Linear cooling control method and environmental test box

Abstract

The invention discloses a linear cooling control method and an environmental test chamber, and the method comprises the steps: determining the initial temperature and the final temperature of linear cooling, respectively recording the initial temperature and the final temperature as Ts and Te, dividing a linear cooling interval corresponding to the initial temperature and the final temperature into n equal parts, and determining the initial temperature and the final temperature corresponding to the ith equal part, respectively recording the initial temperature and the final temperature as (T0) i and (Tsv) i; determining a segmented gain coefficient corresponding to the ith equal division interval by adopting a closed-loop control equation, and constructing an error equation corresponding to the closed-loop control equation by adopting at least one of Ts, Te, (T0) i and (Tsv) i and a measured value of a preset parameter; and determining a control quantity increment, and determining a target control quantity at least by using the segmented gain coefficient and the control quantity increment.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of automatic control technology, and in particular to a linear temperature reduction control method and an environmental test chamber. Background Art

[0002] During linear cooling, as the temperature drops, the cooling capacity demand increases. Furthermore, as the temperature drops, the evaporation temperature also needs to decrease. When the condensing temperature remains constant, the compressor's cooling capacity decreases as the evaporation temperature drops. Therefore, the compressor's capacity varies significantly from the beginning to the end of linear cooling.

[0003] Currently, fixed-frequency compressors are mostly used for linear cooling. Compressor selection is based on the maximum cooling capacity required during the linear cooling process, which results in high overall compressor energy consumption during the linear cooling process. Furthermore, the cooling capacity during the linear cooling process varies significantly, making the control of the evaporator and condenser fans crucial. Low air volume can affect system reliability and cooling performance, while high air volume can reduce energy efficiency.

[0004] In summary, there is an urgent need for a linear cooling control method to optimize the control and operation of the refrigeration system, improve the operational reliability of the refrigeration system, and reduce the operating energy consumption of the refrigeration system. Summary of the Invention

[0005] The present invention provides a linear temperature reduction control method and an environmental test chamber to achieve the purpose of solving at least one defect existing in the prior art.

[0006] In a first aspect, an embodiment of the present invention provides a linear temperature reduction control method, comprising:

[0007] Determine the starting temperature and ending temperature of linear cooling, which are respectively recorded as T s 、T e , divide the linear cooling interval corresponding to the starting temperature and the ending temperature into n equal parts, determine the starting temperature and the ending temperature corresponding to the i-th equal part, and record them as (T0) i 、(T sv ) i ;

[0008] The closed-loop control equation is used to determine the segment gain coefficient corresponding to the i-th equally divided interval, and T s 、T e , (T0) i 、(T sv ) i and a measurement value of a preset parameter to construct an error equation corresponding to the closed-loop control equation;

[0009] Determining a control amount increment, at least using the segmented gain coefficient and the control amount increment to determine a target control amount;

[0010] The control amount increment represents a preset fixed step length between the maximum value and the minimum value of the control amount, and the preset fixed step length corresponds to the control accuracy of the control amount;

[0011] The segmented gain coefficient represents an adjustment value corresponding to the control variable calculated by the closed-loop control equation under the error determined by the error equation;

[0012] The target control amount represents a target value of the control amount in each of the equally divided intervals.

[0013] Optionally, the control variable includes the speed of the compressor;

[0014] The preset parameters include the temperature in the environmental test chamber.

[0015] Optionally, the error equation is:

[0016]

[0017] Where τ represents the time constant, T represents the measured value of the temperature in the environmental test chamber, and e1(τ) i Indicates the error corresponding to the compressor speed.

[0018] Optionally, the control variable includes the valve step opening of the expansion valve;

[0019] The preset parameters include the temperature in the environmental test chamber.

[0020] Optionally, the error equation is:

[0021]

[0022] Where τ represents the time constant, T represents the measured value of the temperature in the environmental test chamber, t represents the total cooling time, and e2(τ) i Indicates the error corresponding to the compressor speed.

[0023] Optionally, the controlled variable includes the speed of the evaporating fan;

[0024] The preset parameters include the evaporator air outlet temperature and the evaporator overheat temperature.

[0025] Optionally, the error equation is:

[0026]

[0027] Where τ represents the time constant, (T9) i represents the measured value of the outlet air temperature of the i-th evaporator, SHi represents the measured value of the superheat temperature of the i-th evaporator, e3(τ) i Indicates the error corresponding to the evaporation fan speed.

[0028] Optionally, the controlled variable includes the condenser fan speed;

[0029] The preset parameters include compressor exhaust pressure and condenser subcooling.

[0030] Optionally, the error equation is:

[0031]

[0032] Where τ represents the time constant, HP i represents the measured value of the discharge pressure of the i-th compressor, SC i represents the measured value of the subcooling degree of the i-th condenser, e4(τ) i Indicates the error corresponding to the condenser fan speed.

[0033] In a second aspect, an embodiment of the present invention further provides an environmental test chamber, comprising a controller, wherein the controller executes any one of the linear temperature reduction control methods described in this embodiment.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention proposes a linear cooling control method, in which the cooling interval is divided into n equally divided intervals, and the control parameters of each interval are dynamically adjusted according to the starting temperature and the ending temperature, so as to avoid over-adjustment or under-adjustment of the traditional linear control during the control process, thereby ensuring the control stability of the linear cooling while reducing the energy consumption of the refrigeration system. By adjusting the number of segments and the fixed step size, different refrigeration requirements can be adapted. The control target quantity is determined based on the segmented gain coefficient and the fixed control quantity increment (fixed step size). The segmented gain coefficient is dynamically calculated based on the error equation. The combination of the fixed step size and the segmented gain makes the control curve in the linear cooling process smoother, thereby improving the reliability of the system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flow chart of the linear temperature reduction control method in the embodiment;

[0036] Figure 2 is a structural block diagram of a refrigeration system in an embodiment;

[0037] Figure 3 This is another flow chart of a linear temperature reduction control method in an embodiment. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0039] Example 1

[0040] Figure 1 This is a flow chart of the linear cooling control method in the embodiment, refer to Figure 1 , linear cooling control methods include:

[0041] S101. Divide the linear cooling interval corresponding to the starting temperature and the ending temperature into n equal parts.

[0042] In this solution, the linear cooling control method is used to control the refrigeration system to perform linear cooling. The refrigeration system can be integrated with a designated device (such as an environmental test chamber) or set up independently.

[0043] Figure 2 This is a block diagram of the refrigeration system in the embodiment, refer to Figure 2 For example, the refrigeration system may include a variable frequency compressor 2, a condenser 3, an electronic expansion valve 5, and an evaporator 6, and the variable frequency compressor 2, the condenser 3, the electronic expansion valve 5, and the evaporator 6 constitute a refrigeration circuit.

[0044] The variable frequency compressor 2 is equipped with a compressor suction pressure sensor 10 and a compressor exhaust pressure sensor 11; the condenser 3 is equipped with a condenser fan 4 and a condenser liquid supply temperature sensor 12; the evaporator 6 is equipped with an evaporator fan 7, an evaporator outlet temperature sensor 8, and an evaporator outlet air temperature sensor 9.

[0045] In this solution, a compressor speed control module 14, an evaporator fan speed control module 13, an electronic expansion valve opening control module 15, and a condenser fan speed control module 16 may be configured as control units of the refrigeration system.

[0046] In this solution, the control unit may be configured to include an acquisition and calculation control module 17 , and the temperature sensor 1 may be configured to be connected to the acquisition and calculation control module 17 .

[0047] For example, in this embodiment, the variable frequency compressor 2 is used to compress and transport refrigerant vapor. It draws low-temperature, low-pressure refrigerant vapor from the evaporator 6, compresses it into high-temperature, high-pressure refrigerant vapor by performing work, and then discharges it into the condenser 3.

[0048] The condenser 3 is used to cool and condense the high-temperature and high-pressure refrigerant vapor discharged from the variable frequency compressor 2 into liquid. In this process, the refrigerant releases heat to the external environment.

[0049] The condenser fan 4 is used to accelerate the air flow so that the air absorbs the heat emitted by the condenser 3 more quickly, thereby improving the heat dissipation efficiency.

[0050] The evaporator 6 is used to allow the low-temperature, low-pressure liquid refrigerant to evaporate and absorb heat therein, thereby lowering the ambient temperature and achieving the purpose of refrigeration. The refrigerant in the evaporator absorbs heat from the object or space being cooled during the evaporation process, causing its temperature to drop.

[0051] The evaporator fan 7 is used to circulate the air in the designated space and blow it across the surface of the evaporator 6, so that the air is cooled and then sent back to the above space to achieve cooling.

[0052] The main function of the electronic expansion valve 5 is to throttle and reduce the pressure of the normal temperature and high pressure liquid refrigerant coming out of the condenser 3, turning it into a low temperature and low pressure liquid refrigerant, which then enters the evaporator 6 to evaporate and absorb heat. At the same time, it can also be used to adjust the refrigerant flow rate to ensure the cooling effect of the evaporator 6 and the stable operation of the system.

[0053] In this solution, the refrigeration system achieves refrigeration through the circulation of refrigerant in the system through four processes: compression, condensation, throttling, and evaporation.

[0054] The variable frequency compressor 2 sucks in and compresses the low-temperature, low-pressure refrigerant vapor from the evaporator 6 , converting it into high-temperature, high-pressure vapor, and sends it to the condenser 3 .

[0055] In the condenser 3 , the high-temperature and high-pressure refrigerant vapor is cooled by the air (or cooling water) blown in by the condenser fan 4 , and condenses into a high-pressure and room-temperature liquid refrigerant after releasing heat.

[0056] When the high-pressure liquid refrigerant flows through the electronic expansion valve 5 , it is throttled and reduced in pressure to become a low-temperature and low-pressure gas-liquid two-phase mixture, and then enters the evaporator 6 .

[0057] In the evaporator 6, the low-temperature, low-pressure liquid refrigerant absorbs the surrounding heat and evaporates into low-temperature, low-pressure steam, which reduces the ambient temperature. The evaporated refrigerant steam is then sucked into the variable frequency compressor 2 to start the next cycle.

[0058] Illustratively, in this solution, the compressor speed control module 14 is connected to the variable frequency compressor 2 , and the compressor speed control module 14 can be configured to control the compressor speed of the variable frequency compressor 2 .

[0059] The electronic expansion valve opening control module 15 is connected to the electronic expansion valve 5 , and the electronic expansion valve opening control module 15 is configured to control the expansion valve step opening of the electronic expansion valve 5 .

[0060] The evaporator fan speed control module 13 is connected to the evaporator fan 7 , and the evaporator fan speed control module 13 is configured to control the evaporation fan speed of the evaporator fan 7 .

[0061] The condenser fan speed control module 16 is connected to the condenser fan 4 , and the condenser fan speed control module 16 is configured to control the condenser fan speed of the condenser fan 4 .

[0062] For example, in this solution, by controlling the compressor speed, the expansion valve opening, the evaporator fan speed, and the condenser fan speed, the refrigeration system can be controlled to perform linear cooling.

[0063] For example, in this solution, the starting temperature and the ending temperature of the linear cooling are determined and are respectively recorded as T s 、T e , divide the linear cooling interval corresponding to the starting temperature and the ending temperature into n equal parts, and record the total cooling time as t.

[0064] In this scheme, the starting temperature and ending temperature corresponding to the i-th equal division interval are determined and recorded as (T0) i 、(T sv ) i .

[0065] Exemplarily, in this embodiment, (T0) i 、(T sv ) i They can be determined according to the following formula:

[0066]

[0067] For example, in this solution, the specific value of n can be determined by the desired control accuracy, and the control accuracy can be determined according to the performance of the refrigeration system.

[0068] S102. Use a closed-loop control equation to determine the segment gain coefficient corresponding to the i-th equally divided interval.

[0069] For example, in this solution, the closed-loop control equation may adopt a PID control equation, an incremental control equation, etc. Taking the PID control equation as an example, the closed-loop control equation may be in the form of:

[0070]

[0071] Where K p , K i , K d represents the PID control coefficient, e represents the feedback error, and u represents the control amount.

[0072] In this scheme, the segmented gain coefficient corresponding to each equally divided interval is determined by the closed-loop control equation. The segmented gain coefficient is different from the control quantity. The segmented gain coefficient represents the adjustment value of the corresponding control quantity calculated by the closed-loop control equation under the error determined by the error equation.

[0073] In this solution, the segmented gain coefficient is a dynamic adjustment parameter based on the divided linear cooling equal zones. In each equal zone, the segmented gain coefficient that adapts to the needs of that stage needs to be calculated.

[0074] During linear cooling, demand parameters (such as cooling capacity, evaporating temperature, and condensing pressure) vary significantly across temperature ranges. The segmented gain factor dynamically adjusts the corresponding control variables (such as compressor and fan speeds) to precisely match the cooling capacity of the refrigeration system within each equally spaced range to the demand, reducing inefficient power consumption and preventing system fluctuations caused by insufficient cooling capacity.

[0075] Existing technologies, which adjust control variables using fixed PID parameters, are unable to adapt to varying cooling demands at different stages. Traditional PID control can result in high energy consumption throughout the cooling cycle, and a mismatch between air volume and cooling capacity and stage demand can lead to system instability.

[0076] In this solution, the linear cooling process is decomposed into n equally divided intervals, and the segmented gain coefficient is calculated independently for each equally divided interval. The segmented gain coefficient is used to dynamically adjust the control quantity, which can solve the problems of high energy consumption, delayed response and poor stability of traditional refrigeration systems during the temperature change process.

[0077] In this scheme, T s 、T e , (T0) i 、(T sv ) i At least one of them and the measured value of the preset parameter are used to construct an error equation corresponding to the closed-loop control equation.

[0078] refer to Figure 2 In this solution, the control quantity can be one or more of the compressor speed, expansion valve step opening, evaporator fan speed, and condenser fan speed, and the preset parameters correspond to the control quantity.

[0079] For example, if the controlled quantity is the evaporator fan speed, the preset parameters can be the evaporator outlet temperature and the evaporator air outlet temperature. The evaporator outlet temperature can be measured by the evaporator outlet temperature sensor 8, and the evaporator air outlet temperature can be measured by the evaporator air outlet temperature sensor 9.

[0080] In this solution, the error equation is used to determine the error that is introduced into the closed-loop control equation.

[0081] Different from the traditional PID control method that uses the difference between the set value and the measured value to determine the error, this solution considers that the entire cooling process is divided into different intervals when constructing the error equation, and compares the measured value of the preset parameter with the T s 、Te , (T0) i 、(T sv ) i In association, the error equation integrates the starting, ending and segmented temperature conditions, and the error calculated by it can reflect the influence of the temperature of each equal interval on the control quantity.

[0082] By combining the temperature range of each equally divided interval with the calculated error, the error can better meet the control requirements of the linear cooling process. This satisfies the cooling needs of different stages, matches the control quantity with the characteristics of the refrigeration system, and makes the refrigeration control more accurately adaptable to each stage.

[0083] For example, in this solution, the specific form of the error equation is not limited, and it can be a nonlinear function, and its specific form can be determined through simulation experiments and the like.

[0084] S103. Determine the control amount increment, and determine the target control amount using at least the segmented gain coefficient and the control amount increment.

[0085] In this solution, the control amount increment represents a preset fixed step length between the maximum value and the minimum value of the control amount, and the preset fixed step length corresponds to the control accuracy of the control amount.

[0086] For example, in this solution, the preset fixed step size reflects the control accuracy of the control variable. The smaller the step size, the more finely the compressor speed can be adjusted, and the higher the control accuracy.

[0087] Taking the control quantity as the compressor speed as an example, if the preset fixed step size is 10r / min, the speed can change at intervals of 10r / min, and the actual speed may deviate from the ideal speed by a maximum of 10r / min; if the step size is 1r / min, the speed adjustment is more precise, and the deviation between the actual speed and the ideal speed may be up to 1r / min, which can more accurately meet the system's demand for cooling capacity.

[0088] In this solution, the preset fixed step size can be determined through experience, simulation tests, etc., or (taking the compressor speed as an example) can be determined by the following formula:

[0089]

[0090] In the above formula, Δf represents the preset fixed step size (control amount increment) corresponding to the compressor speed, F max is the maximum value of the compressor speed, F min is the minimum value of the compressor speed, and M is an integer (determines the control accuracy).

[0091] In this solution, the target control variable represents the target value of the control variable in each equally divided interval. For example, if the control variable is the evaporator fan speed, the target control variable is the target speed of the evaporator fan.

[0092] Exemplarily, in this solution, the target control quantity can be calculated using a preset function, for example, the product of the segmented gain coefficient and the control quantity increment is used as the target control quantity; or, the target control quantity can be calculated using neural networks, fuzzy logic, etc.

[0093] For example, in this solution, after the target control amount is determined, there is no specific limitation on the control method of the control amount, which can be freely selected according to needs.

[0094] This embodiment proposes a linear cooling control method. In this method, the cooling interval is divided into n equal intervals. The control parameters of each interval are dynamically adjusted according to the starting temperature and the ending temperature, thereby avoiding over-adjustment or under-adjustment of traditional linear control during the control process. This can ensure the control stability of linear cooling while reducing the energy consumption of the refrigeration system. By adjusting the number of segments and the fixed step size, different cooling needs can be adapted. The control target quantity is determined based on the segmented gain coefficient and the fixed control quantity increment (fixed step size). The segmented gain coefficient is dynamically calculated based on the error equation. The combination of the fixed step size and the segmented gain makes the control curve smoother during the linear cooling process, thereby improving the reliability of the system operation.

[0095] Based on any of the foregoing solutions, in one possible implementation scheme, the controlled variable includes the speed of the compressor; and the preset parameter includes the temperature in the environmental test chamber.

[0096] In this solution, the refrigeration system is set to linearly control the temperature in the environmental test chamber. Figure 2 , the temperature sensor 1 can be used for measuring the temperature in the environmental test chamber.

[0097] For example, in this solution, the error equation corresponding to the compressor speed can be determined as follows:

[0098] By T s 、T e , (T0) i 、(T sv ) i Construct a nonlinear error term by measuring the temperature and (T0) i 、(T sv ) i Construct a linear error term. Set a nonlinear error term to amplify or reduce the linear error term. This term reflects the nonlinear effect of the temperature of different equal-division intervals on the error calculation results. Set a linear error term to determine the deviation of the temperature measurement from the start and end temperatures of the current equal-division interval.

[0099] For example, in this solution, the nonlinear error term can be specifically an exponential operation of the cooling progress (the ratio of the cooling amplitude to the total amplitude of the stage). The temperature difference in the linear error term is amplified by the nonlinear error term, thereby compensating for the efficiency attenuation of the compressor at low temperatures and avoiding temperature control lag caused by insufficient cooling capacity.

[0100] In this scheme, the relationship between the actual temperature in the test chamber and the stage temperature characteristics is comprehensively reflected through nonlinear error terms and linear error terms, so that the calculation results can more flexibly reflect the characteristics of the system under different temperature conditions, providing a basis for subsequent control strategies (adjusting the compressor speed).

[0101] In one embodiment, when the controlled variable is the compressor speed and the preset parameter includes the temperature in the environmental test chamber, the corresponding error equation is:

[0102]

[0103] Where τ represents the time constant, T represents the measured value of the temperature in the environmental test chamber, and e1(τ) i Indicates the error corresponding to the compressor speed.

[0104] In this solution, by considering the stage temperature characteristics (starting and ending temperatures) and introducing a nonlinear exponential adjustment part, the deviation between the actual temperature and the expected temperature state can be more accurately characterized. Compared with the simple comparison of the actual temperature and the set temperature, the temperature control can be closer to the target value, meeting the high-precision temperature control requirements of the environmental test chamber.

[0105] The nonlinear exponential component adaptively changes the regulation intensity across different temperature ranges or operating conditions. For the same temperature deviation in high and low temperature regions, the exponential component can achieve varying degrees of regulation, ensuring stable system operation under a variety of operating conditions.

[0106] Based on any of the foregoing solutions, in one possible implementation scheme, the controlled variable includes the valve step opening of the expansion valve; and the preset parameter includes the temperature in the environmental test chamber.

[0107] In this solution, the expansion valve step opening represents the valve opening of the electronic expansion valve when it is driven by a stepper motor. The valve opening is measured in steps, and each step corresponds to a fixed flow area.

[0108] For example, in this solution, the error equation corresponding to the expansion valve step opening can be determined as follows:

[0109] Using the temperature in the environmental test chamber, (T0) i 、(T sv ) iConstruct the temperature deviation term and use the temperature in the environmental test chamber, T s 、T e Construct a dynamic correction term and use the temperature deviation term to represent the difference between the temperature measurement value and (T0) i 、(T sv ) i The degree of deviation is determined by the dynamic correction term, which represents the nonlinear correction of the temperature deviation when considering the dynamic characteristics of the system (such as time constant and temperature change rate).

[0110] Exemplarily, in this solution, the dynamic correction term may include the time accumulation of the temperature change rate and the offset of the temperature measurement value from the starting temperature. The time type and offset may constitute a linear combination function, which is then normalized to obtain a nonlinear function.

[0111] In one possible implementation scheme, the controlled variable includes the expansion valve opening, the preset parameter includes the temperature in the environmental test chamber, and the error equation is:

[0112]

[0113] Where τ represents the time constant, T represents the measured value of the temperature in the environmental test chamber, t represents the total cooling time, and e2(τ) i It represents the error corresponding to the compressor speed, and V represents the temperature change rate.

[0114] In this scheme, the error equation comprehensively reflects the actual temperature and the partition temperature characteristics ((T0) i 、(T sv ) i ) and the influence of factors such as the temperature change rate on the deviation. By introducing the time constant τ and V reflecting the temperature change rate, the error equation can adapt to complex working conditions such as different cooling stages and different cooling rates of the environmental test chamber.

[0115] By adjusting the expansion valve opening based on this error equation, the refrigerant flow rate can be better matched to the cooling requirements of the environmental test chamber. This avoids problems such as low cooling efficiency and temperature fluctuations caused by excessive or insufficient refrigerant flow, improves the stability and cooling efficiency of the entire temperature control system, and optimizes overall system performance.

[0116] Based on any of the foregoing solutions, in one possible implementation, the controlled variable includes the evaporator fan speed; the preset parameters include the evaporator air outlet temperature and the evaporator overheat temperature.

[0117] In this solution, the evaporator outlet air temperature refers to the temperature of the air (or refrigerant) leaving the evaporator after heat exchange in the evaporator.

[0118] In this solution, the evaporator superheat temperature refers to the temperature at which the refrigerant continues to absorb heat and rises after it completely evaporates (becomes gaseous) in the evaporator, that is, the difference between the refrigerant gas temperature and the evaporation temperature (saturation temperature).

[0119] In this solution, the error equation is constructed through the dual parameters of the evaporator air outlet temperature and the superheat temperature (superheat degree) to adjust the evaporator fan speed, thereby achieving precise temperature control and energy efficiency optimization of the refrigeration system.

[0120] Specifically, the error equation may include a stage temperature correction term, which uses the overall starting temperature and ending temperature to reflect the progress of the current equal-division interval in the total cooling process, and is configured to automatically adjust the control intensity according to the equal-division interval.

[0121] The error equation can also include an outlet air temperature trend correction term, which is configured to predict the trend of heat exchange based on the difference between the evaporator outlet air temperature and the starting temperature in adjacent stages, and dynamically adjust the fan speed (for example, increase the speed to enhance heat exchange when the heat exchange decreases).

[0122] The error equation may also include a superheat response correction term, which is configured to increase the speed of the evaporator fan to accelerate evaporation when the superheat of the evaporator fan is low, thereby ensuring the safety of the refrigeration system.

[0123] In this solution, the stage temperature correction term, the outlet temperature trend correction term, and the superheat response correction term can form a nonlinear combination function to form an error equation.

[0124] In this solution, the dual parameters of evaporator outlet air temperature and superheat are integrated, combined with segmented temperature correction and trend prediction, which can significantly improve energy efficiency and adaptability to working conditions while ensuring temperature control accuracy and equipment safety.

[0125] In one possible implementation scheme, the controlled variable includes the evaporator fan speed; the preset parameters include the evaporator outlet air temperature and the evaporator superheat temperature. Based on this scheme, the error equation is:

[0126]

[0127] Where τ represents the time constant, (T9) i represents the measured value of the outlet air temperature of the i-th evaporator, SH i represents the measured value of the superheat temperature of the i-th evaporator, e3(τ) i Indicates the error corresponding to the evaporation fan speed.

[0128] In this scheme, the error equation comprehensively reflects the temperature state and dynamic characteristics of the refrigeration system through exponential functions and radical operations, providing a nonlinear error signal for the evaporating fan speed regulation.

[0129] In this scheme, the first term of the error equation reflects the relative relationship between the final temperature of the current partition and the starting temperature and final temperature of the overall linear cooling. sv ) i Close to T s , the error response tends to be gentle, avoiding over-adjustment in the high temperature section. If (T sv ) i Close to T e , the error is amplified, and the evaporator fan responds quickly to control requirements.

[0130] In this solution, the second term of the error equation reflects the heat transfer trend of the evaporator. This term can indicate the need to increase or decrease the evaporator fan speed. For example, when the calculated value of this term is greater than 1, it can indicate that the temperature difference is getting larger (the cooling capacity provided is reduced, resulting in poor heat transfer), and the evaporator fan speed should be appropriately increased.

[0131] In this solution, the third phase of the error equation reflects the vaporization state of the refrigerant. When the evaporator superheat temperature decreases, the value of this item increases, and the evaporator fan speed needs to be increased to accelerate the evaporator heat exchange to evaporate the liquid refrigerant. When the evaporator superheat temperature is maintained in a safe range (for example, 5 to 8°C), the normal evaporator fan speed control force is maintained.

[0132] For example, in this solution, the evaporator superheat temperature SH can be expressed by the following formula:

[0133] SH=T8-Teva

[0134] In the above formula, T8 is the evaporator outlet temperature, Teva is the evaporation temperature, and the evaporation temperature can be calculated by the compressor suction pressure.

[0135] refer to Figure 2 For example, the evaporator outlet temperature can be measured by the evaporator outlet temperature sensor 8 , and the compressor suction pressure can be measured by the compressor suction pressure sensor 10 .

[0136] Exemplarily, in this embodiment, (T9) i It can specifically represent the evaporator outlet air temperature corresponding to time t×(i) / n, SH i Specifically, it represents the evaporator superheat corresponding to the time t×(i) / n.

[0137] In this scheme, using T s and T e Determine the overall cooling target, and achieve fast response to large temperature differences and precise control of small temperature differences through exponential correction; quantify the refrigerant phase change characteristics (superheat) and the airflow heat exchange trend (outlet air temperature change) into error factors, so that the control strategy is closer to the essence of the refrigeration system.

[0138] Based on any of the foregoing solutions, in one possible implementation scheme, the controlled variable includes the condenser fan speed; the preset parameters include the compressor exhaust pressure and the condenser subcooling degree.

[0139] In this solution, the compressor exhaust pressure refers to the pressure of the refrigerant vapor when it is discharged from the compressor after being compressed by the compressor.

[0140] In this solution, the condenser subcooling degree represents the difference between the refrigerant liquid temperature at the condenser outlet and the saturated liquid temperature at the corresponding pressure.

[0141] In this solution, the error equation corresponding to the condenser fan speed can be determined as follows:

[0142] Use the compressor exhaust pressure to set the pressure trend response item. When the compressor exhaust pressure increases, the condenser fan speed can be triggered to increase.

[0143] The stage temperature correction term is determined by using the final temperature of the current partition and the start and end temperatures of the overall linear cooling process. This term uses the overall start and end temperatures to reflect the progress of the current partition in the overall cooling process. This term is configured to automatically adjust the control intensity according to the partition.

[0144] Use the condenser subcooling to set the subcooling correction item. This item is used to strengthen the adjustment force when the subcooling is insufficient. When the refrigerant is not fully liquefied, the condenser fan is accelerated to dissipate heat to increase the subcooling degree and prevent flash gas from affecting the cooling efficiency.

[0145] In this scheme, the pressure trend response term, the stage temperature correction term and the subcooling correction term can form a nonlinear combination function to form an error equation.

[0146] In this solution, based on the set pressure trend response item and subcooling correction item, the condenser fan speed is associated with the compressor exhaust pressure and the condenser subcooling. This can reduce the impact of unstable liquid supply on the refrigeration efficiency and avoid triggering the exhaust pressure overlimit protection mechanism. It can effectively reduce the control fluctuation of the condenser fan speed, while ensuring efficient heat dissipation of the refrigeration system, achieving precise temperature control and energy saving and consumption reduction.

[0147] In one possible implementation scheme, the controlled variable includes the condenser fan speed; the preset parameters include the compressor exhaust pressure and the condenser subcooling. Based on this scheme, the error equation is:

[0148]

[0149] Where τ represents the time constant, HP i represents the measured value of the discharge pressure of the i-th compressor, SC irepresents the measured value of the subcooling degree of the i-th condenser, e4(τ) i Indicates the error corresponding to the condenser fan speed.

[0150] In this solution, based on HP i Determine a pressure change index term. This term reflects the relative change in the discharge pressure of compressors in adjacent zones. Based on this change, the condenser fan speed can be automatically increased to enhance heat dissipation, or the condenser fan workload can be reduced.

[0151] In this scheme, the condenser subcooling SC can be expressed by the following formula:

[0152] SC=Tcon-T12

[0153] Where Tcon is the condensing temperature, which can be calculated from the compressor exhaust pressure. The compressor exhaust pressure can be calculated from Figure 2 The compressor exhaust pressure sensor 11 in the condenser is measured. T12 represents the condenser liquid supply temperature, which can be Figure 2 It is measured by the condenser supply liquid temperature sensor 12.

[0154] In this solution, HP i It can specifically represent the compressor exhaust pressure corresponding to time t×(i) / n, SC i It can specifically represent the condenser subcooling corresponding to time t×(i) / n.

[0155] In this scheme, the logarithmic term of the partition progress is determined by the final temperature of the current partition and the starting temperature and final temperature of the linear cooling system. sv ) i Close to T e , the error response tends to be smooth, avoiding over-adjustment.

[0156] In this solution, based on SC i Determine the subcooling response correction term, which is directly related to SC i , when SC i When the temperature is too low (such as insufficient subcooling resulting in a decrease in cooling capacity), the index value rises, and the condenser fan speed is increased accordingly to enhance the condenser heat exchange. When the index value is close to 1, the normal adjustment force is maintained.

[0157] This solution integrates the compressor discharge pressure trend with the condenser subcooling state to construct a nonlinear error equation to adjust the condenser fan speed. This precisely balances cooling requirements and rapidly responds to load fluctuations based on discharge pressure index correction, preventing flash gas from impacting cooling efficiency. It also achieves phased energy efficiency optimization, reducing overall system energy consumption. This improves the safety and energy efficiency of the refrigeration system.

[0158] Figure 3This is another linear cooling control method flow chart in the embodiment, refer to Figure 3 Based on any of the foregoing solutions, in one possible implementation method, the method includes:

[0159] S201. Determine the starting temperature and ending temperature of the linear cooling, and divide the linear cooling interval corresponding to the starting temperature and the ending temperature into n equal parts.

[0160] In this scheme, the starting temperature and ending temperature of linear cooling are respectively recorded as T s 、T e , divide the linear cooling interval corresponding to the starting temperature and the ending temperature into n equal parts, and record the total cooling time as t.

[0161] The starting temperature and ending temperature corresponding to the i-th equal division interval are respectively recorded as (T0) i 、(T sv ) i . (T0) i 、(T sv ) i They can be determined according to the following formula:

[0162]

[0163] S202. Use a closed-loop control equation to determine the first segment gain coefficient corresponding to the compressor speed in the i-th equally divided interval.

[0164] In this scheme, the first segment gain coefficient is determined by the following formula:

[0165]

[0166] Where w i Represents the first segment gain coefficient, and P1, I1, and D1 represent the first set of PID coefficients.

[0167] S203. Determine a first increment, and use the first segmented gain coefficient and the first increment to determine a target control amount of the compressor speed.

[0168] In this solution, the first increment is determined by the following formula:

[0169]

[0170] Where Δf represents the first increment, F max Indicates the maximum value of the compressor speed, F min It represents the minimum value of the compressor speed, and M represents an integer.

[0171] In this solution, the target control amount of the compressor speed is determined by the following formula:

[0172] Fi =F min +Δfw i

[0173] Where, F i Indicates the target control amount of the compressor speed.

[0174] S204. Use the closed-loop control equation to determine the second segment gain coefficient corresponding to the expansion valve step opening in the i-th equally divided interval.

[0175] In this solution, the second segment gain coefficient is determined by the following formula:

[0176]

[0177] Where k i represents the second segment gain coefficient, and P2, I2, and D2 represent the second set of PID coefficients.

[0178] S205: Determine a second increment, and use the second segmented gain coefficient and the second increment to determine a target control value for the expansion valve step opening.

[0179] In this solution, the second increment is determined by the following formula:

[0180]

[0181] Where Δe represents the second increment, E max Indicates the maximum value of the expansion valve step opening, E min It represents the minimum value of the expansion valve step opening, and A represents an integer.

[0182] In this solution, the target control amount of the expansion valve step opening is determined by the following formula:

[0183] E i =E min +Δek i

[0184] In the above formula, E i Indicates the target control quantity of the expansion valve step opening.

[0185] S206. Use the closed-loop control equation to determine the third segment gain coefficient corresponding to the evaporating fan speed in the i-th equally divided interval.

[0186] In this solution, the third segment gain coefficient is determined by the following formula:

[0187]

[0188] Where r i Represents the third segment gain coefficient, and P3, I3, and D3 represent the third set of PID coefficients.

[0189] S207 . Determine a third increment, and use the third segmented gain coefficient and the third increment to determine a target control value of the evaporating fan speed.

[0190] In this solution, the third increment is determined by the following formula:

[0191]

[0192] Where Δh represents the third increment, H max Indicates the maximum speed of the evaporating fan, H min Indicates the minimum value of the evaporation fan speed, and B represents an integer.

[0193] In this scheme, the target control quantity of the evaporation fan speed is determined by the following formula:

[0194] H i =H min +Δhr i

[0195] Where H i Indicates the target control value of the evaporator fan speed.

[0196] S208. Use the closed-loop control equation to determine the fourth segment gain coefficient corresponding to the condenser fan speed in the i-th equally divided interval.

[0197] In this solution, the fourth segment gain coefficient is determined by the following formula:

[0198]

[0199] Where p i Represents the fourth segment gain coefficient, and P4, I4, and D4 represent the fourth set of PID coefficients.

[0200] S209. Determine a fourth increment, and use the fourth segmented gain coefficient and the fourth increment to determine a target control value for the condenser fan speed.

[0201] In this solution, the fourth increment is determined by the following formula:

[0202]

[0203] Where Δd represents the fourth increment, D max Indicates the maximum speed of the condenser fan, D min Indicates the minimum value of the condenser fan speed, and C represents an integer.

[0204] In this solution, the target control value of the condenser fan speed is determined by the following formula:

[0205] D i =D min +Δdpi

[0206] Where D i Indicates the target control value of the condenser fan speed.

[0207] refer to Figure 2 In this solution, when the linear cooling interval corresponding to the starting temperature and the ending temperature is divided into n equal parts, in the i-th equal part, the variable frequency compressor 2, the electronic expansion valve 5, the evaporator fan 7, and the condenser fan 4 are controlled according to the target control amount of the compressor speed, the target control amount of the expansion valve valve step opening, the target control amount of the evaporator fan speed, and the target control amount of the condenser fan speed, thereby realizing linear cooling control of the refrigeration coefficient.

[0208] In this solution, the refrigeration system is controlled by the target control quantities determined above to achieve coordinated optimization of the compressor, expansion valve and fan, which can reduce the overall energy consumption of the refrigeration system.

[0209] Specifically, in this solution, the compressor speed is accurately calculated based on the real-time load (such as ambient temperature, target cooling rate) so that the compressor output cooling capacity is fully matched with the system demand. Combining the dual parameters of superheat (evaporator outlet) and subcooling (condenser outlet), the throttle valve opening is calculated in real time to ensure that the refrigerant is fully evaporated in the evaporator and completely liquefied in the condenser. The fan speed is dynamically adjusted according to the evaporator outlet air temperature and superheat. The fan energy consumption can be reduced to a certain extent compared to constant speed control. Based on the dual parameters of compressor exhaust pressure and condenser subcooling, the fan speed is adjusted in real time. The energy consumption of the fan heat dissipation can be reduced.

[0210] Example 2

[0211] This embodiment proposes an environmental test chamber, including a controller, which is configured to execute any one of the linear cooling control methods recorded in Example 1. The implementation method and beneficial effects of the method are the same as the corresponding content recorded in Example 1, and the specific content will not be repeated here.

[0212] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A linear cooling control method, characterized in that: include: Determine the starting temperature and ending temperature of linear cooling, which are respectively recorded as T s 、T e , divide the linear cooling interval corresponding to the starting temperature and the ending temperature into n equal parts, determine the starting temperature and the ending temperature corresponding to the i-th equal part, and record them as (T0) i 、(T sv ) i ; The closed-loop control equation is used to determine the segment gain coefficient corresponding to the i-th equally divided interval, and T s 、T e , (T0) i 、(T sv ) i and a measurement value of a preset parameter to construct an error equation corresponding to the closed-loop control equation; Determining a control amount increment, at least using the segmented gain coefficient and the control amount increment to determine a target control amount; The control amount increment represents a preset fixed step length between the maximum value and the minimum value of the control amount, and the preset fixed step length corresponds to the control accuracy of the control amount; The segmented gain coefficient represents an adjustment value corresponding to the control variable calculated by the closed-loop control equation under the error determined by the error equation; The target control amount represents a target value of the control amount in each of the equally divided intervals.

2. The linear temperature reduction control method according to claim 1, wherein: The control variable includes the compressor speed; The preset parameters include the temperature in the environmental test chamber.

3. The linear temperature reduction control method according to claim 2, wherein: The error equation is: Where τ represents the time constant, T represents the measured value of the temperature in the environmental test chamber, and e1(τ) i Indicates the error corresponding to the compressor speed.

4. The linear temperature reduction control method according to claim 1, wherein: The control quantity includes the valve step opening of the expansion valve; The preset parameters include the temperature in the environmental test chamber.

5. The linear temperature reduction control method according to claim 4, wherein: The error equation is: Where τ represents the time constant, T represents the measured value of the temperature in the environmental test chamber, t represents the total cooling time, and e2(τ) i Indicates the error corresponding to the compressor speed.

6. The linear temperature reduction control method according to claim 1, wherein: The control quantity includes the evaporation fan speed; The preset parameters include the evaporator air outlet temperature and the evaporator overheat temperature.

7. The linear temperature reduction control method according to claim 6, wherein: The error equation is: Where τ represents the time constant, (T9) i represents the measured value of the outlet air temperature of the i-th evaporator, SH i represents the measured value of the superheat temperature of the i-th evaporator, e3(τ) i Indicates the error corresponding to the evaporation fan speed.

8. The linear temperature reduction control method according to claim 1, wherein: The control quantity includes the condenser fan speed; The preset parameters include compressor exhaust pressure and condenser subcooling.

9. The linear temperature reduction control method according to claim 8, wherein: The error equation is: Where τ represents the time constant, HP i represents the measured value of the discharge pressure of the i-th compressor, SC i represents the measured value of the subcooling degree of the i-th condenser, e4(τ) i Indicates the error corresponding to the condenser fan speed.

10. An environmental test chamber, characterized in that: The invention comprises a controller, wherein the controller executes the linear temperature reduction control method according to any one of claims 1 to 9.

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