Ship motion control method and system for fixed-point approach operation

Abstract

The application relates to the technical field of ship motion control, and particularly discloses a ship motion control method and system for fixed-point approaching operation, which comprises the following steps: a ship receives an approaching operation instruction, and in the process of sailing to an approaching target, the ship uses real-time bow direction, relative straight-line distance of the ship and the target, and target relative ship bow azimuth; fixed-point approaching operation is performed through guidance control of a long-distance alignment mode, a medium-distance fusion mode and a short-distance approaching mode; when the axial projection length of the ship on the reference track is greater than the total distance of the reference track at the switching moment, the ship is switched to a super-charge surrounding mode in the short-distance approaching mode; fixed-point approaching operation is performed until the operation is completed. The application completes the whole-process guidance operation only by relying on three types of local perception information of relative distance, azimuth of the ship and the target, and self bow direction of the ship, and can significantly improve environmental adaptability and operation fault tolerance.

Description

Technical Field

[0001] This invention relates to the field of ship motion control technology, and in particular to a ship motion control method and system for fixed-point approach operations. Background Technology

[0002] Emergency approach operations at sea are a core operational component of maritime rescue and ship maintenance. Conventional ship-to-point approach guidance methods rely heavily on global coordinate information provided by satellite navigation systems. Tracking and control commands are constructed based on the global position difference between the ship and the target to achieve point-to-point approach operations.

[0003] However, in complex marine environments, there are many navigation-limited conditions. For example, proximity to islands and reefs, as well as obstructions from buildings, can cause satellite signal attenuation and breakage. Electromagnetic interference at sea can trigger satellite navigation denial, preventing ships from obtaining effective global positioning data. In these situations, traditional global trajectory guidance methods become completely ineffective, making it impossible to complete point approach operations.

[0004] Existing local sensing guidance schemes mostly adopt a single line-of-sight guidance mode, which has obvious technical defects: single line-of-sight guidance has weak anti-disturbance capability at close range and is easily affected by wind, waves and ocean currents, resulting in approach deviation; at the same time, existing technologies do not have a perfect fault-tolerance and recovery mechanism, and ships are very prone to approach overshoot problems due to the inertia of the hull and the influence of ocean disturbances. After a single operation fails, it cannot be retried autonomously, which directly leads to the interruption of emergency missions and low operation success rate.

[0005] In addition, existing guidance technologies are mostly designed for unmanned vessel scenarios, with limited algorithm adaptability, unable to meet the needs of manned vessel-assisted approach operations, and have a limited range of scenarios, making it difficult to meet the engineering requirements of diverse emergency approach operations in complex sea conditions. Summary of the Invention

[0006] This invention aims to address the problems of existing ship guidance technologies, such as reliance on satellite navigation for global positioning, poor adaptability to complex and constrained operating conditions, susceptibility to oscillations during segmented guidance, lack of fault tolerance and recovery from approach overshoot, and weak versatility across scenarios. To this end, this invention provides a ship motion control method and system for fixed-point approach operations. It breaks through the technical limitations of traditional guidance methods that rely on global satellite coordinates, completing the entire guidance process solely based on three types of local perception information: the relative distance and bearing between the ship and the target, and the ship's own heading. This method is applicable to fixed-point approach operations for various manned and unmanned vessels in complex marine conditions such as satellite navigation denial, electromagnetic interference, and signal blockage, including maritime emergency search and rescue, material delivery, ship rendezvous, and hazardous target handling. It significantly improves environmental adaptability and operational fault tolerance.

[0007] This invention provides a ship motion control method for fixed-point approach operations, and the technical solution adopted is as follows: including: The vessel receives the approach operation instruction, sails towards the approach target, and enters the long-range alignment mode; during the journey, it acquires the vessel's real-time heading, the straight-line relative distance between the vessel and the target, and the target's azimuth relative to the vessel's bow; In the long-range alignment mode, when the straight-line relative distance between the ship and the target is less than the long-range / medium-range switching threshold, or when the absolute value of the target's relative bow azimuth is less than the bow aiming threshold, the ship switches from the long-range alignment mode to the medium-range fusion mode; and records the relevant parameters of the reference track, including the total distance of the reference track at the switching time. In the mid-range fusion mode, the ship adopts adaptive weighted fusion forward-looking guidance, and obtains the heading guidance command based on the ship's real-time heading to control the ship to approach the target; In the medium-distance fusion mode, when the straight-line relative distance between the ship and the target is less than the medium-distance / close-distance switching threshold, the ship switches from the medium-distance fusion mode to the close-distance approach mode. In the close approach mode, when the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed; when the straight-line relative distance between the ship and the target is greater than the operation arrival accuracy threshold, and the axial projection length of the ship on the reference track is greater than the total distance of the reference track at the switching time, the ship switches from the close approach mode to the overshoot circling mode. In the overshoot circling mode, the ship uses tangent-point circular circling guidance. Based on the ship's real-time heading calculation, the heading guidance command is obtained to control the ship to periodically approach the target. When the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed.

[0008] Furthermore, guidance and control for close-in operations can be completed solely based on the straight-line relative distance between the ship and the target, the target's relative bow azimuth, and the ship's real-time heading.

[0009] Furthermore, the long-range alignment mode, mid-range fusion mode, close-range approach mode, and overshoot surround mode adopt unidirectional irreversible switching logic.

[0010] Furthermore, in tangent-point circular guidance, the ship moves continuously along a circle, with the reference track as the tangent of the circle, the approach to the target as the tangent point of the circle, the center of the circle in the direction of the reference heading normal, and the circumference is calculated based on the ship's length and speed.

[0011] Furthermore, the calculation process for the bow guidance command in tangent-point circular guidance is as follows: The orbital radius is calculated based on the ship's length and speed, and the center coordinates are obtained by combining the reference heading at the switching moment. The ship's position relative to the center of the circle is calculated based on the center coordinates and the ship's current coordinates. Then, the polar angle of the ship relative to the center of the circle is calculated, and finally, the tangential command is calculated. Correction commands are calculated based on the ship's position relative to the center of the orbit and the orbital radius. The bow guidance command is calculated based on the tangential and correction commands; In the northeast coordinate system established with the approaching target as the origin, the ship's current coordinates are derived from the ship's real-time heading, the ship-to-target straight-line distance, and the target's azimuth relative to the ship's bow. The center coordinates are the coordinates in the northeast coordinate system established with the approaching target as the origin. The reference track parameters include the reference heading at the switching time.

[0012] Furthermore, the axial projection length of the ship on the reference track The calculation formula is: In the northeast coordinate system established with the approaching target as the origin, The ship's current eastward coordinates, The ship's current northward coordinates, To approach the target's eastward coordinates, To approach the target's north coordinates, The eastward coordinates of the ship at the time of switching. The northbound coordinates of the ship at the time of switching; The total distance of the reference track at the switching time; relevant parameters of the reference track include and .

[0013] Furthermore, the calculation process for the bow guidance command of adaptive weighted fusion forward-looking guidance is as follows: Calculate the real-time alignment command for the target point based on the ship's real-time bow direction and the target's azimuth relative to the ship's bow. The trajectory correction command is calculated based on the ship's current coordinates, the coordinates of the approaching target, the reference heading at the time of switching, and the forward sight distance. In the northeast coordinate system established with the approaching target as the origin, the ship's current coordinates are derived from the ship's real-time bow, the ship-to-target straight-line distance, and the target's azimuth relative to the ship's bow. The relevant parameters of the reference trajectory include the reference heading at the time of switching. Adaptive fusion weights are calculated based on real-time ship-to-eye straight-line relative distance. The calculation formula is: in, The straight-line relative distance between the ship and the target. The threshold for switching between medium and short range. The total distance of the reference track at the time of switching; By using adaptive fusion weights to fuse real-time target point alignment commands and track correction commands, the heading guidance commands are calculated.

[0014] Furthermore, the long-range / medium-range switching threshold The calculation formula is: Where L is the length of the ship. Let g be the speed of the ship, and g be the acceleration due to gravity. The mid-range / near-range handover threshold is less than the far-range / mid-range handover threshold; The heading aiming threshold is 10°~20°.

[0015] Furthermore, the bow guidance command is subject to single-step steering saturation limiting to match the maximum steering limit of the ship's steering gear.

[0016] This invention also provides a ship motion control system for fixed-point approach operations, the technical solution of which includes: The local observation acquisition module is used to acquire the ship's real-time heading, the ship-to-target straight-line relative distance, and the target's azimuth relative to the ship's bow, and transmit them to the long-range alignment mode control module, the medium-range fusion mode control module, the close-range approach mode control module, and the overshoot and surround mode control module. The long-range alignment mode control module is used to receive approach operation instructions, control the vessel to approach the target, and enter the long-range alignment mode; and when the straight-line relative distance between the vessel and the target is less than the long-range / medium-range switching threshold, or the absolute value of the target's relative bow azimuth is less than the bow aiming threshold, it switches from the long-range alignment mode to the medium-range fusion mode; and records the relevant parameters of the reference track, including the total distance of the reference track at the time of switching; The mid-range fusion mode control module is used to adopt adaptive weighted fusion forward-looking guidance in mid-range fusion mode. Based on the real-time heading of the ship, the heading guidance command is calculated to control the ship to approach the target. When the straight-line relative distance between the ship and the target is less than the mid-range / close-range switching threshold, the ship switches from mid-range fusion mode to close-range approach mode. The close approach mode control module is used to control the ship to approach the target in close approach mode; and when the ship-to-target straight-line relative distance is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed; when the ship-to-target straight-line relative distance is greater than the operation arrival accuracy threshold, and the axial projection length of the ship on the reference track is greater than the total distance of the reference track at the switching time, the ship switches from close approach mode to overshoot circling mode. The super-impact circling mode control module is used to obtain the heading guidance command based on the real-time heading of the ship, and control the ship to periodically approach the target. When the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed.

[0017] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: 1. This invention relies solely on local ranging and angle measurement information to complete guidance throughout the entire process, without requiring global coordinates from satellite navigation. It can be fully adapted to complex marine confined conditions such as satellite navigation denial, electromagnetic interference, and signal blockage, filling the technological gap of traditional guidance technology in scenarios without global positioning.

[0018] 2. This invention adopts a four-stage unidirectional irreversible mode switching logic to solve the problems of frequent mode switching, ship heading oscillation and track disorder caused by ocean disturbances, and greatly improves the stability and reliability of emergency approach operations.

[0019] 3. This invention adopts an overshoot discrimination mechanism based on track projection, which can accurately identify near-failure conditions caused by inertia and disturbance; in the overshoot circling mode, through the tangent-point circular circling retry configuration, autonomous recovery is achieved after a single operation failure, and the closed-loop fault tolerance mechanism significantly improves the success rate of emergency operations under complex sea conditions.

[0020] 4. In the mid-range fusion mode, this invention adopts an adaptive weighted fusion strategy to achieve seamless transition of guidance commands, combined with close-range small-amplitude correction and servo motor amplitude limiting constraints, which closely matches the actual motion characteristics of ships; the algorithm is lightweight and has low computational load, can be quickly embedded and deployed, and is compatible with various ship control systems.

[0021] 5. This invention breaks through the limitations of traditional unmanned vessel exclusive adaptation, and is compatible with manned vessel assisted approach and unmanned vessel autonomous approach operations. It can be widely used in various emergency approach operations such as maritime personnel search and rescue, emergency material delivery, ship docking, and navigation mark correction, and has high industrialization and engineering value.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the method provided by the present invention.

[0025] Figure 2 This is a simulation trajectory diagram of a fixed-point approach under stable sea conditions provided by the present invention.

[0026] Figure 3 This is a time-history diagram of a fixed-point approach simulation under stable sea conditions provided by the present invention.

[0027] Figure 4 This is a simulation trajectory diagram of a fixed-point approach under severe sea conditions provided by the present invention.

[0028] Figure 5 This is a time-history diagram of a fixed-point approach simulation under severe sea conditions provided by the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0030] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0031] The following is combined Figures 1 to 5 The present invention will be further described in detail below, providing a method and system for ship motion control in fixed-point approach operations: In this embodiment, as Figure 1 As shown, a method for ship motion control for fixed-point approach operations is provided, including the following steps: This invention designs a four-stage modal progressive guidance mechanism that does not rely on global coordinates from satellite navigation throughout the entire process, but only on the ship-to-target straight-line relative distance output by shipborne sensors. Target bearing relative to bow and the ship's real-time heading It completes closed-loop guidance and control for close-range operations.

[0032] Four-mode progressive guidance mechanism: This invention divides the operation into four modes based on the relative distance gradient between the ship and the target: long-range alignment mode, medium-range fusion mode, close-range approach mode, and overshoot / circling mode. The four operation modes employ unidirectional irreversible switching logic; modes can only be progressively advanced and reverse switching is prohibited. For example, the medium-range fusion mode can only switch to the close-range approach mode, and cannot switch to the long-range alignment mode or the overshoot / circling mode.

[0033] To facilitate switching between four operating modes, this invention defines four thresholds: long-distance / medium-distance switching threshold. Mid-range / near-range switching threshold Bow aiming threshold and the task reaches the accuracy threshold .in, ,when When the target approach operation is completed, the guidance process is terminated.

[0034] In this embodiment, Determined based on ship length and speed, specifically... L is the captain. Let g be the speed of the ship, and g be the acceleration due to gravity. The value can be set larger so that the ship can quickly aim and adjust its bow at a long distance. Too small a value can easily cause heading command jitter. Generally taken 1 / 2 to 2 / 3 of it is used for online connection. Generally, an angle of 10° to 20° is chosen to allow the ship to transition more smoothly from bow control to track control.

[0035] This invention constructs a four-modal guidance architecture: based on the distance gradient between the ship and the target, it divides the operation into long-range, medium-range, and short-range operation sections. At long range, pure line-of-sight guidance is used to quickly eliminate the initial heading deviation. At medium range, adaptive weighted fusion of line-of-sight guidance and reference track LOS guidance is achieved to ensure a smooth track transition. At short range, small-amplitude LOS correction is used to complete the steady-state fixed-point approach operation. At the same time, an autonomous overshoot fault discrimination mechanism is added. In response to the problem of single approach overshoot and operation failure caused by ocean waves, ocean current disturbances, and ship inertia, a circular circumferential guidance configuration with the approach target as the tangent point and the reference track as the tangent is constructed to realize autonomous fault diagnosis and cyclic repeated approach.

[0036] (1) The long-distance alignment mode of the ship.

[0037] The vessel receives the approach command, identifies the target, heads towards the target, and enters the long-range alignment mode. During its voyage, the vessel uses onboard sensors to collect local observations in real-time at fixed intervals, obtaining the vessel's real-time heading, the straight-line distance between the vessel and the target, and the target's azimuth relative to the vessel's bow. The target's azimuth relative to the vessel's bow has undergone angle normalization preprocessing and is constrained to the [-π, π] interval. All guidance angle parameters are standardized using a unified coordinate system to eliminate angle jump errors.

[0038] When a vessel receives an approach maneuver instruction, it will generally enter the long-range alignment mode; there is a small probability that it will directly enter the medium-range fusion mode (after entering the long-range alignment mode, it will immediately switch to the medium-range fusion mode); it is almost impossible for it to directly enter the close-range approach mode or the overshoot circling mode.

[0039] This embodiment focuses on approaching the target. Origin A northeast coordinate system is established; the ship's current coordinates are then calculated based on real-time local observations collected from the ship (real-time ship heading, ship-to-target straight-line distance, and target-to-ship azimuth). The calculation formula is as follows: in, The ship's current eastward coordinates, The ship's current northward coordinates, To approach the target's eastward coordinates, To approach the target's north coordinates, For real-time ship heading, The straight-line relative distance between the ship and the target. The target's azimuth relative to the bow. ; It represents the geographical line-of-sight angle from which a ship points toward a target.

[0040] Guidance and control in long-range alignment mode: In long-range alignment mode, the ship employs long-range pure line-of-sight alignment guidance. Long-range alignment mode emphasizes line-of-sight guidance to ensure target accuracy while maintaining speed. In long-range alignment mode, the initial ship-target distance is large, and the initial heading deviation is significant. Priority is given to quickly eliminating large-angle alignment deviations, employing continuous and direct line-of-sight guidance to align with the target, using bow guidance commands. for: This mode does not introduce lateral deviation constraints and prioritizes improving long-distance convergence speed.

[0041] The switching condition from long-range alignment mode to medium-range fusion mode is as follows: In long-range alignment mode, the real-time ship-to-target straight-line relative distance and the target's relative bow azimuth are compared with the long-range / medium-range switching threshold and the bow aiming threshold, respectively. When the ship-to-target straight-line relative distance is less than the long-range / medium-range switching threshold, or the absolute value of the target's relative bow azimuth is less than the bow aiming threshold, the ship enters the medium-range fusion mode. That is, when... or At that time, the ship switches from the long-distance alignment mode to the medium-distance fusion mode.

[0042] When switching modes, latching reference track parameters, including the ship's coordinates at the time of switching ( and ), ship's heading, target's bearing relative to the ship's bow, reference heading, and reference track (total distance from the ship to the approaching target).

[0043] Reference heading at the time of switching for: Total distance of the reference track at the switching time for: .in, The eastward coordinates of the ship at the time of switching. The northbound coordinates of the ship at the time of switching. To change the ship's heading at different times, The target's relative bow azimuth at the time of switching. Modulo operation.

[0044] (2) Mid-distance fusion mode of ships.

[0045] Guidance and control in mid-range fusion mode: In mid-range fusion mode, the ship employs adaptive weighted fusion forward-looking guidance. Bow guidance commands are calculated based on the ship's real-time bow direction to control the ship's approach to the target. The mid-range fusion mode dynamically calculates adaptive fusion weights based on the real-time ship-to-target straight-line relative distance, achieving a smooth transition between line-of-sight guidance and track-of-sight (LOS) guidance without abrupt changes.

[0046] The calculation process for the bow guidance command in mid-range fusion mode is as follows: S2.1: Calculate the real-time alignment command for the target point based on the ship's real-time heading and the target's azimuth relative to the ship's bow. The calculation formula is: ; S2.2: Calculate the lateral deviation of the reference track based on the ship's current coordinates, the coordinates of the approaching target, and the reference heading at the time of switching. The calculation formula is: ; S2.3: Calculate the track correction command based on the reference heading, lateral deviation of the reference track, and forward sight distance at the time of switching. The calculation formula is: in, Forward sight distance; S2.4: Adaptive fusion weights calculated based on real-time ship-to-eye straight-line relative distance The calculation formula is: in, To obtain the minimum value, To obtain the maximum value; S2.5: Calculate heading guidance commands by fusing real-time target alignment commands and trajectory correction commands using adaptive fusion weights. Achieving a smooth transition between line-of-sight guidance and trajectory guidance: .

[0047] The switching condition from medium-distance fusion mode to close-range approach mode is as follows: In medium-distance fusion mode, the real-time ship-to-eye straight-line relative distance is compared with the medium-distance / close-range switching threshold. When the ship-to-eye straight-line relative distance is less than the medium-distance / close-range switching threshold, the ship enters the close-range approach mode. That is, when... At this time, the ship switches from the mid-range fusion mode to the close-range approach mode. The mid-range / close-range switching threshold is less than the long-range / mid-range switching threshold.

[0048] (3) Close approach mode of the ship.

[0049] Guidance and control in close approach mode: The ship employs small-amplitude LOS correction guidance in close approach mode. Relying on small-amplitude LOS correction, the close approach mode counteracts ocean disturbances, achieves steady-state approach, and ensures stable approach.

[0050] As the vessel approaches the target area, it maintains its track guidance and makes minor corrections to offset slight deviations from ocean currents and waves, and approaches steadily along the locked reference course.

[0051] The calculation process for the heading guidance command in the close approach mode is as follows: The lateral deviation of the reference track is calculated based on the ship's current coordinates, the coordinates of the approach target, and the reference heading at the switching time. By combining the forward look-ahead distance and the reference heading at the switching moment, the heading guidance command is calculated. The calculation formula is expressed as: .

[0052] The switching conditions from the close approach mode to the overshooting and circling mode, and the conditions for completing the close approach operation.

[0053] In the close-range approach mode, the real-time ship-to-target straight-line relative distance is compared with the operational arrival accuracy threshold. When the ship-to-target straight-line relative distance is less than or equal to the operational arrival accuracy threshold ( Once the target approach operation is determined to be complete, the guidance process is terminated.

[0054] When the straight-line relative distance between the ship and the target exceeds the operational arrival accuracy threshold, the axial projection length of the ship on the reference track is also calculated in real time. The calculation formula is: .

[0055] When the distance exceeds the total distance of the reference track at the switching moment, overshoot failure is determined, and the ship enters the overshoot circling mode. and At that time, the ship switched from the close approach mode to the overshoot circling mode.

[0056] (4) Overshoot circling mode of the ship.

[0057] Overshoot Circling Mode Guidance and Control: In overshoot circling mode, the ship employs tangent-point circular circling guidance. Heading guidance commands are obtained based on real-time ship heading calculations, controlling the ship to periodically approach the target and perform periodic retries for a fixed-point approach. The overshoot circling mode uses circular curves, with the center dynamically determined based on the normal direction of the reference track heading. The circling radius is calculated based on the ship's length and speed, ensuring the ship's approach trajectory has no abrupt changes in heading or track curvature.

[0058] When a ship passes the target due to random factors such as ocean disturbances, it enters the overshoot circling mode. The ship moves continuously along a stable circumference, passing the tangent point of the target every time it circles, and repeatedly attempts to approach the target at a fixed point: the reference track is the tangent of the circumference, the target is the tangent point of the circumference, and the center of the circle is in the direction of the normal to the reference heading.

[0059] The calculation process for the bow guidance command in the overshoot and orbit mode is as follows: S4.1: Calculate the orbital radius based on ship length and speed, and calculate the center coordinates using the reference heading at the switching moment: in, The coordinates are eastward from the center of the circle. The coordinates are north of the center. The radius of the circle. , For the captain's weight, Weighted by speed, and It was set by humans.

[0060] S4.2: Real-time tangential command for calculating the ship's circular tracking: Calculate the ship's position relative to the center of the circle based on the center coordinates and the ship's current coordinates: , ,in, This represents the northward coordinate difference between the ship and the center of the circle. This represents the eastward coordinate difference between the ship and the center of the circle. Calculate the ship's polar angle relative to the center of the circle based on the ship's position relative to the center of the circle it orbits. The calculation formula is: ; Calculate the tangential direction of the ship along the circumference based on the ship's polar angle relative to the center of the circle. for: .

[0061] S4.3: Correction commands for calculating the ship's circular tracking based on the ship's relative position to the center of the circle and the radius of the circle. The calculation formula is: .

[0062] S4.4: Calculate the bow guidance command based on the tangential and correction commands. The calculation formula is as follows: .

[0063] In the overshoot circling mode, the relative distance between the ship and the target is monitored in real time. When it is less than or equal to the accuracy threshold of the operation, ( Once the target approach operation is determined to be complete, the guidance process is terminated.

[0064] Furthermore, this embodiment also applies a full-range steering amplitude constraint to the bow-oriented guidance command: a single-step steering saturation limit is applied to the bow-oriented guidance command throughout the entire range (long-range alignment mode, medium-range fusion mode, close-range approach mode, and overshoot / circling mode), matching the maximum steering limit of the ship's rudder to prevent hull instability and rudder saturation. The calculation formula is expressed as: in, This is the single-step steering limit value. This is the heading deviation angle.

[0065] This embodiment verifies the effectiveness of the method through the following process.

[0066] Initial moment: The ship receives the approach command at the simulation starting point. At this time, the ship's initial heading is 90°, and the target is detected at 135° to starboard of the bow, at a distance of... Meters away.

[0067] Guidance parameter settings: Long-range / medium-range switching threshold Set the distance to 80 meters for medium / short range switching. Take 50 meters as the heading aiming threshold. Take 10°, and the operation reaches the accuracy threshold. Take 0.5 meters as the circumference radius. Take 10 meters.

[0068] like Figure 2 and Figure 3 In calm sea conditions, after detecting a target, the ship first enters the long-range alignment mode (mode 1), and the ship turns rapidly. When the deviation between the bow and the target azimuth is less than 10°, it enters the medium-range fusion mode (mode 2), and at the same time generates a guidance line. It continues to approach the target using a fusion of line-of-sight guidance and track guidance, and can maintain a smooth transition with the long-range alignment mode and the close-range approach mode. When the distance to the target is less than 50 meters, it enters the close-range approach mode (mode 3), locks onto the track guidance, and accurately sails along the track line to approach the target. Figure 2 The simulated trajectory of the ship is shown in the northeast coordinate system with the approaching target as the origin. Figure 3 It demonstrates the ship's unidirectional irreversible switching between Mode 1, Mode 2 and Mode 3; and the ship's current coordinates (eastward position, northward position) in the northeast coordinate system with the target as the origin, as well as the target distance, throughout the entire approach operation.

[0069] like Figure 4 and Figure 5 In rough sea conditions, the ship also goes through long-range alignment mode, medium-range fusion mode and close-range approach mode; however, due to the interference of wind and waves in rough sea conditions, the position deviation is greater than the judgment error of 0.5 meters when passing the target. Then it enters the overshoot circling mode to perform cyclic approach. After circling around the guidance circle once, it finally sails accurately to the target.

[0070] This embodiment also provides a ship motion control system for fixed-point approach operations, including: The local observation acquisition module is used to acquire the real-time heading of the ship, the straight-line relative distance between the ship and the target, and the target's azimuth relative to the ship's bow. It then transmits these parameters to the long-range alignment mode control module, the medium-range fusion mode control module, the close-range approach mode control module, and the overshoot circling mode control module. The long-range alignment mode control module is used to receive approach operation instructions, control the vessel to approach the target, and enter the long-range alignment mode; and when the straight-line relative distance between the vessel and the target is less than the long-range / medium-range switching threshold, or the absolute value of the target's relative bow azimuth is less than the bow aiming threshold, it switches from the long-range alignment mode to the medium-range fusion mode; and records the relevant parameters of the reference track, including the total distance of the reference track at the time of switching; The mid-range fusion mode control module is used to adopt adaptive weighted fusion forward-looking guidance in mid-range fusion mode. Based on the real-time heading of the ship, the heading guidance command is calculated to control the ship to approach the target. When the straight-line relative distance between the ship and the target is less than the mid-range / close-range switching threshold, the ship switches from mid-range fusion mode to close-range approach mode. The close approach mode control module is used to control the ship to approach the target in close approach mode; and when the ship-to-target straight-line relative distance is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed; when the ship-to-target straight-line relative distance is greater than the operation arrival accuracy threshold, and the axial projection length of the ship on the reference track is greater than the total distance of the reference track at the switching time, the ship switches from close approach mode to overshoot circling mode. The super-impact circling mode control module is used to obtain the heading guidance command based on the real-time heading of the ship, and control the ship to periodically approach the target. When the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed.

[0071] This invention eliminates reliance on satellite navigation systems, enabling the entire point-to-point approach guidance operation to be completed solely based on local ranging and angle measurement information under conditions of limited perception, such as satellite navigation denial, signal blockage, and electromagnetic interference. This invention constructs a unidirectional, irreversible, multimodal, hierarchical guidance architecture, which can suppress frequent mode switching and ship trajectory oscillations caused by operational disturbances, improving the stability of the approach operation. In particular, this invention designs an overshoot circling mode; after an approach overshoot occurs, a circular circling retry mechanism is adopted to solve the problem of single approach overshoot failure, improving the fault tolerance and success rate of emergency operations. This invention is compatible with manned and unmanned vessel operation scenarios, with a lightweight and easily deployed algorithm, adaptable to various maritime emergency approach operation conditions, broadening the scope of technology applications.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling ship motion in fixed-point approach operations, characterized in that, include: The vessel receives the approach operation instruction, sails toward the approach target, and enters the long-range alignment mode; During navigation, the vessel's real-time heading, the straight-line relative distance between the vessel and the target, and the target's azimuth relative to the vessel's bow are obtained. In the long-range alignment mode, when the straight-line relative distance between the ship and the target is less than the long-range / medium-range switching threshold, or when the absolute value of the target's relative bow azimuth is less than the bow aiming threshold, the ship switches from the long-range alignment mode to the medium-range fusion mode; and records the relevant parameters of the reference track, including the total distance of the reference track at the switching time. In the mid-range fusion mode, the ship adopts adaptive weighted fusion forward-looking guidance, and obtains the heading guidance command based on the ship's real-time heading to control the ship to approach the target; In the medium-distance fusion mode, when the straight-line relative distance between the ship and the target is less than the medium-distance / close-distance switching threshold, the ship switches from the medium-distance fusion mode to the close-distance approach mode. In the close approach mode, when the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed; when the straight-line relative distance between the ship and the target is greater than the operation arrival accuracy threshold, and the axial projection length of the ship on the reference track is greater than the total distance of the reference track at the switching time, the ship switches from the close approach mode to the overshoot circling mode. In the overshoot circling mode, the ship uses tangent-point circular circling guidance. Based on the ship's real-time heading calculation, the heading guidance command is obtained to control the ship to periodically approach the target. When the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed.

2. The ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, Guidance and control for close-in operations can be completed solely based on the straight-line relative distance between the ship and the target, the target's azimuth relative to the ship's bow, and the ship's real-time heading.

3. The ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, The long-range alignment mode, mid-range fusion mode, close-range approach mode, and overshoot surround mode adopt unidirectional irreversible switching logic.

4. The ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, In tangent-point circular guidance, the ship moves continuously along a circle, with the reference track as the tangent of the circle, the approach to the target as the tangent point of the circle, the center of the circle in the direction of the reference heading normal, and the circumference is calculated based on the ship's length and speed.

5. A ship motion control method for fixed-point approach operations as described in claim 1 or 4, characterized in that, The calculation process for the bow guidance command in tangent-point circular guidance is as follows: The orbital radius is calculated based on the ship's length and speed, and the center coordinates are obtained by combining the reference heading at the switching moment. The ship's position relative to the center of the circle is calculated based on the center coordinates and the ship's current coordinates. Then, the polar angle of the ship relative to the center of the circle is calculated, and finally, the tangential command is calculated. Correction commands are calculated based on the ship's position relative to the center of the orbit and the orbital radius. The bow guidance command is calculated based on the tangential and correction commands; In the northeast coordinate system established with the approaching target as the origin, the ship's current coordinates are derived from the ship's real-time heading, the ship-to-target straight-line distance, and the target's azimuth relative to the ship's bow. The center coordinates are the coordinates in the northeast coordinate system established with the approaching target as the origin. The reference track parameters include the reference heading at the switching time.

6. The ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, axial projection length of the ship on the reference track The calculation formula is: In the northeast coordinate system established with the approaching target as the origin, The ship's current eastward coordinates, The ship's current northward coordinates, To approach the target's eastward coordinates, To approach the target's north coordinates, The eastward coordinates of the ship at the time of switching. The northbound coordinates of the ship at the time of switching; The total distance of the reference track at the switching time; relevant parameters of the reference track include and .

7. A ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, The calculation process for the heading guidance command in adaptive weighted fusion forward-looking guidance is as follows: Calculate the real-time alignment command for the target point based on the ship's real-time bow direction and the target's azimuth relative to the ship's bow. The trajectory correction command is calculated based on the ship's current coordinates, the coordinates of the approaching target, the reference heading at the time of switching, and the forward sight distance. In the northeast coordinate system established with the approaching target as the origin, the ship's current coordinates are derived from the ship's real-time bow, the ship-to-target straight-line distance, and the target's azimuth relative to the ship's bow. The relevant parameters of the reference trajectory include the reference heading at the time of switching. Adaptive fusion weights are calculated based on real-time ship-to-eye straight-line relative distance. The calculation formula is: in, The straight-line relative distance between the ship and the target. The threshold for switching between medium and short range. The total distance of the reference track at the time of switching; By using adaptive fusion weights to fuse real-time target point alignment commands and track correction commands, the heading guidance commands are calculated.

8. A ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, Long-distance / medium-distance switching threshold The calculation formula is: Where L is the length of the ship. Let g be the speed of the ship, and g be the acceleration due to gravity. The mid-range / near-range handover threshold is less than the far-range / mid-range handover threshold; The heading aiming threshold is 10°~20°.

9. A ship motion control method for fixed-point approach operations as described in claim 1, characterized in that, Single-step steering saturation limiting is applied to the bow guidance command to match the maximum steering limit of the ship's steering gear.

10. A ship motion control system for fixed-point close-range operations, characterized in that, A ship motion control method for performing a fixed-point approach operation as described in any one of claims 1 to 9 includes: The local observation acquisition module is used to acquire the ship's real-time heading, the ship-to-target straight-line relative distance, and the target's azimuth relative to the ship's bow, and transmit them to the long-range alignment mode control module, the medium-range fusion mode control module, the close-range approach mode control module, and the overshoot and surround mode control module. The long-range alignment mode control module is used to receive approach operation instructions, control the vessel to approach the target, and enter the long-range alignment mode; and when the straight-line relative distance between the vessel and the target is less than the long-range / medium-range switching threshold, or the absolute value of the target's relative bow azimuth is less than the bow aiming threshold, it switches from the long-range alignment mode to the medium-range fusion mode; and records the relevant parameters of the reference track, including the total distance of the reference track at the time of switching; The mid-range fusion mode control module is used to adopt adaptive weighted fusion forward-looking guidance in mid-range fusion mode. Based on the real-time heading of the ship, the heading guidance command is calculated to control the ship to approach the target. When the straight-line relative distance between the ship and the target is less than the mid-range / close-range switching threshold, the ship switches from mid-range fusion mode to close-range approach mode. The close approach mode control module is used to control the ship to approach the target in close approach mode; and when the ship-to-target straight-line relative distance is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed; when the ship-to-target straight-line relative distance is greater than the operation arrival accuracy threshold, and the axial projection length of the ship on the reference track is greater than the total distance of the reference track at the switching time, the ship switches from close approach mode to overshoot circling mode. The super-impact circling mode control module is used to obtain the heading guidance command based on the real-time heading of the ship, and control the ship to periodically approach the target. When the straight-line relative distance between the ship and the target is less than or equal to the operation arrival accuracy threshold, the fixed-point approach operation is determined to be completed.

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