Research On Integrated Navigation System Of High Speed Autonomous Underwater Vehicle

Today,with the increasing scarcity of natural resources on the land,the ocean of natural resources attracts more and more attention.The development of ocean resources has been listed as an important strategic goal of many countries in twenty-first Century.As a device that can operate autonomously under water,the Autonomous Underwater Vehicle(AUV)has become the key equipment for people to conduct marine exploration.The high precision and high reliability navigation system is the key to realize the independent operation and the security recovery of AUV.Due to the limitation of underwater working environment and the inherent drift error of inertial sensors,single navigation equipment has been unable to meet the requirements of navigation applications for underwater vehicles.Therefore,the integrated navigation technology of multi-sensor data fusion has become an inevitable choice.Based on the working mode of "underwater self-navigation-water surface correction-Underwater self-navigation" of the AUV,and combined with the research status and development trend of domestic and international navigation system,this article has established an underwater integrated navigation and positioning system which takes the photoelectric integrated navigation system(PHINS)as a core and supplemented with Doppler Velocity Logger(DVL),Global Positioning System(GPS),Depth Meter(DM)and Altimeter(AM).The feasibility and reliability of the navigation system has been verified by plenty of experiments.The navigation accuracy meets the test mission requirements of the high-speed AUV.First of all,the navigation system of the AUV is designed based on the navigation requirements of AUV,and the combination method,equipment layout and system framework of the navigation system are determined.The basic principle and the process of strapdown calculation of Strapdown Inertial Navigation System are introduced in detail,and the corresponding nonlinear error model is established on this basis.In addition,the measurement principle and measurement error of DVL,GPS,DM and Altimenter are discussed,and the error model of each sensor are established.Among them,an on-line calibration method of DVL installation angle and scale factor is proposed based on Kalman Filter technology,which can effectively reduce the speed measurement error of DVL and improve the navigation accuracy in PHINS/DVL integrated mode.Next,according to the information requirements of navigation systems for AUV,filtering of the navigation system can be divided into two parts: height information processing of DVL and Altimeters and combined filtering of PHINS/GPS/DVL/DM.The former adopts the method of optimal adaptive weighted fusion,which based on the principle of minimizing the ensemble mean square error and fuse the Kalman filter estimates of DVL and Altimeter,in order to output accurate and stable height information;The latter chose the federated Kalman filter with better fault tolerance and flexible performance as the data fusion algorithm of the integrated navigation system.Based on the nonlinear state equations and linear quantities of the sub-filters,a simplified UKF combine with federated filtering algorithm is designed,which reduces the computational complexity.In addition,for improving the filter performance of the Federal Filter under high-speed navigation,the federated UKF is improved by using the predictive UKF algorithm.Simulations show that the improved filtering algorithm can effectively enhance the navigation performance of underwater integrated navigation system when DVL output limited.Then,according to the requirements of the navigation system of the AUV,the software requirement analysis of the navigation system was performed.Through the functional requirements of the navigation system,the overall structure of the software is designed.On this basis,the software modular design process based on the VxWorks operating system is given.Finally,Through plenty of tests,including single experiments,half-physical experiment,the pool test,lake test and AUV lake state test,verify working performance from the single device to the entire navigation system step by step.Through the final lake state test of AUV shows that the integrated navigation system has good feasibility and high navigation accuracy,and satisfies the actual mission requirements of AUV.