| Our country is located between the Pacific Ring of Fire and the asia-europe earthquake belt.Strengthening Research on monitoring and emergency response capabilities for destructive earthquakes is an effective measure to reduce disaster losses,protect people’s lives and property safety,and ensure sustainable economic and social development,has important scientific and practical significance.When a large earthquake occurs,it is urgent for people to know the distribution of earthquake damage in strong earthquake areas so as to make timely assessment of the disaster situation and emergency response,it provides scientific and accurate basis for making rescue plan and distributing relief materials.When a large earthquake occurs,it is very important to know the distribution of earthquake damage in strong earthquake area for the timely assessment of disaster situation,emergency response,rescue plan and the formulation and distribution of relief materials.On the other hand,seismic data transmission based on cable or 3G/4G/5G wireless relies on base stations and other public infrastructure,which may lead to bandwidth limitation and network outage.In recent years,MEMS(Micro Electro Mechanical System)sensors are widely used in seismic monitoring because of their small size,low cost and easy installation.Lora-based long-range(range from several kilometers to tens of kilometers)wireless communication has the ability of ad hoc network independent of public infrastructure,which can be used as a supplement to the main wireless communication mode of Internet cable or 3G/4G/5G.In order to solve these problems,a MEMS seismic data acquisition device with Wired Network and Lora Wireless transmission is designed by using ARM + Linux embedded control technology.Through monitoring the MEMS seismic data acquisition device in the seismic risk area,the vibration intensity can be monitored and recorded in real-time,thus achieving high-precision earthquake intensity quick report;When the earthquake is coming,the monitoring node can transmit the seismic parameters of the main communication through the wireless network,or directly to the mobile emergency communication station.The main tasks are as follows:(1)The prototype of low-cost seismic data acquisition device based on MEMS accelerometer is developed.Through system function design,device selection,circuit design,software design,ARM + Linux embedded system development,etc.,the functions of MEMS seismic data acquisition device,GNSS high precision timing,large capacity TF card local data storage and network real-time transmission are realized.The method of multi-chip ADXL355 parallel acquisition and correlation average is used to reduce the self-noise of the instrument and improve the signal-to-noise ratio of the weak seismic signal,real-time filtering of acquired signal,PGA/PGV based on Kanamori algorithm,real-time output of ground motion parameters,intelligent design of edge calculation,etc.(2)LoRa module is used to design the long-distance wireless communication network as the assistant communication means of MEMS seismic sensor,which can realize the emergency transmission of seismic parameters when the infrastructure is damaged.In this paper,the effect of spreading factor,coding rate and bit rate on the channel transmission in Lora modulation technology and the network structure of LoRa WAN protocol are analyzed,by analyzing various network topologies and choosing to use hybrid star and mesh network topologies,a networking protocol is designed,it realizes the function requirements of multi-hop network transmission,long data transmission distance(from a few kilometers to 20 kilometers),high efficiency and high reliability.(3)The experiment of Lora wireless network communication is carried out with the prototype.In this paper,the actual effective distance of point-to-point communication and multi-hop network communication and the effect of data packet size on communication are studied,it provides reference data for network monitoring application. |
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