Accurate Localization for Space Rovers and its Computational Reduction

Abstract

AbstractTo localize a rover on small planetary body, a method using round-trip propagation delay of radio waves is most promising. In order to improve the estimation accuracy, it is necessary to estimate rotational motion of the small planetary body. A method of localization has been expanded to estimate also the rotational parameters of the small planetary body. The expanded problem includes complex nonlinear and dynamical issues that it cannot be solved analytically. So, the estimation problem has been formulated as an optimization problem to minimize the loss function defined based on the estimation errors derived in comparison with actual measurement data. A solution for the optimization problem has been proposed, which uses Powell's conjugate direction method for local searches. Although this solution does not require calculation of derivatives, it requires a large amount of computation since several forward calculations of the state are required for each minimum search. In this paper, a method to select measurement data is described, which provides as accurate estimation as the original results with reducing the computational amount. The main idea of selection is to conserve the sensitivity of the measurement data. The proposed method to select data is compared with the results using the decimated data of equal interval. Simulation results and experimental results are shown to evaluate computational reduction and estimation accuracy.