CN115903802A - H∞ heading control method based on nonlinear variable parameter unmanned ship model - Google Patents

Abstract

The invention provides an H infinity heading control method based on a nonlinear variable parameter unmanned ship model, which considers the complex and changeable impact of water flow on a ship, obtains the circulation force borne by the ship by using a low aspect ratio wing theory and further establishes the nonlinear variable parameter heading control model. And (3) deducing a nonlinear matrix inequality condition meeting the H infinity robust stability of the system by a parameter-related Lyapunov function aiming at the established nonlinear variable parameter heading control model, and solving the nonlinear matrix inequality condition by an SOS (sequence of oriented services) tool box in MATLAB to obtain a nonlinear variable parameter H infinity robust controller.

Description

H∞ heading control method based on nonlinear variable parameter unmanned ship model

Technical Field

The invention belongs to the technical field of unmanned ship heading control, and in particular relates to an H∞ heading control method based on a nonlinear variable parameter unmanned ship model.

Background Art

With the development of ocean and river-related commerce and military, unmanned ships have become an important platform for performing search and rescue, reconnaissance, monitoring and other tasks due to their advantages such as small size, high speed, low cost and no risk of personnel being online. Bow control is one of the key technologies for unmanned ships to achieve autonomous, reliable and safe navigation. However, during the navigation of unmanned ships, the state of the unmanned ships is often time-varying, such as time-varying speed, which makes the hydrodynamic force received by the unmanned ships constantly changing, destroying the stable structure of the system. The change in hydrodynamic force is mainly reflected in the uncertainty of the parameters of the unmanned ship model. This phenomenon causes the unmanned ship system to have strong time-varying nonlinearity.

In the current field of unmanned ship heading control, the unmanned ship models used mainly include Fossen, Norrbin and Nomoto. In order to facilitate model parameter identification and system control, these models are simplified to simple forms, and even only show linear time-invariant characteristics. However, in the actual navigation process of unmanned ships, there are various time-varying factors such as speed, wind and waves, and water flow, which cause model parameter uncertainty, which will destroy the stable structure of the unmanned ship system. In addition, the unmanned ship model itself has inherent nonlinear characteristics, which makes it difficult for the linear time-invariant characteristic model to characterize the actual situation of the unmanned ship, thereby further increasing the difficulty of unmanned ship heading control. On the other hand, the heading controller is designed for the unmanned ship model with nonlinear time-varying characteristics to suppress external interference and parameter uncertainty. Sliding mode control, backstepping method and H∞ robust control can be used. However, the sliding mode control method has the fatal disadvantage of chattering when switching the system, and the backstepping method requires accurate information about the model of the ship heading control system and its changing parameters, which is very difficult in practical applications. The H∞ robust control method suppresses disturbances and uncertainties by suppressing the maximum gain of the transfer function from disturbance to desired output. It has the advantages of strong robustness, good control effect and independence from disturbance model. When designing an H∞ robust controller, the model needs to be substituted into the control framework of a linear variable parameter system to describe the nonlinear time-varying characteristics of the controlled model. However, its essence is to linearize the model around a specific operating point of the model's time-varying parameters. Therefore, the control framework of a linear variable parameter system cannot reflect the complete dynamic characteristics of the controlled model, especially the nonlinear characteristics.

Summary of the invention

In order to solve the defects and shortcomings of the prior art, the present invention proposes an H∞ heading control method based on a nonlinear variable parameter unmanned ship model. Aiming at a small under-actuated unmanned ship, a nonlinear variable parameter heading control model is established, and a nonlinear variable parameter H∞ robust controller is designed to enable the system to obtain interference suppression and robust performance, thereby achieving fast and high-precision tracking of the heading.

Considering the complex and changeable impact of water flow on ships, the circulation force on the ship is obtained by using the low aspect ratio wing theory, and then a nonlinear variable parameter bow control model is established. According to the established nonlinear variable parameter bow control model, the nonlinear matrix inequality conditions that satisfy the H∞ robust stability of the system are derived through the parameter-related Lyapunov function, and the nonlinear variable parameter H∞ robust controller is obtained by solving the nonlinear matrix inequality conditions through the SOS toolbox in MATLAB. The nonlinear variable parameter bow control model is established based on the low aspect ratio wing theory. The hydrodynamic term has a relatively clear physical meaning, which can fully describe the hydrodynamic force on the ship and reflect the nonlinear time-varying characteristics of the unmanned ship. The nonlinear variable parameter H∞ robust controller can well suppress external interference while ensuring the stability of the system, and by including the nonlinear state and time-varying parameters of the system, it overcomes the parameter perturbation phenomenon caused by the inherent nonlinearity and time-varying parameters of the system, thereby realizing the tracking of the given unmanned ship's bow angle and ensuring fast, smooth and high-precision bow tracking performance. The present invention enables the unmanned ship to have a new nonlinear variable parameter heading control model, and at the same time proposes a nonlinear variable parameter H∞ robust control solution for the heading control problem of the model.

The technical solution adopted by the present invention to solve the technical problem is:

A H∞ heading control method based on a nonlinear variable parameter unmanned ship model, characterized in that the control system for a small underactuated unmanned ship is based on a nonlinear variable parameter heading control model and a nonlinear variable parameter H∞ robust controller, and specifically includes the following steps:

Step S1: Establish a ship dynamics model under the Fossen framework, ignore heave, roll and pitch motions during the establishment process, and simplify the six-degree-of-freedom unmanned ship into a three-degree-of-freedom dynamics model related to pitch, roll and bow motions;

Step S2: According to the low aspect ratio wing theory, the hydrodynamic damping matrix in the established three-degree-of-freedom dynamic model is decomposed into the circulation force and cross-flow resistance matrix of the ship, and a three-degree-of-freedom unmanned ship model based on the low aspect ratio wing is obtained;

Step S3: According to the actual physical characteristics of the small underactuated unmanned ship, ignoring the swaying motion and cross-flow resistance, the three-degree-of-freedom unmanned ship model based on the low-aspect-ratio wing is decomposed to obtain a maneuvering dynamics model;

Step S4: According to the relationship between the heading angle and the heading angular velocity, the heading angle state variable is introduced into the maneuvering dynamics model, and the heading angle error is used as feedback to obtain a nonlinear variable parameter heading error model;

Step S5: Substituting the assumed nonlinear state feedback controller into the nonlinear variable parameter heading error model to establish a nonlinear variable parameter heading control closed-loop system;

Step S6: construct the state and parameter-related Lyapunov function, prove the H∞ robust performance and stability of the nonlinear variable parameter heading control closed-loop system, and derive the conditions for the system to have H∞ robust stability;

Step S7: The H∞ robust stability condition can be converted into a polynomial linear matrix inequality by using the Schur complement, SOS and other lemmas;

Step S8: Solve the polynomial linear matrix inequality by using the SOS toolbox in MATLAB software to obtain the nonlinear state feedback controller assumed in step S5 as a nonlinear variable parameter H∞ robust controller;

Step S9: The unmanned ship system uses the measured heading angle and heading angular velocity as feedback, analyzes the heading angle error and inputs it into the H∞ robust controller to achieve tracking of the given heading angle, suppression of external disturbances and parameter perturbations.

Furthermore, the three-degree-of-freedom dynamic model obtained in step S1 is:

Among them, v = [u, v, r] ^T is the state vector of the unmanned ship, u, v, r are the surge velocity, sway velocity and bow pitch velocity respectively; M∈R ^3×3 is the inertia matrix; C(v)∈R ^3×3 is the Coriolis centripetal force matrix; D(v)∈R ^3×3 is the hydrodynamic damping matrix; τ = [τ _u ,τ _v ,τ _r ] ^T is the thruster output torque, τ _u ,τ _v ,τ _r are the torques of surge, sway and bow pitch motion respectively; τ _w = [τ _uw ,τ _vw ,τ _rw ] ^T is the external disturbance, τ _uw ,τ _vw ,τ _rw are the external disturbances of surge, sway and bow pitch motion respectively.

Further, step S2 is specifically as follows: according to the low aspect ratio wing theory, the hydrodynamic damping matrix in the ship model is replaced by the circulation and cross flow forces on the ship, that is,

D(v)＝F _LD (v)+F _cf (v)

Wherein, F _cf (v) is the transverse flow resistance of the ship; F _LD (v) = F _L (v) + F _D (v) is the circulating force of the ship, F _L (v) = [X _L , Y _L , N _L ] ^T is the circulating lift of the ship, and F _D (v) = [X _D , Y _D , N _D ] ^T is the circulating resistance of the ship; _XL and X _D are the circulating lift and drag of surge motion respectively, Y _L and Y _D are the circulating lift and drag of surge motion respectively, and _NL and _ND are the circulating lift moment and drag moment of yaw motion respectively.

Furthermore, the manipulation dynamics model of step S3 is specifically:

为系统参数，m为船舶质量，x_g为重心到船舶坐标原点的x轴距离，

为附加质量系数，N_(u,v,r)为艏摇环流力矩系数。in,

is the system parameter, m is the ship mass, _xg is the x-axis distance from the center of gravity to the origin of the ship coordinate system,

is the additional mass coefficient, and N _(u,v,r) is the yaw circulation moment coefficient.

Further, in step S4, the nonlinear variable parameter heading error model is:

B₁＝B₂＝[1,0]^T，C＝[0,1]为非线性变参数模型系统矩阵。Among them, x = [r, ψ _e ] ^T is the state variable; u _τ = c ₄ τ _r is the actuator output; w = c ₄ τ _rw is the total external disturbance; z = ψ _e is the controlled output, and the sway speed u is the time-varying parameter denoted as u(t);

B ₁ =B ₂ =[1,0] ^T , C =[0,1] is the nonlinear variable parameter model system matrix.

使得多项式线性矩阵不等式：Further, in step S5, the assumed nonlinear state feedback controller is specifically: for the unmanned ship heading control system, if there is a symmetric positive definite polynomial matrix P(u(t)) that depends on time-varying parameters, a polynomial matrix

This makes the polynomial linear matrix inequality:

If it holds, the control system is asymptotically stable, and the H∞ norm of the external disturbance w is less than γ, where γ is the H∞ performance index. At this time, the state feedback controller of the closed-loop system is in the form of:

从而设计出控制律u_τ。Further, in step S8, the polynomial linear matrix inequality is converted into a square sum form and solved by the SOS toolbox in MATLAB software to obtain a symmetric positive definite polynomial matrix P(u(t)) and a polynomial matrix

Thus the control law u _τ is designed.

Compared with the prior art, the present invention and its preferred embodiment have the following beneficial effects:

1. The nonlinear variable parameter bow control model provided establishes a ship hydrodynamic mechanism model at the physical level, replacing the previous hydrodynamic empirical model and having a clearer physical meaning;

2. Compared with other heading control models, the nonlinear variable parameter heading control model provided not only has a simple form, but also fully restores the nonlinear time-varying characteristics of the unmanned ship system, which is helpful for designing a controller that can accurately adjust the heading;

3. The nonlinear variable parameter H∞ robust controller provided by the system incorporates the system state and time-varying parameters and their derivatives, and does not need to linearize the system, thus no longer hiding the nonlinear time-varying characteristics of the system, reducing the conservatism of the controller design and improving the dynamic performance and robustness of the unmanned ship bow control system;

4. The design of nonlinear variable parameter H∞ robust controller is transformed into the problem of solving polynomial linear matrix inequality conditions, which can be solved using the SOS toolbox of MATLAB software, reducing the computational difficulty and facilitating engineering implementation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

1 is a structural diagram of an H∞ heading control method based on a nonlinear variable parameter unmanned ship model in an embodiment of the present invention;

FIG2 is a flow chart of establishing a nonlinear variable parameter unmanned ship model according to an embodiment of the present invention;

FIG3 is a flow chart of the design of a nonlinear variable parameter H∞ robust controller according to an embodiment of the present invention;

FIG4 is a simulation diagram of heading tracking according to an embodiment of the present invention;

FIG5 is a simulation diagram of the actual error of tracking the heading angle according to an embodiment of the present invention.

DETAILED DESCRIPTION

In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail as follows:

It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and/or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and/or combinations thereof.

Please refer to Figure 1. The present invention provides an H∞ bow control method based on a nonlinear variable parameter unmanned ship model. According to the low aspect ratio wing theory, the circulation and cross flow forces on the ship are obtained, a nonlinear variable parameter bow control model is established, and a polynomial linear matrix inequality is derived, which is then solved using the SOS toolbox in the MATLAB software to finally obtain a nonlinear variable parameter H∞ robust controller. This method designs a nonlinear variable parameter H∞ robust controller based on the establishment of a model that fully describes the nonlinear time-varying characteristics of the unmanned ship, which provides good stability and strong robustness for the unmanned ship bow control system. Specifically, it includes the following steps:

Step 1: As shown in Figure 2, according to the ship theory of the Fossen framework, a three-degree-of-freedom dynamic model of surge, sway and pitch motion is established:

Among them, v = [u, v, r] ^T is the state vector of the unmanned ship, u, v, r are the surge velocity, sway velocity and bow pitch velocity respectively; M∈R ^3×3 is the inertia matrix; C(v)∈R ^3×3 is the Coriolis centripetal force matrix; D(v)∈R ^3×3 is the hydrodynamic damping matrix; τ = [τ _u ,τ _v ,τ _r ] ^T is the thruster output torque, τ _u ,τ _v ,τ _r are the torques of surge, sway and bow pitch motion respectively; τ _w = [τ _uw ,τ _vw ,τ _rw ] ^T is the external disturbance, τ _uw ,τ _vw ,τ _rw are the external disturbances of surge, sway and bow pitch motion respectively.

Step 2: As shown in Figure 2, the ship is regarded as a low aspect ratio wing. According to the low aspect ratio wing theory, the hydrodynamic damping matrix in the ship model is replaced by the circulation and cross flow forces on the ship, that is,

D(v)＝F _LD (v)+F _cf (v)

Wherein, F _cf (v) is the transverse flow resistance of the ship; F _LD (v) = F _L (v) + F _D (v) is the circulating force of the ship, F _L (v) = [X _L , Y _L , N _L ] ^T is the circulating lift of the ship, and F _D (v) = [X _D , Y _D , N _D ] ^T is the circulating resistance of the ship; _XL and X _D are the circulating lift and drag of surge motion respectively, Y _L and Y _D are the circulating lift and drag of surge motion respectively, and _NL and _ND are the circulating lift moment and drag moment of yaw motion respectively.

Step 3: As shown in Figure 2, the circulation and cross-flow forces on the ship are analyzed in different directions of movement to obtain the unmanned ship dynamics model based on the low aspect ratio wing. The unmanned ship dynamics model based on the low aspect ratio wing is decomposed according to the under-actuated characteristics of the small unmanned ship to obtain the maneuvering dynamics model:

为系统参数，m为船舶质量，x_g为重心到船舶坐标原点的x轴距离，

为附加质量系数，N_(u,v,r)为艏摇环流力矩系数。in,

is the system parameter, m is the ship mass, _xg is the x-axis distance from the center of gravity to the origin of the ship coordinate system,

is the additional mass coefficient, and N _(u,v,r) is the yaw circulation moment coefficient.

Step 4: As shown in Figure 3, according to the physical relationship between the heading angle and the heading angular velocity, the heading angle variable is introduced into the maneuvering dynamics model to obtain a nonlinear variable parameter heading control model. Considering that the heading angle is given unchanged within a heading sampling step, a nonlinear variable parameter heading error model is established according to the heading angle error ψ _e = ψ _d - ψ:

B₁＝B₂＝[1,0]^T，C＝[0,1]为非线性变参数模型系统矩阵。Among them, x = [r, ψ _e ] ^T is the state variable; u _τ = c ₄ τ _r is the actuator output; w = c ₄ τ _rw is the total external disturbance; z = ψ _e is the controlled output, and the sway speed u is the time-varying parameter denoted as u(t);

B ₁ =B ₂ =[1,0] ^T , C =[0,1] is the nonlinear variable parameter model system matrix.

推导出无人船艏向控制系统H∞鲁棒稳定的控制器求解条件为：对于无人船艏向控制系统，若存在一个依赖时变参数的对称正定多项式矩阵P(u(t))，一个多项式矩阵

使得多项式线性矩阵不等式：Step 5: As shown in Figure 3, for the nonlinear variable parameter heading error model, construct the Lyapunov function V(x,t)=x ^T P ^-1 (u(t))x. According to the system H∞ stability condition: (1) V(x,u,t)＞0;

The controller solution condition for the H∞ robust stability of the unmanned ship bow control system is derived as follows: For the unmanned ship bow control system, if there exists a symmetric positive definite polynomial matrix P(u(t)) that depends on time-varying parameters, a polynomial matrix

This makes the polynomial linear matrix inequality:

If it holds, the control system is asymptotically stable, and the H∞ norm of the external disturbance w is less than γ, where γ is the H∞ performance index. At this time, the state feedback controller of the closed-loop system is in the form of:

从而设计出具有H∞鲁棒性能的控制律u_τ。Step 6: As shown in Figure 3, the polynomial linear matrix inequality is converted into a square sum form and solved by the SOS toolbox in MATLAB software to obtain a symmetric positive definite polynomial matrix P(u(t)) and a polynomial matrix

Thus, a control law u _τ with H∞ robust performance is designed.

Step 7: As shown in Figures 1 and 3, the system is set to give a given heading angle ψ _d , the unmanned ship's heading angular velocity r and the heading angle error ψ _e as state feedback according to the requirements, so as to build an unmanned ship heading control simulation system. Substitute the solved control law into the u _τ simulation system, and optimize the parameters to achieve the expected control performance, and finally achieve tracking of the given heading angle. The simulation results are shown in Figures 4 and 5.

Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

The present application is described with reference to the flowchart and/or block diagram of the method, device (system) and computer program product according to the embodiment of the present application. It should be understood that each process and/or box in the flowchart and/or block diagram, and the combination of the process and/or box in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one process or multiple processes in the flowchart and/or one box or multiple boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of H∞ bow control methods based on nonlinear variable parameter unmanned ship models under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims (7)

1. An H infinity heading control method based on a nonlinear variable parameter unmanned ship model is characterized in that the H infinity heading control method is used for a control system of a small under-actuated unmanned ship, is based on the nonlinear variable parameter heading control model and a nonlinear variable parameter H infinity controller, and specifically comprises the following steps:

step S1: building a ship dynamic model under a Fossen frame, neglecting heaving, rolling and pitching motions in the building process, and simplifying the six-freedom-degree unmanned ship into a three-freedom-degree dynamic model related to the heaving, rolling and pitching motions;

step S2: decomposing a hydrodynamic damping matrix in the established three-degree-of-freedom dynamic model into a circulating flow force and a cross flow resistance matrix borne by a ship according to a low-aspect-ratio wing theory to obtain a low-aspect-ratio wing-based three-degree-of-freedom unmanned ship model;

and step S3: according to the actual physical characteristics of the small under-actuated unmanned ship, ignoring the swaying motion and the cross flow resistance, decomposing a three-degree-of-freedom unmanned ship model based on the low-aspect-ratio wing to obtain an operation dynamic model;

and step S4: according to the relation between the heading angle and the heading angular velocity, introducing a heading angle state variable into the control dynamic model, and taking a heading angle error as feedback to obtain a nonlinear variable parameter heading error model;

step S5: substituting the assumed nonlinear state feedback controller into a nonlinear variable parameter heading error model to establish a nonlinear variable parameter heading control closed-loop system;

step S6: constructing a Lyapunov function related to states and parameters, carrying out H-infinity robust performance and stability verification on a nonlinear variable parameter heading control closed-loop system, and deducing the condition that the system has H-infinity robust stability;

step S7: converting the H infinity robust stability condition into a polynomial linear matrix inequality;

step S8: solving a polynomial linear matrix inequality through an SOS tool box in MATLAB software to obtain a nonlinear state feedback controller assumed in the step S5 as a nonlinear variable parameter H infinity robust controller;

step S9: the unmanned ship system takes the measured heading angle and heading angular velocity as feedback, analyzes the obtained heading angle error and inputs the error into an H infinity controller so as to realize the tracking of the given heading angle, the suppression of external disturbance and parameter perturbation.

2. The H infinity heading control method based on nonlinear variable parameter unmanned ship model according to claim 1 wherein: the three-degree-of-freedom dynamic model obtained in the step S1 is as follows:

wherein v = [ u, v, r] ^T The unmanned ship state vector is shown, and u, v and r are respectively a longitudinal oscillation speed, a transverse oscillation speed and a heading speed; m belongs to R ^3×3 Is an inertia matrix; c (v) is epsilon to R ^3×3 Is a coriolis centripetal force matrix; d (v) epsilon R ^3×3 Is a hydrodynamic damping matrix; τ = [ τ ] _u ,τ _v ,τ _r ] ^T For the output torque of the propeller, τ _u ,τ _v ,τ _r Moments of surge, sway and yaw motions, respectively; tau is _w ＝[τ _uw ,τ _vw ,τ _rw ] ^T For external interference, τ _uw ,τ _vw ,τ _rw External disturbances of surge, sway and yaw motions, respectively.

3. The H infinity heading control method based on the nonlinear variable parameter unmanned ship model according to claim 2, characterized in that: the step S2 specifically comprises the following steps: according to the low aspect ratio wing theory, the hydrodynamic damping matrix in the ship model is replaced by circulation and cross flow force borne by the ship, namely:

D(v)＝F _LD (v)+F _cf (v)

wherein, F _cf (v) The ship is subjected to cross flow resistance; f _LD (v)＝F _L (v)+F _D (v) Is the circulation force to which the ship is subjected, F _L (v)＝[X _L ,Y _L ,N _L ] ^T Is the circulation lift force borne by the ship, F _D (v)＝[X _D ,Y _D ,N _D ] ^T The circulation resistance of the ship; x _L And X _D Lift and drag of the surging motion, Y, respectively _L And Y _D Circulating lift and drag, N, respectively, of the oscillatory motion _L And N _D And respectively the circular flow lifting moment and the resisting moment of the yawing motion.

4. The H infinity heading control method based on nonlinear variable parameter unmanned ship model according to claim 3 wherein: the operation dynamic model of the step S3 is specifically as follows:

wherein,

is the system parameter, m is the vessel mass, x _g Is the x-axis distance from the center of gravity to the origin of coordinates of the vessel>

To add a mass coefficient, N _(u,v,r) Is the coefficient of the heading circulation moment.

5. The H infinity heading control method based on nonlinear variable parameter unmanned ship model according to claim 4 wherein: in step S4, the nonlinear variable parameter heading error model is:

wherein x = [ r, ψ) _e ] ^T Is a state variable; u. u _τ ＝c ₄ τ _r Outputting for the actuator; w = c ₄ τ _rw Is the total external interference; z = ψ _e For controlled output, the surging speed u is a time-varying parameter and is recorded as u (t);

B ₁ ＝B ₂ ＝[1,0] ^T ，C＝[0,1]is a nonlinear variable parameter model system matrix.

6. The H infinity heading control method based on nonlinear variable parameter unmanned ship model according to claim 5 wherein: in step S5, the assumed nonlinear state feedback controller is specifically: for the unmanned ship heading control system, if the unmanned ship heading control system existsA symmetric positive definite polynomial matrix P (u (t)) dependent on time-varying parameters, a polynomial matrix

Such that the polynomial linear matrix inequality:

if yes, the control system is asymptotically stable, the H infinity norm for the external disturbance w is less than gamma, gamma is the H infinity performance index, and the state feedback controller of the closed-loop system has the form:

7. the H infinity heading control method based on nonlinear variable parameter unmanned ship model according to claim 6 wherein: in step S8, the polynomial linear matrix inequality is converted into a sum of squares form and solved by SOS toolbox in MATLAB software to obtain a symmetric positive definite polynomial matrix P (u (t)) and a polynomial matrix

Thereby designing a control law u _τ 。/>

Images