Ship route planning method and device based on artificial potential field and storage medium

Abstract

The application discloses a ship route planning method and device based on an artificial potential field and a storage medium, and comprises the following steps: S1, data of each obstacle in a specific water area range is acquired; S2, an unreachable range of a certain distance around the obstacle is preset; S3, a target position of the ship is set; S4, a repulsive force field is added to the obstacle, and an attractive force field is added to the target position; S5, an angle threshold value of ship turning is set, all reachable coordinates of the ship in the next unit time are calculated, and the coordinates overlapping with the unreachable range set in step S2 are removed; S6, based on the constructed artificial potential field, potential field values of each reachable coordinate are acquired, and a direction with the smallest potential field value is selected as the next direction; S7, the ship sails for a unit time according to the next direction acquired in step S6; and steps S1 to S7 are circularly performed. The application considers the collision avoidance rules and combines a ship dynamics model, reasonably plans a navigable route for the ship to sail out of the specific water area range after the ship sails into the specific water area range, and provides strong technical support for maritime water area supervision.

Description

Technical Field

[0001] This invention relates to the field of ship navigation technology, and in particular to a ship route planning method, apparatus, and storage medium based on an artificial potential field. Background Technology

[0002] The large-scale construction of offshore wind farms worldwide has brought new challenges to the navigation safety of coastal vessels. When ships navigate in the waters of offshore wind farms, the complex environment and other factors can interfere with normal lookout and wireless communication, alter individual ship navigation behavior, increase the probability of collisions between ships, and also create additional risks of collisions between ships and wind farm equipment, causing irreparable economic losses to ships and wind turbines. Timely planning of reasonable navigable routes for ships that intrude into wind farms is one of the important means to reduce the occurrence of accidents.

[0003] Common local path planning methods include the artificial potential field (APF) method, the dynamic window method, the velocity obstacle method, and intelligent optimization algorithms. Among these, the artificial potential field (APF) method is a path planning approach used in robot research. Its basic idea is to design the robot's motion in its surrounding environment as motion within an abstract artificial gravitational field. Target points exert an "attractive force" on the moving robot, while obstacles exert a "repulsive force." Finally, the resultant force is used to control the robot's motion, allowing it to move along the downward direction of the potential field within the sum of multiple repulsive and one attractive potential fields. The APF method is a widely used path planning method applicable to both known and unknown environments, as exemplified by the virtual force-based ship navigation method described in application number CN202010460158.2. However, when applying the APF method to ship collision avoidance, issues arise such as under-optimized collision avoidance paths and the need to reduce the risk of ship collisions. For example, the path planning algorithm published in the paper "Path Planning Algorithm for Unmanned Vessels Based on Improved Artificial Potential Field Method" (published in 2016, by Liu Kun, Zhang Yonghui, and Ren Jia) uses the traditional artificial potential field method to determine the radius of influence of obstacles. However, for wind farm waters, the wind farms within them are mostly rectangular. The radius of influence of obstacles determined by the traditional artificial potential field method will result in different repulsive forces around the long and short sides of the obstacles, which is not conducive to reducing the risk of ship collisions and ensuring the safety of wind farms in the wind farm waters. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a ship route planning method, device, and storage medium based on an artificial potential field, in order to optimize ship collision avoidance paths, reduce the likelihood of ship collisions, ensure the safe departure of ships from wind farm waters, and guarantee the safety of wind farms within the wind farm waters.

[0005] To achieve the above objectives, the technical solution proposed by this invention is as follows:

[0006] A ship route planning method based on artificial potential fields is used for route planning when a ship enters and leaves a specific water area. The method includes the following steps:

[0007] S1. Obtain data on all obstacles within the water area.

[0008] S2. According to step S1, set an inaccessible range at a certain distance around the obstacle.

[0009] S3. Set the target position of the ship.

[0010] S4. According to step S2, a repulsive field is applied to the obstacle, and according to step S3, a gravitational field is applied to the target location, thereby constructing an artificial potential field for the water area.

[0011] S5. Set the angle threshold for ship turning, calculate all reachable coordinates for the ship in the next unit of time, and remove coordinates that overlap with the inaccessible range set in S2.

[0012] S6. Based on the constructed artificial potential field, obtain the potential field value of each reachable coordinate, and select the direction with the smallest potential field value as the next direction.

[0013] S7. The next direction travel unit time obtained from step S6.

[0014] Repeat steps S1 to S7 until the vessel leaves the waterway.

[0015] Preferably, the inaccessible area of ​​the obstacle in step S2 is constructed as follows: Let the coordinates of the i-th obstacle within the water area be q. i The maximum length of the obstacle is h. i The maximum width is w i Set the inaccessible distance of the obstacle to d. i Then the inaccessible range K of the obstacle i The length is: h i +2×d i Width: w i +2×d i A rectangle.

[0016] The preferred formula for calculating the repulsive field is as follows:

[0017]

[0018] In the formula, A is the area of ​​the obstacle, (σ x ,σ yLet q(x,y) be the length and width of the inaccessible area of ​​the obstacle, S be the set of inaccessible areas of the obstacle, and q(x,y) be the latitude and longitude coordinates of any point within the water area. obs (x obs ,y obs ) represents the coordinates of the obstacle.

[0019] The formula for calculating the gravitational field is as follows:

[0020]

[0021] In the formula, q(x,y) represents the latitude and longitude coordinates of any point within the water area, and q obj (x obj ,y obj ) represents the target position coordinates, η represents the proportional gain coefficient, and ρ(q,q) represents the target position coordinates. obj Let q be a vector representing the coordinates of the point relative to the target position. obj Euclidean distance between them | qq obj | indicates the direction from that point to the target location.

[0022] The formula for calculating the potential field value is as follows:

[0023]

[0024] In the formula, U att (q) is the gravitational field experienced at any point within the water area, U rep (q,q obsi ) is the repulsive force field of the i-th obstacle on that point.

[0025] Preferably, step S5 includes:

[0026] S51. Preset the ship's turning angle threshold α, obtain the ship's current speed, and then all reachable coordinates of the ship in the next unit time form a continuous arc-shaped range with radius r, where r is the ship's distance in the unit time.

[0027] S52. Discretize a continuous range into α reachable coordinates with an interval of one degree, where the set of α reachable coordinates is Q={O1,O2,O3,...,O...} α},O i =(O xi O yi ).

[0028] S53. Iterate through each reachable coordinate obtained in S52. If the reachable coordinate is within the inaccessible range set in step S2, remove it as a filter point, as shown in the following formula: K is the set of unreachable ranges.

[0029] S54. Determine whether all the obtained reachable coordinates have been filtered out. If so, obtain all reachable coordinates in the remaining directions and return to step S52. Otherwise, proceed to step S6.

[0030] Furthermore, step S6 includes:

[0031] S61. Traverse all reachable coordinates obtained in step S7 and obtain the potential field value for each reachable coordinate.

[0032] S62. Compare the potential field values ​​of all reachable coordinates, select the coordinate with the smallest potential field value, and move in that direction.

[0033] If the reachable coordinates are obtained twice, i.e., not within the turning angle threshold, then the ship will remain stationary for the next unit of time and use that unit of time for turning. Only after turning is completed will the ship sail towards the coordinate with the smallest potential field.

[0034] The present invention also includes a ship route planning device based on an artificial potential field, which includes a memory and a processor. The memory stores at least one program, which is executed by the processor to implement the ship route planning method based on the artificial potential field of the present invention.

[0035] The present invention also includes a computer-readable storage medium storing a processor-executable program, which, when executed by a processor, is used to implement the artificial potential field-based ship route planning method of the present invention.

[0036] The beneficial effects of adopting the above technical solution are as follows: This invention addresses the special characteristics of wind farm waters by improving the applicability of artificial potential fields in wind farm waters to optimize ship collision avoidance paths, thereby reducing the possibility of ship collisions. It can promptly plan reasonable navigable routes for ships that intrude into wind farm waters, enabling ships to safely leave the wind farm waters and ensuring the safety of wind farms within the wind farm waters. It can also provide strong technical support for the supervision of offshore wind farm waters. Attached Figure Description

[0037] Figure 1 This is a flowchart of the ship route planning method based on artificial potential field in Example 1.

[0038] Figure 2 This is a schematic diagram of the inaccessible area of ​​an obstacle using the traditional artificial potential field method.

[0039] Figure 3 This is a schematic diagram of the inaccessible area of ​​the wind farm in Example 1.

[0040] Figure 4 This is a schematic diagram of the inaccessible area of ​​a ship in Example 1.

[0041] Figure 5This is a schematic diagram of a method for determining a target location according to Embodiment 1.

[0042] Figure 6 This is a diagram of the repulsive potential field of a wind farm in Example 1.

[0043] Figure 7 This is a schematic diagram of the ship's reachable position in the next unit of time, as shown in Example 1.

[0044] Figure 8 This is a schematic diagram of the reachable coordinates in Example 1. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0046] Example 1

[0047] The ship route planning method based on artificial potential fields in this embodiment can be used to plan the safe departure of ships that have entered wind farm waters. This method can reduce the probability of collisions between ships and obstacles, thus helping to eliminate the risk of such collisions. Please refer to... Figure 1 The method in this embodiment includes, but is not limited to, the following steps:

[0048] Step S1: Obtain data on all obstacles within the wind farm's waters. The wind farm's waters contain both wind farms and vessels. For any vessel within these waters, both the wind farm and other vessels are obstacles, requiring collision avoidance. Therefore, for the wind farm, its coordinates and size need to be obtained. For other vessels, their latitude, longitude, width, and length can be obtained by acquiring their AIS data.

[0049] Step S2: Predetermine an inaccessible range at a certain distance around the obstacle.

[0050] Please refer to Figure 2 The following describes the construction of the inaccessible area of ​​obstacles using the traditional artificial potential field method: Assume there are n obstacles within the water area of ​​the wind farm, and the center coordinates of the i-th obstacle are q. i (x) i y i ), with q i Let r be the radius of the unreachable area of ​​the obstacle, centered at the center. i The circular inaccessible area K corresponding to the obstacle i Obtain the circular inaccessible ranges corresponding to all obstacles, forming an inaccessible range set K={K1,K2,...,K...} n}

[0051] The inaccessible range of obstacles constructed using the traditional artificial potential field method radiates outwards from the coordinates of the obstacle (i.e., wind farm / other vessel), with the same gradient in both the lateral and longitudinal directions. However, since wind farms are mostly rectangular and vessels are mostly long and narrow geometric shapes, the same gradient in the lateral and longitudinal directions will result in different repulsive forces around the long and short sides of the obstacle. Moreover, the obstacle radius needs to be manually input and cannot be automatically set according to the size of the wind farm or vessel.

[0052] Therefore, in order to further optimize collision avoidance paths and the application of artificial potential field methods in wind farm water areas, this embodiment proposes another method for constructing artificial potential fields.

[0053] Taking a wind farm as an example, since wind farms are mostly rectangular, let the center coordinates of the wind farm be q0(x0,y0), the maximum length of the wind farm be h0, the maximum width be w0, and the inaccessible distance of the wind farm be d1. Then the inaccessible range K0 of the wind farm is as follows: Figure 3 As shown, the rectangle has vertices EFGH, with a length of h0 + 2 × d1 and a width of w0 + 2 × d1.

[0054] Taking ships as an example, since ships are elongated geometric shapes, if there are m other ships in the wind farm water area, the latitude and longitude coordinates q of the i-th ship can be obtained from the AIS data of the i-th ship. i (x i ,y i ), length h i and width w i Let d2 be the unreachable distance around a ship. Then the unreachable range of the i-th ship is as follows: Figure 4 As shown, this is a rectangle with vertices ABCD and a length of h. i +2×d2, width is: w i +2×d2.

[0055] Step S3: Set the target position for the vessel. This embodiment aims to ensure the vessel safely leaves the wind farm waters; therefore, the target position can be any point outside the wind farm waters. To allow the vessel to leave the wind farm waters as quickly as possible, the target position can be set as the coordinates 'a' of the vessel's shortest distance from the wind farm waters, such as... Figure 5 As shown. In this embodiment, the water area of ​​the wind farm is rectangular, and the shortest distance from the water area of ​​the wind farm is perpendicular to the side line of the rectangle.

[0056] Step S4: Based on the acquired obstacle data, apply a repulsive field to the obstacles and, based on the target location coordinates, apply a gravitational field to the target location to construct an artificial potential field in the wind farm's water area. Details are as follows:

[0057] The gravitational field originates from the driving force propelling the ship away from the obstacle and into a safe area. Let the latitude and longitude coordinates of any point within the wind farm's water area be q(x,y), and the latitude and longitude coordinates of the target location be q0. obj (x obj ,y obj The formula for calculating the gravitational field is as follows:

[0058]

[0059] In the formula, η is the proportional gain coefficient, and ρ(q,q) obj Let q be a vector representing the coordinates of the point relative to the target position. obj Euclidean distance between them | qq obj The direction is from the point to the target location. The gravitational potential field is mainly related to the distance between the point and the target location; the greater the distance, the greater the potential energy, and the smaller the distance, the smaller the potential energy.

[0060] The repulsive field originates from the risk between the ship and the obstacle. Consider any obstacle, with coordinates q. obs (x obs ,y obs The formula for calculating the repulsive field is as follows:

[0061]

[0062] In the formula, A is the area of ​​the obstacle, (σ x ,σ y Let q(x,y) be the length and width of the inaccessible area of ​​the obstacle, S be the set of inaccessible areas of the obstacle, and q(x,y) be the latitude and longitude coordinates of any point within the water area of ​​the wind farm. obs (x obs ,y obs () represents the coordinates of the obstacle. For example, a repulsive potential field diagram of a wind farm 30 km long and 30 km wide is shown below. Figure 6 As shown.

[0063] By superimposing all the repulsive and gravitational fields, the potential field value can be obtained, calculated as follows:

[0064]

[0065] In the formula, U att (q) is the gravitational field experienced at any point within the water area of ​​the wind farm, U rep (q,q obsi ) is the repulsive force field of the i-th obstacle on that point.

[0066] Step S5: Set the angle threshold for ship turning, calculate all reachable coordinates for the ship in the next unit of time based on the ship's speed, and remove coordinates that overlap with the inaccessible range set in step S2.

[0067] Please refer to Figure 7 and Figure 8 In this embodiment, the step of calculating the effective reachable coordinates in step S5 includes:

[0068] S51: Preset the ship's turning angle threshold α, obtain the ship's current speed, and then all reachable positions of the ship in the next unit time form a continuous arc-shaped range with radius r, where r is the ship's distance in unit time. If the ship travels at a constant speed, then r = v × t0, where t0 is the unit time.

[0069] S52: Discretize the continuous range into α reachable coordinates O with a one-degree interval. i Among them, there are α reachable coordinate sets Q={O1,O2,O3,...,O...} α},O i =(O xi O yi ).

[0070] S53: Iterate through each reachable coordinate O obtained in S52 i If the coordinates O are reachable i If the unreachable range set K is within the range set set in step S2, then it is removed as a filter point, as shown in the following formula: .

[0071] S54: Determine the reachable coordinates O obtained. i If all points are rejected as filter points, obtain all reachable coordinates in the remaining directions and return to step S52; otherwise, proceed to step S6.

[0072] It is understood that step S4 can be executed either before or after step S5. The execution order of step S4 does not affect the construction of the repulsive and gravitational fields. Therefore, the execution order of step S4 does not constitute a limitation on the present invention.

[0073] Step S6: First, based on the artificial potential field constructed in step S4, obtain the potential field value of the ship at each reachable coordinate. Then, compare the potential field values ​​corresponding to each reachable coordinate and select the direction with the smallest potential field value as the next direction of the ship to obtain the optimal collision avoidance path, reduce the possibility of ship collision, and enable the ship to leave the wind farm waters safely.

[0074] Understandably, one can construct an artificial potential field for the entire wind farm water area, or only for specific coordinate points. The former starts from the overall wind farm water area, first calculating the potential field values ​​for all coordinate points within the area, and then directly selecting the potential field values ​​corresponding to the calculated reachable coordinates for comparison. This facilitates the wind farm water area monitoring center in simultaneously planning the routes of various vessels within the wind farm water area, providing technical support for wind farm water area monitoring. The latter calculates and compares the potential field values ​​for each reachable coordinate, which has the advantage of less computation and improved processing speed.

[0075] Step S7: After obtaining the next direction navigation unit time from Step S6, return to Step S1 to obtain the planned ship route.

[0076] This embodiment establishes a new artificial potential field model by changing the range of the repulsive field and calculates the repulsive field using the two-dimensional Gaussian formula. Compared with the traditional artificial potential field method, the path planning capability is significantly improved, and it is more suitable for ship collision avoidance path planning in the waters of wind farms, further reducing the risk of ship collisions and ensuring the safety of wind farms in the waters of wind farms.

[0077] Example 2

[0078] This embodiment provides a computer-readable storage medium storing a processor-executable program that can be executed by one or more control processors, for example, performing the methods described in the above embodiments.

[0079] Example 3

[0080] This embodiment provides a ship route planning device based on artificial potential field, which includes a memory and a processor. The memory stores a program, and the processor is used to execute the above-described ship route planning method based on artificial potential field.

[0081] This invention, by considering collision avoidance rules and combining them with ship dynamics models, can provide real-time and reasonable navigable route planning suggestions for ships leaving wind farm waters, thereby reducing the risk of ship collisions, ensuring the safe departure of ships from wind farm waters, guaranteeing the safety of facilities within wind farm waters, and providing strong technical support for the supervision of offshore wind farm waters.

[0082] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail to the invention without departing from the spirit and scope of the invention as defined in the appended claims are within the scope of protection of the invention.

Claims

1. A ship route planning method based on artificial potential fields, used for route planning when a ship enters and then leaves a specific water area, characterized in that, Includes the following steps: S1. Obtain data on each obstacle within the water area; S2. According to step S1, set an inaccessible range at a certain distance around the obstacle; Let the coordinates of the i-th obstacle within the water area be q. i The maximum length of the obstacle is h. i The maximum width is w i Set the inaccessible distance of the obstacle to d. i Then the inaccessible range K of the obstacle i The length is: h i +2×d i Width: w i +2×d i A rectangle; S3. Set the target position of the ship; S4. According to step S2, a repulsive field is applied to the obstacle, and according to step S3, a gravitational field is applied to the target location, thereby constructing an artificial potential field in the water area. The formula for calculating the repulsive field is as follows: Where A is the area of ​​the obstacle, (σ x ,σ y Let q(x,y) be the length and width of the inaccessible area of ​​the obstacle, S be the set of inaccessible areas of the obstacle, and q(x,y) be the latitude and longitude coordinates of any point within the water area. obs (x obs ,y obs () represents the coordinates of the obstacle; S5. Set the angle threshold for ship turning, calculate all reachable coordinates of the ship in the next unit of time, and remove coordinates that overlap with the inaccessible range set in S2; S6. Based on the constructed artificial potential field, obtain the potential field value of each reachable coordinate, and select the direction with the smallest potential field value as the next direction; S7. The next direction travel unit time obtained in step S6; Repeat steps S1 to S7.

2. The ship route planning method based on artificial potential field according to claim 1, characterized in that, The formula for calculating the gravitational field is as follows: Where q(x,y) represents the latitude and longitude coordinates of any point within the water area, q obj (x obj ,y obj ) represents the target position coordinates, η represents the proportional gain coefficient, and ρ(q,q) represents the target position coordinates. obj Let q be a vector representing the coordinates of the point relative to the target position. obj Euclidean distance between them | qq obj | indicates the direction from that point to the target location; The formula for calculating the potential field value is as follows: Among them, U att (q) is the gravitational field experienced at any point within the water area, U rep (q,q obsi ) is the repulsive force field of the i-th obstacle on that point.

3. The ship route planning method based on artificial potential field according to claim 1, characterized in that, Step S5 includes: S51. Preset the ship's turning angle threshold α, obtain the ship's current speed, and then all reachable coordinates of the ship in the next unit time form a continuous arc-shaped range with radius r, where r is the ship's distance in the unit time. S52. Discretize a continuous range into α reachable coordinates with an interval of one degree, where the set of α reachable coordinates is Q={O1,O2,O3,...,O...} α },O i =(O xi O yi ); S53. Iterate through each reachable coordinate obtained in S52. If the reachable coordinate is within the inaccessible range set in step S2, remove it as a filter point, as shown in the following formula: K is the set of unreachable ranges; S54. Determine whether all the obtained reachable coordinates have been filtered out. If so, obtain all reachable coordinates in the remaining directions and return to step S52. Otherwise, proceed to step S6.

4. The ship route planning method based on artificial potential field according to claim 3, characterized in that, Step S6 includes: S61. Traverse all reachable coordinates obtained in step S5 and obtain the potential field value for each reachable coordinate; S62. Compare the potential field values ​​of all reachable coordinates, select the coordinate with the smallest potential field value, and move in that direction; If the reachable coordinates are obtained twice, i.e., not within the turning angle threshold, then the ship will remain stationary for the next unit of time and use that unit of time for turning. Only after turning is completed will the ship sail towards the coordinate with the smallest potential field.

5. The ship route planning method based on artificial potential field according to claim 1, characterized in that, The water area refers to the wind farm area, and the obstacles include the wind farm and other vessels. The data of the obstacles includes the coordinates and size of the wind farm, as well as the AIS data of the other vessels.

6. The ship route planning method based on artificial potential field according to claim 1, characterized in that, The target location is the coordinate of the endpoint where the vessel leaves the water area with the shortest distance.

7. A ship route planning device based on an artificial potential field, characterized in that, The system includes a memory and a processor, wherein the memory stores at least one program, which is executed by the processor to implement the ship route planning method based on an artificial potential field as described in any one of claims 1 to 6.

8. A computer-readable storage medium storing a processor-executable program, characterized in that, The processor-executable program, when executed by the processor, is used to implement the ship route planning method based on any one of claims 1 to 6.

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