Research On Indoor Localization Techniques For Harsh Environment

Indoor localization techniques generally refers to the techniques of providing loca-tion information in environments where satellite signals cannot penetrate.It is widely used in mines,tunnels,buildings,factories and other environments,and provides basic location information for applications such as intelligent sensing,safety supervision,storage and lo-gistics systems.It plays a very important role in the Internet of Things(IoT),Wireless Sensor Networks(WSN),and Cyber-Physical Systems(CPS).Outdoor positioning tech-niques based on satellite signals can provide mature solutions for outdoor environments,such as BeiDou Navigation Satellite System(BNSS),Global Positioning System(GPS),and so on.However,penetration of satellite signals are very weak,this type of outdoor positioning system like GPS cannot be used in indoor environments.In recent years,with the increasing demand for location information in various indoor environments,indoor lo-calization techniques have received widespread attention.For the environment with good communication environment,there have been many related studies and commercial ap-plications,but in the complex environment with a lot of interference,the current indoor localization techniques still have many problems.In harsh environments(or complex environments),there are many factors that in-terfere with the localization signal,and they will reduce the localization accuracy,such as high concentrations of dust,obstacles,multipath refraction caused by complex envi-ronments,and humid environments.The specific interference modes caused by these interference sources can be divided into three types:(1)Multipath,which means that the transmitted wireless signals may reach one single receiver through multiple pathes due to occlusion,reflection,etc.Multipath causes great interference to the indoor localization algorithm based on signal strength.Ultra-wideband communication already has mature solutions to such interference,but the cost is also high.(2)The non-line-of-sight(NLoS)communication.Signals transmit obstacles make the NLoS communication,which will cause signal attenuation,increase time delay,or even make signals interruption.Moreover,to a certain extent,it will also interfere with the identification of Multipath in UWB com-munications.(3)Electromagnetic interference,which will cause abnormal signal strength or signal interruption.There are three important factors affecting the popularization of localization tech-niques,including costs,system performance,and localization accuracy.This disserta-tion considers three aspects and proposes corresponding high-precision localization ap-proaches for harsh indoor environments.The main contributions of this dissertation can be summarized as follows:(1)Based on the signal strength,a polynomial fitting filtering method and a distance scaling algorithm are proposed to realize the localization in harsh environments.This approach is mainly aimed at achieving acceptable localization accuracy in harsh envi-ronments under low cost and low power consumption conditions.It estimates the one-dimensional and two-dimensional coordinates of the target through the signal intensity ratio model.Compared with the traditional general-purpose path loss model(Log-normal Distance Path Loss,LDPL),the localization results of this method are theoretically bi-ased,but When in a harsh environment,it has better robustness,but the accuracy will be higher.This method has the lowest cost,the lowest power consumption,the lowest im-plementation complexity,and the lowest accuracy among the three localization methods.(2)A hybrid localization method combining UWB and inertial sensors is proposed.This method is mainly for cost-insensitive applications and high-precision localization re-quirements in harsh environments.The indoor localization techniques based on UWB signals have high accuracy,but weak anti-interference ability.The inertial sensor-based Pedestrian Dead Reckoning(PDR)has a strong anti-interference ability,but there is cu-mulative error that cannot be eliminated by itself.Combining the two algorithms,the approach can obtain high localization accuracy and have strong anti-interference ability.This approach has the highest cost and accuracy among the three methods.But it requires the deployment of a complex PDR algorithm in the tag,its battery life will be reduced.(3)An UWB localization enhancement techniques in NLoS environment are pro-posed.This approach only depends on a UWB localization technique to achieve high-precision localization in a harsh environment.This approach is based on UWB commu-nications and can use the time-of-flight(TOF)or time-of-arrival(TDOA)algorithm for localization.When the UWB signals work in LOS communication,the speed and direc-tion of the target are calculated in real time.In the area where the UWB signal work in NLoS and cannot complete the localization,this approach can calculate the moving path of the target.Path information can be used to assist positioning.Compared with the traditional NLoS communication recognition and elimination algorithm,it has better robustness facing UWB NLoS commutation.Among the three localization methods,this approach is at a medium level in terms of cost,accuracy,performance,and implementa-tion complexity.In summary,this dissertation studies the high-precision indoor localization approach in a harsh environment.Considering three aspects of cost,system performance,localiza-tion accuracy,and this dissertation proposes three indoor localization solutions with high robustness.