Atmospheric remote sensing optical surface gas-heat synergistic self-cleaning control method

Abstract

The invention discloses a gas-heat cooperative self-cleaning control method for an atmospheric remote sensing optical surface. The method comprises the following steps: (1) monitoring environment temperature, lens temperature and environment relative humidity through a real-time sensing module, and uploading data to a control module; (2) the control module triggers cleaning operation based on any condition; (3) when the cleaning condition is not met any more, the cleaning operation is stopped; the device not only has the function of blowing away dust, accumulated water and other impurities, but also can meet the requirements under different environmental conditions by adjusting the airflow temperature, and provides a non-contact heating function, so that dew condensation is effectively prevented, and the cleanliness and dryness of lenses are kept.

Description

Technical Field

[0001] The present invention relates to the technical field of atmosphere detection laser radar, and in particular to a method for controlling gas-heat coordinated self-cleaning of an atmospheric remote sensing optical surface. Background Art

[0002] LiDAR has been used to detect atmospheric temperature, humidity, pressure, wind and other meteorological parameters with high temporal and spatial resolution. In the process of laser atmospheric remote sensing, keeping the telescope lens clean is crucial for the effective detection capability of LiDAR. Usually, LiDAR is placed directly in the outdoor environment. The harsh environment makes it easy for dust, rain, snow and condensed dew to accumulate on the surface of the telescope lens. These substances will cause serious attenuation of the outgoing laser and echo signals, thereby reducing the detection accuracy of atmospheric parameters and the detection distance of LiDAR.

[0003] Traditional cleaning methods mainly use automatic wipers or manual wiping to remove impurities on the surface of the lens, but this method has significant disadvantages. First, the direct friction between the mechanical wiper and the lens is easy to accelerate the wear of the mirror in a windy and dusty environment. Long-term use will cause surface scratches and blurring, resulting in a decrease in light transmittance, which directly affects the accuracy of the detection data; secondly, in a rainy environment, after the wiper works, a layer of water film will still remain on the surface of the lens, which will produce a reflection and absorption effect on the laser radar working in the near-infrared band, resulting in a serious attenuation of the echo signal intensity; in addition, the existing cleaning method is completely ineffective for the condensed water mist inside the lens, and this type of condensation will directly block the laser transmission path; furthermore, manual wiping has problems such as large randomness of operation and delayed response, which makes it difficult to meet the real-time cleaning requirements of the atmospheric detection laser radar under unattended working conditions. These shortcomings have brought challenges to the long-term automatic and stable operation of the laser radar. The above problems have seriously restricted the long-term reliable operation of the laser radar in extreme environments, but there is no integrated cleaning method and system that can simultaneously solve the external pollution removal, water film reduction and anti-condensation. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention proposes a method for controlling the air-heat coordinated self-cleaning of the atmospheric remote sensing optical surface, which effectively utilizes high-speed airflow to clean the lens surface. It not only has the function of blowing away impurities such as dust and accumulated water, but also can adjust the airflow temperature to meet the needs of different environmental conditions and provide non-contact heating function, thereby effectively preventing dew condensation and keeping the lens clean and dry, solving the problem of infrared laser transmission loss caused by condensed water mist in the lidar telescope.

[0005] Technical solution: The present invention discloses a method for controlling the thermal-gas coordinated self-cleaning of an atmospheric remote sensing optical surface, comprising the following steps: (1) Monitor ambient temperature through real-time sensing module , lens temperature , relative humidity 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.

[0006] Furthermore, the 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 at each time in the past t moments.

[0007] Furthermore, the determination of a precipitation event includes: analyzing the spectrum characteristics of the echo signal in real time through a Doppler lidar, 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.

[0008] Furthermore, the method for determining the temperature T2 of the heated air flow is: according to the ambient temperature T0 and the 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.

[0009] Furthermore, the dynamic time threshold formula is as follows: ; in, is the reference relative humidity, .

[0010] Furthermore, the dew point temperature formula is as follows: ; in, , RH is the relative humidity of the environment measured by the humidity sensor.

[0011] The atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control system described in the present invention is used to support an atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control method, comprising: Jet and heating module: includes high-pressure gas source, heating element, jet nozzle and rotating spindle. The rotating spindle drives the jet nozzle to rotate to spray airflow evenly. 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 of the methods described, and control the start and stop of the jet and heating modules and adjust parameters.

[0012] Furthermore, 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.

[0013] Furthermore, 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.

[0014] Furthermore, the control module detects the maximum real-time detection distance L of the radar. M Rate of change , dynamically adjust the working power of the jet and heating modules , until The specific control process is as follows: First set the initial system operating power , and at the same time with step size Gradually increase the power. The working power is adjusted with time t to: ; At the same time, according to the relative change rate of the maximum detection distance fed back by the radar in real time: ; when When the system reaches the optimal working state, the current power As the final working power.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following advantages: The present invention utilizes high-speed airflow to clean the lens surface, has the characteristic of not directly contacting the telescope lens, can avoid the wear of the mirror surface caused by the friction of traditional wipers, can improve the working life of the equipment and the effective working time, and ensure effective detection capabilities. The present invention detects rainfall events and sets a continuous hot air flow washing 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 utilizes temperature and humidity sensors to actively determine the risk of condensation, and by adjusting the temperature of the ejected airflow, effectively avoids the condensation of water mist on the lens, solving the problem that the traditional cleaning object can only be external contaminants on the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of the present invention; Figure 2 It is a schematic diagram of the system structure of the present invention; Figure 3 It is a schematic diagram of the system operation of the present invention; Figure 4 This is an experimental effect diagram provided by Example 1 of the present invention; Figure 5 This is an experimental effect diagram provided by Example 2 of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further explained and illustrated below in conjunction with 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.

[0018] Example 1: Dust The lens surface of LiDAR equipment deployed in desert arid areas is often seriously affected by sand and dust. The traditional windshield wiper cleaning method of LiDAR will cause serious wear and tear on the mirror surface, affecting the transmission of light signals and resulting in reduced detection capabilities. 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 can effectively clean dust attached to radar telescope plates through the following steps: Step S1: The real-time sensing module monitors the mirror reflectivity R and uploads it to the radar industrial computer for storage (control module). The mirror reflectivity R is defined as the reflected light intensity With the incident light intensity Ratio of: ; Step S2: The control system compares the mirror reflectivity R provided by the radar industrial computer with the dynamic reference reflectivity threshold value when the lens is in a clean state. The reference reflectivity threshold Using the historical average lens reflectivity over a preset time window in the past gives: ; Where N is the length of the historical data window; is the reflectivity at each time in the past t moments. Figure 4 (a) in the figure gives an example verification. In this example, N = 24 hours of historical mirror reflectivity data length is used to calculate the current reference reflectivity threshold. During the dust coverage process, the reflectivity rises and the signal echo weakens. When the increase in the real-time reflectivity R exceeds the set dynamic reference reflectivity threshold When the lens surface is covered with sand and dust, the control system determines that there is sand and dust pollution, generates a sand and dust pollution warning signal and activates the cleaning program. In this embodiment, the lens is only cleaned by blowing air through the jet module, and the particles on the lens surface can be quickly removed without starting the heating device. The jet module uses a brushless motor to drive the fan to supply airflow, and the rotating main shaft drives the jet port to rotate and spray airflow, ensuring that the airflow covers the entire surface of the lens.

[0019] Step S3: Figure 4 As shown in (b), after about 1 minute of cleaning, the CNR (signal-to-noise ratio) measured by the radar is significantly enhanced, and 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 has been met, stops the cleaning operation, and enters the standby state.

[0020] At the same time, operators can monitor the cleaning status of the lens in real time through a micro camera, which supports operators to remotely evaluate the cleanliness and record contamination characteristics.

[0021] Example 2: Rain and Snow Rain and snow adhering to the lens will cause scattering and absorption on 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 data acquisition interruption or increase in errors, thus adversely affecting the performance of the lidar. Figure 1 As shown, an embodiment of the present invention provides a method for controlling the air-heat coordinated self-cleaning of an atmospheric remote sensing optical surface, which cleans rain and snow attached to radar telescope plates through the following steps: Step S1: The radar industrial computer obtains the spectrum width and skewness data measured by the Doppler laser radar. The real-time sensing module monitors the ambient temperature , lens temperature , environmental relative humidity RH and other parameters and upload them to the radar industrial computer for storage (control module).

[0022] Step S2: Based on the spectral echo characteristics of the Doppler lidar, the high-order moment characteristics (spectral width, skewness) of the echo signal are analyzed in real time to effectively distinguish the aerosol and precipitation particle echoes: aerosol particles have narrow spectrum characteristics due to Brownian motion (typical spectral width <0.8m / s, skewness ... ), and precipitation particles produce wide spectrum characteristics due to terminal velocity differences and turbulent disturbances: raindrop echo spectrum width ≥ 1.2m / s, skewness ≥ 0.35 (asymmetric velocity distribution). The control system analyzes the spectral characteristics of the echo signal and sets a double threshold condition: the signal with a spectrum width exceeding 1m / s and a skewness exceeding 0.3 is set as the threshold and used as the standard for determining precipitation. Figure 5 As shown, in this embodiment, a Doppler laser radar with a pulse width of 400ns is used, and the spectral width threshold is set to 4MHz. There is precipitation that lasts for 1 hour between 15:00 and 16:00. At the beginning of precipitation, the signal decays rapidly, and the spectral width increases to 4MHz, and the skewness exceeds 0.3. The system determines that precipitation has occurred, and the control system sends a rain and snow warning signal and starts the heating and jet device. The rotating spindle drives the jet head to rotate and continuously sprays to cover the entire surface of the lens. The temperature is The heated airflow accelerates the evaporation of rainwater on the lens surface. Then the CNR signal gradually changes from weak to strong and remains stable, indicating that the lens surface can continue to remain relatively clean during precipitation. Determined by: To ensure that the relative humidity of the blown air is lower than the relative humidity threshold value of 70% set in this embodiment, The corresponding saturated water vapor pressure The following relationship should be satisfied: ; 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: ; 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: , is a known constant.

[0023] 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.

[0024] Example 3: Condensed water mist (such as frost or fog) 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: 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).

[0025] 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 continuous dynamic risk response time When , the system determines that there is a condensation risk. The dynamic risk response time threshold is: ; In this embodiment, the relative humidity threshold is set to , , minutes; RH is the relative humidity of the environment.

[0026] The control system issues a condensation risk warning signal and starts the pneumatic cleaning mode. The spray temperature is The constant temperature hot air flow continuously heats and cleans the lens. At the same time, the rotating main shaft drives the jet nozzle to rotate back and forth, and the air flow is continuously ejected through the jet nozzle to form a flow field covering the surface of the lens, 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 detects the temperature change of the lens in real time and transmits it to the radar industrial computer. The temperature of the heated air flow used above is Determined by: To ensure that the relative humidity of the blown air is lower than the relative humidity threshold value of 70% set in this embodiment, The corresponding saturated water vapor pressure The following relationship should be satisfied: ; 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: ; Calculated. Where t is the temperature in 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: , is a known constant.

[0027] Step S3: When the When the system determines that the condensation risk has been eliminated and the cleaning stop conditions have been met, the system stops the cleaning operation and enters the standby state.

[0028] The embodiment of the present invention also provides an atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control system, which is used to support an atmospheric remote sensing optical surface gas-heat coordinated self-cleaning control method, such as Figure 2 As shown: a fan 1, a brushless motor 2, a heating element 3, a rotating spindle 5, an air jet 7 and a device 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, a miniature camera 6 installed outside the sensor and facing the mirror, and a radar telescope piece 9; like Figure 3 As shown, the jet and heating module includes a high-pressure gas source, a heating element, a jet nozzle and a rotating spindle. The rotating spindle drives the jet nozzle to rotate to uniformly spray the airflow. 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 jet nozzle is adjustable. The temperature sensor includes two probes, which measure the ambient temperature T0 and the lens temperature T1 respectively. 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.

[0029] 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 of the methods described, control the start and stop of the jet and heating modules and adjust parameters. 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 The specific control process is as follows: First set the initial system operating power , and at the same time with step size Gradually increase the power. The working power is adjusted with time t to: ; At the same time, according to the relative change rate of the maximum detection distance fed back by the radar in real time: ; when When the system reaches the optimal working state, 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 , relative humidity 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 at each time in the past t moments.

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, is the base relative humidity, .

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 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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