Greenhouse air temperature sensing system

Abstract

The invention provides a greenhouse air temperature sensing system, and relates to the technical field of sensors. The greenhouse air temperature sensing system comprises an anti-radiation device which comprises a top cover, a cylinder body and a flow guide base plate; wherein a fan which blows air upwards is arranged in the barrel body; an airflow channel is arranged between the flow guide base plate and the cylinder body; the ventilation quantity control unit is used for controlling the rotating speed of the fan; the temperature sensor is arranged in the cylinder body; and the microcontroller is electrically connected with the ventilation quantity control unit and the temperature sensor and is used for controlling the rotating speed of the fan according to a preset temperature measurement error. According to the technical scheme, the defect that an existing anti-radiation cover cannot meet the precision requirements of different planting scenes can be overcome.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a greenhouse air temperature sensing system. Background Art

[0002] Temperature is one of the important indicators of greenhouse environmental parameters and directly affects the growth of crops. In order to accurately measure the air temperature in a greenhouse environment, a radiation shield is required to prevent the direct solar radiation and ground reflected radiation from affecting the sensor, while also preventing the spraying operations and farming activities in the greenhouse from interfering with the sensor.

[0003] At present, greenhouse air temperature measurement mainly adopts two schemes: natural ventilation radiation shield and active ventilation radiation shield. Among them, the natural ventilation radiation shield has a simple structure, but the measurement error is large under low wind speed and strong light conditions; the active ventilation radiation shield reduces the radiation error through fan forced ventilation.

[0004] However, different greenhouse planting scenarios have different requirements for temperature measurement accuracy. For example, high-value-added low-temperature economic crops have higher requirements for temperature measurement accuracy, while general crops have relatively lower requirements for temperature measurement accuracy. Existing radiation shields cannot adjust the measurement accuracy according to the actual needs of different planting scenarios. Summary of the invention

[0005] The present invention provides a greenhouse air temperature sensing system, which can overcome the defect that the existing radiation protection cover cannot adapt to the accuracy requirements of different planting scenes.

[0006] The present invention provides a greenhouse air temperature sensing system, comprising: a radiation protection device, including a top cover, a cylinder and a guide bottom plate; wherein: A fan for blowing air upwards is arranged in the cylinder; An air flow channel is provided between the guide chassis and the cylinder; A ventilation volume control unit, used to control the speed of the fan; A temperature sensor is disposed in the cylinder; A microcontroller is electrically connected to the ventilation volume control unit and the temperature sensor, and is used to control the rotation speed of the fan according to a preset temperature measurement error.

[0007] Optionally, the top cover comprises two layers of a first radiation protection sheet and a second radiation protection sheet which are arranged in parallel, wherein the first radiation protection sheet is used for sunshade, and the second radiation protection sheet is used for heat insulation.

[0008] Optionally, the top cover comprises two layers of a first radiation protection sheet and a second radiation protection sheet which are arranged in parallel, wherein the first radiation protection sheet is used for sunshade, and the second radiation protection sheet is used for heat insulation.

[0009] Optionally, the distance between the first radiation protection sheet and the second radiation protection sheet is greater than 5 centimeters, and a support column is provided between the first radiation protection sheet and the second radiation protection sheet.

[0010] Optionally, the first radiation protection sheet and the second radiation protection sheet are made of a high-reflectivity metal material.

[0011] Optionally, a filter screen for filtering dust is provided on the upper portion of the cylinder, and the cylinder is trumpet-shaped.

[0012] Optionally, a reflective layer is provided on the lower surface of the guide chassis.

[0013] Optionally, the ventilation volume control unit includes: A constant current driving circuit, electrically connected to the microcontroller, and configured to provide a driving current for the fan according to a control signal of the microcontroller; The current detection circuit has an input end electrically connected to the fan and an output end electrically connected to the microcontroller, and is used to detect the driving current and feed back the detection result to the microcontroller.

[0014] Optionally, the greenhouse air temperature sensing system further comprises a power supply system, wherein the power supply system comprises: A lithium battery, electrically connected to the temperature sensor, the ventilation volume control unit and the microcontroller, for power supply; An external power supply interface, electrically connected to the lithium battery, for charging the lithium battery; Wherein, the lithium battery provides backup power for the fan when the external power interface is powered off.

[0015] Optionally, the microcontroller is used to: Obtain a preset temperature measurement error value; Determining the required wind speed difference according to the current greenhouse radiation value and the temperature measurement error value; Calculating the fan wind speed based on the wind speed in the greenhouse and the wind speed difference; The fan driving current is determined according to the preset corresponding relationship between the wind speed and the current.

[0016] Optionally, the microcontroller is further used for: When the fan wind speed exceeds a preset maximum wind speed, calculating a minimum measurement error under the current greenhouse environment; When the minimum measurement error is greater than a preset error, adjusting the fan speed to the preset maximum speed; When the actually achievable minimum measurement error is less than or equal to the set temperature measurement error value, the driving current corresponding to the preset maximum wind speed is determined according to the corresponding relationship between the wind speed and the current.

[0017] In summary, one or more technical solutions provided in the present invention have at least the following technical effects or advantages: By arranging an upward-blowing fan in the barrel of the radiation protection device, and using a microcontroller to control the ventilation volume control unit to adjust the fan speed according to the preset temperature measurement error, the greenhouse air temperature sensing system of the present invention can flexibly adjust the measurement accuracy according to the accuracy requirements of different planting scenarios. Specifically, the top cover adopts a double-layer structure, the first radiation protection sheet is used for sunshade, and the second radiation protection sheet is used for heat insulation, which cooperates with the air flow channel between the guide chassis and the barrel to form a good ventilation and heat dissipation structure. When planting high-value-added crops requires higher measurement accuracy, the ventilation effect can be improved by increasing the fan speed; when planting general crops, the fan speed can be reduced to extend the service life. This adjustable measurement accuracy design overcomes the defect that the existing radiation protection cover cannot adapt to the accuracy requirements of different planting scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 is a structural schematic diagram of a greenhouse air temperature sensing system provided in an embodiment of the present application; Figure 2 It is a structural schematic diagram of a top cover provided in an embodiment of the present application; Figure 3 It is a structural schematic diagram of a cylinder provided in an embodiment of the present application; Figure 4 It is a structural schematic diagram of a guide chassis provided in an embodiment of the present application; Figure 5 This is a schematic diagram of various units of a circuit board provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Please refer to Figure 1 , Figure 11 is a schematic diagram of the structure of a greenhouse air temperature sensing system provided in an embodiment of the present application. The greenhouse air temperature sensing system comprises: a radiation protection device, including a top cover 1, a cylinder 2 and a guide chassis 3; wherein: A fan 23 for blowing air upward is provided in the cylinder 2; An air flow channel is provided between the guide chassis 3 and the cylinder 2; A ventilation control unit, used to control the rotation speed of the fan 23; A temperature sensor 25 is disposed in the cylinder 2; The microcontroller is electrically connected to the ventilation volume control unit and the temperature sensor 25, and is used to control the rotation speed of the fan 23 according to a preset temperature measurement error.

[0022] Specifically, greenhouse air temperature is one of the key parameters affecting crop growth, and its measurement accuracy is directly related to the effect of greenhouse environment control. The greenhouse air temperature sensing system provided in this embodiment adopts an integrated design, mainly including a radiation protection device, a ventilation control unit, a temperature sensor 25 and a microcontroller. The radiation protection device includes a top cover 1, a cylinder 2 and a guide chassis 3 from top to bottom, and each component works together to ensure measurement accuracy.

[0023] Furthermore, the design of the radiation protection device fully considers the particularity of the greenhouse environment. In the greenhouse, there are generally no wind, low wind and strong light conditions, which can easily lead to large errors in the sensor measurement values. The measurement error of the traditional naturally ventilated radiation shield can reach between +2.5°C and -0.5°C under low wind speed and strong sunlight conditions. To solve this problem, the present embodiment is provided with an upward blowing fan 23 in the cylinder 2, and adopts active ventilation instead of natural ventilation.

[0024] The upward blowing design of the fan 23 can enhance the heat dissipation of the top cover 1 and effectively reduce the temperature rise caused by solar radiation; secondly, when the fan 23 is working, a negative pressure area is formed in the cylinder 2, and a suction effect is generated through the air flow channel reserved between the guide chassis 3 and the cylinder 2, ensuring that the air in the greenhouse can continuously and stably flow through the sensing area of ​​the temperature sensor 25; in addition, this airflow organization method can also effectively prevent the dust in the greenhouse from being enriched in the measurement area.

[0025] Optionally, the temperature sensor 25 adopts a digital temperature chip, which is installed at an appropriate position in the cylinder 2 to collect temperature data in real time.

[0026] Optionally, the microcontroller adjusts the speed of the fan 23 by collecting data from the temperature sensor 25 and controlling the ventilation control unit. The ventilation control unit can control and monitor the working state of the fan 23. This closed-loop control method enables the system to dynamically adjust the speed of the fan 23 according to the preset temperature measurement error requirements, while ensuring the measurement accuracy and avoiding the life loss caused by the long-term high-speed operation of the fan 23.

[0027] The design of this embodiment is particularly suitable for the differentiated needs of different greenhouse planting scenarios. For example, when planting temperature-sensitive high-value-added crops such as enoki mushrooms, the system can ensure higher measurement accuracy by increasing the speed of fan 23; while when planting ordinary crops with a wide temperature adaptability range such as corn, the speed of fan 23 can be appropriately reduced to extend the service life of the equipment. This flexible control strategy not only ensures measurement performance, but also takes into account economy.

[0028] Please refer to Figure 2 , Figure 2 It is a schematic diagram of the structure of a top cover provided in an embodiment of the present application. Based on the above embodiment, as an optional embodiment, the top cover 1 includes two layers of parallel first radiation protection sheet 12 and second radiation protection sheet 13, the first radiation protection sheet 12 is used for sunshade, and the second radiation protection sheet 13 is used for heat insulation.

[0029] Specifically, the top cover 1 adopts a double-layer anti-radiation sheet structure, including a first anti-radiation sheet 12 and a second anti-radiation sheet 13 arranged in parallel. This double-layer structure is designed to better cope with the strong light conditions in the greenhouse environment. In a greenhouse, especially on sunny days, direct solar radiation and ground reflected radiation will significantly affect the accuracy of temperature measurement. Traditional single-layer anti-radiation structures are often difficult to effectively isolate these radiation effects, which can easily cause the measured value to deviate from the actual temperature.

[0030] Furthermore, the first radiation protection sheet 12 is mainly used for sunshade, directly facing the solar radiation, and can reflect most of the incident light, significantly reducing the radiation heat entering the measurement area. The second radiation protection sheet 13 is located below the first radiation protection sheet 12, and mainly plays a heat insulation role, further blocking the residual heat radiation after passing through the first radiation protection sheet 12, forming a double protection. This step protection design can minimize the interference of solar radiation on temperature measurement.

[0031] The double-layer radiation protection structure cooperates with the fan 23 that blows air upward to form an efficient heat dissipation system. The airflow generated by the fan 23 can not only enhance the heat dissipation effect of the second radiation protection sheet 13, but also significantly improve the heat dissipation performance of the entire radiation protection device by forming forced convection between the two layers of radiation protection sheets. This active heat dissipation method is more controllable and efficient than natural ventilation, and can still maintain good temperature measurement accuracy under strong light conditions.

[0032] Based on the above embodiment, as an optional embodiment, the distance between the first radiation protection sheet 12 and the second radiation protection sheet 13 is greater than 5 centimeters, and a support column 14 is provided between the first radiation protection sheet 12 and the second radiation protection sheet 13 .

[0033] Specifically, in the double-layer radiation protection structure design, the spatial arrangement between the first radiation protection sheet 12 and the second radiation protection sheet 13 has an important influence on the temperature measurement accuracy. In this embodiment, through in-depth research on the influence of the spacing between the radiation protection sheets on the heat dissipation effect, it is determined that the optimal spacing between the first radiation protection sheet 12 and the second radiation protection sheet 13 should be greater than 5 cm, and a support column 14 is set between the two layers of radiation protection sheets to maintain structural stability.

[0034] The above spacing design is determined based on the heat transfer characteristics in a greenhouse environment. Under strong light conditions, although the first radiation protection sheet 12 can reflect most of the solar radiation, it will still absorb a certain amount of heat and cause temperature rise. If the distance between the two layers of radiation protection sheets is too small, it is easy to cause heat accumulation, affecting the thermal insulation effect of the second radiation protection sheet 13. Through experiments, it was found that when the spacing is less than 5 cm, even if there is a fan 23 to generate forced convection, the heat between the radiation protection sheets is difficult to dissipate in time, resulting in an increase in the temperature of the measurement area. When the spacing is greater than 5 cm, under the action of the fan 23, a good convection channel can be formed between the two layers of radiation protection sheets, effectively taking away the accumulated heat.

[0035] In order to ensure the stability between the first radiation protection sheet 12 and the second radiation protection sheet 13, the embodiment of the present application sets a support column 14 between the first radiation protection sheet 12 and the second radiation protection sheet 13. The design of the support column 14 should not only consider the structural strength, but also take into account the airflow organization. The support column 14 can be designed to be slender to minimize the obstruction to the airflow, while ensuring the parallelism and spacing stability of the two layers of radiation protection sheets.

[0036] The spacing designed in the above technical solution cooperates with the active ventilation of the fan 23 to form an efficient heat control system. When the fan 23 is working, the upward airflow first passes through the second radiation protection sheet 13 to take away the heat absorbed by it, then forms forced convection between the two layers of radiation protection sheets, and finally flows through the surface of the first radiation protection sheet 12 to achieve multi-stage heat dissipation. This airflow organization method can minimize the overall temperature rise of the radiation protection device and ensure that the temperature in the measurement area is close to the actual greenhouse temperature.

[0037] Based on the above embodiment, as an optional embodiment, the first radiation protection sheet 12 and the second radiation protection sheet 13 are made of a high reflectivity metal material.

[0038] In terms of material selection for the double-layer radiation protection structure, in this embodiment, both the first radiation protection sheet 12 and the second radiation protection sheet 13 are made of high reflectivity metal materials. Material selection is determined based on the radiation characteristics and heat transfer laws in the greenhouse environment. In a greenhouse, strong direct solar radiation and ground reflected radiation will significantly affect the accuracy of temperature measurement, so the optical and thermal properties of the radiation protection sheet material directly determine the performance of the temperature measurement system.

[0039] For example, a high reflectivity aluminum sheet 35 can be selected as the material for making the radiation protection sheet. Aluminum not only has excellent reflective properties and can efficiently reflect incident solar radiation, but also has a small heat capacity and good thermal conductivity, which makes it particularly suitable as a material for radiation protection devices.

[0040] In practical applications, the first radiation protection sheet 12 is used as the first layer of protection directly facing solar radiation. Its high reflectivity can effectively reflect most of the incident radiation and significantly reduce the heat transferred to the second radiation protection sheet 13. The second radiation protection sheet 13 further reflects and isolates the residual radiation. The stepped protection system formed by the two layers of high reflectivity metal materials can minimize the impact of radiation on temperature measurement.

[0041] Please refer to Figure 3 , Figure 3 It is a schematic diagram of the structure of a cylinder provided in an embodiment of the present application. Based on the above embodiment, as an optional embodiment, a filter screen for filtering dust is provided on the upper part of the cylinder 2, and the cylinder 2 is trumpet-shaped.

[0042] Specifically, the structural design of the cylinder 2 fully considers the actual application requirements of the greenhouse environment. Agricultural operations such as spraying and fertilizing are often carried out in the greenhouse, which will generate a large amount of dust and water vapor. If these impurities enter the measurement area, it will not only affect the temperature measurement accuracy, but also accelerate the aging of the sensor. To solve this problem, the present embodiment sets a circular filter 21 on the upper part of the cylinder 2 to filter the dust particles entering the cylinder 2.

[0043] Furthermore, the cylinder 2 adopts a trumpet-shaped design, that is, a variable cross-section structure that is wider at the top and narrower at the bottom. This structural design cooperates with the upward blowing method of the fan 23 to produce a good airflow organization effect. When the fan 23 is working, the airflow moves upward along the trumpet-shaped cylinder 2, and the gradual change of the cross-sectional area causes the airflow speed to change accordingly. In the lower part of the cylinder 2, the smaller cross-section makes the airflow speed faster, which is conducive to forming a stronger negative pressure area and enhancing the suction effect of the airflow channel between the guide chassis 3 and the cylinder 2; while in the upper part of the cylinder 2, the larger cross-section makes the airflow speed appropriately reduced, reducing the impact of the airflow on the filter and extending the service life of the filter.

[0044] The filter is set at the upper part of the cylinder 2. The upper part is far away from the greenhouse ground and is relatively less affected by dust. Secondly, the upper part is in the large cross-sectional area of ​​the trumpet-shaped cylinder 2, and the air flow velocity is low, which is conducive to the effective filtering of dust. Finally, the upper part is convenient for regular cleaning and replacement of the filter.

[0045] Please refer to Figure 4 , Figure 4 1 is a schematic diagram of the structure of a guide chassis 3 provided in an embodiment of the present application. Based on the above embodiment, as an optional embodiment, a reflective layer is provided on the lower surface of the guide chassis 3.

[0046] In a greenhouse environment, not only direct solar radiation from the top should be considered, but also thermal radiation reflected from the ground will affect the accuracy of temperature measurement. In order to comprehensively solve the problem of radiation interference, a reflective layer is provided on the lower surface of the guide chassis 3 in this embodiment. The reflective layer is made of the same high reflectivity aluminum sheet 35 as the radiation protection sheet, which can effectively reflect thermal radiation from the ground and prevent it from entering the measurement area through the airflow channel between the guide chassis 3 and the cylinder 2, thereby improving the measurement accuracy.

[0047] Furthermore, the guide chassis 3, as the bottom support structure of the entire sensor system, not only bears the function of isolating the ground heat radiation, but also integrates various electrical components required for the operation of the system. A circuit board 33 is provided on the guide chassis 3 for installing control components such as a constant current drive circuit and a current detection circuit. The layout of the circuit board 33 fully considers the heat dissipation and protection requirements, and adopts a reasonable layout design to ensure that each electronic component can work stably in a greenhouse environment. The external power supply interface 34 is arranged at the edge of the guide chassis 3, which is convenient for connecting an external power supply without affecting the normal function of the airflow channel.

[0048] In order to ensure reliable operation of the system, the signal line 32 driving the fan 23 and the temperature collection sensor 25 is arranged through the wiring groove inside the guide chassis 3. This design not only protects the line from the influence of the greenhouse environment, but also avoids the airflow interference caused by the exposed cables.

[0049] Please refer to Figure 5 , Figure 5 Schematic diagram of various units of a circuit board provided in an embodiment of the present application. Based on the above embodiment, as an optional embodiment, the ventilation volume control unit includes: A constant current driving circuit, electrically connected to the microcontroller, for providing a driving current to the fan 23 according to a control signal of the microcontroller; The current detection circuit has an input end electrically connected to the fan 23 and an output end electrically connected to the microcontroller, and is used to detect the driving current and feed back the detection result to the microcontroller.

[0050] Specifically, precise control of the speed of the fan 23 is the key to achieving adjustable measurement accuracy. The ventilation volume control unit of this embodiment adopts a closed-loop control scheme based on constant current drive, which mainly includes two core parts: a constant current drive circuit and a current detection circuit. This design can ensure that the fan 23 maintains a stable speed output under different working conditions.

[0051] Further, the constant current drive circuit is electrically connected to the microcontroller, receives the control signal from the microcontroller, and converts it into a corresponding drive current output to the fan 23. The constant current drive mode is adopted instead of the traditional constant voltage drive, mainly considering the influence of the voltage fluctuation and temperature change that may exist in the greenhouse environment on the rotation speed of the fan 23. The constant current drive can still maintain a stable driving ability when these external conditions change, ensuring the consistency of the rotation speed of the fan 23. At the same time, the input end of the current detection circuit is electrically connected to the fan 23, and the output end is electrically connected to the microcontroller, forming a complete feedback loop. By monitoring the actual working current of the fan 23 in real time and feeding back the detection result to the microcontroller, the system can promptly detect and correct the deviation of the rotation speed of the fan 23.

[0052] Based on the above embodiment, as an optional embodiment, the greenhouse air temperature sensing system may further include a power supply system, the power supply system including: A lithium battery, electrically connected to the temperature sensor 25, the ventilation volume control unit and the microcontroller, for power supply; An external power supply interface 34, electrically connected to the lithium battery, for charging the lithium battery; The lithium battery provides backup power for the fan 23 when the external power interface 34 is powered off.

[0053] Specifically, the power supply in the greenhouse environment may be unstable, especially during agricultural operations or in severe weather conditions, where short-term power outages or voltage fluctuations may occur. These power supply anomalies will directly affect the normal operation of the fan 23, thereby causing the internal temperature of the radiation protection device to rise rapidly, affecting the temperature measurement accuracy. To solve this problem, this embodiment designs a dual power supply system with a backup power supply function, including two key parts: a lithium battery and an external power supply interface 34.

[0054] Furthermore, the lithium battery, as the core power supply unit of the system, forms a complete power supply circuit with the temperature sensor 25, the ventilation control unit and the microcontroller. The lithium battery is selected as the backup power supply mainly because it has the advantages of high energy density, low self-discharge rate, long service life, etc., and can provide reliable power supply guarantee under the requirements of miniaturization design. The external power supply interface 34 is electrically connected to the lithium battery. Under normal working conditions, it not only supplies power to the entire system, but also has the function of charging the lithium battery to ensure that the backup power supply is always available.

[0055] Based on the above embodiment, as an optional embodiment, the microcontroller is used for: Get the preset temperature measurement error value.

[0056] The required wind speed difference is determined based on the current greenhouse radiation value and temperature measurement error value.

[0057] The wind speed of fan 23 is calculated based on the wind speed in the greenhouse and the wind speed difference.

[0058] The driving current of the fan 23 is determined according to the preset corresponding relationship between the wind speed and the current.

[0059] The preset temperature measurement error value refers to the maximum deviation range allowed between the actual measurement value of the greenhouse air temperature sensor 25 and the true temperature value. In the embodiment of the present application, it can be understood as an upper limit of the acceptable temperature measurement error set artificially according to the requirements of temperature control accuracy for different greenhouse crops. It is used to guide the system to adjust the speed of the fan 23, and to reduce the speed of the fan 23 as much as possible to extend the service life of the equipment under the premise of meeting the measurement accuracy requirements.

[0060] In practical applications, the microcontroller obtains the temperature measurement error value input by the user through the human-computer interaction interface. For example, when planting temperature-sensitive high-value-added crops such as Enoki mushrooms, considering the sensitivity of their growth process to temperature changes, the operator can set the error value within the range of ±0.1°C; when planting ordinary crops with a wide temperature adaptability range such as corn, the error value can be appropriately relaxed to ±0.5°C. After receiving this preset value, the microcontroller uses it as an important basis for subsequent control decisions to calculate the required wind speed difference.

[0061] After obtaining the preset temperature measurement error value, the microcontroller needs to determine the appropriate wind speed difference according to the current radiation environment in the greenhouse. The key is to accurately establish the correspondence between radiation intensity, measurement error and wind speed difference. Please refer to Tables 1 to 5. Through the accumulation and analysis of a large amount of experimental data, the embodiment of the present application has established a complete set of parameter mapping tables, covering different radiation intensity ranges from 200W / ㎡ to 1000W / ㎡.

[0062] Table 1 The influence of wind speed difference inside and outside the hood on the difference between inside and outside the hood under the solar radiation intensity of 200 W / ㎡

[0063] Table 2 The influence of wind speed difference inside and outside the hood on the difference between inside and outside the hood under the solar radiation intensity of 400 W / ㎡

[0064] Table 3 The influence of wind speed difference inside and outside the hood on the difference between inside and outside the hood under the solar radiation intensity of 600 W / ㎡

[0065] Table 4 The influence of wind speed difference inside and outside the hood on the difference between inside and outside the hood under the solar radiation intensity of 800 W / ㎡

[0066] Table 5 The influence of wind speed difference inside and outside the hood on the difference between inside and outside the hood under the solar radiation intensity of 1000 W / ㎡

[0067] Specifically, the microcontroller first detects the radiation value in the current greenhouse and divides it into the corresponding range. For example, when the detected radiation value is 380W / ㎡, the system will classify it into the range of 400±100W / ㎡. Then, according to this radiation range and the preset temperature measurement error value, the experimental data table is queried to determine the required wind speed difference. Taking the 400W / ㎡ radiation intensity range as an example, when the temperature measurement error requirement is 0.1℃, it can be seen from the table that a wind speed difference of 2.5m / s needs to be maintained; if the allowable error is relaxed to 0.3℃, the wind speed difference can be reduced to about 1.5m / s.

[0068] After determining the required wind speed difference, the microcontroller needs to calculate the target working wind speed of the fan 23 in combination with the actual wind speed in the greenhouse. The wind speed in the greenhouse is a dynamically changing parameter, which is affected by many factors such as the ventilation system, the opening and closing of doors and windows, etc. In order to maintain stable measurement accuracy, the system needs to adjust the output wind speed of the fan 23 in real time according to these changes.

[0069] The microcontroller collects wind speed data in the greenhouse in real time through the wind speed sensor, and calculates it with the wind speed difference determined in the previous step. The calculation formula is: fan 23 wind speed = greenhouse wind speed + wind speed difference. For example, when the wind speed in the greenhouse is 0.5m / s and the required wind speed difference is 2.5m / s, the system will set the target wind speed of fan 23 to 3.0m / s. This calculation method takes into account the real-time changes in the ambient wind speed, so that sufficient ventilation can always be maintained inside the radiation protection device.

[0070] Furthermore, in order to accurately convert the calculated target wind speed into the actual operating parameters of the fan 23, the microcontroller needs to determine the appropriate driving current value based on the pre-calibrated correspondence between wind speed and current. This correspondence is obtained through a large number of experimental tests and is described by a quadratic function model, i.e., I=aw²+bw+c, where I is the driving current, w is the wind speed, and a, b, and c are experimentally calibrated coefficients. In this embodiment, after repeated testing and optimization, the coefficients a=1.2, b=0.5, and c=3.2 are determined. This set of parameters can provide good control accuracy within the entire working range.

[0071] Exemplarily, the process of determining the corresponding relationship between wind speed and current is as follows: First, the system can automatically match the corresponding data table based on the sensor error ∆T set by human-computer interaction and the real-time detected greenhouse radiation value. For example, when the radiation value is 380W / ㎡, the system will select Table 2 (corresponding to the range of 400±100W / ㎡) as a reference. After determining the data table, the system will find the required wind speed difference ∆w based on the preset temperature measurement error ∆T. For each wind speed difference data point, use Its actual applicable range is determined by the method of, where w1 and w2 are the wind speed values ​​of adjacent data points respectively.

[0072] After obtaining the wind speed difference, the system uses the formula ; Calculate the required wind speed of fan 23. The calculated result needs to be compared with the maximum wind speed of fan 23 to ensure that the system operates within the effective range. If the calculated wind speed is within the working range of fan 23, substitute it into the quadratic function equation: The required driving current is calculated; if the maximum wind speed of fan 23 is exceeded, the system will prompt on the display screen that the current measurement accuracy requirement cannot be met.

[0073] Based on the above embodiment, as an optional embodiment, the microcontroller is further used for: When the wind speed of the fan 23 exceeds the preset maximum wind speed, the minimum measurement error under the current greenhouse environment is calculated.

[0074] When the minimum measurement error is greater than the preset error, the wind speed of the fan 23 is adjusted to the preset maximum wind speed.

[0075] When the actually achievable minimum measurement error is less than or equal to the set temperature measurement error value, the driving current corresponding to the preset maximum wind speed is determined according to the corresponding relationship between the wind speed and the current.

[0076] Specifically, in a greenhouse environment, especially under strong light and high radiation conditions, the fan 23 wind speed required by the microcontroller may exceed the preset maximum wind speed limit. This situation usually occurs at noon in summer, when the solar radiation intensity is close to or exceeds 1000W / ㎡. In order to maintain a high measurement accuracy, the theoretically required fan 23 wind speed may exceed the actual working range of the fan 23. In order to reasonably deal with this situation, the system needs to accurately evaluate the minimum measurement error that can be achieved under the current environmental conditions.

[0077] The microcontroller first detects the radiation value in the current greenhouse and matches it to the corresponding data table range. For example, when the radiation value is detected to be 950W / ㎡, the system will select Table 5 (corresponding to the range of 1000±100W / ㎡) as the reference data source. After determining the reference data table, the microcontroller reads the temperature measurement error value corresponding to the preset maximum wind speed of fan 23. Specifically, if the preset maximum wind speed of fan 23 is 8m / s, it can be seen from Table 5 that when the radiation intensity is 1000W / ㎡ and the wind speed difference is 8.02m / s, the corresponding temperature measurement error is 3.44℃. This error value is the minimum measurement error that the system can achieve under the current environmental conditions.

[0078] After determining the minimum measurement error in the current greenhouse environment, the microcontroller needs to compare this error value with the preset temperature measurement error and make corresponding control decisions. When the calculated minimum measurement error is greater than the preset error, it means that even if the fan 23 is adjusted to the maximum wind speed, the expected measurement accuracy requirement cannot be achieved. This situation usually occurs under strong light conditions in summer. For example, when the radiation intensity is close to 1000W / ㎡, even if the fan 23 works at the maximum wind speed of 8m / s, the measurement error may still exceed the preset temperature measurement error value.

[0079] In the face of the above situation, the microcontroller can directly adjust the wind speed of the fan 23 to the preset maximum wind speed. This is because continuing to increase the wind speed can no longer improve the measurement accuracy, but will cause the fan 23 to be overloaded; secondly, although maintaining the maximum wind speed cannot achieve the expected accuracy, it can ensure that the system obtains the best possible measurement effect under the current conditions.

[0080] In the actual operation of the greenhouse temperature measurement system, when the system detects that the required wind speed of the fan 23 exceeds the preset maximum wind speed, in addition to the need to handle the situation where the minimum measurement error is greater than the preset error, it is also necessary to consider the situation where the minimum measurement error meets the preset requirements. Specifically, when the calculated minimum measurement error is less than or equal to the set temperature measurement error value, it indicates that the system is capable of meeting the measurement accuracy requirements under the current environmental conditions, and at this time, a suitable control strategy needs to be adopted to ensure the stable operation of the system.

[0081] Furthermore, the microcontroller substitutes the preset maximum wind speed into the formula to calculate the corresponding driving current value according to the pre-calibrated wind speed and current correspondence formula. For example, when the preset maximum wind speed is 8m / s, substituting it into the formula can obtain a specific driving current value. The calculated driving current will be provided to the fan 23 through the constant current driving circuit, and the current detection circuit will monitor the actual driving current in real time to form a closed-loop control to ensure that the fan 23 operates stably at the preset maximum wind speed state.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A greenhouse air temperature sensing system, characterized in that: include: The radiation protection device comprises a top cover, a cylinder and a guide bottom plate; wherein: A fan for blowing air upwards is arranged inside the cylinder; An air flow channel is provided between the guide chassis and the cylinder; A ventilation volume control unit, used to control the speed of the fan; A temperature sensor is disposed in the cylinder; A microcontroller is electrically connected to the ventilation volume control unit and the temperature sensor, and is used to control the rotation speed of the fan according to a preset temperature measurement error.

2. The greenhouse air temperature sensing system according to claim 1, characterized in that: The top cover comprises two layers of a first radiation protection sheet and a second radiation protection sheet arranged in parallel, wherein the first radiation protection sheet is used for sunshade, and the second radiation protection sheet is used for heat insulation.

3. The greenhouse air temperature sensing system according to claim 2, characterized in that: The distance between the first radiation protection sheet and the second radiation protection sheet is greater than 5 centimeters, and a support column is provided between the first radiation protection sheet and the second radiation protection sheet.

4. The greenhouse air temperature sensing system according to claim 2 or 3, characterized in that: The first radiation protection sheet and the second radiation protection sheet are made of a high reflectivity metal material.

5. The greenhouse air temperature sensing system according to claim 1, characterized in that: A filter screen for filtering dust is arranged on the upper part of the cylinder, and the cylinder is in a trumpet shape.

6. The greenhouse air temperature sensing system according to claim 1, characterized in that: A reflective layer is provided on the lower surface of the guide chassis.

7. The greenhouse air temperature sensing system according to claim 1, characterized in that: The ventilation volume control unit comprises: A constant current driving circuit, electrically connected to the microcontroller, and configured to provide a driving current for the fan according to a control signal of the microcontroller; The current detection circuit has an input end electrically connected to the fan and an output end electrically connected to the microcontroller, and is used to detect the driving current and feed back the detection result to the microcontroller.

8. The greenhouse air temperature sensing system according to claim 1, characterized in that: Also included is a power supply system, the power supply system comprising: A lithium battery, electrically connected to the temperature sensor, the ventilation volume control unit and the microcontroller, for power supply; An external power supply interface, electrically connected to the lithium battery, for charging the lithium battery; Wherein, the lithium battery provides backup power for the fan when the external power interface is powered off.

9. The greenhouse air temperature sensing system according to claim 1, characterized in that: The microcontroller is used to: Obtain a preset temperature measurement error value; Determining the required wind speed difference according to the current greenhouse radiation value and the temperature measurement error value; Calculating the fan wind speed based on the wind speed in the greenhouse and the wind speed difference; The fan driving current is determined according to the preset corresponding relationship between the wind speed and the current.

10. The greenhouse air temperature sensing system according to claim 8, characterized in that: The microcontroller is also used to: When the fan wind speed exceeds a preset maximum wind speed, calculating a minimum measurement error under the current greenhouse environment; When the minimum measurement error is greater than a preset error, adjusting the fan speed to the preset maximum speed; When the actually achievable minimum measurement error is less than or equal to the set temperature measurement error value, the driving current corresponding to the preset maximum wind speed is determined according to the corresponding relationship between the wind speed and the current.

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