Parallel State Estimation under Flexible Connections in Small Celestial Body Landings

In this paper, the problem of multi-node state estimation during small celestial body flexible landing is investigated. Considering the restrained effect imposed by the flexible connections between the nodes, an equivalent restrained state is defined. The actual state of the node can be regarded as the combination of its free state and the equivalent restrained state. The equivalent restrained state is then treated as the extended state of the node. A parallel state estimation algorithm is designed, which accomplishes a simultaneous estimation of both the actual state and the equivalent restrained state. In view of the bidirectional restrained effect of the flexible connections, a correction method that fuses equivalent restrained state estimates is further proposed. By exchanging state estimates and measurements among the sensors, consensus of the adjacent nodes’ estimation results with respect to the equivalent restrained state can be guaranteed. The proposed method is validated and compared with the standard distributed EKF algorithm through numerical simulations. It shows that, for cooperative navigation systems with time-variant internal constraints, the precision of state estimation can be effectively improved by implementing the proposed estimation method.