Cloud detection method and system for low-altitude aircraft

Abstract

The invention provides a cloud detection method and system for a low-altitude aircraft, and relates to the field of meteorological detection of low-altitude aircrafts. The system comprises a laser measurement module and a control assembly, and the laser measurement module can emit laser pulses, receive back scattering light signals reflected by a target cloud layer and transmit the back scattering light signals to the control assembly. The control assembly can determine the distance from the low-altitude aircraft to the target cloud layer and the thickness of the target cloud layer in the sailing direction based on the signal intensity time sequence of the backward scattering light signals. Compared with an image sensor, the influence of illumination on the laser pulse and the back scattering light signal is low, so that the accuracy of detecting the distance from the low-altitude aircraft to the target cloud layer and the thickness of the target cloud layer in the navigation direction is high; and compared with the existing measuring equipment, the low-altitude aircraft is limited in maneuvering flight scene use and is difficult to be suitable for small and medium-sized low-altitude aircrafts. Therefore, the cloud detection system provided by the invention is relatively high in practicability.

Description

Technical Field

[0001] This application belongs to the field of meteorological detection for low-altitude aircraft, specifically relating to a cloud detection method and system for low-altitude aircraft. Background Technology

[0002] Low-altitude aircraft (such as drones) may encounter clouds during their flight path. Upon entering cloud cover, they may face low visibility and icing, impacting their flight safety. Therefore, low-altitude aircraft need to detect their distance from clouds during takeoff, landing, and flight to avoid cloud cover in a timely manner.

[0003] Currently, low-altitude aircraft typically use onboard cameras to acquire images during their flight and use these images to determine the distance between the aircraft and the clouds. However, cloud detection relying solely on camera images is greatly affected by light conditions, resulting in low accuracy in determining the distance. Furthermore, it is difficult to adapt to maneuvering flight scenarios for low-altitude aircraft, as well as nighttime and low-light conditions, thus limiting its applicability. Summary of the Invention

[0004] This application provides a cloud detection method and system for low-altitude aircraft, which can solve the problems of low accuracy and limited applicability in determining the distance between low-altitude aircraft and clouds in related technologies.

[0005] In a first aspect, this application provides a cloud detection system for low-altitude aircraft, the cloud detection system comprising: a laser measurement module and a control component; The laser measurement module is used to emit laser pulses, receive backscattered light signals reflected by the target cloud, and transmit the backscattered light signals to the control components. The target cloud is the cloud located in the flight direction of the low-altitude aircraft. The control component is used to determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight, based on the time series of the signal intensity of the backscattered light signal.

[0006] Optionally, the control component is used for: Based on the signal intensity time series of the backscattered light signal, a first distance and a second distance are obtained. The first distance is the distance from the low-altitude aircraft to the first boundary of the target cloud layer, and the second distance is the distance from the low-altitude aircraft to the second boundary of the target cloud layer. In the direction of travel, the first boundary is closer to the low-altitude aircraft than the second boundary. Based on the initial distance, determine the distance between the low-altitude aircraft and the target cloud layer; The thickness of the target cloud layer in the direction of travel is determined based on the difference between the second distance and the first distance.

[0007] Optionally, the control component is also used for: Obtain the reception time of each signal strength in the signal strength time series; Based on the reception time of each signal strength, the transmission distance of the backscattered light signal to which each signal strength belongs is obtained, so as to obtain the function of signal strength and transmission distance; The derivative function is obtained by taking the first derivative of the function, and the first and second distances are obtained based on the derivative function; In the derivative function, the function values ​​corresponding to the first distance and the second distance are both zero.

[0008] Optionally, the control component is also used for: When operating in trigger response mode, after receiving a detection command, a detection signal is sent to the laser measurement module to instruct the laser measurement module to emit a laser pulse; When operating in continuous mode, a detection signal is sent to the laser measurement module according to the drive cycle to instruct the laser measurement module to emit laser pulses.

[0009] Optionally, the control component is also used for: When operating in continuous mode, it switches from continuous mode to trigger response mode in response to a mode switching command. The mode switching command is triggered when the distance between the low-altitude aircraft and the target cloud layer is greater than a distance threshold.

[0010] Optionally, the laser measurement module includes: a laser source module, a transmitting optical system module, a receiving optical system module, and a photoelectric detection module; Laser source module, used to emit laser pulses; The transmitting optical system module is used to collimate and transmit laser pulses. The receiving optical system module is used to receive the backscattered light signal reflected by the target cloud layer and transmit the backscattered light signal to the photoelectric detection module; The photoelectric detection module is used to convert backscattered light signals into electrical signals and then transmit them to the control components.

[0011] Optionally, the control components include: a data acquisition and processing unit, and a control circuit; The control circuit is connected to the laser source module and is used to drive the laser source module to emit laser pulses. The data acquisition and processing unit is connected to the photoelectric detection module. The data acquisition and processing unit is used to acquire the signal intensity time series of the backscattered light signal based on the electrical signal, and to determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight, based on the signal intensity time series.

[0012] Secondly, this application provides a cloud detection method for low-altitude aircraft, applied to a cloud detection system, which includes: a laser measurement module and a control component; The laser measurement module emits laser pulses and receives backscattered light signals reflected by the target cloud layer, and transmits the backscattered light signals to the control components. The target cloud layer is the cloud layer located in the flight direction of the low-altitude aircraft. By controlling the signal intensity time series of backscattered light signals, the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight, are determined.

[0013] Thirdly, this application provides a low-altitude aircraft, which includes the cloud detection system as described in the first aspect.

[0014] Fourthly, this application provides a computer-readable storage medium storing a program or instructions that, when executed by a processor, implement the steps of the cloud detection method for low-altitude aircraft as described in the second aspect.

[0015] Fifthly, this application provides a computer program product that, when executed by a processor of a vehicle or a cloud server, implements the steps of the cloud detection method for low-altitude aircraft as described in the second aspect.

[0016] This application provides a cloud detection method and system for low-altitude aircraft, comprising a laser measurement module and a control component. The cloud detection system includes a laser measurement module and a control component. The laser measurement module can emit laser pulses, receive backscattered light signals reflected from a target cloud layer, and transmit the backscattered light signals to the control component. The target cloud layer is located in the flight direction of the low-altitude aircraft. The control component can determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the flight direction, based on the signal intensity time series of the backscattered light signals. Compared to images acquired by a camera, laser pulses and backscattered light signals are less affected by light; therefore, the accuracy of the distance between the low-altitude aircraft and the target cloud layer, and the thickness of the target cloud layer in the flight direction, determined based on the intensity series of the backscattered light signals, is higher. Furthermore, the navigation direction can be horizontal, vertical, or diagonal. Compared to microwave radiometers, which can only obtain the vertical distance between a low-altitude aircraft and the target cloud layer with a ground reference, limiting their use in maneuvering low-altitude aircraft scenarios, and because existing measurement equipment is difficult to apply to small and medium-sized low-altitude aircraft, the cloud detection system provided in this application is highly practical. Attached Figure Description

[0017] Figure 1A schematic diagram of a cloud detection system for low-altitude aircraft provided in this application embodiment; Figure 2 A schematic diagram of another cloud detection system for low-altitude aircraft provided in this application embodiment; Figure 3 An example diagram illustrating a first distance and a second distance provided in an embodiment of this application; Figure 4 This is a flowchart of a cloud detection method for low-altitude aircraft provided in an embodiment of this application. Detailed Implementation

[0018] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0019] With the gradual opening of low-altitude airspace control and the increasing prosperity of the low-altitude economy, low-altitude aircraft such as electric vertical take-off and landing (eVTOL) aircraft and drones (such as rotary-wing drones) are being used more and more widely in fields such as passenger transport, logistics transportation and emergency rescue.

[0020] During operation, low-altitude aircraft may inadvertently enter cloud cover, potentially facing low visibility and icing conditions, which could compromise flight safety. Furthermore, the visual flight rules (VFR) for low-altitude aircraft require that, when flying outside cloud cover, the horizontal distance to the cloud layer be no less than 1500 meters, and the vertical distance no less than 300 meters. Therefore, cloud detection capabilities are of paramount importance for low-altitude aircraft in areas where mobile meteorological monitoring and ground-based high-precision airway meteorological support services, such as those covering islands and mountainous regions, are difficult to access, and in situations where multiple cloud layers are present in the flight area.

[0021] Currently, low-altitude aircraft are equipped with measuring devices that can be used to obtain cloud height. These devices can include microwave radiometers or camera image sensors. However, microwave radiometers currently primarily detect clouds in the vertical direction, making it difficult to detect clouds in the horizontal direction. The vertical direction is perpendicular to the horizontal direction, and refers to the direction perpendicular to the Earth's surface (or the ground plane at the observation point). That is, the vertical direction can be parallel to the direction of gravity.

[0022] Taking a microwave radiometer as an example: A microwave radiometer primarily receives microwave radiation from the atmosphere and clouds, utilizing the sensitivity of different frequencies to different altitudes to invert the distribution characteristics of clouds in the vertical direction (i.e., the altitude dimension). In other words, it inverts the cloud state at different altitudes vertically upwards from the ground. A microwave radiometer is designed with multiple microwave frequency channels, each most sensitive to the radiation signal at a specific altitude layer in the atmosphere. If the cloud radiation signal received in a certain channel suddenly increases, the microwave radiometer can determine that the altitude corresponding to that microwave frequency channel is the height of the cloud base. Therefore, this method can only determine the height of the cloud layer, but cannot determine the distance between a low-altitude aircraft and the cloud layer in other directions (such as the horizontal direction), making it unsuitable for low-altitude aircraft maneuvering scenarios.

[0023] Taking a camera image sensor as an example: Low-altitude aircraft can be equipped with camera image sensors. These sensors can acquire optical images during flight and detect cloud distribution ahead of the aircraft based on these images. However, accurately measuring the distance to the clouds is difficult. Furthermore, this method is greatly affected by lighting conditions, resulting in low accuracy of the measured distances, and it is not suitable for nighttime use.

[0024] Figure 1 This is a schematic diagram of a cloud detection system for a low-altitude aircraft, provided as an embodiment of this application. The cloud detection system can be installed in the low-altitude aircraft. Optionally, the low-altitude aircraft can be a small to medium-sized aircraft. The low-altitude aircraft can fly in low-altitude areas, such as urban islands or mountainous airspace. The low-altitude aircraft can fly within island or mountainous airspace and use the cloud detection system provided in this embodiment to detect target clouds. Figure 1 As shown, the cloud detection system may include a laser measurement module 11 and a control component 12.

[0025] The laser measurement module 11 is used to emit laser pulses, receive backscattered light signals reflected by the target cloud layer, and transmit the backscattered light signals to the control component 12. The target cloud layer is located in the flight direction of the low-altitude aircraft. The transmission direction of the backscattered light signal is opposite to the transmission direction of the laser pulses emitted by the laser measurement module 11.

[0026] Control component 12 is used to determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of travel, based on the signal intensity time series of the backscattered light signal. The direction of travel can be horizontal, vertical, or oblique. Oblique refers to any direction other than horizontal or vertical. For example, if the low-altitude aircraft is ascending or descending, the direction of travel can be vertical. If the low-altitude aircraft is traveling in a straight line parallel to the ground or moving backward in a straight line parallel to the ground, the direction of travel can be horizontal.

[0027] In summary, this application provides a cloud detection system for low-altitude aircraft. The system includes a laser measurement module and a control component. The laser measurement module emits laser pulses, receives backscattered light signals reflected from a target cloud layer, and transmits these backscattered light signals to the control component. The target cloud layer is located in the flight direction of the low-altitude aircraft. The control component can determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the flight direction, based on the signal intensity time series of the backscattered light signal. Compared to images captured by a camera, laser pulses and backscattered light signals are less affected by light. Therefore, the accuracy of the distance between the low-altitude aircraft and the target cloud layer, and the thickness of the target cloud layer in the flight direction, determined based on the intensity series of the backscattered light signal, is higher. Furthermore, the flight direction can be horizontal, vertical, or oblique. This is significant compared to microwave radiometers, which can only obtain the vertical distance between the low-altitude aircraft and the target cloud layer with a ground reference, making them unsuitable for maneuvering aircraft flight scenarios; and existing measurement equipment is also unsuitable for small and medium-sized low-altitude aircraft. Therefore, it can be seen that the cloud detection system provided in this application embodiment has high practicality.

[0028] In this embodiment, the laser measurement module 11 and the control component 12 can be integrated. Alternatively, the laser measurement module 11 and the control component 12 can be independently configured (i.e., separately configured). In this case, the laser measurement module 11 and the control component 12 can be connected via a connecting cable. Separating the laser measurement module 11 and the control component 12 facilitates system maintenance. For example, if the laser measurement module 11 is damaged while the control component 12 is not damaged, only the laser measurement module 11 can be replaced, thereby reducing maintenance costs.

[0029] The low-altitude aircraft includes an aircraft fuselage and a gimbal assembly. In scenarios where the laser measurement module 11 and the control assembly 12 are set up independently, in an optional implementation, both the laser measurement module 11 and the control assembly 12 can be installed in the aircraft fuselage.

[0030] In another alternative implementation, the control component 12 can be installed in the aircraft fuselage, while the laser measurement module 11 can be installed in the gimbal assembly. Thus, compared to installing both the laser measurement module 11 and the control component 12 on the gimbal assembly, installing only the laser measurement module 11 on the gimbal assembly reduces the load and energy consumption of the gimbal assembly. This also facilitates the rotation of the laser measurement module 11 by the gimbal assembly, thereby making it easier to control the laser emission direction.

[0031] See Figure 2 The laser measurement module 11 may include: a laser source module 01, a transmitting optical system module 02, a receiving optical system module 03, and a photoelectric detection module 04. The control component 12 may include: a data acquisition and processing unit 05, and a control circuit 06 connected to the data acquisition and processing unit 05.

[0032] The control circuit 06 is connected to the laser source module 01. The control circuit 06 supplies power to the laser source module 01 and drives it to emit laser pulses. Specifically, the laser source module 01 includes a laser source and a source driving circuit for driving the laser source. The control circuit 06 can control the source driving circuit to drive the laser source to emit laser pulses.

[0033] The transmitting optical system module 02 is used to collimate the laser pulse before transmitting it. The receiving optical system module 03 is connected to the photoelectric detection module 04, and the receiving optical system module 03 is used to receive the backscattered light signal reflected by the target cloud layer and transmit the backscattered light signal to the photoelectric detection module 04.

[0034] The photoelectric detection module 04 is connected to the data acquisition and processing unit 05, and the photoelectric detection module 04 can be used to convert the backscattered light signal into an electrical signal and transmit it to the data acquisition and processing unit 05. The data acquisition and processing unit 05 can, after receiving the electrical signal, obtain the signal intensity time series of the backscattered light signal based on the electrical signal, and determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight, based on the signal intensity time series of the backscattered light signal.

[0035] In addition, the low-altitude aircraft also includes a control system 10. The data acquisition and processing unit 05 can also transmit the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the flight direction, to the control system 10, so that the control system 10 can control the low-altitude aircraft's flight based on the distance and thickness. The control system 10 can provide power to the cloud detection system.

[0036] Optionally, the laser source can be a laser diode, which reduces the size and weight of the laser measurement module 11, achieving a lightweight design. The transmitting optical system module 02 may include a collimator, such as a fiber optic collimator. The receiving optical system module 03 may include a receiving optical lens. This receiving optical lens can be an optical lens with a pigtail and an aperture less than 25.4 mm. Because the pigtail has good electromagnetic shielding and anti-interference performance, it can effectively avoid the influence of external interference on the backscattered light signal, thereby improving the accuracy of calculating the distance between the low-altitude aircraft and the target cloud layer, as well as the accuracy of the thickness of the target cloud layer in the flight direction.

[0037] In this embodiment, the laser source module 01 can continuously emit laser pulses according to the emission frequency, that is, the laser source module 01 can emit multiple laser pulses.

[0038] Optionally, the laser pulse can be a near-infrared laser pulse. For example, the wavelength of the laser pulse can be 905 nanometers (nm). In this way, on the one hand, the near-infrared spectral band can reduce the absorption of laser energy by water vapor in the atmosphere, thereby reducing the energy loss of the laser signal and achieving lower laser emission energy and a longer detection distance. On the other hand, the strong atmospheric penetration of near-infrared laser pulses can reduce energy attenuation and changes in the propagation path, enabling the laser to reach the target and return a sufficiently strong backscattered light signal to maintain a sufficient signal-to-noise ratio for subsequent reception and analysis.

[0039] The meteorological conditions required by the Visual Flight Rules (VFR) for low-altitude aircraft are: when flying outside clouds, the horizontal distance between the aircraft and the cloud layer must be no less than 1500 meters, and the vertical distance must be no less than 300 meters. Generally, the meteorological conditions required by the Instrument Flight Rules (IFR) are lower than those required by the VFR. Taking VFR as an example, the round-trip time of a laser signal over 1500 meters is 10 microseconds. To avoid signal overlap, the round-trip time of the laser signal needs to be less than or equal to the pulse interval of the laser pulse. Since the pulse interval is 10... The corresponding transmission frequency is 100 kilohertz (kHz). Therefore, to ensure that the low-altitude aircraft meets flight regulations when flying horizontally, the transmission frequency of the laser source module 01 should be less than or equal to 100 kHz. This ensures that the pulse interval is greater than the round-trip time of the laser signal (1500 meters), thus guaranteeing that when the flight direction is horizontal, there will be no signal overlap when the laser measurement module 11 detects clouds at a distance of less than or equal to 1500 meters from the low-altitude aircraft.

[0040] Pulse width (PW) is the duration of a single laser pulse emission, which determines the accuracy of distance measurement and the minimum detection range (blind zone). At a vertical distance of 300 meters, the laser's round-trip transmission distance is 600 meters. Because a shorter pulse width results in a smaller blind zone, when a low-altitude aircraft is traveling vertically, to avoid the detection blind zone and ensure that clouds at a vertical distance of less than 300 meters can be detected, the pulse width of the laser pulse emitted by laser source module 01 must be less than or equal to 2. .

[0041] Optionally, both the laser measurement module 11 and the control component 12 can be connected to the control system 10 of the low-altitude aircraft. In this case, if the control system 10 requires the cloud detection system to perform cloud detection, it can send control commands to the laser measurement module 11 and the control component 12 respectively to control the operation of the laser measurement module 11 and the control component 12.

[0042] Alternatively, the control component 12 is connected to the control system 10 of the low-altitude aircraft, while the laser measurement module 11 is not connected to the control system 10 of the low-altitude aircraft. In this case, in an optional implementation, after the low-altitude aircraft is started, the control component 12 can drive the laser measurement module 12 to emit laser pulses for cloud detection.

[0043] In another alternative implementation, the control system 10 can send a detection command to the control component 12 when cloud detection is required. In response to this detection command, the control component 12 can send a detection signal to the laser measurement module 11. This detection signal instructs the laser measurement module 11 to emit a laser pulse.

[0044] It is understandable that while the control component 12 controls the laser measurement module 12 to emit laser pulses, it can simultaneously record the emission time of the laser pulses.

[0045] Specifically, after receiving a detection command from the control system 10 of the low-altitude aircraft, the control circuit 06 of the control component 12 can send a detection signal to the light source driving circuit of the laser light source module 01 and a recording signal to the data acquisition and processing unit 05. The detection signal instructs the light source driving circuit to drive the laser light source to emit laser pulses. The recording signal instructs the data acquisition and processing unit 05 to synchronously record the emission time of the laser pulses.

[0046] Optionally, the detection and recording signals can be clock-synchronized gating signals.

[0047] In this embodiment, the low-altitude aircraft further includes an image sensor. When the control system 10 of the low-altitude aircraft detects clouds in the flight direction using the image sensor, it can send a detection command to the control component 12. Therefore, the method provided in this embodiment can send a detection command to the control component 12 only when clouds are detected, triggering the cloud detection system to detect the distance between the low-altitude aircraft and the target cloud, as well as the thickness of the target cloud in the flight direction. This avoids continuous cloud detection by the cloud detection system, reducing its power consumption while maintaining good hazard response capabilities, thus saving energy for the low-altitude aircraft.

[0048] The process by which control component 12 determines the distance between the low-altitude aircraft and the target cloud layer, and the thickness of the target cloud layer in the flight direction, based on the signal intensity time series of the backscattered light signal, may include: Step A1: Based on the signal intensity time series of the backscattered light signal, obtain the first distance and the second distance.

[0049] The first distance is the distance from the low-altitude aircraft to the first boundary of the target cloud layer, and the second distance is the distance from the low-altitude aircraft to the second boundary of the target cloud layer. In terms of the flight direction, the first boundary is closer to the low-altitude aircraft than the second boundary. That is, the first boundary is closer to the low-altitude aircraft.

[0050] In this embodiment, the control component 12 can acquire the reception time of each signal intensity in the signal intensity time series, and based on the reception time of each signal intensity, acquire the transmission distance of the backscattered light signal to which each signal intensity belongs, thus obtaining a function of signal intensity and transmission distance. Then, the control component 12 can perform a first-order derivative on this function to obtain a derivative function, and acquire a first distance and a second distance based on the derivative function. The function values ​​corresponding to the first distance and the second distance in the derivative function are both zero. The reception time of the signal intensity corresponding to the first distance is earlier than the reception time of the signal intensity corresponding to the second distance.

[0051] In this embodiment of the application, the process by which the control component 12 obtains the transmission distance of the backscattered light signal corresponding to each signal strength based on the reception time of each signal strength may include: For each signal strength, the control component 12 determines the transmission duration based on the reception time of the backscattered light signal to which the signal strength belongs and the emission time of the laser pulse corresponding to the recorded backscattered light signal. Then, the control component 12 can determine the transmission distance of the backscattered light signal as half of the product of the transmission duration and the transmission speed of the backscattered light signal.

[0052] After obtaining multiple transmission distances of multiple backscattered light signals, the control component 12 can sort the multiple backscattered light signals in order from early to late according to the receiving time, and obtain a function of signal strength and transmission distance based on the transmission distance and signal strength of the sorted multiple backscattered light signals.

[0053] For example, if the laser pulse is emitted at time T0, and the backscattered light signal of that laser pulse is received at time T... z If the transmission speed of the laser pulse is c, then the transmission distance can satisfy the following formula (1): (1) During its propagation through the atmosphere, a laser pulse continuously interacts with aerosol particles, generating backscattered light signals. When the laser reaches clouds, it interacts with water droplets or ice crystals, also producing backscattered light signals. Because aerosol particles are small and have a low concentration, the reflected backscattered light signals have low intensity. Conversely, because water droplets or ice crystals are large and have a high concentration, the reflected backscattered light signals have high intensity. In other words, the signal intensity of the backscattered light signal after reflection from the laser pulse through clouds is greater than the signal intensity of the backscattered light signal after reflection from aerosol particles.

[0054] Aerosol particle scattering is weak and uniform, and the concentration of aerosol particles changes gradually with transmission distance, while laser energy gradually attenuates with distance. Therefore, the signal strength of the backscattered signal reflected by aerosol particles decreases steadily with increasing transmission distance. When the laser pulse enters the cloud, it undergoes strong scattering, and the signal strength of the backscattered signal changes from a gradual decrease to a sharp increase. When the laser pulse exits the cloud, the signal strength of the backscattered signal decreases sharply. In other words, a "sudden change point" in signal strength occurs during the process of the laser pulse entering and exiting the cloud. The distance corresponding to this "sudden change point" is the distance from the low-altitude aircraft to the cloud boundary.

[0055] Based on this, the control component 12 can perform a first-order derivative of the function of signal strength and transmission distance to obtain the derivative function, thereby identifying the function point where the intensity of the backscattered light signal changes drastically. Then, based on this function point, the first distance and the second distance are obtained. This derivative function describes the rate of change of the intensity of the backscattered light signal with respect to the transmission distance. In the cloudless phase, since the signal strength of the backscattered light signal decreases steadily and the rate of change is stable, the derivative function is negative in this phase. When the laser pulse enters the cloud layer, the signal strength of the backscattered light signal changes from a steady decrease to a sudden increase, and the derivative function (rate of change) changes from negative to zero. When the laser pulse exits the cloud layer, the signal strength of the backscattered light signal decreases sharply, and the derivative function becomes zero when the transmission distance reaches the boundary of the exiting cloud layer.

[0056] Therefore, the control component 12 can determine the transmission distance corresponding to the signal strength when the derivative function has a value of zero as the first distance and the second distance.

[0057] In this embodiment, the first and second boundaries of the target cloud layer are determined by differentiation, allowing for a direct identification of the "abrupt change point" in the intensity of the backscattered light signal. Because this method can quickly locate the first and second boundaries of the target cloud layer, it improves the efficiency of obtaining the distance between the low-altitude aircraft and the target cloud layer in the flight direction, as well as the efficiency of obtaining the target cloud layer's thickness. Furthermore, it can accurately capture the boundaries of weak clouds (with few or very small water droplet and ice crystal particles) where the intensity of the backscattered light signal does not increase significantly, thus improving the reliability of identifying the first boundary of the target cloud layer.

[0058] Step A2: Based on the first distance, determine the distance between the low-altitude aircraft and the target cloud layer.

[0059] In this embodiment, the control component 12 can directly determine the first distance as the distance between the low-altitude aircraft and the target cloud layer. Alternatively, the control component 12 can determine the distance between the low-altitude aircraft and the target cloud layer as the product of the first distance and a first preset coefficient. The first preset coefficient can be pre-stored by the control component 12, for example, it can be 0.999.

[0060] Step A3: Based on the difference between the second distance and the first distance, determine the thickness of the target cloud layer in the direction of navigation.

[0061] Since the thickness of the target cloud layer in the navigation direction is equal to the distance between the first boundary and the second boundary, the control component 12 can obtain the difference between the second distance and the first distance. Then, the control component 12 can directly determine this difference as the thickness of the target cloud layer in the navigation direction. Alternatively, the control component 12 can determine the thickness of the target cloud layer in the navigation direction by multiplying this difference by a second preset coefficient. This second preset coefficient can be pre-stored by the control component 12, for example, it can be 0.99.

[0062] Optionally, assume the first distance is The first distance is The intensity of the corresponding backscattered light signal is The second distance is The second distance is The intensity of the corresponding backscattered light signal is Control component 12 can be and Under the condition that the following formula (2) is satisfied, the second distance is determined as the distance between the low-altitude aircraft and the second boundary of the target cloud layer.

[0063] (2) Optionally, when the control component 12 obtains the second distance, the control component 12 can obtain the thickness of the target cloud layer in the direction of flight of the low-altitude aircraft.

[0064] Understandably, when the cloud layer is too thick and contains a large number of water droplets or ice crystals, these particles will significantly attenuate the laser energy and cause multiple scatterings. Multiple scatterings disperse the laser energy in all directions, drastically reducing the proportion of energy returning along the backscattering direction. In other words, the signal strength of the backscattered light signal received by the receiving optical system module 03 will be very low, or it may not receive the backscattered light signal at all. The low-intensity backscattered light signal will be superimposed on the noise signal, causing the control component 12 to be unable to distinguish the backscattered light signal. Consequently, the control component 12 cannot obtain the second distance, and therefore cannot obtain the thickness of the target cloud layer.

[0065] For example, see Figure 3 Assuming that in the flight direction of the low-altitude aircraft, the first distance between the low-altitude aircraft and the first boundary is... The second distance between the low-altitude aircraft and the second boundary is Therefore, the thickness of the target cloud layer in the direction of travel can be... - .

[0066] In this embodiment, the control component 12 operates in two modes: a trigger-response mode and a continuous mode. In trigger-response mode, upon receiving a detection command, the control component 12 sends a detection signal to the laser measurement module 11 to instruct it to emit a laser pulse. In continuous mode, the control component 12 sends a detection signal to the laser measurement module 11 according to a driving cycle to instruct it to emit a laser pulse.

[0067] When operating in continuous mode, control component 12 can switch from continuous mode to trigger-response mode in response to a mode switching command. The mode switching command is triggered when the distance between the low-altitude aircraft and the target cloud exceeds a distance threshold. A distance greater than the threshold indicates that the target cloud is far enough away that it will not affect the safe flight of the low-altitude aircraft. In this case, control component 12 switches to trigger-response mode, thus preventing the laser measurement module 11 from continuously emitting laser pulses, thereby reducing the energy consumption of the low-altitude aircraft.

[0068] Figure 4This is a flowchart illustrating a cloud detection method for low-altitude aircraft provided in an embodiment of this application. This method can be applied to... Figure 1 or Figure 2 Any of the cloud detection systems shown. For example... Figure 4 As shown, the method includes: Step 41: The laser measurement module emits laser pulses and receives backscattered light signals reflected by the target cloud layer, and transmits the backscattered light signals to the control component. The target cloud layer is the cloud layer located in the flight direction of the low-altitude aircraft.

[0069] The target cloud layer is the cloud layer located in the flight direction of the low-altitude aircraft.

[0070] Step 42: By controlling the signal intensity time series of the backscattered light signal, determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight.

[0071] The method provided in this application can be referred to the above-described cloud detection system embodiments, and will not be repeated here.

[0072] In summary, this application provides a cloud detection method. Compared to images captured by a camera, laser pulses and backscattered light signals are less affected by light. Therefore, the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight, determined based on the intensity sequence of the backscattered light signal, are more accurate. Furthermore, the flight direction can be horizontal, vertical, or oblique. Compared to cloud meters and microwave radiometers, which can only obtain the vertical distance between the low-altitude aircraft and the target cloud layer regardless of the flight direction, the cloud detection method provided in this application is more practical.

[0073] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0074] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0075] In the description of this specification, the references to terms such as "optional," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0076] Furthermore, the terms "first," "second," etc., used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this application can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this application, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly and specifically defined in the embodiments.

[0077] In this application, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication between two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific implementation.

[0078] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A cloud detection system for low-altitude aircraft, characterized in that, The cloud detection system includes: a laser measurement module and a control component; The laser measurement module is used to emit laser pulses, receive backscattered light signals reflected by the target cloud layer, and transmit the backscattered light signals to the control component. The target cloud layer is a cloud layer located in the flight direction of the low-altitude aircraft. The control component is used to determine the distance between the low-altitude aircraft and the target cloud layer, and the thickness of the target cloud layer in the flight direction, based on the signal intensity time series of the backscattered light signal.

2. The cloud detection system according to claim 1, characterized in that, The control component is used for: Based on the signal intensity time series of the backscattered light signal, a first distance and a second distance are obtained, wherein the first distance is the distance from the low-altitude aircraft to the first boundary of the target cloud layer, and the second distance is the distance from the low-altitude aircraft to the second boundary of the target cloud layer. In the direction of travel, the first boundary is closer to the low-altitude aircraft than the second boundary. Based on the first distance, the distance between the low-altitude aircraft and the target cloud layer is determined; The thickness of the target cloud layer in the direction of travel is determined based on the difference between the second distance and the first distance.

3. The cloud detection system according to claim 2, characterized in that, The control component is also used for: Obtain the reception time of each signal strength in the signal strength time series; Based on the reception time of each signal strength, the transmission distance of the backscattered light signal to which each signal strength belongs is obtained, so as to obtain the function of the signal strength and the transmission distance; The derivative function is obtained by taking the first derivative of the function, and the first distance and the second distance are obtained based on the derivative function; In the derivative function, the function value corresponding to the first distance and the function value corresponding to the second distance are both zero.

4. The cloud detection system according to any one of claims 1 to 3, characterized in that, The control component is also used for: When operating in trigger response mode, upon receiving a detection command, a detection signal is sent to the laser measurement module to instruct the laser measurement module to emit a laser pulse; When operating in continuous mode, the detection signal is sent to the laser measurement module according to the drive cycle to instruct the laser measurement module to emit laser pulses.

5. The cloud detection system according to claim 4, characterized in that, The control component is also used for: When operating in continuous mode, in response to a mode switching command, the system switches from continuous mode to trigger response mode; The mode switching command is triggered when the distance between the low-altitude aircraft and the target cloud layer is greater than a distance threshold.

6. The cloud detection system according to any one of claims 1 to 3, characterized in that, The laser measurement module includes: a laser source module, a transmitting optical system module, a receiving optical system module, and a photoelectric detection module; The laser source module is used to emit laser pulses; The transmitting optical system module is used to collimate the laser pulse before transmitting it; The receiving optical system module is used to receive the backscattered light signal reflected by the target cloud layer and transmit the backscattered light signal to the photoelectric detection module; The photoelectric detection module is used to convert the backscattered light signal into an electrical signal and then transmit it to the control component.

7. The cloud detection system according to claim 6, characterized in that, The control components include: a data acquisition and processing unit, and a control circuit; The control circuit is connected to the laser source module, and the control circuit is used to drive the laser source module to emit laser pulses; The data acquisition and processing unit is connected to the photoelectric detection module. The data acquisition and processing unit is used to acquire the signal intensity time series of the backscattered light signal based on the electrical signal, and to determine the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the direction of flight, based on the signal intensity time series.

8. A cloud detection method for low-altitude aircraft, characterized in that, Applied to a cloud detection system, the cloud detection system includes: a laser measurement module and a control component; The laser measurement module emits laser pulses, receives backscattered light signals reflected by the target cloud, and transmits the backscattered light signals to the control component. The target cloud is a cloud located in the flight direction of the low-altitude aircraft. The control component determines the distance between the low-altitude aircraft and the target cloud layer, as well as the thickness of the target cloud layer in the flight direction, based on the signal intensity time series of the backscattered light signal.

9. A low-altitude aircraft, characterized in that, The low-altitude aircraft includes the cloud detection system according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The readable storage medium stores a program or instructions that, when executed by a processor, implement the steps of the cloud detection method as described in claim 8.

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