Ship stabilization control method and system based on multi-layer sliding mode structure

Abstract

The invention discloses a ship stabilization control method and system based on a multi-layer sliding mode structure, and belongs to the field of aircraft path tracking and attitude control. Firstly, a single-parameter ITTC spectrum model is established, encounter frequency is calculated in combination with the navigational speed and the wave direction angle, and an effective wave inclination angle is obtained; the method comprises the following steps: constructing a ship rolling kinetic equation by adopting a Conoll model, and converting the ship rolling kinetic equation into a state space form containing a composite interference term; a double-layer sliding mode surface is defined, an error fractional order derivative and a nonlinear term are fused in the first layer, and a nonlinear combination function is constructed in the second layer; the control law comprises an equivalent compensation item and a switching item with a parameter adaptive law, and the uncertainty of the model is suppressed by updating an estimated parameter in real time. And finally, the control torque is converted into a fin stabilizer rudder angle to drive an execution mechanism. According to the invention, ship stabilization control under the conditions of uncertain ship parameters and unknown external interference is realized, and the ship stabilization control effect is improved.

Description

Technical Field

[0001] The present invention belongs to the field of vehicle path tracking and attitude control, and in particular relates to a ship roll reduction control method and system based on a multi-layer sliding mode structure. Background Art

[0002] A ship's roll can adversely affect equipment, cargo, and the ship's operation under wind and wave disturbances. Ships are typically equipped with roll stabilization devices to effectively reduce the ship's roll and enhance navigation safety. Several devices are used to mitigate wave-induced roll, including bilge keels, water tanks, gyroscopes, rudder stabilizers, and fin stabilizers. Fin stabilizers are generally considered the best anti-roll device. Currently, the control strategy used for shipboard fin stabilizers is primarily PID control. However, when faced with complex sea conditions and various model uncertainties, PID control is not ideal.

[0003] Sliding mode control (SMC) offers advantages such as strong robustness, fast dynamic response, and good resistance to external disturbances. Its core concept is to introduce a sliding surface, allowing the system state to slide along the surface, thereby achieving stability and tracking the desired state. However, in practical applications, sliding mode control methods can introduce chattering. Reducing or eliminating this oscillation can effectively improve system control performance. To address chattering, tanh functions, inverse hyperbolic functions, or other forms can be used instead of conventional sign functions. Extensive research has also been conducted on the structure of the sliding surface. For example, nonlinear disturbance observers are introduced to incorporate observed disturbances into the system model; a terminal sliding mode control strategy that converges within a finite time is introduced; a nonsingular terminal sliding mode method is introduced to address singularities in the terminal sliding surface; high-order terms in the system state, namely high-order fast nonsingular terminal sliding mode control, are introduced to improve the convergence speed of the system state; the time-decrease property of fractional-order terms is used to suppress chatter in sliding mode control systems; and adaptive methods are introduced to adaptively adjust the coefficients of the control rate switching term to account for unknown disturbances. Summary of the Invention

[0004] The object of the present invention is to provide a method and system for controlling ship fin stabilizers with good anti-rolling effect.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A ship rolling stabilization control method based on a multi-layer sliding mode structure comprises the following steps:

[0007] Step 1: Use a single-parameter wave energy spectrum model to model irregular waves, set the wave height H, wave angular frequency ω and gravity acceleration g; establish a wave inclination model, and use the ship width correction coefficient K B , Draft correction factor K TCorrected wave inclination spectrum; calculated encounter frequency ω based on ship speed V and wave direction angle ψ e and encounter frequency energy spectrum S αe (ω e ) ; The effective encounter wave inclination angle is obtained by converting the encounter frequency energy spectrum;

[0008] Step 2: The ship rolling motion model adopts the Conolly model, and ignores the high-order small quantities in it, and then transforms the model into a state space form;

[0009] Step 3: Design a sliding film controller. The sliding surface is a fractional-order non-singular adaptive terminal sliding mode control surface, specifically:

[0010]

[0011] Where: k1=0.5(o1+1)+0.5(1-o1)sign(|e|-1), 0<o1<1; 0<α<1, α1>0; 2<k1<3; K2 and K3 are both greater than 0, 1<a / b<g / h c <2, and a, b, g, h c All are positive odd numbers; D α e is the fractional derivative of e; let e = θ - θ d ,θ d The expected roll angle of the ship is 0, that is, e = θ;

[0012] Design the sliding film controller to output the stable torque M c for:

[0013]

[0014] in, is the derivative of the equivalent control torque, is the derivative of the switching control torque;

[0015] Step 4: Output the stabilizing torque M according to the sliding membrane controller c Calculate the fin angle α through the fin torque conversion relationship q ; Verify the anti-sway effect through simulation experiments and set controller parameters and adaptive gain parameters.

[0016] Furthermore, the step 1 uses a single parameter ITTC spectrum:

[0017]

[0018] The formula for establishing the wave inclination angle model is:

[0019]

[0020] Among them, ω iis the discrete wave angular frequency, ε i is a random initial phase and is evenly distributed between 0 and 2π, S α (ω) is the wave inclination spectrum, N is the number of discretizations, and dω is the differential term;

[0021] Wave inclination spectrum S α (ω) is:

[0022]

[0023] Considering the ship width correction factor K B , Draft correction factor K T , and the wave dip spectrum is corrected to:

[0024]

[0025] Encounter frequency ω e and encounter frequency energy spectrum S αe (ω e ) is:

[0026]

[0027]

[0028] In summary, the effective encounter angle of the wave The formula is:

[0029]

[0030] Among them, dω e is the differential term, ω ei Discrete encounter frequency.

[0031] Furthermore, the ship rolling motion model in step 2 is:

[0032] I xx =I xx +J xx

[0033]

[0034] in: is the ship's rolling angular velocity, is the ship's roll angular acceleration, h is the ship's initial metacentric height, M w is the wave disturbance moment, N is the ship roll damping coefficient, and D is the ship displacement.

[0035] The model is converted into state space form:

[0036]

[0037] Among them, state x1 is the ship's roll angle θ, and state x2 is the ship's roll angular velocity Output y is the roll angle, M c Output stable torque for the sliding film controller, is the error of the nominal value of ship parameters and the wave disturbance moment M w The linear combination of , Δ represents the error.

[0038] Furthermore, the error Δ is within 20%.

[0039] Furthermore, the derivative of the equivalent control torque in step 3 is and the derivative of the switching control torque for:

[0040]

[0041] in,

[0042]

[0043]

[0044] in, ε is a parameter to be set, and ε>0, sign is a sign function, ||*|| represents the absolute value of *, is the adaptive coefficient, is the adaptive coefficient derivative, is the nominal term of the ship parameter.

[0045] Furthermore, the fin stabilizer force conversion relationship in step 4 is:

[0046] M c =2P y I r

[0047]

[0048] Among them, P y is the lift of the fin, I r is the ship's lifting arm, ρ is the seawater density, V is the ship's speed, A F is the fin stabilizer area, C y is the fin lift coefficient, α q is the fin angle of the fin stabilizer.

[0049] Furthermore, the controller parameters in step 4 are set as follows:

[0050] k1=2.3,k2=0.7,k3=0.5,a=7,b=5,g=5,h c =3,α1=0.3,ε=0.2,α=0.8;

[0051] Adaptive parameters

[0052] A computer device / equipment / system comprises a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of a ship rolling stabilization control method based on a multi-layer sliding mode structure.

[0053] The beneficial effects of the present invention are:

[0054] This paper investigates a control strategy based on fractional-order nonsingular adaptive fast terminal sliding mode control (FNAFTSMC) for fin stabilizers. The proposed controller employs a fractional-order nonsingular terminal sliding mode formulation to design the control law, incorporating an adaptive reaching law to estimate unknown uncertainties. Furthermore, the time derivative of the control signal is used as an additional control input to eliminate chatter. This adaptive adjustment method requires an upper bound on the system uncertainty.

[0055] The design of the sliding surface of the present invention includes two layers of sliding surfaces. The first layer of sliding surface is a low-order sliding surface combined with fractional-order derivatives, and the second sliding surface nests the high-order form of the low-order sliding surface; the design of the reaching law adopts an adaptive parameter switching form.

[0056] The irregular wave model of the present invention adopts a single-parameter wave energy spectrum model, and the main modified parameters are wave height, frequency and direction angle to simulate the impact of waves under different sea conditions.

[0057] The ship rolling motion model of the present invention mainly includes restoring moment, damping moment, inertia moment, wave disturbance moment and anti-rolling moment generated by the fin stabilizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Ship roll control framework;

[0059] Figure 2 Spectral density of different wave heights;

[0060] Figure 3 Effective wave inclination at different wave heights;

[0061] Figure 4 Ship roll and roll reduction effect under 2m wave height; (a) Ship roll angle under 2m wave height; (b) Total ship roll angle with roll reduction under 2m wave height; (c) Specific ship roll angle under 2m wave height; (d) Fin angle under 2m wave height;

[0062] Figure 5Ship roll and roll reduction effect in 3m wave height; (a) Ship roll angle in 3m wave height; (b) Total ship roll angle with roll reduction in 3m wave height; (c) Specific ship roll angle in 3m wave height; (d) Fin angle in 3m wave height;

[0063] Figure 6 Ship rolling and roll reduction effect under wave height of 5 m; (a) Ship roll angle under wave height of 5 m; (b) Total ship roll angle with roll reduction under wave height of 5 m; (c) Specific ship roll angle under wave height of 5 m; (d) Fin angle under wave height of 5 m. DETAILED DESCRIPTION

[0064] The present invention will be further described below with reference to the accompanying drawings.

[0065] The present invention provides a ship anti-rolling control method and system based on a multi-layer sliding mode structure, the method comprising the following steps:

[0066] Step 1: Irregular ocean wave modeling;

[0067] When establishing the amplitude model and spectrum, the spectral density function S ζ (ω), currently commonly used are PM spectrum, ITTC spectrum, ISSC spectrum, JONSWAP spectrum, etc. In the present invention, the single-parameter ITTC spectrum is selected as the simulation spectrum.

[0068] The single-parameter ITTC spectrum expression is:

[0069]

[0070] Where H is the wave height, ω is the wave angular frequency, and g is the acceleration due to gravity.

[0071] In actual ship rolling motion, the effect of wave inclination on the ship's rolling motion must be considered. Generally, the wave inclination is considered to be a stationary zero-mean random process. The mathematical model of the wave inclination at a fixed point in space is:

[0072]

[0073] Among them, ω i is the discrete wave angular frequency, ε i is a random initial phase and is evenly distributed between 0 and 2π, S α (ω) is the wave inclination spectrum, N is the number of discretizations, and dω is the differential term. The wave inclination spectrum calculation formula is:

[0074]

[0075] The shape and size of the ship will have different effects on the wave heel angle, so the ship width correction factor K is introduced. B , Draft correction factor KT Wave dip spectrum S αe (ω) is corrected to:

[0076]

[0077] When a ship's speed and wave direction are constant, the natural frequency of the wave is not equal to the actual frequency acting on the hull. The actual frequency acting on the hull is usually called the encounter frequency ω. e The calculation formula of encounter frequency and encounter frequency energy spectrum is:

[0078]

[0079] Where V is the ship speed and ψ is the wave direction angle (ψ = 0° when sailing with the waves).

[0080] In summary, the effective encounter angle of the wave The calculation formula is:

[0081]

[0082] Among them, dω e is the differential term, ω ei Discrete encounter frequency.

[0083] Step 2: Modeling the ship's rolling motion;

[0084] The present invention adopts the Conolly model of ship motion. The Conolly model considers the moment of the ship under the action of waves and includes the following parts:

[0085] (1) Restoring torque

[0086] When a ship rolls, the center of buoyancy and the center of gravity of the ship are not on the same vertical line, so the buoyancy will generate a torque relative to the center of gravity, causing the ship to return to equilibrium. Assuming the ship's roll angle is θ, the restoring torque is expressed as:

[0087] M R (θ)=Dhθ (8)

[0088] Where h is the initial metacentric height of the ship, and D is the displacement of the ship.

[0089] (2) Damping torque

[0090] During the rolling process, the relative motion between the ship and the waves causes resistance on both sides of the ship, which generates a resistance torque relative to the center of gravity. Assume that the ship's rolling angular velocity is The damping torque is expressed as:

[0091]

[0092] Where N is the roll damping coefficient, B N2 is the nonlinear damping coefficient.

[0093] Considering that the second term is smaller, it simplifies to:

[0094]

[0095] (3) Moment of inertia

[0096] There is angular acceleration during the ship's rolling process. Under the action of rotational inertia, the rolling motion will be affected by the inertia moment. The rotational inertia of the ship includes the rotational inertia of the ship itself and the additional rotational inertia. Assume that the ship's rolling angular acceleration is The moment of inertia is then expressed as:

[0097]

[0098] (4) Wave interference torque

[0099] The wave disturbance torque is proportional to the effective wave inclination angle, the effective wave inclination angle velocity and the effective wave inclination angle acceleration, which can be expressed as:

[0100]

[0101] In actual rolling motion, Term relative to Dhγ m The term is small and can be ignored. Therefore, the wave disturbance torque can be simplified as:

[0102]

[0103] where γ m is the effective wave inclination angle of the ocean wave.

[0104] In summary, according to the force balance of the ship under the action of waves, the equilibrium equation can be obtained:

[0105]

[0106] When the ship is equipped with anti-roll fins, adjusting the fin angle can generate a torque to resist wave interference and reduce the ship's rolling motion. In general, the sliding film controller outputs a stabilizing torque M c It can be expressed as:

[0107] M c =2P y I r (15)

[0108]

[0109] Where: P y is the lift of the fin, Ir is the ship's lifting arm, ρ is the seawater density, V is the ship's speed, A F is the fin stabilizer area, C y is the lift coefficient, α q The fin angle.

[0110] Therefore, the rolling model of a ship equipped with fin stabilizers is:

[0111] I' xx =I xx +J xx (17)

[0112]

[0113] When the right side of equation (18) is 0, that is, M c =-M w When the roll angle is 0, the roll reduction effect is the best.

[0114] Taking into account the inaccuracy of system parameters, the error terms of restoring torque, damping torque and inertia torque are set as Then the corresponding moment should be modified as:

[0115]

[0116] in: and is a nominal item.

[0117] In practice, the error term should be bounded, i.e. b0, b1, and b2 are all positive numbers. Then equation (18) can be rewritten as:

[0118]

[0119] in: is the nominal term of the ship parameter.

[0120] Assumption 1: The roll angle θ is bounded and θ∈[-π / 2,π / 2];

[0121] Assumption 2: M w ,ΔI' xx ,2ΔN and ΔDh represent the disturbance and uncertain ship parameters, such as hydrodynamic coefficients, mass, moment of inertia and other terms, which are assumed to be bounded.

[0122] In summary, based on the Conolly model, it is rewritten as the ship roll state space. Let state x1 be the ship roll angle θ, and state x2 be the ship roll angular velocity The output y is the roll angle, and the ship roll state space is:

[0123]

[0124] The goal of the controller is to design a sliding film controller to output a stable torque M c This ensures that the ship's roll angle is within the expected value.

[0125] Step 3: Design of synovial controller;

[0126] The designed sliding surface is a fractional-order non-singular adaptive terminal sliding control surface; the specific form is:

[0127]

[0128] Where: k1=0.5(o1+1)+0.5(1-o1)sign(|e|-1), 0<o1<1; 0<α<1, α1>0; 2<k1<3; K2 and K3 are both greater than 0, 1<a / b<g / h c <2, and a, b, g, h c All are positive odd numbers; D α e is the fractional derivative of e.

[0129] Let e ​​= θ - θ d ,θ d is the expected roll angle of the ship, which should be 0 here, that is, e = θ; then:

[0130]

[0131]

[0132] The sliding surface derivative is:

[0133]

[0134] in:

[0135]

[0136] From (26), we can get:

[0137] From equations (24), (25), and (26), we can conclude that the derivative of the output stabilizing torque of the sliding film controller is: is the derivative of the equivalent control torque; is the derivative of the switching control torque.

[0138] in:

[0139]

[0140] in: ε is a parameter to be set, and ε>0, sign is a sign function, ||*|| represents the absolute value of *, is the adaptive coefficient, is the adaptive coefficient derivative, is the nominal term of the ship parameter.

[0141] Finally, the output stability torque M of the sliding film controller is obtained c for:

[0142]

[0143] The block diagram of the fin stabilizer control strategy is as follows: Figure 1 When the ship is subjected to the wave disturbance torque, the sensor can measure the roll angle θ and roll angular velocity. The signal is transmitted to the controller, and the anti-tilt torque required for the anti-wave torque is obtained in real time according to formula (28), and the fin angle α is calculated according to formulas (15) and (16): q The optimal fin angle signal is then transmitted to the regulator, which can adjust the optimal fin angle according to sea conditions and ship speed. After the signal is amplified by the amplifier, it is transmitted to the servo system, which drives the anti-roll fin to the required fin angle α q In summary, the fin stabilizer generates a sliding film controller outputting a stabilizing torque M c To offset the wave interference torque M w , thereby reducing the ship's roll.

[0144] Step 4: Verify the anti-roll effect through simulation experiment;

[0145] In this invention, simulation studies were conducted under several sea conditions to verify the superiority of the proposed FNAFTSMC scheme. Furthermore, a comprehensive comparison was conducted among several control strategies: PID (Ship Roll Motion Modeling and Control Simulation Research, 2014), Adaptive Second-Order Fast Nonsingular Terminal Sliding Mode Tracking Control for Fully Actuated Autonomous Underwater Vehicles (ASOFNTSMC), Multi-Loop Recurrent Neural Network Fractional-Order Terminal Sliding Mode Control of MEMS Gyroscope (FOTSMC), and Adaptive Fast Terminal Sliding Mode Control (AFTSMC). The present invention selected waves with significant wave heights of 2m, 3m, and 5m to simulate the varying sea conditions encountered by ships during navigation. The wave direction angle in the simulation is 76.7° (at this wave direction angle, the ship's rolling angle is the most severe). Figure 2 is the single parameter ITTC spectrum at different wave heights, Figure 3 is the effective wave angle curve under different wave heights. Figure 2 and Figure 3 By comparison, it can be seen that the higher the sea conditions, the greater the wave spectrum density; the larger the effective wave angle, the more severe the roll.

[0146] A certain type of ship is taken as the research object. The nominal parameters of the ship are shown in Table 1. The ship speed in each scenario is 16.7 knots.

[0147] Table 1 Ship and fin stabilizer parameters

[0148]

[0149] In order to achieve satisfactory anti-roll performance of the system in the presence of irregular waves, the design parameters of the controller need to be adjusted. Select k1 = 2.3, k2 = 0.7, k3 = 0.5, a = 7, b = 5, g = 5, h c =3,α1=0.3,ε=0.2,α=0.8; adaptive parameters The initial roll and roll angles were set to zero in all cases. Similarly, the tanh function was used instead of the sign function to better suppress buffeting. In all cases, a 20% uncertainty was considered in the nominal parameters of mass and rotational inertia to further verify the robustness of the proposed control strategy. The anti-roll control effect η between different controllers was calculated and compared using the following equation:

[0150]

[0151] in: is the trinary value of the roll angle of the ship without the action of the fin stabilizer, It is the trinary value of the roll angle of the ship with the fin stabilizer.

[0152] Scenario 1, wave height is 2m (sea state level 4), the effect is as follows Figure 4 shown. Figure 4 (a) is the ship rolling without fin stabilizers, Figure 4 (b) is the comparison of the anti-shake effect of different controllers. Figure 4 (c) is the specific anti-shake effect of the controller, Figure 4 (d) is the specific output of the controller (stabilizer fin angle). In scenario 2, the wave height is 3m (sea state level 5), and the effect is as follows: Figure 5 As shown in the following scenario: In scenario 3, the wave height is 5m (sea state level 6), the effect is as follows: Figure 6 shown.

[0153] from Figure 4 (a) Figure 4 (b) Figure 5 (a) Figure 5 (b) Figure 6 (a) Figure 6 (b) It can be seen that under external time-varying disturbances (irregular waves), the five controllers can provide satisfactory control performance, which effectively proves the effectiveness of the anti-roll technology. Nevertheless, the control scheme proposed by us can guarantee the best control performance than the other four methods, such as Figure 4 (c), Figure 5 (c) Figure 6(c) shows the effective and superior performance of our proposed control scheme. Furthermore, the advantages of the five controllers can be demonstrated. The PID controller, despite lacking vessel information, also achieves generally satisfactory results. Its implementation is the most straightforward compared to the other control systems. The AFTSMC controller exhibits good convergence speed, reaching equilibrium within 5 seconds; however, during the steady-state phase, fluctuations near the equilibrium point are barely satisfactory. In contrast, the FOTSMC controller exhibits good stability during the steady-state phase, but exhibits significant overshoot in the initial phase and takes a long time to reach stability. The ASOFNTSMC controller builds on the AFTSMC (Adaptive Fast Terminal Sliding Mode Control) controller by implementing a higher-order sliding mode. It implements control output in an indirect integral form, resulting in faster convergence and less rolling motion near the equilibrium point than the AFTSMC controller. However, its stability during the steady-state phase still lags behind that of the FOTSMC controller. Furthermore, the proposed controller combines the advantages of both the ASOFNTSMC and FOTSMC controllers. It exhibits minimal overshoot and extremely short settling time, excellent stability during the steady-state phase, and offers optimal control performance.

[0154] To better illustrate the comparative roll reduction control effects, Table 2 shows a comparison of the roll reduction effects of the five controllers. This comparison of roll damping control further demonstrates the superiority of our proposed method. The study also found that while FOTSMC exhibits good characteristics during the stable phase, significant overshoot and a long settling time before stabilization reduce its roll reduction effectiveness. Furthermore, both FOTSMC and the proposed method demonstrate the advantages of fractional-order control over integer-order control.

[0155] Table 2 Comparison of anti-roll effect

[0156]

[0157] The trinity value of a ship's roll angle, as shown in the table, is a key parameter in ship seakeeping analysis, used to describe the statistical characteristics of roll motion. The trinity value is the average of the largest values ​​in the top one-third of all roll angle measurements in random waves, sorted by magnitude. It reflects the magnitude of a ship's roll in adverse sea conditions and better captures extreme motion than the average roll angle.

[0158] In terms of convergence time, the time required for the control effect to reach stability was used as the basis for comparison between different controllers. The results are shown in Table 3. Under three different wave height conditions, the control method proposed in this paper achieved the fastest stabilization speed, requiring less than 3 seconds. In contrast, the stabilization times of other controllers were all greater than 3 seconds. Therefore, the simulation results of this paper compared with other methods have been improved, and it has a higher convergence speed.

[0159] Table 3 Convergence time comparison

[0160]

[0161] In summary, the AFNFTSMC method proposed in this paper can achieve a good anti-roll effect. In addition, it shows excellent robustness and can handle various sea conditions and random uncertainties.

[0162] This paper investigates the issue of insufficient stability during the stabilization phase of high-order terminal sliding mode control methods. Considering that fractional-order systems have better stability than integer-order systems, a new sliding mode control strategy is proposed. This strategy naturally combines high-order terminal sliding mode control theory with fractional-order control theory. This strategy can handle random, multi-parameter uncertainties and various sea conditions while improving anti-roll performance. Simulation analysis under three different sea conditions demonstrates the advantages of this design over traditional sliding mode control:

[0163] (1) Faster convergence speed. The control method proposed in this paper reaches stability the fastest, with all stabilization times within 3 seconds. In comparison, the stabilization time of other controllers is greater than 3 seconds. The convergence time is shortened by more than 1 second.

[0164] (2) It has good characteristics in the stable stage. The method proposed in the present invention can maintain the position within a small range near the equilibrium point.

[0165] (3) The control effect is good. The proposed control method has the smallest residual roll angle and the roll reduction effect is above 98%, showing excellent anti-roll performance.

[0166] (4) The introduction of fractional derivatives and hyperbolic tangent (tanh) prevents the frequent switching of the system, making the dynamic response of the system smoother and effectively reducing chattering, indicating that the proposed method also has good industrial implementation feasibility.

[0167] (5) The control strategy has strong robustness, which is a key feature to ensure the reliable operation of the system under unknown conditions and when the system is uncertain.

[0168] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A ship rolling stabilization control method based on a multi-layer sliding mode structure, characterized by: The following steps are involved: Step 1: Use a single-parameter wave energy spectrum model to model irregular waves, setting the wave height H, wave angular frequency ω, and gravitational acceleration g; Establish the wave inclination model and use the ship width correction factor K B , Draft correction factor K T Corrected wave inclination spectrum; calculated encounter frequency ω based on ship speed V and wave direction angle ψ e and encounter frequency energy spectrum S αe (ω e ); obtain the effective encounter wave inclination angle by converting the encounter frequency energy spectrum; Step 2: The ship rolling motion model adopts the Conolly model, and ignores the high-order small quantities in it, and then transforms the model into a state space form; Step 3: Design a sliding film controller. The sliding surface is a fractional-order non-singular adaptive terminal sliding mode control surface, specifically: Where: k1=0.5(o1+1)+0.5(1-o1)sign(|e|-1), 0<o1<1; 0<α<1, α1>0; 2<k1<3; K2 and K3 are both greater than 0, 1<a / b<g / h c <2, and a, b, g, h c All are positive odd numbers; D α e is the fractional derivative of e; let e = θ - θ d ,θ d The expected roll angle of the ship is 0, that is, e = θ; Design the sliding film controller to output the stable torque M c for: in, is the derivative of the equivalent control torque, is the derivative of the switching control torque; Step 4: Output the stabilizing torque M according to the sliding membrane controller c Calculate the fin angle α through the fin torque conversion relationship q ; Verify the anti-sway effect through simulation experiments and set controller parameters and adaptive gain parameters.

2. The ship rolling stabilization control method based on a multi-layer sliding mode structure according to claim 1, characterized in that: The step 1 uses a single parameter ITTC spectrum: The formula for establishing the wave inclination angle model is: Among them, ω i is the discrete wave angular frequency, ε i is a random initial phase and is evenly distributed between 0 and 2π, S α (ω) is the wave inclination spectrum, N is the number of discretizations, and dω is the differential term; Wave inclination spectrum S α (ω) is: Considering the ship width correction factor K B , Draft correction factor K T , and the wave dip spectrum is corrected to: Encounter frequency ω e and encounter frequency energy spectrum S αe (ω e ) is: In summary, the effective encounter angle of the wave The formula is: Among them, dω e is the differential term, ω ei Discrete encounter frequency.

3. The ship rolling stabilization control method based on a multi-layer sliding mode structure according to claim 1, characterized in that: The ship rolling motion model in step 2 is: I′ xx =I xx +J xx in: is the ship's rolling angular velocity, is the ship's roll angular acceleration, h is the ship's initial metacentric height, M w is the wave disturbance moment, N is the ship roll damping coefficient, and D is the ship displacement. The model is converted into state space form: Among them, state x1 is the ship's roll angle θ, and state x2 is the ship's roll angular velocity Output y is the roll angle, M c Output stable torque for the sliding film controller, is the error of the nominal value of ship parameters and the wave disturbance moment M w The linear combination of , Δ represents the error.

4. The ship rolling stabilization control method based on a multi-layer sliding mode structure according to claim 3 is characterized by: The error Δ is within 20%.

5. The ship rolling stabilization control method based on a multi-layer sliding mode structure according to claim 1, characterized in that: The derivative of the equivalent control torque in step 3 is and the derivative of the switching control torque for: in, in, ε is a parameter to be set, and ε>0, sign is a sign function, ||*|| represents the absolute value of *, is the adaptive coefficient, is the adaptive coefficient derivative, is the nominal term of the ship parameter.

6. The ship rolling stabilization control method based on a multi-layer sliding mode structure according to claim 1, characterized in that: The fin stabilizer force conversion relationship in step 4 is: M c =2P y I r Among them, P y is the lift of the fin, I r is the ship's lifting arm, ρ is the seawater density, V is the ship's speed, A F is the fin stabilizer area, C y is the fin lift coefficient, α q is the fin angle of the fin stabilizer.

7. The ship rolling stabilization control method based on a multi-layer sliding mode structure according to claim 1, characterized in that: The controller parameters in step 4 are set as follows: k1=2.3,k2=0.7,k3=0.5,a=7,b=5,g=5,h c =3,α1=0.3,ε=0.2,α=0.8; Adaptive parameters 8. A computer device / apparatus / system comprising a memory, a processor, and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

Images