Enhanced instrument landing system based on the aided inertial navigation

Localizer and Glideslope signal were susceptible to the environmental interference in current instrument landing system (ILS) during the precision approach and landing, which affected the safety of landing guidance. In order to solve this problem, this paper proposed a method of integrating ILS receiver signal with inertial navigation system (INS) to improve the landing guidance performance. Localizer and Glideslope deviation were selected as state variables, which were obtained via the ILS outputdifference of degree of modulation (DDM), and measurements were acquired by the difference between output position of INS and ILS. Then Kalman filter was employed to estimate Localizer and Glideslope deviation. The simulation results showed the angle error range of ILS receiver reduced greatly through integration of INS/ILS, with the deviation range of Localizer decreased from 0.3° to less than 0.1° and Glideslope decreased from 0.2° to less than 0.1°. Moreover, the integrated navigation system restrained the receiver noise in ILS effectively and positioning accuracy achieved significant improvement.