Method and system for measuring resistance in towing test of underwater vehicle

Abstract

The invention provides a method and system for measuring resistance in an underwater vehicle towing test, and relates to the technical field of underwater vehicle hydrodynamic performance testing, and the method comprises three links of gravity center adjustment, measurement data processing and uncertainty analysis. Firstly, it is ensured that the gravity center and the buoyancy center of a test model are consistent in height, model attitude stability is ensured, and resistance measurement errors caused by attitude changes are eliminated. Secondly, measuring the sailing resistance of the test model in the towing test, and post-processing the measured data to obtain the total resistance coefficient of the test model at the test temperature; and finally, quantizing errors of each link and synthesizing expansion uncertainty by adopting a deviation limit and precision limit combined uncertainty analysis method. Compared with a traditional single-index evaluation method, the method not only can reveal error sources and quantify the influence of each link on the measurement result, but also can accurately reflect the composite effect of errors, and ensures the reliability of the resistance measurement result.

Description

Technical Field

[0001] The present application relates to the technical field of hydrodynamic performance testing of underwater vehicles, and more particularly, to a method and system for measuring resistance in a towing test of an underwater vehicle. Background Art

[0002] In the research and development process of underwater vehicles, experimental analysis is an important means to evaluate the performance of the vehicle, and among them, the measurement of the navigation resistance is crucial. The navigation resistance is the resistance force suffered by the vehicle when moving in water, which directly affects the propulsion efficiency, endurance, and energy consumption estimation. Accurately measuring the resistance can provide reliable data for the hull line design and the selection of the propulsion system, thereby improving the overall performance of the underwater vehicle.

[0003] Due to the high cost of full-scale underwater vehicle tests, in engineering practice, hydrodynamic tests are usually carried out using a scaled-down model. The resistance of the model is measured in a pool or a water channel, and is extrapolated to the actual size according to the similarity principle, in order to save costs and detect flow field anomalies at an early stage of design, which helps to optimize the hull and propeller structures.

[0004] Although scaled-down model tests are widely used in actual engineering, there are still deficiencies in the existing resistance measurement methods in terms of data quality assurance. Traditional methods usually only rely on a single error evaluation index (such as the sensor deviation limit or the repeatability accuracy limit) for uncertainty analysis, ignoring the combined effect of errors, and it is easy to underestimate or overestimate the errors, and it is impossible to comprehensively and objectively evaluate the credibility of the measurement data. Summary of the Invention

[0005] The purpose of the present application is to provide a method and system for measuring resistance in a towing test of an underwater vehicle in view of the above deficiencies in the technology.

[0006] To achieve the above purpose, the technical solutions adopted in the present application are as follows: On the one hand, the present application provides a method for measuring resistance in a towing test of an underwater vehicle, including: Center of gravity adjustment: determining the center of buoyancy and the center of gravity of the test model of the underwater vehicle; adjusting the center of gravity of the test model to be directly below the center of buoyancy of the test model, and adjusting the ballast so that the test model has neutral buoyancy; Measurement data processing: measuring the navigation resistance of the test model in the towing test, and post-processing the measurement data to obtain the total resistance coefficient of the test model at the test temperature; Uncertainty analysis: correcting the total resistance coefficient at the test temperature to the total resistance coefficient at the standard temperature, respectively calculating the deviation limit and the precision limit of the total resistance coefficient at the standard temperature, and obtaining the uncertainty of the total resistance coefficient at the standard temperature according to the deviation limit and the precision limit. The calculation formula is:

[0007] Among them, is the uncertainty of the total drag coefficient at the standard temperature, is the deviation limit of the total drag coefficient at the standard temperature, is the precision limit of the total drag coefficient at the standard temperature.

[0008] Furthermore, in the uncertainty analysis: The calculation formula for the deviation limit of the total drag coefficient at the standard temperature is:

[0009] Among them, is the total drag coefficient at the standard temperature, R is the total drag of the test model, ρ is the density of water, V is the sailing speed of the test model, S is the wetted surface area of the test model, is the deviation limit of the wetted surface area, is the deviation limit of the speed, is the deviation limit of the drag, is the deviation limit of the density.

[0010] Furthermore, in the uncertainty analysis: The calculation formula for the precision limit of the total drag coefficient at the standard temperature is:

[0011] Among them, K is the coverage factor, SDev is the standard deviation determined by multiple tests, M is the number of tests, is the i total drag coefficient at the standard temperature obtained from the th test,

[0012] is the average value of the total drag coefficients at the standard temperature obtained from multiple tests.

[0013] Among them, is the total drag coefficient at the test temperature, is the friction drag coefficient at the standard temperature, calculated by CFD software, is the friction drag coefficient at the test temperature, Re T is the Reynolds number at different temperatures.

[0014] Further, in the measurement data processing, the post-processing of the measurement data to obtain the total drag coefficient of the test model at the test temperature includes: performing fast Fourier transform analysis on the measurement data, identifying the vibration noise frequency distribution range in the measurement data, filtering the vibration noise, and retaining the drag signal in the measurement data; performing post-processing on the drag signal to obtain the total drag coefficient of the test model at the test temperature. Further, before the measurement data processing, the method further includes: settlement detection: detecting the settlement of the ends of the test model along the length direction and the ends along the width direction, and adjusting the ballast or the connection position of the test model so that the settlement is less than or equal to 1.0 mm.

[0015] On the other hand, the present application provides a drag measurement system in an underwater vehicle towing test for implementing any one of the above methods, including an underwater vehicle test model, a force measuring sensor, a connecting device, and a towing test platform. The force measuring sensor is fixedly installed in the test model, and the measurement origin of the force measuring sensor coincides with the center of gravity of the test model. One end of the connecting device is connected to the force measuring sensor, and the other end is connected to the towing test platform.

[0016] Further, the connecting device includes a connecting rod and a connecting piece. One end of the connecting rod is flange-connected to the towing test platform, and the other end is flange-connected to the force measuring sensor through the connecting piece.

[0017] Further, a wire groove is provided on the flange plate at one end of the connecting piece close to the force measuring sensor, so that the data line of the force measuring sensor passes through the wire groove and is connected to the interface box located on the towing test platform.

[0018] Further, the system further includes a vibration damping device for suppressing the vibration generated by the towing test platform during the process of driving the test model to navigate, so as to reduce the vibration transmitted to the test model.

[0019] The beneficial effects of the present application include: The present application provides a method for measuring the resistance in the towing test of an underwater vehicle, including three steps: center of gravity adjustment, measurement data processing, and uncertainty analysis. First, the method combines the suspension method and ballast adjustment to make the heights of the center of gravity and the center of buoyancy of the test model consistent, ensuring the stable attitude of the model and eliminating the resistance measurement error caused by attitude changes. Second, the navigation resistance of the test model in the towing test is measured, and the measurement data is post-processed to obtain the total resistance coefficient of the test model at the test temperature. Finally, an uncertainty analysis method combining the deviation limit and the precision limit is adopted to quantify the errors in each step and synthesize the expanded uncertainty. Compared with the traditional single-index evaluation method, this method can not only reveal the error sources, quantify the influence of each step on the measurement result, but also accurately reflect the combined effect of the errors, ensuring the reliability of the resistance measurement result, meeting the requirements of international standards such as ISO for uncertainty evaluation, and achieving the traceability and international mutual recognition of the results. In summary, this method is superior to the existing technologies in terms of accuracy, traceability, and implementation convenience, providing a high-precision and high-reliability resistance measurement solution for the towing test of underwater vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a flowchart of a method for measuring the resistance in the towing test of an underwater vehicle provided by the present application; Figure 2 It is a schematic structural diagram of a measurement system for the resistance in the towing test of an underwater vehicle provided by the present application; Figure 3 It is a schematic connection diagram of a test model, a force measuring sensor, and a connecting device provided by the present application; Figure 4 It is a diagram of the filtering process of measurement data.

[0022] Reference Signs: 1 - Towing test platform; 2 - Test model; 3 - Connecting device; 4 - Force measuring sensor; 5 - Base; 6 - Connecting member; 7 - Connecting rod. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. The components of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents the selected embodiments of this application. It should be noted that, without conflict, the various features in the embodiments of this application can be combined with each other, and the combined embodiments are still within the protection scope of this application.

[0025] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] In the description of this application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this application is usually placed when in use. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application. In addition, the terms "first", "second", "third", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0027] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0028] In the description of this application, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0029] The technical solutions of this application will be described in detail below with specific embodiments.

[0030] On the one hand, the present application provides a method for measuring the drag force in the towing test of an underwater vehicle, as Figure 1 shown, including: S1, center of gravity adjustment: Determine the center of buoyancy of the test model 2 of the underwater vehicle; determine the center of gravity of the test model 2 by the suspension method; arrange ballast so that the center of gravity of the test model 2 is directly below the center of buoyancy of the test model 2 in the vertical direction, and adjust the ballast so that the test model 2 has neutral buoyancy.

[0031] Specifically, the first step is to determine the center of buoyancy position based on the CAD model data. The specific method is to extract the drainage volume and calculate the center of volume of the geometric shape of the test model 2 in the designed static equilibrium attitude. By numerically analyzing the three-dimensional geometric information of the CAD model, the drainage volume of the test model 2 in the assumed horizontal attitude can be obtained, and then according to the concept of the geometric center in fluid mechanics, the position of the center of volume of the drainage body, that is, the center of buoyancy, can be calculated. The accurate acquisition of the center of buoyancy position is a prerequisite for adjusting the center of gravity to directly below it later, because only when the center of gravity coincides with the center of buoyancy and is directly below it, the test model 2 can maintain balance in the vertical direction under the combined action of gravity and buoyancy, thus avoiding pitching or rolling phenomena.

[0032] The second step is to determine the center of gravity position of the test model 2 by the suspension method. The principle of the suspension method is based on static equilibrium: for any freely suspended rigid body in the equilibrium state, its center of gravity must fall directly below the connection point of the line in order to make the gravity moment zero. In this embodiment, the test model 2 of the rotary underwater vehicle is used for analysis. For the test model 2 of the rotary underwater vehicle with left-right symmetry, two different suspension points can be selected on its side for two suspension tests. Specifically, first suspend one end of the test model 2 by a thin line at a fixed point, make the test model 2 statically suspended in the air, and use a plumb line or an optical positioning device to record the vertical projection position of the center of gravity in the geometric coordinate system of the test model 2. Then change the suspension point and repeat the above operation to obtain the position of the second gravity line in the coordinate system of the test model 2. The intersection point of the two gravity lines obtained by the two suspensions is the center of gravity coordinate of the test model 2. By this method, the center of gravity of the test model 2 can be accurately located without the aid of complex measuring instruments, and since the test model 2 and the internal equipment layout are symmetric, the center of gravity can be determined efficiently by suspending twice on the side.

[0033] After determining the center of buoyancy and the center of gravity, the next step is to reasonably arrange ballast blocks inside the test model 2 so that the center of gravity of the test model 2 is directly below the center of buoyancy in the vertical direction, and adjust the overall mass to achieve neutral buoyancy. First, based on the known displacement volume and the density of water, the total mass required for the test model 2 to achieve neutral buoyancy can be calculated = displacement volume × density of water. On the basis of the dry mass of the test model 2, by gradually adding or moving ballast blocks in the internal brackets or compartments, the mass distribution of the test model 2 is adjusted so that the calculated center of gravity position aligns with the center of buoyancy in the vertical direction, and the overall mass is made to reach the total mass required for neutral buoyancy through mass accumulation or adjustment. Then, gently place the test model 2 into the still water tank and observe its floating and sinking state. If the test model 2 floats or sinks, slightly increase or decrease the weight of the ballast blocks to fine-tune the mass so that the test model 2 can float and maintain a horizontal attitude at any depth.

[0034] After the above-mentioned center of gravity and ballast adjustment of the test model 2, the last step is to verify its static attitude stability in water. The specific method is to apply a small pitching or rolling perturbation to the test model 2 when it is floating in still water and observe whether the test model 2 can return to the original horizontal state within a short time. If it takes a long time for the test model 2 to reset or it is difficult to return to the initial position completely, it indicates that the center of gravity may not be fully aligned with the center of buoyancy or the internal mass distribution is uneven. At this time, the ballast position or weight needs to be readjusted until the test model 2 can quickly and autonomously restore horizontal balance after being perturbed. Through this verification step, it can be ensured that in the subsequent towing test, the test model 2 will not introduce redundant motion components due to hydrostatic instability, so that the measured drag signal is both pure and highly repeatable.

[0035] Through the above center of gravity adjustment process, an ideal balanced state of the test model 2 in water without pitching, rolling, or floating and sinking can be achieved. At this time, the main force acting on the test model 2 is the drag force along the forward direction, without being doped with additional torques caused by attitude changes and gravitational torques. Coupled with the installation and precision calibration of the subsequent measurement system, the entire test process can minimize systematic errors to a great extent, thereby significantly improving the accuracy and reliability of drag measurement and providing a solid experimental data basis for the performance evaluation and design optimization of underwater vehicles.

[0036] It should be noted that before S1, the surface of the test model 2 should be inspected and processed first: check whether there are sharp edges, seams, or protrusions on the surface of the test model 2 to ensure that it meets the requirements of streamline design. If the surface is found to be uneven, polishing treatment is required, and paint or coating is sprayed if necessary to improve the surface smoothness. Before the test, thoroughly clean the surface of the test model 2 with a cleaner and a lint-free cloth to remove pollutants such as dust and debris to avoid disturbing the flow field.

[0037] S2, Calibration of Measuring Instruments: Place the force sensor 4 under static conditions, calibrate the zero point of the force sensor 4 under no-load conditions, and then use standard weights to calibrate the sensitivity of the force sensor 4 so that its output value is consistent with the load value of the standard weights.

[0038] Specifically, before assembling the measurement system, the force sensor 4 must first be fully calibrated to ensure the accuracy and stability of its output data. Specifically, in this embodiment, an ATI series six-degree-of-freedom force sensor 4 (Force / Torque Sensor) is used. During the calibration process, the force sensor 4 needs to be placed under static no-load conditions. First, set the zero point, and then verify and correct the sensitivity through standard weights, so that the sensor can accurately reflect the actual force during subsequent dynamic measurements.

[0039] First, fixedly install the ATI force sensor 4 on a special test platform or a rigid bracket to ensure that there is no looseness or slippage between the sensor and the platform. When installing, it should be noted to ensure that the flange surface of the sensor is parallel to the bottom plate of the bracket, and use matching bolts to firmly lock it to avoid mechanical deviation during calibration or testing. Subsequently, insert the sensor cable into the NET F / T interface box (Ethernet Interface Box) and connect it to a stable DC power supply (12V - 24V). After starting the power supply, the interface box and the sensor perform communication initialization through Ethernet. After the status indicator light is constantly on and the host computer can recognize the device, the next step can be carried out. At this time, the NET F / T interface box can be connected to the host computer through Ethernet or a USB transfer module, and the special software of the F / T Net Box can be opened or a data channel can be established through interface programs such as LabVIEW and MATLAB.

[0040] Under no-load conditions (including eliminating the influence of the sensor's own gravity), click the ZeroBias, Set Zero, or Tare button in the software interface to record the static output of the six channels (Fx, Fy, Fz, Mx, My, Mz) of the current force sensor 4 as the "zero point reference". Only when the no-load output of the sensor is set to zero can the subsequent force changes correspond one-to-one with the actual external load, avoiding measurement errors caused by initial deviation. After completing the zero point setting, the current configuration file should be saved to ensure that the same zero point reference can be called even if the system is powered off or restarted during the measurement process.

[0041] After zero calibration is completed, it is necessary to perform axis-by-axis calibration of the sensor sensitivity. Taking the force calibration along the Z-axis (in the towing direction) as an example, first select a standard weight of known mass, and vertically suspend the standard weight on the axis to be measured of the sensor through a thin and flexible nylon thread or a lightweight bracket. At this time, it must be ensured that only a force is generated in the Z-axis direction during the loading process, without introducing obvious shear or torque components. Subsequently, read the Fz value output by the force sensor 4 through the software, and compare it with the theoretical weight value of the standard weight. If there is a deviation between the output value of the force sensor 4 and the theoretical value, the following aspects need to be rechecked: whether the connection between the sensor and the bracket is firm; whether the position and method of adding the standard weight are perpendicular; whether there is interference in the communication of the cable or interface box; whether the calibration coefficient in the software is correctly imported, etc. After excluding the above factors, the current output value can be linearly corrected through the software or the Set Zero operation can be performed again until the output is within the specified tolerance range of the standard weight load value. After completing the Z-axis calibration, if necessary, the same loading calibration can also be performed on other axes (Fx, Fy, Mx, My, Mz) respectively to ensure that the linearity and accuracy of the sensor in all force directions meet the test requirements.

[0042] After the calibration process is completed, a review test should be carried out: after both zero calibration and sensitivity calibration pass, first remove all standard weights, let the sensor return to the unloaded state, and confirm that the outputs of all its channels return to zero; then reload several standard weights of different masses and check whether the outputs of the sensor at different load points always match the theoretical values and maintain a linear relationship. Only when the multi-point test results meet the accuracy indicators (such as the linear error and hysteresis error are both within ±0.1% FS) can the calibration results be solidified and saved. At this point, the zero and sensitivity calibration of the force sensor 4 is truly completed, laying a solid foundation for the subsequent assembly and testing of the measurement system.

[0043] S3, Assembly of the measurement system: Fix and install the force sensor 4 on the test model 2, and make the measurement origin of the force sensor 4 coincide with the center of gravity of the test model 2; Connect the towing test platform 1 to the force sensor 4 through the connecting device 3; Specifically, such as Figure 2 and Figure 3As shown in the figure, first fixedly install a base 5 inside the test model 2 that matches the bottom surface of the flange of the force sensor 4. Place the force sensor 4 at this position and firmly fix the sensor to the base 5 using a positioning pin (or mating bolts) to ensure that there is no obvious relative slip or tilt in all directions. Since the test model 2 has aligned the center of gravity with the center of buoyancy through the previous center-of-gravity adjustment step, at this time, only a fine adjustment of the sensor is required to make the measurement origin exactly coincide with the center of gravity of the model. During the fixing process, a scale or optical alignment device can be used to ensure that the three-dimensional coordinates of the sensor center and the model center of gravity accurately coincide, avoiding measurement deviations caused by installation errors.

[0044] After the force sensor 4 is fixed in place, it is necessary to establish a reliable mechanical connection between it and the towing test platform 1 through the connecting device 3. Generally, a high-strength, low-elasticity tie rod or precision metal connecting rod 7 is used. One end is connected to the force sensor 4 through a flange or bolt, and the other end is docked with the hanging point on the towing test platform 1 through a flange or universal joint device. This connecting device 3 should not only ensure that the resistance received by the test model 2 during towing can be completely transmitted to the sensor, but also prevent horizontal position deviation or platform vibration from being introduced into the force measuring element. For this purpose, a small rotating pin connection can be designed between the connecting rod 7 and the sensor to allow vertical or lateral displacement to be absorbed without affecting the axial force, and to eliminate unnecessary torque caused by the small misalignment between the test platform and the model.

[0045] When the towing test platform 1 starts, the connecting device 3 will drive the test model 2 to move forward at a constant speed in the towing tank. At this time, the resistance generated by the water flow acting on the model surface acts along the front and rear center line direction of the model and is transmitted to the measurement origin of the force sensor 4 through the connecting rod 7. Since the measurement origin of the sensor coincides with the center of gravity of the model, the sensor only senses pure axial thrust or tension and will not generate additional bending or torque components due to eccentric installation. Through this design, the authenticity and accuracy of the resistance signal are ensured, making subsequent signal acquisition, filtering, and calculation of the resistance coefficient all based on a pure force basis without additional errors.

[0046] Furthermore, after S3, the sinkage detection should be carried out: detect the sinkage at the ends of the test model 2 along the length direction and the ends along the width direction, and adjust the ballast or the connection position between the test model 2 and the connecting device 3 so that the sinkage is less than or equal to 1.0 mm.

[0047] Specifically, after the measurement system is assembled and it is confirmed that the sensor is firmly installed, it is necessary to detect the sinkage of test model 2 in accordance with the specifications of the International Towing Tank Conference (ITTC) to ensure that the model is in the correct draft and balanced state in water. The sinkage defined by the ITTC specifications includes the draft differences at the two pairs of ends of the model in the longitudinal and width directions in still water. The purpose is to ensure that the model will not have excessive longitudinal or lateral inclination due to uneven ballast or connection deviation without the action of towing force, thus causing systematic errors in subsequent resistance tests. According to the ITTC regulations, the sinkage differences at the longitudinal front and rear ends and the two lateral ends of the model should be less than or equal to 1.0 mm. Otherwise, it should be corrected by adjusting the ballast or modifying the position of connection device 3.

[0048] The specific detection method can be carried out in two steps. First, place the test model 2 with the assembled measurement system statically in a calm water tank to ensure no external disturbance. Then, use a precision water gauge or a laser rangefinder to measure the still water drafts at the longitudinal front end and the rear end of the model respectively. When measuring, select measurement positions parallel to the reference line of the model on the horizontal plane to ensure that the optical path of the instrument is perpendicular to the water surface to avoid parallax errors caused by the observation angle. Similarly, at the corresponding positions on both sides of the model, the transverse sinkage should also be measured in the same way. If it is found that the draft difference between the longitudinal front and rear ends exceeds 1.0 mm, it means that the model has an up-and-down inclination and needs to be readjusted; if the draft difference between the two lateral sides exceeds 1.0 mm, it indicates that the model has a transverse inclination and also needs to be corrected. The entire measurement process needs to be carried out cyclically multiple times until the draft differences at all four ends meet the ITTC specification requirement of ≤1.0 mm.

[0049] When it is determined that the sinkage does not meet the specifications, it can be adjusted in two ways. One is to reconfigure the ballast blocks inside the model: according to the detection results, move the ballast blocks longitudinally or transversely to redistribute the centroid position of the model; for example, if the draft at the front end of the model is too large, the front ballast should be appropriately reduced or the ballast should be moved backward to reduce the front-end sinkage; if the sinkage on one side is deeper, ballast should be added to the opposite side or the connection point position should be finely adjusted to make the model level again. The other is to finely adjust the hanging point position of connection device 3 between test model 2 and the towing test platform 1: since the connecting rod 7 may generate a small overturning moment on the model, by slightly moving the connection point in the up-and-down or left-and-right directions, the still water attitude of the model can be corrected. During the adjustment process, it is necessary to always keep the measurement origin of the force sensor 4 still coincident with the center of gravity of the model to avoid introducing new center of gravity deviations when correcting the sinkage. After each adjustment, the sinkage values at the front and rear ends and the two lateral ends need to be measured again until all draft differences meet the ITTC ≤1.0 mm requirement.

[0050] After the settlement calibration is completed, the subsequent dynamic towing test phase can be entered. Start the towing test platform 1, perform uniform towing at a preset speed, and simultaneously record the data of the force measuring sensor 4. On this basis, the resistance data collected by the force measuring sensor 4 will be more reliable because the test model 2 is in a state of zero pitch and zero roll in still water, eliminating the asymmetric flow field and additional additional torque caused by the settlement deviation. This can not only ensure the accuracy of resistance measurement, but also provide a stable and consistent spatial reference for subsequent spectrum analysis and resistance coefficient calculation, making the entire towing test link highly repeatable and comparable.

[0051] S4, Measurement data processing: Perform fast Fourier transform analysis on the measurement data of the force measuring sensor 4, identify the vibration noise frequency distribution range in the measurement data, use a low-pass filter to filter the vibration noise, and retain the resistance signal in the measurement data; perform post-processing on the resistance signal to obtain the total resistance coefficient of the test model 2 at the test temperature.

[0052] Specifically, since the towing test platform 1 will inevitably generate mechanical vibrations when driving the test model 2 to sail, these vibrations will be transmitted to the test model 2 along the connecting device 3, thus mixing high-frequency noise components in the output of the force measuring sensor 4. In order to extract the low-frequency signal only related to the model sailing resistance, it is necessary to perform frequency domain analysis and filtering processing on the original data to eliminate vibration interference and retain the true resistance information.

[0053] In specific implementation, first in the data acquisition stage, the six-channel (Fx, Fy, Fz, Mx, My, Mz) original time-domain data of the ATI force measuring sensor 4 are acquired to the upper computer at a sampling frequency not lower than 1 kHz. After the acquisition is completed, discrete frequency domain analysis is performed on the time-domain signal using the Fast Fourier Transform (FFT). FFT analysis can decompose the time-domain signal into the superposition of different frequency components. By calculating the amplitude of each frequency component, it is possible to intuitively identify which frequency bands contain obvious vibration noise. For example, the mechanical vibrations of the towing test platform 1 are usually concentrated in the high-frequency band of dozens to hundreds of hertz, while the frequency of the resistance signal generated by the model itself during steady sailing often concentrates in the range below 10 Hz. By finding the peak of the energy spectrum in the FFT result, the main frequency band and harmonic components of the vibration noise can be determined, providing a basis for subsequent filter design.

[0054] After identifying the vibration noise frequency spectrum range, it is necessary to perform low-pass filtering on the time-domain data to eliminate high-frequency interference. For this purpose, a Butterworth low-pass filter with a phase-free order of 4 to 6 can be selected. Its characteristics include a smooth passband response, a moderate roll-off band slope, and the ability to maintain the time characteristics of the drag signal after filtering. Set the cut-off frequency of the filter slightly higher than the maximum drag signal frequency generated during the actual movement of Test Model 2 (usually selected around 15 Hz) to ensure that both the high-frequency noise caused by platform vibration can be effectively filtered out and the low-frequency components related to the navigation drag can be completely retained. The filtering process usually includes: inputting the time-domain data into the filter function to obtain a stationary time-domain signal after removing high-frequency noise; then performing short-time averaging or sliding window smoothing on the filtered signal to further reduce the influence of random noise. As Figure 4 shown, after this filtering is completed, the output is the pure drag waveform in the forward direction received by Test Model 2, which helps to accurately calculate the total drag coefficient subsequently.

[0055] After obtaining a clean time-domain drag signal, the post-processing stage can be entered to calculate the total drag coefficient of Test Model 2 at the current flow velocity and test temperature. Then, compare and analyze the total drag coefficient obtained from the test with the theoretical value corrected based on the similarity theory or the numerical simulation result. If the two match well within an acceptable error range, it indicates that the accuracy and repeatability of the measurement process have been verified; if there is a systematic deviation, it is necessary to further check the filtering parameters, the measurement accuracy of the flow velocity, or the calibration status of the sensor to find out the potential error sources and make improvements.

[0056] Through the processing method combining FFT analysis and low-pass filtering, the high-frequency components caused by the vibration of the towing test platform 1 and environmental interference can be effectively eliminated, thus retaining the low-frequency drag signal that only reflects the hydrodynamic action on Test Model 2. The subsequent calculation of the drag coefficient based on the accurate flow velocity and model geometric parameters not only achieves high fidelity of the drag test data of the underwater vehicle Test Model 2 but also provides a reliable basis for comparison with the theoretical or simulation results, thus verifying the scientificity and effectiveness of the measurement system and process and laying a solid experimental foundation for the subsequent hull design optimization and propulsion system selection.

[0057] It should be noted that after completing the assembly of the measurement system and the calibration of the sinkage, before entering the data acquisition and processing link, the vibration of the towing test platform 1 should be effectively suppressed first to reduce the interference transmitted from the platform vibration to the model and the force measuring sensor 4. The core of vibration suppression lies in selecting appropriate vibration damping devices to isolate or attenuate the high-frequency vibration generated by the platform, so that its amplitude is significantly reduced when transmitted to Test Model 2, thus providing a cleaner original signal for the subsequent fast Fourier transform and low-pass filtering.

[0058] In specific implementation, it is first necessary to conduct a preliminary analysis of the vibration source and vibration spectrum characteristics of the towing test platform 1. Under no-load or static state with a model, the vibration frequency, acceleration amplitude, and main vibration direction of the platform during the start-up, acceleration, and uniform motion phases can be measured and recorded online through acceleration sensors installed at key structural nodes of the platform. By performing frequency-domain analysis on the collected data, it can be identified that the platform vibration mainly concentrates in the range of dozens to hundreds of hertz, especially the vibration components caused by the imbalance of the motor rotor, insufficient rigidity of the transmission structure, and water surface wave excitation. Only after mastering the vibration spectrum characteristics can the type and installation position of the vibration damping device be selected targeted.

[0059] The vibration damping device generally consists of an elastic element and a damping element, and forms such as a damping rubber buffer pad, a spring shock absorber, or an air spring can be adopted. Taking the damping rubber buffer pad as an example, its internal material has good elasticity and energy dissipation characteristics, and can convert part of the vibration energy generated by the platform into heat energy and consume it. During implementation, several rubber pads with calculated thickness and hardness are placed between the platform legs and the support structure, or a rubber elastic connecting sleeve is added between the connecting rod 7 and the platform hanging point. In this way, the longitudinal vibration and lateral vibration generated by the platform during operation will be significantly attenuated through the rubber pads. If higher vibration damping requirements are needed, a non-clearance helical spring shock absorber can also be installed at the nodes vulnerable to vibration and used in conjunction with a mechanical damper, so that the system can achieve different degrees of vibration isolation and attenuation in the low-frequency band (5 - 20 Hz) and the medium-high frequency band (20 - 200 Hz). In addition, an air spring can be utilized - that is, an appropriate amount of nitrogen is filled into the rubber bladder, and the natural frequency is finely adjusted by adjusting the air pressure to be slightly lower than the main frequency of the platform vibration, thereby further reducing the transmission of the platform vibration to the model. After all the vibration damping devices are installed, it is necessary to conduct an unloaded vibration test again to verify whether the vibration damping effect meets the expectations: measure the vibration spectrum of the platform after vibration damping through the acceleration sensors at the same positions and compare it with the initial data to ensure that the main vibration energy is attenuated by at least more than 50%.

[0060] After the vibration suppression is completed, the residual vibration generated when the towing test platform 1 drives the test model 2 to navigate will be significantly weakened. At this time, the vibration amplitudes received by the test model 2 and the force measuring sensor 4 are significantly reduced, making the subsequent signal acquisition closer to the pure drag signal generated by the hydrodynamic action, rather than the mechanical vibration noise of the platform structure. Through the collaborative design of software and hardware, combined with various vibration reduction technologies such as elastic elements, damping elements, and air pressure regulation, the high-frequency vibration transmission can be effectively isolated from the model while maintaining the stable operation of the platform and the power output. In this way, the original time-domain data output by the force measuring sensor 4 will be more valuable for reference. The subsequent fast Fourier transform and low-pass filtering processing can identify the true drag signal faster and more accurately, and significantly improve the accuracy and reliability of the drag coefficient calculation results, providing a solid experimental basis for the entire towing test process.

[0061] S5. Uncertainty analysis: Correct the total drag coefficient at the test temperature to the total drag coefficient at the standard temperature, calculate the deviation limit and precision limit of the total drag coefficient at the standard temperature respectively, and obtain the uncertainty of the total drag coefficient at the standard temperature based on the deviation limit and precision limit.

[0062] First, according to the ITTC specification, first correct the total drag coefficient at the test temperature used for uncertainty analysis to the total drag coefficient at the standard temperature. The standard temperature is generally 15°C or 20°C. In this embodiment, the standard temperature is taken as 15°C. Only the change in the friction drag coefficient caused by the temperature change is considered during the correction. The temperature correction formula is as follows:

[0063] Among them, is the total drag coefficient at the standard temperature, is the total drag coefficient at the test temperature, which can be obtained through experimental tests, is the friction drag coefficient at the standard temperature, calculated by computational fluid dynamics (CFD) software, is the friction drag coefficient at the test temperature, Re T is the Reynolds number at different temperatures.

[0064] The following table shows the total drag coefficient (×10 -3 ) of the test model 2 at different sailing speeds at the standard temperature. For repeated tests, its standard deviation is also calculated to facilitate the analysis of the precision limit of multiple tests. Observing the standard deviation of the total drag coefficient at the standard temperature of the underwater vehicle test model 2 at different sailing speeds at a depth of 2.4 m, it is found that the standard deviation under high-speed conditions is significantly lower than that under low-speed conditions. Therefore, when formulating the test conditions, the speed range needs to be set reasonably. The number of test repetitions needs to be increased for low-speed conditions, and can be appropriately reduced for high-speed conditions.

[0065]

[0066] Next, identify the sources of uncertainty in the drag force measurement process of the test model 2. There are mainly the following four parts: (1) Deviations in the key parameters such as the length, width, and hull form of the test model 2 caused by factors such as tool wear and processing technology. Such deviations will change the wetted surface area, length-width ratio and other important geometric features of the test model 2. These errors can all affect the flow state of the water on the surface of the test model 2, and ultimately have an uncertain impact on the drag force measurement. (2) In the test preparation stage, if the installation of the test model 2 is not adjusted to the optimal state, the attitude of the test model 2 in the water will deviate from the ideal state, affecting its force distribution. When there is a deviation in the direction of the force measuring balance, the direction of the measured force is inconsistent with the actual drag force direction, resulting in a force decomposition error. (3) During the entire test process, due to the different calibration accuracies of the instrument in different measurement ranges and conditions, this uncertainty will continuously affect the accuracy of the measurement data. (4) The data to be tested in the drag force test includes speed, water temperature, drag force value, etc. The measurement accuracy of the water temperature directly affects the accuracy of the physical property parameters of the water (such as density and viscosity), and further affects the calculation of the total drag coefficient.

[0067] After determining the sources of uncertainty, the above influencing factors are analyzed for uncertainty from the perspectives of the precision limit and the bias limit. The bias limit sets the allowable range of the systematic error, reflecting the inherent deviation degree of the measurement system; the precision limit stipulates the discrete boundary of the repeated measurement data, which is related to the measurement repeatability; the two constitute an important basis for deeply analyzing the test results.

[0068] The bias limit measures the degree of data dispersion. There are various sources of the bias limit of the drag force in the underwater vehicle towing test. The following analyzes different sources of the bias limit.

[0069] (1) Test model 2 According to the assumption of ITTC 01 Edition Regulation 7.5-01-01-01, the surface coordinate error of the model processed according to the hull form is ±1 mm, the length error is ±1 mm or 0.05% of the total length (whichever is the maximum), and the wetted surface area increases by 0.019 m 2 or decreases by 0.029 m 2 . It is calculated that the length bias limit caused by the estimated error of the outer shape of the test model 2 of the underwater vehicle of the body of revolution is 0.001395 mm, and then the wetted surface area bias limit is obtained as 0.029 m 2 ; (2) Speed The model speed accuracy is the same as that of the trailer of the towing test platform 1. The trailer is driven by an AC servo four-wheel synchronous drive method. The accuracy of the optoelectronic encoder used is 0.1%, and the display error of the digital instrument is 1 mm / s. The calculation formula for the speed deviation limit can be obtained as follows: B V = 0.1% ×V+ 0.001. For the convenience of calculation, take the maximum value of the speed deviation limit in this test, that is, the speed is 5.0 m / s, B V = 0.006 m / s.

[0070] (3) Model installation Since there is a certain error in the rotation angle adjustment of the vertical lifting mechanism of the towing test platform 1, the influence of this deviation on the resistance needs to be considered. When the sideslip angle is small, the total resistance of the test model 2 and the sideslip angle can be approximately expressed by a linear relationship: R = R 0 + kβ , where, R is the total resistance of the test model 2, R 0 is the total resistance of the test model 2 when the sideslip angle is 0°, k is the fitting coefficient, β is the sideslip angle. The sideslip angle deviation Δβ = 0.1°, and the installation resistance deviation limit B R1 = kΔβ , according to the fitting experience of the resistance of the underwater vehicle at a very small sideslip angle, the k value of the test model 2 is determined to be 0.02 N / °, B R1 = 0.002 N.

[0071] (4) Resistance measurement system The main error source of the resistance measurement system comes from the calibration of the force sensor 4. Therefore, only the measurement accuracy of the six-component balance in the straight-ahead direction is concerned. According to the calibration of the balance when it leaves the factory, the balance deviation limit B R2 = 0.125 N. Combining the installation resistance deviation limit caused by model installation, the resistance deviation limit B R = B R1 + B R2 = 0.127 N.

[0072] (5) Density deviation limit The resolution of the thermometer selected in this test is 0.1 °C, that is, the temperature deviation limit BT = 0.1 °C.

[0073] According to ITTC 7.5 - 02 - 01 - 03, when g = 9.81 m / s 2 the relationship between the density of water and temperature is given by the following equation:

[0074] where, ρ is the density of water, t is the standard temperature of water. When t = 15 °C, ρ = 999.34 kg / m 3 .

[0075] The sensitivity coefficient of density to temperature is:

[0076] When t = 15 ° C , B T = 0.1 ° C the first density deviation is:

[0077] According to the ITTC - 78 method, the nominal density of water ρ 0 = 1000 kg / m 3 . Then ρ = 999.34 kg / m 3 and ρ 0 = 1000 kg / m 3 introduce a second density deviation, that is = 1000 - 999.345 = 0.655 kg / m 3 . At this time, the density deviation limit is:

[0078] (6) Total resistance coefficient deviation limit The calculation formula for the deviation limit of the total resistance coefficient at standard temperature is:

[0079] Since the total resistance coefficient at standard temperature is defined as follows:

[0080] It can be obtained that:

[0081] where, is the deviation limit of the total resistance coefficient at standard temperature,R is the total resistance of Test Model 2, ρ is the density of water, V is the sailing speed of Test Model 2, S is the wetted surface area of Test Model 2, is the limit of deviation of wetted surface area, is the limit of speed deviation, is the limit of resistance deviation, is the limit of density deviation.

[0082] The following table shows the limit of deviation of the total resistance coefficient of Test Model 2 at different sailing speeds under standard temperature (×10 -3 ), and the limit of deviation measures the degree of data dispersion. Accurately analyzing the limit of deviation can improve the accuracy of test results.

[0083]

[0084] Precision reflects the degree of consistency between independent test results under specified conditions. An accurate limit of precision helps to ensure the consistency and comparability of data between different tests and different measurement points. Defining the limit of precision can ensure that the measured data fluctuates within a certain error range, making the measurement results highly reliable. The limit of precision of the test is analyzed below.

[0085] The formula for calculating the limit of precision of the total resistance coefficient under standard temperature is:

[0086] where, is the limit of precision of the total resistance coefficient under standard temperature, K is the coverage factor, given by referring to the uncertainty evaluation method in ITTC. In this embodiment, K = 2, corresponding to a confidence probability of approximately 95%, SDev is the standard deviation determined by multiple tests, M is the number of tests. When M = 1, , is the total resistance coefficient under standard temperature obtained from the i -th test, is the average value of the total resistance coefficients under standard temperature obtained from multiple tests.

[0087] The uncertainty of the total resistance coefficient under standard temperature can give a numerical range, indicating the possible fluctuation interval of the test results, enabling researchers to intuitively understand the accuracy of the measurement results. Based on the limit of deviation and the limit of precision, the uncertainty of the total resistance coefficient under standard temperature can be obtained, and the calculation formula is:

[0088] Among them, is the uncertainty of the total drag coefficient at the standard temperature.

[0089] The following table shows the uncertainty (×10 -3 ) of the total drag coefficient of the test model 2 at different sailing speeds under the standard temperature. Taking a depth of 2.4 m and a speed of 5 m / s as an example, the uncertainty interval of the average value of the total drag coefficient in 5 tests under the standard temperature = (3.2985 ± 0.0366)×10 -3 , and the confidence probability p = 95%.

[0090]

[0091] Through the uncertainty analysis of this system, this method can not only quantify the errors introduced in different links, but also combine these errors in the form of uncertainty. Finally, the test results are given with a 95% confidence probability, which can effectively improve the accuracy of the drag measurement in the underwater vehicle towing test and ensure the reliability and accuracy of the test data. The determination of this confidence level enables users to be confident in the authenticity and stability of the measurement data within a 95% probability range, providing a highly credible and internationally recognized test basis for subsequent design optimization, thrust system selection, and comparison with numerical simulation or theoretical analysis.

[0092] On the other hand, the present application provides a drag measurement system in an underwater vehicle towing test for implementing any of the above methods, such as Figure 2 and Figure 3 shown, including an underwater vehicle test model 2, a force measuring sensor 4, a connecting device 3, and a towing test platform 1. The force measuring sensor 4 is fixedly installed in the test model 2, and the measurement origin of the force measuring sensor 4 coincides with the center of gravity of the test model 2. One end of the connecting device 3 is connected to the force measuring sensor 4, and the other end is connected to the towing test platform 1.

[0093] Among them, the test model 2 selected is a rotary body underwater vehicle test model 2, and its main body adopts a thin-walled five-section design, namely a model bow section, two model middle sections, a stern section, a balance section, and a cover plate. The sections are connected by bolts and kept waterproof through O-ring seals, significantly reducing the model weight and ensuring the connection strength. The fin rudder of the test model 2 is connected to the main body by bolts, and the processing material is high-strength aluminum alloy 2A12, and the surface is treated with an anodic oxidation process to ensure smoothness.

[0094] The towing test platform 1 adopts the existing towing test platform 1 of Northwestern Polytechnical University (for relevant content, refer to the literature "Design of the Towing Tank Trailer Structure Scheme [J]. Mechanical & Electrical Engineering, 2015, 32(12): 1586-1589+1594."), and mainly consists of a towing tank, a towing system, and a central measuring bridge. The dimensions of the towing tank are 170m×7m×6m. This tank can measure hydrodynamic parameters such as the drag coefficient, lift coefficient, and position derivative of a full-scale model at different sideslip angles and rudder angles; it can also be used as an equipment installation and fixing device for the mooring and open-water tests of power propulsion devices. The towing system mainly includes a trailer, a driving device, a guiding device, a speed measuring device, and a hydraulic braking device, etc. The trailer runs in an AC servo four-wheel synchronous driving mode. When running forward in the working state, it can reach a maximum speed of 7m / s, with an acceleration greater than 0.06g, and it can ensure that the stable test time at a working speed of 7m / s is not less than 6s. When the speed is lower than 1m / s, the relative error of the steady-state speed is within 0.3%, and when the speed is higher than 1m / s, the relative error of the steady-state speed is within 0.1%.

[0095] The central measuring bridge includes a transverse moving trolley, a vertical lifting mechanism, a slewing mechanism, and a hydraulic locking mechanism, etc., which can realize the lifting, slewing, and hydraulic locking of the test model 2. The transverse moving trolley can be adjusted according to the installation position of the test model 2 and position the model at the center of the two side walls of the pool during the test. The vertical lifting mechanism is divided into two levels. The upper level is a winch lifting, and the lower level is a screw lifting. Both levels of lifting are driven by servo motors and independently controlled. The upper-level lifting has only two target positions, the lowest and the highest, and needs to be adjusted to the lowest position and locked during the test. The target position of the lower-level lifting can be any position within 0 to 1m, and the lifting error is 5mm. The vertical lifting mechanism can deepest achieve the height of the test model 2 to be 2.5m below the water surface. The slewing angle adjustment range is ±90°, and the adjustment error is less than 0.1°. By adjusting the transverse moving trolley, the vertical lifting mechanism, and the slewing mechanism through the measurement and control system of the towing test platform 1, the test model 2 can be controlled to be located at the center of the pool and reach the specified depth and angle to measure the drag data at different depths and angles.

[0096] The force sensor 4 is an ATI six-component force measuring device with model DELTA-IP68, which consists of a NET F / T interface box, a power supply system and an ATI sensor. The NET F / T interface box supports the standard Ethernet transmission protocol, and can realize real-time observation of force and torque in the application. The ATI sensor is based on the principle of strain gauge sensors. When force and torque act on the sensor to cause the strain gauge to deform, the mechanical strain is converted into resistance change, and finally the resistance change of the strain gauge is converted into electrical signal change through the Wheatstone bridge circuit. By combining multiple strain gauges in a specific way inside the sensor, the three force components (Fx, Fy, Fz) and three torque components (Mx, My, Mz) in three-dimensional space can be measured simultaneously.

[0097] Furthermore, the connecting device 3 includes a connecting rod 7 and a connecting member 6, one end of the connecting rod 7 is connected to the flange plate carried by the vertical lifting mechanism of the towing test platform 1, and the other end is flange-connected to the force sensor 4 through the connecting member 6, and the flange surface of the force sensor 4 facing away from the connecting member 6 is fixed to the base 5 inside the model through a positioning pin.

[0098] Furthermore, a wire groove is provided on the flange of the connector 6 near one end of the force sensor 4, so that the data line of the force sensor 4 passes through the wire groove and is connected to the interface box located on the towing test platform 1. The connector 6 not only serves as a transition between the force sensor 4 and the connecting rod 7, but also allows the data transmission line of the force sensor 4 to be connected to the NET F / T interface box through the designed wire groove, which can effectively avoid the interference of the data transmission line on the flow field.

[0099] Furthermore, the system also includes a vibration reduction device, which is used to suppress the vibration generated by the towing test platform 1 when driving the test model 2 to sail, so as to reduce the vibration transmitted to the test model 2.

[0100] During the test, the calibrated and aligned test model 2 is hung on the towing test platform 1, and the trailer is started to make the test model 2 move at a set speed, generating a hydrodynamic load and transmitting it to the force sensor 4, which accurately outputs a resistance signal to achieve resistance measurement in the underwater vehicle towing test. Through the modular design of this system, not only the measurement origin of the force sensor 4 is consistent with the center of gravity of the model, the torque interference is eliminated, but also the influence of the line and structural vibration on the measurement is effectively isolated, so that the collected resistance data has higher authenticity and repeatability, laying a solid test data foundation for subsequent spectrum analysis, filtering processing and uncertainty evaluation.

[0101] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various modifications and variations can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for measuring the resistance in a towing test of an underwater vehicle, characterized in that, Including: Center of gravity adjustment: determining the center of buoyancy and the center of gravity of the underwater vehicle test model (2); Adjusting the center of gravity of the test model (2) to be directly below the center of buoyancy of the test model (2), and adjusting the ballast so that the test model (2) has neutral buoyancy; Measured data processing: measuring the navigation resistance of the test model (2) in the towing test, and post-processing the measured data to obtain the total resistance coefficient of the test model (2) at the test temperature; Uncertainty analysis: correcting the total resistance coefficient at the test temperature to the total resistance coefficient at the standard temperature, respectively calculating the deviation limit and the precision limit of the total resistance coefficient at the standard temperature, and obtaining the uncertainty of the total resistance coefficient at the standard temperature according to the deviation limit and the precision limit. The calculation formula is: wherein, is the uncertainty of the total drag coefficient at the standard temperature, is the deviation limit of the total drag coefficient at the standard temperature, is the precision limit of the total drag coefficient at the standard temperature.

2. The method according to claim 1, wherein In the uncertainty analysis: the calculation formula for the deviation limit of the total resistance coefficient at the standard temperature is: wherein, is the total drag coefficient at the standard temperature, R is the total drag of the test model (2), ρ is the density of water, V is the sailing speed of the test model (2), S is the wetted surface area of the test model (2), is the limit of wetted surface area deviation, is the limit of speed deviation, is the limit of drag deviation, is the limit of density deviation.

3. The method according to claim 2, characterized in that In the uncertainty analysis: the calculation formula for the precision limit of the total resistance coefficient at the standard temperature is: Among them, K is the inclusion factor, SDev is the standard deviation determined through multiple tests, M is the number of tests, is the i total drag coefficient at the standard temperature obtained from the is the average value of the total drag coefficients at the standard temperature obtained from multiple tests.

4. The method according to claim 2 or 3, characterized in that, In the uncertainty analysis, the correction formula for the total resistance coefficient at the test temperature is: Among them, is the total drag coefficient at the test temperature, is the frictional drag coefficient at the standard temperature, which is calculated by CFD software, is the frictional drag coefficient at the test temperature, Re T is the Reynolds number at different temperatures.

5. The method according to any one of claims 1 to 3, characterized in that, In the measured data processing, the post-processing of the measured data to obtain the total resistance coefficient of the test model (2) at the test temperature includes: performing fast Fourier transform analysis on the measured data, identifying the vibration noise frequency distribution range in the measured data, filtering the vibration noise, and retaining the resistance signal in the measured data; post-processing the resistance signal to obtain the total resistance coefficient of the test model (2) at the test temperature.

6. The method according to any one of claims 1 to 3, characterized in that, Before the measured data processing, the method further includes: sinking amount detection: detecting the sinking amounts at the ends of the test model (2) along the length direction and the width direction, and adjusting the ballast or the connection position of the test model (2) so that the sinking amount is less than or equal to 1.0 mm.

7. A measurement system for the resistance in the towing test of an underwater vehicle, characterized in that, A device for implementing the method according to any one of claims 1 to 6, including an underwater vehicle test model (2), a force measuring sensor (4), a connecting device (3), and a towing test platform (1). The force measuring sensor (4) is fixedly installed in the test model (2), and the measurement origin of the force measuring sensor (4) coincides with the center of gravity of the test model (2). One end of the connecting device (3) is connected to the force measuring sensor (4), and the other end is connected to the towing test platform (1).

8. The system according to claim 7, wherein The connecting device (3) includes a connecting rod (7) and a connecting piece (6). One end of the connecting rod (7) is flange-connected to the towing test platform (1), and the other end is flange-connected to the force measuring sensor (4) through the connecting piece (6).

9. The system according to claim 8, wherein A wire groove is provided on the flange plate at one end of the connecting piece (6) close to the force measuring sensor (4) so that the data line of the force measuring sensor (4) passes through the wire groove and is connected to the interface box located on the towing test platform (1).

10. The system according to any one of claims 7 to 9, characterized in that, The system further includes a vibration damping device, which is used to suppress the vibration generated during the process of the towing test platform (1) driving the test model (2) to sail, so as to reduce the vibration transmitted to the test model (2).

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