Under-actuated unmanned ship automatic berthing control method considering time-varying constraint, electronic equipment and storage medium

Abstract

The invention discloses an underactuated unmanned ship automatic berthing control method considering time-varying constraints, electronic equipment and a storage medium, and belongs to the technical field of ship automatic berthing. The invention aims to ensure that the unmanned ship has better operation performance and safety performance under the time-varying constraint. The method comprises the following steps: establishing an under-actuated unmanned ship mathematical model according to the movement condition of the under-actuated unmanned ship on the water surface; constructing a tangent obstacle Lyapunov function, and setting a constraint boundary as a judgment basis; differential homeomorphic transformation is carried out on the mathematical model of the under-actuated unmanned ship, then variable substitution is carried out on the mathematical model of the under-actuated unmanned ship after differential homeomorphic transformation, and a transformed surging subsystem model and a transformed heading subsystem model are obtained; using a tangent obstacle Lyapunov function to design a surging automatic berthing controller considering a time-varying constraint boundary; a tangent obstacle Lyapunov function is used for designing a heading automatic berthing controller considering a time-varying constraint boundary, and then simulation verification is carried out on an under-actuated unmanned ship.

Description

Technical Field

[0001] The present invention belongs to the technical field of automatic berthing of ships, and in particular relates to an automatic berthing control method for an underactuated unmanned ship considering time-varying constraints, an electronic device and a storage medium. Background Art

[0002] With the development of automation and intelligent technology, maritime operations have gradually attracted human attention. Underactuated unmanned ships are small in size, light in weight, and flexible, and can replace humans to complete many dangerous maritime tasks. Among them, the study of automatic berthing control of underactuated unmanned ships is an indispensable part of unmanned ship research. However, with the increase in the number of unmanned ships and the complexity of the port environment, the difficulty and risk of automatic berthing of unmanned ships have also increased. Therefore, in order to achieve safe berthing of the ship, it is very necessary to develop a highly stable automatic berthing control method.

[0003] The design of automatic berthing control algorithms for underactuated unmanned ships faces many challenges. For example, when an unmanned ship moves at a low speed in shallow water, it not only needs to deal with the impact of shallow water effects, but also needs to overcome the constraints brought by environmental factors such as the shore. Therefore, when berthing, the underactuated unmanned ship needs to ensure that there is enough safe distance between the hull and the shore, thereby improving the safety of automatic berthing. Summary of the invention

[0004] The problem to be solved by the present invention is to ensure that the unmanned ship has better operating performance and safety performance under time-varying constraints, and propose an automatic berthing control method, electronic equipment and storage medium for an underactuated unmanned ship considering time-varying constraints.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] An automatic berthing control method for an underactuated unmanned ship considering time-varying constraints comprises the following steps:

[0007] S1. According to the motion of the underactuated unmanned ship on the water surface, a mathematical model of the underactuated unmanned ship is established based on the three degrees of freedom of the unmanned ship on the water surface, namely, swaying, rolling and pitching;

[0008] S2. Construct a tangent barrier Lyapunov function and set a constraint boundary as a judgment basis. When the system output error is greater than the constraint boundary, the Lyapunov function is met. When the system output error is less than or equal to the constraint boundary, the tangent barrier Lyapunov function is applied.

[0009] S3. Performing a differential homeomorphic transformation on the mathematical model of the underactuated unmanned ship obtained in step S1, and then performing variable substitution on the mathematical model of the underactuated unmanned ship after the differential homeomorphic transformation to obtain a transformed longitudinal subsystem model and a transformed bow subsystem model;

[0010] S4. Based on the transformed surge subsystem model obtained in step S3, the position and surge velocity constraints of the unmanned ship when berthing near the shore are considered, and the tangent obstacle Lyapunov function designed in step S2 is used to design a surge automatic berthing controller considering the time-varying constraint boundary;

[0011] S5. Based on the transformed heading subsystem model obtained in step S3, the constraints of the heading angle and heading angular velocity of the unmanned ship when berthing near the shore are considered, and the tangent obstacle Lyapunov function designed in step S2 is used to design a heading automatic berthing controller considering the time-varying constraint boundary;

[0012] S6. Based on the surge automatic berthing controller taking into account the time-varying constraint boundary obtained in step S4 and the bow automatic berthing controller taking into account the time-varying constraint boundary obtained in step S5, simulation verification is performed on an under-actuated unmanned ship.

[0013] Furthermore, the specific implementation method of step S1 includes the following steps:

[0014] S1.1. Construct the kinematic model of the underactuated unmanned ship in the earth coordinate system, and the expression is:

[0015]

[0016] in, are the first-order derivatives of the north and east positions of the under-actuated unmanned ship in the geodetic coordinate system, ψ is the bow angle of the under-actuated unmanned ship in the geodetic coordinate system, is the first-order derivative of the bow angle of the underactuated unmanned ship in the geodetic coordinate system, u is the longitudinal velocity, v is the transverse velocity, and r is the bow angular velocity;

[0017] S1.2. Construct the dynamic model of underactuated unmanned ship in the appendage coordinate system, and the expression is:

[0018]

[0019] in, are the first-order derivatives of the surge velocity, lateral velocity, and bow angular velocity, respectively. is the inertial parameter, where m is the mass of the underactuated unmanned ship, and are the additional mass coefficients of the underactuated unmanned ship in surge, sway and bow pitch, d 11 =-X u , d 22 =-Y v , d 33 =-N r , X u , Y vand N r are the linear damping coefficients of the underactuated unmanned ship on surge, sway and bow pitch, τ u , τ r are the surge thrust and steering torque of the unmanned ship respectively;

[0020] S1.3. Construct the matrix form of the mathematical model of the underactuated unmanned ship, the expression is:

[0021]

[0022] in, is the first-order derivative vector of the position of the underactuated unmanned ship in the earth coordinate system, η=[x,y,ψ] T is the position vector of the underactuated unmanned ship in the geodetic coordinate system, υ=[u,v,r] T is the velocity vector of the underactuated unmanned ship in the appendage coordinate system, J(ψ) is the transformation matrix, M is the inertia parameter matrix, C(υ) is the Coriolis centripetal force matrix, D(υ) is the damping parameter matrix, and τ is the control input vector of the unmanned ship motion. The expression is as follows:

[0023]

[0024] τ=[τ u ,0,τ r ] T

[0025] Furthermore, the specific implementation method of step S2 includes the following steps:

[0026] S2.1. Construct the tangent barrier Lyapunov function, the expression is:

[0027]

[0028] Among them, V i is the i-th tangent barrier Lyapunov function, e i is the system output i-th error, F i is the constraint boundary of the ith error of the system output, and n is the total number of system outputs;

[0029] S2.2. Set the specific constraints of the tangent barrier Lyapunov function, the expression is:

[0030] F i =e a-bt +c

[0031] F i is an exponential decay function with respect to time t, where a ≥ 0, b ∈ [0, 1), c > 0; c is the constraint boundary F when time t approaches infinity iThe steady-state value of b is the constraint boundary F i The convergence rate of is equal to when the constraint boundary is infinite. At this time i is the unconstrained case; a is the constraint boundary F i The reference value determines the initial value of the constraint boundary (please give the meaning of the letter); the system output error satisfies |e i |≤|F i |;

[0032] S2.3. Take the derivative of V obtained in step S2.1 and obtain the expression:

[0033]

[0034] in,

[0035] Furthermore, the specific implementation method of step S3 includes the following steps:

[0036] S3.1. Perform differential homeomorphism transformation on the mathematical model of the underactuated unmanned ship obtained in step S1, and the expression is:

[0037] H=J T (ψ)η

[0038] Where H = [h1,h2,h3] T are the transformed position vectors, which are the transformed north position h1, east position h2 and heading angle h3 respectively. The position and attitude information of the underactuated unmanned ship in the geodetic coordinate system are converted to the follower coordinate system through differential homeomorphism transformation;

[0039] S3.2. Derivative the transformed position vector obtained in step S3.1 with respect to time t to obtain the derivative of the transformed position vector The expression is:

[0040]

[0041] based on Substituting the derivative of the transformed position vector, the mathematical model of the underactuated unmanned ship after differential homeomorphism transformation is as follows:

[0042]

[0043] S3.3. In order to simplify the subsequent controller design process, the following variable substitutions are defined;

[0044] definition make And introduce variables The mathematical model of the underactuated unmanned ship after variable substitution is as follows:

[0045]

[0046] S3.4. Let l1 = h1, l2 = H2, l3 = h3, l4 = θ, l5 = v, l6 = r, and obtain the mathematical model of the mutually cascaded underactuated unmanned ship, which is expressed as:

[0047]

[0048] in,

[0049] The transformed swing subsystem model is expressed as:

[0050]

[0051] The transformed heading subsystem model is expressed as:

[0052]

[0053] Furthermore, the specific implementation method of step S4 includes the following steps:

[0054] S4.1. Based on the transformed sloshing subsystem model obtained in step S3, define the position error e1 and sloshing velocity error e2, expressed as:

[0055]

[0056] Among them, α1 is the virtual controller of the swing subsystem to be designed;

[0057] S4.2. Design the virtual controller α1 of the swing subsystem, which is expressed as:

[0058]

[0059] Among them, k1 and k3 are constants greater than zero, and F1 is the constraint boundary of the position error e1;

[0060] S4.3. Derivative the virtual controller α1 of the swing subsystem, and the expression is:

[0061]

[0062] S4.4. Design of a surge automatic berthing controller τ considering time-varying constraints θ , the expression is:

[0063]

[0064] in, k2>0 and is a constant, and F2 is the constraint boundary of the surge velocity error e2.

[0065] Furthermore, the specific implementation method of step S5 includes the following steps:

[0066] S5.1. Based on the transformed heading subsystem model obtained in step S3, the steering angle error e3 and the angular velocity error e4 are defined as follows:

[0067]

[0068] Among them, α2 is the virtual controller of the heading subsystem to be designed;

[0069] S5.2. Design the virtual controller of the heading subsystem, the expression is:

[0070]

[0071] Among them, k4>0 and is a constant, F3 is the constraint boundary of the steering angle error e3;

[0072] S5.3. Derivative the virtual controller α2 of the heading subsystem, and the expression is:

[0073]

[0074] S5.4. Design the bow automatic berthing controller τ3 considering the time-varying constraint, and obtain the expression:

[0075]

[0076] in, k5>0 and is a constant.

[0077] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the automatic berthing control method of an underactuated unmanned ship considering time-varying constraints are implemented.

[0078] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the automatic berthing control method for an underactuated unmanned ship taking into account time-varying constraints.

[0079] Beneficial effects of the present invention:

[0080] The present invention discloses an automatic berthing control method for an underactuated unmanned ship taking into account time-varying constraints. Aiming at the problem that the unmanned ship is subject to position and speed constraints when berthing near the shore after completing the operation, an automatic berthing control method for an underactuated unmanned ship of a tangent obstacle Lyapunov function taking into account time-varying constraints is designed. By constructing a decaying exponential function constraint boundary, it is ensured that the unmanned ship is not restricted by the constraints in the initial stage of berthing because it is far away from the shore. When the hull reaches a certain distance from the shore, it is restricted by the constraints, so as to improve the safety of the unmanned ship during the automatic berthing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 A flow chart of an automatic berthing control method for an underactuated unmanned ship considering time-varying constraints according to the present invention;

[0082] Figure 2 The automatic berthing motion trajectory of the underactuated unmanned ship;

[0083] Figure 3 The following are the curves of the position and heading angle of the underactuated unmanned ship. (a) is the east position, (b) is the north position, and (c) is the turning angle.

[0084] Figure 4 The speed and bow angular velocity change curves of the underactuated unmanned ship, where (a) is the swell velocity, (b) is the lateral velocity, and (c) is the turning angle;

[0085] Figure 5 The curves of position error and swell speed error of underactuated unmanned ship are shown in Figure 1. (a) is the position error and (b) is the swell speed error.

[0086] Figure 6 The following are the curves of steering angle error and angular velocity error of underactuated unmanned ship. (a) is the steering angle error and (b) is the angular velocity error.

[0087] Figure 7 This is the change curve of the control input of the under-actuated unmanned ship, where (a) is the surge thrust and (b) is the steering torque. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0089] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0090] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 -Attached Figure 7 The detailed instructions are as follows:

[0091] Embodiment 1:

[0092] An automatic berthing control method for an underactuated unmanned ship considering time-varying constraints comprises the following steps:

[0093] S1. According to the motion of the underactuated unmanned ship on the water surface, a mathematical model of the underactuated unmanned ship is established based on the three degrees of freedom of the unmanned ship on the water surface, namely, swaying, rolling and pitching;

[0094] Furthermore, the specific implementation method of step S1 includes the following steps:

[0095] S1.1. Construct the kinematic model of the underactuated unmanned ship in the earth coordinate system, and the expression is:

[0096]

[0097] in, are the first-order derivatives of the north and east positions of the under-actuated unmanned ship in the geodetic coordinate system, ψ is the bow angle of the under-actuated unmanned ship in the geodetic coordinate system, is the first-order derivative of the bow angle of the underactuated unmanned ship in the geodetic coordinate system, u is the swell velocity, v is the lateral velocity, and r is the bow angular velocity;

[0098] S1.2. Construct the dynamic model of underactuated unmanned ship in the appendage coordinate system, and the expression is:

[0099]

[0100] in, are the first-order derivatives of the surge velocity, lateral velocity, and bow angular velocity, respectively. is the inertial parameter, where m is the mass of the underactuated unmanned ship, and are the additional mass coefficients of the underactuated unmanned ship in surge, sway and bow pitch, d 11 =-X u, d 22 =-Y v , d 33 =-N r , X u , Y v and N r are the linear damping coefficients of the underactuated unmanned ship on surge, sway and bow pitch, τ u , τ r are the surge thrust and steering torque of the unmanned ship respectively;

[0101] S1.3. Construct the matrix form of the mathematical model of the underactuated unmanned ship, the expression is:

[0102]

[0103] in, is the first-order derivative vector of the position of the underactuated unmanned ship in the earth coordinate system, η=[x,y,ψ] T is the position vector of the underactuated unmanned ship in the geodetic coordinate system, υ=[u,v,r] T is the velocity vector of the underactuated unmanned ship in the appendage coordinate system, J(ψ) is the transformation matrix, M is the inertia parameter matrix, C(υ) is the Coriolis centripetal force matrix, D(υ) is the damping parameter matrix, and τ is the control input vector of the unmanned ship motion. The expression is as follows:

[0104]

[0105] τ=[τ u ,0,τ r ] T ;

[0106] S2. Construct a tangent barrier Lyapunov function and set a constraint boundary as a judgment basis. When the system output error is greater than the constraint boundary, the Lyapunov function is met. When the system output error is less than or equal to the constraint boundary, the tangent barrier Lyapunov function is applied.

[0107] Furthermore, the specific implementation method of step S2 includes the following steps:

[0108] S2.1. Construct the tangent barrier Lyapunov function, the expression is:

[0109]

[0110] Among them, V i is the i-th tangent barrier Lyapunov function, e i is the system output i-th error, F i is the constraint boundary of the ith error of the system output, and n is the total number of system outputs;

[0111] S2.2. Set the specific constraints of the tangent barrier Lyapunov function, the expression is:

[0112] F i =e a-bt +c

[0113] F i is an exponential decay function with respect to time t, where a ≥ 0, b ∈ [0, 1), c > 0; c is the constraint boundary F when time t approaches infinity i The steady-state value of b is the constraint boundary F i The convergence rate of is equal to when the constraint boundary is infinite. At this time i is the unconstrained case; a is the constraint boundary F i The baseline value determines the initial value of the constraint boundary; the system output error satisfies |e i |≤|F i |;

[0114] S2.3. Take the derivative of V obtained in step S2.1 and obtain the expression:

[0115]

[0116] in,

[0117] S3. Performing a differential homeomorphic transformation on the mathematical model of the underactuated unmanned ship obtained in step S1, and then performing variable substitution on the mathematical model of the underactuated unmanned ship after the differential homeomorphic transformation to obtain a transformed longitudinal subsystem model and a transformed bow subsystem model;

[0118] Furthermore, the specific implementation method of step S3 includes the following steps:

[0119] S3.1. Perform differential homeomorphism transformation on the mathematical model of the underactuated unmanned ship obtained in step S1, and the expression is:

[0120] H=J T (ψ)η

[0121] Where H = [h1,h2,h3] T are the transformed position vectors, which are the transformed north position h1, east position h2 and heading angle h3 respectively. The position and attitude information of the underactuated unmanned ship in the geodetic coordinate system are converted to the follower coordinate system through differential homeomorphism transformation;

[0122] S3.2. Derivative the transformed position vector obtained in step S3.1 with respect to time t to obtain the derivative of the transformed position vector The expression is:

[0123]

[0124] based on Substituting the derivative of the transformed position vector, the mathematical model of the underactuated unmanned ship after differential homeomorphism transformation is as follows:

[0125]

[0126] S3.3. In order to simplify the subsequent controller design process, the following variable substitutions are defined;

[0127] definition make And introduce variables The mathematical model of the underactuated unmanned ship after variable substitution is as follows:

[0128]

[0129] S3.4. Let l1 = h1, l2 = H2, l3 = h3, l4 = θ, l5 = v, l6 = r, and obtain the mathematical model of the mutually cascaded underactuated unmanned ship, which is expressed as:

[0130]

[0131] in,

[0132] The transformed sloshing subsystem model is expressed as:

[0133]

[0134] The transformed heading subsystem model is expressed as:

[0135]

[0136] S4. Based on the transformed surge subsystem model obtained in step S3, the position and surge velocity constraints of the unmanned ship when berthing near the shore are considered, and the tangent obstacle Lyapunov function designed in step S2 is used to design a surge automatic berthing controller considering the time-varying constraint boundary;

[0137] Furthermore, the specific implementation method of step S4 includes the following steps:

[0138] S4.1. Based on the transformed sloshing subsystem model obtained in step S3, define the position error e1 and sloshing velocity error e2, expressed as:

[0139]

[0140] Among them, α1 is the virtual controller of the swing subsystem to be designed;

[0141] Furthermore, we select the barrier Lyapunov function with time-varying constraints:

[0142]

[0143] Wherein, F1 is an exponential decay function with respect to time t, which is the constraint boundary of the position error e1, and the position error e1 satisfies |e1|≤|F1|;

[0144] Taking the derivative of V1, we get:

[0145]

[0146] S4.2. In order to stabilize the position error e1, a virtual controller α1 of the oscillation subsystem is designed, which is expressed as:

[0147]

[0148] Among them, k1 and k3 are constants greater than zero;

[0149] but for:

[0150]

[0151] S4.3. Taking the derivative of the virtual controller α1 of the swing subsystem, we get the expression:

[0152]

[0153] Choose a barrier Lyapunov function with a time-varying constraint:

[0154]

[0155] Wherein, F2 is an exponential decay function with respect to time t, which is the constraint boundary of the sway velocity error e2, and the sway velocity error e2 satisfies |e2|≤|F2|;

[0156] Taking the derivative of V2, we get:

[0157]

[0158] S4.4. Design a surge automatic berthing controller τθ considering time-varying constraints, expressed as:

[0159]

[0160] in, k2>0 and is a constant, k2>0 and is a constant.

[0161] The controller τ θ Substitution We can get:

[0162]

[0163] Lyapunov's stability theorem shows that the position error e1 and the sloshing velocity error e2 are asymptotically stable.

[0164] S5. Based on the transformed heading subsystem model obtained in step S3, the constraints of the heading angle and heading angular velocity of the unmanned ship when berthing near the shore are considered, and the tangent obstacle Lyapunov function designed in step S2 is used to design a heading automatic berthing controller considering the time-varying constraint boundary;

[0165] Furthermore, the specific implementation method of step S5 includes the following steps:

[0166] S5.1. Based on the transformed heading subsystem model obtained in step S3, the steering angle error e3 and the angular velocity error e4 are defined as follows:

[0167]

[0168] Among them, α2 is the virtual controller of the heading subsystem to be designed;

[0169] Furthermore, we select the barrier Lyapunov function with time-varying constraints:

[0170]

[0171] Wherein, F3 is an exponential decay function with respect to time t, which is the constraint boundary of the steering angle error e3, and the steering angle error e3 satisfies |e3|≤|F3|;

[0172] Taking the derivative of V3, we get:

[0173]

[0174] S5.2. In order to stabilize the steering angle error e3, a virtual controller of the heading subsystem is designed, and the expression is:

[0175]

[0176] Among them, k4>0 and is a constant;

[0177] S5.3. Derivative the virtual controller α2 of the heading subsystem, and the expression is:

[0178]

[0179] Choose a barrier Lyapunov function with a time-varying constraint:

[0180]

[0181] Wherein, F4 is an exponential decay function with respect to time t, which is the constraint boundary of the steering angular velocity error e4, and the steering angular velocity error satisfies |e4|≤|F4|.

[0182] Taking the derivative of V4, we get:

[0183]

[0184] S5.4. Design the bow automatic berthing controller τ3 considering the time-varying constraint, and obtain the expression:

[0185]

[0186] in, k5>0 and is a constant;

[0187] Substituting the controller τ3 into the equation, we get:

[0188]

[0189] Therefore, according to Lyapunov's stability theorem, the steering angle error e3 and the steering angular velocity e4 are asymptotically stable;

[0190] S6. Based on the surge automatic berthing controller taking into account the time-varying constraint boundary obtained in step S4 and the bow automatic berthing controller taking into account the time-varying constraint boundary obtained in step S5, simulation verification is performed on an under-actuated unmanned ship.

[0191] Furthermore, in order to verify the effectiveness of the proposed method, the designed under-actuated unmanned ship surge automatic berthing controller and bow automatic berthing controller considering time-varying constraints were applied to a certain type of unmanned ship. The under-actuated unmanned ship is 1.19m long and has a mass of 17.6kg.

[0192] The initial state of the unmanned ship is [x, y, ψ, u, v, r] = [-10m, -10m, π / 3rad, 0.5m / s, 0m / s, 0rad / s]; the time-varying constraint boundary of the eastward position error is selected as F1 = e 2-0.3t +1; the time-varying constraint of the surge velocity error is F2 = e 2.5-0.3t +0.5; the steering angle error boundary is selected as a constant F3 = 1.2; the steering angular velocity error boundary is selected as a constant F4 = 0.15. The effectiveness of the automatic berthing control method of an underactuated unmanned ship considering time-varying constraints of the present invention is verified by Matlab / Simulink software. The simulation results are as follows: Figure 2-7 shown.

[0193] Figure 2It represents the automatic berthing motion trajectory of the under-actuated unmanned ship. From the motion trajectory of the unmanned ship in the figure, it can be seen that the under-actuated unmanned ship can complete the automatic berthing task under the action of the automatic berthing controller of the present invention. The berthing trajectory is relatively smooth and can eventually dock at the set berthing point.

[0194] Figure 3 It represents the change curve of the position and heading angle of the under-actuated unmanned ship, specifically the change curve of the east position x, the north position y and the steering angle ψ. It can be seen from the figure that under the action of the controller of the present invention, the east position x and the north position y can converge to 0 in about 15s; the steering angle ψ can converge to 0 in about 30s.

[0195] Figure 4 It represents the speed change curve of the under-actuated unmanned ship, specifically the change curves of the longitudinal speed u, the lateral speed v and the steering angle r. From the speed change curve in the figure, it can be seen that the automatic berthing controller of the present invention has a good control effect and can control the speed to converge to 0, thereby realizing the automatic berthing operation.

[0196] Figure 5 Figure 2 shows the position error and surge speed error variation curves of the under-actuated unmanned ship. The solid line in the figure represents the error variation curve, the dotted line represents the upper bound of the time-varying constraint, and the dashed line represents the lower bound of the time-varying constraint. It can be seen from the figure that under the action of the controller designed in the present invention, the position error and the surge speed error converge to 0 in about 10 seconds, and always keep changing within the constraint range. In addition, within about 15 seconds, it is not subject to the constraint restriction due to the long distance from the shore. After 15 seconds, it is subject to the constraint restriction as the distance to the shore gets closer and closer.

[0197] Figure 6 The figure represents the changing curves of the steering angle error and angular velocity error of the under-actuated unmanned ship. The solid line in the figure represents the error changing curve, the dotted line represents the upper bound of the time-varying constraint, and the dashed line represents the lower bound of the time-varying constraint. It can be seen from the figure that under the action of the controller designed in the present invention, the steering angle error converges to 0 in about 30 seconds and the steering angular velocity error converges to 0 in about 10 seconds, and always keeps changing within the constraint range. The automatic berthing controller designed in the present invention can handle situations with different constraints, not only time-varying constraints and constant constraints, but also constrained and unconstrained situations.

[0198] Figure 7 Represents the change curve of the control input of the underactuated unmanned ship, specifically the surge thrust τ u and steering torque τ r As can be seen from the figure, the surge and bow automatic berthing controller designed in the present invention changes relatively smoothly without jumps and overshoots, which is in line with actual engineering design.

[0199] Embodiment 2:

[0200] An electronic device, characterized in that it includes a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps of the automatic berthing control method of an under-actuated unmanned ship considering time-varying constraints described in Example 1 are implemented.

[0201] The computer device of the present invention may be a device including a processor and a memory, such as a single chip microcomputer including a central processing unit. Furthermore, the processor is used to implement the steps of the above-mentioned automatic berthing control method of an underactuated unmanned ship considering time-varying constraints when executing the computer program stored in the memory.

[0202] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0203] The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0204] Embodiment 3:

[0205] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the automatic berthing control method for an under-actuated unmanned ship considering time-varying constraints described in Example 1 is implemented.

[0206] The computer-readable storage medium of the present invention can be any form of storage medium that can be read by the processor of a computer device, including but not limited to non-volatile memory, volatile memory, ferroelectric memory, etc. The computer-readable storage medium stores a computer program. When the processor of the computer device reads and executes the computer program stored in the memory, the steps of the above-mentioned method for automatic berthing control of an under-actuated unmanned ship considering time-varying constraints can be implemented.

[0207] The computer program includes computer program code, which may be in source code form, object code form, executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0208] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0209] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An automatic berthing control method for an underactuated unmanned vessel considering time-varying constraints, characterized in that: The steps include: S1. According to the motion of the underactuated unmanned ship on the water surface, a mathematical model of the underactuated unmanned ship is established based on the three degrees of freedom of the unmanned ship on the water surface, namely, swaying, rolling and pitching; S2. Construct a tangent barrier Lyapunov function and set a constraint boundary as a judgment basis. When the system output error is greater than the constraint boundary, the Lyapunov function is met. When the system output error is less than or equal to the constraint boundary, the tangent barrier Lyapunov function is applied. S3. Performing a differential homeomorphic transformation on the mathematical model of the underactuated unmanned ship obtained in step S1, and then performing variable substitution on the mathematical model of the underactuated unmanned ship after the differential homeomorphic transformation to obtain a transformed longitudinal subsystem model and a transformed bow subsystem model; S4. Based on the transformed surge subsystem model obtained in step S3, the position and surge velocity constraints of the unmanned ship when berthing near the shore are considered, and the tangent obstacle Lyapunov function designed in step S2 is used to design a surge automatic berthing controller considering the time-varying constraint boundary; S5. Based on the transformed heading subsystem model obtained in step S3, the constraints of the heading angle and heading angular velocity of the unmanned ship when berthing near the shore are considered, and the tangent obstacle Lyapunov function designed in step S2 is used to design a heading automatic berthing controller considering the time-varying constraint boundary; S6. Based on the surge automatic berthing controller taking into account the time-varying constraint boundary obtained in step S4 and the bow automatic berthing controller taking into account the time-varying constraint boundary obtained in step S5, simulation verification is performed on an under-actuated unmanned ship.

2. The automatic berthing control method of an underactuated unmanned vessel considering time-varying constraints according to claim 1, characterized in that: The specific implementation method of step S1 includes the following steps: S1.

1. Construct the kinematic model of the underactuated unmanned ship in the earth coordinate system, and the expression is: in, are the first-order derivatives of the north and east positions of the under-actuated unmanned ship in the geodetic coordinate system, ψ is the bow angle of the under-actuated unmanned ship in the geodetic coordinate system, is the first-order derivative of the bow angle of the underactuated unmanned ship in the geodetic coordinate system, u is the swell velocity, v is the lateral velocity, and r is the bow angular velocity; S1.

2. Construct the dynamic model of underactuated unmanned ship in the appendage coordinate system, and the expression is: in, are the first-order derivatives of the surge velocity, lateral velocity, and bow angular velocity, respectively. is the inertial parameter, where m is the mass of the underactuated unmanned ship, and are the additional mass coefficients of the underactuated unmanned ship in surge, sway and bow pitch, and d 11 =-X u , d 22 =-Y v , d 33 =-N r , X u , Y v and N r are the linear damping coefficients of the underactuated unmanned ship on surge, sway and bow pitch, τ u , τ r are the surge thrust and steering torque of the unmanned ship respectively; S1.

3. Construct the matrix form of the mathematical model of the underactuated unmanned ship, the expression is: in, is the first-order derivative vector of the position of the underactuated unmanned ship in the earth coordinate system, η=[x,y,ψ] T is the position vector of the underactuated unmanned ship in the geodetic coordinate system, υ=[u,v,r] T is the velocity vector of the underactuated unmanned ship in the appendage coordinate system, J(ψ) is the transformation matrix, M is the inertia parameter matrix, C(υ) is the Coriolis centripetal force matrix, D(υ) is the damping parameter matrix, and τ is the control input vector of the unmanned ship motion. The expression is as follows: τ=[τ u ,0,t r ] T 。 3. The automatic berthing control method of an underactuated unmanned vessel considering time-varying constraints according to claim 2, characterized in that: The specific implementation method of step S2 includes the following steps: S2.

1. Construct the tangent barrier Lyapunov function, the expression is: Among them, V i is the i-th tangent barrier Lyapunov function, e i is the system output i-th error, F i is the constraint boundary of the ith error of the system output, and n is the total number of system outputs; S2.

2. Set the specific constraints of the tangent barrier Lyapunov function, the expression is: F i =e a-bt +c F i is an exponential decay function with respect to time t, where a ≥ 0, b ∈ [0, 1), c > 0; c is the constraint boundary F when time t approaches infinity i The steady-state value of b is the constraint boundary F i The convergence rate of is equal to when the constraint boundary is infinite. At this time i is the unconstrained case; a is the constraint boundary F i The baseline value determines the initial value of the constraint boundary; the system output error satisfies |e i |≤|F i |; S2.

3. Take the derivative of V obtained in step S2.1 and obtain the expression: in, 4. The automatic berthing control method for an underactuated unmanned vessel considering time-varying constraints according to claim 3 is characterized in that: The specific implementation method of step S3 includes the following steps: S3.

1. Perform differential homeomorphism transformation on the mathematical model of the underactuated unmanned ship obtained in step S1, and the expression is: H=J T (ψ)η Where H = [h1,h2,h3] T are the transformed position vectors, which are the transformed north position h1, east position h2 and heading angle h3 respectively. The position and attitude information of the underactuated unmanned ship in the geodetic coordinate system are converted to the follower coordinate system through differential homeomorphism transformation; S3.

2. Derivative the transformed position vector obtained in step S3.1 with respect to time t to obtain the derivative of the transformed position vector The expression is: based on Substituting the derivative of the transformed position vector, the mathematical model of the underactuated unmanned ship after differential homeomorphism transformation is as follows: S3.

3. In order to simplify the subsequent controller design process, the following variable substitutions are defined; definition make And introduce variables The mathematical model of the underactuated unmanned ship after variable substitution is as follows: S3.

4. Let l1 = h1, l2 = H2, l3 = h3, l4 = θ, l5 = v, l6 = r, and obtain the mathematical model of the mutually cascaded underactuated unmanned ship, which is expressed as: in, The transformed sloshing subsystem model is expressed as: The transformed heading subsystem model is expressed as:

5. The automatic berthing control method of an underactuated unmanned vessel considering time-varying constraints according to claim 4, characterized in that: The specific implementation method of step S4 includes the following steps: S4.

1. Based on the transformed sloshing subsystem model obtained in step S3, define the position error e1 and sloshing velocity error e2, expressed as: Among them, α1 is the virtual controller of the swing subsystem to be designed; S4.

2. Design the virtual controller α1 of the swing subsystem, which is expressed as: Among them, k1 and k3 are constants greater than zero, and F1 is the constraint boundary of the position error e1; S4.

3. Taking the derivative of the virtual controller α1 of the swing subsystem, we get the expression: S4.

4. Design of a surge automatic berthing controller τ considering time-varying constraints θ , the expression is: in, k2>0 and is a constant, and F2 is the constraint boundary of the sloshing velocity error e2.

6. The automatic berthing control method for an underactuated unmanned vessel considering time-varying constraints according to claim 5, characterized in that: The specific implementation method of step S5 includes the following steps: S5.

1. Based on the transformed heading subsystem model obtained in step S3, the steering angle error e3 and the angular velocity error e4 are defined as follows: Among them, α2 is the virtual controller of the heading subsystem to be designed; S5.

2. Design the virtual controller of the heading subsystem, the expression is: Among them, k4>0 and is a constant, F3 is the constraint boundary of the steering angle error e3; S5.

3. Derivative the virtual controller α2 of the heading subsystem, and the expression is: S5.

4. Design the bow automatic berthing controller τ3 considering the time-varying constraint, and obtain the expression: in, k5>0 and is a constant.

7. An electronic device, characterized in that: The invention comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the automatic berthing control method of an underactuated unmanned ship considering time-varying constraints as described in any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the automatic berthing control method for an under-actuated unmanned ship considering time-varying constraints as described in any one of claims 1 to 6 is implemented.

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