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WO2024160150A1 - 无线传感网络时间同步方法及建筑结构健康监测系统 - Google Patents

无线传感网络时间同步方法及建筑结构健康监测系统 Download PDF

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Publication number
WO2024160150A1
WO2024160150A1 PCT/CN2024/074267 CN2024074267W WO2024160150A1 WO 2024160150 A1 WO2024160150 A1 WO 2024160150A1 CN 2024074267 W CN2024074267 W CN 2024074267W WO 2024160150 A1 WO2024160150 A1 WO 2024160150A1
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node
time
nodes
data
time synchronization
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PCT/CN2024/074267
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English (en)
French (fr)
Inventor
熊琛
黄杰
解琳琳
刘力子
龙武剑
罗启灵
梅柳
李利孝
吴环宇
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深圳大学
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Publication of WO2024160150A1 publication Critical patent/WO2024160150A1/zh

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    • G—PHYSICS
    • G08—SIGNALLING
    • G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
    • G08C17/00—Arrangements for transmitting signals characterised by the use of a wireless electrical link
    • G08C17/02—Arrangements for transmitting signals characterised by the use of a wireless electrical link using a radio link
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present application relates to the field of building monitoring technology, and in particular to a wireless sensor network time synchronization method and a building structure health monitoring system.
  • GPS and conventional radio signals have the disadvantage of weak penetration ability, and are difficult to be used in high-rise buildings.
  • the environment where the radio signals are isolated by structural components is denied. For example, it is not applicable to the scenario where the time synchronization signal inside the building needs to penetrate multiple floors or walls. Therefore, how to use wireless communication technology inside the building structure to monitor the health of the building structure and ensure the accuracy of time synchronization is an urgent problem to be solved.
  • the purpose of this application is to provide a wireless sensor network time synchronization method and a building structure health monitoring system to alleviate the above-mentioned technical problems. It not only realizes the health monitoring of the building structure, but also ensures the time synchronization accuracy and communication stability of the wireless sensor network, and has good practical value.
  • an embodiment of the present application provides a method for time synchronization in a wireless sensor network, wherein the wireless sensor network includes a parent node and multiple child nodes, and the method includes: the parent node obtains a reference clock and sends a synchronization Sync message to the child node closest to the parent node; wherein the synchronization Sync message carries the sending time T 1 of the parent node; the child node records the receiving time T 2 of the synchronization Sync message, and sends a synchronization request Req message to the parent node; wherein the synchronization The request Req message carries the receiving time T 2 and the sending time T 3 of the synchronization request Req message; the parent node receives the synchronization request Req message and feeds back a Resp message to the child node; wherein the Resp message carries the receiving time T 4 of the synchronization request Req message and the sending time T 5 of the Resp message; the child node records the receiving time T 6 of the Resp message
  • the step of calculating the clock difference according to the sending time T 1 , the receiving time T 2 , the sending time T 3 , the receiving time T 4 , the sending time T 5 , the receiving time T 6 and the correcting time T 7 comprises: calculating the clock difference according to the following formula: Wherein, ⁇ 7 represents the clock difference and k represents the linear drift rate.
  • an embodiment of the present application also provides a building structure health monitoring system, which includes a perception layer, an information transmission layer and a cloud platform management application layer; wherein the perception layer includes multiple nodes, and the multiple nodes achieve time synchronization based on the wireless sensor network time synchronization method of the first aspect; the perception layer is configured to collect monitoring data of the building structure to be monitored, and send the monitoring data to the cloud platform management application layer through the information transmission layer; wherein the monitoring data includes the monitoring data collected by each node, and the monitoring data includes at least one of the following: building internal stress data, acceleration data, velocity data, displacement data, building settlement data, inclination data and crack data; the cloud platform management application layer is configured to receive the monitoring data and analyze the monitoring data to generate a health assessment result of the building to be monitored.
  • the multiple nodes include a root node, multiple relay nodes, and an end node; wherein the root node is set on the top floor of the building to be monitored, the end node is set on the bottom floor of the building to be monitored, and multiple relay nodes are deployed in sequence between the top floor and the bottom floor of the building to be monitored.
  • each node includes: a main control unit, and a time synchronization unit, a sensor unit and a data transmission unit that are communicatively connected to the main control unit;
  • the time synchronization unit is configured to achieve time synchronization between multiple nodes through a wireless sensor network time synchronization method;
  • the sensor unit is configured to collect monitoring data within the corresponding monitoring area and send the monitoring data to the main control unit;
  • the main control unit is configured to obtain the monitoring data and clean the monitoring data; and the cleaned monitoring data is sent to the information transmission layer through the data transmission unit, so that the information transmission layer sends the monitoring data to the cloud platform management application layer.
  • the main control unit is also configured to periodically initiate time synchronization requests to the remaining multiple nodes at preset intervals; or, obtain the time synchronization instructions sent by the cloud platform management application layer, and initiate time synchronization requests to the remaining multiple nodes according to the time synchronization instructions, so that the root node and the remaining multiple nodes can achieve time synchronization; wherein the multiple remaining nodes include end nodes and multiple relay nodes.
  • the node is a root node, it also includes a satellite timing unit that is communicatively connected to the main control unit; the satellite timing unit is configured to obtain a reference clock and use the reference clock as the reference time of the perception layer so that multiple nodes can achieve time synchronization according to the reference clock.
  • the satellite timing unit is configured to obtain a reference clock and use the reference clock as the reference time of the perception layer so that multiple nodes can achieve time synchronization according to the reference clock.
  • each node also includes a power supply unit; wherein, if the node is a root node, the power supply unit is configured to supply power to the main control unit, the time synchronization unit, the satellite timing unit, the sensor unit and the data transmission unit; if the node is a relay node or an end node, the power supply unit is configured to supply power to the main control unit, the time synchronization unit, the sensor unit and the data transmission unit.
  • the sensor unit includes at least one sensor; wherein the type of the sensor includes at least one of the following: a vibration acceleration sensor, a vibration velocity sensor, a vibration displacement sensor, an ambient temperature sensor, an ambient humidity sensor, an ambient wind speed sensor and a MEMS sensor.
  • the type of the sensor includes at least one of the following: a vibration acceleration sensor, a vibration velocity sensor, a vibration displacement sensor, an ambient temperature sensor, an ambient humidity sensor, an ambient wind speed sensor and a MEMS sensor.
  • the root node, the terminal node and multiple relay nodes form a chain sensor network; wherein each node in the chain sensor network serves as a parent node, and is communicatively connected with multiple child nodes arranged on the same floor, and each parent node and the corresponding multiple child nodes form a star subnet.
  • the priority of the chain sensor network is higher than that of the star subnet.
  • the root node and the relay node also have the capability of variable frequency sampling; wherein the sampling frequency varies in the range of 1 Hz to 1000 Hz.
  • the above-mentioned cloud platform management application layer includes a cloud platform, and a cloud database and a display module that are communicatively connected to the cloud platform;
  • the cloud platform is configured to obtain monitoring data, and analyze the monitoring data based on a cloud algorithm to generate a health assessment result of the building to be monitored; and send the monitoring data and the health assessment results to the cloud database for storage; and send the health assessment results to the display module so that the display module displays the health assessment results.
  • the cloud platform is also configured to obtain retrieved data from the cloud database, and analyze the monitoring data and the retrieved data based on the cloud algorithm to generate a health assessment result; wherein the retrieved data includes building internal stress data, acceleration data, velocity data, displacement data, building settlement data, inclination data and crack data under various building safety hazards.
  • the health assessment result includes at least one of the following: building structure dynamic characteristics analysis, vibration classification, abnormal structural behavior identification and location, structural health status assessment and structural damage level assessment prediction.
  • the embodiments of the present application provide a wireless sensor network time synchronization method and a building structure health monitoring system.
  • the nodes in the wireless sensor network complete time synchronization through a top-down, three-way information interaction method, and serve as a perception layer in the building structure health monitoring system to collect monitoring data of the building structure to be monitored, and send the monitoring data to the cloud platform management application layer through the information transmission layer;
  • the cloud platform management application layer receives the monitoring data, analyzes the monitoring data, and generates a health assessment result of the building to be monitored, thereby using wireless communication technology inside the building structure to monitor the health of the building structure, that is, through low-power spread spectrum communication technology, strong penetration, wide coverage and low-power transmission of signals across multiple floors or walls are achieved, thereby ensuring the time synchronization of the sensor network; and the above-mentioned spread spectrum communication technology also takes into account the linear drift of the clock difference between nodes, further ensuring the time synchronization accuracy of the perception layer network, and has good practical value.
  • FIG1 is a schematic diagram of the synchronization principle of the RBS protocol in the existing time synchronization method
  • FIG2 is a schematic diagram of TPSN protocol synchronization in an existing time synchronization method
  • FIG3 is a schematic diagram of PTP protocol synchronization in an existing time synchronization method
  • FIG4 is a flow chart of a wireless sensor network time synchronization method provided in an embodiment of the present application.
  • FIG5 is a schematic diagram of a wireless sensor network time synchronization method provided in an embodiment of the present application.
  • FIG6 is a schematic diagram of the structure of a building structure health monitoring system provided in an embodiment of the present application.
  • FIG7 is a schematic diagram of the structure of a node provided in an embodiment of the present application.
  • FIG8 is a schematic diagram of the structure of another node provided in an embodiment of the present application.
  • FIG. 9 is a schematic diagram of a sensor network structure provided in an embodiment of the present application.
  • the existing methods for time synchronization in wireless networks mainly use synchronization protocols, including but not limited to: RBS (Reference Broadcast Synchronization) protocol, TPSN (Timing-Sync Protocol for Sensor Networks) protocol, PTP (Precision Time Synchronization Protocol) protocol and FTSP (Flooding Time Synchronization Protocol) protocol, etc.
  • RBS Reference Broadcast Synchronization
  • TPSN Timing-Sync Protocol for Sensor Networks
  • PTP Precision Time Synchronization Protocol
  • FTSP Flooding Time Synchronization Protocol
  • RBS protocol As shown in Figure 1, a parent node sends a broadcast message, and two different child nodes (child node 1 and child node 2) receive the broadcast message and record the time of receiving the message. The two child nodes exchange the recorded time of receiving the parent node broadcast message, thereby obtaining the clock difference ⁇ t between the child nodes. Any of the two child nodes updates the local time according to this clock difference, thereby completing the time synchronization between the two receiving nodes.
  • This method requires multiple child nodes to exchange information to complete time synchronization. However, in fact, the chain wireless sensor network link arranged vertically along the building is very long, and the nodes are separated by multiple floors.
  • the parent node (n level) can generally only communicate with the nodes of the previous level (n-1) and the next level (n+1), while the n-1 level node and the n+1 level node cannot communicate due to the dozens of floors between them.
  • the parent node cannot communicate with all child nodes, resulting in the signal sent by the parent node being difficult to cover the entire building. Therefore, this method is not suitable for the synchronization of wireless sensor networks in high-rise building structures;
  • (2) TPSN protocol This protocol includes a hierarchical discovery phase and a time synchronization phase.
  • the time synchronization phase adopts a “bottom-up”, two-way information exchange method.
  • the parent and child nodes exchange messages with timestamps. Specifically, the child node first sends a request to the parent node at time t1 to complete time synchronization. The parent node then sends a request to the parent node at time t2. The request is received at time t2 , and the response information is sent at time t3 . The child node obtains the response information at time t4 . The child node calculates the clock difference ⁇ t with the parent node, and updates the local time according to this clock difference to complete the synchronization.
  • the synchronization error of this method depends on the number of synchronization hops in the network.
  • the number of network hops is large, which will lead to poor time synchronization accuracy of the entire network;
  • PTP protocol This protocol adopts a "top-down" synchronization method with four information interactions.
  • the parent and child nodes exchange messages with timestamps. Specifically, the parent node first sends a synchronization request to the child node at time t1 . The child node receives the request at time t2 and sends a response message at time t3 . The parent node obtains the response message at time t4 . The child node calculates the clock difference ⁇ t with the parent node and updates the local time based on this clock difference to complete synchronization with the parent node.
  • this method achieves high time synchronization accuracy, it requires a large number of information interactions to complete a single synchronization between nodes, and the communication efficiency is low.
  • satellite and conventional radio signals are difficult to achieve communication between nodes in high-rise buildings. Therefore, spread spectrum communication technology is considered.
  • the characteristic of spread spectrum communication technology is that the modulation and demodulation time is long. The time required to complete a single synchronization between nodes increases with the increase in the number of information interactions between nodes, which will lead to an increase in the system time linear drift error in the sensor network time synchronization process;
  • This protocol uses the root node to periodically broadcast synchronization information packets containing time stamps.
  • the receiving node records the local time when the synchronization message arrives.
  • the node obtains a set of time stamp pairs (the global time stamp sent and the local received time stamp, called reference points).
  • the node uses linear regression to calculate the clock drift rate relative to the time source node, thereby estimating the global time and finally completing synchronization.
  • this method has high accuracy and good scalability, it has high network overhead.
  • Each node needs to collect enough reference points to complete time synchronization with the upper-level node. Since it takes too long to complete a single time synchronization between nodes, the linear drift error of the system time in the sensor network time synchronization process will increase significantly.
  • the above TPSN protocol, PTP protocol and FTSP protocol are mainly used in wired transmission and wireless transmission protocols with faster transmission rates (such as Zigbee, Bluetooth, 4G), but the signal penetration ability of these protocols is weak; and the wireless transmission protocol (LoRa) with strong signal penetration ability has a slow data transmission rate, and it takes a long time to complete network time synchronization, resulting in excessive cumulative errors in the linear drift of system time in the sensor network time synchronization process.
  • the existing wireless time synchronization protocol is not applicable, and the efficient network level synchronization mechanism for this type of network structure needs to be further studied.
  • Spread spectrum technology is a technology that uses a frequency bandwidth much wider than the signal bandwidth to transmit information. It has the advantages of strong anti-interference ability, low power consumption, and anti-multipath effect. It is widely used in radar detection, underwater acoustic communication, laser communication, ultra-wideband communication, etc.
  • radar detection underwater acoustic communication
  • laser communication ultra-wideband communication
  • spread spectrum technology has the problem of long air transmission time of signals.
  • the existing wireless time synchronization methods cannot eliminate the linear drift problem of time error during time synchronization. Take LoRa technology as an example, as shown in Table 1:
  • the signal air transmission time Toa increases exponentially with the increase of SF (Spreading Factor).
  • SF Spread Factor
  • the network link is very long, the more floors the nodes cross, the more severe the isolation of the radio signal by the floor slab, the larger the SF needs to be, and the longer it takes to complete a single time synchronization between nodes.
  • the cumulative error caused by clock drift during network synchronization increases significantly. Therefore, it is necessary to propose a time synchronization mechanism that adapts to the characteristics of spread spectrum technology to ensure the accuracy of time synchronization based on spread spectrum communication.
  • the embodiment of the present application provides a wireless sensor network time synchronization method and a building structure health monitoring system, in which the nodes in the wireless sensor network complete time synchronization through a top-down, three-way information interaction method.
  • the parent node can actively synchronize with the child node at the first time after completing the synchronization, thereby shortening the time synchronization time of the entire wireless sensor network as much as possible and reducing the error caused by the system time drift.
  • the wireless sensor network time synchronization method proposed in the embodiment of the present application can also consider the influence of the linear drift of the system time during synchronization, further reducing the time synchronization error.
  • the wireless sensor network time synchronization method and the acquisition system serve as the perception layer in the building structure health monitoring system to collect the monitoring data of the building structure to be monitored, and send the monitoring data to the cloud platform management application layer through the information transmission layer; the cloud platform management application layer receives the monitoring data, analyzes the monitoring data, and generates the health assessment results of the building to be monitored, thereby using wireless communication technology inside the building structure to perform health monitoring on the building structure.
  • the embodiment of the present application can use low-power spread spectrum communication technology to realize wireless time synchronization between monitoring nodes across multiple floors or walls, which has good practical value.
  • the embodiment of the present application provides a method for time synchronization of a wireless sensor network, wherein the wireless sensor network includes a parent node and multiple child nodes, and the parent node is sequentially connected to the multiple child nodes for communication. As shown in FIG4 , the method includes the following steps:
  • Step S402 the parent node obtains the reference clock and sends a synchronization Sync message to the child node closest to the parent node; wherein the synchronization Sync message carries the sending time T 1 of the parent node;
  • the time synchronization is completed between nodes in the wireless sensor network in a “top-down” and three-way information interaction manner.
  • the parent node obtains the reference clock, where the reference clock can be sent by the GPS system or the Beidou satellite, and can be set according to the actual situation.
  • the parent node After the parent node obtains the reference clock, it sends a synchronization Sync message to the child node closest to the parent node to request the child node to perform time synchronization; at the same time, the sending time T 1 of the parent node sending the synchronization Sync message is recorded, and the sending time T 1 of the parent node is carried in the synchronization Sync message, where the message contains 2 T 1 (the message information volume is equal to avoid additional errors caused by asymmetric paths).
  • Step S404 the child node records the receiving time T 2 of the synchronization Sync message, and sends a synchronization request Req message to the parent node; wherein the synchronization request Req message carries the receiving time T 2 and the sending time T 3 of the synchronization request Req message;
  • Step S406 the parent node receives the synchronization request Req message, and feeds back a Resp message to the child node; wherein the Resp message carries the reception time T 4 of the synchronization request Req message and the sending time T 5 of the Resp message;
  • Step S408 the child node records the receiving time T 6 of receiving the Resp message and the corrected time T 7 before the child node corrects the local clock, and calculates the clock difference according to the sending time T 1 , receiving time T 2 , sending time T 3 , receiving time T 4 , sending time T 5 , receiving time T 6 and corrected time T 7 , and performs time synchronization correction on the corrected time T 7 according to the clock difference to obtain the corrected system time;
  • T master T slave + ⁇ i .
  • Ti is the time of the child node
  • k is the linear drift rate of ⁇ i
  • ⁇ 2 is the clock difference between the parent node and the child node corresponding to time T2 .
  • T 1 the propagation time of the radio signal in the actual building space.
  • T 2 -T 1 - ⁇ 2 + ⁇ t (2)
  • T 4 -T 3 ⁇ 4 + ⁇ t (3)
  • T 6 -T 5 - ⁇ 6 + ⁇ t (4)
  • the child node corrects the clock difference corresponding to the time T 7 of the local clock:
  • ⁇ 7 represents the clock difference
  • k represents the linear drift rate. Therefore, the child node performs time correction (T 7 + ⁇ 7 ) according to the correction time T 7 and the clock difference ⁇ 7 to obtain the corrected system time of the child node.
  • Step S410 after the sub-node synchronization is completed, the system time is sent to the next sub-node that is in communication connection with the sub-node, so that the next sub-node completes the time synchronization, and so on, until the last sub-node completes the time synchronization.
  • the sub-node After the above-mentioned sub-node completes time synchronization, it sends the corrected system time to the next sub-node that is connected to the sub-node for communication, so that the sub-node completes time synchronization in accordance with the above-mentioned "top-down" and three-way information interaction method; and so on, until the last sub-node among multiple sub-nodes completes time synchronization, thereby realizing time synchronization between multiple nodes in the wireless sensor network.
  • the parent node obtains the reference clock of the satellite timing as the clock reference of the entire sensor network, and the parent node initiates time synchronization to the subordinate node, and each child node calculates the time difference with the parent node and updates the local clock (the synchronization between the two nodes is equivalent to completing a transmission of the precise clock), thereby realizing the time synchronization between the nodes of the wireless sensor network.
  • the linear drift of the clock difference is also considered in the time synchronization, thereby reducing the impact of the transmission error and further ensuring the accuracy of time synchronization between nodes.
  • the embodiment of the present application provides a building structure health monitoring system, as shown in Figure 6, the system includes a perception layer 110, an information transmission layer 120 and a cloud platform management application layer 130; wherein the perception layer 110 includes multiple nodes, and the multiple nodes achieve time synchronization based on the above wireless sensor network time synchronization method. It should be noted that the specific number of nodes can be determined according to the height of the building to be monitored.
  • the perception layer 110 is configured to collect monitoring data of the building structure to be monitored, and send the monitoring data to the cloud platform management application layer 130 through the information transmission layer 120; wherein the monitoring data includes the monitoring data collected by each node, and the monitoring data includes at least one of the following: internal stress data of the building, acceleration data, velocity data, displacement data, building settlement data, inclination data and crack data; the cloud platform management application layer 130 is configured to receive the monitoring data, and analyze the monitoring data to generate a health assessment result of the building to be monitored, where the health assessment result includes but is not limited to analysis of dynamic characteristics of the building structure (such as vibration amplitude, natural frequency, modal analysis, etc.), vibration classification, identification and positioning of abnormal structural behavior, structural health status assessment and structural damage level assessment prediction, etc., which can be specifically set according to actual conditions.
  • the health assessment result includes but is not limited to analysis of dynamic characteristics of the building structure (such as vibration amplitude, natural frequency, modal analysis, etc.), vibration classification, identification and positioning of abnormal structural behavior, structural health status assessment and structural
  • the multiple nodes in the perception layer 110 include a root node R, multiple relay nodes J, and an end node K; wherein the root node R is arranged on the top floor of the building to be monitored, the end node K is arranged on the bottom floor of the building to be monitored, and multiple relay nodes J are sequentially deployed between the top floor and the bottom floor of the building to be monitored, where the multiple relay nodes J include J 1 , J 2 ??J n .
  • each node includes: a main control unit 21, and a time synchronization unit 22, a sensor unit 23 and a data transmission unit 24 that are communicatively connected to the main control unit 21;
  • the time synchronization unit 22 is configured to achieve time synchronization between multiple nodes through spread spectrum communication technology and linear drift of clock differences between nodes;
  • the sensor unit 23 is configured to collect monitoring data of structures in the corresponding monitoring area, and send the monitoring data to the main control unit 21;
  • the main control unit 21 is configured to obtain monitoring data and clean the monitoring data; and, send the cleaned monitoring data to the information transmission layer 120 through the data transmission unit 24, so that the information transmission layer 120 sends the monitoring data to the cloud platform management application layer 130.
  • the main control unit 21 may be composed of one or more MCU modules, including but not limited to Raspberry Pi, STM and iOS MCU modules; in addition, in practical applications, the main control unit 21 is also configured to perform command control on all operation behaviors of the monitoring node, such as initiating control commands through the MCU module and executing related operations; and the main control unit 21 may also be implanted with edge algorithms, and perform lightweight computing tasks such as data cleaning, data feature recognition, and threshold trigger alarms on the monitoring data according to the edge algorithms. Therefore, for each node, due to the use of edge algorithms for data cleaning and lightweight processing, the burden on the data transmission unit 24 and the cloud platform management application layer 130 is further reduced, and the overall performance of the monitoring system is optimized.
  • the time synchronization unit 22 includes but is not limited to the LoRa spread spectrum communication module, and any communication module using spread spectrum communication technology is acceptable; the data transmission unit 24 uses conventional wireless transmission technology to upload the monitoring data and node status data (such as time synchronization status, operating status, chip temperature, remaining power, etc.) sent by the main control unit 21 to the cloud platform management application layer 130.
  • the data transmission unit 24 includes but is not limited to 4G and Wi-Fi wireless communication modules, and any communication module using conventional wireless communication technology is acceptable.
  • the Internet of Things application layer protocols used include but are not limited to MQTT (Message Queuing Telemetry Transport), CoAP (The Constrained Application Protocol), and HTTP (Hyper Text Transfer Protocol).
  • a single communication module can also be responsible for both time synchronization and data transmission.
  • the sensor unit 23 includes at least one sensor; wherein the types of sensors include but are not limited to: vibration acceleration sensor, vibration velocity sensor, vibration displacement sensor, ambient temperature sensor, ambient humidity sensor, etc. The type and quantity of the specific sensors can be set according to actual conditions.
  • the main control unit 21 of each node can transmit the monitoring data directly to the cloud platform management application layer 130 through the information transmission layer 120; it can also transmit its own corresponding monitoring data to the previous node, such as starting from the bottom floor of the building to be monitored, and transmitting the monitoring data from bottom to top in sequence, that is, on the basis of time synchronization, the end node K sends the collected monitoring data to the previous node, that is, the last relay node, and the relay node sends the corresponding monitoring data and the monitoring data sent by the end node to the previous relay node at the same time, and so on, until the root node forwards the corresponding monitoring data and the monitoring data of the remaining multiple nodes to the cloud platform management application layer 130 through the information transmission layer 120 at the same time. Due to the time synchronization between each node, the transmission efficiency of the monitoring data is also guaranteed, thereby improving the health monitoring efficiency of the building.
  • the root node R and the relay node J in the perception layer 110 also have the ability of variable frequency sampling, and the sampling frequency range is 1Hz to 1000Hz. In practical applications, according to actual needs, a lower sampling frequency can be used for daily monitoring.
  • the cloud platform management application layer 130 can send a sampling frequency setting instruction, and the main control unit 21 sets the sampling frequency of each sensor in the sensor unit 23 according to the sampling frequency setting instruction, thereby increasing the sampling frequency of the node, obtaining more intensive data samples, and thus improving the accuracy of the health assessment results of the monitored building.
  • the main control unit 21 is also configured to periodically initiate time synchronization requests to the remaining multiple nodes at a preset interval; or, obtain the time synchronization instruction sent by the cloud platform management application layer 130, and initiate time synchronization requests to the remaining multiple nodes according to the time synchronization instruction, so that the root node and the remaining multiple nodes can achieve time synchronization; wherein the multiple remaining nodes include terminal nodes and multiple relay nodes.
  • the main control unit 21 in the root node can periodically initiate system time synchronization at a fixed time interval, thereby achieving time synchronization between multiple nodes in the perception layer 110; it can also control the root node to initiate network time synchronization at any time through the time synchronization instruction issued by the cloud platform management application layer 130 under abnormal conditions.
  • the relay node J and the end node K are the same.
  • the root node R is further provided with a satellite timing unit 26 in communication connection with the main control unit 21 on the structure of the relay node J or the end node K; the satellite timing unit 26 is configured to obtain a reference clock and use the reference clock as the reference time of the perception layer 110, so that multiple nodes can achieve time synchronization according to the reference clock, that is, multiple relay nodes J and the end node K are time synchronized based on the reference clock obtained by the satellite timing unit 26 in the root node R.
  • each node also includes a power supply unit 25; wherein, if the node is a root node, as shown in FIG8, the power supply unit 25 is configured to supply power to the main control unit 21, the time synchronization unit 22, the satellite timing unit 26, the sensor unit 23 and the data transmission unit 24; if the node is a relay node or an end node, as shown in FIG7, the power supply unit 25 is configured to supply power to the main control unit 21, the time synchronization unit 22, the sensor unit 23 and the data transmission unit 24.
  • the power supply unit 25 includes but is not limited to UPS (Uninterrupted Power Supply) power supply, city power, solar energy and micro wind power generation, etc., and can be specifically set according to actual conditions.
  • UPS Uninterrupted Power Supply
  • the information transmission layer 120 includes a time synchronization layer 121 and a data transmission layer 122; wherein the time synchronization layer 121 refers to a time synchronization signal transmission link between nodes based on spread spectrum communication technology, and the data transmission layer 122 refers to a data transmission link between the perception layer 110 and the cloud platform management application layer 130, such as transmission of monitoring data, etc.
  • the cloud platform management application layer 130 includes a cloud platform 131, a cloud database 132, and a display module 133; the cloud platform 131 is configured to obtain monitoring data, and analyze the monitoring data based on a cloud algorithm to generate a health assessment result of the building to be monitored; and the monitoring data and the health assessment result are sent to the cloud database 132 for storage, and the health assessment result is also sent to the display module 133 so that the display module 133 displays the health assessment result.
  • the cloud platform 131 may also retrieve the data stored in the cloud database 132, such as the internal stress data, acceleration data, velocity data, displacement data, building settlement data, inclination data and crack data of various building safety hazards, and analyze the monitoring data and the retrieved data.
  • the analysis content includes but is not limited to structural dynamic characteristics analysis (such as vibration amplitude, natural frequency, modal analysis, etc.), vibration classification, abnormal structural behavior identification and positioning, structural health status assessment and prediction, etc., so as to generate the health assessment results of the building to be monitored.
  • the relay node J1 can use the root node R as the parent node and implement time synchronization between multiple nodes according to the above-mentioned wireless sensor network time synchronization method; similarly, between two adjacent relay nodes and between the last relay node and the end node, time synchronization between multiple nodes can be implemented according to the above-mentioned wireless sensor network time synchronization method, thereby realizing time synchronization between multiple nodes in the perception layer.
  • each relay node multiple nodes can be set on the corresponding floor.
  • the root node, the terminal node and the multiple relay nodes form a chain sensor network; wherein each node in the chain sensor network can also serve as a parent node, communicating with multiple child nodes set on the same floor, and each parent node and the corresponding multiple child nodes form a star subnet; and, in the time synchronization process, the priority of the chain sensor network is higher than that of the star subnet.
  • the root node R is arranged on the top floor of the building, and relay nodes J of each level are deployed from the top floor to the end node K in sequence, forming a chain sensor network.
  • All nodes in the chain sensor network can be used as parent nodes, connected to multiple child nodes, forming multiple star subnets, corresponding to the scenario of arranging multiple monitoring nodes on the same floor in actual buildings.
  • the above constitutes a chain-star sensor network, thereby meeting the actual needs of high-rise building structure monitoring.
  • the root node R obtains the reference clock through the satellite timing unit 26 and initiates the time synchronization of the entire network.
  • the reference clock is transmitted from top to bottom along the chain network to the end node, realizing cross-level chain time synchronization; and, in each star subnet, the reference clock is transmitted from the parent node to the child node.
  • the time synchronization of the chain sensor network takes precedence over the time synchronization of the star subnet, that is, after the parent node obtains the reference clock, it first transmits the reference clock to the lower relay node, and then to the child node in the network at this level, thereby realizing the rapid transmission of the reference clock in the network.
  • the two nodes complete synchronization according to the time synchronization mechanism between nodes in the previous part.
  • the relay node After the relay node completes the time synchronization with the upper-level relay node, it immediately sends a time synchronization request to the lower-level relay node and the child node at this level, and quickly passes on the latest reference clock (that is, the corrected system time), thereby ensuring the overall time synchronization accuracy of the network.
  • the node After completing the time synchronization with the upper-level node, the node also stores the synchronization information record locally and uploads it to the cloud platform management application layer 130.
  • the sensor network can adopt a simple chain structure.
  • multiple root nodes can be set, such as setting the relay node in the middle of the link as the root node (corresponding to setting the root node in the middle equipment layer of a high-rise building), forming a tree structure, and transmitting the reference clock from the middle of the building to the upper and lower directions, thereby shortening the network's time synchronization link by half without significantly increasing the communication pressure of the root node, and improving the system's time synchronization accuracy.
  • the sensor network structure includes but is not limited to a chain structure, a star structure, a tree structure, and a hybrid structure can also be used, which can be set according to the specific structure of the building.
  • the time synchronization unit 22 in each node also uses spread spectrum communication technology to realize the time synchronization of the sensor network in the satellite and conventional radio denial environment inside the high-rise building.
  • the adaptive adjustment mechanism of the spread spectrum factor SF allows long-distance low-power transmission and short-distance high-speed transmission to be achieved.
  • SF spread spectrum factor
  • the relay nodes at adjacent levels use different transmission frequencies, that is, the anti-interference ability of the synchronization signal is enhanced by frequency hopping technology.
  • the building structure health monitoring system realizes system integration from the perception layer to the cloud platform management application layer.
  • the system at least includes: a perception layer, an information transmission layer and a cloud platform management application layer; wherein the perception layer includes sensors, MCU modules, spread spectrum communication data transmission units, etc., and through integrated design, a high-performance, low-power wireless monitoring node is developed; the information transmission layer includes a time synchronization mechanism between nodes and a sensor network level time synchronization mechanism; the cloud platform management application layer analyzes the monitoring data based on the cloud algorithm, and displays the generated health assessment results through the display module.
  • the system has the following advantages: (1) For the satellite and conventional radio denial environment inside high-rise buildings, the low-power spread spectrum communication technology is used to achieve strong penetration, wide coverage and low-power transmission of signals across multiple floors or walls, ensuring the time synchronization and communication stability of the sensor network; (2)
  • the time synchronization mechanism includes the node-to-node time synchronization mechanism and the sensor network level time synchronization mechanism. The linear drift of the clock difference between nodes is taken into account.
  • the sensor network level adopts the principle of chain synchronization priority to ensure the overall time synchronization accuracy of the network; (3)
  • the system integration from the perception layer to the cloud platform management application layer is realized.
  • the front-end visualization web page displays the analysis results in real time, thereby not only realizing the health monitoring of high-rise buildings, but also ensuring the time synchronization accuracy and communication stability of the sensor network during the monitoring process, thereby ensuring the accuracy of health monitoring, and having good practical value.
  • the terms “installed”, “connected”, and “connected” should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components.
  • installed should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components.
  • the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium that is executable by a processor.
  • the technical solution of the present application or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application.
  • the aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.
  • the wireless sensor network time synchronization method and building structure health monitoring system provided in the embodiments of the present application can use wireless communication technology inside the building structure to monitor the health of the building structure, and through low-power spread spectrum communication technology, achieve strong penetration, wide coverage and low-power transmission of signals across multiple floors or walls, thereby ensuring the time synchronization of the sensor network; and, the above-mentioned spread spectrum communication technology also takes into account the linear drift of the clock difference between nodes, further ensuring the time synchronization accuracy of the perception layer network, and has good practical value.

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Abstract

本申请提供了无线传感网络时间同步方法及建筑结构健康监测系统；其中，无线传感网络中节点间通过自上而下、三次信息交互的方式完成时间同步，并作为建筑结构健康监测系统中的感知层，以采集待监测建筑结构的监测数据，并将监测数据通过信息传输层发送至云平台管理应用层；云平台管理应用层接收监测数据，并对监测数据进行分析，生成待监测建筑的健康评估结果，从而在建筑结构内部利用无线通信技术对建筑结构进行健康监测，即通过低功耗扩频通信技术实现了信号在跨越多重楼板或墙体情况下的强穿透、广覆盖和低功耗传输，保证了传感器网络的时间同步。

Description

无线传感网络时间同步方法及建筑结构健康监测系统
相关申请的交叉引用
本申请要求于2023年02月03日提交中国专利局的申请号为2023100535763、名称为“无线传感网络时间同步方法及建筑结构健康监测系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及建筑监测技术领域，尤其是涉及无线传感网络时间同步方法及建筑结构健康监测系统。
背景技术
目前，高层建筑数量越来越多，且，建筑物的使用年限较长，建筑外部激振、内部设备异常振动可能导致结构振动幅值过大、变形过大、舒适性降低以及群众恐慌等，因此，对高层建筑进行结构的健康监测具有重要意义。
为了对建筑结构进行健康监测，现有考虑时间同步的无线基础设施监测系统主要采用GPS(Global Positioning System，全球定位系统)授时同步或者常规无线通信技术(如紫蜂协议ZigBee、无线网络通信技术Wi-Fi和蓝牙等)实现时间同步，但是，GPS及常规无线电信号具有穿透能力弱的缺点，难以用于高层建筑内部无线电信号被结构构件隔绝的拒止环境，例如，对于建筑内部时间同步信号需要穿透多层楼板或墙体的场景不适用，因此，如何在建筑结构内部利用无线通信技术对建筑结构进行健康监测，并保证时间同步精度是亟需解决的问题。
申请内容
有鉴于此，本申请的目的在于提供无线传感网络时间同步方法及建筑结构健康监测系统，以缓解上述技术问题，不仅实现了对建筑结构进行健康监测，还保证了无线传感网络的时间同步精度和通信稳定性，具有较好的实用价值。
第一方面，本申请实施例提供了一种无线传感网络时间同步方法，无线传感网络包括父节点以及多个子节点，该方法包括：父节点获取基准时钟，并向距离父节点最近的子节点发送同步Sync报文；其中，同步Sync报文携带有父节点的发送时刻T1；子节点记录接收同步Sync报文的接收时刻T2，并向父节点发送同步请求Req报文；其中，同步 请求Req报文携带有接收时刻T2，以及同步请求Req报文的发送时刻T3；父节点接收同步请求Req报文，并向子节点反馈Resp报文；其中，Resp报文携带有同步请求Req报文的接收时刻T4和Resp报文的发送时刻T5；子节点记录接收Resp报文的接收时刻T6，以及子节点修正本地时钟前的修正时刻T7，并根据发送时刻T1、接收时刻T2、发送时刻T3、接收时刻T4、发送时刻T5、接收时刻T6和修正时刻T7计算得到时钟差值，并根据时钟差值对修正时刻T7进行时间同步修正，得到修正后的系统时间；子节点同步完成后，将系统时间发送至与该子节点通信连接的下一子节点，以使下一子节点完成时间同步，以此类推，直至最后一个子节点完成时间同步。
优选地，上述根据发送时刻T1、接收时刻T2、发送时刻T3、接收时刻T4、发送时刻T5、接收时刻T6和修正时刻T7计算得到时钟差值的步骤，包括：根据下式计算时钟差值：其中，θ7表示时钟差值，k表示线性漂移率。
第二方面，本申请实施例还提供一种建筑结构健康监测系统，该系统包括感知层、信息传输层和云平台管理应用层；其中，感知层包括多个节点，且，多个节点基于第一方面的无线传感网络时间同步方法实现时间同步；感知层，配置成采集待监测建筑结构的监测数据，并将监测数据通过信息传输层发送至云平台管理应用层；其中，监测数据包括每个节点采集的监测数据，监测数据包括以下至少之一：建筑内应力数据、加速度数据、速度数据、位移数据、建筑沉降数据、倾斜度数据和裂缝数据；云平台管理应用层，配置成接收监测数据，并对监测数据进行分析，以生成待监测建筑的健康评估结果。
优选地，多个节点包括根节点、多个中继节点、以及末端节点；其中，根节点设置在待监测建筑的顶层，末端节点设置在待监测建筑的底层，待监测建筑的顶层和底层之间依次部署多个中继节点。
优选地，每个节点均包括：主控单元，以及与主控单元通信连接的时间同步单元、传感器单元和数据传输单元；时间同步单元，配置成通过无线传感网络时间同步方法实现多个节点之间的时间同步；传感器单元，配置成采集对应监测区域内的监测数据，并将监测数据发送至主控单元；主控单元，配置成获取监测数据，并对监测数据进行清洗；以及，将清洗后的监测数据通过数据传输单元发送至信息传输层，以使信息传输层将监测数据发送至云平台管理应用层。
优选地，若节点为根节点，主控单元还配置成按照预设间隔周期性向其余多个节点发起时间同步请求；或者，获取云平台管理应用层发送的时间同步指令，并根据时间同步指令向其余多个节点发起时间同步请求，以使根节点和其余多个节点实现时间同步；其中，多个其余节点包括末端节点以及多个中继节点。
优选地，若节点为根节点，还包括与主控单元通信连接的卫星授时单元；卫星授时单元，配置成获取基准时钟，并将基准时钟作为感知层的基准时间，以使多个节点根据基准时钟实现时间同步。
优选地，每个节点还包括供电单元；其中，若节点为根节点，供电单元配置成对主控单元、时间同步单元、卫星授时单元、传感器单元和数据传输单元进行供电；若节点为中继节点或末端节点，供电单元配置成对主控单元、时间同步单元、传感器单元和数据传输单元进行供电。
优选地，所述传感器单元包括至少一个传感器；其中，所述传感器的类型包括以下至少之一：振动加速度传感器、振动速度传感器、振动位移传感器、环境温度传感器、环境湿度传感器、环境风速传感器以及MEMS传感器。
优选地，根节点、末端节点以及多个中继节点组成链式传感器网络；其中，链式传感器网络中每个节点作为父节点，与设置在同一楼层中的多个子节点通信连接，且，每个父节点与对应的多个子节点组成星型子网。
优选地，在时间同步过程中，链式传感器网络的优先级高于星型子网。
优选地，根节点和中继节点还具备变频采样的能力；其中，采样频率变化范围为1Hz～1000Hz。
优选地，上述云平台管理应用层包括云平台，以及与云平台通信连接的云数据库和显示模块；云平台，配置成获取监测数据，并基于云端算法对监测数据进行分析，生成待监测建筑的健康评估结果；并将监测数据和健康评估结果发送至云数据库进行存储；以及，将健康评估结果发送至显示模块，以使显示模块展示健康评估结果。
优选地，云平台，还配置成获取云数据库中的调取数据，并基于云端算法对监测数据和所述调取数据进行分析，生成健康评估结果；其中，调取数据包括各类建筑安全隐患下的建筑内应力数据、加速度数据、速度数据、位移数据、建筑沉降数据、倾斜度数据和裂缝数据。
优选地，健康评估结果包括以下至少之一：建筑结构动力特性分析、振动分类、异常结构行为识别与定位、结构健康状况评估与结构损伤等级评估预测。
本申请实施例带来了以下有益效果：
本申请实施例提供了无线传感网络时间同步方法及建筑结构健康监测系统，无线传感网络中节点间通过自上而下、三次信息交互的方式完成时间同步，并作为建筑结构健康监测系统中的感知层，以采集待监测建筑结构的监测数据，并将监测数据通过信息传输层发送至云平台管理应用层；云平台管理应用层接收监测数据，并对监测数据进行分析，生成待监测建筑的健康评估结果，从而在建筑结构内部利用无线通信技术对建筑结构进行健康监测，即通过低功耗扩频通信技术实现了信号在跨越多重楼板或墙体情况下的强穿透、广覆盖和低功耗传输，保证了传感器网络的时间同步；以及，上述扩频通信技术还考虑了节点间时钟差的线性漂移，进一步保证了感知层网络的时间同步精度，具有较好的实用价值。
本申请的其他特征和优点将在随后的说明书中阐述，并且，部分地从说明书中变得显而易见，或者通过实施本申请而了解。本申请的目的和其他优点在说明书以及附图中所特别指出的结构来实现和获得。
为使本申请的上述目的、特征和优点能更明显易懂，下文特举较佳实施例，并配合所附附图，作详细说明如下。
附图说明
为了更清楚地说明本申请具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为现有时间同步方法中RBS协议同步原理图；
图2为现有时间同步方法中TPSN协议同步原理图；
图3为现有时间同步方法中PTP协议同步原理图；
图4为本申请实施例提供的一种无线传感网络时间同步方法的流程图；
图5为本申请实施例提供的一种无线传感网络时间同步方法的原理图；
图6为本申请实施例提供的一种建筑结构健康监测系统的结构示意图；
图7为本申请实施例提供的一种节点的结构示意图；
图8为本申请实施例提供的另一种节点的结构示意图；
图9为本申请实施例提供的一种传感器网络结构示意图。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合附图对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
在实际应用中，针对无线网络中的时间同步问题，现有方法主要通过同步协议，包括但不仅限于：RBS(Reference Broadcast Synchronization，参考广播同步)协议、TPSN(Timing-Sync Protocol for Sensor Networks，传感器网络时间同步协议)协议、PTP(Precision Time Synchronization Protocol，精确时间同步协议)协议和FTSP(Flooding Time Synchronization Protocol，泛洪时间同步协议)协议等；具体地，对各个同步协议介绍如下：
(1)RBS协议：如图1所示，通过父节点发出广播消息，两个不同子节点(子节点1和子节点2)接收广播消息并记录接收到消息的时间，两个子节点相互交换所记录的接收到父节点广播消息的时间，从而得到子节点间的时钟差Δt，两个子节点中的任意一个子节点根据这个时钟差更新本地时间，从而完成两个接收节点之间的时间同步。该方法需要多个子节点之间进行信息交换完成时间同步，然而，实际上沿着建筑竖向布置的链式无线传感器网络链路很长，节点相隔多层楼板，由于无线通信距离有限，父节点(n级)一般只能实现与上一级(n-1)和下一级(n+1)的节点进行通信，而n-1级节点与n+1级节点之间由于间隔数十层楼板无法进行通信，且，父节点无法与所有子节点进行通信，导致父节点发送的信号难以覆盖整栋建筑，因此该方法并不适用于高层建筑结构的无线传感器网络同步；
(2)TPSN协议：该协议包括层次发现阶段和时间同步阶段；其中，时间同步阶段采用“自下而上”、两次信息交互的方式，如图2所示，父、子节点间交换带有时间戳的消息，具体地，由子节点在t1时刻首先向父节点发出请求来完成时间同步，父节点在 t2时刻接收到请求，并在t3时刻发送应答信息，子节点在t4时刻获取到应答信息，子节点计算出与父节点的时钟差Δt，并根据这个时钟差更新本地时间完成同步。该方法的同步误差取决于网络中的同步跳数，在高层建筑内部链式传感器网络中，对于网络末端附近的节点而言，网络的跳数较多，将导致整个网络的时间同步精度差；
(3)PTP协议：该协议采用“自上而下”、四次信息交互的同步方式，如图3所示，父、子节点间交换带有时间戳的消息，具体地，由父节点在t1时刻首先向子节点发出同步要求，子节点在t2时刻接收到请求，并在t3时刻发送应答信息，父节点在t4时刻获取到应答信息，子节点计算出与父节点的时钟差Δt，并根据这个时钟差更新本地时间完成与父节点的同步。该方法虽然达到的时间同步精度高，但是，该方法完成节点间单次同步所需的信息交互次数较多，通信效率较低。此外，卫星及常规无线电信号难以在高层建筑中实现节点间的通信，因此考虑采用扩频通信技术，但扩频通信技术的特点在于调制解调时间长，节点间完成单次同步所需的时间随节点间信息交互次数的增加而延长，将导致传感器网络时间同步过程的系统时间线性漂移误差增大；
(4)FTSP协议：该协议利用根节点周期性地广播包含时间标的同步信息包，接收节点记录同步消息达到的时刻的本地时间，当节点接收到一个同步信息，即获得了一组时间标对(发送的全局时间标和本地接收时间标，称为参考点)。当节点收集到足够多的参考点，利用线性回归计算其相对时间源节点的时钟漂移率，从而估算出全局时间，最终完成同步。该方法虽然精度高、扩展性好，但是网络开销大，每个节点需要收集到够多的参考点才能完成与上级节点的时间同步，由于完成节点间单次时间同步的耗时过长，将导致传感器网络时间同步过程的系统时间线性漂移误差显著增大。
综上，上述TPSN协议、PTP协议和FTSP协议还主要应用于传输速率较快的有线传输以及无线传输协议(如Zigbee、蓝牙、4G)，但这些协议的信号穿透能力弱；且，信号穿透能力强的无线传输协议(LoRa)的数据传输速率较慢，完成网络时间同步耗时长，导致传感器网络时间同步过程的系统时间线性漂移累积误差过大。以及，由于采用扩频通信技术的高层建筑内传感器网络链路较长，且高层建筑中节点之间通信条件受限，现有无线时间同步协议并不适用，针对该类网络结构的高效网络层级同步机制有待深入研究。
扩频技术是一种以利用比信号带宽宽得多的频带宽度来传输信息的技术，具有抗干扰能力强、低功耗、抗多径效应的优点，在雷达探测、水声通信、激光通信、超宽带通 信中得到了大量的应用。然而，目前尚无对高层建筑内部基于扩频技术的传感器网络时间同步研究，且扩频技术存在信号空中传输时间长的问题，现有无线时间同步方法无法消除时间同步过程中的时间误差线性漂移问题。以LoRa技术为例，如表1所示：
表1
根据上表可知，信号空中传输时间Toa随SF(Spreading Factor,扩频因子)增大而成倍延长。对于高层建筑链式监测传感器网络，网络链路很长，节点间跨层数越多，无线电信号受楼板隔绝越严重，SF需越大，节点间完成单次时间同步耗时越长。此时，网络同步过程中随时钟漂移产生的累积误差显著增大，因此，有必要提出一种适应扩频技术特点的时间同步机制以保证基于扩频通信时间同步精度。
基于此，本申请实施例提供了无线传感网络时间同步方法及建筑结构健康监测系统，无线传感网络中节点间通过自上而下、三次信息交互的方式完成时间同步。父节点可以在完成同步后第一时间主动与子节点同步，从而尽可能缩短整个无线传感器网络时间同步时间，减少系统时间漂移产生的误差。与此同时，本申请实施例提出的无线传感网络时间同步方法还可在同步时考虑系统时间线性漂移的影响，进一步减小了时间同步误差。无线传感网络时间同步方法和采集系统作为建筑结构健康监测系统中的感知层，以采集待监测建筑结构的监测数据，并将监测数据通过信息传输层发送至云平台管理应用层；云平台管理应用层接收监测数据，并对监测数据进行分析，生成待监测建筑的健康评估结果，从而在建筑结构内部利用无线通信技术对建筑结构进行健康监测。本申请实施例可利用低功耗扩频通信技术实现监测节点间跨越多重楼板或墙体情况下的无线时间同步，具有较好的实用价值。
为便于对本实施例进行理解，下面首先对本申请实施例提供的一种无线传感网络时间同步方法进行详细介绍。
本申请实施例提供了一种无线传感网络时间同步方法；其中，无线传感网络包括父节点以及多个子节点，且，父节点与多个子节点依次通信连接。如图4所示，该方法包括以下步骤：
步骤S402，父节点获取基准时钟，并向距离父节点最近的子节点发送同步Sync报文；其中，同步Sync报文携带有父节点的发送时刻T1；
具体地，如图5所示，无线传感网络中节点间采用“自上而下”、三次信息交互的方式完成时间同步。首先，父节点获取基准时钟，这里基准时钟可以为GPS系统发送，也可以为北斗卫星发送，具体可以根据实际情况进行设置。然后，父节点获取基准时钟后，向与父节点距离最近的子节点发送同步Sync报文，以要求子节点进行时间同步；同时，记录父节点发送同步Sync报文的发送时刻T1，以及，在同步Sync报文中携带有父节点的发送时刻T1，这里报文包含2个T1(报文信息量等长，以避免非对称路径带来额外的误差)。
步骤S404，子节点记录接收同步Sync报文的接收时刻T2，并向父节点发送同步请求Req报文；其中，同步请求Req报文携带有接收时刻T2，以及同步请求Req报文的发送时刻T3；
步骤S406，父节点接收同步请求Req报文，并向子节点反馈Resp报文；其中，Resp报文携带有同步请求Req报文的接收时刻T4和Resp报文的发送时刻T5；
步骤S408，子节点记录接收Resp报文的接收时刻T6，以及子节点修正本地时钟前的修正时刻T7，并根据发送时刻T1、接收时刻T2、发送时刻T3、接收时刻T4、发送时刻T5、接收时刻T6和修正时刻T7计算得到时钟差值，并根据时钟差值对修正时刻T7进行时间同步修正，得到修正后的系统时间；
具体地，设置父节点和子节点的时钟差为θi，即Tmaster＝Tslave+θi。假设同步过程中传感器时钟误差线性漂移，则θi的表达式如下公式所示：
θi＝k(Ti-T2)+θ2   (1)
其中，Ti为子节点的时间，k为θi的线性漂移率，θ2为T2时刻对应的父节点和子节点的时钟差。
以及，子节点得到了T1～T6之间的相关关系如式(2)-(4)所示，其中，Δt为上、下行链路网络延迟，包括Tcode、Toa和Ts，这里Tcode表示MCU(Micro Control Unit，微控制单元)编码解码时间，Toa为扩频通信调制解调时间，T1为无线电信号在实际建筑空间中的传播时间。
T2-T1＝-θ2+Δt   (2)
T4-T3＝θ4+Δt   (3)
T6-T5＝-θ6+Δt   (4)
将公式(1)代入到(3)-(4)，得到公式(5)和(6)。特殊的是，父节点在T4时刻对应子节点T3时刻，近似取T4＝T3+Δt，需将T4代入式(1)再代入(3)中得式(6)：
T4-T3＝k(T3+Δt-T2)+θ2+Δt   (5)
T6-T5＝-k(T6-T2)-θ2+Δt   (6)
根据上述公式(2)(6)，消去θ2和Δt，可以得到：
根据公式(2)和(5)，消去θ2，得到：
将上述公式(8)代入公式(2)，可以得到：
则子节点修正本地时钟的时刻T7对应的时钟差值：
其中，θ7表示时钟差值，k表示线性漂移率。因此，子节点根据修正时刻T7和时钟差值θ7进行时间修正(T7+θ7)，得到子节点修正后的系统时间。
步骤S410，子节点同步完成后，将系统时间发送至与该子节点通信连接的下一子节点，以使下一子节点完成时间同步，以此类推，直至最后一个子节点完成时间同步。
上述子节点完成时间同步后，将修正后的系统时间发送至与该子节点通信连接的下一子节点，以使子节点按照上述“自上而下”、三次信息交互的方式完成时间同步；依次类推，直至多个子节点中最后一个子节点完成时间同步，从而实现无线传感网络中多个节点间的时间同步。
因此，本申请实施例提供的无线传感网络时间同步方法，父节点获取卫星授时的基准时钟，作为整个传感器网络的时钟基准，并由父节点向下级节点发起时间同步，各个子节点计算出与父节点的时间差，更新本地时钟(两个节点之间的同步相当于完成了精准时钟的一次传递)，实现了无线传感网络节点间的时间同步。此外，由于基准时钟在网络中的传递实际上是存在传递误差的(节点间完成一次同步的时间越长，精准时钟的传递误差越大)，因此，在时间同步中还考虑了时钟差的线性漂移，从而减小传递误差的影响，进一步保证了节点间时间同步精度。
基于上述无线传感网络时间同步方法，本申请实施例提供了一种建筑结构健康监测系统，如图6所示，该系统包括感知层110、信息传输层120和云平台管理应用层130；其中，感知层110包括多个节点，且，多个节点基于上述无线传感网络时间同步方法实现了时间同步。需要说明的是，具体节点的数量可以根据待监测建筑的高度确定。
具体地，感知层110配置成采集待监测建筑结构的监测数据，并将监测数据通过信息传输层120发送至云平台管理应用层130；其中，监测数据包括每个节点采集的监测数据，且，监测数据包括以下至少之一：建筑内应力数据、加速度数据、速度数据、位移数据、建筑沉降数据、倾斜度数据和裂缝数据；云平台管理应用层130，配置成接收监测数据，并对监测数据进行分析，生成待监测建筑的健康评估结果，这里健康评估结果包括但不仅限于建筑结构动力特性分析(如振动幅值、自振频率、模态分析等)、振动分类、异常结构行为识别与定位、结构健康状况评估与结构损伤等级评估预测等，具体可以根据实际情况进行设置。
优选地，如图6所示，感知层110中多个节点包括根节点R、多个中继节点J、以及末端节点K；其中，根节点R设置在待监测建筑的顶层，末端节点K设置在待监测建筑的底层，待监测建筑的顶层和底层之间依次部署多个中继节点J，这里多个中继节点J包括J1、J2…Jn。
此外，如图7所示，每个节点均包括：主控单元21，以及与主控单元21通信连接的时间同步单元22、传感器单元23和数据传输单元24；时间同步单元22配置成通过扩频通信技术和节点间时钟差的线性漂移实现多个节点之间的时间同步；传感器单元23则配置成采集对应监测区域内的结构的监测数据，并将监测数据发送至主控单元21；主控单元21配置成获取监测数据，并对监测数据进行清洗；以及，将清洗后的监测数据通过数据传输单元24发送至信息传输层120，以使信息传输层120将监测数据发送至云平台管理应用层130。
具体地，主控单元21可由一个或多个MCU模块组成，包括但不仅限于树莓派、STM和Arduino MCU模块等；此外，在实际应用中，主控单元21还配置成对监测节点的所有操作行为进行指令控制，如通过MCU模块发起控制指令并执行相关操作来完成；以及，主控单元21中还可植入边缘算法，并根据边缘算法对监测数据进行数据清洗、数据特征识别、阈值触发警报等轻量计算工作。因此，对于每个节点，由于采用边缘算法进行了数据清洗和轻量化处理，进一步减小了数据传输单元24和云平台管理应用层130的负担，优化了监测系统的整体性能。
此外，时间同步单元22包括但不仅限于采用LoRa扩频通信模块，采用扩频通信技术的通信模块均可；数据传输单元24则利用常规无线传输技术将主控单元21发送的监测数据和节点状态数据(如时间同步状态、运行状态、芯片温度、剩余电量等)上传至云平台管理应用层130，在实际应用中，数据传输单元24包括但不限于4G、Wi-Fi无线通信模块，采用常规无线通信技术的通信模块均可，使用的物联网应用层协议包括但不限于MQTT(Message Queuing Telemetry Transport，消息队列遥测传输)、CoAP(The Constrained Application Protocol)、HTTP(Hyper Text Transfer Protocol，超文本传输协议)协议；根据实际应用条件，也可由单一通信模块同时承担时间同步和数据传输两部分工作。以及，传感器单元23包括至少一个传感器；其中，传感器的类型包括但不仅限于：振动加速度传感器、振动速度传感器、振动位移传感器、环境温度传感器、环境湿 度传感器和环境风速传感器，以及MEMS传感器，具体传感器的类型和数量可以根据实际情况进行设置。
需要说明的是，对于感知层110中各个节点采集的监测数据，每个节点的主控单元21可以将监测数据直接通过信息传输层120传输至云平台管理应用层130；也可以将自身对应的监测数据传输至上一节点，如从待监测建筑的底层开始，由下向上依次传递监测数据，即在时间同步的基础上，末端节点K将采集的监测数据发送至上一个节点即最后一个中继节点，该中继节点将对应的监测数据以及末端节点发送的监测数据同时发送至上一中继节点，以此类推，直至根节点将对应的监测数据和其余多个节点的监测数据同时经信息传输层120转发至云平台管理应用层130，由于各个节点间的时间同步，从而还保证了监测数据的传递效率，进而提高了建筑的健康监测效率。
以及，感知层110中根节点R与中继节点J还具备变频采样的能力，采样频率变化范围为1Hz～1000Hz。在实际应用中，根据实际需求，日常监测时可使用较低的采样频率，当发生异常结构行为或有特殊监测需求时，可通过云平台管理应用层130下发采样频率设置指令，主控单元21根据采样频率设置指令设置传感器单元23中各个传感器的采样频率，从而提高节点的采样频率，获取更加密集的数据样本，进而提高了待监测建筑的健康评估结果的精确度。
优选地，若节点为根节点，主控单元21还配置成按照预设间隔周期性向其余多个节点发起时间同步请求；或者，获取云平台管理应用层130发送的时间同步指令，并根据时间同步指令向其余多个节点发起时间同步请求，以使根节点和其余多个节点实现时间同步；其中，多个其余节点包括末端节点以及多个中继节点。具体地，根节点中的主控单元21可以按固定时间间隔，周期性地发起系统的时间同步，从而实现感知层110中多个节点间的时间同步；也可在异常工况下，通过云平台管理应用层130发出的时间同步指令控制根节点在任意时刻发起网络的时间同步。
优选地，对于感知层110中的多个节点，除根节点R之外，中继节点J和末端节点K相同。如图8所示，根节点R在中继节点J或末端节点K的结构上，还另设置有与主控单元21通信连接的卫星授时单元26；卫星授时单元26配置成获取基准时钟，并将基准时钟作为感知层110的基准时间，以使多个节点根据基准时钟实现时间同步，即多个中继节点J和末端节点K基于根节点R中卫星授时单元26获取的基准时钟进行时间同步。
此外，每个节点还包括供电单元25；其中，若节点为根节点，如图8所示，供电单元25配置成对主控单元21、时间同步单元22、卫星授时单元26、传感器单元23和数据传输单元24进行供电；若节点为中继节点或末端节点，如图7所示，供电单元25配置成对主控单元21、时间同步单元22、传感器单元23和数据传输单元24进行供电。在实际应用中，供电单元25包括但不仅限于UPS(Uninterrupted Power Supply，不间断电源)电源、市电、太阳能和微型风力发电等，具体可以根据实际情况进行设置。
优选地，如图6所示，上述信息传输层120包括时间同步层121和数据传输层122；其中，时间同步层121指节点间基于扩频通信技术的时间同步信号传输链路，数据传输层122指感知层110与云平台管理应用层130之间的数据传输链路，如传输监测数据等。以及，云平台管理应用层130云平台131、云数据库132和显示模块133；云平台131配置成获取监测数据，并基于云端算法对监测数据进行分析，生成待监测建筑的健康评估结果；以及，将监测数据和健康评估结果发送至云数据库132进行存储，以及，还将健康评估结果发送至显示模块133，以使显示模块133展示健康评估结果。需要说明的是，云平台131在基于云端算法对监测数据进行分析时，还可能调取云数据库132中存储的数据，如各类建筑安全隐患下的建筑内应力数据、加速度数据、速度数据、位移数据、建筑沉降数据、倾斜度数据和裂缝数据等，并将监测数据和调取的数据进行分析，分析内容包括但不限于结构动力特性分析(如振动幅值、自振频率、模态分析等)、振动分类、异常结构行为识别与定位、结构健康状况评估与预测等，从而生成待监测建筑的健康评估结果。
因此，多个感知层110中的多个节点，在时间同步过程中，中继节点J1可以将根节点R作为父节点，按照上述无线传感网络时间同步方法实现多个节点间的时间同步；同理，相邻两个中继节点之间以及最后一个中继节点和末端节点之间，均可以按照上述无线传感网络时间同步方法实现多个节点间的时间同步，从而实现感知层中多个节点间的时间同步。
优选地，由于建筑同一楼层距离较远，仅设置一个节点不能满足监测需求，因此，对于每个中继节点，在对应的楼层还可设置多个节点。具体点，根节点、末端节点以及多个中继节点组成链式传感器网络；其中，链式传感器网络中每个节点还可作为父节点，与设置在同一楼层中的多个子节点通信连接，且，每个父节点与对应的多个子节点组成星型子网；以及，在时间同步过程中，链式传感器网络的优先级高于星型子网。
具体地，如图9所示，根节点R布置在建筑顶层，从顶层往下依次部署各个层级中继节点J直至末端节点K，构成链式传感器网络。链式传感器网络中的所有节点均可以作为父节点，与多个子节点相连，组成多个星型子网，对应实际建筑中同一楼层内布置多个监测节点的情景。以上构成链式-星型传感器网络，从而满足高层建筑结构监测的实际需求。
其中，链式传感器网络中，根节点R通过卫星授时单元26获取基准时钟，并发起整个网络的时间同步，基准时钟沿着链式网络、自上而下向末端节点传递，实现跨层级的链式时间同步；以及，各个星型子网中，基准时钟从父节点向子节点传递。同时，为保证系统时间同步的时效性，链式传感器网络的时间同步优先于星型子网的时间同步，即父节点获得基准时钟后首先将基准时钟传达给下级中继节点，再传达给本级网络中的子节点，从而实现基准时钟在网络中的快速传达。
因此，基准时钟在传感器网络的传递过程中，两个节点之间均按照上一部分节点间时间同步机制完成同步，当中继节点完成与上级中继节点的时间同步后，立即向下级中继节点及本级子节点发出时间同步要求，将最新获得的基准时钟(即修正后的系统时间)快速传递下去，从而保证网络整体的时间同步精度，以及，节点在完成与上级节点的时间同步后，还将同步信息记录存储在本地并上传至云平台管理应用层130中。
此外，对于简单的监测需求，传感器网络可以采用单纯的链式结构。对于节点数量较多、链路较长的网络，可设置多个根节点，如将链路中间的中继节点设为根节点(对应在高层建筑中间设备层设置根节点)，形成树状结构，由建筑中间向上下两个方向传递基准时钟，从而在没有明显增加根节点通信压力的情况下，将网络的时间同步链路缩短了一半，可提高系统的时间同步精度。需要说明的是，传感器网络结构包括但不限于链式结构、星型结构、树状结构，也可使用混合结构，具体可以根据建筑的具体结构进行设置。
以及，各个节点中的时间同步单元22还采用扩频通信技术实现了高层建筑内部卫星及常规无线电拒止环境下的传感器网络时间同步，通过扩频因子SF自适应调节机制，可以实现远距低功耗传输和近距高速率传输。优选地，在链式同步中，跨层级的两个节点间隔多个楼层，中间的结构遮挡较多，取SF＝7～12；在星型同步中，同层级的父、子节点距离近，中间的结构遮挡较少，取SF＝6～10。此外，为避免同频干扰，相邻层级的中继节点采用不同的发射频率，即通过跳频技术增强同步信号的抗干扰能力。
综上，本申请实施例提供的建筑结构健康监测系统，实现了从感知层到云平台管理应用层的系统集成。该系统至少包括：感知层、信息传输层和云平台管理应用层；其中，感知层包含传感器、MCU模块、扩频通信数据传输单元等，通过集成设计，开发了高性能、低功耗的无线监测节点；信息传输层则包括节点间时间同步机制和传感器网络层次时间同步机制；云平台管理应用层则基于云端算法对监测数据进行分析，并将生成的健康评估结果通过显示模块进行展示。因此，该系统具有以下优点：(1)针对高层建筑内部卫星及常规无线电拒止环境，通过低功耗扩频通信技术实现了信号在跨越多重楼板或墙体情况下的强穿透、广覆盖和低功耗传输，保证了传感器网络的时间同步和通信稳定性；(2)时间同步机制包括节点间时间同步机制和传感器网络层次时间同步机制，考虑了节点间时钟差的线性漂移，传感器网络层次采用链式同步优先的原则，保证了网络整体的时间同步精度；(3)实现了从感知层到云平台管理应用层的系统集成，通过集成设计，开发了高性能、低功耗的无线监测节点，在感知层和云平台植入算法模型，实现了一套边缘计算与云计算协同工作的监测系统，并由前端可视化网页(显示模块)实时展示分析结果，从而不仅实现了高层建筑的健康监测，还保证了监测过程中传感器网络的时间同步精度和通信稳定性，进而保证了健康监测精确度，具有较好的实用价值。
在本申请实施例的描述中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以具体情况理解上述术语在本申请中的具体含义。
所述功能如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个处理器可执行的非易失的计算机可读取存储介质中。基于这样的理解，本申请的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本申请各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、磁碟或者光盘等各种可以存储程序代码的介质。
在本申请的描述中，需要说明的是，术语“中心”、“上”、“下”、“左”、“右”、“竖直”、“水平”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。此外，术语“第一”、“第二”、“第三”仅用于描述目的，而不能理解为指示或暗示相对重要性。
最后应说明的是：以上所述实施例，仅为本申请的具体实施方式，用以说明本申请的技术方案，而非对其限制，本申请的保护范围并不局限于此，尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，其依然可以对前述实施例所记载的技术方案进行修改或可轻易想到变化，或者对其中部分技术特征进行等同替换；而这些修改、变化或者替换，并不使相应技术方案的本质脱离本申请实施例技术方案的精神和范围，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应所述以权利要求的保护范围为准。
工业实用性
本申请实施例所提供的无线传感网络时间同步方法及建筑结构健康监测系统，能够在建筑结构内部利用无线通信技术对建筑结构进行健康监测，通过低功耗扩频通信技术实现了信号在跨越多重楼板或墙体情况下的强穿透、广覆盖和低功耗传输，保证了传感器网络的时间同步；以及，上述扩频通信技术还考虑了节点间时钟差的线性漂移，进一步保证了感知层网络的时间同步精度，具有较好的实用价值。

Claims (15)

  1. 一种无线传感网络时间同步方法，其特征在于，所述无线传感网络包括父节点以及多个子节点，所述方法包括：
    所述父节点获取基准时钟，并向距离所述父节点最近的所述子节点发送同步Sync报文；其中，所述同步Sync报文携带有所述父节点的发送时刻T1；
    所述子节点记录接收所述同步Sync报文的接收时刻T2，并向所述父节点发送同步请求Req报文；其中，所述同步请求Req报文携带有所述接收时刻T2，以及所述同步请求Req报文的发送时刻T3；
    所述父节点接收所述同步请求Req报文，并向所述子节点反馈Resp报文；其中，所述Resp报文携带有所述同步请求Req报文的接收时刻T4和所述Resp报文的发送时刻T5；
    所述子节点记录接收所述Resp报文的接收时刻T6，以及所述子节点修正本地时钟前的修正时刻T7，并根据所述发送时刻T1、所述接收时刻T2、所述发送时刻T3、所述接收时刻T4、所述发送时刻T5、所述接收时刻T6和所述修正时刻T7计算得到时钟差值，并根据所述时钟差值对所述修正时刻T7进行时间同步修正，得到修正后的系统时间；
    所述子节点同步完成后，将所述系统时间发送至与该子节点通信连接的下一子节点，以使所述下一子节点完成时间同步，以此类推，直至最后一个所述子节点完成时间同步。
  2. 根据权利要求1所述的方法，其特征在于，根据所述发送时刻T1、所述接收时刻T2、所述发送时刻T3、所述接收时刻T4、所述发送时刻T5、所述接收时刻T6和所述修正时刻T7计算得到时钟差值的步骤，包括：
    根据下式计算所述时钟差值：

    其中，θ7表示所述时钟差值，k表示线性漂移率。
  3. 一种建筑结构健康监测系统，其特征在于，所述系统包括感知层、信息传输层和云平台管理应用层；其中，所述感知层包括多个节点，且，多个所述节点基于权利要求1～2任一项所述的无线传感网络时间同步方法实现时间同步；
    所述感知层，配置成采集待监测建筑结构的监测数据，并将所述监测数据通过所述信息传输层发送至所述云平台管理应用层；其中，所述监测数据包括每个所述节点采集的监测数据，所述监测数据包括以下至少之一：建筑内应力数据、加速度数据、速度数据、位移数据、建筑沉降数据、倾斜度数据和裂缝数据；
    所述云平台管理应用层，配置成接收所述监测数据，并对所述监测数据进行分析，以生成所述待监测建筑的健康评估结果。
  4. 根据权利要求3所述的系统，其特征在于，多个所述节点包括根节点、多个中继节点、以及末端节点；其中，所述根节点设置在所述待监测建筑的顶层，所述末端节点设置在所述待监测建筑的底层，所述待监测建筑的顶层和底层之间依次部署多个所述中继节点。
  5. 根据权利要求4所述的系统，其特征在于，每个所述节点均包括：主控单元，以及与所述主控单元通信连接的时间同步单元、传感器单元和数据传输单元；
    所述时间同步单元，配置成通过所述无线传感网络时间同步方法实现多个所述节点之间的时间同步；
    所述传感器单元，配置成采集对应监测区域内的监测数据，并将所述监测数据发送至所述主控单元；
    所述主控单元，配置成获取所述监测数据，并对所述监测数据进行清洗；以及，将清洗后的所述监测数据通过所述数据传输单元发送至所述信息传输层，以使所述信息传输层将所述监测数据发送至所述云平台管理应用层。
  6. 根据权利要求5所述的系统，其特征在于，若所述节点为所述根节点，所述主控单元还配置成按照预设间隔周期性向其余多个所述节点发起时间同步请求；或者，获取所述云平台管理应用层发送的时间同步指令，并根据所述时间同步指令向其余多个所述节点发起时间同步请求，以使所述根节点和其余多个所述节点实现时间同步；其中，多个其余所述节点包括所述末端节点以及多个所述中继节点。
  7. 根据权利要求5所述的系统，其特征在于，若所述节点为所述根节点，还包括与所述主控单元通信连接的卫星授时单元；
    所述卫星授时单元，配置成获取基准时钟，并将所述基准时钟作为所述感知层的基准时间，以使多个所述节点根据所述基准时钟实现时间同步。
  8. 根据权利要求7所述的系统，其特征在于，每个所述节点还包括供电单元；其中，若所述节点为所述根节点，所述供电单元配置成对所述主控单元、所述时间同步单元、所述卫星授时单元、所述传感器单元和所述数据传输单元进行供电；若所述节点为所述中继节点或所述末端节点，所述供电单元配置成对所述主控单元、所述时间同步单元、所述传感器单元和所述数据传输单元进行供电。
  9. 根据权利要求5所述的系统，其特征在于，所述传感器单元包括至少一个传感器；其中，所述传感器的类型包括以下至少之一：振动加速度传感器、振动速度传感器、振动位移传感器、环境温度传感器、环境湿度传感器、环境风速传感器以及MEMS传感器。
  10. 根据权利要求4所述的系统，其特征在于，所述根节点、所述末端节点以及多个所述中继节点组成链式传感器网络；其中，所述链式传感器网络中每个所述节点作为父节点，与设置在同一楼层中的多个子节点通信连接，且，每个所述父节点与对应的多个所述子节点组成星型子网。
  11. 根据权利要求10所述的系统，其特征在于，在时间同步过程中，所述链式传感器网络的优先级高于所述星型子网。
  12. 根据权利要求4所述的系统，其特征在于，所述根节点和所述中继节点还具备变频采样的能力；其中，所述采样频率变化范围为1Hz～1000Hz。
  13. 根据权利要求3所述的系统，其特征在于，所述云平台管理应用层包括云平台，以及与所述云平台通信连接的云数据库和显示模块；
    所述云平台，配置成获取所述监测数据，基于云端算法对所述监测数据进行分析，生成所述待监测建筑的健康评估结果；并将所述监测数据和所述健康评估结果发送至所述云数据库进行存储；以及，将所述健康评估结果发送至所述显示模块，以使所述显示模块展示所述健康评估结果。
  14. 根据权利要求13所述的系统，其特征在于，所述云平台，还配置成获取所述云数据库中的调取数据，并基于云端算法对所述监测数据和所述调取数据进行分析，生成所述健康评估结果；其中，所述调取数据包括各类建筑安全隐患下的建筑内应力数据、加速度数据、速度数据、位移数据、建筑沉降数据、倾斜度数据和裂缝数据。
  15. 根据权利要求13所述的系统，其特征在于，所述健康评估结果包括以下至少之一：建筑结构动力特性分析、振动分类、异常结构行为识别与定位、结构健康状况评估与结构损伤等级评估预测。
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