Unmanned ship path tracking control method based on improved LOS guidance law and backstepping method

Abstract

The invention discloses an unmanned ship path tracking control method based on an improved LOS guidance law and a backstepping method, and relates to the technical field of unmanned ship control methods, and the method comprises the steps: building an unmanned ship kinematics model, building a dynamics model, and simplifying a control system to obtain a simplified model; and an LOS guidance law is designed, and controller parameters are optimized by adopting a backstepping method, so that the unmanned ship obtains better dynamic characteristics in the actual movement process. According to the method, the improved LOS guidance law and the backstepping method are combined, and the course and the position of the unmanned ship can be more accurately controlled in the path tracking process. By accurately calculating the expected heading angle and optimizing the controller parameters, the unmanned ship can more accurately track the expected path, the transverse following error and the course angle deviation are effectively reduced, and the path tracking precision is improved.

Description

Technical Field

[0001] The invention relates to the technical field of unmanned ship control methods, and in particular to an unmanned ship path tracking control method based on an improved LOS guidance law and a backstepping method. Background Art

[0002] Unmanned ship technology, as a key technology for autonomous surface operation platforms, is gaining increasing attention. It has shown broad application potential in many fields such as military reconnaissance, ocean monitoring, and resource exploration. The motion control technology of unmanned ships, especially path tracking control, is the core of realizing their autonomous operation. The solution of the present invention mainly designs the content of path tracking control of unmanned ships.

[0003] In complex and changing water environments, the motion state of unmanned ships is not only affected by the instability of the system itself, but also by external environmental factors such as wind, waves, and currents. These factors put forward higher requirements on the control strategy of unmanned ships. In order to meet these challenges, researchers have developed a variety of control methods, including but not limited to LOS guidance law control, sliding mode control, predictive model control, and intelligent algorithm control. These methods often improve the performance and reliability of unmanned ships in practical applications by improving or integrating multiple technologies.

[0004] In the research of navigation and control technology of unmanned ships, the current methods have limitations, which are specifically manifested in the following aspects: (1) Current path tracking technology usually needs to rely on highly accurate ship models. However, in actual operation, the inaccuracy of the model and the interference of external environmental factors (such as wind speed, waves, and water currents) may cause significant deviations in navigation, thereby reducing the control effect. (2) In actual operation, the parameters of the unmanned ship model or the parameters of the controller are often manually adjusted by trial and error. This process is computationally intensive and has a slow response speed, which is not conducive to rapid implementation and engineering application. Summary of the invention

[0005] In view of the above technical problems, the present invention provides an unmanned ship path tracking control method based on an improved LOS guidance law and backstepping method. Step S1: establishing a kinematic model of the unmanned ship:

[0006]

[0007] Among them, η represents the displacement angle vector, which is used to represent the position and direction information of the unmanned ship in the plane; v represents the velocity vector, which is used to represent the movement speed of the unmanned ship in the plane; τ represents the thrust and torque vector, which is used to control the movement of the unmanned ship; M represents the inertia matrix, C(v) represents the Coriolis force-centripetal force matrix, and D(v) represents the damping effect on the movement of the unmanned ship;

[0008] Building a kinetic model:

[0009] Among them, X represents the thrust on the longitudinal surge, that is, the longitudinal propulsion force of the unmanned ship; N represents the moment on the bow roll, K T represents the rudder coefficient, represents the thrust coefficient, ρ represents the water density, n represents the speed of the drive motor, D p represents the motor propeller diameter, u represents the propulsion speed, l r represents the length of the unmanned ship, δ r Indicates the rudder deflection angle;

[0010] Step S2, design the LOS guidance law and define a series of waypoints p1, p2…p k-1 ,p k …p n , assuming that the waypoint p currently needs to be tracked k (x k ,y k ), whose previous waypoint is Place two adjacent waypoints and p k (x k ,y k ) is connected, and the reference value of LOS is P los (x los ,y los )The solution formula is as follows;

[0011] The radius of the LOS acceptable circle made with the unmanned ship as the center is R, and the LOS angle ψ is calculated los for:

[0012]

[0013] Step S3, optimizing the controller parameters by backstepping method;

[0014] Step S4, by establishing corresponding models in MATLAB and Simulink, the observer-based LOS guidance combined with backstepping control is simulated and the effect is evaluated.

[0015] In step S1, η = [xy ψ] T ,v=[uvr] T ,τ=[τ u ·0··τ r ] T , τ u represents the propulsion force, τ r represents torque, τ d =[τ du ·τ dv ·τ dr ]T Represents the disturbance forces and moments on the hull in all directions.

[0016] Furthermore, in step S3, the desired ship heading ψ is tracked. d When the subsystem is constructed using the backstepping method, r d As a subsystem Input, again need to find the appropriate r d So that ψ approaches ψd.

[0017] Furthermore, the control method includes,

[0018] Step S101, model construction and initialization, establish the kinematic and dynamic models of the unmanned ship, clarify the relationship between displacement, speed, thrust vector and related matrix, consider the under-actuated simplified model, and determine various parameters; input the expected path information, define waypoints, calculate LOS related parameters such as reference value, angle, and set the acceptable circle radius;

[0019] Step S102, information acquisition and error judgment, obtain the current attitude information of the unmanned ship, use the sensor to obtain the position, heading angle, and speed data; determine whether there is a track error, calculate the deviation between the actual position and the expected path, and determine the subsequent process based on the deviation;

[0020] Step S103, control parameter calculation and adjustment. If there is an error, the desired heading angle is calculated using the improved LOS guidance law, and the visual distance optimization calculation is introduced; the backstepping method is used to optimize the controller parameters by defining the error, constructing the equation for derivation, and designing the control law operation;

[0021] Step S104, control the steering angle of the servo according to the desired heading angle to adjust the course of the unmanned ship; determine whether the unmanned ship has reached the end point, if it has reached the end point, end the task, if not, return to the information acquisition step to continue tracking.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention combines the improved LOS guidance law with the backstepping method to more accurately control the heading and position of the unmanned ship during the path tracking process. By accurately calculating the desired heading angle and optimizing the controller parameters, the unmanned ship can track the desired path more accurately, effectively reduce the lateral following error and heading angle deviation, and improve the accuracy of path tracking; (2) The control method of the present invention enables the unmanned ship to navigate more stably in complex environments, and can show better control effects regardless of whether it is a straight or curved trajectory tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a flowchart of an exemplary step of a path control method according to an embodiment of the present invention.

[0024] Figure 2It is a structural flow chart of the control path according to the present invention.

[0025] Figure 3 It is a schematic diagram of the hull motion coordinate system of the present invention.

[0026] Figure 4 It is a schematic diagram of the principle diagram of the improved LOS guidance law of the present invention. DETAILED DESCRIPTION

[0027] Example: Figure 3 The figure shows a schematic diagram of the hull motion coordinate system of this embodiment. According to the hull motion coordinate system, step S1 is to establish a kinematic model of the unmanned ship:

[0028]

[0029] Among them, η represents the displacement angle vector, which is used to represent the position and direction information of the unmanned ship in the plane; v represents the velocity vector, which is used to represent the movement speed of the unmanned ship in the plane; τ represents the thrust and torque vector, which is used to control the movement of the unmanned ship; M represents the inertia matrix, C(v) represents the Coriolis force-centripetal force matrix, and D(v) represents the damping effect on the movement of the unmanned ship;

[0030] Building a kinetic model:

[0031] Among them, X represents the thrust on the longitudinal surge, that is, the longitudinal propulsion force of the unmanned ship; N represents the moment on the bow roll, K T represents the rudder coefficient, represents the thrust coefficient, ρ represents the water density, n represents the speed of the drive motor, D p represents the motor propeller diameter, u represents the propulsion speed, l r represents the length of the unmanned ship, δ r Indicates the rudder deflection angle.

[0032] Step S11, further simplify the control system of the unmanned ship, assuming that the unmanned ship is bilaterally symmetrical, so the non-diagonal elements in the matrix M and D can be ignored. The control model of the unmanned ship is further simplified:

[0033]

[0034] In step S1, η = [xy ψ] T ,v=[uvr] T ,τ=[τ u ·0··τ r ] T , τ u represents the propulsion force, τ r represents torque, τ d =[τ du·τ dv ·τ dr ] T Represents the disturbance forces and moments on the hull in all directions.

[0035] By further expanding it, we can get the unmanned ship motion control model, which is as follows:

[0036]

[0037] Step S2, design the LOS guidance law and define a series of waypoints p1, p2…p k-1 ,p k …p n , assuming that the waypoint p currently needs to be tracked k (x k ,y k ), whose previous waypoint is Place two adjacent waypoints and p k (x k ,y k ) is connected, and the reference value of LOS is P los (x los ,y los )The solution formula is as follows;

[0038] The radius of the LOS acceptable circle made with the unmanned ship as the center is R, and the LOS angle ψ is calculated los for:

[0039]

[0040] Step 21 can introduce the visual distance Δ for control, and the position and the desired heading point P los (x los ,y los ) The projection distance on the desired track is the visible distance Δ = nL pp , where n ranges from 2 to 5. Lpp is the length of the unmanned ship. The expected heading angle ψ is expressed as follows:

[0041]

[0042] Step S3, optimizing the controller parameters by backstepping method.

[0043] Step 31: Assume τ u and τ r The trajectory tracking error e = [x e ,y e , ψ e ] can converge to 0, and its longitudinal velocity u converges to u d .

[0044] Step 32: Define the error ψ e =ψ-ψ d , construct the Lyapunov equation And its derivative is:

[0045] In the formula, the control parameter to be designed is Kψ>0.

[0046] Step 33: Define a new error r e =rr d , we can get:

[0047] Constructing the Lyapunov equation And its derivative is:

[0048]

[0049] , where Kr>0, from formula (11) we can get:

[0050]

[0051] Step 34: Design the unmanned ship speed controller and obtain the following control law:

[0052]

[0053] Among them, u d Speed ​​is the expected propulsion speed, u represents the propulsion speed, and the speed error is u e =uu d . k u >0, then according to the Lyapunov function derivation we can get: It can be concluded that the designed speed closed-loop system reaches asymptotic stability.

[0054] The unmanned ship trajectory tracking control law can be obtained:

[0055]

[0056] In step S3, the desired ship heading ψ is tracked d When the subsystem is constructed using the backstepping method, r d As a subsystem Input, again need to find the appropriate r d So that ψ approaches ψd.

[0057] Step S4, by establishing corresponding models in MATLAB and Simulink, the observer-based LOS guidance combined with backstepping control is simulated and the effect is evaluated.

[0058] In this embodiment, Figure 1 and Figure 2 As shown, the control method includes,

[0059] Step S101, model construction and initialization, establish the kinematic and dynamic models of the unmanned ship, clarify the relationship between displacement, speed, thrust vector and related matrices, consider the under-actuated simplified model, and determine various parameters; input the expected path information, define waypoints, calculate LOS related parameters such as reference value, angle, and set the acceptable circle radius.

[0060] Step S102, information acquisition and error judgment, obtain the current posture information of the unmanned ship, use sensors to obtain position, heading angle, and speed data; determine whether there is a track error, calculate the deviation between the actual position and the expected path, and determine the subsequent process based on the deviation.

[0061] Step S103, control parameter calculation and adjustment. If there is an error, the desired heading angle is calculated using the improved LOS guidance law, and the visual distance optimization calculation is introduced. The backstepping method is used to optimize the controller parameters by defining errors, constructing equations for derivation, and designing control law operations.

[0062] Step S104, control the steering angle of the servo according to the desired heading angle to adjust the course of the unmanned ship; determine whether the unmanned ship has reached the end point, if it has reached the end point, end the task, if not, return to the information acquisition step to continue tracking.

[0063] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. An unmanned ship path tracking control method based on improved LOS guidance law and backstepping method is characterized by: Step S1, establish the kinematic model of the unmanned ship: Among them, η represents the displacement angle vector, which is used to represent the position and direction information of the unmanned ship in the plane; v represents the velocity vector, which is used to represent the movement speed of the unmanned ship in the plane; τ represents the thrust and torque vector, which is used to control the movement of the unmanned ship; M represents the inertia matrix, C(v) represents the Coriolis force-centripetal force matrix, and D(v) represents the damping effect on the movement of the unmanned ship; Building a kinetic model: Among them, X represents the thrust on the longitudinal surge, that is, the longitudinal propulsion force of the unmanned ship; N represents the moment on the bow roll, K T represents the rudder coefficient, represents the thrust coefficient, ρ represents the water density, n represents the speed of the drive motor, D p represents the motor propeller diameter, u represents the propulsion speed, l r represents the length of the unmanned ship, δ r Indicates the rudder deflection angle; Step S2, design the LOS guidance law and define a series of waypoints p1, p2…p k-1 , p k ... pn , assuming that the waypoint p currently needs to be tracked k (x k ,y k ), whose previous waypoint is p k-1 (x k-1 ,y k-1 ), two adjacent waypoints p k-1 (x k-1 ,y k-1 ) 和 p k (x k ,y k ) is connected, and the reference value of LOS is P los (x los ,y los )The solution formula is as follows; The radius of the LOS acceptable circle made with the unmanned ship as the center is R, and the LOS angle ψ is calculated los for: Step S3, optimizing the controller parameters by backstepping method; Step S4, by establishing corresponding models in MATLAB and Simulink, the observer-based LOS guidance combined with backstepping control is simulated and the effect is evaluated. In step S1, η = [xy ψ] T ,v=[uvr] T , τ=[τ u ·0··τ r ] T , τ u represents the propulsion force, τ r represents torque, τ d =[τ du ·τ dv ·τ dr ] T Represents the disturbance forces and moments on the hull in all directions.

2. The unmanned ship path tracking control method based on improved LOS guidance law and backstepping method according to claim 1, characterized in that: In step S3, the desired ship heading ψ is tracked d When the subsystem is constructed using the backstepping method, r d As a subsystem Input, again need to find the appropriate r d So that ψ tends to ψd.

3. The unmanned ship path tracking control method based on improved LOS guidance law and backstepping method according to claim 1, characterized in that: Control methods include, Step S101, model construction and initialization, establish the kinematic and dynamic models of the unmanned ship, clarify the relationship between displacement, speed, thrust vector and related matrix, consider the under-actuated simplified model, and determine various parameters; input the expected path information, define waypoints, calculate LOS related parameters such as reference value, angle, and set the acceptable circle radius; Step S102, information acquisition and error judgment, obtain the current attitude information of the unmanned ship, use the sensor to obtain the position, heading angle, and speed data; determine whether there is a track error, calculate the deviation between the actual position and the expected path, and determine the subsequent process based on the deviation; Step S103, control parameter calculation and adjustment, if there is an error, use the improved LOS guidance law to calculate the desired heading angle, and introduce the visual distance optimization calculation; The backstepping method is used to optimize the controller parameters by defining errors, constructing equations for derivation, and designing control law operations; Step S104, control the steering angle of the servo according to the desired heading angle to adjust the course of the unmanned ship; determine whether the unmanned ship has reached the end point, if it has reached the end point, end the task, if not, return to the information acquisition step to continue tracking.

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