| Global Navigation Satellite system(GNSS,Global Navigation Satelite Sysyem)can provide global,real-time and continuous positioning services,ranging from meter-level standard positioning services to centimeter-level precision positioning services.Among them,attitude determination is an important branch of GNSS application.With the characteristics of low cost,high precision and simple implementation,it is widely used in aviation,navigation,land vehicle driving and many other fields and has broad application prospects.However,in the application of land vehicles,the low-cost single-frequency GPS receiver is usually used,which have lower measurement accuracy,and in dense urban environments with high-rise buildings,the orientation accuracy is further reduced by external factors such as multipath effect and low satellite visibility.Due to the use of low-quality receiver and challenging urban environment,the effect of the receiver in calculating attitude angle is not good.In order to improve the performance of directional attitude measurement,a GPS/BDS dual-antenna combined attitude measurement technology based on MEMS(Micro-Electro Mechanical System)is designed in this thesis.The specific research contents are as follows:(1)The key of precision positioning service is to use high precision carrier phase observation.Based on the theory of double-difference relative positioning model and combined with the characteristics of BDS satellite signal,this thesis deduces the GPS/BDS combined double-difference observation model to improve the orientation accuracy and the ability to deal with low satellite visibility scenes.(2)The research of GNSS/INS(Inertial Navigation System)integrated attitude determination technology further realizes reliable orientation.Making use of the advantages that INS does not depend on external information and GNSS navigation errors do not accumulate with time,the integrated attitude determination system based on MEMS is studied,and the orientation attitude determination principle and error model of inertial navigation system are analyzed,which is committed to realize a low-cost,high-precision and reliable qualitative attitude measurement system.(3)The accuracy of solving integer ambiguity is of great significance for precision positioning service.This paper introduces the ambiguity solving process in detail,including float estimation,integer ambiguity solution and integer ambiguity verification,and focuses on the classical method commonly used in integer ambiguity search process-LAMDBA(Leastsquares Ambiguity Decorrelation Adjustment)algorithm.Then,an improved integer ambiguity search method,LAMBDA algorithm with baseline constraint and pitch constraint,is proposed to greatly improves the efficiency of ambiguity search.Finally,aiming at the attitude angle obtained by integer ambiguity resolution,a yaw smoothing algorithm is proposed to further optimize the orientation performance.(4)Based on the research results of orientation principle and algorithm,the design and development of orientation attitude measurement system is realized.The receiver orientation card is formed by using the A402-3 orientation module of Techtotop as the core hardware,and according to the requirements of the host computer for the orientation system,the corresponding host computer software is designed to form a set of reliable high-precision orientation system,and experiments are carried out in the open environment scene and complex environment to verify the feasibility and accuracy of the orientation system.The experimental results show that in the open environment,the orientation system has good attitude measurement performance,the orientation success rate is as high as 99.8%,and the measurement deviations of yaw,pitch angle and roll angle are 0.08 °,0.05 °and0.06 °respectively.In the complex environment,the large deviations in the measurement of yaw,pitch angle and roll angle are 1.66 °,0.97 °and 1.06 °.Its performance index has met the actual needs of most scenarios. |
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