Research And Implementation Of GPS Carrier Attitude Measurement Algorithm Under Baseline Constraints

Compared with the traditional inertial attitude measurement system,the attitude measurement based on GPS has the characteristics of low cost,high precision,low influence by environmental factors and no time limit.In addition,the GPS-based attitude measurement system is easy to set up,easy to use.Among technologies that use different GPS observations to measure the attitude of a carrier,GPS attitude measurement technology based on carrier phase observations is one of the more accurate techniques.The correct solution of the integer ambiguity is a very important part of this technology.LAMBDA algorithm is a commonly used algorithm for solving the integer ambiguity.However,LAMBDA algorithm has some shortcomings in the process of fixing the integer ambiguity.On the one hand,there is a certain integer Gaussian transformation redundancy in the process of decorrelating covariance matrix,which reduces the transformation efficiency to some extent.On the other hand,when the algorithm is to fix multiple optimal values,there is some redundancy in the searching space of the LAMBDA algorithm.After determining the integer ambiguity,the baseline vector which is composed by the antennas can be solved directly in the observation equation,and the attitude of the carrier can be further determined.However,when there are fixed multiple baselines in the carrier,the attitude measurement method can not effectively utilize the other measurement information of the antennas.Aiming at these deficiencies of LAMBDA algorithm,this paper attempts to optimize thereductionandsearchingprocessofLAMBDA algorithm,respectively,so as to improve the efficiency of solving the integer ambiguity of the LAMBDA algorithm.In the first place,using the R-processing algorithm to optimize the reduction process of the LAMBDA algorithm.The R-processing algorithm uses the permutation process routing and the optimization path to reduce the transformation redundancy,and uses the symmetric transformation algorithm to reduce the integer Gauss transformation redundancy.In the second place,using the S-process algorithm to optimize the searching process of the lambda algorithm,this algorithm can reduce the size of the search space by replacing?~2with the integer ambiguity based on the size of the original search space.Aiming at the fixed multiple baselines in the carrier,this paper constructs the antenna coordinate system in the carrier by using the baseline length as the constraint condition,and then uses the least squares estimation method to determine the carrier's attitude.By introducing the prior condition of the baseline length,This algorithm reduces the error of the carrier's attitude solution to some extent.In the end of this paper,based on the hardware environment of I7-4700,16GB memory and the software environment of WINDOWS10,MATLAB2014A,simulation experiments are done to verify these algorithms above.The experimental results of the lambda optimization algorithm show that the optimization of R-processing algorithm can reduce the time of ambiguity resolution,and the R-processing combined with the S-processing algorithm can further reduce the time of ambiguity resolution.The experimental results of the carrier attitude measurement algorithm for fixed multiple baselines show that in a fixed multiple baselines which were composed by one main and three slave antennas in this paper of the carrier,the error of the attitude solving algorithm based on the baseline length as a priori condition is less than the direct solution of the attitude.