Design And Implementation Of Indoor Multi-Node Dead Reckoning In WSN Based On MEMS Sensor

In recent years,location-oriented techniques and services have been getting increased attention,especially the problems of locating and navigating in complicated indoor environment.Owing to wireless signals being hindered by buildings and other unknown factors in indoor environment,GPS(Global Positioning System)signals cannot cover the enclosure space,which make it difficult to obtain the position information and further execute locating.With the development of WSN(Wireless Sensor Networks),it becomes a hotspot for many research institutes to develop a high-precision and low-cost indoor dead reckoning system with WSN techniques.Considering that MEMS(MicroElectro-Mechanical Systems)sensors are being widely applied in many related applications,this thesis designs and builds an indoor WSN multi-node dead reckoning system using MEMS sensors and RF(Radio Frequency)modules based on the achievements of our team in the field of inertial navigation and my own experience in networking and dead reckoning for nodes with important theoretical and practical value.This thesis analyzes the fundamentals of these techniques,for addressing the problems of existing indoor locating such as overly depending on the parameters of wireless signals and position jumping,utilizes PDR(Pedestrian Dead Reckoning)algorithm to get the positions of nodes and further realizes multi-node dead reckoning and inter-node locating.Then,this thesis designs relative algorithm for gait detection,step estimation and attitude fusion involved in multi-node dead reckoning and optimizes these parameters using a compensation algorithm.The experiment proved that the algorithm proposed in this thesis can effectively get node location information.Multi-node dead reckoning requires constructing the network among nodes so as to transmit inter-node information.After analyzing the abstract model of networking for nodes,this thesis proposes a Simple-Modbus protocol for building an inter-node communication network based on Modbus communication protocol,and conducts tests to evaluate the performance of the network.The results demonstrate that the proposed system has good performance on networking,reliable transmitting distance and strong penetrating power,and it can persistently report the location information of nodes.This thesis conducts simulation experiments for the proposed multi-node dead reckoning system by Matlab and real experiments for the system on the upper computer.In the test of walking along the trajectories,when the nodes move 100 meters in practice,the average error between the calculated distances and the real distances is ±3 meters.Tests were taken in different scenarios,each of them is tested 30 times,the statistical results show that more than 85% of the tests reach the standard that the error is less than 3%.