Analysis of predictive entry guidance for a Mars lander under high model uncertainties

The problem of precision landing on Mars is now considered to be an essential challenge in the planned Mars missions. The paper focused on the guided atmospheric entry as a predominant phase in achieving a desired target state, as compared with the following parachute and powered descent. The predictive algorithms for the longitudinal guidance of a low-lift entry vehicle are treated. The purpose is to investigate applicability of the predictive strategy under possible high discrepancies between the on-board dynamic model and real environment while in entry trajectory. The comparative performance analysis based on computer simulation has been made between the standard one-parametric “shooting” predictive algorithm and a more complex two-parametric algorithm providing lower final velocity and, thus, expanding the interval of admissible downrange. However, both algorithms display considerable degradation of downrange accuracy in the cases when the actual drag force is larger than the modelled one. An acceptable solution has been found by including to both predictive guidance schemes an identification algorithm that repeatedly adapts the on-board model to varied environment in real time scale.     

卫星姿控用无铁心永磁无刷飞轮电机综述

取消了定子铁心的外转子永磁无刷直流飞轮电机,以其高效性、轻量化、转矩密度大、寿命长和无污染等优点被广泛应用于微小卫星姿态控制系统。依据磁场的形成原理对定子无铁心永磁无刷直流飞轮电机进行了分类,主要包括径向磁场型和轴向磁场型。阐述了不同结构拓扑下定子无铁心永磁无刷直流电机的特征和关键技术,包括定子绕组、转子和永磁体、磁悬浮轴承技术、损耗与振动等。报告了定子无铁心永磁无刷直流飞轮电机的研究进展,总结了定子无铁心永磁无刷直流飞轮电机的效率、转矩等特性,讨论了该类无铁心永磁无刷直流飞轮电机的研究方向和发展趋势。