Thermal comfort evaluation method based on infrared thermal imaging technology

Abstract

This invention provides a thermal comfort evaluation method based on infrared thermal imaging technology, comprising: real-time acquisition of infrared thermal imaging data of a target object; determination of skin temperature data of the region of interest on the target object's face based on the infrared thermal imaging data; calculation of the thermal sensation level using the skin temperature data and a thermal sensation evaluation model; and adjustment of the temperature setting of the target device according to the thermal sensation level. This invention uses only the skin temperature of a single area (e.g., facial skin temperature) to evaluate thermal sensation, which is simple, convenient, and highly accurate; it does not require the user to wear a smart device to collect skin temperature, directly acquiring the user's facial skin temperature in a non-contact manner.

Description

Technical Field

[0001] This invention relates to the field of thermal comfort evaluation technology, and more specifically, to a thermal comfort evaluation method based on infrared thermal imaging technology. Background Technology

[0002] With improved living standards, people's demands for indoor thermal environments have moved beyond simply providing cooling in summer and heating in winter; they increasingly prefer a comfortable and healthy environment. A good, healthy, and comfortable thermal environment not only benefits physical health but also effectively improves work efficiency. Furthermore, controlling the indoor thermal environment at a comfortable level is also of great significance for research on building energy conservation.

[0003] Currently, the main methods used to create a comfortable indoor environment in air conditioning systems are empirical methods, PMV models, and user feedback on thermal preferences. Empirical methods involve setting indoor set temperatures based on the comfort temperature ranges for winter and summer as defined in the "Design Code for Heating, Ventilation and Air Conditioning of Industrial Buildings" (GB50019-2015). The comfort temperature range for winter is 18-24℃, and for summer it is 25-28℃. PMV models are used to predict human thermal comfort under steady-state conditions. PMV values ​​within the range of [-0.5 0.5] are considered to satisfy 80% of people who feel thermally comfortable in their air-conditioned environment. However, numerous studies have found that PMV does not necessarily accurately reflect human thermal comfort. For example, Dear and Brager argue that human thermal comfort is not only related to ambient temperature, radiant temperature, relative humidity, and wind speed, but also influenced by physiological thermal adaptation, psychological expectations, and window opening. Huizenga et al. conducted a field survey of 215 office environments in the United States, Canada, and France, finding that only 11% of these environments met the thermal comfort requirements of 80% of the population. On the other hand, the PMV model requires real-time collection of indoor air temperature, relative humidity, radiant temperature, clothing thermal resistance, wind speed, and human metabolic rate parameters. In practical applications, a large number of parameters need to be collected. User-reported thermal preferences refer to users actively inputting their thermal preferences into the air conditioning system. The system adjusts the indoor air temperature and humidity based on the user's feedback. Compared to the PMV model, this method can better reflect individual thermal comfort levels. However, it still has some limitations: users need to input a large number of thermal preferences; it can only be applied to specific users and cannot be widely applied to other users.

[0004] To address the problems of existing technologies, this invention provides a thermal comfort evaluation method based on infrared thermal imaging technology. Summary of the Invention

[0005] To address the problems of the prior art, this invention provides a thermal comfort evaluation method based on infrared thermal imaging technology, the method comprising the following steps:

[0006] S1. Real-time acquisition of infrared thermal imaging data of the target object;

[0007] S2. Based on the infrared thermal imaging data, determine the skin temperature data of the region of interest on the face of the target object;

[0008] S3. The thermal sensation level is calculated by combining the skin temperature data with the thermal sensation evaluation model;

[0009] S4. Adjust the temperature setting of the target device according to the thermal sensation level.

[0010] According to an embodiment of the present invention, step S1 includes: acquiring infrared thermal imaging data of the target object's face by means of an infrared thermal imaging device set on the target device within the acquisition range, according to a detection time interval.

[0011] According to an embodiment of the present invention, the acquisition range is determined by the following expression:

[0012] ;

[0013] ;

[0014] in, This indicates the minimum distance between the target object's face and the infrared thermal imaging device; Indicates the height of the target person; , These represent the horizontal and vertical field of view of the infrared thermal imaging device, respectively. This indicates the maximum distance between the target object's face and the infrared thermal imaging device; , This indicates the pixel value of the infrared thermal imaging device.

[0015] According to an embodiment of the present invention, step S2 includes:

[0016] Based on the current season and the priority order of facial regions corresponding to the season, determine the facial region of interest;

[0017] Extract the temperature measurement value of the region of interest on the face from the infrared thermal imaging data;

[0018] Taking into account the influence of ambient temperature, the temperature measurement value is corrected to obtain the corrected temperature measurement value;

[0019] The skin temperature data of the facial region of interest is calculated using the corrected temperature measurements.

[0020] According to an embodiment of the present invention, the temperature measurement value is corrected by the following formula:

[0021] ;

[0022] in, This indicates the corrected temperature measurement value; , , , Indicates the correction factor; This indicates the temperature measurement value before correction; This indicates the ambient temperature around the target object.

[0023] According to one embodiment of the present invention, skin temperature data of the facial region of interest is calculated using the following formula:

[0024] ;

[0025] in, This represents skin temperature data for the area of ​​interest on the face. Indicates the spectral transmittance of the atmosphere; This indicates the relationship between the shooting angle of the infrared thermal imaging device and the refractive index coefficient of the object's material; It is the angle between the radiation normal to the surface of the target object and the observation direction; , These represent the target's visible area and the distance to the target object, respectively, corresponding to the minimum spatial angle of the infrared thermal imaging device. Indicates the shooting distance of the infrared thermal imaging device; Indicates the ambient temperature around the target object; Indicates atmospheric temperature; This indicates the temperature measurement value before correction, or the corrected temperature measurement value can be used; This represents a constant determined by the integral of Planck's law.

[0026] According to an embodiment of the present invention, step S3 includes: comparing the skin temperature data of the region of interest with the thresholds of different thermal sensation levels in the thermal sensation evaluation model to obtain the thermal sensation level, wherein, when constructing the thermal sensation evaluation model, the skin temperature data is corrected using the following formula:

[0027] ;

[0028] In the formula, , They represent the previous temperature. and the next temperature The corresponding difference is equal to the actual measured value minus the calibration value; Let represent the corrected skin temperature value and the actual measured value at time i, respectively, in °C.

[0029] According to an embodiment of the present invention, step S4 includes:

[0030] If the current thermal sensitivity level is thermal neutral, do not adjust the temperature setting of the target device;

[0031] If the current thermal sensation level is cold, increase the temperature setting of the target device;

[0032] If the current thermal sensation level is hot, lower the temperature setting of the target device.

[0033] According to another aspect of the invention, a storage medium is also provided, which includes a series of instructions for performing the steps of the method described in any of the preceding claims.

[0034] According to another aspect of the present invention, a thermal comfort evaluation system based on infrared thermal imaging technology is also provided, which performs the method described in any of the preceding claims, the system comprising: a mobile terminal and a target device, wherein:

[0035] The mobile terminal performs the following steps:

[0036] Based on infrared thermal imaging data, determine the skin temperature data of the region of interest on the face of the target object;

[0037] The thermal sensation level is calculated by combining the skin temperature data with a thermal sensation evaluation model.

[0038] Generate temperature adjustment instructions for the target device based on the thermal sensitivity level;

[0039] The target device includes:

[0040] Infrared thermal imaging equipment, used to acquire infrared thermal imaging data of target objects in real time;

[0041] A wireless microcontroller is used to transmit the infrared thermal imaging data to the mobile terminal and to receive the thermal sensing level and the temperature adjustment command transmitted by the mobile terminal.

[0042] A display screen is used to display skin temperature data of the area of ​​interest on the face and the thermal sensation level.

[0043] The thermal comfort evaluation method based on infrared thermal imaging technology provided by this invention has the following advantages:

[0044] (1) Evaluating thermal sensation using only the skin temperature of a single site (e.g., facial skin temperature) is simple, convenient, and highly accurate;

[0045] (2) Users do not need to wear smart devices to collect skin temperature; the user's facial skin temperature can be collected directly in a non-contact manner.

[0046] (3) The thermal sensation evaluation model can effectively evaluate an individual's thermal sensation, and the prediction accuracy can reach up to 93%;

[0047] (4) It can collect the temperature of human facial skin in real time / intermittently and predict the thermal comfort state of the human body, so as to adjust the indoor temperature in real time.

[0048] (5) The facial area was divided into zones. Based on seasonal factors, the optimal facial area was adjusted in a timely manner to evaluate human thermal sensation, which can truly reflect the thermal comfort state of the human body.

[0049] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description and the drawings. Attached Figure Description

[0050] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0051] Figure 1 A flowchart of a thermal comfort evaluation method based on infrared thermal imaging technology according to an embodiment of the present invention is shown;

[0052] Figure 2 This shows an imaging schematic diagram of an infrared thermal imaging device according to an embodiment of the present invention;

[0053] Figures 3(a)-3(d) show the facial skin temperature thresholds corresponding to thermal neutrality in winter and summer according to an embodiment of the present invention;

[0054] Figure 4 A flowchart of a thermal comfort evaluation method based on infrared thermal imaging technology according to another embodiment of the present invention is shown;

[0055] Figure 5 A schematic diagram of a thermal comfort evaluation system based on infrared thermal imaging technology according to an embodiment of the present invention is shown. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0057] The prior art (CN205493785U) discloses a non-contact human thermal comfort monitoring device, and the prior art (CN205403064U) discloses a central air conditioning energy-saving control system based on human thermal comfort. However, neither of them discloses how to process the user's facial image through an internal program to obtain human thermal comfort parameters.

[0058] Prior art (CN217154338U) discloses a fresh air adjustment device and air conditioning system, which determines the fresh air volume based on the number of people, the initial carbon dioxide concentration, and the carbon dioxide concentration of the fresh air; however, it does not take into account the temperature sensation of the people themselves. Prior art (CN104315652A) discloses an air conditioning control system and method that calculates the human body's thermal sensation based on ambient temperature and humidity data; however, its technical solution may not accurately reflect the human body's thermal sensation.

[0059] Prior art (CN110617608A) discloses an indoor temperature control method, device, air conditioner, and storage medium; prior art (CN109869871A) discloses an air conditioning control method, device, air conditioner, and computer-readable storage medium; prior art (CN103868196B) discloses an air conditioning control method, control device, and air conditioner with the control device; prior art (CN105783183A) discloses a portable air conditioner and its control method and device; prior art (CN107726562A) discloses a computer-readable storage medium for temperature control and an air conditioner; prior art (CN104501369B) discloses an air conditioner and its temperature adjustment method. However, all of the above prior art collects human body surface temperature through contact or non-contact temperature acquisition devices, without considering the differences in how different parts of the human body's surface temperature reflects human thermal sensation.

[0060] Existing technology (CN114322230A) discloses a smart bracelet, a thermal environment regulation system, and a method. The smart bracelet is worn on the user's wrist to detect ambient temperature and the user's body temperature. Existing technology (CN110454930B) discloses a method, device, and air conditioning control method and apparatus for estimating optimal human thermal comfort, which acquires real-time local skin temperature, heart rate, blood pressure, and heat generation. Existing technology (CN105066356A) discloses an automatic air conditioning adjustment method based on the thermal comfort zone of an elderly care environment. The data acquisition module automatically collects indoor temperature and humidity data, determines the thermal resistance of clothing based on the data transmitted by sensors, and then sets the temperature and humidity comfort zone range. However, the above-mentioned existing technologies require the user to wear a smart bracelet or collect multiple user vital signs parameters or collect the thermal resistance value of the user's clothing, which is cumbersome and cannot easily reflect the user's thermal sensation.

[0061] To address the aforementioned shortcomings of existing technologies, this invention, from a developmental perspective, creatively employs facial skin temperature as a single physiological indicator to reflect human thermal sensation, thereby controlling the temperature of target devices. Specifically, the face may be the most suitable area for dynamic skin temperature monitoring via non-contact infrared imaging in the future. Advances in information technology allow for the automatic identification of various facial features. Furthermore, and most importantly, the face is typically exposed to the air without clothing, allowing for direct collection of skin temperature. Human skin temperature is widely considered a physiological indicator reflecting human thermal sensation. Firstly, skin temperature and thermal sensation exhibit a strong linear correlation. Secondly, using skin temperature from a single location to evaluate thermal sensation also provides high accuracy. Thirdly, because skin temperature can be continuously measured and collected, dynamic evaluation of thermal sensation can be achieved based on skin temperature. Fourthly, compared to body temperature and heart rate, literature indicates a stronger correlation between skin temperature and thermal sensation, resulting in higher accuracy in evaluating thermal sensation. Therefore, automatic evaluation of human thermal sensation based on skin temperature can provide a reliable basis for perceiving human needs in highly intelligent devices (such as air conditioners). This is also an inevitable development direction for future building thermal environment design.

[0062] Figure 1 A flowchart of a thermal comfort evaluation method based on infrared thermal imaging technology according to an embodiment of the present invention is shown.

[0063] like Figure 1 As shown, in step S1, infrared thermal imaging data of the target object is acquired in real time.

[0064] In one embodiment, step S1 includes: acquiring infrared thermal imaging data of the target object's face within the acquisition range using an infrared thermal imaging device mounted on the target device, according to a detection time interval.

[0065] In one embodiment, an infrared thermal imager (Fluke TiX1000) was used to collect facial skin temperature distribution maps. Detailed instrument parameters are shown in Table 1.

[0066] Table 1. Parameters of Infrared Thermal Imager

[0067] .

[0068] Ignoring the effects of light intensity in the shooting area and the internal optical system of the infrared thermal imaging device, the imaging schematic diagram of a certain infrared thermal imaging device is as follows: Figure 2 As shown. The size of the image taken by the infrared thermal imaging device is a×b (m). 2 The corresponding pixel value is x1×y1 (pixels). The focal length of the infrared thermal imaging device is... fThe horizontal and vertical field angles are α (m) and β (rad), respectively. The length and width of the target object are N (m) and M (m), respectively, and N ≥ M. When the target object is at a focal length of R (m), the size of the entire field of view (i.e., the background area) is L × W (m). 2 The target object appears to be m×n (m) in the photograph. 2 ).

[0069] Based on imaging principles, the relationship between the background area and the image size is calculated using focal length, expressed as:

[0070] (1)

[0071] The equation for calculating the size of the background region using a field perspective is as follows:

[0072] (2)

[0073] After imaging, the proportion of the target object to the background area is calculated as follows:

[0074] (3)

[0075] At this time, the number of pixels occupied by the target object is According to formula (3), it can also be written as .

[0076] In this invention, the target object captured by the infrared thermal imaging device is a human face or a portion of the face. Typically, a human face is approximately one-eighth of its height (H, cm). On average, the nose is one-fifth the width of the face and one-third the height. Assuming the width and height of the face are the same, i.e., N=M, then the size of the face is... cm. The width x height of the nose is... cm 2 .

[0077] Considering that the nose can effectively improve face recognition, the minimum and maximum distances for face detection are further obtained according to formulas (2) and (3). The minimum distance between the target object and the detector is achieved when the length ratio of the target object to the background region is 1:1:

[0078] (4)

[0079] Considering that the target object can be distinguished, when the pixel count exceeds 18 pixels, the probability of distinguishing the target object can exceed 90%. At this point, the maximum shooting distance that can distinguish a human face should be:

[0080] (5)

[0081] Considering the maximum shooting distance that can distinguish the nose, it is:

[0082] (6)

[0083] in, This indicates the minimum distance between the target object's face and the infrared thermal imaging device; Indicates the height of the target person; , These represent the horizontal and vertical field of view of the infrared thermal imaging device, respectively. This indicates the maximum distance between the target object's face and the infrared thermal imaging device; , This indicates the pixel value of the infrared thermal imaging device.

[0084] In one embodiment, the collection range is determined by formula (4) and formula (5) or by formula (4) and formula (6).

[0085] like Figure 1 As shown, in step S2, the skin temperature data of the region of interest on the face of the target object is determined based on infrared thermal imaging data.

[0086] In one embodiment, step S2 includes determining the facial region of interest based on the current season and the corresponding facial region priority order. Specifically, the priority order from high to low for spring and summer is: nose > left cheek > left ear > forehead = right cheek = chin > right ear; the priority order from high to low for autumn and winter is: nose > forehead > right cheek = left cheek = chin > right ear = left ear.

[0087] Spearman correlation analysis (two-tailed) was used to test the correlation between skin temperature values ​​and thermal sensation in different facial regions. A Pearson correlation coefficient in the range of 0.8–1 was considered a very strong correlation, while a coefficient in the range of 0.6–0.79 was considered a strong correlation. The priority of regions of interest was then determined based on the correlation coefficient. The results are shown in Table 2.

[0088] Table 2. Correlation coefficients and priority of facial skin temperature and thermal sensation in winter and summer, respectively.

[0089]

[0090] Note: I and V represent the highest and lowest priority, respectively.

[0091] Table 2 shows that skin temperature at the nose has the highest correlation with thermal sensation, making it suitable for assessing human thermal sensation. Skin temperature at the ear has a lower correlation with thermal sensation and is difficult to collect in practice; therefore, skin temperature at this location is not very suitable for assessing thermal sensation. However, when skin temperature at other locations cannot be measured or is abnormal, skin temperature at the ear can still be used to assess human thermal sensation.

[0092] In one embodiment, step S2 includes: extracting temperature measurements of a region of interest on the face from infrared thermal imaging data. In one embodiment, when the region of interest is the nose, the temperature measurements at the nose are extracted from the infrared thermal imaging data.

[0093] In one embodiment, step S2 includes: taking into account the influence of ambient temperature, correcting the temperature measurement value to obtain a corrected temperature measurement value.

[0094] The main factors affecting infrared thermal imaging temperature measurement include thermal imaging equipment parameters, the environment, and the human body. Among these, thermal imaging equipment parameters include field of view and shooting distance. ,angle Operating band, resolution, or size; environmental factors include the ambient temperature around the target object. Atmospheric temperature Human factors include surface emissivity. And face size. When the imaging device parameters are fixed, its temperature measurement error is mainly affected by the ambient temperature.

[0095] Based on the specifications of the infrared thermal imaging equipment, according to formulas (4) to (6), the minimum distance between the infrared thermal imaging equipment and the human face in this invention is calculated to be 0.54m, the maximum distance to the face is 22.97m, and the maximum distance to the nose is 2.84m. In practice, it can be seen from the collected infrared thermal images that when the shooting distance is less than 3m, the various parts of the target object's face can be clearly distinguished.

[0096] To minimize the impact of individual differences, this invention uses the temperature difference (ΔT = infrared thermal imaging temperature value - ambient temperature) between the temperature measurement value acquired by the infrared imaging device and the ambient temperature to analyze the influence of ambient temperature on the infrared temperature measurement results. Measurement error (Diff) = reference temperature value (Tsk) - infrared acquisition temperature value (Th).

[0097] Furthermore, the temperature measurement value is corrected using the following formula:

[0098] (7)

[0099] in, This indicates the corrected temperature measurement value; , , , Indicates the correction factor; This indicates the temperature measurement value before correction; This indicates the ambient temperature around the target object.

[0100] In one embodiment, Table 3 below lists the error correction models for different parts:

[0101] Table 3 Error correction models for different parts

[0102] .

[0103] Table 4 shows the corrected temperature measurement error results of the infrared thermal imaging equipment. Practical experience shows that when ΔT ≤ 15℃, the maximum range of the corrected infrared thermal imaging equipment's temperature measurement error is ±0.173℃ (95% CI). Considering the reference temperature accuracy is ±0.1℃, the error range of the corrected infrared thermal imaging equipment is ±0.273℃ (95% CI). Similarly, when ΔT > 15℃, the error range of the corrected infrared thermal imaging equipment is ±0.783℃ (95% CI).

[0104] Table 4. Corrected Temperature Measurement Error Results of Infrared Thermal Imaging Equipment

[0105] .

[0106] In one embodiment, step S2 includes: calculating skin temperature data of the facial region of interest using the corrected temperature measurement values.

[0107] In actual measurement, the effective radiation received by the radiometer in the thermal imaging equipment mainly consists of three parts: radiation from the target object itself, reflected radiation from the surrounding environment, and atmospheric radiation. Based on Planck's law of radiation and Lambert's cosine law, the relationship between the true temperature of the target object and the temperature measured by the radiometer and the surrounding environment is obtained. The skin temperature data of the region of interest on the face is then calculated using the following formula:

[0108] (8)

[0109] in, This represents skin temperature data for the area of ​​interest on the face. Indicates the spectral transmittance of the atmosphere; This indicates the relationship between the shooting angle of the infrared thermal imaging device and the refractive index coefficient of the object's material; It is the angle between the radiation normal to the surface of the target object and the observation direction; , These represent the target's visible area and the distance to the target object, respectively, corresponding to the minimum spatial angle of the infrared thermal imaging device. Indicates the shooting distance of the infrared thermal imaging device; Indicates the ambient temperature around the target object; Indicates atmospheric temperature; This indicates the temperature measurement value before correction, or the corrected temperature measurement value can be used; This represents a constant determined by the integral of Planck's law.

[0110] It is a function of the viewing angle and the refractive index of the object's material, expressed as:

[0111] (9)

[0112] In the formula, , It represents the refractive index of the material.

[0113] like Figure 1 As shown, in step S3, the thermal sensation level is calculated by combining skin temperature data with a thermal sensation evaluation model.

[0114] The thermal sensation evaluation model based on facial skin temperature was developed using data from a climate chamber simulation experiment. The experiment was conducted in two phases, winter and summer. A total of 40 healthy participants were recruited. All participants were undergraduate or graduate students aged 20-30 years. All participants were in good health, with no history of cardiovascular or other serious illnesses, and were non-smokers. All participants had lived in Changsha for over a year and were acclimatized to the hot-winter, cold-summer climate. Winter clothing included a long-sleeved shirt, thick sweater, thick socks, and athletic shoes, with a thermal resistance of approximately 1.1 clo. Summer clothing included underwear, a thin short-sleeved T-shirt, athletic pants, thin socks, and athletic shoes, with an estimated thermal resistance of approximately 0.39 clo. Throughout the experiment, participants wore the same clothing under each condition.

[0115] All experimental temperatures were common indoor temperatures. Winter experimental temperatures included 12, 15, 18, 21, and 24°C, while summer experimental temperatures included 24, 26, 28, 30, and 32°C. The relative humidity was 60%. The experimental duration was 140 minutes for each experiment.

[0116] In the experiment, a temperature measuring device (such as an iButton temperature recorder) was used to continuously and automatically measure the skin temperature of various local areas of the face, including the center of the forehead, nose, right cheek, behind the right ear, left cheek, behind the left ear, and center of the chin. Infrared thermal imaging was used to record the skin temperature distribution of the subjects' faces at exposure times of 0-5, 20-25, and 135-140 minutes.

[0117] In practical applications, to ensure the accuracy of skin temperature measurement, the temperature measuring device is first calibrated and adjusted. Then, by comparing the difference between the corrected temperature measuring device value and the value acquired by the infrared thermal imaging, an accurate value based on the infrared thermal imager is obtained.

[0118] The subjects' skin temperature was continuously and automatically measured using an iButton (Opulus, US) button-type temperature recorder. The iButton had a diameter of 17 mm, a thickness of 6 mm, a factory accuracy of ±0.5℃, a reading resolution of ±0.0625 ºC, and a response time of 19 s. Skin temperature was automatically collected once per minute during the experiment. To improve the accuracy of the iButton recorder, each iButton was calibrated before the experiment. The calibration temperatures were 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, and 45℃, covering human skin temperature within the ambient temperature range of 15–32 degrees Celsius. To further improve the accuracy of skin temperature measurement, linear interpolation was used to correct the measured values ​​based on the calibration values. The formula is as follows:

[0119] (10)

[0120] In the formula, , They represent the previous temperature. and the next temperature The corresponding difference is equal to the actual measured value minus the calibration value; Let represent the corrected skin temperature value and the actual measured value at time i, respectively, in °C.

[0121] The corrected iButton measurements deviated from the calibrated reference temperature by 0℃ at the aforementioned seven calibrated temperatures. To further verify the accuracy of the correction (10), the iButton was compared with the air temperature measurements of 18, 28, and 33℃ using a reference thermometer YET-720L, YOWEXA, China, as shown in Table 4. The reference thermometer consists of a main unit and a PT1000 sensor, with a total accuracy of ±(0.05%|t|+0.05)℃, where t is the measured value, and the PT1000 sensor has an accuracy of 0.03℃. The values ​​listed in Table 4 are the differences between the average values ​​of the two instrument readings after they stabilize within five minutes of measurement (the difference between the current reading and the next reading is less than 0.05℃), and the 95% confidence interval of the average error. The upper limit of the maximum 95% confidence interval and the lower limit of the minimum 95% confidence interval at the three temperatures are 0.019 and -0.022, respectively. In addition, according to the instrument measurement accuracy formula, the larger the absolute value of the measured value, the lower the accuracy. The local skin temperature of a human body exposed to heat can reach a maximum of 43℃. When the measured temperature is 43℃, the minimum measurement accuracy of the YET-720L is ±0.072℃. Considering both aspects, the corrected iButton accuracy is within the range of -0.094 and 0.091. The results show that the accuracy of the corrected iButton is within 0.1℃ (95% confidence level). The corrected accuracy, response time, and skin temperature measurement method of the iButton all meet the requirements of ISO 9886.

[0122] The subjects' thermal sensation was obtained through a subjective questionnaire. The questionnaire used a 9-point continuous scale to evaluate the level of thermal sensation. These 9 levels included very cold (-4), cold (-3), cool (-2), slightly cool (-1), neutral (0), slightly warm (1), warm (2), hot (3), and very hot (4). The 9-point scale of thermal sensation is an extension of the ISO 10551 scale based on the ASHARE 7-point scale, and is applicable to a wider temperature range than the room temperature range.

[0123] Thermal comfort was also obtained through a questionnaire. Thermal comfort was measured using a break scale. Thermal comfort was measured using a 5-point break scale with ratings of: very comfortable (2), comfortable (1), just comfortable (0.01) / just uncomfortable (-0.01), uncomfortable (-1), and very uncomfortable (-2). The ratings were broken between "just comfortable" and "just uncomfortable".

[0124] In one embodiment, based on experimental data, high-dimensional samples are projected onto the optimal discrimination vector space to achieve dimensionality reduction and obtain sample classification information, thereby constructing a thermal sensation evaluation model.

[0125] Step a: Divide the training sample set from the two classes into two subsets: X0 and X1;

[0126] Step b: Calculate the mean vector of each class:

[0127] (11)

[0128] Step c: Calculate the discrete matrix within each class:

[0129] (12)

[0130] Step d: Calculate the total discrete matrix within the class:

[0131] (13)

[0132] Step e: Use the Lagrange multiplication method to solve for the optimal projection direction for linear discrimination:

[0133] (14)

[0134] In the formula, yes The inverse matrix.

[0135] Step f, Discriminant function:

[0136] (15)

[0137] In the formula, yes The transpose of .

[0138] Step g: Determine the threshold of the discriminant function:

[0139] (16)

[0140] Step h: Calculate the sample classification threshold x0 based on the discriminant function y and the threshold w0. .

[0141] Furthermore, the skin temperature thresholds corresponding to thermoneutrality were obtained, as shown in Figures 3(a)-3(d). Figures 3(a) and 3(b) represent winter, while Figures 3(c) and 3(d) represent summer. Figures 3(a) and 3(c) represent exposure times of 10–30 minutes, and Figures 3(b) and 3(d) represent exposure times of 30–135 minutes. The thresholds given in Figures 3(a)-3(d) can be used to determine whether a person feels thermoneutrally sensitive in the current state. For example, in summer, if a person enters the environment within 10–30 minutes and the detected skin temperature on their forehead is 33.1°C, which falls within the thermoneutrality range, then the person is thermoneutral.

[0142] In one embodiment, step S3 includes: comparing the skin temperature data of the region of interest with the thresholds of different thermal sensation levels in the thermal sensation evaluation model to obtain the thermal sensation level.

[0143] In one embodiment, step S3 includes: calculating a thermal comfort level based on skin temperature data of the region of interest, so as to adjust the temperature setting of the target device in step S4 according to the thermal comfort level. For example, if the current thermal comfort level is very comfortable (2), comfortable (1), or just comfortable (0.01), then the temperature setting of the target device is not adjusted; if the current thermal comfort level is just uncomfortable (-0.01), uncomfortable (-1), or very uncomfortable (-2), then the temperature setting of the target device is adjusted.

[0144] like Figure 1 As shown, in step S4, the temperature setting of the target device is adjusted according to the thermal sensation level.

[0145] In one embodiment, step S4 includes: if the current thermal sensation level is thermally neutral, not adjusting the temperature setting of the target device; if the current thermal sensation level is cold, increasing the temperature setting of the target device; if the current thermal sensation level is hot, decreasing the temperature setting of the target device.

[0146] Figure 4 A flowchart of a thermal comfort evaluation method based on infrared thermal imaging technology according to another embodiment of the present invention is shown. The method involves real-time acquisition, identification, extraction, and correction of skin temperature at points of interest on the human face using a non-contact approach; obtaining skin temperature thresholds corresponding to different thermal sensations based on climate chamber experimental data; and comparing the real-time acquired skin temperature values ​​with the thresholds to determine the current thermal sensation and thermal comfort state of the person.

[0147] like Figure 4 As shown, step one: use an infrared camera to capture infrared thermal images of the human body;

[0148] like Figure 4 As shown, step two: Use a face recognition algorithm to identify facial features, including local areas of interest and regions of interest;

[0149] like Figure 4 As shown, step three: Based on the priority of the parts of interest obtained from a series of climate chamber experiments, determine the parts of interest; at the same time, determine the skin temperature thresholds corresponding to different thermal sensation levels.

[0150] like Figure 4 As shown, step four: noise reduction processing to obtain a clean skin temperature signal;

[0151] like Figure 4 As shown, step five: use a linear equation to correct the skin temperature value acquired by infrared thermal imaging;

[0152] like Figure 4 As shown, Step Six: Based on the skin temperature threshold obtained in Step Three, determine whether the thermal sensation corresponding to the corrected skin temperature value is "thermally neutral" or "thermally comfortable". If yes, proceed to Step Nine. If no, proceed to Step Seven.

[0153] like Figure 4 As shown, step seven: Determine if it's too cold. If so, increase the air conditioner's set temperature. If not, decrease the air conditioner's set temperature.

[0154] like Figure 4 As shown, step eight: when the timer reaches the set time, proceed to step one.

[0155] like Figure 4 As shown, Step Nine: End.

[0156] The thermal comfort evaluation method based on infrared thermal imaging technology provided by this invention can also be used in conjunction with a computer-readable storage medium. The storage medium stores a computer program, which is executed to run the thermal comfort evaluation method based on infrared thermal imaging technology. The computer program can execute computer instructions, which include computer program code. The computer program code can be in the form of source code, object code, executable file, or some intermediate form.

[0157] Computer-readable storage media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0158] It should be noted that the contents of computer-readable storage media may be appropriately added to or subtracted from the contents according to the requirements of legislation and patent practice in a jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable storage media may not include electrical carrier signals and telecommunication signals.

[0159] Figure 5 A schematic diagram of a thermal comfort assessment system based on infrared thermal imaging technology according to an embodiment of the present invention is shown. The system includes: a mobile terminal and a target device, wherein:

[0160] The mobile terminal performs the following steps: Based on infrared thermal imaging data, it determines the skin temperature data of the region of interest on the face of the target object; it calculates the thermal sensation level by combining the skin temperature data with a thermal sensation evaluation model; and it generates a temperature adjustment command for the target device based on the thermal sensation level.

[0161] The target device includes: an infrared thermal imaging device, a wireless microcontroller, and a display screen. The infrared thermal imaging device is used to acquire infrared thermal imaging data of the target object in real time; the wireless microcontroller is used to transmit infrared thermal imaging data to a mobile terminal and receive thermal sensation level and temperature adjustment commands from the mobile terminal; the display screen is used to display skin temperature data and thermal sensation level of the area of ​​interest on the face.

[0162] In one embodiment, the infrared thermal imaging device, acting as an infrared dot matrix temperature measurement module, employs multiple AMG8833 modules (8x8 matrix) connected in parallel to acquire the skin temperature of the human face. A WiFi & Bluetooth microcontroller is used to receive the skin temperature values ​​acquired by the AMG8833 modules and transmit the data to a mobile app via WiFi or Bluetooth, while simultaneously displaying it on a TFT LCD screen. The display screen, a TFT LCD module connected to the wireless microcontroller, is used solely to display the currently detected skin temperature data and thermal sensation / thermal comfort status. The mobile terminal is a smartphone or tablet, used to display and control input information, and simultaneously send feedback signals to the main controller of the target device (e.g., an air conditioner).

[0163] In summary, the thermal comfort evaluation method based on infrared thermal imaging technology provided by this invention has the following advantages:

[0164] (1) Evaluating thermal sensation using only the skin temperature of a single site (e.g., facial skin temperature) is simple, convenient, and highly accurate;

[0165] (2) Users do not need to wear smart devices to collect skin temperature; the user's facial skin temperature can be collected directly in a non-contact manner.

[0166] (3) The thermal sensation evaluation model can effectively evaluate an individual's thermal sensation, and the prediction accuracy can reach up to 93%;

[0167] (4) It can collect the temperature of human facial skin in real time / intermittently and predict the thermal comfort state of the human body, so as to adjust the indoor temperature in real time.

[0168] (5) The facial area was divided into zones. Based on seasonal factors, the optimal facial area was adjusted in a timely manner to evaluate human thermal sensation, which can truly reflect the thermal comfort state of the human body.

[0169] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0170] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0171] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0172] Certain terms are used throughout this application to refer to specific system components. As those skilled in the art will recognize, the same components may often be referred to by different names, and therefore this application is not intended to distinguish those components that differ only in name and not in function. In this application, the terms “comprise,” “include,” and “have” are used in an open-ended manner and should therefore be interpreted as meaning “including, but not limited to…”. Furthermore, the terms “substantially,” “materially,” or “approximately” as used herein refer to industry-accepted tolerances for the corresponding terms. The term “coupling,” as may be used herein, includes direct coupling and indirect coupling via additional components, elements, circuits, or modules, wherein, for indirect coupling, the intermediate component, element, circuit, or module does not alter the information of the signal but may adjust its current level, voltage level, and / or power level. Inferred coupling (e.g., one element inferredly coupled to another element) includes direct and indirect coupling between two elements in the same manner as “coupling.”

[0173] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0174] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

[0175] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for evaluating thermal comfort based on infrared thermal imaging technology, characterized in that, The method includes the following steps: S1. Real-time acquisition of infrared thermal imaging data of the target object; S2. Based on the infrared thermal imaging data, determine the skin temperature data of the region of interest on the face of the target object; S3. The thermal sensation level is calculated by combining the skin temperature data with the thermal sensation evaluation model; S4. Adjust the temperature setting of the target device according to the thermal sensation level; Step S1 includes: acquiring infrared thermal imaging data of the target object's face using an infrared thermal imaging device installed on the target device within the acquisition range, according to the detection time interval; Step S2 includes: determining the region of interest (ROI) of the face based on the current season and the priority order of facial regions corresponding to the season; extracting the temperature measurement value of the ROI from the infrared thermal imaging data; and correcting the temperature measurement value considering the influence of ambient temperature to obtain the corrected temperature measurement value. The skin temperature data of the facial region of interest is calculated using the corrected temperature measurement values. The collection range is determined by the following expression: ； ； in, This indicates the minimum distance between the target object's face and the infrared thermal imaging device; Indicates the height of the target person; , These represent the horizontal and vertical field of view of the infrared thermal imaging device, respectively. This indicates the maximum distance between the target object's face and the infrared thermal imaging device; , This represents the pixel value of an infrared thermal imaging device; The skin temperature data of the facial region of interest is calculated using the following formula: ； in, This represents skin temperature data for the area of ​​interest on the face. Indicates the spectral transmittance of the atmosphere; This indicates the relationship between the shooting angle of the infrared thermal imaging device and the refractive index coefficient of the object's material; It is the angle between the radiation normal to the surface of the target object and the observation direction; , These represent the target's visible area and the distance to the target object, respectively, corresponding to the minimum spatial angle of the infrared thermal imaging device. Indicates the shooting distance of the infrared thermal imaging device; Indicates the ambient temperature around the target object; Indicates atmospheric temperature; This indicates the temperature measurement value before correction, or the corrected temperature measurement value can be used; This represents a constant determined by the integral of Planck's law; Step S3 includes: comparing the skin temperature data of the region of interest with the thresholds of different thermal sensation levels in the thermal sensation evaluation model to obtain the thermal sensation level, wherein, when constructing the thermal sensation evaluation model, the skin temperature data is corrected using the following formula: ； In the formula, , They represent the previous temperature. and the next temperature The corresponding difference is equal to the actual measured value minus the calibration value; Let represent the corrected skin temperature value and the actual measured value at time i, respectively, in °C.

2. The thermal comfort evaluation method based on infrared thermal imaging technology as described in claim 1, characterized in that, The temperature measurement value is corrected using the following formula: ； in, This indicates the corrected temperature measurement value; , , , Indicates the correction factor; This indicates the temperature measurement value before correction; This indicates the ambient temperature around the target object.

3. A thermal comfort evaluation method based on infrared thermal imaging technology as described in any one of claims 1-2, characterized in that, Step S4 includes: If the current thermal sensitivity level is thermal neutral, do not adjust the temperature setting of the target device; If the current thermal sensation level is cold, increase the temperature setting of the target device; If the current thermal sensation level is hot, lower the temperature setting of the target device.

4. A storage medium, characterized in that, It contains instructions for performing the method as described in any one of claims 1-3.

5. A thermal comfort evaluation system based on infrared thermal imaging technology, characterized in that, The system, which performs the method as described in any one of claims 1-3, comprises: a mobile terminal and a target device, wherein: The mobile terminal performs the following steps: Based on infrared thermal imaging data, determine the skin temperature data of the region of interest on the face of the target object; The thermal sensation level is calculated by combining the skin temperature data with a thermal sensation evaluation model. Generate temperature adjustment instructions for the target device based on the thermal sensitivity level; The target device includes: Infrared thermal imaging equipment, used to acquire infrared thermal imaging data of target objects in real time; A wireless microcontroller is used to transmit the infrared thermal imaging data to the mobile terminal and to receive the thermal sensing level and the temperature adjustment command transmitted by the mobile terminal. A display screen is used to display skin temperature data of the area of ​​interest on the face and the thermal sensation level.

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