An Atmospheric Remote Sensing Optical Surface Gas-Thermal Synergistic Self-Cleaning Control Method

Abstract

The present invention discloses a method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface, comprising the following steps: (1) monitoring the ambient temperature, the lens temperature, and the ambient relative humidity through a real-time sensing module and uploading the data to a control module; (2) the control module triggers a cleaning operation based on any condition; (3) when the cleaning condition is no longer satisfied, the cleaning operation is stopped. The present invention not only has the function of blowing away impurities such as dust and accumulated water, but also can meet the requirements under different environmental conditions by adjusting the air flow temperature, and provide a non-contact heating function, thereby effectively preventing dew condensation and keeping the lens clean and dry.

Description

Technical Field

[0001] The present invention relates to the technical field of atmospheric detection lidar, and particularly relates to a method for self-cleaning control of gas-thermal coordination on an optical surface for atmospheric remote sensing. Background Art

[0002] Lidar has been used for the detection of meteorological parameters such as temperature, humidity, pressure, and wind in the atmosphere with high spatio-temporal resolution. During the process of lidar remote sensing of the atmosphere, keeping the telescope lens clean is crucial for the effective detection ability of the lidar. Generally, the lidar is directly placed in an outdoor environment, and the harsh environment causes substances such as dust, rain, snow, and condensed dew to easily accumulate on the surface of the telescope lens. These substances will cause severe attenuation of the emitted laser and the echo signal, thereby reducing the detection accuracy of atmospheric parameters and the detection range of the lidar.

[0003] Traditional cleaning methods mainly use automatic windshield wipers or manual wiping to remove impurities on the lens surface, but this method has significant drawbacks. First, the direct friction between the mechanical wiper and the lens easily accelerates the wear of the lens surface in a sandy and dusty environment. Long-term use will cause surface scratches and blurring, resulting in a decrease in light transmittance and directly affecting the accuracy of detection data. Second, in a rainy environment, after the wiper works, a water film will still remain on the lens surface, which will produce reflection and absorption effects on the lidar operating in the near-infrared band, resulting in severe attenuation of the echo signal intensity. In addition, the existing cleaning methods are completely ineffective for the condensed water mist inside the lens, and such condensation will directly block the laser transmission path. Moreover, manual wiping has problems such as large operation randomness and response lag, and it is difficult to meet the real-time cleaning requirements of the lidar for unattended operation in atmospheric detection. These drawbacks pose challenges to the long-term automatic and stable operation of the lidar. The above problems have severely restricted the long-term reliable operation of the lidar in extreme environments, but there is currently no integrated cleaning method and system that can synchronously solve the problems of external pollution removal, water film reduction, and anti-condensation. Summary of the Invention

[0004] To solve the above problems in the prior art, the present invention proposes a method for self-cleaning control of gas-thermal coordination on an optical surface for atmospheric remote sensing, which effectively uses high-speed airflow to clean the lens surface. It not only has the function of blowing off impurities such as dust and accumulated water, but also can meet the requirements under different environmental conditions by adjusting the airflow temperature, providing a non-contact heating function, thereby effectively preventing dew condensation, keeping the lens clean and dry, and solving the problem of infrared laser transmission loss caused by condensed water mist on the lidar telescope lens.

[0005] Technical Solution: A method for self-cleaning control of gas-thermal coordination on an optical surface for atmospheric remote sensing according to the present invention includes the following steps:

[0006] (1) Monitoring the ambient temperature through a real-time sensing module , the lens temperature , the ambient relative humidity and upload the data to the control module;

[0007] (2) The control module triggers the cleaning operation based on any of the following conditions:

[0008] Condition 1: When the reflectivity R of the lens exceeds the dynamic reference reflectivity threshold , and the duration exceeds the threshold , start the jet module to jet air flow to clean the lens;

[0009] Condition 2: When a precipitation event is detected, start the jet and heating module to jet heated air flow with temperature T2;

[0010] Condition 3: When the lens temperature T1 is lower than the ambient dew point temperature , and the duration exceeds the dynamic time threshold , start the jet and heating module to jet heated air flow with temperature T2;

[0011] (3) When the cleaning condition is no longer satisfied, stop the cleaning operation.

[0012] Further, the dynamic reference reflectivity threshold The formula is as follows: Given by the historical average lens reflectivity in the past preset time window:

[0013] ;

[0014] where, N is the length of the historical data window; is the reflectivity at each time of the past t moment.

[0015] Further, the determination of the precipitation event includes: Analyze the spectral characteristics of the echo signal in real time through a Doppler lidar. When the spectral width exceeds the preset spectral width threshold and the skewness exceeds the preset skewness threshold, it is determined as a precipitation event.

[0016] Further, the method for determining the temperature T2 of the heated air flow is: According to the ambient temperature T0 and relative humidity RH, calculate T2 through the following formula,

[0017] ;

[0018] where, RH is the actual ambient relative humidity measured by the humidity sensor, is the preset relative humidity threshold, and is obtained based on the Tetens saturation vapor pressure formula:

[0019] ;

[0020] where t is the Celsius temperature, and a, b are constants.

[0021] Furthermore, the dynamic time threshold formula is as follows:

[0022] ;

[0023] where is the reference relative humidity, .

[0024] Furthermore, the dew point temperature formula is as follows:

[0025] ;

[0026] where , and RH is the ambient relative humidity measured by the humidity sensor.

[0027] An atmospheric remote sensing optical surface gas-heat collaborative self-cleaning control system according to the present invention is used to support an atmospheric remote sensing optical surface gas-heat collaborative self-cleaning control method, and includes:

[0028] Jet and heating module: including a high-pressure gas source, a heating element, a jet nozzle, and a rotating main shaft, and the rotating main shaft drives the jet nozzle to rotate to uniformly eject air flow;

[0029] Real-time sensing module: including a temperature sensor, a humidity sensor, a precipitation sensor, and a micro camera, which are used to monitor environmental parameters and the state of the lens surface;

[0030] Control module: used to receive sensor data, execute any of the above methods, and control the start and stop and parameter adjustment of the jet and heating module.

[0031] Furthermore, the high-pressure gas source is a high-pressure fan or a high-pressure gas cylinder driven by a brushless motor, and the air flow pressure of the jet nozzle is adjustable; the temperature sensor includes two probes, which respectively measure the environmental temperature T0 and the lens temperature T1.

[0032] Furthermore, the heating element is an electric heating wire, a ceramic heating sheet, or a PTC heater; the system supports a timed working mode and automatically starts jet cleaning at a preset time interval.

[0033] Furthermore, the control module dynamically adjusts the working power M of the jet and heating module according to the change rate of the real-time farthest detection distance L of the radar until and then stops adjusting. The specific control process is as follows:

[0034] First, set the initial system working power , and at the same time with a step size gradually increase the power. The working power is adjusted with time t as:

[0035] ;

[0036] At the same time, according to the relative change rate of the farthest detection distance real-time feedback by the radar:

[0037] ;

[0038] When , it is considered that the system reaches the optimal working state, and the current power is used as the final working power.

[0039] Advantageous effects: Compared with the prior art, the present invention has the following advantages: The present invention uses high-speed air flow to clean the surface of the lens, has the characteristic of not directly contacting the telescope lens, can avoid the wear of the mirror surface caused by the friction of the traditional wiper, can improve the working life of the equipment and extend the effective working duration, and ensure the effective detection ability. The present invention detects rainfall events and sets a continuous hot air flow flushing working mode to effectively remove the water film on the surface of the telescope, greatly reducing the attenuation of the near-infrared laser signal by the water film and the data loss caused by untimely manual wiping. The present invention uses a temperature and humidity sensor to actively determine the risk of condensation, and effectively avoids the condensation of water mist on the lens by adjusting the temperature of the ejected air flow, solving the problem that the traditional cleaning object can only be external pollutants on the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of the present invention;

[0041] Figure 2 is a schematic structural diagram of the system of the present invention;

[0042] Figure 3 is a schematic diagram of the system working of the present invention;

[0043] Figure 4 is an experimental effect diagram provided by Embodiment 1 of the present invention;

[0044] Figure 5 is an experimental effect diagram provided by Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention will be further explained and illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are only used to illustrate and explain the present invention, and do not impose any limitation on the scope of implementation of the present invention.

[0046] Embodiment 1: Dust

[0047] The lidar device deployed in desert arid areas often has its lens surface severely affected by dust and sand. The traditional wiper cleaning method of lidar will cause serious wear to the mirror surface, affect the transmission of optical signals, and lead to a decline in detection ability. As Figure 1 shown, an air-heat collaborative self-cleaning control method for the optical surface of atmospheric remote sensing provided by an embodiment of the present invention effectively cleans the dust adhering to the radar telescope lens through the following steps:

[0048] Step S1: The real-time sensing module monitors the mirror reflectivity R and uploads it to the radar industrial control computer for storage (control module). The mirror reflectivity R is defined as the ratio of the reflected light intensity to the incident light intensity :

[0049] ;

[0050] Step S2: The control system compares the mirror reflectivity R provided by the radar industrial control computer with the dynamic reference reflectivity threshold under the clean state of the lens. Among them, the reference reflectivity threshold is given by using the historical average lens reflectivity in the past preset time window:

[0051] ;

[0052] where, N is the length of the historical data window; is the reflectivity at each time of the past t moment. Figure 4 In (a) of , the embodiment verification is given. In this embodiment, the current reference reflectivity threshold is calculated by taking the historical mirror reflectivity data length of N = 24 hours. During the dust coverage process, the reflectivity rises and the signal echo weakens. When the rising amplitude of the real-time reflectivity R exceeds the set dynamic reference reflectivity threshold , the control system determines that there is dust coverage on the lens surface, generates a dust pollution warning signal and activates the cleaning program. In this embodiment, only by blowing air on the lens through the air jet module, without starting the heating device, the particulate matter on the lens surface can be quickly removed. The air jet module uses a brushless motor to drive the fan to supply air flow, and at the same time rotates the main shaft to drive the air jet port to rotate and jet air flow to ensure that the air flow covers the entire surface of the lens.

[0053] Step S3: As shown in (b) of Figure 4 , after about 1 minute of cleaning, the CNR (signal-to-noise ratio) measured by the radar is significantly enhanced, and at the same time the mirror reflectivity drops back to the reference reflectivity, indicating that the pneumatic cleaning process effectively removes the dust on the lens surface. The control system determines that the cleaning stop condition is met, stops the cleaning operation, and enters the standby preparation state.

[0054] ​Meanwhile, the operator can monitor the cleaning status of the lens in real time through a micro camera, which supports the operator to remotely evaluate the cleanliness and record the pollution characteristics.

[0055] Embodiment 2: Rain and snow

[0056] The attachment of rain and snow to the lens will cause scattering and absorption of the optical surface, reduce the transmission efficiency of the laser signal, and affect the detection accuracy and range of the laser. These environmental factors will not only weaken the measurement signal, but may also cause the interruption of data acquisition or an increase in errors, thus having an adverse impact on the performance of the lidar. As Figure 1 shown, an air-heat collaborative self-cleaning control method for the optical surface of atmospheric remote sensing provided by the embodiment of the present invention realizes the cleaning of rain and snow attached to the radar telescope lens through the following steps:

[0057] Step S1: The radar industrial control computer obtains the spectral width and skewness data measured by the Doppler lidar. The real-time sensing module monitors environmental temperature , lens temperature , environmental relative humidity RH and other parameters and uploads them to the radar industrial control computer for storage (control module).

[0058] Step S2: Regarding the spectral echo characteristics of the Doppler lidar, by real-time analyzing the high-order moment characteristics (spectral width, skewness) of the echo signal, effectively distinguish the aerosol and precipitation particle echoes: aerosol particles show narrow-spectrum characteristics due to Brownian motion (typical spectral width < 0.8 m / s, skewness ), while precipitation particles produce wide-spectrum characteristics due to the difference in terminal velocity and turbulent disturbance: the spectral width of raindrop echoes ≥ 1.2 m / s, skewness ≥ 0.35 (asymmetric velocity distribution). The control system sets double-threshold conditions by analyzing the spectral characteristics of the echo signal: signals with a spectral width exceeding 1 m / s and a skewness exceeding 0.3 are set as thresholds and used as the criteria for determining precipitation. As Figure 5 shown, in this embodiment, a Doppler lidar with a pulse width of 400 ns is used, and the spectral width threshold is set to 4 MHz. There is continuous precipitation for 1 hour between 15:00 and 16:00. At the beginning of the precipitation, the signal decays rapidly, and at the same time the spectral width increases to 4 MHz and the skewness exceeds 0.3. The system determines that precipitation has occurred, and the control system issues a rain and snow warning signal and activates the heating and air jetting devices. The rotating main shaft drives the air jet head to rotate and continuously jets a heating air flow with a temperature of to accelerate the evaporation of rainwater on the lens surface. Subsequently, the CNR signal gradually becomes stronger from weak and remains stable, indicating that the lens surface can also maintain a relatively clean state during the precipitation process. The temperature of the ejected hot air flow is determined by the following method:

[0059] To satisfy that the relative humidity of the blown air is lower than the set relative humidity threshold of 70% in this embodiment, then The corresponding saturated water vapor pressure The following relationship should be satisfied:

[0060] ;

[0061] Among them, RH is the actual relative humidity of the environment measured by the humidity sensor, To preset the relative humidity threshold, and Based on the Tetens saturated water vapor pressure formula; As the threshold of thermal air temperature. Saturated water vapor pressure and Tetens saturated water vapor pressure formula:

[0062] ;

[0063] Calculated. Where t is the temperature in degrees Celsius, is the saturated water vapor pressure at 0°C. a and b are constants, and their specific values ​​depend on the temperature range. For the water surface: ; For ice: ,

[0064] is a known constant.

[0065] Step S3: The precipitation stops at around 16:00, and the real-time spectrum width and skewness drop back below the threshold. At this time, the system determines that the cleaning stop condition has been met and stops the cleaning operation.

[0066] Example 3: Condensed water mist (such as frost or fog)

[0067] Under conditions of high relative humidity, water vapor condensation is likely to occur on the surface of the telescope lens, which will seriously attenuate the laser energy, thereby weakening the echo signal and affecting the detection performance of the telescope. Water vapor condensation mainly occurs in environments with low temperature and high humidity, especially near the dew point temperature. Figure 1 As shown, an atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control method provided by an embodiment of the present invention realizes the cleaning of condensed water mist on radar telescope sheets through the following steps:

[0068] Step S1: Real-time sensing module monitors ambient temperature , lens temperature , environmental relative humidity RH and other parameters and upload them to the radar industrial computer for storage (control module).

[0069] Step S2: In this embodiment, the control system uses a dew point temperature difference ( ) dynamic condensation risk determination mechanism, its control logic and execution process are as follows: Below ambient dew point temperature And continuously dynamic risk response time When the system determines that there is a risk of condensation. The dynamic risk response time threshold is as follows:

[0070] ;

[0071] Among them, in this embodiment, the reference relative humidity threshold is set , , minutes; RH is the ambient relative humidity.

[0072] The control system issues a condensation risk warning signal and starts the pneumatic cleaning mode to eject a constant-temperature hot air flow with a temperature of to continuously heat and clean the lens. At the same time, the rotating main shaft drives the air jet to rotate back and forth, and the air flow continuously ejects through the air jet to form a flow field covering the lens surface, accelerating the evaporation of the water mist on the lens surface, thereby quickly cleaning the lens. At the same time, during the jet operation, the temperature sensor continuously detects the temperature change of the lens and transmits it to the radar industrial control computer. The temperature of the heated air flow adopted above is determined by the following method:

[0073] To satisfy that the relative humidity of the blown air is lower than the relative humidity threshold of 70% set in this embodiment, then The corresponding saturated water vapor pressure should satisfy the following relationship:

[0074] ;

[0075] Among them, RH is the actual ambient relative humidity measured by the humidity sensor, is the preset relative humidity threshold, and are obtained based on the Tetens saturated water vapor pressure formula; the obtained is used as the threshold of the hot air flow temperature. The saturated water vapor pressure and are obtained from the Tetens saturated water vapor pressure formula:

[0076] ;

[0077] Calculated. In the formula, t is the Celsius temperature, is the saturated water vapor pressure at 0°C. a and b are constants, and their specific values depend on the temperature range. For the water surface: ; For the ice surface: ,

[0078] are known constants.

[0079] Step S3: When satisfying When the system determines that the condensation risk is lifted and the cleaning stop condition is met, the system stops the cleaning operation and enters the standby preparation state.

[0080] An embodiment of the present invention also provides an air-heat collaborative self-cleaning control system for an atmospheric remote sensing optical surface, which is used to support an air-heat collaborative self-cleaning control method for an atmospheric remote sensing optical surface, as Figure 2 shown: a fan 1, a brushless motor 2, a heating element 3, a rotating main shaft 5, a jet nozzle 7, and an equipment housing 8; a real-time sensing module, including a combined sensor 4 that combines a thermocouple temperature sensor, a humidity sensor, and a precipitation sensor, and a micro camera 6 installed outside the sensor and facing the mirror surface, as well as a radar telescope lens 9;

[0081] As Figure 3 shown, the jet and heating module: includes a high-pressure gas source, a heating element, a jet nozzle, and a rotating main shaft. The rotating main shaft drives the jet nozzle to rotate to uniformly eject air; the high-pressure gas source is a high-pressure fan or a high-pressure gas cylinder driven by a brushless motor, and the air pressure of the jet nozzle is adjustable; the temperature sensor includes two probes, which respectively measure the ambient temperature T0 and the lens temperature T1. The heating element is an electric heating wire, a ceramic heating sheet, or a PTC heater; the system supports a timed working mode and automatically starts jet cleaning at a preset time interval.

[0082] The real-time sensing module: includes a temperature sensor, a humidity sensor, a precipitation sensor, and a micro camera, and is used to monitor environmental parameters and the surface state of the lens;

[0083] The control module: is used to receive sensor data, execute any of the above methods, and control the start and stop and parameter adjustment of the jet and heating module. The control module dynamically adjusts the working power of the jet and heating module according to the change rate M of the real-time farthest detection distance L of the radar, until it stops adjusting when . The specific control process is as follows:

[0084] First, set the initial system working power , and at the same time gradually increase the power with a step size . The working power is adjusted with time t as:

[0085] ;

[0086] At the same time, according to the relative change rate of the real-time farthest detection distance feedback by the radar:

[0087] ;

[0088] When , it is considered that the system reaches the optimal working state, and the current power As the final working power.

Claims

1. A method for controlling the thermal-gas coordinated self-cleaning of an atmospheric remote sensing optical surface, characterized in that: The following steps are involved: (1) Monitor ambient temperature through real-time sensing module , lens temperature , Actual relative humidity of the environment And upload the data to the control module; (2) The control module triggers the cleaning operation based on any of the following conditions: Condition 1: When the lens reflectivity R exceeds the dynamic reference reflectivity threshold , and the duration exceeds the threshold When the air jet module is started, the air jet is sprayed to clean the lens; Condition 2: When a precipitation event is detected, the jet and heating module is started to spray a heated airflow with a temperature of T2; Condition 3: When the lens temperature T1 is lower than the ambient dew point temperature , and the duration exceeds the dynamic time threshold When the jet and heating module is started, a heating airflow with a jet temperature of T2 is ejected; (3) When the cleaning conditions are no longer met, stop the cleaning operation.

2. According to claim 1, a method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface, characterized in that: Dynamic baseline reflectivity threshold The formula is as follows: Using the historical average lens reflectivity of the past preset time window gives: ； Where N is the length of the historical data window; is the reflectivity of each sampling time within the length of the historical data window, and t is the current time.

3. According to claim 1, a method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface, characterized in that: The determination of precipitation events includes: analyzing the spectrum characteristics of the echo signal in real time through the Doppler laser radar, and determining it as a precipitation event when the spectrum width exceeds a preset spectrum width threshold and the skewness exceeds a preset skewness threshold.

4. According to claim 1, a method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface, characterized in that: The method for determining the heating air flow temperature T2 is: according to the ambient temperature T0 and relative humidity RH, T2 is calculated by the following formula: ； Among them, RH is the actual relative humidity of the environment measured by the humidity sensor, To preset the relative humidity threshold, and Based on the Tetens saturated water vapor pressure formula: ； Where t is the temperature in degrees Celsius, , a and b are constants.

5. According to claim 1, a method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface, characterized in that: The dynamic time threshold formula is as follows: ； in, , , ; RH is the actual relative humidity of the environment measured by the humidity sensor.

6. The method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface according to claim 1, characterized in that: The dew point temperature formula is as follows: ； in, , RH is the actual relative humidity of the environment measured by the humidity sensor.

7. An atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control system, characterized in that: Used to support a method for the coordinated self-cleaning control of atmospheric remote sensing optical surfaces, including: The jet and heating module includes a high-pressure gas source, a heating element, a jet port and a rotating spindle, wherein the rotating spindle drives the jet port to rotate to uniformly jet the gas flow; Real-time sensing module: including temperature sensor, humidity sensor, precipitation sensor and micro camera, used to monitor environmental parameters and lens surface status; Control module: used to receive sensor data, execute any method described in claims 1-6, and control the start and stop of the jet and heating modules and adjust parameters.

8. The atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control system according to claim 7, characterized in that: The high-pressure gas source is a high-pressure fan or a high-pressure gas cylinder driven by a brushless motor, and the airflow pressure of the air jet is adjustable; the temperature sensor includes two probes, which respectively measure the ambient temperature T0 and the lens temperature T1.

9. The atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control system according to claim 7, characterized in that: The heating element is an electric heating wire, a ceramic heating plate or a PTC heater; the system supports a timing working mode and automatically starts jet cleaning at a preset time interval.

10. The atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control system according to claim 7, characterized in that: The control module is based on the real-time maximum detection distance L of the radar M Rate of change , dynamically adjust the working power of the jet and heating modules , until Stop adjusting.

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