Research On Multi-node Cooperative Positioning And Navigation Technology Formoving Objects

With the enhance of military requirement,stealth technology is getting more and more important.In the meanwhile,passive location estimation based on far-field signals plays an immeasurable role in the military and has caused the wide attention from academia and military.With this method,detectors find the targets by receiving signals passively and need not emit signals.With the rapid increase in the quality of people's daily life,there is badly in deed of a convenient way to the indoor location.However,traditional satellite signals cannot be applied indoor.Therefore,the indoor location and navigation is worth of studying,and some scholars have obtained several achievements in it.In this thesis,we aim to study the indoor location estimation and navigation method based on swarm intelligence perception,the passive location estimation method based on far-field signal and the location estimation and navigation method based on UWB.To be specific,the main contribution of this thesis can be concluded as follows:Firstly,this thesis studies the strategy of the indoor location estimation and navigation methods based on swarm intelligence perception.Most indoor positioning and navigation technologies need to provide structural maps of buildings,but it is difficult to obtain these structural maps in practice.Therefore,we design a geomagnetism based indoor positioning and navigation system without structure map of buildings by applying offloading strategy in Narrow Band Internet of Things(NB-Io T).Why the geomagnetic signal is used to achieve indoor navigation is due to its stability.We divide the indoor navigation into two parts: the construction of signal fingerprint database and the user navigation.Firstly,the navigator carries out the signal acquisition of navigation route,and transfers the original signals to cloud server so as to construct the fingerprint database.Secondly,users can choose online navigation or offline navigation according to the actual situation.When choosing offline navigation,the users will employ dynamic time warping(DTW)algorithm for fingerprint matching.When users would like to obtain better navigation results,they will choose online navigation.In this case,navigation system will offload the users' sampling data to remote cloud,and then the cloud matches the fingerprint of geomagnetic signals by using particle filter(PF)algorithm and sends the computation results to the users so as to indicate the users' moving direction.Experiment results demonstrate that our method is effective and the turning error is only 5 centimeters.Secondly,considering the accuracy of passive location estimation is crucial in target tracking systems,the traditional passive location estimation methods have good performance for the signals with high signal-to-noise ratio(SNR),however,they are inefficient for weak signals with low SNR.In practice,passive location signal usually has low SNR.We propose a new joint estimation method for Doppler frequency,directions of arrival(DOA)and time delay to improve the location accuracy.The proposed method consists of four steps: the first step is to improve SNR of the received signal by wavelet de-nosing,i.e.,design a new wavelet threshold function to reduce noise so as to achieve high SNR.The second step is to extract Doppler frequency by using appropriate circuit modules and simple mathematical transformation in time domain,which aims to reduce computational complexity.Specifically,we take advantage of synchronous circuits to precisely control the input of local oscillation signal and then obtain Doppler frequency accurately.The third step is to estimate DOA according to the simple mathematical rules and the relation between the DOA and Doppler frequency.Thirdly,the location estimation and navigation method based on UWB is to be studied.With the rapid development of intelligent Internet of things,UWB has been widely used in indoor location estimation and navigation.By means of high-speed pulse time synchronization and double-sided two-way ranging method,we build an UWB targets positioning and tracking system based on DW1000.In the meanwhile,in order to reduce the location estimation and navigation errors,a curve fitting method is proposed and the fitting formula is included into the program to improve the accuracy of location estimation and navigation.Experiments show that this method is more effective than the one using high frequency pulse directly.