A method for guiding the landing of an unmanned helicopter based on a sea motion platform

Abstract

The application discloses a kind of unmanned helicopter landing guide method based on offshore platform, which comprises the following steps: 1) according to the unmanned helicopter parking apron position on offshore platform, determine the landing guide area;2) when unmanned helicopter flies into landing guide area, record the position and flight speed and direction of unmanned helicopter when switching to landing guide stage time, and the position and movement speed and direction of offshore platform;3) based on the acquisition information of step 2), plan the course of landing guide stage;4) according to the height of offshore platform unmanned helicopter parking apron and the height of unmanned aerial vehicle at M point, calculate the expected track angle of unmanned helicopter in vertical direction;5) guide unmanned helicopter landing.The application proposes a method for planning the trajectory and flight speed of unmanned helicopter in landing guide stage, which can improve the success rate of unmanned helicopter landing on offshore platform in moving state in space and time.

Description

TECHNICAL FIELD

[0001] The present application relates to unmanned aerial vehicle technology, in particular to a method for guiding the landing of an unmanned helicopter based on a sea platform. BACKGROUND

[0002] Compared with a compound wing unmanned aerial vehicle and a rotor unmanned aerial vehicle, the unmanned helicopter has the characteristics of large load, strong wind interference resistance and long endurance, and is widely used in the fields of sea law enforcement monitoring, sea rescue, sea monitoring and aerial survey. According to the motion characteristics of the sea platform, the unmanned helicopter on the sea needs to consider the parking space, working environment and electromagnetic environment, and focuses on solving the problem of autonomous landing guidance of the unmanned helicopter, so as to improve the success rate of the unmanned helicopter landing on the sea and ensure the normal use of the unmanned helicopter.

[0003] The sea platform is disturbed by waves and wind, and produces irregular and complex motion such as roll, pitch, yaw and deep motion, and combined motion, which greatly increases the difficulty of the unmanned helicopter landing. Secondly, the unmanned helicopter is autonomously landed, and lacks the active identification ability and risk avoidance ability of the helicopter pilot, so the risk of landing the unmanned helicopter is more difficult to control than the helicopter. In addition, for the unmanned helicopter controlled automatically, the landing on the sea platform during the movement is more complex and dangerous than on land. In order to improve the success rate of the autonomous landing of the unmanned helicopter on the sea platform, the landing guidance method needs to be studied. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for guiding the landing of an unmanned helicopter based on a sea platform, aiming at the defects in the prior art.

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

[0006] 1) determining a landing guidance area according to the position of the unmanned helicopter parking apron on the sea platform;

[0007] Taking the unmanned helicopter parking apron on the sea platform as the center, a cylindrical region with a set distance as the radius R and a height h as the landing guidance area;

[0008] 2) when the unmanned helicopter flies into the landing guidance area, that is, the state of the unmanned helicopter is switched to the landing guidance phase, recording the position of the unmanned helicopter at the moment when the landing guidance phase is switched , the flight speed and direction , and the position of the sea platform , and the motion speed and direction ;

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

[0010] 3.1) Based on the current position and flight direction of the unmanned helicopter, and the current position and navigation direction of the offshore platform, the first-stage landing guidance route of the unmanned helicopter is planned using the three-dimensional Dubins algorithm;

[0011] 3.2) When the unmanned helicopter reaches the end of the first-stage landing guidance route, the end of the route is used as the starting point of the second-stage landing guidance route. The second-stage landing guidance route and the expected flight speed are planned by using the trajectory prediction method, taking into account the position and direction of the maritime motion platform at this time.

[0012] 4) Based on the height of the unmanned helicopter landing pad on the offshore platform and the altitude of the drone at point M Calculate the desired vertical trajectory angle of the unmanned helicopter. ;

[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 consists of two circular arcs and a straight line. The two circular arcs are the two circular arcs passing through points S and M, and the straight line is the line connecting the tangent points of the two circular arcs. The endpoint of the landing guidance route of the unmanned helicopter in the first stage is the unmanned helicopter flying 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 of the unmanned helicopter at point S. Flight speed and direction and turning radius The coordinates of the unmanned helicopter at point M Speed ​​and direction of motion and turning radius 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, use the three-dimensional Dubins algorithm to plan the three-dimensional 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] In the formula, and All coordinates are three-dimensional, including longitude, latitude, and altitude; , These are the right and left center coordinates of the unmanned helicopter at point S, respectively. , These are the right and left center coordinates of the unmanned helicopter at point M, respectively.

[0021] According to the above scheme, the specific steps for 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 circular arcs and a straight line. The circular arcs are glide spirals, which are calculated in Cartesian coordinates using the following formula:

[0023] ;

[0024] In the formula, The angular velocity of the uniform spiral sliding down is The flight path angle for the unmanned helicopter's descent. Let the radius of the arc segment of the downward spiral be denoted as . The time it takes for the unmanned helicopter to descend in a spiral;

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

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

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

[0028] 3.2.2) Based on the current position and direction of movement of the offshore platform, plan the landing guidance route for the second phase;

[0029] Specifically as follows:

[0030] 3.2.2.1) If the offshore platform is in a straight-line navigation state, and the direction of its movement is... Deviating from its velocity direction at point M At this point, the second-stage landing guidance path is planned using a combination of circular arcs and straight lines, where the circular arc segment still follows... The trajectory length is calculated as follows, with the radius as the target:

[0031] ;

[0032] in, Let be the length of the arc segment. The length of the straight line segment; This represents the total trajectory length.

[0033] 3.2.2.2) The offshore platform is in a straight-line navigation state, and its direction of movement is similar to the speed at point M. Same direction: 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, and the trajectory length is... The calculation is as follows:

[0034] ;

[0035] 3.2.2.3) If the offshore platform is in a turning state, directly plan the circular trajectory from point M to the predicted position of the offshore platform and the expected flight speed of the unmanned helicopter according to the trajectory prediction method. The circular trajectory passes through point E and intersects with point M. The length of the trajectory of a circle that is tangent in direction is calculated. With circle radius Calculate according to the following formula:

[0036] .

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

[0038] ;

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

[0040] ;

[0041] In the formula, This represents the first stage of flight speed for the unmanned helicopter. For the speed of movement of the offshore platform, The horizontal trajectory distance of the first-stage landing guidance path. This represents the maximum turning radius of the unmanned helicopter. This is the local gravitational acceleration.

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

[0043] ;

[0044] in, The planned trajectory length for the second-stage landing guidance route.

[0045] The beneficial effects of this invention are: This invention makes full use of the flight characteristics of unmanned helicopters and proposes a method for planning the trajectory and flight speed of unmanned helicopters during the landing guidance phase through the three-dimensional Dubins algorithm and trajectory prediction, which can improve the success rate of unmanned helicopters landing on moving sea platforms in both space and time. Attached Figure Description

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

[0047] Figure 1 This is a flowchart of a method according to an embodiment of the present invention;

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

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

[0050] Figure 4 This is a schematic diagram of the second-stage trajectory planning in an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] like Figure 1 As shown, a landing guidance method for unmanned helicopters based on a maritime motion platform includes the following steps:

[0053] 1) Centered on the unmanned helicopter landing pad on the sea platform, a cylinder with a radius R and a height h at a set distance is used as the landing guidance area and the landing guidance phase switching mark. When the unmanned helicopter flies into the range of the cylinder, the unmanned helicopter status is switched to the unmanned helicopter entering the landing guidance phase.

[0054] Equation (1)

[0055] like Figure 2 virtual cylinder radius The guide distance for horizontal landing should be based on the size of the unmanned helicopter and the manufacturer's recommended distance, generally between 1000m and 3000m, and the cylinder height. The cruising altitude of the drone can be used as a reference. Due to the influence of the service ceiling of unmanned helicopters, it can generally be set between 3,000m and 5,000m.

[0056] 2) Record the position of the unmanned helicopter at the moment of switching to the landing guidance phase. and flight speed and direction and the location of the offshore platform and the speed and direction of motion ;

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

[0058] 3.1) Based on the current position and flight direction of the unmanned helicopter, and the current position and navigation direction of the offshore platform, plan the first-stage landing guidance route for the unmanned helicopter; such as... Figure 3 ;

[0059] 3.1.1) Determine the current position coordinates of the unmanned helicopter at point S. Flight speed and direction and turning radius The coordinates of the unmanned helicopter at point M Speed ​​and direction of motion and turning radius Calculate the left and right center positions of the unmanned helicopter at points S and M according to equation (2):

[0060] Equation (2)

[0061] In the formula, and All coordinates are three-dimensional, including longitude, latitude, and altitude; , These are the right and left center coordinates of the unmanned helicopter at point S, respectively. , These 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 3D Dubins path consists of two circular arcs and a straight line. The circular arcs are glide spirals, which are calculated in Cartesian coordinates using the following formula:

[0064] Equation (3)

[0065] In the formula, The angular velocity of the uniform spiral sliding down is The flight path angle for the unmanned helicopter's descent. Let the radius of the arc segment of the downward spiral be denoted as . The time it takes for the unmanned helicopter to descend in a spiral;

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

[0067] Equation (4)

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

[0069] The principle of the 3D Dubins algorithm is to calculate, using the methods described above for calculating arc segments and line segments, the result of... Figure 2 The distances in the horizontal paths of the four three-dimensional flight paths shown are relative to the flight path angles during the descent of the unmanned helicopter. Under certain conditions, the 3D Dubins path is also the shortest when the horizontal route distance is shortest, which is the final path planned by the 3D Dubins algorithm. The shortest distance of the 3D Dubins path can be obtained by calculating the horizontal distance of the four types of routes using equations (5) to (8) and then taking the shortest path. The calculation process of the circular arc straight line segment trajectory of the four types of routes is as follows:

[0070] Equation (5)

[0071] Equation (6)

[0072] Equation (7)

[0073] Equation (8)

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

[0075] Equation (9)

[0076] In equation (5), express azimuth angle, express The modulus (distance), in equation (6), express azimuth angle, express The modulus (distance), in equation (7), express azimuth angle, express The modulus (distance), in equation (8), express azimuth angle, express The modulus (distance). In equation (9), For points S and M, The angle formed by the points.

[0077] The vertical direction of the 3D Dubins path follows a fixed track angle. The descent is calculated according to formula (10) for the shortest vertical distance. :

[0078] Equation (10)

[0079] The unmanned helicopter guided the landing path at speed during the first phase of the landing. flight.

[0080] The endpoint of the landing guidance path for the unmanned helicopter in the first stage is: point M on the arc segment where the unmanned helicopter flies to point M.

[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 of the first-stage landing guidance path, it uses that end as the starting point of the second-stage landing guidance path. Combining this with the current position and direction of the maritime platform, it uses trajectory prediction methods to plan the second-stage landing guidance path and the desired flight speed, thereby completing the landing. Figure 4 ;

[0083] 4.1) Determine the expected flight speed for the second stage;

[0084] Equation (11)

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

[0086] Equation (12)

[0087] In the formula, This represents the first stage of flight speed for the unmanned helicopter. For the speed of movement of the offshore platform, The horizontal trajectory distance of the first-stage landing guidance path. This represents the maximum turning radius of the unmanned helicopter. This refers to the local gravitational acceleration.

[0088] 4.2) Based on the current position and direction of movement of the offshore platform, plan the landing guidance route for the second phase;

[0089] Specifically as follows:

[0090] 4.2.1) The offshore platform is in a straight-line navigation state, and the direction of its movement is... Deviating from its velocity direction at point M At this point, the second-stage landing guidance path should be replanned using a combination of circular arcs and straight lines. The circular arc segment should still follow... The trajectory length is calculated according to equation (13):

[0091] Equation (13)

[0092] 4.2.2) The offshore platform is in a straight-line navigation state, and its direction of movement is the same as the speed at point M. Same direction: 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] Equation (14)

[0094] 4.2.3) When the offshore platform is turning, directly plan the circular trajectory from point M to the predicted position of the offshore platform and the expected flight speed of the unmanned helicopter according to the trajectory prediction method. The circular trajectory passes through point E and intersects with point M. The length of the trajectory of a circle that is tangent in direction is calculated. With circle radius Calculate according to formula (15):

[0095] Equation (15)

[0096] 5) Based on the height of the unmanned helicopter landing pad on the offshore platform and the altitude of the drone at point M Calculate the desired vertical trajectory angle of the unmanned helicopter. The calculation method is shown in equation (16):

[0097] Equation (16)

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

[0099] If the unmanned helicopter completes its flight according to the trajectory prediction method and adjusts its speed and direction to align with the maritime platform, it can land autonomously. If there is still a horizontal deviation between the unmanned helicopter and the helicopter landing pad on the maritime platform, manual control of the unmanned helicopter's landing will be required.

[0100] In this application, the horizontal and vertical distances between the unmanned helicopter and the center point of the unmanned aerial vehicle (UAV) landing pad on the offshore platform are calculated in real time using the unmanned helicopter flight control system. Once these distances reach a threshold range, the landing guidance phase is initiated. The main purpose of this landing guidance phase is to allow the unmanned helicopter to reduce its altitude and speed, reaching a suitable landing altitude and speed before reaching the UAV landing pad.

[0101] The process involves two phases: Phase 1, landing guidance path planning, which shortens the distance between the unmanned helicopter and the offshore platform through a relatively short flight distance, and ensures that the helicopter's flight direction aligns with the platform as closely as possible; and Phase 2, landing guidance path planning, which uses trajectory prediction methods to predict the meeting point (landing point) between the moving platform and the helicopter, thereby planning the flight trajectory and desired speed. In Phase 2, except for unpredictable irregular movements of the platform, normal straight-line and turning maneuvers can be predicted using this method.

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

Claims

1. A landing guidance method for unmanned helicopters based on a maritime motion platform, characterized in that, Includes the following steps: 1) Determine the landing guidance area based on the location of the unmanned helicopter landing pad on the maritime sports platform; Centered on the unmanned helicopter landing pad on the maritime sports platform, a cylindrical area with a radius R and a height h at a set distance is used as the landing guidance area; 2) When the unmanned helicopter flies into the landing guidance area, i.e., when the unmanned helicopter switches to the landing guidance phase, record the position of the unmanned helicopter at the moment of switching to the landing guidance phase. and flight speed and direction and the location of the offshore sports platform and the speed and direction of motion ; 3) Based on the information collected in step 2), plan the flight path for the landing guidance phase; 3.1) Based on the current position and flight direction of the unmanned helicopter, and the current position and navigation direction of the offshore platform, the first-stage landing guidance route of the unmanned helicopter is planned using the three-dimensional Dubins algorithm; 3.2) When the unmanned helicopter reaches the end of the first-stage landing guidance route, the end of the route is used as the starting point of the second-stage landing guidance route. The second-stage landing guidance route and the expected flight speed are planned by using the trajectory prediction method, taking into account the position and direction of the maritime motion platform at this time. 4) Based on the height of the unmanned helicopter landing pad on the offshore platform and the altitude of the drone at point M Calculate the desired vertical trajectory angle of the unmanned helicopter. ; 5) Guide the unmanned helicopter to land.

2. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 1, characterized in that, In step 3.1), the path planned by the three-dimensional Dubins consists of two circular arcs and one straight line. The two circular arcs are the two arcs passing through points S and M, and the straight line is the line connecting the tangent points of the two circular arcs. The endpoint of the landing guidance route of the unmanned helicopter in the first stage is the unmanned helicopter flying to point M.

3. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 1, 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 of the unmanned helicopter at point S. Flight speed and direction and turning radius The coordinates of the unmanned helicopter at point M Speed ​​and direction of motion and turning radius 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, use the three-dimensional Dubins algorithm to plan the three-dimensional Dubins path from point S to point M.

4. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 3, 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: ； In the formula, and All coordinates are three-dimensional, including longitude, latitude, and altitude; , These are the right and left center coordinates of the unmanned helicopter at point S, respectively. , These are the right and left center coordinates of the unmanned helicopter at point M, respectively.

5. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 3, characterized in that, The specific steps for planning the 3D 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 circular arcs and a straight line. The circular arcs are glide spirals, which are calculated in Cartesian coordinates using the following formula: ； In the formula, The angular velocity of the uniform spiral sliding down is The flight path angle for the unmanned helicopter's descent. Let the radius of the arc segment of the downward spiral be denoted as . The time it takes for the unmanned helicopter to descend in a spiral; The straight line segment is the line connecting the tangent points of two circular arc segments. The shortest trajectory of the four three-dimensional routes that exist in the path planning is calculated by the Dubins algorithm to determine the route type, which is the final straight line segment path planned by the three-dimensional Dubins algorithm.

6. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 3, characterized in that, Step 3.2) involves using a trajectory prediction method to plan the second-stage landing guidance route and desired flight speed, as follows: 3.2.1) Determine the expected flight speed for the second stage based on the first-stage flight speed of the unmanned helicopter, the moving speed of the maritime platform, and the maximum turning radius of the unmanned helicopter; 3.2.2) Based on the current position and direction of movement of the offshore platform, plan the landing guidance route for the second phase; Specifically as follows: 3.2.2.1) If the offshore platform is in a straight-line navigation state, and the direction of its movement is... Deviating from its velocity direction at point M At this point, the second-stage landing guidance path is planned using a combination of circular arcs and straight lines, where the circular arc segment still follows... The trajectory length is calculated as follows, with the radius as the target: ； in, Let be the length of the arc segment. The length of the straight line segment; This represents the total trajectory length. 3.2.2.2) The offshore platform is in a straight-line navigation state, and its direction of movement is similar to the speed at point M. Same direction: 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, and the trajectory length is... The calculation is as follows: ； 3.2.2.3) If the offshore platform is in a turning state, directly plan the circular trajectory from point M to the predicted position of the offshore platform and the expected flight speed of the unmanned helicopter according to the trajectory prediction method. The circular trajectory passes through point E and intersects with point M. The length of the trajectory of a circle that is tangent in direction is calculated. With circle radius Calculate according to the following formula: 。 7. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 6, characterized in that, In step 3.2.1), the desired flight speed for the second stage is determined as follows: ； The desired flight speed should satisfy the following constraints: ； In the formula, This represents the first stage of flight speed for the unmanned helicopter. For the speed of movement of the offshore platform, The horizontal trajectory distance of the first-stage landing guidance path. This represents the maximum turning radius of the unmanned helicopter. This is the local gravitational acceleration.

8. The unmanned helicopter landing guidance method based on a maritime motion platform according to claim 6, characterized in that, In step 4), the desired trajectory angle of the unmanned helicopter in the vertical direction. The calculation is as follows: ； in, 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 Storage device for storing one or more programs. Wherein, when the one or more programs are executed by the one or more processors, the one or more processors 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, it implements the method described in any one of claims 1 to 8.

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