An unmanned underwater vehicle hydrodynamic coefficient calculation method
By combining MATLAB system identification with the kinematic model and flight test data of the unmanned underwater vehicle, and using gray box model identification and approximate formula estimation, the high cost and low accuracy problems of hydrodynamic coefficient calculation for unmanned underwater vehicles were solved, and economical and efficient hydrodynamic coefficient calculation was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NO 719 RES INST CHINA SHIPBUILDING IND
- Filing Date
- 2022-10-09
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies for calculating the hydrodynamic coefficients of unmanned underwater vehicles (UUVs) rely on constrained model tests, which are time-consuming and require significant manpower and resources. Semi-theoretical and semi-empirical methods lack accuracy, while computational fluid dynamics simulations require sophisticated computers and validation data, making it difficult to calculate hydrodynamic coefficients quickly and accurately.
The MATLAB system identification method is adopted, combined with the kinematic model of the unmanned underwater vehicle and the flight test data. The hydrodynamic coefficients are calculated by using the kinematic model of the unmanned underwater vehicle and the test data, including the establishment of the idnlgrey object and multiple iterative calculations to improve accuracy.
It achieves a balance between economy and accuracy, avoids the high cost and long cycle of constrained ship model testing, improves calculation accuracy by utilizing actual navigation data, and is suitable for regular ellipsoidal unmanned underwater vehicles.
Smart Images
Figure CN115688383B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of underwater equipment technology in shipbuilding and marine engineering, and specifically to a method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle. Background Technology
[0002] Maneuverability is a crucial component of the overall performance of an unmanned underwater vehicle (UUV). Good maneuverability is essential for safe navigation and for fully utilizing the UUV's comprehensive technological capabilities. Hydrodynamic coefficients are key parameters in the UUV's maneuverability equations. Simulating maneuverability and predicting maneuverability based on these equations requires highly accurate calculations of hydrodynamic coefficients.
[0003] Hydrodynamic coefficient calculation is fundamental to the maneuverability research of underwater unmanned vehicles (UUVs). Currently, there are three main methods for calculating hydrodynamic coefficients of UUVs: semi-theoretical and semi-empirical estimation methods, constrained model experiments, and computational fluid dynamics (CFD) simulations. Among these, constrained model experiments are the most effective method for determining hydrodynamic coefficients, but they typically require significant manpower and resources and have a long testing cycle. Semi-theoretical and semi-empirical estimation methods are suitable for the early design stages, but the calculation results currently do not meet engineering accuracy requirements, and in practical research, they are mostly used in combination with other methods. Computational fluid dynamics simulations require comparative verification using sea trial data, and are therefore mostly used for Suboff-type submarines. Furthermore, the hydrodynamic coefficient calculation cycle for complex models is long, and it also places certain demands on the computing power of computers.
[0004] MATLAB system identification uses an algorithm to continuously correct model parameters (least squares criterion) based on the error between the model output and the actual output, ultimately obtaining the optimal model result. For kinematic models of systems with known mathematical structures, MATLAB gray-box models can be used for parameter identification. Only initial values are needed to determine the range of feasible solutions, and the desired hydrodynamic coefficients can be obtained through multiple iterative calculations. Summary of the Invention
[0005] In view of this, the present invention provides a method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle. Based on an approximate estimation method, the hydrodynamic coefficient of the underwater unmanned underwater vehicle is identified using MATLAB software. This method is both economical and accurate, and is applicable to underwater unmanned underwater vehicles whose main body is a regular ellipsoid.
[0006] A method for calculating the hydrodynamic coefficients of an unmanned underwater vehicle includes the following steps:
[0007] Step 1: Establish the kinematic model of the unmanned underwater vehicle;
[0008] Step 2: Create an idnlgrey object;
[0009] Step 3: Estimate the hydrodynamic coefficient of the unmanned underwater vehicle as the initial value for the subsequent Step 5;
[0010] Step 4: Processing and importing data from the unmanned underwater vehicle flight test;
[0011] Step 5: Substitute the unmanned underwater vehicle test data and initial values from Step 4 into the idnlgrey object from Step 2 to perform gray box model identification;
[0012] Step 6: If the hydrodynamic coefficient calculation result obtained in Step 5 meets the accuracy requirements, it shall be used as the final calculation result; otherwise, the calculation result in Step 5 shall be used as the initial value for the next calculation, and Steps 4 to 6 shall be repeated.
[0013] Furthermore, the expression for the horizontal plane maneuvering motion of the unmanned underwater vehicle in step one is:
[0014]
[0015] The expression for the vertical plane maneuvering motion of the unmanned underwater vehicle is:
[0016]
[0017] Where u, v, w, P, q, and r are the speed and angular velocity of the underwater vehicle in the x, y, and z directions, respectively; δ is the rudder angle coefficient, and θ is the Euler angle. X vv X rr X vr , Y r Y v|v| Y r|r| Y v|r| , N v|v| N |v|r N r|r| , Z w Z w|w| Z w|q| , M w M |w| M w|q| M w|w| These are the values of the partial derivatives of the hydrodynamic components with respect to the motion parameters of the submersible at the expansion point, collectively referred to as hydrodynamic coefficients;
[0018] Based on the calculation requirements of the motion state and hydrodynamic coefficients of the unmanned underwater vehicle (UUV), a kinematic model of the UUV is established with reference to the typical spatial maneuvering motion expression of the UUV.
[0019] Furthermore, the process of establishing the idnlgrey object in step two is as follows: define the state variable X, the control variable u, and the output Y = X;
[0020] The kinematic model of the unmanned underwater vehicle is returned as an idnlgrey object, which returns the output and state derivatives as functions of time, input, state, and parameter values.
[0021] Furthermore, in step three, the hydrodynamic coefficients are initially determined using an approximate formula estimation method. The hydrodynamic coefficients include acceleration coefficient, velocity coefficient, angular velocity coefficient, and rudder angle coefficient. Based on empirical formulas and reference charts, the hydrodynamic coefficients of the unmanned underwater vehicle are initially estimated.
[0022] 1) Acceleration coefficient:
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030] Where L, B, and H are the main axis dimensions of the submersible, λ is the aspect ratio of each appendage, μ(λ) is the correction value for a finite wingspan, and K ij (ij=11,22,33,55,66) is the additional quality coefficient, x ap The coordinates of the hydrodynamic center of each appendage area relative to the origin;
[0031] 2) Velocity coefficient
[0032]
[0033]
[0034]
[0035]
[0036] Where ε is the interference coefficient. For the lift derivative, Let α be the derivative of the torque. ∞ The derivative is the lift correction factor, and k is the thickness correction factor.
[0037] 3) Angular velocity coefficient
[0038]
[0039]
[0040]
[0041]
[0042] in, For the lift derivative, The derivative of the torque;
[0043] 4) Rudder angle coefficient
[0044]
[0045]
[0046] Among them, B p K is the load factor of the propeller. T denoted as the propeller thrust coefficient, J as the propeller advance ratio, and n, D, and w as the propeller rotational speed, diameter, and wake coefficient, respectively.
[0047] Beneficial effects:
[0048] 1. The hydrodynamic coefficient calculation method of the unmanned underwater vehicle of the present invention is based on the kinematic model of the unmanned underwater vehicle and the actual boat sailing test data. It utilizes theoretical estimation and parameter identification methods. Compared with the restrained boat model test method, this method uses free sailing test data, which saves a lot of test costs and time costs incurred in the restrained boat model test process, and is more economical.
[0049] 2. Compared with hydrodynamic simulation calculation methods, the present invention is based on actual test data, and the effect of the real navigation environment in the test field is more accurate than that of computer simulation.
[0050] 3. Step three of the present invention uses an approximate formula estimation method to preliminarily determine the hydrodynamic coefficients, which include acceleration coefficient, velocity coefficient, angular velocity coefficient and rudder angle coefficient, and can realize the preliminary estimation of the hydrodynamic coefficients of unmanned underwater vehicles. Attached Figure Description
[0051] Figure 1 This is a flowchart of the method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle according to the present invention;
[0052] Figure 2 A schematic diagram of the kinematic parameters of an underwater unmanned submersible.
[0053] Figure 3Identify the fitted curve for the gray box model. Detailed Implementation
[0054] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0055] This invention provides a method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle. The calculation steps of this method are as follows:
[0056] Step 1: Establish the kinematic model of the unmanned underwater vehicle;
[0057] Hydrodynamic coefficients were calculated using a certain underwater unmanned vehicle (UUV) as the research object. The input for the calculation was the test data of the UUV's horizontal plane maneuvering motion at a small rudder angle. Ignoring second-order and higher-order terms in the Taylor expansion of the hydrodynamic equations, only linear terms were retained, and the motion of the roll surface was not considered. A kinematic model of the UUV was then established.
[0058]
[0059] Where the heading speed U is 1 m / s; v, r, ψ, y are the lateral speed, yaw rate, yaw angle, and lateral deviation of the unmanned underwater vehicle, respectively, as shown in the attached figure. Figure 2 As shown; δ r y is the rudder deflection angle; m is the mass; I is the rudder deflection angle. z This is the yaw moment of inertia.
[0060] Step 2: Create an idnlgrey object;
[0061] Define the state variables X = [v, r, ψ, y] T Control quantity u = δ r The output is Y = X.
[0062] The kinematic model of the unmanned underwater vehicle is returned as an idnlgrey object, which returns the output and state derivatives as functions of time, input, state, and parameter values.
[0063]
[0064] Step 3: Estimate the hydrodynamic coefficient of the unmanned underwater vehicle as the initial value for the subsequent Step 5;
[0065] Parameters required for approximate estimation of unmanned underwater vehicles: underwater total displacement volume The following table shows the following parameters: length L of the aircraft, height B, width H, projected area s of each appendage, span l, chord length b, ordinate x from the center of the area to the origin of the moving coordinate system (center of gravity), and aspect ratio λ:
[0066]
[0067]
[0068] 1) Acceleration coefficient:
[0069]
[0070]
[0071]
[0072]
[0073]
[0074]
[0075]
[0076] 2) Speed coefficient:
[0077] Let the interference coefficients ε1=ε2=1, from From the table:
[0078]
[0079]
[0080]
[0081]
[0082]
[0083]
[0084] 3) Angular velocity coefficient:
[0085] The buoyancy center position correction factor is set to 1, and the interference coefficients ε5 = ε6 = 1. B / H = 1, from the table we get:
[0086]
[0087]
[0088]
[0089]
[0090]
[0091] 4) Rudder angle derivative:
[0092] Let the interference coefficients ε3 = ε4 = 1
[0093]
[0094]
[0095]
[0096] Step 4: Processing and importing data from the unmanned underwater vehicle flight test;
[0097] Acquire flight test data for the unmanned underwater vehicle, selecting lateral velocity v, yaw rate r, yaw angle ψ, side slip distance y, and rudder deflection angle δ. r Data preprocessing is performed, which includes: exporting the data stored inside the submarine; decoding the stored data (raw hexadecimal data) and converting it into readable data, which is then imported into the workspace as an iddata object, that is, converting the data into a form that can be processed by the software.
[0098] Step 5: Gray box model identification;
[0099] Set the continuous simulation time to t = 0.2s, substitute the unmanned underwater vehicle test data and initial values from step four into the idnlgrey object from step two for gray box model identification, and dimensionlessize the results:
[0100] Y v =-0.0112,Y r =0.00662,N v =-0.00723,N r =-0.00109,N d = -0.00353.
[0101] Step 6: Iterate the calculation multiple times.
[0102] If the hydrodynamic coefficient calculation result obtained in step five meets the accuracy requirements, it is taken as the final calculation result. Otherwise, the calculation result in step five is used as the initial value for the next calculation, and steps four to six are repeated until the simulation curve fitting result meets the requirements (fitting error not greater than 15%). The simulation result interface is shown in the attached figure. Figure 3 As shown.
[0103] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle, characterized in that, The calculation steps include the following: Step 1: Establish the kinematic model of the unmanned underwater vehicle; Step 2: Create an idnlgrey object; Step 3: Estimate the hydrodynamic coefficient of the unmanned underwater vehicle as the initial value for the subsequent Step 5; Step 4: Processing and importing data from the unmanned underwater vehicle flight test; Step 5: Substitute the unmanned underwater vehicle test data and initial values from Step 4 into the idnlgrey object from Step 2 to perform gray box model identification; Step 6: If the hydrodynamic coefficient calculation result obtained in Step 5 meets the accuracy requirements, it shall be used as the final calculation result; otherwise, the calculation result in Step 5 shall be used as the initial value for the next calculation, and Steps 4 to 6 shall be repeated. The expression for the horizontal maneuvering motion of the unmanned underwater vehicle in step one is: The expression for the vertical plane maneuvering motion of the unmanned underwater vehicle is: in, , , , , , These are the velocity and angular velocity of the submersible in the x, y, and z directions; This is the rudder angle coefficient. Euler angles; , , , , , , , , , , , , , , , , , , , , , , These are the values of the partial derivatives of the hydrodynamic components with respect to the motion parameters of the submersible at the expansion point, collectively referred to as hydrodynamic coefficients; Based on the calculation requirements of the motion state and hydrodynamic coefficients of the unmanned underwater vehicle (UUV), a kinematic model of the UUV is established with reference to the typical spatial maneuvering motion expression of the UUV.
2. The method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle as described in claim 1, characterized in that, The process of creating the idnlgrey object in step two is as follows: Define state variables Control quantity Output ; The kinematic model of the unmanned underwater vehicle is returned as an idnlgrey object, which returns the output / state derivatives as functions of time, input, state, and parameter values.
3. The method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle as described in claim 1, characterized in that, Step three uses an approximate formula estimation method to preliminarily determine the hydrodynamic coefficients, which include acceleration coefficient, velocity coefficient, angular velocity coefficient, and rudder angle coefficient. Based on empirical formulas and reference charts, the hydrodynamic coefficients of the unmanned underwater vehicle are preliminarily estimated.
4. The method for calculating the hydrodynamic coefficient of an unmanned underwater vehicle as described in claim 3, characterized in that, The formulas for the acceleration coefficient, velocity coefficient, angular velocity coefficient, and rudder angle coefficient are as follows: 1) Acceleration coefficient: in, , , For the main shaft dimensions of the submersible, For the aspect ratio of each appendage, For finite wingspan, For the additional quality coefficient, The coordinates of the hydrodynamic center of each appendage area relative to the origin; 2) Speed coefficient in, The interference coefficient is... For the lift derivative, For the derivative of torque, For the lift correction derivative, This is the thickness correction factor; 3) Angular velocity coefficient in, For the lift derivative, The derivative of the torque; 4) Rudder angle coefficient in, The load factor of the propeller. This represents the propeller's thrust coefficient. The propeller's advance rate ratio. These are the propeller's rotational speed, diameter, and wake coefficient, respectively.