A dynamic collision avoidance method for USV and HROV cable-stayed cooperative operation systems

Abstract

This invention discloses a dynamic collision avoidance method for a USV and HROV cable-based collaborative operation system. It integrates the construction of cable safety perception plane domain, target tracking guidance, collision avoidance decision planning, and smooth generation of control commands into a unified design. This enables the unmanned surface vessel to adjust its motion commands in real time based on obstacle status, umbilical cable status, and tracking error when performing surface tracking tasks, thus maintaining continuous tracking of the HROV while ensuring collision avoidance safety.

Description

Technical Field

[0001] This invention relates to the field of collaborative control and intelligent collision avoidance technology for marine unmanned systems, and in particular to a dynamic collision avoidance method for USV and HROV cable-tethered collaborative operation systems. Background Technology

[0002] With the increasing demands of marine engineering and underwater operations, heterogeneous marine robotic systems, consisting of unmanned surface vehicles (USVs) and hybrid remotely operated underwater vehicles (ROVs), are gradually being applied to scenarios such as submarine cable inspection. In these operations, the HROV typically performs detection and inspection tasks along a predetermined submarine cable path, while the USV tracks the cable on the surface and provides power and communication support to the HROV via an umbilical cable. Since submarine cables are often laid in near-shore waters with frequent maritime traffic, the USV is prone to encountering passing vessels while tracking the HROV, thus facing a high risk of dynamic collisions. To ensure operational safety and mission continuity, the USV needs to possess dynamic collision avoidance capabilities during tracking operations.

[0003] For example, Chinese patent document CN118457862A discloses a ship remote monitoring device and method based on the collaboration of underwater robot and surface vessel, including a motion carrier unit; the motion carrier unit includes a surface vessel that wirelessly communicates with a shore-based control center and an underwater robot that communicates with the surface vessel via wire and is carried or deployed by the surface vessel; the surface vessel includes a control cabin that carries a wireless communication module, a Beidou positioning and navigation module and a drive module, a deployment cabin that carries a deployment and recovery module and a power supply cabin that carries an onboard power supply, wherein the control cabin and the power supply cabin are located at the stern of the surface vessel.

[0004] Most existing dynamic collision avoidance technologies for unmanned surface vessels (USVs) are geared towards independently operating USVs, primarily for point-to-point collision avoidance or ensuring safe navigation while adhering to maritime collision avoidance rules. Some research has also addressed collision avoidance control in target tracking scenarios, but these typically assume no physical connection between the tracked target and the USV, making them difficult to directly apply to collaborative operations between USVs and HROVs connected by umbilical cables. Other methods use explicit modeling of cable morphology for motion planning, which accurately describes cable states but suffers from high computational complexity, making them more suitable for static environments and less effective for real-time collision avoidance in dynamic obstacle scenarios.

[0005] Furthermore, during USV tracking HROV, the umbilical cable is typically distributed in a catenary shape under the influence of gravity and fluid, and its spatial footprint may exceed the USV's projection area on the horizontal plane. Existing collision avoidance methods that rely solely on the safe distance between the USV and the obstacle vessel are insufficient to effectively reflect the collision risk between the umbilical cable and the obstacle. This could result in the USV avoiding the obstacle vessel, but the underwater umbilical cable still scraping or even entangled with the obstacle vessel's underwater structure, leading to cable wear, breakage, or system failure.

[0006] Furthermore, since the umbilical cable mechanically connects the USV and HROV, there is a significant kinematic coupling between them. When the USV performs an evasive maneuver, if the cable length is not adjusted in time, the umbilical cable may be stretched and generate significant tension, which may interfere with the HROV's inspection posture and operating trajectory, and in severe cases, may even cause equipment damage.

[0007] Therefore, there is an urgent need to provide a dynamic collision avoidance method that can simultaneously take into account continuous target tracking, dynamic obstacle avoidance, umbilical cable collision risk constraints, and cable tension risk control. Summary of the Invention

[0008] To address the challenges of simultaneously ensuring continuous target tracking, dynamic obstacle avoidance, umbilical cable safety, and cable tension risk control during the tracking of hybrid remotely operated underwater vehicles (HROVs) in existing technologies, this invention provides a dynamic collision avoidance method for USV and HROV cable-based collaborative operation systems. This method integrates cable safety perception plane domain construction, target tracking guidance, collision avoidance decision planning, and smooth generation of control commands into a unified design. This allows the unmanned surface vessel to adjust its motion commands in real time based on obstacle status, umbilical cable status, and tracking errors during surface tracking tasks, maintaining continuous tracking of the HROV while ensuring collision avoidance safety.

[0009] A dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system, characterized by the following steps: (1) Define the umbilical cable as a continuous curve connecting the USV position and the HROV position, and restrict the potential occupied area of ​​the umbilical cable in three-dimensional space to the umbilical cable ellipsoidal envelope; at the same time, construct the underwater occupied area of ​​the obstacle vessel as the obstacle vessel ellipsoidal envelope. (2) Reduce the ellipsoidal envelope of the umbilical cable and the ellipsoidal envelope of the obstacle ship to a planar safety region in the horizontal plane; when the planar safety region of the umbilical cable and the planar safety region of the obstacle ship do not intersect, it is assumed that there is no risk of collision between the umbilical cable and the obstacle ship at the current moment. (3) Based on the relative positional relationship between the USV and HROV, the nominal tracking heading of the USV is generated using line-of-sight guidance. Based on the horizontal tracking distance error between the USV and HROV, the nominal tracking speed of the USV is generated. ; In a no-collision-risk or low-risk condition, the USV nominally tracks the course. and nominal tracking speed Continuous tracking of HROV; (4) To prevent the umbilical cable from tightening due to the increased distance between the USV and HROV during the avoidance process, cable release and cable retrieval conditions are set; subsequently, based on the constructed planar safety domain, a set of prohibited speeds formed by multiple obstacle vessels is constructed. Simultaneously, a cable constraint velocity set is set. This is used to limit the separation rate of the USV and HROV within the current planning cycle; Based on the set of restricted speeds and umbilical cable constrained velocity set Define a safe speed set When the set of safe speeds is not empty, the final safe speed is obtained. ; (5) A safe speed will be obtained Convert to original heading command and original speed command The processed heading command obtained after smoothing. and speed command The final control command is sent to the USV actuator, thereby achieving a smooth transition from collision avoidance planning results to underlying motion control.

[0010] In step (1), the potential occupied area of ​​the umbilical cable in three-dimensional space is restricted to the envelope of the umbilical cable ellipsoid, specifically as follows: Set time The lower umbilical cable is the location for connecting to the USV. and HROV location The continuous curve has a released cable length of... If the sum of the distances from any point on the umbilical cable to its two endpoints is no greater than the cable length, then the potential occupied area of ​​the umbilical cable is restricted to the following set of ellipsoids. middle: ; in, This represents three-dimensional Euclidean space. This represents any point within the potential area occupied by the umbilical cable; Ellipsoid set Using the USV and HROV as two foci, an outer envelope is constructed for any spatial morphology of the umbilical cable. Furthermore, a local coordinate system is established along the principal axis of this ellipsoid, and the center point and principal axis direction of the umbilical cable ellipsoidal envelope are obtained. Finally, the representation of the umbilical cable ellipsoidal envelope in the inertial coordinate system is obtained. .

[0011] In step (1), the underwater occupied area of ​​the obstacle vessel is constructed as the ellipsoidal envelope of the obstacle vessel, specifically as follows: Let the first The length, width, and draft of the obstacle vessel are respectively... , and The obstacle vessel's course is Then the semi-axis of its ellipsoidal envelope is represented as: ; Moving the center of the ellipsoid downwards by half a draft in the vertical direction, we get: ; Accordingly, the first The ellipsoidal envelope of the obstacle ship Represented as: ; in, Indicates the first The center of the ellipsoidal envelope of the obstacle ship This indicates the position of the reference point on the water surface of the i-th obstacle vessel. Indicates the first The shape matrix of the ellipsoidal envelope of the obstacle ship.

[0012] In step (2), the ellipsoidal envelope of the obstacle vessel is reduced to a planar safety region in the horizontal plane, specifically: The horizontal cross-sections of the obstacle vessel at different depths are concentric ellipses, and at the median depth... The maximum cross-section is reached at this point, thus defining the planar safety zone of the obstacle vessel in the horizontal plane. Defined as the maximum cross section.

[0013] In step (2), the umbilical cable ellipsoidal envelope is reduced to a planar safety region in the horizontal plane, specifically as follows: For the depth range where collisions may occur within the draft of the obstacle vessel Perform stratified sampling, assuming the number of sampling layers is . Then the first Each sampling depth is: ; At each sampling depth, extract the horizontal cross-section of the umbilical cable ellipsoidal envelope. The union of all cross-sectional boundaries is defined as: ; With the USV's current position on the horizontal plane A circular planar region is constructed with the center as the boundary, covering all sampling sections and simultaneously including the safety range of the USV hull, with a radius of: ; in, For sampling dilation margin, The safe radius of the USV hull is given; therefore, the planar safe zone corresponding to the umbilical cable is defined as: ; in, For any point within the horizontal plane, It is a two-dimensional Euclidean space. for The position coordinates of the USV in the horizontal plane at that moment. In order to target the The radius of the circular planar safety zone constructed by the obstacle vessel.

[0014] In step (3), the nominal tracking heading of the USV is represented as: ; in, for At any given moment, the nominal tracking heading angle of the USV pointing towards the HROV is... and They are respectively The horizontal and vertical coordinates of HROV in the horizontal plane of the inertial coordinate system at time t. and They are respectively The horizontal and vertical coordinates of USV in the horizontal plane of the inertial coordinate system at time 1; The nominal tracking velocity vector of the USV is represented as: ; in, for At any given moment, the nominal tracking velocity vector of the USV in the horizontal plane is... This is a nominal tracking speed scalar generated based on the horizontal tracking distance error between the USV and HROV.

[0015] In step (4), the cable release condition is: ; The cable retrieval conditions are as follows: ; in, and These are the release threshold coefficient and the recovery threshold coefficient, respectively. To represent the horizontal distance between the USV and HROV, For the minimum allowable cable length, For the set of prohibited speeds, Let t be the length of the cable at the current time t.

[0016] In step (4), based on the prohibited speed set and umbilical cable constrained velocity set and define a safe speed set Specifically: ; in, This represents the set of maximum and minimum feasible speeds for the USV.

[0017] In step (4), when the safe speed set When not empty, the final safe speed is selected by the following formula: ; ; in, The objective function is defined as follows: the first term of the objective function is used to reduce the deviation between the safe speed and the nominal tracking speed to maintain tracking continuity; the second term is used to reduce the deviation between the safe speed and the current actual speed of the USV to suppress abrupt changes and improve motion smoothness.

[0018] The specific process of step (5) is as follows: Original heading instructions and original speed command They are respectively: ; ; Define the heading difference as: ; Original heading instructions Smoothing is performed to obtain the processed heading instructions. : ; For the original speed command Smoothing is performed, specifically using a first-order low-pass filter for recursive updates, to obtain the processed speed command. : ; The result obtained after the above processing and The final control command is sent to the USV actuator, thereby achieving a smooth transition from collision avoidance planning results to underlying motion control.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs a cable safety perception planar domain, transforming the three-dimensional cable collision risk into planar geometric constraints, thereby achieving cable safety constraints without explicitly solving for complex cable morphologies.

[0020] 2. By combining planar domain constraints with the velocity obstacle method and in conjunction with an online cable length management strategy, this invention can simultaneously reduce the risk of obstacle collisions and cable tension during dynamic collision avoidance.

[0021] 3. This invention improves the continuity of system operation, control stability, and adaptability to engineering applications by automatically restoring the tracking state after collision avoidance and smoothing the control commands. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a scenario corresponding to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the ellipsoidal envelope in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of a planar security domain in an embodiment of the present invention.

[0026] Figure 4 This is a flowchart illustrating the framework of a dynamic collision avoidance method for a USV and HROV cable system cooperative operation system according to an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that, unless otherwise specified, the features in the following embodiments and implementation methods can be combined with each other.

[0029] Figure 1 The illustration depicts a scenario corresponding to an embodiment of the present invention. A hybrid remotely operated underwater vehicle (HROV) typically performs detection and inspection tasks along a predetermined submarine cable path, while an unmanned surface vessel (USV) tracks the HROV from the surface, providing power and communication support via an umbilical cable. During the tracking process, the USV is prone to encountering oncoming obstacles, thus facing a high risk of dynamic collisions. To ensure operational safety and mission continuity, the USV needs to possess dynamic collision avoidance capabilities during tracking operations.

[0030] This invention provides a dynamic collision avoidance method for a USV and HROV cable-based cooperative operation system. The method focuses on solving for a safe speed, which satisfies the following optimization objective: ; and constraints: ; ; ; in, For safe speed set, To optimize the objective function for speed, For the planar security domain corresponding to the umbilical cable, For the first The planar domain corresponding to each obstacle ship. The current length of cable released. For nominal cable length, For the maximum permissible cable length, This represents the Euclidean distance between the USV and HROV. These constraints simultaneously ensure collision avoidance safety, cable safety, and prevent excessive cable tension.

[0031] like Figure 4 As shown, the present invention mainly includes the following steps: (1) Construction of the cable safety perception plane domain.

[0032] The construction of the tether safety perception planar domain is the foundation for subsequent collision avoidance decisions and planning. Since the umbilical cable is subjected to both gravity and hydrodynamic forces in actual operations, its spatial morphology is difficult to solve accurately online. This invention first conservatively encloses the potential occupied area of ​​the umbilical cable in three-dimensional space, and then transforms it into a planar safety domain suitable for USV horizontal plane motion planning, thereby characterizing the tether-related collision risks without explicit cable morphology modeling.

[0033] Specifically, such as Figure 2 As shown, let the umbilical cable at time t be the position where the USV is connected. and HROV location The continuous curve has a released cable length of... If the sum of the distances from any point on the umbilical cable to its two endpoints is no greater than the cable length, then the potential occupied area of ​​the umbilical cable can be restricted to the following set of ellipsoids: ; in, This represents three-dimensional Euclidean space. This represents any point within the potential area occupied by the umbilical cable; The aforementioned ellipsoid set, with USV and HROV as its two foci, can enclose any possible spatial shape of the umbilical cable. To facilitate subsequent calculations, a local coordinate system is further established along the principal axis of this ellipsoid, and the center point and principal axis direction of the umbilical cable ellipsoidal envelope are obtained. Its center point can be represented as: ; Its major axis unit vector can be expressed as: ; in, This represents the distance between the USV and HROV. Therefore, the semi-major and semi-minor axes of the umbilical cable ellipsoidal envelope are respectively: ; ; Therefore, the ellipsoidal envelope of the umbilical cable can be expressed in an inertial coordinate system as: ; To ensure a unified assessment of collision risks with the umbilical cable, this invention also constructs the underwater occupied area of ​​the obstacle vessel as an ellipsoidal envelope. Let the... The length, beam, and draft of the obstacle vessel are respectively... , and The obstacle vessel's course is Then the semi-axis of its ellipsoidal envelope can be expressed as: ; Considering that the position of the obstacle vessel is usually represented by a waterline reference point, the center of the ellipsoid is shifted downwards by half a draft in the vertical direction, resulting in: ; Accordingly, the first The ellipsoidal envelope of the obstacle ship can be represented as: ; in, Indicates the first The center of the ellipsoidal envelope of the obstacle ship Indicates the first The location of the obstacle vessel's surface reference point. Indicates the first The shape matrix of the ellipsoidal envelope of the obstacle ship.

[0034] After obtaining the ellipsoidal envelopes of the umbilical cable and the obstacle vessel, this invention further reduces both to a planar safety domain within the horizontal plane. For example... Figure 3 As shown, for the obstacle vessel, its horizontal cross-sections at different depths are concentric ellipses, and at the median depth... The maximum cross-section is reached at this point, therefore the planar domain of the obstacle vessel in the horizontal plane can be defined as this maximum cross-section: ; For umbilical cables, since their ellipsoidal envelope is typically inclined along the line connecting the USV and HROV, the position and size of their horizontal cross-section vary at different depths, and a single maximum cross-section cannot be simply used as a substitute. Therefore, this invention targets the depth range within the draft of the obstacle vessel where collisions may occur. Perform stratified sampling. Let the number of sampling layers be . Then the first Each sampling depth is: ; At each sampling depth, extract the horizontal cross-section of the umbilical cable ellipsoidal envelope. The union of all cross-sectional boundaries is defined as: ; To facilitate direct coupling with the subsequent velocity barrier method, this invention further uses the current position of the USV in the horizontal plane. A circular planar region is constructed with the center as the boundary, covering all sampling sections and simultaneously including the safety range of the USV hull, with a radius of: ; in, For sampling dilation margin, Let be the safety radius of the USV hull. Therefore, the planar safety domain corresponding to the umbilical cable is defined as: ; in, For any point within the horizontal plane, It is a two-dimensional Euclidean space. for The position coordinates of the USV in the horizontal plane at that moment. In order to target the The radius of the circular planar safety zone constructed by the obstacle vessel.

[0035] When the safe zone of the umbilical cable plane and the plane of the obstacle vessel do not intersect, the following condition is satisfied: ; Therefore, it is assumed that there is no risk of collision between the umbilical cable and the obstacle vessel at the current moment. Through the above-mentioned cable safety perception plane domain construction process, the originally difficult-to-handle three-dimensional cable collision problem can be transformed into a computable and constrainable geometric safety problem in the horizontal plane, providing a foundation for subsequent dynamic collision avoidance planning.

[0036] (2) Track heading and speed generation.

[0037] After completing the construction of the cable safety perception plane domain, this invention generates the nominal tracking heading of the USV based on the relative positional relationship between the USV and HROV using a line-of-sight guidance method. The nominal heading can be expressed as: ; in, for At any given moment, the nominal tracking heading angle of the USV pointing towards the HROV is... and They are respectively The horizontal and vertical coordinates of HROV in the horizontal plane of the inertial coordinate system at time t. and They are respectively The horizontal and vertical coordinates of USV in the horizontal plane of the inertial coordinate system at time t.

[0038] Regarding nominal velocity generation, the longitudinal velocity of the USV is adjusted online based on the horizontal tracking distance error between the USV and HROV. The nominal velocity satisfies: ; ; ; ; The nominal tracking velocity vector of the USV can be written as: ; in, for At any given moment, the nominal tracking velocity vector of the USV in the horizontal plane is... This is a nominal tracking speed scalar generated based on the horizontal tracking distance error between the USV and HROV.

[0039] The above formula enables the USV to continuously track the HROV at an appropriate speed and heading under conditions of no or low collision risk, and provides a reference speed input for subsequent collision avoidance planning.

[0040] (3) Collision avoidance decision-making and planning.

[0041] After obtaining the nominal tracking speed Subsequently, the present invention further performs collision avoidance decision-making and planning. First, to prevent the umbilical cable from tightening due to the increased distance between the USV and HROV during the collision avoidance process, cable release and cable retrieval conditions are set. The cable release condition is as follows: ; The cable retrieval conditions are as follows: ; Based on the above conditions, the cable length is updated online as follows: ; in, and These are the release threshold coefficient and the recovery threshold coefficient, respectively. To represent the horizontal distance between the USV and HROV, For the minimum allowable cable length, For the set of prohibited speeds, Let t be the length of the cable at the current time t.

[0042] Subsequently, based on the established planar safety domain, the prohibited speed zones corresponding to each dynamic obstacle are constructed using the speed obstacle method. For the first... For a single obstacle ship, its expanded obstacle planar domain can be represented as: ; ; ; Based on this, the first The set of finite-time velocity obstacles corresponding to each obstacle ship is: ; ; The set of prohibited speeds formed by multiple obstructing vessels is as follows: ; Considering the limited cable release rate, this invention also sets a cable constraint velocity set to limit the separation speed of the USV and HROV within the current planning cycle. The separation direction unit vector can be expressed as: ; The corresponding set of cable constraint velocities is: ; ; ; Based on this, the present invention defines the safe speed set as follows: ; in, This represents the set of maximum and minimum feasible speeds for the USV. When the set of safe speeds is not empty, the final safe speed is selected using the following formula: ; ; The first term of the objective function is used to reduce the deviation between the safe speed and the nominal tracking speed to maintain tracking continuity; the second term is used to reduce the deviation between the safe speed and the current actual speed of the USV to suppress abrupt changes and improve motion smoothness.

[0043] (4) Tracking instruction generation and smoothing.

[0044] At a safe speed Subsequently, this invention converts them into heading and speed commands executable by the underlying controller. The original heading and speed commands are as follows: ; ; To reduce control abrupt changes caused by online replanning, this invention performs smoothing processing on both heading and speed commands. The heading difference is initially defined as: ; The heading instructions are satisfied: ; The recursive update is performed using a first-order low-pass filter, and its expression is: ; The result obtained after the above processing and As the final control command, it is sent to the USV actuator, thereby achieving a smooth transition from collision avoidance planning results to underlying motion control, improving control continuity and engineering feasibility in complex dynamic environments.

[0045] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system, characterized in that, Includes the following steps: (1) Define the umbilical cable as a continuous curve connecting the USV position and the HROV position, and restrict the potential occupied area of ​​the umbilical cable in three-dimensional space to the umbilical cable ellipsoidal envelope; at the same time, construct the underwater occupied area of ​​the obstacle vessel as the obstacle vessel ellipsoidal envelope. (2) Reduce the ellipsoidal envelope of the umbilical cable and the ellipsoidal envelope of the obstacle ship to a planar safety region in the horizontal plane; when the planar safety region of the umbilical cable and the planar safety region of the obstacle ship do not intersect, it is assumed that there is no risk of collision between the umbilical cable and the obstacle ship at the current moment. (3) Based on the relative positional relationship between the USV and HROV, the nominal tracking heading of the USV is generated using line-of-sight guidance. Based on the horizontal tracking distance error between the USV and HROV, the nominal tracking speed of the USV is generated. ; In a no-collision-risk or low-risk condition, the USV nominally tracks the course. and nominal tracking speed Continuous tracking of HROV; (4) To prevent the umbilical cable from tightening due to the increased distance between the USV and HROV during the avoidance process, cable release conditions and cable retrieval conditions are set. Subsequently, based on the established planar safety domain, a set of prohibited speeds formed by multiple obstacle vessels is constructed. Simultaneously, a cable constraint velocity set is set. This is used to limit the separation rate of the USV and HROV within the current planning cycle; Based on the set of restricted speeds and umbilical cable constrained velocity set Define a safe speed set When the set of safe speeds is not empty, the final safe speed is obtained. ; (5) A safe speed will be obtained Convert to original heading command and original speed command The processed heading command obtained after smoothing. and speed command The final control command is sent to the USV actuator, thereby achieving a smooth transition from collision avoidance planning results to underlying motion control.

2. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (1), the potential occupied area of ​​the umbilical cable in three-dimensional space is restricted to the envelope of the umbilical cable ellipsoid, specifically as follows: Set time The lower umbilical cable is the location for connecting to the USV. and HROV location The continuous curve has a released cable length of... If the sum of the distances from any point on the umbilical cable to its two endpoints is no greater than the cable length, then the potential occupied area of ​​the umbilical cable is restricted to the following set of ellipsoids. middle: ； in, This represents three-dimensional Euclidean space. This represents any point within the potential area occupied by the umbilical cable; Ellipsoid set Using the USV and HROV as two foci, an outer envelope is constructed for any spatial morphology of the umbilical cable. Furthermore, a local coordinate system is established along the principal axis of this ellipsoid, and the center point and principal axis direction of the umbilical cable ellipsoidal envelope are obtained. Finally, the representation of the umbilical cable ellipsoidal envelope in the inertial coordinate system is obtained. .

3. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (1), the underwater occupied area of ​​the obstacle vessel is constructed as the ellipsoidal envelope of the obstacle vessel, specifically as follows: Let the first The length, width, and draft of the obstacle vessel are respectively... , and The obstacle vessel's course is Then the semi-axis of its ellipsoidal envelope is represented as: ； Moving the center of the ellipsoid downwards by half a draft in the vertical direction, we get: ； Accordingly, the first The ellipsoidal envelope of the obstacle ship Represented as: ； in, Indicates the first The center of the ellipsoidal envelope of the obstacle ship Indicates the first The location of the obstacle vessel's surface reference point. Indicates the first The shape matrix of the ellipsoidal envelope of the obstacle ship.

4. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (2), the ellipsoidal envelope of the obstacle vessel is reduced to a planar safety region in the horizontal plane, specifically: The horizontal cross-sections of the obstacle vessel at different depths are concentric ellipses, and at the median depth... The maximum cross-section is reached at this point, thus defining the planar safety zone of the obstacle vessel in the horizontal plane. Defined as the maximum cross section.

5. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (2), the umbilical cable ellipsoidal envelope is reduced to a planar safety region in the horizontal plane, specifically as follows: For the depth range where collisions may occur within the draft of the obstacle vessel Perform stratified sampling, assuming the number of sampling layers is . Then the first Each sampling depth is: ； At each sampling depth, extract the horizontal cross-section of the umbilical cable ellipsoidal envelope. The union of all cross-sectional boundaries is defined as: ； With the USV's current position on the horizontal plane A circular planar region is constructed with the center as the boundary, covering all sampling sections and simultaneously including the safety range of the USV hull, with a radius of: ； in, For sampling dilation margin, The safe radius of the USV hull is given; therefore, the planar safe zone corresponding to the umbilical cable is defined as: ； in, For any point within the horizontal plane, It is a two-dimensional Euclidean space. for The position coordinates of the USV in the horizontal plane at that moment. In order to target the The radius of the circular planar safety zone constructed by the obstacle vessel.

6. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (3), the nominal tracking heading of the USV is represented as: ； in, for At any given moment, the nominal tracking heading angle of the USV pointing towards the HROV is... and They are respectively The horizontal and vertical coordinates of HROV in the horizontal plane of the inertial coordinate system at time t. and They are respectively The horizontal and vertical coordinates of the USV in the horizontal plane of the inertial coordinate system at any given time; The nominal tracking velocity vector of the USV is represented as: ； in, for At any given moment, the nominal tracking velocity vector of the USV in the horizontal plane is... This is the nominal tracking speed scalar generated based on the horizontal tracking distance error between the USV and HROV.

7. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (4), the cable release condition is: ； The cable retrieval conditions are as follows: ； in, and These are the release threshold coefficient and the recovery threshold coefficient, respectively. To represent the horizontal distance between the USV and HROV, For the minimum allowable cable length, For the set of prohibited speeds, Let t be the length of the cable at the current time t.

8. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (4), based on the prohibited speed set and umbilical cable constrained velocity set and define a safe speed set Specifically: ； in, This represents the set of maximum and minimum feasible speeds for the USV.

9. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, In step (4), when the safe speed set When not empty, the final safe speed is selected by the following formula: ； ； in, The objective function is defined as follows: the first term of the objective function is used to reduce the deviation between the safe speed and the nominal tracking speed to maintain tracking continuity; the second term is used to reduce the deviation between the safe speed and the current actual speed of the USV to suppress abrupt changes and improve motion smoothness.

10. The dynamic collision avoidance method for a USV and HROV cable-stayed cooperative operation system according to claim 1, characterized in that, The specific process of step (5) is as follows: Original heading instructions and original speed command They are respectively: ； ； Define the heading difference as: ； Original heading instructions Smoothing is performed to obtain the processed heading instructions. : ； For the original speed command Smoothing is performed, specifically using a first-order low-pass filter for recursive updates, to obtain the processed speed command. : ； The result obtained after the above processing and The final control command is sent to the USV actuator, thereby achieving a smooth transition from collision avoidance planning results to underlying motion control.

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