Research And Implementation Of Indoor Positioning Technology Based On RFID

The computer technology is developing rapidly,and the demand for positioning technology is more and more stronger.In the outdoor environment,global positioning system has developed very mature.However,due to the shielding of satellite signals in indoor environments,outdoor positioning technologies often fail to achieve the accuracy required by indoor positioning.Compared with other indoor positioning technologies such as Bluetooth and Ultrasonic,the indoor positioning technology based on Radio Frequency Identification(RFID)is favored by scholars at home and abroad for its advantages of non-line-of-sight transmission,lower cost and higher communication efficiency.This thesis mainly studies the indoor single target positioning technology based on RFID.The static target and dynamic target are analyzed respectively,,and then the corresponding localization algorithm is proposed.The details are as follows:(1)This thesis optimizes the LANDMARC algorithm based on Received Signal Strength Indicator(RSSI)for indoor static target positioning scenarios,focusing on the instability and inprecision problems.Firstly,it aims at the shortcomings of the original algorithm: when the target tag is close to a reference tag,the Euclidean distance of the reference tag calculated by the positioning system is zero,which leads to the disorder value of the system.In this thesis.This thesis improves the weight formula by replacing the zero-value so as to eliminate the outliers in the system.As a result,the stability of the system is improved.Secondly,the concept of neighborhood error correction method is introduced.In this method,the initial positioning result of the target tag is corrected by calculating the average error of the neighborhood reference tags,so as to improve the accuracy of the system.Experimental results show that the stability and accuracy of this method are improved remarkably.The positioning error can be reduced to 25 cm.(2)In the aspect of indoor dynamic target positioning,the triangulation positioning based on phase difference in space domain is proposed to realize trajectory tracking,with the aid of the least square method.Firstly,two sets of antenna pairs are arranged in the location scene,and the distance measurement algorithm based on phase difference in spatial domain is used to calculate the arrival angle of the tag to be tested.Then the trigonometric function method is used to convert the arrival angle into distance,so as to calculate the specific position coordinates of the label to be measured.Secondly,the position data of a group of tags to be measured obtained by the above method is fitted into a curve by the least square method,which can roughly reflect the movement trend of dynamic targets.Experimental results show that this method is feasible for dynamic target tracking,while its movement trajectory can be reflected in real time.(3)This thesis combines the above two positioning algorithms to achieve an RFID indoor positioning system.The system works for both the static location scene and the dynamic location scene.It mainly consists of the indoor static target positioning module in the storage environment and the dynamic target positioning module in the nursing home environment.Finally,the functions of the two modules are tested to prove the feasibility and practicability of the two algorithms.