CNS/Pulsar Integrated Navigation Using Two-level Filter

To improve the position accuracy, a CNS (Celestial navigation system)/pulsar integrated navigation system with clock drift is proposed. In the pulsar navigation subsystem, the epoch-difference method is adopted to eliminate clock drift, but it induces colored noise. The two-level filter, which is composed of an UKF (Unscented Kalman filter) and an H-infinity. filter in series connected, is proposed for fusing the data from the celestial navigation and pulsar navigation subsystems. The celestial navigation subsystem adopts the UKF because of its good performance in nonlinear estimation, while the pulsar navigation subsystem utilizes the H-infinity filter due to its robustness to colored noise. Compared with CNS and two CNS/pulsar integrated navigation methods without two-level filter, the proposed method can provide higher navigation accuracy. Simulation results show that the position estimation accuracy of the proposed method can achieve 140m in the presence of clock drift.