Ship collision avoidance method and system based on artificial potential field method

Abstract

The present invention proposes a ship collision avoidance method based on an artificial potential field method, comprising the following steps: (S1) obtaining ship information of a ship, obstacle information of at least one obstacle and target point information of a target point; (S2) establishing an artificial potential field including a target point attraction potential field and at least one obstacle repulsion potential field based on the ship information, the obstacle information and the target point information; (S3) synthesizing the target point attraction potential field and the at least one obstacle repulsion potential field to obtain a first resultant force; (S4) adding an external force based on the ship information or the obstacle information; (S5) synthesizing the first resultant force and the external force to obtain a second resultant force; and (S6) the ship navigates according to the direction of the second resultant force to avoid the at least one obstacle.

Description

Technical Field

[0001] The present invention relates to a ship collision avoidance method and system, in particular to a ship collision avoidance method and system based on an artificial potential field method. Background Art

[0002] Ship collision risk prediction and obstacle avoidance research is a hot topic and a difficult problem in the field of ship research. It involves using a variety of data sensing and channel information, simulating the characteristic behaviors of ships under different situation models based on a variety of algorithms, and then driving the ship itself to avoid collisions through data fusion.

[0003] In recent years, the artificial potential field method has been widely used in the path planning of land mobile vehicles because of its simple model and convenient calculation. Its core theory is to superimpose the gravitational field generated by the target point in the environment on the road mobile vehicle and the repulsive field generated by the obstacle on it to form a composite potential field for the mobile agent. However, there are many shortcomings in practical applications. For example, land mobile vehicles often appear in dead loops in factories; or if a sudden obstacle is extremely close to the position of the land mobile vehicle, the repulsive force generated is too strong; or if the direction of the obstacle and the land mobile vehicle is close to the same direction as the resultant force, it may cause the land mobile vehicle to be unable to escape from the restraint of the obstacle, and the practicality is weak.

[0004] In addition, marine vehicles also need to consider the problem of no brakes, so the artificial potential field method has not yet been found to be fully applied in the field of ship collision avoidance. Summary of the invention

[0005] In order to solve the problems mentioned in the prior art, the present invention proposes a ship collision avoidance method based on the artificial potential field method, comprising the following steps: (S1) obtaining ship information of a ship, obstacle information of at least one obstacle, and target point information of a target point. (S2) establishing an artificial potential field based on the ship information, the obstacle information, and the target point information, including a target point attraction potential field and at least one obstacle repulsion potential field. (S3) synthesizing the target point attraction potential field and the at least one obstacle repulsion potential field to obtain a first resultant force. (S4) adding an external force based on the ship information or the obstacle information. (S5) synthesizing the first resultant force and the external force to obtain a second resultant force. And (S6) the ship navigates according to the direction of the second resultant force to avoid the at least one obstacle.

[0006] Furthermore, the present invention proposes another ship collision avoidance method based on the artificial potential field method, comprising the following steps: (S11) Detecting whether an obstacle enters the collision avoidance range of the ship, if so, executing step (S12); if not, maintaining the navigation path of the ship. (S12) Determining whether the obstacle is a static obstacle or a dynamic obstacle, if it is a static obstacle, executing step (S13); if it is a dynamic obstacle, executing step (S14). (S13) The ship avoids the static obstacle based on the ship collision avoidance method of the first artificial potential field method. (S14) The ship determines whether to start avoiding the dynamic obstacle based on the time to the closest point of approach (TCPA) and the distance to the closest point of approach (DCPA) to the dynamic obstacle. And (S15) The ship avoids the dynamic obstacle based on the ship collision avoidance method of the second artificial potential field method.

[0007] In addition, the present invention also proposes a ship collision avoidance system based on an artificial potential field method, comprising: an information acquisition module to obtain ship information, at least one obstacle information and a target point information; a central processing module connected to the information acquisition module, the central processing module generates a navigation control instruction based on a ship collision avoidance method based on an artificial potential field method; and a navigation control module connected to the central processing module, the navigation control module controls the navigation of the ship according to the navigation control instruction.

[0008] The above brief description of the present invention is intended to provide a basic description of several aspects and technical features of the present invention. The summary of the invention is not a detailed description of the present invention, so its purpose is not to specifically list the key or important components of the present invention, nor is it to define the scope of the present invention. It is only to present several concepts of the present invention in a concise way. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a flow chart of the ship collision avoidance method based on the artificial potential field method according to the first embodiment of the present invention.

[0010] Figure 2 Schematic diagram of the ship collision avoidance method based on the artificial potential field method of the present invention.

[0011] Figure 3 Schematic diagram of the ship collision avoidance method based on the artificial potential field method of the present invention.

[0012] Figure 4 This is a flow chart of a ship collision avoidance method based on an artificial potential field method according to a second embodiment of the present invention.

[0013] Figure 5Schematic diagram of the shortest acceptable range for DCPA of the present invention to judge between a ship and a dynamic obstacle.

[0014] Figure 6 It is a schematic diagram of obstacle zoning of the International Convention for Preventing Collisions at Sea of ​​the present invention.

[0015] Figure 7 Schematic diagram of a ship collision avoidance system based on an artificial potential field method according to a preferred embodiment of the present invention.

[0016] Description of Figure Numbers:

[0017] 1…Ship Collision Avoidance System

[0018] 10…Information acquisition module

[0019] 20…Central Processing Module

[0020] 30…Navigation control module

[0021] 32…Direction control module

[0022] 34…Power Propulsion Module

[0023] 40…Information Security Module

[0024] O…Obstacle

[0025] V, V'…Ship

[0026] T…Target point

[0027] X…ship position

[0028] X g ...target point location

[0029] X g '…Temporary target point position

[0030] F att …target point attraction

[0031] F rep …Obstacle repulsion

[0032] F ext …external forces

[0033] F 1 …First Force

[0034] F 2 ...Second Force

[0035] L1, L2…Captain

[0036] θc…angle

[0037] ρ…distance

[0038] ρ 0 …distance

[0039] A…Zone 1

[0040] B…Second District

[0041] C…Third District

[0042] D…District 4

[0043] (S1)-(S6)…steps

[0044] (S11)-(S15)...steps

[0045] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0046] In order to understand the technical features and practical effects of the present invention and implement it according to the contents of the specification, a preferred embodiment as shown in the figure is further described in detail as follows:

[0047] The present invention proposes a ship collision avoidance method based on an artificial potential field method, and a ship collision avoidance system based on an artificial potential field method; the purpose of which is to guide the ship to automatically avoid obstacles during the navigation process of the ship. It should be particularly emphasized that the ship described in the present invention can be not only a general ship with crew members on board to control its navigation, but also an unmanned ship such as an automatic driving ship, an autonomous sailing ship, an unmanned marine vehicle and an automatic surface vehicle, as well as the "Maritime Autonomous Surface Ships (MASS)" (collectively referred to as "unmanned ships" in this article) specified by the International Maritime Organization (IMO). All those involving automatically controlled ship or vehicle navigation routes should fall within this scope.

[0048] Please refer to Figure 1 , which is a flow chart of the ship collision avoidance method based on the artificial potential field algorithm of the first embodiment of the present invention. In this embodiment, the artificial potential field algorithm is improved to simulate the mutual repulsion and attraction of magnetic forces, and the ship collision avoidance rules are constructed according to the position and relative speed of the ship and the obstacle to avoid the obstacles detected during the navigation process of the ship.

[0049] First, if Figure 1As shown, the ship collision avoidance method based on the artificial potential field method of this embodiment includes the following steps: (S1) obtaining ship information of a ship, obstacle information of at least one obstacle, and target point information of a target point. (S2) establishing an artificial potential field based on the ship information, the obstacle information, and the target point information, including a target point attraction potential field and at least one obstacle repulsion potential field. (S3) synthesizing the target point attraction potential field and the at least one obstacle repulsion potential field to obtain a first resultant force. (S4) adding an external force based on the ship information or the obstacle information. (S5) synthesizing the first resultant force and the external force to obtain a second resultant force. And (S6) the ship navigates according to the direction of the second resultant force to avoid the at least one obstacle.

[0050] In step (S1), the ship can obtain data such as ship information of the ship, obstacle information of at least one obstacle, and target point information of a target point through the ship-borne information acquisition module. Specifically, the information acquisition module can be an image acquisition device, a posture sensing device, a radar sensing device, a lidar sensing device, a sonar sensing device, a wireless positioning device or an automatic identification system (Automatic Identification System, AIS); the ship information includes the ship's speed, position, sailing direction, hull length, or length between perpendiculars (LPP) and hull width; the obstacle information includes the moving speed, position, moving direction, obstacle size and distance from the ship; the target point information includes the position of the target point and the distance from the ship.

[0051] For example, in addition to the ship's length and width, which are known information about the ship, the ship can detect the ship's speed, sailing direction, and the speed and direction of the obstacle through a posture sensing device; it can also detect the obstacle's speed, position, direction, size, and distance from the ship, as well as the position of the target point and the distance from the ship through an image acquisition device, a radar sensing device, a lidar sensing device, or a sonar sensing device; it can also obtain the ship's position, the obstacle's position, and the target point's position through a wireless positioning device. In addition, if the obstacle is another sailing ship, the ship's information (including speed, position, sailing direction, and ship length, etc.) can be obtained through an automatic identification system.

[0052] In steps (S2) to (S6), reference may be made to Figure 2The central processing module of the ship can guide the ship V to avoid the obstacle O through an artificial potential field algorithm. The concept of the algorithm is to generate a navigation path that will not collide with obstacles by artificially constructing the attraction Fatt and repulsion Frep of the potential field, thereby guiding the ship to travel along the path. Specifically, in step (S2), an artificial potential field is established based on the aforementioned ship information, the obstacle information and the target point information, and the artificial potential field includes an attraction potential field generated by a target point and a repulsion potential field generated by at least one obstacle.

[0053] The artificial potential field U is defined as follows: U = U att +∑U rep , where U att represents the attractive potential field of the target point, U rep represents the attractive potential field of the target point. Further, the attractive potential field U att is defined as follows: Where k represents the constant gain, X represents the position of the ship, and X g Represents the position of the target point; the at least one obstacle repulsive force potential field U rep is defined as follows: Where k represents a constant gain, n represents any number greater than zero, X represents the position of the ship, and X g represents the position of the target point, ρ represents the shortest distance from the ship to the at least one obstacle, and ρ 0 Indicates the maximum distance at which the at least one obstacle produces a repulsive force.

[0054] It is obvious from the above definition that at the target point, the attractive potential field U att In the figure, when the ship enters the action area of ​​the target point T, as the distance between the ship and the target point T becomes smaller and smaller, the attraction it receives gradually increases.

[0055] In addition, when the ship V detects that an obstacle O has entered the collision avoidance range of the ship V (here, a circle with a radius of two to five times the ship's hull), it will be repelled by the potential field U of the obstacle O. repAs the distance between the ship V and the obstacle O becomes smaller and smaller, the repulsive force Frep it experiences gradually increases. When the ship V is infinitely close to the obstacle O, the repulsive force Frep it experiences tends to infinity, indicating a great risk of collision. For the dynamic obstacle O, the moving speed and moving direction of the dynamic obstacle O must also be considered. For example, the greater the component of the speed of the obstacle O in the direction of the ship V's navigation speed, the greater the repulsive force on the ship V from the obstacle O. On the other hand, if the shortest distance between the ship V and the at least one obstacle O is greater than the farthest distance at which the at least one obstacle generates a repulsive force, it means that the ship V is not within the range of action of the obstacle repulsive force potential field, and the repulsive force potential field U rep is zero.

[0056] Next, in step (S3), the aforementioned target point attraction potential field and at least one obstacle repulsion potential field are combined to form a composite potential field, and a first resultant force F is generated. 1 , and the first resultant force F 1 is defined as follows: Among them, F att represents the attraction of the target point, F rep represents the repulsive force of the at least one obstacle. So far, if the obstacle O is a static obstacle in a general state, the vessel V is subjected to the first resultant force F 1 However, if the obstacle O is a dynamic obstacle and suddenly appears very close to the ship V (such as an aquatic creature suddenly swimming out of the water), resulting in a sudden generation of an excessively large repulsive force potential field; or the obstacle O is located exactly between the ship V and the target point T and is on the same axis as the ship and the target point, and the moving direction of the dynamic obstacle O is exactly the same as the first resultant force F 1 The same direction (causing the first resultant force F 1 The direction will still be towards the obstacle), resulting in the ship V being unable to escape from the constraint of the obstacle O.

[0057] In view of this, please refer to steps (S4) to (S6). Steps (S4) to (S6) can be used to avoid the problem that the direction of the resultant force is the same as the position of the obstacle (or the moving direction), the target point is too close to have insufficient attraction, or the obstacle is too close to have excessive repulsion, which may cause the ship to be unable to be correctly guided to the target point. The concept is that while the ship is subject to the repulsive force potential field generated by the obstacle, a custom force is added pointing to the target point (i.e., a force is generated in one direction toward the target point) to maintain the strength of the resultant force toward the target point.

[0058] In step (S4), an external force F is added to the artificial potential field according to the aforementioned ship information or the obstacle information. ext Specifically, the external force F extThe weight value of depends on the speed of the ship V, the length or width of the ship, the moving speed of the obstacle O, the size of the obstacle, and the relative distance between the obstacle and the ship. Figure 3 , when the moving speed of the obstacle O or the sailing speed of the ship V is faster, or when the relative distance between the obstacle O and the ship V is shorter, the repulsive force on the ship V from the obstacle will also increase; in other words, a larger external force F is required ext Point to the target point T to avoid the ship V being pulled by the repulsive force Frep of the obstacle O. On the contrary, if the relative distance between the obstacle O and the ship V is far, or the moving speed of the obstacle O is slow compared to the sailing speed of the ship V, it means that there is enough time for buffering, so a weaker external force F can be added. ext , the ship can go around and avoid obstacles at a slower angle.

[0059] Next, in step (S5), the aforementioned attractive force potential field is combined with at least one obstacle repulsive force potential field to generate the first resultant force F 1 , and the added external force F ext The synthesis has obtained a second force F 2 , the second resultant force is defined as follows: F 2 =F 1 +F ext , where F 1 represents the first resultant force, F ext Finally, in step (S6), the vessel V can be subjected to the second resultant force F 2 The unmanned ship avoids the at least one obstacle O and sails toward the target T, thereby completing the autonomous collision avoidance navigation of the unmanned ship.

[0060] In addition to taking into account the static and moving states of obstacles, this embodiment avoids such obstacles through an artificial field potential algorithm, and further solves the problem that the ship cannot be correctly guided to the target point due to the obstacle's moving direction being the same as the first resultant force direction, the target point being too close and the attraction being insufficient, or the obstacle being too close and the repulsion being too strong, etc., which can effectively avoid the probability of a ship colliding with an obstacle during navigation in practice.

[0061] In addition, please refer to Figure 4 As shown in FIG. 1 , it is a ship collision avoidance method based on the artificial potential field method according to the second embodiment of the present invention. Figure 4As shown, another ship collision avoidance method based on artificial potential field proposed in this embodiment includes the following steps: (S11) Detect whether an obstacle enters the collision avoidance range of the ship. If so, execute step (S12); if not, maintain the navigation path of the ship. (S12) Determine whether the obstacle is a static obstacle or a dynamic obstacle. If it is a static obstacle, execute step (S13); if it is a dynamic obstacle, execute step (S14). (S13) The ship avoids the static obstacle based on the ship collision avoidance method of the first artificial potential field method. (S14) The ship determines whether to start avoiding the dynamic obstacle based on the time to the closest point of approach (TCPA) and the distance to the closest point of approach (DCPA) to the dynamic obstacle. And (S15) The ship avoids the dynamic obstacle based on the ship collision avoidance method of the second artificial potential field method.

[0062] In step (S11), the information acquisition module of the ship can detect whether an obstacle enters the collision avoidance range of the ship; specifically, the information acquisition module can obtain the ship information of the ship, the target point information of a target point and other data, and the obstacle information of detecting at least one obstacle. The information acquisition module can be an image acquisition device, a posture sensing device, a radar sensing device, a lidar sensing device, a sonar sensing device, a wireless positioning device or an automatic identification system (Automatic Identification System, AIS); the ship information includes the ship's speed, position, sailing direction, hull length, or length between perpendiculars (LPP) and hull width; the obstacle information includes the moving speed, position, moving direction, obstacle size and distance from the ship; the target point information includes the position of the target point and the distance from the ship.

[0063] In this step, after the information acquisition module detects an obstacle, it can know the position of the obstacle and the distance from the ship, and judge whether the obstacle enters the collision avoidance range of the ship based on the position of the obstacle and the distance from the ship. If so, execute step (S12) to continue to enter the collision avoidance step; if not, maintain the navigation path of the ship and continue to move towards the target point. The collision avoidance range is generally set to a circular range with a radius of one to three nautical miles, but in other cases it can be determined based on the size of the ship, the speed of the ship or the speed of the obstacle (i.e. the ship and the obstacle).

[0064] Next, in step (S12), the size and movement mode (dynamic or static) of the obstacle are obtained from the obstacle information detected by the information acquisition module. If the obstacle is a static obstacle such as a reef, a bridge pier or a floating log, the static obstacle avoidance step is performed; if the obstacle is a dynamic obstacle such as an aquatic creature or other sailing ship, the dynamic obstacle avoidance step is performed.

[0065] In step (S13), the central processing module of the ship can calculate a path to avoid the static obstacle based on the first artificial field potential method, and guide the ship to avoid the static obstacle. Specifically, the first artificial field potential method is to establish an artificial potential field based on the aforementioned ship information, the obstacle information and the target point information, and the artificial potential field includes an attractive potential field generated by a target point and a repulsive potential field generated by at least one obstacle.

[0066] The artificial potential field U is defined as follows: U = U att +∑U rep , where U att represents the attractive potential field of the target point, U rep represents the attractive potential field of the target point. Further, the attractive potential field U att is defined as follows: Where k represents the constant gain, X represents the position of the ship, and X g Represents the position of the target point; the at least one obstacle repulsive force potential field U rep is defined as follows: Where k represents a constant gain, n represents any number greater than zero, X represents the position of the ship, and X g represents the position of the target point, ρ represents the shortest distance from the ship to the at least one obstacle, and ρ 0 Indicates the maximum distance at which the at least one obstacle produces a repulsive force.

[0067] It is obvious from the above definition that at the target point, the attractive potential field U att In the process of navigation, when a ship enters the action area of ​​the target point, as the distance between the ship and the target point becomes smaller and smaller, the attraction it receives gradually decreases.

[0068] In addition, when the ship detects an obstacle entering the collision avoidance range (here, a circle with a radius of two to five times the ship's hull) during navigation, the obstacle will be repelled by the potential field U repAs the distance between the ship and the obstacle becomes smaller and smaller, the repulsive force it experiences gradually increases. When the ship is infinitely close to the obstacle, the repulsive force it experiences tends to infinity, indicating a great risk of collision. For dynamic obstacles, the moving speed and direction of the dynamic obstacles must also be considered. For example, the greater the component of the obstacle's speed in the direction of the ship's sailing speed, the greater the repulsive force the ship experiences from the obstacle. On the other hand, if the shortest distance between the ship and the at least one obstacle is greater than the farthest distance at which the at least one obstacle generates repulsive force, it means that the ship is not within the range of action of the repulsive force potential field of the obstacle, and the repulsive force potential field U rep is zero.

[0069] Next, the aforementioned target point attraction potential field and at least one obstacle repulsion potential field are combined to form a composite potential field, and a first resultant force F is generated. 1 , and the first resultant force is defined as follows: Among them, F att represents the attraction of the target point, F rep represents the repulsive force of the at least one obstacle. If the obstacle is a static obstacle in a general state, the ship is subjected to the first resultant force F 1 The robot is guided to avoid the static obstacle and continue to navigate towards the target point.

[0070] In step (S14), the central processing module of the ship determines whether to start avoiding the dynamic obstacle based on the time to the closest point of approach (TCPA) and the distance to the closest point of approach (DCPA) between the ship and the dynamic obstacle. When TCPA is greater than or equal to zero, it means that the ship and the dynamic obstacle are approaching and there is a possibility of collision; when TCPA is less than zero, it means that the ship and the dynamic obstacle are moving away from each other. On the other hand, you can also refer to Figure 5 , DCPA is used to determine the shortest acceptable range between the ship and the dynamic obstacle. When the DCPA is less than the safety range threshold, the collision avoidance mode is activated; the safety range threshold ρ0 is defined as follows:

[0071] ρ 0 =L C +L=d cri

[0072]

[0073] Wherein, the collision length LC (Collision Length) is the length of the midpoint of the two ships V and V' when they collide, L1 is the length of the ship V' as a dynamic obstacle, L2 is the length of the ship V (the width is not considered here), Xc is the angle θc between the ship V and the dynamic obstacle ship V', and L is the key collision avoidance length (a variable parameter value). The key collision avoidance length should take into account the maneuverability of the ship V and should be at least three times the length of the ship V. Wherein, ρ0 is also called the critical collision avoidance length, which is the distance at which the repulsive field begins to act in the artificial potential field method. The parameter ρ0 is an important key to the success of collision avoidance; calculate whether TCPA>0 and DCPA<ρ0, and if the conditions are met, immediately enable the artificial potential field method for collision avoidance. Finally, in step (S15), the central processing module of the ship can calculate the path to avoid the dynamic obstacle based on the second artificial field potential method, and guide the ship to avoid the static obstacle. In view of the fact that the dynamic obstacle suddenly appears at a position extremely close to the ship (such as an aquatic creature suddenly swimming out of the water), resulting in a sudden generation of an excessively large repulsive force potential field; or the moving direction of the dynamic obstacle is exactly the same as the direction of the first resultant force (causing the direction of the first resultant force to still be toward the obstacle), resulting in the ship being unable to escape from the restraint of the dynamic obstacle, the second artificial field potential method proposed in this embodiment can add an external force F to the artificial potential field based on the aforementioned ship information or the dynamic obstacle information. ext , in order to maintain the strength of the resultant force toward the target point.

[0074] Specifically, the external force F ext The weight value depends on the ship's speed, length or width, as well as the moving speed of the dynamic obstacle, the size of the dynamic obstacle, and the relative distance between the dynamic obstacle and the ship. When the moving speed of the dynamic obstacle or the sailing speed of the ship is faster, or when the relative distance between the dynamic obstacle and the ship is shorter, the repulsive force on the ship from the dynamic obstacle will also increase; in other words, a larger external force F is required. ext Point to the target point to avoid the ship being pulled by the repulsive force of the dynamic obstacle. On the contrary, if the relative distance between the dynamic obstacle and the ship is far, or the moving speed of the dynamic obstacle is slow compared to the sailing speed of the ship, it means that there is enough time for buffering, so a weaker external force F can be added. ext , the ship can go around and avoid the dynamic obstacle at a gentler angle.

[0075] Next, the first resultant force F is generated by combining the attractive force potential field in the first artificial field potential method with the repulsive force potential field of the dynamic obstacle 1 , and the additional external force F ext The synthesis has obtained a second force F 2 , the second resultant force is defined as follows: F 2 =F1 +F ext , where F 1 represents the first resultant force, F ext Finally, the ship can avoid the dynamic obstacle and sail towards the target point through the guidance of the second combined force, thus completing the autonomous collision avoidance navigation of the unmanned ship.

[0076] It is worth noting that after step (S14), there is also a step (S14a) of dividing the relative position of the dynamic obstacle and the ship into the first, second, third and fourth zones according to the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS) (see Figure 6 ); wherein the first zone is 345° to 15° of the collision avoidance range, the second zone is 15° to 112.5° of the collision avoidance range, the third zone is 112.5° to 247.5° of the collision avoidance range, and the fourth zone is 112.5° to 247.5° of the collision avoidance range. The International Convention for Preventing Collisions at Sea specifically refers to the implementation method in which the dynamic obstacle is other sailing ships.

[0077] After step (S14a), the method further includes: if the dynamic obstacle is located in the first or second zone, executing step (S15); if the dynamic obstacle is located in the third or fourth zone, maintaining the navigation path of the ship. Figure 3 If the dynamic obstacle is located in the first zone, it means that there is an obstacle in front of the ship, so it is necessary to add a temporary attraction potential field to the artificial potential field, which is offset to the right of the ship's forward direction and is one times the length of the ship's distance from the ship, so as to meet the COLREGs specifications. If the dynamic obstacle is located in the second zone, it means that there is an obstacle on the right side of the ship, so it is also necessary to add a temporary attraction potential field to the artificial potential field, which is offset to the right of the ship's forward direction and is one times the length of the ship's distance from the ship. If the dynamic obstacle is located in the third or fourth zone, it means that there is an obstacle behind or on the left side of the ship, then the obstacle does not need to be ignored; the reason is that, under the premise that the dynamic obstacle is another ship sailing, according to the International Convention for Preventing Collisions at Sea, the other ship should avoid our ship to the right (because relatively speaking, our ship is in front of and on the right side of the other ship), and our ship can maintain the original path.

[0078] In this embodiment, an artificial potential field algorithm is improved to simulate magnetic attraction and repulsion, and the COLREGS International Convention for Preventing Collisions at Sea is combined to establish a ship collision avoidance method. This method guides autonomous ships to automatically avoid obstacles based on conditions such as the ship's position and speed, the obstacle's position and speed, the DCPA's acceptable range and detection distance.

[0079] In addition, please refer to Figure 7 As shown in FIG. 1 , it is a ship collision avoidance system based on the artificial potential field method according to a preferred embodiment of the present invention. Figure 7 As shown, the ship collision avoidance system 1 based on the artificial potential field method of this embodiment includes: an information acquisition module 10 to obtain ship information, at least one obstacle information and a target point information; a central processing module 20, connected to the information acquisition module 10, the central processing module 20 generates a navigation control instruction based on a ship collision avoidance method based on an artificial potential field method; and a navigation control module 30, connected to the central processing module, the navigation control module 30 controls the navigation of the ship according to the navigation control instruction.

[0080] It should be particularly emphasized that the ship in this embodiment is not only a general ship with crew members, but also refers to the "Maritime Autonomous Surface Ships (MASS)" specified by the International Maritime Organization (IMO), and they are collectively referred to as "unmanned ships" in this article.

[0081] The following will further describe the ship collision avoidance system based on the artificial potential field method of the present invention. First, the information acquisition module 10 can obtain a ship information, at least one obstacle information and a target point information; specifically, the information acquisition module 10 can be an image acquisition device, a posture sensing device, a radar sensing device, a lidar sensing device, a sonar sensing device, a wireless positioning device or an automatic identification system (Automatic Identification System, AIS); the ship information includes the ship's speed, position, sailing direction, hull length, or length between perpendiculars (LPP) and hull width; the obstacle information includes the obstacle's moving speed, position, moving direction, obstacle size and distance from the ship; the target point information includes the position of the target point and the distance from the ship.

[0082] For example, in addition to the ship's length and width, which are known information about the ship, the ship can detect the ship's speed, sailing direction, and the speed and direction of the obstacle through a posture sensing device; it can also detect the obstacle's speed, position, direction, size, and distance from the ship, as well as the position of the target point and the distance from the ship through an image acquisition device, a radar sensing device, a lidar sensing device, or a sonar sensing device; it can also obtain the ship's position, the obstacle's position, and the target point's position through a wireless positioning device. In addition, if the obstacle is another sailing ship, the ship's information (including speed, position, sailing direction, hull length, etc.) can be obtained through an automatic identification system.

[0083] The central processing module 20 connected to the information acquisition module 10 can generate a navigation control instruction based on the aforementioned ship information, at least one obstacle information and target point information, and based on a ship collision avoidance method of an artificial potential field method; the ship collision avoidance method of the artificial potential field method can be Figure 1 The ship collision avoidance method using the artificial potential field method can also be Figure 4 The ship collision avoidance method using the artificial potential field method includes the navigation control instruction including a heading control instruction and a speed control instruction.

[0084] The navigation control module 30 connected to the central processing module 20 can control the navigation of the ship according to the navigation control command. Specifically, the navigation control module 30 includes a direction control module 32 and a power propulsion module 34; and the direction control module 32 receives the aforementioned heading control command, and the power propulsion module 34 receives the aforementioned speed control command. In other words, the direction control module 32 connected to the central processing module 20 can control (change the direction of the rudder angle) the navigation direction of the ship according to the heading control command; on the other hand, the power propulsion module 34 connected to the central processing module 20 can control the navigation speed of the ship according to the speed control command. Accordingly, the ship can avoid obstacles according to the set collision avoidance path.

[0085] In this embodiment, the central processing module 20 includes a programmable logic controller (PLC), a microcontroller unit (MCU) or a combination thereof. Any device that can receive information transmission between system modules and send control commands after performing calculations falls within the protection scope, and the present invention should not be limited to this.

[0086] In this embodiment, the direction control module 32 includes a rudder, an electronic steering system or a combination thereof, and its purpose is to adjust the angle of the rudder after receiving the command from the central module 20, so as to control the navigation direction of the ship. The power propulsion module 34 includes a generator, an engine, a thruster (lateral thruster), a throttle, a battery, a motor or a combination thereof, and its purpose is to adjust the output power after receiving the command from the central processing module 20, so as to control the speed of the ship. Further, the battery can be a lithium-ion battery, a lithium polymer battery, a lithium iron phosphate battery, a fuel cell or a combination thereof, and can be designed according to the requirements of the power propulsion module; the power propulsion module can also be a hybrid power system, which collects autonomous energy such as solar energy, wind energy and wave energy through solar panels, sails or wave energy drive devices configured on the ship, and converts these autonomous energy into electrical energy and stores it in the battery, so as to assist the power source of the power propulsion module.

[0087] Furthermore, the ship collision avoidance system based on the artificial potential field method of the present invention may also include an information security module 40 connected to the central processing module 20 and / or the information acquisition module 10. The information security module 40 is responsible for providing a safety protection mechanism for the ship when the information received by the central processing module 20 is incorrect, or when there is a problem with the information acquisition module 10 and the external connection (including the acquisition of sensing information and the communication with the shore station). When the information acquisition module 10 is abnormally connected, resulting in the inability to deliver external or sensing information, the information acquisition module 10 is disturbed during communication, or a third-party user (such as malware or virus, etc.) improperly controls the operation of the central processing module 20, the ship will be automatically put into neutral; at the same time, the information acquisition module 10 of the ship is prohibited from receiving external sensing information or commands to avoid collision accidents, and it can also allow staff to safely board the ship for maintenance operations.

[0088] Among them, the information security module 40 can be an intrusion detection system (IDS) to monitor wireless communication transmission, check whether there is any suspicious activity or violation of ship navigation regulations, and issue an alarm or take active response measures when detected; an identity verification system (Authentication), only authorizing users who have passed identity verification (such as shared key or biometric verification) to communicate with the ship; a firewall system (Firewall) is established between the external device and the wireless communication module, which can monitor the transmission in and out according to the preset protection content of the ship and intercept inappropriate external information; or through a whitelisting system or an application whitelisting system (Application Whitelisting) to execute the modules or applications listed in the positive list, and not allow the execution of applications outside the list. In other words, the information security module 40 only allows all modules or applications inside the collision avoidance system to transmit and execute information to each other. Once a module or application outside the list appears, the collision avoidance system will not execute and immediately issue a warning reminder, and isolate at the first line through the whitelist to ensure that malware intrusion is prevented from interfering with the navigation of the ship.

[0089] The present invention takes into account the static and moving states of obstacles, and uses the absolute shortest distance between the ship and the obstacle in the coordinate system as the basis for the detection distance to determine whether an obstacle with a collision risk is encountered and avoid it, so that the ship can smoothly avoid obstacles in the waterway and maintain the path to the target point, providing a reliable and safe method for the field of autonomous navigation and collision avoidance. In addition, the speed and heading of the ship are controlled during the obstacle avoidance process. At the same time, for static obstacles such as buoys, bridge piers, etc., as well as dynamic obstacles such as other ships in the waterway, the ship collision avoidance method and system based on the artificial potential field method of the present invention can greatly reduce the probability of collision with obstacles, and because it is easy to control in time and has a small amount of calculation, it can play a greater role in the field of autonomous ship obstacle avoidance.

[0090] However, what is described above is only a preferred embodiment of the present invention, and should not be used to limit the scope of the present invention. That is, simple changes and modifications made according to the scope of the patent application and the description of the present invention are still within the scope of the present invention.

Claims

1. A ship collision avoidance system based on artificial potential field method, characterized in that: include: An information acquisition module is used to acquire ship information, at least one obstacle information and a target point information; a central processing module connected to the information acquisition module, the central processing module generating a navigation control instruction based on a ship collision avoidance method of an artificial potential field; an information security module connected to the central processing module and the information acquisition module; and a navigation control module connected to the central processing module, the navigation control module controlling the navigation of a ship according to the navigation control instruction; Wherein, the information security module includes an intrusion detection system, an identity verification system, an authorization and encryption system, a firewall system, a whitelist system or a combination thereof; When the information acquisition module is abnormally connected and the external or sensor information cannot be delivered, the information acquisition module is disturbed during communication, or a third-party user improperly controls the central processing module, the ship will be automatically put into neutral and the information acquisition module of the ship will be prohibited from receiving external sensor information or commands; Among them, the ship collision avoidance method based on the artificial potential field includes: Obtaining ship information of the ship, obstacle information of at least one obstacle, and target point information of a target point; According to the ship information, the obstacle information and the target point information, an artificial potential field is established, wherein the artificial potential field includes a target point attraction potential field and at least one obstacle repulsion potential field; Combining the target point attraction potential field and the at least one obstacle repulsion potential field to obtain a first resultant force; When the at least one obstacle is a dynamic obstacle and suddenly appears extremely close to the ship, resulting in a sudden generation of an excessive repulsive force potential field of the at least one obstacle, or the at least one obstacle is located exactly between the ship and the target point and is on the same axis as the ship and the target point, and the moving direction of the at least one obstacle is exactly the same as the direction of the first resultant force, an external force is added according to the ship information or the obstacle information; synthesizing the first resultant force and the external force to obtain a second resultant force; and The vessel sails according to the direction of the second resultant force to avoid the at least one obstacle.

2. The ship collision avoidance system based on the artificial potential field method as claimed in claim 1, characterized in that: The information acquisition module includes an image acquisition device, a posture sensing device, a radar sensing device, a lidar sensing device, a sonar sensing device, a wireless positioning device, an automatic identification system or a combination thereof.

3. The ship collision avoidance system based on the artificial potential field method as claimed in claim 1, characterized in that: The central processing module includes a programmable logic controller, a microcontroller or a combination thereof.

4. The ship collision avoidance system based on the artificial potential field method as claimed in claim 1, characterized in that: The navigation control module includes a direction control module and a power propulsion module.

5. The ship collision avoidance system based on the artificial potential field method as claimed in claim 4, characterized in that: The directional control module includes a rudder, an electronic steering system, or a combination thereof.

6. The ship collision avoidance system based on the artificial potential field method as claimed in claim 4, characterized in that: The power propulsion module includes a generator, an engine, a thruster, a throttle, a battery, a motor or a combination thereof.

7. A ship collision avoidance method based on artificial potential field method, characterized in that: include: (S1) obtaining ship information of a ship, obstacle information of at least one obstacle, and target point information of a target point; (S2) establishing an artificial potential field according to the ship information, the obstacle information and the target point information, the artificial potential field comprising a target point attraction potential field and at least one obstacle repulsion potential field; (S3) synthesizing the target point attraction potential field and the at least one obstacle repulsion potential field to obtain a first resultant force; (S4) when the at least one obstacle is a dynamic obstacle and suddenly appears extremely close to the ship, resulting in a sudden generation of an excessive repulsive force potential field of the at least one obstacle, or when the at least one obstacle is located exactly between the ship and the target point and is on the same axis as the ship and the target point, and when the moving direction of the at least one obstacle is exactly the same as the direction of the first resultant force, an external force is added according to the ship information or the obstacle information; (S5) synthesizing the first resultant force and the external force to obtain a second resultant force; and (S6) the vessel navigates according to the direction of the second resultant force to avoid the at least one obstacle; Wherein, the ship collision avoidance method based on the artificial potential field method is operated on the ship collision avoidance system based on the artificial potential field method as described in claim 1.

8. The ship collision avoidance method based on the artificial potential field method as claimed in claim 7, characterized in that: The ship information includes the ship's speed, position, sailing direction, hull length and hull width.

9. The ship collision avoidance method based on the artificial potential field method as claimed in claim 7, characterized in that: The obstacle information includes the moving speed, position, moving direction, size of the obstacle and the distance from the ship.

10. The ship collision avoidance method based on the artificial potential field method according to claim 7, characterized in that: The target point information includes the location of the target point and the distance from the ship.

11. The ship collision avoidance method based on artificial potential field method according to claim 7, characterized in that: The artificial potential field is defined as follows: , in represents the attractive potential field of the target point, Represents the repulsive force of the at least one obstacle.

12. The ship collision avoidance method based on the artificial potential field method according to claim 11, characterized in that: The attractive potential field of the target point is defined as follows: ， in represents a constant gain, indicates the position of the vessel, Indicates the location of the target point.

13. The ship collision avoidance method based on the artificial potential field method according to claim 12, characterized in that: The at least one obstacle repulsive force potential field is defined as follows: ， in represents a constant gain, represents any number greater than zero, indicates the position of the vessel, Indicates the location of the target point. represents the shortest distance from the ship to the at least one obstacle, Indicates the maximum distance at which the at least one obstacle produces a repulsive force.

14. The ship collision avoidance method based on the artificial potential field method according to claim 13, characterized in that: The first resultant force is defined as follows: ， in represents the attraction of the target point, Represents the repulsive force of the at least one obstacle.

15. The ship collision avoidance method based on the artificial potential field method according to claim 14, characterized in that: The second resultant force is defined as follows: ,in represents the first resultant force, represents the external force.

16. A ship collision avoidance method based on artificial potential field method, characterized in that: include: (S11) detecting whether an obstacle enters the collision avoidance range of the ship, if so, executing step (S12); if not, maintaining the navigation path of the ship; (S12) Determine whether the obstacle is a static obstacle or a dynamic obstacle. If it is a static obstacle, execute step (S13); if it is a dynamic obstacle, execute step (S14); (S13) the ship avoids the static obstacle based on the first artificial potential field method; (S14) the vessel determines whether to start avoiding the dynamic obstacle based on the time when the vessel is closest to the dynamic obstacle and the distance to the vessel from the dynamic obstacle; as well as (S15) The ship avoids the dynamic obstacle based on the ship collision avoidance method based on the artificial potential field method according to claim 7.

17. The ship collision avoidance method based on artificial potential field method according to claim 16, characterized in that: The step (S14) further includes a step (S14a) of dividing the relative positions of the dynamic obstacle and the vessel into first, second, third and fourth zones according to the International Convention for Preventing Collisions at Sea (COLREGS).

18. The ship collision avoidance method based on artificial potential field method according to claim 17, characterized in that: The method further comprises a step (S14b) after step (S14a), wherein if the dynamic obstacle is located in the first or second zone, step (S15) is executed; and if the dynamic obstacle is located in the third or fourth zone, the navigation path of the ship is maintained.

19. The ship collision avoidance method based on artificial potential field method according to claim 18, characterized in that: The first zone is from 345° to 15° of the collision avoidance range, the second zone is from 15° to 112.5° of the collision avoidance range, the third zone is from 112.5° to 247.5° of the collision avoidance range, and the fourth zone is from 112.5° to 247.5° of the collision avoidance range.

20. The ship collision avoidance method based on artificial potential field method according to claim 16, characterized in that: When the distance of the closest point of the dynamic obstacle is less than a safety range threshold, the dynamic obstacle is avoided, wherein the safety range threshold depends on the length of the ship, the speed of the ship or the speed of the obstacle.

21. The ship collision avoidance method based on the artificial potential field method according to claim 20, characterized in that: The threshold is affected by an external parameter, which includes the size of the ship or the relative speed between the ship and the dynamic obstacle.

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