An energy-harvesting wireless sensor node network for underwater environments and a monitoring method thereof

Abstract

The application discloses an energy collection wireless sensor node network for underwater environment, characterized in that the network comprises a plurality of wireless sensor nodes and a positioning cable; the wireless sensor node comprises an energy supply device carrying a wireless sensor, the energy supply device supplies power to the wireless sensor through tidal current power generation, one end of the positioning cable is anchored on the water bottom, the other end is connected with a floating ball, the floating ball drives the positioning cable to extend upward, when the wireless sensor is insufficient in energy, the energy supply device moves to a position with high tidal current speed along the positioning cable, generates power after positioning through a parking mechanism, and returns to a monitoring position along the positioning cable when the wireless sensor is fully charged. Since the sea current speed decreases with the increase of depth, the energy collected by the bottom layer node is small, and energy starvation is prone to occur, at this time, the buoyancy can be adjusted according to the energy compensation strategy and the energy can be charged in the high flow speed area. The sea current energy is used for self-power supply, and the working time of the underwater wireless sensor node is prolonged.

Description

Technical Field

[0001] This invention relates to marine power generation and monitoring devices, specifically to a wireless sensor node network for energy harvesting in underwater environments and its monitoring method. Background Technology

[0002] In recent years, as an extension of sensor networks in underwater environments, underwater wireless sensor networks have been widely used in numerous underwater scenarios, playing a vital role in various situations. Underwater wireless sensor networks consist of multiple nodes that self-organize. Each node typically integrates sensors, data processing, and communication units. These nodes offer advantages such as small size, high flexibility, low power consumption, flexible deployment, and real-time remote monitoring capabilities. Through the various sensors built into these underwater wireless sensor nodes, people can monitor and control the real world.

[0003] Because wireless sensor networks operate underwater, their power supply is severely limited. Nodes rely solely on their own batteries for energy, preventing continuous monitoring of nearshore sea conditions. Regular battery replacements are necessary to maintain network operation, significantly increasing labor and time costs. Ocean currents and waves offer wide energy distribution and high energy density, making them a reliable way to extend network lifespan. However, current velocity decreases with depth, resulting in lower-level nodes collecting less energy and increasing the likelihood of energy starvation, thus affecting monitoring efficiency. Furthermore, constantly changing currents reduce the surface area of ​​underwater sensor nodes, decreasing their energy harvesting efficiency. Summary of the Invention

[0004] Purpose of the invention: To address the above problems, this invention provides an energy harvesting wireless sensor node network and its monitoring method for underwater environments, ensuring normal monitoring operations.

[0005] Technical Solution: To solve the above problems, this invention employs an energy harvesting wireless sensor node network for underwater environments, comprising several wireless sensor nodes and a positioning cable. Each wireless sensor node includes a power supply device carrying a wireless sensor. The power supply device supplies power to the wireless sensor via tidal current generation. One end of the positioning cable is anchored to the seabed, and the other end is connected to a buoy. The buoy drives the positioning cable upwards. When the wireless sensor's energy is insufficient, the power supply device moves along the positioning cable to a position with high tidal current velocity and, after positioning via a stopping mechanism, generates power. Once the wireless sensor is sufficiently charged, the power supply device returns to the monitoring position along the positioning cable.

[0006] Furthermore, the power supply device includes a power generation compartment that houses the generator and a buoyancy adjustment compartment. The front end of the power generation compartment is provided with blades, which are connected to the input end of the generator in the power generation compartment via a rotating shaft. The buoyancy adjustment compartment is used to adjust the buoyancy of the power supply device and control the rising and sinking of the power supply device in the water.

[0007] Furthermore, the shaft of the front blade of the generator compartment is connected to the generator compartment body through a flange and bearings. The shaft is connected to the speed increaser through a coupling, and then to the generator input end through a coupling. The generator output end is connected to the battery through a step-down and voltage-stabilizing module.

[0008] Furthermore, an external oil bladder is installed between the power generation compartment and the buoyancy adjustment compartment. The buoyancy adjustment compartment is equipped with an internal oil tank, a check valve, a hydraulic pump, and a solenoid valve. The external oil bladder and the internal oil tank are connected by two oil supply pipes. One oil supply pipe is equipped with a hydraulic pump and a check valve, and the other oil supply pipe is equipped with a solenoid valve. The hydraulic pump drives the oil from the internal oil tank through the check valve into the external oil bladder. By controlling the solenoid valve, the oil in the external oil bladder is allowed to flow back to the internal oil tank by water pressure, thereby reducing the volume of the external oil bladder.

[0009] Furthermore, a stopping mechanism is provided between the power generation compartment and the buoyancy adjustment compartment. The stopping mechanism includes an annular buckle sleeved on the positioning cable and a V-shaped block that moves along the annular buckle. The V-shaped block has a threaded hole and is threadedly connected to a threaded shaft. The annular buckle is fixedly connected to the buoyancy adjustment compartment, and a stopping motor is fixedly provided in the buoyancy adjustment compartment. The stopping motor drives the threaded shaft to rotate, thereby driving the V-shaped block to move on the annular buckle, thereby clamping or releasing the positioning cable.

[0010] The present invention also employs a monitoring method for an energy harvesting wireless sensor node network. The energy harvesting wireless sensor node network includes working nodes and redundant nodes at different depths in the same monitoring area. The working nodes and redundant nodes are located at different depths. When a working node is low on energy, the redundant node descends to the working node to perform monitoring work, and the working node rises to a depth with high flow velocity to recharge.

[0011] Furthermore, the number of redundant nodes M satisfies the following formula in, The energy collected for the m-th redundant node, E sinkm P represents the energy consumed by the sinking of the m-th redundant node. cn t represents the energy consumed by the nth working node, E floatn The energy consumed for the nth worker node to ascend, where N is the number of worker nodes.

[0012] This invention also employs a monitoring method for an energy harvesting wireless sensor node network. The energy harvesting wireless sensor node network includes several groups of monitoring nodes for the same monitoring area. Each group of monitoring nodes includes several wireless sensor nodes set on the same positioning cable. During operation, the wireless sensor nodes of some groups of monitoring nodes are all at the depth of high-velocity water and do not perform monitoring tasks. The wireless sensor nodes of other groups of monitoring nodes are evenly distributed at different depths to perform monitoring tasks. When the monitoring nodes performing monitoring tasks are below the energy threshold, the wireless sensor nodes of that group of monitoring nodes rise to the depth of high-velocity water, and at the same time, a corresponding number of wireless sensor nodes at the depth of high-velocity water sink to perform monitoring tasks.

[0013] Beneficial Effects: Compared to existing technologies, the significant advantage of this invention is that because ocean current velocity decreases with increasing depth, bottom-level nodes collect less energy and are more prone to energy starvation. This invention can adjust buoyancy according to an energy compensation strategy to rise to a high-velocity area for recharging. Utilizing ocean current energy for self-powered operation extends the working time of the underwater wireless sensor node. Simultaneously, the node can adapt to the ocean current direction, ensuring the blades are always facing the water flow, improving blade efficiency. Multiple nodes can perform real-time monitoring of the desired monitoring area through a node distribution strategy. The buoyancy adjustment method proposed in this patent allows the underwater sensor node to rise and replenish energy by filling its external oil bladder when it is at the bottom. After recharging, the oil returns due to seawater pressure, causing it to sink. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the single-node working system in this invention.

[0015] Figure 2 This is a schematic diagram of the functional device in this invention.

[0016] Figure 3 This is a top view of the functional device in this invention (excluding the motor compartment and hydraulic compartment).

[0017] Figure 4 This is a front view of the functional device in this invention (excluding the motor compartment and hydraulic compartment).

[0018] Figure 5 This is a partial structural diagram of the end cap seal in this invention.

[0019] Figure 6 This is an overall structural diagram of the stopping mechanism in this invention.

[0020] Figure 7 This is a partial cross-sectional view of the stopping mechanism in this invention.

[0021] Figure 8 This is a schematic diagram of the buoyancy adjustment system in this invention.

[0022] Figure 9 This is a schematic diagram of the buoyancy adjustment process in this invention.

[0023] Figure 10 This is a three-dimensional schematic diagram of the monitoring range of a single node.

[0024] Figure 11 This is a schematic diagram of the layout of a multi-node network monitoring system with redundant nodes.

[0025] Figure 12 This is a schematic diagram showing the arrangement of even-numbered monitoring nodes when multiple monitoring nodes are in operation.

[0026] Figure 13 This is a schematic diagram showing the arrangement of odd-numbered monitoring nodes when multiple monitoring nodes are in operation. Detailed Implementation

[0027] Example 1

[0028] like Figure 1 As shown, an energy harvesting wireless sensor node network for underwater environments includes several wireless sensor nodes and a positioning cable 3. When the wireless sensor is working, the node is connected to a surface float 1 and an anchor 4 via the cable 3. The cable 3 and the wireless sensor node 2 are connected via a stopping mechanism 2-13.

[0029] Wireless sensor nodes include power supply devices that carry wireless sensors, such as... Figure 2 , 3 As shown in Figure 4, the power supply device comprises components such as blades 2-1, generator nacelle 2-2, external oil bladder 2-4, hydraulic control compartment 2-6, and tail fin 2-7. The front end of the power supply device is blade 2-1, which rotates under the impact of ocean currents, collecting ocean current energy and converting it into mechanical energy. The front fan blade shaft of the generator nacelle is connected to the nacelle via flange 2-202 and bearing 2-203, and is connected to speed increaser 2-204 via coupling 2-206, and then to the input end of generator 2-207 via coupling. The generator output end is connected to battery 2-208 via voltage reduction and stabilization module 2-205. The rear end cover of the generator nacelle is connected to the external oil bladder 2-4 of the hydraulic system. The parking mechanism 2-5 is located in the middle of the power supply device and is connected to the bearing of the front end cover of the hydraulic control compartment. The rear end of the power supply device is the hydraulic control compartment, whose front end is connected to the parking mechanism and its rear end is connected to tail fin 2-7.

[0030] like Figure 5 As shown, the main sealing measures for the engine room are as follows: the front cover of the generator nacelle and the rotating shaft are connected by bolts 2-209 and flanges 2-202. A flange gasket is installed inside the flange, and a bearing 2-203 is installed behind the flange. The remaining end covers are also sealed to the compartment by bolts and gaskets.

[0031] like Figure 6 , Figure 7As shown, the stopping mechanism consists of a ring buckle 2-501, a V-block 2-502, a bearing cover 2-503, a connecting plate 2-504, a threaded shaft 2-505, a motor compartment 2-506, a worm gear reducer motor 2-510, a coupling 2-508, and a motor compartment end cover 2-511. The positioning cable 3 passes through the ring buckle, which is rigidly connected to the motor compartment. The V-block can move along the ring buckle, and its center is machined with threads to mate with the threaded shaft. Inside the motor compartment is a worm gear reducer motor, which is fixed to the motor compartment end cover by bolts 2-509. The worm gear output end is connected to the threaded shaft via coupling 2-508, and the threaded shaft is connected to the motor compartment 2-506 via bearing 2-507. The threaded shaft extends outside the compartment after achieving a dynamic seal by pressing in two sealing rings 2-512, and the extended portion of the threaded shaft is also machined with threads. After being reduced in speed by a worm gear, the motor drives the threaded shaft to rotate. Under the constraint of the ring buckle and the threaded engagement, the V-block moves along the ring buckle, clamping or releasing the cable. At the same time, the worm gear reducer motor has a self-locking function, so the V-block will not move even if the motor is not working when clamping the cable.

[0032] like Figure 8 As shown, the hydraulic control compartment 2-6 includes an outer oil bladder 2-4, an inner oil tank 2-601, a hydraulically controlled check valve 2-604, a hydraulic pump 2-603, and a solenoid valve 2-602, etc., with the hydraulic components connected by oil supply pipes. This node adjusts its buoyancy by changing the volume of the outer oil bladder. When the node needs to float, the hydraulic pump pump forces oil through the check valve into the outer oil bladder, increasing its volume and causing the node's buoyancy to exceed its weight, thus generating movement. When the node needs to submerge, the solenoid valve is energized, allowing hydraulic oil to flow back to the inner oil tank under seawater pressure, reducing the volume of the outer oil bladder and causing the node's buoyancy to fall below its weight, resulting in vertical downward movement.

[0033] like Figure 9 As shown, the power supply device is self-locked to the seabed operating area via the stopping mechanism 2-5, and the outer oil bladder of the node is full of oil. The microcontroller periodically detects whether the node lacks energy. If so, it needs to float to a high-velocity area to recharge. The microcontroller controls the stopping mechanism to release the cable 3, and the node moves due to buoyancy exceeding gravity. When it reaches the high-velocity area, the microcontroller controls the stopping mechanism to clamp the cable. When it needs to sink after recharging, the solenoid valve 2-602 is opened, and the oil in the outer oil bladder flows back to the inner oil tank due to water pressure, thereby reducing the volume of the outer oil bladder. The buoyancy of the node is less than its gravity, and the stopping mechanism is then controlled to release the cable. The node moves vertically downward. When it reaches the preset position, the stopping mechanism clamps the cable to fix the position. The pressure is monitored to determine whether the outer oil bladder is full of oil. Otherwise, the outer oil bladder is full of oil.

[0034] Example 2

[0035] like Figure 10As shown, combining the energy harvesting sensor node network in Example 1, energy-neutral ocean monitoring is achieved. Assume the monitored sea area is a cube of size H*H*H, the monitoring radius of a single node is R, its sensing range is a cubic sphere, and its inscribed cube is the node's maximum sensing cube with a side length L, satisfying the following conditions: There are two monitoring methods that can be used to achieve ocean monitoring.

[0036] Node monitoring method one:

[0037] First, the sea area to be monitored is divided into several cubes, each with a side length of L. An energy harvesting sensor node is placed at the center of each cube, and each node is equipped with a cable, forming full coverage of the monitored sea area. For ease of demonstration, only the node deployment on the side closest to the screen is shown, as follows: Figure 11 As shown. Since the ocean current velocity decreases with increasing depth, there must be two regions based on energy gain: an upper region and a lower region. In the upper region, the node energy harvesting power P... h Greater than the communication monitoring power P c In the lower region, the node energy harvesting power P h Less than the communication monitoring power P c Therefore, redundant nodes are deployed in the upper region. These nodes are in a sleep state, only harvesting energy and not participating in region monitoring. The number of redundant nodes satisfies the following formula: That is, the energy gain of m redundant nodes: energy harvesting Subtract the energy E consumed by the node sinking sinkm The energy consumption P for communication and monitoring of a total of n nodes in the lower layer region is greater than or equal to that of the lower layer region. cn t and node rise energy consumption E floatn When the energy of some nodes in the lower layer region falls below a threshold, an election method is used to generate a request to rise and recharge. Redundant nodes, upon receiving the command, descend to the monitoring area to take over the work, while the nodes requesting to rise then move to a high-flow-rate area to recharge. This process is repeated sequentially.

[0038] Node monitoring method two: Similarly, the sea area to be monitored is divided into several cubes, each with a side length of L. To more clearly illustrate the network monitoring method, a two-dimensional plane is used to display the deployment of the monitoring network, such as... Figure 12 As shown. An energy harvesting sensor node is placed at the center of each cube, with multiple nodes distributed along the same cable, represented by even-numbered columns. Simultaneously, a cable is placed at the boundary of each cube, with multiple nodes arranged along the same cable, all located in the upper region to harvest energy, represented by odd-numbered columns. At the start of ocean monitoring operations, the monitoring network is configured as follows: Figure 13The deployment and monitoring are conducted in the following manner: even-numbered columns of nodes monitor the entire area, while odd-numbered columns collect energy in high-velocity waters and remain in a sleep state; once the minimum energy of even-numbered columns falls below a threshold, the nodes will... Figure 13 The network operates as follows: even-numbered nodes send messages to odd-numbered nodes, which then descend along the cable, evenly distributed across different ocean depths to ensure coverage of the monitored area. Even-numbered nodes then surface to replenish their energy in high-velocity areas. Once the energy levels of the odd-numbered nodes drop below the energy threshold, the monitoring network restarts according to the specified procedure. Figure 12 The monitoring is conducted in this manner, and this process is repeated.

Claims

1. A monitoring method for an energy harvesting wireless sensor node network for underwater environments, characterized in that, The energy harvesting wireless sensor node network includes several wireless sensor nodes and a positioning cable (3); the wireless sensor node includes a power supply device (2) equipped with a wireless sensor. The power supply device (2) supplies power to the wireless sensor through tidal current power generation. One end of the positioning cable (3) is positioned at the bottom of the water by an anchor (4), and the other end is connected to a float (1). The float (1) drives the positioning cable to extend upward. When the wireless sensor is low on energy, the power supply device moves along the positioning cable to a position with high tidal current velocity and generates power after positioning by a stopping mechanism. When the wireless sensor is sufficiently charged, the power supply device returns to the monitoring position along the positioning cable. The energy harvesting wireless sensor node network includes working nodes and redundant nodes at different depths for the same monitoring area. The working nodes and redundant nodes are located at different depths. When a working node is low on energy, the redundant node descends to the working node to perform monitoring work, and the working node rises to a depth with high flow velocity to recharge. The number of redundant nodes M satisfies the following formula ,in, The energy collected for the m-th redundant node. The energy consumed by the sinking of the m-th redundant node. Monitor the energy consumed by the nth working node. The energy consumed for the nth worker node to ascend, where N is the number of worker nodes.

2. The monitoring method for an energy harvesting wireless sensor node network according to claim 1, characterized in that, The power supply device includes a power generation compartment (2-2) that houses the generator and a buoyancy adjustment compartment (2-6). The front end of the power generation compartment (2-2) is provided with blades (2-1). The blades (2-1) are connected to the input end of the generator (2-207) in the power generation compartment through a rotating shaft. The buoyancy adjustment compartment (2-6) is used to adjust the buoyancy of the power supply device and control the rising and sinking of the power supply device in the water.

3. The monitoring method for an energy harvesting wireless sensor node network according to claim 2, characterized in that, The shaft of the front blade (2-1) of the generator compartment is connected to the generator compartment body through a flange (2-202) and a bearing (2-203). The shaft is connected to the speed increaser (2-204) through a coupling (2-206), and then connected to the input end of the generator (2-207) through a coupling. The output end of the generator is connected to the battery (2-208) through a step-down voltage regulator module (2-205).

4. The monitoring method for an energy harvesting wireless sensor node network according to claim 2, characterized in that, An outer oil bladder (2-4) is installed between the power generation compartment (2-2) and the buoyancy adjustment compartment (2-6). The buoyancy adjustment compartment (2-6) is equipped with an inner oil tank (2-601), a check valve (2-604), a hydraulic pump (2-603), and a solenoid valve (2-602). The outer oil bladder (2-4) and the inner oil tank (2-601) are connected by two oil supply pipes. One oil supply pipe is equipped with a hydraulic pump and a check valve, and the other oil supply pipe is equipped with a solenoid valve. The hydraulic pump causes the oil to flow from the inner oil tank (2-601) through the check valve (2-604) into the outer oil bladder. By controlling the solenoid valve, the oil in the outer oil bladder is allowed to flow back to the inner oil tank by water pressure, thereby reducing the volume of the outer oil bladder.

5. The monitoring method for an energy harvesting wireless sensor node network according to claim 2, 3, or 4, characterized in that, A stopping mechanism (2-5) is provided between the power generation compartment (2-2) and the buoyancy adjustment compartment (2-6). The stopping mechanism (2-5) includes an annular buckle (2-501) sleeved on the positioning cable (3) and a V-shaped block (2-502) that moves along the annular buckle (2-501). The V-shaped block (2-502) is provided with a threaded hole and a threaded shaft is threadedly connected to it. The annular buckle (2-501) is fixedly connected to the buoyancy adjustment compartment, and a stopping motor is fixedly provided in the buoyancy adjustment compartment. The stopping motor drives the threaded shaft to rotate, thereby driving the V-shaped block (2-502) to move on the annular buckle (2-501), thereby clamping or loosening the positioning cable.

6. The monitoring method for an energy harvesting wireless sensor node network according to claim 2, characterized in that, The rear end of the buoyancy regulating chamber (2-6) is provided with a tail fin (2-7), which is used to align with the tidal current when the tidal current direction changes.

7. A monitoring method for an energy harvesting wireless sensor node network as described in claim 1, characterized in that, The energy harvesting wireless sensor node network includes several groups of monitoring nodes for the same monitoring area. Each group of monitoring nodes includes several wireless sensor nodes set on the same positioning cable. During operation, the wireless sensor nodes of some groups of monitoring nodes are all in the high-velocity water depth and do not perform monitoring tasks. The wireless sensor nodes of other groups of monitoring nodes are evenly distributed at different depths to perform monitoring tasks. When the monitoring nodes performing monitoring tasks are below the energy threshold, the wireless sensor nodes of that group of monitoring nodes rise to the high-velocity water depth, and at the same time, a corresponding number of wireless sensor nodes in the high-velocity water depth sink to perform monitoring tasks.

8. The monitoring method according to claim 7, characterized in that, The sea area monitored by the energy harvesting wireless sensor node network is a cube of shape H*H*H. The monitoring radius of a single wireless sensor node is R, and its sensing range is a cubic sphere. The cube inscribed in the cubic sphere is the maximum sensing cube of a single wireless sensor node, with a side length of L, and satisfies the following conditions: .

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