INS/USBL Integrated Navigation Technology Research

Inertial navigation system (INS) relies on inertial measurement unit and other supporting facilities, and outputs complete navigation information, like attitude, velocity and position. It possesses high precision within a short time, and does not contact with the outside sound and light signal. INS is often used as the main navigation equipment. In the opaque waters,whether it is light or electromagnetic wave, their energy attenuation is large, the propagation distance is very limited. But the acoustic owns good performance of propagation with little attenuation in sea water, more suitable for underwater positioning technology than light,electromagnetic wave. So it is possible using INS/USBL integrated navigation system on underwater positioning. This will not only overcome the problem of error accumulation in pure inertial navigation system, but also provide high-precision navigational information to carrier and underwater targets for special environment underwater navigation. The loose and tightly integrated technology of inertial navigation system with ultra-short baseline (USBL)system is researched based on an inverted USBL acoustic arrays in the paper, the main contents are as follows:1. Several common motion parameters, the coordinate system and the transform relationship are defined, and the mathematical solve processes of inertial navigation system is deduced based on Newton’s laws of mechanics theory. INS error model is established to analyze the error characteristics of INS. Then, the principle of USBL positioning system is researched based on the phase difference, and the block diagram of adaptive phase estimator is designed combined with the criteria of minimum mean square error. The positioning error of USBL is analyzed and compensated.2. Based on acoustic propagation round trip time (RTT) and plane wave approximation,the position of transponder relative to USBL positioning system is solved, laid the foundation for the system mathematical model. The basic theory of Kalman filter and its filtering process are studied; the state equation and measurement equation of INS/USBL loose integrated navigation system are established on the basis of the INS error equations and USBL solving equations. For the purpose of improving the dynamic performance and robustness, INS/USBL tightly integrated technology is designed, which examines the USBL original slope distance,slope distance difference and the spatial distribution information of acoustic arrays. Therein error is relatively uncomplicated and easy to be compensated, which is more beneficial to navigation algorithm.3. In order to improve the navigation accuracy of integrated navigation system, nonlinear filtering methods are studied,like EKF and UKF algorithm. The linearization process of EKF algorithm nonlinear state equation and measurement equation is derived, and the implementation process of UKF algorithm is designed base on unscented transformation process further. Finally,Numerical simulation is performed,and the curves and statistics table show that linear and nonlinear INS/USBL navigation technology are able to effectively estimate the error, and the estimation error of nonlinear filtering algorithm is smaller, its navigation accuracy is higher.