Unmanned helicopter landing guiding method based on offshore motion platform

Abstract

The invention discloses an unmanned helicopter landing guide method based on an offshore motion platform, and the method comprises the following steps: 1) determining a landing guide region according to the position of an unmanned helicopter parking apron on the offshore motion platform; (2) when the unmanned helicopter flies into the landing guide area, recording the position, the flight speed and the flight direction of the unmanned helicopter at the moment of switching to the landing guide stage, and the position, the movement speed and the movement direction of the offshore movement platform; 3) based on the acquired information in the step 2), planning a route of a landing guide stage; 4) calculating an expected track angle of the unmanned helicopter in the vertical direction according to the height of the offshore platform unmanned helicopter parking apron and the height of the unmanned helicopter at the M point; and 5) guiding the unmanned helicopter to land. The invention provides a method for planning the track and the flight speed of an unmanned helicopter in a landing guide stage. The success rate of landing of the unmanned helicopter on an offshore platform in a moving state can be improved in space and time.

Description

Technical Field

[0001] The invention relates to unmanned aerial vehicle technology, and in particular to an unmanned helicopter landing guidance method based on an offshore motion platform. Background Art

[0002] Compared with composite wing drones and rotary wing drones, unmanned helicopters have the characteristics of heavy load, strong wind interference resistance, and long endurance, and are widely used in the fields of maritime law enforcement monitoring, maritime rescue, ocean monitoring, and aerial survey. According to the motion characteristics of offshore platforms, offshore unmanned helicopters need to consider uncertain factors such as parking space, working environment, and electromagnetic environment, and focus on solving the problem of autonomous landing guidance of unmanned helicopters, thereby improving the success rate of unmanned helicopter landing at sea and ensuring the normal use of unmanned helicopters.

[0003] The offshore platform is subject to random irregular and complex motions such as roll, pitch, yaw, deep motion and compound motion due to the interference of waves and sea breeze, which greatly increases the difficulty of landing unmanned helicopters. Secondly, unmanned helicopters are unmanned and autonomously land, lacking the active identification and risk avoidance capabilities of manned helicopter pilots. The risk of navigating unmanned helicopter landing is more difficult to control than that of helicopters. In addition, for automatically controlled unmanned helicopters, landing during the movement of offshore platforms is much more complicated and dangerous than on land. In order to improve the success rate of autonomous landing of unmanned helicopters on moving offshore platforms, it is necessary to study their landing guidance methods. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a landing guidance method for an unmanned helicopter based on an offshore motion platform in view of the defects in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for guiding the landing of an unmanned helicopter based on an offshore motion platform, comprising the following steps:

[0006] 1) Determine the landing guidance area based on the location of the unmanned helicopter landing pad on the offshore sports platform;

[0007] Taking the unmanned helicopter landing pad on the offshore sports platform as the center, a cylinder with a set distance of radius R and height h is used as the landing guide area;

[0008] 2) When the unmanned helicopter flies into the landing guidance area, the state of the unmanned helicopter switches to the landing guidance stage, and the position P of the unmanned helicopter at the time of switching to the landing guidance stage is recorded. S And the flight speed and direction (V1, θ1), as well as the position P of the offshore motion platform M and movement speed and direction (V2,θ2);

[0009] 3) Based on the information collected in step 2), plan the route for the landing guidance phase;

[0010] 3.1) According to the current position and flight direction of the unmanned helicopter, as well as the current position and navigation direction of the offshore platform, the first stage landing guidance route of the unmanned helicopter is planned by the three-dimensional Dubins algorithm;

[0011] 3.2) When the unmanned helicopter reaches the end point of the first stage landing guidance route, the end point is used as the starting point of the second stage landing guidance route. Combined with the position and navigation direction of the offshore motion platform at this time, the second stage landing guidance route and the expected flight speed are planned using the track prediction method;

[0012] 4) According to the height H0 of the unmanned helicopter landing pad on the offshore platform and the height H0 of the drone at point M M , calculate the expected track angle γ of the unmanned helicopter in the vertical direction g ;

[0013] 5) Guide the unmanned helicopter to land.

[0014] According to the above scheme, in step 3.1), the path planned by the three-dimensional Dubins is composed of two arcs and a straight line, wherein the two arcs are two arcs passing through points S and M, and the straight line is a line connecting the tangent points of the two arcs. The end point of the unmanned helicopter's first stage landing guidance route is when the unmanned helicopter flies to point M.

[0015] According to the above scheme, the specific steps of the three-dimensional Dubins planning in step 3.1) are as follows:

[0016] 3.1.1) Determine the current position coordinates P of the unmanned helicopter at point S S , flight speed and direction (V1, θ1) and turning radius r1, the position coordinates P of the unmanned helicopter at point M M , movement speed and direction (V2, θ2) and turning radius r2, calculate the left and right center positions of the unmanned helicopter at points S and M;

[0017] 3.1.2) Considering the no-landing zone constraint, the 3D Dubins algorithm is used to plan the 3D Dubins path from point S to point M.

[0018] According to the above scheme, in step 3.1.1), the left and right center positions of the unmanned helicopter at points S and M are calculated as follows:

[0019]

[0020] Where P S and P M All are three-dimensional coordinates, including longitude, latitude, and altitude;rs , O ls are the right and left center coordinates of the unmanned helicopter at point S, respectively. rm , O lm They are respectively the right center coordinates and left center coordinates of the unmanned helicopter at point M.

[0021] According to the above scheme, the specific steps of planning the three-dimensional Dubins path from point S to point M in step 3.1.2) are as follows:

[0022] 3.1.2.1) The three-dimensional Dubins path consists of two arc segments and a straight line, where the arc segment is a descending spiral. The descending spiral in the Cartesian coordinate system is calculated as follows:

[0023]

[0024] Where ω is the angular velocity of the uniform spiral descent, γ is the track angle of the unmanned helicopter descent, and R d is the radius of the arc segment of the descending spiral, and t is the time for the spiral descent of the unmanned helicopter;

[0025] The straight line segment is the line connecting the tangent points of two arc segments. The shortest trajectory of the four three-dimensional routes in path planning is calculated by the Dubins algorithm to determine the route type, which is used as the final straight line segment path planned by the three-dimensional Dubins algorithm.

[0026] According to the above scheme, the step 3.2) uses the track prediction method to plan the second stage landing guidance route and the expected flight speed, as follows:

[0027] 3.2.1) Determine the expected flight speed of the second phase based on the first phase flight speed of the unmanned helicopter, the moving speed of the offshore platform, and the maximum turning radius of the unmanned helicopter;

[0028] 3.2.2) Plan the second stage landing guidance route according to the current position and moving direction of the offshore platform;

[0029] The details are as follows:

[0030] 3.2.2.1) If the offshore platform is in a straight-line navigation state, and the moving speed direction (V2, θ3) deviates from the speed direction (V2, θ2) at point M, the second-stage landing guidance route is planned in the form of an arc plus a straight line. The arc segment is still planned with r2 as the radius, and its trajectory length is calculated as follows:

[0031]

[0032] Among them, S 1-R is the arc segment length, S 1-Sis the length of the straight line segment trajectory; S 1-R-S is the total trajectory length;

[0033] 3.2.2.2) The offshore motion platform is in a straight-line navigation state, and the moving direction is the same as the speed V2 at point M: At this time, the horizontal flight trajectory and the expected flight speed of the unmanned helicopter are planned according to the straight-line trajectory and trajectory prediction method. The trajectory length S 2-S The calculation is as follows:

[0034] S 2-S =(S Dubins-水平 V2V g / [(V g -V2)V1]);

[0035] 3.2.2.3) If the offshore platform is in a turning state, the arc trajectory from point M to the predicted offshore platform position and the expected flight speed of the unmanned helicopter are directly planned according to the trajectory prediction method. The arc trajectory is planned as a circle passing through point E and tangent to the V2 direction of point M, and its trajectory length S 3-S The circle radius r3 is calculated as follows:

[0036]

[0037] According to the above scheme, in step 3.2.1), the expected flight speed in the second stage is determined as follows:

[0038]

[0039] The expected flight speed should satisfy the following constraints:

[0040]

[0041] Where V1 is the first-stage flight speed of the unmanned helicopter, V2 is the moving speed of the offshore platform, and S Dubins-水平 is the horizontal trajectory distance of the first stage landing guidance route, φ max is the maximum turning radius of the unmanned helicopter, and g is the local gravity acceleration.

[0042] According to the above scheme, in step 4), the desired track angle γ of the unmanned helicopter in the vertical direction is g The calculation is as follows:

[0043]

[0044] Among them, S e The planned trajectory length for the second stage landing guidance route.

[0045] The beneficial effects of the present invention are as follows: the present invention makes full use of the flight characteristics of the unmanned helicopter, and proposes a method for planning the trajectory and flight speed of the unmanned helicopter in the landing guidance stage through a three-dimensional Dubins algorithm and trajectory prediction, which can improve the success rate of the unmanned helicopter landing on a moving offshore platform in space and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0047] Figure 1 is a method flow chart of an embodiment of the present invention;

[0048] Figure 2 is a schematic diagram of a landing guidance area according to an embodiment of the present invention;

[0049] Figure 3 is a schematic diagram of the first stage trajectory planning of an embodiment of the present invention;

[0050] Figure 4 4 is a schematic diagram of the second stage trajectory planning of an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] like Figure 1 As shown, a method for guiding an unmanned helicopter to land based on an offshore motion platform comprises the following steps:

[0053] 1) With the unmanned helicopter landing pad on the offshore platform as the center, a cylinder with a set distance of radius R and height h is used as the landing guidance area and the landing guidance stage switching mark. When the unmanned helicopter flies into the range of the cylinder, the state of the unmanned helicopter is switched to the unmanned helicopter entering the landing guidance stage;

[0054]

[0055] like Figure 2 The radius R of the virtual cylinder can be based on the size of the unmanned helicopter and the horizontal landing guidance distance recommended by the manufacturer, and can generally be set between 1000m and 3000m. The height h of the cylinder can be based on the cruising altitude of the unmanned helicopter, which is affected by the ceiling of the unmanned helicopter and can generally be set between 3000m and 5000m.

[0056] 2) Record the position P of the unmanned helicopter when it switches to the landing guidance phase Sand the flight speed and direction (V1,θ1), as well as the position P of the offshore platform M and movement speed and direction (V2,θ2);

[0057] 3) Based on the information collected in step 2), plan the route for the landing guidance phase;

[0058] 3.1) According to the current position and flight direction of the unmanned helicopter, as well as the current position and navigation direction of the offshore platform, plan the first stage landing guidance route of the unmanned helicopter; Figure 3 ;

[0059] 3.1.1) Determine the current position coordinates P of the unmanned helicopter at point S S , flight speed and direction (V1, θ1) and turning radius r1, the position coordinates P of the unmanned helicopter at point M M , the speed and direction of movement (V2, θ2) and the turning radius r2, and the left and right center positions of the unmanned helicopter at points S and M are calculated according to formula (2):

[0060]

[0061] Where P S and P M All are three-dimensional coordinates, including longitude, latitude, and altitude; rs , O ls are the right and left center coordinates of the unmanned helicopter at point S, respectively. rm , O lm They are the right and left center coordinates of the unmanned helicopter at point M respectively;

[0062] 3.1.2) Considering the no-landing zone constraint, the 3D Dubins algorithm is used to plan the 3D Dubins path from point S to point M. The 3D Dubins path planning method is as follows:

[0063] The three-dimensional Dubins path consists of two arc segments and a straight line. The arc segment is a descending spiral. The descending spiral in the Cartesian coordinate system is calculated as follows:

[0064]

[0065] Where ω is the angular velocity of the uniform spiral descent, γ is the track angle of the unmanned helicopter descent, and R d is the radius of the arc segment of the descending spiral, and t is the time for the spiral descent of the unmanned helicopter;

[0066] The horizontal distance L of the descending spiral is calculated as follows:

[0067] L=R d ωt Formula (4)

[0068] The trajectory of the path planning is calculated by the Dubins algorithm to determine the route type. The straight line segment is the line connecting the tangent points of the two arc segments.

[0069] The principle of the three-dimensional Dubins algorithm is to calculate the following by using the calculation method of arc segments and straight line segments: Figure 2 The distances of the horizontal routes of the four types of three-dimensional routes shown in the figure are such that when the flight path angle γ of the unmanned helicopter is constant, when the horizontal route distance is the shortest, the three-dimensional Dubins path is also the shortest, which is the final path planned by the three-dimensional Dubins algorithm. The shortest distance of the three-dimensional Dubins path can be obtained by calculating the horizontal distances of the four types of routes using equations (5) to (8) and then taking the shortest path. The calculation process of the arc straight line segment trajectory of the four types of routes is as follows:

[0070]

[0071]

[0072]

[0073]

[0074] The last arc segment in equations (5) to (8) has a constraint condition, namely, the shortest horizontal distance S of the three-dimensional Dubins path Dubins-水平 The calculation method is:

[0075]

[0076] In formula (5), express The azimuth of express The model (distance), in formula (6), express The azimuth of express The model (distance), in formula (7), express The azimuth of express The model (distance), in formula (8), express The azimuth of express In formula (9), ∠SMO1 is the distance between point S, point M, and point O. lm The angle between the points.

[0077] The vertical direction of the three-dimensional Dubins path descends at a fixed track angle γ, and the shortest vertical distance S is calculated according to formula (10):Dubins-垂直 :

[0078] S Dubins-垂直 =S Dubins-水平 *tanγ Formula (10)

[0079] The unmanned helicopter flies at a speed of V1 during the first stage of landing guidance.

[0080] The end point of the unmanned helicopter landing guidance route in the first stage is: the unmanned helicopter flies to point M of the arc segment where point M is located;

[0081] 4) Plan the horizontal and vertical flight speeds of the unmanned helicopter during the landing guidance phase;

[0082] When the unmanned helicopter reaches the end point of the first stage landing guidance route, it takes the end point as the starting point of the second stage landing guidance route, combines the position and navigation direction of the offshore platform at this time, and uses the track prediction method to plan the second stage landing guidance route and the expected flight speed, so as to complete the landing; Figure 4 ;

[0083] 4.1) Determine the desired flight speed for the second phase;

[0084]

[0085] The expected flight speed should satisfy the following constraints:

[0086]

[0087] Where V1 is the first-stage flight speed of the unmanned helicopter, V2 is the moving speed of the offshore platform, and S Dubins-水平 is the horizontal trajectory distance of the first stage landing guidance route, φ max is the maximum turning radius of the unmanned helicopter, and g is the local gravity acceleration;

[0088] 4.2) Plan the second-stage landing guidance route according to the current position and moving direction of the offshore platform;

[0089] The details are as follows:

[0090] 4.2.1) The offshore platform is in a straight-line navigation state, and the moving speed direction (V2, θ3) deviates from the speed direction (V2, θ2) at the position of point M: At this time, the second-stage landing guidance route is replanned in the form of arc + straight line. The arc segment is still planned with r2 as the radius. Its trajectory length is calculated according to formula (13):

[0091]

[0092] 4.2.2) The offshore platform is in a straight-line navigation state, and the moving direction is the same as the speed V2 at point M: At this time, the horizontal flight trajectory and the expected flight speed of the unmanned helicopter are replanned according to the straight-line trajectory and trajectory prediction method. The trajectory length is calculated according to formula (14):

[0093] S 2-S =(S Dubins-水平 V2V g / [(V g -V2)V1]) Formula (14)

[0094] 4.2.3) When the offshore platform is in a turning state, the arc trajectory from point M to the predicted offshore platform position and the expected flight speed of the unmanned helicopter are directly planned according to the trajectory prediction method. The arc trajectory is planned as a circle passing through point E and tangent to the V2 direction of point M. The trajectory length and circle radius r3 are calculated according to formula (15):

[0095]

[0096] 5) According to the height H0 of the unmanned helicopter landing pad on the offshore platform and the height H0 of the drone at point M M , calculate the expected track angle γ of the unmanned helicopter in the vertical direction g , the calculation method is shown in formula (16):

[0097]

[0098] 6) Guide the unmanned helicopter to land.

[0099] After the flight is completed according to the trajectory prediction method, the unmanned helicopter's flight speed and direction are adjusted to be consistent with the offshore platform, and it can land autonomously. If there is still a deviation between the horizontal position of the unmanned helicopter and the offshore platform's helipad, it is necessary to switch to manual control of the unmanned helicopter landing.

[0100] In this application, the unmanned helicopter flight control system calculates the horizontal and vertical distances from the center point of the offshore platform drone landing pad in real time, and determines that the landing guidance stage is in progress when the threshold is reached. The main purpose of the landing guidance stage is to make the unmanned helicopter slow down and reach a suitable landing height and speed before reaching the drone landing pad;

[0101] Among them, through the first stage landing guidance route planning, the distance between the unmanned helicopter and the offshore platform is shortened with a relatively short flight distance, and the flight direction of the unmanned helicopter is kept consistent with the offshore platform as much as possible; through the second stage landing guidance route planning, the track prediction method is used to predict the meeting point (i.e., landing point) of the offshore platform in motion and the unmanned helicopter, so as to plan the flight trajectory and expected flight speed. In the second stage, except for the irregular movement of the offshore platform, which cannot be predicted, normal straight and turning driving can be predicted according to this method.

[0102] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for guiding an unmanned helicopter to land based on an offshore mobile platform, characterized in that: The following steps are involved: 1) Determine the landing guidance area based on the location of the unmanned helicopter landing pad on the offshore sports platform; Taking the unmanned helicopter landing pad on the offshore sports platform as the center, a cylinder with a set distance of radius R and height h is used as the landing guide area; 2) When the unmanned helicopter flies into the landing guidance area, the state of the unmanned helicopter switches to the landing guidance stage, and the position P of the unmanned helicopter at the time of switching to the landing guidance stage is recorded. S And the flight speed and direction (V1, θ1), as well as the position P of the offshore motion platform M and movement speed and direction (V2,θ2); 3) Based on the information collected in step 2), plan the route for the landing guidance phase; 3.1) According to the current position and flight direction of the unmanned helicopter, as well as the current position and navigation direction of the offshore platform, the first stage landing guidance route of the unmanned helicopter is planned by the three-dimensional Dubins algorithm; 3.2) When the unmanned helicopter reaches the end point of the first stage landing guidance route, the end point is used as the starting point of the second stage landing guidance route. Combined with the position and navigation direction of the offshore motion platform at this time, the second stage landing guidance route and the expected flight speed are planned using the track prediction method; 4) According to the height H0 of the unmanned helicopter landing pad on the offshore platform and the height H0 of the drone at point M M , calculate the expected track angle γ of the unmanned helicopter in the vertical direction g ; 5) Guide the unmanned helicopter to land.

2. The unmanned helicopter landing guidance method based on an offshore motion platform according to claim 1 is characterized in that: In the step 3.1), the path planned by the three-dimensional Dubins is composed of two arc segments and a straight line segment, wherein the two arc segments are two arc segments passing through points S and M, and the straight line segment is a line connecting the tangent points of the two arc segments. The end point of the unmanned helicopter's first stage landing guidance route is when the unmanned helicopter flies to point M.

3. The unmanned helicopter landing guidance method based on an offshore mobile platform according to claim 1 is characterized in that: The specific steps of the three-dimensional Dubins planning in step 3.1) are as follows: 3.1.1) Determine the current position coordinates P of the unmanned helicopter at point S S , flight speed and direction (V1, θ1) and turning radius r1, the position coordinates P of the unmanned helicopter at point M M , movement speed and direction (V2, θ2) and turning radius r2, calculate the left and right center positions of the unmanned helicopter at points S and M; 3.1.2) Considering the no-landing zone constraint, the 3D Dubins algorithm is used to plan the 3D Dubins path from point S to point M.

4. The unmanned helicopter landing guidance method based on an offshore mobile platform according to claim 3 is characterized in that: In step 3.1.1), the left and right center positions of the unmanned helicopter at points S and M are calculated as follows: Where P S and P M All are three-dimensional coordinates, including longitude, latitude, and altitude; rs , O ls are the right and left center coordinates of the unmanned helicopter at point S, respectively. rm , O lm They are respectively the right center coordinates and left center coordinates of the unmanned helicopter at point M.

5. The unmanned helicopter landing guidance method based on an offshore mobile platform according to claim 3 is characterized in that: The specific steps of planning the three-dimensional Dubins path from point S to point M in step 3.1.2) are as follows: 3.1.2.1) The three-dimensional Dubins path consists of two arc segments and a straight line, where the arc segment is a descending spiral. The descending spiral in the Cartesian coordinate system is calculated as follows: Where ω is the angular velocity of the uniform spiral descent, γ is the track angle of the unmanned helicopter descent, and R d is the radius of the arc segment of the descending spiral, and t is the time for the spiral descent of the unmanned helicopter; The straight line segment is the line connecting the tangent points of two arc segments. The shortest trajectory of the four three-dimensional routes in path planning is calculated by the Dubins algorithm to determine the route type, which is used as the final straight line segment path planned by the three-dimensional Dubins algorithm.

6. The unmanned helicopter landing guidance method based on an offshore mobile platform according to claim 3 is characterized in that: The step 3.2) uses the trajectory prediction method to plan the second stage landing guidance route and the expected flight speed, and the steps are as follows: 3.2.1) Determine the expected flight speed of the second phase based on the first phase flight speed of the unmanned helicopter, the moving speed of the offshore platform, and the maximum turning radius of the unmanned helicopter; 3.2.2) Plan the second stage landing guidance route according to the current position and moving direction of the offshore platform; The details are as follows: 3.2.2.1) If the offshore platform is in a straight-line navigation state, and the moving speed direction (V2, θ3) deviates from the speed direction (V2, θ2) at point M, the second-stage landing guidance route is planned in the form of an arc plus a straight line. The arc segment is still planned with r2 as the radius, and its trajectory length is calculated as follows: Among them, S 1-R is the arc segment length, S 1-S is the length of the straight line segment trajectory; S 1-R-S is the total trajectory length; 3.2.2.2) The offshore motion platform is in a straight-line navigation state, and the moving direction is the same as the speed V2 at point M: At this time, the horizontal flight trajectory and the expected flight speed of the unmanned helicopter are planned according to the straight-line trajectory and trajectory prediction method. The trajectory length S 2-S The calculation is as follows: S 2-S =(S Dubins-水平 V2V g / [(V g -V2)V1]); 3.2.2.3) If the offshore platform is in a turning state, the arc trajectory from point M to the predicted offshore platform position and the expected flight speed of the unmanned helicopter are directly planned according to the trajectory prediction method. The arc trajectory is planned as a circle passing through point E and tangent to the V2 direction of point M, and its trajectory length S 3-S The circle radius r3 is calculated as follows:

7. The unmanned helicopter landing guidance method based on an offshore mobile platform according to claim 6 is characterized in that: In step 3.2.1), the expected flight speed in the second stage is determined as follows: The expected flight speed should satisfy the following constraints: Where V1 is the first-stage flight speed of the unmanned helicopter, V2 is the moving speed of the offshore platform, and S Dubins-水平 is the horizontal trajectory distance of the first stage landing guidance route, φ max is the maximum turning radius of the unmanned helicopter, and g is the local gravity acceleration.

8. The unmanned helicopter landing guidance method based on an offshore mobile platform according to claim 6, characterized in that: In step 4), the desired track angle γ of the unmanned helicopter in the vertical direction g The calculation is as follows: Among them, S e The planned trajectory length for the second stage landing guidance route.

9. An electronic device, characterized in that: include: one or more processors; as well as a storage device for storing one or more programs, When the one or more programs are executed by the one or more processors, the one or more processors are caused to perform the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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