CN110289917B - Anchor node location acquisition method for underwater optical communication network - Google Patents

Abstract

The invention discloses an anchor node position acquisition method for an underwater optical communication network. When the speed is constant, the anchor node is subjected to force analysis in a balanced state to obtain the cable end tension; when the water flow speed is not constant, the set movement time of the anchor node is evenly divided into multiple time slots, and under each time slot, The dynamic analysis of the anchor node is carried out to obtain the equivalent cable end tension; the anchor node coordinates and rotation angle are iteratively solved using the cable end tension and the coordinates of the anchor point of the cable. The method of the invention can accurately obtain the moving position of the anchor node in the water flow, and then analyze the influence of the movement of the anchor node on the received light intensity, so as to design more reasonable communication parameters and deployment scheme, and reduce the influence of the water flow on the network communication performance , and even use water flow to a certain extent to achieve better communication effects.

Description

Anchor node location acquisition method for underwater optical communication network

technical field

The invention belongs to the field of underwater optical communication, and more particularly, relates to an anchor node position acquisition method of an underwater optical communication network.

Background technique

Underwater wireless sensor networks have a wide range of applications in pollution monitoring, marine data collection, assisted navigation, and national defense security, but they also face many challenges because of the complex underwater environment.

Underwater acoustic sensing technology is a communication technology that has been extensively studied and used in the underwater environment. A large number of experimental results and practical experience show that underwater acoustic communication has slow speed and high delay. Compared with terrestrial electromagnetic wave communication, the speed is several orders of magnitude lower, which seriously affects the real-time performance of communication. Secondly, the bandwidth of underwater acoustic communication is low, and its The typical communication bandwidth is several hertz to several kilohertz, which is not suitable for the transmission of large amounts of data. Underwater optical communication provides another solution for underwater communication. Compared with underwater acoustic communication, underwater optical communication has many advantages: in the range of tens of meters, its data transmission rate can reach Gbps level, which can be applied to Transmission of a large amount of data; the transmission rate in water is close to the speed of light, which can meet the needs of real-time communication. In addition, the underwater optical communication node has small size, low cost, high reliability and good security.

However, underwater optical communication usually requires the alignment of the communication link. However, the drift of the anchor node is often caused by the movement of the water flow underwater, which eventually leads to the failure of the communication link and seriously affects the performance of the network. In order to reduce the impact of the water flow on the underwater The influence of optical communication network performance, it is necessary to study the movement of anchor nodes under the action of water flow.

At present, although there are many underwater mobile models, they are all aimed at underwater acoustic networks, and the nodes are free to move with the water flow without any constraints. In terms of water-optical communication, most of the research is aimed at channel models and modulation of optical signals. The effect of water flow on the movement of the anchor node has not been studied.

SUMMARY OF THE INVENTION

In view of the defects of the prior art, the purpose of the present invention is to provide a method for obtaining the position of an anchor node in an underwater optical communication network, aiming to obtain the moving position of the anchor node under the action of water flow in underwater optical communication, so as to analyze the effect of water flow on the network. impact on communication performance.

In order to achieve the above object, the present invention provides a method for obtaining an anchor node position of an underwater optical communication network, including:

(1) Initialize the state of cables and anchor nodes in the underwater optical communication network, so that the anchor nodes can conduct aligned communication and obtain underwater environment parameters;

Wherein, the anchor node refers to the underwater optical communication equipment anchored by the cable;

(2) judge whether the water flow speed is constant, if yes, then enter step (3); otherwise enter step (4);

(3) Carry out the force analysis of the anchor node under the equilibrium state, and obtain the tensile force at the end of the cable;

(4) Divide the set anchor node movement time into multiple time slots evenly, and under each time slot, perform dynamic analysis on the anchor node to obtain the equivalent cable end tension;

(5) Use the cable end tension and the cable anchor point coordinates to iteratively solve the anchor node coordinates and rotation angle.

Further, the anchor node is a spherical structure.

Further, the underwater environmental parameters described in step (1) include: water density, water flow velocity, drag coefficient and hydrodynamic coefficient.

Further, the non-constant water flow should satisfy the laminar flow state without generating turbulence or eddies.

Further, step (3) specifically includes obtaining the cable end tensile force according to the buoyancy of the anchor node in the vertical direction, the gravity of the anchor node and the resistance of the water flow in the horizontal direction to the anchor node.

Further, step (4) specifically includes:

(4.1) In each time slot, according to the component force of the cable tension in the horizontal direction and the resistance of the horizontal water flow to the anchor node, the speed of the anchor node in the corresponding time slot is obtained, and the obtained speed is integrated in the time slot. Get the displacement of the anchor node in the corresponding time slot;

(4.2) Accumulate the displacement in each time slot to obtain the horizontal displacement of the anchor node during the movement time;

(4.3) Obtain the inclination angle of the cable according to the horizontal displacement and the length of the cable; the inclination angle of the cable is the angle between the end of the cable and the horizontal direction;

(4.4) According to the vertical component of the tensile force acting on the anchor node by the cable and the inclination angle of the cable, the tensile force at the end of the cable is obtained.

Further, step (5) specifically includes:

(5.1) The cable is evenly divided into multiple cable micro-elements, and the force balance analysis of each cable micro-element is carried out. Iterative solution to get the cable rotation angle;

(5.2) According to the cable anchor point coordinates and the cable rotation angle corresponding to each micro-element, iteratively solve the cable position coordinates.

Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

(1) The method of the present invention can accurately obtain the moving position of the anchor node in the water flow, and then analyze the influence of the movement of the anchor node on the received light intensity, so as to design more reasonable communication parameters and deployment plans, and reduce the impact of water flow on network communication. The impact of performance, and even to a certain extent, the use of water flow to achieve better communication results.

(2) The method of the present invention is suitable for underwater optical communication equipment anchored by cables. Aiming at the unique angle alignment problem of anchor nodes in underwater optical communication, it is studied that the initial alignment of the communication anchor nodes generated under the action of water flow offset, so as to realize the dynamic analysis of underwater optical communication network performance.

(3) The method of the present invention considers the situation of constant water flow and non-constant water flow respectively, and when the speed of the non-constant water flow changes slowly, a method is proposed that the dynamic instantaneous position is equivalent to the static equilibrium position, which can accurately measure the dynamic water flow. Get the moving position of the anchor node.

Description of drawings

1 is a flowchart of a method for obtaining an anchor node position of an underwater optical communication network according to an embodiment of the present invention;

2 is a flowchart of node position estimation in a non-constant water flow provided by an embodiment of the present invention;

FIG. 3 is a force analysis diagram of a cable micro-element provided by an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Referring to FIG. 1 , a method for obtaining an anchor node position of an underwater optical communication network provided by the present invention includes:

(1) Initialize the state of cables and anchor nodes in the underwater optical communication network, so that the anchor nodes can conduct aligned communication and obtain underwater environment parameters;

Specifically, the anchor node of the present invention refers to an underwater optical communication device anchored by a cable, which is a spherical structure. Initialize the state of cables and anchor nodes in the underwater optical communication network, including: designing the length and quality of the cables, so that the anchor nodes are suspended in the water to form an underwater optical communication network; making the anchor nodes perform aligned communication; and then obtain the information including: water Underwater environmental parameters such as density, flow velocity, drag coefficient, and hydrodynamic coefficient.

(2) judge whether the water flow speed is constant, if yes, then enter step (3); otherwise enter step (4);

(3) Carry out the force analysis of the anchor node under the equilibrium state, and obtain the tensile force at the end of the cable;

Specifically, according to the buoyancy of the anchor node in the vertical direction, the gravity of the anchor node and the resistance of the water flow in the horizontal direction to the anchor node, the tensile force at the end of the cable is obtained;

In a three-dimensional underwater environment, the coordinates of the anchor nodes are solved from the perspective of dynamics. The anchor nodes reach a state of equilibrium in a constant water flow, and the force analysis of the anchor nodes in the equilibrium state is carried out:

F _b +F _d +G+T=0 (1)

Among them, F _b is the buoyancy force on the anchor node in the vertical direction, G is the gravity of the anchor node, F _d is the resistance of the horizontal water flow to the anchor node, T is the pulling force of the cable to the anchor node, and the buoyancy force F _b and gravity G are related to the water flow size does not matter;

得到水平方向水流对锚节点的阻力F_d，然后通过平衡受力方程(1)可求得缆索拉力T的大小和方向；According to the volume of the anchor node, the buoyancy force F _b received by the anchor node in the vertical direction is obtained, and the gravity G of the anchor node is obtained according to the mass of the anchor node.

The resistance F _d of the horizontal water flow to the anchor node is obtained, and then the magnitude and direction of the cable tension T can be obtained through the equilibrium force equation (1);

Among them, A is the characteristic area, which in the present invention refers to the equivalent area of the anchor node affected by the water flow, v _w is the water flow velocity, v _n is the anchor node velocity, ρ is the density of water, C _D is the resistance coefficient, which is related to the Reynolds coefficient Re related.

(4) Divide the set anchor node movement time into multiple time slots evenly, and under each time slot, perform dynamic analysis on the anchor node to obtain the cable end tension;

Specifically, in the non-constant water flow, the motion of the node is limited to a specified area, and the dynamic position of the node at a certain moment can be equivalent to the static equilibrium position of the node under a constant velocity water flow.

Referring to Figure 2, step (4) specifically includes:

(4.1) Under each time slot, according to the component force of the cable tension in the horizontal direction and the resistance of the horizontal water flow to the anchor node, the speed of the anchor node in the corresponding time slot is obtained, and the obtained speed is integrated in the time slot. Get the displacement of the anchor node in the corresponding time slot;

In the horizontal direction, regardless of the influence of the cable bending moment on the position of the anchor node, the anchor node satisfies the following equation at any time:

Among them, F _T is the component force of the cable tension in the horizontal direction, the cable is vertical at the initial moment, the horizontal component force is 0, M is the mass of the anchor node, and v is the speed of the anchor node;

Divide the movement time t of the anchor node into several small time slots _{Tw on average. Assuming that vw and} F _T are unchanged in any time slot, and the boundary conditions are known, the anchor node velocity can be obtained as v(t), the displacement of the anchor node in any time slot is:

Among them, t _k is the time slot start time, _Tw is the time slot size;

(4.2) Accumulate the displacement in each time slot to obtain the horizontal displacement of the anchor node during the movement time;

During the movement time t, the displacement of the anchor node in the horizontal direction is:

Wherein, n is the total number of time slots, satisfying t=n× _Tw ;

(4.3) The inclination angle of the cable is obtained according to the horizontal displacement and the length of the cable; the inclination angle of the cable is the angle between the end of the cable and the horizontal direction;

In an equivalent equilibrium system, the angle between the end of the cable and the horizontal direction is approximated by the following equation:

where L is the cable length;

(4.4) According to the vertical component of the tensile force acting on the anchor node by the cable and the inclination angle of the cable, the tensile force at the end of the cable is obtained;

In the Z-axis direction, since the gravity and buoyancy of the node have nothing to do with the water flow, the vertical component F _h of the pulling force acting on the anchor node by the cable remains unchanged, and the pulling force at the end of the cable can be obtained from the following formula:

(5) According to the cable end tension and the cable anchor point coordinates, the anchor node coordinates and rotation angle are obtained;

Specifically, step (5) includes:

(5.1) The cable is evenly divided into multiple cable micro-elements, and the force balance analysis of each cable micro-element is carried out. Iterative solution to get the cable rotation angle;

The cable will also reach a stable state. Take any section of the cable micro-element, and its force analysis is shown in Figure 2. The cable micro-element for this section has the following equation:

Among them, w is the underwater gravity of the cable micro-element (self-gravity minus buoyancy), Fdt, Fdn are the tangential resistance and normal resistance of the water flow to the cable micro-element, respectively, which are obtained by the following equations:

是缆索与水平面的夹角，对某段缆索微元，已知其中一端张力的大小和方向，联合上式可以求得另一端张力的大小和方向；C _n is the normal hydrodynamic coefficient, C _t is the tangential hydrodynamic coefficient, V is the velocity of the water flow relative to the cable, ρ is the water density,

is the angle between the cable and the horizontal plane. For a certain cable element, the magnitude and direction of the tension at one end are known, and the magnitude and direction of the tension at the other end can be obtained by combining the above formula;

(5.2) According to the cable anchor point coordinates and the cable rotation angle corresponding to each micro-element, iteratively solve to obtain the cable position coordinates;

When the coordinates of one end of the cable element are (x _c , y _c , z _c ), the coordinates of the other end of the node (x _c ′, y _c ′, z _c ′) can be obtained by the following equation:

ω is the angle between the projection of the cable in the horizontal direction and the x-axis, the coordinates of the anchor point are known, and the coordinates of the anchor node can be obtained by iterative solution;

The rotary motion of the anchor node is mainly the rotary motion around the connection point between the anchor node and the cable. The rotation direction is perpendicular to the direction of the water flow. When the node is balanced, the direction of the pulling force of the cable to the anchor node passes through the ball center of the anchor node, and the end of the anchor cable is connected to the Z axis. The included angle is the rotation angle of the anchor node.

The method of the invention is used to study the problem that the underwater optical communication equipment anchored by the cable moves under the action of the water flow in the underwater optical communication wireless sensor network. position, the influence of the movement of the anchor node on the received light intensity can be analyzed by the method of the present invention.

Using the method of the present invention to obtain the moving position of the anchor node under the action of the water flow, the influence of the movement of the anchor node on the received light intensity can be studied by referring to the analysis method of the connectivity of the underwater acoustic communication network, so as to design more reasonable communication parameters and deployment schemes to reduce the impact of water flow on network communication performance, and even use water flow to a certain extent to achieve better communication effects.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (5)

1. an anchor node position acquisition method of underwater optical communication network is characterized in that, comprising: (1) Initialize the state of cables and anchor nodes in the underwater optical communication network, so that the anchor nodes can conduct aligned communication and obtain underwater environment parameters; Wherein, the anchor node refers to the underwater optical communication equipment anchored by the cable; (2) judge whether the water flow speed is constant, if yes, then enter step (3); otherwise enter step (4); (3) Carry out the force analysis of the anchor node under the equilibrium state, and obtain the tensile force at the end of the cable; (4) The set movement time of the anchor node is evenly divided into multiple time slots, and under each time slot, the dynamic analysis of the anchor node is performed to obtain the equivalent cable end tension; Step (4) specifically includes: (4.1) In each time slot, according to the component force of the cable tension in the horizontal direction and the resistance of the horizontal water flow to the anchor node, the speed of the anchor node in the corresponding time slot is obtained, and the obtained speed is integrated in the time slot. Get the displacement of the anchor node in the corresponding time slot; (4.2) Accumulate the displacement in each time slot to obtain the horizontal displacement of the anchor node during the movement time; (4.3) Obtain the inclination angle of the cable according to the horizontal displacement and the length of the cable; the inclination angle of the cable is the angle between the end of the cable and the horizontal direction; (4.4) According to the vertical component of the cable pulling force acting on the anchor node and the cable inclination angle, the equivalent cable end pulling force is obtained; (5) Use the cable end tension and the cable anchor point coordinates to iteratively solve the anchor node coordinates and rotation angle; step (5) specifically includes: (5.1) The cable is evenly divided into multiple cable micro-elements, and the force balance analysis of each cable micro-element is carried out. Iterative solution to get the cable rotation angle; (5.2) According to the cable anchor point coordinates and the cable rotation angle corresponding to each micro-element, iteratively solve the cable position coordinates. 2 . The method for obtaining the position of an anchor node of an underwater optical communication network according to claim 1 , wherein the anchor node is a spherical structure. 3 . 3. the anchor node position acquisition method of a kind of underwater optical communication network according to claim 1 and 2, is characterized in that, described in step (1), underwater environment parameter, comprises: density of water, water flow velocity, Drag coefficient and hydrodynamic coefficient. 4 . The method for obtaining the anchor node position of an underwater optical communication network according to claim 1 , wherein the non-constant water flow should satisfy that the water flow is in a laminar flow state without generating turbulence or eddies. 5 . 5. the method for obtaining the anchor node position of a kind of underwater optical communication network according to claim 1, is characterized in that, step (3) specifically comprises, according to the buoyancy, anchor node gravity and horizontal direction that anchor node receives according to vertical direction The resistance of the water flow to the anchor node, the tension at the end of the cable is obtained.

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