Design Of Reliable System For Real-time Monitoring Data Acquisition And Transmission Of Slope Based On LoRa

With the increase of global climate change and human activities,the frequency and influence of natural disasters such as landslides are gradually increasing.Slope monitoring system is a kind of engineering technology for monitoring slope stability.It can obtain real-time slope deformation,displacement and other information by installing sensors and data acquisition equipment.In this thesis,a reliable LoRa real-time data acquisition system suitable for slope is designed.The main research contents are as follows:Firstly,the architecture composition of slope monitoring system at home and abroad is investigated,the wireless networking mode suitable for slope monitoring is analyzed,and the technologies such as Zigbee,4G,NB-lo T and LoRa are compared.In view of monitoring requirements,LoRa is selected as the main wireless communication mode of the system.In addition,we investigate WSN data link layer scheduling algorithm,compare and analyze the advantages and disadvantages of current scheduling algorithm,and plan to use master-slave scheduling algorithm as the MAC layer algorithm of the system.In addition,the fault-tolerant design of the system in recent years is investigated,and the idea of system layering and redundancy is proposed to design the fault-tolerant mechanism.Secondly,the overall design of slope monitoring system is carried out.Based on the reliability theory,the fault-tolerant mechanism is designed respectively at the sink node level,the acquisition node level and the sensor level.At the sink node level,a backup node is added,the active/standby switchover logic is designed,and the timeout threshold and periodic heartbeat frame are set to determine the fault.At the acquisition node and sensor level,the system reliability and robustness are enhanced by setting the response timeout value and using data retransmission in fault diagnosis messages according to the master-slave scheduling policy.Then,the basic principle of LoRa WAN is introduced,and on this basis,the scheduling algorithm of data transmission in LoRa system is studied,the problems of ALOHA and TDMA algorithms in LoRa network are analyzed,and an uplink bandwidth allocation scheduling algorithm based on master-slave scheduling strategy is designed.By estimating the generation time of periodic data,The upstream bandwidth and transmission time of nodes are dynamically allocated so that the transmission time is as close to the data generation time as possible.Compared with ALOHA algorithm and TDMA algorithm,the simulation results show that the improved master-slave scheduling algorithm has lower average delay and better performance.In addition,the encapsulation of Modbus messages in LoRa protocol is completed,and function design is carried out on the basis of Modbus protocol.The function can support the transmission and control of Beidou RTK sensor,soil temperature and humidity sensor,weather station and other data.In order to realize the normal operation of the system,the operation strategy of the server,sink node and collection node is designed.On the server side,the process of system configuration and man-machine interface are designed,and the state display in system operation is realized.At the sink node,the running flow is designed based on the master-slave scheduling strategy and the server instruction.At the acquisition node,three working modes are designed.In working mode 1,the node performs continuous periodic data collection;in working mode 2,the node completes single aperiodic data collection according to wake up,fetch and sleep instructions;in working mode 3,the node completes aperiodic data collection according to fetch and fetch instructions.In order to realize the three-layer fault diagnosis scheme of the system,under the fault-tolerant mechanism of the sink node,the master/standby switching logic is designed for fault processing and recovery,and the timeout value and heartbeat frame period of the master and standby nodes are set for fault diagnosis of the master node.In the fault-tolerant mode of the acquisition node and sensor node,the fault is diagnosed by setting the timeout threshold,and the fault is processed and recovered according to the instructions of the server.Finally,the three working modes and fault diagnosis modes designed in this thesis are tested through the multi-sensor data transmission environment equipped with laboratory conditions.In the verification of the three working modes,the message list parameters of the sink node were set,and then the bus utilization rate was calculated.In order to maximize the bus utilization rate,the error correction and repeated tests were carried out constantly,which verified the correctness of the master-slave scheduling strategy designed in this thesis.In the three-layer fault diagnosis experiment of the system,through the design of the fault,and according to the time-out value set by the nodes of each layer as the diagnosis basis,through the man-machine UI interface to compare the state before and after the fault,the results show that the measured results of the three-layer fault diagnosis experiment are consistent with the expected results,so as to improve the reliability and robustness of the system.To sum up,a high reliability slope monitoring system based on LoRa is designed in this thesis.The nodes have the functions of continuous,burst and variable sampling.The system can handle faults step by step,and has the characteristics of flexibility and reliability,and provides certain reference value and application value for the subsequent engineering practice.