A curved surface guidance based unmanned aerial vehicle landing optimization method

Abstract

The application belongs to the technical field of unmanned aerial vehicles, and specifically discloses an unmanned aerial vehicle landing optimization method based on a curved surface guide, which comprises the following steps: a guide curved surface design model considering the size of an unmanned aerial vehicle landing platform is established, and a guide curved surface for unmanned aerial vehicle landing is set through the guide curved surface design model; the unmanned aerial vehicle is controlled to land through the guide curved surface, the state of the unmanned aerial vehicle is continuously judged during the landing process, and the guide curved surface and the unmanned aerial vehicle landing control are optimized according to the judgment result; until the unmanned aerial vehicle completes landing on the guide curved surface, the guide curved surface and the unmanned aerial vehicle landing control corresponding to the guide curved surface are output; and the method has the following advantages: the guide curved surface is optimized and designed according to the sliding friction coefficient and the height of the gravity center of the unmanned aerial vehicle, an unmanned aerial vehicle accurate landing method is proposed based on the optimized and designed curved surface, the strategy to be adopted by the unmanned aerial vehicle when the guide curved surface is stuck is determined, and the success rate of unmanned aerial vehicle sliding and guiding is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of unmanned aerial vehicles, in particular to an unmanned aerial vehicle landing optimization method based on curved surface guidance. BACKGROUND

[0002] An unmanned aerial vehicle is a pilotless aircraft that is controlled by radio remote control equipment and self-provided program control device, and has wide application in military and civilian fields. In actual application, due to the limited endurance of the unmanned aerial vehicle, it is often necessary to cooperate with a mobile or fixed landing platform to realize tasks such as loading and unloading goods, battery replacement, data exchange, etc. In order to realize the above tasks, the unmanned aerial vehicle needs to land accurately on the landing platform to realize storage and maintenance. During the landing process, the unmanned aerial vehicle is easily disturbed by ground effect and crosswind, affecting the landing accuracy. In order to solve this problem, auxiliary mechanisms or devices are usually used on the landing platform to push or guide the unmanned aerial vehicle to a certain target point to eliminate the landing error in the air. The auxiliary mechanisms or devices on the landing platform can be divided into active, passive and hybrid types. The active type usually pushes or extrudes the unmanned aerial vehicle to a certain position by driving a connecting rod or a clamping plate, such as invention patent CN202210176477.X. The passive type usually relies on the self-weight of the unmanned aerial vehicle to guide it to a certain position by using an inclined curved surface (hereinafter referred to as a guide curved surface). The hybrid type is a combination of the above two schemes. Among them, the passive type mechanism is the most widely used due to its simple structure and no need for additional energy.

[0003] In the passive type mechanism, a rotating curved surface with a conical shape (such as invention patent CN201611255017.7) or a circular arc shape (such as invention patent CN201610962576.5) is usually used. The key to the design lies in the matching form of the unmanned aerial vehicle and the guide curved surface and the design of the inclined curved surface. However, the guide curved surface currently used is usually a flat and smooth plane or a curved surface determined by experience, which has the following shortcomings: (1) It lacks design pertinence for unmanned aerial vehicles of different sizes and center of gravity heights. Unmanned aerial vehicles with mismatched center of gravity and bottom size and landing platform may have problems such as side turning and excessive friction causing interruption of guidance during guidance; (2) When the unmanned aerial vehicle has excessive friction on the guide surface and support surface, it cannot continue to slide, and it is not clear what strategy can be taken to facilitate the smooth progress of the guidance process.

[0004] Therefore, an unmanned aerial vehicle landing optimization method based on curved surface guidance is proposed to solve the above problems. SUMMARY

[0005] The present application aims to provide an unmanned aerial vehicle landing optimization method based on curved surface guidance to solve or improve at least one of the above technical problems.

[0006] In view of this, a first aspect of the present invention is to provide a method for optimizing UAV landing based on surface guidance.

[0007] The first aspect of the present invention provides a method for optimizing UAV landing based on a curved surface, comprising the following steps: establishing a guide surface design model that takes into account the size of the UAV landing platform, and setting a guide surface for UAV landing through the guide surface design model; controlling the UAV to land through the guide surface, continuously judging the state of the UAV during the landing process, and optimizing the guide surface and UAV landing control according to the judgment results; until the UAV completes landing on the guide surface, and outputting the guide surface and the corresponding UAV landing control.

[0008] This invention provides an optimized landing method for unmanned aerial vehicles (UAVs) based on curved surface guidance. Based on an optimized guiding curved surface and utilizing the force provided by the UAV itself, the method passively guides the center of the UAV to a set target point. This reduces the accuracy requirements of the UAV landing algorithm through physical methods, and the landing guidance effect can be enhanced by increasing the size of the mechanism.

[0009] Furthermore, by using a closed-loop design-verification iterative process, a better result for the guidance surface can be obtained within a few iterations. At the same time, it is possible to make a preliminary judgment on whether the UAV can successfully land during the design phase, saving the number of tests and reducing economic expenditure and raw material consumption.

[0010] In addition, the technical solutions provided by embodiments of the present invention may also have the following additional technical features:

[0011] In any of the above technical solutions, the guiding surface is formed by rotating a guiding curve circumferentially along an axis, the axis being perpendicular to the target ground for landing; the guiding curve is located in a plane perpendicular to the target ground, starting from the guiding starting point (l). c ,0,h c ) to the guiding endpoint (l v A smooth curve consisting of multiple nodes connected sequentially between (l, 0, 0); the node coordinates of the smooth curve are (l, 0, 0). c ,0,h c ), (l1, 0, h1), ..., (l n ,0,h n ), (l v (0, 0); the horizontal coordinates of the nodes in the smooth curve l i Let i = 1, 2, ..., n satisfy: l c >l1>l n >l v >0; the vertical coordinate h of the node in the smooth curve i Let i = 1, 2, ..., n satisfy h c >h1>hn >0; wherein, the bottom edge of the guiding surface intersecting with the target ground is a horizontal coordinate l i The closed circle formed by rotating around the axis, and the closed circle encloses a closed plane on the target ground, and the guiding surface and the closed plane jointly constitute the landing platform.

[0012] In this technical solution, the discrete point description is based on engineering needs to avoid excessive numerical optimization calculation; the closed circle surface design is to ensure that the guiding surface is effective for random air landing errors in any direction of the UAV and to reduce design complexity, and the landing gear should also be designed in a symmetrical manner about the center point.

[0013] In any of the above technical solutions, the UAV has a center of gravity Q0, the UAV and the guiding surface have a contact point Q1, and the UAV and the closed plane have a contact point Q2; the state of the UAV includes: glide, roll, guidance interruption, and landing completion, and the state is judged using the following rules: the judgment rule for the UAV landing completion is that when the current speed of the UAV is zero, and the center of gravity line on the center of gravity Q0 is parallel to the axis and the distance is less than a preset distance, the current state of the UAV is judged as landing completion; the judgment rule for the UAV roll is that when the triangle formed by the center of gravity Q0, the contact point Q1 and the contact point Q2 in the plane has less than two intersection points with the center of gravity line of the UAV, the current state of the UAV is judged as roll; the judgment rule for the UAV guidance interruption is that when the current speed of the UAV is zero, and the UAV and the guiding surface have a contact point Q1, the current state of the UAV is judged as guidance interruption; the judgment rule for the UAV glide is that when the speed of the UAV is greater than zero and not in the state of roll, the state of the UAV is judged as glide.

[0014] In this technical solution, the coordinates of the contact points Q1 and Q2 are determined naturally by considering the UAV sliding process as a quasi-static process and the UAV only having the landing gear protruding edge in contact with the surface, ensuring that the contact points will not exceed two, and the h c and l c The upper limit of the value range ensures that the contact points will not be less than two.

[0015] Further, in the judgment of the landing completion state, considering the angle calculation or measurement error, when the angle between the UAV axis and the gravity line is less than 3 degrees, the two lines are considered parallel.

[0016] Further, in the judgment of the landing completion state and the guidance interruption state, considering the speed calculation or measurement error, when the maximum speed of the UAV is less than 0.01 m / s, the speed is considered to be 0, and the continuous judgment time is 5s.

[0017] Specifically, the length between Q1 and Q2 is the length of the unmanned aerial vehicle landing gear, which is the same as the diameter of the closed circle of the target ground, i.e. 2l v .

[0018] Further, the unmanned aerial vehicle has a circular ring-shaped landing gear base, and the length between Q1 and Q2 is the diameter of the circular ring.

[0019] In any of the above technical solutions, the continuous judgment is performed along a time axis, and for each time point A t , t = 0, 1, 2, …, m, the state of the unmanned aerial vehicle is judged, and the process of optimizing the guiding surface and the unmanned aerial vehicle landing control further comprises: S1, when the state of the unmanned aerial vehicle is judged as rolling over, the guiding surface is redesigned at a lower height by the guiding surface design model, and the unmanned aerial vehicle is controlled to land again; when the state of the unmanned aerial vehicle is judged as landing completed, the time point A t at which the current state is located is taken as the termination time point of this landing, and the process is terminated; when the state of the unmanned aerial vehicle is judged as gliding, the intersection Q3 of the contact point Q1 and the contact point Q2 along the respective moment directions is obtained, and the landing direction of the unmanned aerial vehicle at the current time point A t is obtained, the positional relationship between the intersection Q3 and the center of gravity Q0 along the landing direction at the current time point is judged, and the point on the guiding surface corresponding to the contact point Q1 at the current time point is recorded as a defect point when the intersection Q3 is located behind the center of gravity Q0 along the landing direction for the first time; when the state of the unmanned aerial vehicle is judged as guiding interruption, the point on the guiding curve corresponding to the contact point Q1 at which the unmanned aerial vehicle is in guiding interruption is taken as a fault point.

[0020] In this technical solution, all situations of the unmanned aerial vehicle guiding process are divided by the state of the unmanned aerial vehicle, including gliding, rolling over, guiding interruption and landing completion, etc. The state of the unmanned aerial vehicle is determined by the on-board sensors of the unmanned aerial vehicle and prior measurement knowledge, without the need for other measurement and calibration instruments, which facilitates the subsequent experimental verification.

[0021] In any of the above technical solutions, the step of setting a guiding surface for the unmanned aerial vehicle landing by the guiding surface design model comprises: setting the parameters of the unmanned aerial vehicle, including the length of the line connecting the contact point Q1 and the contact point Q2, and the distance between the center of gravity Q0 and the line; setting the value range of the height h c of the landing platform, the horizontal distance l c of any point on the top to the axis, the horizontal distance l v of any point on the bottom to the axis, and the surface friction coefficient of the landing platform; selecting the height h c from high to low and the horizontal distance l cand horizontal distance l v ; and the guide curved surface design model is as follows: l v ≤ x ≤ l c A ≥ l c x is a horizontal coordinate independent variable in a plane perpendicular to a target ground surface, c(x) is a vertical coordinate dependent variable in the plane perpendicular to the target ground surface, A is an overall convexity parameter of the guide curved surface, B is a parameter representing a relief degree of the guide curved surface, and π is a circular constant.

[0022] In the technical solution, the description of c(x) is to intuitively describe the shape through the parameters, facilitate to give a qualitative result of the guide curved surface shape, and according to a given coordinate and a current guide curved surface shape and l v The gravity center position of the unmanned aerial vehicle, the coordinate of another contact point Q2, and the coordinate of the intersection Q3 can be obtained, so that the moment of the gravity moment of the unmanned aerial vehicle on the intersection can be obtained, and all the moment values can be obtained for all possible Q1 in the interval, so that subsequent optimization and adjustment can be carried out.

[0023] Further, the dynamic friction coefficient of the surface of the landing platform is less than 0.3.

[0024] In any of the above technical solutions, the landing control includes gravity sliding, continuous force application, and pulse force application; and the process of optimizing the guide curved surface and the landing control of the unmanned aerial vehicle further includes: S2, when the unmanned aerial vehicle lands again and passes through the defect point, the landing control is changed to the unmanned aerial vehicle providing continuous force application to itself, and after the guide interruption occurs, the continuous force application is increased to control the unmanned aerial vehicle to land repeatedly until the continuous force application reaches the maximum.

[0025] In the technical solution, the continuous force application and the pulse force application are used to deal with the guide interruption problem, ensure the unmanned aerial vehicle to land more stably and quickly, and avoid the unmanned aerial vehicle to land in the air again as much as possible, and save energy consumption.

[0026] In any of the above technical solutions, step S2 further includes: if the maximum continuous force application provided to the unmanned aerial vehicle still cannot complete the landing, when the unmanned aerial vehicle lands again and passes through the defect point, the landing control is changed to the unmanned aerial vehicle generating pulse force application to itself, and after the guide interruption occurs, the pulse force application is increased to control the unmanned aerial vehicle to land repeatedly until the pulse force application reaches the maximum; if the unmanned aerial vehicle still cannot complete the landing by applying the maximum pulse force application, the slope of the defect point along the tangent of the guide curved surface is increased, and the unmanned aerial vehicle is controlled to land by applying the maximum pulse force application until the slope reaches the maximum; if the slope of the defect point along the tangent of the guide curved surface reaches the maximum and cannot make the unmanned aerial vehicle complete the landing, a height h is designed in the value range through the guide curved surface design modelc Lower the guide curve, and control the unmanned aerial vehicle to land by gravity sliding; when the minimum height in the value range cannot make the unmanned aerial vehicle land, reduce the surface friction coefficient of the landing platform, and design a guide curve through the guide curve design model with the maximum height; and / or reduce the contact point of the unmanned aerial vehicle and the distance between the contact points; and / or increase the initial landing speed of the unmanned aerial vehicle when contacting the guide curve.

[0027] In the technical scheme, the F=G sin theta is used to distinguish between the continuous force and the pulse force, when F=G sin theta, the support force at the Q1 point tends to 0, if the continuous force is still used, the unmanned aerial vehicle may be overturned, and the pulse force is safer.

[0028] In any of the above technical schemes, the gravity center line and the unmanned aerial vehicle axis have an angle theta; and the value of the continuous force has a first preset range, and the first preset range is (0, G sin theta); the value of the pulse force has a second preset range, and the second preset range is [G sin theta, T]; wherein G is the gravity of the unmanned aerial vehicle, T is the rated maximum lift of the unmanned aerial vehicle, the direction of the continuous force and the pulse force is perpendicular to the line connecting the contact point Q1 and the contact point Q2, and the torque formed by Q3 is opposite to the gravity torque.

[0029] In the technical scheme, the optimization scheme is to improve the flexibility of the method application, and can be applied to more extensive cases.

[0030] In any of the above technical schemes, for the unmanned aerial vehicle of the same size, when the guide curve design model designs the guide curve, the value of the height h c is taken in the value range in descending order of integer, so as to obtain the guide curve with the largest average slope for the unmanned aerial vehicle to land and complete in the value range; wherein the average slope is the average value of each discrete point on the guide curve, the value range of the height h c is

[0031] In the technical scheme, the minimum value of h c is limited by the dynamic friction of the surface, and the maximum value is to avoid the contact points of the unmanned aerial vehicle and the guide curve and the contact surface being less than two in the sliding process.

[0032] The present application has the following beneficial effects compared with the prior art:

[0033] The center of the unmanned aerial vehicle can be passively adjusted to the set target point, the physical method reduces the landing algorithm accuracy requirement of the unmanned aerial vehicle, and the sliding guide effect can be enhanced by increasing the size of the mechanism.

[0034] Through the closed-loop design-verification iteration process, the optimal result of the guide surface can be given in a few iterations, and it can be preliminarily judged whether the unmanned aerial vehicle can successfully glide in the design stage, so that the number of tests is saved, and economic expenditure and material consumption are reduced.

[0035] Additional aspects and advantages of embodiments according to the present application will become apparent from the following description with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0036] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood by considering the following detailed description, from which the novel concepts will become apparent to those skilled in the art, with reference to the drawings, wherein:

[0037] Figure 1 A flow chart of the method of the present application;

[0038] Figure 2 A schematic diagram of the guide surface calculation model of the present application;

[0039] Figure 3 A schematic diagram of the guide surface calculation model of the present application considering the force applied by the unmanned aerial vehicle;

[0040] Figure 4 An example diagram of the guide surface of the present application. DETAILED DESCRIPTION

[0041] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0042] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0043] Referring to Figures 1-4 , the following describes an unmanned aerial vehicle landing optimization method based on surface guidance according to some embodiments of the present application.

[0044] Embodiments of the first aspect of the present application propose an unmanned aerial vehicle landing optimization method based on surface guidance. In some embodiments of the present application, as shown in Figures 1-4 , an unmanned aerial vehicle landing optimization method based on surface guidance is provided, the unmanned aerial vehicle landing optimization method based on surface guidance comprising:

[0045] The guiding surface can be divided into inner sliding type and outer sliding type. The guiding surface is of outer sliding type at the outside of the contact point with the UAV, and is of inner sliding type at the inside of the contact point with the UAV. In the calculation model of the outer sliding type, it is assumed that the UAV lands at a low initial speed, simultaneously contacts the guiding surface and the landing platform support surface and dynamically slides down. O is the center of the bottom surface of the UAV and the origin of the coordinate system, Q0 is the center of gravity of the UAV, G is the gravity, the dash-dot line represents the guiding surface and the end point coordinates are (l v 0) and (l c h c ). Q1 and Q2 are respectively the contact points of the UAV with the guiding surface and the support surface, Q1Q2 is the bottom surface of the landing gear of the UAV, and Q3 is the intersection of the contact forces F1 and F2.

[0046] The first step is guiding surface design. According to the moment equation, when Q3 is located in the right shadow area of Q0, the UAV can be passively slid down under the action of gravity, when l v , l c , h c , the center of gravity height of the UAV and the friction coefficient are known, the coordinates of Q3 and Q0 can be obtained, and the UAV can be passively slid down at any time on the guiding surface, and the condition for realizing the precise condition is that for any time t, there is

[0047]

[0048] The physical meaning of the formula is that when the mass of the UAV does not change, the size of the righting moment, the greater the righting moment, the faster the UAV slides down. Define j as the negative value of the integral of the moment in the complete sliding process, and the independent variable x ranges from l v to l c . That is:

[0049]

[0050] The smaller j, the faster the expected average sliding speed of the UAV. The optimization goal of the surface is min(j), and the result of the guiding surface is obtained by optimization.

[0051] The second step is the UAV force control design. When the size of the guiding surface is limited, the center of gravity height of the UAV is too high or the friction coefficient of the contact surface is too large, the above judgment condition may not be established, which may cause the UAV to be unable to overcome the friction and interrupt the guiding process. At this time, the initial landing speed of the UAV can be appropriately increased to overcome the friction, or the UAV can generate an applied force to change the range of the shadow area, as shown in Figure 3 For the outer sliding type, the lift of the UAV changes the force direction of the UAV, and the UAV provides the applied force according to the method, so as to ensure that Q3 is still located in the shadow area determined by the combined force direction of the lift and the gravity.

[0052] If the drone's center of gravity is too high or its initial velocity is too high during actual guidance, causing it to roll over, the guidance process will completely fail. In this case, the drone's initial velocity should be reduced or the position adjusted. v h c The guidance surface was redesigned.

[0053] The third step involves iterative correction of the guidance surface during the landing verification process. During actual landing, the UAV will collide with the guidance surface and will not be in constant contact with the support surface. Furthermore, it is susceptible to ground effects during landing. Therefore, the above guidance surface design method should be validated to determine the final guidance surface shape. For example... Figure 1 As shown, the verification process includes: the UAV receives landing commands and landing platform status information, and flies to directly above the landing position based on its own attitude; the UAV maintains a horizontal attitude and descends to perform the aerial landing process, contacting the guide surface of the landing device; the UAV shuts off its power and lands under the guidance of gravity. If the UAV can finally glide to the target position, the guidance is considered successful, and the guidance process ends. If the guidance fails, such as a rollover or guidance interruption due to excessive friction, appropriate measures are required. If the UAV rolls over, the initial landing velocity or center of gravity height needs to be reduced, or the guide surface needs to be redesigned, and the new guide surface needs to be re-verified to correct the results; if the UAV experiences guidance interruption, the aforementioned force pulse needs to be generated to continue the guidance process. Based on the above closed-loop iterative process, the final guide surface shape and the final precise landing strategy can be determined.

[0054] Furthermore, in the design of the guiding surface, the radius l of the guiding surface... c It is 43mm, and the height is h. c Given a diameter of 30 mm, and assuming the guiding surface function is c(x), we have...

[0055]

[0056] The guiding surface is determined by parameters A and B. The function can take different forms in practice. Define j as l v to l c Integral with respect to torque

[0057]

[0058] The optimization objective is min(j), which yields the initial shape of the guiding surface. In practical applications, the weights of various parts of the guiding surface can be adjusted by modifying the optimization objective.

[0059] Furthermore, the force control design of the UAV ensures that j satisfies the following conditions during the descent. The drone cannot be reversed to provide the pressure required for the inner sliding guide surface, so no force needs to be applied.

[0060] Specifically, in combination with the iterative correction of the guide surface in the verification process, the quadrotor UAV with an axis distance of 250 is tested, the width of the landing gear base ring of the UAV is 10% of the radius, and the ground landing platform carrying the guide mechanism is tested, the quadrotor starts landing from a height of 6-8 cm from the landing platform, and the landing speed is 0.5 m / s. During the verification process, the UAV rolled over. According to the design method, the height of the center of gravity of the UAV is reduced, and the shape of the guide surface is redesigned.

[0061] The application provides a quadrotor landing optimization method based on a guide surface, which gives a relatively optimal result of the guide surface in a few iterations through a closed-loop design-verification iteration process, and the guide tolerance error is similar to the radius of the guide surface. The method reduces the accuracy requirement of the UAV landing algorithm in a physical way, and the relative landing tolerance error of the guide method can be adjusted according to the size of the aircraft, and is suitable for UAV-landing platform combinations of different sizes.

[0062] Another embodiment of the first aspect of the application provides a progressive optimization method for quadrotor landing based on a guide surface. In some embodiments of the application, as shown in Figure 1 The application provides a quadrotor landing optimization method based on a guide surface, which comprises the following steps:

[0063] S1, start, select the maximum value in the optional design height range of the guide surface from top to bottom, and obtain the shape information of the UAV;

[0064] S2, based on the current given design height, judge whether the design height is the minimum value of the design height range, if yes, proceed to S11, if not, design a guide surface through the guide surface model, reset the landing control and select gravity sliding, and proceed to S3;

[0065] S3, the UAV has an air landing contact with the guide surface, continuously judges and obtains defect points and fault points during landing, continuously judges whether the UAV lands successfully during landing, if yes, proceeds to S4, if not, proceeds to S5;

[0066] S4, end of guide, and output the guide surface of this landing and the landing control adopted by the UAV;

[0067] S5, judge whether the state of the UAV is rolling, if yes, proceed to S6, if not, proceed to S7;

[0068] S6, based on the design height of the guide surface adopted by the UAV landing failure, reduce the design height of the guide surface by one unit, and return to S2;

[0069] S7, change the landing control to a sustained application force starting from the defect point, and determine whether the sustained application force is the maximum value in the applicable range, if not, increase the sustained application force and return to S3, if yes, proceed to S8;

[0070] S8, change the landing control to a pulse application force at the failure point, and determine whether the pulse application force is the maximum value in the applicable range, if not, increase the pulse application force and proceed to S9, if yes, proceed to S11;

[0071] S9, control the unmanned aerial vehicle to land in the air, and continuously determine whether the state of the unmanned aerial vehicle is successful landing, if yes, return to S4, if not, proceed to S10;

[0072] S10, determine whether the slope of the failure point is the maximum value in the applicable range, if yes, proceed to S2, if not, proceed to S11;

[0073] S11, increase the slope of the failure point of the guide surface by one unit, and return to S9;

[0074] S12, reduce the surface friction coefficient of the landing platform, and return to S1.

[0075] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0076] The above-described embodiments are only preferred modes of the present application, and do not limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A method for optimizing UAV landing based on surface guidance, characterized in that, Includes the following steps: Establish a guide surface design model that takes into account the size of the UAV landing platform, and set a guide surface for UAV landing through the guide surface design model; The drone is controlled to land via the guide surface. During the landing process, the state of the drone is continuously judged, and the guide surface and drone landing control are optimized based on the judgment results. Until the drone completes its landing on the guide surface, output the guide surface and the corresponding drone landing control; The step of setting a guide surface for UAV landing using the guide surface design model includes: Set the drone's parameters: the length of the line connecting contact point Q1 and contact point Q2. And the distance between the center of gravity Q0 and the line connecting them; Set the height h of the landing platform c The range of values ​​for , the horizontal distance l between any point on the top and the axis c and the horizontal distance l between any point at the bottom and the axis v and the surface friction coefficient μ of the landing platform; Select height h from high to low within the range of values. c Select horizontal distances l from smallest to largest. c and horizontal distance l v The guide surface design model designs the guide surface using the following formula: Among them, l v ≤x≤l c ,A≥l c x is the independent variable of the horizontal coordinate in a plane perpendicular to the target ground, c(x) is the dependent variable of the vertical coordinate in a plane perpendicular to the target ground, A is the overall convexity parameter of the guide surface, B is the undulation parameter of the guide surface, and π is pi.

2. The method for optimizing UAV landing based on curved surface guidance according to claim 1, characterized in that, The guide surface is formed by rotating a guide curve circumferentially along an axis, the axis being perpendicular to the target ground upon landing. The guide curve is set in a plane perpendicular to the target ground, starting from the guide starting point (l). c ,0,h c ) to the guiding endpoint (l v A smooth curve consisting of multiple nodes connected sequentially between (0, 0); The node coordinates of the smooth curve are (l c ,0,h c ), (l1, 0, h1), ..., (l n ,0,h n ), (l v (0, 0); the horizontal coordinates of the nodes in the smooth curve l i Let i = 1, 2, ..., n satisfy: l c >l1>l n >l v >0; the vertical coordinate h of the node in the smooth curve i Let i = 1, 2, ..., n satisfy h c >h1>h n >0; Wherein, the bottom edge where the guide surface intersects the target ground is determined by the horizontal coordinate l i The landing platform is formed by rotating circumferentially around an axis to form a closed circle, and the closed plane enclosed by the closed circle on the target ground together with the guide surface.

3. The method for optimizing UAV landing based on surface guidance according to claim 2, characterized in that, The drone has a center of gravity Q0, a contact point Q1 between the drone and the guide curved surface, and a contact point Q2 between the drone and the closed plane; the states of the drone include: descent, rollover, guidance interruption, and landing completion, and the determination of the state is based on the following rules: The rule for determining whether the drone has completed landing is as follows: when the drone is not in a rollover state, its speed is stable at zero for a period of time, and the center line of gravity on the drone's center of gravity Q0 is parallel to the axis and the distance between them is less than a preset distance, the drone will determine its current state as a completed landing. The rule for determining whether a drone is overturned is as follows: when the triangle formed by the center of gravity Q0, contact point Q1, and contact point Q2 in the plane intersects with the drone's center of gravity line less than two times, the drone's current state is determined to be overturned. The rule for determining the interruption of drone guidance is as follows: when the drone is not in a rollover state, and its speed is stable at zero for a period of time, and the center line of gravity on the drone's center of gravity Q0 is not parallel to the axis, the drone will determine the current state as a guidance interruption. The rule for determining whether a drone is descending is as follows: when the drone's speed is greater than zero and it is not in a rollover state, the drone is determined to be descending.

4. The method for optimizing UAV landing based on surface guidance according to claim 3, characterized in that, The continuous judgment is performed along the time axis, for each time point A on the time axis. t The state determined by the UAV at t = 0, 1, 2, ..., m, and the optimization process for the guide surface and UAV landing control also includes: S1, when the drone's state is determined to be overturned, the guide surface is redesigned at a lower height using the guide surface design model, and the drone is controlled to land again. When the drone's status is determined to be that landing is complete, at time point A of the current status... t This will be used as the termination point for the landing, and the process will be terminated. When the drone's state is determined to be gliding, obtain the intersection point Q3 of contact points Q1 and Q2 along their respective torque directions, and the drone's position at the current time point A. t The landing direction is determined, and the positional relationship between the lower intersection point Q3 and the center of gravity Q0 at the current time point is determined along the landing direction. When the intersection point Q3 along the time axis is first located behind the center of gravity Q0 along the landing direction, the point on the guide surface corresponding to the lower contact point Q1 at the current time point is taken as the defect point. When the drone's status is determined to be a guidance interruption, the point on the guidance curve corresponding to the drone's guidance interruption contact point Q1 is taken as the fault point.

5. The method for optimizing UAV landing based on surface guidance according to claim 4, characterized in that, The landing control includes: gravity descent, continuous force application, and pulsed force application; and the optimization process for the guide surface and UAV landing control also includes: S2, for the guide surface where the drone's guidance is interrupted due to gravity descent, when the drone lands again and passes the defect point, the landing control is changed to the drone providing a continuous force to itself, and after the guidance interruption, the continuous force is increased to control the drone to land repeatedly until the continuous force reaches its maximum.

6. The method for optimizing UAV landing based on curved surface guidance according to claim 5, characterized in that, Step S2 also includes: If the maximum continuous force applied to the drone is still insufficient to complete the landing, when the drone lands again and passes the fault point, the landing control switches to the drone generating a pulse force on itself, and after the guidance interruption occurs, the pulse force is increased to control the drone to repeat the landing until the pulse force reaches the maximum. If the drone still fails to land after applying the maximum pulse force, increase the slope of the fault point along the tangent of the guide surface and control the drone to land with the maximum pulse force until the slope reaches the maximum. If the slope of the fault point along the tangent of the guide surface reaches its maximum, preventing the drone from landing, a height h can be designed within the range of values ​​using the guide surface design module. c A lower guide surface is used to control the drone to land using gravity descent; when the minimum altitude within the range cannot allow the drone to land successfully, Reduce the surface friction coefficient of the landing platform and design a guide surface using a guide surface design model at the maximum height; and / or Reduce the contact point of the drone and the distance between contact points; and / or Increase the initial landing speed of the UAV when it contacts the guide surface.

7. The method for optimizing UAV landing based on surface guidance according to claim 5, characterized in that, The center line of gravity forms an angle θ with the axis of the UAV; and The value of the continuously applied force has a first preset range, and the first preset range is (0, G sinθ); The value of the pulsed force has a second preset range, and the second preset range is [G sinθ, T]; Wherein, G is the gravity acting on the UAV, T is the rated maximum lift of the UAV, and the directions of the continuously applied force and the pulsed force are both perpendicular to the line connecting contact point Q1 and contact point Q2, and form a torque on Q3 in the opposite direction to the gravitational torque.

8. The method for optimizing UAV landing based on surface guidance according to claim 5, characterized in that, For drones of the same size, when designing the guide surface using the guide surface design model, the height h is considered within a given value range. c The values ​​are taken in descending order of integers to obtain the guide surface with the largest average slope for the drone to land within the range of values; Wherein, the average slope is the average value of each discrete point on the guide surface, and the height h c The range of values ​​is

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