Research On Underwater Geomagnetic Assisted Navigation Matching Algorithm

Inertial navigation has a cumulative time error that does not meet the high-precision requirements for long-haul underwater navigation.Geomagnetic aided navigation can correct the cumulative error of inertial navigation system.One of the key techniques is the matching algorithm.The matching region affects the matching probability of the algorithm,and the region adaptability is closely related to the geomagnetic map feature.Therefore,the adaptive region selection rule based on improved geomagnetic entropy is proposed.For the environmental noise and magnetometer measurement error,the RANSAC algorithm is used to eliminate the sequence to be matched.The outliers in the field enhance the fault-tolerance ability of the matching algorithm;the Hausdorff distance criterion based on the short-side median solid line is used for rough matching,and the genetic search strategy is used for fine matching in a small range,which improves the matching efficiency of the ICCP algorithm;The ICCP matching algorithm based on geomagnetic vector is used to improve the matching precision in the gentle region of geomagnetic intensity change.Simulation experiments show that the proposed adaptive region selection rule can improve the matching probability of the algorithm,and the vector matching algorithm against the wild value processing can further improve matching efficiency and accuracy.The main research contents of the thesis are as follows:(1)Explain the definition and calculation methods of several geomagnetic graph characteristic parameters,analyze the influence of each parameter on geomagnet map adaptability and their relationship with each other,and propose an adaptive region selection rule based on improved geomagnetic entropy.And the adaptation area and the non-adaptation area are divided under the rule.The simulation experiment analyzes the positioning accuracy of matching results in different regions.The results show that the selection rule can screen out the regions with rich geomagnetic information,which is beneficial to select the geomagnetic adaptation region with high matching probability.(2)Due to the presence of environmental noise and magnetometer measurement error,the wild value points in the geomagnetic sequence to be matched will seriously reduce the matching accuracy.The RANSAC algorithm with anti-field value is used to preprocess the measurement sequence,eliminate the outliers and fit.The measurement sequence is used as an input to the matching algorithm.The simulation results show that the RANSAC algorithm can effectively eliminate the outliers,and the matching results after fitting the measurement sequence are more accurate,which makes the matching algorithm fault-tolerant and enhances the robustness of the matching algorithm.(3)For the limitation of ICCP matching algorithm on the accuracy requirements and time complexity of the inertial navigation system,the Hausdorff distance criterion based on the short-side median solid line is used for rough matching,and the large probability search area is delineated and adopted.The genetic algorithm searches the nearest point for fine matching,which can effectively shorten the matching time.An improved ICCP matching algorithm based on geomagnetic vector is proposed.The three-component geomagnetic intensity is used instead of the Euclidean distance to improve the matching objective function,and the matching result is more comprehensively evaluated.The degree makes up for the shortcomings of the algorithm that are prone to mismatch in the similar regions of the geomagnetic total feature.Simulation experiments show that the improved algorithm reduces the matching positioning error and heading error by 2/3 and the matching time by 1/2,which effectively improves the accuracy and efficiency of the matching algorithm.