Bed device, acceleration sensor unit, and correction value calculation method

Abstract

To provide a bed device capable of improving correction accuracy of an acceleration sensor in a range of 0-90 degrees.SOLUTION: A bed device 1 includes: a mattress 11 configured so that a back part 13 can perform a rising / falling operation; a frame 10 for supporting the mattress 11; an acceleration sensor 21 attached to the back part 13 of the mattress 11 for detecting an angle θ of the back part 13 performing a rising / falling operation; a driving part 15 for driving the mattress 11; and a control part 16 for controlling the driving part 15. The value of the acceleration sensor 21 is configured to be corrected using a correction value. The correction value is a value calculated from a value of the acceleration sensor 21 when gravity acceleration is +1 g, and a value of the acceleration sensor 21 when gravity acceleration is 0 g.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a bed apparatus, an acceleration sensor unit, and a correction value calculation method. [Background technology]

[0002] In recent years, bed devices equipped with mattresses whose backs can be raised and lowered have been widely used in hospitals, nursing homes, etc. The raising and lowering movement of such bed devices can be achieved using, for example, a hydraulic actuator or a motor-driven actuator. Patent Document 1 discloses a technology related to a bed back-raising angle display device that can confirm the back-raising angle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-136579 Summary of the Invention [Problem to be solved by the invention]

[0004] In a bed device equipped with a mattress whose back can be raised and lowered, an acceleration sensor is provided on the back of the mattress to detect the angle of the back as it is raised and lowered. Since acceleration sensors vary from one to another, the output value of the acceleration sensor must be corrected. In conventional technology, the acceleration sensor is corrected using the maximum output value (+1g) and minimum output value (-1g) of the acceleration sensor.

[0005] However, in a bed apparatus, the movement range of the back is generally 0 to 90 degrees. Therefore, when the acceleration sensor is corrected using the maximum output value (+1 g) and minimum output value (-1 g) of the acceleration sensor (when corrected in the movement range of 0 to 180 degrees), there is a problem that the correction accuracy of the acceleration sensor decreases in the range of 0 to 90 degrees.

[0006] In view of the above-mentioned problems, an object of the present disclosure is to provide a bed apparatus, an acceleration sensor unit, and a correction value calculation method that can improve the correction accuracy of an acceleration sensor in the range of 0 degrees to 90 degrees. [Means for solving the problem]

[0007] A bed apparatus according to one aspect of the present disclosure includes: a mattress having a back configured to be able to rise and fall; The device comprises a frame that supports the mattress, an acceleration sensor attached to the back of the mattress and detecting the angle of the back during the up-and-down motion, a drive unit that drives the mattress, and a control unit that controls the drive unit. The acceleration sensor value can be corrected using a correction value, which is calculated using the acceleration sensor value when the gravitational acceleration is +1 g and the acceleration sensor value when the gravitational acceleration is 0 g.

[0008] An acceleration sensor unit according to one aspect of the present disclosure is attached to a mattress configured so that the back can be raised and lowered, and detects the angle of the back during the raising and lowering movement. The acceleration sensor unit includes an acceleration sensor and a correction value storage unit that stores a correction value of the acceleration sensor, and the correction value is calculated using the value of the acceleration sensor when the gravitational acceleration is +1g and the value of the acceleration sensor when the gravitational acceleration is 0g.

[0009] A correction value calculation method according to one aspect of the present disclosure is a correction value calculation method for calculating a correction value of an acceleration sensor provided in a mattress whose back is configured to be able to move up and down, and includes the steps of: determining a first acceleration value, which is the value of the acceleration sensor when the gravitational acceleration is +1g; determining a second acceleration value, which is the value of the acceleration sensor when the gravitational acceleration is 0g; and calculating the correction value of the acceleration sensor using the first acceleration value and the second acceleration value. [Effects of the Invention]

[0010] The present disclosure can provide a bed apparatus, an acceleration sensor unit, and a correction value calculation method that can improve the correction accuracy of an acceleration sensor in the range of 0 degrees to 90 degrees. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a side view illustrating an example of a bed apparatus according to an embodiment. [Figure 2] FIG. 2 is a side view illustrating an example of a bed apparatus according to an embodiment. [Figure 3] FIG. 2 is a block diagram illustrating an example of an acceleration sensor unit. [Figure 4] 4A and 4B are cross-sectional views for explaining the operation of the acceleration sensor. [Figure 5] 4A and 4B are cross-sectional views for explaining the operation of the acceleration sensor. [Figure 6] 4A and 4B are cross-sectional views for explaining the operation of the acceleration sensor. [Figure 7] 4A and 4B are cross-sectional views for explaining the operation of the acceleration sensor. [Figure 8] FIG. 4 is a diagram for explaining a correction mode (first correction mode) of the bed apparatus according to the embodiment. [Figure 9] FIG. 10 is a diagram for explaining a correction mode (second correction mode) of the bed apparatus according to the embodiment. [Figure 10] FIG. 10 is a diagram for explaining a correction mode (second correction mode) of the bed apparatus according to the embodiment. [Figure 11] FIG. 10 is a block diagram illustrating another example of the configuration of the acceleration sensor unit. [Figure 12] FIG. 10 is a block diagram illustrating another example of the configuration of the acceleration sensor unit. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment will be described with reference to the drawings. 1 and 2 are side views for explaining an example of a bed apparatus according to an embodiment. As shown in Fig. 1 and Fig. 2, the bed apparatus 1 according to this embodiment includes a frame 10, a mattress 11, a driving unit 15, a control unit 16, and an acceleration sensor 21. The frame 10 is the base of the bed apparatus 1 and is configured to be able to support the mattress.

[0013] The mattress 11 supports the user when the user lies on the mattress 11. As shown in FIG. 2, in the bed apparatus 1 according to this embodiment, the mattress 11 has a reclining function. Specifically, the mattress 11 has a lower limb section 12 on which the user's lower limbs are placed and a back section 13 on which the user's back is placed, and the back section 13 is configured to be able to rise and fall. With this configuration, the user can raise their upper limbs while lying on the mattress 11.

[0014] An acceleration sensor 21 is attached to the back portion 13 of the mattress 11. The acceleration sensor 21 detects the angle θ of the back portion 13 during the up-and-down motion. Details of the acceleration sensor 21 will be described later.

[0015] The drive unit 15 drives the mattress 11. Specifically, the drive unit 15 raises and lowers the back portion 13 of the mattress 11. The drive unit 15 can be configured using, for example, a hydraulic actuator or a motor-type actuator.

[0016] Furthermore, in this embodiment, the surface of the mattress 11 may be configured to become convex on at least one of the left and right sides of the user when the angle θ of the back portion 13 of the mattress 11 becomes equal to or greater than a predetermined angle. This configuration can prevent the user lying on the surface of the mattress 11 from falling. For example, the drive unit 15 is a pump, and the surface of the mattress 11 can be made convex by injecting air from the pump into a bag-shaped inflation cell (not shown) provided on at least one of the left and right sides of the user.

[0017] The control unit 16 controls the drive unit 15. Specifically, the control unit 16 controls the drive unit 15 so that the angle θ of the back portion 13 of the mattress 11 becomes a predetermined angle. At this time, the control unit 16 may control the drive unit 15 so that the angle θ of the back portion 13 of the mattress 11 becomes a set angle input from an input device (not shown).

[0018] Furthermore, the control unit 16 may control the drive unit (pump) 15 so that air is injected into a bag-shaped inflation cell (not shown) provided on at least one of the left and right sides of the user when the angle θ of the back 13 of the mattress 11 becomes equal to or greater than a predetermined angle. At this time, information regarding the angle θ of the back 13 detected by the acceleration sensor 21 is supplied to the control unit 16.

[0019] Next, the acceleration sensor 21 provided in the bed apparatus 1 according to this embodiment will be described in detail. Fig. 3 is a block diagram illustrating an example of an acceleration sensor unit. As shown in Fig. 3, in this embodiment, for example, the acceleration sensor 21 is built into the acceleration sensor unit 20. The acceleration sensor unit 20 includes the acceleration sensor 21, a correction value storage unit 22, and a correction unit 23. The acceleration sensor unit 20 has the acceleration sensor 21 built in, and is attached to the back 13 of the mattress 11.

[0020] Correction value storage unit 22 stores the correction value of acceleration sensor 21. Correction value storage unit 22 can be configured using, for example, a register or the like capable of storing data. Correction unit 23 corrects the value of acceleration sensor 21 using the correction value stored in correction value storage unit 22. Correction unit 23 can be configured using, for example, a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array). The angle data corrected by correction unit 23 is supplied to control unit 16.

[0021] Next, the correction value of the acceleration sensor will be described. 4 to 7 are cross-sectional views illustrating the operation of the acceleration sensor. For example, if acceleration sensor 21 is a one-axis acceleration sensor, as shown in FIG. 4, angle θ can be calculated using the detected acceleration s detected by acceleration sensor 21. Specifically, when angle θ is 0 degrees, the output of acceleration sensor 21 is 1 g (maximum), and as angle θ increases from 0 degrees, the output of acceleration sensor 21 decreases, and when angle θ is 90 degrees, the output of acceleration sensor 21 is 0 g (minimum). In other words, at angle θ, the value of acceleration sensor 21 is 1 g × cos θ. Therefore, angle θ can be obtained by using the detected acceleration s of acceleration sensor 21.

[0022] Generally, acceleration sensors vary in performance from one sensor to another, making it necessary to correct their output values. In conventional technology, the acceleration sensor's maximum output value (+1g) and minimum output value (-1g) are used to correct the acceleration sensor. That is, the single-axis acceleration sensor 21 has a maximum output value (+1g) in the case shown on the left in FIG. 5 (i.e., angle θ=0 degrees), and a minimum output value (-1g) in the case shown on the right in FIG. 5 (i.e., angle θ=180 degrees). In this case, the range of the detected acceleration s is -1g≦s≦+1g.

[0023] Then, the offset correction value and gain correction value are calculated using the detected values ​​of +1g and -1g as follows: OFFSET The gain correction value is Gain, and the detected value of the acceleration sensor when the gravitational acceleration is +1g is A +1g Let A be the detected value of the acceleration sensor when the gravitational acceleration is -1g. -1g In this case, the offset correction value A OFFSET The gain correction value Gain is as follows:

[0024] A OFFSET =0.5×(A +1g +A -1g ) Gain=0.5×{(A +1g -A -1g ) / 2}

[0025] In addition, the corrected output value of the acceleration sensor is A ACTUAL The output value of the acceleration sensor before correction is A OUT Then, the corrected output value of the acceleration sensor is A ACTUAL becomes:

[0026] A ACTUAL =(A OUT -A OFFSET ) / Gain

[0027] That is, as shown in FIG. 6, the output value of the acceleration sensor before correction is corrected using the offset correction value and the gain correction value, thereby calculating the corrected output value of the acceleration sensor.

[0028] While this method can correct the acceleration sensor's output value, it is a two-point correction method and does not correct for the effects of acceleration sensor distortion. The effects of acceleration sensor distortion here refer to output changes due to external environmental factors such as temperature, and distortion caused by misalignment between the detection axis and the axis along which the reclining mechanism operates, which occurs when the acceleration sensor unit is installed. For this reason, as shown in the left diagram of Figure 7, if correction is performed using the acceleration sensor's maximum output value (+1g) and minimum output value (-1g), the acceleration range will be -1g≦s≦+1g, which means that the value will be significantly affected by errors caused by distortion.

[0029] On the other hand, in the bed apparatus 1, the motion range of the back 13 is generally 0 to 90 degrees. Therefore, when the acceleration sensor is corrected using the maximum output value (+1 g) and minimum output value (-1 g) of the acceleration sensor 21 (when corrected in the motion range of 0 to 180 degrees), there is a problem that the correction accuracy of the acceleration sensor decreases in the range of 0 to 90 degrees.

[0030] Therefore, in this embodiment, a correction value calculated using the value of acceleration sensor 21 when the gravitational acceleration is +1 g and the value of acceleration sensor 21 when the gravitational acceleration is 0 g is used as the correction value of acceleration sensor 21. In other words, a first acceleration value, which is the value of acceleration sensor 21 when the gravitational acceleration is +1 g, is obtained, and a second acceleration value, which is the value of acceleration sensor 21 when the gravitational acceleration is 0 g, is obtained, and the correction value of acceleration sensor 21 is calculated using the first acceleration value and the second acceleration value.

[0031] In this way, when the value of acceleration sensor 21 when the gravitational acceleration is +1 g (corresponding to angle θ=0 degrees) and the value of acceleration sensor 21 when the gravitational acceleration is 0 g (corresponding to angle θ=90 degrees) are used, the influence of distortion can be reduced as shown in the right diagram of Fig. 7. In other words, since the angle range when acceleration sensor 21 is used in bed apparatus 1 is narrow, the angle for calculating the correction value of acceleration sensor 21 can be narrowed accordingly, thereby reducing the influence of distortion. Therefore, the correction accuracy of the acceleration sensor can be improved in the range of 0 to 90 degrees.

[0032] For example, the correction values ​​are offset correction values ​​and gain correction values, and the offset correction value is A OFFSET The gain correction value is Gain, and the value of the acceleration sensor 21 when the gravitational acceleration is +1g is A +1g When the gravitational acceleration is 0g, the value of the acceleration sensor 21 is A 0g In this case, the offset correction value A OFFSET The gain correction value Gain is as follows:

[0033] A OFFSET =A +1g Gain=A +1g -A 0g

[0034] In the bed apparatus 1 according to the present embodiment, the control unit 16 may be configured to be able to operate in a correction mode for obtaining a correction value of the acceleration sensor 21. For example, the control unit 16 may operate in the correction mode when the bed apparatus 1 is initially set up.

[0035] Furthermore, the control unit 16 may operate in a correction mode when the number of times of the raising and lowering motion of the mattress 11 reaches a predetermined number or more. For example, a threshold value for the angle θ of the back portion 13 of the mattress 11 may be set in advance, and the number of times that the angle θ of the back portion 13 exceeds the preset threshold value may be used as the number of times the raising and lowering motion of the mattress 11 has occurred. The number of times the mattress 11 has raised and lowered may be stored in a register or the like provided in the acceleration sensor unit 20.

[0036] Furthermore, the control unit 16 may operate in a correction mode when the usage time of the mattress 11 exceeds a predetermined time. For example, the usage time of the mattress 11 can be measured by counting the internal clock with a counter. For example, if the clock frequency of the internal clock is 1 MHz, one clock is 1 μsec. In this case, 2 hours is 7.2×10 9 It becomes a clock, so 7.2 x 10 9 The count of 1 per clock may be recorded as the usage time of the mattress 11. If the mattress 11 is used for 10 years, it will be 87,600 hours, which is 43,800 counts, and can be output in 16-bit representation as (1010 1011 0001 1000).

[0037] 8 is a diagram for explaining the correction mode (first correction mode) of the bed apparatus according to the embodiment. In the correction mode, the control unit 16 may obtain the value of the acceleration sensor 21 when the gravitational acceleration is +1 g with the back 13 of the mattress 11 held horizontal (angle θ=0 degrees), and may obtain the value of the acceleration sensor 21 when the gravitational acceleration is 0 g with the back 13 of the mattress 11 held vertical (angle θ=90 degrees). Then, these values ​​are used to calculate the offset correction value A OFFSET The gain correction value Gain may be calculated as follows:

[0038] FIG. 9 is a diagram for explaining the correction mode (second correction mode) of the bed apparatus according to the embodiment. In the second correction mode shown in FIG. 9, an acceleration sensor capable of detecting acceleration in at least two axial directions (x-axis and z-axis directions) is used as the acceleration sensor 21. Typically, in the second correction mode, an acceleration sensor capable of detecting acceleration in three axial directions (x-axis, y-axis, and z-axis directions) can be used as the acceleration sensor 21. Here, the acceleration in the x-axis direction is the acceleration x in the longitudinal direction of the mattress 11 shown in FIG. 9 (1), and the acceleration in the z-axis direction is the acceleration z in the thickness direction of the mattress 11. The y-axis direction is a direction perpendicular to the x-axis and z-axis.

[0039] In the second correction mode, the control unit 16 moves the back portion 13 from a horizontal position to an angle exceeding the vertical position, and sets the angle at which acceleration x reaches a maximum during this movement to 90 degrees, and sets the angle at which acceleration z reaches a maximum to 0 degrees. That is, in the second correction mode, the control unit 16 controls the back portion 13 of the mattress 11 to increase the angle θ of the back portion 13 from a state in which the back portion 13 of the mattress 11 is at angle θ = 0 degrees as shown in Fig. 9(1) to as shown in Fig. 9(2). Then, after the back portion 13 of the mattress 11 reaches angle θ = 90 degrees as shown in Fig. 9(3), the control unit 16 controls the angle θ of the back portion 13 of the mattress 11 to be greater than 90 degrees as shown in Fig. 9(4).

[0040] At this time, the acceleration x in the x-axis direction and the acceleration z in the z-axis direction of acceleration sensor 21 change as shown in Fig. 10. That is, acceleration x is minimum (0g) when back portion 13 of mattress 11 is at angle θ = 0 degrees, and maximum (1g) when angle θ = 90 degrees. Acceleration z is maximum (1g) when back portion 13 of mattress 11 is at angle θ = 0 degrees, and minimum (0g) when angle θ = 0 degrees.

[0041] Control unit 16 sets the angle when acceleration x is at its maximum to 90 degrees, and sets the angle when acceleration z is at its maximum to 0 degrees. Specifically, control unit 16 stores the maximum value of acceleration x and the value of acceleration z at this time in correction value storage unit 22. Control unit 16 also stores the maximum value of acceleration z and the value of acceleration x at this time in correction value storage unit 22. At this time, if existing correction values ​​are stored in correction value storage unit 22, and if each currently measured maximum value is greater than each maximum value stored in correction value storage unit 22, control unit 16 updates each maximum value stored in correction value storage unit 22 to each currently measured maximum value.

[0042] Furthermore, the control unit 16 sets the maximum value of the acceleration z to the above-mentioned A +1g The value of acceleration z when acceleration x is at its maximum value is the value of A 0g As the above offset correction value A OFFSET and set the gain correction value Gain.

[0043] Since the maximum value of acceleration x is 1 g, the angle θ of the back 13 at this time is 90 degrees. Also, since the maximum value of acceleration z is 1 g, the angle θ of the back 13 at this time is 0 degrees (flat state). Even if there is an error in the acceleration sensor 21, each value will always be maximum at 0 degrees and 90 degrees. Therefore, when the second correction mode is used, accurate angle information is not required, and the above-mentioned correction value can be determined in a single operation.

[0044] In the above description, the control unit 16 automatically controls the angle of the back 13 in the second correction mode. However, in the present embodiment, the user may manually change the angle of the back 13 in the second correction mode. Also, in the above description, the control unit 16 operates in the correction mode (first correction mode, second correction mode). However, in the present embodiment, the correction unit 23 may be configured to operate in the correction mode. Specifically, a program for operating in the correction mode may be stored in the correction unit 23, and the bed apparatus may be configured to operate in the correction mode by executing the program in the correction unit 23. In this case, the correction unit 23 itself operates in the correction mode. Also, for example, a program for operating in the correction mode may be stored in the correction unit 23, and the control unit 16 may read the program from the correction unit 23 and execute the program in the control unit 16, causing the bed apparatus to operate in the correction mode. In this case, the correction unit 23 and the control unit 16 cooperate to operate in the correction mode.

[0045] The bed apparatus according to the present embodiment described above can provide a bed apparatus capable of improving the correction accuracy of the acceleration sensor in the range of 0 to 90 degrees.

[0046] 11 and 12 are block diagrams illustrating other configuration examples of the acceleration sensor unit. In this embodiment, as in the configuration example shown in Fig. 11, a sensor board 40 may be provided separately from the acceleration sensor unit 20. The sensor board 40 includes an acceleration sensor B (41), and by adding more sensor boards 40, the number of acceleration sensors in the acceleration sensor unit 20 can be increased.

[0047] The correction value storage unit 22 is configured to store a correction value for the acceleration sensor B (41) of the sensor substrate 40. The correction unit 23 is also configured to correct the value of the acceleration sensor B (41) using the correction value stored in the correction value storage unit 22. In this way, the correction value storage unit 22 and the correction unit 23 can store the correction value for the added acceleration sensor B (41) and correct the value of the acceleration sensor. Therefore, there is no need to add a new correction value storage unit 22 and correction unit 23 for the added acceleration sensor B (41), which simplifies the system configuration. Note that two or more sensor substrates 40 may be provided.

[0048] In this embodiment, the acceleration sensor unit 20 may be configured with the correction circuit board 50 and the sensor board 60 separated, as in the configuration example shown in FIG. 12. In this configuration, the sensor board 60 may be installed on the mattress 11, and the correction circuit board 50 may be installed in a location other than the mattress 11. For example, the correction circuit board 50 may be configured integrally with the control unit 16. Also, in the configuration shown in FIG. 12, two or more sensor boards 60 may be provided. In this case, one correction circuit board 50 can store correction values ​​for the acceleration sensors of multiple sensor boards 60 and correct the acceleration sensor values.

[0049] The bed apparatus according to this embodiment may also be configured so that the lower limbs 12 can also be raised and lowered. In this case, an acceleration sensor 21 may be separately provided at a location of the lower limbs 12 where the lower limbs 12 are raised and lowered.

[0050] Furthermore, in this embodiment, the mattress itself may not be configured to rise and fall, but rather the floorboard may be configured to rise and fall. That is, the mattress (bedding) may be placed on the floorboard, and the mattress may rise and fall in conjunction with the floorboard's rising and falling movement. In this case, the acceleration sensor 21 may be provided on the floorboard. In this specification, "providing the acceleration sensor 21 on the mattress" includes the case where "providing the acceleration sensor 21 on the floorboard" as well.

[0051] The present invention has been described above in accordance with the above-mentioned embodiment, but the present invention is not limited to the configuration of the above-mentioned embodiment, and naturally includes various modifications, alterations, and combinations that a person skilled in the art can make within the scope of the invention as defined in the claims of this application. [Explanation of symbols]

[0052] 1 Bed device 10 frames 11 Mattress 12 Lower limbs 13 Back 15 Drive unit 16 Control Unit 20 Acceleration sensor unit 21 Acceleration sensor 22 Correction value storage section 23 Correction unit 40 Sensor board 41 Acceleration sensor 50 Correction circuit board 60 Sensor board

Claims

1. a mattress configured so that the back can be raised and lowered; a frame supporting the mattress; An acceleration sensor attached to the back of the mattress to detect the angle of the back that is moving up and down; A drive unit that drives the mattress; a control unit that controls the drive unit, The value of the acceleration sensor can be corrected using a correction value, The correction value is a value calculated using the value of the acceleration sensor when the gravitational acceleration is +1 g and the value of the acceleration sensor when the gravitational acceleration is 0 g. Bed equipment.

2. the correction values ​​are an offset correction value and a gain correction value, The offset correction value is A ＯＦＦＳＥＴ The gain correction value is Gain, and the value of the acceleration sensor when the gravitational acceleration is +1 g is A ＋１ｇ When the gravitational acceleration is 0 g, the value of the acceleration sensor is A ０ｇ In this case, The offset correction value A ＯＦＦＳＥＴ A ＯＦＦＳＥＴ = A ＋１ｇ and The gain correction value Gain is Gain=A ＋１ｇ -A ０ｇ That is, The bed apparatus according to claim 1 .

3. the acceleration sensor is provided in an acceleration sensor unit attached to a back of the mattress, The acceleration sensor unit a correction value storage unit for storing a correction value of the acceleration sensor; a correction unit that corrects the value of the acceleration sensor using the correction value stored in the correction value storage unit, 3. The bed apparatus according to claim 1 or 2.

4. the control unit is configured to be operable in a correction mode for determining a correction value of the acceleration sensor, In the correction mode, the control unit With the back of the mattress horizontal, a value of the acceleration sensor is obtained when the gravitational acceleration is +1 g; With the back of the mattress in a vertical position, a value of the acceleration sensor is obtained when the gravitational acceleration is 0 g. The bed apparatus according to claim 1 .

5. the control unit is configured to be operable in a correction mode for determining a correction value of the acceleration sensor, The acceleration sensor is configured to be able to measure an acceleration x in a longitudinal direction of the mattress and an acceleration z in a thickness direction of the mattress, In the correction mode, the control unit moves the back portion from a horizontal state to an angle exceeding a vertical state, and during the movement, sets the angle when the acceleration x becomes maximum to 90 degrees, and sets the angle when the acceleration z becomes maximum to 0 degrees. The bed apparatus according to claim 1 .

6. The bed device of claim 5, wherein the control unit stores the maximum value of the acceleration x, the value of the acceleration z when the acceleration x is at its maximum value, and the maximum value of the acceleration z, and the value of the acceleration x when the acceleration z is at its maximum value in a correction value storage unit.

7. the correction values ​​are an offset correction value and a gain correction value, The offset correction value is A ＯＦＦＳＥＴ The gain correction value is Gain, and the value of the acceleration sensor when the gravitational acceleration is +1 g is A ＋１ｇ When the gravitational acceleration is 0 g, the value of the acceleration sensor is A ０ｇ In this case, The above A ＋１ｇ is the maximum value of the acceleration z, The above A ０ｇ is the value of the acceleration z when the acceleration x is at its maximum value, The offset correction value A ＯＦＦＳＥＴ Is A ＯＦＦＳＥＴ =A ＋１ｇ and The gain correction value Gain is Gain=A ＋１ｇ -A ０ｇ That is, The bed apparatus according to claim 5.

8. The bed apparatus according to any one of claims 4 to 7, wherein the control unit operates in the correction mode when the number of times of the raising and lowering movements of the mattress reaches a predetermined number or more.

9. The bed apparatus according to any one of claims 4 to 7, wherein the control unit operates in the correction mode when the usage time of the mattress reaches or exceeds a predetermined time.

10. An acceleration sensor unit attached to a mattress configured so that a back portion can be raised and lowered, and detecting an angle of the back portion that is raising and lowering, The acceleration sensor unit An acceleration sensor; a correction value storage unit that stores a correction value of the acceleration sensor, The correction value is a value calculated using the value of the acceleration sensor when the gravitational acceleration is +1 g and the value of the acceleration sensor when the gravitational acceleration is 0 g. Acceleration sensor unit.

11. A correction value calculation method for calculating a correction value of an acceleration sensor provided in a mattress having a back portion configured to be able to rise and fall, comprising: determining a first acceleration value, which is a value of the acceleration sensor when the gravitational acceleration is +1 g; determining a second acceleration value, which is a value of the acceleration sensor when the gravitational acceleration is 0 g; and calculating a correction value for the acceleration sensor using the first acceleration value and the second acceleration value. Correction value calculation method.

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