A heading-keeping control method based on a dual feedback mechanism

Abstract

This invention discloses a course-keeping control method based on a dual feedback mechanism, belonging to the field of ship course control and maintenance. The method includes the following steps: acquiring the forces under the coupled interference of wind, waves, and current; obtaining ship position data during navigation based on the forces under the coupled interference of wind, waves, and current; processing the ship position data during navigation to obtain the ship's trajectory; subtracting the trajectory data from the ship's heading data to obtain the combined pressure difference generated by the ship under the coupled interference of wind, waves, and current; using the dual feedback signal obtained by combining the combined pressure difference under the coupled interference of wind, waves, and current and the heading feedback signal as the input signal, and designing a controller using a closed-loop gain shaping algorithm to generate rudder angle commands to achieve trajectory tracking control.

Description

Technical Field

[0001] This invention belongs to the field of ship course control and maintenance, and relates to a course maintenance control method based on a dual feedback mechanism. Background Technology

[0002] When ships navigate at sea, external environmental factors such as wind, waves, and currents can easily cause deviations from the planned route, resulting in drift. This drift can lead to ships straying from their course and entering dangerous areas, increasing the risk of grounding or hitting reefs. In congested waters, drifting increases the likelihood of collisions with other vessels and offshore facilities. In maritime practice, to overcome the effects of wind, waves, and currents on ship drift, ship operators often rely on their experience to manually compensate for these errors. This process involves subjectivity and operational errors. Frequent adjustments to course and speed also consume additional time, extending course time and affecting transport timeliness. Continuously adjusting the ship's motion increases main engine power output, leading to increased fuel consumption and higher operating costs. Therefore, addressing the impact of combined pressure differences caused by wind, waves, and currents on ship navigation safety, as well as the inaccuracies, instabilities, and insensitivity in manually measuring and adjusting environmental pressure differences, on navigation efficiency, is crucial for maintaining a ship's course.

[0003] Several feasible research methods exist, such as the ship heading control method based on a nonlinear composite function disclosed in patent CN202411151791.8 under severe sea conditions. This method includes the following steps: establishing a Nomoto ship motion model; designing a controller based on the Nomoto ship motion model using a third-order closed-loop gain shaping algorithm; incorporating wind and wave interference into the Nomoto ship model to obtain a ship motion model for severe sea conditions; designing a nonlinear composite function based on the ship motion model for severe sea conditions; combining the nonlinear composite function with the controller to obtain an integrated controller; and achieving effective heading control under severe sea conditions based on the integrated controller. This method, by cascading the nonlinear composite function between the PD controller and the second-order oscillating element, can better achieve the purpose of heading control and reduces rudder angle output, resulting in better energy-saving effects.

[0004] Most current research methods do not consider external environmental disturbances during ship navigation separately, nor do they calculate the impact of disturbances and pressure differences caused by factors such as wind, waves, and currents on the ship's course maintenance. Summary of the Invention

[0005] To address the aforementioned problems, the technical solution adopted by this invention is: a heading-keeping control method based on a dual feedback mechanism, comprising the following steps:

[0006] Obtain the interference models for wind, waves, and flow;

[0007] The interference models of wind, waves, and current are used to obtain the forces under the coupled interference of wind, waves, and current on ships, considering the coupled interference of wind, waves, and current.

[0008] Acquire the navigation position data of the ship model under the coupled interference forces of wind, wave and current disturbances;

[0009] The ship's position data during navigation is processed using the least squares method to obtain the ship's trajectory.

[0010] The difference between the trajectory data and the ship's bow data is used to obtain the combined pressure difference generated by the ship under the coupled interference of wind, wave and current.

[0011] The dual feedback signal obtained by combining the combined pressure difference under the coupled interference of wind, wave and current interference and the bow feedback signal is used as the input signal. A controller is designed using a closed-loop gain shaping algorithm to generate rudder angle commands to achieve tracking control of the course.

[0012] Furthermore: the specific calculation formula for the combined pressure difference generated by the ship under the coupled interference of wind, waves, and current is as follows:

[0013]

[0014] In the formula: For the combined pressure difference, For the ship's trajectory relative to the ground, It's the bow of the ship.

[0015] Furthermore, the force expression for the coupled interference of wind, waves, and current on the ship is as follows:

[0016] in, The combined force of wind, waves, and current interference The wind-wave modulation coefficient, The flow-wind modulation coefficient, For flow direction, For average wind-induced lateral force, The resultant force of the high-frequency primary wave force along the y-axis; For wind angle, The absolute direction of the flow. The lateral force exerted by the water flow on the hull;

[0017] When the wind and waves are in different directions, the impact on the ship's course is significantly different; the direction of the tidal current also modulates the direction of wave propagation, changing the encounter frequency, thereby achieving indirect interference coupling.

[0018] Furthermore, the formula for determining the wind-wave modulation coefficient is as follows:

[0019]

[0020] The formula for determining the flow-wind modulation coefficient is as follows:

[0021]

[0022] in: , The coupling strength constant is , Take 0.1, Take 0.05, , These are standardized parameters used for dimensionless processing. Take 10 m / s, Taking 2m as the trigonometric function term of the direction angle, dynamic modulation of the enhancement and cancellation of interference between environmental factors is achieved.

[0023] Furthermore: The process of designing a controller using a closed-loop gain shaping algorithm is as follows: The dual feedback signal obtained by combining the corrected signal of the combined pressure difference under the coupled interference of wind, wave, and current interference with the bow feedback signal is used as the input signal:

[0024] Second-order linearized model transfer function for:

[0025]

[0026] The yaw rate index represents the steady yaw rate per unit rudder angle when a ship enters a steady turn after being steered. The following index represents the time constant during which the angular acceleration of a ship approaches a steady angular velocity after it has been steered.

[0027] Let the bandwidth frequency of the closed-loop system be... Then, at this time, the complementary sensitivity function of the ship's heading control system... That is, the closed-loop transfer function of the system is:

[0028]

[0029] Then the controller for:

[0030]

[0031] in: The bandwidth frequency set for the closed-loop system. It is a constant.

[0032] Furthermore, the process of processing the ship's position data during navigation based on the least squares method to obtain the ship's trajectory is as follows:

[0033] For a set of points on a two-dimensional plane where the ship is located ( , ), =1, 2, 3, ... Where i and n are positive integers; assume a set of points on a two-dimensional plane satisfy a linear relationship. ,in and These are coefficients to be determined. It is an error term, and They are independent and follow a pattern with a mean of 0 and a variance of . The normal distribution;

[0034] The goal of the least squares method is to minimize the sum of squared errors. Minimum, The formula is

[0035]

[0036] in, The horizontal coordinate of the ship's position. The vertical coordinate of the ship's position. and These are the fitting parameters;

[0037] To find smallest and , respectively and Find the partial derivatives and set them to zero to determine the... and The value;

[0038] right Find the partial derivatives as follows:

[0039]

[0040] Expanding, we get: Further obtained ,in Indicates the preceding The average value of the x-coordinate of each ship's position. Indicates the preceding The average of the longitudinal coordinates of each ship's position;

[0041] right Find the partial derivatives as follows:

[0042]

[0043] Will Substituting into the above formula: In the formula for finding partial derivatives:

[0044]

[0045] When the number of collected coordinate points reaches a certain threshold When, select the previous By fitting the line to a given number of points, the slope of the fitted line can be obtained. That is, the direction of the ship's trajectory :

[0046] .

[0047] This invention provides a course-keeping control method based on a dual feedback mechanism. The method includes: First, processing the ship's position data during navigation using real-time ship navigation data and the least squares method to obtain the ship's track heading. Then, combining this with the bow heading obtained from a compass sensor, the resultant pressure difference is calculated, solving the problem of accurately predicting or measuring various environmental disturbances. Based on this, an innovative course-keeping control method is proposed. In addition to traditional bow heading feedback control, a correction signal based on the resultant pressure difference measured by GPS and compass sensors is added. The reference signal is continuously corrected through dual feedback technology, thus breaking through the traditional control method based on bow heading tracking of the planned course and achieving precise tracking of the track heading and the planned course. Simulation results verify the effectiveness of the proposed method, showing that dual feedback control based on measured resultant pressure difference can significantly improve the ship's course-keeping capability and effectively reduce the impact of external environmental fluctuations on ship motion. In summary, this invention not only improves the automation level of ship navigation but also ensures that ships can safely and accurately navigate along the planned course, possessing significant practical application value.

[0048] It has the following advantages:

[0049] 1. Improve heading accuracy: Through a dual feedback mechanism, the impact of environmental disturbances on the heading is significantly reduced.

[0050] 2. Enhanced system stability: The controller is designed with strong robustness and adapts to complex sea conditions.

[0051] 3. Reduced need for manual intervention: High degree of automation reduces human error. Attached Figure Description

[0052] 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.

[0053] Figure 1 This is a flowchart of the present invention;

[0054] Figure 2 This is a schematic diagram of the controller;

[0055] Figure 3 This is a schematic diagram for calculating average wind speed.

[0056] Figure 4 A schematic diagram of wave force;

[0057] Figure 5 A schematic diagram of flow interference;

[0058] Figure 6 This is a schematic diagram of the combined pressure difference;

[0059] Figure 7 This is a schematic diagram of the trajectory and bow direction of a conventional feedback controller.

[0060] Figure 8 A schematic diagram of the dual feedback controller's trajectory and bow direction;

[0061] Figure 9 A comparison chart of flight paths;

[0062] Figure 10 A comparison diagram of flight paths;

[0063] Figure 11 This is a comparison diagram of the bow and arrow directions;

[0064] Figure 12 A comparison diagram of rudder angles;

[0065] Figure 13 This is a comparison chart of combined pressure differences. Detailed Implementation

[0066] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0067] 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, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0068] Figure 1 This is a flowchart of the present invention;

[0069] A heading-keeping control method based on a dual feedback mechanism includes the following steps:

[0070] S1: Obtain the interference models of wind, waves, and flow;

[0071] S2: Based on the wind interference model, wave interference model and flow interference model, considering the coupled interference of wind, waves and flow, the forces under the coupled interference of wind, wave and flow interference of the ship are obtained;

[0072] S3: Obtain the navigation position data of the ship model under the coupled interference forces of wind, wave and current interference;

[0073] S4: The ship's position data during navigation is processed based on the least squares method to obtain the ship's trajectory; the ship's position data is acquired in real time via GPS, and the ship's heading data is acquired in real time via a compass sensor;

[0074] The ship's trajectory points are fitted using the least squares method to calculate the current trajectory direction. The number of fitted points is adaptively adjusted according to the bow roll rate to improve the accuracy of the dynamic trajectory curve.

[0075] S5: Subtract the trajectory data from the ship's heading data to obtain the combined pressure difference generated by the ship under the coupled interference of wind, wave, and current; the heading data is provided by the compass sensor;

[0076] Here, the combined pressure difference refers to the total effect of wind pressure difference, current pressure difference, and wave pressure difference on a ship, causing it to deviate from its intended course. Wind pressure difference refers to the angle at which a ship deviates from its intended course due to the wind when sailing in the wind. Wave pressure difference refers to the angle at which a ship deviates from its intended course due to the waves when sailing in the waves. Current pressure difference refers to the angle at which a ship deviates from its intended course due to the current when sailing in the water.

[0077] S6: The dual feedback signal obtained by combining the combined pressure difference under the coupled interference of wind interference, wave interference and current interference and the bow feedback signal is used as the input signal. The controller is designed using a closed-loop gain shaping algorithm to generate rudder angle commands to achieve tracking control of the course.

[0078] The steps S1 / S2 / S3 / S4 / S5 / S6 are executed sequentially;

[0079] The process of constructing the nonlinear Norrbin model for ship simulation motion control is as follows:

[0080] The mathematical model for the planar motion of a three-degree-of-freedom ship is as follows:

[0081] (1)

[0082] It is the quality of the ship. The disturbance value of the forward velocity. The derivative of the forward velocity disturbance value, In order to combine external forces The component on the axis affects the forward velocity. The partial derivatives, In order to combine external forces The component on the axis of forward acceleration The partial derivatives, The drift speed, For drift acceleration, This serves as a reference value for forward speed. The coordinates of the ship's center of gravity are taken as the origin in the appendage coordinate system within the ship. The bow roll angular velocity, For the bow roll acceleration, In order to combine external forces The component on the axis affects the drift velocity. The partial derivatives, In order to combine external forces The component on the axis of the drift acceleration The partial derivatives, In order to combine external forces Components on the axis right The partial derivatives, for rudder angle The partial derivatives, Let be the moment of inertia of the ship's hull about a vertical axis passing through its center of gravity. for right The partial derivatives, The rotational torque of the external force acting on the ship about a vertical axis passing through its center of gravity. right The partial derivatives, for right The partial derivatives, for right The partial derivatives, The rotational torque of the external force acting on the ship about a vertical axis passing through its center of gravity. rudder angle The partial derivatives;

[0083] The nonlinear Norrbin mathematical model is presented as follows:

[0084] (2)

[0085] in: Let be the inertial force derivative matrix. The matrix represents the derivatives of viscous forces. The rudder force derivative matrix, The derivative of the state vector. For state vectors, For control input, i.e., rudder angle; For nonlinear fluid dynamics, For wind power, For the force of the waves, For the density of water, The length of the ship; The solution is as follows:

[0086] (3)

[0087] (4)

[0088] (5)

[0089] in: It is a nonlinear lateral force. It is a nonlinear yaw force. For the transverse nonlinear hydrodynamic component, The nonlinear hydrodynamic torque about the vertical axis The dimensionless crossflow coefficient is taken as 0.3 to 0.8; The depth of a ship's draft.

[0090] Figure 2 This is a schematic diagram of the controller;

[0091] The process of designing a controller using a closed-loop gain shaping algorithm based on a ship model under wind, wave, and current interference is as follows:

[0092] Second-order linear Nomoto transfer function for:

[0093] (6)

[0094] The turning index represents the steady turning angular velocity per unit rudder angle when a ship enters a steady turn after being steered. It reflects the quality of a ship's turning performance. The following performance index represents the time constant during which the angular acceleration of a ship approaches a steady angular velocity after steering. It reflects the quality of a ship's following performance.

[0095] Let the bandwidth frequency of the closed-loop system be... Then, at this time, the complementary sensitivity function of the ship's heading control system... That is, the closed-loop transfer function of the system is:

[0096] (7)

[0097] Then the controller for:

[0098] (8)

[0099] in: The bandwidth frequency set for the closed-loop system. It is a constant, usually taken as 1-10, and is taken as 2 in this application.

[0100] Figure 3 This is a schematic diagram for calculating average wind speed.

[0101] Furthermore, the ship model under wind, wave, and current interference includes wind interference models, wave interference models, and current interference models as follows:

[0102] The wind disturbance model is determined as follows:

[0103] The wind disturbance model uses wind to excite lateral forces. Gentle wind excites yaw moment To characterize;

[0104] The wind-induced lateral force Including mean wind-induced lateral force And pulsating wind excites lateral force ;

[0105] The mean wind excites the lateral force The expression is as follows:

[0106] (9)

[0107] The wind-induced yaw moment Including mean wind-induced yaw moment and pulsating wind-induced yaw moment ;

[0108] Wherein: mean wind-induced yaw moment The expression is as follows:

[0109] (10)

[0110] In the formula: For dimensionless wind force, The dimensionless wind moment coefficient, The projected area of ​​the ship above the waterline. air density, The density of water, Relative wind speed, For wind hull angle; for pulsating wind, it is equivalent to white noise, the standard deviation of which is proportional to the absolute wind speed;

[0111] The disturbance of waves is determined as follows: See the wave force diagram. Figure 4 ;

[0112] The wave disturbance model uses wave-induced lateral force. With wave-induced yaw moment To characterize;

[0113] Wave-induced lateral force With wave-induced yaw moment Both are characterized by high-frequency primary wave force and low-frequency secondary wave force;

[0114] The high-frequency primary wave force is generated by the resultant force of the wave force in the y-axis direction. The resultant moment of the wave force about the z-axis The specific representation is as follows:

[0115] (11)

[0116] (12)

[0117] in:

[0118]

[0119] In the formula: Indicates the wave excitation amplitude coefficient. The dimensionless parameter representing the projection of the wave along the x-axis. The dimensionless parameter representing the projection of the wave along the y-axis. For the width of the boat, This represents the oscillation of the wavefront at the origin of the attached coordinate system. This indicates the wave surface along the direction of wave propagation. The value of the slope at the origin. For wave number, For the frequency of encounters, This represents the wave height at that encounter frequency.

[0120] There is currently no simple and reliable method for calculating the secondary force. It can be equivalent to a simple linear model, which is to use white noise to drive a typical second-order oscillating element and apply it to the output heading.

[0121] The low-frequency secondary wave force is characterized by driving a typical second-order oscillation with white noise.

[0122] Nearshore vessels are significantly affected by tidal currents, often exhibiting a reciprocating flow. The variation pattern of this reciprocating flow is basically consistent with a sine function curve and can be calculated using the following formula. For flow disturbances, see [link to relevant documentation]. Figure 5 The formula for characterizing flow disturbance is as follows:

[0123] (14)

[0124] In the formula: For maximum flow rate, The tidal time difference between the desired time and the time of tidal transition. The duration of the flood (ebb) tide is approximately 6 hours. The maximum current speed can be estimated using chart diagrams. It is generally believed that the maximum current speed one or two days before and after a spring tide is the same as the maximum current speed on the day of the spring tide; the maximum current speed one or two days before and after a neap tide is the same as the maximum current speed on the day of the neap tide; the maximum current speed for other days can be taken as the average of the maximum current speeds of the spring and neap tides.

[0125] Typically, simulations assume that the flow only changes the position and speed of the ship, but not its course, resulting in the following velocity balance equations:

[0126] (15)

[0127] in, The velocity component of the ship along the x-axis under the influence of the flow. The velocity component of the ship along the y-axis under the influence of the current. For the bow direction, The absolute velocity of the flow. The absolute direction of the flow.

[0128] The ship's position data during navigation is preprocessed using the least squares method, and the ship's position coordinate sequence is collected in real time by GPS sensors. , ), =1, 2, 3, ... Where i and n are positive integers k, outliers (such as jump data when satellite signal lock is lost) are filtered out synchronously, and sliding window filtering is used to smooth the data. Let the window length be L. w Then the k-th filter output value x(k) is:

[0129] (16)

[0130] when In this case, the mean of the first k data points is usually used as the initial output.

[0131] Window length L w Design speed V d The decision is made using the following formula:

[0132] (17)

[0133] The force expression for the coupled interference of wind, wave, and current on the ship is as follows:

[0134] in, The combined force of wind, waves, and current interference The first modulation coefficient, These are the second modulation coefficients. For flow direction, For average wind-induced lateral force, The resultant force of the high-frequency primary wave force along the y-axis; For wind angle, The absolute direction of the flow. The lateral force exerted by the water flow on the hull;

[0135] When the wind and waves are in different directions, the impact on the ship's course is significantly different; the direction of the tidal current also modulates the direction of wave propagation, changing the encounter frequency, thereby achieving indirect interference coupling.

[0136] The process of processing the ship's position data during navigation based on the least squares method to obtain the ship's trajectory is as follows:

[0137] For the preprocessed ship position coordinate sequence , =1, 2, 3, ... Where k and n are positive integers; assuming ( , The coordinates of the points satisfy a linear relationship. ,in and These are coefficients to be determined. It is an error term, and They are independent and follow a pattern with a mean of 0 and a variance of . The normal distribution;

[0138] The goal of the least squares method is to minimize the sum of squared errors. Minimum, The formula is:

[0139] (18)

[0140] in, The horizontal coordinate of the ship's position. The vertical coordinate of the ship's position is , and These are the fitting parameters;

[0141] To find smallest and , respectively and Find the partial derivatives and set them to zero to determine the... and The value;

[0142] right Find the partial derivatives as follows:

[0143] (19)

[0144] Expand to obtain Further obtained ,in Indicates the preceding The average value of the x-coordinate of each ship's position. Indicates the preceding The average of the longitudinal coordinates of each ship's position;

[0145] right Find the partial derivatives as follows:

[0146] (20)

[0147] Will Substitute into equation (18):

[0148] (twenty one)

[0149] The least squares method is used to perform linear fitting on the ship's coordinates. Specifically, when the number of collected coordinates reaches a certain threshold... When, select the previous Fitting at points, threshold Related to ship steering characteristics, the calculation formula is as follows:

[0150]

[0151] in Base points To adjust the coefficient, The bow roll angular velocity, This is the threshold for determining the turning direction. When the ship turns, the number of fitted points is automatically increased to improve the fitting accuracy of the dynamic trajectory.

[0152] Obtain the slope of the fitted line That is, the direction of the ship's trajectory :

[0153] .

[0154] Obtain the slope of the fitted line That is, the direction of the ship's trajectory .

[0155] Figure 6 This is a schematic diagram of the combined pressure difference;

[0156] The specific calculation formula for obtaining the pressure difference generated by the ship under wind, wave, and current interference by subtracting the trajectory data from the bow data is as follows:

[0157] (twenty two)

[0158] In the formula: For the combined pressure difference, For the ship's trajectory relative to the ground, It's the bow of the ship.

[0159] The combined pressure difference As a correction signal, it is input to the controller along with the traditional bow feedback signal, forming a coordinated control structure of "environmental correction feedback + hull attitude feedback". This structure has the following innovations and advantages:

[0160] Innovation Point 1: For the first time, the combined pressure difference calculated based on the ship's heading is introduced as an independent feedback signal. Unlike existing control methods that rely solely on ship heading tracking, this method introduces GPS heading into the control loop, which can more realistically reflect the ship's motion relative to the ground, compensate for the deviation caused by wind, waves, and current pressure differences, and significantly improve the ship control system's ability to resist interference from environmental factors such as wind, waves, and currents.

[0161] Innovation Point Two: Dual Feedback Mechanism Enhances System Robustness and Control Accuracy. The differential pressure feedback channel can dynamically correct trajectory deviations caused by wind, waves, and current disturbances, enhancing the responsiveness to the planned course; the bow feedback channel maintains attitude stability and rapid servo response. Together, these two mechanisms enable the controller to operate effectively even in complex environments.

[0162] Innovation Point Three: Enhancing Adaptive Control Capabilities and Unmanned Control Levels. The dual feedback mechanism can adaptively adjust control commands based on the actual motion state of the ship, eliminating the need for the ship's operator to rely on subjective experience. This greatly reduces human error and operational intensity, laying the technological foundation for future autonomous navigation systems.

[0163] The effectiveness and feasibility of the proposed control method were verified through simulation experiments. The experimental object was the training vessel "Yu Kun" Norrbin, whose parameters are shown in Table 1.

[0164] Table 1. Main Design Parameters of "Yu Kun"

[0165]

[0166] Simulation scenario: The planned headings were set to 030°, 050°, and 040°, and updated every 500 seconds. The ship's initial heading was 000°, the wind force was Beaufort scale 3, the wind direction was northwest, the current speed was 1 knot, and the current direction was south-southeast. Simulation results are as follows: Figures 7 to 12 As shown in the figure. Experimental results show that the proposed method significantly reduces the impact of complex sea conditions on ship drift, thereby effectively reducing the deviation between the track and the planned course, improving the stability and resilience of the control system, and demonstrating good control performance.

[0167] Figure 7 This demonstrates the performance of a conventional feedback controller in track and heading control. It can be observed that when the ship's heading follows the planned course, the actual track deviates from the set planned course due to interference from complex sea conditions. In navigation practice, the reference heading of the autopilot is usually adjusted manually to keep the ship on the planned route.

[0168] Figure 8 This paper demonstrates the effectiveness of a dual feedback controller in controlling the course and bow. The figures show a faster response in the bow direction, while a significant deviation exists in the course, reflecting the influence of the combined environmental pressure differential. Despite the difference between the bow and the planned course, the ship's actual course almost perfectly tracks the planned course. As the planned course changes, the controller automatically adjusts to compensate for the combined environmental pressure differential, ensuring consistency between the course and the planned course. This demonstrates that the control strategy effectively addresses these disturbances, significantly reducing reliance on human intervention and providing important reference for controller design of unmanned surface vessels.

[0169] Figure 9The control effects of a dual feedback controller and a conventional feedback controller on ship trajectory were compared. As shown in the figure, under the action of the conventional feedback controller, the ship's trajectory gradually deviated from the planned route, highlighting the significant impact of the combined pressure difference on ship motion under complex sea conditions. In contrast, the dual feedback controller effectively maintained the trajectory through course-keeping control when the ship's initial position was close to the planned route.

[0170] Figure 10 The figure compares the course of the two controllers. It shows that with the conventional feedback controller, the course changes smoothly during control, and although there is no overshoot, there is always a certain deviation between the course and the planned course. With the dual feedback controller, the course is almost identical to the planned course, with only slight overshoot occurring during turning. This overshoot phenomenon stems from the continuous changes in environmental disturbances under complex sea conditions; the controller is in an adjustment state, and the control effect gradually stabilizes over time.

[0171] Figure 11 The figure compares the heading of the two controllers. As can be seen, under the conventional feedback controller, the ship's heading can track the planned course without overshoot, demonstrating its excellent heading-keeping capability. However, under the dual feedback controller, the ship's heading failed to fully track the planned course. This is mainly due to the influence of external disturbances such as wind, waves, and currents in complex sea conditions. To achieve good track tracking, the controller made reasonable adjustments to the ship's heading.

[0172] Figure 12 This figure compares the rudder angles of the two controllers. As can be seen from the graph, except during the turning phase, the rudder angle changes of the two controllers are generally consistent, with a low steering frequency and gradual changes. During the turning phase, the rudder angle changes more significantly, which aligns with the operational requirements in maritime practice. This helps improve the controller's response speed, enabling the vessel to quickly adjust its course and track the updated planned course.

[0173] Figure 13 This is a comparison chart of combined pressure differences. By analyzing these combined pressure difference angles, the deviation between the ship's course and bow can be accurately assessed, and this deviation information can be fed back to the ship model, thereby effectively overcoming the influence of external environmental factors on ship navigation. The data in the chart further shows that, under constant interference conditions, the effect of interference varies depending on the bow direction. When the ship's bow is nearly perpendicular to the direction of the interference force, the interference has the greatest impact on the course.

[0174] Simulation results show that this method can significantly reduce the impact of environmental disturbances on ship drift and improve the stability and accuracy of course maintenance.

[0175] 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 heading-keeping control method based on a dual feedback mechanism, characterized in that, Includes the following steps: S1: Obtain the interference models of wind, waves, and flow; S2: Based on the wind interference model, wave interference model, and current interference model, considering the coupled interference of wind, waves, and current, the forces under the coupled interference of wind, waves, and current on the ship are obtained: in, The combined force of wind, waves, and current interference The wind-wave modulation coefficient, The flow-wind modulation coefficient, For flow direction, For average wind-induced lateral force, The resultant force of the high-frequency primary wave force along the y-axis; For wind angle, The absolute direction of the flow. The lateral force exerted by the water flow on the hull; When the wind and wave directions are different, the impact on the ship's course is significantly different; the direction of the tidal current also modulates the direction of wave propagation, changing the encounter frequency, thereby achieving indirect interference coupling; S3: Obtain ship position data of the ship model under the coupled interference forces of wind, wave and current interference; S4: The ship's position data during navigation is processed using the least squares method to obtain the ship's trajectory. The process is as follows: For a set of points on a two-dimensional plane where the ship is located ( , ), =1, 2, 3, ... Where i and n are positive integers; assume a set of points on a two-dimensional plane satisfy a linear relationship. ,in and These are coefficients to be determined. It is an error term, and They are independent and follow a pattern with a mean of 0 and a variance of . The normal distribution; The goal of the least squares method is to minimize the sum of squared errors. Minimum, The formula is: in, The horizontal coordinate of the ship's position. The vertical coordinate of the ship's position; To find smallest and , respectively and Find the partial derivatives and set them to zero to determine the... and The value; right Find the partial derivatives as follows: Expanding, we get: ,get ,in Indicates the preceding The average value of the x-coordinate of each ship's position. Indicates the preceding The average of the longitudinal coordinates of each ship's position; right Find the partial derivatives as follows: Will Substituting into the above equation, we get: When the number of collected coordinate points reaches a threshold, the first [points] are selected. By fitting the line to a given number of points, the slope of the fitted line can be obtained. That is, the direction of the ship's trajectory : S5: Subtract the trajectory data from the ship's bow data to obtain the combined pressure difference generated by the ship under the coupled interference of wind, wave and current. S6: The dual feedback signal obtained by combining the combined pressure difference generated by the ship under the coupled interference of wind, wave and current interference and the bow feedback signal is used as the input signal. The controller is designed using the closed-loop gain shaping algorithm to generate rudder angle commands in order to achieve tracking control of the course. The dual feedback mechanism includes a differential pressure feedback channel that dynamically corrects trajectory deviations caused by wind, waves, and current disturbances, enhancing responsiveness to the planned course; and a bow feedback channel that maintains attitude stability and rapid rudder response.

2. The heading-keeping control method based on a dual feedback mechanism according to claim 1, characterized in that: The specific calculation formula for the combined pressure difference generated by the ship under the coupled interference of wind, wave, and current is as follows: In the formula: For the combined pressure difference, For the ship's trajectory relative to the ground, It's the bow of the ship.

3. The heading-keeping control method based on a dual feedback mechanism according to claim 1, characterized in that: The formula for determining the wind-wave modulation coefficient is as follows: The formula for determining the flow-wind modulation coefficient is as follows: in: , The coupling strength constant is , Take 0.1, Take 0.05, To standardize parameters, , This is to achieve dynamic modulation of the enhancement and cancellation of interference between environmental factors through trigonometric function terms of the directional angle.

4. The heading-keeping control method based on a dual feedback mechanism according to claim 1, characterized in that, The process of designing a controller using a closed-loop gain shaping algorithm is as follows: The dual feedback signal obtained by combining the corrected signal of the combined pressure difference generated by the ship under the coupled interference of wind, wave, and current disturbances with the bow feedback signal is used as the input signal. Second-order linearized model transfer function for: The yaw rate index represents the steady yaw rate per unit rudder angle when a ship enters a steady turn after being steered. The following index represents the time constant during which the angular acceleration of a ship approaches a steady angular velocity after it has been steered. Let the bandwidth frequency of the closed-loop system be... Then, at this time, the complementary sensitivity function of the ship's heading control system... That is, the closed-loop transfer function of the system is: Then the controller for: in: It is a constant.

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