Patent Publication Number: US-2023164890-A1

Title: Thawing method for heating apparatus, and heating apparatus

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of food treatment, and in particular to a thawing method for a heating apparatus, and the heating apparatus. 
     BACKGROUND OF THE INVENTION 
     In the freezing process of food, the quality of the food is maintained, but the frozen food needs to be thawed before processing or eating. In order to facilitate food thawing, electromagnetic wave heating devices are usually used to thaw food. 
     Using the electromagnetic wave heating devices to thaw food is not only fast and efficient, but also realizes low loss of nutrients. However, in the prior art, the end of thawing is generally determined by the time or temperature set by a user, which puts forward too high requirements for the user, and easily causes the thawed food to be overcooled or overheated. Moreover, due to the different penetration and absorption of water and ice by microwave and the uneven distribution of substances in the food, the melted areas absorb more energy, which easily leads to the problems of uneven thawing and local overheating. 
     BRIEF DESCRIPTION OF THE INVENTION 
     An object of a first aspect of the present invention is to overcome at least one technical defect in the prior art, and to provide a thawing method for a heating apparatus. 
     A further object of the first aspect of the present invention is to obtain the weight of an object to be treated more precisely. 
     Another further object of the first aspect of the present invention is to improve the efficiency of acquiring a feature parameter. 
     An object of a second aspect of the present invention is to provide a heating apparatus. 
     According to the first aspect of the present invention, provided is a thawing method for a heating apparatus, the heating apparatus including a cavity capacitor for placement of an object to be treated, and an electromagnetic wave generation module that generates an electromagnetic wave signal for heating the object to be treated. The thawing method includes: 
     receiving a thawing instruction input by a user; 
     acquiring a feature parameter that reflects the weight of the object to be treated, a power value of the electromagnetic wave signal, and a rate of change in a dielectric coefficient of the object to be treated; and 
     determining the thawing progress of the object to be treated according to the feature parameter, the power value and the rate of change. 
     Optionally, the step of determining the thawing progress of the object to be treated according to the feature parameter, the power value and the rate of change includes: 
     determining a threshold value of change in the dielectric coefficient of the object to be treated according to the feature parameter and the power value; and 
     when the rate of change is less than the threshold value of change, controlling the electromagnetic wave generation module to stop working. 
     Optionally, the step of determining a threshold value of change in the dielectric coefficient of the object to be treated according to the feature parameter and the power value includes: 
     according to the feature parameter and the power value, matching a corresponding threshold value of change based on a preset comparison relationship, where 
     in the case of the same power value, the threshold value of change is inversely proportional to the weight reflected by the feature parameter; and/or 
     in the case of the same weight reflected by the feature parameter, the threshold value of change is proportional to the power value. 
     Optionally, the step of acquiring a feature parameter that reflects the weight of the object to be treated includes: 
     acquiring a capacitance value of the cavity capacitor, the feature parameter being the capacitance value. 
     Optionally, the heating apparatus further includes a matching module that adjusts a load impedance of the electromagnetic wave generation module by adjusting its own impedance, where the step of acquiring a feature parameter that reflects the weight of the object to be treated includes: 
     controlling the electromagnetic wave generation module to generate an electromagnetic wave signal with a preset initial power; and 
     adjusting the impedance of the matching module, and determining an impedance value of the matching module that realizes an optimal load matching of the electromagnetic wave generation module. 
     Optionally, the matching module includes a plurality of matching branches that can be switched on and off independently, where the step of adjusting the impedance of the matching module, and determining an impedance value of the matching module that realizes the optimal load matching of the electromagnetic wave generation module includes: 
     traversing on-off combinations of the plurality of matching branches, and obtaining a matching degree parameter that corresponds to each on-off combination and reflects a load matching degree of the electromagnetic wave generation module; 
     comparing the matching degree parameters of the on-off combinations of the plurality of matching branches; and 
     determining, according to a comparison result, the on-off combination that realizes the optimal load matching. 
     Optionally, the step of traversing on-off combinations of the plurality of matching branches, and obtaining a matching degree parameter that corresponds to each on-off combination and reflects a load matching degree of the electromagnetic wave generation module includes: 
     acquiring a pre-configured number set, the number set including combination numbers of the on-off combinations of the plurality of matching branches, and the combination numbers corresponding to the impedance values; and 
     determining, based on the number set, branch numbers of the matching branches corresponding to each of the combination numbers one by one, and controlling the on-off of the corresponding matching branches according to the branch numbers. 
     Optionally, the feature parameter is the impedance value of the matching module or the combination number for the optimal load matching. 
     Optionally, the step of acquiring a feature parameter that reflects the weight of the object to be treated includes: 
     controlling the electromagnetic wave generation module to generate an electromagnetic wave signal with a preset initial power; and 
     adjusting the frequency of the electromagnetic wave signal in a candidate frequency range, and determining a frequency value of the electromagnetic wave signal that realizes an optimal frequency matching of the cavity capacitor, the feature parameter being the frequency value of the electromagnetic wave signal that realizes the optimal frequency matching. 
     According to the second aspect of the present invention, provided is a heating apparatus, including: 
     a cavity capacitor, used for placement of an object to be treated; 
     an electromagnetic wave generation module, configured to generate an electromagnetic wave signal for heating the object to be treated in the cavity capacitor; and 
     a controller, configured to perform any one of the above-mentioned thawing methods. 
     Compared with determining, according to a sensed temperature of the object to be treated, the thawing progress of the object to be treated, the present invention that determines the thawing progress according to the power of the electromagnetic wave signal, the weight of the object to be treated and the rate of change in the dielectric coefficient of the object to be treated is less influenced by the precision of a sensing device itself, and achieves relatively accurate determination, thereby facilitating further treatment by the user on the thawed object to be treated. 
     Further, the present invention determines whether the thawing is completed by comparing the rate of change in the dielectric coefficient of the object to be treated with a threshold value of change determined by the power of the electromagnetic wave signal and the weight of the object to be treated, which can effectively prevent the object to be treated from being excessively thawed, is especially suitable for objects to be treated whose thawing temperature is expected to be −4 to −1° C. The thawed meat foods produce no blood and water and are easy to cut, and thawed vegetable foods have no moisture outflow and are less in nutrient loss. 
     Further, the present invention reflects the weight of the object to be treated through the parameters related to the capacitance of the cavity capacitor (the capacitance itself, the impedance value of the matching module that realizes optimal load matching, the frequency value of the electromagnetic wave signal that realizes optimal frequency matching, etc.). There is no need for the user to manually input the weight of the object to be treated based on experience or measurement, or to add a load cell in the cavity capacitor, which not only saves costs, but also improves the fault tolerant rate. 
     Further, the present invention, by numbering all the on-off combinations of the matching module and all the matching branches respectively, can quickly match matching branches corresponding to each of the on-off combinations for on and off in the process of determining the impedance value of the matching module that realizes the optimal load matching of the electromagnetic wave generation module, thereby shortening the time required for determining the feature parameter of the object to be treated, and greatly improving the user experience. In particular, according to the numbering method of the present invention, the corresponding threshold value of change can be matched directly by using the combination number, which simplifies the control process and further shortens the time required for determining the feature parameter of the object to be treated. 
     The above and other objectives, advantages, and characteristics of the present invention will be better understood by those skilled in the art according to the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some specific embodiments of the present invention will be described in detail below in an exemplary rather than limited manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. Those skilled in the art should understand that these accompanying drawings are not necessarily drawn to scale. In figures: 
         FIG.  1    is a schematic structural diagram of a heating apparatus according to an embodiment of the present invention; 
         FIG.  2    is a schematic structural diagram of a controller in  FIG.  1   ; 
         FIG.  3    is a schematic circuit diagram of a matching module according to an embodiment of the present invention; 
         FIG.  4    is a schematic flowchart of a thawing method for a heating apparatus according to an embodiment of the present invention; 
         FIG.  5    is a detailed flowchart of a thawing method for a heating apparatus according to an embodiment of the present invention; and 
         FIG.  6    is a schematic flowchart of determining a threshold value of change in a dielectric coefficient of an object to be treated according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a schematic structural diagram of a heating apparatus  100  according to an embodiment of the present invention. Referring to  FIG.  1   , the heating apparatus  100  may include a cavity capacitor  110 , an electromagnetic wave generation module  120  and a controller  140 . 
     Specifically, the cavity capacitor  110  may include a cavity for placement of an object to be treated  150 , and a radiation pole plate disposed in the cavity. In some embodiments, a receiving pole plate may further be provided in the cavity to form a capacitor with the radiation pole plate. In some other embodiments, the cavity may be made of metal, which serves as the receiving pole plate to form the capacitor together with the radiation pole plate. 
     The electromagnetic wave generation module  120  may be configured to generate an electromagnetic wave signal and be electrically connected to the radiation pole plate of the cavity capacitor  110  to generate electromagnetic waves in the cavity capacitor  110 , thereby heating the object to be treated  150  in the cavity capacitor  110 . 
       FIG.  2    is a schematic structural diagram of the controller  140  in  FIG.  1   . Referring to  FIG.  2   , the controller  140  may include a processing unit  141  and a storage unit  142 . The storage unit  142  stores a computer program  143 , and the computer program  143  is used to implement the control method of the embodiment of the present invention when executed by the processing unit  141 . 
     In particular, the processing unit  141  may be configured to, after receiving a thawing instruction input by a user, acquire a feature parameter that reflects the weight of the object to be treated  150 , a power value (i.e., heating power) of the electromagnetic wave signal used to heat the object to be treated  150 , and a rate of change in a dielectric coefficient of the object to be treated  150 , and further determine the thawing progress of the object to be treated  150  according to the feature parameter, the heating power and the rate of change in the dielectric coefficient of the object to be treated  150 . 
     Compared with determining, according to a sensed temperature of the object to be treated  150 , the thawing progress of the object to be treated  150 , the heating apparatus  100  of the present invention that determines the thawing progress according to the power of the electromagnetic wave signal for heating the object to be treated  150 , the weight of the object to be treated  150  and the rate of change in the dielectric coefficient of the object to be treated  150  is less influenced by the precision of a sensing device itself, and achieves relatively accurate determination, thereby facilitating further treatment by the user on the thawed object to be treated  150 . 
     In some embodiments, the processing unit  141  may be further configured to determine a threshold value of change in the dielectric coefficient of the object to be treated  150  according to the feature parameter and the heating power for determining whether the thawing is complete. 
     When the rate of change in the dielectric coefficient of the object to be treated  150  is less than the threshold value of change, the processing unit  141  can control the electromagnetic wave generation module  120  to stop working, that is, to stop heating the object to be treated  150  to prevent the object to be treated  150  from being overly thawed. 
     The processing unit  141  may be configured to match, according to the feature parameter and the power value, the corresponding threshold value of change based on a preset comparison relationship. In the case of the same power value, the threshold value of change is substantially inversely proportional to the weight reflected by the feature parameter. In the case of the same weight reflected by the feature parameter, the threshold value of change is substantially proportional to the power value, so as to be suitable for different kinds and weights of foods, and avoid excessive or incomplete thawing. The comparison relationship may be a formula, a comparison table, etc. 
     In some further embodiments, the processing unit  141  may be configured to determine, according to a food group of the object to be treated  150 , the power value of the electromagnetic wave signal used for heating of the object to be treated  150 , so as to alleviate the phenomena of uneven heating and local overheating caused by different contents of substances in different foods. 
     The food group may be input by the user, or judged by means of image recognition or spectrum recognition. Each food group may include at least one food variety, so that the fault tolerant rate is increased, and the requirements for users are lowered. 
     The threshold value of change can be determined specifically by performing heating experiments with different heating powers on different kinds and weights of objects to be treated  150 , and detecting the rate of change in the dielectric coefficient of the object to be treated  150  at −4 to −1° C., so as to further improve the accuracy of judging whether the thawing is completed, make thawed meat foods produce no blood and water and easy to cut, and ensure thawed vegetable foods to have no moisture outflow and be less in nutrient loss. 
     In some embodiments, the feature parameter reflecting the weight of the object to be treated  150  may be a capacitance value of the cavity capacitor  110 , and there is no need for the user to manually input the weight of the object to be treated  150  based on experience or measurement, or to add a load cell in the cavity capacitor  110 , which not only saves costs, but also improves the fault tolerant rate. 
     In some further embodiments, the heating apparatus  100  further includes a matching module  130 . The matching module  130  may be connected in series between the electromagnetic wave generation module  120  and the cavity capacitor  110  or in parallel at both ends of the cavity capacitor  110 , and is configured to adjust the load impedance of the electromagnetic wave generation module  120  by adjusting its own impedance, so as to achieve load matching and improve heating efficiency. 
     The processing unit  141  may be configured to control the electromagnetic wave generation module  120  to generate an electromagnetic wave signal with a preset initial power, adjust the impedance of the matching module  130  to perform load matching, determine an impedance value of the matching module  130  that realizes the optimal load matching of the electromagnetic wave generation module  120 , and further determine, according to the impedance value of the matching module  130  that realizes the optimal load matching, the capacitance of the cavity capacitor  110  or directly take the impedance value of the matching module  130  that realizes the optimal load matching as the feature parameter. 
     The matching module  130  may include a plurality of matching branches that can be switched on and off independently. The processing unit  141  may be further configured to traverse the on-off combinations of the plurality of matching branches and obtain a matching degree parameter that corresponds to each on-off combination and reflects the load matching degree of the electromagnetic wave generation module  120 , compare the matching degree parameters of the on-off combinations of the plurality of matching branches, and determine, according to a comparison result, the on-off combination that realizes the optimal load matching as well as the impedance value corresponding to the on-off combination. 
     Specifically, the storage unit  142  may store a pre-configured number set, the number set may include combination numbers of the on-off combinations of the plurality of matching branches, and the combination numbers correspond to the impedance values of the matching module  130 . The processing unit  141  may be further configured to obtain the pre-configured number set after obtaining a heating instruction, and then determine the branch number of the matching branch corresponding to each combination number one by one based on the number set, and control the on and off of the corresponding matching branches according to the branch numbers, so as to realize traversing of the on-off combinations of the plurality of matching branches. 
     The heating apparatus  100  of the present invention, by numbering all the on-off combinations of the matching module  130  and all the matching branches respectively, can quickly match the matching branches corresponding to each of the on-off combinations for on and off in the process of determining the impedance value of the matching module 130  that realizes the optimal load matching of the electromagnetic wave generation module  120 , thereby shortening the time required for determining the capacitance of the cavity capacitor  110 , and greatly improving the user experience. 
     In this embodiment, the feature parameter may be the impedance value of the matching module  130  for the optimal load matching, or the combination number, so as to simplify the control process and further shorten the time required for determining the feature parameter of the object to be treated  150 . 
     The branch numbers of the plurality of matching branches may be 0 to n−1 power of a constant A in turn, and the combination number may be the sum of the branch numbers of conducting matching branches in the on-off combination, so that the only group of conducting matching branches can be accurately determined by only the branch numbers. The constant A may be 2, 3, 4, or the like, and n is the number of the matching branches. In the present invention, the constant A may be 2, so as to reduce the storage space occupied by the numbers and improve the matching efficiency. 
       FIG.  3    is a schematic circuit diagram of the matching module  130  according to an embodiment of the present invention. Referring to  FIG.  3   , in some further embodiments, the matching module  130  may include a first matching unit  131  connected in series between the electromagnetic wave generation module  120  and the cavity capacitor  110 , and a second matching unit  132  with one end electrically connected between the first matching unit  131  and the cavity capacitor  110  and the other end grounded. The first matching unit  131  and the second matching unit  132  may respectively include a plurality of matching branches connected in parallel, and each matching branch includes a fixed-value capacitor and a switch, so as to improve the reliability and adjustment range of the matching module  130  while making a circuit simple, and thus increase the acquired impedance value of the matching module  130  that realizes the optimal load matching. 
     The capacitance values of a plurality of fixed-value capacitors of the first matching unit  131  and the second matching unit  132  may all be unequal, and the capacitance value of the minimum fixed-value capacitor of the second matching unit  132  may be greater than that of the maximum fixed-value capacitor of the first matching unit  131 . The numbers of the plurality of branches may be sequentially increased from small to large according to the capacitance values of the corresponding matching branches. 
     Referring to  FIG.  3   , the capacitance values of the capacitors C 1 , C 2 , . . . , C a  of the first matching unit  131  increase in turn, and the capacitance values of the capacitors C x1 , C x2 , . . . , C xb  (where a+b=n) of the second matching unit  132  increase in turn, and the capacitance value of the capacitor C x1  is greater than that of the capacitor C a . In an embodiment where the constant A is 2, the matching branches corresponding to C 1 , C 2 , . . . , C 1 , C x1 , C x2 , . . . , C xb  can be numbered as 2 0 , 2 1 , . . . ,  2   a−1 , 2 a , 2 a+1 , . . . , 2 n−1  in turn. 
     According to a resonant frequency calculation formula f=1/(2π·sqrt(L·C), for the same heating apparatus  100  (inductance L remains unchanged), when the capacitance value C of the cavity capacitor  110  changes due to the placement of different objects to be treated  150 , the resonant frequency f applicable to the cavity capacitor  110  also changes. In some other embodiments, the electromagnetic wave generation module  120  may include a variable frequency source and a power amplifier. 
     The processing unit  141  may be configured to control the electromagnetic wave generation module  120  to generate an electromagnetic wave signal with a preset initial power after obtaining a heating instruction, adjust the frequency of the electromagnetic wave signal generated by the electromagnetic wave generation module  120  within a candidate frequency range, determine a frequency value of the electromagnetic wave signal that realizes the optimal frequency matching of the cavity capacitor  110 , and further determine a capacitance of the cavity capacitor  110  according to the frequency value that realizes the optimal frequency matching, or directly use the frequency value that realizes the optimal frequency matching as the feature parameter. 
     The minimum value and the maximum value of the candidate frequency range may be 32-38 MHz and 42-48 MHz respectively, so that the penetration of electromagnetic waves is improved, and uniform heating is achieved. For example, the candidate frequency range is 32-48 MHz, 35-48 MHz, 35-45 MHz, 38-45 MHz, 38-42 MHz, etc. 
     The processing unit  141  may be configured to adjust the frequency of the electromagnetic wave signal within the candidate frequency range in a dichotomy manner, gradually narrow the frequency approximation range for realizing the optimal frequency matching to a minimum approximation range, and further determine the frequency value of the electromagnetic wave signal that realizes the optimal frequency matching. 
     Specifically, the processing unit  141  may be configured to adjust the frequency of the electromagnetic wave signal to be the minimum, intermediate and maximum values of the frequency approximation range, obtain the matching degree parameter that corresponds to each frequency and reflects a frequency matching degree of the cavity capacitor  110  for comparison, and re-determine, according to the comparison result, the frequency approximation range, which are repeated until the frequency approximation range is the minimum approximation range; and the frequency of the electromagnetic wave signal is adjusted to the minimum, intermediate and maximum values of the minimum approximation range, the matching degree parameter that corresponds to each frequency and reflects the frequency matching degree of the of the cavity capacitor  110  is obtained for comparison, and an optimal frequency value is determined according to the comparison result, where an initial frequency approximation range may be the aforementioned candidate frequency range. 
     The heating apparatus  100  of the present invention determines the frequency value for realizing the optimal frequency matching in the candidate frequency range by using a dichotomy method, which can quickly narrow the range where the optimal frequency value is located, and then quickly determine the optimal frequency value, thus shortening the time required for determining the capacitance of the cavity capacitor  110  and greatly improving the user experience. 
     It should be noted that the minimum approximation range in the present invention is not a specific frequency range, but a minimum range of the frequency approximation range, that is, the accuracy of the optimal frequency value. In some embodiments, the minimum approximation range may be any value in a range of 0.2 to 20 KHz, such as 0.2 KHz, 1 KHz, 5 KHz, 10 KHz, or 20 KHz. The time interval between every two adjacent times of adjusting the frequency of the electromagnetic wave signal may be 10-20 ms, such as 10 ms, 15 ms, or 20 ms. 
     In some embodiments, the variable frequency source may be a voltage-controlled oscillator whose input voltage corresponds to the output frequency. The processing unit  141  may be configured to determine the capacitance of the cavity capacitor  110  according to the input voltage of the voltage-controlled oscillator or directly use the input voltage as the feature parameter. 
     In the present invention, the optimal load matching of the electromagnetic wave generation module  120  and the optimal frequency matching of the cavity capacitor  110  mean that with the same heating apparatus  100 , the output power allocated by the electromagnetic wave generation module  120  to the cavity capacitor  110  accounts for the largest proportion. 
     In the present invention, the preset initial power may be 10-20 W, such as 10 W, 15 W or 20 W, so as to obtain an impedance value that realizes the optimal load matching or a frequency value that achieves the optimal frequency matching with high accuracy while saving energy. 
     In some embodiments, the heating apparatus  100  may further include a bidirectional coupler, which is connected in series between the cavity capacitor  110  and the electromagnetic wave generation module  120 , and is used for real-time monitoring a forward power signal output by the electromagnetic wave generation module  120  and a reverse power signal returned to the electromagnetic wave generation module  120 . 
     The processing unit  141  may also be configured to acquire the forward power signal output by the electromagnetic wave generation module  120  and the reverse power signal returned to the electromagnetic wave generation module  120  after each time the impedance values of the matching module  130  are adjusted or the frequency of the electromagnetic wave signal is adjusted, and calculate the matching degree parameter according to the forward power signal and the reverse power signal. 
     The matching degree parameter may be a return loss S 11 , which can be calculated according to a formula S 11 =−20 log (reverse power/forward power). In this embodiment, the smaller the value of return loss S 11 , the higher the load matching degree of the electromagnetic wave generation module  120  or the frequency matching degree of the cavity capacitor  110 , and the impedance value or frequency value corresponding to the minimum return loss S 11  is the impedance value that realizes the optimal load matching or the frequency value that realizes the optimal frequency matching. 
     The matching degree parameter may alternatively be an electromagnetic wave absorption rate, which can be calculated according to a formula of the electromagnetic wave absorption rate=(1−reverse power/forward power). In this embodiment, the greater the value of the electromagnetic wave absorption rate, the higher the load matching degree of the electromagnetic wave generation module  120  or the frequency matching degree of the cavity capacitor  110 , and the impedance value or frequency value corresponding to the maximum electromagnetic wave absorption rate is the impedance value that realizes the optimal load matching or the frequency value that realizes the optimal frequency matching. The matching degree parameter may alternatively be other parameters that can reflect a proportion of the output power allocated by the electromagnetic wave generation module  120  to the cavity capacitor  110 . 
     In some further embodiments, the capacitance of the cavity capacitor  110  can be directly measured by means of a capacitance measuring instrument. 
       FIG.  4    is a schematic flowchart of a thawing method for a heating apparatus  100  according to an embodiment of the present invention. Referring to  FIG.  4   , the thawing method for the heating apparatus  100  executed by the controller  140  of any of the above embodiments of the present invention may include the following steps: 
     Step S 402 : a thawing instruction input by a user is received. 
     Step S 404 : a feature parameter that reflects the weight of an object to be treated  150 , a power value of an electromagnetic wave signal used to heat the object to be treated  150 , and a rate of change in a dielectric coefficient of the object to be treated  150  are acquired. 
     Step S 406 : the thawing progress of the object to be treated  150  is determined according to the feature parameter, the power value and the rate of change. 
     Compared with determining, according to the sensed temperature of the object to be treated  150 , the thawing progress of the object to be treated  150 , the thawing method of the present invention that determines the thawing progress according to the power of the electromagnetic wave signal, the weight of the object to be treated  150  and the rate of change in the dielectric coefficient of the object to be treated  150  is less influenced by the precision of the sensing device itself, and achieves relatively accurate determination, thereby facilitating further treatment by the user on the thawed object to be treated  150 . 
     In some embodiments, the step S 406  may include the following steps: 
     determining a threshold value of change in the dielectric coefficient of the object to be treated  150  according to the feature parameter and the power value of the electromagnetic wave signal used to heat the object to be treated  150 ; and 
     detecting in real time the rate of change in the dielectric coefficient of the object to be treated  150 , and when the rate of change is less than the threshold value of change, controlling the electromagnetic wave generation module  120  to stop working. 
     The threshold value of change may be determined from the feature parameter and the power value by matching based on a preset comparison relationship; in the case of the same power value, the threshold value of change is inversely proportional to the weight reflected by the feature parameter. In the case of the same weight reflected by the feature parameter, the threshold value of change is proportional to the power value. 
     The feature parameter reflecting the weight of the object to be treated  150  may be the capacitance itself of the cavity capacitor  110  after the object to be treated  150  is put into the cavity, the impedance value of the matching module  130  that realizes the optimal load matching, the frequency value of the electromagnetic wave signal that realizes the optimal frequency matching, or the like, and there is no need for the user to manually input the weight of the object to be treated  150  based on experience or measurement, or to add a load cell in the cavity capacitor  110 , which not only saves the costs, but also improves the fault tolerant rate. 
     In some embodiments, the step of acquiring a feature parameter that reflects the weight of the object to be treated  150  includes: 
     controlling the electromagnetic wave generation module  120  to generate an electromagnetic wave signal with a preset initial power; and 
     adjusting the impedance of the matching module  130 , determining an impedance value of the matching module  130  that realizes the optimal load matching of the electromagnetic wave generation module  120 , and further determining, according to the impedance value of the matching module  130  that realizes the optimal load matching, the capacitance of the cavity capacitor  110  or directly taking the impedance value of the matching module  130  that realizes the optimal load matching as the feature parameter. 
     Specifically, adjusting the impedance of the matching module  130 , and determining an impedance value of the matching module  130  that realizes the optimal load matching of the electromagnetic wave generation module  120  include: traversing on-off combinations of the plurality of matching branches, and obtaining the matching degree parameter that corresponds to each on-off combination and reflects the load matching degree of the electromagnetic wave generation module  120 ; comparing the matching degree parameters of the on-off combinations of the plurality of matching branches; and determining, according to a comparison result, the on-off combination that realizes the optimal load matching. 
       FIG.  5    is a detailed flowchart of a thawing method for a heating apparatus  100  according to an embodiment of the present invention (in the accompanying drawings of the present invention, ‘Y’ means ‘Yes’; ‘N’ means ‘No’). Referring to  FIG.  5   , the thawing method for the heating apparatus  100  according to an embodiment of the present invention may include the following detailed steps: 
     Step S 502 : a thawing instruction input by a user is acquired. 
     Step S 504 : a food group of an object to be treated  150  is acquired. In this step, the food group may be input by the user or judged by means of image recognition or spectrum recognition. Each food group may include at least one food variety, so that the fault tolerant rate is increased, and the requirements for users are lowered. 
     Step S 506 : the heating power of an electromagnetic wave signal used for heating the object to be treated  150  is determined according to the food group, so as to alleviate the phenomena of uneven heating and local overheating caused by different contents of substances in different foods. 
     Step S 508 : the electromagnetic wave generation module  120  is controlled to generate the electromagnetic wave signal with a preset initial power. 
     Step S 510 : a pre-configured number set is acquired. 
     Step S 512 : branch numbers of matching branches corresponding to each of the combination numbers are determined one by one based on the number set, and the on-off of the corresponding matching branches is controlled based on the branch numbers; and after switching on and off the matching branches corresponding to each on-off combination, a forward power signal output by the electromagnetic wave generation module and a reverse power signal returned to the electromagnetic wave generation module  120  are obtained, and matching degree parameters are calculated according to the forward power signal and the reverse power signal, so as to quickly match the matching branches corresponding to each on-off combination for on and off, thereby shortening the time required for determining the capacitance of a cavity capacitor  110 . 
     Step S 514 : the matching degree parameters of the on-off combinations of a plurality of matching branches are compared. 
     Step S 516 : the on-off combination that realizes optimal load matching is determined according to a comparison result. 
     Step S 518 : according to the combination number of the on-off combination that realizes the optimal load matching as well as the heating power, a threshold value of change in a dielectric coefficient of the object to be treated  150  is matched based on a preset comparison relationship, so as to simplify a control process and further shorten the time required for determining the feature parameter of the object to be treated  150 . 
     Step S 520 : the electromagnetic wave generation module  120  is controlled to generate the electromagnetic wave signal whose power is the heating power. Step S 522 : a rate of change in the dielectric coefficient of the object to be treated  150  is acquired. 
     Step S 524 : whether the rate of change in the dielectric coefficient of the object to be treated  150  is smaller than the threshold value of change is judged. If yes, step S 526  is performed; and if not, it returns to step S 522 . 
     Step S 526 : the electromagnetic wave generation module  120  is controlled to stop working. It returns to step S 502  to start a next thawing cycle. 
     In some other embodiments, the difference from the previous embodiment is that acquiring a feature parameter that reflects the weight of the object to be treated  150  may include the following steps: 
     controlling the electromagnetic wave generation module  120  to generate the electromagnetic wave signal with the preset initial power; and 
     adjusting the frequency of the electromagnetic wave signal within a candidate frequency range, determining a frequency value of the electromagnetic wave signal that realizes optimal frequency matching of the cavity capacitor  110 , and further determining the capacitance of the cavity capacitor  110  according to the frequency value that realizes the optimal frequency matching, or directly using the frequency value that realizes the optimal frequency matching as the feature parameter. 
       FIG.  6    is a schematic flowchart of determining the threshold value of change in the dielectric coefficient of the object to be treated  150  according to another embodiment of the present invention. Referring to  FIG.  6   , in another embodiment of the present invention, determining the threshold value of change in the dielectric coefficient of the object to be treated  150  may include the following steps: 
     Step S 602 : an initial frequency approximation range is acquired. The initial frequency approximation range may be the aforementioned candidate frequency range. 
     Step S 604 : the frequency of the electromagnetic wave signal is adjusted to be minimum, intermediate and maximum values of the frequency approximation range, and the matching degree parameter that corresponds to each frequency and reflects a frequency matching degree of the cavity capacitor  110  is obtained. 
     Step S 606 : the matching degree parameters of all the frequencies are compared. 
     Step S 608 : whether the frequency approximation range is a minimum approximation range is judged. If yes, step S 610  is performed; and if not, step S 612  is performed. 
     Step S 610 : a frequency value of the electromagnetic wave signal that realizes the optimal frequency matching is determined according to a comparison result, and according to the frequency value and the heating power, the threshold value of change in the dielectric coefficient of the object to be treated  150  is matched based on a preset comparison relationship. 
     Step S 612 : the frequency approximation range is re-determined according to the comparison result to gradually narrow the frequency approximation range for realizing optimal frequency matching to the minimum approximation range, rapidly narrow the range where the optimal frequency value is located, and then quickly determine the optimal frequency value. The flow returns to step S 604 . 
     Hereto, those skilled in the art should realize that although a plurality of exemplary embodiments of the present invention have been shown and described in detail herein, without departing from the spirit and scope of the present invention, many other variations or modifications that conform to the principles of the present invention can still be directly determined or deduced from the contents disclosed in the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all these other variations or modifications.