Research On UHF RFID Relative Positioning Method Based On Non-ideal Phase Informatio

With the advent of the era of “Internet of Things”,Radio Frequency Identification(RFID)technology has developed rapidly in the past decade.With its advantages of low cost,non-contact,corrosion resistance and easy deployment RFID has been applied to emerging Io T scenarios,such as smart libraries,unmanned supermarkets and intelligent warehousing.In the tag-intensive scene,whether the relative position of the target tag in the tag group can be quickly and accurately perceived is an important factor affecting the user self-service experience and resource management efficiency.Therefore,for tag-intensive applications,it is an important topic to study the RFID relative positioning method with high precision and low cost,which has important academic significance and practical value.Although the existing relative positioning methods can obtain better recognition accuracy,they have certain limitations,which are mainly reflected in the following aspects:(1)Most relative positioning methods are based on the premise that the phase contour has no extrusion distortion,which puts forward higher requirements for the stable speed performance of the acquisition platform and the ideal degree of the scene.In practical application scenarios,the movement and appearance of users and obstacles cause frequent variable speed movement of the acquisition platform,and it is difficult to achieve high precision positioning due to serious contour extrusion distortion.(2)Most relative positioning methods do not take into account the influence of the tag attitude on the phase contour.In the actual scene,the diversity of the target attitude leads to the change of the tag attitude,which leads to the distortion of the phase contour,so it is difficult to achieve high precision positioning.Based on the above problems,this paper focuses on the tag position estimation method suitable for variable speed and the phase contour correction algorithm suitable for tag attitude change:1.In view of the situation that the reader antenna is mostly variable,firstly,the influence of the speed of the reader antenna on the change of phase information is analyzed,and the phase profile model of the reader antenna in the case of variable speed motion is established.Then,the relationship between the speed of the reader antenna and the phase profile estimation model is analyzed,and a UHF RFID relative positioning method suitable for the non-ideal carrier phase acquisition scenario is proposed.Aiming at the uniform motion of the reader antenna,a relative positioning method based on weak estimator is proposed.The derivation of the weak estimator is based on the uniform motion of the reader antenna.In order to avoid the uniform motion condition of the reader,a position estimation model based on robust estimator is proposed for the variable-speed movement of the reader antenna.The simulation results show that the robust estimator can effectively overcome the problem of phase contour distortion under the condition of variable speed movement of the reader antenna and the computational complexity is low,but the robust estimator can’t well deal with the serious phase profile distortion caused by the frequent change of reader antenna velocity and the large change range.Based on this,this paper further proposes a relative positioning method based on enhanced robust estimator.The simulation results show that the proposed method can effectively deal with the serious problem of phase contour distortion caused by the variable speed motion of the reader and has high positioning accuracy.2.In view of the changeable tag attitude in the non-ideal phase acquisition scene,a phase correction based UHF RFID relative positioning method is proposed.Firstly,the influence of tag attitude on phase contour is analyzed,and a phase correction method based on neural network spatial mapping technology is proposed.The neural network spatial mapping technology is used to establish the phase contour solution model.The weight coefficient in the neural network space is used as the optimization variable,and the improved chicken swarm optimization algorithm is used to optimize the solution.Finally,the modified phase contour is obtained,and the phase correction model is used to solve the attitude of the tag to be tested.Finally,the valley point timestamp in the modified phase contour is used to obtain the relative position relationship of the tag to realize the relative positioning method.The simulation results show that the proposed algorithm can effectively correct the phase contour and identify the tag attitude,and improve the relative positioning accuracy.