Fitting analysis method and system for calculating ice-breaking force of uuv in ice edge zone

Abstract

The application discloses an ice edge area UUV ice crushing force calculation fitting analysis method and system, relates to the vehicle technical field, and comprises the following steps: obtaining full calculation conditions according to an ice edge area UUV ice crushing scene setting numerical simulation calculation model; and completing ice edge area UUV ice crushing force calculation fitting analysis through the numerical simulation, the ice crushing force amplitude fitting, the ice crushing force angle frequency fitting, the stability determination and the multi-speed rotary condition stability determination. The application establishes a high-fidelity CFD-DEM coupling calculation framework, calculates the ice crushing force suffered by the UUV when sailing in the ice edge area, and accurately captures the dynamic load fluctuation caused by the ice crushing. By using the established motion simulation platform, the influence of different ice crushing environments on the UUV control stability and robustness is quantitatively evaluated, and the demand of quickly predicting the dynamic load in engineering is met.

Description

Technical Field

[0001] This invention relates to the field of aircraft technology, and in particular to a method and system for calculating, fitting and analyzing the ice-breaking force of UUVs in the periglacial region. Background Technology

[0002] When vehicles perform cross-medium communication, navigation, positioning, or sub-ice observation missions in polar ice periglacial regions, their operating environment differs significantly from that of open water. The presence of sea ice not only alters the boundary conditions of the free surface but also introduces complex ice-water coupling interference. To meet mission requirements, vehicles often need to surface near the ice surface or even perform icebreaking or ice removal operations. At this time, complex multi-body strong coupling effects form between the vehicle, ice fragments, and the flow field, greatly affecting the vehicle's hydrodynamic characteristics and structural safety. Accurately predicting the hydrodynamic loads and their variation characteristics experienced by vehicles navigating near the polar ice surface is a core prerequisite for the design of polar vehicle hull optimization and control systems.

[0003] In recent years, numerical prediction and experimental techniques for the navigation performance of vehicles in ice-covered areas have received widespread attention. However, current hydrodynamic predictions for vehicles in ice-covered areas mainly focus on continuous ice environments, emphasizing icebreaking resistance estimation or simple sub-ice depth straight-line flow field analysis. In contrast, vehicles spend a higher proportion of their navigation time and encounter more frequently in peri-ice zones (containing a large amount of ice flakes and floating ice) during polar operations. Research on ice flake environments is still in its early stages, and existing numerical prediction methods (such as CFD coupled with discrete element method) are computationally expensive, making it difficult to meet the engineering requirements for rapid prediction of dynamic loads; while traditional empirical formulas cannot accurately capture the dynamic fluctuation characteristics of loads caused by ice flakes. These shortcomings have become obstacles to in-depth research on vehicle navigation under complex ice conditions in polar regions.

[0004] Furthermore, the vehicle exhibits multi-degree-of-freedom spatial maneuvering characteristics when performing complex tasks. Under intense maneuvering, the flow field around the vehicle already exhibits highly asymmetric and unsteady characteristics; when superimposed with random collisions, slippage, and viscous disturbances from ice fragments, the nonlinearity and randomness of the flow field distribution are further aggravated, and the hydrodynamics exhibits extremely strong coupled nonlinearity. If an efficient and reliable system for calculating and fitting ice fragment forces cannot be established, the robustness of the motion control algorithm for polar vehicles will be directly affected, and the conduct of their navigation safety assessment will be restricted. Summary of the Invention

[0005] This invention provides a method and system for calculating and fitting the force of UUV ice fragmentation in the periglacial region. This method addresses the problem that existing numerical prediction methods, such as CFD coupled with discrete element method, have high computational costs and are difficult to meet the engineering requirements for rapid prediction of dynamic loads. Furthermore, traditional empirical formulas cannot accurately capture the dynamic load fluctuations caused by ice fragmentation.

[0006] On one hand, embodiments of the present invention provide a method for calculating and fitting the force of UUV ice fragmentation in the periglacial region, including: A numerical simulation model was constructed to represent all computational conditions based on the UUV ice fragmentation scenario in the periglacial zone. Numerical simulations of each working condition in the full computational working condition were carried out using the computational fluid dynamics-discrete element coupling method to obtain the original time-domain data of the total force and total torque of the UUV. The fluid background load and ice fragmentation load in the original time-domain data are separated by the time-domain trend separation method to extract core analysis samples. Based on the core analysis samples, a multi-factor coupling model was constructed and parameters were solved to complete the fitting of the ice-breaking force amplitude. The angular frequency fitting of the ice-breaking force was completed by replacing the coupled model with the amplitude model architecture; Based on the results of fitting the amplitude of the ice-breaking force and fitting the angular frequency of the ice-breaking force, a six-degree-of-freedom dynamic equation for the UUV is constructed. Stability determination is achieved by combining the longitudinal dynamic equation, the small perturbation theory, and the aforementioned six-degree-of-freedom dynamic equation of the UUV. Stability determination for turning conditions at multiple speeds is achieved through lateral dynamics equations and the aforementioned six-degree-of-freedom UUV dynamics equations. The calculation, fitting, and analysis of the ice-breaking force of UUVs in the ice edge zone were completed through numerical simulation, fitting of the amplitude of the ice-breaking force, fitting of the angular frequency of the ice-breaking force, stability determination, and stability determination under multi-speed turning conditions.

[0007] In one possible implementation, the full computational conditions include navigation depth, speed, ice density, and pitch angle.

[0008] In one possible implementation, the total force of the UUV includes viscous drag, wave-making drag, and ice-breaking induced force.

[0009] In one possible implementation, the viscous drag is generated by fluid viscosity; the wave-making drag is generated by navigation wave-making; and the ice-breaking induced force is generated by the reaction of wave-making disturbance ice swarms on the UUV surface.

[0010] In one possible implementation, the amplitude of the ice-breaking force is composed of a cubic polynomial of the ice-breaking density, a quartic polynomial of the UUV pitch angle, and a coupling term between the UUV's travel depth and the Froude number.

[0011] In one possible implementation, the fitting of the angular frequency of the ice-breaking force is achieved by replacing the coupling model with an amplitude model architecture, including: Replace the bi-exponential-quadratic coupling model in the coupling term between UUV navigation depth and Froude number with a multivariate quadratic polynomial regression model.

[0012] On the other hand, embodiments of the present invention provide a system for calculating, fitting, and analyzing the ice-breaking forces of UUVs in the periglacial region, comprising: The scene construction module is used to set up a numerical simulation calculation model based on the UUV ice fragmentation scene in the periglacial zone to construct the full calculation conditions; The data analysis module is used to conduct numerical simulations of various operating conditions in the full computational operating conditions using the computational fluid dynamics-discrete element coupling method to obtain the original time-domain data of the total force and total torque of the UUV; to separate the fluid background load and ice fragmentation load from the original time-domain data using the time-domain trend separation method to extract core analysis samples; to construct a multi-factor coupling model and solve the parameters based on the core analysis samples to complete the fitting of the ice fragmentation force amplitude; to replace the coupling model with the amplitude model architecture to complete the fitting of the ice fragmentation force angular frequency; to construct the UUV six-degree-of-freedom dynamic equations based on the results of the ice fragmentation force amplitude fitting and the ice fragmentation force angular frequency fitting; to achieve stability determination by combining the longitudinal dynamic equations, small perturbation theory and the UUV six-degree-of-freedom dynamic equations; and to achieve stability determination of the turning condition at multiple speeds using the lateral dynamic equations and the UUV six-degree-of-freedom dynamic equations. The result calculation module is used to complete the calculation and fitting analysis of the ice breaking force of UUVs in the ice edge zone through the numerical simulation, the fitting of the amplitude of the ice breaking force, the fitting of the angular frequency of the ice breaking force, the stability determination, and the stability determination of the turning condition under multiple speeds.

[0013] The method and system for calculating and fitting the ice-breaking force of UUVs in the periglacial region disclosed in this invention have the following advantages: (1) By establishing a high-fidelity CFD-DEM (computational fluid dynamics-discrete element coupling) coupled calculation framework, the force of ice fragments on UUVs when navigating in the ice edge zone is calculated, and the dynamic load fluctuations caused by ice fragments are accurately captured.

[0014] (2) Using the established motion simulation platform, the modulating effect of the ice crushing environment on the stability and robustness of UUV operation was quantitatively evaluated, which meets the engineering requirements for rapid prediction of dynamic loads. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart illustrating a method for calculating and fitting the ice-breaking force of a UUV in the periglacial region, provided in this application embodiment; Figure 2 A UUV model diagram for a method of calculating and fitting the ice-breaking force of a UUV in the periglacial region, provided in an embodiment of this application; Figure 3 A schematic diagram of the UUV computational domain and boundary condition settings for a method for calculating and fitting the ice-breaking force of a UUV in the periglacial region, provided in an embodiment of this application; Figure 4 A time history diagram of the axial force of ice-breaking action provided in this application embodiment for a method of calculating and fitting the ice-breaking force of a UUV in the periglacial region; Figure 5 The original data and the schematic diagram of the ice-breaking force extracted by the RLOESS method for a method of calculating and fitting the ice-breaking force of a UUV in the periglacial region provided in this application embodiment; Figure 6 A schematic diagram of the free decay characteristics of state disturbance in equilibrium state of a method for calculating and fitting the ice-breaking force of a UUV in the periglacial region provided in this application embodiment; Figure 7 A schematic diagram illustrating the linear velocity decay characteristics of state disturbance at different speeds in a method for calculating and fitting the ice-breaking force of a UUV in the peri-ice zone, provided in an embodiment of this application. Figure 8 A schematic diagram illustrating the sideslip angle attenuation characteristics of a method for calculating and fitting the ice-breaking force of a UUV in the peri-ice zone at different speeds, provided for embodiments of this application; Figure 9 A schematic diagram illustrating the yaw rate decay characteristics of a method for calculating and fitting the ice-breaking force of a UUV in the peri-ice zone at different speeds, provided as an embodiment of this application. Figure 10 This is a schematic diagram illustrating the yaw angle attenuation characteristics of a method for calculating and fitting the ice-breaking force of a UUV in the peri-ice zone at different speeds, provided as an embodiment of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Figure 1This is a flowchart illustrating a method for calculating and fitting the ice-breaking force of a UUV in the periglacial region, provided by an embodiment of the present invention. The embodiment of the present invention provides a method for calculating and fitting the ice-breaking force of a UUV in the periglacial region, comprising: A numerical simulation model was constructed to represent all computational conditions based on the UUV ice fragmentation scenario in the periglacial zone. Numerical simulations of each working condition in the full computational working condition were carried out using the computational fluid dynamics-discrete element coupling method to obtain the original time-domain data of the total force and total torque of the UUV. The fluid background load and ice fragmentation load in the original time-domain data are separated by the time-domain trend separation method to extract core analysis samples. Based on the core analysis samples, a multi-factor coupling model was constructed and parameters were solved to complete the fitting of the ice-breaking force amplitude. The angular frequency fitting of the ice-breaking force was completed by replacing the coupled model with the amplitude model architecture; Based on the results of fitting the amplitude of the ice-breaking force and fitting the angular frequency of the ice-breaking force, a six-degree-of-freedom dynamic equation for the UUV is constructed. Stability determination is achieved by combining the longitudinal dynamic equation, the small perturbation theory, and the aforementioned six-degree-of-freedom dynamic equation of the UUV. Stability determination for turning conditions at multiple speeds is achieved through lateral dynamics equations and the aforementioned six-degree-of-freedom UUV dynamics equations. The calculation, fitting, and analysis of the ice-breaking force of UUVs in the ice edge zone were completed through numerical simulation, fitting of the amplitude of the ice-breaking force, fitting of the angular frequency of the ice-breaking force, stability determination, and stability determination under multi-speed turning conditions.

[0019] The full calculation conditions include navigation depth, speed, ice density, and pitch angle.

[0020] The total forces acting on the UUV include viscous drag, wave-making drag, and ice-breaking induction force.

[0021] The viscous drag is generated by fluid viscosity; the wave-making drag is generated by the wave-making during navigation; and the ice-breaking induced force is generated by the reaction of wave-making disturbance ice fragments on the surface of the UUV.

[0022] The amplitude of the ice-breaking force is composed of a cubic polynomial of the ice-breaking density, a quartic polynomial of the UUV pitch angle, and a coupling term between the UUV's travel depth and the Froude number.

[0023] The fitting of the angular frequency of ice-breaking force by replacing the coupled model with an amplitude model architecture includes: Replace the bi-exponential-quadratic coupling model in the coupling term between UUV navigation depth and Froude number with a multivariate quadratic polynomial regression model.

[0024] For example, UUV models such as Figure 2 As shown in Table 1, the parameters of the UUV model are as follows: Table 1 Main Parameters of UUV

[0025] The computational domain and boundary conditions for the numerical simulation of ice-breaking forces are as follows: Figure 3 As shown, its length × width × height is 60 m × 15 m × 20 m, the UUV origin is 40 m from the entrance, and the ice fragmentation area is set to start 10 m from the UUV origin and extend 30 m along the UUV's forward direction (longitudinal).

[0026] The calculation of the working conditions for the ice-breaking force of the UUV is shown in Table 2: Table 2 Calculation Condition Table

[0027] Constructing a numerical model of ice fragments: The thickness of the ice model is 2 cm. The ice material parameters are: paraffin wax, used to create the unfrozen model ice, with a density of 917.0 kg / m³. 3 The Poisson coefficient is 0.3, the Young's modulus is 3.0E8 Pa, and the normal and tangential stiffness coefficients are 1000 N.

[0028] The ice fragments are approximated by discrete cylindrical particles, with seven different diameters, and their probabilities are shown in Table 3. Table 3. Probability of ice formation for seven different sized models

[0029] Numerical simulation analysis of ice breaking forces: The navigation depth and speed are used as coupled variables for comprehensive analysis.

[0030] The calculated total force is decomposed into three parts: viscous drag mainly caused by fluid viscosity, wave-making drag caused by navigation waves, and ice-induced force formed by the reaction of ice fragments caused by wave disturbances on the flow field. To extract the key characteristics of the ice-forming force, this high-frequency disturbance must be separated from the low-frequency background fluid drag.

[0031] A robust local weighted regression-based temporal trend separation method (RLOESS) is used to process the total axial force. The robustened local regression curves are connected to form the trend term in the data. By directly subtracting this trend term from the original data, the ice-breaking force is obtained. It mainly contains high-frequency dynamic disturbance components excited by the coupling of wave-ice fragment flow fields.

[0032] Fitting the formula for calculating the amplitude of ice-breaking force: The expression for the amplitude of the ice-breaking force is: ; in, This is the proportionality coefficient; It is a cubic polynomial concerning the density of ice fragments; It is a fourth-order polynomial in terms of pitch angle; It is the depth of navigation With Froude The coupling terms.

[0033] To quantitatively characterize the coupling relationship between the amplitude of ice-breaking force experienced by a UUV and its navigation depth and speed, a system based on navigation depth was established. With Froude The bi-exponential-quadratic coupling model is in the form of: ; This model has 8 parameters (two exponents). and and 6 polynomial coefficients ).

[0034] sailing depth With Froude The parameter calculation of the double exponential coupling model involves representing the amplitude of the ice-breaking force experienced by the UUV under the coupled effects of navigation depth and speed as components: ; in, They are respectively The magnitude of the force in the direction.

[0035] Using amplitude data of ice-breaking forces and moments covering 15 operating conditions at 5 navigation depths and 3 Froude numbers, a nonlinear least squares method was used to globally fit 8 parameters in the model. The optimal parameter combination was obtained by minimizing the sum of squared residuals between the predicted and measured values, and the coefficient of determination was used as the final set of parameters. The fitting accuracy is evaluated using the root mean square error (RMSE), thus obtaining a parameterized load prediction surface that continuously reflects the depth-velocity coupling effect.

[0036] The amplitude of the ice-breaking force experienced by the UUV under different ice-breaking densities is expressed in components as follows: ; in, These are the polynomial fitting coefficients. It refers to the density of ice fragments.

[0037] Using the amplitude data of ice-breaking force and torque covering seven working conditions with ice-breaking concentration (30%~75%), the least squares method is used to globally fit the four coefficients in the cubic polynomial model of each force and torque component, thereby obtaining a parameterized curve that can continuously reflect the relationship between ice-breaking concentration and load.

[0038] The amplitude of the ice-breaking force experienced by the UUV under different pitch angles is expressed in components as follows: ; in, These are the fitting coefficients. It is the pitch angle.

[0039] Using the amplitude data of ice-breaking force and moment covering seven pitch angles (-15° to +15°), the least squares method is used to globally fit five coefficients in the fourth-order polynomial model of each force and moment component, thereby obtaining a parameterized curve that can continuously reflect the relationship between pitch angle and load.

[0040] In order to determine Select a common operating point (ice crush concentration 60%, pitch angle 0 degrees, navigation depth 2). d , Froude number Using this as the calculation benchmark, the specific calculation formula is as follows: ; in, It is a density polynomial. It is a pitch angle polynomial.

[0041] Fitting the formula for calculating angular frequency: Assume the expression for the angular frequency of the force acting on the ice breakers is: ; in, This is the proportionality coefficient; It is a cubic polynomial concerning the density of ice fragments; It is a fourth-order polynomial in terms of pitch angle; For navigation depth With Froude The coupling term. To quantitatively characterize the coupling relationship between the amplitude of the ice-breaking force experienced by a UUV and its navigation depth and speed, a multivariate quadratic polynomial regression model based on the least squares method is established: ; sailing depth With Froude The parameters of the multivariate quadratic polynomial model are calculated, where... These are the polynomial regression fitting coefficients; The amplitude of the ice-breaking force experienced by a UUV under the coupled effects of navigation depth and speed is expressed in components as follows: ; Utilizing a range of 5 navigation depths With 3 Froude numbers The angular frequency data of ice-breaking forces and moments from 15 combined working conditions were used to fit all 8 coefficients by constructing a design matrix and solving the normal equations, thereby obtaining a parameterized load prediction surface that can continuously reflect the depth-velocity coupling effect.

[0042] Parameter calculation of a cubic polynomial model for angular frequency under ice fragmentation concentration: The angular frequency of the ice-breaking force experienced by the UUV under different ice-breaking intensities is expressed in components as follows: ; Parameter calculation of the fourth-order polynomial model for angular frequency at pitch angle: The angular frequency of the ice-breaking force experienced by the UUV under different pitch angles is expressed in components as follows: ; In order to determine Select a common operating point (ice crush concentration 60%, pitch angle 0°, navigation depth 2). d , Froude number Using this as the calculation benchmark, the specific calculation formula is as follows: ; Longitudinal motion stability study: The dynamic equation of UUV is: ; in, 、 、 It is the velocity of the body axis in the carrier coordinate system. For longitudinal velocity, For lateral speed, Vertical velocity, 、 、 These are the accelerations of the longitudinal velocity, lateral velocity, and vertical velocity, respectively. , , They are respectively 、 、 The moment of inertia of the shaft about the body axis. It's UUV quality. , , The coordinates of the center of gravity in the carrier coordinate system are... It is angular velocity, where, It is the roll angular velocity. It is the pitch angular velocity. It is the yaw rate. , , These are roll angle, pitch angle, and yaw acceleration. , , Indicates the resultant external force. , , It represents the net external torque (roll, pitch, and yaw torque).

[0043] The longitudinal motion equation of a UUV is as follows: ; in, , , , , Add mass to the fluid. It is propeller thrust. , and These are fluid drag, lift, and pitching moment, respectively. The net restoring force is the difference between buoyancy and gravity. It is gravity.

[0044] The matrix form of the first-order longitudinal perturbation equations for the UUV is as follows; ; in, It is a disturbance in sailing speed. It is a pitch angular velocity disturbance. It is an angle-of-attack disturbance. It is a pitch angle disturbance. , These are the rudder angle disturbances for raising and lowering the rudder, respectively.

[0045] In the formula: ; ; ; in, , and These are the balance points for speed, angle of attack, and pitch angle, respectively. The UUV feature length. , , For the dimensionless hydrodynamic derivatives of angle of attack, angular velocity, and rudder angle, for rudder deflection, for rudder deflection, In equilibrium state The baseline trim angle of the control surface. In equilibrium state The baseline trim angle of the control surface.

[0046] The above equation can be rewritten in state-space form as follows: ; In the formula, Let be a fourth-order identity matrix, and have: ; ; ; Longitudinal motion stability analysis: To study the motion stability of a UUV, it is necessary to first determine its equilibrium parameters under steady motion conditions. In equilibrium, the UUV performs longitudinal, constant-depth straight-line motion, at which point the translational acceleration, angular acceleration, and angular velocity are all zero, and the speed remains constant.

[0047] ; When the UUV only operates the stern vertical rudder, its longitudinal equilibrium equation is: ; Among them, the subscript longitudinal velocity Taking two consecutive partial derivatives, the subscript Yes Taking two consecutive partial derivatives of the control surface deflection angle, with subscripts... It is for vertical velocity Taking partial derivatives twice in succession, subscript It is vertical velocity Asymmetric nonlinear terms, It is the dimensionless hydrodynamic derivative of the zero rudder deflection angular velocity. It is the dimensionless hydrodynamic derivative of zero rudder deflection angle.

[0048] The equilibrium angle of attack and velocity of a UUV are: ; ; The state vector Substituting the equations into the perturbation equations yields the equilibrium state matrices. By substituting the initial disturbance into the homogeneous equation of the small disturbance state equation, the free decay process of the state disturbance under each equilibrium state can be obtained.

[0049] Lateral motion stability study: The equations of lateral motion of a UUV: ; The matrix form of the lateral motion disturbance equations for the UUV system is as follows: ; In the formula,

[0050]

[0051]

[0052]

[0053]

[0054] Rewritten in state-space form: ; In the formula, It is a fourth-order identity matrix: ; ; ; in, It is a sideslip angle disturbance. It is a bow angle perturbation. It is a yaw angle disturbance. It is a rudder angle disturbance (single input). It is the steady-state sideslip angle. Each column is a 4-column vector, with each column corresponding to a state. The hydrodynamic derivative. This is the actual rudder angle. It is a small disturbance of the thrust vector rudder angle.

[0055] Lateral motion stability analysis: When the UUV operates the stern rudder, its lateral equilibrium equation is: ; Among them, the subscript lateral velocity Taking two consecutive partial derivatives, the subscript yaw rate Taking two consecutive partial derivatives, the subscript opposite rudder angle Taking two consecutive partial derivatives, the subscript It is the lateral velocity. Asymmetric nonlinear terms.

[0056] By substituting the initial disturbance into the homogeneous equation of the small disturbance state equation, the free decay process of the state disturbance under each equilibrium state can be obtained.

[0057] In one possible embodiment, the pitch angle was obtained through numerical calculation. The density of crushed ice is 60%. , Time history data of the axial force exerted by ice fragmentation on the UUV. For example... Figure 4 As shown.

[0058] Raw data and ice-breaking forces extracted using the RLOESS method ,like Figure 5 As shown.

[0059] Longitudinal motion stability analysis of a UUV, taking a speed of 7 knots as an example, during constant depth straight-line navigation, the equilibrium pitch angle... Equal to the angle of attack At the point of fastest decay, the equilibrium vector of the UUV under a negative buoyancy of 100N and a center of gravity coordinate of 0.05m is: ; Substituting this vector into the longitudinal disturbance equation, the system state matrix under this equilibrium state is obtained as shown in the following equation.

[0060] ; Calculate the eigenvalues ​​of this state matrix. , , Since the real parts of all eigenvalues ​​are negative, the system is asymptotically stable in this equilibrium state.

[0061] The initial disturbance amount Homogeneous equations obtained by substituting into the small perturbation state equations Solving this problem yields the free decay characteristics of the state disturbance in this equilibrium state, such as... Figure 6 As shown.

[0062] ; Lateral motion stability analysis of a UUV, taking a cruising speed of 7 knots as an example, shows that its turning angular velocity is 0.0005. rad / s The equilibrium state is as follows: ; Substituting this vector into the lateral disturbance equations, the system state matrix under this equilibrium state is obtained as follows: ; The eigenvalues ​​of the lateral equilibrium state matrix of the UUV under steady rotational motion at initial speeds of 7kn, 5kn, and 3kn are calculated and shown in Table 4. According to Lyapunov's first stability theorem, the UUV also has lateral stability under these conditions.

[0063] Table 4. Matrix of steady rotational motion at different speeds Eigenvalue table

[0064] The initial disturbance amount Homogeneous equations obtained by substituting into the small perturbation state equations Solving this problem yields the free decay characteristics of the state disturbance in this equilibrium state, such as... Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown.

[0065] This invention provides a system for calculating, fitting, and analyzing the ice-breaking forces of UUVs in the periglacial region, comprising: The scene construction module is used to set up a numerical simulation calculation model based on the UUV ice fragmentation scene in the periglacial zone to construct the full calculation conditions; The data analysis module is used to conduct numerical simulations of various operating conditions in the full computational operating conditions using the computational fluid dynamics-discrete element coupling method to obtain the original time-domain data of the total force and total torque of the UUV; to separate the fluid background load and ice fragmentation load from the original time-domain data using the time-domain trend separation method to extract core analysis samples; to construct a multi-factor coupling model and solve the parameters based on the core analysis samples to complete the fitting of the ice fragmentation force amplitude; to replace the coupling model with the amplitude model architecture to complete the fitting of the ice fragmentation force angular frequency; to construct the UUV six-degree-of-freedom dynamic equations based on the results of the ice fragmentation force amplitude fitting and the ice fragmentation force angular frequency fitting; to achieve stability determination by combining the longitudinal dynamic equations, small perturbation theory and the UUV six-degree-of-freedom dynamic equations; and to achieve stability determination of the turning condition at multiple speeds using the lateral dynamic equations and the UUV six-degree-of-freedom dynamic equations. The result calculation module is used to complete the calculation and fitting analysis of the ice breaking force of UUVs in the ice edge zone through the numerical simulation, the fitting of the amplitude of the ice breaking force, the fitting of the angular frequency of the ice breaking force, the stability determination, and the stability determination of the turning condition under multiple speeds.

[0066] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for calculating and fitting the force of UUV ice fragmentation in the periglacial zone, characterized in that, include: A numerical simulation model was constructed to represent all computational conditions based on the UUV ice fragmentation scenario in the periglacial zone. Numerical simulations of each working condition in the full computational working condition were carried out using the computational fluid dynamics-discrete element coupling method to obtain the original time-domain data of the total force and total torque of the UUV. The fluid background load and ice fragmentation load in the original time-domain data are separated by the time-domain trend separation method to extract core analysis samples. Based on the core analysis samples, a multi-factor coupling model was constructed and parameters were solved to complete the fitting of the ice-breaking force amplitude. The angular frequency fitting of the ice-breaking force was completed by replacing the coupled model with the amplitude model architecture; Based on the results of fitting the amplitude of the ice-breaking force and fitting the angular frequency of the ice-breaking force, a six-degree-of-freedom dynamic equation for the UUV is constructed. Stability determination is achieved by combining the longitudinal dynamic equation, the small perturbation theory, and the aforementioned six-degree-of-freedom dynamic equation of the UUV. Stability determination for turning conditions at multiple speeds is achieved through lateral dynamics equations and the aforementioned six-degree-of-freedom UUV dynamics equations. The calculation, fitting, and analysis of the ice-breaking force of UUVs in the ice edge zone were completed through numerical simulation, fitting of the amplitude of the ice-breaking force, fitting of the angular frequency of the ice-breaking force, stability determination, and stability determination under multi-speed turning conditions.

2. The method for calculating and fitting the force of UUV ice fragmentation in the periglacial region according to claim 1, characterized in that, The full calculation conditions include navigation depth, speed, ice density, and pitch angle.

3. The method for calculating and fitting the ice-breaking force of UUVs in the periglacial region according to claim 1, characterized in that, The total forces acting on the UUV include viscous drag, wave-making drag, and ice-breaking induction force.

4. The method for calculating and fitting the ice-breaking force of UUVs in the periglacial region according to claim 3, characterized in that, The viscous drag is generated by fluid viscosity; the wave-making drag is generated by the wave-making during navigation; and the ice-breaking induced force is generated by the reaction of wave-making disturbance ice fragments on the surface of the UUV.

5. The method for calculating and fitting the force of UUV ice fragmentation in the periglacial region according to claim 1, characterized in that, The amplitude of the ice-breaking force is composed of a cubic polynomial of the ice-breaking density, a quartic polynomial of the UUV pitch angle, and a coupling term between the UUV's travel depth and the Froude number.

6. The method for calculating and fitting the ice-breaking force of UUVs in the periglacial region according to claim 1, characterized in that, The fitting of the angular frequency of ice-breaking force by replacing the coupled model with an amplitude model architecture includes: Replace the bi-exponential-quadratic coupling model in the coupling term between UUV navigation depth and Froude number with a multivariate quadratic polynomial regression model.

7. A system for calculating, fitting, and analyzing the ice-breaking forces of UUVs in the periglacial region, the system being used to implement the method for calculating, fitting, and analyzing the ice-breaking forces of UUVs in the periglacial region as described in any one of claims 1-6, characterized in that, include: The scene construction module is used to set up a numerical simulation calculation model based on the UUV ice fragmentation scene in the periglacial zone to construct the full calculation conditions; The data analysis module is used to perform numerical simulations of each working condition in the full computational working condition using the computational fluid dynamics-discrete element coupling method to obtain the original time-domain data of the total force and total torque of the UUV; The fluid background load and ice fragmentation load in the original time-domain data are separated by the time-domain trend separation method to extract core analysis samples. Based on the core analysis samples, a multi-factor coupling model was constructed and parameters were solved to complete the fitting of the ice-breaking force amplitude. The amplitude model architecture is used to replace the coupling model to complete the angular frequency fitting of the ice breaking force; the UUV six-degree-of-freedom dynamic equations are constructed based on the results of the ice breaking force amplitude fitting and the ice breaking force angular frequency fitting; the stability is determined by combining the longitudinal dynamic equation, the small disturbance theory and the UUV six-degree-of-freedom dynamic equations; the stability of the turning condition at multiple speeds is determined by the lateral dynamic equation and the UUV six-degree-of-freedom dynamic equations. The result calculation module is used to complete the calculation and fitting analysis of the ice breaking force of UUVs in the ice edge zone through the numerical simulation, the fitting of the amplitude of the ice breaking force, the fitting of the angular frequency of the ice breaking force, the stability determination, and the stability determination of the turning condition under multiple speeds.

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