عنوان مقاله [English]
In this paper, the accuracy of integrated inertial-radar navigation systems used for autonomous landing of unmanned air vehicles is studied. These navigation systems use the inertial instruments as the main navigation and the radar data as the navigation aids. The radar system provides the position and velocity measurements with respect to the runway coordinate system. Navigation of aircrafts is classified to terminal and non-terminal phases. The terminal phase involves the parts of flight which are related to arrival and departure from a runway. The requirements of the navigation system in the terminal phase are more complicated than the non-terminal phase. The final condition of the non-terminal phase will be set as the initial condition of the terminal phase. Thus, the designer of the navigation system should consider the interaction of these two phases.In this study, the accuracy of an integrated navigation system with velocity matching algorithm is analyzed during the landing phase of a fixed wing aircraft. The relation between accuracy of inertial instruments, flight parameters, and accuracy of integrated navigation are extracted in the form of differential equations. The initial conditions of these equations are calculated from the terminal phase parameters.The mentioned differential equations can not be solved analytically. Thus, based on the nominal behavior of an aircraft in the landing phase, some reasonable assumptions are made and the equations are solved in a closed form. The analytical solutions are used to express the accuracy of the integrated navigation in the terminal phase. The designer of the navigation system of an aircraft can use the analytical results obtained in this study to select the accuracy of the aircraft inertial instruments.In order to verify the analytical results, landing phase of a famous unmanned air vehicle, Shadow-200, which uses a system named TALS as the navigation aids, is simulated numerically. It is shown that the analytical results are well matched with the numerical ones.