An unmanned aerial vehicle-based signal shielding bridge health state detection relay system

Abstract

The present application relates to the technical field of unmanned aerial vehicles, and particularly relates to a signal shielding bridge health state detection relay system based on an unmanned aerial vehicle. In a complex environment where GPS signals are limited or invalid, the system can realize identification of bridge surface diseases and structural vibration analysis to provide comprehensive bridge health state evaluation. The system comprises a ground terminal, an unmanned aerial vehicle-borne relay unit, a bridge structure information collection unit, a bridge surface disease information collection unit, a data storage unit and an unmanned aerial vehicle ground station. Through the multi-link automatic switching function of the ground terminal, stable communication between the unmanned aerial vehicle and the ground terminal can be ensured in a signal shielding environment. The system can efficiently and accurately detect bridge surface cracks and corrosion diseases, and analyze vibration signals to evaluate the inherent frequency and damping ratio of the bridge, thereby evaluating the health state of the bridge structure. The multi-modal data fusion and intelligent analysis function of the system can help to find potential structural hazards of the bridge in advance, thereby improving the efficiency and reliability of bridge detection.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) technology, and in particular to a relay system for detecting the health status of bridges with signal obstruction based on UAVs. Background Technology

[0002] Among the existing technologies, CN 115981355 A discloses an automatic cruise system for drones capable of rapid and accurate landing, including a drone, a drone remote control device, a GPS positioning device, a drone take-off and landing platform, visual recognition markers, and cruise control equipment; CN 109445454 A provides a drone-based beam-around cruise detection method for bridge inspection, which can perform fully automatic and accurate detection of bridge columns, eliminate blind spots, and ensure comprehensive and accurate detection data; CN 113821044 A provides a reinforcement learning-based autonomous navigation and stability control method for bridge inspection drones to solve the problems of missing positioning signals under bridges and unstable flight control under strong wind interference in drone bridge inspection technology; CN 114778551 A provides a drone-based bridge surface defect detection method based on laser and machine vision fusion; CN 106645205 A provides a drone-based method and system for detecting cracks on the bottom surface of bridges.

[0003] However, the drone relay system involved in the above patents still has many shortcomings in practical applications:

[0004] The aforementioned patent describes a drone system that relies on GPS for positioning and navigation. However, in complex environments such as under bridges and in tunnels, GPS signals are easily blocked or interfered with by the bridge structure, leading to signal instability or even complete loss. This prevents the drone from accurately positioning itself in these areas, hindering its ability to autonomously complete flight missions. Existing GPS-based drone systems have significant limitations in bridge-under environments, easily causing interruptions or failures in detection tasks. Furthermore, existing single-sensor-based positioning technologies are prone to positioning drift, data distortion, or signal noise issues when visual features are insufficient, ambient lighting is unstable, or dynamic obstacles are present, resulting in unstable flight trajectories and consequently affecting detection accuracy.

[0005] In bridge underpass inspection environments, drones not only need precise navigation and positioning but also require real-time perception of surrounding obstacles (such as bridge supports and cables) and autonomous avoidance. Existing drone obstacle avoidance technologies exhibit significant limitations in complex environments, especially in confined spaces, densely packed obstacles, or high-speed flight, making them prone to collisions or attitude instability. In signal-obstructed environments such as under bridges, the communication link between the drone and the ground control station is also severely affected. Most existing systems rely on traditional radio communication, which is easily blocked or interfered with when drones enter areas like under bridges, causing unstable or even interrupted data transmission. In such cases, inspection data cannot be transmitted back to the ground control station in a timely manner, hindering real-time analysis and processing of inspection results, thus impacting inspection efficiency and effectiveness. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the problem to be solved by this invention is how to solve the problems of drones being unable to accurately locate themselves in areas such as under bridges and tunnels, drone positioning and flight stability in the environment under bridges, drone autonomous obstacle avoidance and flight stability, and unstable communication links.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] In a first aspect, embodiments of the present invention provide a relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs), which includes constructing a relay system, including deploying a ground terminal, an UAV-borne relay unit, a bridge structure information collection unit, a bridge surface defect information collection unit, a data storage unit, and an UAV ground station.

[0010] The ground terminal is fixedly installed on the side of the bridge and continuously collects bridge vibration signals through a multi-sensor fusion module; the drone is equipped with a camera and lidar to collect information on bridge surface defects.

[0011] When a drone enters an area with signal obstruction, the relay system automatically switches the communication mode:

[0012] a) The ground terminal acts as a relay node, receiving UAV data and forwarding it to the base station;

[0013] b) In drone swarm mode, the host drone acts as a relay node, receiving and forwarding data from the slave drones;

[0014] Ground terminals or base stations upload the collected data to the cloud platform, extract key parameters of the bridge's health status using modal analysis methods, and generate an assessment report.

[0015] The relay system monitors signal strength in real time. When all communication paths fail to meet the requirements, an anomaly handling mechanism is triggered to temporarily store the data and re-upload it after the signal is restored.

[0016] As a preferred embodiment of the relay system for detecting bridge health status based on UAV signal obstruction as described in this invention, the ground terminal unit is the core control and communication relay node for bridge health monitoring, used for the acquisition of bridge vibration signals, UAV communication relay, and data management and transmission.

[0017] When the UAV performs inspection tasks and in environments with signal obstruction, the ground terminal unit ensures the integrity and accuracy of data transmission through its relay function. The ground terminal switches between Wi-Fi, LoRa, and public communication networks according to the actual communication environment. The ground terminal processes and temporarily stores the collected bridge vibration signals and inspection data to ensure the continuity and integrity of the data.

[0018] As a preferred embodiment of the relay system for bridge health status detection based on UAV signal obstruction according to the present invention, the UAV-borne relay unit is used to provide communication relay function during bridge health monitoring, and ensures continuous data transmission in the event of signal obstruction or communication link interruption.

[0019] The UAV-borne relay unit integrates 5GHz Wi-Fi and LoRa modules to achieve reliable communication with ground terminals or other UAVs. During the inspection process, when the direct connection between the UAV and the ground terminal is blocked, the relay unit can automatically switch to the host role and act as a relay node to provide communication support for other UAVs.

[0020] As a preferred embodiment of the relay system for detecting bridge health status based on UAV signal obstruction as described in this invention, the bridge structure information collection unit is used to collect dynamic characteristic data of the bridge structure during the bridge health monitoring process, mainly including the bridge's vibration signal, displacement, tilt angle and other structure-related physical parameters. The bridge structure information collection unit integrates multiple high-precision sensor modules, and provides important data for the analysis and evaluation of the bridge's health status by collecting the bridge's structural status information in real time.

[0021] As a preferred embodiment of the relay system for detecting bridge health status based on signal obstruction by unmanned aerial vehicles (UAVs) as described in this invention, the bridge surface defect information collection unit is used to collect defect information on the bridge surface during bridge health monitoring, mainly including the detection and recording of defect features such as cracks, corrosion, and peeling; the bridge surface defect information collection unit integrates imaging equipment with high-definition cameras and infrared sensors, which can collect high-resolution images and other relevant data in complex bridge environments, providing basic data for the assessment of bridge surface defects.

[0022] As a preferred embodiment of the relay system for detecting bridge health status based on signal obstruction by UAV as described in this invention, the data storage unit is used to store various types of data collected during the bridge health monitoring process, including vibration signals, displacement data, tilt angle information, and image data of bridge surface defects; the data storage unit can record data from multiple sensor modules in real time through a high-speed storage device.

[0023] The UAV ground station serves as the command and control center in the UAV bridge health monitoring system, responsible for the UAV's flight control, data management, mission scheduling, and communication relay functions. The ground station communicates with the UAV in real time via a wireless communication link, receives bridge inspection data transmitted by the UAV, and sends control commands to ensure the smooth completion of the inspection mission.

[0024] As a preferred embodiment of the relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs) according to the present invention, the relay system automatically switches communication modes when the UAV enters the signal obstruction area.

[0025] When drone inspections are not in progress, a ground terminal is fixedly installed on the side of the bridge to continuously collect vibration signals. The ground terminal transmits the vibration signals to a nearby base station via a multi-sensor fusion module. The base station then uploads the data to a cloud platform. On the cloud platform, the relay system analyzes the bridge's vibration characteristics using modal analysis, extracting parameters such as natural frequency and damping ratio to assess the bridge's health status. The specific process is as follows:

[0026] The relay system monitors the vibration signals of the bridge in real time through ground terminals. The ground terminals are fixedly installed at the structural nodes of the bridge and collect vibration signals through an integrated multi-sensor fusion module.

[0027] Vibration data undergoes preliminary processing via a Linux controller, and the pre-processed vibration data is stored in the data storage module of the ground terminal.

[0028] The ground terminal uploads vibration signals to the cloud server for centralized storage and management via the LoRa wireless communication module; when the communication link between the ground terminal and the base station is lost, the relay system will automatically traverse other ground terminals in the vicinity and establish a connection via Wi-Fi or LoRa; the relay system transmits data to the cloud through the connectable ground terminals to ensure timely data upload;

[0029] During data transmission, the relay system differentiates data from different nodes and identifies which nodes have experienced communication link disruptions, ensuring clear traceability records for subsequent data analysis and maintenance. Simultaneously, the relay system dynamically adjusts communication paths based on node connection status, guaranteeing the continuity of bridge health monitoring. On the cloud platform, data undergoes in-depth analysis using modal analysis methods to extract key parameters such as the bridge's natural frequency and damping ratio. Based on these parameters, the relay system generates a bridge health assessment report, providing a reference for subsequent maintenance.

[0030] The relay system is equipped with a real-time detection function for abnormal signals, which can promptly identify significant frequency changes or modal anomalies in vibration signals. When an anomaly occurs in the bridge vibration signal, the relay system will automatically trigger an early warning and notify relevant maintenance personnel to conduct inspections and maintenance to ensure the safety of the bridge.

[0031] As a preferred embodiment of the relay system for detecting bridge health status based on UAV signal obstruction as described in this invention, when the UAV enters complex structural areas such as the bottom of the bridge for inspection, the wireless communication link directly with the base station or ground terminal may be blocked due to the obstruction of the bridge bottom structure. This includes ground terminals acting as relay nodes and UAV swarm relay modes, as detailed below:

[0032] The method of using ground terminals as relay nodes:

[0033] When the drone is conducting inspections, the ground terminal automatically switches between the Wi-Fi and LoRa modules based on the signal strength of the communication environment. If the drone's direct communication with the base station is blocked while inspecting the bottom of the bridge, the ground terminal acts as a relay node, receiving the data transmitted by the drone and transmitting it to the base station to ensure the real-time and completeness of the bridge inspection data. The specific process is as follows:

[0034] When the drone begins to inspect the bottom of the bridge, it first establishes a communication connection with the ground terminal and base station simultaneously through the 5GHz Wi-Fi and LoRa communication modules. The communication link between the drone and the base station is used to receive the bridge defect image data collected by the drone, while the communication link between the drone and the ground terminal remains silent.

[0035] During the drone inspection process, the relay system will monitor the communication signal strength with the base station in real time. When the drone enters areas with complex structures such as the bottom of a bridge, the relay system will automatically detect that the communication signal between the drone and the base station is blocked due to obstruction or signal attenuation.

[0036] When the system detects that the drone cannot communicate directly with the base station, the relay system automatically switches to the mode of the ground terminal as the relay node. At this time, the drone will send the collected bridge defect image data to the ground terminal through Wi-Fi or LoRa module.

[0037] The ground terminal acts as a relay node, responsible for receiving data transmitted by the UAV. This data includes information on bridge surface cracks, thread defects, and images of bridge corrosion. The ground terminal performs preliminary preprocessing on the received data through its internal buffer and data processing modules.

[0038] As a preferred embodiment of the relay system for detecting the health status of bridges with signal obstruction based on UAVs as described in this invention, the ground terminal, after receiving data from the UAV, transmits the data to the base station via a LoRa communication link with the base station. When the wireless signal environment is poor, the ground terminal has the ability to automatically select the best signal to ensure stable data transmission.

[0039] After receiving data transmitted from the ground terminal, the base station uploads it to the cloud server for centralized processing and storage. At this time, the relay system performs in-depth analysis of the data through the analysis platform and generates a bridge health status report.

[0040] As a preferred embodiment of the relay system for bridge health status detection based on UAV signal obstruction as described in this invention, the UAV swarm relay mode is as follows: In some complex situations, ground terminals may not be able to directly connect with the UAVs during inspection, so a UAV swarm collaborative working mode is introduced; the UAV swarm is divided into master UAVs and slave UAVs; when the ground terminal cannot communicate directly with the UAVs, the UAVs in the system will automatically adjust to a master-slave structure.

[0041] The host drone acts as a relay node: the host drone is responsible for maintaining a connection with the ground terminal and transmitting the received inspection data back to the ground terminal or base station;

[0042] Slave drones: Drones that cannot communicate directly with ground terminals transmit data to host drones that can connect to ground terminals. The host drone acts as a relay, transmitting this data back to the ground terminal or base station.

[0043] In a second aspect, embodiments of the present invention provide a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, they implement the steps of the relay system for detecting the health status of bridges with signal blockage based on unmanned aerial vehicles as described in the first aspect of the present invention.

[0044] Thirdly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, they implement the steps of the relay system for detecting the health status of bridges with signal blockage based on unmanned aerial vehicles as described in the first aspect of the present invention.

[0045] The beneficial effects of this invention are as follows: The relay communication mechanism proposed in this invention effectively solves the signal obstruction problem at the bottom of bridges and other complex structural areas. Through the relay mode of ground terminals and UAV formations, UAVs can maintain reliable communication with ground terminals or base stations in complex environments, ensuring the real-time performance and integrity of detection data.

[0046] This invention introduces a ground terminal as a relay node and a collaborative working mode for UAV formations. Whether it's the ground terminal acting as a relay or the adjustment of the master-slave structure among UAVs, it provides the system with great flexibility, enabling it to adapt to inspection needs in different bridge structures and environments, and ensuring smooth data transmission.

[0047] In addition to the drone inspection mode, this invention also provides a mechanism for ground terminals to continuously monitor bridge vibration signals. Even when the drone is not performing inspection tasks, the ground terminal can monitor the health status of the bridge in real time, and collect and transmit data through multi-sensor fusion technology to ensure the safety of the bridge in daily operation.

[0048] The system employs modal analysis and other methods to conduct in-depth analysis of the bridge's vibration characteristics, extracting key parameters such as natural frequency and damping ratio. This data can accurately assess the bridge's health status, help predict potential structural risks, and provide a basis for bridge maintenance. Furthermore, the system integrates image processing and pattern recognition algorithms to identify surface defects on the bridge, such as cracks, corrosion, and spalling. High-resolution cameras mounted on drones acquire high-definition images of the bridge surface, and combined with defect identification algorithms, automatically detect and classify structural damage to the bridge surface. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 A flowchart of a relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs);

[0051] Figure 2 A diagram of computer equipment for a relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs).

[0052] Figure 3 A block diagram of an intelligent UAV relay system for detecting the health status of bridges with signal obstruction based on UAVs;

[0053] Figure 4 A physical image of the Linux controller development board for a relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs).

[0054] Figure 5 A relay system communication link diagram for a relay system for bridge health status detection based on UAV signal blockage;

[0055] Figure 6 A comparison chart of various data for a relay system for detecting the health status of bridges with signal obstruction based on drones. Detailed Implementation

[0056] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0057] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0058] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0059] Example 1

[0060] Reference Figures 1-2 This is the first embodiment of the present invention, which provides a relay system for detecting the health status of bridges affected by signal obstruction from unmanned aerial vehicles (UAVs), comprising:

[0061] Constructing a relay system includes deploying ground terminals, UAV-borne relay units, bridge structure information collection units, bridge surface defect information collection units, data storage units, and UAV ground stations;

[0062] The ground terminal is fixedly installed on the side of the bridge and continuously collects bridge vibration signals through a multi-sensor fusion module; the drone is equipped with a camera and lidar to collect information on bridge surface defects.

[0063] When a drone enters an area with signal obstruction, the relay system automatically switches the communication mode:

[0064] a) The ground terminal acts as a relay node, receiving UAV data and forwarding it to the base station;

[0065] b) In drone swarm mode, the host drone acts as a relay node, receiving and forwarding data from the slave drones;

[0066] Ground terminals or base stations upload the collected data to the cloud platform, extract key parameters of the bridge's health status using modal analysis methods, and generate an assessment report.

[0067] The relay system monitors signal strength in real time. When all communication paths fail to meet the requirements, an anomaly handling mechanism is triggered to temporarily store the data and re-upload it after the signal is restored.

[0068] The ground terminal unit is the core control and communication relay node for bridge health monitoring, used for the acquisition of bridge vibration signals, UAV communication relay, and data management and transmission.

[0069] When the UAV is performing inspection missions, and in environments with signal obstruction, the ground terminal unit ensures the integrity and accuracy of data transmission through its relay function. The ground terminal switches between Wi-Fi, LoRa, and public communication networks according to the actual communication environment. The ground terminal processes and temporarily stores the collected bridge vibration signals and inspection data to ensure the continuity and integrity of the data.

[0070] The UAV-borne relay unit provides communication relay functionality during bridge health monitoring and ensures continuous data transmission even when signals are blocked or communication links are interrupted.

[0071] The UAV-borne relay unit integrates 5GHz Wi-Fi and LoRa modules to achieve reliable communication with ground terminals or other UAVs. During inspections, when the direct connection between the UAV and the ground terminal is blocked, the relay unit can automatically switch to the host role and act as a relay node to provide communication support for other UAVs.

[0072] The bridge structure information collection unit is used to collect dynamic characteristic data of bridge structures during bridge health monitoring. This data mainly includes bridge vibration signals, displacement, tilt angle, and other structure-related physical parameters. The bridge structure information collection unit integrates multiple high-precision sensor modules and provides important data for the analysis and evaluation of bridge health status by collecting bridge structural status information in real time.

[0073] The bridge surface defect information collection unit is used to collect information on bridge surface defects during bridge health monitoring, mainly including the detection and recording of defect characteristics such as cracks, corrosion, and peeling. The bridge surface defect information collection unit integrates imaging equipment with high-definition cameras and infrared sensors, which can collect high-resolution images and other relevant data in complex bridge environments, providing basic data for the assessment of bridge surface defects.

[0074] The data storage unit is used to store various types of data collected during bridge health monitoring, including vibration signals, displacement data, tilt angle information, and image data of bridge surface defects. The data storage unit can record data from multiple sensor modules in real time through high-speed storage devices.

[0075] The UAV ground station serves as the command and control center in the UAV bridge health monitoring system, responsible for the UAV's flight control, data management, mission scheduling, and communication relay functions. The ground station communicates with the UAV in real time via a wireless communication link, receives bridge inspection data transmitted by the UAV, and sends control commands to ensure the smooth completion of the inspection mission.

[0076] Preferably, the ground terminal unit includes a Linux controller, a WiFi module, and a LoRa module. The Linux controller, as the core processing unit of the ground terminal, is responsible for managing and processing the received data, and controlling communication with the drone and other terminal devices. The WiFi module is used to establish a high-speed wireless communication link between the ground terminal and the drone. The LoRa module provides a long-range, low-power communication link, especially suitable for data transmission when the drone is inspecting under bridges or in areas with limited signal.

[0077] Furthermore, the UAV-borne relay unit includes a Linux controller, a Wi-Fi module, and a LoRa module. The Linux controller, as the core control module of the UAV-borne relay unit, is responsible for managing the UAV's flight status, mission execution, and real-time processing of multi-sensor data. The Wi-Fi module is used to establish a high-bandwidth communication link over short distances, particularly suitable for real-time data transmission between the UAV and ground terminals or other UAVs. The LoRa module is used for long-range, low-power communication, particularly suitable for data transmission in situations where signals are obstructed or in complex environments.

[0078] Furthermore, the bridge structure information collection unit includes a multi-sensor fusion module, accelerometers, tilt angle sensors, and temperature sensors. The multi-sensor fusion module is the core of this information collection unit, responsible for integrating data from different sensors. Accelerometers are used to accurately capture vibration signals of the bridge under different operating conditions, helping to identify parameters such as the bridge structure's vibration modes and natural frequencies, providing crucial data for bridge health status assessment. Tilt angle sensors are used to monitor changes in the bridge structure's tilt, especially under external conditions such as strong winds and heavy loads, where even small changes in tilt may indicate structural health problems. Temperature sensors are used to detect temperature changes on or inside the bridge surface.

[0079] Furthermore, the bridge surface defect information collection unit includes a camera and a lidar unit. The camera is used to acquire high-resolution images of the bridge surface, clearly capturing details of surface defects such as the shape of cracks, the location and extent of corrosion. The lidar unit is used to construct a three-dimensional model of the bridge surface, accurately capturing minute changes in the bridge surface shape.

[0080] Furthermore: The data storage unit includes a data storage module and a data collection manager. The data storage module stores various data acquired from the bridge health monitoring system, including bridge structural vibration data, displacement information, tilt angles, and images of bridge surface defects. The data collection manager is responsible for the centralized management and preliminary processing of the acquired data.

[0081] like Figure 3 The diagram shown is a block diagram of an intelligent UAV relay system for bridge health status detection, which will be explained in detail below.

[0082] Figure 3 The ground terminal shown includes a Linux controller, a WiFi module, and a LoRa module.

[0083] Linux Controller: The Linux controller is the core processing unit of the ground terminal, transmitting data with other modules via an RS232 interface. The Linux controller connects to the data collection manager via RS232 to start the system and receive data from multiple sensors. The data collection manager manages data collection, including connectivity, vibration data collection, and custom system settings. The Linux controller also connects to an external network via a 1000BaseT Ethernet port for further data transmission.

[0084] Wi-Fi and LoRa modules: The Wi-Fi module operates in the 5GHz band for high-speed data transmission over short distances. The LoRa module operates in the 433MHz band, suitable for long-distance, low-power data transmission. These two modules communicate with the Wi-Fi and LoRa modules on the drone via wireless communication links, ensuring real-time data transmission.

[0085] Figure 3 The UAV-borne relay shown includes a Linux controller, a WiFi module, and a LoRa module.

[0086] Linux Controller: The core processing unit on the drone, controlling flight status, mission execution, and sensor data processing. The Linux controller connects to other devices on the drone via a USB interface and connects to the Wi-Fi and LoRa modules via an RS232 interface for data transmission. The data collection manager manages data collection, including connectivity, disease image acquisition, and custom system settings.

[0087] Wi-Fi module and LoRa module: used to communicate with the ground terminal, ensuring a stable communication link between the drone and the ground terminal.

[0088] Figure 3 The multi-sensor fusion module connects to various sensors such as accelerometers, tilt sensors, and temperature sensors via the SPI interface, and is responsible for integrating and processing data from different sensors.

[0089] Damage image data collection: By connecting a camera, high-resolution images of the bridge surface are acquired to detect surface defects such as cracks and corrosion.

[0090] Data storage module: Used to store data from the sensors.

[0091] Figure 3 The data transmission is shown in the diagram. The drone transmits the collected data to the ground terminal via a Wi-Fi or LoRa module. The ground terminal then uploads the data to the cloud or ground station via a 1000BaseT Ethernet port for centralized processing and storage.

[0092] This invention provides an adaptive relay switching mechanism for UAV-ARS (Unmanned Aerial Vehicle) drones used for bridge health status detection in signal-obstructed environments:

[0093] Mechanism 1: Monitoring and transmission of bridge vibration signals.

[0094] When drone inspections are not in progress, a ground terminal is fixedly installed on the side of the bridge to continuously collect vibration signals. The ground terminal transmits the vibration signals to a nearby base station via a multi-sensor fusion module, and the base station then uploads the data to a cloud platform. On the cloud platform, the system analyzes the bridge's vibration characteristics using modal analysis methods, extracting parameters such as natural frequency and damping ratio to assess the bridge's health status. The specific process is as follows:

[0095] S1: Vibration Data Acquisition. When the UAV is not performing inspection tasks, the system monitors the vibration signals of the bridge in real time via a ground terminal. The ground terminal is fixedly installed at the structural nodes of the bridge and acquires vibration signals through an integrated multi-sensor fusion module (including accelerometers, tilt sensors, and temperature sensors). Each sensor is connected to the central control unit (Linux controller) via an SPI interface and transmits the acquired real-time data to the ground terminal.

[0096] S2: Data Processing and Storage. Vibration data undergoes preliminary processing via a Linux controller, including data filtering, noise reduction, and preprocessing algorithms to ensure data accuracy and integrity. The preprocessed vibration data is stored in the ground terminal's data storage module and connected to a memory via an RS232 interface, ensuring stable data recording and long-term preservation.

[0097] S3: Data Transmission. Ground terminals upload vibration signals to a cloud server for centralized storage and management via a LoRa wireless communication module. When the communication link between the ground terminal and the base station is lost, the system automatically searches for other nearby ground terminals and establishes a connection via Wi-Fi or LoRa. The system transmits data to the cloud through connectable ground terminals, ensuring timely data upload. During data transmission, the system differentiates data from different nodes and identifies which nodes have experienced communication link disruptions, ensuring clear traceability records for subsequent data analysis and maintenance. Simultaneously, the system can dynamically adjust communication paths based on node connection status, ensuring the continuity of bridge health monitoring.

[0098] S4: Data Analysis and Health Status Assessment. On the cloud platform, data undergoes in-depth analysis using modal analysis methods to extract key parameters such as the bridge's natural frequency and damping ratio. Based on these parameters, the system generates a bridge health status assessment report, providing a reference for subsequent maintenance.

[0099] S5: Real-time Early Warning Mechanism. The system is equipped with a real-time abnormal signal detection function, which can promptly identify significant frequency changes or modal anomalies in vibration signals. When an anomaly is detected in the bridge vibration signal, the system will automatically trigger an early warning, notifying relevant maintenance personnel to conduct inspections and maintenance to ensure the safety of the bridge.

[0100] Mechanism 2: Relay communication in drone inspection mode.

[0101] When a drone enters complex structural areas such as the underside of a bridge for inspection, the wireless communication link directly with the base station or ground terminal may be blocked due to the obstruction of the bridge's underside structure. To address this, this invention proposes a flexible relay communication mechanism to ensure that the drone can maintain its connection with the ground terminal or base station from any location, as detailed below:

[0102] 1. Ground terminal as relay node: During drone inspection, the ground terminal automatically switches between Wi-Fi and LoRa modules based on signal strength in the communication environment to ensure continuous and stable connection with the drone. If direct communication between the drone and the base station is blocked while the drone is inspecting under the bridge, the ground terminal will act as a relay node, receiving data transmitted by the drone and transmitting it to the base station to ensure the real-time nature and integrity of the bridge inspection data. The specific process is as follows:

[0103] S1: Initial Communication Establishment. When the drone begins its inspection of the bridge's underside, it first establishes communication connections with both the ground terminal and the base station via 5GHz Wi-Fi and LoRa communication modules. The communication link between the drone and the base station is used to receive bridge defect image data collected by the drone, while the communication link between the drone and the ground terminal remains silent.

[0104] S2: Signal Interference Detection. During drone inspections, the system monitors the communication signal strength with the base station in real time. When the drone enters areas with complex structures, such as under bridges, the system will automatically detect signal obstruction between the drone and the base station due to blockages or signal attenuation.

[0105] S3: Switching of ground terminal relay node. When the system detects that the UAV cannot communicate directly with the base station, it automatically switches to the mode where the ground terminal acts as a relay node. At this time, the UAV will send the collected bridge defect image data to the ground terminal via Wi-Fi or LoRa module.

[0106] S4: Data Reception and Processing. The ground terminal acts as a relay node, responsible for receiving data transmitted by the UAV. This data includes information such as surface cracks, thread defects, and images of bridge corrosion. The ground terminal performs preliminary preprocessing on the received data through its internal buffer and data processing modules, such as data cleaning, filtering, and packaging.

[0107] S5: Data is uploaded to the base station. After receiving data from the drone, the ground terminal transmits this data to the base station via the LoRa communication link. If the wireless signal environment is poor, the ground terminal has the ability to automatically select the best signal to ensure the stability of data transmission.

[0108] S6: Data synchronization from base station to cloud platform. After receiving data transmitted from the ground terminal, the base station uploads it to the cloud server for centralized processing and storage. At this time, the system performs in-depth analysis of the data through the analysis platform and generates a bridge health status report.

[0109] 2. Drone Swarm Relay Mode: In some complex situations, ground terminals may not be able to directly connect with drones during inspections. Therefore, this system introduces a drone swarm collaborative working mode. The drone swarm consists of master drones and slave drones. When the ground terminal cannot communicate directly with the drones, the drones in the system will automatically adjust to a master-slave structure.

[0110] The host drone acts as a relay node: the host drone is responsible for maintaining a connection with the ground terminal and transmitting the received inspection data back to the ground terminal or base station.

[0111] Slave drones: Drones that cannot communicate directly with ground terminals transmit data to host drones that can connect to ground terminals. The host drone acts as a relay, transmitting this data back to the ground terminal or base station.

[0112] Based on the above mechanism, a UAV relay communication algorithm for bridge health status detection under UAV-ARS signal obstruction environment is proposed:

[0113] S1: Input settings:

[0114] Signal strength between the UAV and the base station (Signal_Strength_UAV_BaseStation);

[0115] Signal strength of communication between the UAV and the ground terminal (Signal_Strength_UAV_GroundTerminal);

[0116] The signal strength between the ground terminal and the base station (Signal_Strength_GroundTerminal_BaseStation);

[0117] The preset signal strength threshold (Threshold_Strength);

[0118] UAV inspection data (UAV_Data);

[0119] Ground terminal buffer capacity;

[0120] The identifier of the master drone in a drone formation (Master_UAV);

[0121] Identification of the slave UAV in the UAV formation (Slave_UAV);

[0122] Set output: The UAV inspection data is successfully uploaded to the base station or cloud platform

[0123] S2: Initial communication establishment

[0124] The UAV starts the inspection task: When the inspection starts, the UAV attempts to establish communication connections with the base station and the ground terminal simultaneously through the 5GHz Wi-Fi and LoRa modules.

[0125] The communication link between the UAV and the base station is used to transmit inspection data (such as images of cracks and rust on the bridge surface). The communication link between the UAV and the ground terminal remains in a silent state and waits to be activated when needed.

[0126] S3: Signal blocking detection

[0127] Real-time monitoring of signal strength:

[0128] The system continuously monitors the communication signal strength Signal_Strength_UAV_BaseStation between the UAV and the base station.

[0129] If Signal_Strength_UAV_BaseStation ≥ Threshold_Strength, the UAV continues to transmit data through the base station. [[ID=2�]]

[0130] If Signal_Strength_UAV_BaseStation < Threshold_Strength, proceed to step 3.

[0131] S4: Switching of the ground terminal as a relay node

[0132] Detect the signal strength of the ground terminal:

[0133] The system detects the communication signal strength Signal_Strength_UAV_GroundTerminal between the UAV and the ground terminal.

[0134] If Signal_Strength_UAV_GroundTerminal ≥ Threshold_Strength, the UAV switches to the ground terminal as a relay node and proceeds to step 4.

[0135] If Signal_Strength_UAV_GroundTerminal < Threshold_Strength, proceed to step 6 (UAV formation relay mode).

[0136] S5: The ground terminal receives and processes data

[0137] Data transmission to the ground terminal: The UAV transmits the inspection data UAV_Data to the ground terminal through the Wi-Fi or LoRa module. After receiving the data, the ground terminal performs preliminary processing, including data cleaning, filtering, and packaging.

[0138] Caching data: The ground terminal stores the processed data in GroundTerminal_Buffer to ensure that the data is not lost.

[0139] S6: The ground terminal uploads data to the base station

[0140] [[ID=1,2]]Detecting the signal strength between the ground terminal and the base station: The system detects the communication signal strength Signal_Strength_GroundTerminal_BaseStation between the ground terminal and the base station.

[0141] If Signal_Strength_GroundTerminal_BaseStation ≥ Threshold_Strength, the ground terminal transmits the data to the base station through the LoRa module.

[0142] If Signal_Strength_GroundTerminal_BaseStation < Threshold_Strength, the ground terminal caches the data and waits for the signal to recover before transmitting.

[0143] Data upload to the cloud platform: After receiving the data, the base station uploads it to the cloud platform, and the system performs further analysis and processing.

[0144] S7: UAV formation relay mode

[0145] The UAV formation switches to the master-slave mode: If the communication between the ground terminal and the UAV cannot be established, the system switches the UAV to the formation mode. The system designates one UAV as the master UAV Master_UAV, and the remaining UAVs as slave UAVs Slave_UAV.

[0146] Data transmission of slave UAVs: The slave UAVs Slave_UAV that cannot directly communicate with the ground terminal transmit the collected data to the master UAV Master_UAV.

[0147] The master UAV acts as a relay node: The master UAV Master_UAV is responsible for maintaining a connection with the ground terminal or the base station and transmitting the data of the slave UAVs to the ground terminal or the base station together.

[0148] Data upload from the host drone: The host drone packages the data from the slave drone and uploads it through the communication link with the ground terminal or base station.

[0149] S8: Data upload successful confirmation

[0150] Data upload confirmation: The system confirms whether the data has been successfully uploaded to the base station or cloud platform.

[0151] If the data upload is successful, the current inspection task will end.

[0152] If the data upload fails, the system will continue to attempt to re-establish the communication link and repeat the above steps until the data is successfully uploaded.

[0153] S9: Exception Handling Mechanism

[0154] Communication link persistent abnormality: If the signal strength remains below the threshold Threshold_Strength for a certain period of time (e.g., 5 minutes), the system will trigger an early warning mechanism to notify maintenance personnel to check for interference factors in the communication equipment or bridge environment.

[0155] The following is in conjunction with the appendix Figure 4 The content involved in the above embodiments will be explained.

[0156] Step 1: UAV Inspection Mission Initiation. After the UAV begins its inspection mission, the system first attempts to establish communication connections with the ground terminal and base station. At this time, the system uses a wireless communication module (Wi-Fi or LoRa module) to detect the signal strength between the UAV and the base station (Signal_Strength_UAV_BaseStation) and between the UAV and the ground terminal (Signal_Strength_UAV_GroundTerminal).

[0157] Step 2: Detect the signal strength between the drone and the base station. The system first detects the signal strength (Signal_Strength_UAV_BaseStation) between the drone and the base station. Based on the comparison between this signal strength and a preset threshold (Threshold_Strength), the system makes the following judgment:

[0158] If Signal_Strength_UAV_BaseStation ≥ Threshold_Strength, it indicates sufficient signal strength, and the system will continue to maintain direct communication with the base station. At this point, the drone uploads detection data to the cloud platform via the base station to continue executing subsequent steps.

[0159] If Signal_Strength_UAV_BaseStation < Threshold_Strength, it indicates that the signal between the UAV and the base station is weak or interrupted. The system will enter the next step to detect the signal strength between the UAV and the ground terminal.

[0160] Step 3: Detect the signal strength between the UAV and the ground terminal. If the communication signal between the UAV and the base station is insufficient, the system automatically detects the signal strength between the UAV and the ground terminal (Signal_Strength_UAV_GroundTerminal). Similarly, by comparing this signal strength with the preset threshold (Threshold_Strength), the system takes corresponding measures:

[0161] If Signal_Strength_UAV_GroundTerminal ≥ Threshold_Strength, the system will switch to the ground terminal as a relay node to ensure that the UAV can transmit data through the ground terminal. At this time, the UAV transmits data to the ground terminal via Wi-Fi or LoRa technology.

[0162] If Signal_Strength_UAV_GroundTerminal < Threshold_Strength, it indicates that the signal of the ground terminal is also insufficient. The system will not be able to directly transmit data through the base station or the ground terminal and will transfer to Step 5 to switch to the UAV formation mode.

[0163] Step 4: Data transmission with the ground terminal as a relay node. When the signal strength between the UAV and the ground terminal meets the conditions, the system automatically switches to the ground terminal as a communication relay node. The UAV transmits data to the ground terminal via the Wi-Fi or LoRa module. After receiving the data, the ground terminal processes the data, including data cleaning, filtering, and packaging operations to ensure data integrity. The processed data is transmitted to the base station via the LoRa module of the ground terminal, and then the base station uploads the data to the cloud platform.

[0164] Step 5: Switch to the UAV formation relay mode. If the signals between the UAV and the base station and the ground terminal are both insufficient, the system will automatically switch to the UAV formation mode. In this mode, the system divides the UAVs into a master UAV (MasterUAV) and slave UAVs (Slave UAV). The master UAV is responsible for acting as a relay node to maintain a communication connection with the ground terminal or the base station.

[0165] The master UAV establishes communication with the ground terminal: The master UAV will establish a communication link with the ground terminal via the Wi-Fi or LoRa module and simultaneously receive the inspection data transmitted by the slave UAVs.

[0166] Data transmission from slave drones: The slave drone transmits the detection data to the host drone via a wireless communication module. The host drone then packages all the data together and transmits it to the ground terminal or base station.

[0167] Step 6: The base station uploads data to the cloud platform. After the ground terminal or the host drone completes data aggregation and preprocessing, the system transmits the processed data to the base station via a LoRa module or Wi-Fi module. Upon receiving the data, the base station uploads it to the cloud platform via the network.

[0168] The data processing system on the cloud platform will further analyze the received data, including modal analysis, vibration signal analysis, image recognition, and other operations, and generate a bridge health status report for management personnel to refer to.

[0169] Step 7: Successful Data Upload and Task Completion. After each data transmission, the system checks whether the data has been successfully uploaded to the cloud platform. If the data upload is successful, the system marks the inspection task as complete and ends the task process.

[0170] If the upload is successful: the system records the task as completed and notifies the drone to return.

[0171] If the upload fails, the system will continue to attempt to re-establish the communication link until the data is successfully uploaded.

[0172] Step 8: Communication Handling in Abnormal Situations. If, in an environment with signal obstruction, all communication paths (base station, ground terminal, and host UAV) fail to meet signal strength requirements, the system will enter an abnormal handling mechanism. In this case, the UAV will temporarily store the detection data and automatically attempt to re-upload it once the signal is restored. Simultaneously, the system will send an alarm to the ground control station, indicating an abnormal communication environment or a malfunction in the UAV inspection system, so that technicians can address the problem promptly.

[0173] The following is in conjunction with the appendix Figure 5 The content involved in the above embodiments will be explained.

[0174] Figure 5 The ground terminal and the drone swarm shown are connected via Wi-Fi and LoRa modules; the ground terminal and the base station are connected via LoRa module; the drone swarm is connected to the base station via LoRa module; when the drone swarm loses connection with the base station, it reconnects to the base station via a relay from the ground terminal.

[0175] Figure 5The drone cluster shown is connected to the ground terminal via a Wi-Fi module and a LoRa module. When the drone cluster is disconnected from the ground terminal, the drones connected to the ground terminal act as the master drones and the drones disconnected act as slave drones. The master drones and slave drones are connected via a Wi-Fi module, and the slave drones transmit data to the ground terminal through the master drones.

[0176] Figure 5 The base station shown is connected to the data center via LoRa; the data center is connected to the monitoring cloud database, which is responsible for storing and managing the bridge inspection data transmitted from the base station; the monitoring cloud database is connected to the monitoring cloud server, which is responsible for processing and analyzing the bridge inspection data; and the monitoring cloud server is connected to the data display platform, allowing users to view the analysis results and bridge health status reports in real time.

[0177] This embodiment also provides a computer device suitable for a relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs), including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the relay system for detecting the health status of bridges with signal obstruction based on UAVs as proposed in the above embodiment.

[0178] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0179] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, it implements the relay system for detecting the health status of bridges with signal blockage based on UAVs, as proposed in the above embodiments.

[0180] In summary, 1. Efficient data transmission in complex environments:

[0181] The relay communication mechanism proposed in this invention effectively solves the signal obstruction problem at the bottom of bridges and other complex structural areas. Through ground terminals and UAV swarm relay mode, UAVs can maintain reliable communication with ground terminals or base stations in complex environments, ensuring the real-time performance and integrity of detection data.

[0182] 2. Flexible relay mechanism:

[0183] This invention introduces a ground terminal as a relay node and a collaborative working mode for UAV formations. Whether it's the ground terminal acting as a relay or the adjustment of the master-slave structure among UAVs, it provides the system with great flexibility, enabling it to adapt to inspection needs in different bridge structures and environments, and ensuring smooth data transmission.

[0184] 3. 24 / 7 monitoring and data transmission:

[0185] In addition to the drone inspection mode, this invention also provides a mechanism for ground terminals to continuously monitor bridge vibration signals. Even when the drone is not performing inspection tasks, the ground terminal can monitor the health status of the bridge in real time, and collect and transmit data through multi-sensor fusion technology to ensure the safety of the bridge in daily operation.

[0186] 4. Bridge health assessment:

[0187] The system employs modal analysis and other methods to conduct in-depth analysis of the bridge's vibration characteristics, extracting key parameters such as natural frequency and damping ratio. This data can accurately assess the bridge's health status, help predict potential structural risks, and provide a basis for bridge maintenance. Furthermore, the system integrates image processing and pattern recognition algorithms to identify surface defects on the bridge, such as cracks, corrosion, and spalling. High-resolution cameras mounted on drones acquire high-definition images of the bridge surface, and combined with defect identification algorithms, automatically detect and classify structural damage to the bridge surface.

[0188] Example 2

[0189] Reference Figure 2 - Figure 6 This is the second embodiment of the present invention. This embodiment conducts experimental verification on the relay switching function of the UAV communication relay system in complex signal environments. The purpose is to evaluate the system's stability, switching delay, packet loss rate, and communication interruption duration under signal obstruction conditions.

[0190] The experimental site for this study was the Nanjing Yangtze River Bridge No. 5. A total of 25 experiments were conducted to evaluate the performance of the UAV communication relay system in a real-world bridge environment. Through multiple experiments, the stability of the system under different flight paths and environmental conditions was tested, with a focus on key indicators such as relay switching capability, signal strength variation, transmission delay, and data loss in signal obstruction scenarios.

[0191] Experimental methods:

[0192] Step 1: Simulation Environment Setup:

[0193] Step 1.1: Select the environment under the Yangtze River Bridge No. 5 to simulate a signal obstruction scenario and ensure that the GPS signal is partially or completely disabled.

[0194] Step 1.2: Set up obstacles to block the direct communication link between the drone and the ground terminal, and test the signal weakening and loss.

[0195] Step 2: Equipment Installation

[0196] Step 2.1: The ground terminal is installed in an open area outside the bridge to receive data from the UAV.

[0197] Step 2.2: Equip the UAV with a communication module and set up a relay UAV for data transmission. Ensure that the relay UAV can cover areas with signal obstruction and act as a relay node with the ground terminal.

[0198] Step 3: Data Monitoring and Collection

[0199] Step 3.1: Use signal strength analysis tools to monitor the communication signal strength between the UAV and the ground terminal, and between the UAV and the relay equipment in real time.

[0200] Step 3.2: Use logging tools to monitor key performance indicators such as packet loss rate, transmission delay, and duration of communication interruption during handover.

[0201] Experimental procedure:

[0202] The drone begins flight in a simulated environment, initially maintaining direct communication with the ground terminal. During this phase, the strength of the communication signal and data transmission latency are recorded to obtain baseline data under normal communication conditions.

[0203] When a drone enters an area with signal obstruction, the direct communication signal gradually weakens. At this time, UAV-ARS technology should automatically activate relay mode to continue data transmission with the ground terminal via a relay drone.

[0204] Record key data before and after the relay handover, including signal strength, transmission delay, and data loss during the handover process. This data is used to analyze the performance and stability of the relay handover process.

[0205] The following is in conjunction with the appendix Figure 6 The content involved in the above embodiments will be explained.

[0206] Figure 6 Signal strength comparison chart (top left): Before switching, the signal strength was generally low, fluctuating between 40.43dB and 59.87dB, showing the signal attenuation phenomenon in direct communication mode. After switching to relay mode, the signal strength significantly improved, recovering to the range of 62.39dB to 79.22dB, indicating that the relay drone effectively improved the stability of the communication signal in obstructed environments.

[0207] Figure 6 b. Data transmission delay comparison chart (top right): The transmission delay showed a relatively high and gradually increasing trend before the switchover, ranging from 83.04ms to 117.15ms, with a significant increase in delay, especially when the signal weakened. After switching to relay mode, the transmission delay was significantly reduced, remaining between 52.28ms and 88.87ms, with small fluctuations, indicating that relay communication has a significant effect on reducing delay and ensuring the stability of data transmission.

[0208] Figure 6 c. Packet loss rate comparison chart (bottom left): The packet loss rate was relatively high before the switchover, ranging from 10.15% to 23.83%, especially when the signal was severely weakened, the packet loss rate increased significantly. However, after switching to relay mode, the packet loss rate decreased significantly, dropping to 2% to 7.92%, indicating that the system can effectively reduce data loss after switching to relay mode, ensuring the continuity and integrity of data transmission.

[0209] Figure 6 d. Switching interruption duration graph (bottom right): The switching interruption time is displayed. There is a certain interruption time during the switching process, ranging from 0.55 seconds to 1.92 seconds. However, the overall interruption duration is short, and in most experiments, the interruption time is kept within 1.5 seconds, indicating that the system can quickly complete the relay switching and maintain the stability of the communication link.

[0210] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles (UAVs), characterized in that: include, Constructing a relay system includes deploying ground terminals, UAV-borne relay units, bridge structure information collection units, bridge surface defect information collection units, data storage units, and UAV ground stations; The ground terminal is fixedly installed on the side of the bridge and continuously collects bridge vibration signals through a multi-sensor fusion module; the drone is equipped with a camera and lidar to collect information on bridge surface defects. When a drone enters an area with signal obstruction, the relay system automatically switches the communication mode: The ground terminal acts as a relay node, receiving data from the drone and forwarding it to the base station; The ground terminal unit is the core control and communication relay node for bridge health monitoring, used for the acquisition of bridge vibration signals, UAV communication relay, and data management and transmission. When the UAV performs inspection tasks and in signal-blocked environments, the ground terminal unit ensures the integrity and accuracy of data transmission through relay function. The ground terminal switches between Wi-Fi, LoRa and public communication networks according to the actual communication environment. The ground terminal processes and temporarily stores the collected bridge vibration signals and inspection data to ensure the continuity and integrity of the data. The UAV-borne relay unit is used to provide communication relay function during bridge health monitoring, and ensures continuous data transmission in the event of signal obstruction or communication link interruption. The UAV-borne relay unit integrates 5GHz Wi-Fi and LoRa modules to achieve reliable communication with ground terminals or other UAVs. During the inspection process, when the direct connection between the UAV and the ground terminal is blocked, the relay unit can automatically switch to the host role and act as a relay node to provide communication support for other UAVs. In drone swarm mode, the host drone acts as a relay node, receiving and forwarding data from the slave drones. Drone Swarm Relay Mode: In certain complex situations, ground terminals may not be able to directly connect with drones during inspections. Therefore, a drone swarm collaborative working mode is introduced. The drone swarm consists of master drones and slave drones. When ground terminals cannot communicate directly with drones, the drones in the system will automatically adjust to a master-slave structure. The host drone acts as a relay node: the host drone is responsible for maintaining a connection with the ground terminal and transmitting the received inspection data back to the ground terminal or base station; Slave drones: Drones that cannot communicate directly with ground terminals transmit data to host drones that can connect to ground terminals. The host drone acts as a relay, transmitting this data back to the ground terminal or base station. Ground terminals or base stations upload the collected data to the cloud platform, extract key parameters of the bridge's health status using modal analysis methods, and generate an assessment report. The relay system monitors signal strength in real time. When all communication paths fail to meet the requirements, an anomaly handling mechanism is triggered to temporarily store the data and re-upload it after the signal is restored. When drone inspections are not in progress, a ground terminal is fixedly installed on the side of the bridge to continuously collect vibration signals. The ground terminal transmits the vibration signals to a nearby base station via a multi-sensor fusion module. The base station then uploads the data to a cloud platform. On the cloud platform, the relay system analyzes the bridge's vibration characteristics using modal analysis, extracting parameters such as natural frequency and damping ratio to assess the bridge's health status. The specific process is as follows: The relay system monitors the vibration signals of the bridge in real time through ground terminals. The ground terminals are fixedly installed at the structural nodes of the bridge and collect vibration signals through an integrated multi-sensor fusion module. Vibration data undergoes preliminary processing via a Linux controller, and the pre-processed vibration data is stored in the data storage module of the ground terminal. The ground terminal uploads vibration signals to the cloud server for centralized storage and management via the LoRa wireless communication module; when the communication link between the ground terminal and the base station is lost, the relay system will automatically traverse other ground terminals in the vicinity and establish a connection via Wi-Fi or LoRa; the relay system transmits data to the cloud through the connectable ground terminals to ensure timely data upload; During data transmission, the relay system distinguishes data from different nodes and marks which nodes have lost communication links, ensuring clear traceability records for subsequent data analysis and maintenance. At the same time, the relay system can dynamically adjust the communication path according to the node connection status to ensure the continuity of bridge health status monitoring. On the cloud platform, the data is analyzed in depth using modal analysis methods to extract key parameters such as the bridge's natural frequency and damping ratio. Based on these parameters, the relay system generates a bridge health status assessment report and provides a reference for subsequent maintenance. The relay system is equipped with a real-time detection function for abnormal signals, which can promptly identify significant frequency changes or modal anomalies in vibration signals. When an anomaly occurs in the bridge vibration signal, the relay system will automatically trigger an early warning and notify relevant maintenance personnel to conduct inspections and maintenance to ensure the safety of the bridge.

2. The relay system for detecting bridge health status based on signal obstruction by unmanned aerial vehicles as described in claim 1, characterized in that: The bridge structure information collection unit is used to collect dynamic characteristic data of the bridge structure during bridge health monitoring, including physical parameters such as bridge vibration signals, displacement, and tilt angle. The bridge structure information collection unit integrates multiple high-precision sensor modules and provides important data for the analysis and evaluation of bridge health status by collecting bridge structural status information in real time.

3. The relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles as described in claim 2, characterized in that: The bridge surface defect information collection unit is used to collect defect information on the bridge surface during bridge health monitoring, including the detection and recording of defect characteristics such as cracks, corrosion, and peeling. The bridge surface defect information collection unit integrates imaging equipment with high-definition cameras and infrared sensors, which can collect high-resolution images in complex bridge environments, providing basic data for the assessment of bridge surface defects.

4. The relay system for detecting bridge health status based on signal obstruction by unmanned aerial vehicles as described in claim 3, characterized in that: The data storage unit is used to store various types of data collected during bridge health monitoring, including vibration signals, displacement data, tilt angle information, and image data of bridge surface defects. The data storage unit can record data from multiple sensor modules in real time through a high-speed storage device. The UAV ground station serves as the command and control center in the UAV bridge health monitoring system, responsible for the UAV's flight control, data management, mission scheduling, and communication relay functions. The ground station communicates with the UAV in real time via a wireless communication link, receives bridge inspection data transmitted by the UAV, and sends control commands to ensure the smooth completion of the inspection mission.

5. The relay system for detecting bridge health status based on signal obstruction by unmanned aerial vehicles as described in claim 4, characterized in that: When a drone enters the complex structural area at the bottom of a bridge for inspection, the wireless communication link directly with the base station or ground terminal may be blocked due to the obstruction of the bridge's bottom structure, including when the ground terminal acts as a relay node and in drone swarm relay mode, as detailed below: Based on ground terminals as relay nodes: When the drone is conducting inspections, the ground terminal automatically switches between the Wi-Fi and LoRa modules based on the signal strength of the communication environment. If the drone's direct communication with the base station is blocked while inspecting the bottom of the bridge, the ground terminal acts as a relay node, receiving the data transmitted by the drone and transmitting it to the base station to ensure the real-time and completeness of the bridge inspection data. The specific process is as follows: When the drone begins to inspect the bottom of the bridge, it first establishes a communication connection with the ground terminal and base station simultaneously through the 5GHz Wi-Fi and LoRa communication modules. The communication link between the drone and the base station is used to receive the bridge defect image data collected by the drone, while the communication link between the drone and the ground terminal remains silent. During the drone inspection process, the relay system will monitor the communication signal strength with the base station in real time. When the drone enters the complex area at the bottom of the bridge, the relay system will automatically detect that the communication signal between the drone and the base station is blocked due to obstruction or signal attenuation. When the system detects that the drone cannot communicate directly with the base station, the relay system automatically switches to the mode of the ground terminal as the relay node. At this time, the drone will send the collected bridge defect image data to the ground terminal through Wi-Fi or LoRa module. The ground terminal acts as a relay node, responsible for receiving data transmitted by the UAV, including information on bridge surface cracks, thread defects, and images of bridge corrosion. The ground terminal performs preliminary preprocessing on the received data through its internal buffer and data processing modules.

6. The relay system for detecting the health status of bridges with signal obstruction based on unmanned aerial vehicles as described in claim 5, characterized in that: After receiving data from the UAV, the ground terminal transmits the data to the base station via a LoRa communication link. When the wireless signal environment is poor, the ground terminal has the ability to automatically select the best signal to ensure stable data transmission. After receiving data transmitted from the ground terminal, the base station uploads it to the cloud server for centralized processing and storage. At this time, the relay system performs in-depth analysis of the data through the analysis platform and generates a bridge health status report.

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