| The submarine is required a high concealment because it is a major strategic deterrent weapon on the information battlefield in the future,Therefore,the submarine is required to adopt a high-precision navigation system to ensure its autonomy and concealment.However,underwater navigation technology in most countries cannot meet such requirements,only have the inertial navigation system,satellite navigation system,etc.However,such methods require that the submarine rises to the surface to receive signals regularly,and that will increase the probability of exposure.The gravity field is an inherent resource of the Earth,and it provides a natural coordinate system for aviation,aerospace and navigation.The gravity assisted navigation has the advantages of no radiation、low energy consumption,and it can work all day no matter the weather and location.The principle is to match the real-time gravity data which measured by the gravity sensor with the gravity base map which stored in the computer.Constructing the accurate gravity base map is the precondition of gravity-assisted navigation.In this paper,downward continuation of gravity filed be used to construct the base map,hence,four kind of downward continuation methods are studied,and Selecting the Taylor series downward continuation which is relative stable after model comparison experiments,then on the basic of this method,the constrained downward continuation method with known points is studied,also achieved good results in the actual data processing.Then a comparison experiment is made between the conventional rectangular decision region and the probability error elliptic decision region which concluded that the probability error ellipse has less computational and also can contain the point of real location.finally,combined with the idea of vehicle navigation,the gravity point matching is carried out with the constraints of slope anddistance.the set of algorithms used in two-dimensional and three-dimensional simulation experiments and all can locate the deviated track to the effect of the real track,and achieve efficient and accurate underwater gravity-assisted positioning.so this set of algorithms meets the requires of efficient and accurate underwater gravity-assisted navigation. |
