Temperature control method and system for walk-in test box

Abstract

The invention relates to the technical field of data processing, in particular to a step-in test box temperature control method and system. The method comprises the following steps: acquiring a temperature difference sequence and a normalized temperature value of each position containing the current moment in a test box in real time, and a power difference sequence of each heating element containing the current moment; determining an objective function of the heating effectiveness of each position, and obtaining the backtracking time enabling the heating effectiveness of each position at the current moment to be maximum; calculating the temperature control lag degree of the test box at the current moment; acquiring the temperature control quantity at the current moment by using a PID algorithm; calculating a weighted temperature control quantity at the current moment; and performing temperature regulation according to the weighted temperature control quantity to complete the temperature control of the step-in test box. According to the method, the target function of the heating effectiveness is constructed, the optimal backtracking time is solved, and the weighted temperature control quantity is calculated, so that the temperature overshoot phenomenon caused by hysteresis is reduced, and the accuracy of temperature adjustment is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of data processing, and in particular to a temperature control method and system for a walk-in test chamber. Background Art

[0002] The walk-in test chamber is a large environmental testing equipment with a large internal space that can simulate various environmental conditions such as temperature, humidity, and light. It is used in many industries such as electronics, automobiles, and aerospace to test the performance and reliability of products in different environments, such as temperature resistance tests of electronic products and aging tests of materials. Since temperature is one of the key factors affecting product performance, precise temperature control can ensure the stability and repeatability of test conditions, making product test results more accurate and comparable, helping companies to discover product defects in advance, improve product design, improve product quality, enhance market competitiveness, and ensure the stability and safety of products in actual use.

[0003] The patent application document with publication number CN117631723A discloses a PID automatic temperature control device, including: a 24V DC power supply, a 485 conversion analog module, an analog conversion 485 module, a current transmitter, a thermal resistor temperature sensing probe, an RS485 communication twisted pair, a PLC controller, an analog control module and a direct-fired engine proportional valve; the thermal resistor temperature sensing probe converts and amplifies the real-time collected temperature into a current signal through the current transmitter, and the analog conversion 485 module converts the current signal into a 485 communication message, which is transmitted over a long distance to the 485 conversion analog module and the PLC controller through the RS485 communication twisted pair. The 485 conversion analog module restores the 485 communication message into a current signal and outputs it to the input end of the analog control module, and the analog control module collects and transmits the signal to the PLC controller.

[0004] However, the above patent application document does not address the problem that when the temperature of the walk-in test chamber is controlled by the PID algorithm, the walk-in test chamber has a large internal space and the heat transfer takes time, resulting in a lag in temperature control, which can cause the temperature to overshoot, resulting in inaccurate temperature regulation and affecting the temperature control of the walk-in test chamber. Summary of the invention

[0005] In order to solve the problem that when controlling the temperature of a walk-in test chamber by a PID algorithm, the test chamber has a large internal space and the heat transfer takes time, resulting in a lag in temperature control, which causes temperature overshoot, leads to inaccurate temperature adjustment, and affects the temperature control of the walk-in test chamber, the present invention provides a walk-in test chamber temperature control method and system.

[0006] In a first aspect, the present invention provides a method for controlling the temperature of a walk-in test chamber, which adopts the following technical solution: A temperature control method for a walk-in test chamber comprises: obtaining in real time a temperature difference sequence and a normalized temperature value of each position in the test chamber including the current moment, and a power difference sequence of each heating element including the current moment; for any position, based on the value of each moment in the temperature difference sequence of the position in the time period to which the current moment belongs, the value of each moment in the power difference sequence corresponding to the time before the backtracking time of each moment in the time period to which the current moment belongs, and the Euclidean distance from each heating element to the position, constructing an objective function of the heating effectiveness at the position at the current moment, solving the objective function by the least square method, and obtaining the backtracking time that maximizes the heating effectiveness at the position at the current moment as a value. The target backtracking time for the position; based on the variance of the normalized temperature values ​​at each position at the current moment and the maximum value of the target backtracking time of all positions, the temperature control lag of the test chamber at the current moment is calculated; the average of the temperature values ​​at each position at the current moment is used as the test chamber temperature at the current moment, and according to the test chamber temperature at the current moment and the preset temperature curve, the temperature control amount at the current moment is obtained by using the PID algorithm; based on the test chamber temperature, the value in the preset temperature curve at the current moment, the temperature control lag, and the temperature control amount, the weighted temperature control amount at the current moment is calculated; the temperature is adjusted according to the weighted temperature control amount to complete the temperature control of the walk-in test chamber.

[0007] The beneficial effects are as follows: by acquiring the temperature difference sequence and the power difference sequence in real time, and combining the heating effectiveness optimization control strategy, the temperature control lag is effectively reduced, the temperature overshoot is avoided, and the accuracy of temperature regulation is improved; by calculating the backtracking time and the temperature control lag, the control parameters are dynamically adjusted to avoid excessive temperature fluctuations and overshoot, and to ensure stable temperature changes; since the temperature changes slowly due to the large space inside the test chamber, the use of this method can effectively solve the lag problem and enhance the system's adaptability to large space environments; by adjusting the heating effectiveness in real time, the temperature changes at different positions in the test chamber are ensured to be synchronized, the temperature distribution is kept uniform, and local temperature fluctuations are avoided.

[0008] Furthermore, the temperature difference sequence and the power difference sequence are obtained by filtering and denoising the temperature sequence of each position and the power sequence of each heating element collected in the test box at the current moment, and then performing first-order difference on the denoised temperature sequence of each position and the power sequence of each heating element to obtain the temperature difference sequence and the power difference sequence.

[0009] The beneficial effects are: through filtering and denoising, the noise interference in the temperature and power data is reduced, making the data more stable and reliable, providing an accurate basis for subsequent analysis and control; the first-order difference processing can extract the rate of change of temperature and power, so that the control system can better understand the dynamic characteristics of temperature changes, thereby making more accurate control decisions.

[0010] Furthermore, the filtering and denoising adopts Gaussian filtering.

[0011] Furthermore, the normalized temperature value is obtained by performing linear normalization processing on the temperature sequence of each position after denoising to obtain the normalized temperature value of each position at the current moment.

[0012] Furthermore, the objective function is: ; In the formula, The current time at the location The heating effectiveness, is the number of moments in the time period to which the current moment belongs, The current time period At the moment The values ​​in the temperature difference series, is the number of heating elements, For the The moment the heating element The values ​​in the power difference sequence are is the backtracking time, the value range is , For heating elements To location The Euclidean distance of is the normalization function, is the absolute value symbol.

[0013] The beneficial effects are as follows: the objective function can accurately evaluate the heating effectiveness of the heating system at each position by calculating the difference between the temperature difference and the power difference, thereby reflecting whether the system heating achieves the expected effect; by introducing the Euclidean distance between the heating element and the target position, the objective function effectively adjusts the influence of different heating elements on the target position, ensuring that the influence weight of the heating element far away from the target position on the temperature is smaller, thereby improving the accuracy of the heating system; by obtaining the backtracking time corresponding to the optimal solution, the objective function can take into account the influence of historical power on the current temperature, optimize the hysteresis characteristics of heat transfer, thereby improving the accuracy of the control system.

[0014] Furthermore, the temperature control hysteresis degree satisfies the following relationship: ; In the formula, is the temperature control hysteresis of the test chamber at the current moment, is the variance of the normalized temperature value at each location at the current moment, It is the maximum value of the target backtracking time at all locations at the current moment.

[0015] The beneficial effects are: by combining the variance of the normalized temperature value at each location at the current moment and the maximum value of the target backtracking time at all locations, the degree of temperature control lag is quantified, thereby facilitating the monitoring and evaluation of the temperature control response time of the system and providing real-time feedback; and through the size of the temperature control lag, it can help identify potential problems in the control system or equipment, such as slow heating / cooling response, uneven temperature, etc., and provide data support for optimization measures.

[0016] Furthermore, the weighted temperature control amount satisfies the following relationship: ; In the formula, is the weighted temperature control quantity at the current moment, is the current chamber temperature, is the value in the preset temperature curve at the current moment, is the temperature control hysteresis of the test chamber at the current moment, is the temperature control value at the current moment, is the absolute value symbol.

[0017] The beneficial effects are: by calculating the temperature control error in real time and dynamically adjusting the temperature control amount according to the degree of temperature control lag, the system can be ensured to respond accurately and reduce temperature deviation; the introduction of the lag factor can compensate for the lag effect during the heating or cooling process of the system, optimize the temperature adjustment speed, and avoid temperature overshoot or undershoot due to lag; by dynamically adjusting the control amount, the system's adaptability in the face of different environments or working conditions is enhanced, ensuring that the temperature control system can work stably and maintain a high level of control accuracy; by flexibly adjusting the control amount according to the actual temperature deviation and lag, the system can be avoided from overheating or cooling, thereby improving energy efficiency and reducing unnecessary energy consumption.

[0018] In a second aspect, the present invention provides a walk-in test chamber temperature control system, which adopts the following technical solution: A temperature control system for a walk-in test chamber includes: a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the above-mentioned temperature control method for a walk-in test chamber is implemented.

[0019] By adopting the above technical solution, the above-mentioned walk-in test chamber temperature control method is generated into a computer program and stored in a memory so as to be loaded and executed by a processor, thereby making a terminal device based on the memory and the processor for easy use.

[0020] The present invention has the following technical effects: Due to the large internal space of the test box and the time-consuming heat transfer, the temperature control has hysteresis, temperature overshoot, inaccurate adjustment and other situations. The present invention constructs the objective function of heating effectiveness and uses the least square method to solve the target backtracking time of each position, which helps to accurately grasp the effective situation of heating at different positions, taking into account the key factor of heat transfer time difference, so that the temperature adjustment can be better arranged in advance, reducing the temperature overshoot caused by hysteresis, and improving the accuracy of temperature adjustment. At the same time, the temperature control hysteresis is calculated based on the variance of the normalized temperature value of each position and the maximum value of the target backtracking time of all positions, comprehensively considering the temperature difference at different positions inside the test box and the overall hysteresis; combining the test box temperature, the preset temperature curve, the temperature control hysteresis and the temperature control amount to calculate the weighted temperature control amount, this multi-factor comprehensive consideration method makes the final temperature adjustment more in line with the actual situation of the test box, achieves more accurate and scientific temperature control, ensures the temperature control effect of the walk-in test box, and meets the strict requirements of the temperature environment of the relevant experiments. Through the above operations, the shortcomings of the PID algorithm in dealing with the lag problem of temperature control in large-space test chambers are compensated, the application effect of the PID algorithm in the temperature control of the test chamber is further optimized, the quality and stability of the overall temperature control are improved, and the temperature in the test chamber can change more stably and accurately according to the preset temperature curve. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts.

[0022] Figure 1 The present invention is a method flow chart of a method for controlling the temperature of a walk-in test chamber according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0024] It should be understood that when the terms "first", "second", etc. are used in the claims, descriptions, and drawings of the present invention, they are only used to distinguish different objects, rather than to describe a specific order. The terms "include" and "comprise" used in the description and claims of the present invention indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their collections.

[0025] The embodiment of the present invention discloses a temperature control method for a walk-in test chamber, referring to Figure 1 , comprising steps S1 to S6: S1: Real-time acquisition of the temperature difference sequence and normalized temperature value of each position in the test chamber at the current moment, as well as the power difference sequence of each heating element at the current moment.

[0026] It should be noted that since the temperature reflects the actual thermal state of each location inside the test chamber and its changing trend over time, and the power directly reflects the energy input provided by the heating element in different time periods, it is helpful to identify the temperature uniformity and heating efficiency when identifying the degree of lag in the temperature control of the walk-in test chamber. Due to the large space of the test chamber, when installing the sensor, it is necessary to ensure that the sensor can fully cover the test chamber space and capture the temperature changes in key areas.

[0027] Temperature sensors are arranged at the center of the four walls, top and bottom of the test box to collect the temperature sequence at different positions in the test box in real time. Power sensors are arranged at the positions of the heating elements in the test box to collect the power sequence of each heating element in real time. The sampling frequency of all sensors is set to (The implementation personnel can be adjusted according to the specific implementation situation).

[0028] Specifically, the temperature difference sequence and the power difference sequence are obtained as follows: The collected temperature sequence of each position in the test box including the current moment and the power sequence of each heating element are filtered and denoised, and then the denoised temperature sequence of each position and the power sequence of each heating element are first-order differentiated to obtain the temperature difference sequence and the power difference sequence.

[0029] Specifically, the filtering and denoising adopts Gaussian filtering.

[0030] Specifically, the normalized temperature value is obtained as follows: The denoised temperature sequence at each location is linearly normalized to obtain the normalized temperature value at each location at the current moment.

[0031] S2: Determine the objective function of the heating effectiveness at each position, and obtain the backtracking time that maximizes the heating effectiveness at each position at the current moment.

[0032] It should be noted that, since the heating element has a certain lag when heating, the power of the heating element corresponding to the dimension of the test chamber position at the current moment should be the power corresponding to the moment before the backtracking time of the current moment. Therefore, the backtracking time that makes the temperature change rate and the heating element power change rate in the time period to which each moment belongs as positively correlated as possible can be found; since the distances between each heating element and the temperature sensor at each position are different, the heat transfer efficiency is different. In order to effectively identify the degree of influence of each heating element on each position, it is also necessary to obtain the Euclidean distance between each heating element and each position, establish a spatial rectangular coordinate system with any vertex of the test chamber body as the origin, and then obtain the corresponding Euclidean distance.

[0033] For any position, based on the value of the temperature difference sequence at the position at each moment in the time period to which the current moment belongs, the value of the power difference sequence at the moment corresponding to the backtracking time of each moment in the time period to which the current moment belongs, and the Euclidean distance from each heating element to the position, an objective function of the heating effectiveness at the position at the current moment is constructed.

[0034] The implementer sets the length of the time period according to the specific implementation situation, for example, the current time and the previous 5 times.

[0035] Specifically, the objective function is: ; In the formula, The current time at the location The heating effectiveness, is the number of moments in the time period to which the current moment belongs, The current time period At the moment The values ​​in the temperature difference series, is the number of heating elements, For the The moment the heating element The values ​​in the power difference sequence are is the backtracking time, the value range is , For heating elements To location The Euclidean distance of is the normalization function, is the absolute value symbol.

[0036] in, is the location weighted by Euclidean distance The average power of each heating element before the retrospective time is The smaller the difference between the temperature change rate and the average power, the higher the possibility that the temperature change rate of the test chamber is positively correlated with the power change rate of the heating element when the current time delay is added, and the higher the heating effectiveness.

[0037] It should be noted that the time delay that makes the heating effectiveness at the target sensor the highest can be solved by the least square method, that is, the current lookback time of the heating element.

[0038] The objective function is solved by the least square method, and the backtracking time that maximizes the heating effectiveness at the current moment at the position is obtained as the target backtracking time for the position.

[0039] S3: Calculate the temperature control hysteresis of the test chamber at the current moment.

[0040] It should be noted that the PID algorithm controls the temperature based on the difference between the measured temperature and the target temperature. However, the walk-in test chamber has a large space and heat transfer takes time. After the heating element generates heat, the distance between the heating element and different temperature sensors is different, and the time required for heat transfer is different. In the heat transfer process, there will be uneven heat distribution. At this time, the measured temperature of the test chamber cannot reflect the actual temperature. When the PID algorithm is used directly to control the temperature, the heating element will continue to release heat when the heat transfer is not completed, which makes the temperature control lag, resulting in temperature overshoot. Therefore, it is necessary to evaluate the temperature control lag of the test chamber at each moment to reduce the temperature overshoot. At the same time, the temperature control lag depends on the time when each heating element starts to generate heat and is transmitted to the temperature sensor at each position. Therefore, the variance of the normalized temperature value of the test chamber at each position at the current moment can be obtained as the temperature uniformity and the backtracking time, and the temperature control lag can be calculated. Since the longest backtracking time among all sensors in the test chamber determines the temperature overshoot, the longest backtracking time among all sensors in the test chamber can be selected to evaluate the temperature control lag of the test chamber.

[0041] Based on the variance of the normalized temperature values ​​at each location at the current moment and the maximum value of the target backtracking time at all locations, the temperature control hysteresis degree of the test chamber at the current moment is calculated.

[0042] Specifically, the temperature control hysteresis degree satisfies the following relationship: ; In the formula, is the temperature control hysteresis of the test chamber at the current moment, is the variance of the normalized temperature value at each location at the current moment, It is the maximum value of the target backtracking time at all locations at the current moment.

[0043] S4: Use PID algorithm to obtain the temperature control value at the current moment.

[0044] It should be noted that PID control algorithms are often used in industrial automation and process control. They can make fine adjustments based on the difference between the actual measured temperature and the set temperature to ensure that the temperature always remains within the ideal range. During the operation of the walk-in test chamber, the PID algorithm is used to adjust the temperature. In order to facilitate the subsequent adjustment of the temperature regulation intensity, it is necessary to first obtain the temperature control amount through the PID algorithm.

[0045] The average of the temperature values ​​at each position at the current moment is taken as the test chamber temperature at the current moment. According to the test chamber temperature at the current moment and the preset temperature curve, the temperature control amount at the current moment is obtained using the PID algorithm.

[0046] S5: Calculate the weighted temperature control amount at the current moment.

[0047] It should be noted that when the temperature control lag of the test chamber is higher and the temperature is closer to the preset temperature, the lagging temperature control will cause the heating element to continue to release heat when the total heat meets the temperature requirement, thereby causing overshoot. At this time, it is necessary to reduce the temperature control amount obtained by the PID algorithm to avoid temperature overshoot.

[0048] The weighted temperature control amount at the current moment is calculated based on the test box temperature, the value in the preset temperature curve at the current moment, the temperature control hysteresis degree, and the temperature control amount.

[0049] Specifically, the weighted temperature control amount satisfies the following relationship: ; In the formula, is the weighted temperature control quantity at the current moment, is the current chamber temperature, is the value in the preset temperature curve at the current moment, is the temperature control hysteresis of the test chamber at the current moment, is the temperature control value at the current moment, is the absolute value symbol.

[0050] S6: Adjust the temperature according to the weighted temperature control amount to complete the temperature control of the walk-in test chamber.

[0051] The weighted temperature control amount at the current moment is used to obtain the adjustment size, and the PWM wave is adjusted according to the adjustment size to control the power of the heating element and complete the temperature control of the walk-in test chamber.

[0052] An embodiment of the present invention further discloses a temperature control system for a walk-in test chamber, including a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, a temperature control method for a walk-in test chamber according to the present invention is implemented.

[0053] The above system also includes other components well known to those skilled in the art, such as a communication bus and a communication interface, and their configuration and functions are known in the art, so they will not be described in detail here.

[0054] In the present invention, the aforementioned memory may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. For example, a computer-readable storage medium may be any suitable magnetic storage medium or magneto-optical storage medium, or any other medium that can be used to store the required information and can be accessed by an application, module, or both. Any such computer storage medium may be part of the device or accessible or connectable to the device.

[0055] Although this specification has shown and described a number of embodiments of the present invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art will conceive of many modifications, changes and alternatives without departing from the ideas and spirit of the present invention. It should be understood that in the practice of the present invention, various alternatives to the embodiments of the present invention described herein may be employed.

[0056] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the temperature of a walk-in test chamber, characterized in that: include: Acquire in real time the temperature difference sequence and normalized temperature value of each position in the test chamber at the current moment, as well as the power difference sequence of each heating element at the current moment; For any position, based on the value of the temperature difference sequence at the position at each moment in the time period to which the current moment belongs, the value of the moment corresponding to the backtracking time before each moment in the time period to which the current moment belongs in the power difference sequence, and the Euclidean distance from each heating element to the position, an objective function of the heating effectiveness at the position at the current moment is constructed, and the objective function is solved by the least squares method to obtain the backtracking time that maximizes the heating effectiveness at the position at the current moment as the target backtracking time of the position; Based on the variance of the normalized temperature values ​​at each location at the current moment and the maximum value of the target backtracking time at all locations, the temperature control hysteresis degree of the test chamber at the current moment is calculated; The average of the temperature values ​​at each position at the current moment is taken as the test chamber temperature at the current moment, and the temperature control amount at the current moment is obtained by using the PID algorithm according to the test chamber temperature at the current moment and the preset temperature curve; based on the test chamber temperature, the value at the current moment in the preset temperature curve, the temperature control hysteresis degree, and the temperature control amount, the weighted temperature control amount at the current moment is calculated; The temperature is adjusted according to the weighted temperature control amount to complete the temperature control of the walk-in test chamber.

2. A walk-in test chamber temperature control method according to claim 1, characterized in that: The temperature difference sequence and the power difference sequence are obtained in the following manner: The collected temperature sequence of each position in the test box including the current moment and the power sequence of each heating element are filtered and denoised, and then the denoised temperature sequence of each position and the power sequence of each heating element are first-order differentiated to obtain the temperature difference sequence and the power difference sequence.

3. A walk-in test chamber temperature control method according to claim 2, characterized in that: The filtering and denoising adopts Gaussian filtering.

4. A walk-in test chamber temperature control method according to claim 3, characterized in that: The normalized temperature value is obtained as follows: The denoised temperature sequence at each location is linearly normalized to obtain the normalized temperature value at each location at the current moment.

5. A walk-in test chamber temperature control method according to claim 1, characterized in that: The objective function is: ； In the formula, The current position The heating effectiveness, is the number of moments in the time period to which the current moment belongs, The current time period At the moment The values ​​in the temperature difference series, is the number of heating elements, For the The moment the heating element The values ​​in the power difference sequence are is the backtracking time, the value range is , For heating elements To location The Euclidean distance of is the normalization function, is the absolute value symbol.

6. A walk-in test chamber temperature control method according to claim 1, characterized in that: The temperature control hysteresis degree satisfies the following relationship: ； In the formula, is the temperature control hysteresis of the test chamber at the current moment, is the variance of the normalized temperature value at each location at the current moment, It is the maximum value of the target backtracking time at all locations at the current moment.

7. A walk-in test chamber temperature control method according to claim 1, characterized in that: The weighted temperature control amount satisfies the following relationship: ； In the formula, is the weighted temperature control quantity at the current moment, is the current chamber temperature, is the value in the preset temperature curve at the current moment, is the temperature control hysteresis of the test chamber at the current moment, is the temperature control value at the current moment, is the absolute value symbol.

8. A temperature control system for a walk-in test chamber, characterized in that: include: A processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, a temperature control method for a walk-in test chamber according to any one of claims 1 to 7 is implemented.

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