Method for controlling heating in aerosol generation system

Abstract

To provide a method for controlling heating in an aerosol generation system (100) equipped with a heater (119).SOLUTION: A method of the present invention includes: a first control step in which predetermined power is supplied to a heater (119), and resistance of the heater (119) is determined, the determined resistance showing the temperature of the heater; monitoring a predetermined condition and recording the resistance of the heater (119) accompanying the detection of the predetermined condition; determining target resistance (RT) in correspondence with a target temperature of the heater (119) on the basis of the recorded resistance; and a second control step in which the power supplied to the heater (119) is adapted so as to be controlled to drive the resistance of the heater (119) toward the target resistance (RT) so that the heater (119) is driven toward the target temperature corresponding to the target resistance (RT).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for controlling heating in an aerosol generation system comprising a heater, and also to such an aerosol generation system. In particular, the present invention relates to a portable electrically operated aerosol generation system that vaporizes an aerosol-forming substrate by heating to generate an aerosol.

Background Art

[0002] Electrically operated aerosol generation systems are well known. Such systems typically consist of a device portion having a battery and control electronics, an aerosol-forming substrate, an electric heater comprising at least one resistive heating element arranged to heat the aerosol-forming substrate, and a mouthpiece. In some systems, the aerosol-forming substrate contains a liquid and an elongated wick is used to carry the liquid aerosol-forming substrate to the heater. The heater typically comprises a coil of resistive heating wire wound around the elongated wick. The heater, wick, and liquid aerosol-forming substrate are often contained within a cartridge that can be mounted within or received by the device portion. When the user activates the device, an electric current passes through the heater, causing resistive heating, which vaporizes the liquid in the wick. By inhaling through the mouthpiece or smoking the mouthpiece, air is drawn through the system, entraining the vapor, which then cools to form an aerosol. The aerosol-laden air leaves the system via the mouthpiece and enters the user's mouth.

[0003] As used herein, the term "aerosol generation substrate" relates to a substrate having the ability to release a volatile compound capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. Conveniently, the aerosol-forming substrate may be part of an aerosol-generating article or system.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In general, it is desirable for an aerosol generation system to be able to produce consistent aerosols over time. This is particularly true when the aerosol is for human consumption, as aerosol variations can impair the user experience and extreme variations can potentially be dangerous. Also in general, it is desirable for an aerosol generation system to generate aerosols as efficiently as possible with respect to the amount of energy required to generate the aerosol. However, this can be difficult to achieve due to variations in the system manufacturing process, variations in the properties of the aerosol-forming substrate used in such systems, and the different operating conditions under which such systems are used.

[0005] In an aerosol generation system that uses a liquid aerosol-forming substrate, it is also desirable to be able to detect and avoid "dry heating" situations, i.e., situations where the heater is heated in the absence of sufficient liquid aerosol-forming substrate. This situation is also known as "dry puffing" and can also lead to overheating and potentially thermal decomposition of the liquid aerosol-forming substrate, which can produce undesirable by-products such as formaldehyde.

[0006] It may be desirable to control or regulate the temperature of the heater used to heat the aerosol-forming substrate in order to produce consistent aerosols.

[0007] It is an object of the present invention to provide an aerosol generation system that provides more consistent aerosols during heating of the aerosol-forming substrate. It is a further object of the present invention to provide an aerosol generation system that heats the aerosol-forming substrate more efficiently and reduces the likelihood of dry puffing.

Means for Solving the Problems

[0008] According to a first aspect of the present invention, there is provided a method for controlling heating in an aerosol generation system comprising a heater, the method comprising: a first control step in which a predetermined power is supplied to the heater and the resistance of the heater is determined, the determined resistance indicating the temperature of the heater; monitoring a predetermined condition and recording the resistance of the heater upon detection of the predetermined condition; determining a target resistance corresponding to a target temperature of the heater based on the recorded resistance; and a second control step in which the power supplied to the heater is controllably adapted to drive the resistance of the heater towards the target resistance, whereby the heater is driven towards a target temperature corresponding to the target resistance.

[0009] One way to control or regulate the temperature of a heater is by power regulation. In a system where the power is regulated, a predetermined or constant power is supplied to the heater and the resistance of the heater is monitored. Since the relationship between the electrical resistance of the heater and the temperature of the heater is generally known or can be determined, the resistance of the heater can serve as an indication of the temperature of the heater. For example, the electrical resistance of the heater may be known to be proportional to the temperature of the heater, in which case there is a substantially linear relationship between the resistance and the temperature.

[0010] With the supply of a specified or constant power, the temperature of the heater initially rises rapidly (e.g., within approximately 0.3 seconds) towards the target temperature. Generally, the power is selected such that the temperature of the heater begins to stabilize within the region of the target temperature. However, the power required to maintain the temperature of the heater at the target temperature is generally less than the power required to heat the heater. As a result, if a constant power continues to be supplied to the heater, the temperature of the heater will continue to rise above the target temperature, but at a lower rate, over a certain period. If the resistance becomes too high, i.e., the temperature of the heater rises above the target temperature, the power to the heater can be reduced or stopped by monitoring the resistance. However, the temperature of the heater has a tendency to "rise above" the target temperature in a power-regulated system. This can lead to an increase in aerosol generation and, consequently, may lead to variations in aerosol delivery during user inhalation, which may not be desirable. Additionally, a temperature rise above the target temperature means that energy is wasted and it has an adverse effect on the efficiency of the device.

[0011] Another way to control or regulate the temperature of the heater is resistance regulation. In a resistance regulation system, a target resistance indicating the target temperature is set, and the power supplied to the heater is adapted such that the resistance of the heater is driven towards, or maintained at, or within the region of the target resistance. However, due to the difficulty in calculating the target resistance caused by various factors affecting the resistance of the heater, such as manufacturing variations, variations in contact resistance, changes in the characteristics of the aerosol generation substrate, different ambient temperatures, and different geometric shapes, materials, resistances, etc. of various heaters, using resistance regulation to adjust the temperature can potentially pose problems.

[0012] The method of the first aspect of the present invention uses two control steps to control heating in an aerosol generation system, namely a first control step based on power regulation and a second control step based on resistance regulation. This results in a hybrid method of regulation, which means that the advantages of both types of regulation can be utilized while reducing the disadvantages of each type. Such a hybrid method provides a number of benefits as follows.

[0013] The first control step based only on power regulation requires supplying a constant power to the heater and determining the resistance of the heater. There is no need to adapt the power during this control step, so controlling is relatively simple and uses fewer control resources compared to resistance regulation. This is beneficial during the initial stage of the heating cycle, i.e., while the heater is simply heating, as there is less need to regulate the temperature during this time.

[0014] With the detection of a predetermined condition, the resistance is recorded and the recorded resistance can be used to determine a target resistance based on the recorded resistance. The target resistance is based solely on the resistance of the heater recorded when the predetermined condition was detected, so it can be determined independently of various factors that may otherwise affect the resistance of the heater, such as manufacturing variations, variations in contact resistance, changes in the characteristics of the aerosol generation substrate, different ambient temperatures, and different geometric shapes, materials, resistances, etc. of various heaters.

[0015] Following the determination of the target resistance, a second control step based on resistance adjustment can then be used, in which the power supplied to the heater is controllably adapted to drive the resistance of the heater towards the target resistance, whereby the heater is driven towards the target temperature corresponding to the target resistance. This reduces the likelihood of the temperature of the heater rising above the target temperature. As a result, the consistency or uniformity of the properties of the generated aerosol is improved during inhalation and for subsequent inhalations. For example, the volume of the aerosol delivered can be made more consistent, as can the components contained within the aerosol. This leads to an overall improvement in the user experience. Furthermore, by reducing excessive temperature rises, energy waste is reduced and the efficiency of the system is improved.

[0016] As used herein, the term "target resistance" refers to the electrical resistance of the heater determined based on the resistance of the heater recorded upon detection of a predetermined condition. As described above, since the relationship between the electrical resistance of the heater and the temperature of the heater is generally known or can be determined, the resistance of the heater can serve as an indication of the temperature of the heater. Thus, the target resistance has a corresponding target temperature, and vice versa.

[0017] As used herein, the term "target temperature" refers to the temperature or temperature range corresponding to the target resistance. The target temperature is sufficient to generate an aerosol from the aerosol-forming substrate but is below the temperature at which thermal decomposition of the aerosol-forming substrate occurs or undesirable by-products are produced.

[0018] The method may switch from the first control step to the second control step upon detection of a predetermined condition. This allows for a rapid response to the predetermined condition.

[0019] As used herein, the term "predetermined condition" refers to a condition or criterion indicating that the resistance of the heater is at or near the target resistance. The condition may be known or determined before performing the method. As described above, when power is supplied to the heater, the temperature of the heater, and thus the resistance of the heater, initially rises rapidly and then begins to stabilize around the target temperature. The point at which the resistance begins to stabilize can be monitored, and various points within the stabilization can be set as the predetermined condition.

[0020] The predetermined condition may be selected from one or more different conditions as follows.

[0021] As an example, the predetermined condition may be the elapsed time since the start of user inhalation. The time it takes for the resistance to stabilize at or near the target temperature may be known or determinable, and this time can be used as the predetermined condition.

[0022] As another example, the predetermined condition may be the derivative of the resistance that is less than a predetermined threshold. As used herein, the term "derivative of the resistance" refers to a measure of the sensitivity of the change in resistance with respect to the change in another variable. For example, the derivative may be the rate of change of resistance with time (e.g., the slope of the resistance-versus-time curve), or the derivative may be the absolute change in resistance within the sampling time. When the resistance begins to stabilize around the target temperature, the rate of change of resistance with time begins to decrease. The predetermined condition may be a specific value for the rate of change of resistance, and the method may monitor the time when the rate of change of resistance drops below this value.

[0023] As yet another example, the predetermined condition may be the derivative of the resistance equal to zero. When the temperature of the heater reaches the maximum temperature, a given power is reached, the rate of temperature change becomes zero, and thus the rate of resistance change becomes zero. This zero rate of change of resistance may be used as the predetermined condition.

[0024] Additionally, the predetermined condition can be any suitable criterion based on resistance and / or time.

[0025] The first control step and the second control step may be performed during user inhalation and optionally during each user puff or smoking. This enables setting a target resistance value and effectively optimizing it for each puff. This is particularly useful when, for example, the aerosol-forming substrate is depleting or the ambient operating conditions are changing rapidly, where the target resistance may vary between puffs.

[0026] As used herein, the terms "inhalation" and "puff" are used interchangeably and are intended to mean the act of a user sucking on the end of the system to draw aerosol from the system.

[0027] The first control step and the second control step may be performed during the first user inhalation, and the second user inhalation and subsequent user inhalations may use only the second control step. This enables setting the target resistance by the first user inhalation and using the target resistance in all subsequent inhalations so that a consistent aerosol is produced over all subsequent inhalations in a particular usage session by the user. If desired, the temperature of the heater can be raised to the target temperature more quickly than using the first control step based on power regulation because the second control step is not limited by the need to supply a constant power. In other words, the system can increase the power beyond a certain output of the first control step if needed to drive the temperature of the heater towards the target temperature more quickly.

[0028] The target resistance may be determined after a plurality of initial user inhalations. Optionally, only the first control step and the step of monitoring and detecting a predetermined condition and recording the resistance may be performed during a plurality of initial user inhalations. In this option, the switch to the second control mode will occur between puffs rather than during a puff.

[0029] The target resistance may be determined based on the average of the resistances recorded from a plurality of initial user inhalations. The target resistance based on the average of the resistances recorded from a plurality of initial user inhalations may take into account, for example, the fluctuations in the initially recorded resistance during the initial startup of the aerosol generation system before the system thermally stabilizes, or when the ambient operating conditions suddenly change at startup (e.g., by the user moving from outdoors to indoors), or may make it possible to eliminate or make constant such fluctuations in the resistance.

[0030] User inhalations after a plurality of initial user inhalations may use only the second control step, and the target resistance may be based on the average of the resistances recorded from a plurality of initial user inhalations. This may provide consistent aerosol generation for subsequent inhalations in a particular usage session by the user. If desired, the temperature of the heater can be raised to the target temperature more quickly than using the first control step based on power regulation, since the second control step is not limited by the need to supply a constant power.

[0031] According to a second aspect of the present invention, there is provided an aerosol generation system comprising a heater, a power source, and a controller, the controller being adapted to supply a predetermined power to the heater and to determine the resistance of the heater in a first control mode such that the determined resistance indicates the temperature of the heater; to monitor a predetermined condition and, upon detection of the predetermined condition, record the resistance of the heater; to determine a target resistance corresponding to the target temperature of the heater based on the recorded resistance; and to control the power supplied to the heater to drive the resistance of the heater towards the target resistance in a second control mode, whereby the heater is configured to be driven towards a target temperature corresponding to the target resistance.

[0032] The system of the second aspect of the present invention uses two control modes to control heating in an aerosol generation system, namely a first control mode based on power regulation and a second control mode based on resistance regulation. The first control mode and the second control mode correspond to the first control step and the second control step of the method of the first aspect of the present invention. As a result, the system is configured with hybrid temperature control, which means that the advantages of both types of control can be utilized while reducing the disadvantages of each type. Such hybrid control provides numerous benefits, which are described above under the first aspect of the present invention and will not be repeated here for the sake of brevity.

[0033] The controller may be configured to switch from the first control mode to the second control mode upon detection of a predetermined condition. This enables a rapid response to the predetermined condition.

[0034] The predetermined condition may be selected from one or more of i) the elapsed time since the start of the user's inhalation, ii) the derivative of the resistance below a predetermined threshold, and iii) the derivative of the resistance equal to zero. Each of these predetermined conditions is the same as the predetermined condition in the first aspect of the present invention and is described above. For the sake of brevity, the description will not be repeated here. In addition, the predetermined condition can be any suitable criterion based on resistance and / or time.

[0035] The first control mode and the second control mode may be used during user inhalation and optionally during each user inhalation. This makes it possible to set a target resistance value and effectively optimize it for each inhalation. This is particularly useful when, for example, the aerosol-forming substrate is depleting or when the ambient operating conditions are changing rapidly, such that the target resistance may vary during a smoking session.

[0036] The first control mode and the second control mode may be used during the first user inhalation, and the second user inhalation and subsequent user inhalations may use only the second control mode. This enables setting a target resistance by the first user inhalation and using the target resistance in all subsequent inhalations so that a consistent aerosol is generated over all subsequent inhalations in a particular usage session by the user. Optionally, the temperature of the heater can be raised to the target temperature faster using the first control mode based on power regulation than using the second control mode, as the second control mode is not limited by the need to supply a constant power. In other words, if the system requires it, the power can be increased beyond a constant output of the first control mode to drive the temperature of the heater towards the target temperature faster.

[0037] The target resistance may be determined after a plurality of initial user inhalations. Optionally, only the first control mode and monitoring and detecting predetermined conditions and recording the resistance may be used during a plurality of initial user inhalations. In this option, the switch to the second control mode will occur between inhalations rather than during an inhalation.

[0038] The target resistance may be determined based on the average of the recorded resistances from a plurality of initial user inhalations. The target resistance based on the average of the recorded resistances from a plurality of initial user inhalations may account for or eliminate fluctuations in the determined target resistance, for example, during the initial startup of the aerosol generation system before the system has thermally stabilized or when the ambient operating conditions change suddenly at startup (e.g., when the user moves from outdoors to indoors).

[0039] After a plurality of initial user inhalations, subsequent user inhalations may use only the second control mode, and the target resistance may be based on the average of the recorded resistances from the plurality of initial user inhalations. This may provide consistent aerosol generation for subsequent inhalations in a particular usage session by the user. If desired, the temperature of the heater can be raised to the target temperature more quickly than using the first control mode based on power regulation, as the second control mode is not limited by the need to supply a constant power.

[0040] In both the first and second aspects of the present invention, the heater may include an electrically resistive heating element. The heater may include an electrically resistive material. Suitable electrically resistive materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composite materials made of ceramic materials or metal materials. Such composite materials may include doped ceramics or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, platinum, gold, and silver. 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, gold-containing, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal (registered trademark), and iron-manganese-aluminum-based alloys. In the composite material, the electrically resistive material may optionally be embedded in, encapsulated in, or coated with a thermal insulation material, or vice versa, depending on the required energy transfer dynamics and external physico-chemical properties.

[0041] In both the first and second aspects of the present invention, the heater may comprise an internal heating element, or an external heating element, or both an internal and an external heating element, where "internal" and "external" refer to the position relative to the aerosol-forming substrate. The internal heating element may take any suitable form. For example, the 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 conductive portions or an electrically resistive metal tube. Alternatively, the internal heating element may be one or more heating needles or rods passing through the center of the aerosol-forming substrate. Other alternatives include heating wires or filaments, such as Ni-Cr (nickel-chromium), platinum, tungsten, or alloy wires, or heating plates. Optionally, the internal heating element may be disposed within or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a well-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 within another insulating material, such as glass. The heater formed in this manner may be used both for heating the heating element and monitoring its temperature during operation.

[0042] The heater may comprise a fluid-permeable heating element. The fluid-permeable heating element may be substantially flat and may comprise conductive filaments. The conductive filaments may be disposed within a single plane. In other embodiments, the substantially flat heating element may be curved along one or more dimensions, for example, to form a dome shape or a bridge shape.

[0043] The conductive filaments may define gaps therebetween, and the gaps may have a width of from 10 μm to 100 μm. The filaments may cause capillary action in the gaps, whereby during use, the liquid aerosol-forming substrate is drawn into the gaps, increasing the contact area between the heating element and the liquid.

[0044] The conductive filaments may form a mesh sized 160 - 600 US mesh (±10%) (i.e., 160 - 600 filaments (±10%) per inch). The width of the gaps is preferably 75 μm - 25 μm. The proportion of the opening area of the mesh, which is the ratio of the area of the gaps to the total area of the mesh, is preferably 25 - 56%. The mesh may be formed using different types of weaving structures or lattice structures. As another method, the conductive filaments consist of an array of filaments arranged parallel to each other.

[0045] The conductive filaments may have a diameter of 10 μm - 100 μm, preferably have a diameter of 8 μm - 50 μm, and more preferably have a diameter of 8 μm - 39 μm. The filaments may have a round cross-section or a flat cross-section. The heater filaments may be formed by etching a sheet material (such as foil). When the heater assembly includes a mesh or fabric of filaments, the filaments may be formed individually and woven together.

[0046] The area of the fluid-permeable heating element may be, for example, 50 square millimeters or less, preferably 25 square millimeters or less, and more preferably approximately 15 square millimeters.

[0047] The electrical resistance of the mesh, array, or fabric of the conductive filaments of the heating element may be 0.3 ohms - 4 ohms. The electrical resistance is preferably 0.5 ohms or more. The electrical resistance of the mesh, array, or fabric of the conductive filaments is more preferably 0.6 ohms - 0.8 ohms.

[0048] The aerosol-forming substrate may be a liquid aerosol-forming substrate. When a liquid aerosol-forming substrate is provided, the aerosol-generating system preferably comprises means for holding the liquid. For example, the liquid aerosol-forming substrate may be held in a liquid storage part or container. Alternatively, or additionally, the liquid aerosol-forming substrate may be absorbed in a porous carrier material. The porous carrier material may be made of any suitable absorbent plug or body, such as a foamed metal or plastic material, polypropylene, terylene, nylon fibres, or ceramic.

[0049] When a liquid aerosol-forming substrate is provided, both the first and second aspects of the invention may be configured to detect dry smoking, for example by detecting when a recorded resistance increases above a threshold or by detecting when the power required to maintain the heater at a target resistance decreases below a threshold.

[0050] The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, the aerosol-forming substrate may comprise both a solid component and a liquid component. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds released from the substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0051] The aerosol generating system may comprise a housing having a mouthpiece portion and a body portion. The body portion may include a power source (e.g., a rechargeable lithium-ion battery), a control circuit having a controller (e.g., a microcontroller), and a user interface (e.g., a smoking detection device or a push button) for activating the heater. The mouthpiece portion may include a liquid storage portion, such as a cartridge containing a liquid aerosol generating substrate. The cartridge may include a capillary material for transporting the liquid aerosol forming substrate to the heater. The cartridge may also include a heater.

[0052] The control circuit may be arranged to supply power to the heating element as a series of voltage pulses. Next, the power supplied to the heating element may be adjusted by adjusting the duty cycle of the voltage pulses. The duty cycle may be adjusted by varying the pulse width, or the frequency of the pulses, or both. As another method, the circuit may be arranged to supply power to the heating element as a continuous DC signal. A proportional integral derivative (PID) control loop may be used to drive the resistance of the heater towards a target resistance.

[0053] According to a third aspect of the present invention, a controller for an aerosol generating system is provided, the controller being configured to execute any of the methods described above.

[0054] According to a fourth aspect of the present invention, a computer program is provided, which when executed on a programmable controller for an aerosol generating system, causes the programmable controller to execute any of the methods described above.

[0055] Features described in relation to one aspect may equally apply to other aspects of the present invention.

[0056] Here, by way of example only, embodiments of the present invention will be described with reference to the following accompanying drawings.

Brief Description of the Drawings

[0057]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0058] Figure 1 is a schematic diagram of an aerosol generation system. System 100 includes a housing 101 having a mouthpiece portion 103 and a body portion 105. In the body portion 105, a power source 107 (e.g., a rechargeable lithium-ion battery, etc.), a control circuit 109 having a controller 110 (e.g., a microcontroller), and a smoking detection device 111 are provided. In the mouthpiece portion 103, a liquid storage portion 113 (e.g., a cartridge containing a liquid aerosol generation substrate 115), a wick 117 formed of a capillary material, and a heater 119 having at least one heating element are provided. One end of the wick 117 extends into the cartridge 113, and the other end of the wick 117 is surrounded by the heater 119. The heater 119 is connected to the smoking detection device 111 via a connection 121, which is in turn connected to the control circuit 109 by a further connection (not shown). The housing 101 also includes an air inlet 123 in the region of the smoking detection device 111, an air outlet 125 exiting from the mouthpiece portion 103, and an aerosol formation chamber 127 surrounding the heater 119.

[0059] The liquid aerosol generation substrate 115 is moved or carried from the cartridge 113 to the end of the wick surrounded by the heater 119 by the wick 117 via capillary action. In use, the user inhales through the mouthpiece portion 103 or smokes the mouthpiece portion 103, and ambient air is drawn in through the air inlet 123. Inhalation or smoking is detected or sensed by the smoking detection device 111, which activates the heater 119. The battery 107 supplies energy to the heater 119 to heat the end of the wick 117 surrounded by the heater. The liquid at that end of the wick 117 is vaporized by the heater 119 to create a supersaturated vapor. At the same time, the vaporized liquid is replaced by further liquid moving along the wick 117 by capillary action. The created supersaturated vapor is mixed with the air stream from the air inlet 123 and carried in the air stream, condensing in the aerosol formation chamber 127 to form an inhalable aerosol, which is carried towards the outlet 125 and into the user's mouth.

[0060] The controller 110 is programmable and has embedded software or firmware for controlling the power supplied to the heater 119 in order to regulate the temperature of the heater. This will in turn affect the temperature profile of the heater, which will affect the amount of aerosol produced. The controller 110 supplies power to the heater 119 by pulse width modulation (PWM) that transfers power using a series of voltage pulses. The power supplied to the heater can be varied by changing the duty cycle of the pulses at a constant frequency. The duty cycle is the ratio of the time the power switch is on to the time the power switch is off. In other words, it is the ratio of the width of the voltage pulse to the time between voltage pulses. For example, a low duty cycle of 5% provides much less power than a 95% duty cycle.

[0061] FIG. 2 shows a graph of resistance R versus time t and the temperature profile of the heater of an aerosol generation system heated by a method according to an embodiment of the present invention. In particular, FIG. 2 shows the first three inhalations or puffs of a user usage session where all three inhalations are controlled by a hybrid regulation, i.e., a combination of power regulation and resistance regulation.

[0062] The system is activated at time t0, for example, by the user turning on the power of the system. The user begins the first inhalation or puff at time t1, which activates the heater. The heater is initially controlled by a first control step or mode based on power regulation (shown as PR in the figure), where a certain predetermined power corresponding to a predetermined duty cycle is provided to the heater. The predetermined power may be relatively high (e.g., a duty cycle of 80% - 95%) in order to rapidly increase the temperature of the heater. Providing the predetermined power causes the temperature of the heater to rise, and the resistance of the heater is determined at regular intervals to provide an indication of the temperature of the heater. The predetermined power is at time t L1Until a predetermined condition is detected at [time point], it is supplied to the heater. At this time point, the resistance is locked or recorded, and the target resistance is determined based on the recorded resistance. RT1 Generally, the target resistance is the same as the recorded resistance, but it is also possible for the target resistance to be different from the recorded resistance (e.g., depending on the recorded resistance or to include known error correction) according to the requirements of the system. Using this method, the target resistance is determined regardless of any variations in the resistance of the heater or the characteristics of the system. The target resistance corresponds to the target temperature to which the heater is to be heated.

[0063] In the embodiment of FIG. 2, the predetermined condition is the point at which the rate of change of resistance drops below a specific threshold, i.e., the point at which the gradient of the temperature profile decreases to a predetermined value. In particular, in FIG. 2, the predetermined condition is the point at which the gradient of the temperature profile approaches zero.

[0064] Time t L1 At [time point], the control of the heater switches to a second control step or mode based on resistance regulation (represented by RR in the figure). In this step or mode, the power supplied to the heater is controlled to drive the resistance of the heater towards the target resistance R such that the heater is driven towards the target temperature corresponding to the target resistance R. T1 The second control step or mode is adapted to be controllable to drive the resistance of the heater towards the target resistance R so that the heater is driven towards the target temperature corresponding to the target resistance R. The second control step or mode uses PID control to adjust the resistance. The PID control is incorporated into the software programmed in the controller. To adjust the resistance, the resistance of the heater is determined, and the error between the determined resistance and the target resistance R is calculated. Next, the power load cycle is adjusted using PID control to correct the error and drive the heater towards the target resistance. The resistance is determined at a frequency selected to match the frequency at which the load cycle is controlled and may be determined every 100 ms or more frequently as needed. T1 T1

[0065] Time t L1Following the switch to a second control step or mode based on resistance adjustment at, the resistance remains substantially constant at the target resistance R until the user stops their first inhalation or puff at time t2. T1 is maintained substantially constantly.

[0066] In the embodiment of Figure 2, a hybrid adjustment similar to that described above is used in each subsequent inhalation or puff. The user starts their second inhalation and third inhalation at times t3 and t5 respectively, and the corresponding target resistances R T2 and R T3 are determined at times t L2 and t L3 respectively. Each of the three inhalations in Figure 2 has its own target resistance, namely R T1 、R T2 、R T3 respectively. The target resistances are substantially similar but slightly different due to slightly different conditions in each inhalation, whereby the target resistances R T1 、R T2 、R T3 are optimized for each inhalation.

[0067] Figure 3 shows a graph of resistance R against time t and the temperature profile of the heater of an aerosol generating system heated by a method according to another embodiment of the invention. In particular, Figure 3 shows the first three inhalations or puffs of a user session, in which only the first inhalation is adjusted by hybrid adjustment and the second and subsequent inhalations are adjusted using only resistance adjustment.

[0068] In Figure 3, the system is activated at time t0 and the user starts their first inhalation or puff at time t1, which activates the heater. The first inhalation in Figure 3 is adjusted in the same way as the inhalation in Figure 2. During the first inhalation, the heater is initially controlled by a first control step or mode based on power adjustment. At time t L1 with the detection of a predetermined condition, the resistance is recorded and the target resistance R TIt is determined. At this point, the control of the heater switches to a second control step or mode based on resistance adjustment, which is used for the remaining inhalations until inhalation ends at time t2.

[0069] The second and third inhalations in Figure 3 start at times t3 and t5 respectively, at which point the heater is restarted, but are controlled only by the second control step based on resistance adjustment until inhalation ends at times t4 and t6 respectively. Therefore, the second and subsequent inhalations are adjusted based on the target resistance R of the first inhalation. T This provides consistent aerosol generation throughout all inhalations. Additionally, the second control step or mode is not limited to supplying a constant predetermined power and can supply power up to a 100% load cycle if necessary to bring the temperature of the heater to the target temperature as quickly as possible, so that the heater can be brought to the target temperature corresponding to the target resistance R more quickly if required. As can be seen in Figure 3, the temperature profiles of the second and third inhalations have a steeper gradient compared to the first inhalation, indicating a faster rate of temperature change. The second control step or mode used to adjust the second and third inhalations adjusts the resistance using PID control, which is incorporated into the software programmed into the controller. T Figure 4 shows a graph of resistance R versus time t and the temperature profile of the heater of an aerosol generation system heated by a method according to another embodiment of the present invention. In particular, Figure 4 shows the first 5 inhalations or puffs of a user session, in which the first 3 inhalations are adjusted by hybrid adjustment and the fourth and subsequent inhalations are adjusted using only resistance adjustment.

[0070]

[0071] ​In Figure 4, the system is activated at time t0, and the user takes the first inhalation or puff at time t1, at which point the heater is activated. The first inhalation in Figure 4 is adjusted in the same way as the inhalation in Figure 2. During the first inhalation, the heater is initially controlled by a first control step or mode based on power regulation, where a certain predetermined power corresponding to a predetermined load cycle is provided to the heater. The predetermined power is supplied to the heater until a predetermined condition is detected at time t L1 at which point the resistance R1 is locked or recorded. The predetermined condition in the example of Figure 4 is the point at which the gradient of the temperature profile approaches zero again. The target resistance is not determined at this point. Instead, the method first monitors one or more additional inhalations or puffs before determining the target resistance.

[0072] At time t L1 in Figure 4, the control of the heater switches to a second control step or mode based on resistance regulation, in which the power supplied to the heater is controllably adapted to drive the resistance of the heater towards the recorded resistance R1 such that the heater is driven towards the temperature corresponding to the recorded resistance R1. The second control step or mode uses a PID control incorporated into the software programmed into the controller to adjust the resistance.

[0073] At time t L1 in Figure 4, following the switch to the second control step or mode based on resistance regulation, the resistance is maintained substantially constantly at the recorded resistance R1 until the user stops the user's first inhalation or puff at time t2.

[0074] The second and third inhalations in Figure 4 are adjusted in the same way as the first inhalation. The second and third inhalations are started at times t3 and t5 respectively, at which point the heater is activated again. The heater is initially controlled by a first control step or mode based on power regulation, at times t L2 and t L3With the detection of predetermined conditions, resistances R2 and R3 are respectively recorded. Subsequently, the control of the heater switches to a second control step or mode based on the resistance adjustment, which is used for the remaining inhalations until the second and third inhalations end at times t4 and t6 respectively.

[0075] The three separate recorded resistances R1, R2, and R3 from the first three inhalations are used to determine a target resistance R based on the average of the three recorded resistances R1, R2, and R3. T The fourth and fifth inhalations are adjusted in the same way as the second and third inhalations in Figure 3. The fourth and fifth inhalations in Figure 4 start at times t7 and t9 respectively, at which point the heater is restarted, but are controlled only by the second control step based on the resistance adjustment until the inhalations end at times t8 and t 10 respectively. The fourth and subsequent inhalations are adjusted using the target resistance R based on the average of the recorded resistances R1, R2, and R3. T This provides consistent aerosol generation for the fourth and subsequent inhalations.

[0076] Figure 5 shows a graph of resistance R against time t and the temperature profile of the heater of an aerosol generation system heated by a method according to another embodiment of the present invention. In particular, Figure 5 shows the first 7 inhalations or puffs of a user session, in which the first 5 inhalations are adjusted by hybrid adjustment and the sixth inhalation and subsequent inhalations are adjusted using only resistance adjustment. This method may be used when the recorded resistances in the first few inhalations vary significantly, i.e., when the resistance variation is outside a predetermined or acceptable range, which may occur, for example, at the initial startup of the aerosol generation system before the system thermally stabilizes.

[0077] In FIG. 5, the system is activated at time t0, and the user takes the first three inhalations or puffs at times t1, t3, t5, at which point the heater is activated. The first three inhalations in FIG. 5 are adjusted in the same way as the first three inhalations in FIG. 4. During the first three inhalations, the heater is initially controlled by a first control step or mode based on power regulation. For each inhalation, at times t L1 、t L2 、t L3 respectively, with the detection of predetermined conditions for each inhalation, separate resistances, namely R1, R2, R3 are recorded respectively. At this point, the control of the heater switches to a second control step or mode using resistance regulation based on the three respectively recorded resistances R1, R2, R3, and this step or mode is used for the remainder of each inhalation until the inhalation ends at times t2, t4, t6 respectively.

[0078] The condition for determining the target resistance may be that the resistances recorded for the last n inhalations or puffs fall within the range of a maximum predetermined range ΔRmax. In that case, the target resistance may be based on either the last recorded resistance or the average of the last n inhalations.

[0079] In FIG. 5, n is set to 3, and the values of the resistances R1, R2, R3 are outside the maximum predetermined range ΔR max . In other words, the value obtained by subtracting the minimum value of R1, R2, R3 from the maximum value of R1, R2, R3 is greater than the maximum △R of the predetermined range max , that is, max{R1, R2, R3} - min{R1, R2, R3}>△R max . As a result, the method does not determine a target resistance but monitors further inhalations made by the user.

[0080] The fourth inhalation is performed at time t7 and is adjusted in the same way as the first three inhalations, that is, using hybrid regulation. The fourth resistance R4 is at time t L4When a predetermined condition is detected at [condition detection point], it is recorded, and the fourth inhalation ends at time t8. Next, the method examines the resistances recorded for the last three inhalations (i.e., R2, R3, R4). However, in Figure 5, these three resistances also fall outside the maximum predetermined range ΔR max outside. Therefore, the method does not determine the target resistance but monitors further inhalations performed by the user.

[0081] The fifth inhalation is performed at time t9 and is adjusted in the same manner as the first four inhalations, i.e., using hybrid regulation. The fifth resistance R5 is recorded when a predetermined condition is detected at time t L5 and the fourth inhalation ends at time t 10 . Next, the method examines the resistances recorded for the last three inhalations (i.e., R3, R4, R5). In Figure 5, these three resistances fall within the maximum predetermined range ΔR max and thus the target resistance R T can be determined. The target resistance R T can be based on the last recorded resistance, i.e., R5, or on the average of the recorded resistances of the last three inhalations, i.e., R3, R4, R5. In Figure 5, the target resistance R T is based on the average of the recorded resistances of the last three inhalations, i.e., R3, R4, R5.

[0082] The sixth and seventh inhalations are adjusted in the same manner as the second and third inhalations in Figure 3. The sixth and seventh inhalations in Figure 5 start at times t 11 and t 13 respectively, at which point the heater is restarted, but are controlled only by the second control step based on resistance regulation until the inhalations end at times t 12 and t 14 respectively. The sixth and subsequent inhalations are adjusted using the target resistance R T based on the average of the recorded resistances R3, R4, R5. This provides consistent aerosol generation for the sixth and subsequent inhalations.

[0083] FIG. 6 shows a graph of resistance R versus time t and the temperature profile of a heater of an aerosol generation system heated by a method according to another embodiment of the present invention. In particular, FIG. 6 shows the first 5 inhalations or puffs of a user session, in which session the first 3 inhalations are regulated only by power regulation and the 6th inhalation and subsequent inhalations are regulated using only resistance regulation.

[0084] The first 3 inhalations in FIG. 6 differ from the initial inhalations in other examples shown in the figure in that they are regulated only by power regulation. In FIG. 6, the system is activated at time t0, and the user takes the first inhalation or puff at time t1, at which point the heater is activated. During the inhalation, the heater is controlled by a first control step or mode based only on power regulation, where a constant predetermined power corresponding to a predetermined duty cycle is provided to the heater until the inhalation ends at time t2. At the detection of a predetermined condition at time t L1 the resistance R1 is recorded. The predetermined condition in the example of FIG. 6 is that the gradient of the temperature profile approaches zero.

[0085] As described above, the power regulation system generally uses a relatively high predetermined power (e.g., 80% - 95% duty cycle) to raise the temperature of the heater towards the target temperature as quickly as possible. Once the target temperature is reached, generally less power is used to maintain the heater at the target temperature than to heat it, so the power can be gradually reduced. However, since the first inhalation does not switch to a second control step or mode during the inhalation, i.e., upon detection of a predetermined condition, the resistance is not regulated at the recorded resistance, and thus the temperature of the heater continues to rise above the recorded resistance, albeit at a lower rate.

[0086] The target resistance based on the recorded resistance R1 is a predetermined condition, i.e., time t L1It may be determined with the detection in []. For example, the target temperature can be determined when R1 is within a predetermined range. However, the method shown in FIG. 6 takes an alternative approach and uses power regulation alone to first monitor two more inhalations or puffs before determining the target resistance due to resistance fluctuations in the first few inhalations.

[0087] The second and third inhalations in FIG. 6 are adjusted in the same way as the first inhalation. The second and third inhalations are started at times t3 and t5 respectively, at which point the heater is restarted. The heater is controlled only by the first control step or mode based only on power regulation until the inhalations end at times t4 and t6 respectively. Time t L2 and t L3 With the detection of predetermined conditions at [], the resistances R2 and R3 are recorded respectively.

[0088] The three recorded resistances 1, R2, R3 from the first three inhalations are used to determine the target resistance R T based on the average of the three recorded resistances R1, R2, R3. The fourth and fifth inhalations are adjusted in the same way as the second and third inhalations in FIG. 3, i.e., using only resistance regulation. The fourth and fifth inhalations in FIG. 6 are started at times t7 and t9 respectively, at which point the heater is restarted, but are controlled only by the second control step based on resistance regulation until the inhalations end at times t8 and t 10 respectively. The fourth and subsequent inhalations are adjusted using the target resistance R T based on the average of the recorded resistances R1, R2, R3. This provides consistent aerosol generation for the fourth and subsequent inhalations.

[0089] As another method, if the three recorded resistances R1, R2, R3 are not within the maximum predetermined range, the system can wait until the resistance stabilizes and is within the predetermined range, and then calculate the target resistance based on the average of the recorded resistances in the same way as the method described in FIG. 5.

[0090] Figure 7 shows a graph of resistance R against time t and the temperature profile of the heater of an aerosol generation system according to another embodiment of the present invention in which the heater exhibits a dry smoking situation. In particular, Figure 7 shows the first three inhalations or puffs of a user session where all inhalations are controlled by a hybrid adjustment, i.e., a combination of power adjustment and resistance adjustment. As described above, a "dry smoking" or "dry heating" situation occurs when the heater is heated with an insufficient presence of the liquid aerosol forming substrate. This can lead to overheating and potentially thermal decomposition of the liquid aerosol forming substrate, which can produce undesirable by-products such as formaldehyde.

[0091] In Figure 7, the system is activated at time t0 and the user begins the first inhalation or puff at time t1, which activates the heater. During the first inhalation, liquid is present in the heater, which is initially controlled by a first control step or mode based on power adjustment. With the detection of a predetermined condition at time t L1 a resistance R1 may be recorded and a target resistance determined based on the recorded resistance R1. At this point, the control of the heater switches to a second control step or mode based on resistance adjustment, which is used for the remaining inhalations until the inhalation ends at time t2.

[0092] The second and third inhalations in Figure 7 are adjusted in the same way as the first inhalation and are started at times t3 and t5, respectively. However, there is insufficient liquid aerosol generation substrate available for the second and third inhalations, resulting in dry smoking. With the detection of a predetermined condition, resistance R2 is recorded at time t L2 during the second inhalation and resistance R3 is recorded at time t L3It is recorded at. Resistors R2 and R3 are significantly higher than resistor R1 due to dry smoking. The reason for this is that in the power regulation system, when a certain predetermined power is supplied to the heater and the liquid aerosol forming substrate present in the heater is insufficient, for example, when the cartridge storing the liquid aerosol forming substrate is empty, less power is consumed or no power is consumed in the vaporization of the liquid, resulting in a significant increase in the final temperature achieved and thus the recorded resistance. Furthermore, the temperature rises at a faster rate compared to when liquid is present, which is evident from the more rapid rate of temperature rise during the second and third inhalations.

[0093] The system is configured to detect this significant and abrupt increase in the recorded resistance due to insufficient liquid. In particular, the system is configured to detect when the recorded resistance increases above a threshold value. Upon detection, the system can disconnect the heater to prevent further dry smoking, thereby reducing the possibility of the user being exposed to undesirable by-products. Instructions for detecting dry smoking and disconnecting the heater can be implemented in the software programmed in the controller.

[0094] Figure 8 shows a graph of resistance R against time t and the temperature profile of the heater of an aerosol generation system according to another embodiment of the invention where the heater exhibits another dry smoking situation. In particular, Figure 8 shows the first three inhalations or puffs of a user session where the first inhalation is regulated by hybrid regulation and subsequent inhalations are regulated by resistance regulation.

[0095] In Figure 8, the system is activated at time t0 and the user starts the first inhalation or puff at time t1, which activates the heater. The first inhalation in Figure 8 is regulated in the same way as the first inhalation in Figure 7. During the first inhalation, liquid is present at the heater, which is initially controlled by a first control step or mode based on power regulation. Time t L1Upon detection of a predetermined condition, the resistance is recorded, and based on the recorded resistance, a target resistance R T is determined. At this point, the control of the heater switches to a second control step or mode based on the resistance adjustment, which is used for the remaining inhalation until the inhalation ends at time t2.

[0096] In the second and third inhalations, the liquid aerosol generation matrix available for use in the heater is insufficient, resulting in dry smoking. The second and third inhalations in FIG. 8 are started at times t3 and t5 respectively, at which point the heater is restarted but is controlled only by the second control step based on the resistance adjustment, where the resistance is adjusted to the target resistance R of the first inhalation until the inhalation ends at times t4 and t6 respectively. T The system is adapted to maintain a constant resistance for the power in the second and third inhalations, so since the resistance is held constant, the change in resistance cannot be used to detect the situation of dry smoking. Instead, it is necessary to monitor the power required to maintain the target temperature and thus the target resistance. When the liquid aerosol generation matrix in the heater is insufficient, no power is consumed in the vaporization of the liquid, so the power required to keep the temperature constant is significantly lower than when the liquid is present.

[0097] The system is configured to detect a significant reduction in the power required to maintain the heater at the target resistance. In particular, the system is configured to detect when the power required to maintain the heater at the target resistance decreases below a threshold value. Upon detection, the system can disconnect the heater to prevent further dry smoking, thereby reducing the possibility of the user being exposed to undesirable by-products. Instructions for detecting dry smoking and disconnecting the heater can be implemented in the software programmed in the controller.

[0098] FIG. 9 illustrates a control circuit 200 used to provide the temperature regulation described in one embodiment of the present invention.

[0099] Circuit 200 includes a heater 214 with a resistive heating element that is connected to a power source via connection 222. The power source supplies voltage V2. An additional resistor 224 having a known resistance r is inserted in series with the heater 214. At a point in the circuit between the heater 214 and the additional resistor 224, i.e., on the ground side of the heater 214, there is a voltage V1. The voltage V1 is intermediate between ground and voltage V2. Software for providing temperature control is incorporated in software programmed in a microcontroller 218, which can transmit a pulse-width modulated voltage signal to a transistor 226 via an output 230 of the microcontroller 218, and this transistor acts as a simple switch to activate the heater 214 in accordance with the pulse-width modulated voltage signal.

[0100] The display of the temperature of the heater 214 (in this example, the electrical resistance of the heater 214) is determined by measurement of the electrical resistance of the heater 214. The temperature display is used to adjust the duty cycle of the pulse-width modulated voltage supplied to the heater 214 in order to maintain the heater near a target resistance. The temperature display is determined at a frequency selected to coincide with the timing required for the control process and may be determined every 100 ms or more frequently as needed.

[0101] The analog input 221 at the microcontroller 218 is used to monitor the voltage V2 on the power supply side of the heater 214. The analog input 223 at the microcontroller is used to monitor the voltage V1 on the ground side of the heater 214.

[0102] The heater resistance measured at a specific temperature is R ヒーター . To measure the resistance R ヒーター of the heater 214 by the microprocessor 218, both the current passing through the heater 214 and the voltage across the two ends of the heater 214 can be determined. Then, Ohm's law can be utilized to determine the resistance. TIFF2025113330000002.tif11160

[0103] In FIG. 9, the voltage applied across both ends of the heater is V2 to V1, and the current flowing through the heater is I. Therefore, TIFF2025113330000003.tif16160

[0104] Using an additional resistor 224 with a known resistance r, and using the above (1) again, the current I is determined. The current flowing through the resistor 224 is also I, and the voltage applied across both ends of the resistor 224 is V1. Therefore, TIFF2025113330000004.tif16160

[0105] Therefore, by combining (2) and (3), TIFF2025113330000005.tif16160

[0106] Therefore, since the aerosol generation system is used, the microprocessor 218 can measure V2 and V1, and since it knows the value of r, the resistance R of the heater at a specific temperature ヒーター can be determined.

[0107] The resistance R of the heater ヒーター is correlated with the temperature. Using linear approximation, the temperature T corresponding to the measured resistance R ヒーター can be determined according to the following formula. TIFF2025113330000006.tif16160Where A is the thermal conduction resistance coefficient of the heater material, and R0 is the resistance of the heater at the ambient temperature T0.

[0108] The advantage of the control circuit 200 is that it does not require a temperature sensor. Such sensors can be bulky and expensive. Also, the microcontroller can directly use the resistance value instead of the temperature. The heater resistance R ヒーターWhen it is maintained within a desirable range, the temperature of the heater 214 will also be maintained within a desirable range. As a result, the actual temperature of the heater 214 does not need to be calculated during the control process, which improves the efficiency of the operation. However, if desired, a separate temperature sensor can be used and connected to the microcontroller to provide the necessary temperature information.

[0109] The software programmed in the microcontroller 218 is configured to monitor a predetermined condition and record the resistance of the heater when the predetermined condition is detected. The predetermined condition and the resistance can be stored in the memory of the microcontroller 218. The software programmed in the microcontroller 218 is configured to determine a target resistance based on the recorded resistance.

[0110] The microcontroller 218 is also configured to adapt the duty cycle of the pulse-width modulation voltage signal to control the power supplied to the heater in order to drive the resistance of the heater towards the target resistance so that the heater is driven towards the target temperature corresponding to the target resistance. To adjust the resistance, the heater resistance R ヒーター is determined, and the error between the determined heater resistance R ヒーター and the target resistance is calculated. Next, the duty cycle of the power is adjusted using proportional-integral-derivative (PID) control to correct the error and drive the heater towards the target resistance. The PID control is incorporated into the software programmed in the controller 218.

[0111] The power P supplied to the heater 214 can be determined by the following formula. TIFF2025113330000007.tif6160Where V is the voltage applied across both ends of the heater, i.e., V2~V1, and I is the current passing through the heater that can be determined using the above (3). The determined power can be used, for example, to detect the situation of dry smoking illustrated in FIG. 8.

Claims

1. A method for controlling heating in an aerosol generation system comprising a heater, comprising: a first control step in which a predetermined power is supplied to the heater and the resistance of the heater is determined, the determined resistance indicating the temperature of the heater; monitoring a predetermined condition and, upon detection of the predetermined condition, recording the resistance of the heater; determining a target resistance corresponding to a target temperature of the heater based on the recorded resistance; a second control step in which the power supplied to the heater is controllably adapted to drive the resistance of the heater towards the target resistance, whereby the heater is driven towards a target temperature corresponding to the target resistance.

2. The method according to claim 1, wherein the method switches from the first control step to the second control step upon detection of the predetermined condition.

3. The predetermined condition is ● the elapsed time since the start of user inhalation, ● the derivative of the resistance that is less than a predetermined threshold, ● the derivative of the resistance that is equal to zero, selected from one or more of the above. The method according to claim 1 or claim 2.

4. The method according to any one of claims 1 to 3, wherein the first control step and the second control step are performed during user inhalation and optionally during each user inhalation.

5. The method according to any one of claims 1 to 3, wherein the first control step and the second control step are performed during the first user inhalation, and the second user inhalation and subsequent user inhalations use only the second control step.

6. The method according to any one of claims 1 to 3, wherein the target resistance is determined after a plurality of initial user inhalations.

7. The method according to any one of claims 1 to 3, wherein only the first control step and the step of monitoring and detecting a predetermined condition and recording the resistance are performed during a plurality of initial user inhalations.

8. The method according to claim 6 or claim 7, wherein the target resistance is determined based on an average of the recorded resistances from the plurality of initial user inhalations.

9. The method according to claim 8, wherein subsequent user inhalations after the plurality of initial user inhalations use only the second control step and the target resistance is based on an average of the recorded resistances from the plurality of initial user inhalations.

10. An aerosol generation system comprising: a heater; a power source; a controller, wherein the controller supplies a predetermined power to the heater and determines the resistance of the heater in a first control mode, the determined resistance indicating the temperature of the heater; monitors a predetermined condition and records the resistance of the heater upon detection of the predetermined condition; determines a target resistance corresponding to a target temperature of the heater based on the recorded resistance; is configured to controllably adapt the power supplied to the heater in a second control mode to drive the resistance of the heater towards the target resistance, whereby the heater is driven towards a target temperature corresponding to the target resistance. An aerosol generation system.

11. The aerosol generation system according to claim 10, wherein the controller is configured to switch from the first control mode to the second control mode upon detection of the predetermined condition.

12. The predetermined condition is selected from one or more of: - the elapsed time since the start of user inhalation; - the derivative of the resistance being less than a predetermined threshold; - the derivative of the resistance being equal to zero. The aerosol generation system according to claim 10 or claim 11.

13. The aerosol generation system according to any one of claims 10 to 12, wherein the first control mode and the second control mode are used during user inhalation and optionally during each user's inhalation.

14. The aerosol generation system according to any one of claims 10 to 12, wherein the first control mode and the second control mode are used during the first user inhalation, and the second user inhalation and subsequent user inhalations use only the second control mode.

15. The aerosol generation system according to any one of claims 10 to 12, wherein the target resistance is determined after a plurality of initial user inhalations.

16. The aerosol generation system according to any one of claims 10 to 12, wherein only the first control mode, and the monitoring and detection of the predetermined condition, and the recording of the resistance are used during a plurality of initial user inhalations.

17. The aerosol generation system according to claim 15 or claim 16, wherein the target resistance is determined based on the average of the recorded resistances from the plurality of initial user inhalations.

18. The aerosol generation system according to claim 17, wherein the user inhalations after the plurality of initial user inhalations use only the second control mode, and the target resistance is based on the average of the recorded resistances from the plurality of initial user inhalations.

19. A controller for an aerosol generation system, the controller being configured to execute the method according to any one of claims 1 to 9.

20. A computer program that, when executed by a programmable controller for an aerosol generation system, causes the programmable controller to perform the method according to any one of claims 1 to 9.

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