Aerosol Generating Device Having Temperature-Based Control - Patent application

Abstract

The present invention relates to an aerosol generating device comprising a cavity for receiving an aerosol-forming substrate, an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received in the cavity, a rechargeable power source, and a controller arranged to control the supply of power from the rechargeable power source to the electric heater during a first time period and a second time period following the first time period. The controller is arranged to determine an initial temperature of the electric heater and to determine a rate of temperature rise of the electric heater during the first time period by determining a time taken to raise the temperature of the electric heater from a first predetermined temperature to a second predetermined temperature during the first time period. The controller is also arranged to adjust the supply of power from the power source to the electric heater during the second time period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first time period. The present invention relates to an aerosol generating system comprising an aerosol generating device. The present invention relates to a method of controlling an aerosol generating device and a computer program for carrying out the method.

Description

[Technical field]

[0001] The present invention relates to an aerosol generating device having a controller arranged to control the supply of power to the electric heater based on a determined temperature of the electric heater. The present invention also relates to an aerosol generating system comprising the aerosol generating device. The present invention also relates to a method of controlling an aerosol generating device. [Background technology]

[0002] One type of aerosol generating system is an electrically operated aerosol generating system. Known handheld electrically operated aerosol generating systems generally comprise an aerosol generating device comprising a battery, control electronics, and an electric heater for heating an aerosol generating article specifically designed for use with the aerosol generating device. The aerosol generating article comprises an aerosol-forming substrate. In some embodiments, the aerosol-forming substrate is in the form of a plug, such as a cigarette plug, and an electric heater contained within the aerosol generating device is inserted into the aerosol-forming substrate when the smoking article is inserted into the aerosol generating device.

[0003] Typically, an aerosol generating device is configured to generate heat using an electric heater according to a predetermined heating profile. However, changes in the aerosol-forming substrate may result in undesirable changes in the user experience. For example, in a high humidity environment, the aerosol-forming substrate may exhibit a high water content. Because water is aerosolized at the typical operating temperature of the aerosol generating device, the high water content may result in an unnecessarily high aerosol temperature perceived by the user.

[0004] A high moisture content may also result in a slower rate of temperature rise at the beginning of the user experience. This rate of temperature rise may therefore be used to determine whether the aerosol-forming substrate has a normal moisture content or a high moisture content. The controller is arranged to regulate the supply of power from the power source to the electric heater based on the determined rate of temperature rise.

[0005] It has been observed that during normal use of an aerosol generating device, situations arise where determining the rate of temperature rise alone may not be sufficient to draw a reliable conclusion regarding the moisture content of the aerosol-forming substrate.

[0006] The aerosol generating device may provide a user with more than one user experience without intermediate recharging of the on-board power source. It is recognized that an aerosol generating device that allows for multiple user experiences may lead to new challenges in enabling consistent aerosol formation throughout a full operating cycle.

[0007] It would be desirable to provide an aerosol generating device that alleviates or overcomes at least some of the disadvantages associated with known aerosol generating devices.

[0008] It would be desirable to provide an aerosol generating device that allows more reliable conclusions to be drawn regarding the moisture content of the aerosol-forming substrate so that an appropriate heating profile can be selected.

[0009] It would further be desirable to provide an aerosol generating device that allows for the selection of a suitable heating profile, particularly for an aerosol generating device that provides multiple user experiences without the need for intermediate recharging. Summary of the Invention

[0010] According to one embodiment of the present invention, there is provided an aerosol generating device comprising a cavity for receiving an aerosol-forming substrate and an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received in the cavity, The aerosol generating device also comprises a power source and a controller arranged to control the supply of power from the power source to the electric heater during a first time period and during a second time period after the first time period.

[0011] The controller is arranged to determine a rate of temperature rise of the electric heater during a first period of time by determining the time it takes to raise the temperature of the electric heater from a first predetermined temperature to a second predetermined temperature during the first period of time.

[0012] The controller is arranged to determine an initial temperature of the electric heater.

[0013] The controller is also arranged to adjust the supply of power from the power source to the electric heater during the second time period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first time period.

[0014] Advantageously, the determined rate of temperature rise may be indicative of a moisture content of the aerosol-forming substrate received within the cavity. A determined relatively low rate of temperature rise may be indicative of a relatively high moisture content. A determined relatively high rate of temperature rise may be indicative of a relatively low moisture content. Advantageously, based on the determined rate of temperature rise, the controller varies the supply of power to the electric heater during a subsequent second time period to regulate further heating of the electric heater.

[0015] The first period of time is preferably long enough to ensure a measurable temperature increase of the electric heater over a wide range of moisture contents of the aerosol-forming substrate, and is preferably at least about 1 second, more preferably at least about 2 seconds, and more preferably at least about 3 seconds.

[0016] The first period of time is preferably short enough to minimize the time before the controller alters the supply of power to the electric heater during the second period of time to provide a desired user experience. The first period of time is preferably less than about 15 seconds, more preferably less than about 14 seconds, more preferably less than about 13 seconds, more preferably less than about 12 seconds, more preferably less than about 11 seconds, and more preferably less than about 10 seconds.

[0017] The controller may be arranged to determine a rate of temperature rise of the electric heater by determining a time taken for a predetermined temperature increase of the electric heater to occur. The controller may be arranged to determine a rate of temperature rise of the electric heater during a portion of a first time period. The controller may be arranged to determine a time taken to increase the temperature of the electric heater from a first predetermined temperature to a second predetermined temperature during the first time period, the determined time being the determined rate of temperature rise.

[0018] The first predetermined temperature is preferably above any anticipated ambient temperature. Advantageously, a first predetermined temperature above ambient temperature may minimize or eliminate any change in ambient temperature at the determined temperature rise rate of the electric heater. The first predetermined temperature is preferably at least about 50 degrees Celsius, preferably at least about 60 degrees Celsius, preferably at least about 70 degrees Celsius, preferably at least about 80 degrees Celsius, and preferably at least about 90 degrees Celsius. The first predetermined temperature may be 100 degrees Celsius.

[0019] It is understood that numerical values ​​specified herein encompass a range of values ​​around the specified value based on variations resulting from manufacturing tolerances and precision of measuring instruments.

[0020] The second predetermined temperature is preferably below a target operating temperature of the electric heater during the second time period. Advantageously, a second predetermined temperature below the target operating temperature may facilitate determining the rate of temperature rise of the electric heater before the controller needs to begin regulating the supply of power to the electric heater during the second time period. The second predetermined temperature is preferably less than about 300 degrees Celsius, preferably less than about 290 degrees Celsius, preferably less than about 280 degrees Celsius, preferably less than about 270 degrees Celsius, preferably less than about 260 degrees Celsius. The second predetermined temperature may be 250 degrees Celsius.

[0021] The controller is preferably arranged to supply power from the power source to the electric heater at a constant rate during the first time period. Advantageously, supplying power to the electric heater at a constant rate during the first time period may facilitate accurate determination of a rate of temperature rise of the electric heater during the first time period. The controller may be arranged to supply power from the power source to the electric heater at a duty cycle of at least about 85 percent during the first time period. The controller may be arranged to supply power from the power source to the electric heater at a duty cycle of at least about 90 percent during the first time period. The controller may be arranged to supply power from the power source to the electric heater at a duty cycle of at least about 95 percent during the first time period.

[0022] The controller is preferably arranged to supply power from the power source to the electric heater according to a first heating profile or a second heating profile during a second time period based on a comparison of the determined rate of temperature rise with a first threshold, the second heating profile providing more power than the first heating profile. The first heating profile may be described as a reduced heating profile or as a moist heating profile. The second heating profile may be described as a standard heating profile. The first threshold may indicate a threshold between a normal moisture content of the aerosol-forming substrate and a high moisture content of the aerosol-forming substrate. In other words, a determined rate of temperature rise below the first threshold may indicate a high moisture content of the aerosol-forming substrate. A determined rate of temperature rise above the first threshold may indicate a normal moisture content of the aerosol-forming substrate.

[0023] The two heating profiles may differ with respect to the total power delivered during the experience. The two heating profiles may differ with respect to the duty cycle or duty cycles applied during the experience.

[0024] In embodiments in which the controller determines the rate of temperature rise of the electric heater by determining the time taken for a predetermined temperature rise of the electric heater to occur, the first threshold may be a time threshold. The controller is arranged to supply power to the electric heater according to a first heating profile when the determined time exceeds the first threshold. The controller is arranged to supply power to the electric heater according to a second heating profile when the determined time falls below the first threshold. The first threshold may be a time between about 3 seconds and about 10 seconds. The first threshold may be a time between about 5 seconds and about 7 seconds, more preferably a time between 5.5 and 6.5 seconds. The first threshold may be a time of 5.7 seconds, or alternatively a time of 6.1 seconds. The first threshold time may depend on the design of the electric heater.

[0025] The controller is preferably arranged to prevent the supply of power from the power source to the electric heater based on a comparison of the determined rate of temperature rise with a second threshold value, the second threshold value being different from the first threshold value. The second threshold value may indicate a threshold value between a normal moisture content of the aerosol-forming substrate and a low moisture content of the aerosol-forming substrate. In other words, a determined rate of temperature rise below the second threshold value may indicate a normal moisture content of the aerosol-forming substrate. A determined rate of temperature rise above the second threshold value may indicate a low moisture content of the aerosol-forming substrate.

[0026] The controller may be arranged to supply power to the electric heater according to a second heating profile when the determined time is below a first threshold and above a second threshold. The controller is arranged to prevent supplying power to the electric heater when the determined time is below the second threshold. The second threshold may be a time between about 4 seconds and about 5 seconds.

[0027] The controller is also preferably arranged to determine the ambient temperature.

[0028] Preferably, when the determined ambient temperature is below the ambient temperature threshold, the controller is arranged to supply power from the power supply to the electric heater in accordance with a second heating profile.

[0029] The inventors of the present invention have recognized that when the ambient temperature is low, the temperature rise rate of an aerosol-forming substrate having a normal moisture content may be significantly slower. In other words, the determined temperature rise rate of the electric heater when used with an aerosol-forming substrate having a normal moisture content in a low temperature environment may be similar to the determined temperature rise rate of the electric heater when used with an aerosol-forming substrate having a high moisture content at a normal ambient temperature. Thus, advantageously, supplying power to the electric heater according to the first heating profile during the second time period only when the ambient temperature is above the ambient temperature threshold may reduce or prevent the controller from supplying energy according to the first heating profile when using the aerosol generating device with an aerosol-forming substrate having a normal moisture content at a low ambient temperature. The inventors of the present invention have recognized that when the ambient temperature is low, power may not necessarily be supplied to the electric heater according to the first heating profile for an aerosol-forming substrate having a high moisture content. In particular, advantageously, the cool ambient air entering the aerosol generating device during use is sufficient to maintain the temperature of the generated aerosol at a level acceptable to the user, even when the aerosol-forming substrate has a high moisture content. The ambient temperature threshold is preferably between about 15 degrees Celsius and about 25 degrees Celsius, and preferably between about 17 degrees Celsius and about 23 degrees Celsius. The ambient temperature threshold may be 18 degrees Celsius.

[0030] The aerosol generating device may include a temperature sensor arranged to sense an ambient temperature, and the controller is arranged to determine the ambient temperature based on a signal received from the temperature sensor. The temperature sensor may comprise a thermistor. The temperature sensor may comprise a thermocouple. The temperature sensor may comprise a semiconductor temperature sensor.

[0031] A controller is arranged to determine an initial temperature of the electric heater. The controller is arranged to adjust a supply of power from the power source to the electric heater during a second time period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first time period.

[0032] The controller may also be arranged to supply power from the power source to the electric heater according to a first or second heating profile during a second time period based on an initial temperature of the electric heater and based on a determined rate of temperature rise of the electric heater during the first time period.

[0033] The controller may include an electrical storage element. The controller may be arranged to communicate with the electrical storage element. The controller may be arranged to write to and read from the electrical storage element parameters or other information relevant to control of the aerosol generating device. The controller may be arranged to store a last used heating profile in the electrical storage element. The electrical storage element may be a memory element.

[0034] The controller may be arranged to determine an initial temperature of the electric heater and may be further arranged to supply power from the power source to the electric heater according to a last used heating profile if the initial temperature of the electric heater exceeds a predetermined temperature threshold. To this end, the last used heating profile may be stored in an electrical storage element.

[0035] The predetermined temperature threshold for the initial temperature of the electric heater may be between about 50 degrees Celsius and about 150 degrees Celsius, between about 60 degrees Celsius and about 120 degrees Celsius, or preferably between about 80 degrees Celsius and about 100 degrees Celsius. The predetermined temperature threshold for the initial temperature of the electric heater may be 80 degrees Celsius.

[0036] When the initial temperature of the electric heater is increased, the time required for the temperature of the electric heater to increase to the second predetermined temperature during the first time period can be significantly reduced, and thus, in such a case, even an aerosol-generating article including an aerosol-forming substrate having a rather high moisture content can heat up very quickly and may be erroneously heated by the normal second heating profile.

[0037] To avoid such a situation, the determination of the rate of temperature rise is bypassed and the controller is arranged to power the electric heater from the power source according to the last used heating profile. Such a control strategy is justified because it can be assumed that the aerosol generating device has been used recently and will subsequently be used for a second experience. Because of the close temporal relationship with the first or previous experience, it is even more likely that the ambient conditions and the conditions of the aerosol-forming substrate will also be identical to those of the previous experience.

[0038] In embodiments, the aerosol generating device may include a rechargeable power source capable of providing at least a first experience and a second experience without intermediate recharging between the first experience and the second experience. In these embodiments, the controller may be arranged to determine whether the instantaneous experience is the first experience or the second experience. The controller may be further arranged to adjust the supply of power from the power source to the electric heater during the second time period based on whether the instantaneous experience is the first experience or the second experience.

[0039] The controller may be arranged to store in the electrical storage element whether the current experience is the first experience or the second experience. The controller may be further arranged to store the last used heating profile.

[0040] If the controller detects that the experience is a second experience, the controller may be arranged to supply power from the power source to the electric heater in accordance with a heating profile used in said first experience.

[0041] Surprisingly, it was noticed that the rate of temperature rise of the electric heater during the first period may vary if there is an extended time gap between two successive experiences without intermediate recharging of the rechargeable power source. More specifically, it was noticed that in the second experience, the time taken for the temperature of the electric heater to rise from a first predetermined temperature to a second predetermined temperature during the first period increases. The reasons for this increase are not yet fully clarified, but most likely must be found in the chemistry of the battery. Apparently, a long waiting time after the first experience may not allow the battery to provide a power boost that would increase the temperature as quickly as the first experience or a second experience performed immediately after the first experience.

[0042] To avoid application of an incorrect heating profile, the second experience may always be performed using the heating profile used in the first experience. It will be appreciated that the risk of such an approach is that if a consumable with a higher moisture content is inserted after a previous experience with a "dry" consumable (using the normal heating profile), the "wet" consumable may be heated with the normal heating profile and cause a hot aerosol effect for the user. However, this is considered to be a rather unlikely scenario. Instead, typically the consumables used for the second experience after the first experience are more likely to have the same properties as the consumables used in the previous experience, to be obtained from the same pack of consumables and to be exposed to the same climatic conditions.

[0043] The controller may further be arranged to reset to the first experience after a full recharge of the power source of the aerosol generating device, thus ensuring that the first experience is taken as it is when a fully charged battery is available.

[0044] To facilitate determining the rate of temperature rise of the electric heater, the controller is preferably arranged to determine the temperature of the electric heater. The electric heater preferably comprises at least one resistive heating element, and the controller is arranged to determine the temperature of the at least one resistive heating element based on the resistance of the at least one resistive heating element. The controller may comprise circuitry arranged to measure the resistance of the at least one resistive heating element. The controller may be arranged to determine the temperature of the at least one resistive heating element by comparing the measured resistance to a calibration curve of resistance versus temperature.

[0045] The electric heater preferably comprises a plurality of resistive heating elements. The resistive heating elements are preferably electrically connected in a parallel arrangement. Advantageously, providing a plurality of resistive heating elements electrically connected in a parallel arrangement may facilitate delivery of a desired power to the electric heater while reducing or minimizing the voltage required to provide the desired power. Advantageously, reducing or minimizing the voltage required to operate the electric heater may facilitate reducing or minimizing the physical size of the power supply.

[0046] The electric heater may comprise an electrically insulating substrate, with at least one resistive heating element provided on the electrically insulating substrate.

[0047] The electrically insulating substrate is preferably stable at the operating temperature of the electric heater. The electrically insulating substrate is preferably stable at a temperature of up to about 400 degrees Celsius, more preferably about 500 degrees Celsius, more preferably about 600 degrees Celsius, more preferably about 700 degrees Celsius, and more preferably about 800 degrees Celsius. The operating temperature of the electric heater in use may be at least about 200 degrees Celsius. The operating temperature of the electric heater in use may be less than about 700 degrees Celsius. The operating temperature of the electric heater in use may be less than about 600 degrees Celsius. The operating temperature of the electric heater in use may be less than about 500 degrees Celsius. The operating temperature of the electric heater in use may be less than about 400 degrees Celsius.

[0048] The electrically insulating substrate may be a ceramic material such as zirconia or alumina. The electrically insulating substrate preferably has a thermal conductivity of about 2 watts per meter per Kelvin or less.

[0049] Suitable materials for forming the at least one resistive heating element include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys, and composites made of ceramic and metallic materials. Such composites may include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel-, iron-, cobalt-, and stainless steel-based superalloys, Timetai®, and iron-manganese-aluminum-based alloys.

[0050] In some embodiments, the at least one resistive heating element comprises one or more stamped sections of an electrically resistive material (such as stainless steel). Alternatively, the at least one resistive heating element may comprise a heating wire or filament (e.g., Ni-Cr (nickel-chromium), platinum, tungsten, or alloy wire).

[0051] The electric heater may be arranged for insertion into the aerosol-forming substrate when the aerosol-forming substrate is received within the cavity. The electric heater may be positioned within the cavity. The electric heater may be an elongated electric heater. The elongated electric heater may be blade-shaped. The elongated electric heater may be pin-shaped. The elongated electric heater may be cone-shaped. The elongated electric heater may be blade-shaped.

[0052] The power source may be a DC voltage source. In a preferred embodiment, the power source is a battery. For example, the power source may be a nickel metal hydride battery, a nickel cadmium battery, or a lithium-based battery (e.g., a lithium cobalt battery, a lithium iron phosphate battery, or a lithium polymer battery). Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging and may have a capacity that allows for the storage of sufficient energy to use the aerosol-generating device with one or more aerosol-forming substrates.

[0053] The aerosol generating device preferably comprises a housing, the housing preferably at least partially defining a cavity for receiving the aerosol-forming substrate.

[0054] The aerosol generating device preferably comprises at least one air inlet in fluid communication with the cavity. In embodiments in which the aerosol generating device comprises a housing, the housing preferably at least partially defines the at least one air inlet. The at least one air inlet is preferably in fluid communication with an upstream end of the cavity. In embodiments in which the electric heater is an elongated electric heater positioned within the cavity, the elongated electric heater preferably extends into the cavity from the upstream end of the cavity.

[0055] The aerosol generating device may include a sensor for detecting airflow indicative of a consumer taking a puff. The airflow sensor may be an electromechanical device. The airflow sensor may be any of a mechanical device, an optical device, an opto-mechanical device, and a microelectromechanical system (MEMS) based sensor. The aerosol generating device may include a manually operable switch for a consumer to initiate a puff.

[0056] The aerosol generating device preferably comprises an indicator to indicate when the electric heater is activated. The indicator may comprise a light which is activated when the electric heater is activated.

[0057] The aerosol generating device may include at least one external plug or socket and at least one external electrical contact that allows the aerosol generating device to be connected to another electrical device. For example, the aerosol generating device may include a USB plug or socket that allows the aerosol generating device to be connected to another USB-enabled device. For example, the USB plug or socket may allow the aerosol generating device to be connected to a USB charging device to charge a rechargeable power source within the aerosol generating device. Additionally or alternatively, the USB plug or socket may accommodate data transfer to, from, or both to and from the aerosol generating device. Additionally or alternatively, the aerosol generating device may be connected to a computer to transfer data to the device, such as a new heating profile for a new aerosol-generating article.

[0058] In embodiments in which the aerosol generating device comprises a USB plug or socket, the aerosol generating device may further comprise a removable cover for covering the USB plug or socket when not in use. In embodiments in which the USB plug or socket is a USB plug, the USB plug may additionally or alternatively be selectively retractable within the device.

[0059] According to an embodiment of the present invention, there is provided an aerosol-generating system comprising an aerosol-generating device according to the present invention and an aerosol-generating article comprising an aerosol-forming substrate according to any of the embodiments described herein.

[0060] As used herein, the term "aerosol-generating article" refers to an article that includes an aerosol-forming substrate that, when heated, releases volatile compounds that can form an aerosol.

[0061] The aerosol-forming substrate may comprise tobacco.

[0062] The aerosol-forming substrate may comprise a tobacco plug. The tobacco plug may comprise one or more of powders, granules, pellets, pieces, spaghetti, strips, or sheets containing one or more of tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Optionally, the tobacco plug may contain additional tobacco or non-tobacco, volatile flavor compounds that are released upon heating of the tobacco plug. Optionally, the tobacco plug may also contain capsules, for example, containing additional tobacco or non-tobacco, volatile flavor compounds. Such capsules may melt during heating of the tobacco plug. Alternatively, or additionally, such capsules may be crushed before, during, or after heating of the tobacco plug.

[0063] When the tobacco plug includes homogenized tobacco material, the homogenized tobacco material may be formed by agglomerating particulate tobacco. The homogenized tobacco material may be in the form of a sheet. The homogenized tobacco material may have an aerosol former content of greater than 5 percent on a dry weight basis. Alternatively, the homogenized tobacco material may have an aerosol former content of 5 to 30 percent by weight on a dry weight basis. The homogenized tobacco material sheet may be formed by agglomerating particulate tobacco obtained by grinding or otherwise comminuted one or both of tobacco lamina and tobacco stems, and alternatively, or additionally, the homogenized tobacco material sheet may include one or more of tobacco dust, tobacco fines and other particulate tobacco by-products formed, for example, during tobacco processing, handling and transportation. The homogenized tobacco material sheet may include one or more intrinsic binders (i.e., tobacco intrinsic binders), or one or more extrinsic binders (i.e., tobacco extrinsic binders), or a combination thereof, to assist in agglomerating the particulate tobacco. Alternatively, or in addition, the homogenized tobacco material sheet may include other additives, including, but not limited to, tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavorants, fillers, aqueous and non-aqueous solvents, and combinations thereof. The homogenized tobacco material sheet is preferably formed by a casting process of a type that generally involves casting a slurry including particulate tobacco and one or more binders onto a conveyor belt or other supporting surface, drying the cast slurry to form a homogenized tobacco material sheet, and removing the homogenized tobacco material sheet from the supporting surface.

[0064] The aerosol-generating article may have a total length of from about 30 millimeters to about 100 millimeters. The aerosol-generating article may have an outer diameter of from about 5 millimeters to about 13 millimeters.

[0065] The aerosol-generating article may include a mouthpiece located downstream of the tobacco plug. The mouthpiece may be located at the downstream end of the aerosol-generating article. The mouthpiece may be a cellulose acetate filter plug. The mouthpiece is preferably approximately 7 millimeters in length, but may have a length of approximately 5 millimeters to approximately 10 millimeters.

[0066] The tobacco plug may have a length of approximately 10 mm.The tobacco plug may have a length of approximately 12 mm.

[0067] The tobacco plug may have a diameter of from about 5 millimeters to about 12 millimeters.

[0068] In a preferred embodiment, the aerosol-generating article has an overall length of between about 40 millimeters and about 50 millimeters. Preferably, the aerosol-generating article has an overall length of about 45 millimeters. Preferably, the aerosol-generating article has an outer diameter of about 7.2 millimeters.

[0069] According to one embodiment of the present invention, there is provided a method of controlling an aerosol generating device having a cavity for receiving an aerosol-forming substrate, a power source, and an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received within the cavity. The method includes controlling a supply of power from the power source to the electric heater during a first time period. The method also includes determining an initial temperature of the electric heater and determining a rate of temperature rise of the electric heater during the first time period. The method also includes adjusting the supply of power from the power source to the electric heater during a second time period after the first time period, where the supply of power from the power source to the electric heater during the second time period is adjusted based on the determined initial temperature of the electric heater based on the determined rate of temperature rise during the first time period.

[0070] As described herein with respect to one embodiment of the invention, the determined rate of temperature rise of the electric heater may be indicative of the moisture content of the aerosol-forming substrate. A determined relatively low rate of temperature rise may be indicative of a relatively high moisture content. A determined relatively high rate of temperature rise may be indicative of a relatively low moisture content. Advantageously, based on the determined rate of temperature rise, the supply of power to the electric heater during a subsequent second time period may be adjusted to regulate further heating of the electric heater.

[0071] The first period of time is preferably long enough to ensure a measurable temperature increase of the electric heater over a wide range of moisture contents of the aerosol-forming substrate, and is preferably at least about 1 second, more preferably at least about 2 seconds, and more preferably at least about 3 seconds.

[0072] The first period of time is preferably short enough to minimize the time before adjusting the supply of power to the electric heater during the second period of time to provide a desired user experience. The first period of time is preferably less than about 15 seconds, more preferably less than about 14 seconds, more preferably less than about 13 seconds, more preferably less than about 12 seconds, more preferably less than about 11 seconds, and more preferably less than about 10 seconds.

[0073] The step of determining a rate of temperature rise of the electric heater may include determining a time taken for a predetermined temperature rise of the electric heater to occur. The step of determining a rate of temperature rise of the electric heater may include determining a rate of temperature rise of the electric heater during a portion of a first time period. The step of determining a rate of temperature rise of the electric heater may include determining a time taken for the temperature of the electric heater to rise from a first predetermined temperature to a second predetermined temperature during the first time period, the determined time being the determined rate of temperature rise.

[0074] The first predetermined temperature is preferably above any anticipated ambient temperature. Advantageously, a first predetermined temperature above ambient temperature may minimize or eliminate any change in ambient temperature at the determined temperature rise rate of the electric heater. The first predetermined temperature is preferably at least about 50 degrees Celsius, preferably at least about 60 degrees Celsius, preferably at least about 70 degrees Celsius, preferably at least about 80 degrees Celsius, and preferably at least about 90 degrees Celsius. The first predetermined temperature may be about 100 degrees Celsius.

[0075] The second predetermined temperature is preferably below a target operating temperature of the electric heater during the second time period. Advantageously, a second predetermined temperature below the target operating temperature may facilitate determining a rate of temperature rise of the electric heater before adjusting the supply of power to the electric heater during the second time period. The second predetermined temperature is preferably less than about 300 degrees Celsius, preferably less than about 290 degrees Celsius, preferably less than about 280 degrees Celsius, preferably less than about 270 degrees Celsius, preferably less than about 260 degrees Celsius. The second predetermined temperature may be about 250 degrees Celsius.

[0076] In a method step of the present invention, an initial temperature of the electric heater is determined, and the supply of power from the power source to the electric heater during a second time period is adjusted based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first time period.

[0077] Power from the power source may be supplied to the electric heater according to the first heating profile or the second heating profile during the second time period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first time period.

[0078] The controller may include an electrical storage element. The controller may be arranged to communicate with the electrical storage element. The controller may be arranged to write to and read from the electrical storage element parameters or other information relevant to control of the aerosol generating device. The controller may be arranged to store a last used heating profile in the electrical storage element. The electrical storage element may be a memory element.

[0079] An initial temperature of the electric heater may be determined by the controller, and power from the power source may be supplied to the electric heater according to a last used heating profile if the initial temperature of the electric heater is above a predetermined temperature threshold. To this end, the last used heating profile may be stored in an electrical storage element.

[0080] The predetermined temperature threshold for the initial temperature of the electric heater may be between about 50 degrees Celsius and about 150 degrees Celsius, between about 60 degrees Celsius and about 120 degrees Celsius, or preferably between about 80 degrees Celsius and about 100 degrees Celsius. The predetermined temperature threshold for the initial temperature of the electric heater may be 80 degrees Celsius.

[0081] When the initial temperature of the electric heater is increased, the time required for the temperature of the electric heater to increase to the second predetermined temperature during the first time period can be significantly reduced, and thus, in such a case, even an aerosol-generating article including an aerosol-forming substrate having a rather high moisture content can heat up very quickly and may be erroneously heated by the normal second heating profile.

[0082] To avoid such a situation, the determination of the rate of temperature rise may be bypassed and the controller may be arranged to power the electric heater from the power source according to the last used heating profile. Such a control strategy is justified because it may be assumed that the aerosol generating device has been used recently and will subsequently be used for a second experience. Because of the close temporal relationship with the first or previous experience, it is even more likely that the ambient conditions and the conditions of the aerosol-forming substrate will also be identical to those of the previous experience.

[0083] In embodiments, the aerosol generating device may include a rechargeable power source capable of providing at least a first experience and a second experience without intermediate recharging between the first experience and the second experience. In these embodiments, the controller may be arranged to determine whether the instantaneous experience is the first experience or the second experience. The controller may be further arranged to adjust the supply of power from the power source to the electric heater during the second time period based on whether the instantaneous experience is the first experience or the second experience.

[0084] The controller may be arranged to store in the electrical storage element whether the current experience is the first experience or the second experience. The controller may be further arranged to store the last used heating profile.

[0085] If the controller detects that the experience is a second experience, the controller may be arranged to supply power from the power source to the electric heater according to a heating profile used in said first experience.

[0086] To avoid application of a wrong heating profile, the second experience may always be performed using the heating profile used in the first experience. It will be appreciated that the risk of such an approach is that if a consumable with a higher moisture content is inserted after a previous experience with a "dry" consumable (using the normal heating profile), the "wet" consumable may be heated with the normal heating profile and cause a hot aerosol effect for the user. However, this may be considered a rather unlikely scenario. Instead, typically the consumable used for the second experience after the first experience is more likely to have the same characteristics as the consumable used in the previous experience, to be obtained from the same pack of consumables and to be exposed to the same climatic conditions.

[0087] The controller may further be arranged to reset to the first experience after a full recharge of the power source of the aerosol generating device, thus ensuring that the first experience is taken as it is when a fully charged battery is available.

[0088] According to an embodiment of the present invention, there is provided a computer program which, when executed on a computer or other processing device, performs the inventive method according to any of the embodiments described herein. The computer program may be implemented as a software product suitable for running on an aerosol generating device having a programmable controller as well as other required hardware elements such as an electric heater and a power supply. EXAMPLES

[0089] The following provides a non-exhaustive list of non-limiting examples, any one or more of the features of which may be combined with any one or more features of the other examples, embodiments, or aspects described herein.

[0090] Example A: 1. An aerosol generating device comprising: a cavity for receiving an aerosol-forming substrate; an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received in the cavity; and a controller arranged to control a supply of power from a power source to the electric heater during a first time period and a second time period following the first time period, wherein the controller is arranged to determine an initial temperature of the electric heater and to determine a rate of temperature rise of the electric heater during the first time period by determining the time it takes for the temperature of the electric heater to rise from a first predetermined temperature to a second predetermined temperature during the first time period, and the controller is arranged to adjust the supply of power from the power source to the electric heater during the second time period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first time period. Example B: An aerosol generating device as described in Example 1, wherein the controller is configured to supply power from the power source to the electric heater according to a first or second heating profile during a second period of time based on an initial temperature of the electric heater and based on a determined rate of temperature rise of the electric heater during the first period of time. Example C: The aerosol generating device of embodiment B, wherein the controller comprises an electrical storage element, and wherein the controller is configured to store the last used heating profile. Example D: An aerosol generating device as described in any of Examples A to C, wherein the controller is configured to determine an initial temperature of the electric heater, and the controller is further configured to power the electric heater from the power source according to the last used heating profile if the initial temperature of the electric heater exceeds a predetermined temperature threshold. Example E: An aerosol generating device as described in any of Examples A to C, wherein the controller is configured to determine an initial temperature of the electric heater, and the controller is configured to supply power from the power source to the electric heater according to a first or second heating profile during a second time period based on the determined rate of temperature rise of the electric heater during the first time period if the initial temperature of the electric heater is below a predetermined temperature threshold. Example F: The aerosol generating device of embodiment D or E, wherein the temperature threshold is within the range of 60 degrees Celsius to 120 degrees Celsius, the temperature threshold is within the range of 80 degrees Celsius to 100 degrees Celsius, or the temperature threshold is approximately 80 degrees Celsius. Example G: The aerosol generating apparatus of any of embodiments A-F, wherein the controller is arranged to provide power from the power source to the electric heater at a constant rate during the first period of time. Example H: An aerosol generating device as described in embodiment F or G, wherein the controller is configured to supply power from the power source to the electric heater according to a first heating profile for a second period of time when the determined time exceeds a first threshold. Example I: An aerosol generating device as described in embodiment F or G, wherein the controller is configured to power the electric heater from the power source according to a second heating profile for a second period of time when the determined time is below a first threshold, and in the second heating profile more heating power is delivered to the electric heater than in the first heating profile. Example J: An aerosol generating device as described in embodiment F or G, wherein the controller is configured to prevent the supply of power from the power source to the electric heater during a second period of time if the determined time is below a second threshold, the second threshold being less than the first threshold. Example K: An aerosol generating device described in any of Examples A to J, wherein the controller is configured to determine the ambient temperature, and when the determined ambient air is below an ambient temperature threshold, the controller is configured to supply power from the power source to the electric heater according to a second heating profile. Example L: An aerosol generating device as described in embodiment K, further comprising a temperature sensor arranged to sense ambient temperature, wherein the controller is arranged to determine the ambient temperature based on a signal received from the temperature sensor. Example M: An aerosol generating apparatus according to any of claims A to L, wherein the electric heater comprises a resistive heating element, and the controller is arranged to determine the temperature of the resistive heating element based on the resistance of the resistive heating element. Example N: 1. An aerosol generation system comprising: An aerosol generating apparatus according to any one of Examples A to M, an aerosol-generating article comprising an aerosol-forming substrate; Example O: The aerosol-generating system of embodiment N, wherein the aerosol-forming substrate comprises tobacco. Example P: 1. A method of controlling an aerosol generating device having a cavity for receiving an aerosol-forming substrate, a power source, and an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received within the cavity, the method comprising: controlling a supply of power from a power source to an electric heater during a first period of time; determining an initial temperature of the electric heater; determining a rate of temperature rise of the electric heater during a first period of time by determining the time it takes for the temperature of the electric heater to rise from a first predetermined temperature to a second predetermined temperature; and adjusting a power supply from the power source to the electric heater during a second time period after the first time period, wherein the power supply from the power source to the electric heater during the second time period is adjusted based on the determined initial temperature of the electric heater and based on the determined rate of temperature rise during the first time period. Example Q: The method of embodiment P, wherein controlling the supply of power from the power source to the electric heater during the first time period comprises supplying power from the power source to the electric heater at a constant rate during the first time period. Example R: A computer program product which performs the method of example P or Q when run on a computer or other processing device.

[0091] Features described with respect to one embodiment may be equally applied to other embodiments of the invention.

[0092] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0093] [Figure 1] FIG. 1 shows a cross-sectional view of an aerosol generating device according to an embodiment of the present invention. [Diagram 2] FIG. 2 shows a cross-sectional view of an aerosol generation system including the aerosol generation device of FIG. [Diagram 3] FIG. 3 illustrates a method implemented by the controller of the aerosol generating device of FIG. [Figure 4] FIG. 4 illustrates a further method implemented by the controller of the aerosol generating device of FIG. [Diagram 5] FIG. 5 shows the test results for the required heating time under ISO conditions. [Figure 6] FIG. 6 shows the test results of the required heating time under tropical conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0094] Figure 1 shows a cross-sectional view of an aerosol generation device 10 according to an embodiment of the invention. The aerosol generation device 10 comprises a generally cylindrical housing 12 comprising a front housing portion 13 and a rear housing portion 15. The front housing portion 13 is slidably removable from the rear housing portion 15 and is shown in Figure 1 in a partially removed position.

[0095] The front housing portion 13 includes an outer wall 17 and an inner wall 19 that defines a cavity 14 for receiving an aerosol-forming substrate. A plurality of air inlets 16 for admitting air into the aerosol generating device 12 are defined between the outer wall 17 and the inner wall 19 at an end of the front housing portion 13.

[0096] The rear housing portion 15 includes a cylindrical wall 21 that is received between the outer wall 17 and the inner wall 19 of the front housing portion 13 when the front housing portion 13 is received in the rear housing portion 15. The cylindrical wall 21 defines a plurality of elongated slots 23.

[0097] The aerosol generating device 10 also includes an electric heater 18 positioned on the rear housing part 15 and arranged to extend through an opening 25 defined by the inner wall 19 and into the cavity 14 when the front housing part 13 is received in the rear housing part 15. In use, air flows into the aerosol generating device 10 through the air inlet 16, through a slot 23 defined by the cylindrical wall 21, and through the opening 25 into the cavity 14.

[0098] The electric heater 18 comprises a base portion 20 and an elongated, electrically insulating substrate 22 extending from the base portion 20. The elongated, electrically insulating substrate 22 is formed from a ceramic material. The elongated, electrically insulating substrate 22 is blade-shaped to facilitate insertion of the elongated, electrically insulating substrate 22 into the aerosol-forming substrate when the aerosol-forming substrate is received within the cavity 14.

[0099] The elongated electric heater 18 also includes a plurality of resistive heating elements 24 positioned on the elongated electrically insulating substrate 22 .

[0100] The aerosol generating device 10 also includes a power supply 26, a controller 28, and a temperature sensor 29. The controller 28 may be arranged to perform several functions, including controlling the supply of power from the power supply 26 to the resistive heating element 24 of the electric heater 18. The power supply 26 includes a rechargeable battery.

[0101] Figure 2 shows a cross-sectional view of an aerosol generation system 50 comprising the aerosol generating device 10 of Figure 1 and an aerosol-generating article 52 received within the cavity 14 of the aerosol generating device 10. The aerosol generating device 10 is shown in Figure 2 with the front housing part 13 completely received in the rear housing part 15.

[0102] The aerosol-generating article 52 comprises an aerosol-forming substrate 54 in the form of a tobacco plug, a hollow acetate tube 56, a polymeric filter 58, a mouthpiece 60, and an outer wrapper 62. When the aerosol-generating article 52 is received within the cavity 14 of the aerosol generating device 10, the elongated electrically insulating substrate 22 and the resistive heating element 24 of the electric heater 18 are received within the tobacco plug.

[0103] The controller 28 of the aerosol generating device 10 is configured to execute the method 100 illustrated in FIG. 3 when the aerosol generating article 52 is inserted into the cavity 14 and when the aerosol generating device 10 is turned on by a user.

[0104] Upon start-up of the device, an experience begins. In step 102, controller 28 determines the ambient temperature using temperature sensor 29. If the ambient temperature is below 18 degrees Celsius, power is supplied from power source 26 to electric heater 24 according to a second heating profile (step 104). The second heating profile corresponds to a standard heating profile used for aerosol-generating articles having normal moisture content.

[0105] If the ambient temperature is above 18 degrees Celsius, the controller 28 determines an initial temperature of the electric heater 24 in step 106. To this end, the controller 28 measures the electrical resistance of the electric heater 24. Based on the measured electrical resistance, the controller 28 determines an initial temperature of the electric heater 24.

[0106] If the initial temperature of the electric heater is below 80 degrees Celsius, the controller 28 begins supplying power from the power supply 26 to the electric heater 18 at a constant rate in step 108 .

[0107] The controller 28 records the time required for the electric heater 18 to heat from the first predetermined temperature of 100 degrees Celsius to the second predetermined temperature of 250 degrees Celsius. If it takes less than 6.1 seconds to increase the temperature of the electric heater 18 to 250 degrees Celsius, the aerosol-forming substrate 54 of the aerosol-generating article 52 is deemed to have a normal moisture content. Thus, in this situation, the controller is arranged to supply power to the electric heater according to the second normal heating profile (step 104).

[0108] If it takes more than 6.1 seconds to raise the temperature of the electric heater 18 to 250 degrees Celsius, the aerosol-forming substrate 54 of the aerosol-generating article 52 is deemed to have an increased moisture content. Thus, in this situation, the controller is arranged to supply power to the electric heater according to a first heating profile (step 110), in which less power is supplied to the heater and thus the so-called "hot aerosol effect" is avoided or at least reduced.

[0109] If, in step 106, it is determined that the initial temperature of the electric heater is greater than 80 degrees Celsius, then the time required for the electric heater to reach the second predetermined temperature of 250 degrees Celsius will likely be significantly shorter. In this case, an aerosol-generating article 52 that includes an aerosol-forming substrate 54 with a high moisture content may heat up too quickly and may erroneously heat according to the second heating profile.

[0110] To avoid such false detections, step 108 is bypassed if the initial temperature of the electric heater is determined to be above 80 degrees Celsius. In this case, the controller is instead configured to use the same heating profile that was used during the previous experience. To this end, the controller retrieves from its internal memory a stored previously used heating profile (step 112).

[0111] If the heating profile previously used was the second heating profile, then the current experience is also performed using the second heating profile (step 114).

[0112] If the previously used heating profile was the first heating profile, then the current experience is also performed using the first heating profile (step 110).

[0113] The controller is further configured to store in a local memory the heating profile used during the current experience.

[0114] The controller 28 of the aerosol generating device 10 may also be configured to execute the method 100 illustrated in FIG. 4 when the aerosol generating article 52 is inserted into the cavity 14 and the aerosol generating device 10 is turned on by a user.

[0115] The method illustrated in Figure 4 is generally similar to the method of Figure 3, and like reference numbers are used to indicate like method steps. This method is particularly useful in embodiments in which the aerosol generating device includes a power source capable of providing multiple experiences without the need for an intermediate.

[0116] The method of FIG. 4 includes the additional step 120 in which the controller 28 determines whether the current experience is the first experience or the second experience.

[0117] If, in step 120, it is determined that the current experience is the first experience, the method continues with step 106 as described above to determine the initial temperature of the electric heater 24.

[0118] If, at step 120, it is determined that the current experience is a second experience, method steps 106 and 108 are bypassed. Instead, the controller retrieves from local memory the heating profile used in the previous, first experience. It is assumed that the second experience will most likely be performed using the same aerosol-generating article as used in the first experience, or at least an aerosol-generating article that has been subjected to the same environmental and climatic conditions.

[0119] Thus, if the heating profile used for the first experience was the second heating profile, then the current experience is also performed using the second heating profile (step 114).

[0120] If the heating profile used for the first experience was the first heating profile, then the current experience is also performed using the first heating profile (step 110).

[0121] The results of tests conducted to measure the time required to raise the temperature of an electric heater from 100 degrees Celsius to 250 degrees Celsius are shown in Figure 5. These tests were conducted using an aerosol generating device as illustrated in Figure 1. The aerosol generating article was a US amber stick. The experiments were conducted under both standard ISO conditions and TROPICAL conditions. ISO conditions mean that an ambient temperature of 22 degrees Celsius and a relative humidity of 60 percent were applied. TROPICAL conditions mean that an ambient temperature of 30 degrees Celsius and a relative humidity of 75 to 80 percent were applied.

[0122] In the experiments shown in Figures 5 and 6, two user experiences were conducted without intermediate recharging of the aerosol generating device battery. The first experience was conducted with a fully charged battery. The second experience was conducted thereafter without intermediate recharging. The second experience, which was conducted within 5 minutes of the first experience, is referred to as the "subsequent" experience. The second experience, which was conducted within 15-30 minutes of the first experience, is referred to as the "remote" experience.

[0123] The results, illustrated in Figure 5, show a surprising effect. For both conditions, the time required to heat an electric heater from 100 degrees Celsius to 250 degrees Celsius is shown for three different situations under ISO and TROPICAL conditions.

[0124] The column marked "1st" relates to the first experience, which means that a fully charged battery was available. As shown, an average time of 5.9±0.6 seconds was recorded for the ISO condition and an average time of 7.7±1.3 seconds was recorded for the TROPICAL condition.

[0125] The column marked "Subsequent" relates to a second experience that was performed immediately after the first experience. More specifically, the following experience was triggered approximately three minutes after the first experience. Similar mean times of 5.8±0.5 seconds were recorded for the ISO condition and 7.8±0.7 seconds for the TROPICAL condition.

[0126] The column marked "Remote" also relates to a second experience, however this experience was carried out approximately 20 minutes after the first experience. In this situation, the ISO condition recorded an increase in the mean time of 6.4 ± 0.5 seconds, and the TROPICAL condition recorded an increase in the mean time of 8.5 ± 1.5 seconds.

[0127] Surprisingly, for both conditions (ISO and TROPICAL), the measured time increased significantly for the second experience performed after 20 minutes, most likely due to the battery chemistry. At long wait times after the first experience, the battery does not appear to be able to provide a power boost to raise the temperature to 100 degrees Celsius to 250 degrees Celsius, as it does in the first experience or in the second experience performed immediately after the first experience.

[0128] By using the method described above in FIG. 4, the risk of accidentally activating a moist heating profile is reduced due to the increased heating time required to heat the electric heater from 100 degrees Celsius to 250 degrees Celsius.

Claims

1. An aerosol generating device, comprising: a cavity for receiving an aerosol-forming substrate; an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received within the cavity; Power supply and a controller arranged to control the supply of power from the power source to the electric heater during a first time period and a second time period subsequent to the first time period; the controller is arranged to determine an initial temperature of the electric heater and to determine a rate of temperature rise of the electric heater during the first time period by determining the time taken to raise the temperature of the electric heater from a first predetermined temperature to a second predetermined temperature during the first time period; The aerosol generating device, wherein the controller is configured to adjust the power supply from the power source to the electric heater during the second period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first period.

2. 2. The aerosol generating device of claim 1, wherein the controller is configured to supply power from the power source to the electric heater according to a first or second heating profile during the second period based on the initial temperature of the electric heater and based on the determined rate of temperature rise of the electric heater during the first period.

3. 2. The aerosol generating device of claim 1, wherein the controller is configured to determine the initial temperature of the electric heater, and the controller is further configured to power the electric heater from the power source according to a last used heating profile if the initial temperature of the electric heater exceeds a predetermined temperature threshold.

4. 2. The aerosol generating device of claim 1, wherein the controller is configured to determine the initial temperature of the electric heater, and wherein the controller is configured to supply power from the power source to the electric heater according to a first or second heating profile during the second period based on the determined rate of temperature rise of the electric heater during the first period if the initial temperature of the electric heater is below the predetermined temperature threshold.

5. 5. The aerosol generating device of claim 4, wherein the controller is configured to power the electric heater from the power source according to a first heating profile during the second period when the determined time exceeds a first threshold.

6. 5. The aerosol generating device of claim 4, wherein the controller is configured to supply power from the power source to the electric heater according to a second heating profile during the second period when the determined time is below the first threshold, wherein the second heating profile delivers more heating power to the electric heater than the first heating profile.

7. 5. The aerosol generating device of claim 4, wherein the controller is configured to prevent the supply of power from the power source to the electric heater during the second period if the determined time is below a second threshold, the second threshold being smaller than the first threshold.

8. 2. The aerosol generating device of claim 1, wherein the controller is configured to determine an ambient temperature, and the controller is configured to supply power from the power source to the electric heater according to a second heating profile when the determined ambient air temperature is below the ambient temperature threshold.

9. 9. The aerosol generating device of claim 8, further comprising a temperature sensor arranged to sense the ambient temperature, and wherein the controller is arranged to determine the ambient temperature based on a signal received from the temperature sensor.

10. 2. The aerosol generating device of claim 1, wherein the electric heater comprises a resistive heating element, and the controller is arranged to determine the temperature of the resistive heating element based on the resistance of the resistive heating element.

11. 1. An aerosol generating system comprising: The aerosol generating device according to any one of claims 1 to 10, an aerosol-generating article comprising an aerosol-forming substrate.

12. 12. The aerosol-generating system of claim 11, wherein the aerosol-forming substrate comprises tobacco.

13. 1. A method for controlling an aerosol-generating device having a cavity for receiving an aerosol-forming substrate, a power source, and an electric heater arranged to heat the aerosol-forming substrate when the aerosol-forming substrate is received in the cavity, the method comprising: controlling the supply of power from the power source to the electric heater during a first period of time; determining an initial temperature of the electric heater; determining a rate of temperature rise of the electric heater during the first period by determining the time it takes for the temperature of the electric heater to rise from a first predetermined temperature to a second predetermined temperature; and adjusting the power supply from the power source to the electric heater during a second time period after the first time period, wherein the power supply from the power source to the electric heater during the second time period is adjusted based on the determined initial temperature of the electric heater and based on the determined rate of temperature rise during the first time period.

14. 14. The method of claim 13, wherein the step of controlling the supply of power from the power source to the electric heater during the first period of time comprises supplying power from the power source to the electric heater at a constant rate during the first period of time.

15. A computer program for carrying out the method of claim 13 or 14 when run on a computer or other processing device.

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