Zhengshi Yu
Beijing Institute of Technology
China
Title: An Online Batch-Based Fusion Filter for Navigation in Mars Final Approach Phase
Biography
Biography: Zhengshi Yu
Abstract
Statement of the Problem: An accurate knowledge of Mars entry condition is the significant for a successful aerocapture and pinpoint landing. However, the traditional navigation scheme during the final approaching phase based on the Deep Space Network cannot achieve an accurate result because of the severe time delay. Navigation based on the X-ray pulsars has been proposed to improve the navigation performance. But highly nonlinear dynamic model and relatively low updating rate of measurement may result in filter divergence. The purpose of this study is to develop a novel online Batch-based Fusion Filter (BFF) dealing with the difficulties in Mars final approaching phase. Methodology & Theoretical Orientation: In the algorithm, a batch-based estimation method with fixed batch length is developed to optimally determine the state of spacecraft. Unlike the traditional Moving Horizon Estimation, only the cost function of previous measurements is used so that the differential correction method can be used. The computation cost is also reduced. To incorporate the a priori information of state, a data fusion process is also employed. The stability and accuracy of batch-based estimation method is discussed, and the factors affecting the position and velocity estimation accuracy are also investigated. Findings: The configuration of X-ray pulsars is a main contribution to the estimation error. The navigation pulsars should be carefully chosen to guarantee an accurate estimation. If three pulsars are used, the direction of three pulsars should be orthogonal, which is identical to the analysis result using Fisher information matrix. Conclusion & Significance: The proposed online Batch-based Fusion Filter gives a potential solution to the navigation for Mars final approaching phase. If the configuration of pulsars are carefully chosen, the navigation performance can also be further improved. The accuracy analysis method can also be extended to other navigation schemes based on relative position measurements.
