A method, system, device, and medium for drone landing in a deny environment

Abstract

The application discloses a UAV landing method, system, device and medium for a denial environment, coordinates of a landing point and a ground marker are calibrated in advance, a laser range finder and a tracker are used to track the marker by an airborne photoelectric pod, a UAV position is calculated in real time by combining an attitude angle of the photoelectric pod and a UAV attitude information, longitudinal and lateral deviations of the UAV relative to the landing point are further calculated, and a reliable voting height is obtained by three-redundancy height data fusion; finally, a longitudinal guidance instruction is generated based on the deviations and the voting height, and a rudder and throttle control instruction is calculated by combining a UAV attitude and a motion state, so that the UAV can realize safe and accurate autonomous landing under the condition that no satellite navigation signal is available, and the application has the advantages of strong anti-interference capability, high landing precision, good system reliability and the like, and is suitable for landing guidance of a medium or large UAV in a complex environment.

Description

Technical Field

[0001] This application relates to the field of unmanned aerial vehicle (UAV) control technology, and more specifically, to a method, system, device, and medium for landing UAVs in denied environments. Background Technology

[0002] With the rapid development of UAV technology, medium and large UAVs have been widely used in critical missions such as military reconnaissance and battlefield supply delivery. These missions typically place extremely high demands on the autonomous landing accuracy of UAVs. High-precision landing is crucial for ensuring mission success, payload safety, and equipment reusability. Currently, UAV landing navigation largely relies on satellite navigation systems and their augmentation technologies, which can provide relatively reliable position, velocity, and attitude information in open environments with good signal coverage, supporting precise guidance and control.

[0003] However, in real combat or complex adversarial environments, drones often face the severe challenge of navigation signal denial. For example, in battlefield areas, they may encounter man-made GPS interference or strong electromagnetic suppression. When performing missions in mountainous areas, canyons, or between urban buildings, terrain obstruction can cause severe attenuation or even complete failure of satellite signals. In such environments, existing widely used satellite-based navigation methods, such as differential positioning, will not function properly. If relying solely on a pure inertial navigation system, its positioning error accumulates over time and grows exponentially, potentially leading to unacceptable deviations within a short period during the landing phase. This not only fails to meet the mission requirements for precise landing but also seriously threatens the landing safety of the drone, potentially causing mission failure or even equipment damage.

[0004] Therefore, in denial environments where satellite navigation signals are unavailable, how to achieve stable, reliable, and high-precision landing of UAVs has become a key technical challenge that urgently needs to be overcome in the field of UAV navigation and control. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of existing technologies and provide a method, system, device and medium for UAV landing in denied environments. By combining airborne optoelectronic pod laser ranging with ground marker positioning, high-precision autonomous landing control of UAVs in GPS denied environments is achieved, solving the technical problems of traditional satellite navigation-dependent landing systems failing in strong interference environments and landing safety being difficult to guarantee.

[0006] The objective of this application is achieved through the following technical solution:

[0007] Firstly, this application proposes a method for landing a drone in a denied environment, comprising: The coordinates of the landing point on the landing runway, the landing direction, and the coordinates of the landmarks at a certain distance from the landing runway are calibrated and loaded into the airborne control computer. The landing point coordinates include longitude, latitude, altitude, and landing direction. When the drone is aligned with the landing runway and initiates the landing procedure, it continuously tracks the markers and performs periodic laser ranging to obtain laser ranging values ​​through the onboard electro-optical pod. Based on laser rangefinder values, the attitude angle of the optoelectronic pod, the coordinates of the marker, and the UAV's own attitude information, the UAV's position coordinates are calculated in real time. Based on the UAV's position coordinates and landing point coordinates, calculate the UAV's longitudinal and lateral deviations relative to the landing point; Based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the altitude of the radio altimeter, a triple-redundancy altitude data fusion is performed to obtain the UAV's voting altitude; Calculate the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude; Based on lateral deviation, UAV voting altitude, longitudinal guidance commands, and UAV attitude and motion status information, control commands for UAV control surfaces and throttle are generated to achieve precise landing.

[0008] In one possible implementation, the step of calculating the UAV's position coordinates in real time based on laser rangefinder values, the attitude angle of the electro-optical pod, marker coordinates, and the UAV's own attitude information includes: Based on the laser ranging value, the azimuth and pitch angles of the optoelectronic pod, the three-dimensional distance components in the computer body coordinate system; By combining the UAV's heading angle, pitch angle, and roll angle, the three-dimensional distance components are converted to the geographic coordinate system; Based on the coordinates of the landmark and the distance components in the geographic coordinate system, the longitude, latitude, and altitude of the UAV are calculated.

[0009] In one possible implementation, the step of calculating the longitudinal and lateral deviations of the UAV relative to the landing point based on the UAV's position coordinates and the landing point coordinates includes: Calculate the northward and eastward distances between the drone and the landing point; Calculate the horizontal distance and the angular deviation relative to the landing direction based on the northward and eastward distances; The longitudinal and lateral deviations are obtained by decomposing the horizontal distance and angular deviations.

[0010] In one possible implementation, the step of performing triple-redundant altitude data fusion based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the radio altimeter altitude to obtain the UAV's voting altitude includes: The optical altitude, atmospheric altitude, and radio altitude are sorted and the errors between each pair are calculated. Based on whether the error exceeds a preset threshold, the median and / or mean are selected as the voting height.

[0011] In one possible implementation, the step of calculating the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude includes: During the guided descent segment, the guide height is calculated based on the longitudinal deviation, the preset descent angle, and the initial height of the pull-up segment. During the landing pull-up phase, the guidance altitude is calculated based on the longitudinal deviation and glide slope angle.

[0012] In one possible implementation, the control commands include elevator, aileron, rudder, and throttle commands, which are calculated through pitch control loop, roll control loop, yaw control loop, and speed control loop, respectively.

[0013] The pitch control loop generates an upward velocity command based on the altitude deviation and glide trajectory, and then achieves altitude tracking through pitch angle control.

[0014] The roll control loop generates roll angle commands based on lateral deviation, and then achieves lateral trajectory tracking through aileron control; The throttle control circuit generates axial acceleration commands based on the speedometer deviation, and then achieves speed tracking through engine throttle control.

[0015] Secondly, this application proposes a drone landing system for a denied environment, the system comprising: The calibration module is used to calibrate the landing point coordinates and landing direction of the landing runway, as well as the coordinates of the markers at a certain distance from the landing runway, and load them into the airborne control computer. The landing point coordinates include longitude, latitude, altitude, and landing direction. The ranging module is used to continuously track the marker and perform periodic laser ranging to obtain the laser ranging value when the UAV is aligned with the landing runway and starts the landing procedure; The first calculation module is used to calculate the position coordinates of the UAV in real time based on the laser range measurement value, the attitude angle of the optoelectronic pod, the coordinates of the marker, and the attitude information of the UAV itself. The second calculation module is used to calculate the longitudinal and lateral deviations of the UAV relative to the landing point based on the UAV's position coordinates and landing point coordinates. The data fusion module is used to perform triple-redundancy altitude data fusion based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the radio altimeter altitude to obtain the UAV's voting altitude. The third calculation module is used to calculate the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude; The generation module is used to generate control commands for the UAV's control surfaces and throttle based on lateral deviation, UAV voting altitude, longitudinal guidance commands, and UAV attitude and motion state information, so as to achieve precise landing.

[0016] Thirdly, this application also proposes a computer device including a processor and a memory, wherein the memory stores a computer program that is loaded and executed by the processor to implement the unmanned aerial vehicle landing method as described in any of the first aspects.

[0017] Fourthly, this application also proposes a computer-readable storage medium storing a computer program that is loaded and executed by a processor to implement the UAV landing method as described in any of the first aspects.

[0018] The main solution and its various further alternatives described above can be freely combined to form multiple solutions, all of which are solutions that can be adopted and are claimed in this application; furthermore, the (non-conflicting alternatives) can also be freely combined with each other and with other alternatives. Those skilled in the art, after understanding the solution of this application, will realize from the prior art and common general knowledge that there are many combinations, all of which are technical solutions to be protected in this application, and will not be exhaustively listed here.

[0019] This application discloses a method for precise landing of unmanned aerial vehicles (UAVs) in navigation denied environments. By pre-calibrating the coordinates of the landing point and ground markers, an airborne electro-optical pod continuously performs laser ranging and tracking of the markers. Combining the attitude angles of the electro-optical pod with the UAV's own attitude information, the UAV's position is calculated in real time. Furthermore, the longitudinal and lateral deviations of the UAV relative to the landing point are calculated, and a reliable voting altitude is obtained through triple-redundant altitude data fusion. Finally, longitudinal guidance commands are generated based on the deviations and voting altitude. Combined with the UAV's attitude and motion state, control surface and throttle commands are comprehensively calculated to guide the UAV to achieve safe and precise autonomous landing in the absence of satellite navigation signals. This method has advantages such as strong anti-interference capability, high landing accuracy, and good system reliability, and is suitable for landing guidance of medium and large UAVs in complex environments. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart illustrating a method for landing a drone in a navigation denied environment, as proposed in an embodiment of this application, is shown.

[0022] Figure 2 This diagram illustrates the longitudinal and lateral deviations between the UAV and the runway center. Figure 3 A schematic diagram showing the relative altitude of the drone to the center of the runway is provided.

[0023] Figure 4 A schematic diagram of the longitudinal trajectory of the drone landing is shown.

[0024] Figure 5 A schematic diagram of the longitudinal control structure for UAV landing is shown.

[0025] Figure 6 A schematic diagram of the lateral navigation control structure for UAV landing is shown. Detailed Implementation

[0026] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0027] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] To address the high landing risk of UAVs in navigation-denied environments, this application provides a method for precise UAV landing in such environments. Utilizing the laser ranging and positioning capabilities of an airborne optoelectronic pod, the method calculates the UAV's position by performing real-time laser ranging on landmarks at known ground locations. This allows for the calculation of the UAV's longitudinal deviation, lateral deviation, and relative altitude relative to the landing runway and landing point during landing flight. Based on the optically guided three-dimensional position deviation and data fusion, this method effectively addresses the problem of precise landing for medium to large-sized UAVs in navigation-denied environments.

[0029] Please refer to Figure 1 , Figure 1 This paper presents a flowchart illustrating a method for landing a UAV in a navigation-denied environment, as proposed in an embodiment of this application. This method is applicable to medium to large UAVs equipped with an airborne electro-optical pod and includes: Step S1: The coordinates of the landing point and landing direction of the landing runway, as well as the coordinates of the markers at a certain distance from the landing runway, are calibrated and loaded into the airborne control computer. The landing point coordinates include longitude, latitude, altitude, and landing direction.

[0030] Step S1 calibrates the landing point coordinates, landing direction, and coordinates of landmarks at a certain distance from the landing runway, and pre-loads these parameters into the onboard control computer. The landing point coordinates include longitude (…). ),latitude( ), altitude ( ) and landing direction ( These parameters are acquired through high-precision measuring equipment (GPS or geodetic instruments) and stored in the onboard computer's memory to ensure that the UAV can still perform positioning calculations based on pre-stored data even in navigation-denied environments. Simultaneously, the markers must have a rough, easily identifiable surface and a size no smaller than 1m × 1m × 1m to ensure stable tracking and laser ranging by the onboard electro-optical pod at long distances. The markers should be prominently positioned, facing the direction of the UAV's landing approach without obstruction, and should avoid interference from terrain or buildings. Their coordinate parameters include longitude. ,latitude and altitude It was also loaded into the onboard computer.

[0031] Step S2: When the UAV is aligned with the landing runway and starts the landing procedure, the UAV continuously tracks the markers and performs periodic laser ranging to obtain the laser ranging value through the onboard electro-optical pod.

[0032] The optoelectronic pod is equipped with a television camera sensor or an infrared camera sensor and a laser rangefinder, enabling it to stably track targets and continuously perform laser ranging on them, with a laser ranging accuracy of no more than 2m.

[0033] Once the UAV is aligned with the runway and has initiated the automatic landing procedure, ground station mission operators intervene and remotely control the onboard electro-optical pod to stably point and continuously track the line of sight of its optical sensors (television camera sensors or infrared camera sensors) at pre-calibrated coordinates. Based on this stable tracking, the laser rangefinder integrated into the electro-optical pod is triggered to continuously and periodically perform laser ranging on the marker at an adjustable period of no more than 0.5 seconds, thereby acquiring a series of high-frequency laser ranging values ​​in real time.

[0034] Step S3: Calculate the UAV's position coordinates in real time based on the laser rangefinder value, the attitude angle of the optoelectronic pod, the coordinates of the marker, and the UAV's own attitude information; To calculate the precise position coordinates of a UAV in a navigation-denied environment in real time, this method utilizes the laser rangefinder D reported by the onboard electro-optical pod, the pod's azimuth angle a and pitch angle b, pre-calibrated marker coordinates, and the UAV's own heading angle Psi, pitch angle Pitch, and roll angle Roll. The laser rangefinder values ​​and pod attitude angles are used to calculate the three-dimensional distance components in the body coordinate system, transforming the optical measurements into spatial vectors in the UAV's body coordinate system. Then, through a coordinate transformation matrix, these components are converted to the geographic coordinate system using the UAV's attitude angles, yielding the north, east, and ground distances X, Y, and Z, thus eliminating the influence of attitude changes on positioning. Finally, based on the marker coordinates and geographic offset, a geodetic model is applied to calculate the UAV's absolute longitude Lon. f Latitude f and altitude H f This enables real-time positioning with meter-level accuracy.

[0035] Step S3 includes: Based on the laser ranging value, the azimuth and pitch angles of the optoelectronic pod, the three-dimensional distance components in the computer body coordinate system; By combining the UAV's heading angle, pitch angle, and roll angle, the three-dimensional distance components are converted to the geographic coordinate system; Based on the coordinates of the landmark and the distance components in the geographic coordinate system, the longitude, latitude, and altitude of the UAV are calculated.

[0036] First, the onboard control computer uses laser ranging values. and the azimuth angle of the pod and pitch angle The three axial distance components of the UAV relative to the marker in the body coordinate system are calculated using trigonometric functions: X-axis distance component. pass Calculate the projected distance between the drone and the marker in the forward / backward direction of the drone; Y-axis distance component. pass Calculate the projected distance in the left and right directions; the Z-axis distance component z passes through... The calculation represents the projected distance in the vertical direction, converting optical measurement data into a spatial vector in the UAV's body coordinate system. Its accuracy directly depends on the accuracy of the laser rangefinder value and the stability of the pod's pointing angle.

[0037] Then, combining the UAV's heading, pitch, and roll angles, the three-dimensional distance components in the aforementioned body coordinate system are transformed to the geographic coordinate system. Since the body coordinate system rotates with the UAV's attitude, it needs to be transformed to a fixed geographic coordinate system using a coordinate transformation matrix. The heading angle Psi defines the angle between the UAV's longitudinal axis and geographic north, the pitch angle Pitch defines the angle between the longitudinal axis and the horizontal plane, and the roll angle Roll defines the tilt angle of the transverse axis. Through a series of rotation matrix operations, the x, y, and z components in the body coordinate system are transformed into the X, Y, and Z components in the geographic coordinate system:

[0038] Similarly, the Y and Z components are calculated. This transformation eliminates the influence of the UAV's attitude on relative position measurements, ensuring accurate representation of distance data in the geographic coordinate system.

[0039] Finally, based on the distance components of the marker coordinates and the geographic coordinate system, the absolute longitude, latitude, and altitude of the UAV are calculated. The X, Y, and Z components in the geographic coordinate system represent the distance offset of the UAV relative to the marker in the north, east, and geocentric directions, respectively. This is achieved by converting the X and Y components from meters to degrees and combining them with the known coordinates of the marker (…). ), using a geodetic model for inverse calculation: latitude The formula is obtained by iteratively calculating the reference ellipsoid parameters (Earth's radius of curvature R0 and RF) and latitudinal offset:

[0040] in Longitude is an intermediate variable. The formula, calculated by considering the latitude-dependent longitude scaling factor, is as follows:

[0041] Altitude Then directly through The calculation involves finding Z, where Z represents the vertical offset. This process converts the relative distance into absolute geographic coordinates, enabling the drone to locate itself even without satellite signals.

[0042] Step S4: Calculate the longitudinal and lateral deviations of the UAV relative to the landing point based on the UAV's position coordinates and landing point coordinates.

[0043] The spatial relationship between the real-time position coordinates of the UAV and the preset landing point coordinates is calculated to accurately obtain the longitudinal and lateral deviations of the UAV relative to the landing point. This process first calculates the northward and eastward distances between the two using geodetic formulas, then calculates the horizontal distance and the geographic azimuth of the landing point relative to the UAV. By projecting and decomposing the horizontal distance along the landing direction and its normal, the longitudinal deviation is obtained, followed by the lateral deviation, thus converting the absolute geographic coordinates into path tracking deviations.

[0044] Figure 2 The diagram shows the longitudinal and lateral deviations of the UAV from the runway center. The lateral deviation (△Y) is represented by the distance between the horizontal dashed line and the vertical line of the runway center. When it is greater than 0, the UAV is deviated to the right, and when it is less than 0, it is deviated to the left. The longitudinal deviation (△X) is represented by the distance between the vertical dashed line and the vertical line where the UAV is located. When it is greater than 0, the UAV is behind the runway center (has not flown over), and when it is less than 0, it is in front (has flown over).

[0045] Step S4 includes: Calculate the northward and eastward distances between the drone and the landing point; Calculate the horizontal distance and the angular deviation relative to the landing direction based on the northward and eastward distances; The longitudinal and lateral deviations are obtained by decomposing the horizontal distance and angular deviations.

[0046] First, step S5 calculates the northward distance between the UAV and the landing point ( ) and eastward distance ( Northward distance The north-south offset of the drone from the landing point is calculated using geodetic formulas:

[0047] in For the latitude of the landing point, Here, π represents the latitude of the UAV, and π is the mathematical constant pi. It takes into account the curvature of the Earth's ellipsoid, using the latitude difference and the radius of curvature at the average latitude for precise calculation, ensuring accuracy over long distances. Similarly, the eastward distance d_e represents the east-west offset, calculated using the following formula:

[0048] in For the longitude of the landing point, Here is the longitude of the UAV. The negative sign indicates direction compensation; the coefficients in the formula are optimized based on Earth reference ellipsoid parameters to handle projection distortion in the longitude direction.

[0049] Calculate the horizontal distance based on the northward and eastward distances. ) and angular deviation relative to the landing direction. Horizontal distance Calculated using the Euclidean distance formula: , representing the straight-line distance between the UAV and the landing point. Then, the geographic azimuth angle of the runway landing point relative to the UAV is calculated. : This azimuth angle represents the angle (in radians or degrees) between the direction from the UAV's position towards the landing point and geographic north. Angle deviation is determined by comparison. relative to the preset landing direction (i.e., runway direction) is obtained, i.e., the difference ( - It reveals the directional deviation between the drone's current position and the ideal landing path. A positive difference indicates that the drone is veering to the right, while a negative difference indicates that it is veering to the left.

[0050] Finally, the longitudinal deviation is obtained based on the decomposition of horizontal distance and angular deviation. ) and lateral deviation ( Longitudinal deviation Indicates the drone's movement along the land (Phi) 0 The forward and backward offset on the ) is calculated using the following formula: .like >0 indicates that the drone is located behind the landing point (has not flown past the landing point); <0 indicates that the landing point has been passed. Lateral deviation This represents the left and right offset perpendicular to the landing direction, calculated using the following formula: .like >0 indicates that the drone is located to the right of the landing point; <0 indicates that it is on the left; =0 indicates that it is precisely located on the center line of the runway.

[0051] Step S5: Based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the radio altimeter altitude, perform triple-redundancy altitude data fusion to obtain the UAV's voting altitude; The accuracy and reliability of altitude information are crucial during precise drone landing, especially in navigation-denied environments where a single altitude source may fail due to sensor errors or external interference. Step S5 improves the robustness and accuracy of altitude measurement through a triple-redundant altitude data fusion voting mechanism. Based on the calculated drone optical altitude (i.e., altitude H), f (Obtained through laser ranging and coordinate inversion) and the UAV's own atmospheric altitude (H) a (measured by barometer) and altitude by radio altimeter (H) ra (Obtained through radar ranging), these three altitude sources are fused to ultimately output a reliable UAV voting altitude (H).d ).

[0052] The steps for obtaining the drone's voting altitude by fusing triple-redundant altitude data based on the drone's position coordinates, atmospheric altitude, and radio altimeter altitude include: The optical altitude, atmospheric altitude, and radio altitude are sorted and the errors between each pair are calculated. Based on whether the error exceeds a preset threshold, the median and / or mean are selected as the voting height.

[0053] The optical altitude, atmospheric altitude, and radio altitude are sorted, and the pairwise errors between each pair are calculated. The onboard control computer first preprocesses the three altitude sources: among which, the radio altimeter altitude... This is a relative height with respect to the ground. It needs to be converted to absolute altitude for accurate calculation. The formula is as follows: ( (where the altitude is the runway landing point), thus obtaining the altitude based on the radio altitude source. . Figure 3 The diagram shows the relative altitude between the drone and the center of the runway, where ΔH represents the difference between the drone's current altitude and the altitude of the runway center, i.e., the relative altitude.

[0054] Subsequently, the system compared optical altitudes. Atmospheric altitude and converted radio altitude The minimum value among the three is determined by a sorting algorithm. ), median ( ) and maximum value ( After sorting, calculate the height error between the minimum and median values. And the height error between the maximum and the median values. These error calculations aim to quantify the consistency between different altitude sources. Small errors indicate reliable sensor data, while large errors suggest potential sensor malfunctions or interference. Error thresholds are typically preset based on sensor accuracy and landing safety requirements, for example, 5-10 meters. The selection of thresholds requires a trade-off between fault tolerance and measurement accuracy. In this embodiment, the threshold value can be adjusted based on the actual application scenario.

[0055] Secondly, based on whether the error exceeds a preset threshold, the median and / or mean are dynamically selected as the voting height. This voting mechanism is based on the majority consensus principle, prioritizing data with high consistency: if the height error... and All three height sources are within the error threshold, indicating that the height data is consistent and reliable. Therefore, the voting height is now determined. Take the arithmetic mean of the three, that is To average out random errors and improve accuracy; if Within the threshold If the threshold is exceeded, it indicates that the maximum value may be abnormal. The system discards the maximum value and takes the average of the median and minimum values ​​for the voting height. ;like Within the threshold Exceeding the threshold indicates that the minimum value may be abnormal. The voting height is the average of the median and the maximum value. ;like and If all values ​​exceed the threshold, it indicates that there is a significant difference between at least two data streams, and the system conservatively selects the median value. As a voting altitude, the median is generally insensitive to outliers and provides basic reliability. This dynamic voting strategy effectively overcomes the risks associated with single-sensor failures, such as radio altitude inaccuracies under strong electromagnetic interference or atmospheric altitude drift caused by pressure fluctuations. Data fusion ensures the continuity and accuracy of altitude information.

[0056] Step S6: Calculate the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude; Based on the longitudinal deviation of the UAV relative to the runway landing point and the UAV's initial altitude, the longitudinal guidance command for landing is calculated, providing the UAV with a precise altitude trajectory reference. This step employs differentiated calculation formulas depending on the different landing phases the UAV is in (guided glide or landing pull-up phase), dynamically generating guidance altitude commands that match the ideal glide path to ensure a smooth and safe landing. It includes two core sub-steps: in the guided glide phase, the guidance altitude is calculated based on the longitudinal deviation, the preset glide angle, and the initial altitude of the pull-up phase; in the landing pull-up phase, the guidance altitude is calculated based on the longitudinal deviation and the glide angle. Figure 4 This diagram illustrates the longitudinal trajectory of the drone as it descends from the air to the runway landing point. The complete trajectory of the drone is clearly divided into two key phases: the guided glide phase and the landing and pull-up phase. During the guided glide phase, the drone glides at a large angle. A steady decline, its height from Indicates the initial height of the pull-up section as it approaches the ground. At that time, during the landing pull-up phase, the glide angle decreases to... The trajectory is flattened to ensure a smooth grounding.

[0057] Step S6 includes: During the guided descent phase, guidance commands are calculated based on longitudinal deviation, preset descent angle, and initial height of the lift phase. : ; During the landing pull-up phase, guidance commands are calculated based on longitudinal deviation and glide slope angle. : .

[0058] The longitudinal deviation of the landing point, where γ1 is the preset glide angle during the guide glide phase and γ2 is the glide angle during the landing pull-up phase. The altitude of the landing point. The initial field height for the landing pull-up phase.

[0059] During the glide phase, the guidance altitude is calculated based on the longitudinal deviation, the preset glide angle, and the initial height of the pull-up phase. When the UAV is in the initial approach phase, which is far from the landing point, the system uses a formula... Perform calculations. Among them... This refers to the altitude of the runway landing point. To achieve the initial field height for the landing pull-up phase, To guide the glide angle of the glide segment, To prepare for landing, a glide slope angle was established. (This is followed by a series of steps.) The actual longitudinal position of the drone Compared to the ideal pull-up position (distance from the landing point) The values ​​at each location are compared, and the difference is then multiplied by . Converted to a height correction value, thereby enabling the guidance instructions This creates a virtual gliding path that extends forward. If △X is large (the drone is far from the landing point), Increase accordingly to guide the drone to maintain its glide angle. ;like Decrease The smooth descent prepares the drone for the pull-up phase. This design ensures that the drone consistently tracks a sloping trajectory that seamlessly connects with the final pull-up phase during the guided glide, avoiding abrupt changes in altitude commands and improving trajectory smoothness.

[0060] During the landing pull-up phase, the guidance altitude is calculated based on the longitudinal deviation and glide slope angle. After the UAV flies over the pull-up point, it enters the final landing adjustment phase, at which point the formula is... At this stage, the drone is close to the landing point, and guidance commands no longer depend on the pull-up parameters. and Instead, it is based directly on the remaining longitudinal deviation. and a fixed glide angle Generate height instructions. Because... This value is negative. Below the reference height Its absolute value increases with The value decreases linearly as the landing velocity decreases, guiding the drone to a smooth glide angle γ1 for final touchdown. This simplified model reduces reliance on the accuracy of near-field sensors while ensuring the stability and predictability of the landing trajectory. In practice, the stage switching logic is usually based on whether ΔX is less than a preset threshold for automatic judgment.

[0061] Step S7: Based on lateral deviation, UAV voting altitude, longitudinal guidance commands, and UAV attitude and motion state information, generate UAV control surface and throttle commands to achieve precise landing.

[0062] The control commands include elevator, aileron, rudder, and throttle commands, which are calculated through pitch control loop, roll control loop, yaw control loop, and speed control loop, respectively.

[0063] The pitch control loop generates an upward velocity command based on the altitude deviation and glide trajectory, and then achieves altitude tracking through pitch angle control.

[0064] The roll control loop generates roll angle commands based on lateral deviation, and then achieves lateral trajectory tracking through aileron control; The throttle control circuit generates axial acceleration commands based on the speedometer deviation, and then achieves speed tracking through engine throttle control.

[0065] Based on the obtained lateral deviation (△Y) and drone voting altitude (H) d ), landing longitudinal guidance command (H c The system uses the UAV's attitude angles, three-axis angular rates (pitch rate Q, roll rate P, yaw rate R), speed (ground speed, indicated airspeed), and altitude information to generate elevator, aileron, rudder, and throttle control commands. A multi-loop control strategy is then employed to achieve precise landing. This step transforms the path deviation and guidance commands calculated in the preceding steps into specific control surface deflections and throttle control quantities, forming a closed-loop control system to ensure the UAV stably tracks its landing trajectory even in navigation-denied environments.

[0066] The calculation of control commands is based on four independent but coordinated control loops: pitch control loop for altitude tracking, roll control loop for lateral trajectory tracking, yaw control loop for heading stabilization, and speed control loop for airspeed management. Each loop achieves fine adjustment through a proportional-integral-derivative or proportional-integral controller.

[0067] Figure 5 The diagram shows the longitudinal control structure for UAV landing. The elevator command is calculated as follows: the elevator's internal loop achieves stabilization control through pitch rate feedback. Based on the pitch angle and the pitch command deviation, a proportional controller controls the pitch angle. The specific control structure is as follows: , For the pitch rate of the UAV, For the drone's pitch angle, For the drone's pitch angle command, To control the gain for pitch rate, The gain is controlled by the pitch angle ratio. This is the elevator deflection command.

[0068] Pitch angle command Based on the overhead velocity and the overhead velocity command deviation, the calculation is first performed using a proportional-integral controller, and then the calculation results are set with upper and lower limits. , The limiting processing, specifically the control structure, is as follows: , For the drone's aerial speed, For the UAV's aerial velocity feedforward command, The aerial speed command is calculated by the UAV based on the altitude deviation. For the upward velocity proportional control gain, The gain is the integral control gain for the upward velocity.

[0069] Skyward velocity feedforward command The upward speed command is calculated using ground speed and glide angle. Based on the deviation between the UAV's altitude and longitudinal guidance commands, a proportional controller calculates the vertical speed and pitch angle commands in real time when there is a deviation between the UAV's altitude and longitudinal guidance commands. This allows the UAV to track its landing glide path by controlling its pitch. The specific control structure is as follows: and , For the ground speed of the drone, To guide the glide slope for landing. = Landing pull-up section = , For landing longitudinal guidance commands, Voting altitude for drones and Height deviation needs to be set with upper and lower limits. , Amplitude limiting processing Gain is controlled by a high degree of proportionality.

[0070] Throttle command calculation: The engine throttle command is calculated based on axial acceleration and axial acceleration command deviation through a proportional-integral controller. The specific control structure is as follows: , For the axial acceleration of the drone, For the axial acceleration command of the UAV, The gain is the proportional control gain for axial acceleration. The integral control gain is for axial acceleration.

[0071] Based on the speedometer reading and the speedometer command deviation, calculations are first performed using a proportional controller, and then the calculation results are set with upper and lower limits. , The limiting processing, specifically the control structure, is as follows: , For drone speedometer, This is the drone's airspeed command. Calculated based on landing weight and aerodynamic data trim. The gain is used for proportional control of the speedometer.

[0072] Figure 6 The diagram shows the lateral control structure for UAV landing. The aileron command is calculated as follows: The inner loop of the aileron achieves stability enhancement control through roll rate feedback. Based on the roll angle and the roll angle command deviation, the UAV roll angle is controlled by a proportional controller. The specific control structure is as follows: , For the roll rate of the drone, For the drone's roll angle, This is the roll angle command for the drone. To control the gain for roll rate, The gain is controlled by the roll angle ratio. This is the aileron deflection command.

[0073] Roll angle command Based on the lateral position deviation, calculations are first performed using a proportional-integral-derivative controller, and then the calculation results are set with upper and lower limits. , [Amplitude limiting processing: When the UAV deviates from the runway centerline, the roll angle command is updated in real time. Then, by controlling the UAV to roll left and right, the lateral deviation is eliminated, achieving lateral trajectory tracking. The specific control structure is as follows:] , The lateral deviation of the drone relative to the landing point. For the lateral deviation derivative, considering that the derivative will amplify high-frequency noise, a low-pass filter is needed to perform a lateral deviation derivative result. The filter structure is as follows: , These are the filter parameters. The gain is used to control the lateral deviation. For lateral deviation integral control gain, The gain is the differential control gain for lateral deviation.

[0074] Rudder command calculation: The rudder achieves stability augmentation control through yaw rate feedback. The specific control structure is as follows: , The yaw rate of the drone. The gain is used to control the yaw rate.

[0075] In another possible embodiment, firstly, a general aviation airport is selected as the landing airport for the UAV flight. The coordinates of the runway landing point are 104.612466° east longitude, 29.3669° north latitude, with an altitude of 354m and a landing direction of 212°.

[0076] Second, a permanent statue near the north end of the airport runway was selected as a landmark, with coordinates of 104.619788°E, 29.377129°N, and an altitude of 358m.

[0077] Third, during the landing process, the airborne optoelectronic pod stably tracks the marker and performs laser ranging on it. The ranging value is 10004m. At this time, the azimuth angle of the pod is 0.16°, the pitch angle is -0.1°, the heading angle of the UAV is 212°, the pitch angle is 2.1°, and the roll angle is 0.3°.

[0078] Fourth, the onboard control computer calculates the UAV's longitude, latitude, and altitude in real time based on the laser rangefinder value reported by the electro-optical pod, the azimuth and pitch angles of the electro-optical pod, the coordinates of the marker, and the UAV's own heading, pitch, and roll angles. The calculation process is as follows: X-axis distance in the computer's body coordinate system: .

[0079] Y-axis distance in computer volume coordinate system: .

[0080] Z-axis distance in computer volume coordinate system: .

[0081] Transform X from the body coordinate system to the geographic coordinate system:

[0082] Transform the Y coordinate system from the body coordinate system to the geographic coordinate system:

[0083] Transform Z from the body coordinate system to the geographic coordinate system:

[0084] Calculate the latitude of the drone: ; ; ; ;

[0085] ; ;

[0086] ; ; ;

[0087] Calculate the longitude of the drone:

[0088] Calculate the drone's altitude: .

[0089] Fifth, the UAV obtained by the onboard control computer ,latitude and altitude The longitudinal deviation ΔX and lateral deviation ΔY relative to the runway center are calculated using the following method: Calculate the northward distance between the drone and the runway center:

[0090] Calculate the eastward distance between the drone and the runway center:

[0091] Calculate the horizontal distance between the drone and the center of the runway. .

[0092] Calculate the azimuth angle of the runway center relative to the UAV in the geographic system: .

[0093] Calculate the longitudinal deviation of the runway center relative to the UAV in the landing direction. .

[0094] Calculate the lateral deviation of the runway center relative to the UAV in the landing direction. We can obtain that the current position of the UAV relative to the center of the runway is 29.7m to the left, the relative height is 388m, and the longitudinal distance from the center of the runway is 11334.7m.

[0095] Sixth, the onboard control computer uses the UAV's altitude Hf obtained in step 4 and the UAV's own atmospheric altitude H to... a Radio altimeter height H raThe three-redundancy height data fusion voting is performed to obtain the UAV voting height H. d At the time of the vote, the atmospheric altitude was 751m and the radio altimeter altitude was 380m. The specific voting method was as follows: Calculate altitude H based on radio altitude source ra0 : H ra0 =H ra +H 0 =734m Calculate altitude H f Atmospheric altitude H a and altitude H ra0 The height difference between the three: H was obtained through calculation and comparison. f H a and H ra0 The minimum value H among the three min =734m, median value H mid =742m, maximum value H max =751m; Calculate the height error H between the minimum and median values. err1 H err1 =H mid -H min =8m; Calculate the height error H between the maximum and median values. err2 H err2 =H max -H mid =9m.

[0096] The triple-redundancy altitude data is used for voting to obtain the drone's voting altitude H. d : Height error H err1 and H err2 All are within the error threshold of 10m, H d =(H max +H mid +H min ) / 3=742.3m.

[0097] Seventh, the onboard control computer calculates the landing longitudinal guidance command Hc based on the obtained longitudinal deviation ΔX of the UAV relative to the runway landing point and the UAV's voting altitude Hd. The specific calculation method is as follows: At the calculated moment, the UAV is in the guided glide phase, and the landing longitudinal guidance command is: , To guide the glide slope angle, the value is 3°. The glide slope angle for the landing pull-up phase is 0.5°, and Hs is the initial field height for the landing pull-up phase, which is 20m.

[0098] Eighth, the onboard control computer determines the UAV's lateral deviation ΔY relative to the runway landing point and the UAV's altitude H based on these parameters. d Landing longitudinal guidance command H c The calculation method involves using the drone's attitude angles, three-axis angular rates, speed, and altitude information to generate control commands for the elevator, ailerons, rudder, and throttle, thereby controlling the drone to achieve a precise landing. Elevator command calculation: The specific control structure of the elevator is as follows: ; ; ; .

[0099] At the time of calculation, the UAV's pitch rate is 0.05° / s, pitch angle is 2.1°, altitude velocity is -2.3m / s, ground velocity is 48.6m / s, altitude velocity integral value is 3.5, and elevator command calculation result is: =4.5m / s.

[0100] =-2.5m / s.

[0101] =4.9°.

[0102] =-3.7°.

[0103] Throttle command calculation: The specific control structure of the engine throttle is as follows: .

[0104] .

[0105] At the time of calculation, the axial acceleration is 0.1. The integral value of axial acceleration is 0.32, the indicated speed is 47.1 m / s, the indicated speed command is 48.2 m / s, and the calculated result of the engine throttle command is: =0.2 .

[0106] =0.31.

[0107] Aileron command calculation.

[0108] The specific control structure of the aileron is as follows: .

[0109] .

[0110] At the calculation time, the lateral deviation is -29.7m, the differential of the lateral deviation is 2.7m / s, the roll angle is 0.3°, the roll rate is 0.5° / s, and the aileron command calculation result is: =5.6°.

[0111] =-1.2°.

[0112] Rudder command calculation: The specific control structure of the rudder is as follows: .

[0113] At the calculation time, the yaw rate is 0.12° / s, and the calculated rudder result is: =-0.06°.

[0114] Compared with the prior art, the embodiments of this application have the following beneficial effects: First, by completely replacing the reliance on satellite navigation signals through optical guidance, it effectively overcomes the problems of differential positioning failure and pure inertial navigation error accumulation in harsh environments such as GPS interference and strong electromagnetic suppression, ensuring the continuity and autonomy of the landing process.

[0115] Secondly, the airborne optoelectronic pod is used to perform high-frequency laser ranging on markers with known coordinates. Combined with coordinate inversion algorithms, the precise position of the UAV is calculated in real time, and the longitudinal and lateral deviations relative to the landing point are further calculated. The positioning accuracy is high, providing a reliable input for precise control.

[0116] Third, a triple-redundant altitude data fusion voting mechanism is adopted to perform real-time cross-verification and intelligent voting on optical altitude, atmospheric altitude and radio altitude. When a single sensor fails or data is abnormal, the optimal value can be automatically selected, which greatly improves the reliability of altitude measurement and avoids the landing risk caused by the failure of a single sensor.

[0117] Fourth, by designing a segmented longitudinal guidance law, altitude commands are dynamically generated based on the real-time position of the UAV, ensuring a smooth transition of the trajectory throughout the entire process from long-distance approach to final pull-up, avoiding sudden changes in commands, and improving landing comfort and safety.

[0118] The following is a possible implementation of a drone landing system for a denied environment, which performs the various execution steps and corresponding technical effects of the drone landing method shown in the above embodiments and possible implementations. The system includes: The calibration module is used to calibrate the landing point coordinates and landing direction of the landing runway, as well as the coordinates of the markers at a certain distance from the landing runway, and load them into the airborne control computer. The landing point coordinates include longitude, latitude, altitude, and landing direction. The ranging module is used to continuously track the marker and perform periodic laser ranging to obtain the laser ranging value when the UAV is aligned with the landing runway and starts the landing procedure; The first calculation module is used to calculate the position coordinates of the UAV in real time based on the laser range measurement value, the attitude angle of the optoelectronic pod, the coordinates of the marker, and the attitude information of the UAV itself. The second calculation module is used to calculate the longitudinal and lateral deviations of the UAV relative to the landing point based on the UAV's position coordinates and landing point coordinates. The data fusion module is used to perform triple-redundancy altitude data fusion based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the radio altimeter altitude to obtain the UAV's voting altitude. The third calculation module is used to calculate the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude; The generation module is used to generate control commands for the UAV's control surfaces and throttle based on lateral deviation, UAV voting altitude, longitudinal guidance commands, and UAV attitude and motion state information, so as to achieve precise landing.

[0119] This preferred embodiment provides a computer device that can implement the steps of any embodiment of the UAV landing method provided in this application. Therefore, it can achieve the beneficial effects of the UAV landing method provided in this application. For details, please refer to the previous embodiments, which will not be repeated here.

[0120] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by instructions, or by instructions controlling related hardware. These instructions can be stored in a computer-readable storage medium and loaded and executed by a processor. Therefore, embodiments of this application provide a storage medium storing multiple instructions that can be loaded by a processor to execute the steps of any embodiment of the UAV landing method provided in this application.

[0121] The storage medium may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0122] Since the instructions stored in the storage medium can execute the steps in any of the UAV landing method embodiments provided in this application, the beneficial effects that any UAV landing method provided in this application can achieve can be realized. For details, please refer to the previous embodiments, which will not be repeated here.

[0123] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for landing a drone in a denied environment, characterized in that, include: The coordinates of the landing point on the landing runway, the landing direction, and the coordinates of the landmarks at a certain distance from the landing runway are calibrated and loaded into the airborne control computer. The landing point coordinates include longitude, latitude, altitude, and landing direction. When the drone is aligned with the landing runway and initiates the landing procedure, it continuously tracks the markers and performs periodic laser ranging to obtain laser ranging values ​​through the onboard electro-optical pod. Based on laser rangefinder values, the attitude angle of the optoelectronic pod, the coordinates of the marker, and the UAV's own attitude information, the UAV's position coordinates are calculated in real time. Based on the UAV's position coordinates and landing point coordinates, calculate the UAV's longitudinal and lateral deviations relative to the landing point; Based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the altitude of the radio altimeter, a triple-redundancy altitude data fusion is performed to obtain the UAV's voting altitude; Calculate the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude; Based on lateral deviation, UAV voting altitude, longitudinal guidance commands, and UAV attitude and motion status information, control commands for UAV control surfaces and throttle are generated to achieve precise landing.

2. The UAV landing method as described in claim 1, characterized in that, The steps for calculating the UAV's position coordinates in real time based on laser rangefinder values, the attitude angle of the electro-optical pod, marker coordinates, and the UAV's own attitude information include: Based on the laser ranging value, the azimuth and pitch angles of the optoelectronic pod, the three-dimensional distance components in the computer body coordinate system; By combining the UAV's heading angle, pitch angle, and roll angle, the three-dimensional distance components are converted to the geographic coordinate system; Based on the coordinates of the landmark and the distance components in the geographic coordinate system, the longitude, latitude, and altitude of the UAV are calculated.

3. The UAV landing method as described in claim 1, characterized in that, The steps for calculating the longitudinal and lateral deviations of the UAV relative to the landing point based on the UAV's position coordinates and landing point coordinates include: Calculate the northward and eastward distances between the drone and the landing point; Calculate the horizontal distance and the angular deviation relative to the landing direction based on the northward and eastward distances; The longitudinal and lateral deviations are obtained by decomposing the horizontal distance and angular deviations.

4. The UAV landing method as described in claim 1, characterized in that, The steps for obtaining the drone's voting altitude by fusing triple-redundant altitude data based on the drone's position coordinates, atmospheric altitude, and radio altimeter altitude include: The optical altitude, atmospheric altitude, and radio altitude are sorted and the errors between each pair are calculated. Based on whether the error exceeds a preset threshold, the median and / or mean are selected as the voting height.

5. The unmanned aerial vehicle (UAV) landing method as described in claim 1, characterized in that, The steps for calculating the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude include: During the guided descent phase, guidance commands are calculated based on longitudinal deviation, preset descent angle, and initial height of the lift phase. : ; During the landing pull-up phase, guidance commands are calculated based on longitudinal deviation and glide slope angle. : , Longitudinal deviation of the landing point The preset guide glide angle is the glide angle. To create a glide slope for landing, The altitude of the landing point. The initial field height for the landing pull-up phase.

6. The unmanned aerial vehicle (UAV) landing method as described in claim 1, characterized in that, The control commands include elevator, aileron, rudder, and throttle commands, which are calculated through pitch control loop, roll control loop, yaw control loop, and speed control loop, respectively. The pitch control loop generates an upward velocity command based on the altitude deviation and glide trajectory, and achieves altitude tracking through pitch angle control. The roll control loop generates roll angle commands based on lateral deviation and achieves lateral trajectory tracking through aileron control; The throttle control circuit generates axial acceleration commands based on the speedometer deviation, and achieves speed tracking through engine throttle control.

7. A landing system for unmanned aerial vehicles (UAVs) in a denied environment, characterized in that, The system includes: The calibration module is used to calibrate the landing point coordinates and landing direction of the landing runway, as well as the coordinates of the markers at a certain distance from the landing runway, and load them into the airborne control computer. The landing point coordinates include longitude, latitude, altitude, and landing direction. The ranging module is used to continuously track the marker and perform periodic laser ranging to obtain the laser ranging value when the UAV is aligned with the landing runway and starts the landing procedure; The first calculation module is used to calculate the position coordinates of the UAV in real time based on the laser range measurement value, the attitude angle of the optoelectronic pod, the coordinates of the marker, and the attitude information of the UAV itself. The second calculation module is used to calculate the longitudinal and lateral deviations of the UAV relative to the landing point based on the UAV's position coordinates and landing point coordinates. The data fusion module is used to perform triple-redundancy altitude data fusion based on the altitude information in the UAV's position coordinates, the UAV's atmospheric altitude, and the radio altimeter altitude to obtain the UAV's voting altitude. The third calculation module is used to calculate the landing longitudinal guidance command based on the longitudinal deviation and the UAV's voting altitude; The generation module is used to generate control commands for the UAV's control surfaces and throttle based on lateral deviation, UAV voting altitude, longitudinal guidance commands, and UAV attitude and motion state information, so as to achieve precise landing.

8. A computer device, characterized in that, The computer device includes a processor and a memory, the memory storing a computer program that is loaded and executed by the processor to implement the unmanned aerial vehicle landing method as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which is loaded and executed by a processor to implement the UAV landing method as described in any one of claims 1-6.

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