Bathtub system and bath entry / exit determination method

Abstract

To provide a bathtub system capable of suppressing wrong determination of entering / exiting a bathtub.SOLUTION: A bathtub system 100 includes a bathtub 10, a water-level sensor 20 which is provided in the bathtub and can measure water-level L of the bathtub, and a control device 30. The control device stores the water-level as reference water-level Lr when the water-level is stable beyond a preset stable time T1th, determines entry into the bathtub when water-level difference between the water-level L and the reference water-level Lr is beyond the preset water-level difference threshold Lth and when absolute value of an acceleration speed La of the water-level L is beyond preset acceleration speed threshold Gth, and determines exiting the bathtub when there is nearly no water-level difference after determination of entry into the bathtub and when absolute value of the acceleration speed of the water-level L is beyond acceleration speed threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bathtub system and a bath entry / exit determination method. [Background technology]

[0002] In recent years, drowning has become a common cause of death in residential accidents. In nursing care settings, whether in a facility or at home, care recipients are often monitored by humans while bathing. However, human monitoring is reaching its limits in terms of both time and effort. Therefore, systems that use sensors to monitor care recipients while bathing are being actively studied.

[0003] For example, Patent Document 1 proposes a bath oil supply device that detects the presence or absence of a person using a water level sensor that detects the water level from changes in pressure in the bathtub and a human presence sensor in the bathroom.

[0004] Furthermore, Patent Document 2 proposes a method of determining whether or not a person has entered a bathtub by installing a load meter under the bathtub.

[0005] Furthermore, Patent Document 3 proposes a sensor that calculates the bath volume based on the water level in the bathtub and the bather's vital signs, and determines whether to enter or exit the bath based on the amount of change. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-002643 [Patent Document 2] Japanese Patent Application Publication No. 2019-158289 [Patent Document 3] Japanese Patent Application Publication No. 2019-203621 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with conventional systems, there was a risk of incorrectly determining whether someone had entered the bathtub when they had not, or whether they had left the bathtub when they had not.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a bathtub system and a bath entry / exit determination method that can reduce erroneous bath entry / exit determination. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following aspects. (1) A bathtub system according to one aspect of the present invention includes a bathtub, a water level sensor installed in the bathtub and capable of measuring the water level of the bathtub, and a control device. When the water level remains stable for a predetermined stabilization time, the control device stores the water level as a reference water level, determines that the water has entered the bath when the difference between the water level and the reference water level exceeds a predetermined water level difference threshold and the absolute value of the acceleration of the water level exceeds a predetermined acceleration threshold, and determines that the water has left the bath when, after determining that the water has entered the bath, the water level difference almost disappears and the absolute value of the acceleration of the water level exceeds the acceleration threshold.

[0010] Entering the bathtub here means that a person moves from the outside to the inside of the bathtub. Exiting the bathtub here means that a person moves from the inside to the outside of the bathtub.

[0011] (2) In (1) above, the case where the water level is stable beyond the stabilization time may be the case where the water level is within a predetermined range in the vertical direction beyond the stabilization time. (3) In the above (1) or (2), the case where the water level difference has almost disappeared may be the case where the water level difference over time is ±7 mm.

[0012] (4) In any one of (1) to (3) above, the control device may determine that the water has been discharged from the tank when the water level difference exceeds the water level difference threshold and the water level falls below the reference water level. (5) In any one of (1) to (4) above, when the smaller of the amount of change in water level due to the addition of water to the tank and the amount of change in water level due to the removal of water from the tank is defined as the stable water level change amount, the control device may store as the reference water level the value obtained by adding the water level difference during the reference observation time to the reference water level if there is almost no acceleration of the water level within a predetermined reference observation time, the amount of change in water level is smaller than the stable water level change amount, and the water level continues to rise or fall.

[0013] (6) A bathtub entry / exit determination method according to one embodiment of the present invention includes a storage step of storing the water level in a bathtub as a reference water level when the water level remains stable beyond a predetermined stabilization time; a first determination step of determining that the water has entered the bath when the difference between the water level and the reference water level exceeds a predetermined water level difference threshold and the absolute value of the acceleration of the water level exceeds a predetermined acceleration threshold; and a second determination step of determining that the water has left the bath when the water level difference has almost disappeared after the first determination step and the absolute value of the acceleration of the water level exceeds the acceleration threshold. [Effects of the Invention]

[0014] According to the present invention, a bathtub system and a bath entry / exit determination method that can reduce erroneous bath entry / exit determination can be provided. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram of a bathtub system. [Figure 2] 10 is a graph showing the change over time in water level and the acceleration of the water level. [Figure 3] FIG. 10 is an explanatory diagram showing the water level when no one is in the tank. [Figure 4]FIG. 10 is an explanatory diagram showing the water level when a person is in the bath and taking a half-body bath. [Figure 5] FIG. 10 is an explanatory diagram showing the water level when a person changes their posture from half-bathing to full-bathing. [Figure 6] FIG. 10 is an explanatory diagram showing the water level when a person changes their posture from full-body bathing to half-body bathing. [Figure 7] FIG. 10 is an explanatory diagram showing the water level when a person has left the tank. [Figure 8] 10 is a graph showing the water level and the acceleration of the water level when no one is in the tank. [Figure 9] 10 is a graph showing the change over time in the water level and the reference water level when a person is taking a bath and adding hot water. [Figure 10] 10 is a graph illustrating updating of the reference water level. DETAILED DESCRIPTION OF THE INVENTION

[0016] A bathtub system 100 according to one embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is an explanatory diagram of a bathtub system 100 according to an embodiment. Fig. 2 is a graph showing the change over time in the water level L and the acceleration La of the water level L.

[0017] (bathtub system) As shown in Figure 1, a bathtub system 100 according to one embodiment includes a bathtub 10 having a frame surface 10a, a water level sensor 20 provided in the bathtub 10 and capable of measuring the water level L, and a control device 30.

[0018] (bathtub) The bathtub 10 has an inner tub that forms a downwardly recessed space to store water. The inner tub has a bottom surface and an inner side surface that extends upward from the periphery of the bottom surface. The bathtub 10 has a frame surface 10a that is positioned at the same height as the water surface when the bathtub 10 is filled with water. The bathtub 10 is formed in a cylindrical shape with a bottom that opens upward. Unless otherwise specified, the water level L is expressed as the vertical distance from the bottom of the bathtub 10 (inner tank) to the water surface. For example, when there is no water in the bathtub 10, the water level L is zero, and when the water surface is at the height of the frame surface 10a, the water level L (depth of the bathtub 10) is 450 mm.

[0019] (Water level sensor) Water level sensor 20 is a sensor capable of measuring the water level L of bathtub 10. Water level sensor 20 may be, for example, a pressure-type water level sensor that detects a voltage that changes in response to changes in water pressure. Water level sensor 20 can be installed in the inner tub of bathtub 10. Note that the velocity or acceleration La of water level L may be calculated from changes in water level L by water level sensor 20 or by control device 30. The same applies to the average water level L, which will be described later.

[0020] (Control device) The control device 30 includes a control unit. The control unit is a processor such as a CPU (Central Processing Unit). The control unit functions by the processor executing a program. All or part of the functions of the control unit may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, optical magnetic disks, ROMs, CD-ROMs, and semiconductor storage devices (e.g., solid-state drives (SSDs)), as well as storage devices such as hard disks and semiconductor storage devices built into computer systems. The program may be transmitted via a telecommunications line. The program may include a program that causes a computer to execute a bath entry / exit determination method using bathtub system 100.

[0021] In detail, the control device 30 includes a storage unit 31, a determination unit 32, and a notification unit 33.

[0022] The storage unit 31 stores preset values ​​required for control (acceleration threshold Gth, stabilization time T1th, water level difference threshold Lth, and reference observation time T2th).

[0023] The acceleration threshold Gth is a distance that serves as a reference for the acceleration La of the water level L, which is the condition for determining whether a person has entered or left the tank. The acceleration threshold Gth is a positive value. For example, the acceleration threshold Gth is 6 mV / 2 s 2 (2 mm / s 2 (For example, 1 mm corresponds to 1.5 mV). Note that the voltage value detected by the water level sensor 20 is approximately proportional to the water level L, so hereinafter, for example, 1.5 mV may be read as 1 mm. For example, a 100 mV increase in the detected value of the water level sensor 20 means that the water level L increases by 67 mm.

[0024] As shown in FIG. 2, the acceleration threshold Gth is smaller than the absolute value of the first positive peak a1 of the acceleration La of the water level L that is expected when a person enters the tank. The acceleration threshold Gth is smaller than the absolute value of the negative second peak a2 of the acceleration La of the water level L that is expected when a person enters the tank. The acceleration threshold Gth is smaller than the absolute value of the negative seventh peak a7 of the acceleration La of the water level L that is expected when a person leaves the tank. The acceleration threshold Gth is smaller than the absolute value of the eighth positive peak a8 of the acceleration La of the water level L that is expected when a person leaves the tank.

[0025] The stabilization time T1th is the shortest time that serves as a criterion for determining that the water level L is stable without fluctuating significantly, for example, within a range of ±13 mm, more preferably within a range of ±7 mm, and even more preferably within a range of ±3 mm. The stabilization time T1th is set to, for example, 10 seconds.

[0026] The water level difference threshold Lth is a reference distance for the amount of change in water level L that is the condition for determining whether a person has entered or left the bath. It is set to be smaller than the amount of change in water level L that is expected when a person enters or leaves the bath. The amount of change in water level L that is expected when a person enters or leaves the bath may be, for example, the amount of change in water level L in bathtub 10 that corresponds to the volume of water displaced by a person with a relatively small build while bathing the whole body. The water level difference threshold Lth is a positive value, and is, for example, 50 mV (33 mm).

[0027] The reference observation time T2th is the shortest time that serves as a reference for determining that the water level L is rising or falling at a stable rate. The reference observation time T2th is, for example, 10 seconds.

[0028] For example, determination unit 32 detects the measurement results of water level sensor 20 every 0.2 seconds. Then, determination unit 32 averages the 10 detection results to measure the water level L of bathtub 10. That is, in this example, determination unit 32 calculates the water level L of bathtub 10 (average water level L) every 2 seconds, which is (0.2 seconds x 10). It is preferable to use the average water level L rather than the water level L detected every 0.2 seconds as the water level L referred to below. When calculating the velocity of the water level L and the acceleration La of the water level L referred to below, it is preferable to use the average water level L rather than the water level L detected every 0.2 seconds. It is preferable to use the average water level L as the water level in the claims.

[0029] 2, when the water level L is stable for a period exceeding the stabilization time T1th, the determination unit 32 stores the water level L as a reference water level Lr. Here, the water level L being stable means that the water level L is within a predetermined range in the vertical direction. For example, the predetermined range means a range of ±13 mm (a range of 27 mm in the vertical direction), preferably a range of ±7 mm, and more preferably a range of ±3 mm. Whether the water level L has exceeded the stabilization time T1th and is stable may be determined based on the slope of the water level L with respect to time between the start and end of the stabilization time T1th, which is, for example, 10 seconds.

[0030] For example, the determination unit 32 (water level sensor 20) calculates the velocity of the water level L from two consecutively calculated average water levels L. The velocity of the water level L here refers to the rate of change of the displacement of the average water level L per unit time, and is the first-order derivative of the displacement of the average water level L with respect to time. For example, the determination unit 32 calculates the acceleration La of the water level L from two consecutively calculated velocities of the water level L. The acceleration La of the water level L here is the rate of change of the velocity of the water level L per unit time, and is the value obtained by second-order differentiation of the displacement of the average water level L with respect to time.

[0031] Here, the difference between the water level L and the reference water level Lr is defined as the water level difference ΔL. More specifically, the water level difference ΔL is the value (L-Lr) obtained by subtracting the reference water level Lr from the water level L. The water level difference ΔL can be a positive value, 0, or a negative value. The water level difference ΔL may also be the value (Lr-L) obtained by subtracting the water level L from the reference water level Lr. The determination unit 32 determines that the water has entered the tank when the water level difference ΔL exceeds the water level difference threshold Lth and the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth. Note that, if it is known that the acceleration La of the water level L is substantially equal to or greater than 0, the absolute value of the acceleration La of the water level L may be the acceleration La of the water level L.

[0032] For example, even if a person enters the bathtub 10 when it is full (the water surface is flush with the frame surface 10a), the water level L increases only by the amount due to the surface tension of the water. As a countermeasure against the difficulty in properly measuring the upper limit of the acceleration La of the water level L when a small person enters the bath, it is preferable to use the absolute value of the acceleration La of the water level L. When the bathtub 10 is full and the person enters, the water level L tends to drop after the water overflows (water overflows from the bathtub 10). For this reason, the moment the water level L rises, the acceleration La of the water level L is always calculated as a value exceeding the acceleration threshold Gth.

[0033] After determining that the water has entered the tank, the determination unit 32 determines that the water has been discharged from the tank if the water level difference ΔL has almost disappeared and the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth. The case where the water level difference ΔL has almost disappeared here means, for example, the case where the water level difference ΔL over time is ±7 mm (±20 mV in terms of the voltage value detected by the water level sensor 20).

[0034] The alarm unit 33 may be configured to issue an alarm when the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth. This allows the person or an outsider to be notified that a person has entered or left the bath. Therefore, people using the bathtub 10, such as those receiving care, do not need to be directly monitored, and can bathe safely while maintaining privacy and being watched over. The notification method may be, for example, sound, display, etc. The notification means may be, for example, a speaker or display via a communication means connected to bathtub system 100. Notification unit 33 may also issue a notification to the outside if there is no determination of bath removal within a predetermined time after determination unit 32 determines that the bath has entered the bath.

[0035] (Method of determining whether to enter or leave the tank) Next, a bath entry / exit determination method using bathtub system 100 will be described. The method for determining whether an item is being added or removed from a tank according to one embodiment includes a storing step, a first determining step, and a second determining step. In the storage step, when the water level L of the bathtub 10 exceeds the stabilization time T1th and remains stable, the water level L is stored as the reference water level Lr. In the first determination step, after the storage step, if the water level difference ΔL exceeds the water level difference threshold Lth and the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth, it is determined that the water has entered the tank. In the second determination step, when the water level difference ΔL has almost disappeared after the first determination step and the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth, it is determined that the water has been discharged.

[0036] Next, an example of the bath entry / exit determination method will be explained, focusing on the changes in the water level L and the acceleration La of the water level L and the operation of the bathtub system 100, following the flow from when a person enters the bathtub 10 to when they leave. FIG. 3 is an explanatory diagram showing the water level L when no one is in the bath. FIG. 4 is an explanatory diagram showing the water level L when a person has entered the bath and is taking a half-body bath. FIG. 5 is an explanatory diagram showing the water level L when a person changes their position from a half-body bathing position to a full-body bathing position. FIG. 6 is an explanatory diagram showing the water level L when a person changes their position from a full-body bathing position to a half-body bathing position. FIG. 7 is an explanatory diagram showing the water level L when a person has left the bath. Note that the water level sensor 20 and control device 30 are not shown in FIGS. 3 to 7.

[0037] For example, 40 mV is stored as the water level difference threshold Lth in the storage unit 31 of the bathtub system 100. For example, 8 mV / 2 s is stored as the acceleration threshold Gth. 2 Remember the following.

[0038] (1) First, as shown in FIG. 3, fill the bathtub 10 with water. The bathtub system 100 acquires the water level L measured by the water level sensor 20 at any time, for example, every two seconds. At this time, as shown by arrow A in Figure 2, the water level L is stable at around 1250 mV. The acceleration La is stable at around zero. If the water level L is stable beyond the stabilization time T1th, the reference water level Lr will be 1250 mV, the same as the water level L.

[0039] (2) Next, as shown in Figure 4, a person enters the bathtub 10. In this case, the person is bathing halfway through the bath. As a result, as shown by arrow B in Figure 2, the water level L rises to approximately 1330 mV, equal to the volume of water displaced by the person entering the tank. As the water level L rises, the acceleration La rises to a first peak a1, then falls to a second peak a2, before repeatedly rising and falling and gradually approaching zero, where it stabilizes. The reference water level Lr remains at 1250 mV.

[0040] Here, the bathtub system 100 (the determination unit 32 of the control device 30) determines whether the water level difference ΔL (80 mV (53 mm)) exceeds the preset water level difference threshold Lth (40 mV) and whether the absolute value of the acceleration La of the water level L (14 mV / 2 s 2 ) is greater than the preset acceleration threshold Gth (8mV / 2s 2 ), it is judged as entering or leaving the tank. In this case, the water level difference ΔL is positive, so it is judged as entering the tank. (Entering the tank judgment) When the determination unit 32 determines that a person has entered the bath, the bathtub system 100 (notification unit 33 of the control device 30) may notify the outside of information indicating that the person has entered the bath.

[0041] (3) Next, as shown in Figure 5, the person changes their position from half-bathing to full-body bathing. Then, as shown by arrow C in FIG. 2, the water level L rises from about 1330 mV to about 1350 mV by the volume of water displaced by the person's change of posture.

[0042] (4) Next, as shown in Figure 6, the person changes their position from a full-body bath to a half-body bath. As a result, as shown by arrow D in Figure 2, the water level L drops from approximately 1350 mV to approximately 1330 mV by the volume of water corresponding to the volume of the human body that has moved above the water surface due to the person's change of posture. The reference water level Lr remains at 1250 mV. Here, the water level difference ΔL (100 mV) exceeds the preset water level difference threshold Lth (40 mV). However, the water level L does not fall below the reference water level Lr (1250 mV). Therefore, the bathtub system 100 (determination unit 32 of the control device 30) does not determine that the bath is being filled or unfilled because the conditions for determining whether the bath is being filled or unfilled are not met.

[0043] (5) Next, as shown in FIG. 7, the person gets out of the bathtub 10. As a result, as shown by arrow E in Figure 2, the water level L drops from approximately 1330 mV to approximately 1250 mV, slightly lower than the reference water level Lr. As the water level L drops, the acceleration La drops to a seventh peak a7, then rises to an eighth peak a8, and then repeatedly drops and rises, gradually approaching near zero and stabilizing at that level. The reference water level Lr remains at 1250 mV. Here, the bathtub system 100 (the determination unit 32 of the control device 30) determines whether the water level difference ΔL (80 mV) exceeds the water level difference threshold Lth (40 mV) and whether the absolute value of the acceleration La of the water level L (14 mV / 2 s 2 ) is the acceleration threshold Gth(8mV / 2s 2 ) and is below the reference water level Lr (1250 mV) plus 5 mV, it is determined that the tank has been discharged. In this case, the water level difference ΔL is negative, so it is determined that the tank has been discharged. (Discharge Determination) When the determining unit 32 determines that the bath has been dispensed, the bathtub system 100 (notifying unit 33 of the control device 30) may notify the outside of information indicating that the bath has been dispensed.

[0044] (Delivery decision) Next, the determination of whether or not the bath is to be discharged by the bathtub system 100 will be described. In order to further reduce erroneous determination of whether the product is in or out of the tank, the following algorithm can be added to the conditions for determining whether the product is in or out of the tank in addition to the determination algorithm for determining whether the product is in or out of the tank described above. The control device 30 may determine that the water has been discharged from the tank when the water level L becomes equal to or lower than the reference water level Lr after the water level difference ΔL exceeds the water level difference threshold Lth.

[0045] (Explanation while filling the bath) Next, the relationship between the water level L and the acceleration La of the water level L and the time t when the bathtub is filled with water without a person inside will be described with reference to FIG. FIG. 8 is a graph showing the water level L and the acceleration La of the water level L when no one is in the tank. As shown in Figure 8, when no one is in the bathtub, the water level L of the water being filled in the bathtub 10 usually rises at a constant, stable speed. During this time, the acceleration La remains near zero and barely changes. Therefore, when filling the bathtub with water when no one is in the bath, even if the water level difference ΔL between the water level L and the reference water level Lr exceeds the water level difference threshold Lth, the absolute value of the acceleration La does not exceed the acceleration threshold Gth, so it is not determined that someone has entered the bath.

[0046] (Explanation of adding hot water while in the bath) Next, using FIG. 9, the relationship between the water level L, the reference water level Lr, and the time t when hot water is added (water is poured) between when a person enters the bath and when they leave (during bathing) will be described. FIG. 9 is a graph showing the change over time in the water level L and the reference water level Lr when hot water is being added while a person is taking a bath. As shown by an arrow G in FIG. 9, when the water level L is stable, the control device 30 sets this water level L as the reference water level Lr. Next, when a person enters bathtub 10, water level L rises as shown by arrow H. Here, when hot water is added while a person is taking a bath, the water level L usually rises at a steady rate, as shown by arrow J.

[0047] Here, the amount of change in the water level L due to the water entering the tank or the amount of change in the water level L due to the water leaving the tank, whichever is smaller, is defined as the amount of stable water level change. For example, the amount of stable water level change is 20 mV (20 mm). In this case, as shown by arrow J, if there is almost no acceleration La of the water level L within the reference observation time T2th, the amount of change in the water level L is smaller than the stable amount of change in the water level, and the water level L continues to rise or fall, the control device 30 may store the value (reference water level Lr + water level difference ΔL) obtained by adding the water level difference ΔL at the end of the reference observation time T2th to the reference water level Lr as the reference water level Lr, and update the reference water level Lr, as shown by arrow N. Here, "almost no acceleration La of the water level L" means that the acceleration La of the water level L is, for example, ±1 mV / 2 s 2 (±0.33mm / s 2 ) range.

[0048] Next, when the person leaves the bathtub 10, the water level L drops as shown by the arrow K. At this time, the water level L drops to the updated reference water level Lr. Therefore, the control device 30 can determine that the water has been discharged if the water level L has dropped to the updated reference water level Lr, thereby preventing the water level L from not being determined to have been discharged because it has not dropped to the reference water level Lr before the update. In this way, even if the water level L changes due to a factor other than a change in the water level L caused by a change in the person's posture while bathing, such as when hot water is added, updating the reference water level Lr can prevent erroneous determination of whether the water has been discharged.

[0049] As explained above, the bathtub system 100 and bath exit determination method of this embodiment determine whether a person has entered or left the bath based on a change in the acceleration La of the water level L. The acceleration La of the water level L represents the instantaneous change in the water level L in the bathtub 10, and is correlated with the change per unit time in the volume of the human body immersed in the water stored in the bathtub 10. For this reason, the acceleration La of the water level L changes relatively significantly when a person goes from not being immersed in water to being immersed in water, or when a person goes from being immersed in water to completely leaving it, i.e., when a person enters or leaves the bath.

[0050] In the bathtub system 100 and the bath-exit determination method, a bath entry is determined when the water level difference ΔL exceeds the water level difference threshold Lth and the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth. This prevents a determination that a person has entered the bathtub 10 even though they have not entered it, even if the water level L in the bathtub 10 changes significantly, such as when adding hot water to the bathtub 10 while no one is inside. Furthermore, a bath exit is determined when the water level difference ΔL has almost disappeared after determining that a person has entered the bath and the absolute value of the acceleration La of the water level L exceeds the acceleration threshold Gth. This prevents a determination that a person has left the bathtub 10 even though they have not left it, such as when draining water stored in the bathtub 10 while a person is inside the bathtub 10. This prevents erroneous bath entry / exit determinations.

[0051] In determining whether the water should be discharged, the control device 30 may determine that the water should be discharged if the water level L falls below the reference water level Lr after the water level difference ΔL exceeds the water level difference threshold Lth. In this case, if the water level L does not fall below the reference water level Lr, which may occur when a person changes position while in the bathtub 10 or when the water is drained while in the bathtub 10, the control device 30 can avoid determining that the water should be discharged.

[0052] If, during the reference observation time T2th, there is almost no acceleration La of the water level L, the amount of change in the water level L is smaller than the stable amount of change in the water level, and the water level L continues to rise or fall, the control device 30 may store the value obtained by adding the water level difference ΔL at the end of the reference observation time T2th to the reference water level Lr as the reference water level Lr. In this case, it is possible to detect the addition of hot water or the draining of water from the bathtub 10.

[0053] (Update of reference water level Lr) Next, updating of the reference water level Lr will be described with reference to FIG. FIG. 10 is a graph illustrating the updating of the reference water level Lr. As shown by arrow P in Figure 10, the control device 30 stores the water level L (time average of the water level L) as the reference water level Lr because the water level L has stabilized beyond the stabilization time T1th (the change in the water level L is within a predetermined range). Next, when the water level L rises suddenly as shown by arrow Q, the reference water level Lr is not updated because the water level L does not rise beyond the reference observation time T2th.

[0054] Then, as indicated by arrow R, if there is almost no acceleration La of the water level L, the amount of change in the water level L is smaller than the stable amount of change in water level, and the water level L continues to rise or fall within the reference observation time T2th, the control device 30 stores the value obtained by adding the water level difference ΔL at the end of the reference observation time T2th to the reference water level Lr as the reference water level Lr. Here, when the water level L is continuously rising or falling, this means that when the water level L is obtained from the water level sensor 20 every two seconds, five consecutive points of the obtained water level L form a straight line.

[0055] Specifically, as shown in Figure 10, when the water level L rises at a steady rate for more than 10 seconds, which is the preset reference observation time T2th, the control device 30 adds the water level difference ΔL1 that has increased over the 10 seconds to the initial reference water level Lr0, updating the reference water level Lr to become the reference water level Lr1. Then, when the water level L continues to rise at a steady rate, the control device 30 adds the increased water level difference ΔL2 to the reference water level Lr1, creating the reference water level Lr2. In this way, the control device 30 updates the reference water level Lr. Therefore, even when hot water is added or drained, the reference water level Lr is updated, thereby reducing erroneous determination of whether the water is entering or leaving the tank.

[0056] The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0057] 10 Bathtub 10a Frame surface 20 Water level sensor 30 Control device 31 Storage section 32 Judgment section 33 Information Department 100 Bathtub System Gth Acceleration Threshold L water level La acceleration Lr, Lr0, Lr1, Lr2 Reference water level Lth Water level difference threshold T1th stabilization time T2th reference observation time ΔL, ΔL1, ΔL2 Water level difference

Claims

1. A bathtub system including a bathtub, a water level sensor provided in the bathtub and capable of measuring the water level of the bathtub, and a control device, The control device If the water level remains stable for a predetermined stabilization time, the water level is stored as a reference water level; When the water level difference between the water level and the reference water level exceeds a predetermined water level difference threshold and when the absolute value of the acceleration of the water level exceeds a predetermined acceleration threshold, it is determined that the water has entered the tank; After determining that the water has entered the tank, if the water level difference is almost zero and the absolute value of the acceleration of the water level exceeds the acceleration threshold, it is determined that the water has been discharged from the tank; When the amount of change in the water level due to the water entering the tank and the amount of change in the water level due to the water leaving the tank, whichever is smaller, is defined as the amount of change in the stable water level, The control device, within a preset reference observation time, When there is almost no acceleration of the water level, the amount of change in the water level is smaller than the amount of change in the stable water level, and the water level continues to rise or fall, the value obtained by adding the water level difference at the end of the reference observation time to the reference water level is stored as the reference water level. Bathtub system.

2. The case where the water level is stable beyond the stabilization time means that the water level is within a predetermined range in the vertical direction beyond the stabilization time. The bathtub system of claim 1 .

3. The case where the water level difference is almost zero means that the water level difference over time is ±7 mm. The bathtub system according to claim 1 or 2.

4. The control device After the water level difference exceeds the water level difference threshold, when the water level becomes equal to or lower than the reference water level, it is determined that the water has been discharged from the tank. The bathtub system of claim 1 .

5. a storage step of storing the water level as a reference water level when the water level in the bathtub has stabilized for a predetermined stabilization time; a first determination step of determining that the water has entered the tank when a water level difference between the water level and the reference water level exceeds a predetermined water level difference threshold and when an absolute value of the acceleration of the water level exceeds a predetermined acceleration threshold; a second determination step of determining that the water has been discharged from the tank when the water level difference has almost disappeared after the first determination step and the absolute value of the acceleration of the water level has exceeded the acceleration threshold value; When the amount of change in the water level due to the water entering the tank and the amount of change in the water level due to the water leaving the tank, whichever is smaller, is defined as the amount of change in the stable water level, Within the preset standard observation time, When there is almost no acceleration of the water level, the amount of change in the water level is smaller than the amount of change in the stable water level, and the water level continues to rise or fall, the value obtained by adding the water level difference at the end of the reference observation time to the reference water level is stored as the reference water level. Method for determining entry and exit.

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