A dynamic modeling method for vector-propelled AUV

Abstract

The present application discloses a dynamic modeling method for a vector-propelled AUV, which relates to the field of vector-propelled AUVs. The method uses a CFD simulation method to respectively obtain the vector propulsion performance of a vector propulsion device in a vector-propelled AUV when subjected to different fluid parameters under different operating conditions, and then obtains a relationship between the thrust coefficient of the vector propulsion device and the fluid parameters by fitting. The hydrodynamic parameters of the vector-propelled AUV and the thrust coefficient of the vector propulsion device are used to construct a six-degree-of-freedom dynamic equation. The six-degree-of-freedom dynamic equation can fully consider the coupling effects of various factors on the vector propulsion to accurately characterize the vector propulsion characteristics. The constructed six-degree-of-freedom dynamic equation can more accurately describe the dynamic characteristics of the vector-propelled AUV. Combined with the kinematic equation, a dynamic model for the vector-propelled AUV is established, and the motion process of the vector-propelled AUV can be accurately predicted.

Description

Technical Field

[0001] The present application relates to the field of vector-propelled AUVs, and in particular to a dynamic modeling method for vector-propelled AUVs. Background Art

[0002] An autonomous underwater vehicle (AUV) is a device or tool that can assist or replace humans in completing underwater missions. It can carry various equipment and payloads and perform tasks through autonomous control. Traditional AUVs are under-actuated control systems, where the number of control input dimensions is less than the number of degrees of freedom of motion. They are mainly used in cruise-related operations such as cargo transportation, search, and exploration. The control method is simple, but the maneuverability of under-actuated AUVs at low speeds will be significantly reduced. Therefore, more and more practices are installing vector thrusters on the rear of the AUV to form vector-propelled AUVs, which can achieve higher maneuverability without adding more dimensional control inputs.

[0003] Compared to traditional underactuated AUVs, the motion control of vector-propelled AUVs requires consideration of the vector thrust generated by the thrusters. Currently, a common approach is to simplify the thrusters to a constant thrust that produces an ideal deflection at a defined deflection angle, describing the thrusters using simple trigonometric functions. However, the force and torque generated by the thrusters actually exhibit significant coupling characteristics. This traditional simplification ignores these coupling characteristics, resulting in an inaccurate model describing the dynamics of the vector-propelled AUV and hindering the accurate prediction of the AUV's motion. Summary of the Invention

[0004] In response to the above problems and technical requirements, this application proposes a dynamic modeling method for vector-propelled AUV. The technical solution of this application is as follows:

[0005] A dynamic modeling method for a vector-propelled AUV, the dynamic modeling method comprising:

[0006] The hydrodynamic parameters of the vector-propelled AUV are obtained through CFD simulation method;

[0007] The CFD simulation method is used to obtain the vector propulsion performance of the vector propulsion AUV under different operating conditions and under different fluid parameters. The vector propulsion performance includes the thrust and thrust torque of the thruster.

[0008] According to the vector propulsion performance of the vector propulsion machine under different operating conditions and the action of different fluid parameters, the thrust coefficient K of the vector propulsion machine is obtained by fitting. p Relationship with fluid parameters;

[0009] Hydrodynamic parameters of vector-propelled AUV and thrust coefficient K of vector thruster p , the six-degree-of-freedom dynamic equations related to the working parameters of the vector thruster and the fluid parameters are constructed Where P = m(v + ω × r c ) is the momentum of the vector-propelled AUV, L = Iω + r c ×mv is the angular momentum of the vector-propelled AUV, m is the mass of the vector-propelled AUV, v is the velocity vector of the center of buoyancy of the vector-propelled AUV in the ground coordinate system, ω is the rotational angular velocity vector of the vector-propelled AUV in the ground coordinate system, r c is the radius from the center of mass of the vector-propelled AUV to the center of buoyancy, I represents the inertia tensor matrix of the vector-propelled AUV about the center of buoyancy; F represents the vector of all external forces on the vector-propelled AUV in the body coordinate system, M represents the vector of all external torques on the vector-propelled AUV in the body coordinate system; all external forces on the vector-propelled AUV include hydrodynamic force, buoyancy force and propeller thrust, all external torques on the vector-propelled AUV include hydrodynamic torque, buoyancy torque and propeller thrust, vector propulsion performance and thrust coefficient K p Related to the operating parameters of the vector thruster;

[0010] The motion control of vector propulsion AUV is carried out by using the six-degree-of-freedom dynamic equation combined with the kinematic equation of vector propulsion AUV;

[0011] Among them, the body coordinate system Oxyz takes the buoyancy center of the vector-propelled AUV as the coordinate origin O, the navigation direction of the vector-propelled AUV is the positive x direction, the direction pointing to the port side of the vector-propelled AUV is the positive y direction, and the positive z direction is perpendicular to the xy plane and upward.

[0012] The beneficial technical effects of this application are:

[0013] The present application discloses a dynamic modeling method for a vector-propelled AUV. The method obtains the vector propulsion performance of a vector propulsion device in the vector-propelled AUV under different operating conditions and under the action of different fluid parameters by a CFD simulation method, and then obtains the relationship between the thrust coefficient of the vector propulsion device and the fluid parameters by fitting. The hydrodynamic parameters of the vector-propelled AUV and the thrust coefficient of the vector propulsion device are used to construct a six-degree-of-freedom dynamic equation, so that the six-degree-of-freedom dynamic equation is not only related to the operating parameters of the vector propulsion device, but also to the fluid parameters. The coupling influence of various factors on the vector propulsion can be fully considered to accurately characterize the vector propulsion characteristics. The constructed six-degree-of-freedom dynamic equation can more accurately describe the dynamic characteristics of the vector-propelled AUV. Combined with the kinematic equation, an accurate dynamic model can be established to optimize the accuracy of the prediction of the motion process of the vector-propelled AUV.

[0014] The dynamics modeling method involves the construction method of dynamic equations and kinematic equations, which can be applied to different types of vector thrusters. It can simultaneously ensure the accurate description of vector propulsion performance and the efficiency of modeling calculations, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the relationship between the three coordinate systems involved in the vector propulsion AUV.

[0016] Figure 2 This is a flow chart of a kinetic modeling method according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] The specific implementation of this application will be further described below with reference to the accompanying drawings.

[0018] This application discloses a dynamic modeling method for a vector-propelled AUV. Accurate prediction of the motion process of an underwater device and further motion control often rely on the dynamic and kinematic equations of the underwater device. Therefore, accurately constructing the dynamic and kinematic equations of a vector-propelled AUV is the basis for improving the control accuracy and efficiency of the vector-propelled AUV. This application introduces the following:

[0019] 1. Kinematic equations of vector-propelled AUV

[0020] Please refer to Figure 1 The coordinate system diagram shown in the figure shows that the vector propulsion AUV involves three different coordinate systems when working, including the ground coordinate system O e x e y e z e , body coordinate system Oxyz and velocity coordinate system Ox1y1z1, are introduced as follows:

[0021] (1) Ground coordinate system O e x e y e z e It is fixed to the ground and is used to describe the position and motion of the vector-propelled AUV relative to the ground in space. The ground coordinate system O e x e y e z e Generally, the starting point of the vector-propelled AUV can be selected as the coordinate origin O e Establish, this application for the ground coordinate system O e x e y e z e The three-axis directions are not limited, such as Figure 1 Take O e x e ze Parallel to the horizontal plane, y e Take the vertical direction upward as an example.

[0022] (2) The body coordinate system Oxyz is fixedly connected to the vector-propelled AUV and remains relatively stationary with the vector-propelled AUV. The body coordinate system Oxyz is used to describe the posture of the vector-propelled AUV. The body coordinate system Oxyz takes the center of buoyancy of the vector-propelled AUV as the coordinate origin O, the navigation direction of the vector-propelled AUV as the positive x direction, the direction pointing to the port side of the vector-propelled AUV as the positive y direction, and the positive z direction perpendicular to the xy plane and upward.

[0023] (3) The velocity coordinate system Ox1y1z1 is also fixedly connected to the vector-propelled AUV. The velocity coordinate system Ox1y1z1 is used to refer to the movement speed of the vector-propelled AUV. The velocity coordinate system Ox1y1z1 takes the buoyancy center of the vector-propelled AUV as the coordinate origin O and is used to describe the instantaneous velocity of the vector-propelled AUV.

[0024] The velocity coordinate system Ox1y1z1 is also fixed to the vector-propelled AUV. Its origin is also chosen at the center of buoyancy of the vector-propelled AUV. The velocity coordinate system Ox1y1z1 is used to describe the instantaneous velocity of the vector-propelled AUV. The Ox1 axis points in the direction of the velocity vector of the vector-propelled AUV and is also called the velocity axis. The Oy1 axis lies within the longitudinal symmetry plane of the vector-propelled AUV, perpendicular to the Ox1 axis and pointing upward. The Oz1 axis, along with the plane formed by the Ox1 and Oy1 axes, remains perpendicular, forming a right-handed coordinate system.

[0025] Ground coordinate system O e x e y e z e There is also a conversion relationship between the body coordinate system Oxyz and the velocity coordinate system Ox1y1z1. There is a clear angle definition between different coordinate systems. The coordinate transformation matrix can be obtained by using the azimuth angles between the coordinate axes. The forward and inverse transformation matrices between the coordinate systems are each other's transposed matrices:

[0026] (a) The three azimuth angles of the body coordinate system relative to the ground coordinate system are the attitude angles of the vector-propelled AUV. The attitude angles of the vector-propelled AUV include the pitch angle θ, the yaw angle ψ, and the roll angle φ: the pitch angle θ is the angle between the x-axis of the body coordinate system and the x-axis of the ground coordinate system. e The yaw angle ψ is the angle between the y axis of the body coordinate system and the y axis of the ground coordinate system. e The roll angle φ is the angle between the z axis of the body coordinate system and the z axis of the ground coordinate system. e The ground coordinate system O can be constructed using the pitch angle θ, yaw angle ψ, and roll angle φ. e x e y e z eCoordinate transformation matrix to body coordinate system Oxyz for:

[0027]

[0028] (b) The attack angle α and sideslip angle β of the vector-propelled AUV are used to describe the azimuthal relationship between the motion vector and the AUV’s attitude during motion.

[0029] The angle between the projection of the x1 axis of the velocity coordinate system Ox1y1z1 on the xOy plane in the body coordinate system Oxyz and the x axis of the body coordinate system is the angle of attack α of the vector-propelled AUV. When the x1 axis is deflected downward, the angle of attack α is positive. The angle between the x1 axis of the velocity coordinate system Ox1y1z1 and the xOy plane in the body coordinate system Oxyz is the sideslip angle β of the vector-propelled AUV. When the x1 axis is deflected to the right, the sideslip angle β is positive. The coordinate transformation matrix from the body coordinate system Oxyz to the velocity coordinate system Ox1y1z1 can be constructed using the angle of attack α and the sideslip angle β. for:

[0030]

[0031] (c) Velocity coordinate system Ox1y1z1 relative to ground coordinate system O e x e y e z e The azimuth angle is the ballistic angle of the vector-propelled AUV. The ballistic angle of the vector-propelled AUV includes the ballistic inclination angle Θ, the ballistic deviation angle Ψ, and the tilt angle Φ: the ballistic inclination angle Θ is the difference between the x1 axis of the velocity coordinate system Ox1y1z1 and the ground coordinate system x e The angle between the y1 axis of the velocity coordinate system Ox1y1z1 and the ground coordinate system y e The angle between the axes, the tilt angle Φ is the angle between the z1 axis of the velocity coordinate system Ox1y1z1 and the ground coordinate system z e The ground coordinate system O can be constructed using the trajectory inclination angle Θ, trajectory deviation angle Ψ, and tilt angle Φ. e x e y e z e Coordinate transformation matrix to velocity coordinate system Ox1y1z1 for:

[0032]

[0033] The above three coordinate transformation matrices can be used to transform coordinates between the three coordinate systems, and one of the coordinate transformation matrices can be expressed using the other two coordinate transformation matrices. For example, The same applies to other cases.

[0034] The kinematic equation of the vector-propelled AUV is used to describe the motion process of the vector-propelled AUV, and the motion process of the vector-propelled AUV is described using its ground coordinate system O e x e y e z e The present application uses the position coordinates of the buoyancy center of the vector-propelled AUV to refer to the position coordinates of the vector-propelled AUV as a whole. The position coordinates of the buoyancy center of the vector-propelled AUV are in the ground coordinate system O e x e y e z e Denoted as (x e ,y e ,z e ),based on Figure 1 The ground coordinate system O shown e x e y e z e , x e 、y e 、z e Respectively represent the horizontal displacement, diving depth and lateral displacement of the vector-propelled AUV. Similarly, this application uses the velocity at the buoyancy center of the vector-propelled AUV to refer to the overall motion speed of the vector-propelled AUV. The components of the velocity vector v at the buoyancy center of the vector-propelled AUV in the three directions of the ground coordinate system are (v ex ,v ey ,v ez ).

[0035] Using the coordinate transformation matrix The components of the velocity vector v at the center of buoyancy of the vector-propelled AUV in the three directions of the body coordinate system Oxyz (v x ,v y ,v z ) is expressed as:

[0036]

[0037] in, is x e The derivative with respect to time and other parameters are expressed similarly.

[0038] In addition, it can be determined that the attack angle α and sideslip angle β of the vector propulsion AUV can be expressed as:

[0039]

[0040] The position coordinates of the center of buoyancy of the vector-propelled AUV (x e ,y e ,z e) is the time-varying curve of the vector-propelled AUV. Therefore, the motion trajectory of the vector-propelled AUV at its buoyancy center can be determined in the ground coordinate system as:

[0041]

[0042] The rotation of the vector-propelled AUV is described by the attitude angle. The rotation angular velocity vector ω of the vector-propelled AUV is in the ground coordinate system O e x e y e z e Among them:

[0043]

[0044] Project the attitude angle vector to the body coordinate system, and define the components of the rotational angular velocity vector ω of the vector-propelled AUV in the three directions of the body coordinate system as (ω x ,ω y ,ω z ), then:

[0045]

[0046] The kinematic equations of the vector-propelled AUV can be constructed as follows:

[0047]

[0048] 2. Dynamic equations of vector-propelled AUV

[0049] Based on the momentum theorem and the definition of angular momentum, it can be determined that the six-degree-of-freedom dynamic equation can be expressed as:

[0050]

[0051] Where P is the momentum of the vector-propelled AUV and can be written as:

[0052] P=mv e

[0053] Where m is the mass of the vector-propelled AUV, v e is the velocity vector of the center of mass of the vector-propelled AUV in the ground coordinate system, and is:

[0054] v e =v+ω×r c

[0055] In the above formula, r c is the radius from the center of mass of the vector-propelled AUV to the center of buoyancy, and v is the velocity vector at the center of buoyancy of the vector-propelled AUV.

[0056] So we have:

[0057] P=m(v+ω×r c )

[0058] In the six-degree-of-freedom dynamics equation, L is the angular momentum of the vector-propelled AUV and:

[0059] L=Iω+r c ×mv

[0060] In the above formula, I represents the inertia tensor matrix of the vector-propelled AUV about the center of buoyancy, which is written as:

[0061]

[0062] Where, J xy =J yx , J xz =J zx , J zy =J yz And they are all inertia products. The vector propulsion AUV with rotationally symmetric shape does not take inertia products into account, so we have The inertia tensor matrix I is an inherent property of the vector-propelled AUV and can be obtained in advance through measurement or calculation. It is a known quantity.

[0063] The momentum P and angular momentum L of the vector-propelled AUV are expressed in the body coordinate system Oxyz as:

[0064]

[0065] is the radius r from the center of mass to the center of buoyancy of the vector-propelled AUV c The components of the three directions in the body coordinate system are (x c ,y c , z c ) is an antisymmetric matrix composed of E 3×3 It is a 3*3 identity matrix.

[0066] F represents the vector of all external forces acting on the vector-propelled AUV in the body coordinate system, and M represents the vector of all external torques acting on the vector-propelled AUV in the body coordinate system. In order to accurately construct the six-degree-of-freedom dynamic equations of the vector-propelled AUV, accurate characterization of F and M is the key. All external forces and external torques acting on the vector-propelled AUV correspond to each other and mainly include three categories: All external forces acting on the vector-propelled AUV include hydrodynamic force, weight and buoyancy F ΔB and thruster thrust F THR The total external torque on the vector propulsion AUV includes the hydrodynamic torque, the buoyancy torque M ΔB and thruster torque M THRThe traditional approach simplifies vector propulsion to a constant thrust and ideal deflection at a fixed deflection angle, resulting in inaccurate characterization of the thrust and torque. This is the main reason that affects current control performance. Therefore, the focus of this application is to accurately characterize the thrust and torque of the vector propulsion AUV, as described below:

[0067] 1. The thrust F exerted on the vector propulsion AUV THR and thruster torque M THR Characterization

[0068] Vector propulsion performance and thrust coefficient K of vector thruster p It is related to the working parameters of the vector thruster, and the thruster thrust F generated by the vector thruster on the buoyancy center of the AUV is THR and thruster torque M THR can be expressed as:

[0069]

[0070]

[0071] in, is the dimensionless thrust coefficient of the vector thruster, K Tpx , K Tpy , K Tpz They are thrust coefficient K p The force component coefficients in the three directions of the body coordinate system, K Qpx , K Qpy , K Qpz They are thrust coefficient K p The torque component coefficients in the three directions of the body coordinate system. D is the diameter of the vector thruster, L AC The distance from the center of the vector propulsion system to the center of buoyancy of the vector propulsion system is φ(n). These two parameters are related to the structure of the vector propulsion system. The operating parameters of the vector propulsion system include the speed n of the vector propulsion system.

[0072] From the above expression, it can be determined that the key to accurately characterize the vector propulsion performance of the vector thruster is to obtain the thrust coefficient K of the vector thruster considering the coupling characteristics. p , and the thrust coefficient K of the vector thruster is p Affected by many factors, mainly affected by the operating conditions of the vector thruster and the effects of the fluid parameters, this application first uses the CFD simulation method to obtain the vector propulsion performance of the vector thruster in the vector propulsion AUV under different operating conditions and the effects of different fluid parameters, and then according to the vector propulsion performance of the vector thruster under different operating conditions and the effects of different fluid parameters, the thrust coefficient K of the vector thruster can be fitted.p The relationship between the thrust coefficient K and the fluid parameters is obtained. p It is related to the fluid parameters, so that the characterized vector propulsion performance is also related to the fluid parameters, so that the constructed six-degree-of-freedom dynamic equation is not only related to the working parameters of the vector thruster, but also related to the fluid parameters of the fluid environment, so that the six-degree-of-freedom dynamic equation can fully consider the influence of various influencing factors on the vector propulsion performance.

[0073] Specifically, obtaining the vector propulsion performance of the vector thruster under different operating conditions and under different fluid parameters includes:

[0074] Obtain the vector thruster in open water state at different vector deflection angles δ e Below, different vector deflection angles δ r Under different speed coefficients and different vector deflection angles δ e and δ r Vector propulsion performance in coupled state.

[0075] The control parameter of the vector thruster is defined as the horizontal deflection angle of the auxiliary duct in the vertical axis direction δ e , the vertical deflection angle of the auxiliary duct in the horizontal axis direction is δ r , when the auxiliary guide tube in the vertical axis direction deflects downward, e is positive, looking forward from the rear of the AUV, when the secondary duct deflects to the right in the transverse direction, δ r In the body coordinate system Oxyz, the Oy axis is called the vertical axis and the Oz axis is called the horizontal axis.

[0076] Obtain the vector thruster in the independent maneuvering state at different transverse and longitudinal flow angles α obl Under different vector deflection angles δ e Below, different vector deflection angles δ r Under different speed coefficients and different vector deflection angles δ e and δ r Vector propulsion performance in coupled state.

[0077] Obtain the vector propulsion of the AUV after the vector thruster is assembled on the AUV body and performs maneuvering under straight and oblique flow conditions at different vector deflection angles δ e Below, different vector deflection angles δ r Under different speed coefficients and different vector deflection angles δ e and δ r Vector propulsion performance in coupled state.

[0078] The vector propulsion performance obtained by simulation under each operating condition under the action of a set of fluid parameters includes thrust and thrust torque, from which the thrust coefficient K can be fitted.p The relationship between the influencing factors includes fluid parameters and propeller parameters. The fluid parameters here include the horizontal and vertical oblique flow angle α obl and the advance coefficient J. The propeller parameters include the vector deflection angle δ e and δ r , the installation status of the vector thruster and the AUV body. These fluid parameters have an impact on the thrust coefficient K p The influence of is different, and the thrust coefficient of the vector thruster finally fitted can be written as:

[0079]

[0080] (1)K pJ It is a function related to the advance coefficient J obtained by fitting, which is used to characterize the effect of the advance coefficient J on the thrust coefficient K. p On the one hand, during navigation, the presence of the AUV body will cause the overall offset of the speed coefficient. Therefore, considering the influence of the AUV body on the wake field of the vector thruster, the speed coefficient J can be corrected to J using the wake fraction w. w =J(1-w).

[0081] On the other hand, during navigation, the speed coefficient is maintained near the self-propulsion point, and there will be a small fluctuation during the maneuvering process. Therefore, within the error range, it can be considered that the speed coefficient varies in a small range near the self-propulsion point. p The linearization of the influence near the self-propulsion point can be starved to K pJ =A J J w +Β J , thus obtaining K pJ The relationship between it and the speed coefficient J is:

[0082] K pJ =A J J(1-w)+Β J

[0083] Among them, A J and Β J are the parameter matrices obtained by fitting. In this embodiment, the calculation results of the AUV rear thruster are compared with the calculation results of the open water setting, taking w = 0.1,

[0084] (2) is the fitted vector deflection angle δ e and δ r The related term, the vector deflection angle δ e and δ r Thrust coefficient K pThe influence of K is obviously coupled, so it cannot be pJ It is also represented by a linear function, but is based on the fitting result and the vector deflection angle δ e and δ r The related interpolation surface f δ To characterize Obtained f δ (δ e ,δ r ) represents the interpolation surface f obtained by fitting δ The deflection angle δ of the vector e and δ r The corresponding value.

[0085] (3) is the fitting result with the deflection angle δ and oblique flow angle α obl Related terms, deflection angle δ and oblique flow angle α obl Thrust coefficient K p The influence of the deflection angle δ and the oblique flow angle α can be obtained based on the fitting. obl The related interpolation surface f obl To characterize

[0086] The oblique flow has different effects under different deflection angles. The oblique flow is decomposed into the horizontal and vertical components of the body coordinate system. The effects of the oblique flow angle and the deflection of the auxiliary duct in each direction are considered separately, and the oblique flow effects in each direction are made independent within the error range. obl The oblique flow angle component α in the y direction of the body coordinate system obly and oblique flow angle α obl The oblique flow angle component α in the z direction of the body coordinate system oblz Expressed as:

[0087]

[0088] Among them, L AC It is the distance from the center of the vector thruster in the vector propulsion AUV to the center of buoyancy of the vector propulsion AUV.

[0089] After decomposition in two directions, the oblique flow angle component under different deflection angles δ in each direction is used to calculate the thrust coefficient K p The influence of is used to establish the interpolation surface f in the form of dimensionless coefficient increments obl . Using this interpolation surface f obl The oblique flow angle component α in the y direction of the body coordinate system can be expressed as obly The fluid coefficient increment caused by obl (α obly ,δ e), oblique flow angle component α in the z direction of the body coordinate system oblz The fluid coefficient increment caused by obl (α oblz ,δ r ). f obl (α obly ,δ e ) represents the interpolation surface f obtained by fitting obl The deflection angle δ and the oblique flow angle component α obly The corresponding value, f obl (α oblz ,δ r ) represents the interpolation surface f obtained by fitting obl The deflection angle δ and the oblique flow angle component α oblz The corresponding value.

[0090] Since the interpolation surface f obl It is defined with respect to the deflection angle δ. After interpolation, the oblique flow angle component α in the y direction of the body coordinate system needs to be obly The fluid coefficient increment caused by is converted to the z direction of the body coordinate system, and the conversion matrix is

[0091] So it can be constructed

[0092] Combining the above three items, the thrust coefficient of the fitted vector thruster can be expressed as:

[0093]

[0094] It can also be seen from the above function that the thrust coefficient of the vector thruster is affected by the coupling of multiple fluid parameters.

[0095] 2. Characterization of the hydrodynamic forces and hydrodynamic torques acting on a vector-propelled AUV

[0096] The hydrodynamic force on the vector-propelled AUV includes the position force F during steady translation motion. POS , the damping force F during steady rotation DAM And the inertial force F during unsteady motion INE The corresponding hydrodynamic torque of the vector-propelled AUV also includes the position torque M POS , damping torque M DAM and moment of inertia M INE Each force and moment can be described by a dimensionless hydrodynamic coefficient, which is expressed as follows:

[0097] (1) Position force F acting on the vector-propelled AUV during steady translation POS and position torque M POS

[0098] The position force F on the vector-propelled AUV POS and position torque M POS Expressed as:

[0099]

[0100] Where ρ represents the fluid density, v represents the velocity amplitude of the vector-propelled AUV, S represents the maximum cross-sectional area of ​​the vector-propelled AUV, and L represents the length of the vector-propelled AUV. x0 is the drag factor of the vector-propelled AUV when both the angle of attack α and the sideslip angle β are 0, are the position derivatives, is the position derivative of the lift factor with respect to the angle of attack, is the position derivative of the side force factor with respect to the sideslip angle, is the position derivative of the yaw moment factor with respect to the sideslip angle, is the position derivative of the pitching moment factor with respect to the angle of attack.

[0101] (2) Damping force F on the steady rotational motion of the vector-propelled AUV DAM and damping torque M DAM

[0102] It can be written in component form as follows:

[0103]

[0104] In the formula, i = x, y, z, The value of the rotational angular velocity vector ω = 0 represents the increment of the hydrodynamic component or torque component corresponding to the unit angular velocity of the AUV, which is called the rotational derivative of force and torque. There are 18 of them in total. The dimensionless factors of the corresponding rotational derivatives are obtained by using the definition of hydrodynamics and angular velocity, which are referred to as rotational derivatives for short. For the shape of a rotating body, when the rotation speed is not large, some rotational derivatives are very small and can be ignored. Therefore, the damping force F on the vector-propelled AUV is DAM and damping torque M DAM for:

[0105]

[0106] in, is the rotation derivative, is the lift factor with respect to ω z The rotation derivative of is the lateral force factor to ω y The rotation derivative of is the rolling moment on ω x The rotation derivative of is the rolling moment on ωy The rotation derivative of is the yaw moment about ω x The rotation derivative of is the yaw moment about ω y The rotation derivative of is the pitching moment about ω z The rotation derivative of .

[0107] (3) Inertial force F acting on the unsteady motion of the vector-propelled AUV INE and moment of inertia M INE

[0108] The inertial force represents the hydrodynamic force exerted on a vector-propelled AUV during unsteady motion. When a vector-propelled AUV is in unsteady motion, part of the work done by the external force is converted into kinetic energy, while another part is used to propel the fluid surrounding the AUV to gain kinetic energy. This is equivalent to adding a portion of mass to the AUV, called added mass. The added mass is only related to the AUV's shape and is described by a diagonal added mass matrix, λ. There are 21 independent added masses, which can be simplified to the following form when the vector-propelled AUV has two symmetry planes:

[0109]

[0110] Applying the momentum theorem and angular momentum theorem to this additional fluid, the inertial force F acting on the vector-propelled AUV during unsteady motion can be determined. INE and moment of inertia M INE Expressed as:

[0111]

[0112] Among them are

[0113] Therefore, the position force F POS , damping force F DAM and inertial force F INE The sum of the position torque M is the hydrodynamic force on the vector propulsion AUV. POS , damping torque M DAM and moment of inertia M INE The sum of the two is the hydrodynamic torque of the vector propulsion AUV. The hydrodynamic parameters of the vector propulsion AUV can be obtained through CFD simulation. The obtained hydrodynamic parameters include: the drag factor C of the vector propulsion AUV when the angle of attack α and the sideslip angle β are both 0. x0 , and the position derivative And, the rotation derivative and the additional mass matrix

[0114] 3. The buoyancy force F on the vector-propelled AUV ΔB and buoyancy moment M ΔB Characterization

[0115] A vector-propelled AUV is subject to buoyancy and gravity underwater. The gravity acting on the vector-propelled AUV is G = mg, acting vertically downward at the center of gravity, where g is the acceleration due to gravity. The buoyancy acting on the vector-propelled AUV is B = ρgV, acting vertically upward at the center of buoyancy, where ρ represents the fluid density and V represents the volume of the vector-propelled AUV.

[0116] The net buoyancy of the vector-propelled AUV is ΔB=BG. Converting the net buoyancy ΔB=BG into the body coordinate system is the heavy buoyancy F of the vector-propelled AUV. ΔB for:

[0117]

[0118] The buoyancy moment M in the body coordinate system of the vector-propelled AUV is ΔB for:

[0119]

[0120] in is the radius r from the center of gravity to the center of buoyancy of the vector-propelled AUV cg The components of the three directions in the body coordinate system (x cg ,y cg , z cg ) is an antisymmetric matrix composed of

[0121] In summary, the sum of the thrust, hydrodynamic force and buoyancy force constructed above is taken as the vector F of all external forces acting on the vector propulsion AUV in the body coordinate system, and the sum of the thrust torque, hydrodynamic torque and buoyancy torque constructed above is taken as the vector M of all external torques acting on the vector propulsion AUV in the body coordinate system. Then, the expressions of the above forces and torques are substituted into the six-degree-of-freedom dynamic equations: It can be sorted out into:

[0122]

[0123] in,

[0124]

[0125] Based on the characteristic that the mass of AUV remains unchanged during navigation, it can be determined Since the constructed position force and damping force already include the characteristics of ideal fluid force and viscous fluid force, the six-degree-of-freedom dynamic equation can be simplified as follows:

[0126]

[0127] in,

[0128] The six-degree-of-freedom dynamic equations and kinematic equations of the vector-propelled AUV constructed in this application are used to control the motion of the vector-propelled AUV. Since the coupling characteristics of the vector propulsion are taken into account when constructing the six-degree-of-freedom dynamic equations, the accuracy of the motion control can be improved and the control performance can be optimized.

[0129] The above description is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the scope of protection of the present application.

Claims

1. A dynamic modeling method for a vector-propelled AUV, characterized in that: The kinetic modeling method comprises: The hydrodynamic parameters of the vector-propelled AUV are obtained through CFD simulation method; The CFD simulation method is used to obtain the vector propulsion performance of the vector propulsion AUV under different operating conditions and under the action of different fluid parameters. The vector propulsion performance includes the thrust and thrust torque of the thruster. According to the vector propulsion performance of the vector propulsion machine under different operating conditions and the action of different fluid parameters, the thrust coefficient K of the vector propulsion machine is obtained by fitting. p Relationship with fluid parameters; Hydrodynamic parameters of vector-propelled AUV and thrust coefficient K of vector thruster p , the six-degree-of-freedom dynamic equations related to the working parameters of the vector thruster and the fluid parameters are constructed Where P = m(v + ω × r c ) is the momentum of the vector-propelled AUV, L = Iω + r c ×mv is the angular momentum of the vector-propelled AUV, m is the mass of the vector-propelled AUV, v is the velocity vector of the center of buoyancy of the vector-propelled AUV in the ground coordinate system, ω is the rotational angular velocity vector of the vector-propelled AUV in the ground coordinate system, r c is the radius from the center of mass of the vector-propelled AUV to the center of buoyancy, I represents the inertia tensor matrix of the vector-propelled AUV about the center of buoyancy; F represents the vector of all external forces on the vector-propelled AUV in the body coordinate system, M represents the vector of all external torques on the vector-propelled AUV in the body coordinate system; all external forces on the vector-propelled AUV include hydrodynamic force, buoyancy force and propeller thrust, all external torques on the vector-propelled AUV include hydrodynamic torque, buoyancy torque and propeller thrust, vector propulsion performance and thrust coefficient K p Related to the operating parameters of the vector thruster; A dynamic model of the vector-propelled AUV is established by using the six-degree-of-freedom dynamic equation in combination with the kinematic equation of the vector-propelled AUV, and the dynamic model of the vector-propelled AUV is used to perform motion simulation on the vector-propelled AUV; Among them, the body coordinate system Oxyz takes the buoyancy center of the vector-propelled AUV as the coordinate origin O, the navigation direction of the vector-propelled AUV is the positive x direction, the direction pointing to the port side of the vector-propelled AUV is the positive y direction, and the positive z direction is perpendicular to the xy plane and upward.

2. The dynamic modeling method according to claim 1, characterized in that: Obtaining the vector propulsion performance of the vector thruster under different operating conditions and subjected to different fluid parameters includes: Obtain the vector thruster in open water state at different vector deflection angles δ e Below, different vector deflection angles δ r Under different speed coefficients and different vector deflection angles δ e and δ r Vector propulsion performance in coupled state; And, obtain the vector thruster in the independent maneuvering state at different transverse and longitudinal flow angles α obl Under different vector deflection angles δ e Below, different vector deflection angles δ r Under different speed coefficients and different vector deflection angles δ e and δ r Vector propulsion performance in coupled state; And, the vector propulsion AUV is formed after the vector propulsion device is assembled on the AUV body and performs maneuvering under different vector deflection angles δ under straight and oblique flow conditions. e Below, different vector deflection angles δ r Under different speed coefficients and different vector deflection angles δ e and δ r Vector propulsion performance in coupled state.

3. The dynamic modeling method according to claim 2, characterized in that: The thrust coefficient K of the vector thruster is obtained by fitting p The relationships with fluid parameters include: The thrust coefficient of the vector thruster is obtained by fitting K pJ is the function related to the speed coefficient J obtained by fitting, Based on the fitting and vector deflection angle δ e and δ r The related interpolation surface f δ Sure, Based on the fitting results of deflection angle δ and oblique flow angle α obl The related interpolation surface f obl Sure.

4. The dynamic modeling method according to claim 3, characterized in that: K pJ =A J J w +B J Among them, J w is the corrected advance coefficient obtained by considering the influence of the AUV body on the wake field of the vector thruster, and J w =J(1-w), J is the advance coefficient, w is the wake fraction; A J and Β J are the parameter matrices obtained by fitting.

5. The dynamic modeling method according to claim 3, characterized in that: Among them, f δ (δ e ,δ r ) represents the interpolation surface f obtained by fitting δ The deflection angle δ of the vector e and δ r The corresponding value; f obl (α obly ,δ e ) represents the interpolation surface f obtained by fitting obl The deflection angle δ and the oblique flow angle component α obly The corresponding value, f obl (α oblz ,δ r ) represents the interpolation surface f obtained by fitting obl The deflection angle δ and the oblique flow angle component α oblz The corresponding value; oblique flow angle component is the oblique flow angle α obl The y-direction component in the body coordinate system, the oblique flow angle component is the oblique flow angle α obl The components of the velocity vector v in the body coordinate system in the z direction are: x ,v y ,v z ), the component of the rotational angular velocity vector ω of the vector-propelled AUV in the y direction of the body coordinate system is ω y , the component in the z direction of the body coordinate system is ω z , L AC It is the distance from the center of the vector thruster in the vector propulsion AUV to the center of buoyancy of the vector propulsion AUV.

6. The dynamic modeling method according to claim 1, characterized in that: The thrust force exerted on the vector propulsion AUV Thruster thrust torque on vector-propelled AUV Among them, the thrust coefficient of the vector thruster obtained by fitting is Among them, K Tpx , K Tpy , K Tpz They are thrust coefficient K p The force component coefficients in the three directions of the body coordinate system, K Qpx , K Qpy , K Qpz They are thrust coefficient K p The torque component coefficients in the three directions of the body coordinate system; ρ represents the fluid density, n is the speed of the vector propeller, D is the diameter of the vector propeller, L AC It is the distance from the center of the vector thruster in the vector propulsion AUV to the center of buoyancy of the vector propulsion AUV.

7. The dynamic modeling method according to claim 1, characterized in that: The hydrodynamic parameters of the vector-propelled AUV obtained by CFD simulation include: The drag factor C of a vector-propelled AUV when both the attack angle α and the sideslip angle β are 0 x0 ; and the position derivative of the lift factor with respect to the angle of attack Position derivative of the side force factor with respect to the sideslip angle Position derivative of the yaw moment factor with respect to the sideslip angle Position derivative of the pitching moment factor with respect to the angle of attack And, the lift factor is z The rotational derivative of Lateral force factor versus ω y The rotational derivative of Rolling moment on ω x The rotational derivative of Rolling moment on ω y The rotational derivative of Yaw moment on ω x The rotational derivative of Yaw moment on ω y The rotational derivative of Pitching moment on ω z The rotational derivative of And, the additional mass matrix 8. The kinetic modeling method according to claim 7, characterized in that: The hydrodynamic forces acting on a vector-propelled AUV include position forces Damping force and inertial force F INE ; The hydrodynamic torque on the vector-propelled AUV includes the position torque Damping torque and moment of inertia M INE ; in, v is the velocity vector at the center of buoyancy of the vector-propelled AUV and its components in the three directions of the body coordinate system are (v x ,v y ,v z ), ω is the rotational angular velocity vector of the vector-propelled AUV and its components in the three directions of the body coordinate system are (ω x ,ω y ,ω z ), ρ represents the fluid density, v represents the velocity amplitude of the vector-propelled AUV, S represents the maximum cross-sectional area of ​​the vector-propelled AUV, and L represents the length of the vector-propelled AUV.

9. The kinetic modeling method according to claim 1, characterized in that: The buoyancy force exerted on the vector-propelled AUV The buoyancy torque in the body coordinate system of the vector-propelled AUV G is the gravity acting on the vector-propelled AUV and G=mg, B is the buoyancy acting on the vector-propelled AUV and B=ρgV, m is the mass of the vector-propelled AUV, g is the acceleration due to gravity, ρ represents the fluid density, and V represents the volume of the vector-propelled AUV; The three components of the radius rcg from the center of gravity to the center of buoyancy of the vector-propelled AUV in the body coordinate system (x cg ,y cg , z cg ) is an antisymmetric matrix composed of It is the coordinate transformation matrix from the ground coordinate system to the body coordinate system. The ground coordinate system O e x e y e z e Solidly connected to the ground.

10. The dynamic modeling method according to claim 1, characterized in that: The kinetic modeling method further comprises: The kinematic equations of the vector-propelled AUV are constructed as follows: Among them, the position coordinates of the center of buoyancy of the vector-propelled AUV in the ground coordinate system are (x e ,y e ,z e ), the components of the velocity vector v at the center of buoyancy of the vector-propelled AUV in the three directions of the body coordinate system are (v x ,v y ,v z ); The components of the rotational angular velocity vector ω of the vector-propelled AUV in the three directions of the body coordinate system are (ω x ,ω y ,ω z ); θ is the pitch angle of the vector-propelled AUV relative to the ground coordinate system, ψ is the yaw angle of the vector-propelled AUV relative to the ground coordinate system, and φ is the roll angle of the vector-propelled AUV relative to the ground coordinate system; the ground coordinate system O e x e y e z e Solidly connected to the ground.

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