Automatic landing control method for large-scale fixed-wing unmanned aerial vehicle

Abstract

An automatic landing control method for a large-scale fixed-wing unmanned aerial vehicle. The method comprises: dividing a landing phase of an unmanned aerial vehicle into an approach level flight phase, a final approach glide slope phase, a first landing flare phase, a second landing flare phase and a landing rollout phase; in the approach level flight phase, controlling the unmanned aerial vehicle to maintain a target level flight speed and a target approach level flight altitude, and to align a lateral offset and a track angle with a runway extended centerline and track the runway extended centerline; in the final approach glide slope phase, controlling the unmanned aerial vehicle to maintain a target glide speed and a target glide angle; in the first landing flare phase, controlling the unmanned aerial vehicle to maintain a target vertical speed and an airspeed; in the second landing flare phase, controlling the unmanned aerial vehicle to maintain the target vertical speed and the airspeed; and in the landing rollout phase, controlling the unmanned aerial vehicle to decelerate to 0, and at the same time, controlling the unmanned aerial vehicle to maintain a target lateral offset and a target heading angle and keep same on a runway centerline. The control method enables precise control over the automatic landing of an unmanned aerial vehicle, thereby greatly improving the robustness and safety of the automatic landing of the unmanned aerial vehicle.

Description

A method for automatic landing control of large fixed-wing unmanned aerial vehicles

[0001] Technical Field

[0002] This invention belongs to the field of drone autopilot and relates to an automatic landing control method for large fixed-wing drones. Background Technology

[0003] Autonomous flight of unmanned aerial vehicles (UAVs) is an important direction in the development of UAV technology. It utilizes advanced algorithms and sensors to achieve capabilities such as self-navigation, path planning, environmental perception, and automatic obstacle avoidance. With its advantages of high precision, high efficiency, and high safety, autonomous flight technology for UAVs has shown broad application prospects in multiple fields. With continuous technological advancements and innovation, autonomous flight technology for UAVs will inject new vitality into socio-economic development.

[0004] A complete UAV flight process includes takeoff, cruise, and landing. Compared to the cruise phase, takeoff and landing are more complex and riskier. Most practical experience shows that although takeoff and landing times are shorter, the frequency of accidents during these two phases is much higher than during cruise, and the accident rate during landing is even higher than during takeoff. For fixed-wing UAVs, automatic landing refers to the entire process from the approach flight phase to the landing run and stop. The challenges lie in the more complex control process and the higher precision requirements compared to takeoff. Many constraints need to be considered throughout the landing process, such as the precision of the landing glide path control, ensuring the aircraft doesn't level off too early or too late, and preventing excessive landing speed that could lead to a hard landing or bouncing. Previously, manned aircraft typically used instrument landing for automatic landing, which placed high demands on airport facilities. The automatic landing systems used by drones are generally simple and do not break down the landing phase. Some use vertical speed control while others use attitude control. This is more suitable for small drones or mature models that have been in service for a long time, and is no longer suitable for newly developed large drones. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an automatic landing control method for large fixed-wing unmanned aerial vehicles (UAVs), which can accurately control the automatic landing of UAVs and greatly improve the robustness and safety of automatic landing of UAVs.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] An automatic landing control method for a large fixed-wing unmanned aerial vehicle includes the following processes:

[0008] The landing phase of the drone is divided into the approach level flight phase, the approach glide phase, the first landing leveling phase, the second landing leveling phase, and the landing taxiing phase.

[0009] During the approach and level flight phase, the UAV is controlled to maintain the target level flight speed, target approach level flight altitude, lateral offset and track angle aligned with and track the runway extension line;

[0010] During the approach and descent phase, the UAV is controlled to maintain the target descent speed and target descent angle, while the UAV is controlled to maintain the target side offset and track angle.

[0011] In the first stage of landing and leveling off, the UAV is controlled to maintain the target's vertical speed and airspeed, while simultaneously maintaining the target's lateral offset and track angle.

[0012] In the second phase of landing and leveling off, the UAV is controlled to maintain the target's vertical speed and airspeed, while simultaneously maintaining the target's lateral offset and heading angle.

[0013] During the landing roll, the speed of the UAV is reduced to 0, while the UAV is kept on the target side offset and heading angle on the runway centerline.

[0014] Preferably, the approach level flight phase is the phase from acquisition to the approach level flight waypoint to acquisition to the approach glide path point; the approach glide phase is the phase from acquisition to the approach glide point to an altitude greater than 15m above the ground; the first landing leveling phase is the phase from an altitude of 15m above the ground to an altitude greater than 3m above the ground; the second landing leveling phase is the phase from an altitude of 3m above the ground to the landing touchdown phase; and the landing taxiing phase is the phase from landing touchdown to taxiing deceleration and stopping.

[0015] Preferably, during the approach level flight phase, the speed, altitude, pitch angle, track angle, and lateral deviation of the UAV are used as control target variables.

[0016] Furthermore, during the approach and level flight phase, the airspeed of the UAV is controlled to maintain the aircraft's cruising speed of 200 km / h, while the UAV is controlled to maintain the target cruising altitude of 300 m, and the yaw angle and side offset of the UAV are controlled to track the extended line of the landing airport runway.

[0017] Preferably, during the approach glide phase, the UAV's speed, glide angle, track angle, and lateral offset are used as control target variables.

[0018] Furthermore, during the approach and descent phase, the UAV is controlled to maintain a glide angle of -3° and descend to a ground altitude of 15m, while maintaining a glide airspeed of 168km / h and a target heading angle of 325° and a sideslip of 0m.

[0019] Preferably, in the first stage of landing leveling, the vertical speed, velocity, track angle, and lateral deviation of the UAV are used as control target variables; in the second stage of landing leveling, the vertical speed, velocity, yaw angle, and lateral deviation of the UAV are used as control target variables.

[0020] Furthermore, in the first stage of landing and leveling off, the UAV is controlled to maintain a variable target vertical speed, which changes with the aircraft altitude, and the UAV is controlled to maintain a landing leveling speed of 160 km / h, while maintaining a target track angle of 325° and a side offset of 0m.

[0021] In the second stage of landing and leveling off, the UAV is controlled to maintain a vertical speed of 0.5 m / h at the fixed target and a landing and leveling speed of 160 km / h, while maintaining a target heading angle of 325° and a lateral offset of 0 m.

[0022] Preferably, during the landing phase, the UAV's speed, heading angle, and lateral deviation are used as target control variables.

[0023] Furthermore, during the landing rollout phase, the speed of the UAV is reduced to 0 km / h, while the UAV is kept at a target heading angle of 325°, a lateral offset of 0 m, and on the runway centerline.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention effectively divides the landing phase into approach level flight, approach glide, and landing leveling phase (first phase), landing leveling phase (second phase), and landing roll. It also effectively acquires the target control variables for each sub-phase of the UAV landing phase. Based on these target control variables, the UAV is automatically landed. This high-precision control method addresses the issue of low landing accuracy caused by uncertainties in some parameters and environmental factors in newly developed aircraft, significantly improving the robustness and safety of automatic UAV landing. Attached Figure Description

[0026] Figure 1 is a control flowchart of the automatic landing control method for fixed-wing unmanned aerial vehicles.

[0027] Figure 2 is a diagram showing the stages of automatic landing for fixed-wing UAVs.

[0028] Figure 3 is a control block diagram of the approach level flight phase of the automatic landing control method for fixed-wing UAVs.

[0029] Figure 4 is a control block diagram of the approach and glide phase of the automatic landing control method for fixed-wing UAVs.

[0030] Figure 5 is a control block diagram of the first stage of landing and pull-up in the automatic landing control method for fixed-wing UAVs.

[0031] Figure 6 is a control block diagram of the second stage of landing and pull-up in the automatic landing control method for fixed-wing UAVs.

[0032] Figure 7 is a control block diagram of the second stage of the landing roll in the automatic landing control method for fixed-wing UAVs. Embodiments of the present invention

[0033] Embodiments of the present invention are described in detail below, examples of which 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 are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terms “installation,” “connection,” and “linkage” should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; a mechanical connection, an electrical connection, or a connection that allows communication; a direct connection or an indirect connection via an intermediate medium; or a connection within two elements or an interaction between two elements. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0036] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0037] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0038] This invention proposes an automatic landing control method for large fixed-wing unmanned aerial vehicles (UAVs) to address the problem of improving the robustness and safety of automatic landing under conditions of multiple constraints on landing and uncertainty in UAV-related parameters and environmental parameters.

[0039] As shown in Figure 1, the automatic landing control method for a large fixed-wing unmanned aerial vehicle (UAV) of the present invention includes: dividing and defining different sub-stages of the landing phase of the UAV; obtaining target control variables for the different sub-stages of the landing phase of the UAV; and controlling the UAV to land automatically according to the target control variables for the different sub-stages of the landing phase.

[0040] As shown in Figure 2, the UAV landing phase is divided and defined as follows: approach level flight phase, approach glide phase, landing leveling phase 1, landing leveling phase 2, and landing taxiing phase. The approach level flight phase is defined as the period from acquisition of the UAV to the approach level flight waypoint and before acquisition of the approach glide waypoint; the approach glide phase is defined as the period from acquisition of the UAV to the approach glide point until the UAV's altitude above the ground exceeds 15m; the landing leveling phase 1 is defined as the period from the UAV's altitude above the ground of 15m to the altitude above the ground exceeding 3m; the landing leveling phase 2 is defined as the period from the UAV's altitude above the ground of 3m to the landing touchdown phase; and the landing taxiing phase is defined as the period from the UAV's landing touchdown to its taxiing deceleration and stop.

[0041] During the approach level flight phase, the UAV's speed, altitude, pitch angle, track angle, and lateral deviation are used as control target variables; during the approach glide phase, the UAV's speed, glide angle, track angle, and lateral deviation are used as control target variables; during the first landing leveling phase, the UAV's vertical speed, speed, track angle, and lateral deviation are used as control target variables; during the second landing leveling phase, the UAV's vertical speed, speed, yaw angle, and lateral deviation are used as control target variables; and during the landing touchdown phase, the UAV's speed, heading angle, and lateral deviation are used as target control variables.

[0042] As shown in Figures 3-7, the UAV is automatically landed according to the target control variables of different sub-stages of the landing phase. In the figures, K_I represents the integral gain, and K_P and K_Q are both proportional gains. The process includes the following steps:

[0043] As shown in Figure 3, during the approach and level flight phase, the UAV is controlled to maintain the target's level flight speed, target's approach level flight altitude, lateral offset, and track angle to align with and track the runway extension line.

[0044] Specifically, the airspeed after signal limiting is used as negative feedback for the airspeed command. After being superimposed by proportional gain and integral gain stages, the engine throttle is controlled.

[0045] The altitude value after signal limiting is used as negative feedback for altitude command. After passing through proportional gain and integral gain stages, the pitch rate after signal limiting is used as negative feedback to control the elevator and control the descent speed.

[0046] The yaw rate after signal limiting and proportional gain is used as negative feedback and superimposed with the roll angle after signal limiting and proportional gain to perform rudder control.

[0047] The track angle after signal limiting is used as negative feedback for the track angle command. After passing through signal limiting and proportional gain stages, the side offset change rate is used as positive feedback. After passing through proportional and integral gain stages, the outputs of the above two stages are summed for aileron control to maintain the target side offset and track angle.

[0048] As shown in Figure 4, during the approach glide phase, the UAV is controlled to maintain the target glide speed and target glide angle, while the UAV is also controlled to maintain the target side offset and track angle (along the runway extension line).

[0049] Specifically, the airspeed after signal limiting is used as negative feedback for the airspeed command. After being superimposed by proportional gain and integral gain stages, the engine throttle is controlled.

[0050] The glide angle after signal limiting is used as the negative feedback of the glide angle command. After passing through the proportional gain and integral gain stages, the pitch rate after signal limiting is used as the negative feedback to control the elevator and control the descent speed.

[0051] The yaw rate after signal limiting and proportional gain is used as negative feedback and superimposed with the roll angle after signal limiting and proportional gain to perform rudder control.

[0052] The track angle after signal limiting is used as negative feedback for the track angle command. After passing through signal limiting and proportional gain stages, the side offset change rate is used as positive feedback. After passing through proportional and integral gain stages, the outputs of the above two stages are summed for aileron control to maintain the target side offset and track angle.

[0053] As shown in Figure 5, during the first stage of landing and leveling, the UAV is controlled to maintain the target vertical speed and airspeed while maintaining the target lateral offset and track angle (along the runway extension line).

[0054] Specifically, the airspeed after signal limiting is used as negative feedback for the airspeed command, and the engine throttle is controlled after passing through the signal limiting and proportional gain stages.

[0055] The vertical speed after signal limiting is used as the negative feedback for the vertical speed command. During the landing phase, the vertical speed command changes with the aircraft altitude. After passing through proportional gain and integral gain stages, the pitch rate after signal limiting is used as the negative feedback to control the elevator and control the descent speed.

[0056] The yaw rate after signal limiting and proportional gain is used as negative feedback and superimposed with the roll angle after signal limiting and proportional gain to perform rudder control.

[0057] The track angle after signal limiting is used as negative feedback for the track angle command. After passing through signal limiting and proportional gain stages, the side offset change rate is used as positive feedback. After passing through proportional and integral gain stages, the outputs of the above two stages are summed for aileron control to maintain the target side offset and track angle.

[0058] As shown in Figure 6, in the second stage of landing and leveling, the UAV is controlled to maintain the vertical speed and airspeed of the fixed target, while the UAV is controlled to maintain the target lateral offset and heading angle (along the runway extension line).

[0059] Specifically, the airspeed after signal limiting is used as negative feedback for the airspeed command, and the engine throttle is controlled after passing through the signal limiting and proportional gain stages.

[0060] The vertical velocity after signal limiting is used as the negative feedback for the vertical velocity command. After passing through the proportional gain and integral gain stages, the pitch rate after signal limiting is used as the negative feedback to control the elevator and control the descent speed.

[0061] The yaw rate after signal limiting and proportional gain is used as negative feedback and superimposed with the roll angle after signal limiting and proportional gain to perform rudder control.

[0062] The yaw angle after signal limiting is used as negative feedback for the yaw angle command. After signal limiting and proportional gain, the side offset change rate is used as positive feedback. After proportional and integral gain, the outputs of the above two stages are summed for aileron control to maintain the target side offset and track angle.

[0063] As shown in Figure 7, during the landing and taxiing phase, the speed of the UAV is controlled to decelerate to 0 km / h while maintaining the target side offset and heading angle on the runway centerline.

[0064] Specifically, the current engine throttle after signal limiting is used as negative feedback to reduce the drone speed to 0 km / h, and the engine throttle is controlled after rate limiting.

[0065] The roll angle after signal limiting is used as negative feedback for the roll angle command. After passing through the proportional gain stage, the roll rate is used as negative feedback signal and then passed through the signal limiting and proportional gain stages for roll attitude control to ensure that the UAV always maintains the target roll at 0°.

[0066] The yaw angle after signal limiting is used as negative feedback for the yaw angle command. After signal limiting and proportional gain, the side offset change rate is used as positive feedback. After proportional gain and integral gain, the yaw angle rate is used as negative feedback. After limiting and proportional gain, the outputs of the above four stages are summed for rudder control to ensure that the UAV's yaw angle and side offset are aligned with the runway centerline.

[0067] The specific actual control method is as follows:

[0068] During the approach and level flight phase, the airspeed of the UAV is controlled to maintain the aircraft's cruising speed of 200 km / h, while the UAV is controlled to maintain the target cruising altitude of 300 m, and the yaw angle and side offset of the UAV are controlled to track the extended line of the landing airport runway.

[0069] During the approach and glide phase, the UAV is controlled to maintain a glide angle of -3° and descend to an altitude of 15m above the ground (target landing airport), while maintaining a glide airspeed of 168km / h and a target heading angle of 325° (along the runway extension line) and a lateral offset of 0m.

[0070] In the first stage of landing and leveling off, the UAV is controlled to maintain a variable target vertical speed (the target vertical speed changes with the aircraft altitude), and while maintaining a landing leveling speed of 160 km / h, the UAV is controlled to maintain a target track angle of 325° (along the runway extension line) and a lateral offset of 0m.

[0071] In the second stage of landing and leveling off, the UAV is controlled to maintain a fixed target vertical speed of 0.5 m / h and a landing leveling speed of 160 km / h, while maintaining a target heading angle of 325° (along the runway extension line) and a lateral offset of 0 m.

[0072] During the landing roll, the speed of the UAV is controlled to decelerate to 0 km / h while maintaining the target heading angle of 325°, the lateral offset of 0m, and the runway centerline.

[0073] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0074] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0075] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0076] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0077] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

[0078] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this patent should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A large fixed-wing unmanned aircraft automatic landing control method, characterized by, The process comprises the following steps: The landing stage of the UAV is divided into approach flat flying stage, approach glide stage, landing pull-up first stage, landing pull-up second stage and landing taxiing stage; In the approach flat flying stage, the UAV is controlled to keep the target flat flying speed, target approach flat flying height, and side deviation distance and track angle aligned and track the runway extension line; In the approach glide stage, the UAV is controlled to keep the target glide speed and target glide angle, and to keep the target side deviation distance and track angle; In the landing pull-up first stage, the UAV is controlled to keep the target vertical speed and airspeed, and to keep the target side deviation distance and track angle; In the landing pull-up second stage, the UAV is controlled to keep the target vertical speed and airspeed, and to keep target side deviation distance and heading angle; In the landing taxiing stage, the speed of the UAV is controlled to reduce to 0, and the UAV is controlled to keep the target side deviation distance and heading angle on the runway center line.

2. The automatic landing control method for large fixed-wing drones according to claim 1, characterized in that, The approach flat flying stage is the stage from capturing the approach flat flying point to capturing the approach glide point, the approach glide stage is the stage from capturing the approach glide point to the height above ground being greater than 15 m, the landing pull-up first stage is the stage from the height above ground being 15 m to the height above ground being greater than 3 m, the landing pull-up second stage is the stage from the height above ground being 3 m to landing on the ground, and the landing taxiing stage is the stage from landing on the ground to taxiing deceleration and stopping.

3. The automatic landing control method for large fixed-wing UAVs according to claim 1, wherein, In the approach flat flying stage, the speed, height, pitch angle, track angle and side deviation distance of the UAV are taken as the control target variables.

4. The automatic landing control method for large fixed-wing UAV according to claim 3, wherein, In the approach flat flying stage, the airspeed of the UAV is controlled to keep the cruising speed of the aircraft at 200 km / h, the UAV is controlled to keep the target cruising height at 300 m, and the yaw angle and side deviation distance of the UAV are controlled to track the extension line of the runway of the landing airport.

5. The automatic landing control method for large fixed-wing UAVs according to claim 1, wherein, In the approach glide stage, the speed, glide angle, track angle and side deviation distance of the UAV are taken as the control target variables.

6. The method of claim 5, wherein, The UAV is controlled to keep the target glide angle at -3° and to descend to the height above ground of 15 m, and the UAV is controlled to keep the glide airspeed at 168 km / h, the target heading angle at 325° and the side deviation distance at 0 m.

7. The automatic landing control method for large fixed-wing UAVs according to claim 1, wherein, In the landing pull-up first stage, the vertical speed, speed, track angle and side deviation distance of the UAV are taken as the control target variables, and in the landing pull-up second stage, the vertical speed, speed, yaw angle and side deviation distance of the UAV are taken as the control target variables.

8. The method of claim 7, wherein, In the landing pull-up first stage, the UAV is controlled to keep the variable target vertical speed, the vertical speed changes with the height of the aircraft, and the UAV is controlled to keep the landing pull-up speed at 160 km / h, the target track angle at 325° and the side deviation distance at 0 m; In the landing pull-up second stage, the UAV is controlled to keep the fixed target vertical speed at 0.5 m / h, and the UAV is controlled to keep the landing pull-up speed at 160 km / h, and the target heading angle at 325° and the side deviation distance at 0 m.

9. The automatic landing control method for large fixed-wing UAVs according to claim 1, wherein, The landing ground contact phase, the unmanned aerial vehicle speed, the heading angle and the side offset distance are taken as the target control variables.

10. The method of claim 9, wherein, The landing ground contact phase, the unmanned aerial vehicle speed, the heading angle and the side offset distance are taken as the target control variables.

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