A Novel Method Based On RFID Rotating Antenna For Indoor Localization

With the increasing development of science and technology,we have stepped in the era of INDUSTRIE 4.0.The concept of smart factory proposed in INDUSTRIE 4.0 has revolutionized the technology and equipments employed by manufacturing factories.Meanwhile,it has put forward higher requirements for the factory informatization,especially for accurate indoor localization.There are plenty of intelligent equipments having perceived and autonomous ability in smart factories,such as intelligent transport units,which need to obtain their own positions and then plan movements due to unfixed transmission routes.Location awareness of intelligent transport unit requires indoor localization technology.RFID(Radio Frequency Identification)is one of the core technologies of Internet of things and also one of the key technologies to promote the development of INDUSTRIE 4.0.RFID technology can not only recognize object's information but also find the corresponding position.As a kind of proven technology,RFID has been widely used in the military,agriculture,retail,logistics,manufacturing and so on,and also continually penetrated into our life.At present,RFID technology is a hot spot in the field of indoor localization.The UHF RFID(Ultra High Frequency RFID)leverages high frequency,so its corresponding reader has a good reading and writing range.And it can simultaneously identify a number of different UHF RFID tags as well,thus UHF RFID devices are commonly used in indoor localization.This thesis will explore how to utilize RFID-based indoor localization technology to solve the problem of locating accurately in complex surroundings of smart factory.In the smart factory of INDUSTRIE 4.0,the target which needs to be located is intelligent transport unit.As a significant part of smart factory,it is quite important for intelligent transport unit to perceive its own position,therefore it is supposed to possess computing capability.This thesis regards the AGV(automatic guided vehicle)as an intelligent transport unit because it carries intelligent devices and owns operating system.And we equip the AGV with a rotating antenna and harness RFID interrogator to read the phases of reference tags so as to locate the vehicle by applying SAR(synthetic aperture).SAR stems from radar technology and due to the similarity of RFID system and secondary radar system,it is introduced in the RFID-based localization.The core of SAR is the design of hologram reconstruction algorithm.This thesis first devises basic hologram reconstruction algorithm,and then according to the phase error measured by reader,FHSS and speed measurement error,we improve basic hologram reconstruction algorithm respectively so as to successively infer Gaussian-based hologram reconstruction algorithm,difference-based hologram reconstruction algorithm and redundant speed based hologram reconstruction algorithm.According to the characteristics of synthetic aperture,this thesis explores the factors that affect the resolution of hologram.More specifically,on the one hand,we investigate the relationship between the aperture length and localization error.On the other hand,we theoretically prove that rotational motion can indeed improve the localization accuracy,which has a meaningful impact on localization of the target in the practical application.In addition to the localization algorithm,parameter setting and environmental factors can influence the localization results as well.Through experiments,this thesis explores the influential factors of indoor localization system in the factory in order to improve the localization accuracy.In the end,we leverage redundant speed based hologram reconstruction algorithm and then devise and implement RFID-based indoor localization system based on the rotating antenna.And then experiment results show that the localization system does.