EP3677312A1 - Masque de pollution et procédé de commande - Google Patents

Masque de pollution et procédé de commande Download PDF

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Publication number
EP3677312A1
EP3677312A1 EP19150469.5A EP19150469A EP3677312A1 EP 3677312 A1 EP3677312 A1 EP 3677312A1 EP 19150469 A EP19150469 A EP 19150469A EP 3677312 A1 EP3677312 A1 EP 3677312A1
Authority
EP
European Patent Office
Prior art keywords
fan
mask
breathing
worn
rotation speed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19150469.5A
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German (de)
English (en)
Inventor
William Su
Weizhong Chen
Terry KONG
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips NV filed Critical Koninklijke Philips NV
Priority to EP19150469.5A priority Critical patent/EP3677312A1/fr
Priority to JP2021513877A priority patent/JP6944089B1/ja
Priority to EP19773071.6A priority patent/EP3856360B1/fr
Priority to CN201980063449.3A priority patent/CN112770815B/zh
Priority to PCT/EP2019/075272 priority patent/WO2020064520A1/fr
Priority to CN201910919537.0A priority patent/CN110947114B/zh
Priority to CN201921619383.5U priority patent/CN211751892U/zh
Publication of EP3677312A1 publication Critical patent/EP3677312A1/fr
Withdrawn legal-status Critical Current

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    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
    • A62B18/00—Breathing masks or helmets, e.g. affording protection against chemical agents or for use at high altitudes or incorporating a pump or compressor for reducing the inhalation effort
    • A62B18/006—Breathing masks or helmets, e.g. affording protection against chemical agents or for use at high altitudes or incorporating a pump or compressor for reducing the inhalation effort with pumps for forced ventilation

Definitions

  • This invention relates to a pollution mask, for providing filtered air to the wearer of the breathing apparatus, with the flow assisted by a fan.
  • the World Health Organization estimates that 4 million people die from air pollution every year. Part of this problem is the outdoor air quality in cities. The worst in class are Indian cities like Delhi that have an annual pollution level more than 10 times the recommended level. Well known is Beijing with an annual average 8.5 times the recommended safe levels. However, even in European cities like London, Paris and Berlin, the levels are higher than recommended by the WHO.
  • the benefit to the wearer of using a powered mask is that the lungs are relieved of the slight strain caused by inhalation against the resistance of the filters in a conventional non-powered mask.
  • a powered mask delivers a steady stream of air to the face and may for example provide a slight positive pressure, which may be determined by the resistance of an exhale valve, to ensure that any leakage is outward rather than inward.
  • the pressure inside the mask can be measured and both pressure as well as pressure variation can be used to control the fan.
  • the pressure inside a mask can be measured by a pressure sensor and the fan speed can be varied in dependence on the sensor measurements.
  • a pressure sensor is costly so it would be desirable to provide an alternative method of monitoring pressure inside a mask.
  • Such pressure information may be used to control a fan within a powered mask, but it may be used as part of any other fan-based system where pressure information is desired.
  • Fan-operated masks are battery-operated devices, so that it is desirable to reduce power consumption to a minimum as well as keeping the cost to a minimum.
  • One issue is that the fan may be left on when the mask is not being worn, and this results in unnecessary power consumption. It is possible to provide sensors dedicated to detecting when the mask is worn, but this increases the cost of the breathing mask.
  • This method can work well if the fan speed signal is sampled at a high sampling rate, because detailed analysis of the signal can then be conducted. However, it would be preferred to have a lower sampling rate in order to save power.
  • the breathing can be tracked well, but the background noise will also be included, and there will be high power consumption.
  • a pollution mask comprising:
  • the first value relates to a depth of breathing when there is breathing detected, and by this is meant there is a positive correlation between the first value and the depth of breathing.
  • the second value relates to a rate of breathing when there is breathing detected, and by this is meant there is a positive correlation between the second value and the rate of breathing.
  • the first value may for example relate to (i.e. correlate with) a magnitude of a pressure fluctuation across the fan (whether or not this pressure fluctuation is caused by breathing) and the second value may for example relate to (i.e. correlate with) a rate of a pressure fluctuation (whether or not this pressure fluctuation rate is caused by breathing).
  • the pressure fluctuations are caused by breathing when the mask is worn and in normal use, whereas any detected pressure fluctuations when the mask is not worn will be caused by other factors.
  • the invention relates to a pollution mask.
  • a pollution mask By this is meant a device which has the primary purpose of filtering ambient air to be breathed by the user.
  • the mask does not perform any form of patient treatment.
  • the pressure levels and flows resulting from the fan operation are intended solely to assist in providing comfort (by influencing the temperature or relative humidity in the air chamber) and/or to assist in providing a flow across a filter without requiring significant additional breathing effort by the user.
  • the mask does not provide overall breathing assistance compared to a condition in which the user does not wear the mask.
  • a fan speed (for a fan which drives air into the chamber and/or expels it from the chamber) may be used as a proxy of pressure measurement.
  • the fan itself may be used so that no additional sensors are required.
  • the chamber may be closed in normal use, so that pressure fluctuations in the chamber have an influence on the load conditions of the fan and hence alter the fan electrical characteristics.
  • the fan electrical characteristics may determine the nature of the chamber, for example its volume, and if it is an open or closed volume.
  • the fan rotation signal is analyzed so that false positives (i.e. the mask is wrongly detected as not worn) and false negatives (the mask is wrongly detected as worn) are avoided.
  • This is achieved by taking account both of the pressure fluctuation level, which is indicative of the depth of breathing when breathing is detected, as well as the rate of pressure fluctuation, which is indicative of the breathing rate when breathing is detected. In this way, normal breathing may be detected (as in the already proposed but unpublished solution of the applicant) but also the pressure fluctuations relating during speaking may also be detected. This enables reliable detection of breathing with a reduced sampling rate.
  • the mask design By determining if the mask is worn, the mask design enables power to be saved when the mask is not being worn, but without requiring any additional sensors.
  • this indicates that both sides are at atmospheric pressure and the mask is not being worn.
  • the fan may be turned off if it is detected that the mask is not worn.
  • a threshold may be set for this detection, but the false detection outcomes are avoided by additionally taking account of the rate of pressure fluctuation.
  • the first value is for example a maximum swing in fan rotation speed during a sampling window, and the controller is adapted to set a first threshold to the first value.
  • This swing is representative of the degree of pressure fluctuation, and hence for breathing it relates to the depth of breathing.
  • the sampling window is chosen to be sufficient to capture at least one full breathing cycle, for example 6 seconds to capture a full breathing cycle at the lowest breathing rate of 10 breaths per minute.
  • the data sampling rate within the window can be selected to be as low as possible to save power and data processing.
  • the sampling rate may be fixed so that it can cope with the fastest breathing rate. For example, for a fastest breathing rate of 30 breaths per minute, the sampling rate may be 2Hz (4 times the maximum breathing frequency).
  • an alternative option is to sample the fan rotation speed, while breathing is detected, at a rate which depends on the second value. In this way, a lowest sampling rate can be maintained, to save power,
  • the first threshold is for example dependent on the average fan rotation speed.
  • the change in fan rotation speed caused by breathing may depend on the fan rotation speed itself.
  • a greater change in fan rotation speed may result from a given breathing pattern when the fan is driven to a faster speed.
  • the average fan rotation speed may be obtained by measurement of preceding samples, or it may be known from the drive signal applied to the fan by the controller. Both of these options are intended to be covered.
  • the second value is for example a frequency based on the time between a consecutive maxima and minima in the fan rotation speed. For breathing, this is half the breathing period.
  • the controller may then be adapted to determine that there is breathing detected and hence the mask is worn when the first value exceeds the threshold and the second value lies in a predetermined range.
  • a certain depth of breathing is required to be detected as well as a certain range of breathing rates.
  • the predetermined range is for example 12 to 30 cycles per minute, corresponding to the typical range of breathing rates.
  • the controller may be adapted to apply a time period during which breathing must continuously not be detected before determining that the mask is not worn. In this way, the risk of falsely turning off the fan is reduced.
  • the filter for example forms a boundary directly between the air chamber and the ambient surroundings outside the air chamber. This provides a compact arrangement which avoids the need for flow transport passageways. It means the user is able to breathe in through the filter.
  • the filter may have multiple layers. For example, an outer layer may form the body of the mask (for example a fabric layer), and an inner layer may be for removing finer pollutants. The inner layer may then be removable for cleaning or replacement, but both layers may together be considered to constitute the filter, in that air is able to pass through the structure and the structure performs a filtering function.
  • the filter thus preferably comprises an outer wall of the air chamber and optionally one or more further filter layers. This provides a particularly compact arrangement and enables a large filter area, because the mask body performs the filtering function. The ambient air is thus provided directly to the user, when the user breathes in, through the filter.
  • a maximum pressure in the air chamber in use is for example below 4cm H 2 O, for example below 2cm H 2 O, for example below 1cm H 2 O, higher than the pressure outside the air chamber. If the fan is for providing an increased pressure in the air chamber (e.g. a flow into the air chamber during inhalation), it is only required to provide a small increased pressure, for example for assisting inhalation of the user.
  • the fan may be only for drawing air from inside the air chamber to the outside. In this way, it may at the same promote a supply of fresh filtered air to the air chamber even during exhalation, which improves user comfort.
  • the pressure in the air chamber may be below the outside (atmospheric) pressure at all times so that fresh air is always supplied to the face.
  • the fan is driven by an electronically commutated brushless motor
  • the means for determining rotation speed comprises an internal sensor of the motor.
  • the internal sensor is already provided in such motors to enable rotation of the motor.
  • the motor may even have an output port on which the internal sensor output is provided. Thus, there is a port which carries a signal suitable for determining the rotation speed.
  • the means for determining the rotation speed may comprise a circuit for detecting a ripple on the electrical supply to a motor which drives the fan.
  • the ripple results from switching current through the motor coils, which cause induced changes in the supply voltage as a result of the finite impedance of the input voltage source.
  • the fan may be a two-wire fan and the circuit for detecting a ripple comprises a high pass filter.
  • the additional circuitry needed for a motor which does not already have a suitable fan speed output can be kept to a minimum.
  • the mask may further comprise an outlet valve for controllably venting the air chamber to the outside.
  • the outlet valve may comprise a passive pressure-regulated check valve or an actively driven electrically controllable valve. This may be used to make the mask more comfortable. During inhalation, by closing the valve (actively or passively), it is prevented that unfiltered air is drawn in. During exhalation, the valve is opened so that breathed out air is expelled.
  • the controller may be adapted to determine a respiration cycle, and to control the controllable valve in dependence on the phase of the respiration cycle.
  • the pressure monitoring thus provides a simple way to determine inhalation phases, which may then be used to control the timing of a venting valve of the mask or to determine whether or not the mask is worn and hence in use.
  • the controller may be adapted to turn off the fan during an inhalation time. This may be used to save power. Shutting down the fan during inhalation may be desirable for a user who does not have difficulty breathing through the filter, to save power if configured in such a way.
  • the system may enable the mask to be operated in different modes as well as being turned off when it is not being worn.
  • the mask may further comprise:
  • This feature enables the fan to be started when a mask is worn, by detecting electrical spikes causes by manual rotation of the fan. This rotation is for example caused by the user wearing the mask and breathing through the fan, when the fan is not electrically driven. These movements are then detected, in order to provide automatic turn on of the fan.
  • This approach does not require active sensing that the mask is worn but instead, the breathing of the user provides the energy for the sensing function.
  • the sensing may be integrated into the fan circuitry with low overhead and low power consumption.
  • the fan may be used as a sensor for detecting transition from a worn to not worn status as well as from a not worn to a worn status of the mask.
  • Examples in accordance with another aspect of the invention provide a method of controlling a pollution mask, comprising:
  • the first value may be a maximum swing in fan rotation speed during a sampling window
  • the method comprises setting a first threshold to the first value
  • the second value may be a frequency based on the time between a consecutive maxima and minima in the fan rotation speed
  • the method may further comprise determining that there is breathing detected and hence the mask is worn when the first value exceeds the threshold and the second value lies in a predetermined range.
  • the fan may be turned off if it is detected that the mask is not worn.
  • the fan speed is thus used as a proxy for measurement of a pressure or relative pressure and this proxy measurement is used to detect whether or not the mask is being worn based on both the depth of breathing and rate of breathing. These must both be consistent with breathing of the user.
  • the method may comprise driving the fan using an electronically commutated brushless motor, and the rotation speed is determined by an internal sensor of the motor.
  • the rotation speed may be obtained by detecting a ripple on the electrical supply to a motor which drives the fan. This may be applied to any type of motor, such as a conventional DC motor with brushes.
  • the mask may comprise an electrically controllable valve for controllably venting an air chamber to the outside.
  • a respiration cycle may then be determined from the pressure monitoring system, and the method may comprise controlling the controllable valve in dependence on the phase of the respiration cycle.
  • the mask may instead simply have a pressure-regulating release valve.
  • the invention provides a pollution mask.
  • a fan rotation speed or change in fan rotation speed is monitored, and from this a first value relating to magnitude of a pressure fluctuation across the fan and a second value relating to a rate of pressure fluctuation are obtained. It can then be determined whether or not the mask is worn based on the first and second values. This provides a reliable detection of whether or not the mask is worn and it requires a small amount of sampling data of the fan rotation signal, hence saving power.
  • a first detection function is to provide fan rotation speed monitoring (as a proxy for pressure measurement) and use this to detect if the mask is worn or not, and in particular it enables a transition from worn to not worn to be detected.
  • a second detection function is to enable a transition from not worn (and with the mask fan turned off) to worn to be detected.
  • Both detection functions aim to avoid requiring significant power consumption from any sensors, and without requiring significant additional hardware complexity.
  • Figure 1 shows a monitoring system implemented as part of a face mask.
  • a subject 10 is shown wearing a face mask 12 which covers the nose and mouth of the subject.
  • the purpose of the mask is to filter air before it is breathed in the subject.
  • the mask body itself acts as an air filter 16. Air is drawn in to an air chamber 18 formed by the mask by inhalation. During inhalation, an outlet valve 22 such as a check valve is closed due to the low pressure in the air chamber 18.
  • the filter 16 may be formed only by the body of the mask, or else there may be multiple layers.
  • the mask body may comprise an external cover formed from a porous textile material, which functions as a pre-filter. Inside the external cover, a finer filter layer is reversibly attached to the external cover. The finer filter layer may then be removed for cleaning and replacement, whereas the external cover may for example be cleaned by wiping.
  • the external cover also performs a filtering function, for example protecting the finer filter from large debris (e.g. mud), whereas the finer filter performs the filtering of fine particulate matter.
  • outlet valve 22 When the subject breathes out, air is exhausted through the outlet valve 22.
  • This valve is opened to enable easy exhalation, but is closed during inhalation.
  • a fan 20 assists in the removal of air through the outlet valve 22. Preferably more air is removed than exhaled so that additional air is supplied to the face. This increases comfort due to lowering relative humidity and cooling.
  • the outlet valve may be a simple passive check valve operated by the pressure difference across the filter 16. However, it may instead be an electronically controlled valve.
  • the different prevailing pressure will manifest itself as a different load to the fan, since there is a different pressure drop across the fan. This altered load will then result in a different fan speed.
  • the first detection function is based in part on the recognition that the rotation speed of a fan may be used as a proxy for a measurement of pressure across the fan. It is also based in part of the recognition that pressure levels and cyclic frequency rates may be used to determine whether or not the mask is worn. The invention combines these considerations to create a mask which can save power by switching off when it is not worn, and without requiring complex or costly additional sensors.
  • the pressure monitoring enables determination of a pressure, or at least a pressure change, on the other side of the fan.
  • This other side is for example a closed chamber which thus has a pressure different to atmospheric pressure.
  • it can then be determined that the chamber is not closed but is connected to atmospheric pressure on both sides.
  • This absence of a fan speed variation may thus be used to determine that the mask is not worn and hence not in use. This information can be used to switch off the fan to save power.
  • the applicant has already proposed (but not yet published) a pressure monitoring system which has a means for determining a rotation speed of the fan and a controller for deriving a pressure or detecting a pressure change from the rotation speed of the fan. It is then also proposed to use that pressure information to determine whether the mask is worn or not.
  • the means for determining a rotation speed may comprise an already existing output signal from the fan motor or a separate simple sensing circuit may be provided as an additional part of the fan. However, in either case fan itself is used so that no additional sensors are required.
  • FIG 2 shows one example of the components of the proposed pressure monitoring system.
  • the same components as in Figure 1 are given the same reference numbers.
  • Figure 2 shows a controller 30, a local battery 32 and a means 36 for determining the fan rotation speed.
  • the fan 20 comprises a fan blade 20a and a fan motor 20b.
  • the fan motor 20b is an electronically commutated brushless motor
  • the means for determining rotation speed comprises an internal sensor of the motor.
  • Electronically commutated brushless DC fans have internal sensors that measure the position of the rotor and switch the current through the coils in such a way that the rotor rotates. The internal sensor is thus already provided in such motors to enable feedback control of the motor speed.
  • the motor may have an output port on which the internal sensor output 34 is provided. Thus, there is a port which carries a signal suitable for determining the rotation speed.
  • the means for determining the rotation speed may comprise a circuit 36 for detecting a ripple on the electrical supply to the motor 20b.
  • the ripple results from switching current through the motor coils, which cause induced changes in the supply voltage as a result of the finite impedance on the battery 32.
  • the circuit 36 for example comprises a high pass filter so that only the signals in the frequency band of the fan rotation are processed. This provides an extremely simple additional circuit, and of much lower cost than a conventional pressure sensor.
  • the motor can be of any design, including a two-wire fan with no in-built sensor output terminal. It will also work with a DC motor with brushes.
  • the controller may use the rotation speed information, based on the corresponding pressure information, to determine a respiration cycle.
  • the respiration cycle timing information may then be used to control the outlet valve 22 in dependence on the phase of the respiration cycle.
  • the pressure monitoring thus provides a simple way to determine inhalation phases, which may then be used to control the timing of the outlet valve 22 of the mask.
  • the controller may turn off the fan during an inhalation time or an exhalation time.
  • the controller may also turn off the fan if it is detected that the fan is not worn. This gives the mask different operating modes, which may be used to save power.
  • the calibration process for example involves analyzing the fan speed information over a period during which the subject is instructed to inhale and exhale regularly with normal breathing. The captured fan speed information can then be matched to the breathing cycle, from which threshold values can then be set for discriminating between inhalation and exhalation.
  • Figure 3 shows schematically the rotor position (as a measured sensor voltage) against time.
  • the rotational speed may be measured from the frequency of the AC component (caused by the switching events in the motor) of the DC voltage to the fan.
  • This AC component originates from the current variation that the fan draws, imposed on the impedance of the power supply.
  • Figure 3 shows the signal during inhalation as plot 40 and during exhalation as plot 42. There is a frequency reduction during exhalation caused by an increased load on the fan by the increased pressure gradient. The observed frequency changes thus results from the different fan performance during the breathing cycle.
  • fan operation forces air out of the area between face and mask. This enhances comfort because exhalation is made easier. It can also draw additional air onto the face which lowers the temperature and relative humidity. Between inhalation and exhalation, the fan operation increases comfort because fresh air is sucked into the space between the face and the mask thereby cooling that space.
  • the outlet valve is closed (either actively or passively) and the fan can be switched off to save power. This provides a mode of operation which is based on detecting the respiration cycle.
  • the power to the fan can be increased by 30% for enhanced effectiveness.
  • the pressure monitoring may be used to measure the flow resistance of the filter, in particular based on the pressure drop across the fan and filter. This can be done at switch on, when the mask is not on the face for a period of time. That resistance can be used as a proxy for the age of the filter.
  • the first detection function as described above makes use of the fan to provide a proxy pressure measurement which is then used to detect that the mask is not worn.
  • the pressure information may also be used for many other functions as described above.
  • This first detection function requires the fan to be active, so it enables the transition from worn (with the fan on) to not worn to be detected. When the mask is to be worn again (or for the first time), the user may operate a manual switch to start the fan again.
  • the second detection function mentioned above avoids the need for a main switch or any sensors. Indeed, the fan itself is again used as a sensor. With special electronics this sensing task can be performed even when the fan is switched off.
  • the fan When the mask with the fan is put on the face and the user starts to breathe, the fan will rotate even when not switched on because air is forced through the fan.
  • the speed detection function is based on determining this rotation without the use of additional sensors with the fan switched off. That signal is subsequently used to switch on the fan for proper operation of the mask.
  • a fan using an electronically commutated brushless DC motor has internal sensors that measure the position of the rotor and switch the current through the coils in such a way that the rotor rotates.
  • FIG. 4 shows an H-bridge circuit which functions as an inverter to generate an alternating voltage to the stator coils 50 from a DC supply VDD, GND.
  • the inverter has a set of switches S1 to S4 to generate an alternating voltage across the coil 50.
  • the H-bridge circuit is provided between a high voltage rail VDD and a virtual ground.
  • the virtual ground GND is connected to a low voltage rail VDD- through a transistor arrangement Q1.
  • the virtual ground may vary between VDD+ and VDD- depending on the operating state of the circuit.
  • the fan has a switch control circuit 52, and the fan circuitry, including the switches, coils and control circuit, are connected to VDD+ and GND as the supply voltage lines.
  • the control circuit provides the switching signals to the switches, but to avoid cluttering Figure 5 , these control signal lines are not shown.
  • the control circuit for example include Hall sensors for rotor position sensing.
  • One coil terminal Co1 provides an output to a detection circuit 54. Since there is a DC voltage superimposed, a high pass filter of capacitor C1 and resistor R1 is used between the detection circuit 54 and the coil terminal Co1. The pulses that come from the high pass filter are rectified by a diode D2 and cause charge to be stored in a storage capacitor C2.
  • the storage capacitor builds up a base voltage for the transistor arrangement Q1 (shown as a Darlington pair of bipolar transistors).
  • the storage capacitor prevents the transistor arrangement quickly switching on and off in phase with the pulses.
  • the transistor arrangement Q1 will turn on (creating a closed circuit) and the fan will start to run because the supply voltage is then increased to the full VDD+ top VDD- voltage swing. That running generates enough pulses to keep the fan running.
  • the base of the transistor arrangement Q1 may be driven to ground long enough to stop the fan from rotating. This may be achieved using a shut-down circuit 51 such as a transistor which discharges the capacitor C2.
  • the switch Q1 can be replaced with a MOSFET and optionally a gate amplifier.
  • Digital logic circuits can be used to route the coil rotation signal and mask worn or not worn signal to the gate driver.
  • the pulses that charge the capacitor C2 will raise the voltage of the base of Q1 and eventually turn it ON.
  • the level of the virtual ground GND is then pulled down to VDD-. At that moment, current can flow from VDD+ to VDD-. This give s power to the coils and the control circuit 52 of the fan that subsequently starts to run as long as there is enough voltage.
  • the shut down circuit 51 When C2 is charged and Q1 is on the shut down circuit 51 is used to discharge the capacitor C2 to stop the fan.
  • an npn transistor or a FET transistor maybe used to short circuit the capacitor C2.
  • the shorting signal may be derived from a breathing pattern. If there are no measured frequency fluctuations, the capacitor C2 is shorted to turn off the transistor arrangement, and thereby reduce the supply voltage because GND- rises back up towards the voltage VDD+.
  • This invention provides an enhancement to the automatic turn off function as described above, namely the detection that the mask is not worn.
  • the detection that the mask is not worn is used in the same way as explained above, but the detection is made more accurate while also enabling a low sampling rate of the fan rotation signal to be achieved.
  • the invention may be implemented using the system as shown in Figure 2 but with a different method and hence analysis implemented by the controller.
  • analysis of the fan rotation signal yields a first value relating to magnitude of a pressure fluctuation across the fan.
  • This first value when consistent with a breathing signal, thus relates to the depth of breathing.
  • the first value may comprise the difference between the maximum fan rotation speed and the minimum fan rotation speed during a sampling window.
  • a second value is derived which relates to a rate of pressure fluctuation, i.e. a rate of breathing when consistent with a breathing signal.
  • the normal adult breathing frequency range is 12-18 breaths per minute (BrPM).
  • the breathing frequency will also increase.
  • the breathing rate can reach 30 BrPM.
  • the sampling of the fan rotation signal needs to be carried out at a rate sufficient to collect the variations resulting from the breathing signals.
  • the sampling rate should be at least 2 times the maximum signal frequency (fs ⁇ 2fmax).
  • the maximum breathing frequency is 30 BrPM, namely 0.5Hz.
  • a 1 Hz sampling rate may be used.
  • a 1Hz sampling rate is not enough.
  • Figure 6A shows a fan speed signal (y-axis) over time (x-axis) for a sampling period of 2s at 30 BrPM. With a sampling rate of 1Hz and the sampling points may all be when the fan speed is zero.
  • a 2Hz sampling rate is needed as shown in Figures 6B and 6C .
  • a 2Hz sampling rate is a minimal sampling rate for a 30 BrPM breathing signal.
  • fs is the minimal sampling rate and f is the real time breathing frequency.
  • the breathing frequency will not maintain a stable value, but instead it depends on the user breathing characteristics (normal breathing, talking, laughing etc.). This means there is no fixed minimal sampling rate.
  • One method is to set the sampling rate based on the fastest breathing frequency, as the worst case situation. Based on this fastest breathing frequency, a fixed sampling rate may be set. This is not a power-efficient approach, since in some low breathing frequency cases, this sampling rate will be higher than is actually required.
  • the fastest breathing frequency of 30 BrPM means the fixed sampling rate maybe 2Hz.
  • the alternative method is to set the sampling rate in a dynamic way based on a previous number, such as one or two, of breathing cycles.
  • a previous number such as one or two
  • the frequency fs is dynamically adjusted in real time depending on the breathing characteristics.
  • the resulting frequency is then used to judge whether the frequency corresponds to a reasonable range for a breathing signal (12-30 BrPM).
  • the frequency f is a second value relating to a rate of pressure fluctuation. If the rate i.e. frequency is in the allowed range, then the pressure fluctuation is caused by breathing, but if it is not, it may be caused by other air disturbances.
  • the sampling time window determines the required data buffer size and this data is updated (overwritten) in real time during breath tracking.
  • the sampling time window needs to record at least one breathing cycle. Based on a breathing rate of 10 to 30 BrPM. the sample time period is 6 seconds based on 10 BrPM.
  • Threshold values for the first and second values are used to determine if the detected pressure signal is a real breathing signal or not. If the threshold values are not not properly set, it is likely that the fan will be turned off by mistake, or the mask may need to be turned off while it is still working.
  • Figure 7 shows the pressure (in Pa, plot 70, using the left y-axis) and fan rotation speed (in RPM, plot 72, using the right y-axis).
  • a normal breathing phase 74, a light breathing phase 76 and a talking phase 78 are shown.
  • the first values such as the difference between the maximum fan rotation speed and the minimum fan rotation speed during a sampling window, may be measured from Figure 7 to be:
  • the breathing threshold should consider the worst case (lightest breathing). There is however a risk of false detection if the threshold is too low.
  • the lightest breathing volume takes place during a least active status (such as sitting) with a 0.5L breathing volume.
  • a least active status such as sitting
  • a 0.5L breathing volume Based on a breathing rate of 12 BrPM and 0.5L volume, the difference in fan rotation signal ( ⁇ RPM) can be tested under different fan speed settings.
  • Table 1 below shows such test data based on 12 BrPM, 0.5L, with some leakage, under different fan speed settings.
  • Fan speed setting ⁇ RPM Threshold 5000 RPM 165 RPM 82 RPM 6500 RPM 347 RPM 173 RPM 7400 RPM 365 RPM 132 RPM 8500 RPM 464 RPM 232 RPM
  • the threshold may be set in dependence on the prevailing fan speed setting, i.e. the first threshold for the first value is preferably made dependent on the average fan rotation speed during the sampling window, which corresponds generally to the fan speed setting.
  • the fan speed setting may be known to the controller and provided as input or the actual average fan speed maybe measured (e.g. based on a low pass filtered version of the fan rotation signal).
  • the threshold is set near half the ⁇ RPM value. This is because the use of a reduced sampling rate means the peak and valley of the real breathing signal may not be sampled as seen in Figure 6B .
  • Figure 8 shows plots similar to Figure 7 (pressure plot 70 and RPM plot 72) for the talking period. It shows that the pressure signal amplitude change during talking is more obvious than during normal breathing. However, the fan rotation signal shows a signal amplitude smaller than during normal breathing. This is because a pressure sensor has a response time much faster than the fan signal. The sudden inhaling after talking is detected by pressure sensing but the fan signal does not reflect this peak signal so quickly.
  • the fan rotation signal will react over a longer time so that a reduced sampling rate is able to capture the effect of the sudden inhaling signal after talking. For a 2Hz sample rate, at least a 0.5s time period is needed for the peak breathing signal.
  • Table 2 shows when the pressure peak occurs and when the rotation signal peak occurs for the 12 successive dips in the pressure signal 70 in Figure 8 .
  • Table 2 Cycle Pressure peak time(s) RPM peak time(s) 1 0.5 0.8 2 1 1.1 3 0.3 0.6 4 0.2 0.6 5 0.5 0.6 6 0.5 0.9 7 0.5 0.9 8 0.3 0.6 9 1.3 1.7 10 0.6 0.8 11 0.7 0.4 12 0.6 0.4
  • the detection of breathing is based on applying a first threshold to the first value, e.g. ⁇ RPM > threshold and applying a range to the second value, e.g. 12 ⁇ f ⁇ 30. If these conditions are both met, breathing is detected and the system will keep the fan on.
  • a delay time period may be applied during which breathing must continuously not be detected before determining that the mask is not worn. For example, a 10 second period maybe provided later before a turn off is implemented.
  • Figure 9 shows a mask operating method for detecting a worn to not worn transition.
  • the method may optionally start by turning on the fan automatically in step 80.
  • the method then comprises:
  • step 96 the method comprises determining whether the mask is worn or not based on the first and second values, as explained above. If the mask is not worn, and this is detected for the duration of the delay time, the fan may be switched off to save power.
  • the method may comprise driving the fan using an electronically commutated brushless motor, and the rotation speed is determined by an internal sensor of the motor.
  • the rotation speed may be obtained by detecting a ripple on the electrical supply to a motor which drives the fan.
  • the method may comprise determining a respiration cycle from the pressure monitoring system.
  • an electrically controllable outlet valve When used, it may be controlled dependence on the phase of the respiration cycle.
  • Figure 10 shows a mask operating method for detecting a not worn to worn transition. The method comprises:
  • the method may also include (subsequently) turning off the fan in step 104 if it is detected that the mask is not worn. This detection may be based on steps 91 to 96 of Figure 9 .
  • the initial step 80 in Figure 6 of turning on the fan may be performed based on the steps 100 and 102 of the method of Figure 10 .
  • the mask may be for covering only the nose and mouth (as shown in Figure 1 ) or it may be a full face mask.
  • the example shown is a mask for filtering ambient air.
  • the mask design described above has the main air chamber formed by the filter material, through which the user breathes in air.
  • An alternative mask design has the filter in series with the fan as also mentioned above.
  • the fan assists the user in drawing in air through the filter, thus reducing the breathing effort for the user.
  • An outlet valve enables breathed out air to be expelled and an inlet valve may be provided at the inlet.
  • the invention may again be applied for detecting the pressure variations caused by breathing for controlling the inlet valve and/or the outlet valve.
  • the fan in this example needs to be turned on during inhalation, to assist the user in drawing air through the series filter, but it may be turned off during exhalation when the outlet valve is open.
  • the pressure information derived may again be used to control the fan to save power when the fan operation is not needed.
  • the detection of whether the mask is worn or not may also be implemented.
  • the invention may be applied to many different mask designs, with fan-assisted inhalation or exhalation, and with an air chamber formed by a filter membrane or with a sealed hermetic air chamber.
  • the fan only for drawing air from inside the air chamber to the outside, for example when an exhaust valve is open.
  • the pressure inside the mask volume may be maintained by the fan below the external atmospheric pressure so that there is a net flow of clean filtered air into the mask volume during exhalation.
  • low pressure may be caused by the fan by during exhalation and by the user during inhalation (when the fan may be turned off).
  • An alternative option is the use of the fan only for drawing air from the ambient surroundings to inside the air chamber.
  • the fan operates to increase the pressure in the air chamber, but the maximum pressure in the air chamber in use remains below 4cm H 2 O higher than the pressure outside the air chamber, in particular because no high pressure assisted breathing is intended.
  • a low power fan may be used.
  • the pressure inside the air chamber preferably remains below 2cm H 2 O, or even below 1 cm H 2 O or even below 0.5cm H 2 O, above the external atmospheric pressure.
  • the pollution mask is thus not for use in providing a continuous positive airway pressure, and is not a mask for delivering therapy to a patient.
  • the mask is preferably battery operated so the low power operation is of particular interest.
  • the detection of the respiration cycle is a preferred feature as an additional use of the monitoring capability, but it is optional.
  • controller which can be implemented in numerous ways, with software and/or hardware, to perform the various functions required.
  • a processor is one example of a controller which employs one or more microprocessors that maybe programmed using software (e.g., microcode) to perform the required functions.
  • a controller may however be implemented with or without employing a processor, and also maybe implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions.
  • controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).
  • ASICs application specific integrated circuits
  • FPGAs field-programmable gate arrays
  • a processor or controller may be associated with one or more storage media such as volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM.
  • the storage media may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform the required functions.
  • Various storage media may be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller.
EP19150469.5A 2018-09-27 2019-01-07 Masque de pollution et procédé de commande Withdrawn EP3677312A1 (fr)

Priority Applications (7)

Application Number Priority Date Filing Date Title
EP19150469.5A EP3677312A1 (fr) 2019-01-07 2019-01-07 Masque de pollution et procédé de commande
JP2021513877A JP6944089B1 (ja) 2018-09-27 2019-09-20 汚染用マスク及びその制御方法
EP19773071.6A EP3856360B1 (fr) 2018-09-27 2019-09-20 Masque de pollution et procédé de commande
CN201980063449.3A CN112770815B (zh) 2018-09-27 2019-09-20 防污染面罩和控制方法
PCT/EP2019/075272 WO2020064520A1 (fr) 2018-09-27 2019-09-20 Masque anti-pollution et procédé de commande
CN201910919537.0A CN110947114B (zh) 2018-09-27 2019-09-26 防污染面罩及控制方法
CN201921619383.5U CN211751892U (zh) 2018-09-27 2019-09-26 防污染面罩

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19150469.5A EP3677312A1 (fr) 2019-01-07 2019-01-07 Masque de pollution et procédé de commande

Publications (1)

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EP3677312A1 true EP3677312A1 (fr) 2020-07-08

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EP (1) EP3677312A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0661071A1 (fr) * 1993-12-01 1995-07-05 Resmed Limited Dispositif pour la ventilation spontanée en pression positive continue (VSPPC)
WO2018215225A1 (fr) * 2017-05-22 2018-11-29 Koninklijke Philips N.V. Masque anti-pollution et procédé de commande

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0661071A1 (fr) * 1993-12-01 1995-07-05 Resmed Limited Dispositif pour la ventilation spontanée en pression positive continue (VSPPC)
WO2018215225A1 (fr) * 2017-05-22 2018-11-29 Koninklijke Philips N.V. Masque anti-pollution et procédé de commande

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