Research On Gravity Aided Space Stabilized Inertial Navigation System

As one of high-precision inertial navigation systems space stabilized inertial navigation system(INS)has become the core technology for underwater passive navigation.To improve and enhance the backward current status of underwater navigation technology of traditional inertial and dead reckoning,new correction methods of INS with better performance of concealment have always been the hot research topics in international,in which the idea of correcting INS with the help of information of ocean gravity field has been applied to the practical application.This gravity aided navigation system is able to overcome the shortcome for traditional pure inerial navigation system with higher positioning precision,which makes it possible to ensure the elusive for submarine.Based on the inertial navigation system,the mian idea of gravity aided navigation is that the gravity data output by gravimeter is introduced to correct the navigation error or restrict the increasing speed of navigation error and extend the reset periodic as far as possible,in order to achieve long-term navigation with high precision and concealment.Besides,gravity matching navigation becomes another method of gravity aided navigation,in which the gravity data obtained from gravimeter and that from existing ocean gravity database are compared.The main works and innovative ideas are listed as follows:1.The basic principle of space stabilized inertial navigation system is introduced in which the reference earth model,the defination and transition of coordinate system and the mechanics arrange of space stabilized INS are discussed.Then technical connotation of gravity aided navigation is analysed from the points of gravity compensation and gravity matching,in order to show clear direction for follow-up design of gravity compensation and gravity matching methods of space stabilized inertial navigation system.2.In view of making gravity compensation to the space stabilized INS,firstly the influence of gravity disturbance vector on the system is obtained in theory.Secondly the methods of estimating gravity disturbance vector are discussed based on the EGM2008 earth model and the mechanics arrange of space stabilized INS is improved to achieve the gravity compensation to the space stabilized INS.Finally the result of gravity compensation is analysed through simlation experiment.3.Artificial Bee Colony(ABC)algorithm is applied to the of gravity matching navigation algorithm in this paper.With the development of intelligent algorithms,the powerful search ability of ABC algorithm makes it possible to replace the non-intelligent algorithms in traditional engineering technology.However,existing search mechanism of basic ABC algorithm can not meet the need of gravity aided navigation for high accuracy.Two main modifications to the basic ABC algorithm are done in this paper: adjusting the range of search step and calculation of transition probability adaptively,in order to improve the search ability.Finally,basic test functions are chosen to test the performance of the improved ABC algorithm.4.Based on the improved ABC algorithm,in order to further enhance the diversity of the colony,the search mechanism including main bee colony is employed,which increases the diversity of population and broadens the search scope.5.Considering the multi valuedness of gravity matching method and the gravity measurement errors from gravity database and gravimeter,incidental mismatch can not be avoided though the search precision is high enough.According to this problem,this paper proposes double-group constrained search mechanism,using external velocity information to restrain the matching points.6.In order to make the matching points satisfy the restrain conditions,the threshold values of distance and gravity difference can not be set too small.The matching results will not be the only though external restrain information is introduced,therefore the modified Hausdorff distance is introduced to screen the possible matching results in this paper.7.To verify the feasibility of gravity matching method,simulation conditions are prepared to analyse the matching result in this paper.The results show that the matching efficiency and matching precise of the method is high enough to saitisfy the performance demand for gravity matching navigation.The sea experiment data are used to verify the correctness of simulations further.