Temperature and humidity decoupling control system and method for microwave oven

Abstract

The invention provides a temperature and humidity decoupling control system and method for a microwave oven. The system comprises a decoupling controller, a sensor, a heating device and a humidity adjusting device, the sensor, the heating device and the humidity adjusting device are all in one-way communication connection with the decoupling controller, the sensor is arranged in an oven cavity of the microwave oven, and the decoupling controller, the heating device and the humidity adjusting device are all arranged in the microwave oven body. The method comprises the following steps: step 1, system modeling; 2, acquiring an actual system transfer function matrix; 3, obtaining a nominal model transfer function matrix; 4, obtaining a transfer function matrix Q (s) of the decoupling controller; step 5, integrating to realize precise decoupling control of temperature and humidity; according to the temperature and humidity decoupling control system and method for the microwave oven, the model accuracy can be improved, the working condition stability can be enhanced, the temperature and humidity in the microwave oven in the heating process can be accurately regulated and controlled, and the food cooking quality and effect are comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave ovens, and more particularly, to a temperature and humidity decoupling control system and method for a microwave oven. Background Art

[0002] In the food heating scenario of traditional microwave ovens, the coupling problem of temperature and humidity control has always been a key factor restricting the heating effect. When the temperature is adjusted, the humidity often changes unpredictably, and vice versa. This coupling phenomenon makes it difficult to accurately create a suitable temperature and humidity combination when heating various foods.

[0003] For example, when baking cookies, increasing the temperature to achieve the ideal crispness often leads to a sharp drop in humidity, premature dehydration of the cookies, and a hard and easily broken texture; when heating steamed buns, increasing the humidity to maintain the moist texture of the buns easily causes temperature fluctuations, resulting in undercooked buns. This mutual interference in temperature and humidity control seriously affects the quality and taste of food and cannot meet the needs of consumers for heating diverse and high-quality foods. Therefore, it is of great significance to study how to break through the limitations of traditional microwave oven temperature and humidity control, thereby achieving precise control of temperature and humidity during the heating process and comprehensively improving the quality and effect of food cooking.

[0004] In patent CN109283958A, an enthalpy difference temperature and humidity decoupling control method based on adaptive fuzzy PID decoupling control is disclosed. This method includes collecting data to model G11, G12, and G22; and obtaining a transfer function matrix through the modeled model. After using the least squares method to identify the models of G11, G12, and G22, an enthalpy difference laboratory temperature and humidity decoupling and adaptive fuzzy PID controller are designed in sequence, and then the preparation of the enthalpy difference laboratory temperature and humidity decoupling controller is obtained. It can achieve the decoupling of laboratory temperature and humidity through a feedforward compensation algorithm. However, on the one hand, due to the different requirements for temperature and humidity in the laboratory and in the microwave oven, and considering the requirements for food cooking in the microwave oven, the accuracy requirements for temperature and humidity control are higher. Therefore, this control method is not applicable to the temperature and humidity control in the microwave oven; on the other hand, because this decoupling method uses the fuzzy PID method, it is prone to problems such as low model accuracy and poor operating condition stability. Summary of the Invention

[0005] In view of this, the present invention aims to propose a temperature and humidity decoupling control system and method for a microwave oven, so as to solve the limitations of traditional microwave oven temperature and humidity control in the prior art, which cannot accurately control the temperature and humidity during the heating process, and the existing temperature and humidity decoupling methods have relatively low model accuracy and poor working condition stability; thereby optimizing the control system structure, improving the accuracy of the control system, through the setting of the method, effectively improving the accuracy of the model, enhancing the stability of the working condition, and in cooperation with the control system, being able to accurately control the temperature and humidity inside the microwave oven during the heating process, and comprehensively improving the quality and effect of food cooking.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A temperature and humidity decoupling control system and method for a microwave oven according to the present invention, the temperature and humidity decoupling control system for a microwave oven includes a decoupling controller, a sensor, a heating device, and a humidity adjustment device; the sensor, the heating device, and the humidity adjustment device are all unidirectionally communicatively connected to the decoupling controller, the sensor is arranged inside the furnace cavity of the microwave oven, and the decoupling controller, the heating device, and the humidity adjustment device are all arranged inside the main body of the microwave oven.

[0008] Further, the sensor is used to collect relevant information inside the furnace cavity in real time and transmit the collected relevant information to the decoupling controller; the relevant information includes any one or more of temperature, humidity, and air pressure.

[0009] Further, the sensor includes a temperature sensor, a humidity sensor, and an air pressure sensor; the temperature sensor, the humidity sensor, and the air pressure sensor are all arranged inside the furnace cavity, and the temperature sensor, the humidity sensor, and the air pressure sensor are all unidirectionally communicatively connected to the decoupling controller.

[0010] Further, at least one temperature sensor, humidity sensor, and air pressure sensor are provided.

[0011] Further, the heating device includes a microwave heating component and an infrared heating component; the microwave heating component and the infrared heating component are both arranged inside the microwave oven.

[0012] Further, the microwave heating component includes an inverter and a magnetron; the decoupling controller is connected to the magnetron through the inverter.

[0013] Further, the infrared heating component includes a thyristor and an optical wave tube; the decoupling controller is connected to the optical wave tube through the thyristor.

[0014] Further, the humidity adjustment device includes a water vapor generating device and a water vapor extraction device; the water vapor generating device and the water vapor extraction device are both arranged inside the microwave oven.

[0015] Further, the water vapor generating device includes an atomizer and a control device; the decoupling controller is connected to the atomizer through the control device; both the atomizer and the control device are arranged in the microwave oven.

[0016] A temperature and humidity decoupling control method for a microwave oven, which is applied to the temperature and humidity decoupling control system of the microwave oven, and the method includes the following steps:

[0017] Step 1, Multivariable system modeling: Use the state space model to accurately describe the temperature and humidity decoupling control system;

[0018] Step 2, Obtaining the transfer function matrix of the actual system: Obtain the transfer function matrix G(s) of the actual system by Laplace transform of the state space model;

[0019] Step 3, Obtaining the transfer function matrix of the nominal model: Divide the system model into the transfer function matrix Gn(s) of the nominal model and the transfer function matrix △G(s) of the model error; After scientifically and reasonably simplifying and approximating the actual system, obtain the transfer function matrix Gn(s) of the nominal model; and according to the first formula, obtain △G(s); where the first formula is: G(s)=Gn(s)+△G(s);

[0020] Step 4, Obtaining the transfer function matrix Q(s) of the decoupling controller: According to the required target, obtain the transfer function matrix Q(s) of the decoupling controller through the transfer function matrix Gn(s) of the nominal model;

[0021] Step 5, Integration: Organically combine the transfer function matrix Q(s) of the decoupling controller with the single-variable controllers of temperature and humidity; and make targeted adjustments and optimizations to the input signal, so as to achieve precise decoupling control of the temperature and humidity in the microwave oven.

[0022] Compared with the prior art, the temperature and humidity decoupling control system and method for a microwave oven of the present invention have the following beneficial effects:

[0023] Through the setting of the system, the structure of the control system can be optimized, and the accuracy of the control system can be improved. Through the setting of the method, the accuracy of the model can be improved, the stability of the working condition can be enhanced, and in cooperation with the control system, precise control of the temperature and humidity inside the microwave oven during the heating process can be achieved, comprehensively improving the quality and effect of food cooking. Description of the Drawings

[0024] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0025] Figure 1It is a schematic diagram of the overall structure of the decoupling control system;

[0026] Figure 2 It is a schematic diagram of the control method flow chart.

[0027] Explanation of reference numerals: 1. Decoupling controller; 2. Sensor; 21. Temperature sensor; 22. Humidity sensor; 23. Air pressure sensor; 3. Heating device; 31. Microwave heating component; 32. Infrared heating component; 4. Humidity adjustment device; 41. Water vapor generating device; 42. Water vapor extraction device. Detailed implementation manners

[0028] In the following, the inventive concepts of the present disclosure will be described using the terms that are typically used by those skilled in the art to convey the substance of their work to other skilled persons in the art. However, these inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0029] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0030] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0031] This embodiment is directed to a microwave oven. The same as a conventional microwave oven, the overall structure is composed of a magnetron, a fuse, and a door switch assembly.

[0032] In the prior art, in the food heating scenario of a traditional microwave oven, the coupling problem of temperature and humidity control has always been a key factor restricting the heating effect. When the temperature is adjusted, the humidity often changes unpredictably, and vice versa. This coupling phenomenon makes it difficult to accurately create a suitable temperature and humidity combination when heating various foods.

[0033] To address the limitations of traditional microwave oven temperature and humidity control in the existing technology, which cannot accurately regulate temperature and humidity during the heating process, and the problems of low model accuracy and poor operating condition stability in the existing temperature and humidity decoupling methods; this embodiment proposes a temperature and humidity decoupling control system and method for a microwave oven, which focuses on developing an innovative method for achieving efficient temperature and humidity decoupling control during the food heating process in a microwave oven. The temperature and humidity decoupling control system for a microwave oven includes a decoupling controller 1, a sensor 2, a heating device 3, and a humidity adjustment device 4. The sensor 2, the heating device 3, and the humidity adjustment device 4 are all unidirectionally communicatively connected to the decoupling controller 1. The sensor 2 is arranged inside the oven cavity of the microwave oven, and the decoupling controller 1, the heating device 3, and the humidity adjustment device 4 are all arranged inside the main body of the microwave oven. The sensor 2 is used to collect relevant information inside the oven cavity in real time and transmit the collected relevant information to the decoupling controller 1. Among them, the relevant information includes any one or more of temperature, humidity, and air pressure information. The decoupling controller 1 is used to control the heating device 3 and / or the humidity adjustment device 4 to perform corresponding operations after analyzing and processing the collected information.

[0034] Through the setting of the system, the structure of the control system can be optimized, and the accuracy of the control system can be improved.

[0035] The sensor 2 includes a temperature sensor 21, a humidity sensor 22, and an air pressure sensor 23. The temperature sensor 21, the humidity sensor 22, and the air pressure sensor 23 are all arranged inside the oven cavity, and the temperature sensor 21, the humidity sensor 22, and the air pressure sensor 23 are all unidirectionally communicatively connected to the decoupling controller 1. The temperature sensor 21 is used to collect temperature information inside the oven cavity in real time; the humidity sensor 22 is used to collect humidity information inside the oven cavity in real time; the air pressure sensor 23 is used to collect the air pressure change situation inside the oven cavity in real time.

[0036] Through the precise layout of multiple types of sensors 2 inside the oven cavity of the microwave oven, comprehensive and accurate monitoring of the temperature, humidity, and related parameters inside the oven cavity can be achieved.

[0037] Among them, at least one temperature sensor 21, humidity sensor 22, and air pressure sensor 23 are provided.

[0038] Specifically, the temperature sensor 21 adopts a high-precision thermocouple sensor. Due to its unique material properties, the accuracy of the high-precision thermocouple sensor can reach ±0.5°C. The installation positions of the temperature sensor 21 include any one or more of the areas near the heat source inside the oven cavity, the food placement area inside the oven cavity, the corners of the oven cavity, and the central position of the oven cavity.

[0039] By arranging the temperature sensor 21 at the key positions of the oven cavity, it can ensure that the distribution and changes of the temperature field inside the oven cavity are comprehensively captured.

[0040] The humidity sensor 22 uses a capacitive humidity sensor. The accuracy of the capacitive humidity sensor reaches ±2%RH. This sensor can quickly respond to small changes in humidity and accurately measure the humidity inside the furnace. The humidity sensor 22 is arranged on the top, bottom and side surfaces inside the furnace cavity. When the humidity sensor 22 is arranged on the side surface inside the furnace cavity, according to actual needs, the humidity sensor 22 is respectively arranged at different height positions on the side surface inside the furnace cavity.

[0041] Through the distribution setting of the humidity sensor 22 inside the furnace cavity, in terms of layout, considering the movement law and distribution characteristics of water vapor inside the furnace cavity, the humidity sensor 22 is arranged at various positions inside the furnace cavity, which is beneficial to comprehensively monitoring the dynamic changes of the humidity inside the furnace.

[0042] The air pressure sensor 23 uses a high-precision air pressure sensor, and the accuracy of the air pressure sensor 23 is ±0.1kPa. The air pressure sensor 23 is arranged inside the furnace cavity to monitor the change of the air pressure inside the furnace in real time.

[0043] Since air pressure changes will have an unignorable impact on temperature and humidity, through the real-time monitoring of air pressure, more comprehensive and accurate environmental parameter information can be provided for the decoupling control of temperature and humidity.

[0044] The heating device 3 includes an integrated microwave heating component 31 and an infrared heating component 32. Both the integrated microwave heating component 31 and the infrared heating component 32 are arranged inside the microwave oven.

[0045] Through the setting of the combined heating component of the two, it is beneficial to realize the flexibility and accuracy of the decoupling controller 1 for temperature control.

[0046] Specifically, the microwave heating component 31 includes an inverter and a magnetron. The decoupling controller 1 is connected to the magnetron through the inverter. The decoupling controller 1 can control the magnetron to perform corresponding actions through the inverter. The microwave heating component 31 has the function of multi-stage fine power adjustment. The power range of the microwave heating component 31 is set to 300W - 1200W.

[0047] Through the setting of the microwave heating component 31, at the initial stage of microwave oven heating, the power can be quickly increased to a relatively high level to rapidly increase the overall temperature inside the furnace; when the temperature is close to the target value, the power can be precisely fine-tuned to achieve precise control of the temperature.

[0048] The infrared heating component 32 includes thyristors and light wave tubes. The decoupling controller 1 is connected to the light wave tubes through the thyristors. The decoupling controller 1 can control the light wave tubes through the thyristors to perform corresponding actions. Among them, the decoupling controller 1 can adjust the trigger phase of the thyristors by controlling the on / off of the thyristors, thereby regulating the heating power of the light wave tubes. So that the infrared heating component 32 can accurately control the heating power within the power range of 50W - 500W; achieve more efficient and uniform infrared radiation heating.

[0049] The humidity adjustment device 4 includes a water vapor generating device 41 and a water vapor extraction device 42. Both the water vapor generating device 41 and the water vapor extraction device 42 are arranged inside the microwave oven.

[0050] Through the settings of the water vapor generating device 41 and the water vapor extraction device 42, under the action of the decoupling controller 1, accurate control of the humidity inside the microwave oven can be achieved.

[0051] Specifically, the water vapor generating device 41 includes an atomizer and a regulating device. The decoupling controller 1 is connected to the atomizer through the regulating device; both the atomizer and the regulating device are arranged inside the microwave oven. Under the action of the regulating device, the water spraying flow rate of the atomizer ranges from 0 ml / min to 10 ml / min. Among them, the atomizer is a mesh atomizer. The regulating device includes a regulating valve or a power controller.

[0052] Through the setting of the atomizer, fine ultrasonic vibrations and the structure of the mesh spray head can be used to produce a spray, so as to efficiently atomize water into tiny particles. And through the coordinated setting of the regulating device, accurate adjustment of the water spraying amount can be achieved within the water spraying amount range of 0 ml / min - 10 ml / min by adjusting the flow rate with the regulating valve or controlling the power with the power controller. Improve the rapidity, reliability, flexibility and accuracy of the system for humidity adjustment inside the microwave oven.

[0053] The water vapor extraction device 42 includes a vacuum pump. The vacuum pump is connected to the decoupling controller 1; the vacuum pump is arranged inside the microwave oven. The air extraction rate of the vacuum pump ranges from 0 L / min to 15 L / min.

[0054] Through the setting of the vacuum pump, it is possible to effectively extract the water vapor inside the furnace within the required air extraction rate range and condense the water vapor into liquid water for discharge.

[0055] A method for decoupled temperature and humidity control of a microwave oven, the method is applied to the temperature and humidity decoupled control system of the microwave oven, and the method includes the following steps:

[0056] Step 1. Multivariable system modeling: Regarding the temperature and humidity decoupled control system inside the microwave oven as a complex multi-input multi-output system, using the state space model to accurately describe the temperature and humidity decoupled control system.

[0057] Step 2. Obtaining the actual system transfer function matrix: The state - space model is Laplace - transformed to obtain the actual system transfer function matrix \(G(s)\).

[0058] Step 3. Obtaining the nominal model transfer function matrix: Based on the control concept of internal - model control theory, the system model is deeply analyzed and decomposed. The system model is carefully divided into the nominal model transfer function matrix \(G_n(s)\) and the model error transfer function matrix \(\Delta G(s)\); after scientifically and reasonably simplifying and approximating the actual system, the nominal model transfer function matrix \(G_n(s)\) is obtained; and according to the first formula, \(\Delta G(s)\) is obtained. The first formula is: \(G(s)=G_n(s)+\Delta G(s)\). Among them, in the simplification process, the main characteristics and key influencing factors of the system are considered, and some secondary factors with little impact on the overall control effect are ignored to facilitate the subsequent setting and implementation of the decoupling controller 1.

[0059] Step 4. Obtaining the transfer function matrix \(Q(s)\) of the decoupling controller 1: According to the required target, the transfer function matrix \(Q(s)\) of the decoupling controller 1 is obtained through the nominal model transfer function matrix \(G_n(s)\).

[0060] Step 5. Integration: The transfer function matrix \(Q(s)\) of the decoupling controller 1 is organically combined with the single - variable controllers for temperature and humidity; and the input signal is adjusted and optimized specifically, thereby realizing the precise decoupling control of the temperature and humidity in the microwave oven.

[0061] Through the setting of the above - mentioned method, the accuracy of the model can be improved, the stability of the working condition can be enhanced, and in cooperation with the control system, the precise regulation of the temperature and humidity inside the microwave oven during the heating process can be realized, comprehensively improving the quality and effect of food cooking.

[0062] Step 1 includes:

[0063] Step S11: The system is regarded as a multi - input and multi - output system, where the input parameters are set as the heating power \(u\) T and the humidity adjustment \(u\) H . The output parameters are clearly expressed as the temperature \(T\) and the humidity \(H\).

[0064] Step S12: Constructing the state - space model:

[0065] ;

[0066] where \(X\) is the system state vector, \(x\) is the state of the state vector at a specific moment, which is a point in the state space. \(u\) is the input vector, and \(u = [u\) T , \(u\) H T ​, Y is the output vector, Y = [T, H] T , A, B, C, and D are system matrices corresponding to different positions in the state space. In this embodiment, u T is used to precisely regulate the heating power.

[0067] Through the setting of this system architecture, various factors closely related to temperature and humidity control during the microwave heating process and their interactions can be comprehensively covered.

[0068] Specifically, as the system state vector, X selects different state variables closely related to the dynamic changes of temperature and humidity. The different state variables include any one or more of the temperature change rate, humidity change rate, influence factors of heating time accumulation on temperature and humidity, and the change rate of food moisture evaporation rate. These variables comprehensively reflect the real-time state of the system during the heating process from different dimensions, providing a rich and accurate information basis for subsequent precise control.

[0069] In addition, in actual operation, the input vector u is associated with the coordinated operation of the microwave heating component 31 and the infrared heating component 32. For example, the microwave heating component 31 can be flexibly adjusted within the power range of 300 - 1200W according to the instruction of u T to quickly increase or decrease the overall temperature in the furnace; the infrared heating component 32 can accurately control the heating degree of the food surface by adjusting the current within the power range of 50 - 500W according to more refined temperature requirements. u H As the control quantity of the humidity adjustment device 4, it directly determines the water spraying amount of the humidification device or the air extraction rate of the water vapor extraction device 42. Taking the humidification device as an example, based on advanced ultrasonic atomization technology, with the help of a high-precision water level sensor and a flow regulating valve, according to the signal of u H it accurately adjusts within the water spraying amount range of 0 - 80 mL / min to supplement an appropriate amount of water vapor into the furnace; the water vapor extraction device 42 works within the air extraction rate range of 0 - 15 L / min according to the instruction of u H to effectively reduce the humidity in the furnace.

[0070] The output vector Y directly corresponds to the actually measured temperature and humidity values. These measured data are collected in real time by the high-precision sensors 2 arranged in the furnace cavity, providing a direct basis for the feedback control of the system.

[0071] Regarding the system matrices A, B, C, and D, matrix A is determined according to the physical characteristics of the microwave oven and the dynamic evolution law during the temperature and humidity control process. Moreover, the factors reflected by matrix A include any one or more of the material characteristics of the microwave oven cavity, its shape and structure, the indirect effect of temperature change on humidity change, and the feedback effect of humidity change on temperature change. For example, factors such as the material characteristics and shape and structure of the microwave oven cavity affect the propagation and distribution of heat and water vapor in the oven, and these factors are reflected in matrix A, enabling the matrix elements to accurately describe the complex mutual influence relationships between system state variables. For instance, the indirect effect of temperature change on humidity change and the feedback effect of humidity change on temperature change are all reflected in the elements of matrix A.

[0072] Matrix B details the specific manner in which the input signal acts on the system state. It not only considers the direct effects of the heating power and humidity adjustment amount on temperature and humidity but also takes into account the differences in their effects at different time scales and spatial positions. For example, the influence speed and degree of the microwave heating component 31 and the infrared heating component 32 on the temperature in different regions of the oven at different powers, as well as the change patterns of the humidity in the oven by the humidification device, i.e., the water vapor generation device 41 and the water vapor extraction device 42, at different working intensities, are precisely quantified through the elements within matrix B.

[0073] Matrix C constructs an accurate mapping relationship between the system state and the output signal. It comprehensively considers the installation position of the sensor 2, the measurement accuracy, and the conversion relationship between the internal state of the system and the actual measured value. For example, since the distribution of temperature and humidity in the oven cavity is not uniform, the elements of matrix C can accurately convert the complex temperature and humidity states inside the system into the actually measured temperature and humidity values according to the specific position of the sensor 2, ensuring the accuracy and reliability of the output data.

[0074] The direct influence of matrix D on the input to output in the actual system is relatively small. Matrix D can capture some direct action relationships that are difficult to fully describe by other matrices. The direct action relationships that are difficult to fully describe by other matrices include any one or more of the short-term effects of the instantaneous change in heating power on the humidity measurement value, or the minor interference of the rapid startup of the humidity adjustment device 4 on the temperature measurement value. The setting of matrix D makes the entire model more complete and accurate.

[0075] In step two, the setting of the actual system transfer function matrix G(s) comprehensively and accurately reflects the dynamic relationship between the system input and output under various complex conditions. Specifically, G(s) comprehensively considers various physical processes inside the microwave oven and the mutual coupling effects between these processes. Various physical processes include any one or more of microwave heating, infrared radiation, water vapor diffusion, and phase change.

[0076] In Step 3, the model error transfer function matrix △G(s) is specifically used to describe the inevitable differences between the nominal model and the actual system. △G(s) captures those factors that are ignored during the simplification of the nominal model, as well as the deviations of the actual system from the nominal model due to various uncertainty factors during operation. The uncertainty factors include any one or more of environmental temperature changes and food property differences. By accurately characterizing △G(s), it provides a basis for compensating and correcting model errors in the subsequent design of the decoupling controller.

[0077] Step 4 includes:

[0078] Step S41: Preset , the transfer function matrix of the decoupling controller 1; and determine that the required core objective is to make ; where, G11(s) is the temperature transfer function model, G12(s) is the coupling channel transfer function model of humidity rise on temperature, G21(s) is the coupling channel transfer function model of temperature rise on humidity, G22(s) is the humidity transfer function model; Q11(s) is the temperature transfer function decoupling model, Q12(s) is the coupling channel transfer function decoupling model of humidity rise on temperature, Q21(s) is the coupling channel transfer function decoupling model of temperature rise on humidity, Q22(s) is the humidity transfer function decoupling model.

[0079] Step S42: Solve the elements in the transfer function matrix Q(s) of the decoupling controller 1.

[0080] Specifically, the solution process in Step S42 includes:

[0081] Step S421: Derivation of the equations: Expand and derive the equation in detail. After multiplying the matrices, the following equations are obtained:

[0082] .

[0083] Step S422: Element solution process:

[0084] Starting from the second equation , by transposing and transforming, we can get . Substitute this expression into the first equation , and perform a series of algebraic operations, including finding a common denominator, combining like terms, transposing, etc., to finally obtain the exact expression for Q 11 (s): .

[0085] Similarly, starting from the fourth equation , after transposing and transforming, we can get Substitute it into the third equation and through algebraic operations again, the expression of Q 21 (s) is obtained: .

[0086] Based on the obtained expressions of Q 11 (s) and Q 21 (s), the expressions of Q 12 (s) and Q 22 (s) can be completely obtained. The transfer function matrix Q(s) of the decoupling controller 1 composed of these expressions can perform precise decoupling processing on the input signals u T and u H .

[0087] Step five includes:

[0088] Step S51: Organically combine the transfer function matrix Q(s) of the decoupling controller 1 with the single-variable controllers of temperature and humidity;

[0089] Step S52: In the actual food heating control process, the transfer function matrix Q(s) of the decoupling controller 1 plays a key preprocessing role; the transfer function matrix Q(s) of the decoupling controller 1 adjusts and optimizes the input signals u T and u H targetedly according to the real-time operating state of the system and the pre-established accurate model information; and then realizes the precise decoupling control of the temperature and humidity in the microwave oven.

[0090] Through step five, by organically combining Q(s) with the single-variable controllers of temperature and humidity, the temperature and humidity can be precisely controlled separately, avoiding the food surface from being charred due to excessive temperature during the heating process, and at the same time maintaining an appropriate humidity to prevent excessive loss of food moisture, making the internal moisture distribution of the food more uniform and the taste better. For example, when baking a cake, the appropriate temperature and humidity can be precisely maintained, making the cake expand evenly and taste soft and moist. In addition, reasonable temperature and humidity control can reduce the loss and damage of food nutrients during the cooking process. Different foods can retain their vitamin, mineral and other nutrients to the greatest extent when cooked in a specific temperature and humidity environment, improving the nutritional value of the food.

[0091] Among them, step S52 includes:

[0092] Step S521: The decoupling controller 1 judges whether there is an action on the temperature deviation signal or the humidity deviation signal? If yes, execute step S522; if no, repeat step S521 to monitor the status of the temperature or humidity deviation signal in real time;

[0093] Step S522: Determine whether it is a temperature deviation signal that activates? If yes, execute Step S523; if no, execute Step S524;

[0094] Step S523: The temperature control loop attempts to adjust the heating power u according to the temperature deviation signal T When this happens, the transfer function matrix Q(s) of decoupling controller 1 will quickly analyze the current humidity state and the predicted humidity change trend of the model, and automatically make corresponding fine-tuning to the humidity adjustment amount u H ;

[0095] Step S523: The humidity control loop adjusts the humidity adjustment amount u according to the humidity deviation H When this happens, decoupling controller 1 will similarly make corresponding compensation adjustments to the heating power u T to ensure that the temperature is not affected by the humidity adjustment and always changes according to the preset temperature curve.

[0096] Through the fine-tuning of the heating power u by decoupling controller 1 T Based on the accurate calculation of the system's dynamic characteristics, it can compensate for the potential impact that temperature changes may have on humidity, ensuring that the humidity remains stable during the temperature adjustment process and is not disturbed by temperature changes. In addition, through the close cooperation of the transfer function matrix Q(s) of decoupling controller 1 with the temperature and humidity single-variable controllers, high-precision decoupling control of temperature and humidity is achieved, creating a stable and accurate temperature and humidity environment for food heating, thereby significantly improving the quality and effect of food heating.

[0097] Example 1:

[0098] Taking the baking of a 6-inch chiffon cake as an example, the chiffon cake is mainly made of 60g of low-gluten flour, 3 eggs, 40g of granulated sugar, 20g of corn oil, and 30g of milk. When baking in a traditional microwave oven, due to temperature and humidity coupling, problems such as the surface of the cake quickly forming a crust and burning, while the inside is not fully cooked, and excessive water evaporation resulting in a dry and hard texture often occur.

[0099] Multivariable system modeling: For the characteristics of the chiffon cake heating process, a multivariable system model is constructed. Define the system state vector , in addition to including the temperature change rate , the humidity change rate , it also incorporates the batter water evaporation rate and a variable that reflects the impact of the change in the internal structure of the cake on heat transfer (represented by the function α(T, t) and used to correct the heat transfer coefficient).

[0100] Based on the heat transfer principle, the temperature distribution function follows the heat transfer equation:

[0101] where ρ is the density of the cake material, Cp is the specific heat capacity, k is the thermal conductivity, and Q 微波 is the microwave heat source intensity, and Q 红外 is the infrared heat source intensity.

[0102] Through experimental measurement, the density of the cake material ρ = 0.8 g / cm 3 , the specific heat capacity Cp = 3.2 J / (g·K), and the thermal conductivity k = 0.2 W / (m·K).

[0103] For humidity changes, based on the principle of mass conservation, assuming the water vapor concentration in the furnace is C(x, y, z, t), the humidity change equation is:

[0104] where the water vapor diffusion coefficient D = 2.5×10 -5 m 2 / s, the water vapor generation source term S is related to the water evaporation rate of the cake and can be expressed as , where V is the volume of the furnace cavity, E is the water vapor extraction term, and M is the water exchange term with the cake.

[0105] Meanwhile, the pressure sensor, i.e., the barometric pressure sensor 23, monitors the barometric pressure P in the furnace in real time. The barometric pressure change will affect the boiling point of water vapor, the diffusion rate, and the heat transfer efficiency. Research shows that there is a relationship between the barometric pressure P and the water vapor diffusion coefficient D where D 0 is the standard atmospheric pressure, and P 0 is the water vapor diffusion coefficient under the standard atmospheric pressure. In this embodiment, it is assumed that the exponent β of the influence of pressure on the diffusion coefficient is 1.

[0106] Baking process control:

[0107] (1) Initial stage: At the beginning of baking, the decoupling controller calculates according to the model and sets the power P 微波 of the microwave generator to 800 W to quickly increase the overall temperature in the furnace. At this time, the humidity sensor 22 detects the initial humidity H 0 in the furnace = 30%RH. According to the ideal humidity model for cake baking, it is necessary to increase the humidity to prevent the surface from drying and crusting too quickly. Therefore, the decoupling controller 1 controls the water vapor generating device 41 to work with a water spraying rate of q = 1 ml / min. The influence of the increased water vapor on the humidity is estimated through the ideal gas state equation PV = nRT. Where P is the pressure, V is the volume, n is the amount of substance, R is the gas constant, and T is the temperature.

[0108] It is known that the volume of the furnace cavity V = 0.02 m 3 , the ambient temperature T = 300 K, the molar mass of water Mw = 18 g / mol, and the conversion of the water spraying rate q to the change rate of the amount of substance is ( (where ρ is the density of water), the calculation gives .

[0109] Calculate the change in water vapor pressure ΔP from the ideal gas state equation, , then

[0110]

[0111] Assume that at this temperature, the increase in humidity ΔH is estimated by the empirical formula ΔH = kΔP to be ΔH = 0.05%RH / Pa × 0.69 Pa / min ≈ 0.035%RH / min. Here, k = 0.05%RH / Pa, and k is a coefficient related to temperature.

[0112] (2) Middle stage of heating: As heating progresses, when the temperature approaches the temperature T1 = (60 - 70)°C at which the batter begins to solidify, the infrared heating component 32 is activated, and the power is set to P 红外 = 100 W to finely adjust the surface temperature of the cake and prevent the surface temperature from being too high. At this stage, the pressure sensor, i.e., the barometric pressure sensor 23, monitors the barometric pressure change in real time and feeds the data back to the decoupling controller. If the barometric pressure increases, according to , the water vapor diffusion coefficient D decreases, and the decoupling controller 1 adjusts the humidity regulation strategy accordingly. For example, appropriately increase the water spraying amount of the water vapor generating device 41 or adjust the air extraction rate of the water vapor extraction device 42 to maintain a stable humidity environment. At the same time, the decoupling controller 1 dynamically adjusts the water vapor extraction device 42 based on the real-time data of the humidity sensor 22 and the prediction of the internal moisture evaporation of the cake. When the humidity rises to H 1 = 70%RH, to prevent excessive internal moisture of the cake from affecting the taste, start the water vapor extraction device 42 to maintain an appropriate humidity at an air extraction rate of v = 2 L / min.

[0113] (3) Late stage of baking: When the cake is nearly fully cooked, the power of the microwave generator is reduced to P 微波 = 300 W, and the power of the infrared heating component 32 is adjusted to P 红外 = 50 W for heat preservation and fine adjustment to ensure that the inside of the cake is fully cooked and has a uniform texture. During the entire baking process, the decoupling controller 1 continuously coordinates the heating power and the humidity adjustment amount according to the temperature, humidity, and the barometric pressure change feedback by the pressure sensor, achieving precise decoupling control of temperature and humidity and improving the baking quality of the cake.

[0114] In the present invention, for any microwave oven, it may include the structure of the temperature and humidity decoupling control system of a microwave oven described in this embodiment, and on the basis of the relevant structures and assembly relationships of the barometric pressure sensor 23 and the humidity adjustment device 4 provided in this embodiment, the microwave oven further includes conventional components such as a magnetron, a fuse, and a door switch assembly; since they are all prior arts, no further description will be given here.

[0115] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A temperature and humidity decoupling control system for a microwave oven, characterized in that: The invention comprises a decoupling controller (1), a sensor (2), a heating device (3) and a humidity regulating device (4); the sensor (2), the heating device (3) and the humidity regulating device (4) are all connected to the decoupling controller (1) in a one-way communication manner; the sensor (2) is arranged inside the oven cavity of the microwave oven; and the decoupling controller (1), the heating device (3) and the humidity regulating device (4) are all arranged inside the main body of the microwave oven.

2. A temperature and humidity decoupling control system for a microwave oven according to claim 1, characterized in that: The sensor (2) is used to collect relevant information in the furnace cavity in real time, and transmit the collected relevant information to the decoupling controller (1); the relevant information includes any one or more of temperature, humidity and air pressure.

3. A temperature and humidity decoupling control system for a microwave oven according to claim 2, characterized in that: The sensor (2) comprises a temperature sensor (21), a humidity sensor (22) and an air pressure sensor (23); the temperature sensor (21), the humidity sensor (22) and the air pressure sensor (23) are all arranged in the furnace cavity, and the temperature sensor (21), the humidity sensor (22) and the air pressure sensor (23) are all connected to the decoupling controller (1) in a one-way communication manner.

4. A temperature and humidity decoupling control system for a microwave oven according to claim 3, characterized in that: At least one of the temperature sensor (21), humidity sensor (22) and air pressure sensor (23) is provided.

5. The temperature and humidity decoupling control system of a microwave oven according to claim 1, characterized in that: The heating device (3) comprises a microwave heating component (31) and an infrared heating component (32); the microwave heating component (31) and the infrared heating component (32) are both arranged in a microwave oven.

6. A temperature and humidity decoupling control system for a microwave oven according to claim 5, characterized in that: The microwave heating component (31) comprises a frequency converter and a magnetron; the decoupling controller (1) is connected to the magnetron via the frequency converter.

7. A temperature and humidity decoupling control system for a microwave oven according to claim 5, characterized in that: The infrared heating component (32) comprises a thyristor and a light wave tube; the decoupling controller (1) is connected to the light wave tube via the thyristor.

8. The temperature and humidity decoupling control system of a microwave oven according to claim 1, characterized in that: The humidity regulating device (4) comprises a water vapor generating device (41) and a water vapor extracting device (42); the water vapor generating device (41) and the water vapor extracting device (42) are both arranged inside the microwave oven.

9. A temperature and humidity decoupling control system for a microwave oven according to claim 8, characterized in that: The water vapor generating device (41) comprises an atomizer and a regulating device; the decoupling controller (1) is connected to the atomizer via the regulating device; and the atomizer and the regulating device are both arranged in a microwave oven.

10. A temperature and humidity decoupling control method for a microwave oven, characterized in that: The method is applied to a temperature and humidity decoupling control system of a microwave oven according to any one of claims 1 to 9, and the method comprises the following steps: Step 1: Multivariable system modeling: Use the state space model to accurately describe the temperature and humidity decoupling control system; Step 2: Obtaining the actual system transfer function matrix: Obtain the actual system transfer function matrix G(s) by Laplace transforming the state space model; Step 3: Obtaining the nominal model transfer function matrix: carefully divide the system model into the nominal model transfer function matrix Gn(s) and the model error transfer function matrix △G(s); obtain the nominal model transfer function matrix Gn(s) after scientifically and reasonably simplifying and approximating the actual system; and obtain △G(s) according to the first formula; wherein the first formula is: G(s)=Gn(s)+△G(s); Step 4: Obtaining the transfer function matrix Q(s) of the decoupling controller (1): According to the required target, the transfer function matrix Q(s) of the decoupling controller (1) is obtained through the nominal model transfer function matrix Gn(s); Step 5: Integration: Organically combine the transfer function matrix Q(s) of the decoupling controller (1) with the single variable controllers of temperature and humidity; and make targeted adjustments and optimizations to the input signals, thereby achieving precise decoupling control of the temperature and humidity in the microwave oven.

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