On the consistency analyzing of A-SLAM for UAV navigating in GNSS denied environment

In this paper, EKF Based A-SLAM concept is discussed in detail by presenting the formulas and MATLAB Simulink model, along with results. The UAV kinematic model and state-observation models for the EKF Based A-SLAM are developed to analyze the consistency. The covariance value caused by the EKF structure is analyzed. This value was calculated by filtering with error between the UAV's actual and estimated positions. It is concluded that the calculated covariance value diminishes despite error and does not decrease as a result of the inconsistency of the EKF Based A-SLAM structure. The necessary conditions for the consistency of the EKF Based A-SLAM structure are described and the consistency of the EKF Based A-SLAM is consequently investigated by considering these conditions for the first time by using simulation results. The analysis during this landmark observation exhibits that a jagged UAV's trajectory indicates an inconsistency caused by the EKF Based A-SLAM structure with the provocation of error accumulation. Finally, the major reasons of the filter inconsistency can be listed as unobservable subspace and Jacobian matrices used for linearization. As a future work, the methods that can be used to provide consistency of the EKF Based A-SLAM are proposed for better UAV navigation performance.