Vacuum microwave crisp-fried meat slice drying parameter intelligent optimization system

Abstract

The present application relates to food processing equipment and control technology field, disclose a kind of vacuum microwave crisp piece drying parameter intelligent optimization system, including vacuum drying cavity, microwave generating unit, vacuum moisture removal unit, pneumatic excitation unit, pneumatic impedance matching unit and main control unit, and pneumatic excitation unit constructs dynamic change pneumatic excitation response field in cavity;Pneumatic impedance matching unit is installed in microwave waveguide, based on the pressure difference change in field generates hardware linkage response, and transmission impedance is adjusted adaptively by mechanical displacement.Synchronous acquisition of main control unit transient pressure and microwave reflected power, solve the transient gas release impedance of the water release resistance and the net energy coupling factor of the hardware loss, according to this, identify constant-speed dehydration, puffing shaping and drying end point, and generate instruction dynamic adjustment excitation frequency or maintain negative pressure.The present application utilizes physical field coupling, realizes the non-contact monitoring of material drying state under vacuum environment and the self-adaptive precise matching of microwave energy.

Description

Technical Field

[0001] This invention relates to the field of food processing equipment and control technology, specifically to an intelligent optimization system for vacuum microwave meat crisp drying parameters. Background Technology

[0002] Vacuum microwave drying technology uses microwave energy to rapidly vaporize the moisture inside the material, and combined with the internal and external pressure difference in a vacuum environment, it achieves the expansion and shaping of the material structure. It is widely used in the deep processing of meat snack foods.

[0003] However, existing vacuum microwave drying equipment has shortcomings in actual operation. First, regarding energy transmission and matching, the transmission characteristics of microwaves in a vacuum environment differ from those in an atmospheric pressure environment. As the drying process proceeds, the gas pressure inside the vacuum chamber gradually decreases, and the breakdown voltage of the gas decreases accordingly. If the microwave feed power or port impedance is not adjusted in time, glow discharge or even arcing can easily occur at the waveguide port or inside the cavity. Existing solutions mostly rely on electrical parameter feedback for active adjustment, lacking a mechanism to directly drive the microwave transmission components for physical adaptive adjustment using changes in ambient gas pressure. This makes it difficult to balance transmission efficiency and discharge suppression in low-pressure environments.

[0004] Secondly, regarding the monitoring of the drying state, the quality of meat chips depends on controlling the moisture migration rate and phase transition point. Since the vacuum drying chamber is in a closed state and usually operates with rotation, traditional contact sensors are inconvenient to place, while non-contact methods such as infrared thermometry can only reflect the surface temperature of the material and cannot quantitatively characterize the resistance to moisture migration and the drying state inside the material without disrupting the vacuum environment. This results in a lack of effective internal state feedback data during the processing.

[0005] Furthermore, in terms of process control strategies, due to the lack of real-time perception of changes in the microstructure of materials, existing control methods are mostly based on fixed programs or single time parameters. This open-loop control mode is difficult to adapt to the differences in texture and initial moisture content of different batches of meat slices, resulting in the inability to accurately identify the puffing critical point where the surface hardening of the meat slices balances the internal pressure. If the timing of shaping is not chosen properly, it can easily lead to insufficient puffing or over-drying of the meat slices, making it difficult to guarantee the textural characteristics and uniformity of the finished meat crisps. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an intelligent optimization system for vacuum microwave meat crisp drying parameters, which solves the technical problems of difficulty in real-time matching of microwave energy input and material drying state in existing vacuum microwave drying equipment, and difficulty in non-contact monitoring of internal moisture migration and phase change processes in meat slices under vacuum conditions.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A smart optimization system for vacuum microwave meat chip drying parameters includes a vacuum drying chamber, a microwave generating unit, a vacuum dehumidification unit, a pneumatic excitation unit, a pneumatic impedance matching unit, and a main control unit. The vacuum drying chamber forms a sealed processing space for containing the meat chips to be dried. The microwave generating unit is coupled to the vacuum drying chamber to feed microwave energy into it. The vacuum dehumidification unit is connected to the vacuum drying chamber via a pipe interface to establish a negative pressure environment and remove water vapor. The pneumatic excitation unit is connected to the vacuum drying chamber to perform filling and degassing operations within it to construct a dynamically changing pneumatic excitation response field. The pneumatic impedance matching unit is physically mounted on the microwave generating unit and generates a hardware-linked response based on pressure difference changes in the pneumatic excitation response field, adaptively adjusting the transmission impedance through mechanical displacement. The main control unit is electrically connected to the microwave generating unit, the vacuum dehumidification unit, and the pneumatic excitation unit. The main control unit controls the pneumatic excitation unit to generate a pneumatic excitation response field, and calculates the state decoupling parameters based on the physical quantity feedback in the pneumatic excitation response field. Then, based on the state decoupling parameters, it generates drying stage control commands to coordinate the operation of each unit.

[0008] Preferably, the microwave generating unit includes a magnetron and a microwave waveguide, and the microwave energy generated by the magnetron is transmitted through the microwave waveguide. The aerodynamic impedance matching unit is installed at the coupling port on the side wall of the microwave waveguide and can perform linear reciprocating motion relative to the cross-section of the microwave waveguide.

[0009] Preferably, the pneumatic actuation unit includes a gas source, an electromagnetic proportional valve, and a diaphragm pressure gauge. The gas source provides the working medium; the electromagnetic proportional valve is located on the inlet pipe and controlled by the main control unit to inject gas into the vacuum drying chamber; the diaphragm pressure gauge is used to collect the transient absolute pressure in the vacuum drying chamber in real time.

[0010] Preferably, the pneumatic impedance matching unit includes a bellows assembly, an absorbing wedge, and a return spring. The bellows assembly is hermetically fixed to the sidewall of the microwave waveguide via a flange. The inner cavity of the bellows assembly is connected to the atmospheric environment or a constant pressure reference cavity, while the outer wall is placed in the negative pressure environment of a vacuum drying chamber. The absorbing wedge is mechanically connected to the movable end of the bellows assembly and extends into the microwave waveguide. The return spring provides an elastic restoring force opposite to the direction of the internal and external pressure difference driving force. In this structure, when the air pressure in the vacuum drying chamber increases, the return spring drives the absorbing wedge to retract from the microwave waveguide; when the air pressure decreases, the pressure difference drives the absorbing wedge to insert into the microwave waveguide, thereby achieving the aforementioned hardware linkage response.

[0011] Preferably, the main control unit acquires the transient absolute pressure collected in real time by the thin-film pressure gauge, and inputs the transient absolute pressure into the system's preset differential pressure displacement response model to calculate the real-time axial displacement of the absorbing wedge inside the microwave waveguide.

[0012] Preferably, the main control unit controls the electromagnetic proportional valve to open and perform the inflation excitation, and closes the electromagnetic proportional valve after reaching the preset peak value to enter the exhaust recovery stage; the theoretical reference decay pressure trajectory of the vacuum drying chamber in the exhaust recovery stage without material interference is calculated using the theoretical vacuum decay model.

[0013] Furthermore, the system calculates state decoupling parameters based on physical quantity feedback. The physical quantity feedback includes transient absolute pressure and microwave reflected power, while the state decoupling parameters include transient gas release impedance and net energy coupling factor. The specific process includes: simultaneously acquiring the transient absolute pressure output from the thin-film pressure gauge and the microwave reflected power fed back from the microwave generating unit; substituting the deviation between the transient absolute pressure and the theoretical baseline attenuated pressure trajectory into the relevant calculation model to obtain the transient gas release impedance, which characterizes the resistance characteristics of moisture release from the material; and substituting the microwave reflected power and the hardware loss determined based on real-time axial displacement into the relevant decoupling model to obtain the net energy coupling factor, which characterizes the efficiency of the material's actual absorption of microwave energy after deducting hardware losses.

[0014] Preferably, the control commands for the drying stage include pulse modulation commands for the constant-rate dehydration stage. The main control unit calculates the energy density actually acting on the meat slice material by combining the effective heating duty cycle logic with the real-time axial displacement; monitors the real-time numerical change of the net energy coupling factor; and generates pulse modulation commands based on the change of the net energy coupling factor to dynamically adjust the inflation and deflation cycle of the pneumatic excitation unit. This process achieves physical modulation of the microwave energy application time by adjusting the air pressure cycle and utilizing the follow-up characteristics of the pneumatic impedance matching unit.

[0015] Preferably, the drying stage control commands include a negative pressure maintenance command for the puffing and shaping stage. The main control unit performs a second-order differential operation on the transient gas release impedance to obtain the impedance change curvature characteristics; inputs the impedance change curvature characteristics into the puffing trigger criterion model to identify the puffing critical point; when the puffing critical point is identified, a negative pressure maintenance command is generated, triggering the pneumatic excitation unit to stop gas injection and controlling the vacuum dehumidification unit to maintain the ultimate vacuum. The puffing trigger criterion model includes a puffing critical threshold, which is a preset value indicating the inflection point of the hardened layer formation on the surface of the meat slice.

[0016] Preferably, the drying stage control commands include a shutdown command for the drying endpoint. The main control unit monitors whether the transient gas release impedance is continuously lower than the residual moisture impedance lower limit for a preset period, and simultaneously monitors whether the net energy coupling factor is lower than the ineffective energy consumption threshold; when both monitoring conditions are met simultaneously, a shutdown command is generated to cut off the power supply to the microwave generator unit. Here, the residual moisture impedance lower limit is a preset impedance value characterizing when the meat slices reach the drying endpoint, and the ineffective energy consumption threshold is a preset efficiency value characterizing when the meat slices no longer effectively absorb microwave energy.

[0017] This invention provides an intelligent optimization system for vacuum microwave meat crisp drying parameters. It has the following beneficial effects: 1. This invention utilizes a pneumatic impedance matching unit to construct a physical field linkage mechanism. By sensing the pressure change in the vacuum drying chamber through the bellows assembly, it directly drives the absorbing wedge to perform linear reciprocating motion within the microwave waveguide. This mechanism drives the wedge to exit the waveguide during the heating stage when the pressure increases to reduce transmission loss, and drives the wedge to insert into the waveguide during the high vacuum stage when the pressure decreases to increase energy attenuation. It can achieve adaptive adjustment of microwave transmission impedance with vacuum level without the need for additional motor drive, suppressing the risk of microwave discharge and material overheating caused by excessive field strength in high vacuum environment.

[0018] 2. This invention employs a non-contact state monitoring method based on active pneumatic excitation. By applying controllable air pressure disturbance to a confined space and comparing the actual pressure curve during the exhaust recovery phase with the theoretical baseline attenuation trajectory under no material interference, the transient gas release impedance characterizing the internal moisture migration characteristics of the material is calculated. This method indirectly obtains the internal state of the material using fluid pressure signals, overcoming the technical limitations of difficulty in deploying contact sensors in a vacuum-sealed environment and the inability of traditional infrared thermometry to reflect the internal moisture distribution, thus achieving quantitative characterization of the meat slice drying process.

[0019] 3. This invention establishes an intelligent control strategy based on phase change feature recognition. The second-order differential operation is performed on the collected transient gas release impedance to identify the puffing critical point of the hardened layer on the surface of the meat slice. At this critical moment, a negative pressure holding command is automatically triggered to switch the environment to ultimate vacuum. This control logic ensures that the meat slice expands in volume at a specific stage when the surface hardening and internal vapor pressure reach equilibrium. The internal and external pressure difference is used to complete the physical shaping of the porous structure, thereby improving the texture and uniformity of the finished meat crisps. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of a vacuum microwave meat crisp drying parameter intelligent optimization system according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the workflow of an intelligent optimization system for vacuum microwave meat crisp drying parameters according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the time-varying pressure curve of the cavity when the pneumatic excitation unit performs cyclic excitation control according to an embodiment of the present invention.

[0021] Among them, 100 is the vacuum drying chamber; 110 is the microwave generating unit; 111 is the magnetron; 112 is the microwave waveguide; 120 is the vacuum dehumidification unit; 130 is the pneumatic excitation unit; 131 is the gas source; 132 is the electromagnetic proportional valve; 133 is the diaphragm pressure gauge; 140 is the pneumatic impedance matching unit; and 150 is the main control unit. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] See attached document Figure 1 The present invention provides an intelligent optimization system for vacuum microwave meat crisp drying parameters, which mainly includes a vacuum drying chamber 100, a microwave generating unit 110, a vacuum dehumidification unit 120, a pneumatic excitation unit 130, a pneumatic impedance matching unit 140, and a main control unit 150.

[0024] The vacuum drying chamber 100 forms a sealed processing space for containing the meat slices to be dried, and its interior is equipped with a rotating carrier structure for supporting the material. The microwave generating unit 110 includes a magnetron 111 and a microwave waveguide 112. The microwave energy generated by the magnetron 111 is fed into the vacuum drying chamber 100 through the microwave waveguide 112. The vacuum dehumidification unit 120 is connected to the vacuum drying chamber 100 via a pipe interface. This system includes a vacuum pump assembly and a vacuum regulating valve, used to establish and maintain a negative pressure environment within the chamber, while also removing water vapor generated by the evaporation of the material.

[0025] The pneumatic excitation unit 130 is connected to the vacuum drying chamber 100 via an independent gas path interface. This pneumatic excitation unit 130 includes a gas source 131, an electromagnetic proportional valve 132, and a diaphragm pressure gauge 133. The gas source 131 provides nitrogen or dry air as the working medium. The electromagnetic proportional valve 132 is located on the inlet pipe and, controlled by the main control unit 150, injects gas into the vacuum drying chamber 100 in a pulsed manner, thereby generating controllable pressure disturbances within the chamber. The diaphragm pressure gauge 133 is used to acquire the transient absolute pressure signal within the vacuum drying chamber 100 in real time.

[0026] The pneumatic impedance matching unit 140 is physically installed at the coupling port on the side wall of the microwave waveguide 112 or at the terminal load location. This pneumatic impedance matching unit 140 includes a bellows assembly, an absorbing wedge, and a return spring. The inner cavity of the bellows assembly is connected to the atmospheric environment or a constant pressure reference chamber, while its outer wall is placed in the negative pressure environment of the vacuum drying chamber 100, thereby utilizing the internal and external pressure difference to generate an axial driving force. The absorbing wedge is made of silicon carbide ceramic or a polytetrafluoroethylene cone coated with absorbing material, and is mechanically connected to the movable end of the bellows assembly. The return spring provides a reverse elastic restoring force. Under the action of the pressure difference, the absorbing wedge can perform linear reciprocating motion relative to the cross-section of the microwave waveguide 112, thereby changing the transmission impedance and energy attenuation within the microwave waveguide 112.

[0027] The main control unit 150 is electrically connected to the microwave generating unit 110, the vacuum dehumidification unit 120, and the pneumatic excitation unit 130, respectively, and is used to perform logic operations and process control.

[0028] Based on the aforementioned hardware architecture, this invention utilizes physical field coupling logic to achieve adaptive system operation. The pressure change within the vacuum drying chamber 100 constitutes the first physical field, namely the fluid pressure field. This fluid pressure field directly acts on the bellows assembly of the pneumatic impedance matching unit 140. When the pressure inside the vacuum drying chamber 100 increases, the internal and external pressure difference acting on the bellows assembly decreases, the spring force of the return spring becomes dominant, driving the absorbing wedge to displace outward and exit the microwave waveguide 112 region, thus reducing microwave transmission loss. Conversely, when the pressure inside the vacuum drying chamber 100 decreases to a high vacuum state, the internal and external pressure difference increases and overcomes the spring force of the return spring, driving the absorbing wedge to displace inward and insert into the microwave waveguide 112 region, absorbing microwave energy and increasing transmission loss. This mechanical displacement alters the electromagnetic field boundary conditions within the microwave waveguide 112, constituting the second physical field, namely the change in the electromagnetic field distribution.

[0029] See attached document Figure 2 This invention provides a method for intelligent optimization of drying parameters for vacuum microwave meat chips, based on the above-mentioned system architecture, and includes the following steps: S1, System Initialization and Baseline Environment Setup: The vacuum dehumidification unit 120 is activated to pump the pressure inside the vacuum drying chamber 100 to a preset baseline value, establishing an initial high-vacuum equilibrium state. In this state, the internal and external pressure difference generated by the high vacuum drives the pneumatic impedance matching unit 140 to the protection position of maximum insertion depth, while the microwave generator unit 110 is activated for preheating. S2, Physical field excitation and hardware linkage response: Based on the initial high vacuum equilibrium state established in step S1, the pneumatic excitation unit 130 is controlled to apply periodic inflation and deflation operations to the vacuum drying chamber 100, and with the passive cooperation of the pneumatic impedance matching unit 140, a dynamically changing pneumatic excitation response field is formed. This pneumatic excitation response field includes periodically fluctuating chamber air pressure and synchronously linearly displaced absorbing wedges, realizing adaptive adjustment of microwave transmission impedance with air pressure; S3, Multidimensional Signal Acquisition and State Parameter Calculation: Real-time acquisition of process data from the aerodynamic excitation response field in step S2, including the transient pressure curve during the pressure recovery phase and the reflected power of the microwave port, and calculation of state decoupling parameters based on the physical model. These state decoupling parameters include at least the transient gas release impedance characterizing the connectivity of the internal pore channels of the meat slice, and the net energy coupling factor characterizing the actual energy absorption efficiency of the meat slice after removing hardware losses. S4, Phase Change Feature Identification and Staged Intelligent Control: The state decoupling parameters calculated in real time in step S3 are input into the preset decision logic of the main control unit 150 to identify the current physical stage of drying of the meat slices (constant-rate dehydration, puffing and shaping, or drying endpoint), and a drying stage control command is generated accordingly. This drying stage control command is used to dynamically adjust the operating frequency of the pneumatic excitation unit 130 or trigger the negative pressure shaping mode until the drying is determined to be complete.

[0030] To more clearly illustrate the technical details, physical model construction, and specific control strategies of each step in this invention, the key aspects of the above process will be described in detail below.

[0031] The pneumatic impedance matching unit 140, as a physical adjustment component in the microwave transmission link, is installed at the coupling port on the side wall of the microwave waveguide 112 in the microwave generating unit 110. Its main structure includes a bellows assembly, an absorbing wedge, and a return spring. The bellows assembly is made of stainless steel or Inconel alloy and is hermetically fixed to the side wall opening of the microwave waveguide 112 via a flange, forming a local boundary of the vacuum drying chamber 100.

[0032] The bellows assembly physically isolates the atmospheric pressure environment into two regions: the inner cavity of the bellows assembly is connected to the external atmosphere through vents, maintaining a constant reference pressure; the outer wall of the bellows assembly is directly exposed to the negative pressure environment of the vacuum drying chamber 100. An absorbing wedge is rigidly connected to the blind end of the bellows assembly on the vacuum side and extends coaxially to pass through the side wall opening of the microwave waveguide 112 and enter the waveguide interior. The absorbing wedge is made of silicon carbide ceramic sintered body or polytetrafluoroethylene body doped with carbon powder, and its geometry is conical or wedge-shaped to form a gradually changing impedance when inserted into the microwave waveguide 112. A return spring is coaxially disposed on the outside of the bellows assembly, with its two ends abutting against the fixed base and the movable end of the bellows assembly, respectively, to provide an elastic restoring force opposite to the direction of the pressure difference driving force.

[0033] During system operation, the insertion depth of the absorbing wedge within the microwave waveguide 112 is directly controlled by the transient gas pressure within the vacuum drying chamber 100. To establish a quantitative relationship for this physical linkage mechanism, this invention uses a pressure differential displacement response formula to calculate the real-time insertion depth of the absorbing wedge. The pressure differential displacement response formula is as follows: ; in: : The absorbing wedge at time The axial displacement extending into the microwave waveguide 112, in meters; The physical travel limit function indicates that the value is 0 when the calculated value within the square brackets is less than 0, and 0 when the calculated value is greater than the maximum design travel. The time value is When the calculated value is between 0 and When the value is between these two values, take the calculated value itself. The maximum allowable insertion depth of the absorbing wedge structure design, in meters; The effective load-bearing area of ​​the bellows assembly is expressed in square meters. The equivalent axial stiffness coefficient of the pneumatic impedance matching unit 140, in Newtons per meter, is the sum of the stiffness coefficient of the return spring and the elastic stiffness of the bellows assembly itself. The external atmospheric pressure connected to the inner cavity of the bellows assembly, measured in Pascals; The transient absolute pressure inside the vacuum drying chamber 100, collected in real time by the membrane pressure gauge 133, is measured in Pascals. : The preload of the return spring in its initial installation position, measured in Newtons.

[0034] Based on the above structure and formula, the pneumatic impedance matching unit 140 automatically switches between two operating states according to the pressure change in the vacuum drying chamber 100. When the vacuum dehumidification unit 120 evacuates the vacuum drying chamber 100 to a reference high vacuum state, the transient absolute pressure... Much less than the external atmospheric pressure The pressure difference generated by the two forces overcomes the preload. Drive the absorbing wedge to move to the maximum insertion depth. At this time, the absorbing wedge is located in the strong electric field region of the microwave waveguide 112, absorbing most of the microwave energy and reducing the port VSWR of the magnetron 111. When the pneumatic excitation unit 130 operates, it causes transient absolute pressure... As the pressure difference decreases, the return spring drives the absorber wedge to retract outwards. This retraction occurs with the axial displacement. As the microwave waveguide 112 is reduced, the microwave transmission channel within it is opened, and microwave energy acts directly on the material.

[0035] See attached document Figure 3 In this invention, the pneumatic excitation unit 130, under the logic control of the main control unit 150, works in conjunction with the vacuum dehumidification unit 120 to perform periodic pneumatic pulse modulation. This process serves both as the power source for driving the pneumatic impedance matching unit 140 to move and as a physical detection method for acquiring the material drying rate characteristics. The specific cyclic excitation control procedure is implemented through the following steps S201 to S204: S201, Establishment and steady-state maintenance of the reference high vacuum environment: The main control unit 150 controls the operation of the vacuum pump group in the vacuum dehumidification unit 120 and adjusts the vacuum regulating valve to its maximum opening until the transient absolute pressure collected by the diaphragm pressure gauge 133 is reached. Stabilize at the preset reference pressure In one specific embodiment, the reference pressure The pressure is set from 100 Pascal to 1000 Pascal to ensure that the pneumatic impedance matching unit 140 overcomes the internal elasticity and remains at the maximum insertion depth under this pressure condition.

[0036] S202, Pulse-type gas charging excitation trigger: While maintaining continuous pumping by the vacuum pump unit, the main control unit 150 sends an opening command to the pneumatic excitation unit 130, driving the electromagnetic proportional valve 132 to open. Gas from the gas source 131 is injected into the vacuum drying chamber 100 via pipeline. During this stage, the intake flow rate is greater than the instantaneous pumping volume of the vacuum pump unit, resulting in a transient absolute pressure... It increases linearly over time.

[0037] S203, Peak Pressure Cutoff and Hardware-Linked Response: When transient absolute pressure is detected... Reaching the preset peak excitation pressure At this time, the main control unit 150 closes the electromagnetic proportional valve 132, cutting off the gas injection. Excitation peak pressure Set as reference pressure Five to ten times. During this inflation and pressurization process, the increase in air pressure inside the vacuum drying chamber 100 leads to a decrease in pressure difference. The reset spring in the gas-driven solid variable impedance matching unit 140 pushes the absorbing wedge to move outward and exit the microwave waveguide 112, thus physically realizing the low impedance opening of the microwave transmission channel.

[0038] S204, Exponential Exhaust Recovery and Baseline Decay Characteristic Acquisition: After gas injection stops, the system enters the exhaust recovery phase, where the gas in the vacuum drying chamber 100 is extracted by the vacuum pump unit. To subsequently calculate the moisture release of the material, the system is pre-set with a mathematical model describing the pressure drop under no-load conditions. This invention uses the theoretical vacuum decay formula to calculate the theoretical pressure trajectory of the system under no-material interference. The theoretical vacuum decay formula is: ; in: At any moment The calculated theoretical baseline decay pressure, in Pascals, represents the ideal decreasing trajectory that the chamber pressure should follow in the absence of material release and water vapor interference. The peak excitation pressure at the trigger cutoff moment in step S203, in Pascals; The ultimate equilibrium pressure of the vacuum pump unit under current operating conditions, expressed in Pascals; The effective net pumping speed of the vacuum dehumidification unit 120 for the vacuum drying chamber 100 is expressed in cubic meters per second. This parameter is a function of pressure and is measured by a pre-conducted no-load calibration experiment of the system. : The net free volume of the vacuum drying chamber after deducting the volume of its internal components, in cubic meters; The moment when the electromagnetic proportional valve 132 closes in step S203 is the start time of the exhaust recovery phase, in seconds.

[0039] : using natural constant An exponential function with base 0.

[0040] During the actual drying process, the main control unit 150 will collect the transient absolute pressure in real time from the film pressure gauge 133. The theoretical reference attenuation pressure obtained from the above calculation By comparing the two values, the difference reflects the additional gas load generated by the evaporation of moisture inside the meat slices.

[0041] In this invention, the main control unit 150 utilizes the pressure change process generated by the pneumatic excitation unit 130 and the feedback signal from the microwave generator unit 110 to calculate state parameters characterizing the internal moisture migration properties of the meat slice material through synchronous acquisition and algorithm processing. The specific signal acquisition and decoupling calculation process is implemented through the following steps S301 to S303: S301, Time-domain synchronous acquisition of multi-dimensional physical field signals: During the exhaust recovery phase of step S204, the main control unit 150 synchronously triggers signal acquisition at a sampling frequency of not less than 100Hz. The first-dimensional signal is the transient absolute pressure output by the thin-film pressure gauge 133. The second-dimensional signal is the microwave reflected power fed back by the directional coupler located at the port of microwave waveguide 112 in the microwave generator unit 110. The system timestamps the two acquired signal sequences to ensure that the pressure value at each moment corresponds strictly to the microwave reflection state physically.

[0042] S302, Calculation of transient gas release impedance based on effective pumping speed deviation: The main control unit 150 uses the deviation between the actual collected pressure curve and the theoretical reference attenuation curve calculated in step S204 to calculate the impact of moisture evaporation of the meat slices on the load of the vacuum system. This invention introduces the physical quantity of "transient gas release impedance" to quantify the obstruction effect of the internal pore channels of the meat slices on water vapor escape. The system uses the transient gas release impedance calculation formula for real-time calculation. The transient gas release impedance calculation formula is as follows: ; in: At any moment Transient gas release impedance, in seconds per cubic meter ( This value represents the equivalent resistance required to expel a unit volume of water vapor from the inside of the meat slice.

[0043] The transient absolute pressure, measured in Pascals, is acquired in real time by the 133-membrane pressure gauge. In this physical model, this pressure value represents the total potential energy driving the gas out of the vessel.

[0044] The theoretical reference decay pressure is calculated based on the theoretical vacuum decay formula in step S204, and the unit is Pascal.

[0045] The effective net pumping speed of the vacuum dehumidification unit 120 for the vacuum drying chamber 100 is expressed in cubic meters per second.

[0046] : Pressure deviation caused by moisture evaporation from meat slices, in Pascals.

[0047] This combination item indicates the time of the meat slices. The equivalent gas flux load produced is expressed in Pascals per cubic meter per second (Pa). ).

[0048] The calculation compensation constant is set to prevent the denominator from being zero, and its value is [value missing]. .

[0049] S303, Net energy coupling factor decoupling calculation excluding hardware losses: Due to the absorbing wedge in the aerodynamic impedance matching unit 140, the transient absolute pressure will affect the net energy coupling factor decoupling calculation. The position of the meat slice within the microwave waveguide 112 changes with the temperature, and the microwave energy it absorbs is dynamically varying. To obtain the effective energy actually absorbed by the meat slice, the system needs to eliminate this hardware loss. The main control unit 150 first determines the effective energy based on the transient absolute pressure. The real-time axial displacement of the absorbing wedge was calculated using the differential pressure displacement response formula described above. Then, the net energy coupling factor decoupling formula is used for calculation. The net energy coupling factor decoupling formula is as follows: ; in: At any moment The net energy coupling factor is a dimensionless value (between 0 and 1). This parameter characterizes the actual microwave energy efficiency coupled to the meat slice material after deducting system hardware losses.

[0050] Microwave reflected power fed back by microwave generator unit 110, in watts.

[0051] The positive microwave output power set by the magnetron 111 in the microwave generator unit 110 is expressed in watts.

[0052] The axial displacement of the absorbing wedge block, calculated according to the pressure difference displacement response formula, is expressed in meters.

[0053] The inherent loss function of the hardware represents the loss of the absorbing wedge when its displacement is... The energy absorption rate (dimensionless) at that time. This functional relationship is pre-calibrated and stored by the system: under the no-load state of the vacuum drying chamber 100, the absorbing wedge is adjusted by adjusting the air pressure to traverse all displacement positions, and the corresponding energy absorption rate is recorded and fitted.

[0054] The main control unit 150 determines the transient gas release impedance based on the decoupling obtained in step S3. and net energy coupling factor Two state parameters divide the drying process into three logical stages: constant-rate dehydration, expansion and shaping, and endpoint determination. Feedback control of the drying process is achieved by dynamically adjusting the action parameters of the pneumatic excitation unit 130. The specific control strategy is implemented through the following steps S401 to S403: S401, pneumatic mechanical pulse-width modulation heating for constant-rate dehydration: In the initial drying stage, the internal moisture content of the meat slices is high, at which point the net energy coupling factor... Maintaining a high level. The main control unit 150 adjusts the cycle of the air pressure pulse within the vacuum drying chamber 100 by controlling the opening frequency and duration of the electromagnetic proportional valve 132. Since the mechanical action of the pneumatic impedance matching unit 140 is directly controlled by the ambient air pressure, the periodic fluctuations in air pressure drive the absorbing wedge to reciprocate within the microwave waveguide 112, thereby forming the conduction and blocking of the microwave transmission channel. When the air pressure increases, the absorbing wedge exits the waveguide, and microwave energy is transmitted to the material; when the air pressure decreases, the absorbing wedge inserts into the waveguide, and microwave energy is absorbed and cut off. This invention uses an effective heating duty cycle formula to calculate and control the actual energy density acting on the meat slices. The effective heating duty cycle formula is: ; in: The pneumatic modulation duty cycle is a dimensionless value (between 0 and 1). This parameter reflects the proportion of time during which microwave energy is effectively radiated to the material within a single control cycle. The total cycle time of one inflation and deflation cycle performed by the pneumatic excitation unit 130 is in seconds. The start time of the current control cycle, in seconds; Heaviside step function. The function takes a value of 1 when the value within the parentheses is greater than 0, and a value of 0 otherwise. It is used here to count the effective time the microwave channel is in the conducting state. : Preset microwave transmission threshold displacement, in meters. When the axial displacement... When the value is less than this threshold, the system determines that the absorbing wedge has left the affected area and the microwave channel is in the conducting state. The real-time axial displacement of the absorbing wedge block, calculated according to the differential pressure displacement response formula, is expressed in meters.

[0055] The time differential variable in integral operations; The integral symbol indicates cumulative calculations over a specified time interval.

[0056] The main control unit 150 monitors the net energy coupling factor in real time. When its value decreases as moisture content decreases, the system automatically extends the total cycle time. Alternatively, shorten the inflation phase to reduce the pneumatic modulation duty cycle. This prevents the meat slices from overheating or burning due to a decrease in their energy absorption capacity.

[0057] S402, Second Derivative Identification of the Puffing Critical Point and Negative Pressure Shaping Control: As the drying process proceeds, the surface of the meat slices gradually hardens to form a hard shell, hindering the outward diffusion of internal moisture and resulting in transient gas release resistance. It exhibits non-linear growth. When the accumulated vapor pressure inside the meat slice approaches the yield limit of the tissue structure, the puffing critical point is reached. The main control unit 150 continuously collects transient gas release impedance data. Discrete second-order differential operations are performed, and the critical state is identified using the puffing trigger criterion formula, which is as follows: ; in: :time The characteristic value of the impedance change curvature, in Pascals per second per cubic meter per square second (Pa·s / (m)). 3 ·s 2 This value quantifies the acceleration characteristic of changes in resistance to water release; , , : These are the transient gas release impedances calculated at the current time, the previous sampling time, and the sampling time before that, respectively; The time interval for signal sampling, in seconds; Preset puffing threshold, unit same This threshold is preset based on the texture characteristics of the meat slices and is used to indicate the inflection point of surface hardening layer formation.

[0058] once If the above criteria are met, the main control unit 150 immediately stops the gas injection operation of the pneumatic excitation unit 130 and instructs the vacuum dehumidification unit 120 to run at full speed to reduce the transient absolute pressure in the vacuum drying chamber 100. The pressure is rapidly reduced and maintained at an ultimate vacuum. During this process, due to the increased pressure difference, the absorbing wedge is fully inserted into the microwave waveguide 112, cutting off the microwave energy input. At this time, the meat slice utilizes the pressure difference between the high-temperature, high-pressure vapor accumulated inside and the deep vacuum environment outside the cavity to achieve rapid volume expansion and physical shaping of the porous structure.

[0059] S403, Drying endpoint determination based on impedance zeroing and energy consumption threshold: After the negative pressure setting stage, the system continues to monitor the status using a low-frequency gas pressure probe. When the main control unit 150 detects transient gas release impedance... continuous The residual moisture impedance was below the preset lower limit for each cycle, and the net energy coupling factor was also detected simultaneously. When the energy consumption drops below the preset ineffective energy consumption threshold, the drying process is considered complete. The main control unit 150 then cuts off the power supply to the microwave generator unit 110 and controls the vacuum regulating valve to slowly release the vacuum, preventing the finished product from breaking due to sudden pressure changes and achieving a safe shutdown.

Claims

1. A smart optimization system for vacuum microwave meat crisp drying parameters, characterized in that, include: The vacuum drying chamber (100) forms a closed processing space for containing the meat slices to be dried. A microwave generating unit (110) is coupled to the vacuum drying chamber (100) to feed microwave energy; A vacuum dehumidification unit (120) is used to establish a negative pressure environment within the vacuum drying chamber (100) and remove water vapor; A pneumatic excitation unit (130) is used to perform a filling and degassing operation within the vacuum drying chamber (100) to construct a dynamically changing pneumatic excitation response field; A pneumatic impedance matching unit (140) is physically mounted on the microwave generating unit (110) and generates a hardware linkage response based on the pressure difference change in the pneumatic excitation response field, and adaptively adjusts the transmission impedance through mechanical displacement. The main control unit (150) is electrically connected to each unit and is used to control the operation of the pneumatic excitation unit (130), calculate the state decoupling parameters based on the physical quantity feedback under the pneumatic excitation response field, and then generate instructions based on the state decoupling parameters to coordinate the operation of each unit.

2. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 1, characterized in that, The microwave generating unit (110) includes a magnetron (111) and a microwave waveguide (112), and the microwave energy generated by the magnetron (111) is transmitted through the microwave waveguide (112); The aerodynamic impedance matching unit (140) is installed at the coupling port on the side wall of the microwave waveguide (112) and can perform linear reciprocating motion relative to the cross section of the microwave waveguide (112).

3. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 2, characterized in that, The pneumatic actuation unit (130) includes: Gas source (131), which is used to provide the working medium; An electromagnetic proportional valve (132), which is installed on the intake pipe and controlled by the main control unit (150), injects gas into the vacuum drying chamber (100); A thin-film pressure gauge (133) is used to collect the transient absolute pressure inside the vacuum drying chamber (100) in real time.

4. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 3, characterized in that, The pneumatic impedance matching unit (140) includes: The bellows assembly is hermetically fixed to the side wall of the microwave waveguide (112) with a flange. The inner cavity of the bellows assembly is connected to the atmospheric environment or the constant pressure reference cavity, and the outer wall is placed in the negative pressure environment of the vacuum drying cavity (100). A microwave absorbing wedge is mechanically connected to the movable end of the bellows assembly and extends into the microwave waveguide (112); A return spring is used to provide an elastic restoring force opposite to the direction of the driving force of the internal and external pressure difference; When the air pressure inside the vacuum drying chamber (100) increases, the reset spring drives the absorbing wedge to retract from the microwave waveguide (112); when the air pressure decreases, the pressure difference drives the absorbing wedge to insert into the microwave waveguide (112).

5. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 4, characterized in that, The main control unit (150) executes the following logic: The transient absolute pressure collected in real time by the membrane pressure gauge (133) is obtained; The transient absolute pressure is input into the system's preset differential pressure displacement response formula, and the real-time axial displacement of the absorbing wedge inside the microwave waveguide (112) is calculated.

6. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 5, characterized in that, The main control unit (150) executes the following logic: The electromagnetic proportional valve (132) is controlled to open to perform inflation excitation, and after reaching the preset peak value, the electromagnetic proportional valve (132) is closed to enter the exhaust recovery stage; The theoretical baseline decay pressure trajectory of the vacuum drying chamber (100) under the condition of no material interference during the exhaust recovery stage is calculated using the theoretical vacuum decay formula.

7. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 6, characterized in that, The physical quantity feedback includes the transient absolute pressure and microwave reflection power, and the state decoupling parameters include the transient gas release impedance and net energy coupling factor; the main control unit (150) executes the following logic: The transient absolute pressure output by the thin-film pressure gauge (133) and the microwave reflection power fed back by the microwave generating unit (110) are simultaneously acquired. The transient gas release impedance is obtained by substituting the deviation between the transient absolute pressure and the theoretical reference decay pressure trajectory into the transient gas release impedance calculation formula. The net energy coupling factor is obtained by substituting the microwave reflection power and the hardware loss determined based on the real-time axial displacement into the net energy coupling factor decoupling formula.

8. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 7, characterized in that, The drying stage control commands include pulse modulation commands for the constant-rate dehydration stage; the main control unit (150) executes the following logic: The energy density actually acting on the meat slice material is calculated by combining the effective heating duty cycle formula with the real-time axial displacement. Monitor the real-time numerical changes of the net energy coupling factor; The pulse modulation command is generated based on the change of the net energy coupling factor, and the inflation and deflation cycle of the pneumatic excitation unit (130) is dynamically adjusted.

9. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 7, characterized in that, The drying stage control commands include negative pressure maintenance commands for the puffing and shaping stage; the main control unit (150) executes the following logic: The transient gas release impedance is subjected to a second-order differential operation to obtain the impedance change curvature characteristics; The impedance change curvature feature is input into the expansion trigger criterion formula to identify the expansion critical point; When the expansion critical point is detected, the negative pressure holding command is generated, triggering the pneumatic excitation unit (130) to stop the gas injection and control the vacuum dehumidification unit (120) to maintain the ultimate vacuum; The puffing triggering criterion formula includes a puffing critical threshold, which is a preset value indicating the inflection point of the hardened layer on the surface of the meat slice.

10. The intelligent optimization system for vacuum microwave meat crisp drying parameters according to claim 7, characterized in that, The drying stage control commands include a stop command for the drying endpoint; the main control unit (150) executes the following logic: Monitor whether the transient gas release impedance is continuously lower than the residual moisture impedance lower limit for a preset period of time; Simultaneously monitor whether the net energy coupling factor is lower than the ineffective energy consumption threshold; When both of the above monitoring conditions are met simultaneously, the shutdown command is generated to cut off the power supply to the microwave generator unit (110); Wherein, the residual moisture impedance lower limit is a preset impedance value characterizing when the meat slices reach the drying endpoint, and the ineffective energy consumption threshold is a preset efficiency value characterizing when the meat slices no longer effectively absorb microwave energy.

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