Measurement method for steady center height of small-sized unmanned underwater vehicle

Abstract

The invention provides a method for measuring the steady center height of a small unmanned underwater vehicle (UUV), which can accurately measure the actual value of the steady center height of the UUV through a test, specifically, the actual value of the steady center height of the UUV can be accurately measured by changing the position of a balancing weight on the underwater vehicle in a horizontal plane, changing the gravity center position and the buoyancy center position of the underwater vehicle and changing the actual value of the steady center height of the UUV under an unpowered condition. In the process of naturally floating to the water surface from the underwater, the attitude angle is obtained when the attitude is stable, and then the steady center height of the underwater vehicle is obtained. The method is easy to operate, high in practicability and low in cost, the accurate steady center height can be obtained through simple operation steps and common measuring tools, and the method is suitable for most small unmanned underwater vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater unmanned submersibles, and in particular to a method for measuring the center height of a small underwater unmanned submersible. Background Art

[0002] An underwater unmanned vehicle (hereinafter referred to as UUV) is an unmanned device that can navigate underwater through wireless control or automatic control. It can carry a variety of sensors, special equipment or devices to perform underwater tasks. Underwater stability is one of the important overall performances of UUV, and the size of the metacentric height index is closely related to the operation and safety of the unmanned underwater vehicle. The stability of UUV can be measured by the metacentric height, which is the vertical distance between the center of gravity of the UUV and its center of buoyancy.

[0003] Generally, the metacentric height of a UUV can be calculated theoretically in the design phase based on the shape, weight and installation position of each compartment and component. However, there are errors in the actual processing, production and assembly process, and the accumulation of these errors will lead to a deviation between the actual metacentric height and the theoretical value.

[0004] Currently there is no effective method to measure the actual metacentric height of a UUV. Summary of the invention

[0005] In view of this, the present invention provides a method for measuring the metacentric height of a small underwater unmanned submersible, which can accurately measure the actual value of the metacentric height of the UUV through experiments. The specific method is as follows:

[0006] A method for measuring the metacentric height of a small underwater unmanned submersible is disclosed. The metacentric height of the submersible is obtained by changing the position of a counterweight on the submersible in the horizontal plane, changing the position of the center of gravity and the center of buoyancy of the submersible, and changing the attitude angle of the submersible when it is naturally floating from underwater to the surface without power, thereby obtaining the metacentric height of the submersible.

[0007] Further, the specific steps are as follows:

[0008] 1) Obtain the buoyancy B exerted on the UUV when the UUV is completely submerged in water by the counterweight in a static state;

[0009] 2) After the UUV is driven to dive beyond the depth threshold, all the powers are set to zero, and the attitude angle of the UUV when it is naturally floating to the surface is obtained. The attitude angle includes the pitch angle and the roll angle;

[0010] 3) changing the position of any ballast block on the UUV in the horizontal plane, while keeping the longitudinal height unchanged, and obtaining its weight m0 and buoyancy b0 by weighing the weight of the ballast block in the air and in water;

[0011] 4) Repeat 2) to obtain the attitude angle when the UUV is naturally floating to the water surface after the position of the counterweight block is changed and the attitude is stable;

[0012] 5) Using the weight and buoyancy B of the UUV, the weight m0 and buoyancy b0 of the counterweight block of the changed position, and the displacement of the counterweight block, the displacement of the center of gravity and the center of buoyancy of the UUV caused by the change of the position of the counterweight block are obtained;

[0013] 6) The metacentric height of the UUV is obtained by using the displacement of the center of gravity and the center of buoyancy of the UUV caused by the change in the position of the counterweight block, as well as the change in the attitude angle during the natural floating to the water surface.

[0014] Further, the specific method of 1) is as follows:

[0015] Step 1.1: After assembling the UUV, place it in the pool and make sure that all parts of the UUV are completely submerged in the water by adding or removing weights.

[0016] Step 1.2, remove the counterweight from the UUV, and use a crane scale to suspend the counterweight in the water. The reading of the crane scale is the positive buoyancy ΔB of the UUV.

[0017] Step 1.3, adjust the positions of the remaining breeding blocks on the UUV, and adjust the attitude angle of the UUV to a state that satisfies underwater navigation;

[0018] Step 1.4: Use an electronic hanging scale to obtain the weight M of the UUV in the air, and the buoyancy of the UUV is B = M + ΔB.

[0019] Furthermore, the calculation formula of the UUV metacentric height is: GM1 = (Δx G -Δx B ) / (tanα1-tanα2), where Δx G Δx is the distance the UUV center of gravity moves in the x direction due to the change in the position of the counterweight block; B is the movement distance of the UUV buoyancy center in the x direction caused by the change in the position of the counterweight block; α1 is the pitch angle of the UUV when the UUV naturally floats to the water surface before the position of the counterweight block changes; α2 is the pitch angle of the UUV when the UUV naturally floats to the water surface after the position of the counterweight block changes.

[0020] Furthermore, the calculation formula of the UUV metacentric height is: GM 2 = (Δy B -Δy G ) / (tanβ1-tanβ2), where Δy G Δy is the distance the UUV center of gravity moves in the y direction due to the change in the position of the counterweight block; Bis the moving distance of the UUV buoyancy center in the y direction caused by the change of the counterweight position; β1 is the roll angle of the UUV when the UUV naturally floats to the water surface before the counterweight position changes; β2 is the roll angle of the UUV when the UUV naturally floats to the water surface after the counterweight position changes.

[0021] Furthermore, the calculation formula of the UUV metacentric height is: GM=(GM1+GM2) / 2.

[0022] The following beneficial effects can be achieved by adopting the present invention:

[0023] 1. The method of the present invention is simple to operate, highly practical and low in cost;

[0024] 2. Accurate center height can be obtained through simple operation steps and common measuring tools;

[0025] 3. The present invention is applicable to most small underwater unmanned submersibles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 、Method flow chart

[0027] Figure 2a , schematic diagram of displacement change in the horizontal plane after the position of the counterweight block changes;

[0028] Figure 2b , schematic diagram of the change in displacement along the longitudinal direction after the position of the counterweight block changes;

[0029] Figure 3a , Schematic diagram of the principle of calculating the metacentric height of UUV in the first method;

[0030] Figure 3b , Schematic diagram of the second principle for calculating the UUV metacentric height.

[0031] Wherein, G represents the center of gravity of the UUV before the position of the counterweight is changed, G' represents the center of gravity of the UUV after the position of the counterweight is changed, B represents the center of buoyancy of the UUV before the position of the counterweight is changed, and B' represents the center of buoyancy of the UUV before the position of the counterweight is changed. DETAILED DESCRIPTION

[0032] Step 1.1: After assembling the UUV, place it in the pool and make the UUV reach a zero buoyancy state by adding or removing the counterweights, that is, in a static state, all parts of the UUV are completely submerged in the water;

[0033] Step 1.2, remove a counterweight from the UUV (determined according to the tonnage of the UUV, etc.), and use a crane scale to suspend the counterweight in the water. At this time, the reading of the crane scale is the positive buoyancy ΔB of the UUV, and the positive buoyancy ΔB = buoyancy - gravity; if you need to remove multiple counterweights, just add up the readings of these counterweights.

[0034] Step 1.3: Adjust the positions of the remaining ballast blocks on the UUV without adding or reducing any ballast blocks, and adjust the attitude angle of the vehicle to the final state that satisfies underwater navigation.

[0035] Step 1.4, use an electronic crane to weigh the weight M of the UUV in the air, then the buoyancy of the vehicle B = M + ΔB;

[0036] Step 2: After the UUV is driven to dive beyond the depth threshold, all the powers are reset to zero, and the attitude angle of the UUV when it is naturally floating to the surface is obtained. The attitude angle includes the pitch angle and the roll angle. Specifically, the UUV is placed in open waters, and the UUV is driven to dive beyond the depth threshold, and then all the powers are reset to zero, and the vehicle is naturally floated to the surface. The depth threshold is sufficient for the UUV to naturally float to a stable attitude. Check the attitude data of the UUV's inertial navigation device or other sensors, and read the pitch angle α when the attitude is stable during the floating process. 11 (bow lift is positive) and roll angle β 11 (right-leaning is positive), repeat the experiment many times to get n groups of data α 11 ~α 1n , β 11 ~β 1n , take the average value to get the underwater pitch angle α1=(α 11 +α 12 +……+α 1n ) / n, water rolling angle β1=(β 11 +β 12 +……+β 1n ) / n;

[0037] Step 3, remove a ballast block from the craft and mark its position 1, obtain its weight m0 and buoyancy b0 by weighing its weight in air and water, move the ballast block to position 2, keep the horizontal heights of positions 1 and 2 unchanged, measure the longitudinal distance Δx (moving from the stern to the bow is positive) and the lateral distance Δy (moving from the port side to the starboard side is positive) between positions 1 and 2, as shown in Figure 3. Figure 2a As shown, the arrow indicates the moving direction;

[0038] Step 4: Repeat step 2 to obtain the pitch angle of the UUV in the water α2=(α 21 +α 22+……+α 2n ) / n, water rolling angle β2 = (β 21 +β 22 +……+β 2n ) / n;

[0039] Step 5, the measured UUV weight M, buoyancy B, mobile counterweight weight m0, mobile counterweight buoyancy b0, counterweight pitch angle α1 before movement, counterweight roll angle β1 before movement, counterweight pitch angle α2 after movement, counterweight roll angle β2 after movement can be calculated to obtain the metacentric height GM of the UUV.

[0040] When the UUV naturally floats up under a slightly positive buoyancy state, the speed is very small, and its hydrodynamic effect can be ignored. Only the static balance of gravity and buoyancy is considered. Among them, there are three ways to calculate the metacentric height: 1. Use longitudinal calculation; 2. Use transverse calculation; 3. Average the first two.

[0041] 1) Vertical calculation:

[0042] Calculate the longitudinal movement distance of the center of gravity using the existing method: Δx G =Δx*m0 / M;

[0043] Calculate the longitudinal movement distance of the center of buoyancy using the existing method: Δx B =Δx*b0 / B;

[0044] use Figure 3a The quantitative relationship shown can be used to obtain the relationship before and after the counterweight moves, that is, GM1*tanα1+Δx B -Δx G -GM1*tanα2=0;

[0045] From this, we can infer that the metacentric height of UUV is GM1 = (Δx G -Δx B ) / (tanα1-tanα2);

[0046] 2) Horizontal calculation:

[0047] Calculate the lateral displacement distance of the center of gravity using the existing method: Δy G =Δy*m0 / M;

[0048] Calculate the lateral movement distance of the center of buoyancy using the existing method: Δy B =Δy*b0 / B;

[0049] use Figure 3b The quantitative relationship shown can be used to obtain the relationship before and after the counterweight moves, that is, GM*tanβ1+Δy G -Δy B -GM*tanβ2=0;

[0050] It can be deduced from this that the metacentric height GM2 of the UUV is (Δy B -Δy G ) / (tanβ1-tanβ2).

[0051] The test can be considered successful if the difference between the metacenter heights GM1 and GM2 calculated longitudinally and transversely is very small.

[0052] 3) In order to improve the accuracy, the average value of the stable high GM can be GM = (GM1 + GM2) / 2.

Claims

1. A method for measuring the metacentric height of a small underwater unmanned submersible, characterized by: By changing the position of the counterweight on the submersible in the horizontal plane, the displacement of the center of gravity and the center of buoyancy of the submersible can be obtained, and by changing the attitude angle of the submersible when it is naturally floating from underwater to the surface without power, the metacentric height of the submersible can be obtained.

2. A method for measuring the metacentric height of a small underwater unmanned submersible according to claim 1, characterized in that: 1) Obtain the floating force of the UUV when the UUV is completely submerged in water with the counterweight in a static state. Force B; 2) After the UUV is driven to dive beyond the depth threshold, all the powers are set to zero, and the attitude angle of the UUV when it is naturally floating to the surface is obtained. The attitude angle includes the pitch angle and the roll angle; 3) changing the position of any ballast block on the UUV in the horizontal plane, while keeping the longitudinal height unchanged, and obtaining its weight m0 and buoyancy b0 by weighing the weight of the ballast block in the air and in water; 4) Repeat 2) to obtain the attitude angle when the UUV is naturally floating to the water surface after the position of the counterweight block is changed and the attitude is stable; 5) Using the weight and buoyancy B of the UUV, the weight m0 and buoyancy b0 of the counterweight block of the changed position, and the displacement of the counterweight block, the displacement of the center of gravity and the center of buoyancy of the UUV caused by the change of the position of the counterweight block are obtained; 6) The metacentric height of the UUV is obtained by using the displacement of the center of gravity and the center of buoyancy of the UUV caused by the change in the position of the counterweight block, as well as the change in the attitude angle during the natural floating to the water surface.

3. A method for measuring the metacentric height of a small underwater unmanned submersible according to claim 1, characterized in that: 1) The specific method is as follows: Step 1.1: After assembling the UUV, place it in the pool and make sure that all parts of the UUV are completely submerged in the water by adding or removing weights. Step 1.2, remove the counterweight from the UUV, and use a crane scale to suspend the counterweight in the water. The reading of the crane scale is the positive buoyancy ΔB of the UUV. Step 1.3, adjust the positions of the remaining breeding blocks on the UUV, and adjust the attitude angle of the UUV to a state that satisfies underwater navigation; Step 1.4: Use an electronic hanging scale to obtain the weight M of the UUV in the air, and the buoyancy of the UUV is B = M + ΔB.

4. A method for measuring the metacentric height of a small underwater unmanned submersible according to any one of claims 1 to 3, characterized in that: The calculation formula of the UUV metacentric height is: GM1 = (Δx G -Δx B ) / (tanα1-tanα2), where Δx G Δx is the distance the UUV center of gravity moves in the x direction due to the change in the position of the counterweight block; B is the movement distance of the UUV buoyancy center in the x direction caused by the change in the position of the counterweight block; α1 is the pitch angle of the UUV when the UUV naturally floats to the water surface before the position of the counterweight block changes; α2 is the pitch angle of the UUV when the UUV naturally floats to the water surface after the position of the counterweight block changes.

5. A method for measuring the metacentric height of a small underwater unmanned submersible according to any one of claim 4, characterized in that: The calculation formula of the UUV metacentric height is: GM 2 = (Δy B -Δy G ) / (tanβ1-tanβ2), where Δy G Δy is the distance the UUV center of gravity moves in the y direction due to the change in the position of the counterweight block; B is the moving distance of the UUV buoyancy center in the y direction caused by the change of the counterweight position; β1 is the roll angle of the UUV when the UUV naturally floats to the water surface before the counterweight position changes; β2 is the roll angle of the UUV when the UUV naturally floats to the water surface after the counterweight position changes.

6. A method for measuring the metacentric height of a small underwater unmanned submersible according to claim 5, characterized in that: The calculation formula of the UUV metacentric height is: GM=(GM1+GM2) / 2.

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