Air cell mattress system based on low-noise pressure control using dual reservoir

Abstract

An air cell mattress system based on low-noise pressure control using a dual reservoir according to the present invention comprises: a mattress body; a plurality of air cells disposed within the mattress body; a first reservoir storing compressed air at a pressure higher than the target pressure of the air cells to pressurize the air cells; a second reservoir maintaining a pressure lower than the target pressure to depressurize the air cells and collecting air discharged from the air cells without releasing it into the atmosphere; a plurality of pressure sensors measuring the pressure of the air cells and the first and second reservoirs; a valve assembly selectively connecting the first and second reservoirs and the air cells; and a pump connected to the first and second reservoirs. The controller is characterized by including: a sleep determination module that determines whether a user is sleeping based on pressures measured from a plurality of pressure sensors and determines a sleep period; a pump driving module that drives the pump outside the sleep period to maintain the pressure of the first reservoir higher than the target pressure and the pressure of the second reservoir lower than the target pressure; and a low-noise control module that stops the operation of the pump during the sleep period and maintains the pressure of the air cell within the target pressure range solely through valve pulse control of the valve assembly.

Description

Technology Field

[0001] The present invention relates to an air cell mattress system based on low-noise pressure control using a dual reservoir, and more specifically, to an air cell mattress system that reduces noise and vibration during sleep by using a dual reservoir pneumatic structure including a high-pressure reservoir and a low-pressure reservoir, determining whether a user is sleeping using a plurality of pressure sensors, stopping pump operation during the sleep period, and maintaining the pressure of a plurality of air cells within a target pressure range solely through valve pulse control of a valve assembly. Background Technology

[0002] Air cell mattresses are functional mattresses equipped with multiple air cells inside and capable of controlling pressure distribution across different parts of the user's body by independently adjusting the air pressure of each air cell. They are applied in various fields, such as medical beds, home beds, and wheelchair seats, for purposes such as preventing bedsores, correcting sleeping posture, and dispersing body pressure.

[0003] Pressure control in air cell mattresses is generally performed using pumps and valves, and the pump maintains the pressure of each air cell within the target pressure range by compressing air and supplying it to the air cells or releasing the air from the air cells into the atmosphere.

[0004] However, conventional air cell mattress systems had the following problems.

[0005] Conventional technology adopts a method of frequently driving a pump to regulate the pressure of the air cell; however, since the pump is driven whenever fine pressure adjustment is required during sleep, noise and vibration are generated, causing a problem that disturbs the user's sleep.

[0006] In particular, when frequent pressure correction is required during sleep due to changes in the user's weight distribution, micro-leakage within the air cell, and repetitive pressure fluctuations caused by breathing, the number of pump operations increases, leading to a more severe noise problem.

[0007] Furthermore, conventional technology adopts a method of directly releasing internal air into the atmosphere when the air cell is depressurized; however, this process generates noise and allows external moisture and dust to enter the mattress, causing hygiene issues and reduced durability.

[0008] In addition, there was a problem where power consumption increased due to energy loss caused by the compressed air discharged from the air cell being released into the atmosphere.

[0009] Furthermore, conventional technology adopts a method of pressurizing and depressurizing air cells using a single reservoir. Consequently, it is difficult to secure sufficient pressure margin to maintain the air cell pressure within the target pressure range using only valve control without pump operation during the surface section, and since it is impossible to independently manage the pressure margin required for pressurization and depressurization, there was a problem in that precise pressure control during the surface section was difficult.

[0010] Therefore, there is a need to develop a novel and advanced air cell mattress system that utilizes a dual reservoir structure to stop pump operation during sleep and maintains the pressure of each air cell within a target pressure range solely through valve pulse control, thereby reducing noise and vibration during sleep, and improves hygiene and energy efficiency by capturing and reusing air instead of releasing it into the atmosphere when air cells are depressurized. Prior art literature

[0011] Korean Registered Patent No. 10-2878283 The problem to be solved

[0012] The present invention was devised to overcome the problems of the above technology, and its main purpose is to provide an air cell mattress system that reduces noise and vibration during sleep by using a dual reservoir structure comprising a first reservoir that stores compressed air at a pressure higher than the target pressure of the air cell and a second reservoir that collects air without releasing it into the atmosphere when the air cell is depressurized, thereby stopping the pump operation during the sleep period and maintaining the pressure of each air cell within the target pressure range solely through valve pulse control of the valve assembly.

[0013] Another objective of the present invention is to precisely maintain the pressure of each air cell within the target pressure range without pump operation during the water surface period through a valve pulse calculation unit that calculates the valve pulse duration based on the error between the current pressure and the target pressure of the air cell and the pressure difference between the reservoir and the air cell.

[0014] Another objective of the present invention is to protect the user's sleep by extending the sleep period as much as possible without suddenly releasing it through a sleep period extension module that gradually expands the tolerance of the target pressure when the pressure margin of the first reservoir and the second reservoir decreases below a step threshold during the sleep period. means of solving the problem

[0015] To achieve the above objective, a low-noise pressure control-based air cell mattress system using a dual reservoir according to the present invention comprises: a mattress body; a plurality of air cells disposed within the mattress body; a first reservoir storing compressed air at a pressure higher than the target pressure of the air cells to pressurize the air cells; a second reservoir maintaining a pressure lower than the target pressure to depressurize the air cells and collecting air discharged from the air cells without releasing it into the atmosphere; a plurality of pressure sensors measuring the pressure of the air cells and the first and second reservoirs; a valve assembly selectively connecting the first and second reservoirs and the air cells; and a pump connected to the first and second reservoirs. The controller is characterized by including: a sleep determination module that determines whether a user is sleeping based on pressures measured from a plurality of pressure sensors and determines a sleep period; a pump driving module that drives the pump outside the sleep period to maintain the pressure of the first reservoir higher than the target pressure and the pressure of the second reservoir lower than the target pressure; and a low-noise control module that stops the operation of the pump during the sleep period and maintains the pressure of the air cell within the target pressure range solely through valve pulse control of the valve assembly.

[0016] In addition, the controller further includes a pressure compensation module that performs at least one of the following when the pressure of either the first or second reservoir measured by the plurality of pressure sensors during the sleep period exceeds a preset threshold: expanding the allowable range of the target pressure, driving the pump for a limited time only when the sleep determination module determines the user's wake-up, or releasing the sleep period.

[0017] In addition, the controller further includes a sleep section extension module that maintains the sleep section by gradually expanding the allowable error of the target pressure when the pressure margin, which is the difference between the pressure of the first reservoir and the second reservoir measured by the plurality of pressure sensors during the sleep section and the target pressure, decreases sequentially to less than a preset step threshold. Effects of the invention

[0018] According to the low-noise pressure control-based air cell mattress system using a dual reservoir according to the present invention,

[0019] 1) By collecting and reusing air in the second reservoir instead of releasing it into the atmosphere when the air cell is depressurized, thereby blocking discharge noise and the inflow of external air, and by completely stopping the pump operation during the water surface section and maintaining the pressure of each air cell within the target pressure range solely through valve pulse control using the pre-secured pressure margin of the first and second reservoirs, it has the advantage of significantly reducing noise and vibration during water surface operation.

[0020] 2) When the reservoir pressure margin decreases during the sleeping period, the rate of pressure consumption in the reservoir is controlled by gradually increasing the tolerance of the target pressure to reduce the valve pulse control frequency, thereby extending the sleeping period to the maximum extent and improving the user's sleep quality, and

[0021] 3) By applying valve pulses alternately to air cells requiring pressurization and air cells requiring depressurization according to the valve control priority index for each air cell, the pressure consumption of the first reservoir and the second reservoir is offset, and the point at which the pressure margin decreases below the step threshold is delayed, thereby having the effect of delaying the expansion of the allowable error. Brief explanation of the drawing

[0022] FIG. 1 is a block diagram illustrating the configuration of the system of the present invention. FIG. 2 is a plan view illustrating a structure in which a plurality of air cells, a pressure sensor, first and second reservoirs, a pump, and a valve assembly are arranged within a mattress body. FIG. 3 is a pneumatic circuit diagram illustrating the pneumatic circuit configuration and air flow between the first and second reservoirs, pump and valve assembly. FIG. 4 is a flowchart illustrating the overall control flow according to the sleep interval determination of the controller in the system of the present invention. FIG. 5 is a flowchart illustrating the operation flow of stepwise expansion of the tolerance of the sleep section extension module, valve sequence adjustment, and calculation of the remaining duration. FIG. 6 is a flowchart illustrating the calculation of the valve control priority index and the cross-arrangement of pressurized and depressurized air cells of the valve sequence adjustment unit, and the calculation of the remaining duration and the pump drive reservation operation flow of the remaining time calculation unit. Specific details for implementing the invention

[0023] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The attached drawings are not drawn to scale, and the same reference numerals in each drawing refer to the same components.

[0024] The air cell mattress system based on low-noise pressure control using a dual reservoir according to the present invention (hereinafter abbreviated as 'system') applies a dual reservoir pneumatic structure including a first reservoir (30) and a second reservoir (40) to a mattress body (10) in which a plurality of air cells (20) are arranged, and the main purpose is for a controller (100) to determine whether the user is sleeping, stop the operation of the pump (50) during the sleeping period, and maintain the pressure of each air cell (20) within the target pressure range solely through valve pulse control of the valve assembly (60).

[0025] The system of the present invention will be described in detail below with reference to the attached drawings.

[0026] FIG. 1 is a block diagram of the overall configuration of the system of the present invention.

[0027] As can be seen from FIG. 1, the system of the present invention is based on comprising a mattress body (10), a plurality of air cells (20), a first reservoir (30), a second reservoir (40), a pump (50), a valve assembly (60), a plurality of pressure sensors (70), and a controller (100).

[0028] FIG. 2 is a plan view illustrating a structure in which a plurality of air cells, a pressure sensor, first and second reservoirs, a pump, and a valve assembly are arranged within a mattress body, and FIG. 3 is a pneumatic circuit diagram illustrating the pneumatic circuit configuration and air flow between the first and second reservoirs, the pump, and the valve assembly.

[0029] The mattress body (10) is a cushion structure applicable to support structures where a user lies or sits, such as a bed, sofa, wheelchair seat, or medical bed, and is made of an outer shell and an inner frame.

[0030] The outer shell is the part that comes into direct contact with the user's skin and can be formed from a material that is breathable and durable.

[0031] The inner frame provides a structural base that fixes the mounting positions of the air cell (20), the first reservoir (30), the second reservoir (40), the pump (50), the valve assembly (60), and the plurality of pressure sensors (70), and accommodates pneumatic flow paths and electrical wiring.

[0032] The size and shape of the mattress body (10) can be set differently depending on the purpose of use.

[0033] For example, a single mattress can be manufactured with dimensions of 80 cm to 150 cm in width and 150 cm to 250 cm in length, and a double mattress can be manufactured with dimensions of 130 cm to 250 cm in width and 150 cm to 250 cm in length.

[0034] In addition, when applied to a medical bed, it can be manufactured with dimensions of 60 cm to 150 cm in width and 150 cm to 250 cm in length, and when applied to a wheelchair seat, it can be manufactured with dimensions of 30 cm to 80 cm in width and 30 cm to 80 cm in length.

[0035] The air cell (20) is an elastic chamber placed inside the mattress body (10) that expands and contracts by air pressure and serves to independently regulate pressure on different parts of the user's body.

[0036] These air cells (20) are formed from an elastic material having pressure resistance and airtightness, and can be made from materials such as thermoplastic polyurethane (TPU), natural rubber, and silicone rubber.

[0037] The number of air cells (20) can be set differently depending on the size and purpose of use of the mattress, and for example, can be composed of 3 to 50.

[0038] For example, a single-person mattress may be composed of 5 to 20 air cells (20) corresponding to the head, shoulders, waist, hips, and legs, respectively, and a two-person mattress may be composed of 10 to 50 air cells (20) by subdividing the left and right user areas by body part.

[0039] Each air cell (20) is individually connected to the first reservoir (30) and the second reservoir (40) through a valve assembly (60) so that independent pressure control is achieved.

[0040] For example, the connection between each air cell (20) and the valve assembly (60) may be made of a polyurethane tube or a silicone tube having pressure resistance and flexibility, and the inner diameter of the tube may be designed in the range of, for example, 2 mm to 15 mm.

[0041] The main pneumatic flow path between the valve assembly (60) and the first reservoir (30) and the second reservoir (40) may be made of, for example, a rigid pipe or a flexible hose with an inner diameter of 5 mm to 30 mm, and a one-touch fitting or screw joint type connector may be used at each connection to facilitate assembly and maintenance.

[0042] A pressure sensor (70) is connected to each air cell (20) to measure the current pressure in real time, and the measured pressure information is transmitted to the controller (100).

[0043] The target pressure of the air cell (20) can be individually set according to the user's weight, body type, sleeping posture and preference, for example, in the range of 1 kPa to 150 kPa based on the gauge.

[0044] A reservoir is a tank that stores compressed air at a constant pressure and is also referred to as an air tank, air storage tank, or pressure storage tank.

[0045] Conventional pneumatic mattresses utilize a single reservoir to perform pressurization and depressurization of air cells; however, since the air in the cells is released into the atmosphere during depressurization, there are issues such as exhaust noise, hygiene problems caused by the influx of external air, and energy loss.

[0046] In order to resolve these problems and maintain the pressure of each air cell (20) within the target pressure range solely through valve pulse control without pump operation during the sleep period, the present invention includes a dual reservoir, namely a first reservoir (30) and a second reservoir (40), wherein the first reservoir (30) stores compressed air at a pressure higher than the target pressure of the air cell (20) and acts as a pressurizing pressure source, and the second reservoir (40) does not release the air discharged when the air cell (20) is depressurized into the atmosphere but collects it at a pressure lower than the target pressure and acts as a depressurizing pressure source, and the pump (50) sucks in the air collected in the second reservoir (40), compresses it, and supplies it to the first reservoir (30), thereby providing a closed-loop structure in which the air within the system is isolated from the atmosphere.

[0047] In other words, when pressurizing the air cell (20), the valve assembly (60) connects the first reservoir (30) and the air cell (20) so that air flows naturally due to the pressure difference, and when depressurizing, the air cell (20) and the second reservoir (40) are connected so that the air from the air cell (20) is collected in the second reservoir (40), and the pump (50) has a structure that transfers the air collected in the second reservoir (40) outside the water surface area to the first reservoir (30) to restore the pressurization margin and depressurization margin.

[0048] The first reservoir (30) is a tank that stores compressed air for pressurizing each air cell (20) at a pressure higher than the target pressure of the air cell (20), and accumulates compressed air supplied from the pump (50) inside so that the air cell (20) can be pressurized through the valve assembly (60) without the pump (50) operating during the water surface period.

[0049] Since the internal pressure of the first reservoir (30) is always maintained higher than the target pressure of the air cell (20), compressed air can be naturally introduced from the first reservoir (30) into the air cell (20) simply by opening the valve of the valve assembly (60) even when the pump (50) is not driven during the water level period, thereby raising the pressure of the air cell (20) to within the target pressure range. This is the core principle of the present invention, which allows the pressure of the air cell (20) to be maintained without the noise of the pump (50) during the water level period.

[0050] The internal pressure of the first reservoir (30) can be set in the range of, for example, 10 kPa to 150 kPa based on the gauge, and the volume can be designed in the range of, for example, 0.3 L to 10 L.

[0051] The installation position of the first reservoir (30) can be set differently depending on the length of the pneumatic flow path and the structure of the mattress body (10).

[0052] For example, the first reservoir (30) may be positioned adjacent to the pump (50) and valve assembly (60) at the bottom of the inner frame of the mattress body (10) to shorten the pneumatic path, or it may be mounted in a separate housing on one side of the outside of the mattress body (10) to facilitate maintenance.

[0053] It is also possible to install a relief valve in the pneumatic path between the first reservoir (30) and the valve assembly (60) so that the pressure is automatically released when the pressure of the first reservoir (30) exceeds a preset upper limit.

[0054] The second reservoir (40) is a tank that maintains a pressure lower than the target pressure of the air cell (20) to depressurize each air cell (20) and collects the air discharged from the air cell (20) without releasing it into the atmosphere, and plays a symmetrical role to the first reservoir (30) in the double reservoir structure of the present invention.

[0055] The internal pressure of the second reservoir (40) is always maintained lower than the target pressure of the air cell (20). As a result, even when the pump (50) is not operated during the water level period, air can naturally flow from the air cell (20) into the second reservoir (40) simply by opening the valve of the valve assembly (60), thereby lowering the pressure of the air cell (20) to within the target pressure range. In particular, when the air cell (20) is depressurized, the air is not released into the atmosphere but is collected in the second reservoir (40), so no discharge noise is generated and the inflow of external air is blocked, thereby improving hygiene. The collected air is then transferred to the first reservoir (30) via the pump (50) and reused.

[0056] The internal pressure of the second reservoir (40) can be set in the range of, for example, 0 kPa to 30 kPa based on the gauge, and the volume can be designed in the range of, for example, 0.3 L to 20 L.

[0057] The installation location of the second reservoir (40) may be positioned adjacent to the pump (50) and valve assembly (60) at the bottom of the inner frame of the mattress body (10), just like the first reservoir (30), or may be mounted as a separate housing on one side of the outside of the mattress body (10).

[0058] A bypass valve is installed in the pneumatic path between the second reservoir (40) and the valve assembly (60) so that the pressure in the second reservoir (40) can be automatically restored when it drops below a preset lower limit.

[0059] The first reservoir (30) and the second reservoir (40) can be arranged in various ways considering the efficiency of the pneumatic flow path and the space utilization of the mattress body (10).

[0060] For example, the first reservoir (30) and the second reservoir (40) can be placed side by side adjacent to the pump (50) and valve assembly (60) at the bottom of the inner frame of the mattress body (10), in which case the length of the pneumatic flow path can be shortened to reduce pressure loss.

[0061] Alternatively, the first reservoir (30) and the second reservoir (40) may be housed together in a separate housing on one side of the outside of the mattress body (10) to facilitate maintenance, and may also be distributed to the head and foot portions of the mattress body (10) to evenly distribute the pneumatic flow path.

[0062] The volume ratio of the first reservoir (30) and the second reservoir (40) can be set differently depending on the number of air cells (20), the target pressure range, and the expected duration of the water surface period, for example, the volume ratio of the first reservoir (30) and the second reservoir (40) can be designed in the range of 1:1 to 3:1.

[0063] The pressure sensor (70) measures the current pressure of each air cell (20) and the pressure of the first reservoir (30) and the second reservoir (40) in real time and transmits them to the controller (100).

[0064] The controller (100) determines whether to sleep based on pressure information transmitted from the pressure sensor (70) and performs driving of the pump (50) and valve pulse control of the valve assembly (60); in other words, the pressure sensor (70) serves as an input means for the low-noise pressure control of the present invention to be accurately performed.

[0065] The type of pressure sensor (70) can be selected differently depending on the measurement target and installation location.

[0066] For example, the pressure sensor (70) installed in the air cell (20) may be a piezoresistive pressure sensor or a capacitive pressure sensor having high resolution in the low pressure range, and the pressure sensor (70) installed in the first reservoir (30) and the second reservoir (40) may be a strain gauge type pressure sensor having high durability in the medium pressure range.

[0067] The measurement range of the pressure sensor (70) can be set differently depending on the installation location, for example, the pressure sensor (70) for the air cell (20) may have a measurement range of 0 kPa to 150 kPa based on the gauge, the pressure sensor (70) for the first reservoir (30) may have a measurement range of 0 kPa to 300 kPa based on the gauge, and the pressure sensor (70) for the second reservoir (40) may have a measurement range of 0 kPa to 100 kPa based on the gauge.

[0068] The measurement cycle of the pressure sensor (70) can be set in the range of, for example, 10 ms to 1,000 ms, and the measurement cycle can be shortened during the sleep period to increase the responsiveness of the valve pulse control.

[0069] The valve assembly (60) provides the function of selectively opening and closing the pneumatic flow path between the first reservoir (30) and the second reservoir (40) and the plurality of air cells (20) to control the pressurization and depressurization of each air cell (20).

[0070] The valve assembly (60) includes a pressurizing valve and a pressure reducing valve corresponding to each air cell (20).

[0071] The pressurizing valve opens and closes the flow path between the first reservoir (30) and the corresponding air cell (20), and the depressurizing valve opens and closes the flow path between the corresponding air cell (20) and the second reservoir (40).

[0072] When pressurizing, the internal pressure of the first reservoir (30) is always maintained higher than the target pressure of the air cell (20), so that when the pressurizing valve is opened, compressed air naturally flows from the first reservoir (30) to the air cell (20) due to the pressure difference, and the pressure of the air cell (20) rises.

[0073] When depressurizing, the internal pressure of the second reservoir (40) is always maintained lower than the target pressure of the air cell (20). Therefore, when the pressure reduction valve is opened, air naturally flows from the air cell (20) to the second reservoir (40) due to the pressure difference, causing the pressure of the air cell (20) to decrease. In this way, in the present invention, the pressurization and depressurization of the air cell (20) are achieved solely by controlling the opening and closing of the valve assembly (60) without driving the pump (50) during the water surface section, and this becomes the core principle of low-noise pressure control.

[0074] The low-noise control module (130) of the controller (100) described later controls the pressure of each air cell (20) to within the target pressure range through valve pulse control, which opens the pressure boosting valve or pressure reducing valve for a short period of time.

[0075] The pressurizing valve and the depressurizing valve for the same air cell (20) are controlled so that they are not opened simultaneously, which is to prevent a short circuit between the first reservoir (30) and the second reservoir (40).

[0076] Valve pulses for different air cells (20) are applied sequentially in principle, and after the application of a valve pulse for one air cell (20) is completed and a preset waiting time has elapsed, a valve pulse for the next air cell (20) is applied.

[0077] This waiting time is intended to allow time for the reservoir pressure fluctuation caused by the previous valve pulse to stabilize, and can be set in the range of, for example, 100 ms to 5,000 ms.

[0078] The condition prohibiting simultaneous opening applies only to the pressurizing valve and the reducing valve of the same air cell (20). Valves for different air cells (20) may be opened sequentially or simultaneously depending on the design, but sequential opening is preferred to stabilize reservoir pressure fluctuations.

[0079] Even when the control sequence of air cells (20) requiring pressurization and air cells (20) requiring depressurization is arranged alternately during the sleep period, it is carried out within this sequential application structure.

[0080] The type of valve used in the valve assembly (60) can be selected differently depending on the noise reduction and response speed requirements.

[0081] For example, while conventional solenoid valves generate operating noise due to electromagnetic force during opening and closing, latching solenoid valves do not require separate power to maintain the open or closed state, resulting in low power consumption and reduced operating noise.

[0082] In addition, piezo valves are suitable for valve pulse control during the water surface phase because they open and close the flow path using the deformation of a piezoelectric element, resulting in a fast response speed and very low operating noise. In this invention, a latching solenoid valve or a piezo valve may be used to minimize noise during the water surface phase.

[0083] The flow characteristics of the valve assembly (60) are determined by the valve orifice diameter and pressure difference, for example, the orifice diameter can be designed in the range of 0.3 mm to 5 mm, and the valve pulse duration can be set in the range of 10 ms to 500 ms.

[0084] The valve assembly (60) is positioned adjacent to the first reservoir (30), the second reservoir (40), and the pump (50) in the inner frame of the mattress body (10) to shorten the pneumatic path and minimize pressure loss.

[0085] The pump (50) is connected to the first reservoir (30) and the second reservoir (40) and performs the role of transferring air between the two reservoirs.

[0086] Specifically, the pump (50) sucks in air collected in the second reservoir (40) and transfers it to the first reservoir (30), thereby maintaining the pressure in the first reservoir (30) higher than the target pressure of the air cell (20) and maintaining the pressure in the second reservoir (40) lower than the target pressure.

[0087] In this way, by adopting a closed-loop method in which the pump (50) circulates air between the two reservoirs, it is possible to prevent air from being released into the atmosphere when the air cell (20) is depressurized, thereby blocking exhaust noise and the inflow of external air.

[0088] Since the pump (50) is driven only outside the water surface area, the pump driving module (120) of the controller (100) drives the pump (50) to maintain the pressure of the first reservoir (30) and the second reservoir (40) at a target range outside the water surface area.

[0089] Before entering the water surface section, the pump drive module (120) described later drives the pump (50) so that the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) are greater than or equal to a preset threshold, thereby making it possible to maintain the pressure of the air cell (20) within the target pressure range solely through valve pulse control without driving the pump (50) during the water surface section.

[0090] The type of pump (50) can be selected differently depending on flow rate characteristics and noise requirements. For example, a diaphragm pump is suitable for a water surface environment as it has low pulsation and low noise, and a rotary vane pump can supply a continuous flow rate, making it possible to shorten the reservoir filling time. In addition, a linear pump has very low vibration, which is advantageous for minimizing noise even when filling the reservoir outside the water surface area.

[0091] The discharge pressure of the pump (50) can be set in the range of, for example, 10 kPa to 300 kPa based on the gauge, and the flow rate can be designed in the range of, for example, 1 L / min to 50 L / min.

[0092] It is preferable that the installation location of the pump (50) be positioned adjacent to the first reservoir (30) and the second reservoir (40) to shorten the pneumatic path, and it may be mounted on the inner frame of the mattress body (10) via an anti-vibration pad or anti-vibration mount to block vibration transmission.

[0093] The controller (100) of the present invention is a control unit that determines whether a user is sleeping based on pressure information measured from a pressure sensor (70), drives a pump (50) outside of the sleeping period to maintain the pressure of the first reservoir (30) and the second reservoir (40), stops the operation of the pump (50) during the sleeping period, and integrally processes a series of control flows to maintain the pressure of each air cell (20) within the target pressure range solely through valve pulse control of the valve assembly (60).

[0094] The controller (100) can be implemented as a combination of hardware and software. As hardware, processing elements such as an ASIC (Application Specific Integrated Circuit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), and microcontroller (MCU), a memory for storing the computational results and program commands of the processing elements, a communication interface circuit for communication with the pressure sensor (70), and a driver circuit for driving the pump (50) and the valve assembly (60) may be employed. As software, firmware or embedded software may be employed in which the processing elements execute program commands stored in memory to perform the functions of the water level determination module (110), the pump driving module (120), and the low-noise control module (130), respectively described later.

[0095] Each module described below represents a logical functional unit and does not necessarily have to be separated into physically independent circuits or components; it is also possible to implement each function in a form where it is executed separately in software on a single processor.

[0096] Specifically, as can be seen from FIG. 1, the controller (100) includes a water level determination module (110), a pump driving module (120), and a low-noise control module (130).

[0097] The sleep determination module (110) determines whether the user is sleeping based on pressure information measured from the pressure sensor (70) and determines the sleep period.

[0098] The method by which the sleep determination module (110) determines whether or not to sleep can be set in various ways.

[0099] For example, if a user pre-sets the bedtime and waketime through a smartphone application or a control panel installed on the mattress body (10), the sleep determination module (110) can determine the sleep period according to the set timetable.

[0100] Alternatively, the sleep determination module (110) can determine whether the user is sleeping by analyzing the pressure signal of each air cell (20) measured from the pressure sensor (70).

[0101] Specifically, the sleep determination module (110) determines whether sleep is occurring by applying a combination of conditions for the validity of biological cycle components and conditions for the decrease in body movement indicators.

[0102] The biological cycle component validity condition is a condition for verifying whether periodic components caused by respiration and heart rate are effectively detected in the pressure signal. When the user is sleeping, minute pressure fluctuations caused by respiration and heart rate appear periodically in the pressure signal of the air cell (20). The sleep determination module (110) interprets low-frequency components (e.g., 0.1 Hz to 0.5 Hz) in the pressure signal as fluctuations caused by respiration and high-frequency components (e.g., 0.8 Hz to 2.0 Hz) as fluctuations caused by heart rate, and determines that the biological cycle component is valid when components of the corresponding frequency band are detected above a preset threshold.

[0103] The condition for a decrease in the body movement index refers to verifying whether the body movement index—which indicates the magnitude of pressure fluctuations caused by the user's body movements, such as tossing and turning or changes in posture—remains below a preset threshold. When the user is sleeping, body movement decreases, thereby reducing the short-term fluctuation range of the pressure signal; conversely, the body movement index tends to rise when the user wakes up or tosses and turns.

[0104] The sleep determination module (110) determines a sleep phase when a stable state in which a biological cycle component is effectively detected and a body movement index is lowered below a preset threshold is maintained for, for example, 1 minute to 60 minutes or more. By applying the two conditions in combination, it is possible to distinguish between a simple resting state and an actual sleep state and prevent misjudgment.

[0105] In addition, the sleep determination module (110) can utilize the temperature change rate of a temperature sensor installed in the mattress body (10) as an auxiliary condition for sleep determination. When the user is sleeping, the body temperature stabilizes and the temperature change rate is maintained at a low level, whereas when waking up or tossing and turning occurs, the temperature change rate increases. The sleep determination module (110) prevents misjudgment and increases the reliability of sleep segment determination by applying a combination of conditions for the validity of biological cycle components, conditions for the decrease in body movement indicators, and conditions for the temperature change rate.

[0106] The duration of the stable state for the sleep determination module (110) to determine the sleep phase can be set in the range of, for example, 1 minute to 60 minutes, and to prevent misjudgment, it is possible to set it to switch to the sleep phase only when a stable state is detected simultaneously in a plurality of air cells (20).

[0107] However, since the condition for the validity of the biological cycle component and the condition for the decrease in the body movement index can be simultaneously satisfied even when the user remains stationary for a long time without sleeping, the sleep determination module (110) may apply the case where the user explicitly activates the sleep mode through a mobile terminal or control panel or enters a preset sleep time period as a prerequisite for sleep determination in order to prevent such misjudgment.

[0108] In this way, by combining external input or time zone conditions as precedence conditions, it is possible to distinguish more accurately between a simple stationary state and an actual sleep state.

[0109] The pump drive module (120) plays the role of driving the pump (50) to maintain the pressure of the first reservoir (30) higher than the target pressure of the air cell (20) outside the water surface area and to maintain the pressure of the second reservoir (40) lower than the target pressure.

[0110] Specifically, the pump drive module (120) monitors the current pressure of the first reservoir (30) and the second reservoir (40) in real time, measured by the pressure sensor (70) outside the water surface area. When the pressure of the first reservoir (30) drops below a preset lower limit or the pressure of the second reservoir (40) rises above a preset upper limit, the pump drive module (120) applies a drive signal to the pump (50) through the driver circuit.

[0111] When the pump (50) is driven, air collected in the second reservoir (40) is sucked in through the pump (50) and transferred to the first reservoir (30), so that the pressure in the first reservoir (30) rises and the pressure in the second reservoir (40) falls. When the pressure in the first reservoir (30) reaches a preset charging target pressure or the pressure in the second reservoir (40) reaches a preset depressurization target pressure, the pump driving module (120) stops the operation of the pump (50).

[0112] For example, if the target pressure of the air cell (20) is set to 30 kPa based on the gauge, the lower pressure limit of the first reservoir (30) can be set to be higher than the target pressure, for example, 40 kPa to 60 kPa, and the target charging pressure can be set to be, for example, 60 kPa to 100 kPa.

[0113] The pressure upper limit of the second reservoir (40) can be set to be lower than the target pressure, for example, 15 kPa to 25 kPa, and the pressure reduction target pressure can be set to be, for example, 5 kPa to 15 kPa. Thus, outside the water surface area, the first reservoir (30) always maintains a pressure higher than the target pressure and the second reservoir (40) always maintains a pressure lower than the target pressure, thereby preparing a state in which the air cell (20) can be pressurized and depressurized through the valve assembly (60).

[0114] In this case, the target pressure can be set differently depending on the user's body weight, sleeping posture, and purpose of use; for example, it can be set directly by the user via a mobile device or control panel, or automatically set using a target pressure preset received from an external server.

[0115] The target pressure can be set independently for each air cell (20). For example, the target pressure of the air cell (20) corresponding to the head zone can be set in the range of 10 kPa to 40 kPa based on the gauge, and the target pressure of the air cell (20) corresponding to the waist zone can be set in the range of 20 kPa to 80 kPa based on the gauge.

[0116] In relation to the hardware implementation of the pump drive module (120), the drive signal of the pump (50) can be applied in a Pulse Width Modulation (PWM) manner, so it is possible to control the rotational speed and discharge flow rate of the pump (50) by adjusting the PWM duty ratio.

[0117] For example, when the pressure of the first reservoir (30) is significantly lower than the target pressure, the pump (50) can be driven at a high duty cycle (e.g., 50% to 100%) to increase the charging speed, and when it is close to the target pressure, it can be driven at a low duty cycle (e.g., 10% to 60%) to prevent overcharging.

[0118] The driving current of the pump (50) is monitored in real time through a current sensing resistor in the driver circuit, and when an overcurrent occurs, the pump driving module (120) immediately stops the driving of the pump (50) to protect the pump (50) and the circuit.

[0119] In order to minimize the driving noise of the pump (50), the pump driving module (120) can be controlled to drive the pump (50) only during the time period when the user is determined to have fully woken up, even outside of the sleeping period.

[0120] For example, if it is determined that the user has gotten out of the mattress after waking up, or if, for example, 1 minute to 30 minutes have elapsed since the user set the wake-up time, the pump (50) is driven to restore the pressure of the first reservoir (30) and the second reservoir (40).

[0121] The low-noise control module (130) stops the operation of the pump (50) during the sleep period and maintains the pressure of each air cell (20) within the target pressure range solely through valve pulse control of the valve assembly (60).

[0122] This serves as a core control means of the present invention, enabling precise control of the pressure of the air cell (20) without noise from the pump (50) during the sleep period.

[0123] Valve pulse control refers to a control method that finely adjusts the amount of air flowing into or out of an air cell (20) by repeating the action of opening and closing the valve for a short period of time, from a few milliseconds to several hundred milliseconds.

[0124] Compared to the method of driving the pump (50), this has the characteristics of significantly lower noise and vibration, faster response speed, and lower power consumption because it controls pressure only through the opening and closing operation of the valve.

[0125] However, for such valve pulse control to be effectively achieved, the pressure of the first reservoir (30) must be maintained higher than the target pressure of the air cell (20) and the pressure of the second reservoir (40) must be maintained lower than the target pressure, so that a sufficient pressure difference between the two reservoirs is secured even when the pump (50) is stopped.

[0126] This is the reason why the pump drive module (120) pre-charges and depressurizes the pressure of the first reservoir (30) and the second reservoir (40) before entering the water level section.

[0127] Specifically, when the sleep determination module (110) determines that it is a sleep period, the low-noise control module (130) immediately blocks the driving signal of the pump (50) and starts the valve pulse control routine.

[0128] The low-noise control module (130) periodically receives the current pressure of each air cell (20) from the pressure sensor (70) and calculates the error between the current pressure and the target pressure. Depending on the direction of the error, it determines which air cell (20) requires pressurization or depressurization. If pressurization is required, it applies a pulse signal to the pressurization valve between the first reservoir (30) and the corresponding air cell (20) to introduce compressed air from the first reservoir (30) to the air cell (20), and if depressurization is required, it applies a pulse signal to the depressurization valve between the corresponding air cell (20) and the second reservoir (40) to transfer air from the air cell (20) to the second reservoir (40).

[0129] At this time, the duration of the valve pulse is determined by the magnitude of the error and the pressure difference between the reservoir and the air cell (20). Since the amount of air flowing in or out per unit time is greater when the pressure difference is large, the duration of the valve pulse is set short, and as the pressure difference is small, the duration of the valve pulse is set long so that the target pressure is reached precisely.

[0130] Valve pulse control for multiple air cells (20) is performed sequentially.

[0131] That is, if valves for multiple air cells (20) are opened simultaneously at the same time, the pressure of the reservoir may fluctuate rapidly and the control accuracy may be reduced. Therefore, the low-noise control module (130) applies valve pulses sequentially to each air cell (20) and sets a certain waiting time between each pulse so that the pressure stabilizes before applying the valve pulse of the next air cell (20). The waiting time can be set in the range of, for example, 100 ms to 5,000 ms.

[0132] The overall operation flow of the system of the present invention is described below.

[0133] Figure 4 is a flowchart illustrating the overall control flow according to the sleep interval determination of the controller in the system of the present invention.

[0134] First, outside the water section, the pump drive module (120) drives the pump (50) while monitoring the current pressure of the first reservoir (30) and the second reservoir (40) measured by the pressure sensor (70) to maintain the pressure of the first reservoir (30) higher than the target pressure of the air cell (20) and the pressure of the second reservoir (40) lower than the target pressure.

[0135] Before entering the sleep section, pre-charging is performed by charging the pressure of the first reservoir (30) to a sufficiently high level and reducing the pressure of the second reservoir (40) to a sufficiently low level to secure the pressure margin required for valve pulse control during the sleep section.

[0136] Afterwards, when the sleep determination module (110) analyzes the pressure signal measured from the pressure sensor (70) to detect the user's sleep state and determines it as a sleep period, the low-noise control module (130) immediately stops the operation of the pump (50) and starts the valve pulse control routine.

[0137] During the sleep period, the current pressure of each air cell (20) is periodically received from the pressure sensor (70) to calculate the error from the target pressure, and pulse signals are sequentially applied to the pressure boosting valve or pressure reducing valve according to the direction of the error to maintain the pressure of each air cell (20) within the target pressure range. During this process, the pump (50) remains in a completely stopped state, so no noise or vibration is generated at all due to the operation of the pump (50).

[0138] When the sleep period ends and the sleep determination module (110) determines the user's wake-up, the low-noise control module (130) terminates the valve pulse control routine and the pump drive module (120) restarts the pump (50) to restore the pressure of the first reservoir (30) and the second reservoir (40) consumed during the sleep period.

[0139] In summary, the system of the present invention provides the characteristic of blocking discharge noise and external air inflow by collecting and reusing air in the second reservoir (40) without releasing it into the atmosphere when the air cell (20) is depressurized through a double reservoir structure, and completely stopping the operation of the pump (50) during the water level period and precisely maintaining the pressure of each air cell (20) within the target pressure range using only valve pulse control utilizing the pressure margin of the first reservoir (30) and the second reservoir (40) secured in advance.

[0140] Furthermore, in order to stably control the pressure of each air cell (20) while maintaining the sleep period as much as possible even in emergency situations where the pressure of the reservoir exceeds a preset threshold during the sleep period, the controller (100) may further include a pressure compensation module (140).

[0141] The pressure compensation module (140) provides a function to perform at least one of the following when the pressure of the first reservoir (30) or the second reservoir (40) measured by the pressure sensor (70) during the sleep period exceeds a preset threshold: expanding the allowable range of the target pressure, driving the pump (50) for a limited time, or releasing the sleep period only when the sleep determination module (110) determines that the user has woken up.

[0142] Regarding the threshold determination of the pressure compensation module (140), if the pressure of the first reservoir (30) during the water surface period drops below the target pressure of the air cell (20), pressurization from the first reservoir (30) to the air cell (20) becomes impossible, and if the pressure of the second reservoir (40) rises above the target pressure of the air cell (20), depressurization from the air cell (20) to the second reservoir (40) becomes impossible.

[0143] Accordingly, the pressure compensation module (140) monitors the pressure of the first reservoir (30) and the second reservoir (40) measured by the pressure sensor (70) in real time to estimate the pressure margin of each reservoir, and if the pressure margin decreases below a preset threshold, it performs the following operations sequentially. The threshold of the pressure margin can be set, for example, in the range of 3 kPa to 50 kPa based on the gauge for the first reservoir (30) and 1 kPa to 30 kPa based on the gauge for the second reservoir (40).

[0144] Expanding the allowable range of the target pressure is a method of relaxing the pressure control criteria of the air cell (20) while maintaining the water level. For example, if the allowable range of the target pressure is normally set to ±1 kPa, when the reservoir pressure approaches the threshold, the allowable range is gradually expanded to ±2 kPa to ±10 kPa, thereby reducing the frequency of valve pulse control and minimizing the pressure consumption of the reservoir. This method is applied primarily in that it allows the water level to be maintained as much as possible without releasing it.

[0145] The limited-time pump operation is a method that is allowed only when the sleep determination module (110) determines the user's wake-up state, and the pump (50) is driven for a limited time using the time when the user is temporarily determined to be in a wake-up state due to tossing and turning, even during the sleep period, thereby replenishing the pressure of the first reservoir (30) and the second reservoir (40).

[0146] The time limit can be set in the range of, for example, 5 seconds to 300 seconds, and even during the time limit pump operation, the valve pulse control of the low-noise control module (130) continues in parallel without interruption so that the pressure of each air cell (20) is maintained within the target pressure range.

[0147] The time-limited pump operation is terminated according to the condition that is satisfied first, whichever occurs when the preset time limit has elapsed or when the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) are restored above a preset threshold. Immediately after termination, the pump (50) operation is stopped and the routine returns to maintaining the pressure of the air cell (20) solely through valve pulse control.

[0148] Meanwhile, if the pressure of the air cell (20) fluctuates rapidly due to sudden body movement or change in posture of the user immediately after entering the sleep phase, even if sufficient pre-charging has been performed, the pressure boosting and depressurization margins of the reservoir may momentarily decrease below a threshold, causing the pressure compensation module (140) to operate immediately and the sleep phase to be released immediately.

[0149] To prevent this, the controller (100) may apply a relaxed threshold of the pressure compensation module (140) during a preset entry stabilization period from the time of entering the sleep section. The entry stabilization period may be set in a range of, for example, 30 seconds to 120 seconds, and after the entry stabilization period has elapsed, a normal threshold is applied. Additionally, before entering the sleep section, the sleep determination module (110) additionally confirms that the pressure fluctuation range of the air cell (20) remains stable below a preset reference value for several seconds or more, thereby reducing the situation where a sudden pressure fluctuation occurs immediately after entry.

[0150] Release of the sleep section is a last resort applied when it is difficult to maintain the pressure of the air cell (20) within the target pressure range even with the two methods above. When the sleep section is released, the pump drive module (120) drives the pump (50) to restore the pressure of the first reservoir (30) and the second reservoir (40).

[0151] Re-entry into the sleep section is performed only when the sleep determination module (110) determines the sleep state again and confirms that the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) have been restored to a level greater than or equal to a preset threshold.

[0152] This makes it possible to prevent a repetitive situation where the device re-enters the sleep phase before the reservoir pressure is sufficiently restored, causing the sleep phase to be released again within a short period of time.

[0153] Meanwhile, if the water level determination module (110) re-determines the water level state before the reservoir pressure restoration by driving the pump (50) is completed after the water level section is released, the controller (100) suspends the transition to the water level section and maintains a charging standby state until the pressure margin and pressure reduction margin are restored above a preset threshold.

[0154] In the charging standby state, the pump (50) continues to operate to restore the reservoir pressure, but when charging is completed, the determination result of the water level determination module (110) is reconfirmed, and the system enters the water level section only if it is determined to be in a water level state. By doing so, it is possible to prevent a situation where the reservoir pressure restoration and the conditions for re-entering the water level section fall into a deadlock.

[0155] That is, the pressure compensation module (140) can provide the advantage of maintaining the pressure of each air cell (20) stably without disturbing the user's sleep as much as possible by responding stepwise in the order of expanding the allowable range and driving the pump for a limited time, without immediately releasing the sleep section even when the pressure margin of the reservoir is insufficient during the sleep section.

[0156] Furthermore, in order to precisely maintain the pressure of each air cell (20) within the target pressure range during the sleep period, it is preferable to calculate the valve pulse duration based on the pressure error of the air cell (20) and the pressure difference between the reservoir and the air cell (20), so the low-noise control module (130) may include a valve pulse calculation unit (131).

[0157] The valve pulse output unit (131) calculates the valve pulse duration of the valve assembly (60) based on the error between the current pressure and the target pressure of each air cell (20) measured by the pressure sensor (70) and the pressure difference between the first reservoir (30) or the second reservoir (40) and the air cell (20).

[0158] As an operating principle of the valve pulse output unit (131), air flowing into or out of the air cell (20) through the valve causes a pressure change in the air cell (20). When expressed as an ideal gas approximation, the rate of pressure change in the air cell (20) is proportional to the mass flow rate of the air flowing in or out per unit time and inversely proportional to the effective volume of the air cell (20).

[0159] For example, as the effective volume of the air cell (20) increases, the pressure change for the same mass flow rate is smaller, so the valve pulse duration should be set longer, and as the effective volume decreases, it is desirable to set the valve pulse duration shorter.

[0160] The air flow rate per unit time through the valve is determined by the pressure difference between the reservoir and the air cell (20). For example, as the pressure difference increases, the flow rate increases, so the valve pulse duration to correct the same pressure error becomes shorter, and as the pressure difference decreases, the valve pulse duration becomes longer.

[0161] The equivalent amount of air flowing into or out of the air cell (20) during the valve pulse duration τ can be approximated by the product of the valve flow coefficient, a monotonically increasing function of the pressure difference between the reservoir and the air cell (20), and the valve pulse duration, and based on this, the valve pulse calculation unit (131) calculates the valve pulse duration to reach the target pressure.

[0162] That is, the valve pulse output unit (131) calculates the valve pulse duration by comprehensively reflecting the pressure error of the air cell (20) and the pressure difference between the reservoir and the air cell (20), thereby providing the advantage of precisely maintaining the pressure of each air cell (20) within the target pressure range without driving the pump (50) during the water surface period.

[0163] Meanwhile, if the valve pulse output unit (131) generates a valve pulse for every pressure error of the air cell (20), the pressure consumption of the reservoir is accelerated and the number of valve operations increases, which may cause unnecessary noise during the sleep period.

[0164] To prevent this, the valve pulse output unit (131) may be configured to suppress valve pulse generation when the absolute value of the pressure error is within a preset dead band, and to calculate the valve pulse duration τ according to the following mathematical formula 1 only when it exceeds the dead band.

[0165] At this time, the deadband refers to a dead zone in which no valve pulse is generated when the pressure error is within an allowable range, and can be set, for example, within a range of ±0.5 kPa to ±5 kPa of the target pressure. By appropriately setting the deadband, it is possible to prevent the hunting phenomenon, which repeatedly generates valve pulses when the pressure of the air cell (20) fluctuates slightly near the target pressure, and to minimize pressure consumption of the reservoir.

[0166] When the absolute value of the pressure error exceeds the dead band, the valve pulse output unit (131) calculates the valve pulse duration τ according to the following mathematical formula 1.

[0167] Mathematical formula 1.

[0168]

[0169] Here, e is the difference between the target pressure and the current pressure of the air cell (Pa), ΔP is the difference between the pressure of the first reservoir and the pressure of the air cell when pressurizing and the difference between the pressure of the air cell and the pressure of the second reservoir when depressurizing, and is positive in both cases (Pa), f(ΔP) is a monotonically increasing function of ΔP normalized to maintain the pressure unit (Pa), k_τ is a calibration coefficient (s^-1), ε_τ is the minimum value of the denominator (Pa / s), τ_min and τ_max are the lower and upper limits of the valve pulse duration (s), and clamp(x, τ_min, τ_max) is a function that limits x to between τ_min and τ_max.

[0170] Mathematical Equation 1 adopts a non-linear calculation method that simultaneously reflects pressure error and pressure difference between the reservoir and the air cell, and thus has several advantages over the conventional simple proportional control method.

[0171] In other words, since the valve pulse duration is determined solely in proportion to the pressure error in conventional simple proportional control methods, when the reservoir pressure fluctuates, excessive or insufficient air flow occurs for the same error, leading to a problem of repeated overshoot or undershoot.

[0172] In contrast, Equation 1 includes f(ΔP) in the denominator to reflect flow characteristics according to the pressure difference in real time, thereby enabling stable pressure control even when the reservoir pressure fluctuates. Additionally, by limiting the valve pulse duration to between τ_min and τ_max through the clamp function, it prevents the generation of excessive pulses that exceed the physical limits of the valve, and through ε_τ, it prevents the valve pulse duration from diverging when the pressure difference is very small.

[0173] However, if ΔP is less than the preset minimum threshold value ΔP_min, no actual air flow occurs even if the valve is opened, so only valve operation noise is generated without a pressure correction effect and the pressurization or depressurization margin of the reservoir may be unnecessarily consumed. Therefore, the valve pulse generating unit (131) suppresses valve pulse generation when ΔP is less than ΔP_min. ΔP_min can be set in the range of, for example, 1 kPa to 5 kPa depending on the flow rate characteristics of the valve and the volume of the air cell (20).

[0174] f(ΔP) is a monotonically increasing function of the pressure difference between the first reservoir (30) and the air cell (20) when pressurized and the pressure difference between the air cell (20) and the second reservoir (40) when depressurized, reflecting the physical characteristic that the greater the pressure difference, the greater the air flow rate through the valve.

[0175] In actual implementation, f(ΔP) can be set based on the orifice flow equation; for example, since the non-choke region exhibits a monotonically increasing characteristic with respect to the pressure difference, it is possible to set it using a linear approximation, a square root approximation, or a calibration table depending on the valve characteristics. In the case of the linear approximation, f(ΔP) is set as ΔP, so the unit of f(ΔP) is directly maintained as Pa. In the case of the square root approximation, f(ΔP) can be set as ΔP_ref · √(ΔP / ΔP_ref),

[0176] Here, ΔP_ref is a reference pressure difference (Pa) and is a normalization constant that ensures the unit of f(ΔP) remains Pa. For example, if ΔP_ref is set to 10 kPa, then ΔP = 40 kPa, f(ΔP) is calculated as 10,000 · √(40,000 / 10,000) = 10,000 · 2 = 20,000 Pa, so the unit remains Pa. As such, the unit of f(ΔP) is normalized to the pressure unit (Pa) regardless of which approximation method is adopted. This combines with the unit of k_τ (s^-1) so that the unit of k_τ · f(ΔP) becomes Pa / s, and the unit of τ in Equation 1, which is |e| divided by Pa / s, is consistently maintained as seconds (s).

[0177] However, since the flow characteristics of actual valves vary by manufacturer, it is possible to correct f(ΔP) using a calibration table, or to set it using a linear approximation (f(ΔP) = ΔP), a square root approximation (f(ΔP) = ΔP_ref · √(ΔP / ΔP_ref)), or a combination thereof, depending on the valve characteristics.

[0178] Examples 1 and 2, in which actual values ​​were substituted into mathematical formula 1, are explained as follows.

[0179] It is assumed that the air cell (20) is set to an effective volume of 2L, a target pressure of 30kPa, a current pressure of 27kPa (error e = -3kPa), a dead band of ±0.5kPa, τ_min = 20ms, and τ_max = 500ms.

[0180] In Example 1, when the pressure of the first reservoir (30) is maintained at 60 kPa, the pressure difference ΔP between the first reservoir (30) and the air cell (20) is 33 kPa, so the flow rate per unit time is high and the valve pulse duration is calculated to be short. For example, in this case, the valve pulse duration can be calculated in the range of 20 ms to 50 ms, and it is possible for the pressure of the air cell (20) to rise to near the target pressure with only one valve pulse.

[0181] In Example 2, when the water level is maintained and the pressure of the first reservoir (30) decreases to 35 kPa, the pressure difference ΔP between the first reservoir (30) and the air cell (20) is reduced to 8 kPa, and since the flow rate per unit time decreases, the valve pulse duration is automatically calculated to be longer. For example, in this case, the valve pulse duration can be calculated in the range of 80 ms to 200 ms, and even if the reservoir pressure decreases, the valve pulse duration compensates for this, making it possible to accurately reach the target pressure.

[0182] In Comparative Example 1, when a conventional simple proportional control method is applied, the valve pulse duration is fixed in proportion only to the error.

[0183] As in Example 1, when the pressure difference is large, the target pressure is reached close to the target pressure with a fixed valve pulse duration; however, as in Example 2, when the pressure difference is reduced, the same valve pulse duration is applied, resulting in an undershoot where the target pressure is not reached due to insufficient air flow. If valve pulses are repeatedly generated to compensate for this, pressure consumption in the reservoir accelerates and the number of valve operations increases, which may cause noise during the water level period.

[0184] As such, Examples 1 and 2, which apply mathematical formula 1, accurately reach the target pressure with a minimum number of valve pulses regardless of reservoir pressure fluctuations compared to Comparative Example 1, thereby minimizing the number of valve operations and reducing the pressure consumption of the reservoir.

[0185] In addition, if the first reservoir (30) and the second reservoir (40) are not sufficiently secured before entering the sleep section, it may be difficult to maintain the pressure of the air cell (20) within the target pressure range using only valve pulse control during the sleep section.

[0186] To prevent this, the pump drive module (120) may include a margin estimation unit (121) that estimates the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) and secures them above a preset threshold before entering the water surface section.

[0187] Here, the pressurization margin is the value obtained by subtracting the target pressure of the air cell (20) from the pressure of the first reservoir (30), and the depressurization margin is the value obtained by subtracting the pressure of the second reservoir (40) from the current pressure of the air cell (20).

[0188] The threshold can be set differently depending on the number of air cells (20), the reservoir volume, and the expected duration of the sleep period, for example, by the user directly setting it through a mobile terminal or control panel, or by the manufacturer setting it as a default value during the initial setup of the control device (100).

[0189] For example, assume that the target pressure of the air cell (20) is 30 kPa based on the gauge, the threshold for the pressurization margin is 20 kPa, and the threshold for the depressurization margin is 15 kPa.

[0190] In order for the pressurization margin to be greater than or equal to the threshold of 20 kPa, the pressure of the first reservoir (30) must be greater than or equal to the target pressure of 30 kPa plus the threshold of 20 kPa. Therefore, the margin estimation unit (121) charges the pressure of the first reservoir (30) to, for example, 80 kPa to 150 kPa before entering the water surface section so that the pressurization margin is greater than or equal to the threshold.

[0191] Likewise, for the pressure reduction margin to be greater than or equal to the threshold of 15 kPa, the pressure of the second reservoir (40) must be 15 kPa or less, which is the current pressure of the air cell (20) 30 kPa minus the threshold of 15 kPa. The margin estimation unit (121) reduces the pressure of the second reservoir (40) to, for example, 0 kPa to 5 kPa before entering the water surface section so that the pressure reduction margin is greater than or equal to the threshold.

[0192] Thus, the margin estimation unit (121) secures a pressurization margin of 50 kPa or more and a depressurization margin of 15 kPa or more at the time of entering the water surface section, making it possible to maintain the pressure of the air cell (20) within the target pressure range by only valve pulse control without driving the pump (50) during the water surface section.

[0193] Furthermore, in order to calculate the pressurization margin and depressurization margin more accurately by reflecting the combination of the current pressure and target pressure of each of the multiple air cells (20), it is preferable for the margin estimation unit (121) to estimate the pressurization margin M_HP of the first reservoir (30) and the depressurization margin M_LP of the second reservoir (40) according to the following mathematical formulas 2 and 3.

[0194] Mathematical formula 2.

[0195]

[0196] Here, M_HP is the pressurization margin (Pa) of the first reservoir (30), P_HP is the pressure (Pa) of the first reservoir, P_set(z) is the target pressure (Pa) of the z-th air cell, ΔP_guard is the maintenance margin (Pa), the max calculation is performed only on air cells where P_z < P_set(z), i.e., air cells that require pressurization, and if there are no air cells that require pressurization, M_HP is calculated as M_HP = P_HP - max_z(P_z) - ΔP_guard, and z = 1, 2, ..., N (N is the total number of air cells).

[0197] Mathematical formula 3.

[0198]

[0199] Here, M_LP is the pressure reduction margin (Pa) of the second reservoir (40), P_z is the current pressure (Pa) of the z-th air cell, P_LP is the pressure (Pa) of the second reservoir, P_set(z) is the target pressure (Pa) of the z-th air cell, the min calculation is performed only on air cells where P_z > P_set(z), i.e., air cells requiring pressure reduction, and if there are no air cells requiring pressure reduction, M_LP is calculated as M_LP = min_z(P_set(z)) - P_LP, and z = 1, 2, ..., N (N is the total number of air cells).

[0200] In Equation 2, M_HP is the pressurization margin of the first reservoir (30). In the previous explanation, it was defined as the value obtained by subtracting the target pressure of the air cell (20) from the pressure of the first reservoir (30). In Equation 2, it is defined as the value obtained by subtracting the sum of the target pressure and the maintenance margin of the air cell (20) that requires the most pressurization among the air cells (20) that require pressurization, i.e., P_z < P_set(z), from the current pressure of the first reservoir (30). Thus, the previous definition is concretized by calculating it based on the most unfavorable case for all of the multiple air cells (20).

[0201] That is, M_HP represents the pressure head-based pressure margin remaining after the first reservoir (30) pressurizes all air cells (20) that require pressurization at the current pressure level to the target pressure. The larger M_HP is, the more pressure control is possible without driving the pump (50) during the water surface period.

[0202] The max operation of Equation 2 is performed only on air cells where P_z < P_set(z), i.e., air cells that require pressurization. If there are no air cells that require pressurization, M_HP is calculated as M_HP = P_HP - max_z(P_z) - ΔP_guard.

[0203] ΔP_need(z) is the pressure difference required to achieve the target pressure of the z-th air cell, and is defined as ΔP_need(z) = max(0, P_set(z) - P_z) + ΔP_guard.

[0204] P_set(z) is the target pressure value set in the z-th air cell, and P_z is the current pressure value of the z-th air cell (20) measured by the pressure sensor (70). The max(0, P_set(z) - P_z) term reflects a positive pressure difference only when the current pressure is less than the target pressure, and is treated as 0 when the current pressure is greater than or equal to the target pressure to prevent unnecessary additional supply.

[0205] ΔP_guard is a compensation margin (Pa) to compensate in advance for pressure drop due to micro leakage, weight fluctuation, and sensor measurement error within the air cell (20), and can be set by the user directly through a mobile terminal or control panel, for example, or by the manufacturer specifying it as a default value during the initial setup of the control device (100), for example, and can be set in the range of 1 kPa to 10 kPa.

[0206] The specific value of ΔP_guard can be set by considering the leakage characteristics according to the material and size of the air cell (20), the range of variation in the user's weight and sleeping posture, and the measurement resolution and error range of the pressure sensor (70). For example, if the leakage of the air cell (20) is small and the user's weight variation is small, it can be set to a low value of 1 kPa to 3 kPa, and if the leakage is large or the weight variation is large, it can be set to a high value of 5 kPa to 10 kPa.

[0207] Including ΔP_guard in ΔP_need(z) is intended to conservatively secure the charge level of the reservoir before entering the water level section in preparation for such uncertainty. This ensures sufficient pressure margin so that even if an unexpected pressure drop occurs during the water level section, the pressure of the air cell (20) can be maintained within the target pressure range by valve pulse control alone without driving the pump (50).

[0208] In mathematical formula 3, M_LP is the pressure reduction margin of the second reservoir (40). In the previous explanation, it was defined as the value obtained by subtracting the pressure of the second reservoir (40) from the current pressure of the air cell (20). However, in mathematical formula 3, it is defined as the pressure difference of the air cell (20) that requires pressure reduction, i.e., the air cell (20) where P_z > P_set(z), and has the smallest difference between the current pressure and the pressure of the second reservoir (40). This is specified to be calculated based on the case where pressure reduction control is most difficult for all of the multiple air cells (20).

[0209] That is, M_LP represents the pressure head-based pressure reduction margin that allows the second reservoir (40) to receive additional air from the air cell (20) that requires pressure reduction from the current pressure level, and the larger M_LP is, the more pressure reduction control is possible without driving the pump (50) during the water level section.

[0210] The min operation in Equation 3 is performed only on air cells where P_z > P_set(z), i.e., air cells requiring depressurization. For air cells requiring pressurization (P_z < P_set(z)), the current pressure is low, so P_z - P_LP may be small. This can lead to the problem of unnecessarily underestimating M_LP by dominating the min operation; therefore, to prevent this, it is limited to air cells requiring depressurization. If there are no air cells requiring depressurization, M_LP is calculated as M_LP = min_z(P_set(z)) - P_LP.

[0211] The margin estimation unit (121) drives the pump (50) to fill the first reservoir (30) and depressurize the second reservoir (40) so that M_HP and M_LP are above a preset threshold before entering the water level section.

[0212] At this time, the threshold can be set in the range of, for example, 5 kPa to 50 kPa for M_HP and 3 kPa to 30 kPa for M_LP.

[0213] The following relates to examples of mathematical formulas 2 and 3.

[0214] Assume there are three air cells (20) (z=1, 2, 3), each air cell has a target pressure P_set = 20kPa, 25kPa, 30kPa, current pressure P_z = 18kPa, 27kPa, 28kPa, ΔP_guard = 3kPa, M_HP threshold = 10kPa, and M_LP threshold = 5kPa. In this case, z=1 (P_z=18kPa < P_set=20kPa) and z=3 (P_z=28kPa < P_set=30kPa) are air cells that require pressurization, and z=2 (P_z=27kPa > P_set=25kPa) is an air cell that requires depressurization.

[0215] In Example 1, when the margin estimation unit (121) before entering the water surface section applies Equation 2, the max operation is performed only for air cells z=1 and z=3 that require pressurization. Since P_set(1) + ΔP_guard = 20,000 + 3,000 = 23,000 Pa and P_set(3) + ΔP_guard = 30,000 + 3,000 = 33,000 Pa, max = 33,000 Pa.

[0216] When the pressure of the first reservoir (30) is P_HP = 40kPa, M_HP = 40,000 - 33,000 = 7,000Pa = 7kPa, which is less than the pressure margin threshold of 10kPa, the margin estimation unit (121) drives the pump (50) to charge the pressure of the first reservoir (30) to 43kPa or higher.

[0217] When applying mathematical formula 3, the min operation is performed only for air cell z=2, which requires depressurization. When the pressure of the second reservoir (40) is P_LP = 15kPa, M_LP = P_z(2) - P_LP = 27,000 - 15,000 = 12,000Pa = 12kPa, and since this is greater than the depressurization margin threshold of 5kPa, it is possible to enter the surface area without additional depressurization.

[0218] In this way, when entering the sleep section with the pressurization margin M_HP and depressurization margin M_LP secured above the threshold value before entering the sleep section, it is possible to maintain the pressure of all air cells (20) within the target pressure range solely through valve pulse control without driving the pump (50) during the sleep section.

[0219] As a comparative example, if a method is applied where entry into the water surface section is made only when the pressure of the first reservoir (30) is greater than or equal to a preset fixed value without a margin estimation unit (121), the actual required pressure margin and pressure reduction margin may differ depending on the combination of the current pressure and target pressure of the air cell (20), but this is not reflected, and a situation may occur where the pressure of some air cells (20) exceeds the target pressure range after entering the water surface section.

[0220] In this case, the duration of the sleep period is shortened, and noise may occur due to the reactivation of the pump (50) during sleep.

[0221] As such, Example 1, which applies mathematical formulas 2 and 3, quantitatively reflects the actual required pressurization margin and depressurization margin of each air cell (20) compared to the comparative example, thereby preparing the pressure of the reservoir to an optimal level before entering the water surface section, and thus can exhibit the advantage of stable pressure control without driving the pump (50) during the water surface section.

[0222] As previously explained, during the sleep period, the low-noise control module (130) minimizes noise generation by suppressing the operation of the pump (50). However, as sleep progresses, if changes in the user's weight distribution, micro-leakage within the air cell (20), and repetitive pressure fluctuations caused by breathing accumulate, the pressure of the first reservoir (30) and the second reservoir (40) gradually decreases.

[0223] In this case, the pressure margin—the difference from the target pressure—gradually decreases, eventually making pressure replenishment by pump operation inevitable and causing problems where operating noise disturbs sleep.

[0224] To resolve this problem, the water level extension module (150) maintains the water level without driving the pump (50) by gradually increasing the allowable error of the target pressure when the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) described above are sequentially reduced to below a preset step threshold.

[0225] FIG. 5 is a flowchart illustrating the operation flow of stepwise expansion of the tolerance of the sleep section extension module, valve sequence adjustment, and calculation of the remaining duration.

[0226] The sleep section extension module (150) monitors the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) in real time based on the pressure of the first reservoir (30) and the second reservoir (40) measured by the pressure sensor (70) during the sleep section, and maintains the sleep section by gradually expanding the allowable error of the target pressure when the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) sequentially decrease to below a preset step threshold.

[0227] As previously defined, the pressurization margin of the first reservoir (30) is the value obtained by subtracting the target pressure of the air cell (20) from the pressure of the first reservoir (30), representing the margin for the first reservoir (30) to further pressurize the air cell (20), and the depressurization margin of the second reservoir (40) is the value obtained by subtracting the pressure of the second reservoir (40) from the current pressure of the air cell (20), representing the margin for the second reservoir (40) to further receive air from the air cell (20).

[0228] That is, the larger the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40), the more pressure control is possible without driving the pump (50) during the water surface period, and as the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) approach 0, it becomes difficult to maintain the pressure of the air cell (20) within the target pressure range by valve pulse control alone.

[0229] Accordingly, the sleep section extension module (150) extends the sleep section to the maximum extent by gradually increasing the allowable error of the target pressure as the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) decrease, thereby reducing the valve pulse control frequency and slowing down the pressure consumption rate of the reservoir.

[0230] To explain the operating principle of the sleep section extension module (150) in detail, during the sleep section, due to leakage of the air cell (20) and repetitive valve pulse control, the pressure of the first reservoir (30) gradually decreases and the pressure of the second reservoir (40) gradually increases.

[0231] At this time, the tolerance refers to the range of deviation allowed from the target pressure for the current pressure of the air cell (20), and if the current pressure is within the tolerance of the target pressure, the generation of valve pulses is suppressed. The tolerance can be set by the user directly through, for example, a mobile terminal or a control panel, or by the manufacturer designating it as a default value during the initial setup of the control device (100).

[0232] In the initial stage, when there is sufficient pressure margin of the first reservoir (30) and pressure reduction margin of the second reservoir (40), precise pressure control is performed by maintaining a narrow tolerance of the target pressure, but when the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) decrease below the first stage threshold, the tolerance is expanded by one stage, and when they decrease further below the second stage threshold, the tolerance is expanded by two stages.

[0233] By gradually increasing the tolerance in this manner, the valve pulse control frequency is reduced, which decreases the reservoir's pressure consumption rate and makes it possible to extend the water level range.

[0234] The expansion of the tolerance is limited to within a preset maximum tolerance upper limit. If applied simultaneously with the expansion of the tolerance range by the pressure compensation module (140), the actual tolerance is determined as the larger of the values ​​calculated by the two modules. The maximum tolerance upper limit can be set, for example, within a range of ±10kPa to ±20kPa.

[0235] For example, if the initial tolerance is set to ±0.5 kPa, it is possible to expand the tolerance to ±1 kPa when the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) decrease below a first stage threshold (e.g., 15 kPa), expand the tolerance to ±3 kPa when it decreases further below a second stage threshold (e.g., 8 kPa), and expand the tolerance to ±5 kPa to ±10 kPa when it decreases below a third stage threshold (e.g., 3 kPa). The step thresholds and the tolerance expansion range may be set differently depending on the number of air cells (20), the reservoir volume, and the expected duration of the water surface section.

[0236] In addition, as the tolerance is increased, the frequency of valve pulse control is reduced, thereby decreasing the overall number of valve operations; consequently, an additional reduction in valve operation noise during the water surface period can also be achieved.

[0237] The following is an example of the operation of the sleep period extension module (150).

[0238] In the embodiment, it is assumed that four air cells (20) are set with target pressures of 20kPa, 25kPa, 30kPa, and 28kPa respectively, an initial tolerance of ±0.5kPa, an initial pressurization margin of 20kPa for the first reservoir (30), and an initial depressurization margin of 15kPa for the second reservoir (40).

[0239] As the sleep section progresses, the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) gradually decrease due to leakage of the air cell (20) and repetitive valve pulse control. When the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) decrease to less than 15kPa, which is the first stage threshold, the sleep section extension module (150) expands the allowable error to ±1kPa.

[0240] Accordingly, the frequency of valve pulse generation is reduced, thereby decreasing the rate of pressure consumption in the reservoir. When the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40) are further reduced to less than 8 kPa, which is the second stage threshold, the allowable error is expanded to ±3 kPa, and when it is less than 3 kPa, which is the third stage threshold, the allowable error is expanded to ±8 kPa to minimize the valve pulse control frequency.

[0241] As a comparative example, when an initial tolerance of ±0.5 kPa is fixed throughout the sleep period without a sleep period extension module (150), even if the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) decrease, the frequency of valve pulse generation does not decrease, so the pressure consumption of the reservoir is accelerated and the pressure compensation module (140) operates early during the sleep period, resulting in the sleep period being shortened.

[0242] In contrast, in the embodiment described above, it is possible to extend the water level range by, for example, 20% to 50% or more compared to the comparative example by controlling the pressure consumption rate of the reservoir through a stepwise expansion of the tolerance.

[0243] In summary, the sleep interval extension module (150) can extend the sleep interval as much as possible without suddenly releasing it by gradually increasing the allowable error of the target pressure as the pressure margin of the first reservoir (30) and the pressure reduction margin of the second reservoir (40) decrease, thereby providing the advantage of protecting the user's sleep.

[0244] Furthermore, when applying valve pulses to multiple air cells (20) sequentially during the sleep period, if there is no criterion for determining which air cell (20) to control first, the pressure consumption of either the first reservoir (30) or the second reservoir (40) may be uneven, causing the pressure margin to decrease prematurely below the step threshold and the tolerance to be unnecessarily expanded.

[0245] To prevent this, the sleep section extension module (150) includes a valve sequence adjustment unit (151), wherein the valve sequence adjustment unit (151) calculates a valve control priority index for each air cell (20) according to Equation 4 and determines the order of valve pulse application based thereon, and by applying valve pulses alternately to air cells (20) that require pressurization because they are lower than the target pressure and air cells (20) that require depressurization because they are higher than the target pressure, it is possible to offset the pressure consumption of the first reservoir (30) and the second reservoir (40), thereby delaying the point at which the pressure margin (pressurization margin of the first reservoir and depressurization margin of the second reservoir) decreases below the step threshold and delaying the expansion of the allowable error.

[0246] FIG. 6 is a flowchart illustrating the calculation of the valve control priority index and the cross-arrangement of pressurized and depressurized air cells of the valve sequence adjustment unit, as well as the calculation of the remaining duration and the pump drive reservation operation flow of the remaining time calculation unit.

[0247] The valve sequence adjustment unit (151) calculates the valve control priority index I(z) for each air cell (20) according to the following mathematical formula 4.

[0248] Mathematical formula 4.

[0249]

[0250] Here, e(z) is the error (Pa) between the current pressure of the air cell and the target pressure, M_res(z) is the pressure difference between the first reservoir (30) and the air cell (20) when pressurizing or the pressure difference between the air cell (20) and the second reservoir (40) when depressurizing (Pa), f(ΔP(z)) is a monotonically increasing function (Pa) for the directional pressure difference between the reservoir and the air cell, and the larger I(z) is, the more preferentially the valve pulse control of the air cell is performed.

[0251] Mathematical formula 4 is defined as a non-linear index in which the square of the pressure error of the air cell (20) is divided by the product of the directional pressure difference-based index per air cell and the pressure difference function. This is significant in that it determines the control priority by considering the state of the directional pressure difference-based index per air cell together, rather than simply controlling the air cell (20) with the large pressure error first.

[0252] In other words, even if the pressure error is large, the priority is appropriately adjusted if the index based on the directional pressure difference per air cell is sufficient; conversely, even if the pressure error is small, if the index based on the directional pressure difference per air cell is insufficient, valve control in that direction is suppressed to minimize pressure consumption in the reservoir.

[0253] The numerator of mathematical formula 4, |e(z)|², is defined as the square of the pressure error, and reflects the error non-linearly rather than linearly, so that the priority increases rapidly as the error increases. For example, if the error increases by a factor of 2, the numerator increases by a factor of 4, and the priority rises non-linearly, which reflects the fact that quickly correcting the air cell (20) with a large pressure error is more important for maintaining sleep quality.

[0254] The denominator M_res(z) is the difference between the pressure of the first reservoir (30) and the current pressure of the air cell (20) in the case of an air cell (20) that requires pressurization, or the difference between the current pressure of the air cell (20) and the pressure of the second reservoir (40) in the case of an air cell (20) that requires depressurization; in other words, it is a directional pressure difference calculated individually for each air cell (20).

[0255] This is distinguished in that, unlike M_HP of Equation 2 and M_LP of Equation 3, which are used to determine the sufficiency of reservoir charging before entering the sleep phase and are calculated based on the most unfavorable case for all of the multiple air cells (20), M_res(z) is calculated individually for each air cell (20) according to the control direction at that time.

[0256] As M_res(z) decreases, I(z) increases, so it appears that valve control in that direction is prioritized, but in reality, by arranging the air cell (20) that requires pressurization and the air cell (20) that requires depressurization alternately, the consumption of the first reservoir (30) and the capacity of the second reservoir (40) are balanced.

[0257] f(ΔP(z)) is a function that has the characteristic that as the pressure difference between the first reservoir (30) and the air cell (20) during pressurization and the pressure difference between the air cell (20) and the second reservoir (40) during depressurization increases, the function value increases, and as the pressure difference decreases, the function value decreases. In other words, it represents a relationship in which the pressure difference and the function value change in the same direction.

[0258] This serves to prevent overshoot caused by excessive air transfer by lowering the control priority of the air cell (20), as the air flow rate per unit time through the valve increases as the pressure difference increases, allowing sufficient air transfer even with a short valve pulse duration.

[0259] For example, when linearly approximating with f(ΔP(z)) = ΔP(z), if the pressure difference is 10 kPa, f(ΔP) = 10; if the pressure difference is 30 kPa, f(ΔP) = 30; and if the pressure difference is 50 kPa, f(ΔP) = 50.

[0260] Assuming the same pressure error e = 2kPa and the pressurization margin M_res = 5kPa of the first reservoir (30), I(z) of the air cell (20) with a pressure difference of 10kPa is calculated as 2² / (5 × 10) = 4 / 50 = 0.08, and I(z) of the air cell (20) with a pressure difference of 50kPa is calculated as 2² / (5 × 50) = 4 / 250 = 0.016. This confirms that as the pressure difference increases, I(z) becomes smaller and the priority decreases.

[0261] This reflects the fact that air cells (20) with a large pressure difference can sufficiently correct pressure with only short valve pulses, so there is a low possibility of exceeding the target pressure range even if controlled relatively later.

[0262] In actual implementation, f(ΔP(z)) can be set using linear approximation, square root approximation, or a calibration table depending on the valve characteristics, and it is possible to implement it in various function forms as long as the characteristic that the pressure difference and the function value change in the same direction is satisfied.

[0263] Equation 4 is a multi-factor non-linear priority function that comprehensively reflects pressure error, directional pressure difference per air cell (M_res(z)), and pressure difference function, and the three factors are organically combined. The squared pressure error term reflects urgency, the M_res(z) term reflects sustainability, and the pressure difference function term reflects control efficiency.

[0264] By balancing these three factors, it is possible to determine an optimal control sequence that minimizes pressure consumption of the reservoir during the sleep period while maintaining the pressure of each air cell (20) within the target pressure range.

[0265] Meanwhile, if M_res(z) decreases to 0 or less, that is, if the reservoir pressure in that direction drops below the current pressure of the air cell (20) and there is a risk that air will flow in the reverse direction when the valve is opened, the controller (100) suppresses the generation of a valve pulse in that direction for the air cell (20).

[0266] Likewise, even when f(ΔP(z)) decreases below a preset minimum value and the denominator approaches 0 in substance, the divergence of Equation 4 is prevented by suppressing the generation of valve pulses for the corresponding air cell (20).

[0267] When these conditions are met, the sleep interval extension module (150) notifies the pressure compensation module (140) of the situation so that at least one corresponding action is performed, such as expanding the allowable error of the target pressure, scheduling the operation of the pump (50), or releasing the sleep interval.

[0268] The valve sequence adjustment unit (151) sequentially applies valve pulses starting from the air cell (20) with a high valve control priority index calculated according to mathematical formula 4, and alternately applies valve pulses to the air cell (20) that requires pressurization because it is lower than the target pressure and the air cell (20) that requires depressurization because it is higher than the target pressure.

[0269] Specifically, when a valve pulse is applied to an air cell (20) that requires pressurization, the pressurization margin of the first reservoir (30) is consumed, and when a valve pulse is applied to an air cell (20) that requires depressurization, the depressurization margin of the second reservoir (40) is reduced.

[0270] When pressurization and depressurization are performed alternately, the pressure reserve of the first reservoir (30) is consumed and the depressurization reserve of the second reservoir (40) is reduced alternately. This offsets the pressure changes of the two reservoirs, thereby delaying the point at which the pressure reserve and depressurization reserve decrease below the step threshold and delaying the expansion of the allowable error.

[0271] For example, if there are three pressurized air cells (20) and three depressurized air cells (20) each, by applying valve pulses in the order of pressurization → depressurization → pressurization → depressurization, the pressure consumption of the first reservoir (30) and the second reservoir (40) is balanced, making it possible to delay the point at which the allowable error is expanded. If the number of air cells (20) requiring pressurization and air cells (20) requiring depressurization is different, they can be arranged alternately based on the air cells (20) with a higher priority index, while the remaining air cells (20) can be processed sequentially.

[0272] The following relates to an example of calculating the valve control priority index in mathematical formula 4.

[0273] It is assumed that there are 3 air cells (20) (z=1,2,3), target pressure P_set = 20kPa, 25kPa, 30kPa, and current pressure P_z = 17kPa, 26kPa, 28kPa, so that e(1) = -3kPa (pressurization required), e(2) = +1kPa (pressurization required), and e(3) = -2kPa (pressurization required).

[0274] M_res(1) = M_res(3) = 8kPa (pressure difference in the pressurization direction) of the first reservoir (30), M_res(2) = 6kPa (pressure difference in the depressurization direction) of the second reservoir (40), and f(ΔP) is normalized as a monotonically increasing function proportional to ΔP to set f(ΔP(1)) = 10, f(ΔP(2)) = 6, and f(ΔP(3)) = 8.

[0275] If mathematical formula 4 is applied in Example 1,

[0276] I(1) = 3² / (8 × 10) = 9 / 80 = 0.1125,

[0277] I(2) = 1² / (6 × 6) = 1 / 36 = 0.0278,

[0278] I(3) = 2² / (8 × 8) = 4 / 64 = 0.0625.

[0279] The priority order is calculated as I(1) > I(3) > I(2). The valve order adjustment unit (151) applies valve pulses in the order of z=1 (pressurization), z=3 (pressurization), and z=2 (reduction), but in order to alternate between pressurization and reduction, it applies valve pulses by rearranging them in the order of z=1 (pressurization) → z=2 (reduction) → z=3 (pressurization).

[0280] In this way, by applying valve pulses alternately to the pressurizing air cell (20) and the depressurizing air cell (20), the pressure reserve of the first reservoir (30) and the pressure reserve of the second reservoir (40) are alternately consumed, so that the pressure consumption of the two reservoirs is offset and the point at which the pressure reserve and pressure reserve decrease below the step threshold is delayed.

[0281] As a comparative example, when a method is applied in which valve pulses are applied sequentially starting from the air cell (20) with the largest absolute value of pressure error without a priority index, valve pulses are applied in the order of z=1 (pressurization, |e|=3kPa) → z=3 (pressurization, |e|=2kPa) → z=2 (reduction, |e|=1kPa), and the pressurized air cell (20) is continuously controlled.

[0282] In this case, the pressurization margin of the first reservoir (30) is continuously consumed and rapidly decreases, while the depressurization margin of the second reservoir (40) is not fully utilized, resulting in an imbalance in pressure consumption between the reservoirs. Consequently, the pressurization margin of the first reservoir (30) is depleted early during the water surface period, causing the tolerance to expand unnecessarily early, the pressure compensation module (140) to operate, or the water surface period to be shortened.

[0283] In this way, Example 1, which applies mathematical formula 4, can exhibit the advantage of improving water quality by delaying the expansion of the allowable error and further extending the water surface section by cross-arranging the pressurized air cell (20) and the depressurized air cell (20) compared to the comparative example, thereby maintaining a balanced consumption of the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40).

[0284] That is, the valve sequence adjustment unit (151) can apply valve pulses alternately to the air cell (20) requiring pressurization and the air cell (20) requiring depressurization based on a non-linear priority index according to mathematical formula 4, thereby offsetting the consumption of the pressurization margin of the first reservoir (30) and the depressurization margin of the second reservoir (40), and delaying the point at which the pressurization margin and depressurization margin decrease below the step threshold, thereby delaying the expansion of the allowable error and thus providing the advantage of protecting the user's sleep.

[0285] Meanwhile, even if the water level extension module (150) gradually expands the allowable error and the valve sequence adjustment unit (151) offsets the pressure consumption, if the water level becomes sufficiently long, the pressure margin of the reservoir is eventually exhausted and the expansion of the allowable error reaches the final stage.

[0286] In this case, the sleep period must be released and the pump (50) must be driven to restore the reservoir pressure, but sudden driving of the pump (50) may cause noise during sleep.

[0287] To prevent this, the sleep interval extension module (150) may include a remaining time calculation unit (152).

[0288] The remaining time calculation unit (152) calculates the remaining duration T_remain, which can maintain the water level section with the current reservoir pressure margin according to mathematical formula 5, and if T_remain is less than a preset standard, it outputs a pump drive reservation signal to the pump drive module (120) before the tolerance expansion stage reaches the final stage.

[0289] In response to this, the pump drive module (120) maintains a ready state so that when it receives a pump drive reservation signal, it can immediately drive the pump (50) to restore the reservoir pressure at the time when the sleep determination module (110) determines the user's wake-up time.

[0290] Mathematical formula 5.

[0291]

[0292] Here, T_remain is the remaining time (s) during which the above-mentioned water level section can be maintained with the current reservoir pressure margin, M_res(z) is the pressurization margin or depressurization margin (Pa) per air cell according to Equation 4, M_0 is the reference pressure margin (Pa) of the first and second reservoirs, and is a normalization constant with M_res(z) / M_0 as dimensionless, r(z) is the normalized equivalent pressure consumption rate (1 / s) per air cell due to the valve pulse control, and γ is a non-linear damping coefficient greater than 1, which is a coefficient set so that the remaining duration decreases non-linearly as the reservoir pressure margin decreases.

[0293] Mathematical formula 5 is a function that non-linearly calculates the remaining duration of the sleep section based on the pressurization margin or depressurization margin for each of the multiple air cells (20) and the normalized equivalent pressure consumption rate. Unlike a linear prediction method that simply divides the current pressure margin by the pressure consumption rate, it has significance in that it can more accurately predict the end time of the sleep section and preemptively determine the pump operation reservation time by reflecting the characteristic that the remaining time decreases more rapidly as the pressure margin decreases through a non-linear damping coefficient γ.

[0294] M_res(z) is the pressurization margin or depressurization margin for each air cell defined in mathematical formula 4, representing the pressurization margin of the first reservoir (30) in the case of an air cell (20) that requires pressurization, and the depressurization margin of the second reservoir (40) in the case of an air cell (20) that requires depressurization.

[0295] M_0 serves as a reference pressure margin that normalizes M_res(z) / M_0 to a dimensionless state. For example, M_0 can be set as the initial pressure margin at the time of entering the water surface section, and can be set in the range of, for example, 10 kPa to 50 kPa.

[0296] r(z) is a normalized equivalent pressure consumption rate per air cell by valve pulse control, and the difference in reservoir pressure immediately before and after the valve pulse application for each air cell (20) is attributed to the corresponding air cell (20) to estimate.

[0297] Specifically, the change in reservoir pressure before and after the application of the valve pulse to the z-th air cell (20) is calculated by dividing the value by the valve pulse duration, and the value is normalized to a reference pressure margin M_0. It is possible to increase the estimation accuracy by applying a moving average of the previous multiple valve pulses. The unit of r(z) is 1 / s, and can be calculated in the range of, for example, 0.001 / s to 0.5 / s.

[0298] γ is a non-linear damping coefficient greater than 1, which is a coefficient set so that the remaining duration decreases non-linearly as the reservoir pressure margin decreases.

[0299] When γ = 1, T_remain is linearly proportional to the pressure margin, but when γ > 1, as M_res(z) / M_0 decreases to less than 1, (M_res(z) / M_0)^γ decreases faster than M_res(z) / M_0, so T_remain has the characteristic of decreasing non-linearly and rapidly. For example, when M_res(z) / M_0 = 0.5 and γ = 2, (M_res(z) / M_0)^γ = 0.5^2 = 0.25 is calculated, and when γ = 3, it is calculated as 0.5^3 = 0.125, so it is possible for the remaining time to decrease more rapidly as the pressure margin decreases as γ increases. γ can be set in the range of, for example, greater than 1 and less than or equal to 5, and can be set differently depending on the leakage characteristics of the air cell (20) and the reservoir volume.

[0300] In mathematical formula 5, min_z means calculating T_remain based on the air cell (20) with the shortest remaining duration among the multiple air cells (20). By conservatively calculating the remaining time based on the most vulnerable air cell (20), it is possible to prevent a situation where the pressure of any one air cell (20) in the sleep section exceeds the target pressure range.

[0301] Meanwhile, if r(z) decreases to 0 or less than the preset minimum value r_min, that is, if the reservoir pressure consumption of the air cell (20) is almost non-existent, T_remain diverges substantially to infinity, and the pump drive reservation may not be made.

[0302] To prevent this, the controller (100) applies a preset minimum value r_min as a lower limit when calculating r(z) so that r(z) does not decrease to less than r_min. For example, r_min can be set in the range of 0.0001 / s to 0.001 / s.

[0303] In addition, Equation 5 is designed so that the nonlinear damping characteristics operate meaningfully when M_res(z) / M_0 has a value between 0 and 1, that is, when the current reservoir pressure margin is smaller than the reference pressure margin M_0.

[0304] When M_res(z) / M_0 exceeds 1, that is, when the reservoir pressure margin is greater than the reference pressure margin at the beginning of the water level section, (M_res(z) / M_0)^γ exceeds 1 and T_remain may be overcalculated, so the controller (100) calculates T_remain by limiting M_res(z) / M_0 to 1 when it exceeds 1.

[0305] Meanwhile, if the user continues to sleep even after the pump drive reservation signal is output, that is, if T_remain decreases below a preset absolute threshold while the sleep determination module (110) does not determine whether the user has woken up, the controller (100) forcibly releases the sleep period regardless of whether the user has woken up and drives the pump (50) to restore the pressure of the first reservoir (30) and the second reservoir (40).

[0306] The absolute threshold can be set in the range of, for example, 5 to 30 seconds. When the reservoir pressure is restored after the forced release of the sleep section, it is possible to re-enter the sleep section only if the judgment result of the sleep judgment module (110) and the pressure margin and pressure reduction margin are confirmed to be greater than or equal to the preset threshold.

[0307] The following relates to an example applying mathematical formula 5.

[0308] It is assumed that there are 3 air cells (20) (z=1,2,3), M_0 = 20kPa, γ = 2, the current pressurization or depressurization margins are set to M_res(1) = 8kPa, M_res(2) = 12kPa, M_res(3) = 6kPa, and the normalized equivalent pressure consumption rates are set to r(1) = 0.025 / s, r(2) = 0.015 / s, and r(3) = 0.020 / s.

[0309] If you apply mathematical formula 5,

[0310] (M_res(1) / M_0)^γ / r(1) = (8 / 20)^2 / 0.025 = 0.16 / 0.025 = 6.4s,

[0311] (M_res(2) / M_0)^γ / r(2) = (12 / 20)^2 / 0.015 = 0.36 / 0.015 = 24.0s,

[0312] (M_res(3) / M_0)^γ / r(3) = (6 / 20)^2 / 0.020 = 0.09 / 0.020 = 4.5s.

[0313] As T_remain = min(6.4, 24.0, 4.5) = 4.5s is calculated, the air cell (20) with z=3 is determined to be the most vulnerable. If T_remain does not meet the preset standard (e.g., 30 seconds to 300 seconds), the remaining time calculation unit (152) outputs a pump drive reservation signal to the pump drive module (120).

[0314] As a comparative example, if a method is applied in which the pump (50) is driven only after the tolerance expansion reaches the final stage without a remaining time calculation unit (152), the pump (50) is driven suddenly at the final stage, causing noise during sleep and a problem where the pressure of the air cell (20) is out of the target pressure range for a long time.

[0315] In contrast, in the embodiment described above, by preemptively scheduling pump operation when T_remain decreases below a reference level, it is possible to immediately operate the pump (50) at the time the user wakes up to quickly restore the reservoir pressure.

[0316] In summary, the remaining time calculation unit (152) calculates the remaining duration in real time according to mathematical formula 5 and preemptively schedules pump operation before the tolerance expansion reaches the final stage, thereby enabling the advantage of quickly restoring the reservoir pressure after the end of the sleep period and completing preparations for the next sleep period.

[0317] As explained above, the configuration and operation of the low-noise pressure control-based air cell mattress system using a dual reservoir according to the present invention have been described in the above description and drawings; however, this is merely an example, and the concept of the present invention is not limited to the above description and drawings. It is understood that various changes and modifications are possible within the scope of the technical concept of the present invention. Explanation of the symbols

[0318] 10: Mattress body 20: Air cell 30: 1st Reservoir 40: 2nd Reservoir 50: Pump 60: Valve Assembly 70: Pressure sensor 100: Controller 110: Water level determination module 120: Pump drive module 130: Low-noise control module 131: Valve pulse output unit 140: Pressure Compensation Module 150: Sleep Period Extension Module 151: Valve sequence adjustment unit 152: Remaining time calculation unit

Claims

Claim 1 An air cell mattress system based on low-noise pressure control using dual reservoirs, comprising: a mattress body having a plurality of air cells; a first reservoir storing compressed air at a pressure higher than the target pressure of the air cells to pressurize the air cells; a second reservoir maintaining a pressure lower than the target pressure to depressurize the air cells and collecting air discharged from the air cells without releasing it into the atmosphere; a plurality of pressure sensors measuring the pressure of the air cells and the first and second reservoirs; a valve assembly selectively connecting the first and second reservoirs and the air cells; and a pump that sucks in the air collected in the second reservoir, compresses it, and supplies it to the first reservoir. An air cell mattress system characterized by comprising: a controller including a sleep determination module that determines whether a user is sleeping based on pressure measured from a plurality of pressure sensors and determines a sleep period; a pump driving module that drives the pump outside the sleep period to maintain the pressure of the first reservoir higher than the target pressure and the pressure of the second reservoir lower than the target pressure; and a low-noise control module that stops the operation of the pump during the sleep period and maintains the pressure of the air cell within the target pressure range solely through valve pulse control of the valve assembly. Claim 2 An air cell mattress system according to claim 1, wherein the controller further comprises a pressure compensation module that performs at least one of the following: expanding the allowable range of the target pressure, driving the pump for a limited time only when the sleep determination module determines the user's wake-up, or releasing the sleep period, when the pressure of either the first or second reservoir measured by the plurality of pressure sensors during the sleep period deviates from a preset threshold. Claim 3 An air cell mattress system according to claim 1, wherein the low-noise control module comprises a valve pulse calculation unit that calculates the valve pulse duration of the valve assembly based on the error between the current pressure of the air cell measured by the plurality of pressure sensors and the target pressure, and the pressure difference between the first and second reservoirs and the air cell. Claim 4 An air cell mattress system according to claim 3, wherein the valve pulse generating unit suppresses valve pulse generation when the absolute value of the error is within a preset dead band, and calculates the valve pulse duration τ according to the following mathematical formula 1 when the absolute value of the error exceeds the dead band. (Here, e is the difference between the target pressure and the current pressure of the air cell (Pa), ΔP is the difference between the pressure of the first reservoir and the pressure of the air cell during pressurization and the difference between the pressure of the air cell and the pressure of the second reservoir during depressurization, and is positive in both cases (Pa), f(ΔP) is a monotonically increasing function of ΔP normalized to maintain pressure units (Pa), k_τ is a calibration coefficient (s^-1), ε_τ is the minimum value of the denominator (Pa / s), τ_min and τ_max are the lower and upper limits of the valve pulse duration (s), clamp(x, τ_min, τ_max) is a function that limits x to between τ_min and τ_max) Claim 5 An air cell mattress system according to claim 1, wherein the pump driving module includes a margin estimation unit that estimates the pressurization margin of the first reservoir and the depressurization margin of the second reservoir according to the following mathematical formulas 2 and 3, and drives the pump so that the pressurization margin and depressurization margin are greater than or equal to a preset threshold before entering the water surface section. Mathematical formula 2. (Here, M_HP is the pressurization margin (Pa) of the first reservoir (30), P_HP is the pressure (Pa) of the first reservoir, P_set(z) is the target pressure (Pa) of the z-th air cell, ΔP_guard is the maintenance margin (Pa), the max calculation is performed only on air cells where P_z < P_set(z), i.e., air cells requiring pressurization, and if there are no air cells requiring pressurization, M_HP is calculated as M_HP = P_HP - max_z(P_z) - ΔP_guard, z = 1, 2, ..., N (N is the total number of air cells)) Equation 3. (Here, M_LP is the pressure reduction margin (Pa) of the second reservoir (40), P_z is the current pressure (Pa) of the z-th air cell, P_LP is the pressure (Pa) of the second reservoir, P_set(z) is the target pressure (Pa) of the z-th air cell, the min calculation is performed only on air cells where P_z > P_set(z), i.e., air cells requiring pressure reduction, and if there are no air cells requiring pressure reduction, M_LP is calculated as M_LP = min_z(P_set(z)) - P_LP, z = 1, 2, ..., N (N is the total number of air cells)) Claim 6 An air cell mattress system according to claim 1, wherein the controller further comprises a sleep section extension module that maintains the sleep section by progressively expanding the allowable error of the target pressure when the pressurization margin of the first reservoir and the depressurization margin of the second reservoir sequentially decrease to less than a preset step threshold during the sleep section. Claim 7 In claim 6, the above-mentioned sleep interval extension module comprises a valve sequence adjustment unit that calculates a valve control priority index for each of the above-mentioned air cells according to the following mathematical formula 4, and sequentially applies valve pulses starting from the air cells with the highest valve control priority index, thereby offsetting the pressure consumption of the first reservoir and the second reservoir by alternately applying valve pulses to air cells requiring pressurization because they are lower than the target pressure and air cells requiring depressurization because they are higher than the target pressure, thereby delaying the expansion of the allowable error by delaying the point in time when the pressurization margin of the first reservoir and the depressurization margin of the second reservoir decrease below the step threshold. Mathematical Formula 4. (Here, e(z) is the error (Pa) between the current pressure of the air cell and the target pressure, M_res(z) is the pressure difference between the first reservoir (30) and the corresponding air cell (20) when pressurizing or the pressure difference between the corresponding air cell (20) and the second reservoir (40) when depressurizing (Pa), f(ΔP(z)) is a monotonically increasing function (Pa) for the directional pressure difference between the reservoir and the air cell, and the larger I(z) is, the more preferentially the valve pulse control of the corresponding air cell is performed.) Claim 8 An air cell mattress system according to claim 7, wherein the sleep interval extension module includes a remaining time calculation unit that calculates the remaining duration of the sleep interval according to the following mathematical formula 5, and outputs a pump drive reservation signal to the pump drive module before the tolerance expansion step reaches the final step when the remaining duration is less than a preset standard. Mathematical formula 5. (Here, T_remain is the remaining time (s) during which the above water surface section can be maintained with the current reservoir pressure margin, M_res(z) is the pressurization or depressurization margin (Pa) per air cell according to Equation 4 above, M_0 is the reference pressure margin (Pa) of the first and second reservoirs, a normalization constant with M_res(z) / M_0 as dimensionless, r(z) is the normalized equivalent pressure consumption rate (1 / s) per air cell due to the valve pulse control, and γ is a non-linear damping coefficient greater than 1, which is a coefficient set so that the remaining sustainment time decreases non-linearly as the reservoir pressure margin decreases.)

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