Research On Indoor Positioning Based On UWB Technology

Nowadays,with the maturing positioning technologies such as China's Beidou and GPS,those technologies have been widely adopted in business area.However,Chinese indoor positioning technologies still remain experimental level relative to those amounting outdoor positioning technologies.Among various indoor positioning technologies,Ultra Web Band(UWB)technology's merits stand out in this area.Hence,it is potential to utilize UWB on order to achieve indoor positioning.This paper investigates into ranging and positioning functions of the current UBW positioning system with increasing the accuracy of positioning system.This paper analyses the errors of two ranging approaches with concluding that the errors are primarily caused by the below two factors: 1.The clock skew that occurs between the nodes of crystal oscillation will cause deviation on the time of response when ranging models send and receive signals,in which the accuracy of ranging is affected.2.The signal propagation speed changes caused by the refractive index of the air during the propagation of signals between nodes,which in turn affects the accuracy of ranging.Combining the two factors causing the ranging error,two error coefficients are derived and the related measurement methods and application methods are designed.The two error coefficients are respectively applicable to the ranging module using a high-frequency stable crystal oscillator and not using a high frequency Stable crystal ranging module.This paper also designs a method for measuring the refractive index of air and the actual frequency of a crystal oscillator.After comparing several UWB positioning methods,this paper selects the positioning method based on the time difference of arrival(TDOA).After introducing several common algorithms based on TDOA,formula derivation and MATLAB simulation for Fang algorithm,Chan algorithm,Taloy series algorithm,combined with the application of the error coefficient in ranging,obtained the error curves and scatter plots of the three algorithms,compared the error of the three algorithms,and pick out the Chan algorithm with the smallest error among the three algorithms,and then simulated to obtain an error curve and a scatter plot,and analyze the error and standard deviation.Experiments show that using the error coefficient to correct the distance measurement in the positioning system can improve the accuracy of the distance measurement and the accuracy of the corresponding positioning system,and the Kalman filter can further improve the positioning accuracy.The method of correcting the error coefficient in distance measurement can be applied to outdoor positioning.