Underground emergency rescue communication network construction method based on UAV-WSN

Abstract

The invention discloses an underground emergency rescue communication network construction method based on UAV-WSN, and belongs to the field of mine emergency rescue, and the method comprises the steps: carrying out the self-reconstruction of a communication network based on residual WSN nodes, and building a local network with the residual WSN nodes as key nodes; discovering a reconstructed network by using the UAV, constructing a communication link, and establishing a local network comprising the UAV and the WSN; a communication link is constructed between adjacent UAVs, different local networks including the UAVs and the WSN are connected, a global network based on the UAV-WSN is constructed, and construction of the emergency rescue communication network is completed. According to the method, on the premise of starting from the nodes and improving the emergency rescue supporting capacity of the nodes, the global emergency communication network of the accident area is constructed through node self-reconfiguration and UAV auxiliary network communication, the existing emergency rescue method is perfected, the emergency rescue efficiency is improved, and a new thought is provided for emergency rescue.

Description

Technical Field

[0001] The present invention belongs to the field of mine emergency rescue, and particularly relates to a method for constructing an emergency rescue communication network based on UAV-WSN. Background Art

[0002] With the increasingly depletion of shallow coal resources, the coal mining depth in China is gradually increasing. Due to the complex geological conditions and coal occurrence conditions in underground coal mines, coal mine safety accidents occur frequently. As disasters that are prone to occur and have relatively serious consequences in coal mine safety accidents, both gas and roof accidents will cause the collapse of roadway rock masses and the blockage of rock masses. This will not only trap miners and damage communication network terminals, but also seriously affect emergency rescue.

[0003] For emergency rescue tasks, constructing an emergency communication network is an important guarantee for emergency rescue. Wireless sensor networks (WSNs) can be applied to emergency rescue tasks, but due to their limited mobility and energy, and at the same time, affected by the damage of accidents to wireless sensor nodes, their function of emergency rescue is weak. Rescue robots represented by unmanned aerial vehicles (UAVs) can effectively improve the efficiency of emergency rescue. Therefore, the emergency rescue system combining UAVs and WSNs has great application potential in restoring the emergency communication network at the accident site.

[0004] Therefore, it is very necessary to study a method for constructing an underground emergency communication network based on UAV-WSN, which can realize the construction of an emergency communication network after a large-scale roadway collapse and roadway isolation occur due to gas and roof accidents underground, and then guide emergency rescue. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for constructing an underground emergency rescue communication network based on UAV-WSN, which fully combines the advantages of UAVs and WSNs, so as to efficiently establish an emergency communication network after an accident occurs underground and guide emergency rescue.

[0006] To achieve the above purpose, the present invention proposes a method for constructing an underground emergency rescue communication network based on UAV-WSN, and adopts the following technical solutions:

[0007] A method for constructing an underground emergency rescue communication network based on UAV-WSN includes the following steps:

[0008] Step 1: Before an accident occurs, deploy prefabricated WSN nodes in the underground roadway, connect them to the underground communication ring network, and keep them in a low-power working or sleeping state; after the accident occurs, deploy UAVs in the accident area;

[0009] Step 2: After the accident, the remaining WSN nodes switch to the emergency rescue state, send electromagnetic signals to the surroundings, discover other remaining nodes, use the remaining WSN nodes themselves as key nodes, and form a local network with this key node as the core to achieve self-reconfiguration of the communication network;

[0010] Step 3: Use the UAV to discover the local network with the key node as the core and construct a communication link to form a local network including the UAV and WSN;

[0011] Step 4: Construct a communication link between adjacent UAVs to connect different local networks including UAVs and WSNs, form a global network based on UAV-WSN, and complete the construction of the emergency rescue communication network.

[0012] Furthermore, the prefabricated WSN nodes are heterogeneous nodes. A semi-shell-shaped radome protection structure is installed outside the prefabricated WSN nodes. The communication reliability of the prefabricated WSN nodes is achieved through the heterogeneous node method. By installing the semi-shell-shaped radome protection structure, a certain impact protection function is provided for the core components, and at the same time, the electromagnetic loss of electromagnetic waves passing through the shell is reduced to further improve the communication reliability of the nodes.

[0013] Furthermore, the heterogeneous nodes are realized by designing heterogeneous modules with communication methods including WiFi and UWB; the semi-shell-shaped radome adopts a sandwich structure, and the sandwich structure includes a frequency selective surface (FSS). Through frequency selective surfaces with different structures, the high-efficiency transmission of communication frequency bands in different communication methods is realized.

[0014] Furthermore, the switching mechanism for the prefabricated WSN nodes to switch from the low-power working or sleeping state to the emergency rescue state originates from the semi-shell-shaped radome protection structure. The semi-shell-shaped radome protection structure monitors the surface stress through the internal stress monitoring device. When the monitored stress value exceeds the preset threshold, the node is awakened and enters the emergency rescue state.

[0015] Furthermore, when deploying the UAV after the accident, when the accident causes a complete blockage of the roadway, the UAV deployment is realized by means of the pipeline channel opened by the drilling machine in the accident area; when the roadway caused by the accident is not completely blocked, the UAV flies along the top space of the roadway to realize the UAV deployment.

[0016] Furthermore, the communication network self-reconfiguration in step 2 includes self-reconfiguration among the surviving WSN nodes and reconfiguration between the surviving WSN nodes and the surviving nodes of the existing underground safety refuge system. First, the information of neighbor nodes is determined through the handshaking mechanism between nodes and packet exchange, and then communication links are constructed among the surviving prefabricated WSN nodes and between the surviving prefabricated WSN nodes and the surviving nodes of the existing underground safety refuge system; the existing underground safety refuge system nodes are base stations, gateways, and APs applied to underground monitoring and control, personnel positioning, and communication liaison.

[0017] Furthermore, since the prefabricated WSN nodes are heterogeneous nodes and there are also multiple communication methods for the existing underground safety refuge system nodes, during the communication network self-reconfiguration process, the communication methods are switched among the prefabricated WSN nodes according to the heterogeneous communication switching strategy. The heterogeneous communication switching strategy is: when a node senses an accident and starts the self-reconfiguration method, according to the communication link constructed with the discovered neighbor nodes, the electromagnetic wave transmission medium is deduced through the RSSI attenuation formula, and the communication method more suitable for signal transmission under this medium is adaptively switched.

[0018] Furthermore, based on the above heterogeneous communication switching strategy, the efficient discovery strategy for neighbor node discovery in the self-reconfiguration method is:

[0019] Step1: According to the most suitable communication method for after the accident switched by the heterogeneous communication switching strategy, complete the discovery of neighbor nodes and the construction of communication links in the first round;

[0020] Step2: Switch the communication method again to complete the discovery of nodes and the construction of communication links in the subsequent N rounds, where N is the number of communication methods of the prefabricated WSN nodes minus 1, and the self-reconfiguration time of each round is less than the time in Step1.

[0021] Furthermore, in step 3, for the situation of roadway rock mass collapse and blockage caused by the accident, the method of using UAVs to discover and construct communication links is: deploy multiple UAVs to search the locally reconfigured network in the accident area, and then achieve network connectivity in the accident area through the coordinated deployment of UAVs.

[0022] Further, in step 3, for the situation of roadway rock mass collapse and blockage caused by the accident, the specific process of using UAV to discover and construct a communication link is as follows: When the UAV searches for the key nodes of the reconstructed network within the communication radius, set this key node as the center and move outward from the center until reaching the disconnection point with this key node, and search 360° around the center until the search is completed; if other nodes are searched, the final position of the UAV is the coincidence point of the searched nodes, and if no other nodes are searched, the final position of the UAV is the closest position to this key node; after determining the position of the UAV, establish a communication connection between the UAVs, thereby constructing the network topology structure between the UAVs and between the UAV and the WSN, and realizing network connectivity.

[0023] Further, in step 3, for the situation of roadway isolation caused by the accident, the method of using UAV to discover and construct a communication link is: by constructing a stable communication link between the UAV and the key nodes of the reconstructed network; after the stable channel is constructed, adjust the position of the UAV, and then realize network connectivity.

[0024] Further, in step 3, for the situation of roadway isolation caused by the accident, the method of constructing a stable communication channel between the UAV and the nodes is: adjust the different flight speeds and flight heights of the UAV, measure the channel quality between the UAV and the nodes, select the UAV operating parameters with the best channel quality, that is, the least impact on the signal strength of the receiving node, and construct a channel model under the corresponding parameters.

[0025] Further, in steps 3 and 4, when constructing the communication link between the UAV and the WSN and between the UAV and the UAV, it is necessary to consider the influence of the environment, the distance between each other, and electromagnetic interference, so as to obtain a stable communication link; the implementation method of obtaining a stable communication link is to construct an air-ground channel between the UAV and the WSN and an air-air channel between the UAV and the UAV.

[0026] Further, the modeling method of the channel model is a geometry-based statistical method.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The present invention discloses a method for constructing an underground emergency rescue communication network based on UAV-WSN. Combining the advantages of UAV and WSN, starting from the WSN nodes, on the premise of improving the ability of nodes to support emergency rescue, through the self-reconstruction of the remaining WSN nodes and the UAV-assisted network connectivity, the framework of the global emergency communication network in the accident area is realized, improving the existing emergency rescue method and the efficiency of emergency rescue. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flowchart of the method provided by the present invention;

[0030] Figure 2 Schematic diagram of the composition of the node;

[0031] Figure 3 FSS structure that meets the wave-transmitting property of wireless signals in the 2.4 GHz band;

[0032] Figure 4 Composition diagram of the heterogeneous node module with STM32F030C8T6 as the main control chip;

[0033] Figure 5 Schematic diagram of the deployment of nodes and UAVs;

[0034] Figure 6 Schematic diagram of the node self-reconfiguration method;

[0035] Figure 7 Heterogeneous communication switching strategy for prefabricated WSN nodes in the self-reconfiguration method;

[0036] Figure 8 Efficient neighbor node discovery strategy based on the heterogeneous communication switching strategy in the self-reconfiguration method;

[0037] Figure 9 Schematic diagram of network connectivity realized by UAV based on the self-reconfiguration network;

[0038] Figure 10 Schematic diagram of the search for key nodes of the reconfiguration network by a specific UAV;

[0039] Explanation of the labels in the figure: 1. Remaining nodes of the existing underground safety refuge system, 2. Remaining prefabricated WSN nodes, 3. Mobile nodes (miners), 4. Damaged nodes of the safety refuge system, 5. Damaged prefabricated WSN nodes. Specific implementation mode

[0040] The following combines the accompanying drawings and specific implementation modes to further describe the technical solution in detail.

[0041] As Figure 1 shown, a method for constructing an underground emergency rescue communication network based on UAV-WSN provided by the present invention includes the following steps:

[0042] Step 1. Before the accident, deploy prefabricated WSN nodes in the underground roadway, connect to the underground communication ring network, and keep working in a low-power state or in a dormant state; after the accident, deploy a UAV in the accident area.

[0043] Step 2: After the accident, the remaining WSN nodes switch to the emergency rescue state, send electromagnetic signals to the surroundings, detect the remaining other nodes, and form a local network with the remaining WSN nodes themselves as the key nodes to achieve self-reconfiguration of the communication network;

[0044] Step 3: Use the UAV to detect the local network with the key node as the core and build a communication link to form a local network including the UAV and WSN;

[0045] Step 4: Build a communication link between adjacent UAVs to connect different local networks including UAVs and WSNs, and form a global network based on UAV-WSN to complete the construction of the emergency rescue communication network.

[0046] As Figure 2 and 3 shown, the prefabricated WSN nodes are heterogeneous nodes, achieving reliable communication through heterogeneous communication, and protecting the nodes through a protection structure to improve the physical survival ability. The protection structure is realized through a semi-spherical radome with a frequency selective surface (FSS) sandwich structure. Figure 3 The figure shows the FSS structure that meets the wave-transmitting property of wireless signals in the 2.4 GHz band. Among them, D is 40 mm, L2 is 2.415 mm, L1 is 4 mm, h2 is 1.5748 mm, and h1 is 0.035 mm; secondly, the supporting medium shown in blue uses F4B220 with a dielectric constant of 2.2 and a loss tangent of 0.0009, and the metal shown in yellow uses copper.

[0047] The heterogeneous communication of the prefabricated WSN nodes is realized by designing heterogeneous modules. Figure 4 The figure shows the composition diagram of the heterogeneous node module with STM30F030C8T6 as the main control chip. Among them, the communication methods include WiFi and UWB.

[0048] Figure 5 Shows the deployment methods of the prefabricated WSN nodes and UAVs. Before the accident, the prefabricated WSN nodes are deployed, and after the accident, the UAVs are deployed; after the accident, the remaining prefabricated WSN nodes switch from the low-power working or sleeping state to the emergency rescue state; when deploying the UAV, when the accident causes a complete blockage of the roadway, a pipeline channel opened in the accident area by a drilling machine is used to achieve the deployment of the UAV; when the roadway caused by the accident is not completely blocked, the UAV flies along the top space of the roadway to achieve the deployment of the UAV.

[0049] Figure 6 Shows the communication network self-reconfiguration method based on the remaining prefabricated WSN nodes, including the self-reconfiguration between the remaining prefabricated WSN nodes ( Figure 6(as shown in (D)), the reconstruction between the remaining prefabricated WSN nodes and the nodes of the existing underground safety refuge system Figure 6 (as shown in (A), (B), and (C)); first, through a handshake mechanism and data packet exchange between nodes, the information of neighbor nodes is determined, and then the communication link between the remaining nodes is constructed.

[0050] Since the prefabricated nodes are heterogeneous nodes, and there are also various communication methods for the nodes of the existing underground safety refuge system, therefore, during the self-reconstruction process, the prefabricated WSN nodes need to involve the switching of communication methods. Figure 7 Shows the heterogeneous communication switching strategy of the prefabricated nodes in the self-reconstruction method, that is, according to the communication link constructed with the discovered neighbor nodes, through the RSSI attenuation formula, the electromagnetic wave transmission medium is deduced inversely, and then the communication method more suitable for signal transmission under this communication medium is switched adaptively.

[0051] Figure 8 Further shows the efficient neighbor node discovery strategy based on the heterogeneous communication switching strategy in the self-reconstruction method: first, according to the communication method most suitable for after the accident switched by the heterogeneous communication switching strategy, complete the discovery of neighbor nodes and the construction of communication links in the first round; then switch the communication method again to complete the discovery of neighbor nodes and the construction of communication links in the subsequent N rounds; where N is the number of communication methods of the prefabricated WSN nodes minus 1, and the node self-reconstruction time in the subsequent rounds is less than that in the first round.

[0052] Figure 9 Is a schematic diagram of network connectivity realized by UAVs based on the self-reconstructed network. L_1 to L_6 are the communication links for realizing global network connectivity by UAVs. For the situation of roadway rock mass collapse and blockage caused by the accident, deploy multiple UAVs to search for the self-reconstructed network in the accident environment, and then construct the global network of the accident area, such as Figure 9 L_5 in; for the situation of roadway isolation caused by the accident, construct a stable communication channel between the UAV and the nodes, while ensuring that the communication connection between each other will not be disconnected due to the environment and the UAV, adjust the position of the UAV to realize network connectivity, such as Figure 9 L_1 in.

[0053] Figure 10 Shows the schematic diagram of the UAV searching for the key nodes of the self-reconstructed network. The UAV searches for the remaining node N1 at the P1 position, and then sets the node N1 as the center and moves outward along the center until it reaches the disconnection point P2 with the node N1. Taking the distance between the node N1 and P2 as the radius, search 360° around the center; when searching to P2’, the node N2 is found. Therefore, at this time, the position of the UAV may be the midpoint of the connection line between N1 and N2.

[0054] The above are only the preferred specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the technical scope disclosed by the present invention according to the technical solutions and inventive concepts of the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for constructing an underground emergency rescue communication network based on UAV-WSN, characterized in that: The following steps are involved: Step 1: Before the accident occurs, deploy prefabricated WSN nodes in the underground tunnels, connect to the underground communication ring network, and maintain low-power working or dormant state; after the accident occurs, deploy UAVs in the accident area; Step 2: After the accident, the remaining WSN nodes are transformed into emergency rescue state, sending electromagnetic signals to the surroundings to find other remaining nodes. The remaining WSN nodes themselves are used as key nodes to form a local network with the key nodes as the core, realizing self-reconstruction of the communication network. Step 3: Use UAV to discover a local network with key nodes as the core, build a communication link, and form a local network including UAV and WSN; Step 4: Build communication links between adjacent UAVs, connect different local networks containing UAVs and WSNs, form a global network based on UAV-WSN, and complete the construction of the emergency rescue communication network.

2. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 1, characterized in that: The prefabricated WSN node is a heterogeneous node, which is realized by designing a heterogeneous module with WiFi and UWB communication modes; a half-shell antenna cover protection structure is installed outside the prefabricated WSN node, and the half-shell antenna cover protection structure adopts a sandwich structure, and the sandwich structure contains a frequency selective surface.

3. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 2, characterized in that: The switching mechanism of the prefabricated WSN node from low-power working or sleep state to emergency rescue state is derived from the half-shell antenna cover protection structure. The half-shell antenna cover protection structure monitors the surface stress through the internal stress monitoring device. When the monitored stress value exceeds the preset threshold, the node is awakened and enters the emergency rescue state.

4. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 1, characterized in that: When UAV is deployed after an accident, if the accident causes a complete blockage of the tunnel, UAV deployment is achieved with the help of a pipeline channel opened up in the accident area by a drilling machine; when the tunnel caused by the accident is not completely blocked, the UAV flies along the top space of the tunnel to achieve UAV deployment.

5. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 3, characterized in that: The communication network self-reconstruction in step 2 includes self-reconstruction between the remaining WSN nodes and reconstruction between the remaining WSN nodes and the remaining nodes of the existing underground safety and risk avoidance system. First, the information of the neighboring nodes is determined through the handshake mechanism between the nodes and the data packet exchange, and then the communication links between the remaining WSN nodes and the remaining nodes of the existing underground safety and risk avoidance system are established; The existing safety and hazard avoidance system nodes underground are base stations, gateways and APs used for underground monitoring, personnel positioning and communication.

6. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 5, characterized in that: During the self-reconstruction process of the communication network, the prefabricated WSN nodes switch the communication mode according to the heterogeneous communication switching strategy. The specific heterogeneous communication switching strategy is: when the node senses the occurrence of an accident and starts the self-reconstruction method, it reversely infers the electromagnetic wave transmission medium through the RSSI attenuation formula based on the communication link constructed with the discovered neighbor nodes, and adaptively switches to a communication mode that is more suitable for signal transmission under this medium.

7. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 6, characterized in that: Based on the heterogeneous communication switching strategy, the efficient discovery strategy for neighbor node discovery in the self-reconstruction method is: Step 1: According to the heterogeneous communication switching strategy, the most suitable communication mode after the accident is switched to complete the first round of neighbor node discovery and communication link construction; Step 2: Switch the communication mode again to complete the subsequent N rounds of node discovery and communication link construction, where N is the communication mode of the prefabricated WSN node minus 1, and the node self-reconstruction time of each round is less than the time in Step 1.

8. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 4, characterized in that: In response to the rock collapse and blockage in the tunnel caused by the accident, the specific process of using UAV to discover and build communication links is as follows: when the UAV searches for the key node of the reconstructed network within the communication radius, this key node is set as the center and moves outward along the center until it reaches the disconnection point with this key node, and searches 360° around the center until the search is completed; if other nodes are searched, the final position of the UAV is the coincidence point of the searched nodes, if no other nodes are searched, the final position of the UAV is the closest position to the key node; when the UAV position is determined, communication connections are established between the UAVs, thereby constructing the network topology between UAVs and between UAVs and WSNs to achieve network connectivity.

9. The method for constructing an underground emergency rescue communication network based on UAV-WSN according to claim 4, characterized in that: In response to the tunnel isolation caused by the accident, the method of using UAV to discover and build communication links is as follows: adjust the different flight speeds and altitudes of the UAV, measure the channel quality between the UAV and the key nodes, select the UAV operating parameters with the best channel quality, that is, the least impact on the signal strength of the receiving node, and build a stable channel model under the corresponding parameters; after the stable channel is built, adjust the position of the UAV to achieve network connectivity.

10. A method for constructing an underground emergency rescue communication network based on UAV-WSN according to any one of claims 8 or 9, characterized in that: The implementation methods of obtaining stable communication links between UAV and WSN and between UAV and UAV are to construct an air-to-ground channel between UAV and WSN and an air-to-air channel between UAV and UAV respectively.

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