Inertia-based Initial Alignment And Information Fusion Of Integrated Navigation For AUVs

As efficient underwater working platforms for the exploration,development,and utilization of the ocean,autonomous underwater vehicles(AUVs)have been widely used in military and civilian applications.In the complex ocean environment,accurate and reliable navigation and positioning is a key technology for AUV to arrive at the operation site accurately and return safely,and it is usually regarded as one of the standards to evaluate the development maturity and engineering application of AUV.This dissertation is focused on the inertia-based initial alignment and information fusion of integrated navigation for AUVs,and the research is mainly composed of the modeling for the AUV multi-source navigation system,the self-alignment under the moving base,the transfer alignment under moving base,the rapid alignment under large misalignment angle,the information fusion for the integrated navigation system.The main contents of this dissertation are presented as follows:1.In order to solve the problems of building the system model and analyzing the observability of the system,the error modeling of the multi-source navigation sensors and the observable degree analysis of the AUV integrated navigation system are studied respectively.The working principles and error sources of the AUV multi-source navigation sensors are analyzed,and the error models of the navigation sensors are built.The methods of the observability analysis based on PWCS and the observable degree analysis based on SVD for the integrated navigation system are studied respectively.The observability and the observable degree of the AUV integrated navigation system under different trajectories and maneuvering modes are analyzed.2.To solve the self-alignment problem of AUV under different initial conditions,the self-alignment methods of AUV under moving base are studied.The basic principles of the analytic alignment method and the alignment method based on two vectors of gravitational apparent motion are analyzed,and the simulation verifications are carried out.In order to complete the self-alignment of AUV with unknown latitude,an alignment method that uses gravitational apparent motion vectors at three different moments to implement vector operations is proposed,and the basic principle of the self-alignment method using three vectors of gravitational apparent motion is deduced in detail.To avoid generating collinear vectors in the process of vector operations,an adaptive filter is designed to effectively remove accelerometers' random noise.Experimental results show that the proposed method can complete the self-alignment when the latitude information is unknown,and besides,the alignment accuracy can reach the extreme accuracy determined by the errors of inertial devices.3.The transfer alignment method with delay compensation and the transfer alignment method under a complex dynamic environment are proposed respectively for AUV to solve the transfer alignment problem of AUV under moving base.The effect of time delay in the process of transfer alignment is analyzed,and the H? filtering theory and the robust mechanism of H? filter are deduced and analyzed in detail.On this basis,an adaptive H? filtering method with delay compensation is proposed,and the value of the robustness factor can be adaptively adjusted according to the external environment,thus the accuracy and robustness of transfer alignment can be effectively improved.To solve the transfer alignment problem on a moving base under a complex dynamic environment,the cause of filtering divergence has been analyzed and the optimization strategy has been made,and an improved adaptive compensation H?filtering method is proposed.The improved adaptive compensation H? filter can effectively suppress the filtering divergence,and the robustness factor can be dynamically adjusted according to the complex external environment.Moreover,by adding the convergence criterion,the response speed of the system can be effectively improved.Experimental results show that the above two methods can improve the performance of transfer alignment with time delay and the performance of transfer alignment under a complex dynamic environment respectively.4.The nonlinear robust initial alignment technology of AUV is studied to solve the initial alignment problem of AUV with large attitude errors under uncertain disturbances.An adaptive UT-H? filter that combines UKF technology and an H? filter is proposed to increase the robustness of the nonlinear transfer alignment system.By focusing on the time-varying and the uncertain external disturbances,the robustness factor of the adaptive UT-H? filter can be adaptively adjusted to balance the robustness and filtering accuracy of the dynamic system.Considering that the AUV exists the motion states with high maneuvers such as vertically diving,a Dual-Euler whole attitude solution method is studied.The positive/reverse Euler angle differential equations are derived detailedly,and the transformation formula between positive/reverse Euler angles is established.Experimental results show that the initial alignment method based on adaptive UT-H? filter and the Dual-Euler whole attitude solution method can effectively improve the accuracy and robustness of the transfer alignment with large attitude errors under uncertain disturbances,and the singularity problem of attitude solution can also be solved.5.To realize the high accurate and high reliable navigation of AUV in the underwater environment,the information fusion method for AUV integrated navigation system is studied.An adaptive federated interacting multiple model(IMM)information fusion system is designed,and the information fusion system combines adaptive federated filter and IMM algorithm to improve the navigation performance of the AUV in a complex underwater environment.The information-sharing coefficient of the adaptive federated IMM information fusion system can be adaptively adjusted based on the performance of each local system.Meanwhile,the adaptive federated IMM information fusion system designs different models for each local system.When the external disturbances change,the model describing each local system can switch in real-time.Based on the structure of the information fusion system,an AUV integrated navigation system model is established by taking the SINS as the main navigation system aided by other navigation sensors.The semi-physical experiments of integrated navigation demonstrate that the adaptive federated IMM information fusion system can effectively improve the accuracy and reliability of the integrated navigation system under a complex interference environment.