Technology Of GPS Multi-baseline Attitude Determination Based On Multi-antenna Receiver With Common Clock

Three-dimensional attitude information is of great significance for the safe operation of high-speed motion carriers(such as high-speed railway,aircraft,rocket,etc.).How to determine the three-dimensional attitude of carriers efficiently and accurately has become a hot topic in the fields of navigation.The traditional attitude determination technology based on inertial navigation system suffers from shortcomings such as rapid accumulation of system errors and long cold start-up time,which cannot meet the requirements of carrier long-time attitude determination with high accuracy.GPS-based attitude determination technology has gradually gained people's favor due to its advantages of low cost,long navigation time,high precision,etc.With the background and technological objectives of the NSFC project “The Research of High Precision Multi-antennas BDS/GPS Receiver Modelling and Key Technologies” and the Science and Technology Commission of Shanghai project “The Research and Demonstration Application of Multi-antenna GPS/BDS receiver”,this paper aims at researching the single-differenced baseline model for common clocks and multi-baseline attitude determination algorithms.Besides,a GPS multi-baseline attitude determination technique,based on the multi-antenna receiver with commonclock,is proposed for the accurate determination of three-dimensional attitudes of carriers.The main work of this research is as following:(1)This paper analyzes the characteristic of the common-clock multi-antenna receiver and select a kind of four-antenna receiver with common clock,which is rare in China,after researching the development and application of common clock receivers in the market.Based on this new kind of receiver,we propose a new GPS attitude determination technology with multi-baseline.(2)This paper proposes a single-differenced baseline model for common clocks.This model,using the feature that antennas of the receiver share the same clock,only needs to make a single-difference between the observations to eliminate the receiver clock error.The model uses Kalman filter to estimate the parameters,introducing the UPD parameter to separate the fractional part of the ambiguity by using its high correlation with the ambiguity parameter,in order to fix the ambiguity fast.The detection and repair of the cycle slip are realized in the filtering process,and using the integer ambiguity substitution approach to fix the ambiguity of the single-difference model can improve the accuracy of baseline solution.In static experiments(baseline length 1.023 meters),compared to the traditional double-difference model,the single-difference model in this paper improves the heading and pitch accuracy respectively by 42%(from 0.14°to 0.08°)and 63%(by 0.41°to 0.15°).In the dynamic experiment(baseline length 0.512m),the accuracy of the heading and pitch determined by single-difference model was 0.453 degrees and 0.481 degrees.Static and dynamic experimental results show that the single-difference model can ensure attitude determination with high precision and high stability.(3)This paper analyzes some kinds of algorithms for multi-baseline attitude calculation.After comparing with other algorithms through simulation experiments,QUEST method was chosen as the multi-baseline attitude determination algorithm in this paper.For the feature that the selected multi-antenna receiver can constitute the third baseline beyond the two baselines necessary for three-dimensional attitude determination,we propose an idea that the introduction of a redundant baseline can improve the overall attitude determination accuracy.Subsequently,the simulation experiments show that the addition of redundant baseline can optimize the attitude determination results to a certain extent.Especially when the main antenna or the slave antenna has a large error,the redundant baseline can obviously improve the measurement accuracy.When the error of the minor baseline is large,adding the redundant baseline can improves the heading,pitch and roll accuracy respectively by about 8%,87% and 61%.When the errors of major and minor baseline are all large,adding the redundant baseline can improves the heading,pitch and roll accuracy respectively by about 34%,71% and 71%.(4)This paper proposes a multi-baseline attitude determination technique combining single-differenced baseline model based on carrier phase and multi-baseline attitude solution.A complete GPS multi-baseline attitude determination process is constructed,and corresponding static and dynamic experiments are designed.The experimental results show that in the static environment,the heading,pitch and roll accuracy of this technique is 0.057 degrees,0.128 degrees and 0.152 degrees.Due to the large error of the minor baseline in the dynamic environment,adding the redundant baseline can improves the heading,pitch and roll accuracy respectively by about 10%(from 0.219°to 0.196 °),4%(from 0.204°to 0.197°)and 48%(from 0.722°to 0.378°).The experimental results show that the GPS multi-baseline attitude determination technique based on the multi-antenna receiver with common-clock proposed in this paper has better robustness and accuracy than the double-difference model adopted by the receiver.On the other hand,it proves that adding redundant baselines can improve the accuracy and stability of attitude determination,especially for the accuracy of roll.