This paper proposes a hierarchical path-planning algorithm based on a combination of graphical search algorithms and optimization methods. In the global path planning layer, by using the Hybrid A* algorithm, we can quickly obtain an optimal path that can avoid all static obstacles on the map. In the local path planning layer, the global path is optimized by numerical nonlinear numerical optimization to generate a feasible path that satisfies the safety constraints. By processing global path planning and local path planning separately, the computational complexity of path planning can be effectively reduced, and the efficiency and accuracy of the path planning can be improved. Secondly, the hybrid planning algorithm can generate high-quality paths with both safety and flexibility. We simulate and verify the algorithm, and the results show that the method has practical applications in autonomous driving.
KEYWORDS: Stars, Star sensors, Sun, Space operations, Navigation systems, Astronomy, Homogenization, Satellites, Optical character recognition, Solar system
In interstellar travel, parallax and stellar aberration have a non-negligible influence on the star identification of star sensors. Through the analysis of the working principle of star sensors, only the guide star catalog generation can solve this problem. The influence mechanism of parallax and stellar aberration is synthetically analyzed by four-dimensional time-space diagrams, and a generation algorithm of the guide star catalog for the interstellar star identification is presented. The update cycle of the catalog is studied, and a block update method based on the distance distribution is given. The Hipparcos catalog is adopted as the fundamental catalog. On the premise of meeting the accuracy requirement of star identification, the maximum travel distance supported by the catalog is about 0.3 light-years. In order to balance the star identification and the influence of parallax, eliminating 30% to 40% of the nearby guide stars is an optimal criterion for the guide star selection. The analysis of the catalog distribution shows that the parallax and the stellar aberration have opposite effects on the distribution of guide stars. The methods and conclusions provide a theoretical basis for interstellar celestial navigation.
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