A method of controlling an aerosol-generating system

Abstract

There is provided a method of controlling an aerosol-generating system (10, 20). The method comprises: for each puff of a plurality of puffs on the aerosol-generating system (10, 20), receiving or determining an operation period; for each operation period, performing a modification of the operation period to determine a modified operation period; and controlling at least one aspect of the aerosol-generating system (10, 20) based on at least one of the modified operation periods. The modification is such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation periods for multiple puffs having shorter operation periods summing to the longer operation period. Related aerosol-generating systems (10, 20) and devices (100, 200) are also provided.

Description

[0001] FTR3998 / PCT - P / 91046.W001

[0002] 1

[0003] A METHOD OF CONTROLLING AN AEROSOL-GENERATING SYSTEM

[0004] The present disclosure relates to a method of controlling an aerosol-generating system. The present disclosure also relates to related aerosol-generating systems and aerosol-generating devices.

[0005] A typical aerosol-generating system may comprise an aerosol-generating device and an aerosol-generating article comprising an aerosol-generating substrate. Alternatively, the aerosolgenerating device may store the aerosol-generating substrate.

[0006] In use, the aerosol-generating device may heat or otherwise interact with the aerosolgenerating substrate to generate an inhalable aerosol.

[0007] It may be useful to be able to accurately and reliably determine, in a cost-effective way, how much of the aerosol-generating substrate has been depleted or remains. This information may be used to improve user experience by controlling an aspect of the system based on this information. For example, user experience may be improved by accurately estimating and indicating to a user how many puffs remain until the substrate is fully depleted. Alternatively, or in addition, user experience may be improved by preventing further activations of an aerosolgenerating element, such as a heater, of the system when it is estimated that there is no, or very little, substrate left, so as to prevent user frustration by puffing on a system that is not longer generating a sufficient quantity or quality of aerosol.

[0008] There are known mechanisms which attempt to determine how much aerosol-generating substrate has been depleted or remains. However, these mechanisms are sometimes one or more of: inaccurate, dependent on the presence of additional sensors, which increases costs, and computationally demanding, which means that larger and more costly processors are required. In addition, some mechanisms are not applicable to some systems. For example, some systems use a sensor to determine a level of free-flowing, liquid aerosol-generating substrate remaining in a reservoir. But this mechanism may be inappropriate for a system where some or all of the liquid aerosol-generating substrate is absorbed in a wick, instead of being free-flowing.

[0009] It is an aim of the present application to solve one or more of the above problems. It is an aim of the present application to provide an improved method for controlling an aerosol-generating system.

[0010] According to this disclosure, there is provided a method of controlling an aerosolgenerating system. The method may comprise, for each puff of a plurality of puffs on the aerosolgenerating system, receiving or determining an operation period. The method may comprise, for each operation period, performing a modification of the operation period to determine a modified operation period. The method may comprise controlling at least one aspect of the aerosolgenerating system based on at least one of the modified operation periods. The modification may be such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation period for multiple puffs having shorter operation period summing to the longer operation period.

[0011] Thus, according to a first aspect of this disclosure, there is provided a method of controlling an aerosol-generating system. The method comprises, for each puff of a plurality of puffs on the aerosol-generating system, receiving or determining an operation period. The method comprises, for each operation period, performing a modification of the operation period to determine a modified operation period. The method comprises controlling at least one aspect of the aerosolgenerating system based on at least one of the modified operation periods. The modification is such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation period for multiple puffs having shorter operation period summing to the longer operation period.

[0012] According to this disclosure, there is provided an aerosol-generating system comprising a controller. The controller may be configured to carry out a method as described above, for example in relation to the first aspect.

[0013] Thus, according to a second aspect of this disclosure, there is provided an aerosolgenerating system comprising a controller configured to carry out a method as described above, for example in relation to the first aspect.

[0014] The aerosol-generating system described above, for example of the first aspect or the second aspect, may be configured to generate an aerosol, for example from an aerosolgenerating substrate. The system, for example of the first aspect or the second aspect, may comprise an aerosol-generating device. The device may be configured to generate an aerosol, for example from an aerosol-generating substrate. The aerosol-generating device may comprise the controller. The aerosol-generating system may comprise the aerosol-generating substrate.

[0015] The aerosol-generating device may store the aerosol-generating substrate. For example the aerosol-generating device may comprise an integral store of the aerosol-generating substrate.

[0016] Alternatively, the aerosol-generating system may comprise an aerosol-generating article. The aerosol-generating article may comprise the aerosol-generating substrate. The aerosolgenerating device may be for use with the aerosol-generating article, for example to generate an aerosol. The aerosol-generating device may be configured to engage with, and disengage from, the aerosol-generating article.

[0017] References to puffs on the aerosol-generating system may refer to puffs on the aerosolgenerating device or on an aerosol-generating article engaged with the device. References to controlling at least one aspect of the aerosol-generating system may refer to controlling at least one aspect of the aerosol-generating device.

[0018] Thus, according to this disclosure, there is provided an aerosol-generating device comprising a controller. Features described above may be applicable to the device. Thus, the device may be for use in, or part of, an aerosol-generating system as described above, for example as referred to in relation to the first aspect or the second aspect. The controller may be configured to carry out the method described above, for example of the first aspect. The controller may be configured to, for each puff of a plurality of puffs on the aerosol-generating device, or on an aerosol-generating article engaged with the device, receive or determine an operation period. The controller may be configured to, for each operation period, perform a modification of the operation period to determine a modified operation period. The controller may be configured to control at least one aspect of the aerosol-generating device based on at least one of the modified operation periods. The modification may be such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation period for multiple puffs having shorter operation period summing to the longer operation period.

[0019] Thus, according to a third aspect of this disclosure, there is provided an aerosolgenerating device comprising a controller. Features described above may be applicable to the device. Thus, the device may be for us in, or part of, an aerosol-generating system as described above, for example the system referred to in relation to the first aspect or the second aspect above. The controller is configured to carry out the method described above, for example in relation to the first aspect. Thus, the controller is configured to, for each puff of a plurality of puffs on the aerosol-generating device, or on an aerosol-generating article engaged with the device, receive or determine an operation period. The controller is configured to, for each operation period, perform a modification of the operation period to determine a modified operation period. The controller is configured to control at least one aspect of the aerosol-generating device based on at least one of the modified operation periods. The modification may be such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation period for multiple puffs having shorter operation period summing to the longer operation period.

[0020] According to a fourth aspect of this disclosure, there is provided a controller for an aerosolgenerating system. The controller is configured to carry out a method as described above, for example a method according to the first aspect. The controller may be a controller of the aerosolgenerating system described above, for example the system of the second aspect. The controller may be a controller of the aerosol-generating device described above, for example the device of the third aspect.

[0021] Advantageously, the modified operation period for a puff with a longer operation period is greater than a sum of modified operation periods for multiple puffs having a shorter operation periods summing to the longer operation period. This may mean that, compared with the operation periods, the modified operation periods can provide more accurate estimates of the amount of aerosol-generating substrate used for puffs of varying length. This is because there is often a lag between activating an aerosol-generating element, such as a heater, and the aerosol-generating element actually vaporising or atomising aerosol-generating substrate. This may mean that a smaller percentage of a shorter puff is spent actually depleting aerosol-generating substrate compared to a longer puff. So when comparing two puffing regimes over a fixed total puffing period, a user taking more shorter puffs is likely to deplete less aerosol-generating substrate than a user taking fewer longer puffs. So, by having the modified operation period for a puff with a longer operation period being greater than a sum of modified operation periods for multiple puffs having a shorter operation periods summing to the longer operation period, the lag may effectively be taken into account, and the modified operation periods may be used to provide more accurate estimates of the amount of aerosol-generating substrate actually depleted during the puffs.

[0022] As the skilled person would understand after reading this disclosure, the features set out below may be applicable to any of the first, second and third aspects set out above. So, as the skilled person would understand after reading this disclosure, when stating that the system or device may comprise X, this means that the system of the first or second aspects may comprise X, and that the device of the third aspect may comprise X. Similarly, when stating that a feature Y is applicable to the system or device, this means that feature Y is applicable to the system of the first or second aspects, and that feature Y is applicable to the device of the third aspect. References to puffs may refer to puffs on the system, the device, or an article engaged with the device. References to control of the system, or at least one aspect of the system, may refer to control of the device, or at least one aspect of the device, and vice versa.

[0023] Optionally, the operation period of a puff is, or is indicative of or related to, a puff period of the puff. The puff period of a puff may be a period of time from a start of the puff to an end of the puff. Advantageously, this may be a straightforward way to determine the operation period.

[0024] The system or device may comprise a puff sensor. The puff sensor may be connected to the controller. The puff sensor may be for detecting or estimating an air flow rate through the system or device.

[0025] Optionally, the start of the puff corresponds to when an air flow rate through the system increases above a puff start threshold. The puff sensor may determine when the air flow rate through the system increases above the puff start threshold.

[0026] Optionally, the end of the puff corresponds to when an air flow rate through the device decreases below a puff end threshold. The puff sensor may determine when the air flow rate through the system decreases below the puff end threshold.

[0027] The puff start threshold may be the same as the puff end threshold. Advantageously, this may simplify operation of the system or device.

[0028] The puff start threshold may be different to the puff end threshold. Advantageously, this may allow more sophisticated operation of the system or device.

[0029] The system or device may comprise at least one aerosol-generating element. References to the aerosol-generating element below should be taken as references to the at least one aerosol-generating element. Options for the aerosol-generating element are set out later.

[0030] Optionally, the operation period of a puff is, or is indicative of or related to, an activation period of the puff. The activation period of a puff may be a period of time that the aerosolgenerating element of the system or device was activated during the puff. Advantageously, using the activation period of a puff as the operation period may result in a more accurate estimate of how much aerosol-generating substrate is being depleted. In addition, in some embodiments, using the activation period of a puff may not require additional sensors.

[0031] Optionally, the modification is, comprises, or comprises a mathematical equivalent of: raising the operation period, or a function of the operation period, to an exponent greater than 1 . Advantageously, such modification may achieve the result that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation period for multiple puffs having shorter operation periods summing to the longer operation period. As an example to illustrate this, such modification may achieve the result that a modified operation period for a puff with a three-second operation period is greater than a sum of modified operation periods for three puffs each having a one-second operation period. Advantageously, such modification may be less computationally demanding than other possible modifications. So a simple controller can be used to perform the function.

[0032] Optionally, the exponent is at least 1.05, preferably at least 1.1. Optionally, the exponent is no more than 2.9, preferably no more than 1.9, particularly preferably no more than 1.5. Optionally, the exponent is between 1 and 2.9, preferably between 1 and 1.9, particularly preferably between 1 and 1.5. Optionally, the exponent is between 1.05 and 2.9, preferably between 1.05 and 1.9, particularly preferably between 1.05 and 1.5. Optionally, the exponent is between 1.1 and 2.9, preferably between 1.1 and 1 .9, particularly preferably between 1.1 and 1 .5. Advantageously, the inventors have found that using an exponent as set out in this paragraph may mean that the modified operation periods better align with the actual quantity of substrate that is depleted during puffs of typical lengths.

[0033] Optionally, the modification is such that a modified operation period for a puff with a three- second operation period is 20 percent to 200 percent, preferably 35 percent to 150 percent, particularly preferably 50 percent to 100 percent, greater than a sum of modified operation periods for three puffs each having a one-second operation period. Advantageously, such modification may be optimised for the typical puff lengths, which are generally around one to three seconds.

[0034] The controller may comprise a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control.

[0035] Controlling at least one aspect of the system or device may refer to, or comprise, controlling any one or more of: the aerosol-generating element of the system or device, an indicator of the system or device, a power supply of the system or device, and an ability of a user to recharge a power supply of the system or device.

[0036] Optionally, the method may comprise controlling at least one aspect of the system or device based on a sum of multiple modified operation periods, for example based on a sum of the modified operation periods for the plurality of puffs. This may advantageously mean that the at least one aspect of the system or device is being controlled based on an accurate and reliable estimate of the amount of substrate depleted or remaining.

[0037] Optionally, the method may comprise locking the system or device based on a sum of multiple modified operation periods, for example based on a sum of the modified operation periods for the plurality of puffs.

[0038] Optionally, the method may comprise locking the system or device when a sum of the modified operation periods for the plurality of puffs reaches a sum threshold. The sum threshold may be a predetermined threshold. The sum of the modified operation periods reaching the sum threshold may indicate that a predetermined amount, for example most or all, of the aerosolgenerating substrate has been depleted. The initial amount of aerosol-generating substrate may be known. Thus the sum threshold may be used to lock the system or device when it is expected that no, or very little substrate remains.

[0039] The sum threshold may be related to, or based on, a storage capacity of the device or system for aerosol-generating substrate, for example liquid aerosol-generating substrate. The sum threshold may be related to, or based on, an initial amount of aerosol-generating substrate, for example liquid aerosol-generating substrate, stored by the device or system.

[0040] The sum threshold may be at least 2000, 4000 or 6000 seconds. The sum threshold may be no more than 16000, 12000, or 10000 seconds. The sum threshold may be between 2000 and 16000 seconds, preferably between 4000 and 12000 seconds, more preferably between 6000 and 10000 seconds.

[0041] The storage capacity of the system or device may be at least 2, 5 or 8 millilitres. The storage capacity of the system or device may be no more than 25, 22 or 20 millilitres. The storage capacity of the system or device may be between 2 and 25 millilitres, preferably between 5 and 22 millilitres, more preferably between 8 and 20 millilitres. The initial amount of aerosol-generating substrate stored by the device or system may be at least 2, 5 or 8 millilitres. The initial amount of aerosol-generating substrate stored by the device or system may be no more than 25, 22 or 20 millilitres. The initial amount of aerosol-generating substrate stored by the device or system may be between 2 and 25 millilitres, preferably between 5 and 22 millilitres, more preferably between 8 and 20 millilitres.

[0042] The method may be particularly suitable for systems or devices with relatively large capacities or initial amounts of substrate. This is because systems with smaller capacities or initial amounts can be made non-rechargeable, and thus the battery size can be set to run out when the substrate is almost fully depleted. However, with larger capacities or initial amounts, the battery is usually rechargeable, so another mechanism may be required for determining when the substrate is almost fully depleted.

[0043] The sum threshold may be set such that, if each of the plurality of puffs has an operation period of two seconds, when the sum of the modified operation periods for the plurality of puffs reaches the sum threshold, there is an amount of aerosol-generating substrate remaining. That amount may be at least 1 , 4 or 6 millilitres. That amount may be no more than 10, 8 or 7 millilitres. That amount may be between 1 and 10, preferably between 4 and 6, more preferably between 6 and 7 millilitres.

[0044] The sum threshold may be set such that, if each of the plurality of puffs has an operation period of two seconds, when the sum of the modified operation periods for the plurality of puffs reaches the sum threshold, there is a percentage of an initial amount of aerosol-generating substrate of the system, device or article remaining. That percentage may be at least 10, 22 or 33 percent. That percentage may be no more than 55, 45 or 38 percent. That percentage may be between 10 and 55, preferably between 22 and 45, more preferably between 33 and 38, percent.

[0045] The values and ranges in the above two paragraphs may provide an optimal compromise between wanting to make full use of the aerosol-generating substrate available whilst still maintaining a sufficient safety margin of sufficient remaining substrate to have a suitably low risk of dry puffs. The values and ranges in the above two paragraphs may be based on allowing all components of the system or device to cool to around room temperature, for example around 20 degrees Celsius, after each puff. Alternatively, the values and ranges in the above two paragraphs may be based on a typical puffing regime in which subsequent puffs, at least during individual usage sessions, are taken before components such as heaters have had sufficient time to cool back to room temperature since being heated in the last puff.

[0046] Optionally, the method comprises controlling at least one aspect of the aerosol-generating system, preferably at least one aspect of the device, if a sum of multiple modified operation periods, for example if a sum of modified operation periods for a second plurality of puffs, which may be a subset of the plurality of puffs, exceeds a second sum threshold within a predetermined time period. Optionally, the method comprises locking the system or device, for example locking the system or device for a second predetermined time period, if a sum of the modified operation periods for a second plurality of puffs, which may be a subset of the plurality of puffs, reaches a second sum threshold in a predetermined time period. The method may comprise storing a timestamp of each puff in the memory. This may allow the control as described in the previous few sentences. The second sum threshold may be a predetermined threshold. The sum of the modified operation periods reaching the second sum threshold may indicate that a predetermined amount of a particular substance, such as nicotine, has been delivered. Thus the second sum threshold may be used to temporarily lock the system or device when a predetermined amount of a particular substance, such as nicotine, has been delivered in a given time period. This may advantageously prevent too much of the particular substance being delivered to the user in a too short time period.

[0047] The system or device may comprise a power source. The power source may be rechargeable. The power source may be connected to the aerosol-generating element. The power source may be connected to the puff sensor. The power source may be connected to the controller. The controller may control the power supplied from the power source to the aerosol- generating element, for example to generate an aerosol from aerosol-generating substrate. Supplying power to the aerosol-generating element may be referred to as activating the aerosolgenerating element. Stopping supply of power to the aerosol-generating element may be referred to as deactivating the aerosol-generating element.

[0048] The power source may be a battery. The battery may be a Lithium based battery, for example a Lithium-Cobalt, a Lithium-lron-Phosphate, a Lithium Titanate or a Lithium-Polymer battery. The battery may be a Nickel-metal hydride battery or a Nickel cadmium battery. The charge capacity of the rechargeable power source may not be sufficient to aerosolise all of the aerosol-generating substrate it is expected to aerosolise. Reducing the charge capacity of the power source allows smaller power sources to be used. In turn, this helps to reduce the size or form factor of the system or device and the amount of material used in its manufacture.

[0049] Optionally, the locking of the system or device may prevent one or both of: activating the aerosol-generating element of the system or device; and recharging the power source of the system or device.

[0050] The locking of the system or device may be temporary or permanent. Optionally, the locking of the system or device may prevent one or both of: activating the aerosol-generating element; and recharging the power source, until the system or device is re-filled with aerosolgenerating substrate. Optionally, the locking of the system or device may prevent one or both of: activating the aerosol-generating element; and recharging the power source, until an aerosolgenerating article engaged with the device is disengaged from the device or until a new aerosolgenerating article is engaged with the device. Such locking may be particularly advantageous when used in combination with the sum threshold described earlier. Advantageously, such locking may prevent dry puffs.

[0051] Optionally, the locking of the system or device may prevent one or both of: activating the aerosol-generating element; and recharging the power source, for a second predetermined time period. Such locking may be particularly advantageous when used in combination with the second sum threshold described earlier. Advantageously, such locking may prevent delivery of too much of a particular substance in a given time period.

[0052] The system or device may comprise a memory. The memory may be for storing data. The memory may be a non-volatile memory. Advantageously, this may prevent the data being lost if the system or device loses all power, for example if the power source becomes completely depleted of charge. The non-volatile memory may be an electrically erasable programmable readonly memory (EEPROM).

[0053] Optionally, the method may comprise, based on at least one of the modified operation periods, for example based on a sum of multiple modified operation periods or based on a sum of the modified operation periods for the plurality of puffs, storing a value in the memory. The value may be, or be indicative of or related to, an estimate of one or more of: how much of the aerosol-generating substrate has been depleted; how much of the aerosol-generating substrate remains; how much of a particular substance of the aerosol-generating substrate has been depleted or delivered to the user across one or more puffs; how much of a particular substance of the aerosol-generating substrate remains; and a remaining number of puffs on the system or device until the aerosol-generating substrate is depleted or the system or device is locked.

[0054] The method may comprise indicating any one or more of these estimates to a user. The method may comprise alerting a user when any one or more of these estimates reaches a threshold. The system or device may comprise an indicator for said indicating or alerting. The controller may be connected to the indicator. The indicator may be or comprise any one or more of a visual indicator, an audible indicator, and a haptic indicator. The indicator may preferably be or comprise a display. The display may be configured to display any one or more of the above estimates. The display may be configured to display any one or more of: a remaining level of charge in the power source, and a remaining amount of aerosol-generating substrate.

[0055] The estimates and indications referred to above may not be indicated in a precise manner. For example, an estimate or indication of the amount of substrate remaining may be indicated using bars as follows. Showing four bars may indicate that 75 to 100 percent of the initial amount of substrate remains. Showing three bars may indicate that 50 to 75 percent of the initial amount of substrate remains. Showing two bars may indicate that 25 to 50 percent of the initial amount of substrate remains. Showing one bar may indicate that less than 0 to 25 percent of the initial amount of substrate remains.

[0056] The estimate of the remaining number of puffs on the system or device until the aerosolgenerating substrate is depleted or the system or device is locked may be based on previous puffing behaviour, for example based on previous operation periods or previous modified operation periods. The behaviour, for example the previous operation periods or previous modified operation periods, may be stored in the memory of the system or device. This may mean that, if the previous puffing behaviour indicates an average operation period of around three seconds, the estimate of the remaining number of puffs may be lower than if the recorded puffing behaviour indicates an average operation period of two seconds. This may advantageously provide a better estimate.

[0057] Thus, as the skilled person would understand after reading this disclosure, the method may comprise, based on at least one of the modified operation periods, one or both of: indicating to a user an estimate of a remaining number of puffs on the system until an aerosol-generating substrate is depleted or the system is locked; and storing a value in a memory, wherein the value is, or is indicative of or related to, an estimate of a remaining number of puffs on the system until an aerosol-generating substrate is depleted or the system is locked, wherein the estimate of the remaining number of puffs on the system until the aerosol-generating substrate is depleted or the system is locked is based on previous puffing behaviour. As set out above, optionally, the system or device comprises a puff sensor. The puff sensor may be for detecting puffs on the system or device. The puff sensor may be for detecting puffs on an aerosol-generating article engaged with the device. The method may comprise detecting each of the plurality of puffs or each of the second plurality of puffs or both. The puff sensor may provide an input to the controller when a puff, for example each of the plurality of puffs or each of the second plurality of puffs or both, is detected by the puff sensor. The controller may receive an input from the puff sensor when each of the plurality of puffs, or each of the second plurality of puffs, or both, is detected by the puff sensor.

[0058] Optionally, the puff sensor senses or determines one or more of: a pressure and a flow rate, such as an air flow rate.

[0059] Optionally, the controller activates, or deactivates, or both activates and deactivates, the aerosol-generating element based on input from the puff sensor.

[0060] Optionally, the operation period is received from the puff sensor or is determined based on input from the puff sensor. Optionally, when a user starts to puff on the system or device, the puff sensor detects the puff and sends an input to the controller. Optionally, when the user ends a puff on the system or device, the puff sensor detects the end of the puff and stops sending an input to the controller.

[0061] The method may further comprise counting the number of puffs on the system or device. This count may be stored in the memory. The puff sensor may be used to count the number of puffs. Advantageously, this may may allow more sophisticated operation, an example of which is explained in the specific description later.

[0062] Optionally, the system or device comprises an integral store of aerosol-generating substrate. The integral store may be in the form of a reservoir. Advantageously, this may mean that the design of the system or device may be simplified.

[0063] Optionally, the system or device is non-refillable. Optionally, the system or device comprises a store of liquid aerosol-generating substrate and the store is non-refillable. Optionally, the system or device is disposable. Advantageously, this may mean that inexpensive system or device components can be used. For example, a non-refillable aerosol-generating system or device may not be required to be used for an extended period of time. So, components with a lower functional life cycle may be used. These components may be relatively inexpensive. This could lead to an overall reduction in cost for the system or device.

[0064] Optionally, the aerosol-generating element is or comprises an electrically resistive heating element. Advantageously, the electrically resistive heating element may be a simple configuration. For example, the electrically resistive heating element may be a wire comprising a material with a relatively high resistance. The electrically resistive heating element may comprise an electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically “conductive” ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetai® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required.

[0065] The resistive heating element may comprise an internal heating element or an external heating element, or both internal and external heating elements, where “internal” and “external” refer to a position relative to the aerosol-generating substrate. An internal heating element may take any suitable form. For example, an internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heating element may be one or more heating needles or rods that run through the centre of the aerosol-generating substrate. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or a heating plate. Optionally, the internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as a ceramic material, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heating elements during operation.

[0066] The resistive heating element may comprise a fluid permeable heating element. The fluid permeable heating element may be substantially flat. The fluid permeable heating element may comprise electrically conductive filaments. The electrically conductive filaments may lie in a single plane. In other embodiments, the substantially flat heating element may be curved along one or more dimensions, for example forming a dome shape or bridge shape.

[0067] The electrically conductive filaments may define interstices between the filaments and the interstices may have a width of between 10 pm and 100 pm. The filaments may give rise to capillary action in the interstices, so that in use, a liquid aerosol-generating substrate is drawn into the interstices, increasing the contact area between the heating element and the liquid. Optionally, the aerosol-generating element may comprise a mesh. The aerosol-generating element may comprise a rolled mesh.

[0068] The electrically conductive filaments may form a mesh of size between 160 and 600 mesh US (+ / - 10%) (i.e. between 160 and 600 filaments per inch (+ / - 10%)). The width of the interstices is preferably between 75 pm and 25 pm. The percentage of open area of the mesh, which is the ratio of the area of the interstices to the total area of the mesh is preferably between 25 and 56%. The mesh may be formed using different types of weave or lattice structures. Alternatively, the electrically conductive filaments consist of an array of filaments arranged parallel to one another.

[0069] The electrically conductive filaments may have a diameter of between 10 pm and 100 pm, preferably between 8 pm and 50 pm, and more preferably between 8 pm and 39 pm. The filaments may have a round cross section or may have a flattened cross-section. The heater filaments may be formed by etching a sheet material, such as a foil. If the heater assembly comprises a mesh or fabric of filaments, the filaments may be individually formed and knitted together.

[0070] The area of the fluid permeable heating element may be, for example, less than or equal to 50 square millimetres, preferably less than or equal to 25 square millimetres, more preferably approximately 15 square millimetres.

[0071] The electrical resistance of the mesh, array or fabric of electrically conductive filaments of the heating element may be between 0.3 Ohms and 4 Ohms. Preferably, the electrical resistance is equal or greater than 0.5 Ohms. More preferably, the electrical resistance of the mesh, array or fabric of electrically conductive filaments is between 0.6 Ohms and 0.8 Ohms.

[0072] Optionally, the aerosol-generating element is or comprises an inductor such as an inductor coil. The aerosol-generating element may be or a comprise susceptor material. Alternatively, the aerosol-generating element may be configured to interact with susceptor material to generate an aerosol in use. For example, the aerosol-generating element may comprise an inductor configured to generate an alternating magnetic field in use. The alternating magnetic field may be used to heat the susceptor material in use. This may heat aerosol-generating substrate.

[0073] Optionally, the aerosol-generating substrate is or comprises a liquid aerosol-generating substrate or a gel aerosol-generating substrate. These states may be references to the substrate at 20 degrees Celsius and atmospheric pressure.

[0074] As used herein, the term “aerosol-generating substrate” may refer to a substrate capable of releasing volatile compounds that may form an aerosol. Such volatile compounds may be released by heating the aerosol-generating substrate.

[0075] The aerosol-generating substrate may comprise one or more aerosol formers. An aerosol former may be any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the system. Examples of suitable aerosol formers include glycerine and propylene glycol. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dod ecaned io ate and dimethyl tetradecanedioate. The aerosol-generating substrate may comprise water, solvents, ethanol, plant extracts and natural or artificial flavours. The aerosol-generating substrate may comprise nicotine and at least one aerosol former. The aerosol former may be glycerine or propylene glycol. The aerosol former may comprise both glycerine and propylene glycol. The aerosol-generating substrate may comprise nicotine.

[0076] The aerosol-generating substrate may be a solid aerosol-generating substrate. The aerosol-generating substrate may comprise both solid and liquid components. The aerosolgenerating substrate may comprise a tobacco-containing material. The tobacco-containing material may contain volatile tobacco flavour compounds which are released from the substrate upon heating. The aerosol-generating substrate may comprise a non-tobacco material. The aerosol-generating substrate may further comprise an aerosol former. Examples of suitable aerosol formers are given above. Glycerine and propylene glycol may be preferred aerosol formers.

[0077] The system or device may comprise a wick. The wick may store aerosol-generating substrate. The wick may be configured to convey liquid aerosol-generating substrate to the aerosol-generating element. Advantageously, aerosol-generating substrate flow across the atomiser may be facilitated by the wick. The aerosol-generating element may be in fluid communication with the wick.

[0078] The method of the first aspect may be particularly advantageous when used in a system or device comprising a wick. This is because it may be difficult to use other mechanisms for determining how much substrate is left when the substrate is stored in the wick.

[0079] The wick may comprise a porous material. The wick may comprise a sponge material. The wick may comprise layers of wicking material. The wick may comprise layers of cotton.

[0080] The system or device may comprise a longitudinal axis extending between a proximal end and a distal end. The system or device may be an elongate system or device. The user may puff on the proximal end of the system or device.

[0081] The system may comprise an air inlet. The device may comprise the air inlet. The system may comprise an air outlet. The device or the aerosol-generating article may comprise the air outlet. The system may comprise an air passage from the air inlet, through or past the aerosolgenerating element, to the air outlet. The device may comprise the air passage. The device and article may together comprise the air passage.

[0082] As used herein, the term “aerosol-generating system” may refer to a system able to generate an aerosol from an aerosol-generating substrate. The aerosol-generating substrate may or may not be considered part of the system. The aerosol-generating system may comprise an aerosol-generating device. The aerosol-generating system may comprise an aerosol-generating article. The aerosol-generating system is sometimes referred to as the system herein.

[0083] As used herein, the term “aerosol-generating device” may refer to a device able to generate an aerosol from an aerosol-generating substrate. The aerosol-generating device is sometimes referred to as the device herein. As used herein, the term “aerosol-generating article” may refer to an article comprising an aerosol-generating substrate. The aerosol-generating article may be a cartridge. The aerosolgenerating article may comprise one or more components wrapped in a wrapper, for example a paper or cellulosic wrapper. The aerosol-generating article is sometimes referred to as the article herein.

[0084] As used herein, the term “aerosol-generating substrate” may refer to a substrate capable of releasing volatile compounds that can form an aerosol. The volatile compounds may be released by heating or combusting the aerosol-forming substrate. As an alternative to heating or combustion, in some cases, volatile compounds may be released by a chemical reaction or by a mechanical stimulus, such as ultrasound. The aerosol-forming substrate may be solid or liquid or may comprise both solid and liquid components.

[0085] As used herein, the term “aerosol” may refer to a dispersion of solid particles or liquid droplets or a combination of solid particles and liquid droplets in a gas. The aerosol may be visible or invisible. The aerosol may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles or liquid droplets or a combination of solid particles and liquid droplets.

[0086] As used herein, the term “puff” may refer to a single draw, or inhalation, by a user on the system to draw aerosol from the system. The user may draw on the device, for example a mouthpiece of the device. Alternatively, the user may draw on an aerosol-generating article engaged with the device.

[0087] As used herein, the term “usage session” may refer to a series of multiple, consecutive puffs. The term "usage session" may refer to a “smoking session”. A usage session may last for at least 6 or 8 puffs. A usage session may last for no more than 20 or 16 puffs. A usage session may last for between 6 and 20, preferably between 8 and 16 puffs. A usage session may refer to a series of 12 consecutive puffs. Usage sessions may not overlap with one another. In other words, it may be that a second usage session can only begin once a first usage session has ended.

[0088] As used herein, the term “dry puff” may refer to an event in which a user puffs on the system but there is insufficient aerosol-generating substrate present to generate a good quality or quantity of aerosol. This can lead to user frustration. In systems where the aerosol-generating element is a heater, it can also lead to overheating of the heater and, potentially, thermal degradation of any aerosol-generating substrate that is present, which can produce unwanted byproducts.

[0089] As used herein, the term “disposable” may refer to a system or device that is intended to be discarded, or preferably recycled, once the aerosol-generating substrate is substantially depleted. In other words, the system or device may not be configured to receive a replaceable article with aerosol-generating substrate nor to be refilled with aerosol-generating substrate as part of its normal operation. The system or device may be described as non-ref illable. The system or device may be sealed or secured to prevent refilling.

[0090] As used herein, with reference to an aerosol-generating system, device or article, the term “longitudinal” may refer to a direction between a downstream, proximal or mouth end of the system, device or article and an opposed, upstream or distal end of the system, device or article.

[0091] As used herein, the term “initial amount of aerosol-generating substrate” may refer to the initial amount of aerosol-generating substrate in the system or device or article. This initial amount of aerosol-generating substrate may be the amount of aerosol-generating substrate in the system, device or article before the plurality of puffs, for example immediately before the plurality of puffs, or indeed before any puffs, are taken on the system, device or article. So the initial amount of aerosol-generating substrate may refer to the amount of aerosol-generating substrate in the system, device or article before any use of the system, device or article to generate an aerosol.

[0092] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0093] The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0094] Ex1. A method of controlling an aerosol-generating system, the aerosol-generating system preferably comprising an aerosol-generating device, the method comprising: for each puff of a plurality of puffs on the aerosol-generating system, receiving or determining an operation period; for each operation period, performing a modification of the operation period to determine a modified operation period; and controlling at least one aspect of the aerosol-generating system based on at least one of the modified operation periods, wherein the modification is such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation period for multiple puffs having shorter operation period summing to the longer operation period. Ex2. A method according to Example Ex1 , wherein the operation period of a puff is, or is indicative of or related to, an activation period of the puff, the activation period being a period of time that an aerosol-generating element of the system, preferably an aerosol-generating element of the device, was activated during the puff.

[0095] Ex3. A method according to Example Ex1 , wherein the operation period of a puff is, or is indicative of or related to, a puff period of the puff, the puff period being a period of time from a start of the puff to an end of the puff.

[0096] Ex4. A method according to Example Ex3, wherein the start of the puff corresponds to when an air flow rate through the system, preferably through the device, increases above a puff start threshold.

[0097] Ex5. A method according to Example Ex3 or Example Ex4, wherein the end of the puff corresponds to when an air flow rate through the system, preferably through the device, decreases below a puff end threshold.

[0098] Ex6. A method according to any preceding Example, wherein the modification is, comprises, or comprises a mathematical equivalent of: raising the operation period, or a function of the operation period, to an exponent greater than 1 .

[0099] Ex7. A method according to any preceding Example, wherein the modification is, comprises, or comprises a mathematical equivalent of raising the operation period, or a function of the operation period, to an exponent which is at least 1 .05 or 1 .1 .

[0100] Ex8. A method according to any preceding Example, wherein the modification is, comprises, or comprises a mathematical equivalent of raising the operation period, or a function of the operation period, to an exponent which is no more than 2.9, 1 .9, or 1 .5.

[0101] Ex9. A method according to any preceding Example, wherein the modification is, comprises, or comprises a mathematical equivalent of raising the operation period, or a function of the operation period, to an exponent between 1 and 2.9, 1 and 1 .9, 1 and 1 .5, 1 .05 and 2.9, 1 .05 and 1 .9, 1 .05 and 1 .5, 1 .1 and 2.9, 1 .1 and 1 .9, or 1 .1 and 1 .5.

[0102] Ex10. A method according to any preceding Example, wherein the modification is such that a modified operation period for a puff with a three-second operation period is 20 percent to 200 percent, preferably 35 percent to 150 percent, particularly preferably 50 percent to 100 percent, greater than a sum of modified operation periods for three puffs each having a one- second operation period.

[0103] Ex11 . A method according to any preceding Example, wherein the method comprises controlling at least one aspect of the aerosol-generating system, preferably at least one aspect of the device, based on a sum of multiple modified operation periods, for example based on a sum of the modified operation periods for the plurality of puffs.

[0104] Ex12. A method according to any preceding Example, wherein the method comprises locking the system, preferably locking the device, based on a sum of multiple modified operation periods, for example based on a sum of the modified operation periods for the plurality of puffs.

[0105] Ex13. A method according to any preceding Example, wherein the method comprises locking the system, preferably locking the device, based on a sum of multiple modified operation periods, for example based on a sum of the modified operation periods for the plurality of puffs, so as to prevent one or more of: activating an aerosol-generating element of the system, preferably an aerosol-generating element of the device; and recharging a power source of the system, preferably a power source of the device.

[0106] Ex14. A method according to any preceding Example, wherein the method comprises locking the system, preferably locking the device, based on a sum of multiple modified operation periods, for example based on a sum of the modified operation periods for the plurality of puffs, so as to prevent one or more of: activating an aerosol-generating element of the system, preferably an aerosol-generating element of the device; and recharging a power source of the system, preferably a power source of the device, until the system, preferably the device, is refilled with aerosol-generating substrate.

[0107] Ex15. A method according to any preceding Example, wherein the method comprises, based on at least one of the modified operation periods, for example based on a sum of multiple modified operation periods or based on a sum of the modified operation periods for the plurality of puffs, storing a value stored in a memory of the system, preferably in a memory of the device, the value being, or being indicative of or related to, an estimate of one or more of: how much aerosol-generating substrate has been depleted; how much aerosol-generating substrate remains; how much of a particular substance of an aerosol-generating substrate has been depleted or delivered to the user across one or more puffs; how much of a particular substance of an aerosol-generating substrate remains; and a remaining number of puffs on the system or device until the aerosol-generating substrate is depleted or the system or device is locked, optionally wherein the method further comprises indicating to a user any one or more of the above estimates.

[0108] Ex16. A method according to any preceding Example, wherein the method comprises controlling at least one aspect of the aerosol-generating system, preferably at least one aspect of the device, if a sum of multiple modified operation periods, for example if a sum of modified operation periods for a second plurality of puffs, exceeds a second sum threshold within a predetermined time period, optionally wherein said controlling is or comprises locking the aerosol-generating system, preferably locking the device, so as to prevent, for a second predetermined time period, one or both of activating an aerosol-generating element of the aerosol-generating system and recharging a power source of the aerosol-generating system. Ex17. A method according to any preceding Example, wherein the system, preferably the device, comprises a puff sensor for detecting puffs on the system, for example for detecting puffs on the device of the system or on an aerosol-generating article engaged with the device.

[0109] Ex18. A method according to Example Ex17, wherein the puff sensor senses one or more of a pressure and an air flow rate.

[0110] Ex19. A method according to Example Ex17 or 18, wherein the method comprises activating, or deactivating, or both activating and deactivating, an aerosol-generating element of the system, preferably an aerosol-generating element of the device, based on input from the puff sensor.

[0111] Ex20. A method according to any of Examples Ex17 to Ex19, wherein the operation period is received from the puff sensor or is determined based on input from the puff sensor.

[0112] Ex21 . A method according to any preceding Example, wherein the system, preferably the device, comprises an integral store of or for aerosol-generating substrate, preferably liquid aerosolgenerating substrate.

[0113] Ex22. A method according to any preceding Example, wherein the system, preferably the device, is non-refillable.

[0114] Ex23. A method according to any preceding Example, wherein the system, preferably the device, comprises a rechargeable power source.

[0115] Ex24. A method according to any preceding Example, wherein the system, preferably the device, comprises an aerosol-generating element.

[0116] Ex25. A method according to Example Ex23, wherein the aerosol-generating element is or comprises an electrically resistive heating element, or wherein the aerosol-generating element is or comprises an inductor such as an inductor coil.

[0117] Ex26. A method according to any preceding Example, wherein the system, preferably the device, is for generating, and preferably configured to generate, an inhalable aerosol from an aerosolgenerating substrate, particularly preferably wherein the aerosol-generating substrate is or comprises a liquid aerosol-generating substrate or a gel aerosol-generating substrate.

[0118] Ex27. A controller for an aerosol-generating system, the controller being configured to carry out a method according to any preceding Example.

[0119] Ex28. An aerosol-generating system comprising a controller configured to carry out a method according to any of examples Ex1 to Ex26.

[0120] Ex29. An aerosol-generating system according to Example Ex28, wherein the aerosolgenerating system is or consists of the aerosol-generating device.

[0121] Ex30. An aerosol-generating device comprising a controller configured to carry out a method according to any of Examples Ex1 to Ex26.

[0122] Ex31 . An aerosol-generating device, for example the aerosol-generating device referred to in any of Examples Ex1 to Ex26, for use in an aerosol-generating system, for example the aerosol-generating system referred to in any of Examples Ex1 to Ex26, the device comprising a controller configured to carry out a method according to any of Examples Ex1 to Ex26.

[0123] Ex32. An aerosol-generating device according to Example Ex30 or Ex31 , wherein the plurality of puffs on the aerosol-generating system is a plurality of puffs on the aerosol-generating device or on an aerosol-generating article engaged with the aerosol-generating device.

[0124] Ex33. An aerosol-generating device according to Example Ex30 or Ex31 or Ex32, wherein the at least one aspect of the aerosol-generating system is at least one aspect of the aerosolgenerating device.

[0125] Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0126] Figure 1 is a schematic illustration of an aerosol-generating system in accordance with a first embodiment;

[0127] Figure 2 is a schematic illustration of an aerosol-generating system in accordance with a second embodiment;

[0128] Figure 3 is a flow chart of a method according of controlling an aerosol-generating system; and

[0129] Figure 4 is a graph showing operation periods and modified operation periods for the method of the flow chart of Figure 3.

[0130] Figure 1 is a schematic illustration of an aerosol-generating system 10 in accordance with a first embodiment. The system 10 is an aerosol-generating device 100 with a housing 101 having a mouthpiece portion 103 and a body portion 105. The aerosol-generating device 100 extends in a longitudinal axis between a proximal end 131 and a distal end 132.

[0131] In the body portion 105, there is provided an electric power supply 107 and control circuitry 109. The electric power supply 107 is a battery. In other embodiments the electric power supply is a series of batteries. A controller 110 and a puff sensor 111 are electrically connected to the control circuitry 109.

[0132] In the mouthpiece portion 103, there is provided a liquid storage portion 113. The liquid storage portion 113 contains liquid aerosol-generating substrate 115. Suitable liquid aerosolgenerating substrates are known and the skilled person would be able to select a suitable liquid aerosol-generating substrate for use in this system. The mouthpiece portion 103 further comprises a wick 117 and an aerosol-generating element 119. One end of the wick 117 extends into the liquid storage portion 113 and the other end of the wick is surrounded by the aerosolgenerating element 119.

[0133] In the embodiment shown in Figure 1 , the aerosol-generating element 119 is an electrically resistive heating element 119. There may be other embodiments where the aerosol-generating element is a different type of heating element such as one or both of an inductor and a susceptor configured to be heated by the inductor. In other embodiments, the aerosol-generating element may be a mesh heater. The aerosol-generating element 119 is electrically connected to the puff sensor 111 via electrical connections 121 , the puff sensor 111 is also electrically connected to the control circuitry 109 via further electrical connections (not shown). The battery 107 is electrically connected to the resistive heating element 119 in order to supply power to the resistive heating element 119.

[0134] The housing 101 defines an airflow passage, extending from an air inlet 123 to an air outlet 125. The air inlet 123 is located on a side portion of the housing 101. The air outlet 125 is located at the proximal end 131 of the aerosol-generating device 100. The housing 101 comprises an aerosol-generating chamber 127 surrounding the heater 119. Part of the airflow passage extends through the aerosol-generating chamber 127 and is in fluid communication with the wick 117.

[0135] Liquid aerosol-generating substrate 115 is transferred or conveyed by the wick 117 via capillary action from the liquid storage portion 113 to the end of the wick 117 surrounded by the resistive heating element 119.

[0136] In use, the user puffs on the mouthpiece portion 103, which comprises the air outlet 125, and ambient air is drawn through the air inlet 123. The puff is detected or sensed by the puff sensor 111 , which sends a signal to the controller 110, via the control circuitry 109. The battery 107 supplies power to the resistive heating element 119 to heat the liquid aerosol-generating substrate on the end of the wick 117 surrounded by the resistive eating element 119. Liquid aerosol-generating substrate at the end of the wick 117 surrounded by the resistive heating element 119 is vaporized to create a supersaturated vapour. The supersaturated vapour is entrained by air travelling in the airflow path and condenses to form an inhalable aerosol, which is carried towards the air outlet 125 for inhalation by the user.

[0137] The controller 110 is programmable and has embedded software or firmware to control the power supplied to the aerosol-generating element 119. This affects the temperature profile of the aerosol-generating element 119. This, in turn, affects the amount of aerosol produced. The controller 110 modulates power supply from battery 107 by pulse width modulation (PWM) which uses a series of pulses of electrical voltage to transmit power to the aerosol-generating element 119. The power provided to the aerosol-generating element can be varied by varying the duty cycle of the pulses at a constant frequency. The duty cycle is the ratio of the time that the power is switched on to the time the power is switched off. In other words, the ratio of the width of the voltage pulses to the time between the voltage pulses. For example, a low duty cycle of 5% will provide much less power than a duty cycle of 95%.

[0138] Figure 2 is a schematic illustration of an aerosol-generating system in accordance of a second embodiment. The aerosol-generating system comprises an aerosol-generating device 200 and an aerosol-generating article 250.

[0139] As the skilled person would understand, many aerosol-generating articles could be used in this system. Nonetheless, a brief overview of the article 250 of this embodiment is described below. The article 250 comprises: a front plug 251 at an upstream end of the article, a rod of an aerosol-generating substrate 252 abutting a downstream end of the front plug 251 , a susceptor element 253 located along a central longitudinal axis of the rod of the aerosol-generating substrate 252, a support element 254 abutting a downstream end of the rod of aerosol-generating substrate 252, an aerosol-cooling element 255 abutting a downstream end of the support element 254, and a mouthpiece element 256 at a downstream end of the article 250 and abutting the downstream end of the aerosol-cooling element 255, all circumscribed by a paper wrapper 257 of the article 250.

[0140] The front plug 251 is a cylindrical plug of cellulose acetate with a length of about 5 millimetres, an external diameter of about 7.25 millimetres, and a resistance to draw of about 30 millimetres H2O.

[0141] The rod of aerosol-generating substrate 252 has an external diameter of about 7.25 millimetres and a length of about 12 millimetres. The aerosol-generating substrate 252 in this embodiment comprises, on a dry weight basis, around 76 weight percent tobacco, around 18 weight percent glycerin, around 4 weight percent cellulose fibres, and around 2 weight percent guar gum. The rod of substrate 252 is made using a conventional process comprising forming a slurry with the substrate ingredients and water, casting the slurry, drying the slurry to form a sheet, gathering the sheet to form a long rod, then cutting the long rod to provide the rod of substrate 252. After forming the rod of substrate 252, the susceptor element 253 is inserted into the rod and may optionally be adhered to the substrate 252. In this embodiment, the susceptor element 253 is a strip of a ferromagnetic steel and has a length of about 11 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres.

[0142] The support element 254 is a hollow cylindrical tube of cellulose acetate and does not substantially contribute to the overall resistance to draw of the article. In other words, the resistance to draw of the support element is substantially 0 millimetres H2O. The support element 254 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter of about 1 .9 millimetres.

[0143] The aerosol-cooling element 255 is a hollow cylindrical tube of cellulose acetate and does not substantially contribute to the overall resistance to draw of the article. In other words, the resistance to draw of the support element is substantially 0 millimetres H2O. The aerosol-cooling element 255 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter of about 3.25 millimetres.

[0144] The mouthpiece element 256 is a cylindrical plug of low-density cellulose acetate with a length of about 12 millimetres and an external diameter of about 7.25 millimetres. The resistance to draw of the mouthpiece element 256 is about 12 millimetres H2O.

[0145] The aerosol-generating device 200 comprises a housing 201 having a proximal portion 203 and a body portion 205. The aerosol-generating device 200 extends in a longitudinal axis between a proximal end 231 and a distal end 232. In the body portion 205, there is provided an electric power supply 207 and control circuitry 209. The electric power supply 207 is a battery 207. In other embodiments, the electric power supply is a series of batteries. A controller 210 and a puff sensor 211 are electrically connected to the control circuitry 209.

[0146] In the proximal portion 203, there is provided a substrate-receiving cavity 213 configured to receive at least a portion of an aerosol-generating article 250. The substrate-receiving cavity 213 extends in the longitudinal axis from the proximal end 231 of the aerosol-generating device 200. The device 200 comprises an aerosol-generating element 219 in the form of an inductor coil in the cavity 213 and spiralling around the substrate 252 when the article 250 is received in the cavity 213. In other embodiments, an article without a susceptor element could be used and the aerosol-generating element could be an electrically resistive heating element configured to penetrate the substrate upon insertion of the article into the cavity and then heat the substrate from within in use. In other embodiments, the aerosol-generating element could be a tubular electrically resistive heating element arranged in a similar position to the inductor coil in the cavity for heating the substrate from the outside in use.

[0147] The aerosol-generating element 219 is electrically connected to the puff sensor 211 via electrical connections (not shown), and the puff sensor 211 is also electrically connected to the control circuitry 209 via further electrical connections (not shown). The battery 207 is electrically connected to the aerosol-generating element 219 in order to supply an alternating current to the aerosol-generating element 219 and thus create an alternating electromagnetic field in the cavity 213, thereby inducing eddy currents and hysteresis losses in the susceptor element 253 and heating the susceptor element 253, and thus heating the aerosol-generating substrate 252.

[0148] The housing 201 defines an airflow passage, extending from an air inlet 223 to an air outlet 225. The air inlet 223 is located on a side portion of the housing 201 . The air outlet 225 is located at the proximal end 231 of the aerosol-generating device 200. The air outlet 225 has a diameter substantially equal to the diameter of the aerosol-generating article 250. The housing 201 comprises an aerosol-generating chamber 227. At least a portion of the aerosol-generating chamber 227 is defined by the substrate-receiving cavity 213. Part of the airflow passage extends through the aerosol-generating chamber 227 and is in fluid communication with the aerosolgenerating article 250 when it is at least partially received in the substrate receiving cavity 250. The aerosol-generating article 250 defines at least a portion of the airflow path when it is received in the substrate receiving cavity 213. When the aerosol-generating article 250 is received in the substrate receiving cavity 213, at least a portion of the aerosol-generating article 250 extends out from the aerosol-generating device 200 and may be drawn on by a user in a similar way to a conventional cigarette.

[0149] In use, the user puffs on the aerosol-generating article 250 when the aerosol-generating article 250 is at least partially received in the substrate receiving cavity 213, and ambient air is drawn through the air inlet 223. The puff is detected or sensed by the puff sensor 211 , which sends a signal to the controller 210, via the control circuitry 209. The battery 207 supplies an alternating current to the aerosol-generating element 219 and thus creates an alternating electromagnetic field in the cavity 213, thereby inductively heating the susceptor element 253 and thereby heating the aerosol-generating substrate 252 in close thermal contact with the susceptor element 253. At least a portion of the aerosol-generating substrate 252 is vaporized to create a vapour. The vapour is entrained by air travelling in the airflow path and condenses to form an inhalable aerosol.

[0150] The controller 210 is programmable and has embedded software or firmware to control the power supplied to the aerosol-generating element 219. This affects the temperature profile of the susceptor element 253. This, in turn, affects the amount of aerosol produced.

[0151] Figure 3 is a flow chart showing a method of controlling the aerosol-generating systems of Figures 1 and 2.

[0152] In step 301 , a user puffs on the aerosol-generating system. The puff may be on a device of the system, like with the system shown in Figure 1 , or on an article engaged with the device of the system, like with the system shown in Figure 2.

[0153] In step 302, the controller receives or determines an operation period of the puff.

[0154] The controller may receive the operation period from, or determine the operation period based on input from, the puff sensor. The operation period may be a puff period of the puff. This puff period of the puff may be a period of time from when the puff sensor detects a start of the puff to when the puff sensor detects an end of the puff. The puff sensor may detect the start of the puff when the air flow rate through the system increases above a puff start threshold. The puff sensor may detect the end of the puff when the air flow rate through the aerosol-generating system decreases below a puff end threshold.

[0155] Alternatively, the operation period may an activation period of the puff. The activation period of the puff may be a period of time that the aerosol-generating element of the aerosolgenerating system was activated during the puff.

[0156] As another alternative, the operation period may simply be indicative of, or related to, one or both of the puff period and the activation period of the puff. For example, the operation period may be the puff period, or the activation period, minus a small, predetermined amount of time. This small, predetermined amount of time may correspond to an estimate of an amount of time it takes for the aerosol-generating element, or heater, to heat up to an operational temperature and begin aerosolising the substrate. If this function, the puff period, or the activation period, minus the small, predetermined amount of time, results in a negative result, the operation period may be set to zero or ignored. This may be because such a short puff may be considered not to aerosolise any substrate.

[0157] In this particular embodiment, the operation period is the activation period of the puff. The activation period of the puff is the period of time that the aerosol-generating element of the aerosol-generating system was activated during the puff. That is the resistive heating element in the system of Figure 1 and the inductor coil in the system of Figure 2.

[0158] In step 303, the controller performs a modification of the operation period to determine a modified operation period. The modification is such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation periods for multiple puffs having shorter operation periods summing to the longer operation period. This modification may therefore advantageously provide a more accurate estimate of an amount of aerosol-generating substrate depleted as a result of the puff.

[0159] In this particular embodiment, the modification is raising the operation period to an exponent of 1 .2.

[0160] In step 304, the controller controls at least one aspect of the aerosol-generating system based on at least one of the modified operation periods.

[0161] For example, in this embodiment, after determining the modified operation period for the puff, the controller adds the modified operation period to a sum of all previous modified operation periods for previous puffs. When the sum of the modified operation periods reaches a predetermined sum threshold, the system is locked.

[0162] For the system of Figure 1 , the system is locked permanently so as to prevent any further activations of the aerosol-generating element and to prevent recharging the device. At this point, the system should be disposed of.

[0163] For the system of Figure 2, the system is locked temporarily so as to prevent any further activations of the aerosol-generating element until the article currently engaged with the device is disengaged with the device. The device has a sensor (not shown) for detecting engagement of articles with, and disengagement of articles from, the device.

[0164] In addition, in this embodiment, after each puff, the controller estimates a remaining number of puffs on the system and indicates this to a user with a display (not shown). This estimate of the remaining number of puffs is calculated by comparing the number of puffs taken to reach the current sum of the modified operation periods to the predetermined sum threshold. This advantageously takes account of previous puffing behaviour so provides a good estimate. To enable this the controller stores the total number of puffs taken, as detected by the puff sensor, and the current sum of the modified operation periods, in a non-volatile memory of the device.

[0165] As an example, after a number of usage sessions with the system of Figure 1 , the memory may have stored data indicating that the user has taken 1000 puffs and the current sum of modified operation periods is 4000. In addition, the predetermined sum threshold may be stored in the memory and, in this example, may be 8000. Thus, the current estimate of the remaining number of puffs would be 1000, and this may be indicated to the user by the display. After taking another puff with an operation period of around 3.175 seconds and thus a modified operation period of around 4 seconds, the current sum of modified operation periods would be around 4004. Thus, based on the fact that the user has reached the current sum of modified operation periods of 4004 from 1001 puffs, and the fact that the predetermined sum threshold is 8000, the controller would be able to estimate that there is likely around 999 puffs remaining by calculating: (the predetermined sum threshold minus the current sum of modified operation periods) divided by (the current sum of modified operation periods divided by the current number of puffs taken). Numerically, in this example, this calculation is (8000-4004) / (4004 / 1001 ) = 3996 / 4 = 999. The controller may then update the display to show this estimate.

[0166] In addition to the above, after each puff, the controller determines a sum of the modified operation periods for a second plurality of puffs, the second plurality of puffs being the puffs on the system in the previous hour. To enable this, a timestamp of each puff may be stored in the memory along with the operation period and modified operation period of each puff. If the sum of the modified operation periods for a second plurality of puffs reaches a predetermined, second sum threshold, that may be used as an indication that a user has been recently overusing the system, or that the user has already been delivered a sufficient quantity of a particular substance, such as nicotine, of the aerosol-generating substrate in the previous hour. If the sum of the modified operation periods for the second plurality of puffs reaches the predetermined, second sum threshold, the controller temporarily locks the system or device so as to prevent further activations of the aerosol-generating element for the next hour. This may advantageously prevent too much of the particular substance being delivered to the user in a too short time period.

[0167] Figure 4 is a graph. The x-axis shows the operation period 402 for a puff, measured in seconds. The y-axis shows the modified operation period 404 for a puff, measured in seconds. A first line 410 on the graph is dashed and shows the operation period and resulting modified operation period when using the modification described in relation to the embodiment of Figure 3. A second line, 420, is dotted and is used for reference only. The second line plots y=x so, for any given point, shows a modified operation period equal to the operation period. This is the case when no modification of the operation period is performed.

[0168] As is clear from the graph, the modified operation periods for longer puffs are overweighted compared with the modified operation periods for shorter puffs. In other words, the modification is such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation periods for multiple shorter puffs having shorter operation periods summing to the longer operation period.

Claims

26Claims1 . A method of controlling an aerosol-generating system, the method comprising: for each puff of a plurality of puffs on the aerosol-generating system, receiving or determining an operation period; for each operation period, performing a modification of the operation period to determine a modified operation period; and controlling at least one aspect of the aerosol-generating system based on a sum of modified operation periods exceeding a sum threshold within a predetermined time period, wherein the modification is such that a modified operation period for a puff with a longer operation period is greater than a sum of modified operation periods for multiple puffs having shorter operation periods summing to the longer operation period.

2. A method according to claim 1 , wherein the operation period of a puff is, or is indicative of or related to, an activation period of the puff, the activation period of the puff being a period of time that an aerosol-generating element of the aerosol-generating system was activated during the puff.

3. A method according to claim 1 , wherein the operation period of a puff is, or is indicative of or related to, a puff period of the puff, the puff period of the puff being a period of time from a start of the puff to an end of the puff.

4. A method according to claim 3, wherein the start of the puff corresponds to when an air flow rate through the aerosol-generating system increases above a puff start threshold, and the end of the puff corresponds to when an air flow rate through the aerosol-generating system decreases below a puff end threshold.

5. A method according to any preceding claim, wherein the modification is, comprises, or comprises a mathematical equivalent of, raising the operation period, or a function of the operation period, to an exponent greater than 1 .

6. A method according to claim 5, wherein the exponent is between 1 .05 and 2.9.

7. A method according to any preceding claim, wherein the method comprises, based on at least one modified operation period, one or both of: indicating to a user an estimate of a remaining number of puffs on the system until an aerosol-generating substrate is depleted or the system is locked; and storing a value in a memory, wherein the value is, or is indicative of or related to, an estimate of a remaining number of puffs on the system until an aerosol-generating substrate is depleted or the system is locked, wherein the estimate of the remaining number of puffs on the system until the aerosolgenerating substrate is depleted or the system is locked is based on previous puffing behaviour.

8. A method according to any preceding claim, wherein the modification is such that a modified operation period for a puff with a three-second operation period is 35 percent to 150 percent greater than a sum of modified operation periods for three puffs each having a one- second operation period.

9. A method according to any preceding claim, wherein controlling the at least one aspect of the aerosol-generating system is or comprises locking the aerosol-generating system so as to prevent, for a second predetermined time period, one or both of: activating an aerosol-generating element of the aerosol-generating system; and recharging a power source of the aerosol-generating system.

10. A method according to any preceding claim, wherein, based on at least one of the modified operation periods, the method comprises storing a value in a memory of the aerosol-generating system, the value being, or being indicative of or related to, an estimate of one or more of: how much aerosol-generating substrate has been depleted; how much aerosol-generating substrate remains; how much of a particular substance of aerosol-generating substrate has been depleted or delivered to a user across one or more puffs; how much of a particular substance of aerosol-generating substrate remains; and a remaining number of puffs on the aerosol-generating system until an aerosol-generating substrate is considered depleted or the aerosol-generating system is locked.

11. A method according to any preceding claim, wherein the aerosol-generating system comprises a puff sensor for detecting puffs on the aerosol-generating system, and wherein the method comprises one or both of: activating, or deactivating, or both activating and deactivating, an aerosol-generating element of the aerosol-generating system based on input from the puff sensor; and receiving the operation period from the puff sensor or determining the operation period based on input from the puff sensor.

12. A method according to any preceding claim, wherein the aerosol-generating system comprises one or both of: a rechargeable power source and a non-refillable store of aerosolgenerating substrate.

13. A controller for an aerosol-generating system, the controller being configured to carry out the method of any preceding claim.

14. An aerosol-generating system comprising a controller according to claim 13.

15. An aerosol-generating device for use in an aerosol-generating system, the aerosolgenerating device comprising a controller according to claim 13.

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