Submergence determination system and submergence determination method

Abstract

To provide a submergence determination system and submergence determination method with high measurement accuracy of a bather's head position.SOLUTION: A submergence determination system according to the present disclosure comprises: an ultrasonic transmission device and a plurality of ultrasonic reception devices that are disposed above a bathtub in a bathroom; and a submergence determination device that determines whether a bathing posture of a bather indicates a possibility of progressing into a submergence state. Each of the plurality of ultrasonic reception devices is arranged to be equidistant from the ultrasonic transmission device. The submergence determination device acquires the height position of the water surface in the bathtub, calculates the head position of the bather on the basis of at least one of the reflected waves received by the ultrasonic reception devices, and determines whether the bathing posture of the bather indicates a possibility of progressing into a submergence state on the basis of the head position and the height position of the water surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a submersion determination system and a submersion determination method. [Background technology]

[0002] Patent Document 1 discloses a submersion determination system that detects whether a bather is in a bathing posture that may lead to a submerged state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-129930 Summary of the Invention [Problem to be solved by the invention]

[0004] The submersion determination system disclosed in the aforementioned Patent Document 1 uses ultrasonic devices installed on the ceiling to measure the bather's head position. In the submersion determination system disclosed in Patent Document 1, if the distance from each ultrasonic device to the head and the distance from each ultrasonic device to an object attached to the wall or around the bathtub are close to each other, it may not be possible to extract the reflected waves from the bather's head from the reflected waves received by the ultrasonic devices. This has led to the problem of being unable to accurately detect the head position.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a submersion determination system and a submersion determination method that can measure the bather's head position with high accuracy. [Means for solving the problem]

[0006] The submersion determination system according to the present disclosure comprises: an ultrasonic transmitting device and a plurality of ultrasonic receiving devices arranged above a bathtub in a bathroom; a submersion determination device that determines whether the bather is in a bathing posture that may lead to a submerged state; Equipped with each of the plurality of ultrasonic receiving devices is disposed equidistant from the ultrasonic transmitting device; The ultrasonic transmitting device is configured to transmit ultrasonic waves downward so that the ultrasonic waves transmitted from the ultrasonic transmitting device are reflected by the bather's head and received by each of the plurality of ultrasonic receiving devices; The submersion determination device is Acquire the height position of the water surface of the bathtub; Calculating the head position of the bather based on at least one of the reflected waves received by the ultrasonic receiving device; Based on the head position and the height of the water surface, it is determined whether the bather is in a bathing posture that may lead to a submerged state.

[0007] In the submersion determination system according to the present disclosure, each ultrasonic receiving device is positioned at an equal distance from the ultrasonic transmitting device. This configuration allows the detection of the reflected waves from the bather's head, thereby improving the accuracy of measuring the bather's head position.

[0008] The submersion determination method according to the present disclosure includes: A submersion determination method for determining whether a bather is in a bathing posture that may lead to a submerged state, using an ultrasonic transmitting device and a plurality of ultrasonic receiving devices arranged above a bathtub in a bathroom, comprising: each of the plurality of ultrasonic receiving devices is disposed equidistant from the ultrasonic transmitting device; a step of transmitting ultrasonic waves downward from the ultrasonic transmitting device so that the ultrasonic waves transmitted from the ultrasonic transmitting device are reflected by the bather's head and received by each of the plurality of ultrasonic receiving devices; calculating the head position of the bather based on at least one of the reflected waves received by the ultrasonic receiving device; acquiring a height position of the water surface of the bathtub; The method includes a step of determining whether the bather is in a bathing posture that may lead to a submerged state based on the head position and the height position of the water surface.

[0009] In the submersion determination method according to the present disclosure, the ultrasonic receiving devices are arranged at equal distances from the ultrasonic transmitting devices. This configuration allows the detection of the reflected waves from the bather's head, thereby improving the accuracy of measuring the bather's head position. [Effects of the Invention]

[0010] The present disclosure provides a submersion determination system and a submersion determination method that can measure the bather's head position with high accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a submersion determination system according to a first embodiment. [Figure 2] 1 is a schematic diagram of a submersion determination system according to a first embodiment. [Figure 3] 1 is a detailed block diagram of a submergence determination device of a submergence determination system according to a first embodiment. [Figure 4] 10 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers of a submersion determination system according to a comparative example. FIG. [Figure 5] 10 is a diagram showing a reflected wave received by an ultrasonic receiving device of a submersion determination system according to a comparative example. FIG. [Figure 6] 4 is a diagram showing a reflected wave received by an ultrasonic receiving device of the submersion determination system according to the first embodiment. FIG. [Figure 7] 1 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers of a submersion determination system according to a comparative example and the first embodiment. FIG. [Figure 8] FIG. 10 is an explanatory diagram for explaining retroreflection. [Figure 9] 10 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to a modified example. FIG. [Figure 10] 10 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to a modified example. FIG. [Figure 11] 10 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to a modified example. FIG. [Figure 12] 10 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to a modified example. FIG. [Figure 13] 3 is a diagram showing a control flow of the submersion determination system according to the first embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary. In addition, some reference numerals have been omitted to avoid cluttering the drawings. It should be noted that the following drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc., may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following explanation. Furthermore, it goes without saying that the drawings may include portions in which the dimensional relationships and ratios differ from one another.

[0013] Naturally, the right-handed xyz Cartesian coordinate system shown in each drawing is for the convenience of explaining the positional relationship of the components. Normally, the positive direction of the z axis is vertically upward, and the xy plane is the horizontal plane.

[0014] (Embodiment 1) <Submersion detection system> First, the configuration of a submergence determination system according to embodiment 1 will be described with reference to Fig. 1 and Fig. 2. Fig. 1 and Fig. 2 are schematic diagrams of the submergence determination system according to embodiment 1. More specifically, Fig. 1 is an xy plan view showing an outline of the submergence determination system. Fig. 2 is an xz plan view showing an outline of the submergence determination system.

[0015] 1 and 2, the submergence determination system 1 according to this embodiment includes an ultrasonic transmitter 2, an ultrasonic receiver 3, a submergence determination device 4, and an alarm device 5. In the submergence determination system 1 shown in FIG. 1, only the ultrasonic transmitter 2 and the ultrasonic receiver 3 are shown, and the submergence determination device 4 and the alarm device 5 are omitted.

[0016] <Ultrasonic Transmitting Device 2 and Ultrasonic Receiving Device 3> As shown in FIG. 1, ultrasonic transmitting device 2 and ultrasonic receiving device 3 are typically placed on the ceiling above bathtub 6 in bathroom 10, but are not limited to being placed on the ceiling. As shown in FIG. 1, bathroom 10 has walls W1 and W2. Object T1 is provided on wall W2. Object T1 is, for example, an object attached to the wall. Furthermore, object T1 is not limited to an object attached to the wall, and may be an object around the bathtub.

[0017] As shown in Fig. 1, one ultrasonic transmitting device 2 is placed on the ceiling. Two ultrasonic receiving devices 3 are placed on the ceiling. As shown in Fig. 1, the ultrasonic receiving device 3 is composed of an ultrasonic receiving device 31 and an ultrasonic receiving device 32. Here, an example is shown in which two ultrasonic receiving devices 3 are placed on the ceiling, but this is not limited to this, and multiple ultrasonic receiving devices 3 may be placed above the bathtub 6.

[0018] Each of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) is disposed at an equal distance from the ultrasonic transmitting device 2. As shown in Fig. 1, the ultrasonic transmitting device 2 is preferably disposed above the head Q of the bather.

[0019] 1, the ultrasonic receiving device 3 and the ultrasonic transmitting device 2 are arranged above the bathtub 6 in the longitudinal direction, and are arranged parallel to the surrounding wall surface W1. However, this is not limited to this, and the ultrasonic receiving device 3 and the ultrasonic transmitting device 2 may also be arranged above the bathtub 6 in the lateral direction, and are arranged parallel to the surrounding wall surface W2.

[0020] 9 and 10, which will be described later, the ultrasonic transmitting device 2 and the ultrasonic receiving device 3 may be arranged above the bathtub 6 so that a line connecting the center of the ultrasonic transmitting device 2 and the center of each ultrasonic receiving device 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) is not parallel to the surrounding wall surfaces W1 and W2. In other words, each ultrasonic receiving device 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) may be arranged equidistant from the ultrasonic transmitting device 2.

[0021] As shown in Figures 1 and 2, the ultrasonic wave transmitting device 2 is configured to transmit ultrasonic waves downward so that the ultrasonic waves transmitted from the ultrasonic wave transmitting device 2 are reflected by the head Q of the bather P and received by the ultrasonic wave receiving device 3. The ultrasonic wave receiving device 3 is configured to receive ultrasonic waves downward in order to receive the ultrasonic waves transmitted from the ultrasonic wave transmitting device 2. Note that the downward direction is not limited to a vertical downward direction, but may be an inclined downward direction, for example, an oblique downward direction.

[0022] 1 and 2, the ultrasonic waves transmitted from the ultrasonic transmitter 2 follow paths L1 and L2 until they are reflected by the head Q of the bather P and received by the ultrasonic receiver 32. Furthermore, the ultrasonic waves transmitted from the ultrasonic transmitter 2 follow paths L3 and L4 until they are reflected by the object T1 and received by the ultrasonic receiver 32. In FIGS. 1 and 2, the paths taken by the ultrasonic waves transmitted from the ultrasonic transmitter 2 and reflected by the object T1 until they are received by the ultrasonic receiver 31 are omitted.

[0023] <Submersion determination device 4> The submersion determination device 4 is a device that determines whether or not the bathing posture of the bather P may progress to a submerged state. Details of the submersion determination device 4 will be described later.

[0024] The submerged state of bather P is as follows: Drowning in a bathtub occurs when bather P loses consciousness for some reason while immersed in the water of bathtub 6, or when standing up to get out of bathtub 6, a rapid drop in blood pressure causes the brain or heart to become ischemic, causing bather P's head Q to be submerged in the water of bathtub 6, and the water in bathtub 6 blocks the respiratory organs such as the nose and mouth. The submerged state of bather P is defined as the state in which bather P's head Q is submerged in the water of bathtub 6.

[0025] The submersion determination device 4 is connected by wire or wirelessly to the ultrasonic transmitter 2 and the ultrasonic receiver 3. As will be described later, the submersion determination device 4 determines whether the bather P is in a bathing posture that may lead to a submerged state, based on the position of the bather P's head Q and the height of the water surface 8.

[0026] <Alarm device 5> The alarm device 5 is connected to the submersion determination device 4 by wire or wirelessly. The submersion determination device 4 and the alarm device 5 can be installed anywhere inside or outside the bathroom. The submersion determination device 4 and the alarm device 5 may be built into either the ultrasonic transmitting device 2 or the ultrasonic receiving device 3. The alarm device 5 issues a warning when the submersion determination device 4 determines that the bather P is in a bathing position that may lead to a submerged state.

[0027] <Detailed Description of Submersion Determination Device 4> The submergence determination device 4 will be described in detail below with reference to Fig. 3. Fig. 3 is a detailed block diagram of the submergence determination device of the submergence determination system according to embodiment 1. As shown in Fig. 3, the submergence determination device 4 is connected to the ultrasonic wave transmitting device 2 and the ultrasonic wave receiving device 3 by wire or wirelessly.

[0028] 3, the submersion determination device 4 includes a pulse generating circuit 20, an oscillator circuit 21, an interrupter circuit 22, and a transmitting amplifier circuit 23. The submersion determination device 4 also includes a receiving amplifier circuit 38, a filter circuit 39, a waveform analysis circuit 33, a head reflected wave extraction unit 28, a head distance calculation unit 29, a head height position calculation unit 30, and a water surface height position calculation unit 35. The submersion determination device 4 also includes a submersion determination unit 36.

[0029] The head reflected wave extractor 28, head distance calculator 29, head height position calculator 30, water surface height position calculator 35, and submersion determiner 36 are configured by, for example, logic circuits of a central processing unit.

[0030] The oscillator circuit 21 generates an AC signal in the ultrasonic band. The pulse generator circuit 20 generates pulses for determining the ultrasonic wave transmission and reception times, and outputs the pulses to the interrupter circuit 22 and the waveform analyzer circuit 33. The interrupter circuit 22 is controlled by the pulses from the pulse generator circuit 20, and converts the AC signal from the oscillator circuit 21 into an AC waveform with a pulsed amplitude. The transmission amplifier circuit 23 amplifies the AC signal from the interrupter circuit 22.

[0031] The receiving amplifier circuit 38 amplifies the reflected wave received by the ultrasonic receiver 3. The filter circuit 39 removes frequency components other than the frequency components of the ultrasonic waves transmitted from the ultrasonic transmitter 2 from the reflected wave received by the ultrasonic receiver 3. The output from the filter circuit 39 is input to the waveform analysis circuit 33.

[0032] The waveform analysis circuit 33 performs envelope detection on the received waveform input from the filter circuit 39 and outputs an envelope-detected waveform.

[0033] The head reflected wave extraction unit 28 extracts the reflected waves from the head Q of the bather P from the reflected waves received by the ultrasound receiving device 3 based on the envelope detection waveform output from the waveform analysis circuit 33. The method by which the head reflected wave extraction unit 28 extracts the reflected waves from the head Q of the bather P will be described later.

[0034] The head distance calculation unit 29 calculates the head distance D1 (see FIG. 2), which is the distance from the ultrasonic wave transmitting device 2 to the head Q of the bather P, based on the reflected waves from the head Q of the bather P. Specifically, the head distance calculation unit 29 calculates the delay time from when the ultrasonic wave is transmitted from the ultrasonic wave transmitting device 2 until the ultrasonic wave receiving device 3 receives the reflected waves from the head Q of the bather P, multiplies this delay time by the propagation speed of the ultrasonic wave, and calculates half the value as the head distance D1. The head distance calculation unit 29 calculates the head distance D1 (see FIG. 2) based on at least one of the reflected waves received by the ultrasonic wave receiving device 3.

[0035] Note that the distances D1 and D3 shown in Fig. 2 indicate three-dimensional distances, not two-dimensional distances. For ease of explanation, the three-dimensional distances D1 and D3 are shown in the xz plane view in Fig. 2.

[0036] The head height position calculation unit 30 calculates the height position of the head Q of the bather P based on the head distance D1. Specifically, the head height position calculation unit 30 regards the head distance D1 as a vertical distance D11. The head height position calculation unit 30 can then calculate the height position of the head Q of the bather P by subtracting the vertical distance D11 from the known height position of the ultrasonic receiving device 3. In this way, the head height position calculation unit 30 can calculate the height position of the head Q of the bather P by approximating the head distance D1 to the vertical distance D11.

[0037] As another example, the head height position calculation unit 30 calculates the vertical distance D11 between the ultrasonic receiving device 3 and the head Q by a geometric method such as Pythagoras' theorem based on the head distance D1 and the known separation distance D3 between the ultrasonic transmitting device 2 and the ultrasonic receiving device 3. In this case, the reflection angle at the head Q is set to a predetermined angle. Then, the head height position calculation unit 30 can calculate the height position of the bather P's head Q by subtracting the vertical distance D11 from the known height position of the ultrasonic receiving device 3.

[0038] The water surface height position calculation unit 35 calculates the position of the height of the water surface 8 of the bathtub 6 by acquiring information about the water surface height of the bathtub 6. More specifically, it calculates the position of the height of the water surface 8 of the bathtub 6 by acquiring information about the water surface height from a water surface sensor (not shown) of the bathtub 6. Furthermore, the submersion determination device 4 is capable of wireless communication with the bathtub 6, and the water surface height position calculation unit 35 may acquire information about the water surface height set in the bathtub 6 by the user and calculate the position of the height of the water surface 8 of the bathtub 6.

[0039] The submersion determination unit 36 ​​compares the height of the bather P's head Q calculated by the head height calculation unit 30 with the height of the water surface 8 calculated by the water surface height calculation unit 35, and determines, based on the comparison result, whether the bather P is in a bathing posture that could lead to a submerged state. Specifically, the submersion determination unit 36 ​​calculates the difference between the height of the bather P's head Q and the height of the water surface 8, and if this difference is equal to or less than a predetermined value, determines that the bather P is in a bathing posture that could lead to a submerged state. Here, the predetermined value is set appropriately within a range of, for example, 15 cm to 30 cm, and is preferably determined depending on the size of the bather P's head Q, the position of the respiratory organs, etc. The predetermined value is set to 25 cm, for example. The predetermined value is pre-stored in a storage device (not shown) of the submersion determination device 4.

[0040] The warning device 5 issues a warning when the submersion determining unit 36 ​​determines that the bather P is in a bathing posture that may lead to a submerged state.

[0041] The water surface height position calculation unit 35 may calculate the height position of the water surface 8 based on the waves reflected from the water surface 8. In this case, the configuration is as follows: The ultrasonic transmitting device 2 is configured to transmit ultrasonic waves obliquely downward so that the ultrasonic waves transmitted from the ultrasonic transmitting device 2 are conformally reflected from the water surface 8 of the bathtub 6 and received by the ultrasonic receiving device 3.

[0042] The submersion determination device 4 includes a water surface reflected wave extraction unit. More specifically, the water surface reflected wave extraction unit extracts the reflected wave from the water surface 8 from the reflected wave received by the ultrasonic receiving device 3 based on the envelope detection waveform output from the waveform analysis circuit 33. The reflected wave from the water surface 8 has an amplitude significantly larger than that of the reflected wave from the head Q of the bather P. Therefore, by setting a higher threshold value for the envelope detection waveform output from the waveform analysis circuit 33, the water surface reflected wave extraction unit can easily extract the reflected wave from the water surface 8 from the reflected wave received by the ultrasonic receiving device 3.

[0043] The water surface height position calculation unit 35 calculates the height position of the water surface 8 based on the reflected waves from the water surface 8. Specifically, the water surface height position calculation unit 35 calculates the delay time from when the ultrasonic waves are transmitted from the ultrasonic transmitting device 2 until the reflected waves are received by the ultrasonic receiving device 3, and calculates the propagation distance of the V-shaped propagation path of the ultrasonic waves conformally reflected from the water surface 8 by multiplying this delay time by the propagation speed of the ultrasonic waves.

[0044] The water surface height position calculation unit 35 calculates the vertical distance D4 between the ultrasonic receiving device 3 and the water surface 8 by a geometric method such as Pythagoras' theorem based on the propagation distance and the known separation distance D3 between the ultrasonic transmitting device 2 and the ultrasonic receiving device 3. Then, the water surface height position calculation unit 35 can calculate the height position of the water surface 8 by subtracting the vertical distance from the known height position of the ultrasonic receiving device 3.

[0045] <Extraction of reflected waves from head Q> 4 to 6, the method by which the head reflected wave extraction unit 28 extracts reflected waves from the head Q of the bather P will be described. FIG. 4 is a diagram showing the arrangement of the ultrasonic transmitter and ultrasonic receiver in a submersion determination system according to a comparative example. In FIG. 4, an ultrasonic transmitter 2 and an ultrasonic receiver 3 are provided above a bathtub 6. In FIG. 4, there is one ultrasonic transmitter 2 and one ultrasonic receiver 3. In FIG. 4, the ultrasonic transmitter 2 and the ultrasonic receiver 3 are arranged parallel to the longitudinal direction of the bathtub. The rest of the configuration is the same as in FIG. 1. FIG. 5 is a diagram showing reflected waves received by an ultrasonic receiver in a submersion determination system according to a comparative example. FIG. 6 is a diagram showing reflected waves received by an ultrasonic receiver in a submersion determination system according to embodiment 1.

[0046] As shown in Figure 4, the ultrasonic waves transmitted from the ultrasonic transmitter 2 follow paths L11 and L21 until they are reflected by the head Q of the bather P and received by the ultrasonic receiver 3. Furthermore, the ultrasonic waves transmitted from the ultrasonic transmitter 2 follow paths L31 and L41 until they are reflected by an object T1 on the wall W2 and received by the ultrasonic receiver 3.

[0047] <Extraction of reflected waves in a submersion determination system of a comparative example> A method for extracting reflected waves from the head Q of a bather P in a submersion determination system according to a comparative example will be described. The upper part of Figure 5 shows reflected waves received by the ultrasonic receiving device before the bather P entered the bath. The middle part of Figure 5 shows reflected waves received by the ultrasonic receiving device when the heights of the bather P's head Q and the object T1 are different. The lower part of Figure 5 shows reflected waves received by the ultrasonic receiving device when the heights of the bather P's head Q and the object T1 are close to each other. In Figure 5, the horizontal axis represents time, which corresponds to the distance from the ultrasonic transmitting device 2. In Figure 5, the vertical axis represents peak intensity. While Figure 5 shows a noise peak 80 and a frame peak 90, we will focus here on the head peak 60 and the object T1 peak 50. Note that the waveform of the reflected waves in Figure 5 is an example.

[0048] If the height of the head Q position of bather P and object T1 differs, the combined distance of paths L11 and L21 (see Figure 4) will differ from the combined distance of paths L31 and L41 (see Figure 4). Therefore, if the height of the head Q position of bather P and object T1 differs, as shown in the middle of Figure 5, the peak position Y1 of the head Q of bather P will differ from the peak position X1 of object T1.

[0049] Therefore, by subtracting (canceling) the graph of reflected waves shown in the upper part of Figure 5 from the graph of reflected waves shown in the middle part of Figure 5, the head reflected wave extraction unit 28 can extract the reflected waves from the head Q of the bather P.

[0050] When the heights of the head Q position of bather P and object T1 are close to each other, the combined distance of paths L11 and L21 (see Figure 4) and the combined distance of paths L31 and L41 (see Figure 4) may also be close to each other. Therefore, when the heights of the head Q position of bather P and object T1 are close to each other, the peak position Y2 of the head Q of bather P will overlap with the peak position X2 of object T1, as shown in the lower part of Figure 5. At this time, depending on the phase relationship between the reflected wave from the head Q of bather P and the reflected wave from object T1, the peak intensity (wave height) of the composite wave may be equal to or lower than the peak intensity (wave height) of the original object T1 alone.

[0051] Therefore, when the graph of reflected waves shown in the upper part of Figure 5 is subtracted (cancelled) from the graph of reflected waves shown in the lower part of Figure 5, the reflected waves from head Q disappear, and head reflected wave extraction unit 28 cannot extract the reflected waves from head Q of bather P. In this way, when the heights of the head Q position of bather P and object T1 show similar values, the submersion determination system of the comparative example cannot extract the reflected waves from head Q of bather P.

[0052] <Extraction of reflected waves in the submersion determination system of embodiment 1> A method for extracting reflected waves from the head Q of the bather P in the submersion determination system according to the first embodiment will be described. The upper part of FIG. 6 shows reflected waves received by the ultrasonic receiving device 31 before the bather P entered the bath. The second part of FIG. 6 shows reflected waves received by the ultrasonic receiving device 32 before the bather P entered the bath. The third part of FIG. 6 shows reflected waves received by the ultrasonic receiving device 31 when the heights of the bather P's head Q and the object T1 are close to each other. The lower part of FIG. 6 shows reflected waves received by the ultrasonic receiving device 32 when the heights of the bather P's head Q and the object T1 are close to each other. In FIG. 6, the horizontal axis represents time, which corresponds to the distance from the ultrasonic transmitting device. In FIG. 6, the vertical axis represents peak intensity. While FIG. 6 shows a noise peak 80 and a frame peak 90, attention is focused here on the head peak 60 and the object T1 peak 50. Note that the waveform of the reflected waves in FIG. 6 is merely an example. In the following, the arrangement of the ultrasonic transmitting device 2 and the ultrasonic receiving device 3 shown in FIG. 1 will be referred to where appropriate.

[0053] The third row of Figure 6 will now be explained. If the heights of the head Q of the bather P and the object T1 are close to each other, the following occurs: The combined distance of the distance from the ultrasonic transmitter 2 to the head Q and the distance from the head Q to the ultrasonic receiver 31 may be close to the combined distance from the ultrasonic transmitter 2 to the object T1 and the distance from the object T1 to the ultrasonic receiver 31.

[0054] That is, in the third row of Fig. 6, for the same reason as in the bottom row of Fig. 5, peak position Y3 of bather P's head Q overlaps with peak position X3 of object T1. At this time, depending on the phase relationship between the reflected wave from bather P's head Q and the reflected wave from object T1, the peak intensity (wave height) of the composite wave may be equal to or lower than the peak intensity (wave height) of the original object T1 alone. Therefore, if the graph of reflected waves shown in the top row of Fig. 6 is subtracted (cancelled) from the graph of reflected waves shown in the third row of Fig. 6, the reflected wave from head Q disappears, and head reflected wave extraction unit 28 cannot extract the reflected wave from bather P's head Q from the reflected wave received by ultrasound receiving device 31.

[0055] However, even if the heights of the head Q position of bather P and object T1 are similar, the combined distance of paths L1 and L2 (see FIG. 1) and the combined distance of paths L3 and L4 (see FIG. 1) are different. Therefore, as shown in the bottom of FIG. 6, even if the heights of the head Q position of bather P and object T1 are similar, the peak position Y4 of the head Q of bather P is different from the peak position X4 of object T1. Therefore, by subtracting (canceling) the reflected wave graph shown in the second row of FIG. 6 from the reflected wave graph shown in the bottom row of FIG. 6, the head reflected wave extraction unit 28 can extract the reflected wave from the head Q of bather P from the reflected wave received by the ultrasound receiving device 32.

[0056] As described above, since the distance from the head Q located directly below the ultrasonic transmitting device 2 to the ultrasonic receiving device 31 and the ultrasonic receiving device 32 is the same, the head peak 60 appears at the same position in the ultrasonic receiving device 31 and the ultrasonic receiving device 32. On the other hand, since the distance from the object T1 to the ultrasonic receiving device 31 and the ultrasonic receiving device 32 is different, the object peak 50 appears at different positions in the ultrasonic receiving device 31 and the ultrasonic receiving device 32. Therefore, the head peak 60 and the object peak 50 do not overlap in either the ultrasonic receiving device 31 or the ultrasonic receiving device 32. As a result, even if the heights of the head Q position of the bather P and the object T1 are close to each other, the submersion determination system according to the first embodiment can extract the reflected wave from the head Q of the bather P from the reflected wave received by the ultrasonic receiving device 32.

[0057] In other words, in the submersion determination system according to the first embodiment, the ultrasonic receivers 3 are arranged at equal distances from the ultrasonic transmitter 2. Therefore, for both ultrasonic receivers 3, the ultrasonic waves transmitted from the ultrasonic transmitter 2 are reflected by the head Q of the bather P and received by the ultrasonic receiver 3, following paths L1 and L2 (see FIG. 1), which are approximately the same distance. Furthermore, the ultrasonic waves transmitted from the ultrasonic transmitter 2 are reflected by the object T1 on the wall W2 and received by the ultrasonic receiver 32, following paths L3 and L4 (see FIG. 1). The combined distance of paths L1 and L2 (see FIG. 1) and the combined distance of paths L3 and L4 (see FIG. 1) are different values.

[0058] Thus, in one of the multiple ultrasonic receiving devices 3 (ultrasonic receiving device 32 in Figure 1), the peak position of head Q (peak position Y4 in the lower part of Figure 6) and the peak position of object T1 (peak position X4 in the lower part of Figure 6) are different.

[0059] Therefore, in the submersion determination system according to the first embodiment, the head reflected wave extraction unit 28 can extract the reflected waves from the head Q of the bather P. This allows the submersion determination system according to the first embodiment to calculate the position of the bather's head based on at least one of the reflected waves received by the ultrasonic receiving device. Therefore, the submersion determination system according to the first embodiment can improve the accuracy of measuring the position of the head Q of the bather P.

[0060] 5 and 6, as in Fig. 1, an example has been explained in which there are two ultrasonic receiving devices 3. When there are multiple ultrasonic receiving devices 3, the head reflected wave extraction unit 28 is more likely to acquire reflected waves whose peak positions from the head Q and the object T1 are different, so it can be said that the accuracy of measuring the position of the head Q of the bather P is higher.

[0061] <Retroreflection> Here, retroreflection will be explained with reference to Figs. 7 and 8. Fig. 7 is a diagram showing the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to a comparative example and the first embodiment. The upper part of Fig. 7 shows the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to the comparative example. The lower part of Fig. 7 shows the arrangement of ultrasonic transmitters and ultrasonic receivers in a submersion determination system according to the first embodiment. For simplicity of explanation, the lower part of Fig. 7 focuses on the ultrasonic transmitter 2 and ultrasonic receiver 32. Here, attention is focused on the retroreflection of a remote control R1 installed on a wall W1.

[0062] Fig. 8 is an explanatory diagram for explaining retroreflection. The upper part of Fig. 8 shows an explanatory diagram for the arrangement of an ultrasonic transmitter and an ultrasonic receiver in a submersion determination system according to a comparative example. The upper part of Fig. 8 is a yz plan view corresponding to the xy plan view shown in the upper part of Fig. 7. The lower part of Fig. 8 shows an explanatory diagram for the arrangement of an ultrasonic transmitter and an ultrasonic receiver in a submersion determination system according to embodiment 1. The lower part of Fig. 8 is a yz plan view corresponding to the xy plan view shown in the lower part of Fig. 7.

[0063] As shown in the upper part of Fig. 7, in the submersion determination system of the comparative example, the distance from the ultrasonic transmitter 2 to the wall W1 and the distance from the ultrasonic receiver 3 to the wall W1 are both equal, at distance D31. Therefore, as shown in the upper part of Fig. 8, in the submersion determination system of the comparative example, ultrasonic waves transmitted from the ultrasonic transmitter 2 are reflected retrogradely by the right-angle corner of the remote control R1 installed on the wall W1, travel toward the ultrasonic receiver 3, and are received with a high sound pressure. As a result, the submersion determination system of the comparative example lacks accuracy in measuring the bather's head position because unnecessary reflected waves from objects such as the remote control R1 are received with large amplitudes.

[0064] 7, in the submergence determination system according to the first embodiment, the distance from the ultrasonic transmission device 2 to the wall surface W1 is distance D31, whereas the distance from the ultrasonic reception device 32 to the wall surface W1 is distance D32. In other words, the distance from the ultrasonic transmission device 2 to the wall surface W1 is different from the distance from the ultrasonic reception device 32 to the wall surface W1.

[0065] Therefore, as shown in the lower part of Figure 8, in the submergence determination system according to the first embodiment, ultrasonic waves transmitted from the ultrasonic transmitter 2 are reflected retrogradely by the right-angle corner of the remote control R1 installed on the wall W1 and travel in the direction of the ultrasonic transmitter 2, resulting in a low sound pressure being received by the ultrasonic receiver 32. In other words, the submergence determination system according to the first embodiment can prevent the ultrasonic receiver from receiving ultrasonic waves retrogradely reflected by an object having a right-angle corner relative to the wall surface. As a result, the submergence determination system according to the first embodiment can suppress unnecessary reflected waves from objects such as the remote control R1, thereby improving the accuracy of measuring the bather's head position.

[0066] In Figure 8, the remote control R1 is used as an example to explain retroreflection, but this is not limited to this. Retroreflection also occurs on objects that have a right-angle corner with respect to a wall surface, such as a window frame.

[0067] <Modification> Below, a submergence determination system according to a modified example in which the arrangement of the ultrasonic transmitters and ultrasonic receivers is changed will be described with reference to Figures 9 to 11. Figures 9 to 11 are diagrams showing the arrangement of the ultrasonic transmitters and ultrasonic receivers in the submergence determination system according to the modified example. Figures 9 to 11 are xy plan views showing the arrangement of the ultrasonic transmitters and ultrasonic receivers in the submergence determination system.

[0068] <Placement> As shown in Figure 9, in the submersion determination system according to the modified example, the ultrasonic receiving device 3 is composed of two ultrasonic receiving devices 31 and 32. The ultrasonic transmitting device 2 is placed above the bather's head Q. In the bathtub 6, the position of the bather's head Q is often determined by the position of the stopper and the foot rest. Therefore, it is preferable to place the ultrasonic transmitting device 2 in accordance with the position of the bather's head.

[0069] The ultrasonic receiving device 3 is disposed via the ultrasonic transmitting device 2. More specifically, the two ultrasonic receiving devices 31, 32 are disposed so as to sandwich the ultrasonic transmitting device 2. In other words, the ultrasonic transmitting device 2 is disposed between the two ultrasonic receiving devices 31, 32. That is, one ultrasonic receiving device 31 is located on the positive x-axis and positive y-axis sides of the ultrasonic transmitting device 2. The other ultrasonic receiving device 32 is located on the negative x-axis and negative y-axis sides of the ultrasonic transmitting device 2.

[0070] The direction of the straight line connecting the ultrasonic transmitting device 2 and the ultrasonic receiving device 31 is non-parallel to the longitudinal direction and the short side direction of the bathtub 6. Similarly, the direction of the straight line connecting the ultrasonic transmitting device 2 and the ultrasonic receiving device 32 is non-parallel to the longitudinal direction and the short side direction of the bathtub 6.

[0071] 9, the distances from the walls W1 and W2 around the bathtub to the ultrasonic transmitter 2 and the ultrasonic receiver 3 are different. Therefore, the submersion determination system according to the modified example can prevent the ultrasonic receiver 3 from receiving ultrasonic waves that are retroreflected by an object that has a right-angle corner with respect to the walls W1 and W2.

[0072] Furthermore, each of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) is positioned at an equal distance from the ultrasonic transmitting device 2. Therefore, for any of the ultrasonic receiving devices 3, the peak position of the head Q and the peak position of the object (not shown in FIG. 9) are different. Therefore, the submersion determination system according to the modified example can extract the reflected waves from the head Q of the bather P.

[0073] In other words, the submersion determination system according to the modified example shown in FIG. 9 has high accuracy in measuring the position of the bather's head, and can prevent the ultrasonic receiving device 3 from receiving retro-reflected ultrasonic waves.

[0074] <L-shaped> As shown in Figure 10, in the submersion determination system according to the modified example, the ultrasonic receiving device 3 is composed of two ultrasonic receiving devices 31 and 32. The ultrasonic transmitting device 2 is placed above the bather's head Q. In the bathtub 6, the position of the bather's head Q is often determined by the position of the stopper and the foot rest. Therefore, it is preferable to place the ultrasonic transmitting device 2 in accordance with the position of the bather's head.

[0075] The ultrasonic receiving devices 3 are arranged in a dogleg shape with the ultrasonic transmitting device 2 interposed therebetween. More specifically, the ultrasonic receiving devices 3 are arranged so as to form a dogleg shape with the ultrasonic transmitting device 2 at the top. That is, one ultrasonic receiving device 31 is located on the positive x-axis and positive y-axis sides of the ultrasonic transmitting device 2. The other ultrasonic receiving device 32 is located on the positive x-axis and negative y-axis sides of the ultrasonic transmitting device 2.

[0076] 10, the ultrasonic receiving devices 31 and 32 are arranged symmetrically with respect to a center line C1 that passes through the center of the bather's head Q and is parallel to the longitudinal direction of the bathtub 6. The ultrasonic receiving device 31 should be arranged so that the angle formed by the center line C1 and a line connecting the center of the ultrasonic receiving device 31 and the center of the ultrasonic transmitting device 2 is less than 90 degrees. The same can be said for the ultrasonic receiving device 32.

[0077] 10, the distances from the bathtub wall W1 to the ultrasonic transmitter 2 and the ultrasonic receiver 3 are different. Therefore, the submersion determination system according to the modified example can prevent the ultrasonic receiver 3 from receiving ultrasonic waves that are retroreflected by an object (not shown in FIG. 10) that has a right-angle corner relative to the wall W1.

[0078] Furthermore, each of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) is positioned at an equal distance from the ultrasonic transmitting device 2. Therefore, for any of the ultrasonic receiving devices 3, the peak position of the head Q and the peak position of the object (not shown in FIG. 11) are different. Therefore, the submersion determination system according to the modified example can extract the reflected waves from the head Q of the bather P.

[0079] In other words, the submersion determination system according to the modified example shown in FIG. 10 has high accuracy in measuring the position of the bather's head, and can prevent the ultrasonic receiving device 3 from receiving retro-reflected ultrasonic waves.

[0080] When there are three or more ultrasonic receiving devices 3, an example of the arrangement shown in Figure 11 is possible. That is, the lines connecting the ultrasonic transmitting device 2 and each ultrasonic receiving device 3 are non-parallel to the longitudinal direction and the lateral direction of the bathtub 6. Furthermore, each ultrasonic receiving device 3 is arranged so as to be equidistant from the ultrasonic transmitting device 2.

[0081] <Extraction of reflected waves from the head> Here, FIG. 9 shows objects T3 and T4. The height of object T3 or object T4 is assumed to be slightly higher than the height of the bather's head Q. Line C3 is perpendicular to line C4 connecting the centers of ultrasonic receiving device 31 and ultrasonic receiving device 32 and passes through ultrasonic transmitting device 2. In other words, line C3 is the perpendicular bisector of line C4. Object T3 is on line C3 in the xy plane and is attached to the intersection of line C3 and wall W1. Object T3 may also be attached to the frame of bathtub 6 (the edge of bathtub 6). Object T4 is attached to the intersection of line C3 and wall W2 in the xy plane. Below, we will focus on object T4.

[0082] 9, ultrasonic waves transmitted from ultrasonic transmitting device 2 follow paths L51 and L52 until they are reflected by object T4 and received by ultrasonic receiving device 32. Ultrasonic waves transmitted from ultrasonic transmitting device 2 follow paths L53 and L54 until they are reflected by object T4 and received by ultrasonic receiving device 31. Line C3 is the perpendicular bisector of line C4, and object T4 is located on line C3, so the combined distance of paths L51 and L52 and the combined distance of paths L53 and L54 are the same value.

[0083] Here, the ultrasonic waves transmitted from the ultrasonic transmitter 2 reflect off the head Q of the bather P and travel along paths L1 and L2 (see FIG. 1) before being received by the ultrasonic receiver 3. If the height of object T3 is slightly higher than the height of the bather's head Q, the combined distance of paths L51 and L52 may be close to the combined distance of paths L1 and L2. Similarly, the combined distance of paths L53 and L54 may be close to the combined distance of paths L1 and L2. In this case, the peak position of the head Q of bather P overlaps with the peak of object T4 in both the received waveforms of ultrasonic receiver 31 and ultrasonic receiver 32. Therefore, at first glance, the submersion determination system according to the modified example may appear unable to extract the reflected waves from the head Q of bather P.

[0084] However, it is difficult for the bather P to always face the same direction and maintain the same posture, and the direction and posture change slightly from moment to moment. Therefore, the direction in which the ultrasonic waves are strongly reflected by the head Q changes from moment to moment, and the peak intensity of the reflected waves from the head Q received by either of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) increases.

[0085] Furthermore, as the interference state between the waves reflected by object T4 and the waves reflected by head Q changes from moment to moment, the peak intensity of the composite wave of the reflections from object T4 and head Q received by one of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32) increases. As a result, even if the graphs of the reflected waves before bather P entered the bath are subtracted (cancelled), the reflection peak from head Q remains in the reflected waveform of one of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32). Therefore, in the submersion determination system according to the modified example, even if object T4 is attached to wall W2, the reflected wave from bather P's head Q can be extracted from the waveform received by one of the ultrasonic receiving devices 3 (ultrasonic receiving device 31, ultrasonic receiving device 32).

[0086] In this way, the submersion determination system according to the modified example is configured so that the ultrasonic transmitter 2 transmits ultrasonic waves at a predetermined time interval and multiple ultrasonic receivers 3 simultaneously receive the ultrasonic waves at a predetermined time interval, thereby enabling accurate extraction of the reflected waves from the head Q of the bather P. As a result, the submersion determination system according to the modified example can be said to have high accuracy in measuring the position of the bather's head.

[0087] The ultrasonic transmitting device 2 and the ultrasonic receiving device 3 may be arranged as shown in Fig. 12. Fig. 12 shows the arrangement of a submersion determination system according to a modified example. In Fig. 12, the arrangement of the object T1 is different from that in Fig. 1. That is, the object T1 is attached to a wall W1.

[0088] In Figure 12, the ultrasonic waves transmitted from the ultrasonic transmitting device 2 follow paths L1 and L2 until they are reflected by the head Q of the bather P and received by the ultrasonic receiving device 31 or the ultrasonic receiving device 32. Furthermore, the ultrasonic waves transmitted from the ultrasonic transmitting device 2 follow paths L91 and L93 until they are reflected by the object T1 and received by the ultrasonic receiving device 31. Furthermore, the ultrasonic waves transmitted from the ultrasonic transmitting device 2 follow paths L91 and L92 until they are reflected by the object T1 and received by the ultrasonic receiving device 32.

[0089] In Figure 12, the combined distance of paths L1 and L2 and the combined distance of paths L91 and L93 show different values. Also in Figure 12, the combined distance of paths L1 and L2 and the combined distance of paths L91 and L92 show different values. Therefore, for both ultrasonic receiving devices 3 (ultrasonic receiving device 31 and ultrasonic receiving device 32), the peak position of head Q and the peak position of object T1 are different. Therefore, the submersion determination system of the modified example can extract the reflected waves from the bather's head Q.

[0090] <Method for determining submergence> Next, a submergence determination method using the submergence determination system 1 according to an embodiment of the present invention will be described. Fig. 13 is a diagram showing the control flow of the submergence determination system according to embodiment 1. In the following description, the symbols shown in Figs. 1 and 2 will be used as appropriate.

[0091] First, the ultrasonic wave transmitting device 2 transmits ultrasonic waves downward so that the ultrasonic waves transmitted from the ultrasonic wave transmitting device 2 are reflected by the head of the bather P and received by each of the multiple ultrasonic wave receiving devices 3 (step ST100).

[0092] Next, the waveform analysis circuit 33 analyzes the envelope detection waveform of the reflected wave received by the ultrasonic wave receiving device 3 (step ST101).

[0093] Next, the head reflected wave extraction unit 28 extracts the reflected waves from the head Q of the bather P from the reflected waves received by the ultrasound receiving device 3 based on the envelope detection waveform output from the waveform analysis circuit 33 (step ST102).

[0094] Next, the head distance calculation unit 29 acquires the head distance D1 (see Figure 2), which is the distance from the ultrasonic transmitting device 2 to the head Q of the bather P, and the height position of the head Q of the bather P, based on at least one of the reflected waves from the head Q of the bather P received by the ultrasonic receiving device 3 (step ST103).

[0095] Next, the water surface height position calculation unit 35 acquires information about the water surface height of the bathtub 6, thereby acquiring the position of the water surface height of the bathtub 6 (step ST104).

[0096] Next, the submersion determination unit 36 ​​calculates the difference between the height position of the head Q of the bather P and the height position of the water surface 8 (step ST105).

[0097] Next, the submersion determination unit 36 ​​determines whether the difference calculated in step ST105 is equal to or less than a predetermined value (step ST106). If the submersion determination unit 36 ​​determines that the difference is equal to or less than the predetermined value (step ST106 YES), it determines that the bathing posture of the bather P may progress to a submerged state. On the other hand, if the submersion determination unit 36 ​​determines that the difference is not equal to or less than the predetermined value (step ST106 NO), it determines that the bathing posture of the bather P may not progress to a submerged state, and ends the process.

[0098] If the submersion determining unit 36 ​​determines that the bather P is in a bathing posture that may lead to a submerged state (YES in step ST106), the warning device 5 issues a warning (step ST107).

[0099] As described above, in the submersion determination method according to the first embodiment, each of the ultrasonic receiving devices 3 is positioned at an equal distance from the ultrasonic transmitting device 2. This configuration makes it possible to extract the reflected waves from the head Q of the bather P. This improves the accuracy of measuring the position of the head Q of the bather P.

[0100] It is also possible to provide an underwater ultrasonic sensor in the bathtub 6 and use this ultrasonic sensor to determine whether or not a person is bathing before determining whether the person is submerged.

[0101] Furthermore, some or all of the processing in the submergence determination system and submergence determination method according to the first embodiment and its modifications can be implemented as a computer program. Such a program can be stored on various types of non-transitory computer-readable media and provided to a computer. Non-transitory computer-readable media include various types of tangible recording media. Examples of non-transitory computer-readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (Random Access Memory)). The program may also be provided to a computer by various types of temporary computer-readable media. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable media can provide the program to a computer via a wired communication path such as an electric wire or optical fiber, or via a wireless communication path.

[0102] The present disclosure has been described above in accordance with the above-described embodiments, but the present disclosure is not limited to the configurations of the above-described embodiments, and naturally includes various modifications, alterations, and combinations that a person skilled in the art could make within the scope of the claims of the present application. [Explanation of symbols]

[0103] 1. Submersion detection system 2. Ultrasonic transmitter 3, 31, 32 Ultrasonic receiving device 4 Submergence determination device 5 Alarm device 6. Bathtub 8 water surface 10 Bathroom 20 Pulse generating circuit 21 Oscillator Circuit 22 Intermittent Circuit 23 Transmitting amplifier circuit 28 Head reflection wave extraction section 29 Head distance calculation section 30 Head height position calculation unit 33 Waveform analysis circuit 35 Water surface height position calculation unit 36 Submergence determination section 38 Receiving amplifier circuit 39 Filter Circuit D1 Head distance D3 Clearance D4 Vertical distance to water surface D31, D32 distance D11 Vertical head distance P bather Q Head W1, W2 walls

Claims

1. an ultrasonic transmitting device and a plurality of ultrasonic receiving devices arranged above a bathtub in a bathroom; a submersion determination device that determines whether the bather is in a bathing posture that may lead to a submerged state; Equipped with each of the plurality of ultrasonic receiving devices is disposed equidistant from the ultrasonic transmitting device; The ultrasonic transmitting device is configured to transmit ultrasonic waves downward so that the ultrasonic waves transmitted from the ultrasonic transmitting device are reflected by the bather's head and received by each of the plurality of ultrasonic receiving devices; The submersion determination device is Acquire the height position of the water surface of the bathtub; Calculating the head position of the bather based on at least one of the reflected waves received by the ultrasonic receiving device; Based on the head position and the height of the water surface, it is determined whether the bather is in a bathing posture that may lead to a submerged state. Submersion detection system.

2. the plurality of ultrasonic receiving devices are composed of two ultrasonic receiving devices, The ultrasonic transmitting device is placed above the head of the bather, The ultrasonic receiving devices are arranged so as to sandwich the ultrasonic transmitting device, a straight line connecting the ultrasonic transmitting device and each of the two ultrasonic receiving devices is not parallel to the longitudinal direction of the bathtub and the lateral direction of the bathtub; The submersion determination system according to claim 1 .

3. the plurality of ultrasonic receiving devices are composed of two ultrasonic receiving devices, The ultrasonic transmitting device is placed above the head of the bather, The ultrasonic receiving devices are arranged to form a V-shape with the ultrasonic transmitting device at the top. The submersion determination system according to claim 1 .

4. The ultrasonic receiving device is arranged symmetrically with respect to a center line that passes through the center of the bather's head and is parallel to the longitudinal direction of the bathtub. The submersion determination system according to claim 3 .

5. A submersion determination method for determining whether a bather is in a bathing posture that may lead to a submerged state, using an ultrasonic transmitting device and a plurality of ultrasonic receiving devices arranged above a bathtub in a bathroom, comprising: each of the plurality of ultrasonic receiving devices is disposed equidistant from the ultrasonic transmitting device; a step of transmitting ultrasonic waves downward from the ultrasonic transmitting device so that the ultrasonic waves transmitted from the ultrasonic transmitting device are reflected by the bather's head and received by each of the plurality of ultrasonic receiving devices; calculating a head position of the bather based on at least one of the reflected waves received by the ultrasonic receiving device; acquiring a height position of the water surface of the bathtub; A step of determining whether the bather is in a bathing posture that may lead to a submerged state based on the head position and the height position of the water surface; Including, Submergence determination method.

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