Relative Information Assisted Autonomous Navigation for Flexible Landing on Asteroids

Due to the weak gravitational field and the uneven topography of asteroids, the conventional rigid lander is prone to rebound and overturn during the landing process. In comparison, a flexible lander can alleviate this problem with its flexible structure and improve the success rate of the landing mission. For the flexible lander as a whole, when designing navigation methods for the flexible lander, internal structural interactions should be considered. Nevertheless, these interactions are governed by deformations of flexible materials and are challenging to characterize. In this paper, an autonomous navigation method assisted by relative information is proposed for a flexible lander with a multinode configuration. Building upon independently estimated states at each node, relative states between nodes are incorporated to characterize structural interactions and enhance overall estimation accuracy. To accurately predict these relative states, a Flexible Proprioceptive Network (FPN) is developed. By embedding structural constraints into its design, the FPN achieves high prediction accuracy while offering improved interpretability. After that, an optimal multi-source heterogeneous information block-diagonal fusion method is derived. By integrating heterogeneous information from overlapping field of view between nodes and the predictions provided by the FPN, the accuracy of relative state estimation is further improved. Numerical simulations demonstrate that incorporating the relative states improves the state estimation accuracy of the flexible lander. It is also shown that the proposed method maintains reasonable performance by leveraging the introduced relative information under sparse observation conditions.