Underactuated ship control method based on event-triggered optimal heading update strategy

Abstract

The application discloses an under-actuated ship control method based on an event-triggered environment optimal heading updating strategy, and the method comprises the following steps: S1, acquiring the motion information of the under-actuated ship under the condition of environmental disturbance according to the kinematic model of the under-actuated ship; S2, estimating the direction of the environmental disturbance combined force currently suffered by the under-actuated ship by using an extended state observer, so as to acquire the current environment optimal expected heading of the under-actuated ship; S3, constructing the environment optimal heading updating strategy based on the event-triggered mechanism according to the current environment optimal expected heading and the motion information; and S4, designing the PID controller of the under-actuated ship according to the environment optimal heading updating strategy based on the event-triggered mechanism, and realizing the optimal heading positioning control of the under-actuated ship according to the PID controller of the under-actuated ship. The application solves the problem that the traditional environment optimal position control method can make the ship work at the optimal heading angle without any environmental force measuring device, but in the ocean environment with continuously changing external disturbance, the frequent updating of the optimal expected heading angle will inevitably cause the wear of the rudder and the problem of energy consumption.

Description

Technical Field

[0001] This invention relates to the field of optimal control technology for underactuated ships, and in particular to an underactuated ship control method based on an optimal bow update strategy for an event-triggered environment. Background Technology

[0002] With the increasing depletion of land resources, humanity's demand for abundant marine resources is growing daily. Thorough exploration and research of the ocean, and the rational and effective exploitation of its resources, play an immeasurable role in the development of human society. As one of the key technologies for understeerable ships, finding the optimal bow direction for the vessel's environment is of considerable importance.

[0003] In recent years, various ship heading control strategies aimed at achieving energy conservation and emission reduction in ships have been proposed. Among them, the goal of environmentally optimal position control is to enable the offshore operating system to automatically adjust its heading according to changes in the marine environment to achieve the optimal heading angle. Ships operating at sea are subject to various environmental forces such as wind, waves, and currents. The environmentally optimal heading refers to the direction opposite to the resultant force of these environmental forces. The most significant feature of this method is that it can enable the ship to operate at the optimal heading angle without requiring any environmental force measurement devices. However, in the constantly changing marine environment, frequent updates to the optimal expected heading angle inevitably lead to wear and tear on the steering gear and increased energy consumption. Summary of the Invention

[0004] This invention provides an underactuated ship control method based on an optimal heading update strategy in an event-triggered environment, in order to overcome the above-mentioned technical problems.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for controlling an underactuated ship based on an optimal bow update strategy in an event-triggered environment includes the following steps:

[0007] S1: Based on the kinematic model of the underactuated ship, obtain the motion information of the underactuated ship under environmental disturbances; the motion information includes position data and heading data;

[0008] S2: Use the extended state observer to estimate the direction of the resultant force of the environmental disturbance currently experienced by the underactuated ship, so as to obtain the optimal expected heading of the underactuated ship in the current environment.

[0009] S3: Construct an environment-optimal heading update strategy based on an event-triggered mechanism according to the current environment's optimal expected heading and motion information;

[0010] S4: Based on the event-triggered mechanism, design the PID controller for the underactuated ship and implement the optimal heading positioning control of the underactuated ship according to the PID controller of the underactuated ship.

[0011] Furthermore, the process of obtaining the optimal expected heading of the underactuated ship in the current environment, as described in S2, specifically involves:

[0012] Based on the principle of pendulum motion in a gravitational field, the desired position p of the underactuated ship is defined on the sea surface. d With the initial virtual catenary point p c ;

[0013] The initial virtual catenary point p c That is: to determine the desired position p of the underactuated vessel. d Using the current position P of the underactuated ship as the center, compare the desired position p... d distance r c Any point on the virtual circle of ship motion obtained as the radius;

[0014] And the initial virtual catenary point p c The direction pointing to the current position P is defined as the direction θ of the resultant force of the environmental disturbance currently experienced by the underactuated ship, estimated by the extended state observer.

[0015] The opposite direction of the resultant force θ of the current environmental disturbance is the optimal expected bow direction ψ of the underactuated ship in the current environment. c .

[0016] Furthermore, S3 specifically includes the following steps:

[0017] S31: Based on the current position P of the underactuated ship and the initial virtual catenary point p c Obtain the position error, the expression for which is:

[0018]

[0019] In the formula: P c =[x c ,y c ] T With P = [x, y] T These represent the current positions of the virtual catenary point and the underactuated vessel in the northeast coordinate system, respectively; x c ,y c x and y represent the x and y coordinates of the virtual catenary point, respectively; x and y represent the x and y coordinates of the current position of the underactuated vessel, respectively.

[0020] S32: Based on the position error, obtain the desired heading angle of the underactuated vessel, the expression for which is:

[0021]

[0022] In the formula: ψ cIndicates the optimal expected heading in the current environment for an underactuated ship; x e With y e Let P represent the current position P of the underactuated vessel and the initial virtual catenary point p, respectively. c The errors in the horizontal and vertical axes;

[0023] S33: Construct the triggering conditions of the event triggering mechanism and the virtual catenary point update law based on the desired heading angle, so as to obtain the optimal heading update strategy of the environment based on the event triggering mechanism;

[0024] The event-triggered mechanism-based optimal heading update strategy is specifically as follows:

[0025] Set the detection period T of the underactuated ship sensor, and detect the angular difference between the direction of the resultant force of environmental interference at the previous trigger moment and the direction of the resultant force of the current actual environmental interference once every detection period T.

[0026] And determine whether the triggering condition of the event triggering mechanism is met when the direction angle difference reaches a preset threshold;

[0027] The triggering condition expression for the event triggering mechanism is as follows:

[0028] t k+1 =inf{t>t k |C(θ(t k ),θ(t))>ω},t∈[t k ,t k+1 )

[0029] In the formula: C(θ(t) k ),θ(t)) represents the event triggering judgment function; θ(t) k ) and θ(t) represent the previous trigger time t, respectively. k The directional angle relative to the current actual environmental interference, where ω represents the preset threshold for changes in environmental interference; t represents the current time.

[0030] If the triggering conditions of the event triggering mechanism are met, the initial virtual catenary point is updated based on the virtual catenary point update law to update the current environment's optimal expected heading and obtain the environment's optimal expected heading angle.

[0031] The expression for the virtual catenary update law is:

[0032]

[0033]

[0034]

[0035] In the formula: P d =[x d,y d ] T Indicates the desired position in the given northeast coordinate system; x s ,y d Represent the x and y coordinates of the desired position, respectively; r c >0 indicates a virtual radius; ψ d p d p c The angle between the straight line and the north direction; Represents ψ d The update rate; k(ε), k ε Both ε and ξ represent design parameter variables, and both ε and ξ represent adaptive design parameters. Represents ψ c Update rate;

[0036] Otherwise, if the triggering conditions of the event triggering mechanism are not met, the detection will continue according to the detection period T until the triggering conditions of the event triggering mechanism are met.

[0037] Furthermore, S4 specifically includes the following steps:

[0038] S41: Update the current position P of the underactuated ship using an environment-optimal heading update strategy based on an event-triggered mechanism, according to the current position P of the underactuated ship and the initial virtual catenary point p. c The position error is used to obtain the current position P of the underactuated vessel from the initial virtual catenary point p. c Radial distance error P e ;

[0039] The radial distance error P e The expression is

[0040]

[0041] P e =P0-r c

[0042] In the formula: P0 represents the current position P of the underactuated vessel and the initial virtual catenary point p. c Positional distance error;

[0043] S42: From the current position P of the underactuated vessel to the initial virtual catenary point p c Radial distance error P e With heading error ψ e Obtain the desired longitudinal velocity u of the underactuated ship. d With bow rotation speed r d ;

[0044] The desired longitudinal velocity u of the underactuated vessel d With bow rotation speed rd The expression is

[0045]

[0046]

[0047] In the formula: u max This indicates the maximum pitch speed of an underdriven vessel; r max ψ represents the maximum bow turning speed of the underactuated vessel; Δu>0 and Δr>0 both represent design parameters; e =ψ c -ψ represents the distance from the current position P of the underactuated vessel to the initial virtual catenary point p. c The heading error ψ e ;

[0048] S43: Based on the desired longitudinal speed u of the underactuated vessel d With bow rotation speed r d Define the velocity error u of the desired longitudinal velocity. e Speed ​​error r with bow rotation speed e The expression is

[0049] u e =uu d

[0050] r e =rr d

[0051] S44: Based on the velocity error u of the desired longitudinal velocity e Speed ​​error r with bow rotation speed e Design a PID controller for an underactuated vessel. The expression for the PID controller of the underactuated vessel is as follows:

[0052]

[0053]

[0054] In the formula: τ u With τ r These represent the longitudinal control force and bow turning moment of an underactuated vessel, respectively; K p K i and K d These are all proportional coefficients of the design parameters in the PID controller.

[0055] Furthermore, the expression for the kinematic model of the underactuated ship described in S1 is as follows:

[0056]

[0057]

[0058] In the formula: η=[xy ψ] T With v = [uvr] T ψ represents the position, attitude, and velocity of the underactuated vessel, respectively; x, y, and ψ represent the actual northeast position and heading angle of the corresponding underactuated vessel, respectively; u, ν, and r represent the sway velocity, roll velocity, and heading angular velocity of the underactuated vessel, respectively; J(ψ) represents the transformation matrix.

[0059] Beneficial Effects: This invention provides a control method for underactuated ships based on an event-triggered optimal heading update strategy. It utilizes an extended state observer to estimate the direction of the resultant force of environmental disturbances currently experienced by the underactuated ship, thereby obtaining the current optimal desired heading. An event-triggered mechanism based on changes in the direction of marine environmental disturbances is integrated into the optimal heading update strategy, resulting in an event-triggered optimal heading update strategy. This strategy is then used to design a PID controller for the underactuated ship, and the optimal heading positioning control is achieved based on the PID controller. This effectively reduces the wear and tear caused by frequent servo movements due to frequent updates of the optimal desired heading in variable marine environments, enabling the adjustment and updating of the underactuated ship's heading, thereby improving navigation efficiency and reducing energy consumption. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 This is a flowchart of the underactuated ship control method based on the optimal bow update strategy of the event-triggered environment according to the present invention;

[0062] Figure 2 This is a schematic diagram of the core process of the underactuated ship control method based on the optimal bow update strategy of the event-triggered environment in this embodiment;

[0063] Figure 3 This is a schematic diagram illustrating the principle of updating the optimal heading virtual catenary point in this embodiment.

[0064] Figure 4 This is a schematic diagram illustrating the analogy between the motion of a pendulum in a gravitational field and that of an underactuated ship in this embodiment;

[0065] Figure 5 This is a flowchart of the event triggering mechanism in this embodiment. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0067] This embodiment provides an underactuated ship control method based on an optimal bow update strategy in an event-triggered environment, such as... Figures 1 to 2 As shown, it includes the following steps:

[0068] S1: Based on the kinematic model of the underactuated ship, obtain the motion information of the underactuated ship under environmental disturbances; the motion information includes position data and heading data;

[0069] Specifically, the expression for the kinematic model of the underactuated ship is as follows:

[0070]

[0071]

[0072] In the formula: η=[xy ψ] T With v = [uvr] T ψ represents the position, attitude, and velocity of the underactuated vessel, respectively; x, y, and ψ represent the actual northeast position and heading angle of the underactuated vessel in the set northeast coordinate system, respectively; u, ν, and r represent the pitch velocity, sway velocity, and heading angular velocity of the underactuated vessel, respectively; J(ψ) represents the transformation matrix.

[0073] S2: Use the extended state observer to estimate the direction of the resultant force of the environmental disturbance currently experienced by the underactuated ship, so as to obtain the optimal expected heading of the underactuated ship in the current environment.

[0074] Specifically, obtaining the optimal expected heading of the underactuated vessel in the current environment involves:

[0075] Based on the principle of pendulum motion in a gravitational field, the desired position p of the underactuated ship is defined on the sea surface. d With the initial virtual catenary point p c ;

[0076] The initial virtual catenary point p c That is: to determine the desired position p of the underactuated vessel. d Using the current position P of the underactuated ship as the center, compare the desired position p... d distance r c Any point on the virtual circle of ship motion obtained as the radius;

[0077] And the initial virtual catenary point p c The direction pointing to the current position P is defined as the direction θ of the resultant force of the environmental disturbance currently experienced by the underactuated ship, estimated by the extended state observer.

[0078] The opposite direction of the resultant force θ of the current environmental disturbance is the optimal expected bow direction ψ of the underactuated ship in the current environment. c .

[0079] In this embodiment, based on the motion law of the pendulum under the action of gravity, the thrust required by the propeller is minimized when the resultant force of the underactuated ship and the marine environmental disturbance force are on the same straight line and the bow direction is opposite to the direction of the resultant force of the disturbance force. Therefore, taking the opposite direction of the resultant force of the marine environmental disturbance force (the environmentally optimal bow direction) as the desired bow direction of the underactuated ship can significantly reduce the energy consumption of the propeller. The schematic diagram of updating the virtual catenary line points according to the change of the direction of the disturbance force is shown below. Figure 3 As shown, P is the current location of the underactuated vessel. d p represents the desired position of the underdriven vessel. c p represents the initial virtual catenary point. c In p d With p as the center, the ship's initial position is... d The distance is on a circle with radius p. c The distance to the ship's initial position is equal to p d The distance r to the ship's initial position c =‖p c -p d ‖ represents the length of the virtual catenary, ψ d p d p c The angle between the straight line and the actual north direction, where the virtual catenary point update process is described as: p c In p d Center r c Rotate clockwise by an angle (ψ) on a virtual circle with radius . d -ψ c At this point, the virtual catenary point is updated to p'. c When the underdriven vessel is in the desired position p d And the bow points to p' c This ensures that it is in the optimal heading of the environment, at which point ψ = ψ c =θ ± 180° (-180° ≤ ψ ≤ 180°). For example... Figure 4As shown, the motion of an underactuated ship is analogous to the pendulum principle in a gravitational field. Regardless of the initial position of the pendulum, it will move in a circle under the influence of the Earth's gravity and the traction force of the pendulum rope and eventually stop at a stable equilibrium point. By defining a virtual suspension point and a circle radius on the sea surface, while ensuring that the ship is on the arc defined by the circle radius, the ship is guided to point in the direction of the suspension point, thus generating a pendulum effect. Finally, the external environmental disturbance force will push the ship to the optimal bow direction and achieve stability.

[0080] S3: Construct an environment-optimal heading update strategy based on an event-triggered mechanism according to the current environment's optimal expected heading and motion information, specifically including the following steps:

[0081] S31: Based on the current position P of the underactuated ship and the initial virtual catenary point p c Obtain the position error, the expression for which is:

[0082]

[0083] In the formula: P c =[x c ,y c ] T With P = [x, y] T These represent the current positions of the virtual catenary point and the underactuated vessel in the northeast coordinate system, respectively; x c ,y c x and y represent the x and y coordinates of the virtual catenary point, respectively; x and y represent the x and y coordinates of the current position of the underactuated vessel, respectively.

[0084] S32: Based on the position error, obtain the desired heading angle of the underactuated vessel, the expression for which is:

[0085]

[0086] In the formula: ψ c Indicates the optimal expected heading in the current environment for an underactuated ship; x e With y e Let P represent the current position P of the underactuated vessel and the initial virtual catenary point p, respectively. c The errors in the horizontal and vertical axes;

[0087] S33: Construct the triggering conditions of the event triggering mechanism and the virtual catenary point update law based on the desired heading angle, so as to obtain the optimal heading update strategy of the environment based on the event triggering mechanism;

[0088] like Figure 5 As shown, the environment-optimal heading update strategy based on the event-triggered mechanism is specifically as follows:

[0089] Set the detection period T of the underactuated ship sensor, and detect the angular difference between the direction of the resultant force of environmental interference at the previous trigger moment and the direction of the resultant force of the current actual environmental interference once every detection period T.

[0090] And determine whether the triggering condition of the event triggering mechanism is met when the direction angle difference reaches a preset threshold;

[0091] In this embodiment, the event-triggered mechanism refers to a mechanism where the system triggers a corresponding operation or processing flow only when a specific event occurs. Under this mechanism, the system does not continuously monitor and process data, but waits for a specific event to occur before executing the corresponding operation. This mechanism helps improve system efficiency and performance, and reduces resource waste. The triggering condition expression for the event-triggered mechanism is as follows:

[0092] t k+1 =inf{t>t k |C(θ(t k ),θ(t))>ω},t∈[t k ,t k+1 )

[0093] In the formula: C(θ(t) k ),θ(t)) represents the event triggering judgment function; θ(t) k ) and θ(t) represent the previous trigger time t, respectively. k The directional angle relative to the current actual environmental interference, where ω represents the preset threshold for changes in environmental interference; t represents the current time.

[0094] If the triggering conditions of the event triggering mechanism are met, the initial virtual catenary point is updated based on the virtual catenary point update law to update the current environment's optimal expected heading and obtain the environment's optimal expected heading angle.

[0095] like Figure 3 As shown, p is updated in real time. c Position (p) c In p d With the center of the circle, r c Move to p' on a virtual circle with radius p' c To achieve the goal of maintaining the underactuated vessel at the desired position with optimal heading p d Near point, the expression for the virtual catenary point update law is:

[0096]

[0097]

[0098]

[0099] In the formula: P d =[xd ,y d ] T Indicates the desired position in the given northeast coordinate system; x d ,y d Represent the x and y coordinates of the desired position, respectively; r c >0 indicates a virtual radius; ψ d p d p c The angle between the straight line and the north direction; Represents ψ d The update rate; k(ε), k ε Both ε and ξ represent design parameter variables, and both ε and ξ represent adaptive design parameters. Represents ψ c The update rate is ψ. c First derivative; k ε >0 can control the rate of change of ε through the above update law. It can be updated in real time. c The position allows the underactuated vessel to obtain the environmentally optimal expected heading angle;

[0100] Otherwise, if the triggering conditions of the event triggering mechanism are not met, the detection will continue according to the detection period T until the triggering conditions of the event triggering mechanism are met.

[0101] S4: Based on the event-triggered optimal heading update strategy, design a PID controller for the underactuated ship, and implement optimal heading positioning control of the underactuated ship using the PID controller. Specifically, this includes the following steps:

[0102] S41: Update the current position P of the underactuated ship according to the environment-optimal heading update strategy based on the event-triggered mechanism, and update the current position P of the underactuated ship according to the initial virtual catenary point p. c The position error is used to obtain the current position P of the underactuated vessel from the initial virtual catenary point p. c Radial distance error P e ;

[0103] The radial distance error P e The expression is

[0104]

[0105] P e =P0-r c

[0106] In the formula: P0 represents the current position P of the underactuated vessel and the initial virtual catenary point p. c Positional distance error;

[0107] S42: From the current position P of the underactuated vessel to the initial virtual catenary point p c Radial distance error P e With heading error ψ e Obtain the desired longitudinal velocity u of the underactuated ship. d With bow rotation speed r d ;

[0108] To ensure that the underactuated vessel moves on the virtual circle of its motion and always maintains its bow pointing towards the virtual catenary point, i.e., to guarantee the position error P e With heading error ψ e The desired longitudinal velocity u of the underactuated ship is designed to converge within any small zero-value neighborhood. d and bow rotation speed r d The desired longitudinal speed u of the underactuated vessel d With bow rotation speed r d The expression is

[0109]

[0110]

[0111] In the formula: u max This indicates the maximum pitch speed of an underdriven vessel; r max This represents the maximum bow turning speed of the underactuated vessel; Δu>0 and Δr>0 both represent design parameters; ψ e =ψ c -ψ represents the distance from the current position P of the underactuated vessel to the initial virtual catenary point p. c The heading error ψ e ;

[0112] S43: Based on the desired longitudinal speed u of the underactuated vessel d With bow rotation speed r d Define the velocity error u of the desired longitudinal velocity. e Speed ​​error r with bow rotation speed e The expression is

[0113] u e =uu d

[0114] r e =rr d

[0115] S44: Based on the velocity error u of the desired longitudinal velocity e Speed ​​error r with bow rotation speed e Design a PID controller for an underactuated vessel. The expression for the PID controller of the underactuated vessel is as follows:

[0116]

[0117]

[0118] In the formula: τ u With τ r These represent the longitudinal control force and bow turning moment of an underactuated vessel, respectively; K p K i and K d These are all proportional coefficients of the design parameters in the PID controller.

[0119] In this embodiment, since controlling the ship's heading inevitably consumes energy, a method for controlling an underactuated ship with an environmentally optimal heading update strategy is proposed to reduce energy consumption. This method uses an extended state observer to estimate the direction of the resultant force of environmental disturbances currently experienced by the underactuated ship, thereby obtaining the current environmentally optimal desired heading. An event-triggered mechanism based on changes in the direction of marine environmental disturbances is integrated into the environmentally optimal heading update strategy to obtain the event-triggered environmentally optimal heading update strategy. This strategy is then used to design a PID controller for the underactuated ship, and the optimal heading positioning control of the underactuated ship is achieved based on the PID controller. This effectively reduces the wear and tear caused by frequent rudder movements due to frequent updates of the optimal desired heading in a variable marine environment, realizing the adjustment and updating of the underactuated ship's heading to improve navigation efficiency and reduce energy consumption. Unlike typical ship heading update strategies, this embodiment adds an event triggering mechanism so that the predetermined target heading angle only needs to be changed when the disturbance changes significantly. This avoids wear caused by frequent servo motor movements when the disturbance changes are minor.

[0120] 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling an underactuated ship based on an event-triggered environment-optimal heading update strategy, characterized in that, Includes the following steps: S1: Based on the kinematic model of the underactuated ship, obtain the motion information of the underactuated ship under environmental disturbances; the motion information includes position data and heading data; S2: Use the extended state observer to estimate the direction of the resultant force of the environmental disturbance currently experienced by the underactuated ship, so as to obtain the optimal expected heading of the underactuated ship in the current environment. S3: Construct an environment-optimal heading update strategy based on an event-triggered mechanism according to the current environment's optimal expected heading and motion information; specifically including the following steps: S31: Based on the current position of the underactuated vessel With the initial virtual catenary point Obtain the position error, the expression for which is: In the formula: and These represent the current positions of the virtual catenary point and the underactuated vessel in the northeast coordinate system, respectively. These represent the x and y coordinates of the virtual catenary point, respectively. These represent the x and y coordinates of the underactuated vessel's current position, respectively. The initial virtual catenary point That is: to determine the desired position of the underactuated vessel. Using the current position of the underdriven ship as the center, With desired location distance Any point on the virtual circle of ship motion obtained as the radius; S32: Based on the position error, obtain the desired heading angle of the underactuated vessel, the expression for which is: In the formula: This represents the optimal expected heading in the current environment for an underactuated vessel. and These represent the current positions of the underdriven vessel. With the initial virtual catenary point The errors in the horizontal and vertical axes; S33: Construct the triggering conditions of the event triggering mechanism and the virtual catenary point update law based on the desired heading angle, so as to obtain the optimal heading update strategy of the environment based on the event triggering mechanism; The event-triggered mechanism-based optimal heading update strategy is specifically as follows: Set the detection period T of the underactuated ship sensor, and detect the angular difference between the direction of the resultant force of environmental interference at the previous trigger moment and the direction of the resultant force of the current actual environmental interference once every detection period T. And determine whether the triggering condition of the event triggering mechanism is met when the direction angle difference reaches a preset threshold; The triggering condition expression for the event triggering mechanism is as follows: In the formula: This is represented as an event triggering judgment function; and These represent the previous trigger time. The directional angle relative to the current actual environmental interference, This represents a preset threshold for changes in environmental disturbances; Indicates the current time; If the triggering conditions of the event triggering mechanism are met, the initial virtual catenary point is updated based on the virtual catenary point update law to update the current environment's optimal expected heading and obtain the environment's optimal expected heading angle. The expression for the virtual catenary update law is: In the formula: This represents the desired position in the given northeast coordinate system; These represent the x-coordinate and y-coordinate of the desired position, respectively. Indicates the virtual radius; express The angle between the straight line and the north direction; express Update rate; All represent design parameter variables. Indicates adaptive design parameters; express Update rate; Otherwise, if the triggering conditions of the event triggering mechanism are not met, the detection will continue according to the detection period T until the triggering conditions of the event triggering mechanism are met. S4: Based on the event-triggered mechanism, design the PID controller for the underactuated ship and implement the optimal heading positioning control of the underactuated ship according to the PID controller of the underactuated ship.

2. The underactuated ship control method based on an event-triggered environment optimal heading update strategy according to claim 1, characterized in that, The process described in S2 for obtaining the optimal expected heading in the current environment of the underactuated ship is as follows: Based on the principle of pendulum motion in a gravitational field, the desired position of the underactuated ship is defined on the sea surface. With the initial virtual catenary point ; and the initial virtual catenary point Point to current position The direction is defined as the direction of the resultant force of environmental disturbances currently experienced by the underactuated ship, estimated by the extended state observer. ; The direction of the resultant force of the current environmental disturbance. The opposite direction is the optimal expected heading for the underactuated ship in the current environment. .

3. The underactuated ship control method based on an event-triggered environment optimal heading update strategy according to claim 1, characterized in that, S4 specifically includes the following steps: S41: An event-triggered, environment-optimal heading update strategy updates the current position of the underactuated ship. Based on the current position of the underdriven vessel With the initial virtual catenary point The position error is used to obtain the current position of the underactuated vessel. To the initial virtual catenary point radial distance error ; radial distance error The expression is In the formula: Indicates the current position of the underdriven vessel. With the initial virtual catenary point Positional distance error; S42: Based on the current position of the underactuated vessel To the initial virtual catenary point radial distance error With heading error To obtain the desired longitudinal velocity of the underactuated ship With bow turning speed ; The desired longitudinal speed of the underactuated vessel With bow turning speed The expression is In the formula: This indicates the maximum pitch speed of an underactuated vessel. This indicates the maximum bow turning speed of an underdriven vessel; All represent design parameters; Current position of the under-driven ship To the initial virtual catenary point Heading error ; This indicates the heading angle of the corresponding underactuated vessel; S43: Based on the desired longitudinal speed of the underactuated vessel With bow turning speed Define the velocity error of the desired longitudinal velocity. Speed ​​error with bow rotation speed The expression is In the formula: This indicates the pitching speed and bow turning angular velocity of an underactuated vessel. S44: Velocity error based on the desired longitudinal velocity Speed ​​error with bow rotation speed Design a PID controller for an underactuated vessel. The expression for the PID controller of the underactuated vessel is as follows: In the formula: and These are respectively expressed as the longitudinal control force and the bow turning moment of an underactuated vessel; 、 as well as These are all proportional coefficients of the design parameters in the PID controller.

4. The underactuated ship control method based on an event-triggered environment optimal heading update strategy according to claim 1, characterized in that, The expression for the kinematic model of the underactuated ship described in S1 is as follows: In the formula: and These represent the position, attitude, and velocity of the underactuated vessel, respectively. These represent the actual northeast position and heading angle of the corresponding underdriven vessel, respectively; These represent the pitching speed, sway speed, and bow turning angular velocity of the underactuated vessel, respectively. This represents the transformation matrix.

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