A house structure safety monitoring and collecting system based on internet of things

Abstract

This invention belongs to the field of monitoring and measurement technology, specifically relating to an Internet of Things (IoT)-based building structure safety monitoring and acquisition system. The system includes an object-sensing layer, a network transmission layer, and an edge control layer. Wireless sensor nodes in the object-sensing layer collect structural physical parameters and encapsulate them into data frames. The edge control layer's command and control center parses the data frames. The command and control center issues message commands to achieve dynamic channel switching, time synchronization, and allocation of communication time slots. The command and control center associates the measurement data with the node coordinates. This invention adopts a layered collaborative communication architecture, relying on dynamic frequency hopping and time slot allocation to improve communication reliability and anti-interference performance in complex building environments, making it suitable for automated monitoring of building structure safety.

Description

Technical Field

[0001] This invention belongs to the field of monitoring and measurement technology, specifically relating to an Internet of Things-based building structure safety monitoring and data acquisition system. Background Technology

[0002] Building structural safety monitoring is a crucial means of ensuring the safe operation of existing buildings. With the development of Internet of Things (IoT) technology, wireless sensor networks are gradually being introduced into the field of building structural safety monitoring due to their flexible deployment and lower cost.

[0003] Existing building structure safety monitoring systems based on wireless sensor networks use ZigBee or LoRa single-hop communication modes. The reinforced concrete walls and floors inside buildings significantly attenuate wireless signals, limiting communication distance. Some systems introduce multi-hop relays to extend coverage, but these relay protocols are fixed forwarding and lack dynamic routing maintenance capabilities. If a relay node fails, downstream nodes are disconnected from the network. Existing systems often operate on a single fixed frequency. Wi-Fi, Bluetooth, and mobile communication signals in and around the building may overlap with their operating frequency or cause adjacent-channel interference. When the fixed frequency is interfered with, communication quality degrades. Furthermore, existing systems typically rely on manual recording of node deployment locations. If a node is passively moved, the system cannot automatically update the location information. Deployment requires configuring the network identifier, operating channel, and routing parameters for each node individually, resulting in a long implementation cycle for large-scale networks.

[0004] In summary, there is currently no solution in existing building structure safety monitoring systems that systematically addresses communication reliability issues through collaborative design at the physical, data link, and network layers. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the existing technology, the present invention provides a building structure safety monitoring and data acquisition system based on the Internet of Things to solve the problems in the background technology.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An Internet of Things-based building structure safety monitoring and data acquisition system includes an object sensing layer, a network transmission layer, and an edge control layer that are sequentially connected in communication. The object sensing layer includes at least two wireless sensor nodes, each of which includes a sensing and acquisition unit, a microprocessor, a power supply unit, and a wireless communication unit. The sensing and acquisition unit acquires physical parameters of the building structure and outputs them to the microprocessor. The microprocessor converts the physical parameters into measurement data and encapsulates them into data frames. The sensor node includes a sleep state and a working state. It is switched to the working state by an internal timer or a remote wake-up command, and returns to the sleep state after the command is sent. The network transmission layer is connected to the wireless communication unit and the edge control layer respectively to receive and forward data frames; The edge control layer includes a command and control center; the command and control center receives data frames and parses them to obtain measurement data; The command and control center sends message instructions to each sensor node and network transmission layer, controls each sensor node and network transmission layer to switch working channels to transmit data frames, sends time synchronization signals to each node, and allocates communication time slots to each sensor node. The planar coordinates of the sensor nodes are measured on-site and then entered into the command and control center, which then associates the measurement data with the planar coordinates.

[0007] Furthermore, the data frame includes a frame header and a frame body. The frame header consists of a synchronization identifier field, a composite field of frame type and destination address, and a source address field. The total length of the frame header does not exceed 3 bytes.

[0008] Furthermore, the remote wake-up command includes the address code of the target sensor node; the sensor node in sleep mode listens for the wake-up preamble forwarded by the network transport layer, and when the address code in the wake-up preamble matches the address of the sensor node, the sensor node switches to working mode.

[0009] Furthermore, the command and control center generates the frequency hopping sequence by scanning the communication channels within the preset frequency band and measuring the received signal strength indication value and packet error rate of each channel. The command and control center summarizes the received signal strength indication values ​​and packet error rate data of the channels, sorts the channels according to the degree of interference, filters the channels according to the sorting results to construct an available channel pool, and generates frequency hopping sequences. It also sends message instructions and switching time points to each node through broadcast frames; continuously monitors the packet error rate of the current channel, and when the packet error rate is higher than the preset threshold, regenerates the frequency hopping sequence and sends it to each node.

[0010] Furthermore, the sensor nodes select a parent node and join the network based on the signal strength of the beacon frames of the command and control center, forming a tree topology with the command and control center as the root node; each node that has joined the network maintains a neighbor table, which records the address, hop count and link quality parameters of neighboring nodes; and switches to a backup parent node based on the neighbor table when the current parent node's link is interrupted.

[0011] Furthermore, the time synchronization signal is a time synchronization frame periodically sent by the command and control center, and the time synchronization frame includes the current clock value of the command and control center.

[0012] Furthermore, the energy supply unit includes a light energy harvesting module and a hybrid energy storage module; the light energy harvesting module is connected to a buck-boost power supply module through a rectifier circuit, and the output terminal of the buck-boost power supply module is connected to the charging input terminal of the hybrid energy storage module; the hybrid energy storage module is composed of a primary battery and a supercapacitor connected in parallel.

[0013] Furthermore, the command and control center is equipped with an edge computing module; the edge computing module filters and performs threshold comparisons on the received data frames; when data exceeding the threshold is detected, the command and control center outputs an alarm signal and marks the data exceeding the threshold before uploading it.

[0014] Furthermore, the network transmission layer and sensor nodes are each provided with a firmware upgrade storage area; the command and control center divides the upgrade package into multiple fragments and sends the fragments to the target device through the currently specified working channel of the frequency hopping sequence; after receiving all fragments, the target device performs verification and firmware installation.

[0015] Furthermore, the communication time slots are allocated by the command and control center according to the address number of each sensor node in sequence; the command and control center generates a time slot allocation table of the allocated communication time slots and sends it to each node through a broadcast frame; each sensor node only sends data in the allocated communication time slot, and the wireless communication unit is in a turned-off state in the unallocated communication time slot.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a minimally simplistic frame structure with a total frame header length of no more than 3 bytes to compress the amount of data transmitted in a single transmission, reduce transmission time, and lower the probability of collisions and communication power consumption. Through a dynamic frequency hopping mechanism based on RSSI and PER comprehensive evaluation, the system adaptively switches the operating frequency point according to the real-time channel quality. Combined with tree-structured multi-hop routing and a mechanism that automatically switches to a backup parent node based on the neighbor table when a link is interrupted, this invention synergistically improves communication reliability from three levels: frame structure, spectrum management, and network topology. 2. By associating and storing the node's planar coordinates with the measurement data in the command and control center's database, each measurement data entry contains information in four dimensions: node address, acquisition time, physical parameter values, and planar coordinates, ensuring a precise correspondence between the acquired data and the spatial location; in conjunction with the communication time slots allocated to each node by the command and control center, each node sends data only in the designated time slot, avoiding data collisions and improving the reliability of data transmission; 3. Through a dual-mode wake-up mechanism of internal timer and remote wake-up, the sensor node shuts off the power supply to the sensing and acquisition unit, microprocessor and wireless communication unit in sleep mode, and only switches to working mode when the preset acquisition time is reached or when a wake-up command with matching address code is received. After completing the acquisition and transmission, it immediately returns to sleep mode. Combined with light energy acquisition and hybrid energy storage, the system power consumption is effectively reduced, enabling maintenance-free long-term deployment. At the same time, it supports OTA remote firmware upgrades, reducing operation and maintenance costs. Attached Figure Description

[0017] Figure 1 This is a communication flowchart of the present invention; Detailed Implementation To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] Example 1: like Figure 1As shown, the present invention provides a building structure safety monitoring and acquisition system based on the Internet of Things, comprising an object sensing layer, a network transmission layer, and an edge control layer that are sequentially connected in communication. The object perception layer includes at least two wireless sensor nodes. Each wireless sensor node includes a sensing and acquisition unit, a microprocessor, a power supply unit, and a wireless communication unit. The sensing and acquisition unit is connected to the microprocessor, and the microprocessor is connected to the wireless communication unit. The sensing and acquisition unit, the microprocessor, and the wireless communication unit are electrically connected to the power supply unit, and the enable terminal of each unit is connected to the enable control terminal of the intelligent power consumption management unit. The sensing and acquisition unit includes settlement sensors, displacement sensors, tilt sensors, vibration sensors, and temperature sensors, used to collect data on the building structure's settlement, displacement, tilt angle, vibration frequency, and ambient temperature, respectively. The outputs of each sensor are connected to the microprocessor's analog-to-digital converter interface via signal conditioning circuitry. The microprocessor's data output is connected to the data input of the wireless communication unit. The sensing and acquisition unit converts the collected physical parameters of the building structure (settlement, displacement, tilt angle, vibration frequency, and temperature) into electrical signals and outputs them to the microprocessor. The microprocessor converts the electrical signals back into measurement data and encapsulates them into data frames. Sensor nodes have sleep and active states, switched to active state by an internal timer or remote wake-up command, and return to sleep state after completing data acquisition and transmission.

[0022] The sensor node includes a sleep state and an active state. In the sleep state, the intelligent power management unit disconnects the power supply to the sensing and acquisition unit, the microprocessor, and the wireless communication unit, leaving only the internal timer and the wake-up listening circuit working. The sensor node is switched to the active state by the internal timer or a remote wake-up command, and returns to the sleep state after the transmission is completed. The sensor node switches to working state via an internal timer or a remote wake-up command. When the internal timer counts to the preset acquisition time, it outputs a wake-up signal, connecting the power supply to the microprocessor and sensor acquisition unit, and the sensor node enters working state. The preset acquisition time is uniformly configured and issued by the command and control center according to monitoring requirements. The acquisition cycle is set based on the following: building structure safety monitoring is a long-term, slow-change monitoring process, and the structural deformation rate is usually relatively slow. According to the regulations on settlement observation cycles in building deformation measurement standards, the routine monitoring frequency is once a week to once a day. This invention defaults to an acquisition cycle of 3600 seconds, which covers the needs of most building structure safety monitoring scenarios while balancing system power consumption and data real-time performance. This cycle can also be remotely adjusted by the command and control center according to actual monitoring needs.

[0023] Furthermore, the remote wake-up command includes the address code of the target sensor node; the sensor node in sleep mode listens for the wake-up preamble forwarded by the network transport layer, and when the address code in the wake-up preamble matches the address of the sensor node, the sensor node switches to working mode.

[0024] The command and control center generates a remote wake-up command containing the target sensor node's address code, encapsulates the command into a data frame, and sends it to the network transport layer. The network transport layer broadcasts the command via the first radio frequency interface. While in sleep mode, the sensor node periodically activates the receiving path of its wireless communication unit with a fixed duty cycle, listening for the wake-up preamble forwarded by the network transport layer. When the address code in the detected wake-up preamble matches the address of its own sensor node, the sensor node switches to working mode. After completing data acquisition and transmission, the sensor node returns to sleep mode.

[0025] The network transport layer has a first radio frequency (RF) interface and a second RF interface. The first RF interface is communicatively connected to the wireless communication unit of the sensor node, and the second RF interface is communicatively connected to the edge control layer. The network transport layer receives data frames from the sensor node and forwards them to the edge control layer.

[0026] Preferably, the network transport layer also includes at least one repeater for extending communication coverage. When the wireless signal strength between the sensor node and the command and control center meets the requirements for direct communication, the sensor node can communicate directly with the command and control center without the need to deploy a repeater; when the communication distance is long or the signal strength is insufficient due to severe building obstruction, one or more repeaters are deployed on the signal attenuation path to achieve signal relay and coverage extension.

[0027] The network transport layer contains a microprocessor, a routing table memory, and a radio frequency front-end module. The routing table memory stores a neighbor table, which records the address, hop count, and link quality parameters of each neighbor node. The microprocessor executes a tree-structured routing protocol based on the neighbor table, controlling the forwarding path of data frames between multiple levels of the network transport layer.

[0028] The edge control layer includes a command and control center. The command and control center receives data frames and parses them to obtain measurement data. It consists of a main control board, an RF front-end module, a database storage unit, and an edge computing module. The command and control center does not have a local display device but provides web services or API interfaces for access by monitoring service center clients. The operating frequency and modulation method of the RF front-end module are set by writing configuration register values ​​to the main control board. The main control board runs a channel scanner, a frequency hopping sequence generator, a time synchronization server, and a routing manager.

[0029] The command and control center sends message instructions to each sensor node and the network transmission layer, controls each sensor node and the network transmission layer to switch working channels to transmit data frames, sends time synchronization signals to each node, and allocates communication time slots to each sensor node; the message instructions include frequency hopping sequences.

[0030] The nodes referred to are sensor nodes in the object perception layer and repeaters in the network transmission layer, excluding the command and control center in the edge control layer; the command and control center, as the network manager and scheduler, is not included in the scope of the nodes.

[0031] Furthermore, the command and control center generates the frequency hopping sequence by scanning the communication channels within the preset frequency band and measuring the received signal strength indication value and packet error rate of each channel. The command and control center summarizes the received signal strength indication values ​​and packet error rate data of the channels, sorts the channels according to the degree of interference, filters the channels according to the sorting results to construct an available channel pool, and generates frequency hopping sequences. It also sends message instructions and switching time points to each node through broadcast frames; continuously monitors the packet error rate of the current channel, and when the packet error rate is higher than the preset threshold, regenerates the frequency hopping sequence and sends it to each node.

[0032] Specifically, the command and control center sends message commands to each sensor node and the network transport layer, controlling them to switch operating channels to transmit data frames. Specifically, the communication channel is a pre-defined continuous frequency band, which is divided into multiple channels at fixed frequency intervals; for example, the 470MHz to 490MHz band can be divided into 40 channels at 500kHz intervals. The command and control center scans each communication channel within the pre-defined frequency band, measuring the Received Signal Strength Indication (RSSI) and Packet Error Rate (PER) of each channel. Preferably, when repeaters are deployed in the network transport layer, the repeaters can also participate in channel scanning under the control of the command and control center, reporting the RSSI and PER measurement results of each channel to the command and control center. The command and control center then integrates the data reported by the repeaters with its own scanning results to perform channel sorting and frequency hopping sequence generation.

[0033] The Received Signal Strength Indicator (RSSI) is read from the Received Signal Strength Indicator Register inside the RF transceiver chip. RSSI reflects the signal power level within the channel; a larger absolute value (i.e., a more negative value) indicates lower background noise and better communication quality. For example, using -100dBm and -80dBm channels, the background noise of the -100dBm channel is 20dB lower than that of the -80dBm channel, indicating cleaner signal transmission. The Packet Error Rate (PER) is obtained by sending a predetermined number of test data packets on each channel and calculating the ratio of incorrectly received packets to the total number of packets sent, expressed as a percentage. A lower PER indicates higher data transmission quality.

[0034] The command and control center aggregates the Received Signal Strength Indication (RSSI) and Packet Error Rate (PER) data for each channel and ranks the channels according to the degree of interference. Channel classification is based on a comprehensive evaluation of RSSI and PER. The classification method is as follows: For each channel, firstly, it is determined whether its Packet Error Rate (PER) exceeds a preset threshold; if it does, it is directly classified as an unusable channel. Secondly, for channels whose Packet Error Rate (PER) does not exceed the threshold, they are ranked according to their Received Signal Strength Indication (RSSI). The lower the Received Signal Strength Indication (RSSI) value (i.e., the larger the absolute value), the lower the background noise of the channel, and the higher its ranking.

[0035] The command and control center prioritizes selecting the N channels with the lowest Received Signal Strength Indication (RSSI) values ​​based on the sorting results to construct an available channel pool. The number of channels N is dynamically determined by the system based on the total number of available channels, and the number of channels N in the available channel pool is no less than the length of the frequency hopping sequence. A frequency hopping sequence is generated based on the available channel pool, in which the same channel does not appear repeatedly in adjacent time slots to avoid continuous interference that may be caused by the use of the same channel in adjacent time slots. Subsequently, the command and control center sends message commands and handover time points to each node via broadcast frames. Each node synchronously switches to the next channel specified in the frequency hopping sequence at the handover time point.

[0036] During system operation, the command and control center continuously monitors the packet error rate of the current working channel, with a detection cycle of once every 60 seconds. When the packet error rate of a certain working channel is higher than 10% for three consecutive detection cycles (three consecutive detections exclude instantaneous fluctuations, and the hysteresis mechanism ensures that frequency hopping is only triggered when interference persists), the command and control center re-executes the scanning, sorting, and sequence generation process, and sends the updated frequency hopping sequence to each node.

[0037] The preset threshold for packet error rate (PER) is 10%. This threshold is based on the fact that in building structural safety monitoring scenarios, data frame lengths are approximately 20 bytes. When the PER exceeds 10%, the system's effective data throughput on that channel significantly decreases, retransmission overhead increases, and the real-time data transmission requirement cannot be guaranteed. When the PER is below 10%, data integrity can be ensured by combining CRC checksum and automatic retransmission mechanisms. This threshold also considers preventing frequent frequency hopping caused by short-term channel fluctuations. When the PER fluctuates around the 10% threshold, a hysteresis mechanism is used to trigger frequency hopping only after three consecutive measurements. That is, frequency hopping is only triggered when three consecutive detections exceed the threshold, thus avoiding communication overhead caused by frequent channel switching.

[0038] Furthermore, during system deployment, the installation coordinates of each sensor node are obtained by measuring with a laser rangefinder or total station. Specifically, after installing each sensor node on key structural components such as beams, columns, and slabs on each floor of the building, the deployment personnel use a laser rangefinder or total station to measure the two-dimensional coordinates (X, Y) of each sensor node in the building's plane coordinate system. This information is then entered into the node information table in the system database through the human-machine interface of the control center. The data entry method supports both single-point entry and batch import: manual entry can be used for a small number of nodes, while for large-scale deployment scenarios, batch import can be performed using a pre-edited coordinate data table to improve deployment efficiency.

[0039] Each node in the node information table corresponds to one record, containing at least the following fields: node address, X-axis coordinate, Y-axis coordinate, installation location description, and data entry time. After receiving the measurement data reported by each sensor node, the command and control center parses the source address field in the data frame to obtain the node address. Using this address as an index, it queries the node information table, extracts the corresponding plane coordinates, associates the measurement data with these coordinates, and stores them in the data record table. This generates a complete record containing the acquisition time, physical parameter values, and the plane coordinates of the measurement point, for subsequent data analysis and visualization. When a 3D spatial display is required, the floor height information of each node can be further entered as the Z-axis coordinate.

[0040] When a node is passively displaced due to construction or environmental factors, the deployment personnel remeasure the new coordinates of the node, update the coordinate field corresponding to the address in the node information table through the human-machine interface of the command and control center, and record the update time in the entry time field; the subsequent reported measurement data is automatically associated with the new coordinates, and the historical data retains the original coordinates to ensure the integrity of data traceability.

[0041] Furthermore, the sensor nodes select a parent node and join the network based on the signal strength of the beacon frames of the command and control center, forming a tree topology with the command and control center as the root node; each node that has joined the network maintains a neighbor table, which records the address, hop count and link quality parameters of neighboring nodes; and switches to a backup parent node based on the neighbor table when the current parent node's link is interrupted; each node is a sensor node and a network transport layer.

[0042] Specifically, the formation and maintenance of the tree topology are divided into two modes depending on whether repeaters are deployed. When there are no repeaters, the command and control center periodically broadcasts beacon frames. After each sensor node receives the beacon frames, all sensor nodes directly take the command and control center as the parent node, forming a single-layer star topology with the command and control center as the root node. Data frames are directly sent from the sensor nodes to the command and control center.

[0043] When repeaters are present, repeaters and sensor nodes select a parent node based on the signal strength of the received beacon frames. Specifically, each node measures the Received Signal Strength Indicator (RSSI) of each received beacon frame, selects the beacon frame with the strongest RSSI and the fewest hops as its parent node, and sends a network entry request to the parent node. After confirmation by the parent node, that node becomes a layer node in the tree topology. Once in the network, this node continues to broadcast its own beacon frames for other nodes to use as a basis for parent node selection. This process expands level by level, forming a tree topology with the command and control center as the root node.

[0044] Each node already in the network (including sensor nodes and repeaters) maintains a neighbor table after joining the network. The neighbor table records the addresses, hop counts, and link quality parameters of neighboring nodes. The link quality parameters are determined based on the moving average of the most recent received signal strength indicators. Nodes periodically send probe frames to update the link quality parameters in the neighbor table.

[0045] When a node detects that its current parent node has failed to return response frames for several consecutive times, it determines that the parent node's link has been interrupted. The node queries its local neighbor table, selects the neighbor node with the fewest hops and the best link quality as the backup parent node, switches over, and sends a routing update frame to the command and control center.

[0046] Furthermore, the data frame includes a frame header and a frame body. The frame header consists of three fields: the first field is a synchronization identifier (1 byte), used by the receiver to detect the start position of the frame; the second field is a composite field of frame type and destination address (1 byte), where the high two bits indicate the frame type (data frame / / beacon frame) and the low six bits indicate the destination address; the third field is the source address (1 byte), indicating the address number of the sending node. The total length of the frame header is 3 bytes.

[0047] The 3-byte requirement is based on the fact that in building structural safety monitoring scenarios, a single system typically has no more than 64 sensor nodes, and the node address can be covered using 6 bits (the lower six bits); there are two frame types required (data frames and beacon frames), which can be represented using 2 bits; and the synchronization identifier requires 1 byte (8 bits) to provide sufficient code for receiver synchronization. These 3 bytes in total are sufficient to fully express the information contained in the frame header, without the need for additional bytes.

[0048] The frame body follows the frame header. The frame body contains a sensor type identifier field (1 byte), a measurement value field (4 bytes, in IEEE 754 single-precision floating-point format), and a timestamp field (4 bytes, in Unix timestamp format). Following the frame body is a checksum field (2 bytes), using a cyclic redundancy check (CRC) code.

[0049] Furthermore, the time synchronization signal is a time synchronization frame that the command and control center periodically sends. The time synchronization frame includes the current clock value of the command and control center.

[0050] Specifically, after receiving the time synchronization frame, each sensor node and network transmission layer calibrates its local clock using that clock value. The transmission period of the time synchronization frame is determined based on the system crystal oscillator drift rate. In this system, the typical crystal oscillator frequency stability is ±10ppm, and the drift does not exceed ±0.6 milliseconds within a 60-second period. Therefore, sending a time synchronization frame once every 60 seconds can control the clock deviation of each node within ±1 millisecond.

[0051] The command and control center allocates communication time slots to each sensor node according to their address numbers, based on a time synchronization reference. A time slot allocation table is broadcast, representing the specific results of the time slot allocation. The time slot length is set based on the time required for a single data frame transmission (including frame transmission time, propagation delay, and transmit / receive switching time) plus a guard interval. For example, transmitting a 20-byte data frame at a 1.2kbps communication rate results in a single frame transmission time of approximately 133 milliseconds. Adding the propagation delay (approximately 3.3 microseconds over a 1km distance), the transmit / receive switching time (approximately 1 millisecond), and the guard interval (approximately 10 milliseconds), the single time slot length is set to 150 milliseconds. Each sensor node only activates its wireless communication unit to transmit data within its allocated time slot.

[0052] Furthermore, the command and control center is equipped with an edge computing module; the edge computing module filters and performs threshold comparisons on the received data frames; when data exceeding the threshold is detected, the command and control center outputs an alarm signal and uploads the data after marking it.

[0053] Specifically, the edge computing module filters and performs threshold comparisons on the received data frames. The specific processing flow is as follows: a moving average filter is applied to the received measurement value sequence. The filtering window length is 5 sampling points, which means the current measurement value is arithmetically averaged with the measurements from the previous four consecutive moments to eliminate high-frequency noise components introduced by sensor noise and environmental interference. The selection of a window length of 5 sampling points is based on the following principle: while ensuring smoothness, an excessively long window will introduce significant delay (affecting alarm real-time performance), while an excessively short window will result in insufficient smoothing. The 5-sampling-point window length corresponds to 5 sampling periods, with sampling occurring once per hour for a total of 5 hours. In the slowly changing scenario of building structural safety monitoring, this effectively filters out noise without compromising alarm timeliness due to excessive delay.

[0054] The filtered measured values ​​are compared with preset upper and lower threshold values. The preset thresholds are determined based on the allowable deformation values ​​in the building structure design documents. The settlement threshold is set according to the provisions of the building foundation design code regarding the allowable settlement values ​​for different structural types; the tilt threshold is set according to the provisions of the building structure load code regarding the limit of inter-story drift angle.

[0055] When data exceeding the threshold is detected—that is, the measured value is higher than the upper threshold or lower than the lower threshold—the command and control center outputs an alarm signal and uploads the data exceeding the threshold to an external platform after marking it. The alarm signal is pushed to the monitoring service center client via a web service or API interface, and the corresponding measurement point location is displayed as a visual alarm indication on the cloud platform monitoring center page through highlighting, flashing, or color changing.

[0056] Furthermore, the network transport layer and sensor nodes are each equipped with a firmware upgrade storage area; the command and control center divides the upgrade package into multiple fragments and sends the fragments to the target device through the currently specified working channel of the frequency hopping sequence; after receiving all fragments, the target device performs verification and firmware installation.

[0057] Each fragment is no larger than 16 bytes in length of a single frame's data payload and is sent to the target device via the currently specified working channel of the frequency hopping sequence. After receiving all fragments, the target device performs a CRC check on the complete upgrade package. If the check passes, it marks the backup upgrade partition as the running partition for the next startup and performs a reset and firmware installation.

[0058] Furthermore, the energy supply unit includes a solar energy harvesting module and a hybrid energy storage module; the solar energy harvesting module is connected to a buck-boost power supply module through a rectifier circuit, and the output terminal of the buck-boost power supply module is connected to the charging input terminal of the hybrid energy storage module; the hybrid energy storage module is composed of a primary battery and a supercapacitor connected in parallel.

[0059] Specifically, the solar energy harvesting module uses photovoltaic panels to collect ambient light energy. The output of the solar energy harvesting module is connected to the input of the low-voltage input DC-DC buck-boost power supply module via a low-leakage rectifier circuit. The low-leakage rectifier circuit uses Schottky diodes to form a full-wave rectifier bridge to rectify the harvested DC power. The DC-DC buck-boost power supply module converts the rectified voltage into a stable DC voltage, and its output is connected to the charging input of the hybrid energy storage module.

[0060] The preferred primary battery is a lithium thionyl chloride battery with a nominal voltage of 3.6V, providing basic power. The supercapacitor has a nominal capacity of 1F and a rated voltage of 5.5V, providing a large instantaneous current during wireless communication unit transmission. The output of the supercapacitor is connected to the power supply of the wireless communication unit, and the output of the primary battery is connected to the power supply of the sensing and acquisition unit and the microprocessor. A supercapacitor refers to an electrochemical capacitor with high capacitance density (typically in the farad range).

[0061] The supercapacitor has a nominal capacity of 1F and a rated voltage of 5.5V. The capacity is selected based on the following: the peak current of the wireless communication unit is 50mA, the duration of a single transmission is 10ms, and the maximum allowable voltage drop is 0.5V. According to the energy storage calculation formula C = (0.05×0.01) / 0.5 = 0.001F, combined with the actual selection margin and the conventional specifications of supercapacitors, a capacity of 1F is selected.

[0062] In this embodiment, the invention is further illustrated as follows: Taking the structural safety monitoring of a building as an example, the sensor nodes communicate directly with the command and control center. When the distance between the sensor nodes and the command and control center is far or the building obstructs the signal, resulting in insufficient signal strength, a repeater can be added between the sensor nodes and the command and control center to forward data frames and extend the communication coverage.

[0063] Each sensor node uses an STM32L4 series microprocessor with a built-in analog-to-digital converter interface, supporting multiple low-power operating modes. The wireless communication unit uses a Sub-GHz RF transceiver chip, with an operating frequency band set from 470MHz to 490MHz.

[0064] The sensing and acquisition unit includes a settlement sensor, a displacement sensor, a tilt sensor, a vibration sensor, and a temperature sensor. The settlement sensor is a hydrostatic level with a measurement range of 0–50 mm and an accuracy of ±0.1 mm. The displacement sensor is a wire-type displacement sensor with a measurement range of 0–100 mm. The tilt sensor is a MEMS dual-axis tilt chip with a measurement range of ±30° and an accuracy of ±0.01°. The vibration sensor is a piezoelectric accelerometer with a frequency response range of 0.5 Hz–1 kHz. The temperature sensor is a digital temperature chip with a measurement range of -40℃ to +85℃ and an accuracy of ±0.5℃. The outputs of each sensor are connected to the microprocessor's analog-to-digital converter or digital interface via a signal conditioning circuit (composed of an operational amplifier and a low-pass filter).

[0065] The energy supply unit includes a solar energy harvesting module. This module uses flexible thin-film photovoltaic cells with an open-circuit voltage of 5V and a short-circuit current of 50mA. The rectifier circuit uses Schottky diodes to form a full-wave rectifier bridge, with a reverse leakage current not exceeding 1μA. The DC-DC buck-boost power supply module uses a TPS63070 chip with an input voltage range of 0.5V to 5V and an output voltage set at 3.3V. The primary battery is a lithium thionyl chloride battery with a nominal voltage of 3.6V and a capacity of 2400mAh. The supercapacitor is a wound-type supercapacitor with a nominal capacity of 1F and a rated voltage of 5.5V.

[0066] The network transport layer uses an STM32L4 series microprocessor, configured with two Sub-GHz RF transceiver chips as the first and second RF interfaces, respectively. The receiving frequency of the first RF interface is set to 470MHz, consistent with the transmitting frequency of the sensor node; the transmitting frequency of the second RF interface is set to 475MHz, consistent with the receiving frequency of the command and control center.

[0067] The routing table memory in the network transport layer is divided into a neighbor table area. The maximum capacity of the neighbor table is 64 entries. Each entry records the neighbor address (1 byte), hop count (1 byte), link quality moving average (1 byte), and timestamp (4 bytes). The link quality moving average is the arithmetic mean of the most recent 10 RSSI measurements. Every 30 seconds, the network transport layer sends probe frames to each node in the neighbor table and updates the link quality parameters based on whether an acknowledgment frame is received and its RSSI. The link failure threshold is set to three consecutive probes without an acknowledgment.

[0068] The command and control center uses an ARM-based embedded motherboard (such as the RK3568) with a main frequency of 1.8GHz, 2GB of RAM, and 16GB of storage. It runs a Linux operating system and is responsible for data storage, edge computing, and display control. The communication base station uses an STM32L496VE-T6 chip (ARM Cortex-M4 core, 80MHz main frequency, 512KB FLASH, 320KB RAM) and runs the HarmonyOS LiteOS embedded real-time operating system. It is responsible for sensor node registration management, frequency hopping sequence generation and scheduling, and OTA upgrade management.

[0069] The sensor node uses an STM32L431CBT6 chip (ARM Cortex-M4 core, 80MHz clock speed, 128KB FLASH), equipped with the HarmonyOS Lite OS lightweight kernel, which is responsible for data acquisition, low power management, and wireless communication protocol stack operation.

[0070] The command and control center's Linux system connects to the communication base station's HarmonyOS LiteOS via an Ethernet interface, exchanging data using a custom binary protocol. The communication base station's HarmonyOS LiteOS connects to the sensor nodes' HarmonyOS LiteOS via a Sub-GHz radio frequency interface, exchanging data using a simplified frame structure. The communication base station acts as a protocol conversion node, converting the simplified frames reported by the sensor nodes into custom binary protocol messages before uploading them to the command and control center; it also converts control commands issued by the command and control center into simplified frames before sending them to the sensor nodes.

[0071] The RF front-end module adopts a zero-IF architecture and consists of an RF transceiver chip, a local oscillator frequency synthesizer, and a baseband digital signal processor. The operating frequency is set by writing configuration register values ​​to the frequency synthesizer via the main control board, and it supports switching the operating channel in 500kHz steps within the 470MHz to 490MHz frequency band.

[0072] The database storage unit uses an SQLite relational database to establish a node information table and a data record table. The node information table stores the address, last network entry time, current location coordinates, and working status of each sensor node. The data record table stores the measurement values, timestamps, and verification flags reported by each node.

[0073] The command and control center does not have local display equipment but provides web services or API interfaces for access by the monitoring service center's clients. The monitoring service center's clients are PCs that access the command and control center's web services or API interfaces through a browser or dedicated client software. This opens the cloud platform monitoring center page, which displays the real-time online status of each node, the latest measurement values, alarm signs, and the distribution and deformation data of measurement points on the building floor plan.

[0074] The cloud platform monitoring center is a web application running on the PC of the monitoring service center. It uses the building floor plan as the base map and visualizes the measurement values ​​and alarm status of each node in the form of color or icon at the plane coordinate position of each measuring point. When the data of a measuring point exceeds the threshold, the corresponding icon of the measuring point will flash or change color on the monitoring center page, accompanied by a pop-up prompt.

[0075] The system workflow is as follows: First, sixteen sensor nodes are installed at key locations on beams, columns, and slabs on each floor; the command and control center is placed in the monitoring room on the first floor. When signal strength is insufficient and repeaters need to be added, they are installed in locations with less signal obstruction, such as stairwells. After all devices are powered on, the command and control center broadcasts beacon frames, and each node automatically joins the network by selecting a parent node based on the beacon frame signal strength, forming a tree topology. Furthermore, each sensor node is woken up by an internal timer according to a preset acquisition cycle (default 3600 seconds). The sensor acquisition unit acquires various physical parameters and outputs them to the microprocessor. The microprocessor converts the analog electrical signals into digital measurement data, encapsulates them into data frames, and sends them to the parent network transmission layer through the wireless communication unit within the allocated time slots. After the transmission is completed, it returns to the sleep state. Furthermore, in the deployment mode with a repeater, the sensor node sends the data frame to the parent repeater. The parent repeater receives the data frame through the first radio frequency interface, reads the destination address in the frame header, queries the local neighbor table to select the next-hop node, and forwards it to the next-level repeater or directly to the command and control center through the second radio frequency interface. In the deployment mode without a repeater, the sensor node directly sends the data frame to the command and control center, where it is received and processed by the radio frequency front-end module. In this mode, the data frame is not forwarded through intermediate devices.

[0076] Finally, the command and control center activates the RF front-end receiving path in each time slot according to the time slot allocation table to receive data frames. A CRC check is performed on each frame. After successful check, the sensor type identifier, measurement value, and timestamp in the frame body are parsed and stored in the database. The edge computing module reads the measurement value sequence from the database, performs a moving average filter (window length 5), and compares the filter result with a preset threshold. An alarm is triggered when the threshold is exceeded, and the alarm data is pushed to the monitoring service center client via a web service or API interface, where the corresponding measurement point location is marked on the cloud platform monitoring center page.

[0077] The specific dynamic frequency hopping implementation process in the example is as follows: The communication channel is set to a system-preset frequency band of 470MHz to 490MHz, divided into 40 channels at 500kHz intervals, numbered CH0 to CH39.

[0078] After the system starts up, the command and control center performs an initial scan of all 40 channels through each network transport layer. Each network transport layer sends 10 test data packets on each channel, records the received RSSI value and PER, and reports the results to the command and control center.

[0079] After the command and control center aggregates the data, it first filters out channels with a PER higher than 10% (typically including CH3, CH7, and CH15). For the remaining channels, they are sorted by RSSI from low to high (lower RSSI indicates lower background noise and better communication quality), and the top 20 channels form the available channel pool. A frequency hopping sequence is generated based on this pool, with a sequence length of 20 time slots, and each channel appears at most once in the sequence. After the sequence is generated, the command and control center broadcasts the sequence and handover time points to all nodes in the network via broadcast frames.

[0080] During system operation, the command and control center continuously monitors the PER of the current working channel, with a detection cycle of once every 60 seconds. When the PER of a certain working channel is higher than 10% for three consecutive detection cycles (excluding instantaneous fluctuations), the command and control center re-executes the scan and sorting, removes the current high-interference channel from the available channel pool, selects an alternative channel from the candidate channels, generates a new frequency hopping sequence, and issues a handover command.

[0081] In this embodiment, after each sensor node is installed, a laser rangefinder is used to measure the X-axis and Y-axis distances of each sensor node relative to the reference origin, using the benchmark point in the building structure design drawings as the reference origin. For example, if a sensor node P is installed at a column position on the first floor of the building, with the southwest corner of the building as the reference origin (0, 0), the coordinates of the node are measured to be (5.0 meters, 3.0 meters). After the measurement is completed, the address code (e.g., 0x01) and its coordinates (5.0, 3.0) of the node are entered into the node information table through the human-machine interface of the control center.

[0082] When the node subsequently reports measurement data, the source address field in the data frame header is 0x01. After the command and control center parses and obtains the node address, it uses this address as an index to query the node information table and obtains the corresponding plane coordinates (5.0, 3.0). The measurement data is then associated with these coordinates and stored in the data record table to generate a complete record containing the acquisition time, physical parameter values, and plane coordinates of the measurement point.

[0083] When a node is passively displaced due to construction or environmental factors, the new coordinates of the node are remeasured on site, and the coordinate field corresponding to that address is updated in the node information table through the human-machine interface of the command and control center. Subsequent reported data is automatically associated with the new coordinates.

[0084] The above are merely embodiments of the present invention. The circuits, electronic components, and modules involved are all prior art, fully achievable by those skilled in the art, and require no further explanation. The content protected by this application does not involve improvements to the software and methods. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A building structure safety monitoring and data acquisition system based on the Internet of Things, characterized in that: It includes the object sensing layer, network transmission layer and edge control layer that are connected in sequence; The object sensing layer includes at least two wireless sensor nodes, each of which includes a sensing and acquisition unit, a microprocessor, a power supply unit, and a wireless communication unit. The sensing and acquisition unit acquires physical parameters of the building structure and outputs them to the microprocessor. The microprocessor converts the physical parameters into measurement data and encapsulates them into data frames. The network transmission layer is connected to the wireless communication unit and the edge control layer respectively to receive and forward data frames; The edge control layer includes a command and control center; the command and control center receives data frames and parses them to obtain measurement data; The command and control center sends message instructions to each sensor node and network transmission layer, controls each sensor node and network transmission layer to switch working channels to transmit data frames, sends time synchronization signals to each node, and allocates communication time slots to each sensor node according to the time synchronization signals. The planar coordinates of the sensor nodes are measured on-site and then entered into the command and control center, which then associates the measurement data with the planar coordinates.

2. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The data frame includes a frame header and a frame body. The frame header consists of a synchronization identifier field, a frame type and destination address composite field, and a source address field. The total length of the frame header does not exceed 3 bytes.

3. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The sensor node includes a dormant state and an active state; in the dormant state, the sensor node listens for the wake-up preamble forwarded by the network transport layer, and when the address code in the wake-up preamble matches the address of the sensor node, the sensor node switches to the active state.

4. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The command and control center generates a message instruction, which includes a frequency hopping sequence. Specifically, the command and control center scans the communication channels within a preset frequency band and measures the received signal strength indication value and packet error rate of each channel. The command and control center summarizes the received signal strength indication values ​​and packet error rate data of the channels, sorts the channels according to the degree of interference, filters the channels according to the sorting results to construct an available channel pool, and generates frequency hopping sequences. It also sends message instructions and switching time points to each node through broadcast frames; continuously monitors the packet error rate of the current channel, and when the packet error rate is higher than the preset threshold, regenerates the frequency hopping sequence and sends it to each node.

5. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The sensor nodes select a parent node and join the network based on the signal strength of the beacon frames of the command and control center, forming a tree topology with the command and control center as the root node. Each node that has joined the network maintains a neighbor table, which records the address, hop count and link quality parameters of neighboring nodes. When the current parent node's link is interrupted, the node switches to a backup parent node based on the neighbor table.

6. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The time synchronization signal is a time synchronization frame periodically sent by the command and control center. The time synchronization frame includes the current clock value of the command and control center.

7. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The energy supply unit includes a solar energy acquisition module and a hybrid energy storage module; the solar energy acquisition module is connected to a buck-boost power supply module through a rectifier circuit, and the output terminal of the buck-boost power supply module is connected to the charging input terminal of the hybrid energy storage module; the hybrid energy storage module is composed of a primary battery and a supercapacitor connected in parallel.

8. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The command and control center is equipped with an edge computing module; the edge computing module filters and performs threshold comparisons on the received data frames; when data exceeding the threshold is detected, the command and control center outputs an alarm signal and marks the data exceeding the threshold before uploading it.

9. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The network transmission layer and sensor nodes are each equipped with a firmware upgrade storage area; the command and control center divides the upgrade package into multiple fragments and sends the fragments to the target device through the currently specified working channel of the frequency hopping sequence. After receiving all the chips, the target device performs verification and firmware installation.

10. The building structure safety monitoring and data acquisition system based on the Internet of Things as described in claim 1, characterized in that: The communication time slots are allocated by the command and control center according to the address number of each sensor node in sequence; the command and control center generates a time slot allocation table of the allocated communication time slots and sends it to each node through a broadcast frame; each sensor node only sends data in the allocated communication time slot, and the wireless communication unit is in a turned-off state in the unallocated communication time slot.

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