| With the expansion of indoor space and the complexity of layout,the need for indoor positioning has been paid more and more attention.However,the Global Navigation Satellite System(GNSS)is limited by its own conditions,and the signal will be severely attenuated during the process of propagation into the room,which brings great trouble to the receiving positioning.Therefore,people have to seek other ways to achieve indoor positioning,and indoor positioning technology has also ushered in rapid development.Among many technologies,indoor pseudo-satellite technology occupies an important position due to its characteristics of high precision,high security and high coverage.In addition,pseudosatellite adopts GNSS-like signal system,which can not only locate independently,but also assist GNSS to complete the seamless indoor and outdoor positioning,which is of great research value.This paper deeply studies the principle of pseudolite indoor positioning technology,and builds a pseudolite test system for positioning based on carrier phase observations.The main research contents are as follows:1)According to the characteristics of indoor pseudolite technology,several types of positioning methods and typical signal observations are listed in this paper.After analysis,it is decided to use TDOA technology based on carrier phase observations to realize positioning solution.And the satellite signal system is deeply studied,and a set of signal structure suitable for pseudolites is designed on this basis.Based on the principle of TDOA,the network design of indoor pseudolite positioning is completed and the carrier phase observation equation is established.Through the observation equation and the time-satellite double-difference model method,the clock error at both ends of the pseudolite transmitting and receiving ends is eliminated and the ambiguity problem is solved.2)The indoor pseudolite positioning network is improved and innovated,and the design scheme of dual-carrier inverted pseudolite system and indoor and outdoor seamless positioning system is proposed.And the positioning algorithm based on TDOA is deduced in detail.By analyzing the characteristics of the CHAN algorithm and Taylor algorithm,a Doppler-assisted CHAN-Taylor fusion algorithm for pseudolite positioning is proposed.The simulation proves that the algorithm can effectively improve the positioning accuracy.And it can also be used to detect and repair cycle slips.3)According to the principle of indoor pseudolite technology,on the hardware platform based on DSP+FPGA,the frequency synthesis technology was studied to realize the generation of pseudolite signal,and the pulse signal transmission method was proposed to suppress the interference of near-far effect;In order to meet the requirements of small size and low energy consumption of user receivers,the acquisition and tracking of pseudolite signals is realized by means of ARM + FPGA,and the influence of near-far effects is further reduced by serial interference cancellation technology;a Matlab debugging platform is established on the main control end to process the observations sent by the receiver and perform positioning Solve.4)An indoor pseudo-satellite field test environment was set up,and various performance indicators of the pseudo-satellite system were tested,including transmitting signal spectrum,signal capture and tracking results in different states,carrier phase offset and receiver serial port output,to verify the correctness of the system.In addition,the static and dynamic tests prove that the system has the function of repairing cycle slips,and the positioning accuracy can reach centimeter level. |
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