Research On BDS Velocity/Attitude Estimation And Velocity-Attitude Mutual Inspection

Global navigation satellite system(GNSS)plays a more and more important role in the field of national economic construction and national defense.Velocity and attitude determination based on GNSS show a certain advantage than the traditional methods.In our country,with a view to the booming of Beidou satellite navigation system(BDS),it turns to be more significative to study BDS velocity and attitude determination.The main works and creations are as follows:1.Three BDS velocity determination algorithms and error analysis were studied.It is pointed out that they are essentially consistent,and are all based on the Doppler frequency shift between satellites and receiver.The main difference among them is that they respectively adopt raw Doppler measurements,carrier-phase-derived Doppler measurements between 2 At and carrier-phase-derived Doppler measurements between At for velocity estimation.2.The performance of velocity estimation using BDS was analyzed.Static tests demonstrated that velocity precision using raw Doppler measurements was of the order of centimetres per second,whereas the carrier-phase-derived Doppler measurements provided accuracies of the order of millimetres per second.In dynamic conditions,the precision of velocity determination with these three methods was degraded by the sudden acceleration of the vehicle.In addition,the contributions of GEO,IGSO and MEO satellites on velocity estimation were studied.3.The principle and mathematic model of baseline solution using extended kalman filtering(EKF)was introduced.The role of baseline length information plays in ambiguity solution was discussed.Three methods,calculating with baseline length virtual equation,baseline length constraint integer ambiguities(C-LAMBDA method)and assistant screening ambiguities with baseline length(two-steps method)were analyzed in theory and tested in actual.Putting forward baseline length inspection in single-epoch integer ambiguity for the reason that it exists individual error ambiguities form LAMBDA when ratio value is greater than 3.Besides,the performance of BDS and GPS integer ambiguity with baseline length constraint was comparatively analyzed.4.Local horizontal coordinate system,body coordinate system and coordinate rotation matrix were introduced.Attitude parameters from direct calculation method and the least squares filtering method direct calculation method were studied.Static and kinematic experiments were performed to test the performance of the two methods for attitude estimation using BDS and GPS,respectively.5.A single-epoch integer ambiguity algorithm with velocity information was proposed.It can improve the fixed rate of ambiguity with a more accurate initial value for EKF.In addition,we make the difference between displacement based on velocity single difference(difference between receiver)and displacement based on baseline vector single difference(difference between epoch)as a check amount.When the check amount is within the defined threshold,the velocity and attitude parameters are regarded as reliable.