Variable-structure unmanned ship and simulation verification method

Abstract

The invention discloses a variable-structure unmanned ship and a simulation verification method, belongs to the field of water surface robots, and aims to solve the problem that an existing unmanned ship cannot realize cross-medium sailing to cope with complex sea conditions. Two foldable wings are arranged on the two sides of a main boat body respectively, each foldable wing can be turned over up and down, an underwater propeller is arranged on each foldable wing, and the underwater propellers are close to wing tips of the foldable wings and used for water surface and underwater sailing of the variable-structure unmanned boat; the air propeller is arranged at the stern of the main boat body, can turn over up and down and is used for sailing the variable-structure unmanned boat in the air or on the water surface; the number of the sliding wheels is three, and the three sliding wheels are arranged below the main boat body, can be retracted into the main boat body and are used for sliding, taking off and landing of the variable-structure unmanned boat on the land. The variable-structure unmanned ship can be transformed into a ground-effect wing ship mode, a small-waterplane-area triple-hulled ship mode or an underwater glider mode under the overturning of the foldable wings and the air propellers. The method is mainly used for task execution under complex sea conditions.

Description

Technical Field

[0001] The present invention belongs to the field of surface robots, and particularly relates to a variable-structure unmanned boat and a simulation verification method. Background Art

[0002] Unmanned Surface Vehicles (USVs) play an increasingly important role in ocean engineering, ocean scientific research, and military activities. Among them, Variable-Structure Unmanned Surface Vehicles (VS-USVs) have high maneuverability, strong survivability, and multi-task characteristics in complex sea environments. For example, the paper "Experimental investigation on seakeeping performance of variable-structure SWATH in heading regular waves, 2025, Volume 315" proposed by J Zhuang et al. discloses a variable-structure small waterplane area twin hull model, which realizes the rapid transformation of the shape under different sea conditions through adjustable-angle struts and detachable hydrofoil devices. This design combines the advantages of an upright-strut small waterplane area twin hull and an inclined-strut small waterplane area twin hull, ensuring high-speed navigation in low sea conditions and providing stability and wave impact resistance in relatively severe sea conditions. There is also the doctoral thesis "Numerical analysis and experimental research on the hydrodynamic performance of variable-structure planing boats" proposed by Bi Xiaosheng (Harbin Engineering University, October 1, 2021), which discloses a variable-structure planing boat that can freely switch between a monohull form and a trimaran form by freely retracting and deploying the side hulls on both sides, aiming to balance speed and seakeeping performance and meet the multi-task requirements of unmanned boats in complex sea conditions.

[0003] Although the above-mentioned existing technologies attempt to increase the adaptability of unmanned boats to complex environments by making them variable-structure to combine the advantages of each mode, there is little research on multi-medium and cross-platform variable-structure unmanned boats, and a comprehensive solution that can not only navigate at high speed on the water surface but also perform cross-medium navigation on land or in the air has not been formed. Summary of the Invention

[0004] In view of this, the present invention provides a variable-structure unmanned boat, which can be transformed into a wing-in-ground effect vehicle mode, a small waterplane area trimaran mode, or an underwater glider mode under the flipping of foldable wings and an air propeller to adapt to different levels of sea conditions and ensure high-efficiency motion performance in different media.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A variable-structure unmanned boat, comprising a main hull, foldable wings, an air propeller, an underwater propeller and sliding wheels; there are two foldable wings, and the two foldable wings are respectively arranged on the left and right sides of the main hull. Each foldable wing can be turned up and down, and an underwater propeller is arranged on each foldable wing. The underwater propeller is close to the wing tip of the foldable wing and is used for the surface and underwater navigation of the variable-structure unmanned boat; the air propeller is arranged at the stern of the main hull and can be turned up and down, and is used for the air or surface navigation of the variable-structure unmanned boat; there are three sliding wheels, and the three sliding wheels are evenly arranged under the main hull and can be retracted into the main hull, and are used for the sliding, takeoff and landing of the variable-structure unmanned boat on land; the variable-structure unmanned boat can be deformed into a wing-in-ground effect ship mode, a small waterplane area trimaran mode or a underwater glider mode under the flipping of the foldable wings and the air propeller.

[0007] Further, it further includes a GPS for monitoring the position of the variable-structure unmanned boat, an IMU for sensing the attitude of the variable-structure unmanned boat, and an ultrasonic rangefinder for measuring the distance between the variable-structure unmanned boat and the object in front. The GPS and IMU are arranged in the main hull, and the ultrasonic rangefinder is arranged at the front end of the main hull.

[0008] Further, the main hull is made of corrosion-resistant aluminum alloy material.

[0009] Further, the main hull adopts a medium-speed semi-planing boat.

[0010] Further, the foldable wings are streamlined and made of carbon fiber material.

[0011] Further, the underwater propeller adopts a four-blade propeller, and the air propeller adopts an air propeller.

[0012] Another technical solution adopted by the present invention is:

[0013] A simulation verification method for a variable-structure unmanned boat, and the simulation verification process is as follows:

[0014] S1, construct a variable-structure unmanned boat model and import it into the computational fluid dynamics simulation software;

[0015] S2, use the computational fluid dynamics simulation software to calculate the resistance of the variable-structure unmanned boat model;

[0016] S3, selection of the propulsion main engine and propeller of the variable-structure unmanned boat: substitute the resistance of the variable-structure unmanned boat model into the effective propulsion power calculation formula to obtain the minimum main engine power, and the formula is as follows:

[0017] P E =R t V

[0018] In the formula, PE is the main engine propulsion power, R t is the total resistance of the variable structure unmanned boat model, and V is the navigation speed;

[0019] S4, checking stability: When designing the variable structure unmanned boat, it is necessary to meet the flotation condition and the stability condition. The flotation condition is that the center of gravity and the center of buoyancy of the variable structure unmanned boat need to be on the same vertical line, and the maximum buoyancy is greater than the gravity; the stability condition is that the transverse metacentric height of the variable structure unmanned boat is greater than 0.

[0020] Further, the calculation process of the above S2 is as follows:

[0021] S21, creating an experimental pool and dividing regions: Based on the length of the variable structure unmanned boat, a virtual water pool is established in the computational fluid dynamics simulation software, and the variable structure unmanned boat model is in the virtual water pool; the regions are divided according to the position of the water pool. Among them, the upstream is set as the velocity inlet and the fluid velocity components are set, the downstream is set as the pressure outlet, the side walls and the symmetry plane are both set as symmetric boundary conditions, and the hull of the variable structure unmanned boat is set as the no-slip wall condition;

[0022] S22, meshing the variable structure unmanned boat model;

[0023] S23, setting the Euler multiphase flow to air and water respectively, setting the corresponding VOF wave, setting the incoming flow velocities of water and air to control the navigation speed of the variable structure unmanned boat, performing simulations with the fixed attitude of the variable structure unmanned boat, setting the calculation step size and monitoring the resistance situation, and automatically tracking the free liquid surface according to the VOF theory; when the residuals are close to convergence, the resistance of the variable structure unmanned boat model is obtained.

[0024] Further, in the above S4, the flotation condition of the variable structure unmanned boat is:

[0025]

[0026] In the formula, W is the gravity, ρ is the water density, is the maximum displacement volume, x B is the position of the center of buoyancy on the x-axis in the coordinate system, x G is the position of the center of gravity on the x-axis in the x coordinate system, y B is the position of the center of buoyancy on the y-axis in the coordinate system, y G is the position of the center of gravity on the y-axis in the x coordinate system.

[0027] Further, in the above S4, the transverse metacentric height of the variable structure unmanned boat is calculated by the formula:

[0028]

[0029] In the formula, I Tis the transverse moment of inertia of the waterplane area about the longitudinal central axis, is the displacement volume below the waterline, B represents the center of buoyancy, and M represents the metacenter, is the distance from the transverse metacenter to the center of buoyancy, is the distance from the center of gravity to the center of buoyancy.

[0030] The beneficial effects of the present invention compared with the prior art are as follows:

[0031] 1. The variable-structure unmanned boat of the present invention can be deformed into a wing-in-ground effect ship mode, a SWATH mode, and an underwater glider mode under the cooperation of the main hull, the foldable wing, the air propeller, and the underwater propeller. It can utilize the lift-drag ratio characteristics of the wing-in-ground effect ship, the stability characteristics and seakeeping performance of the SWATH, and the characteristics of the underwater glider to resist bad sea conditions to adapt to different levels of sea conditions, ensuring high-efficiency motion performance in different media. It can also use the concealment of the underwater glider to avoid being tracked by the enemy.

[0032] 2. The variable-structure unmanned boat of the present invention is equipped with sensors such as a GPS for monitoring the position of the variable-structure unmanned boat, an IMU (inertial measurement unit) for sensing the attitude of the variable-structure unmanned boat, and an ultrasonic rangefinder for measuring the distance between the variable-structure unmanned boat and the object in front. The GPS and the IMU are arranged in the main hull 1, and the ultrasonic rangefinder is arranged at the front end of the main hull 1 to sense the position, attitude and other information of the variable-structure unmanned boat in real time, and different mission payloads can be carried according to the mission requirements.

[0033] 3. The underwater propeller of the present invention adopts a four-blade propeller, which has the characteristics of high conversion efficiency, low noise and strong concealment.

[0034] 4. The variable-structure unmanned boat of the present invention is verified by a simulation verification method, which proves that the variable-structure unmanned boat of the present invention has small resistance, and at the same time meets the flotation conditions and transverse stability conditions of the unmanned boat, and passes the preliminary verification of the feasibility of the ship type design. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings, as a part of this application, are used to provide a further understanding of the present invention.

[0036] Figure 1 is a schematic front view of the variable-structure unmanned boat in the wing-in-ground effect ship mode.

[0037] Figure 2 is a three-dimensional state schematic of the variable-structure unmanned boat in the wing-in-ground effect ship mode Figure 1 .

[0038] Figure 3 is a three-dimensional state schematic of the variable-structure unmanned boat in the wing-in-ground effect ship mode Figure 2 .

[0039] Figure 4 It is a three-dimensional state schematic diagram of the variable-structure unmanned boat in the small waterplane area twin hull (SWATH) mode.

[0040] Figure 5 It is a front state schematic diagram of the variable-structure unmanned boat in the small waterplane area twin hull (SWATH) mode.

[0041] Figure 6 It is a three-dimensional state schematic diagram of the variable-structure unmanned boat in the underwater glider mode.

[0042] Figure 7 It is a task execution flow chart of the variable-structure unmanned boat.

[0043] Figure 8 It is a resistance calculation curve of the variable-structure unmanned boat.

[0044] Figure 9 It is a waterplane cross-section schematic diagram of the variable-structure unmanned boat in the small waterplane area twin hull (SWATH) mode.

[0045] Explanation of reference numerals: 1 - main hull; 2 - foldable wing; 3 - air propeller; 4 - underwater propeller; 5 - sliding wheel. Detailed implementation manners

[0046] The following makes a detailed description of the present invention in combination with the accompanying drawings and specific embodiments.

[0047] Figures 1 to 6 Shows a structural schematic diagram of a variable-structure unmanned boat of this embodiment, as Figures 1 to 6As shown in the figure, a variable-structure unmanned boat in this embodiment includes a main hull 1, foldable wings 2, an air propeller 3, an underwater propeller 4, and skid wheels 5. There are two foldable wings 2, and these two foldable wings 2 are respectively arranged on the left and right sides of the main hull 1. Each foldable wing 2 can be turned up and down, and the range of the deployment angle of the foldable wing 2 is 0 - 90°. When the deployment angle of the foldable wing 2 is 0°, the foldable wing 2 is horizontally deployed. When the deployment angle of the foldable wing 2 is 90°, the foldable wing 2 is vertically downward, thereby changing the configuration of the unmanned boat to complete cross-medium navigation. An underwater propeller 4 is arranged on each foldable wing 2, and the underwater propeller 4 is near the wing tip of the foldable wing 2, which is used for the surface and underwater navigation of the variable-structure unmanned boat. The air propeller 3 is arranged at the stern of the main hull 1 and can be turned up and down, and the range of its turning angle is also 0 - 90°. Similarly, when the turning angle of the air propeller 3 is 0°, the air propeller 3 turns to the horizontal state to avoid increasing the resistance of the variable-structure unmanned boat during underwater navigation. When the turning angle of the air propeller 3 is 90°, the air propeller 3 is vertically upward, which is used for the air or surface navigation of the variable-structure unmanned boat. There are three skid wheels 5, and these three skid wheels 5 are evenly arranged under the main hull 1 and can be retracted into the main hull 1, which is used for the taxiing, takeoff, and landing of the variable-structure unmanned boat on land.

[0048] As Figure 1 , Figure 2 and Figure 3 shown, when the deployment angles of the two foldable wings 2 are 0° and the turning angle of the air propeller 3 is 90°, the foldable wings 2 on both sides of the variable-structure unmanned boat are horizontally deployed, and the air propeller 3 is vertically upward. Under the propulsion of the air propeller 3, the variable-structure unmanned boat leaves the water relying on a large aerodynamic lift force and becomes a wing-in-ground effect vehicle mode. Due to the lift characteristics of the wing-in-ground effect vehicle, the flight speed of the variable-structure unmanned boat is relatively high at this time, and it also has the characteristics of strong concealment, good wave resistance, and flexible maneuverability. In addition, it should be noted that the variable-structure unmanned boat in the wing-in-ground effect vehicle mode uses the skid wheels 5 for taxiing during the takeoff and landing phases. When taking off, the skid wheels 5 are retracted.

[0049] As Figure 4 and Figure 5 shown, when the deployment angles of the two foldable wings 2 are 90°, the foldable wings 2 on both sides of the variable-structure unmanned boat are vertically downward and partially inserted into the water. Since the waterline of the variable-structure unmanned boat underwater is relatively short, as Figure 9As shown in the figure, at this time, the variable-structure unmanned boat becomes a small waterplane area twin hull (SWATH). This configuration not only ensures the high-speed navigation of the unmanned boat in low sea states but also provides stability and wave impact resistance in relatively rough sea states. At the same time, the waterplane of the variable-structure unmanned boat is a part above the bottom of the main hull 1. Therefore, the variable-structure unmanned boat also has the characteristics of a trimaran. Propelled by the underwater propeller 4 and / or the aerial propeller 3, there will be a part of aerodynamic lift to balance the gravity. At this time, the variable-structure unmanned boat has good stability. Therefore, the variable-structure unmanned boat at this time can also be regarded as a small waterplane area trimaran mode.

[0050] As Figure 6 shown in the figure, when the deployment angle of the two foldable wings 2 is 0° and the flipping angle of the aerial propeller 3 is 0°, the foldable wings 2 on both sides of the variable-structure unmanned boat are horizontally deployed, and the aerial propeller 3 is in a horizontal state. At this time, the variable-structure unmanned boat is completely underwater and is in the mode of an underwater glider. Since the variable-structure unmanned boat is completely underwater and is less affected by wind and waves, the variable-structure unmanned boat can achieve fast underwater gliding in rough sea states under the propulsion of the underwater propeller 4, and the resistance during underwater gliding is the smallest.

[0051] It can be seen that the variable-structure unmanned boat of this embodiment can be deformed into a wing-in-ground effect ship mode, a small waterplane area trimaran mode, and an underwater glider mode under the cooperation of the main hull 1, the foldable wings 2, the aerial propeller 3, and the underwater propeller 4. It uses the lift-to-drag ratio characteristics of the wing-in-ground effect ship, the stability characteristics and wave resistance of the small waterplane area trimaran, and the concealment of the underwater glider to adapt to different levels of sea states and ensure efficient motion performance in different media. At the same time, the variable-structure unmanned boat of this embodiment is equipped with sensors such as a GPS for monitoring the position of the variable-structure unmanned boat, an IMU (inertial measurement unit) for sensing the attitude of the variable-structure unmanned boat, and an ultrasonic rangefinder for measuring the distance between the variable-structure unmanned boat and the object in front. The GPS and IMU are arranged inside the main hull 1, and the ultrasonic rangefinder is arranged at the front end of the main hull 1 to sense the position, attitude and other information of the variable-structure unmanned boat in real time, and different mission payloads can be carried according to mission requirements.

[0052] Among them, the main hull 1 of this embodiment is 4.02 m long and 2.16 m wide, and is made of corrosion-resistant aluminum alloy material. The main hull 1 can adopt a medium-speed semi-planing boat to improve stability and wave resistance during high-speed navigation.

[0053] Among them, the foldable wings 2 of this embodiment are made of carbon fiber material, with the characteristics of light weight, high strength, and strong reliability. The single-wing deployment length is about 2 m.

[0054] Among them, the aerial thruster 3 in this embodiment uses an aerial propeller, the underwater thruster 4 uses a four-blade propeller, and the aerial thruster 3 and the underwater thruster 4 are driven by a propulsion main engine.

[0055] When the variable-structure unmanned boat in this embodiment is in water, its draft is 1.82 m, its displacement is 1.07 t, the waterplane is located 0.6 m below the main hull 1, and the maximum waterline length is 2.6 m. This variable-structure unmanned boat can break through the single-environment limitation through its unique structure, achieve multi-domain collaborative operations, and enhance the adaptability of the unmanned boat in complex terrains and extreme environments.

[0056] The task execution process of the variable-structure unmanned boat is as Figure 7 shown:

[0057] The first step, task planning: The mother ship issues task instructions and plans a path for the variable-structure unmanned boat.

[0058] The second step, autonomous navigation: The variable-structure unmanned boat sails according to the planned path. The normal navigation state is the small waterplane area trimaran mode in Figure 2 , and this mode is applicable to sea states of 0-3 levels, and the sailing speed does not exceed 40 kn. If the IMU monitors that the sea state deteriorates, the variable-structure unmanned boat is adjusted from the small waterplane area trimaran mode in Figure 2 to the wing-in-ground effect vehicle mode in Figure 1 . The wing-in-ground effect vehicle mode is applicable to sea states of 3-4 levels, and the sailing speed is 40-70 kn. Or it is adjusted from the small waterplane area trimaran mode in Figure 2 to the underwater glider mode in Figure 3 . The underwater glider mode is applicable to sea states of 4-5 levels, and the sailing speed is 0.2-1 kn. At this time, the variable-structure unmanned boat is less affected by sea surface waves during sailing, ensuring its own operation efficiency, and can protect its own safety to a certain extent and prevent the hull from capsizing due to overly bad sea conditions.

[0059] The third step, task execution: The variable-structure unmanned boat arrives at the target area, selects the mode required for the task to execute the predetermined task (such as patrolling, monitoring, etc.), and arrives at the designated recovery area after the task is completed.

[0060] Embodiment 2:

[0061] This embodiment provides a simulation verification method for a variable-structure unmanned boat, and the verification process includes the following steps:

[0062] S1, construct a variable-structure unmanned boat model and import it into a computational fluid dynamics simulation software, such as CFD software;

[0063] S2. Calculate the resistance of the variable structure unmanned boat model using CFD software: Use CFD software to calculate the resistance. This calculation method has higher calculation accuracy than the semi-empirical formula method and lower cycle and cost than the scaled model experimental method. The resistance calculation process of the variable structure unmanned boat model includes the following steps:

[0064] S21, create an experimental pool and divide the area: a virtual pool is established in the CFD software based on the length of the variable structure unmanned boat. The variable structure unmanned boat model is in the virtual pool. The upstream distance of the pool to the bow is 1.5L, the downstream distance of the pool to the stern is 4L, the distance between the side wall of the pool and the symmetry plane of the variable structure unmanned boat is 1.5L, and the upper and lower boundaries are 1L and 2L away from the waterline respectively. The area is divided according to the position of the pool. The upstream is the velocity inlet and the fluid velocity component is set. The downstream is the pressure outlet. The side wall and the symmetry plane are set as symmetric boundary conditions. The hull of the variable structure unmanned boat is set as a no-slip wall condition.

[0065] S22, meshing of the variable structure unmanned boat model: The variable structure unmanned boat is automatically meshed through the built-in surface reconstruction, automatic surface repair, cut volume mesh unit generator and prismatic layer mesh generator of STAR-CCM+. The mesh is encrypted at the bow and stern of the variable structure unmanned boat and the free liquid surface. The volume growth rate is set to very slow, and finally 240,000 meshes are generated.

[0066] S23, set the Euler multiphase flow to be air and water, both of which are constant density; set the corresponding VOF wave, and when calculating the resistance, the calculation origin is located at the intersection of the stern of the variable structure unmanned boat model and the waterline surface, and the navigation speed of the variable structure unmanned boat is controlled by setting the incoming flow speed of water and air to 5m / s, and the fixed posture of the variable structure unmanned boat is used for simulation, that is, the static water resistance of the variable structure unmanned boat at a speed of 5m / s calculated in this embodiment. Set the calculation step size to 0.04s and monitor the resistance, and automatically track the free liquid surface according to the VOF theory. In this process, the Euler multiphase flow is determined according to the volume fraction:

[0067]

[0068] Where α is the volume fraction of the q phase in a certain grid;

[0069] Combination Figure 8 , when the residual is close to convergence, the resistance of the variable structure unmanned boat obtained in this embodiment is 1843 N. In order to reduce the amount of calculation and improve the calculation efficiency, this embodiment only uses half of the variable structure unmanned boat model as the object during simulation, so the final resistance of the variable structure unmanned boat model is 3686 N.

[0070] S2, propulsion main engine and propeller selection of variable structure unmanned boat:

[0071] Substitute the resistance of the variable-structure unmanned boat model into the effective propulsion power calculation formula to obtain the minimum main engine power of the variable-structure unmanned boat, that is, the minimum propulsion power to meet the cruise of the unmanned boat. The effective propulsion power calculation formula is as follows:

[0072] P E =R t V = 3686×5 = 18.5kw

[0073] In the formula, P E is the main engine propulsion power, R t is the model resistance, and V is the sailing speed.

[0074] The main engine power obtained in this embodiment is 18.5kw. However, due to factors such as conversion efficiency, actual speed, resistance calculation error, and wake fraction, the actual power required during sailing at a speed of 5m / s is greater than 18.5kw. Therefore, the main engine power should be greater than 18.5kw.

[0075] In the selection of the thruster, the air thruster 3 selects an air propeller, and the underwater thruster 4 selects a four-blade propeller. The four-blade propeller has the advantages of high conversion efficiency, low noise, and strong concealment compared with the ordinary two-blade propeller.

[0076] S3, check the stability: The variable-structure unmanned boat needs to meet the flotation condition and the stability condition during design. The flotation condition is that the center of gravity and the center of buoyancy of the variable-structure unmanned boat need to be on the same vertical line (the x and y of the two are equal), and the maximum buoyancy is greater than the gravity; the stability condition is that the transverse stability height of the variable-structure unmanned boat is greater than 0. The specific checking process is as follows:

[0077] In this embodiment, a three-dimensional space coordinate system is established with the center of gravity point of the variable-structure unmanned boat as the origin. Among them, the X-axis (front and rear axis) is the bow and stern direction of the variable-structure unmanned boat and points to the bow end of the variable-structure unmanned boat, the Y-axis (transverse axis) is perpendicular to the X-axis and points to the starboard side of the variable-structure unmanned boat, and the Z-axis (vertical axis) is perpendicular to the XY plane and points downward of the variable-structure unmanned boat; the flotation condition of the variable-structure unmanned boat is:

[0078]

[0079] In the formula, W is the gravity, ρ is the water density, is the maximum displacement volume, x B is the position of the center of buoyancy on the x-axis in the coordinate system, x G is the position of the center of gravity on the x-axis in the x coordinate system, y B is the position of the center of buoyancy on the y-axis in the coordinate system, y G is the position of the center of gravity on the y-axis in the x coordinate system;

[0080] Then, the gravity, the coordinates of the center of gravity, and the maximum displacement volume of the variable-structure unmanned boat can be obtained by using the mass properties of SolidWorks. For calculating the coordinates of the center of buoyancy, a novel design is adopted in this embodiment, that is, the wetted part of the variable-structure unmanned boat (i.e., the part below the designed waterline) is separated from the whole by the split command to form a solid closed structure, and the density of the material is changed to the density of water, so that the displacement volume and the position of the center of buoyancy under the requirements of the designed waterline can be obtained by using the mass properties tool. The coordinates of the center of buoyancy position of the variable-structure unmanned boat obtained are (1.58, 0, -0.66), the coordinates of the center of gravity position are (1.4, 0, -0.3), the center of buoyancy and the center of gravity are approximately on the same vertical line, the gravity is 839 N, the buoyancy is 1064.77 N, and the buoyancy is greater than the gravity, meeting the flotation condition.

[0081] The metacentric height of the variable-structure unmanned boat is the distance from the metacenter to the center of buoyancy. The greater the metacentric height, the better the stability. However, the greater the metacentric height, the shorter the rolling period of the boat, and it will roll extremely violently when encountering wind and waves at sea. Therefore, a suitable metacentric height should be selected;

[0082] The calculation formula for the distance from the metacenter to the center of buoyancy is:

[0083]

[0084] In the formula, combined with Figure 9 , I T is the transverse moment of inertia of the waterplane area about the longitudinal central axis, is the displacement volume below the waterline, B represents the center of buoyancy, and M represents the metacenter; after calculation, the value of I T is 0.563. Given that the displacement at the designed waterline is 1.06 cubic meters, it can be obtained that is 0.53 meters.

[0085] According to the coordinates of the center of gravity and the center of buoyancy, the distance between the center of gravity and the center of buoyancy is 0.36 meters;

[0086] Thus, the metacentric height of the hull can be calculated as:

[0087]

[0088] The metacentric height of the variable-structure unmanned boat is greater than 0, meeting the transverse stability condition.

[0089] It can be seen that through the simulation verification method of this embodiment for the variable-structure unmanned boat, it is proved that the variable-structure unmanned boat in Embodiment 1 has small resistance, and at the same time meets the flotation condition and the transverse stability condition of the unmanned boat, and the feasibility of the hull design is initially verified.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A variable structure unmanned boat, characterized in that: The invention comprises a main hull, foldable wings, an aerial propeller, an underwater propeller and a sliding wheel; two foldable wings are provided, the two foldable wings are respectively arranged on the left and right sides of the main hull, each foldable wing can be turned up and down, and an underwater propeller is provided on each foldable wing, the underwater propeller is close to the wing tip of the foldable wing, and is used for the surface and underwater navigation of the variable structure unmanned boat; the aerial propeller is provided at the stern of the main hull and can be turned up and down, and is used for the air or surface navigation of the variable structure unmanned boat; three sliding wheels are provided, the three sliding wheels are evenly arranged under the main hull and can be retracted into the main hull, and are used for the sliding, take-off and landing of the variable structure unmanned boat on land; the variable structure unmanned boat can be transformed into a ground effect wing boat mode, a small waterline area trimaran mode or an underwater glider mode under the turning of the foldable wings and the aerial propeller.

2. The variable structure unmanned boat according to claim 1, characterized in that: It also includes a GPS for monitoring the position of the variable structure unmanned boat, an IMU for sensing the posture of the variable structure unmanned boat, and an ultrasonic rangefinder for measuring the distance between the variable structure unmanned boat and objects in front. The GPS and IMU are set in the main hull, and the ultrasonic rangefinder is set at the front end of the main hull.

3. The variable structure unmanned boat according to claim 1, characterized in that: The main hull is made of corrosion-resistant aluminum alloy.

4. The variable structure unmanned boat according to claim 1, characterized in that: The main hull is a medium-speed semi-planing boat.

5. The variable structure unmanned boat according to claim 1, characterized in that: The foldable wings are streamlined and made of carbon fiber material.

6. The variable structure unmanned boat according to claim 1, characterized in that: The underwater propulsion device uses a four-blade propeller, and the aerial propulsion device uses an aerial propeller.

7. A simulation verification method for a variable structure unmanned boat according to any one of claims 1 to 6, characterized in that: The simulation verification process is as follows: S1, construct a variable structure unmanned boat model and import it into computational fluid dynamics simulation software; S2, using computational fluid dynamics simulation software to calculate the resistance of the variable structure unmanned boat model; S3, propulsion main engine and propeller selection of variable structure unmanned boat: Substitute the resistance of the variable structure unmanned boat model into the effective propulsion power calculation formula to find the minimum main engine power. The formula is as follows: P E =R t V Where P E is the main engine propulsion power, R t is the total resistance of the variable structure unmanned boat model, V is the sailing speed; S4, check stability: The variable structure unmanned boat needs to meet the buoyancy and stability conditions during design. The buoyancy condition is that the center of gravity and buoyancy of the variable structure unmanned boat need to be on the same plumb line, and the maximum buoyancy is greater than the gravity; The stability condition is that the transverse metacenter height of the variable structure unmanned boat is greater than 0.

8. The simulation verification method of a variable structure unmanned boat according to claim 7, characterized in that: The calculation process of S2 is as follows: S21, create an experimental pool and divide the area: based on the length of the variable structure unmanned boat, establish a virtual pool in the computational fluid dynamics simulation software, and the variable structure unmanned boat model is in the virtual pool; divide the area according to the position of the pool, wherein the upstream is set as the velocity inlet and the fluid velocity component is set, the downstream is the pressure outlet, the side wall and the symmetry surface are set as symmetric boundary conditions, and the hull of the variable structure unmanned boat is set as a no-slip wall condition; S22, meshing the variable structure unmanned boat model; S23, set the Euler multiphase flow to be air and water respectively, set the corresponding VOF wave, set the incoming flow speed of water and air to control the navigation speed of the variable structure unmanned boat, use the fixed posture of the variable structure unmanned boat for simulation, set the calculation step size and monitor the resistance, and automatically track the free liquid surface according to the VOF theory; when the residual is close to convergence, obtain the resistance of the variable structure unmanned boat model.

9. The simulation verification method of a variable structure unmanned boat according to claim 7, characterized in that: In S4, the buoyancy condition of the variable structure unmanned boat is: Where W is gravity, ρ is water density, is the maximum displacement volume, x B is the position of the center of buoyancy on the x-axis in the coordinate system, x G is the position of the center of gravity on the x-axis in the x-coordinate system, y B is the position of the buoyancy center on the y-axis in the coordinate system, y G is the position of the center of gravity on the y-axis in the x-coordinate system.

10. The simulation verification method of a variable structure unmanned boat according to claim 7, characterized in that: In S4, the lateral stability of the variable structure unmanned boat is The calculation formula is: In the formula, I T is the transverse moment of inertia of the waterplane area about the longitudinal center axis, is the displacement volume below the waterline, B is the center of buoyancy, M is the center of metacentre, is the distance from the transverse metacenter to the buoyancy center, is the distance from the center of gravity to the center of buoyancy.

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