Load detection device and calibration method thereof

Abstract

To provide a load detection device and its calibration method capable of ending up performing accurate calibration even if a minute load is applied at the time of calibration.SOLUTION: A calibration method of a load detection device having a load distribution sensor acquires a load distribution of the load detection device before and after operation of the load detection device, and determines abnormality when a difference in a load distribution before and after the operation is equal to or more than a threshold. The load detection device comprises the load distribution sensor, load distribution acquisition means capable of acquiring a load distribution of the load detection device, and abnormality determination means for determining abnormality, and can determine abnormality by the abnormality determination means when a difference in a load distribution before and after operation of the load detection device acquired by the load distribution acquisition means is equal to or more than a threshold at the time of calibration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a load detection device and a calibration method thereof. [Background technology]

[0002] Patent Document 1 discloses a load measurement system including a sensor device that detects a downward force acting on a subject's foot when the subject's foot is placed on the sensor device, and an information processing device that processes the measurement results measured by the sensor device. The sensor device also includes a foot pressure distribution detection sensor unit in which a plurality of pressure-sensitive elements are arranged, and a load detection sensor unit that is attached to a plurality of supports that support, from the back side, a mounting unit to which the foot pressure distribution detection sensor unit is detachably attached, and detects the load acting on each of the plurality of supports. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-185879 Summary of the Invention [Problem to be solved by the invention]

[0004] When calibrating a load detection device equipped with a load distribution sensor before use, if a load is applied to the load distribution sensor, accurate calibration may not be possible.

[0005] The present disclosure has been made in consideration of such problems, and aims to provide a load detection device and a calibration method thereof that can result in accurate calibration even when a small load is applied during calibration. [Means for solving the problem]

[0006] One aspect for achieving the above object is a calibration method for a load detection device equipped with a load distribution sensor, which obtains the load distribution of the load detection device before and after operation of the load detection device, and determines that an abnormality has occurred if the difference between the load distribution before and after the operation is greater than or equal to a threshold value.

[0007] Furthermore, one aspect for achieving the above object is a load detection device comprising a load distribution sensor, a load distribution acquisition means capable of acquiring the load distribution of the load detection device, and an abnormality judgment means for judging an abnormality, wherein, during calibration, if the difference in the load distribution acquired by the load distribution acquisition means before and after operation of the load detection device is equal to or greater than a threshold value, the abnormality judgment means can judge that an abnormality has occurred.

[0008] In the load detection device and calibration method thereof according to the present disclosure, the load distribution of the load detection device is acquired before and after operation of the load detection device, and if the difference between the load distribution before and after the operation is equal to or greater than a threshold, an abnormality is determined. In this way, an abnormality can be detected even if a small load is applied to the load distribution sensor during calibration, and as a result, accurate calibration can be performed. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a load detection device and a calibration method thereof that can ultimately perform accurate calibration even when a small load is applied during calibration. [Brief explanation of the drawings]

[0010] [Figure 1] 5A and 5B are diagrams illustrating an example of a calibration method for the load detection device according to the present embodiment. [Figure 2] 5A and 5B are diagrams illustrating an example of a calibration method for the load detection device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Specific embodiments to which the present disclosure is applied will be described in detail below with reference to the drawings. However, the present disclosure is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate. Note that FIGS. 1 and 2 are each an example diagram for explaining a calibration method for a load detection device according to this embodiment.

[0012] The load detection device 1 tends to be significantly affected by individual differences in the target (e.g., object 3 such as a person or an object) and changes over time. For this reason, to ensure accurate detection (measurement), the load detection device 1 (more specifically, for example, a sheet-like load distribution sensor 2 as shown in FIGS. 1 and 2) is calibrated before use. Calibration usually needs to be performed every time the system is powered on after installation in the user's environment. However, if calibration is performed while an object 3 such as a person or an object is placed on the load distribution sensor 2, the zero point sensor value may not be obtained correctly, and an accurate zero point map may not be obtained. In this way, if the zero point cannot be adjusted correctly and accurate calibration cannot be performed, the measurement accuracy of the load detection device 1 may decrease after startup. Therefore, the load detection device 1 must be calibrated in an unloaded state where no object 3 is placed on the load distribution sensor 2, and therefore, before use, zero point adjustment is usually performed after confirming that no object 3 is placed on the load distribution sensor 2. For this reason, up until now, during calibration, a warning has been issued to prevent the object 3 from being placed on the load distribution sensor 2. For example, a warning such as "Do not stand on it" has been issued to the person using the load detection device 1, or a threshold value with a certain degree of range has been set, and an error (abnormality) has been displayed if a sensor value is output during calibration.

[0013] However, if a person or object is standing on the load distribution sensor 2 without noticing the warning, or if a minute load below the threshold is applied, the warning may not be detected as an error, and calibration may be performed, potentially resulting in an incorrect zero point map being acquired. Then, using that zero point (zero point map) to detect (measure) the load may result in a decrease in load accuracy. Note that the zero point may vary for each element constituting the load distribution sensor 2, and individual differences in the detection target may also be large, making it difficult to set the threshold too small. For this reason, it may be difficult to detect an error even if a minute load is present on the load distribution sensor 2 during calibration.

[0014] On the other hand, the load detection device 1 according to the present disclosure (hereinafter also referred to as the present device) comprises at least a load distribution sensor 2, a load distribution acquisition means, and an abnormality determination means. When the difference between the load distribution (or zero point map) before and after operation of the load detection device acquired by the load distribution acquisition means during calibration is equal to or greater than a threshold value, the abnormality determination means can determine that an abnormality has occurred. Note that other components of the present device are not particularly limited, and conventionally known components can be used as appropriate. This device will be described in detail below.

[0015] In the present embodiment shown in FIGS. 1(a) and 2(a), after power-on, the load detection device 1 is first calibrated once (first time) to obtain a zero point map P0(x, y). Next, the load detection device 1 (more specifically, for example, the treadmill belt) is driven and moved slightly, for example, to the left (travel direction) of the paper of FIGS. 1 and 2. This movement distance can be appropriately set depending on the resolution of the load distribution sensor 2 included in the load detection device 1. For example, if the resolution (element spacing) of the load distribution sensor 2 is 1 cm, the treadmill belt should be moved by 1 cm or more. If an object 3 is mounted on the load distribution sensor 2, the object 3 will also move in accordance with the movement of the treadmill belt. Note that if a person is standing on the load distribution sensor 2, the movement of the treadmill belt may cause the person to fall, so it is preferable to move the treadmill belt slowly and gradually. Next, as shown in Figures 1(b) and 2(b), the treadmill belt is moved a predetermined distance and then stopped again, and calibration is performed (for the second time) to obtain the zero point map P1(x, y).

[0016] Next, the difference P1(x,y)-P0(x,y) between the two zero point maps is calculated, and if there is an element for which the difference value is equal to or greater than a certain threshold, it is determined that the object 3 is placed on the load distribution sensor 2, and an error (abnormal state) has occurred. Then, if necessary, the function of the load detection device is stopped, or a monitor display is displayed to prompt the user to reacquire the zero point map. Note that the threshold can be set appropriately within a range in which the effects of the present disclosure can be obtained, and is not particularly limited. In the above example, the judgment is made using the difference between the zero point maps, but the difference value may be converted into a load value f(P1-P0) to calculate the load distribution, and the judgment may be made based on the load distribution. Also, the load distribution may be calculated for each zero point map, and the judgment may be made based on the difference between them. Here, f is a characteristic function that converts the sensor output difference value (or sensor output value) into a load value, and is a characteristic obtained when the sensor is manufactured.

[0017] Note that when moving the load detection device between the first and second calibrations, the treadmill belt may be moved, for example, by more than half a revolution. If the treadmill belt is moved by more than half a revolution, the object 3 that was on the load distribution sensor 2 will be pushed out of the load detection device. However, during the first calibration, the zero point map was acquired with the object still on it. Therefore, the difference between the zero point map during the second calibration, in which the object 3 has been pushed out and is no longer on the load distribution sensor 2, and the zero point map during the first calibration is likely to be greater than the threshold value, and will likely be determined to be an abnormality.

[0018] In this way, this device acquires a load distribution (or zero point map) before operating (using) the load detection device 1 (first time) as shown in Figures 1(a) and 2(a), and after moving it a little (second time) as shown in Figures 1(b) and 2(b).The device then calculates the difference between the two load distributions (or sensor output values) acquired before and after operation, and if the difference is equal to or greater than a desired threshold, it determines that an object 3 is placed on the load distribution sensor 2, and displays an error (abnormal) message or a warning, or displays or warns to re-perform calibration.

[0019] In Figure 2(c), the portion where the difference 4 between the first and second load distributions (or sensor output values) becomes large, more specifically, the region where the difference is equal to or greater than a threshold, is indicated by the symbol 4a. In the load detection device 1 shown in Figure 2, since the region 4a where the difference is equal to or greater than a threshold is detected, it is determined that an object 3 is present on the load distribution sensor 2 during calibration, and an error or warning is issued as described above.

[0020] As described above, even if a minute load is present on the load distribution sensor 2 during calibration, this device can determine whether or not an object 3 was present on the load distribution sensor 2 by examining the load distribution before and after the device operates, and can determine whether or not an abnormal state exists.

[0021] The device may have the above configuration, but may also be a load detection device including a treadmill. More specifically, the device may be a walking load measurement device that diagnoses walking ability by measuring changes in sole load distribution and COP movement during treadmill walking. In this device, a load distribution sensor 2 is installed inside the treadmill belt, and the load distribution of objects such as people and things on the belt can be measured. Here, a treadmill is a fitness device for running or walking indoors, and is, for example, a conveyor belt-like platform as shown in Figures 1 and 2, which is driven by a motor and has an adjustable speed.

[0022] The load distribution sensor 2 of this device can be any known sensor, but it may or may not be embedded in the load detection device 1 (more specifically, the treadmill). The resolution of the load distribution sensor can be set as appropriate; for example, a sensor configured with pressure-sensitive elements arranged in a grid at 1 cm intervals can be used. The operation of the load detection device when performing the first and second calibrations can be adjusted as appropriate depending on the resolution of the load distribution sensor, and it is preferable to operate the load detection device at a resolution higher than the resolution of the load distribution sensor.

[0023] Note that the elements constituting the load distribution sensor 2 typically have large variations in zero point, and load output values ​​may vary depending on the element even in the no-load state. Furthermore, the output of each element on the load distribution sensor 2 in the no-load state may not be zero and may differ depending on the element. Therefore, the load detection device performs calibration after powering on and before starting measurement. The sensor output values ​​P(x, y) of all elements are calculated once in the no-load state, and this is obtained as a zero-point map. In this device, more accurate calibration can be performed by creating the zero-point map twice: once immediately after powering on the load detection device and once again after movement. Note that in this embodiment, the difference between the zero-point map (or load distribution) obtained by two calibrations is calculated, but the number of calibrations may be three or more. If calibration is performed three or more times, the presence or absence of an abnormality may be determined, for example, using the difference between the zero-point map (or load distribution) obtained by the first and last calibrations.

[0024] The load distribution acquisition means (not shown) of this device is not particularly limited as long as it can acquire the load distribution of the load detection device 1, and any conventionally known means can be used as appropriate. The load distribution acquisition means can acquire load distribution data of the detection target by measuring the load values ​​of each of these elements in the load distribution sensor 2.

[0025] The abnormality determination means (not shown) of this device determines (detects) an abnormality (error) during calibration and, if necessary, notifies the subject of the abnormality. Any conventionally known abnormality determination means can be used as appropriate, and is not particularly limited.

[0026] When actually measuring load distribution with this device, the load distribution can be calculated by obtaining the output values ​​P(x,y) of all elements in a loaded state, finding the difference P(x,y)-P0(x,y) between the sensor output in a loaded state and the zero point map P0(x,y) in a no-load state, and converting the difference value into a load value f(P-P0).Here, f is a characteristic function that converts the sensor output difference value into a load value, and is a characteristic obtained when the sensor was manufactured.

[0027] Furthermore, the calibration method for a load detection device according to the present disclosure (hereinafter also referred to as the present calibration method) is a calibration method for a load detection device equipped with a load distribution sensor 2. In this calibration method, the load distribution (or zero point map) of the load detection device 1 is acquired before and after operation of the load detection device 1, and if the difference between the load distribution (or zero point map) before and after the operation is equal to or greater than a threshold, it is determined to be abnormal. For details, please refer to the contents of the present device described above.

[0028] In this way, in this device and calibration method, the load detection device 1 is moved slightly during calibration, and the load distribution (or zero point map) on the load distribution sensor 2 before and after the movement is compared to determine whether or not an object 3 is present. Therefore, it is possible to provide a load detection device and a calibration method thereof that can ultimately perform accurate calibration even if a small load is applied during calibration.

[0029] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0030] 1. Load detection device 2 Load distribution sensor 3 objects 4. Difference between the first and second load distributions 4a Area where the difference is greater than or equal to the threshold

Claims

1. A method for calibrating a load detection device including a load distribution sensor, comprising: A load distribution of the load detection device is acquired before and after operation of the load detection device, If the difference in the load distribution before and after the operation is equal to or greater than a threshold, it is determined that an abnormality has occurred. A method for calibrating a load detection device.

2. The calibration method of claim 1 , wherein the load sensing device includes a treadmill.

3. The calibration method according to claim 1 or 2, wherein the load detection device is operated at a resolution greater than or equal to the resolution of the load distribution sensor.

4. a load distribution sensor; a load distribution acquisition means capable of acquiring a load distribution of the load detection device; An abnormality determination means for determining an abnormality; Equipped with A load detection device in which, when a difference in load distribution before and after operation of the load detection device acquired by the load distribution acquisition means during calibration is equal to or greater than a threshold, the abnormality determination means can determine that an abnormality has occurred.

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