration function. Before the balance 1 is shipped from the factory, the built-in weight 17 is weighed in advance by setting the balance 1 on a horizontally secured stand, and the reference mass "mw0" is stored. The weight addition/removal unit 18 has a motor and a cam controlled by the arithmetic processing unit 13, and loads and unloads the built-in weight 17 multiple times with respect to the weight receiving portion 17'. The weight receiving portion 17 ′ is linked to the aforementioned beam, and the load of the built-in weight 17 is transmitted to the weight sensor 12 . A pump type may be employed for the weight addition/removal unit 18 .

The level 19 is a well-known one that allows the user to visually check whether the air bubble is positioned in the center of the reference line. The level 19 is provided on the front side surface of the main body case 10 .

The arithmetic processing unit 13 has a daily inspection unit 135 that executes a daily inspection application. The storage unit 14 stores a program for executing the daily inspection application, the reference mass "mw0" of the built-in weight 17, and the allowable threshold for the reference mass "mw0".

3-2. Weighing Method FIG. 7 is a flowchart of a weighing method using the weighing device according to the second embodiment. Here, in the daily inspection of the balance, (1) confirmation of horizontal condition, (2) confirmation of dirt and foreign matter, (3) confirmation of zero point return, (4) confirmation of reproducibility, (5) confirmation of eccentricity error confirmation, etc. The balance 1 has a "daily check" button on the operation unit 15, and a display unit 16 displays a screen for guiding the check of items (1) to (5) related to daily check by the daily check application. Since the daily inspection application is publicly known, the details are omitted. The weighing method of this embodiment combines part of this daily inspection with the weighing method of the first embodiment.

When the flow is started, the daily inspection unit 135 functions, and in step S200, for item (1): Confirmation of horizontal state, the user is instructed to confirm whether the bubble in the level 19 is within the reference line. A screen prompting you to The user adjusts the adjuster (not shown) connected to the main body case 10 to adjust the position of the bubble. However, since this work is manual, there is a possibility that a very small tilt (0.1° or less) remains.

After the manual horizontal adjustment in step S200 is completed, the flow moves to step S201. In step S201, the acceleration change detection unit 131 acquires the current outputs "Xout(1), Yout(1), Zout(1)" of the acceleration sensor 20, as in step S101.

The subsequent steps S202 to S213 are the same as S102 to S113 of the first embodiment. When the correction setting is completed in each of steps S207, S210, and S213, the flow proceeds to step S214.

In step S214, the daily inspection unit 135 weighs the built-in weight 17 as item (4): confirmation of reproducibility. At this time, the built-in weight 17 is measured with the corrected weighing value m' according to the settings in steps S207, S210, and S213.

Next, the flow moves to step S215, where the daily inspection unit 135 compares the measured value m' of the built-in weight 17 with the reference mass mw0 to determine whether there is any problem. If the error between the weighed value m′ and the reference mass mw0 is within the allowable threshold, the daily inspection unit 135 determines that there is no problem (YES), and considers the balance 1 to have cleared item (1) and item (4). , After confirming the remaining items, shift to weighing mode.

On the other hand, if the error between the measured value m' and the reference mass mw0 exceeds the allowable threshold range in step S215, the daily inspection unit 135 determines that there is a problem (NO), and proceeds to step S216. In step S216, the daily inspection unit 135 determines that software correction cannot eliminate the error in the resolution of the balance 1, and issues a warning to the user. The daily check unit 135 displays, for example, a warning message on the display unit 16 to retry the sensitivity adjustment using an external weight.

3-3. Effect As described above, according to the present embodiment, in addition to the effect of the first embodiment, by combining the weighing method using the triaxial acceleration sensor 20 for the daily inspection of the balance, it is possible to obtain a very small amount that cannot be removed by human operation. It is possible to effectively correct the tilt.

In this embodiment, (4): To confirm reproducibility, the built-in weight 17 is used as the object to be weighed. This embodiment can be implemented because it is only necessary to perform item (4).

4. Mounting Position of Acceleration Sensor It is important to mount the acceleration sensor 20 so that the horizontal plane of the acceleration sensor 20 and the horizontal plane of the weight sensor 12 are aligned. The virtual plane vp on which the acceleration sensor 20 is arranged may be set at any position within the main body case 10 as long as it does not interfere with the weight sensor 12 (Roberval mechanism 12'). is preferred.

FIG. 8 is a diagram showing a suitable attachment form of the acceleration sensor 20 in the first and second embodiments, and is an example in which the acceleration sensor 20 is attached to the "lower case". FIG. 8 is a longitudinal end view of the balance 1. FIG.

The body case 10 has a divided structure of an upper case 10u and a lower case 10d, and the upper case 10u and the lower case 10d are fitted together with a sealing material such as silicone rubber interposed therebetween. The acceleration sensor 20 is placed on a sensor mounting plate 21 and is fixed to the inner surface of the lower case 10d with screws, preferably via three or more mounting bosses 22 in order to prevent the sensor from wobbling. The sensor installation plate 21 has a flush plane, and the sensor installation plate 21 serves as a virtual plane vp. Note that the IC substrate of the acceleration sensor 20 may be used as it is for the sensor mounting plate 21 .

When the balance 1 is assembled, the acceleration sensor 20 is fixed to the lower case 10d after the sensor mounting plate 21 is confirmed to be horizontal by using a level, for example, on a level table. be.

Here, as described above, the weight sensor 12 (Roberval mechanism 12') is placed on a horizontally secured table via the support member 10c, for example, using a level or the like to confirm that it is kept horizontal. and fixed to the body case 10 . Therefore, if the acceleration sensor 20 is also attached horizontally to the main body case 10, it can be attached so that the horizontality of the acceleration sensor 20 and the horizontality of the weight sensor 12 match.

FIG. 9 is a diagram showing a suitable attachment form of the acceleration sensor 20 in the first and second embodiments, and is an example in which the acceleration sensor 20 is attached to the "upper case". The acceleration sensor 20 is similarly mounted on a sensor installation plate 21 and screw-fixed to the case inner surface of the upper case 10u via three or more mounting bosses 22 . Similarly, when the balance 1 is assembled, the acceleration sensor 20 is placed on a horizontally secured stand and, for example, using a level, it is confirmed that the sensor installation plate 21 is kept horizontal. , so that the acceleration sensor 20 and the weight sensor 12 are mounted horizontally.

Although the weight sensor 12 is fixed to the upper case 10u in FIGS. 8 and 9, it is not limited to this, and may be fixed to the lower case 10d. The fixed position of the acceleration sensor 20 is preferably matched with the case on the side where the weight sensor 12 is fixed.

Although preferred embodiments of the present invention have been described above, the above embodiments are examples of the present invention, and it is possible to combine them based on the knowledge of those skilled in the art. included in the range of

1 balance 11 weighing pan 11' horizontal plane of weighing pan 12 weight sensor 13 arithmetic processing unit 14 storage unit 17 built-in weight 20 triaxial acceleration sensor

Claims

a weighing pan;
a weight sensor connected to the weighing pan;
A three-axis acceleration sensor for detecting changes in acceleration in the three axes of x, y, and z by setting x and y in a plane parallel to the horizontal plane of the weight sensor and z in a direction perpendicular to the horizontal plane of the weight sensor. and,
a storage unit that stores the triaxial reference output of the triaxial acceleration sensor when the weight sensor is horizontal;
and an arithmetic processing unit,
The arithmetic processing unit compares the current output of the three axes of the three-axis acceleration sensor with the reference output, detects that there is a tilt when the output of x and/or y has changed, and z A metering device characterized by detecting a change in the installation location and notifying the user when the output of the device has changed.
If the output of x and/or y of the three-axis acceleration sensor has changed, the arithmetic processing unit converts the measured value m detected by the weight sensor to the corrected measured value m using equation (14). The weighing device according to claim 1, wherein the correction is made to '.

however,
g: Gravitational acceleration value θ: Angle formed by the direction of gravity acceleration and the z-axis detected by the triaxial acceleration sensor gx(θ): Output value of x detected by the triaxial acceleration sensor gy(θ): Triaxial y output value detected by the accelerometer
When only the output of z of the three-axis acceleration sensor has changed, the arithmetic processing unit converts the gravitational acceleration value used for calculating the weight value m detected by the weight sensor to the value of the three-axis acceleration sensor. 2. The weighing device according to claim 1, wherein the value glocal of the local gravitational acceleration obtained using the z-axis output is changed to a corrected weighing value m'.
When the outputs of z and x and/or y of the three-axis acceleration sensor have changed, the arithmetic processing unit converts the gravitational acceleration value used in the equation (14) to the 3. The weighing device according to claim 2, wherein the weighing value m detected by the weight sensor is corrected to a corrected weighing value m' by changing to the local gravitational acceleration glocal obtained using three-axis outputs. .
When the corrected weighed value m′ of the object to be weighed exceeds a range of an allowable threshold for the reference mass of the object to be weighed, the arithmetic processing unit warns the user that the error cannot be eliminated by correction. The weighing device according to any one of claims 2 to 4.
A weighing pan, a weight sensor connected to the weighing pan, x and y in a plane parallel to the horizontal of the weight sensor, and z in a direction perpendicular to the horizontal of the weight sensor, x, y , z using a weighing device equipped with a three-axis acceleration sensor that detects changes in acceleration in the three-axis directions,
(A) obtaining current outputs of the three axes of the three-axis acceleration sensor;
(B) comparing the current output to the triaxial reference output when the weight sensor is horizontal;
(C) notifying the user that there is a tilt if the x and/or y outputs have changed in step (B) above;
(D) if the output of z has changed in step (B) above, a step of notifying the user that the installation location has changed;
A weighing method characterized by having
(E) If the output of x and/or y has changed in step (B) above, use equation (14) to convert the measured value m detected by the weight sensor to the corrected measured value m'. a correcting step;
(F) If only the output of z has changed in step (B), the gravitational acceleration value used to calculate the weighing value m detected by the weight sensor is changed to the z a step of changing the value glocal of the local gravitational acceleration obtained using the output of the shaft to obtain a corrected metric value m';
(G) If the outputs of z and x and/or y have changed in step (B), the value of the gravitational acceleration used in the formula (14) is a step of correcting the measured value m detected by the weight sensor to a corrected measured value m' by changing the local gravitational acceleration glocal obtained using the output;
The weighing method according to claim 6, characterized by comprising:
(H) Weighing an object, and if the corrected weight value m′ of the object exceeds the allowable threshold range for the reference mass of the object, warn the user that the error cannot be eliminated by correction. a step;
The weighing method according to claim 7, characterized by comprising: