Glass fryer self-adaptive temperature control method and system and glass fryer

Abstract

The invention relates to the technical field of intelligent kitchen electric appliance control, in particular to a glass fryer self-adaptive temperature control method and system and a glass fryer. The method comprises the steps of obtaining a cooking mode selected by a user; according to the cooking mode, loading a standard set temperature associated with the cooking mode; wherein the standard set temperature is the corresponding standard temperature of air in the cavity when a food material sample is used for cooking and a preset ideal cooking effect is achieved under a standard test condition; in the cooking process, the current dielectric constant of food materials in the pot is obtained in real time through a dielectric sensing module, and the real-time temperature of air in a cavity in the pot is obtained through a temperature sensor; correcting the standard set temperature according to the current dielectric constant to obtain the target temperature of air in the cavity; and according to the target temperature of the air in the cavity, the heating element is controlled to work, so that the real-time temperature of the air in the cavity approaches the target temperature of the air in the cavity. The ideal cooking effect of the glass fryer can be improved.

Description

Technical Field

[0001] This application relates to the field of intelligent kitchen appliance control technology, and in particular to an adaptive temperature control method, system and glass fryer for a glass fryer. Background Technology

[0002] With the popularization of healthy eating concepts, air fryers have become an important appliance in family kitchens due to their low-oil and high-efficiency cooking characteristics. In recent years, in order to improve the product's aesthetics and heat resistance, some manufacturers have begun to use high borosilicate glass as the material for the air fryer cavity. However, glass has a high specific heat capacity and low thermal conductivity, resulting in a significantly slower thermal response speed than traditional metal cavities, and the system exhibits obvious thermal inertia and hysteresis.

[0003] Currently, most mainstream air fryers use a preset temperature-time curve combined with dual-threshold switch control for heating management. After the user selects a cooking mode, the controller drives the heating element to work according to the fixed target temperature corresponding to that mode, and achieves a simple closed loop through feedback from the internal temperature sensor.

[0004] However, while this method is acceptable in metal jars, in glass fryers, due to slow heating and uneven heat distribution, it often requires longer preheating time and higher overshoot to reach the target temperature. This not only prolongs the cooking cycle but may also cause carbonization of the food surface due to local overheating, making it difficult to stably reproduce the preset ideal cooking effect. Therefore, it urgently needs improvement. Summary of the Invention

[0005] Therefore, it is necessary to provide an adaptive temperature control method, system, and glass fryer for improving the ideal cooking effect of glass fryers, in order to address the above-mentioned technical problems.

[0006] In a first aspect, this application provides an adaptive temperature control method for a glass fryer, applied to a control unit, which controls the heating element in the main heating circuit of the glass fryer; the method includes:

[0007] Get the cooking mode selected by the user;

[0008] According to the cooking mode, load the standard set temperature associated with that cooking mode; wherein, the standard set temperature is the standard temperature of the air inside the cavity when the food sample is cooked under standard test conditions and the preset ideal cooking effect is achieved.

[0009] During the cooking process, the current dielectric constant of the food in the pot is obtained in real time through the dielectric sensing module, and the real-time temperature of the air inside the pot cavity is obtained through the temperature sensor.

[0010] The target temperature of the air inside the cavity is obtained by setting the temperature according to the current dielectric constant correction standard.

[0011] The heating element is controlled to operate according to the target temperature of the air inside the cavity, so that the real-time temperature of the air inside the cavity approaches the target temperature of the air inside the cavity.

[0012] Secondly, this application provides an adaptive temperature control system for a glass fryer, the adaptive temperature control system for a glass fryer comprising:

[0013] The control unit is used to control the heating element in the main heating circuit of the glass fryer and execute the above-mentioned adaptive temperature control method for the glass fryer.

[0014] Thirdly, this application provides a glass fryer, which includes the aforementioned glass fryer adaptive temperature control system and main heating circuit.

[0015] The beneficial effects of this application are: 1) Traditional solutions fix the target temperature of the air inside the cavity to a preset value, which cannot respond to changes in the actual state of the food. However, this solution introduces real-time sensing of the physical state of the food, so that the target temperature is no longer a static command, but a variable that is dynamically adjusted according to the initial conditions of the food. When the state of the food deviates from the standard sample, the target temperature is automatically corrected, so that under the inherent thermal response limitations of the glass cavity, the food can still be guided towards a consistent cooking effect;

[0016] 2) Traditional solutions only focus on whether the air temperature reaches the set value, but ignore the actual effect of that temperature on different ingredients. This solution indirectly characterizes the response characteristics of ingredients to heat energy through the dielectric constant, a physical quantity closely related to the thermochemical behavior of ingredients, and uses this to adjust the target air temperature in reverse. Even if there is thermal hysteresis in the glass cavity, the system can still compensate for individual differences in ingredients by advancing or delaying the heating intensity, ensuring the consistency of the final cooking effect.

[0017] 3) Under traditional fixed-temperature strategies, significant overshoot is often required to overcome the slow heating of glass, which can easily lead to overheating later on; if the temperature is controlled conservatively, the heating will be insufficient. This solution dynamically adjusts the target temperature, eliminating the need to rely on a single high overshoot strategy. For foods with a fast thermal response, the target temperature can be actively lowered to avoid overheating; for foods with a slow thermal response, the target temperature can be moderately increased to accelerate the process. This adaptive adjustment mechanism significantly improves the temperature control stability and robustness of the glass fryer without changing the hardware. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below.

[0019] Figure 1 This is a schematic diagram of the internal structure of a control unit provided in one embodiment of this application;

[0020] Figure 2 This is an overall flowchart of an adaptive temperature control method for a glass fryer provided in one embodiment of this application;

[0021] Figure 3 This is a flowchart of a dielectric sensing method using transient ringing signals from the main heating circuit, provided in one embodiment of this application.

[0022] Figure 4 This is a flowchart of a dielectric sensing method based on an embedded LC resonant circuit provided in one embodiment of this application;

[0023] Figure 5 This is a flowchart illustrating a method for calculating the target temperature correction based on dielectric deviation and a preset correction function, provided in one embodiment of this application.

[0024] Figure 6 This is a flowchart illustrating a method for calculating the target temperature correction based on a closed-loop thermal dose model, provided in one embodiment of this application.

[0025] Figure 7 This is an execution flowchart of controlling the operation of a heating element provided in one embodiment of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] Current glass fryers generally follow the control logic of traditional air fryers: after the user selects a cooking mode, the system loads a fixed set of temperature-time parameters and uses this preset temperature as the sole control target throughout the cooking process. However, this strategy implicitly assumes a key fact—that all foods will produce a consistent thermal response under the same temperature setting.

[0028] This assumption is particularly vulnerable in glass fryers. On one hand, the glass cavity itself has high heat capacity and low thermal conductivity, resulting in a slow and non-linear heat transfer process. On the other hand, the initial state of ingredients in actual cooking (such as moisture content, degree of thawing, and density) naturally varies, and these differences significantly affect their rate of heat absorption and chemical reaction processes. When the system mechanically executes a fixed temperature program, it cannot distinguish between "a chicken wing just taken out of the freezer" and "a chicken wing that has been at room temperature for two hours," and can only apply the same heating intensity. As a result, the former may be undercooked inside due to insufficient heat, while the latter may be burnt on the surface due to overheating. Some improvement solutions attempt to "cover up" the worst-case scenario by extending the cooking time or increasing the target temperature, but this not only sacrifices energy efficiency and speed but also exacerbates the risk of overcooking ideally cooked ingredients.

[0029] Therefore, there is an urgent need for a new method to enable the temperature control target to have "food sensing ability". Based on this, this embodiment provides an adaptive temperature control method for a glass fryer. The method is executed by a control unit, which is used to control the heating element in the main heating circuit of the glass fryer.

[0030] Specifically, the internal structure diagram of the control unit can be as follows: Figure 1 As shown, the control unit includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, Near Field Communication (NFC), or other technologies. When the computer program is executed by the processor, it implements an adaptive temperature control method for a glass fryer. The display unit of the control unit is used to form a visually visible image and can be a display screen, projection device, or virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the control unit can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the housing of the control unit, or external keyboards, touchpads, or mice, etc.

[0031] like Figure 2As shown, the adaptive temperature control method for a glass fryer provided in this embodiment includes the following steps:

[0032] S1: Obtain the cooking mode selected by the user;

[0033] "Cooking mode" refers to the preset program name selected by the user through the fryer's human-machine interface, such as "Frozen Fries," "Chicken Wings," or "Vegetables." Each mode has been systematically calibrated during the product development phase and associated with a set of exclusive process parameters, including standard set temperature, food dielectric reference value, correction function identifier, etc.

[0034] Different foods exhibit fundamentally different thermophysical behaviors, and the heat absorption capacity of the same type of food varies significantly under different initial states (e.g., fully frozen, partially thawed, room temperature). The fundamental reason is that moisture is the dominant factor affecting the thermal response of food. High-moisture foods continuously evaporate moisture in the initial stages of heating, and this evaporation requires the absorption of a large amount of latent heat of vaporization (approximately 2260 kJ / kg), creating a strong "evaporative cooling effect," resulting in the food surface temperature being much lower than the air temperature inside the cavity. Low-moisture foods, on the other hand, heat up rapidly and are prone to scorching. Applying the same fixed temperature strategy to all states inevitably fails to ensure consistent results. Therefore, it is essential to first identify the type of food the user intends to process in order to access a benchmark parameter set that matches its typical thermal response characteristics.

[0035] S2: Load the standard set temperature associated with the cooking mode, based on the cooking mode;

[0036] "Standard set temperature" refers to the standard internal air temperature determined after numerous repeated experiments under standard test conditions (ambient temperature 25℃, no residual heat, and using typical brand standard ingredient samples), which is the temperature at which the food achieves the preset ideal cooking effect. Here, "ideal cooking effect" does not refer to "reaching a certain temperature," but rather to the degree to which a specific thermochemical reaction is completed inside the food, such as: crispy and golden-brown fries (due to a full Maillard reaction), fully cooked inside (due to complete starch gelatinization), without any burnt or undercooked parts.

[0037] The fundamental flaw in traditional temperature control methods lies in directly equating "internal air temperature = 200℃" with "achieved desired effect," ignoring the modulating effect of the food's own state on the heat transfer path. In reality, the same internal air temperature will produce drastically different surface temperatures and internal cooking degrees for food with different moisture states. This method aims for "consistent results" as its ultimate goal, and the standard set temperature is merely an initial reference point for achieving this goal. Its physical meaning is "the internal air temperature required to achieve the ideal effect under standard food conditions."

[0038] The control unit extracts the temperature value from the parameter structure loaded by S1, typically stored as an integer (unit: °C), such as 200. This value is not used directly for heating control, but rather serves as the basis for calculating the dynamic target temperature.

[0039] Taking the "frozen fries" mode as an example, its standard set temperature is fixed at 200℃. This value originates from the factory development phase: engineers used the same supplier and the same batch of undried frozen fries, conducting over 50 repeated tests in a constant temperature and humidity laboratory, determining the value based on a comprehensive evaluation of color, crispness, core temperature, and sensory characteristics. This value is written into the product firmware and cannot be modified by the user, ensuring consistent benchmarks.

[0040] S3: During the cooking process, the current dielectric constant of the food in the pot is obtained in real time through the dielectric sensing module, and the real-time temperature of the air inside the pot cavity is obtained through the temperature sensor.

[0041] "Dielectric sensing module" refers to any sensing mechanism that can output a digital signal that is positively correlated with the real part of the complex dielectric constant of the food; "real-time temperature of the air inside the cavity" refers to the air temperature inside the sealed cavity of the fryer, about 2cm above the frying basket, which is measured by an NTC thermistor and calibrated by the control unit.

[0042] Its physical basis stems from the fundamental laws of food electromagnetism: the dielectric constant of water-containing foods is strongly positively correlated with their moisture content. Water molecules are strongly polar molecules, easily undergoing orientational polarization under the influence of an external electromagnetic field; the more moisture, the stronger the overall dielectric response. Therefore, the dielectric constant can serve as a reliable proxy for the moisture state of food, offering advantages such as non-contact operation, low cost, and resistance to contamination. Meanwhile, the internal air temperature is the only directly controllable variable in the heating system, but it differs significantly from the surface temperature of the food—the magnitude of this difference is determined by the evaporative cooling intensity of the food. Temperature feedback alone cannot determine whether the food is "dry enough" or "moist enough," therefore, introducing dielectric sensing is necessary to achieve a closed-loop state.

[0043] The control unit synchronously executes two data acquisition tasks at a fixed interval of 1 second: on the one hand, it reads the dielectric properties output by the dielectric sensing module; on the other hand, it reads the analog voltage of the NTC sensor and obtains the temperature value by looking up a table using a pre-stored RT curve. Both data streams are cached in a circular buffer in RAM.

[0044] When the fries added by the user partially thawed during transportation, their surface moisture content was higher than that of the standard sample. At this point, the dielectric constant output by the dielectric sensing module increased from the standard value of 48 to 52, indicating increased moisture content. Simultaneously, the NTC sensor showed an internal air temperature of 182°C, but the actual surface temperature of the food was likely only around 160°C—the difference being due to a stronger evaporative cooling effect. These two signals together reveal the fact that "the current food is 'wetter' than the standard, has a stronger heat absorption capacity, and requires a higher heating intensity to compensate for its additional heat loss."

[0045] S4: Set the temperature according to the current dielectric constant correction standard to obtain the target temperature of the air inside the cavity;

[0046] "Target temperature of air inside the cavity" refers to the air temperature command that is dynamically generated based on the real-time state of the food and serves as the actual control target. It is a variable that evolves over time. Its essence is the air temperature compensation value that needs to be increased to offset the current evaporative cooling effect of the food. The purpose is to make the surface temperature of the food reach the threshold (usually >140℃) required to trigger key thermochemical reactions (such as Maillard browning) as soon as possible.

[0047] Because the glass cavity has a high specific heat capacity and low thermal conductivity, it heats up slowly and exhibits a significant lag. If heating is still performed at the standard set temperature, high-moisture foods will remain in a state of "heat absorption > heat supply" for an extended period, and their surface temperature will fail to reach the reaction threshold, resulting in undercooking. Conversely, low-moisture foods may burn due to excessively rapid heating. Therefore, the target temperature must be upgraded from a "fixed value" to a "state feedback function" to actively compensate for thermal response deviations caused by individual differences in the ingredients.

[0048] The control unit executes a general correction logic: first, it calculates the deviation between the current dielectric index and the dielectric reference value in this mode; then, based on a pre-stored correction strategy, it converts this deviation into a temperature correction value; finally, it adds the correction value to the standard set temperature to form the target temperature of the air inside the cavity. The parameters of this correction strategy were all calibrated offline during the development phase by conducting cooking experiments on multiple sets of food samples with different initial states, ensuring its physical rationality and engineering practicality.

[0049] For example, if the current dielectric constant is detected as 52, while the baseline value for the "Frozen Fries" mode is 48, the deviation is +4 units. Based on the calibrated linear ratio (approximately 1.2°C / unit), the temperature correction is approximately +5°C, and the dynamic target temperature is updated to 205°C. This adjustment results in a higher internal air temperature and an increased convective heat transfer coefficient, effectively offsetting the cooling effect of additional moisture. This ensures that the food surface temperature reaches the level required for browning in a timely manner, ultimately achieving a cooking effect consistent with the standard sample.

[0050] S5: Based on the target temperature of the air inside the cavity, control the operation of the heating element in the main heating circuit of the glass fryer so that the real-time temperature of the air inside the cavity approaches the target temperature of the air inside the cavity.

[0051] The "main heating circuit" consists of power switching devices and heating elements; "approaching" refers to using a closed-loop control strategy to ensure that the actual temperature stably tracks the dynamic target within the allowable error range (such as ±3℃).

[0052] The reason for adopting closed-loop control is that the glass cavity has significant thermal inertia. If open-loop control (such as fixed-time heating) is used, it cannot cope with disturbances such as ambient temperature, food load, and power grid voltage, which will inevitably cause the actual temperature to deviate from the target. Therefore, it is necessary to dynamically adjust the heating intensity based on real-time temperature feedback to form a "sensing-decision-execution" closed loop to ensure temperature control accuracy.

[0053] In practice, the control unit continuously compares the real-time temperature of the air inside the cavity with the target temperature of the air inside the cavity, and generates a drive signal according to the preset control logic to control the power switching device to turn on or off, thereby adjusting the average power output of the heating element. This control logic can adopt any closed-loop strategy well known to those skilled in the art, including but not limited to dual-threshold switching control, proportional control, or pulse width modulation. Its core objective is to make the actual temperature converge to the vicinity of the target value at a reasonable rate and maintain stability.

[0054] In a typical scenario, when the target temperature of the air inside the cavity is 205°C, the control system activates the heating element. When the NTC sensor detects that the real-time temperature of the air inside the cavity has reached 205°C, the system stops heating. Subsequently, due to heat loss, the temperature drops back to 202°C, and the system restarts heating. Through this cyclical adjustment, the actual temperature fluctuates slightly around the target value, achieving effective tracking. The entire process is completed automatically by the control unit without user intervention.

[0055] In one exemplary embodiment, a method is provided to obtain the current dielectric constant of the food in the pot in real time through a dielectric sensing module. Specifically, this method utilizes the transient switching signal naturally generated during pulse width modulation (PWM) control of the main heating circuit as the excitation source, eliminating the need for additional dedicated radio frequency transmission or sensing hardware. Figure 3 As shown, the specific steps include:

[0056] S21: At the instant the drive switch of the heating element is turned off, the transient ringing signal of the main heating circuit is collected;

[0057] "Transient ringing signal" refers to a high-frequency, damped oscillation waveform generated on the DC bus when the falling edge of the PWM signal output by the control unit triggers the power switch to turn off, causing resonance between the parasitic inductance and distributed capacitance in the main heating circuit. This signal originates from the inherent electromagnetic characteristics of the power electronic system and is not an artificially injected test signal. Optionally, the driving switch can be a MOSFET.

[0058] The reasons for using signal acquisition at the moment of turn-off are as follows: First, the current change rate is extremely high during the MOSFET turn-off process, and the energy of the excited ringing signal spectrum is mainly concentrated in the 1 to 10 MHz frequency band. This frequency band coincides with the dielectric relaxation response frequency band of water molecules, which has the physical conditions to excite the dielectric loss of food. Second, the heating circuit current is zero during the turn-off period, and the acquisition process is not affected by large current electromagnetic interference, resulting in a high signal-to-noise ratio. Furthermore, this acquisition action is embedded in the conventional PWM control cycle and can be executed tens of thousands of times per second, without having a substantial impact on the overall heating power output.

[0059] In practice, the main control unit is configured to use its advanced timer to generate a PWM signal with a frequency of 20 kHz to drive the MOSFET to control the PTC heating element. At the same time, the analog-to-digital converter is set to event-triggered mode, and high-speed sampling is initiated after a 500 nanosecond delay after each falling edge of the PWM signal, lasting for 1 microsecond, to capture the complete ringing waveform segment.

[0060] S22: Extract the current attenuation feature from the transient ringing signal;

[0061] The "current attenuation characteristic" is a quantitative indicator that characterizes the attenuation rate of the ringing signal envelope. It is extracted by performing digital envelope detection on the captured waveform, identifying the first two local maxima, and calculating the ratio of their amplitude difference to the corresponding time interval. The physical meaning of this characteristic is that it reflects the degree of loss of high-frequency electromagnetic energy during the penetration of food.

[0062] According to Debye's dielectric relaxation theory, water-containing substances exhibit significant dielectric loss peaks in the 1 to 10 MHz frequency band. When a ringing signal passes through the food in the frying basket, its high-frequency components are absorbed by water molecules and converted into heat energy, causing the signal amplitude to decay rapidly. Therefore, the attenuation characteristic is positively correlated with the moisture content of the food and can serve as an effective proxy for the dielectric constant.

[0063] When the control unit processes the sampled data, it first suppresses high-frequency noise through a third-order Butterworth low-pass filter, then extracts the envelope using a peak detection algorithm, and finally calculates the attenuation characteristic.

[0064] S23: Based on the pre-stored attenuation characteristic-dielectric constant mapping table, retrieve the current dielectric constant of the food ingredient.

[0065] The "Attenuation Characteristic-Dielectric Constant Mapping Table" is a non-volatile data table established through calibration experiments before the product leaves the factory. The calibration process includes: placing various standard food samples with known moisture content in the frying basket; synchronously recording the historical attenuation characteristic values ​​generated by the main heating circuit under constant temperature conditions; measuring the real part of the complex dielectric constant of the corresponding food samples using a commercial dielectric spectrometer; and establishing the mapping relationship between the two.

[0066] During the user's cooking process, the control unit calculates the current attenuation characteristic in real time and uses it as an index to look up the mapping table. If there is no exact match in the table, the corresponding dielectric constant is estimated using linear interpolation.

[0067] The advantages of this implementation are: it fully reuses the existing main heating drive circuit without adding any additional hardware; it uses the system's inherent EMI as the sensing excitation, thus circumventing radio frequency regulations; and it time-division multiplexes sensing and heating in the time domain, ensuring that they do not interfere with each other and maintaining the consistency between temperature control reliability and sensing accuracy.

[0068] In one exemplary embodiment, a method is provided for a dielectric sensing module to obtain the current dielectric constant of the food in the pot in real time through an embedded LC resonant circuit disposed within the frying basket. Specifically, a miniature passive resonant sensor is integrated into the glass frying basket structure, and the dielectric constant is inferred by measuring its resonant frequency shift, thereby providing high-precision, interference-resistant food status sensing capabilities. Figure 4 As shown, the specific steps include:

[0069] S31: Inject an excitation pulse into the LC resonant circuit and measure the resonant frequency of the LC resonant circuit based on the excitation pulse;

[0070] An "LC resonant circuit" refers to a passive resonant circuit consisting of a parallel-plate capacitor embedded in the bottom of a glass blasting basket and an external high-Q inductor. The capacitor is formed by injection molding a pair of circular copper foil plates within the blasting basket body. This circuit is silent when there is no external excitation and only oscillates freely when triggered.

[0071] The reason for using the LC resonance method is that its resonant frequency is extremely sensitive to changes in the dielectric constant of the surrounding medium, and it provides a pure signal with strong immunity to power supply noise, making it suitable for high-end products with high sensing accuracy requirements. This method also offers a clearer physical model, with measurement results directly related to the dielectric constant, resulting in higher system robustness.

[0072] In practice, one general-purpose input / output pin of the control unit is configured in push-pull output mode, injecting a short pulse with a width of 100 nanoseconds into the LC circuit through a 1 kΩ current-limiting resistor. This pulse excites the LC circuit to generate free-falling oscillations, the frequency of which is determined by the circuit's own inductance and capacitance parameters. The other general-purpose input / output pin of the control unit is configured as a high-impedance input and connected to the capture channel of an internal timer to accurately record the zero-crossing time of the oscillation signal, thereby calculating the complete resonant frequency.

[0073] In a typical configuration, the resonant frequency of the LC circuit is 1.20 MHz when the frying basket is empty. When food is added, it acts as a high-dielectric-constant medium, filling the space between the plates of the parallel-plate capacitor. This increases the effective capacitance of the capacitor, thus lowering the resonant frequency. For example, adding high-moisture vegetables reduces the resonant frequency to 1.10 MHz. This frequency shift can be captured by the control unit with microsecond-level precision, providing raw data for subsequent dielectric constant calculations.

[0074] S32: Calculate the current dielectric constant of the food in the pot based on the resonant frequency and the circuit parameters of the LC resonant circuit;

[0075] The "circuit parameters" include the resonant frequency of the LC resonant circuit under no-load conditions and a proportionality constant. The proportionality constant is the system gain factor obtained through standard liquid calibration during the product's factory calibration phase. The physical mechanism is as follows: when a parallel-plate capacitor is filled with a dielectric material with a higher dielectric constant, its charge storage capacity increases, and the equivalent capacitance increases accordingly. Since the resonant frequency is inversely proportional to the square root of the capacitance, the higher the dielectric constant, the lower the measured resonant frequency.

[0076] This relationship is monotonic, meaning that a decrease in resonant frequency uniquely corresponds to an increase in dielectric constant. Therefore, the dielectric constant can be accurately deduced by measuring the frequency. Compared to indirect sensing methods that rely on signal attenuation characteristics, this scheme has a direct physical causal chain, higher accuracy, and is unaffected by signal amplitude fluctuations or environmental noise.

[0077] The control unit calculates the current dielectric constant by performing one division and one multiplication operation based on the measured resonant frequency, combined with the pre-stored no-load resonant frequency and proportional constant. The calibration process for the proportional constant is as follows: the resonant frequency is measured under no-load conditions; then, a standard liquid with a known dielectric constant (such as deionized water) is placed in the flask, and the resonant frequency is measured again; based on the two measurement results and the known dielectric constant value of the standard liquid, the proportional constant is calculated.

[0078] Optionally, the calculated dielectric constant is used to perform the dynamic target temperature correction steps in S1 to S5.

[0079] In one exemplary embodiment, a method (defined as Method 1) is provided to obtain the target temperature of the air inside the cavity by setting a temperature according to a current dielectric constant correction standard. Method 1 uses a flexible functional form to adapt to the nonlinear thermal response characteristics of different food categories, such as... Figure 5 As shown, the specific steps include:

[0080] S41: Based on the cooking mode, load the dielectric reference value of the ingredients associated with that cooking mode;

[0081] "Ingredient dielectric reference value" refers to the average dielectric constant measured from standard ingredient samples corresponding to this cooking mode under standard testing conditions. This value is determined through numerous repeated experiments during the product development phase and is stored in the non-volatile memory of the control unit, serving as a reference anchor point for determining whether the current ingredient deviates from the standard state.

[0082] The necessity of introducing a dielectric reference value lies in the fact that the absolute values ​​of the dielectric constants of different foods vary greatly (e.g., potatoes are about 48, while chicken wings are about 58). If the current dielectric constant is used directly for correction, it will lead to cross-mode parameter confusion. Therefore, it is necessary to use the standard state of similar foods as a reference and calculate the relative deviation in order to achieve a mode-independent universal correction logic.

[0083] In practice, the control unit extracts the "dielectric_reference" field while loading the cooking mode parameter package. This field is stored as an integer, for example, 48 for the "frozen fries" mode and 58 for the "chicken wings" mode. This value does not change with user operations, ensuring baseline consistency.

[0084] In a typical scenario, when a user selects the "Chicken Wings" mode, the dielectric reference value loaded by the system is 58. This value is derived from the average of multiple measurements taken by the dielectric sensing module at room temperature using standard boneless chicken wings (initial moisture content 68%±2%) in the factory, representing the dielectric level of the "ideal initial state" in this mode.

[0085] S42: Calculate the difference between the current dielectric constant and the reference dielectric value of the food ingredient;

[0086] This difference reflects the degree of deviation in the moisture content of the current food relative to the standard sample. A positive difference indicates that the moisture content of the current food is higher than the standard (possibly due to incomplete thawing or a humid environment), while a negative difference indicates that the moisture content is lower than the standard (e.g., due to excessive drying or partial dehydration). This difference is the sole input variable for subsequent correction calculations, and its physical meaning is clear and its dimensions are consistent.

[0087] The reason for calculating this difference is that the response of food to heating depends primarily on its deviation from its typical state, rather than its absolute dielectric value. For example, whether it's chicken wings or French fries, as long as their moisture content is 5% higher than the standard, the required temperature compensation should be comparable. Therefore, using the difference as a basis for correction can improve the algorithm's generalization ability and robustness.

[0088] The control unit performs an integer subtraction operation: subtracting the dielectric reference value from the current dielectric constant to obtain the signed deviation.

[0089] For example, if a user adds chicken wings that are not fully thawed from refrigeration, and the measured dielectric constant is 61, while the baseline value for the "chicken wings" mode is 58, the difference is +3. This result indicates that the food has a high moisture content, and the target temperature needs to be increased to compensate for its stronger evaporative cooling effect.

[0090] S43: Call the preset correction function associated with the cooking mode;

[0091] The "preset correction function" refers to a mapping relationship generated offline after cooking experiments on food samples with various initial states during the product development phase, recording the optimal temperature correction required to achieve the preset ideal cooking effect. This function can take any form, such as a linear function, a piecewise linear function, or a lookup table, depending on the complexity of the food's thermal response characteristics, and is stored in conjunction with a cooking mode ID.

[0092] The reason for employing multiple function forms is that the nonlinearity of the thermal response varies significantly among different ingredients. For example, the effect of moisture changes in frozen French fries on the required correction is approximately linear; however, chicken legs with skin exhibit significant nonlinearity, with high heat absorption in the high-moisture zone and easy burning in the low-moisture zone. Using a uniform linear function would introduce substantial errors in the nonlinear region; using a uniform lookup table method would increase storage overhead. Therefore, this solution configures function types as needed, achieving an optimal balance between accuracy and resources.

[0093] Specifically, the construction process of the preset correction function is as follows: First, select a standard ingredient sample corresponding to the cooking mode (e.g., boneless chicken wings with an initial moisture content of 68%±2% for the "chicken wings" mode); second, conduct a benchmark experiment in a standard environment (room temperature 25℃, no residual heat) to determine the standard set temperature and corresponding dielectric reference value when the preset ideal cooking effect is achieved (e.g., golden brown surface, internal center temperature 74℃); then, prepare multiple sets of variable samples with different initial states (e.g., refrigerated chicken wings, thawed chicken wings at room temperature, and semi-thawed chicken wings), and perform the following operations on each set of samples: cook at a fixed target temperature, have a professional taster evaluate the effect, and if the full score is not achieved, adjust the target temperature until the ideal effect is obtained, and record the optimal target temperature at this time; finally, calculate the dielectric change and the required temperature correction for each set of samples to form a set of calibration data points.

[0094] Based on this dataset, appropriate function forms are selected and constructed according to the degree of nonlinearity of the thermal response characteristics of the ingredients: for ingredients with approximately linear thermal responses (such as most frozen French fries), linear regression is used to fit the optimal slope to form a linear function; for ingredients with significant differences in response between high-moisture and low-moisture zones (such as chicken legs with skin), the data is divided into multiple intervals, and the slope is fitted for each segment to form a piecewise linear function; for special ingredients with highly nonlinear thermal responses or sparse data (such as mixed vegetables), the calibrated data points are directly quantized and stored as a lookup table.

[0095] S44: Take the difference as input and calculate the target temperature correction amount through a preset correction function.

[0096] The target temperature correction is the final compensation value used to adjust the target temperature of the air inside the cavity. Its sign and magnitude directly determine the increase or decrease in heating intensity. The calculation of this correction depends entirely on a preset correction function to ensure its physical rationality and engineering practicality.

[0097] In the case of a linear function, the control unit reads the pre-stored slope parameter and performs a single multiplication operation to obtain the correction amount. For example, for the chicken wing mode, the slope is -1.6 degrees Celsius per unit difference. When the difference is +3, the correction amount is -4.8℃, which is then quantized to -5℃.

[0098] In the case of piecewise linear functions, the control unit first determines the interval to which the difference belongs, and then uses the slope of the corresponding interval for calculation. For example, the chicken leg mode uses a slope of -1.6 when the difference is greater than 0 and -1.2 when it is less than or equal to 0, in order to more accurately match its nonlinear thermal response.

[0099] In the lookup table scenario, the control unit rounds the difference to the nearest integer index and directly looks up the correction value in the table. For higher precision, linear interpolation can be performed on adjacent points. For example, if the constructed table shows that a difference of +3 corresponds to a correction value of +4.5℃, this value can be used directly.

[0100] Finally, the target temperature correction is added to the standard set temperature to obtain the target temperature of the air inside the cavity, which is used to drive subsequent heating control. Through this mechanism, the system can accurately adapt to the complex thermal response characteristics of different ingredients, ensuring that all kinds of ingredients achieve consistent cooking results under different initial conditions.

[0101] In one exemplary embodiment, a method (defined as Method 2) is provided to obtain the target temperature of the air inside the cavity by setting a temperature according to the current dielectric constant correction standard. Method 2 dynamically adjusts the air temperature to make the actual heat dose approach the preset target value, thereby achieving truly "consistent effect" cooking. Figure 6As shown, the specific steps include:

[0102] S51: Based on the cooking mode, load the target heat dose associated with that cooking mode;

[0103] "Target heat dose" refers to the total dose of thermochemical reactions accumulated when cooking a standard ingredient sample corresponding to the cooking mode under standard test conditions and achieving the preset ideal cooking effect (such as moderate browning or full cooking). This dose is not a unit of energy, but a quantitative characterization of key cooking chemical reaction processes such as Maillard reaction and protein denaturation. Its value is calibrated offline through controlled experiments during the product development stage and stored in the memory of the control unit.

[0104] The necessity of introducing a target heat dose lies in the fact that traditional temperature control only focuses on "how many degrees to heat," ignoring the different thermal reaction rates caused by variations in the composition of different foods (such as protein and sugar content). For example, high-protein chicken breast is more prone to browning than high-starch potatoes; if the same temperature curve is used, the former will easily burn while the latter will not even brown. Therefore, the control target must be elevated from "temperature" to "reaction process" to achieve consistent results across different foods.

[0105] In practice, the control unit loads the "chicken wing" mode parameter package and extracts the "target_thermal_dose" field from it. This value is stored as an integer and represents the complete thermal history integral value required to achieve moderate browning on a standard chicken wing sample. This value cannot be changed once calibrated to ensure a consistent benchmark.

[0106] S52: Estimate the current thermal activation energy of the food in the pot based on the current dielectric constant;

[0107] "Activation energy of thermal reaction" refers to the minimum energy threshold required for food to undergo key culinary chemical reactions (such as Maillard browning). The lower the value, the "easier" the food is to burn. This study found that the imaginary part of the complex dielectric constant of food not only reflects its moisture content but also indirectly reflects the density of its polar molecular groups (such as amino and carbonyl groups), which are the participants in the Maillard reaction. Therefore, there is an intrinsic correlation between dielectric constant and activation energy.

[0108] The scientific basis of this estimation mechanism lies in the fact that the more polar groups there are, the stronger the intermolecular interactions, the easier it is to initiate a chemical reaction, and the lower the activation energy. At the same time, polar groups also enhance the response of food to an applied electromagnetic field, leading to an increase in the dielectric constant. Therefore, the activation energy level can be inferred from the dielectric constant.

[0109] During the factory calibration phase, engineers calibrated various representative ingredients (such as chicken breast, salmon, and potato chunks): using a differential scanning calorimeter to measure the activation energy of their main cooking reactions, and simultaneously measuring their room temperature dielectric constant, establishing a "dielectric constant-activation energy" mapping table. This table is stored in the non-volatile memory of the control unit.

[0110] During the user's cooking process, the system obtains the current dielectric constant in real time and uses it as an index to look up the mapping table to obtain the estimated equivalent activation energy of the current food. For example, when the measured dielectric constant is high, the system determines that the food is rich in polar groups and has a low activation energy, belonging to the "prone to browning" type.

[0111] S53: Calculate the temperature correction amount based on the current thermal reaction activation energy and the target heat dose;

[0112] The "temperature correction" is a compensation value used to adjust the standard set temperature. Its sign and magnitude are determined by the current activation energy of the thermal reaction and the target heat dose. Specifically, the system first determines the direction of the current activation energy's deviation relative to the standard sample: if the activation energy is low (prone to browning), a negative correction is generated to reduce the heating intensity; if the activation energy is high (difficult to brown), a positive correction is generated to enhance heating. Simultaneously, the system continuously tracks the cumulative progress of the actual heat dose. If the progress lags behind the target, the positive correction is increased; if the progress is ahead, the negative correction is increased.

[0113] The value of this correction was determined through offline calibration experiments. For example, for the "chicken wing" mode, a decrease of 1 kJ / mol in activation energy corresponds to a correction of -1.2℃; a deviation of 5% from the target heat dose corresponds to an adjustment of ±0.8℃. All rules are stored in the form of lookup tables or piecewise functions.

[0114] S54: Add the standard set temperature to the temperature correction amount to obtain the target temperature of the air inside the cavity.

[0115] The final target temperature of the cavity air is obtained by algebraically adding the standard set temperature and the temperature correction. For example, if the standard set temperature for the "chicken wing" mode is 190°C, and the system estimates that the current activation energy is low and the heat dose is ahead of schedule, the calculated temperature correction is -10°C, then the target temperature of the cavity air is determined to be 180°C. This target temperature is sent to the lower-level heating control module to drive the main heating circuit.

[0116] Through this mechanism, the system ensures that the actual heat charge accumulated on the surface of the food inside the pot approaches the target heat charge at a reasonable rate, ultimately achieving a professional-grade cooking effect with uniform color and crispy exterior and tender interior, regardless of the initial conditions. The entire process requires no user intervention and is completely automated by the main control microcontroller unit.

[0117] Among them, the target temperature of the air inside the cavity makes the actual heat dose accumulated on the surface of the food inside the pot approach the target heat dose.

[0118] The accumulation of "actual heat dose" depends on the continuous integration of the reaction rate. To reduce computational complexity, this scheme uses a physically homologous proxy variable to replace the true reaction rate: that is, it uses the high-frequency decay characteristic extracted by the dielectric sensing module in each control cycle as a proxy index of the reaction rate. The physical basis for this is that whether it is the energy absorption of the food by the electromagnetic pulse or the internal thermal activation of the chemical reaction, the microscopic driving force originates from the relaxation behavior of polar molecules, and the intensity of the two has an inherent monotonic correlation.

[0119] During product development, engineers created a lookup table for "attenuation characteristic quantity - normalized reaction rate" for each ingredient. When the user cooks, the system executes the following every second: obtain the current attenuation characteristic quantity → look up the reaction rate proxy value in the table → accumulate it to the heat dose counter. The control system continuously compares the actual heat dose with the target heat dose; if it is lower, it slightly increases the target temperature for the next cycle; if it is higher, it slightly decreases it, forming a closed-loop regulation.

[0120] Through this mechanism, the goal of temperature control has been upgraded from "a uniform temperature curve" to applying temperature according to the ingredients, solving the problem of consistent cooking results across ingredients and states.

[0121] Specifically, the actual heat dose accumulated on the surface of the food inside the pot is obtained by the following method: using the current decay characteristic as a proxy index of the thermochemical reaction rate; and accumulating the current decay characteristic to obtain the actual heat dose accumulated on the surface of the food inside the pot.

[0122] The reason for using this attenuation characteristic as a proxy is that the energy absorption process of food by high-frequency electromagnetic pulses and internal thermally activated chemical reactions (such as Maillard browning) share a common microscopic physical basis—the relaxation behavior of polar molecules under the influence of an external field. Whether it is water molecules absorbing electromagnetic energy and converting it into heat energy, or amino and carbonyl groups undergoing a condensation reaction, the driving force originates from the orientation polarization and energy exchange of polar groups. Therefore, the intensity of these two processes exhibits a monotonically positive correlation on a macroscopic scale, making the attenuation characteristic an effective proxy for the reaction rate.

[0123] The current attenuation characteristic reflects the absorption loss of high-frequency electromagnetic energy by the food in the pot. The physical essence of this absorption loss is dielectric loss, mainly caused by the frictional heat generated by water molecules and ions in the food under the action of an alternating electric field. The loss intensity is proportional to the imaginary part of the complex permittivity of the food, which is closely related to the moisture content, ion concentration, and polar group density. Therefore, the attenuation characteristic not only reflects the amount of moisture but also indirectly characterizes the abundance of active ingredients participating in thermochemical reactions.

[0124] For example, high-protein chicken breast, rich in amino groups (-NH2), has a higher density of polar groups than high-starch potatoes. Under the same moisture conditions, it exhibits stronger electromagnetic energy absorption capacity, greater attenuation characteristic, and a faster Maillard reaction rate. This inherent consistency ensures the scientific validity of the proxy indicator.

[0125] "Actual heat dose" is defined here as the cumulative amount of the thermochemical reaction process, and its ideal mathematical form is the integral of the reaction rate over time. This scheme uses discretization to treat the decay characteristic measured in each control cycle (e.g., 1 second) as the average reaction rate proxy value within that period, and adds it to the heat dose counter.

[0126] In practice, the control unit maintains a 32-bit integer thermal dose accumulator. At the end of each control cycle, the system executes: Thermal dose accumulator = Thermal dose accumulator + Current attenuation characteristic × Cycle duration (in seconds). Since the cycle duration is fixed at 1 second, this operation is simplified to a single integer addition, resulting in extremely high computational efficiency.

[0127] During operation, the difference between the actual heat dose and the target heat dose is continuously compared. If the actual value is lower, it indicates a lag in the reaction process, and the target air temperature inside the cavity is slightly increased in the next cycle; if the actual value is higher, the target temperature is slightly decreased. This adjustment range is determined through calibration experiments to ensure convergence stability.

[0128] In an exemplary embodiment, after generating the target temperature of the air inside the cavity, it is further constrained to a preset low-entropy reference heating curve. By smoothing and filtering the target temperature, it is ensured that the overall heating process is close to a thermodynamically reversible path, thereby achieving uniform, efficient, and high-quality cooking results under the high thermal inertia conditions of the glass cavity. Specifically, the process includes the following steps:

[0129] Based on the cooking mode, retrieve the pre-stored reference heating temperature-time curve; perform smoothing filtering on the target temperature of the air inside the cavity, so that the heating temperature-time curve formed by the smoothed target temperature of the air inside the cavity conforms to the trend constraint of the reference heating temperature-time curve.

[0130] The "reference heating temperature-time curve" refers to the ideal heating path calibrated during the product development phase through numerous controlled cooking experiments for specific food categories (such as meat, root vegetables, and frozen foods) with the optimization objective of minimizing system entropy production. This curve is stored in the non-volatile memory of the control unit as a set of temperature-time inflection points, representing the recommended temperature evolution trend throughout the entire process from cold start to the end of cooking.

[0131] The necessity of introducing this curve lies in the fact that traditional temperature control technology treats the slow heating characteristic of glass fryers as a "defect" that must be overcome, often employing aggressive strategies (such as large overshoot) to forcibly accelerate the response. However, according to non-equilibrium thermodynamics, excessively rapid temperature changes can lead to huge temperature gradients and stresses within the system, causing irreversible damage such as localized overheating, carbonization, or uneven texture—a manifestation of high entropy production. The minimum entropy production rate path, on the other hand, pursues a "smooth and efficient" process, making heat transfer closer to a reversible process and minimizing energy dissipation and quality loss.

[0132] In practice, when a user selects the "chicken wings" mode, the control unit not only loads the standard set temperature and dielectric reference value, but also simultaneously retrieves the reference heating curve associated with this mode. For example, this curve might specify: a heating rate of 30°C per minute for the first 3 minutes, maintaining 200±5°C for the 4th to 12th minutes, and a slow cooling process for the last 3 minutes. This process has been verified through simulation and actual testing in the factory, effectively suppressing the temperature difference between the inside and outside of the food and preventing it from becoming "burnt on the outside and raw on the inside."

[0133] "Smoothing filtering" refers to applying a first-order inertial filter or slope limiting algorithm to the target temperature sequence of the cavity air dynamically generated by dielectric sensing, ensuring that its rate of change does not exceed the maximum heating or cooling slope allowed by the reference curve. Its purpose is to prevent drastic jumps in the target temperature command caused by sudden changes in the food's state (such as the sudden detection of extremely low moisture), which would disrupt the smoothness of the overall heating path.

[0134] The engineering significance of this filtering mechanism lies in proactively designing a heating path that matches the thermophysical properties of glass, rather than counteracting them. Glass's high specific heat capacity naturally suppresses temperature fluctuations, and its low thermal conductivity naturally limits the rate at which heat is transferred into the food, perfectly aligning with the "slow and steady" rhythm required by the low-entropy production path. Therefore, the system does not require additional complex algorithms to "compensate" for the glass's lag; instead, it works in harmony with its inherent properties, allowing the glass's physical properties to contribute to high-quality cooking.

[0135] The control unit performs the following operations in each control cycle: First, it calculates the unfiltered dynamic target temperature; then it determines whether the difference between the unfiltered target temperature and the filtered temperature of the previous cycle exceeds the maximum allowable rate of change of the reference curve (e.g., 1°C per second); if it does, it clamps the current target temperature to the allowable range; otherwise, it passes directly.

[0136] Accordingly, controlling the operation of the heating element based on the target temperature of the air inside the cavity specifically includes: controlling the operation of the heating element based on the target temperature of the air inside the cavity after smoothing and filtering.

[0137] For example, even if the dynamic correction suggestion instantly raises the target temperature from 190°C to 210°C, the filtered result may only allow it to rise to 195°C, thereby generating a gentle heating command to avoid local overheating caused by a rapid rise.

[0138] Under this collaborative mechanism, the physical properties of the glass cavity and the control strategy work together: by introducing the path optimization idea of ​​minimizing entropy production rate, the high heat capacity of the glass absorbs the small fluctuations in the command, making the actual temperature curve smoother than the air temperature command; the low thermal conductivity of the glass limits the speed of heat transfer to the interior of the food, effectively preventing the situation where the inside is not cooked while the outside is burnt.

[0139] In an exemplary embodiment, a specific implementation process for controlling the operation of the heating element based on the target temperature of the air inside the cavity is provided. This process involves a multi-stage strategy, including a pre-stored compensation table, historical state correction, compensation value attenuation, and mode switching, to effectively overcome the characteristics of high thermal inertia and slow heating of the glass cavity. This achieves a balance between rapid heating and high-precision steady-state control without relying on complex PID algorithms. Figure 7 As shown, the specific steps include:

[0140] S61: Query the pre-stored standard compensation value table to obtain the standard compensation value corresponding to the target temperature of the air inside the cavity;

[0141] The "Standard Compensation Value Table" is a lookup table obtained during the product development phase through numerous repeated experiments calibrating standard food samples under cold-start conditions (ambient temperature 25°C, no residual heat). The table records the overshoot temperature amplitude corresponding to different target air temperatures within the cavity (e.g., 180°C to 220°C), which represents the additional heating intensity required initially to bring the system to a stable state at the target temperature. For example, the standard compensation value is 16°C when the target temperature is 200°C; and 16.4°C (obtained through linear interpolation) when the target temperature is 205°C.

[0142] The reason for introducing a standard compensation value is that the glass cavity has a high specific heat capacity and low thermal conductivity. If conventional dual-threshold control is used, it may take more than 20 minutes to heat from room temperature to 200°C, and there is a significant ramp-up process. By applying a moderate overshoot at the beginning (such as heating to 216°C), the heat storage characteristics of the glass can be utilized to "boost" the temperature and then allow it to fall back naturally, which can significantly shorten the heating time and avoid the "cooking" effect caused by continuous low temperature.

[0143] S62: Based on the real-time temperature of the air inside the cavity and the historical heating records of the glass fryer, the standard compensation value is corrected to obtain the initial actual compensation value;

[0144] The "historical heating record" includes the number of heating cycles, cumulative heating time, and residual heat status of the cavity at the end of the previous cycle. The system uses this information to determine whether the current start is a cold start, a warm start, or a hot start, and adjusts the standard compensation value accordingly. For example, if the real-time air temperature inside the cavity is detected to be 180℃ (above room temperature), and the historical record shows this is the first heating cycle, then there is a preheating offset of approximately 2℃. This offset needs to be subtracted from the standard compensation value to obtain the initial actual compensation value.

[0145] This correction mechanism ensures that the compensation amount matches the current operating conditions, avoiding excessive or insufficient overshoot due to unconsidered residual heat. For example, if the standard compensation value is 16.4℃, but the system has absorbed the equivalent of 2℃ of heat, the initial actual compensation value will be adjusted to 14.4℃, making the temporary shutdown temperature closer to the actual requirement.

[0146] S63: The sum of the target temperature of the air inside the cavity and the initial actual compensation value is used as the temporary shutdown temperature;

[0147] The temporary shutdown temperature is the heating stop threshold during the compensation phase. During this phase, the system ignores the usual upper and lower limit deviations and continues to drive the heating element at full power until the real-time temperature of the air inside the cavity reaches this temporary shutdown temperature. For example, when the target temperature of the air inside the cavity is 192℃ and the initial actual compensation value is 14.4℃, the temporary shutdown temperature is set to 206.4℃, which is quantized and then taken as 206℃.

[0148] The core of this strategy lies in sacrificing a brief period of temperature overshoot in the early stages of heating in exchange for a significant reduction in the overall heating time. Due to the slow thermal response of the glass cavity, even when heated to 206°C, the surface temperature of the food remains far below this value, preventing scorching. Instead, the enhanced convection heat transfer accelerates the cooking process.

[0149] S64: Controls the heating element to operate continuously at full power until the real-time temperature of the air inside the cavity reaches the temporary shutdown temperature;

[0150] The main control microcontroller outputs a high-level signal to drive the relay to close, enabling the 1500-watt PTC ceramic heating element to operate continuously at 100% duty cycle. The system sets a maximum time limit for a single heating cycle (e.g., 3 minutes) as a safety boundary. If the real-time air temperature inside the cavity has not reached the temporary shutdown temperature by the end of this cycle, the current compensation is deemed insufficient. The initial actual compensation value needs to be multiplied by an attenuation factor (e.g., 0.95) to obtain an updated initial actual compensation value, which is then used to calculate the temporary shutdown temperature for the next heating cycle.

[0151] The mechanism ensures that the system will not heat at full power indefinitely under extreme conditions (such as when a large amount of frozen food is placed in the system or when the ambient temperature is extremely low). Instead, it gradually reduces the compensation amplitude to explore the feasible overshoot under the current load and eventually smoothly transitions to the steady-state control stage.

[0152] S65: When the absolute value of the updated initial actual compensation value is less than or equal to the compensation end threshold, and the difference between the maximum and minimum values ​​of the real-time air temperature in the cavity within N consecutive sampling periods is less than or equal to the steady-state fluctuation threshold, the action of controlling the heating element to work continuously at full power is stopped, and cyclic control is executed.

[0153] Among them, loop control includes:

[0154] The "compensation end threshold" is typically set to 0.5℃, the "steady-state fluctuation threshold" is set to 6℃ (i.e., ±3℃), and "N" is set to 5 (corresponding to 5 seconds). When both conditions are met simultaneously, the system determines that it has entered the steady-state region and immediately exits the compensation phase.

[0155] The system then switches to conventional dual-threshold cyclic control: the on-temperature is set to the target temperature of the air inside the cavity minus the lower limit deviation (e.g., 3°C), and the off-temperature is set to the target temperature of the air inside the cavity plus the upper limit deviation (e.g., 3°C). For example, if the target temperature is 192°C, the on-temperature is 189°C and the off-temperature is 195°C. Heating is switched on and off within this small range to maintain a stable temperature until the cooking timer ends.

[0156] Through the above multi-stage control strategy, the system can quickly and smoothly reach and maintain the new target point regardless of how the target temperature changes dynamically, thus solving the temperature control problem of glass fryers.

[0157] In one exemplary embodiment, an adaptive temperature control system for a glass fryer is provided. This system, serving as the core control hub of the glass fryer, is characterized by integrating a dedicated control unit to fully implement the aforementioned dynamic target temperature correction and rapid, stable heating control strategy based on dielectric sensing. This solves the problem of unstable cooking results caused by the large thermal inertia of the glass cavity without significantly increasing hardware costs.

[0158] The adaptive temperature control system of the glass fryer includes: a control unit, a main heating circuit, a dielectric sensing module, a temperature sensing module, and a human-machine interface. The control unit is the core of the system, containing all the logic for the aforementioned adaptive temperature control method. The main heating circuit includes a PTC ceramic heating element and a power switch, controlled by the control unit. The dielectric sensing module outputs electrical signals reflecting the state of the food. The temperature sensing module collects real-time air temperature data within the fryer cavity. The human-machine interface receives cooking mode commands input by the user.

[0159] The control unit is specifically configured to perform the following operations:

[0160] First, the cooking mode selected by the user is obtained through the human-computer interaction interface, and the standard set temperature associated with that mode is loaded from the internal memory;

[0161] Secondly, the dielectric sensing module continuously acquires the current dielectric constant of the food in the pot during the cooking process, and at the same time, the temperature sensing module acquires the real-time temperature of the air inside the cavity.

[0162] Subsequently, the standard set temperature is dynamically corrected based on the current dielectric constant to generate the target temperature of the air inside the cavity;

[0163] Finally, the heating element in the main heating circuit is controlled to operate according to the target temperature, so that the real-time temperature of the air inside the cavity approaches the target temperature.

[0164] In one exemplary embodiment, a glass fryer is provided. This glass fryer, as a smart cooking device for end users, is characterized by integrating the aforementioned glass fryer adaptive temperature control system and main heating circuit. Through deep collaboration between hardware and software, and under the physical constraints of a high-transmittance glass cavity, it achieves stable, consistent, and high-quality cooking results.

[0165] The glass fryer includes: an outer shell assembly, a cooking cavity made of borosilicate glass, a main heating circuit, a fan assembly, a temperature sensing module, a dielectric sensing module, and an embedded control unit. The cooking cavity is fixed inside the outer shell and features high light transmittance and high-temperature resistance. The main heating circuit is located on the top or side wall of the cavity and includes a PTC ceramic heating element and a power switch. The fan assembly is located below the heating element and drives hot air to circulate at high speed within the cavity. The temperature sensing module is installed on the inner wall of the cavity for real-time monitoring of air temperature. The dielectric sensing module is integrated into the main heating circuit or the frying basket structure. The control unit, serving as the central control unit, is built into the electronics compartment at the bottom of the outer shell and is electrically connected to each of the aforementioned modules.

[0166] During cooking, the user selects a cooking mode via the control panel. The control unit then loads the corresponding standard set temperature and activates the dielectric sensing module to obtain the current dielectric constant of the food. Based on this dielectric constant, the control unit dynamically adjusts the target temperature and generates control commands, which are sent to the main heating circuit. The main heating circuit adjusts the power output of the PTC heating element according to the commands, while the fan assembly maintains a constant airflow to ensure even distribution of hot air. The temperature sensing module continuously provides feedback on the real-time temperature of the air inside the cavity, which is then used by the control unit for closed-loop adjustment. The entire process requires no user intervention; the system automatically completes the entire control chain from sensing and decision-making to execution.

[0167] The control unit is the core of the adaptive temperature control system in the glass fryer. It contains a complete adaptive temperature control algorithm, and the main heating circuit acts as the actuator, directly responding to the commands of the control unit to achieve precise regulation of the internal thermal environment. Together, they form a closed-loop intelligent temperature control system, enabling the glass fryer to "adjust the temperature according to the material".

[0168] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0169] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for adaptive temperature control in a glass fryer, characterized in that, The method is applied to a control unit, which controls the heating element in the main heating circuit of the glass fryer; the control unit includes: Get the cooking mode selected by the user; According to the cooking mode, a standard set temperature associated with the cooking mode is loaded; wherein, the standard set temperature is the standard temperature of the air inside the cavity when the food sample is cooked under standard test conditions and a preset ideal cooking effect is achieved. During the cooking process, the current dielectric constant of the food in the pot is obtained in real time through the dielectric sensing module, and the real-time temperature of the air inside the pot cavity is obtained through the temperature sensor. The target temperature of the air inside the cavity is obtained by correcting the standard set temperature based on the current dielectric constant. The heating element is controlled to operate according to the target temperature of the air inside the cavity, so that the real-time temperature of the air inside the cavity approaches the target temperature of the air inside the cavity.

2. The method according to claim 1, characterized in that, The dielectric sensing module obtains the current dielectric constant of the food inside the fryer in real time by reusing the main heating circuit of the glass fryer, specifically including: At the instant the drive switch for the heating element is turned off, the transient ringing signal of the main heating circuit is acquired; Extract the current attenuation feature from the transient ringing signal; According to the pre-stored attenuation feature-dielectric constant mapping table, the dielectric constant corresponding to the current attenuation feature is queried and used as the current dielectric constant of the food in the pot. The attenuation characteristic-dielectric constant mapping table is generated before the glass fryer leaves the factory by placing various food samples with known moisture content in the frying basket and simultaneously measuring the historical attenuation characteristics generated by the main heating circuit during the cooking process and the historical dielectric constant of the food samples.

3. The method according to claim 1, characterized in that, The method of obtaining the current dielectric constant of the food in the pot in real time through the dielectric sensing module via an embedded LC resonant circuit set in the frying basket specifically includes: An excitation pulse is injected into the LC resonant circuit, and the resonant frequency of the LC resonant circuit in response to the excitation pulse is measured. Calculate the current dielectric constant of the food in the pot based on the resonant frequency and the circuit parameters of the LC resonant circuit; The circuit parameters include the resonant frequency and proportionality constant of the LC resonant circuit under no-load conditions; the proportionality constant is calibrated by measuring the resonant frequency under no-load conditions and under standard liquid conditions with known dielectric constants.

4. The method according to claim 1, characterized in that, The step of correcting the standard set temperature based on the current dielectric constant to obtain the target temperature of the air inside the cavity specifically includes: According to the cooking mode, load the dielectric reference value of the food associated with the cooking mode; wherein, the dielectric reference value of the food is the dielectric constant measured using the food sample under standard test conditions; Calculate the difference between the current dielectric constant and the dielectric reference value of the food ingredient; Invoke the preset correction function associated with the cooking mode; The difference is used as input, and the target temperature correction amount is calculated through the preset correction function. The target temperature correction is added to the standard set temperature to obtain the target temperature of the air inside the cavity; The preset correction function is any one of a linear function, a piecewise linear function, or a lookup table function; The parameters or data of the preset correction function were obtained offline during the development phase of the glass fryer by conducting cooking experiments on food samples with various initial states and recording the optimal temperature correction amount required to achieve the preset ideal cooking effect.

5. The method according to claim 2, characterized in that, The step of correcting the standard set temperature based on the current dielectric constant to obtain the target temperature of the air inside the cavity specifically includes: According to the cooking mode, a target heat dose associated with the cooking mode is loaded; wherein, the target heat dose is the total dose of thermochemical reaction accumulated when the food sample is cooked under standard test conditions and the preset ideal cooking effect is achieved; Based on the current dielectric constant, estimate the current thermal activation energy of the food in the pot; Calculate the temperature correction amount based on the current thermal reaction activation energy and the target heat dose; The standard set temperature is added to the temperature correction amount to obtain the target temperature of the air inside the cavity; wherein, the target temperature of the air inside the cavity makes the actual heat dose accumulated on the surface of the food in the pot approach the target heat dose.

6. The method according to claim 5, characterized in that, Obtaining the actual amount of heat accumulated on the surface of the food inside the pot specifically includes: The current decay characteristic is used as a proxy indicator of the thermochemical reaction rate; wherein the current decay characteristic reflects the absorption and loss of high-frequency electromagnetic energy by the food in the pot. The current attenuation characteristic is accumulated to obtain the actual heat dose accumulated on the surface of the food in the pot.

7. The method according to claim 1, characterized in that, After correcting the standard set temperature according to the current dielectric constant to obtain the target temperature of the cavity air, the method further includes: According to the cooking mode, a pre-stored reference heating temperature-time curve is retrieved; wherein, the reference heating temperature-time curve was obtained during the development stage of the glass fryer by conducting cooking experiments on the food samples and optimizing with minimizing the system entropy production rate; The target temperature of the air inside the cavity is smoothed and filtered so that the heating temperature-time curve formed by the smoothed and filtered target temperature of the air inside the cavity conforms to the trend constraint of the reference heating temperature-time curve. Specifically, controlling the operation of the heating element based on the target temperature of the air inside the cavity includes controlling the operation of the heating element based on the smoothed and filtered target temperature of the air inside the cavity.

8. The method according to claim 1, characterized in that, The step of controlling the heating element to operate based on the target temperature of the air inside the cavity, so that the real-time temperature of the air inside the cavity approaches the target temperature, specifically includes: Query the pre-stored standard compensation value table to obtain the standard compensation value corresponding to the target temperature of the air inside the cavity; wherein, the standard compensation value is the overshoot temperature amplitude required to make the real-time temperature of the air inside the cavity eventually stabilize at the target temperature of the air inside the cavity under standard cold start conditions; Based on the real-time temperature of the air inside the cavity and the historical heating records of the glass fryer, the standard compensation value is corrected to obtain the initial actual compensation value; The sum of the target temperature of the air inside the cavity and the initial actual compensation value is used as the temporary shutdown temperature; The heating element is controlled to operate continuously at full power until the real-time temperature of the air inside the cavity reaches the temporary shutdown temperature. If the real-time temperature of the air inside the cavity does not reach the temporary shutdown temperature during the current heating cycle, the initial actual compensation value is attenuated to obtain an updated initial actual compensation value. When the absolute value of the updated initial actual compensation value is less than or equal to the compensation end threshold, and the difference between the maximum and minimum values ​​of the real-time air temperature inside the cavity over N consecutive sampling periods is less than or equal to the steady-state fluctuation threshold, the action of controlling the heating element to operate continuously at full power is stopped, and the following cyclic control is executed: When the real-time temperature of the air inside the cavity drops below the target temperature of the air inside the cavity minus the lower limit deviation, the heating element is activated. When the real-time temperature of the air inside the cavity rises to a level higher than the target temperature of the air inside the cavity plus the upper limit deviation, the heating element is turned off.

9. A glass fryer adaptive temperature control system, characterized in that, The glass fryer adaptive temperature control system includes: A control unit is used to control the heating element in the main heating circuit of the glass fryer and execute the glass fryer adaptive temperature control method according to any one of claims 1-8.

10. A glass fryer, characterized in that, The glass fryer includes an adaptive temperature control system and a main heating circuit as described in claim 9.

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