Improved control of aerosol generation in an aerosol generating system

Abstract

To provide control of aerosol production in an aerosol-generating system.SOLUTION: A system (100) includes an aerosol-generating element (119), and a housing (101) having an air inlet (123) and an air outlet (125). A flow channel from the air inlet (123) to the air outlet (125) configured to provide a flow of air passing through the aerosol-generating element (119). The system (100) includes a flow sensor (109) configured to detect an air flow in the flow channel. A method includes increasing the power supplied to the aerosol-generating element (119) for at least a second time if the flow sensor (109) detects that the flow rate of the air flow exceeds a threshold. There is also provided an aerosol-generating system comprising circuitry configured to practice the method.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for controlling aerosol generation in an aerosol generating system. The present invention further relates to an aerosol generating system. The present invention finds particular application as a method for controlling aerosol generation in an aerosol generating system through control of power provided to an aerosol generating element of the aerosol generating system. [Background technology]

[0002] WO2012 / 072790 discloses a method for controlling at least one electric heating element of an electrically heated aerosol generating system to heat an aerosol-forming substrate. The aerosol generating system has a sensor for detecting airflow, which indicates that a user is taking a puff having an airflow period. The method includes increasing heating power to the at least one heating element when the sensor detects that the airflow rate has increased to a first threshold, and decreasing heating power to the at least one heating element when the sensor detects that the airflow rate has decreased to a second threshold.

[0003] As disclosed in WO 2012 / 072790, energy usage can be optimized by controlling the heating power supplied to at least one heating element. The heating power can be adjusted for a particular puff profile so that desired aerosol characteristics, such as a particular aerosol concentration or particle size, can be achieved. Unnecessary overheating or underheating, particularly toward the beginning or end of a puff, can also be avoided. Reducing power toward the end of a puff affects the cooling of the heating element and therefore the temperature at and near the heating element. This, in turn, affects the amount of condensation that can form within the system, which can affect liquid leakage.

[0004] The disclosure of WO2012 / 072790 teaches how to minimize condensation of the aerosol produced by an aerosol generating device within the aerosol generating device by reducing the heating power supplied to the aerosol generating element before the end of the user's puff. However, this can be frustrating for the user, particularly during more complex puff profiles, if insufficient aerosol is delivered to the user after the power supplied to the aerosol generating element is reduced.

[0005] It is an object of the present invention to provide an improved method for controlling aerosol generation in an aerosol generating system, and in particular, to provide an improved method for controlling aerosol generation during complex puff profiles. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method for controlling aerosol generation in an aerosol generation system. The system comprises an aerosol generation element and a housing having an air inlet and an air outlet. A flow path is defined through the housing from the air inlet to the air outlet, the flow path providing a flow of air past the aerosol generation element when a user takes a puff on the system. The system further comprises a flow sensor configured to detect airflow in the flow path, which is indicative of the user taking a puff. The method comprises the following chronological steps: increasing the power supplied to the aerosol generation element from power P0 to at least power P1 when the flow sensor detects that the airflow rate is greater than a first threshold; reducing the power supplied to the aerosol generation element to power P2, where power P2 is less than power P1, when the flow sensor detects that the airflow rate is less than a second threshold, the second threshold being at or indicative of a rate that is a predetermined first percentage of a first maximum rate detected by the flow sensor; and increasing the power supplied to the aerosol generation element when the flow sensor detects that the airflow rate is greater than a third threshold before detecting that the airflow rate is less than the puff termination threshold, the third threshold being greater than the second threshold and the puff termination threshold being less than the second threshold.

[0007] The method steps are presented in chronological order, i.e., the order of the steps described above is the order in which the steps are performed. However, there may be more steps performed before, after, or between any of the method steps described above.

[0008] As used herein, the term "aerosol-generating system" may be used to describe a system configured to generate an aerosol. The aerosol may be for inhalation by a user. The aerosol-generating system may include an aerosol-generating device and a cartridge. The aerosol-generating device may include a power source. The cartridge may include an aerosol-forming substrate.

[0009] As used herein, the term "aerosol-generating element" may be used to describe one or more elements configured to generate an aerosol or vapor from an aerosol-forming substrate. One or more of the aerosol-generating elements, or elements that form the aerosol-generating element, may be connected to a power source. That is, the aerosol-generating system may include a power source configured to provide power to the aerosol-generating element.

[0010] As used herein, the term "aerosol-forming substrate" refers to a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound may be released by heating the aerosol-forming substrate. The aerosol generated from the aerosol-forming substrate of the aerosol-generating system according to the present invention may be visible or invisible and may include vapor (e.g., fine gaseous particles of a substance that is normally liquid or solid at room temperature) and liquid droplets of gas and condensed vapor.

[0011] As used herein, the term "flow rate" may be used to describe any parameter indicative of the flow rate through an aerosol generation system. For example, the defined "flow rate" may be one or more of pressure, flow velocity, temperature, mass flow rate, or volumetric flow rate. Thus, the defined "flow sensor" may detect one or more of pressure, flow velocity, temperature, mass flow rate, or volumetric flow rate.

[0012] As used herein, the term "puff detection system" may refer to a system that includes a flow sensor.

[0013] As used herein, the term "airflow" may be used to refer to the flow of air alone, or to the flow of air combined with aerosol droplets.

[0014] As used herein, the term "droplets" may be used to mean droplets or particles. That is, the term "droplets" may refer to liquid droplets. Alternatively, or additionally, the term "droplets" may refer to solid particles.

[0015] The flow sensor may include an electromechanical device, or a mechanical device, or an optical device, or an opto-mechanical device, or a microelectromechanical system (MEMS) based sensor, an acoustic sensor, or any combination of the foregoing.

[0016] As used herein, the term "puff" is used to describe an inhalation by a user that causes a flow of air through the aerosol generation system. The start of a puff is defined by the point at which the flow sensor detects that the flow rate is greater than the puff start threshold, and the end of a puff is defined by the point at which the flow sensor detects that the flow rate has decreased to below the puff end threshold.

[0017] As used herein, the term "predetermined" is used to mean determined prior to the start of a puff.

[0018] According to a first aspect of the present invention, a method for controlling aerosol generation includes increasing the power supplied to the aerosol generation element when the flow sensor detects that the airflow rate is greater than a third threshold before detecting that the airflow rate is less than the end-of-puff threshold. That is, the power supplied to the aerosol generation element may be increased more than once during a puff, depending on the puff profile. This advantageously enables the aerosol generation system to deliver sufficient aerosol to a user during a puff having a complex puff profile. In this context, the term "complex puff profile" is used to mean a puff profile that has at least one local maximum when plotting a graph of flow rate against time. For example, this process may mitigate potential problems in an exemplary puff profile that includes the following steps: Phase 1: The user puffs on the system and increases the detected airflow rate from zero to the first maximum rate. Stage 2: The detected flow rate is then reduced to a first local minimum flow rate that is greater than the end-of-puff threshold. · Phase 3: The flow rate is then increased to a second maximum flow rate. Stage 4: The flow rate then decreases below the end-of-puff threshold, indicating that the puff has ended.

[0019] If the power supplied to the aerosol-generating element is reduced between stages 2 and 3 of a puff and not increased again, the user may become frustrated with inadequate aerosol delivery during stages 3 and 4 of a puff. In a method according to the invention, the power supplied to the aerosol-generating element may be increased during stage 3. Thus, the user may receive adequate aerosol delivery during stages 3 and 4.

[0020] The power P0 may be zero. Advantageously, this may save power, which may mean that the aerosol generating system does not need to be recharged as frequently.

[0021] Alternatively, the power P0 may be a non-zero power, which may advantageously allow the system to more quickly deliver an appropriate aerosol in response to a detected puff.

[0022] Power P2 may be zero. Advantageously, this may conserve power, which may mean that the aerosol generating system does not need to be recharged as frequently.

[0023] Alternatively, power P2 may be a non-zero power, which may advantageously allow the system to more quickly deliver an appropriate aerosol in response to a detected flow rate greater than the third threshold.

[0024] The third threshold can be a predetermined second percentage of the first maximum flow rate, where the predetermined second percentage must be greater than the predetermined first percentage so that the third threshold is greater than the second threshold.

[0025] Alternatively, the third threshold may be a predetermined multiple of the second threshold, which must be greater than 1 so that the third threshold is greater than the second threshold. The predetermined multiple does not have to be an integer.

[0026] The first threshold may be a first constant.

[0027] The puff termination threshold may be a puff termination constant.

[0028] Increasing the power supplied to the aerosol generation element from power P0 to at least power P1 may include increasing the power supplied to the aerosol generation element to power PX, where PX is greater than or equal to power P1. If the flow sensor detects that the airflow rate is greater than a third threshold before detecting that the airflow rate is less than the end-of-puff threshold, increasing the power supplied to the aerosol generation element may include increasing the power supplied to the aerosol generation element to power P3, where P3 is less than PX. A P3 less than PX may be advantageous for typical puff profiles where a first maximum flow rate is the maximum flow rate during a puff.

[0029] The method may include a step of increasing the power supplied to the aerosol generation element if the flow sensor detects that the airflow rate is greater than a third threshold before detecting that the airflow rate is less than the puff termination threshold, followed by a step of reducing the power supplied to the aerosol generation element to power P4 when the flow sensor detects that the airflow rate is less than the puff termination threshold.

[0030] Power P4 may be zero. Advantageously, this may save power, which may mean that the aerosol generating system does not need to be recharged as frequently.

[0031] Alternatively, power P4 may be non-zero, which may advantageously allow the system to more quickly deliver the appropriate aerosol in response to the next detected puff.

[0032] The power P4 does not have to be zero, and the method may further include, after the step of reducing the power supplied to the aerosol generation element to power P4 when the flow sensor detects that the airflow rate is less than the puff termination threshold, reducing the power supplied to the aerosol generation element from power P4 to zero. Reducing the power supplied to the aerosol generation element from power P4 to zero may occur if another puff is not detected within a given time interval, for example, within five minutes or within three minutes after the power supplied to the aerosol generation element is reduced to power P4. That is, reducing the power supplied to the aerosol generation element from power P4 to zero may occur if a flow rate greater than the first threshold is not detected within a given time interval after the power supplied to the aerosol generation element is reduced to power P4.

[0033] The step of increasing the power supplied to the aerosol generation element from power P0 to at least power P1 may include increasing the power from power P0 to at least power P1 substantially instantaneously. That is, the power may be increased from power P0 to at least power P1 over a period of time substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a vertical or substantially vertical line from power P0 to at least power P1. For example, the term "substantially instantaneous" may be used to mean that the power may be increased from power P0 to at least power P1 within 0.1 seconds. Advantageously, increasing the power supplied to the aerosol generation element substantially instantaneously may result in faster generation of aerosol and less lag for the user.

[0034] Alternatively, increasing the power supplied to the aerosol generating element from power P0 to at least power P1 can include increasing the power stepwise from power P0 to at least power P1. That is, the power can be increased stepwise from power P0 to at least power P1 over a period of time. The longer the period, the more gradual the power increase. On a plot of heating power on the vertical axis versus time on the horizontal axis, this can be represented by a line having a positive average slope from power P0 to at least power P1. The slope of the line can be constant or non-constant. That is, the rate of change of power can be constant or non-constant. For example, the term "stepwise" can be used to mean that the power can be increased from power P0 to at least power P1 over a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds.

[0035] The step of reducing the power supplied to the aerosol generation element to power P2 may comprise reducing the power supplied to the aerosol generation element from at least power P1 to power P2.

[0036] The step of reducing the power supplied to the aerosol generation element to power P2 may include substantially instantaneously reducing the power supplied to the aerosol generation element to power P2. That is, the power may be reduced to power P2 over a period of time substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a vertical or substantially vertical line to power P2. For example, the term "substantially instantaneous" may be used to mean that the power may be increased to power P2 within 0.1 seconds.

[0037] Alternatively, the step of reducing the power supplied to the aerosol generating element to power P2 may include gradually reducing the power supplied to the aerosol generating element to power P2. That is, the power may be reduced over a period of time that is not equal to zero. That is, the power may be gradually reduced to power P2 over a period of time. The longer the period of time, the more gradual the power reduction. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a line with a negative average slope to power P2. The slope of the line may or may not be constant. For example, the term "gradually" may be used to mean that the power may be reduced to power P2 within a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds after the flow sensor detects that the airflow rate is less than the second threshold.

[0038] The method may include increasing the power supplied to the aerosol generation element from at least power P1 to power P5 after the step of increasing the power supplied to the aerosol generation element from power P0 to at least power P1 but before the step of decreasing the power supplied to the aerosol generation element to power P2.

[0039] The power supplied to the aerosol generation element may be increased from at least power P1 to power P5, preferably substantially immediately after the step of increasing the power supplied to the aerosol generation element from power P0 to at least power P1. In this context, the term "substantially immediately" may be used to mean within 0.1 seconds.

[0040] Alternatively, the step of increasing the power supplied to the aerosol generation element from power P0 to at least power P1 may comprise increasing the power supplied to the aerosol generation element from power P0 to power P5, where power P5 is greater than power P1.

[0041] Advantageously, this can provide a burst of power near the beginning of the puff. High power near the beginning of the puff can result in an early onset of adequate aerosol generation. This can provide better responsiveness to the user. This can also reduce the aerosol droplet size near the beginning of the puff. Power P5 can be predefined. Power P5 can depend on a number of factors, including, but not limited to, the aerosol-generating element, the type of aerosol-forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power is preferably reduced, for example, to power P1.

[0042] Providing power to the aerosol generation element may include providing a current pulse to the aerosol generation element.

[0043] Increasing or decreasing the power supplied to the aerosol generation element may involve changing the frequency or magnitude, or both the frequency and magnitude, of the current pulses supplied to the aerosol generation element.

[0044] According to a second aspect of the present invention, there is provided an aerosol generation system comprising an aerosol generation element and a flow path configured to allow airflow to pass through the aerosol generation element. The system further comprises a flow sensor configured to detect airflow, where the airflow indicates that the user is taking a puff, and a power source for providing power to the aerosol generation element. The system further comprises electrical circuitry for controlling the supply of power from the power source to the aerosol generation element, the electrical circuitry being configured to carry out a method according to the first aspect of the present invention.

[0045] According to a third aspect of the present invention, there is provided an electrical circuit for an aerosol generation system, the electrical circuit being arranged to carry out a method according to the first aspect of the present invention.

[0046] According to a fourth aspect of the present invention there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to carry out a method according to the first aspect of the present invention.

[0047] According to a fifth aspect of the present invention, there is provided a computer readable storage medium having stored thereon a computer program according to the fourth aspect of the present invention.

[0048] According to a sixth aspect of the present invention, there is provided a method for controlling aerosol generation in an aerosol generation system. The system comprises an aerosol generation element and a housing having an air inlet and an air outlet. A flow path is defined through the housing from the air inlet to the air outlet, the flow path providing a flow of air past the aerosol generation element when a user takes a puff on the system. The system further comprises a flow sensor configured to detect airflow, the airflow indicating that the user is taking a puff. The method comprises increasing the power supplied to the aerosol generation element from power p20 to at least power p21 when the flow sensor detects that the airflow rate is greater than a first threshold t21. The method is performed under the following conditions: the flow sensor detecting that the airflow rate is less than a second threshold value t22, the second threshold value t22 being at or indicative of a predetermined flow rate; or the flow sensor detecting that the airflow rate is less than a third threshold t23, the third threshold t23 being a rate that is a predetermined percentage of a maximum detectable airflow rate; and, after detecting that the airflow rate is greater than the first threshold t21, reducing the power supplied to the aerosol generation element to power p22, where power p22 is less than power p21, depending on which of the following occurs first.

[0049] The second threshold t22 and the third threshold t23 are both greater than zero.

[0050] Advantageously, reducing the power supplied to the aerosol generating element before the flow rate drops to zero can reduce the amount of condensation that can form within the system, which can have an impact on liquid leakage.

[0051] Advantageously, by reducing the power supplied to the aerosol generation element as whichever condition occurs first, power can be reduced at a greater flow rate for puffs having a greater maximum detectable flow rate, although the second threshold t22 provides a minimum flow rate at which power supplied to the aerosol generation element is reduced, regardless of the maximum detectable flow rate of the puff.

[0052] The power p22 may be zero.

[0053] The step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 may include increasing the power from power p20 to at least power p1 substantially instantaneously. That is, the power may be increased from power P20 to at least power P21 over a period of time substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a vertical or substantially vertical line from power p20 to at least power P21. For example, the term "substantially instantaneous" may be used to mean that the power may be increased from power P20 to at least power P21 within 0.1 seconds.

[0054] Alternatively, according to the sixth aspect, the step of increasing the power supplied to the aerosol generating element from power p20 to at least power p21 can include increasing the power stepwise from power p20 to at least power p21. That is, the power can be increased stepwise from power p20 to at least power p21 over a period of time. The longer the period, the more gradual the power increase. On a plot of heating power on the vertical axis versus time on the horizontal axis, this can be represented by a line with a positive average slope from power p20 to at least power p21. The slope of the line can be constant or non-constant. For example, the term "stepwise" can be used to mean that the power can be increased from power p20 to at least power p21 over a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds.

[0055] According to a sixth aspect, the step of reducing the power supplied to the aerosol generation element to power p22 may comprise reducing the power supplied to the aerosol generation element from at least power p21 to power p22.

[0056] According to a sixth aspect, the step of reducing the power supplied to the aerosol generation element to power p22 may comprise substantially instantaneously reducing the power supplied to the aerosol generation element to power p22. That is, the power may be reduced to power p22 over a period of time substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a vertical or substantially vertical line up to power p22. For example, the term "substantially instantaneous" may be used to mean that the power may be increased to power p22 within 0.1 seconds.

[0057] Alternatively, according to the sixth aspect, the step of reducing the power supplied to the aerosol generating element to power p22 may include reducing the power supplied to the aerosol generating element to power p22 stepwise. That is, the power may be reduced over a period not equal to zero. That is, the power may be reduced stepwise to power p22 over a period of time. The longer the period, the more gradual the power reduction. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a line with a negative average slope up to power p22. The slope of the line may or may not be constant. For example, the term "stepwise" may be used to mean that the power may be reduced to power p22 within a period of 0.1 to 1 second, or 0.2 to 0.6 seconds, or 0.2 to 0.4 seconds after the flow sensor detects that the airflow rate is less than the second threshold t22.

[0058] According to a sixth aspect, the method may comprise the step of increasing the power supplied to the aerosol generation element from at least power p21 to power p25 after the step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 but before the step of decreasing the power supplied to the aerosol generation element to power p22.

[0059] According to a sixth aspect, the power supplied to the aerosol generation element may be increased from power p21 to power p25, preferably substantially immediately after the step of increasing the power supplied to the aerosol generation element from power p20 to power p21. In this context, the term "substantially immediately" may be used to mean within 0.1 seconds.

[0060] Alternatively, the step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 may comprise increasing the power supplied to the aerosol generation element from power p20 to power p25, where power p25 is greater than power p21.

[0061] This may provide a burst of power near the beginning of the puff. Such a burst of power near the beginning of the puff may result in an early onset of adequate aerosol generation. This may provide better responsiveness to the user. This may also reduce the aerosol droplet size near the beginning of the puff. The power p25 may be predefined. The power p25 may depend on a number of factors, including, but not limited to, the aerosol-generating element, the type of aerosol-forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power is preferably reduced, for example, to power p21.

[0062] According to a sixth aspect, supplying power to the aerosol generation element may comprise supplying a current pulse to the aerosol generation element.

[0063] According to a seventh aspect, there is provided an aerosol generation system arranged to carry out the method of the sixth aspect. The system comprises an aerosol generation element and a flow path configured to allow airflow to pass through the aerosol generation element. The system further comprises a flow sensor configured to detect airflow, where airflow indicates that a user is taking a puff, and a power source for providing power to the aerosol generation element. The system further comprises electrical circuitry for controlling the supply of power from the power source to the aerosol generation element, the electrical circuitry being arranged to carry out the method according to the sixth aspect.

[0064] According to an eighth aspect, there is provided an electrical circuit for an aerosol generation system, the electrical circuit being arranged to carry out the method of the sixth aspect.

[0065] According to a ninth aspect, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to carry out the method of the sixth aspect.

[0066] According to a tenth aspect, there is provided a computer readable storage medium having a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to perform the method of the sixth aspect.

[0067] According to an eleventh aspect, there is provided a method of controlling aerosol generation in an aerosol generation system. The system comprises an aerosol generation element, a housing having an air inlet and an air outlet, and a flow path defined through the housing from the air inlet to the air outlet, the flow path providing a flow of air past the aerosol generation element when a user takes a puff on the system. The system further comprises a flow sensor configured to detect airflow, the airflow indicating that the user is taking a puff. The method according to the eleventh aspect comprises the following chronological steps: increasing the power supplied to the aerosol generation element from power p30 to at least power p31 when the flow sensor detects that the airflow rate is greater than a first threshold t31; reducing the power supplied to the aerosol generation element to power p32 when the flow sensor detects that the airflow rate is less than a second threshold t32, where power p32 is less than power p31; increasing the power supplied to the aerosol generation elements to a power p33 if, within a predetermined time interval after the flow sensor detects that the airflow rate is less than the second threshold t32, the flow sensor detects that the airflow rate is greater than a third threshold t33, the third threshold t33 being less than the second threshold t32; or increasing the power supplied to the aerosol generation element to power p34 when the flow sensor detects that the airflow rate is less than a fourth threshold t34, where the fourth threshold t34 is less than the second threshold t32, and the time difference between the time when the airflow rate is detected to be less than the second threshold t32 and the time when the airflow rate is detected to be less than the fourth threshold t34 is less than a fifth threshold t35.

[0068] According to an eleventh aspect, the third threshold t33 is less than the second threshold t32, and the fourth threshold t34 is less than the second threshold t32. Advantageously, this enables the aerosol generating system to deliver sufficient aerosol to the user during a slow-ending puff.

[0069] According to an eleventh aspect, the second threshold t32 may be or may indicate a flow rate that is a predetermined first percentage of a first maximum flow rate sensed by the flow sensor.

[0070] According to an eleventh aspect, the flow sensor may detect the flow rate continuously or intermittently.

[0071] According to an eleventh aspect, the flow sensor may detect the flow rate for a first predetermined period of time after the flow sensor detects that the flow rate has decreased below a second threshold value t32. The flow sensor may then compare the detected flow rate for the first predetermined period of time after detecting that the flow rate has decreased below the second threshold value t32 to a third threshold value t33.

[0072] According to an eleventh aspect, the flow sensor may regularly detect the flow rate throughout the puff, meaning that the flow rate is detected every period tp3. The flow sensor may compare the nth flow rate detected after detecting that the flow rate has decreased below a second threshold t32 with a third threshold t33, where n is an integer greater than 1. Advantageously, this means that the nth flow rate is not compared with the third threshold until at least n-1 times the period tp3 has elapsed since the flow sensor first detected that the flow rate had decreased below the second threshold.

[0073] According to the eleventh aspect, any increase or decrease in power supplied to the aerosol generation element may occur substantially immediately or in a stepwise manner. As described in relation to the claimed invention and with reference to the method of the sixth aspect, the term "stepwise" may be used to mean within a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds, and the term "substantially immediately" may be used to mean within 0.1 seconds.

[0074] According to an eleventh aspect, power p32 may be zero. Power p33 may be a predetermined power. Power p34 may be a predetermined power. Power p33 and power p34 may be the same power. Alternatively, power p33 and power p34 may be different powers.

[0075] The method according to the eleventh aspect may comprise the step of increasing the power supplied to the aerosol generation element from at least power p31 to power p35 after the step of increasing the power supplied to the aerosol generation element from power p30 to at least power p31 but before the step of decreasing the power supplied to the aerosol generation element to power p32.

[0076] According to an eleventh aspect, the power supplied to the aerosol generation element may be increased from at least power p31 to power p35, preferably substantially immediately after the step of increasing the power supplied to the aerosol generation element from power p30 to at least power p31. In this context, the term "substantially immediately" may be used to mean within 0.1 seconds.

[0077] Alternatively, according to the eleventh aspect, the step of increasing the power supplied to the aerosol generation element from power p30 to at least power p31 may comprise increasing the power supplied to the aerosol generation element from power p30 to power p35, where power p35 is greater than power p31.

[0078] This may provide a burst of power near the beginning of the puff. Such a burst of power near the beginning of the puff may result in an earlier onset of proper aerosol generation. This may reduce lag for the user. This may also reduce the aerosol droplet size near the beginning of the puff. Power p35 may be predefined. Power p35 may depend on a number of factors, including, but not limited to, the aerosol-generating element, the type of aerosol-forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power is preferably reduced, for example, to power p31.

[0079] The method according to the eleventh aspect may further comprise, after either the step of increasing the power supplied to the aerosol generation element to power p33 or the step of increasing the power supplied to the aerosol generation element to power p34, the step of reducing the power supplied to the aerosol generation element to power p36 when the flow sensor detects that the airflow rate has decreased below the end-of-puff threshold t3e.

[0080] The power p36 may be zero. The puff termination threshold t3e may be a puff termination constant.

[0081] According to an eleventh aspect, supplying power to the aerosol generation element may include supplying a current pulse to the aerosol generation element.

[0082] According to a twelfth aspect, there is provided an aerosol generation system arranged to carry out the method according to the eleventh aspect. The system comprises an aerosol generation element and a flow path configured to allow airflow to pass through the aerosol generation element. The system further comprises a flow sensor configured to detect airflow, where airflow indicates that a user is taking a puff, and a power source for providing power to the aerosol generation element. The system further comprises electrical circuitry for controlling the supply of power from the power source to the aerosol generation element, the electrical circuitry being arranged to carry out the method according to the eleventh aspect.

[0083] According to a thirteenth aspect of the present invention there is provided an electrical circuit for an aerosol generation system, the electrical circuit being arranged to carry out the method according to the eleventh aspect.

[0084] According to a fourteenth aspect, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to carry out the method according to the eleventh aspect.

[0085] According to a fifteenth aspect, there is provided a computer-readable storage medium having a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to perform the method according to the eleventh aspect.

[0086] According to a sixteenth aspect of the present invention, there is provided a method for controlling aerosol generation in an aerosol generation system. The system comprises a data storage means and an aerosol generation element. The system further comprises a housing having an air inlet and an air outlet, and a flow path defined through the housing from the air inlet to the air outlet, the flow path providing a flow of air past the aerosol generation element when a user takes a puff on the system. The system further comprises a flow sensor configured to detect airflow, the airflow indicating that the user is taking a puff. The method includes increasing the power supplied to the aerosol generation element from power p4x to at least power p41 when the flow sensor detects that the airflow rate is greater than a first threshold t41. The method further comprises storing measurements taken by the flow sensor in the data storage means and intermittently calculating an estimate of the remaining volume of the puff using the measurements stored in the data storage means. The method further includes reducing the power supplied to the aerosol generation element to power t42 when the estimated remaining volume of the puff is less than a second threshold t42, the second threshold t42 being or indicative of a measurement of the volume.

[0087] Advantageously, the method of the sixteenth aspect may allow an approximate volume, referred to herein as a flushing volume of air, to pass through the aerosol generation system after the power supplied to the aerosol generation element is reduced, and the second threshold value t42 is indicative of or is the flushing volume.

[0088] According to a sixteenth aspect, the second threshold value t42 may be a predetermined value.

[0089] According to a sixteenth aspect, the second threshold t42 may be or may indicate a volume approximately equal to the internal volume of a flow passage in a mouthpiece of an aerosol generation system. That is, when airflow flows through a flow passage in a mouthpiece of an aerosol generation system, the flushing volume may advantageously be approximately equal to the volume of the flow passage in the mouthpiece. In this context, "approximately equal to the volume of the flow passage" may be used to mean within 1.5 to 0.5 times, or 0.75 to 1.25 times, or 0.9 to 1.1 times the volume of the flow passage, or within 5 ml, or 3 ml, or 1 ml of the flow passage.

[0090] According to the sixteenth aspect, the second threshold value t42 may be or may indicate a volume of 0.1 ml to 10 ml, or 0.1 ml to 5 ml, or 0.1 ml to 3 ml, or 0.1 ml to 1 ml, or 1 ml to 10 ml, or 1 ml to 5 ml.

[0091] The method of the sixteenth aspect may comprise the step of increasing the power supplied to the aerosol generation element to power p43 after the step of reducing the power supplied to the aerosol generation element to power p42 when the estimated value of the remaining volume of the puff is less than second threshold t42. The step of increasing the power supplied to the aerosol generation element to power p43 may occur when the estimated value of the remaining volume of the puff is greater than a third threshold t43, which third threshold t43 is greater than the second threshold t42.

[0092] According to a sixteenth aspect, the flow sensor may measure the measurement continuously or intermittently.

[0093] According to a sixteenth aspect, the intermittent calculation of an estimate of the remaining volume of the puff may be calculated in one or more of several ways.

[0094] As a first example of how the calculation may be performed, the flow sensor may store volumetric flow values ​​intermittently. In this context, "intermittently" means periodically, e.g., for a period T P It can be used to mean every period T PFor each second and subsequent stored value, the processor calculates the average rate of change A of the current flow rate. c The average rate of change of this current flow rate, A c is the current flow rate value Q c The flow rate value Q stored just before c-1 After subtracting, period T P The processor then calculates the average rate of change of this current flow rate, A c remains constant. This means that the average rate of change of the current flow rate, A c If is negative, the remaining time of the current puff T C is the current flow rate value Q c The average rate of change of the current flow rate A c The processor calculates the current remaining volume of the puff, V c The estimated value of the current flow rate Q is set to -0.5. c Multiply by the square of the current average rate of change A c Of course, this calculation is based on the average rate of change of the current flow rate, A c When is negative, the current remaining volume V c The current remaining volume of the puff, V, is positive. c and the current remaining time T C The processor returns a negative value for such a current remaining volume V. c The processor may ignore all of the current average rate of change of flow rate A c In particular, the estimate does not need to be calculated until the current remaining time T C is the current remaining volume V c In equation form, the first embodiment can be summarized as follows:

number

[0095] Alternatively, as a second example, the average rate of change of the current flow rate A cis the flow rate value Q immediately after c+1 The flow rate value Q stored just before c-1 After subtracting, period T p Of course, this estimation can be done by dividing by the flow rate value Q c+1 is measured. In equation form, the second embodiment can be summarized as follows:

number

[0096] Alternatively, as a third example, a non-linear extrapolation of the flow rate may be used. The non-linear extrapolation may use a predetermined polynomial. The non-linear extrapolation may use a predetermined polynomial that more accurately represents the change in puff flow rate towards the end of a typical puff profile. Alternatively, the non-linear extrapolation may rely on previously stored measurements taken by the flow sensor during the current puff. For example, if the average rate of change of flow rate appears to be decreasing in each subsequent measurement taken near the end of the puff, a polynomial may be selected that more accurately estimates the change in flow rate for such puffs, and a different polynomial may be selected for puffs where the rate of change of flow rate is constant or increasing. Advantageously, this may more accurately estimate the change in flow rate towards the end of the puff and therefore provide a better estimate of the remaining volume of the puff.

[0097] According to a sixteenth aspect, the intermittent calculation of the estimated remaining volume of the puff may not begin until the flow sensor detects that the flow rate has decreased below the estimation start threshold t4s. Alternatively, the intermittent calculation of the estimated remaining volume of the puff may not take effect until the flow sensor detects that the flow rate has decreased below the estimation start threshold t4s, meaning that the power supplied to the aerosol generation element does not change. The estimation start threshold t4s may be a predetermined percentage of the maximum flow rate detected. Advantageously, this may help to avoid changing the power supplied to the aerosol generation element based on an inaccurately small estimate of the remaining volume of the puff. For example, if the flow rate decreases significantly after the maximum flow rate is detected, the calculated estimate for the remaining volume of the puff may be too small compared to the actual remaining volume of the puff.

[0098] According to the sixteenth aspect, any increase or decrease in power supplied to the aerosol generation element may occur substantially immediately or in a stepwise manner. As described in relation to the claimed invention and with reference to the method of the sixth aspect, the term "stepwise" may be used to mean within a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds, and the term "substantially immediately" may be used to mean within 0.1 seconds.

[0099] The method of the sixteenth aspect may comprise the step of increasing the power supplied to the aerosol generation element from at least power p41 to power p45 after the step of increasing the power supplied to the aerosol generation element from power p4x to at least power p41 but before the step of decreasing the power supplied to the aerosol generation element to power p42.

[0100] According to a sixteenth aspect, the power supplied to the aerosol generation element may be increased from power p41 to power p45, preferably substantially immediately after the step of increasing the power supplied to the aerosol generation element from power p4x to power p41. In this context, the term "substantially immediately" may be used to mean within 0.1 seconds.

[0101] Alternatively, the step of increasing the power supplied to the aerosol generation element from power p4x to at least power p41 may comprise increasing the power supplied to the aerosol generation element from power p4x to power p45, where power p45 is greater than power p41.

[0102] This may provide a burst of power near the beginning of the puff. Such a burst of power near the beginning of the puff may result in an early onset of adequate aerosol generation. This may provide better responsiveness to the user. This may also reduce the aerosol droplet size near the beginning of the puff. The power p45 may be predefined. The power p45 may depend on a number of factors, including, but not limited to, the aerosol-generating element, the type of aerosol-forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power is preferably reduced, for example, to power p41.

[0103] According to a sixteenth aspect, supplying power to the aerosol generation element may include supplying a current pulse to the aerosol generation element.

[0104] According to another aspect, there is provided an aerosol generation system arranged to carry out the method of the sixteenth aspect. The system comprises an aerosol generation element and a flow path configured to allow airflow to pass through the aerosol generation element. The system further comprises a flow sensor configured to detect airflow, where airflow indicates that a user is taking a puff, and a power source for providing power to the aerosol generation element. The system further comprises electrical circuitry for controlling the supply of power from the power source to the aerosol generation element, the electrical circuitry being arranged to carry out the method of the sixteenth aspect.

[0105] According to another aspect, there is provided an electrical circuit for an aerosol generation system, the electrical circuit being arranged to carry out the method of the sixteenth aspect.

[0106] According to another aspect, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to carry out the method of the sixteenth aspect.

[0107] According to another aspect, there is provided a computer-readable storage medium storing a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to perform the method of the sixteenth aspect.

[0108] The aerosol-generating system may comprise an aerosol-forming substrate, and the aerosol-generating element may include one or more elements configured to interact with the aerosol-forming substrate to generate an aerosol or vapor, for example, by adding aerosol droplets to an airflow to generate an aerosol.

[0109] The aerosol-generating element may comprise a mechanical device such as a vibrating orifice transducer or a piezoelectric device. The aerosol-generating element may comprise an electric heater comprising at least one heater element. The at least one electric heating element may be positioned to heat the aerosol-forming substrate to form the aerosol.

[0110] The aerosol-generating element may comprise a single heating element. Alternatively, the aerosol-generating element may comprise multiple heating elements, for example, two, three, four, five, six, or more heating elements. The heating element(s) may be suitably arranged to most effectively heat the aerosol-forming substrate.

[0111] The aerosol-generating element may include at least one electric heating element. Preferably, the at least one electric heating element comprises an electrically resistive material. Suitable electrically resistive materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide), carbon, graphite, metals, alloys, and composites of ceramic and metal materials. Such composites may include doped or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, constantan, nickel-, cobalt-, chromium-, aluminum-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, and iron-containing alloys, as well as nickel-, iron-, cobalt-, and stainless steel-based superalloys, Timetal®, iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation, 1999 Broadway, Suite 4300, Denver, Colorado. In composite materials, the electrically resistive material may be embedded in, encapsulated in, or coated with an insulating material, or vice versa, depending on the required energy transfer kinetics and external physicochemical properties. The heating element may include a metallic, etched foil insulated between two layers of inert material. In that case, the inert material may include Kapton®, an all-layer polyimide, or mica foil. Kapton® is a registered trademark of EI du Pont de Nemours and Company, 1007 Market Street, Wilmington, Delaware 19898, United States of America.

[0112] Alternatively, or additionally, the aerosol-generating element may include an infrared heating element, a photon source, or an induction heating element.

[0113] The at least one electric heating element may take any suitable form, for example the at least one electric heating element may take the form of a heating blade.

[0114] The at least one electric heating element may comprise a casing or substrate having different conductive portions or an electrically resistive metal tube. Where the aerosol-forming substrate is a liquid provided within the container, the container may incorporate a disposable heating element.

[0115] The at least one electrical heating element may comprise a heating needle or rod that passes through the centre of the aerosol-forming substrate.

[0116] The at least one electric heating element may include a disk-type (terminal) heater or a combination of a disk-type heater and a heating needle or rod.

[0117] The at least one electric heating element may comprise a flexible sheet of material arranged to surround or partially surround the aerosol-forming substrate. Other alternatives include heating wires or filaments, such as Ni-Cr, platinum, tungsten, or alloy wires or heating plates. Optionally, the heating element may be arranged in or on a rigid carrier material.

[0118] Alternatively or additionally, the aerosol-generating element may include a heating element, which includes multiple conductive filaments. As used herein, the term "filament" refers to an electrical path disposed between two electrical contacts. The filament may arbitrarily branch and diverge into several paths or filaments, respectively, or several electrical paths may merge into one path. The filaments may have a cross-section that is round, square, flat, or of any other shape. The filaments may be arranged in a straight or curved manner.

[0119] The heating element may be, for example, an array of filaments arranged parallel to one another. Preferably, the filaments may form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of weave or lattice structures. Alternatively, the conductive heating element may consist of an array of filaments or a woven fabric of filaments. A mesh, array, or woven fabric of conductive filaments may also be characterized by its ability to retain liquid.

[0120] In a preferred embodiment, the substantially flat heating element may be constructed of wires formed into a wire mesh. The mesh preferably has a plain weave design. The heating element is preferably a wire grill made from mesh strips.

[0121] The filaments of the heating element may be formed of any material having suitable electrical properties, including, but not limited to, semiconductors such as doped ceramics, "conductive" ceramics, carbon, graphite, metals, alloys, and composites made of ceramic and metallic materials.

[0122] Preferred materials for the conductive filaments are stainless steel and graphite, with 300 series stainless steel, such as AISI 304, 316, 304L, and 316L, being more preferred. A combination of materials may be used for the conductive heating element to improve control of the element's resistance. For example, a material with a high resistivity may be combined with a material with a low resistivity. This may be advantageous when one of the materials is more advantageous from another perspective, such as price, machinability, or other physical or chemical parameters. Advantageously, a substantially flat filament arrangement with increased resistance reduces parasitic losses. Advantageously, a heater with a high resistance allows for more efficient use of battery energy.

[0123] The filament is preferably made of wire, which is preferably made of metal, most preferably stainless steel.

[0124] The conductive filaments may define gaps between the filaments. The gaps may have widths of 10 micrometers to 100 micrometers. The filaments preferably create capillary action within the gaps so that liquid to be vaporized during use is drawn into the gaps, increasing the contact area between the heating element and the liquid aerosol-forming substrate.

[0125] At least one heating element may heat the aerosol-forming substrate by conduction. The heating element may be in at least partial contact with the substrate or with a carrier on which the substrate is deposited.

[0126] Heat from the heating element may be conducted to the substrate by means of a thermally conductive element.

[0127] The at least one heating element may transfer heat to incoming ambient air drawn through the electrically heated aerosol-generating system during use, which in turn heats the aerosol-forming substrate by convection. The ambient air may be heated before passing through the aerosol-forming substrate.

[0128] If the aerosol-forming substrate is a liquid substrate, ambient air may first be drawn through the substrate and then heated.

[0129] The aerosol-forming substrate may be a solid aerosol-forming substrate. Preferably, the aerosol-forming substrate comprises a tobacco-containing material that contains volatile tobacco flavor compounds that are emitted from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise a tobacco-containing material and a non-tobacco-containing material. Preferably, the aerosol-forming substrate further comprises an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0130] The aerosol-forming substrate may be a liquid aerosol-forming substrate. The aerosol generation system may comprise a liquid storage portion. The liquid aerosol-forming substrate is preferably stored in the liquid storage portion. The aerosol-generating element may include a capillary wick communicating with the liquid storage portion. The aerosol generation system may comprise a capillary wick for holding a liquid without having a liquid storage portion. In this case, the capillary wick may be pre-loaded with liquid.

[0131] A capillary wick is preferably disposed in contact with the liquid in the liquid storage portion. In use, the liquid is then transported from the liquid storage portion toward the at least one electric heating element by capillary action within the capillary wick. In one embodiment, the capillary wick has a first end and a second end, the first end extending into the liquid storage portion for contacting the liquid therein, and the at least one electric heating element may be disposed to heat the liquid in the second end. When the heating element is activated, the liquid at the second end of the capillary wick is vaporized by the heater to form a supersaturated vapor. The supersaturated vapor mixes with and is carried in the airflow. During the flow, the vapor condenses to form an aerosol, which is carried toward the user's mouth. A heating element combined with a capillary wick may provide a fast response because this arrangement may provide a large surface area of ​​liquid for the heating element. Accordingly, control of the heating element according to the present invention may depend on the configuration of the capillary wick arrangement.

[0132] The liquid substrate may be absorbed into any suitable absorbent plug or body, for example, a porous carrier material, which may be made of foamed metal or plastic material, polypropylene, terylene, nylon fiber, or ceramic. The liquid substrate may be retained in the porous carrier material before using the electrically heated aerosol generating system, or alternatively, the liquid substrate material may be released into the porous carrier material during or immediately before use. For example, the liquid substrate may be provided in a capsule. The capsule shell preferably melts upon heating, releasing the liquid substrate into the porous carrier material. The capsule may optionally contain a solid combined with the liquid.

[0133] When the aerosol-forming substrate is a liquid substrate, the liquid has physical properties, such as a boiling point, suitable for use in the aerosol generating system. If the boiling point is too high, the at least one electric heating element cannot vaporize the liquid in the capillary wick, while if the boiling point is too low, the liquid may vaporize without activating the at least one electric heating element. Control of the at least one electric heating element may depend on the physical properties of the liquid substrate. Preferably, the liquid comprises a tobacco-containing material containing volatile tobacco flavor compounds that are released from the liquid when heated. Alternatively or additionally, the liquid may comprise a non-tobacco material. The liquid may comprise water, a solvent, ethanol, a plant extract, and a natural or artificial flavor. Preferably, the liquid further comprises an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0134] An advantage of providing a liquid reservoir is that a high level of hygiene can be maintained. The use of a capillary wick extending between the liquid and the electric heating element allows for a relatively simple construction of the system. The liquid has physical properties, including viscosity and surface tension, that allow the liquid to be transported through the capillary wick by capillary action. The liquid reservoir is preferably a container. The liquid reservoir may not be refillable. Thus, when the liquid in the liquid reservoir is used up, the aerosol generation system is replaced. Alternatively, the liquid reservoir may be refillable. In that case, the aerosol generation system may be replaced after a certain number of refills of the liquid reservoir. The liquid reservoir is preferably arranged to hold liquid for a predetermined number of puffs.

[0135] The capillary wick may have a fibrous or spongy structure. Preferably, the capillary wick comprises a bundle of capillaries. For example, the capillary wick may comprise a plurality of fibers or threads or other fine tubes. The fibers or threads may be generally aligned along the longitudinal axis of the aerosol-generating system.

[0136] Alternatively, the capillary wick may comprise a sponge-like or foam-like material formed into a rod shape. The rod shape may extend along the longitudinal axis of the aerosol generating system. The wick structure forms a plurality of small holes or tubes through which the liquid can travel to the electric heating element by capillary action. The capillary wick may comprise any suitable material or combination of materials. Examples of suitable materials include ceramic or graphite-based materials in the form of fibers or sintered powders. The capillary wick may have any suitable capillary and porosity characteristics that combine different liquid physical properties, such as density, viscosity, surface tension, and vapor pressure. The capillary properties of the wick, combined with the properties of the liquid, ensure that the wick remains moist within the heated area. If the wick is dry, overheating may occur, which can lead to liquid degradation.

[0137] In operation, the substrate may be completely contained within the aerosol generating system, in which case a user may smoke through the mouthpiece of the electrically heated aerosol generating system. Alternatively, in operation, the substrate may be partially contained within the aerosol generating system, in which case the substrate may form part of a separate article, and the user may smoke the separate article directly.

[0138] Preferably, the aerosol generating system is an electrically heated aerosol generating system. Even more preferably, the aerosol generating system is an electrically heated smoking system.

[0139] The aerosol generation system comprises a flow path, a portion of which may be referred to as an aerosol formation chamber. In the aerosol formation chamber, an aerosol is formed from the supersaturated vapor and may then be delivered to the user's mouth. The air inlet, air outlet, and chamber are preferably arranged to define an airflow path from the air inlet, through the aerosol formation chamber, to the air outlet, so as to deliver the aerosol to the air outlet and into the user's mouth. Condensation may form on the walls of the aerosol formation chamber. The amount of condensation may depend on the heating profile, particularly towards the end of the puff.

[0140] The housing of the aerosol generating system is preferably elongated. The structure of the housing, including the surface available for condensation formation, will affect the aerosol characteristics and whether there will be leakage of liquid from the aerosol generating system. The housing may comprise a shell and a mouthpiece. In that case, all components may be contained in either the shell or the mouthpiece. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. Preferably, the material is lightweight and not brittle. The material of the housing may affect the amount of condensation that forms on the housing, which in turn will affect leakage of liquid from the system.

[0141] The aerosol generating system is preferably portable. The aerosol generating system may be a smoking system and may have a size comparable to that of a conventional cigar or cigarette. The smoking system may have a total length of about 30 mm to about 150 mm. The smoking system may have an outer diameter of about 5 mm to about 30 mm.

[0142] Two or more of the methods described herein may be used in combination. For example, the puff termination threshold of the method of the first aspect may be calculated using the method according to the sixteenth aspect. That is, the puff termination threshold of the first aspect may be equal to the flushing volume of the sixteenth aspect.

[0143] Two or more of the methods described herein may be provided as different modes of operation in a single aerosol generating system, and a user may be able to select which method to implement using a user interface.

[0144] Features described in connection with one embodiment described herein may be applicable to other embodiments described herein, and it will be apparent to one skilled in the art that features described in connection with one embodiment may also be applicable to other embodiments.

[0145] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0146] [Figure 1] FIG. 1 is a schematic diagram of an aerosol generation system. [Figure 2] FIG. 2 is a plot of airflow versus time and a plot of heating power versus time for a known aerosol generating system implementing a known method of controlling aerosol generation. [Figure 3] FIG. 3 is a plot of airflow versus time and a plot of heating power versus time for an aerosol generating system according to the present invention. [Figure 4] FIG. 4 is a plot of airflow versus time and a plot of heating power versus time for an aerosol generating system according to the present invention. [Figure 5] FIG. 5 is a plot of airflow versus time and a plot of heating power versus time for an aerosol generating system according to the present invention. [Figure 6] FIG. 6 is a plot showing airflow rate versus time and a plot showing heating power versus time for an aerosol generating system according to a sixth embodiment described herein. [Figure 7] FIG. 7 is a plot showing airflow rate versus time and a plot showing heating power versus time for an aerosol generating system according to an eleventh embodiment described herein. [Figure 8] FIG. 8 is a plot showing airflow rate versus time and a plot showing heating power versus time for an aerosol generating system according to a sixteenth embodiment described herein. DETAILED DESCRIPTION OF THE INVENTION

[0147] 1 is a schematic diagram of an aerosol generation system. System 100 comprises two main components: a cartridge 102 and a control body 104. A connecting end 106 of cartridge 102 is removably connected to a corresponding connecting end 108 of control body 104. Aerosol generation system 100 is portable and has a size comparable to that of a conventional cigar or cigarette.

[0148] The control body 104 houses a battery 110 (which in this embodiment is a rechargeable lithium ion battery) and a control circuit 112. The control circuit 112 includes a puff detection system 111.

[0149] The cartridge 102 includes a housing 114 that houses an atomization assembly 116 and a liquid storage compartment 118. The liquid storage compartment includes a capillary material immersed in a liquid aerosol-forming substrate. In this example, the aerosol-forming substrate includes 39 weight percent glycerin, 39 weight percent propylene glycol, 20 weight percent water and flavorings, and 2 weight percent nicotine. The capillary material is a material that actively transports liquid from one end to the other and may be made of any suitable material. In this example, the capillary material is formed from polyester.

[0150] In this embodiment, the nebulizing assembly includes a plurality of electrically conductive heater filaments that form an electrically heated mesh heating element. When the cartridge 102 is connected to the control body 104, the power supply 110 is electrically connected to the mesh heating element. An airflow passage extends through the cartridge from an air inlet 122, through the nebulizing assembly 116, and to an opening 124 at the mouth end in the housing 114.

[0151] The system is configured to allow a user to draw aerosol into their mouth by drawing on the mouth-end opening 124 of the cartridge 102. In operation, when a user draws on the mouth-end opening 124, air is drawn from the air inlet 122 through the airflow passageway. The puff detection system 111 detects airflow through the airflow passageway and activates the atomization assembly 116. The control circuit 112 controls the supply of power from the power source 110 to the atomization assembly 116. Air flows through the atomization assembly 116. The atomization assembly 116 generates a vapor that is entrained in the airflow passing through the airflow passageway. The amount and characteristics of the vapor generated by the atomization assembly 116 are controlled, at least in part, by the power supplied to the atomization assembly 116 by the power source 110. The air and entrained vapor, or aerosol, flow through the mouth-end opening 124 into the user's mouth.

[0152] FIG. 1 shows one example of an electrically heated aerosol generating system that can be used with the present invention. However, many other examples can be used with the present invention. The present invention can be used with any electrically heated aerosol generating system that includes an aerosol generating element powered by a power source under the control of an electrical circuit. For example, the system need not be a smoking system. For example, the aerosol-forming substrate can be a solid substrate rather than a liquid substrate. Alternatively, the aerosol-forming substrate can be in the form of another substrate, such as a gel or paste. The aerosol-generating element can take any suitable form. The overall shape and size of the housing can vary, and the housing can include a separate shell and mouthpiece. Other variations are, of course, possible.

[0153] In the embodiment of FIG. 1, control circuitry 112, including puff detection system 111, is programmable to control the power supply to the mesh heating element. This, in turn, affects a heating profile that can affect vapor, or aerosol, characteristics. The term "heating profile" refers to a graphical representation of the power supplied to the heating element (or another similar measurement, e.g., the heat generated by the heating element) over the time it takes for a puff to occur. However, if control circuitry 112 and puff detection system 111 are wired to control the power supply to the heating element, the aerosol generation system can function in much the same way. Again, this can affect the heating profile, and in turn, the aerosol droplet size.

[0154] FIG. 2 is a plot of airflow rate versus time and heating power versus time for a known aerosol generating system implementing known methods of controlling aerosol generation.

[0155] Figure 2 is a plot showing airflow rate 201 and heating power 203 on the vertical axis and time 205 on the horizontal axis. Airflow rate 201 is shown by a solid line and heating power 203 is shown by a dotted line. Airflow rate is sensed by a puff detection system, such as puff detection system 111 in Figure 1. Heating power, measured in watts, is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 in Figure 1. Figure 2 shows a single puff by a user on an electrically heated aerosol generating system, such as that shown in Figure 1.

[0156] As can be seen in Figure 2, in this embodiment, the airflow for a puff is illustrated as taking the shape of a normal or Gaussian distribution. The airflow starts at zero, increases stepwise to a maximum 201max, and then decreases back to zero. However, airflow typically does not have an exact Gaussian distribution. In all cases, however, the airflow during a puff increases from zero to a maximum, and then decreases from the maximum to zero. The area under the airflow curve is the total air volume for that puff.

[0157] When the puff detection system senses that airflow 201 has increased to threshold 201a at time 205a, the electrical circuit controls the power to turn on the heating element and increase the heating power 203 directly from zero to power 203a. When the puff detection system senses that airflow 201 has decreased back to threshold 201a at time 205b, the electrical circuit controls the power to turn off the heating element and immediately decrease the heating power 203 from power 203a to zero. Between time 205a and time 205b, the puff detection system detects that the airflow remains greater than threshold 201a, and the heating power to the heating element is maintained at power 203a. Thus, the heating period is from time 205b to 205a.

[0158] In the embodiment of Figure 2, the airflow threshold for turning on the heating element is the same as the airflow threshold for turning off the heating element. An advantage of the arrangement of Figure 2 is design simplicity. However, this arrangement does present the possibility of overheating toward the end of the puff, such as in the circled region 207 of Figure 2. Furthermore, if the puff flow rate increases again after the power supplied to the heater is reduced to zero at time 205b, the heater will remain without power, and the user may be annoyed by inadequate aerosol delivery after time 205b.

[0159] FIG. 3 includes two plots. One plot shows airflow rate 301 on the vertical axis and time 305 on the horizontal axis, while the other plot shows heating power 303 on the vertical axis and time 305 on the horizontal axis. The time 305 shown in both plots is the same. That is, the plots in FIG. 3 show airflow rate and heating power for the same puff. Airflow rate 301 is shown by the solid line, and heating power 303 is shown by the dotted line. Airflow rate is measured in volume per unit time, typically cubic centimeters per second. Airflow rate is sensed by a puff detection system, such as puff detection system 111 in FIG. 1. Heating power is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 in FIG. 1. FIG. 3 illustrates a single puff by a user on an electrically heated aerosol generating system, such as that shown in FIG. 1.

[0160] As can be seen in Figure 3, in this embodiment the puff profile is more complex than the puff profile shown in Figure 2. In this embodiment, the airflow rate 301 increases from zero to a first maximum flow rate 301max1. The airflow rate then decreases to a flow rate 301min1. The airflow rate then increases to a second maximum flow rate 301max2. The airflow rate then decreases to zero.

[0161] When the puff detection system senses that airflow rate 301 has increased to threshold value 301a at time 305a, the electrical circuit controls the power to turn on the heating element, causing the heating power 303 to increase substantially instantaneously from zero to power 303a. When the puff detection system senses that airflow rate 301 has decreased to threshold value 301b at time 305b, the electrical circuit controls the power to turn off the heating element, causing the heating power 303 to decrease substantially instantaneously from power 303a to zero. Between times 305a and 305b, the heating power to the heating element is maintained at power 303a.

[0162] When the puff detection system subsequently senses that airflow rate 301 has increased to threshold value 301c at time 305c, the electrical circuitry controls the power to turn on the heating element, causing the heating power 303 to increase substantially instantaneously from zero to power 303c. When the puff detection system senses that airflow rate 301 has decreased to threshold value 301d at time 305d, the electrical circuitry controls the power to turn off the heating element, causing the heating power 303 to decrease substantially instantaneously from power 303c to zero. Between time 305c and time 305d, the heating power to the heating element is maintained at power 303c.

[0163] In the embodiment of Figure 3, threshold 301a is a predetermined constant and threshold 301d is another end-of-puff predetermined constant. Threshold 305d is less than threshold 301a. Threshold 301b is 50% of 301max1 and threshold 301c is 65% of 301max1. Power 303a and power 303c are equal.

[0164] FIG. 4 includes two plots. The first plot in FIG. 4 shows the same puff profile as shown in FIG. 3. It is copied onto FIG. 4 solely for comparison with the second plot in FIG. 4. The second plot shows heating power 403 on the vertical axis and time 405 on the horizontal axis. The time shown in both plots is the same. That is, the plot in FIG. 4 shows the airflow rate and heating power for the same puff. Airflow rate 301 is shown by the solid line, and heating power 403 is shown by the dotted line. Airflow rate is sensed by a puff detection system, such as puff detection system 111 in FIG. 1. Heating power is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 in FIG. 1. FIG. 4 shows a single puff by a user on an electrically heated aerosol generating system, such as that shown in FIG. 1.

[0165] At time 305z, the user presses a button on the aerosol generation system. In response, the electrical circuitry controls the power to turn on the heating element, increasing the heating power to the heating element to power level 403z. As shown in FIG. 4, the user presses the button immediately after initiating a puff on the system. However, the user may press the button before initiating a puff on the system, causing power to be supplied at power level 403z before the airflow rate increases. In this embodiment, if the user presses the button but the puff detection system does not detect an airflow rate above threshold 301a within 10 seconds of the user pressing the button, the power supplied to the heating element may be reduced back to zero.

[0166] When the puff detection system senses that the airflow rate 301 has increased to the threshold value 301a at time 305a, the electrical circuit controls the power to the heating element to immediately increase the heating power 403 from 403z to power 403a. The power supplied to the heating element is held at this level for a short period relative to the average puff time, approximately 0.2 seconds, before decreasing to power level 403x at time 305x. This provides an initial burst of power to initiate the puff.

[0167] When the smoke detection system senses that the airflow rate 301 has decreased to threshold 301b at time 305b, the electrical circuit controls the power to turn off the heating element and reduce the heating power 403 from power 403x to zero. As shown in Figure 4, this reduction in power occurs in stages at a constant rate between times 305b and 305b2.

[0168] When the puff detection system subsequently senses that airflow 301 has increased to threshold 301c at time 305c, the electrical circuit controls the power to turn on the heating element and immediately increase heating power 403 from zero to power 403c. When the puff detection system senses that airflow 301 has decreased to threshold 301d at time 305d, the electrical circuit controls the power to turn off the heating element and immediately decrease heating power 403 from power 403c to zero. Between time 305c and time 305d, the heating power to the heating element is maintained at power 403c.

[0169] In the embodiment of Figure 4, threshold 301a is a predetermined constant and threshold 301d is another end-of-puff predetermined constant. Threshold 305d is less than threshold 301a. Threshold 301b is 50% of 301max1 and threshold 301c is 65% of 301max1. Power 403a is greater than power 403x, which is greater than power 403c, which is greater than power 403z.

[0170] FIG. 5 includes two plots. One plot shows airflow rate 501 on the vertical axis and time 505 on the horizontal axis, while the other plot shows heating power 503 on the vertical axis and time 505 on the horizontal axis. The time 505 shown in both plots is the same. That is, the plots in FIG. 5 show airflow rate and heating power for the same puff. Airflow rate 501 is shown by the solid line, and heating power 503 is shown by the dotted line. Airflow rate is sensed by a puff detection system, such as puff detection system 111 in FIG. 1. Heating power is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 in FIG. 1. FIG. 5 illustrates a single puff by a user on an electrically heated aerosol generating system, such as that shown in FIG. 1.

[0171] As can be seen in Figure 5, in this embodiment the puff profile is more complex than the puff profile shown in Figure 3. In this embodiment, airflow 501 increases from zero to a first maximum flow rate 501max1. The airflow then experiences another local maximum 501maxz before decreasing to a local minimum flow rate 501min1. The airflow then increases to another local maximum flow rate 501max2 before decreasing to another local minimum flow rate 501min2. The airflow then increases to another local maximum 501max3 before decreasing to zero. In Figure 5, flow rate 501max2 is greater than 501max1, which is greater than 501maxz, which is greater than 501min3, which is greater than 501min1, which is greater than 501min2.

[0172] When the puff detection system senses that airflow 501 has increased to threshold 501a at time 505a, the electrical circuit controls the power to turn on the heating element, increasing heating power 503 directly from zero to power 503a. When the puff detection system senses that airflow 501 has decreased to threshold 501b at time 505b, the electrical circuit controls the power to the heating element, immediately decreasing heating power 503 from power 503a to power 503w1. Between times 505a and 505b, the heating power to the heating element is maintained at power 503a.

[0173] When the puff detection system subsequently senses that airflow 501 has increased to threshold 501c at time 505c, the electrical circuit controls the power to the heating element to immediately increase heating power 503 from power 503w1 to power 503c. When the puff detection system senses that airflow 501 has decreased to threshold 501d at time 505d, the electrical circuit controls the power to the heating element to immediately decrease heating power 503 from power 503c to power 503w2. Between times 505c and 505d, the heating power to the heating element is maintained at power 503c.

[0174] When the puff detection system subsequently senses that airflow 501 has increased to threshold 501e at time 505e, the electrical circuit controls the power to the heating element to immediately increase heating power 503 from power 503w2 to power 503e. When the puff detection system senses that airflow 501 has decreased to threshold 501f at time 505f, the electrical circuit controls the power to the heating element to immediately decrease heating power 503 from power 503e to power 503w3. Between time 505e and time 505f, the heating power to the heating element is maintained at power 503e.

[0175] When the puff detection system senses that the airflow rate 501 has decreased below the threshold 501g, the electrical circuitry controls the power to the heating element to immediately decrease the heating power 503 from power 503w3 to zero.

[0176] In the embodiment of Figure 5, threshold 501a is a predetermined constant and threshold 501g is another end-of-puff predetermined constant, which is less than threshold 501a.

[0177] Because the local maximum flow rate 501maxz is between the flow rate 501max1 and the threshold 501b, and the local maximum flow rate 501maxz is less than the flow rate 501max1, the local maximum flow rate 501maxz does not affect the threshold 501b. If the flow rate 501maxz is greater than the flow rate 501max1, the threshold 501b may be calculated as a percentage of the flow rate 501maxz.

[0178] Threshold 501b is 70% of 501max1. Threshold 501c is 80% of 501max1. Threshold 501d is 70% of 501max2. Threshold 501e is 80% of 501max2. Power 503a, power 503c, power 503e, power 503w1, power 503w2, and power 503w3 are predetermined powers, where the maximum of powers 503w1, 503w2, and 503w3 is less than the minimum of powers 503a, 503c, and 503e.

[0179] It is worth noting that, according to the embodiment of Figure 5, the power supplied to the heating element may be increased indefinitely in response to the airflow rate increasing above a threshold defined by a local maximum, and decreased indefinitely in response to the airflow rate decreasing below the threshold defined by the local maximum. That is, while Figure 5 shows three increases in power supplied to the heating element, different puff profiles may show four, five, or more increases in power supplied to the heating element.

[0180] Figure 6 shows plots of airflow versus time and heating power versus time for an aerosol generating system according to a sixth embodiment described herein. Figure 6 shows a plot of airflow 601 for a first puff 6A and a second puff 6B on the vertical axis and time 605 on the horizontal axis, while a second plot shows heating power 603 for the first puff 6A and the second puff 6B on the vertical axis and time 605 on the horizontal axis. The airflow 601 and heating power 603 for puff 6A are shown as solid lines, and the airflow 601 and heating power 603 for puff 6B are shown as dotted lines. The airflow is sensed by a puff detection system, such as puff detection system 111 of Figure 1. The heating power is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 of Figure 1. Figure 6 shows a single puff by a user on an electrically heated aerosol generating system, such as that shown in Figure 1.

[0181] As can be seen in FIG. 6, in this embodiment the airflow for the puff is illustrated as taking the shape of a normal or Gaussian distribution.

[0182] For puff 6A, the airflow starts at zero and increases incrementally to a maximum value 601maxA before decreasing incrementally back to zero. For puff 6b, the airflow starts at zero and increases incrementally to a maximum value 601maxB before decreasing incrementally back to zero.

[0183] Threshold 601a is a predetermined constant. Threshold 601end is a predetermined constant for the end of a puff. Threshold 601bA applies to puff A but not to puff B and is 50% of local maximum 601maxA. Threshold 601bB applies to puff B but not to puff A and is 50% of local maximum 601maxB.

[0184] For puff 6A, when the puff detection system senses that airflow 601 has increased to threshold 601a at time 605aA, the electrical circuit controls the power to turn on the heating element and immediately increase heating power 603 from zero to power 603a. As can be seen in FIG. 6, threshold 601end is less than threshold 601bA, and for puff A, threshold 601bA is reached before threshold 601end. Thus, when the puff detection system senses that airflow 601 has decreased to threshold 601bA at time 605bA, the electrical circuit controls the power to turn off the heating element and immediately decrease heating power 603 from power 603a to zero. Between times 605a and 605b, the heating power to the heating element is maintained at power 603a.

[0185] For puff 6B, when the puff detection system senses that airflow 601 has increased to threshold 601a at time 605aB, the electrical circuit controls the power to turn on the heating element and immediately increase heating power 603 from zero to power 603a. As can be seen in FIG. 6, for puff B, threshold 601end is reached before threshold 601bB. Thus, when the puff detection system senses that airflow 601 has decreased to threshold 601end at time 605endB, the electrical circuit controls the power to turn off the heating element and immediately decrease heating power 603 from power 603a to zero. The power supplied to the heating element remains unchanged when airflow subsequently decreases to threshold 601bB. Between times 605a and 605b, the heating power to the heating element is maintained at power 603a.

[0186] 7 shows a plot of airflow versus time and a plot of heating power versus time for an aerosol generating system according to an eleventh embodiment described herein. The first plot in FIG. 7 shows airflow versus time, and the second plot in FIG. 7 shows heating power versus time. Both plots relate to a single puff by a user on an electrically heated aerosol generating system such as that shown in FIG. 1.

[0187] The first plot shows airflow rate 701 on the vertical axis and time 705 on the horizontal axis, while the second plot shows heating power 703 on the vertical axis and time 705 on the horizontal axis. The time 705 shown in both plots is the same. That is, the plots in FIG. 7 show airflow rate and heating power for the same puff. Airflow rate 701 is shown by the solid line, and heating power 703 is shown by the dotted line. Airflow rate is sensed by a puff detection system, such as puff detection system 111 in FIG. 1. Heating power is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 in FIG. 1. FIG. 7 shows a single puff by a user on an electrically heated aerosol generating system, such as that shown in FIG. 1.

[0188] The first plot in Figure 7 shows a puff profile where the airflow increases from zero to an airflow 701max, and then decreases from 701max to zero. The plot exhibits a shape similar to a normal distribution, being positively skewed, or right skewed.

[0189] When the puff detection system senses that the airflow rate 701 has increased to a threshold value 701a at time 705a, the electrical circuit controls the power to turn on the heating element, increasing the heating power 703 directly from zero to power 703a. In this embodiment, the threshold value 701a is a predetermined constant.

[0190] When the puff detection system senses that the airflow rate 701 has decreased to threshold value 701b at time 705b, the electrical circuit controls the power to turn off the heating element and immediately reduces the heating power 703 from power 703a to zero. In this embodiment, threshold value 701b is 70% of the flow rate 701max.

[0191] The puff detection system then waits a fixed time of 0.3 seconds from time 705b to time 705c. At time 705c, the puff detection system measures the flow rate as flow rate 701c and compares flow rate 701c to a restart threshold flow rate (not shown). In this embodiment, the restart threshold flow rate is 60% of flow rate 701max. If flow rate 705c is greater than the restart threshold flow rate, the electrical circuit controls the power to turn on the heating element, increasing the heating power. If flow rate 705c is less than the restart threshold flow rate, the heating element remains off until the end of the puff or until there is another reason to turn the heating element back on. In the embodiment of FIG. 7, flow rate 705c is greater than the restart threshold flow rate, so the electrical circuit controls the power to turn on the heating element, immediately increasing the heating power 703 from zero to power 703c. In this embodiment, power 703c is less than power 703a.

[0192] The power to the heating element remains at power 703c until the puff detection system detects that the flow rate is less than flow rate threshold 701d, at which point the electrical circuitry controls the power to turn the heating element off and immediately reduces the heating power 703 from power 703c to zero.

[0193] In this embodiment, the puff detection system measures the flow rate for a given time after the flow rate threshold 701b is reached. This given time is equal to time 705c minus time 705b. However, a similar or identical effect could be achieved in a number of alternative ways. Some of these alternatives can be described with reference to FIG. 7.

[0194] In one exemplary alternative, the puff detection system may periodically measure the flow rate 701c. The puff detection system may compare the measured flow rate 701c to a restart threshold, where flow rate 701c is measured a given number of flow rate measurements after the first measurement after the flow rate has fallen below threshold 701b. Then, similar to the method implemented in the embodiment of Figure 7, if flow rate 705c is greater than the restart threshold flow rate, the electrical circuitry controls the power to turn on the heating element to increase heating power, but if flow rate 705c is less than the restart threshold flow rate, the heating element remains off until the end of the puff or until there is another reason to turn the heating element back on.

[0195] In a second exemplary alternative, the puff detection system may measure the flow rate continuously or intermittently. When the puff detection system detects that the airflow rate is less than threshold 701c, the aerosol generation system may compare the approximate time difference to a restart time threshold, where the approximate time difference is approximately the time between detecting that the flow rate is less than threshold 701b and detecting that the flow rate is less than threshold 701c, where threshold 701b is greater than threshold 701c. Thus, if the approximate time difference is greater than the restart time threshold, the electrical circuit controls the power to turn on the heating element to increase heating power; or, if the approximate time difference is less than the restart time threshold, the heating element remains off until the end of the puff or until there is another reason to turn the heating element back on.

[0196] FIG. 8 is a plot showing airflow rate versus time and a plot showing heating power versus time for an aerosol generating system according to a sixteenth embodiment described herein.

[0197] FIG. 8 is a plot showing airflow rate 801 on the vertical axis and time 805 on the horizontal axis, and a second plot showing heating power 803 on the vertical axis and time 805 on the horizontal axis. Airflow rate 801 is shown by a solid line, and heating power 803 is shown by a dotted line. Airflow rate is sensed by a puff detection system, such as puff detection system 111 of FIG. 1. Heating power is the power provided to the heating element from a power source under the control of an electrical circuit, such as control circuit 112 of FIG. 1. FIG. 8 shows a single puff by a user on an electrically heated aerosol generating system, such as that shown in FIG. 1. In this embodiment, control circuit 112 shown in FIG. 1 should include data storage means capable of storing measurements taken by puff detection system 111.

[0198] As can be seen in Figure 8, in this embodiment the airflow for a puff is illustrated as taking a shape similar to a normal or Gaussian distribution: the airflow starts at zero, increases stepwise to a maximum 801max, and then decreases back to zero.

[0199] In this embodiment, the aerosol generating system continuously stores measurements taken by the puff detection system in a data storage means.

[0200] When the puff detection system senses that the airflow rate 801 has increased to a threshold value 801a at time 805a, the electrical circuit controls the power to turn on the heating element, increasing the heating power 803 directly from zero to power 803a.

[0201] When the puff detection system senses that the airflow rate 801 has decreased to a threshold value 801s at time 805s, the aerosol generation system begins to intermittently calculate an estimate for the remaining volume of the puff based on the current detected flow rate and an estimate of the rate of change of the current flow rate. In this embodiment, the flow rate threshold value 801s is 80% of the maximum detected flow rate 801max.

[0202] In this embodiment, the flow sensor stores volumetric flow values ​​intermittently. In this context, "intermittently" means periodically, every period T, although the system may not function as well if values ​​are not stored periodically. P It is used to mean every time T P is short relative to the average puff duration. In this embodiment, the duration T P is 0.01 seconds. After the threshold 801s is reached, the processor of the aerosol generating system calculates the average rate of change of the current flow rate A c Calculate the average rate of change of the current flow rate A c is the flow value Q, which is the five flow values ​​stored before the current flow value. c-5 The current flow rate value A c Subtract from, then divide by 5, and then the period T P The processor then calculates the average rate of change of this current flow rate, A c remains constant. This means that the average rate of change of the current flow rate, A c If is negative, the remaining time of the current puff T C is the current flow rate value Q c The average rate of change of the current flow rate A c The processor then calculates the current remaining volume of the puff, V c The processor calculates an estimate of the remaining volume of the current puff, V, as -0.5 multiplied by the square of the current flow rate, divided by the average rate of change of the current flow rate. c Each calculated estimate of is compared to a threshold volume, which in this embodiment is 3 ml.

[0203] In the first plot of Figure 8, at time 805b, flow rate 801b is measured and stored in a data storage means. An estimate of the remaining volume of the puff is then calculated. This estimate of the remaining volume of the puff is shown as the shaded volume in the first plot of Figure 8. In the embodiment of Figure 8, this estimate for the remaining volume of the puff is a first estimate that is less than 3 ml. Thus, the electrical circuit controls the power to turn off the heating element and immediately reduces the heating power 803 from power 803a to zero.

[0204] The figures show particular embodiments of the aspects described herein. However, it will be apparent that modifications may be made to the described embodiments within the scope of the invention. It will be apparent to those skilled in the art that, where appropriate, features described in connection with one aspect or embodiment may be applied to one or more of the other aspects or embodiments.

[0205] Advantageously, all of the embodiments described herein provide improved methods of controlling aerosol generation in an aerosol generating system. Specifically, the claimed invention provides improved methods of controlling aerosol generation during complex puff profiles.

Claims

1. 1. A method for controlling aerosol generation in an aerosol generating system, the system comprising: a housing having an aerosol generating element, an air inlet and an air outlet; a flow path defined through the housing from the air inlet to the air outlet, the flow path providing air flow past the aerosol-generating element when a user puffs on the system; and a flow sensor configured to detect airflow, the airflow indicating that a user is taking a puff; and wherein the method comprises: increasing the power supplied to the aerosol generation element from power p20 to at least power p21 when the flow sensor detects that the airflow rate is greater than a first threshold value t21; Reducing the power supplied to the aerosol generation element to a power p22, wherein the power p22 is less than the power p21 and satisfies the following conditions: the flow sensor detecting that the flow rate of the airflow is less than a second threshold value t22, the second threshold value t22 being at or indicative of a predetermined flow rate; or detecting, by the flow sensor, that the flow rate of the airflow is less than a third threshold t23, the third threshold t23 being at or indicative of a flow rate that is a predetermined percentage of a maximum detected flow rate of the airflow; and reducing the power supplied to the aerosol generation element to p22 after detecting that the flow rate of the airflow is greater than the first threshold value t21, according to which of the following occurs first: A method comprising:

2. The method of claim 1 , wherein the second threshold t22 and the third threshold t23 are both greater than zero.

3. The method of claim 1 or 2, wherein the power p22 is zero.

4. 2. The method of claim 1, wherein the step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 comprises increasing the power from power p20 to power p21 within 0.1 seconds.

5. 2. The method of claim 1, wherein the step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 comprises increasing the power from power p20 to at least power p21 over a period of 0.1 to 1 second.

6. 2. The method of claim 1, wherein the step of reducing the power supplied to the aerosol generation element to the power p22 comprises reducing the power supplied to the aerosol generation element from at least the power p21 to the power p22.

7. 2. The method of claim 1, wherein the step of reducing the power supplied to the aerosol generation element to the power p22 comprises reducing the power supplied to the aerosol generation element to the power p22 within 0.1 seconds.

8. 2. The method of claim 1, wherein the step of reducing the power supplied to the aerosol generation element to the power p22 includes reducing the power supplied to the aerosol generation element to the power p22 over a period of 0.1 seconds to 1 second after the flow sensor detects that the flow rate of the airflow is less than a second threshold value t22.

9. 2. The method of claim 1, wherein the method comprises increasing the power supplied to the aerosol generation element from at least power p21 to power p25 after the step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 but before the step of decreasing the power supplied to the aerosol generation element to power p22.

10. 10. The method of claim 9, further comprising increasing the power supplied to the aerosol generation element from power p20 to at least power p21, followed by increasing the power supplied to the aerosol generation element from at least power p21 to power p25.

11. 10. The method of claim 9, wherein the step of increasing the power supplied to the aerosol generation element from power p20 to at least power p21 comprises increasing the power supplied to the aerosol generation element from power p20 to power p25, wherein power p25 is greater than power p21.

12. 1. An aerosol generation system, comprising: an aerosol-generating element and a flow path configured to allow airflow through the aerosol-generating element; a flow sensor configured to detect the airflow, the airflow indicating that a user is taking a puff; and a power source for supplying power to the aerosol generating element; an electrical circuit for controlling the supply of power from the power source to the aerosol generation element, the electrical circuit being arranged to perform the method of claim 1; An aerosol generating system comprising:

13. 10. An electrical circuit for an aerosol generating system, wherein the electrical circuit is arranged to carry out the method of claim 1.

14. 10. A computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to carry out the method of claim 1.

15. 10. A computer readable storage medium having stored thereon a computer program that, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to perform the method of claim 1.

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