| Location Based Services has been an important cornerstone of the advancement of human civilization since ancient times.From the early nautical field to the current aerospace technology,or various types of mobile robots represented by unmanned vehi-cles,drones,etc.,these platforms acquire and perceive their own positions,which is the premise of completing various space-related tasks.In the field of outdoor positioning,the wireless positioning technology represented by global positioning system takes the lead.At the same time,it also set off a research boom for seamlessly connecting indoor and outdoor location services in the field of indoor positioning.With the development of machine intelligence,all kinds of indoor mobile platforms also need to locate and track their own positions urgently.In the existing framework,only mobile platforms with good hardware conditions can acquire more information related to location and re-alize simultaneous location and mapping,while other low intelligent mobile platforms also need to realize location tracking in some way.At this time,the research on indoor positioning technology by wireless signals is more worthy of being applied to indoor mobile platforms as an indoor general positioning system.In this paper,the propagation model of wireless signal in three-dimensional space is studied,and the static base station is used as the target location.Then,according to the characteristics of mobile platform,the moving object equipped with RFID passive tag is used as the tracking target,and the localization of wireless signal on the mobile target is analyzed.By constructing RFID odometer to calibrate the algorithm of common mobile platform,the feasibility of wireless signal application on indoor mobile platform is verified.The main research contents are as follows:(1)The propagation path of electromagnetic wave in indoor environment is studied by using the principle of ray tracing,and the mathematical model of the shortest propa-gation path is established when the reflection and diffraction path occurs in the non sight distance propagation.Then,for the non-line-of-sight propagation path,the position of the alternative base station is calculated according to the diffraction point information of the reflection point,and all non-line-of sight propagation is transformed into the line-of-sight path by using the hybrid genetic algorithm for solution.Through the experiment,compared with other algorithms,good differentiation and positioning performance of the non-line-of-sight path are obtained.Then,we establish the UWB base stations to experiment the whole measurement process.Experimental results show that the non-line-of-sight error of the reconstructed propagation model can be distinguished well,and the positioning accuracy in the non-line-of-sight region is within 0.6m.(2)In order to be easily transplanted and applied to various mobile platforms,pas-sive RFID tags are proposed to locate the mobile platform.Through a series of prelim-inary experiments,the localization of RFID phase information is verified.The results show that the phase value changes can be reflected the change of the tag movement distance.Then a multi-tag system is proposed to decompose the moving process of the target,and the speed of the moving target at a certain time can be obtained by multi group instantaneous velocity projection,thereby completing the positioning of the mov-ing target.The initial position of the mobile platform is also discussed,and the starting point of the mobile platform is determined dynamically during the moving process.The effectiveness of the multi-tag system is verified by a series of experiments The experi-mental results show that the error is less than 18.7cm during 80%tracking.Based on the high precision characteristics of RFID tag,it is proposed to replace the wheel odometer of common mobile platforms with RFID odometer.The accuracy of the state update of the linear and random movements of RFID odometer is discussed.During the establishment of the indoor environment map,the SLAM system with RFID odometer is tested and verified.The results show that the building error of environment map is small,the cumulative error divergence of pose is slow,and it can effectively participate in the improvement of the proposed distribution that is closer to the target distribution.Finally,the failure of RFID odometer is discussed,and the extended appli-cation of multi-antenna system is proposed,at the same time,the scale and pure rotation of multi-tags RFID odometer can be eliminated. |
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