| AUV is currently the key equipment for developing marine resources,investigating marine environment and utilizing marine space.To ensure AUV’s high accuracy,stability and concealment of autonomous navigation,positioning and reliable underwater tasks has become the research emphasis of various countries.SINS has the advantages of high autonomy,high concealment and full output parameters,but its positioning error accumulates with time.The LBL positioning system can obtain the precise positioning of the underwater vehicle,but the deployment,calibration and recovery of the base elements are time-consuming and exhausting.The USBL positioning system avoids the placement of a large number of elements,but it introduces a serious direction measurement error.Therefore,the research on the fusion navigation of multi-source information to improve the accuracy and reliability of AUV navigation and positioning has gradually become the frontier of the times.This paper combines the large array and high accuracy of LBL,single sound source and a single transponder configuration of USBL,and uses a location method base on virtual base iteration aided SINS.Combined with other underwater navigation equipment,the integrated navigation model of SINS/ virtual elements/DVL/MCP/ Depth gauge is established,which avoids the distribution of massive LBL element and the direction finding operation of USBL,and the navigation and positioning requirements of AUV underwater real-time,high precision and high concealment are realized by iterative method.The main contents of this paper are as follows:Firstly,the present situation of the development of AUV equipment at home and abroad and the research status of the navigation algorithm are investigated in detail.According to the underwater real environment,the characteristics of underwater acoustic line are analyzed,especially the main problems such as multipath effect,sound line bending and so on,which are the preparatory work for improving the accuracy of acoustic location.At the same time,for a real underwater environment model can be simulated for subsequent acoustic positioning,the underwater acoustic theory is studied and simulated,and a reasonable transmission signal and received signal are obtained through the underwater channel model simulated by Bellhop software.Secondly,in order to reduce the influence of underwater noise and multipath effect on time-delay measurement,the SCOT frequency domain weighted cross-correlation algorithm is applied,which reduces the amplitude of pseudo peak,sharps the real peak and obtains higher delay difference effectively.Aiming at the uneven distribution of underwater sound velocity,a stratified gradient sound tracking algorithm is proposed,and the location of sound source is calibrated by this method,which improves the calibration accuracy.These underwater acoustic error correction technologies have laid a good foundation for high-precision location later.Subsequently,the navigation principle of the conventional LBL and USBL system is outlined.Aiming at the advantages and disadvantages of these two systems,the virtual elements iterative localization technology is designed,such as the projection of virtual elements based on Gauss Newton iteration and VLBL based on periodic moving time windows.Thirdly,an integrated navigation model based on SINS/ VLBL/DVL/MCP/ depth gauge is proposed.The information fusion algorithm based on the centralized Kalman filter is designed,and its state equation and observation equation are derived.Finally,simulation experiments are carried out on the combined navigation mode of two different virtual elements iterative techniques to assist SINS location,which are the virtual base element projection based on Gauss Newton iteration and the VLBL based on the periodic moving time window.The simulation results show that the introduction of virtual elements technology can modify the position error of SINS effectively,and improve the AUV underwater navigation and positioning accuracy.The whole navigation system can meet the needs of AUV underwater navigation,such as real-time,high concealment,high precision and so on. |
