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着陆器在动力下降段的转移能力是影响定点软着陆的重要因素。文章从转移能力的角度出发,研究火星软着陆动力下降段能量最优制导律,分析燃料质量系数、时间权重以及不同初始高度和速度对转移能力的影响。由于能量最优制导律不能保证满足路径约束,因此对于确定的着陆器初始状态,着陆器转移能力不仅与燃料质量系数有关,还受到制导律本身的制约。当转移距离超过一定的界限时,尽管燃料充足,着陆轨迹会进入地表以下,造成任务失败。时间权重是能量最优制导律的关键参数,既影响燃耗,也影响着陆轨迹的形状。实际工程任务中,为实现燃料的充分利用,需根据着陆器状态调整制导律中的时间权重。本文给出了最优时间权重的确定方法,实现了一定燃料质量系数下的最大转移能力。
The ability of the lander to transfer power during the descending phase is an important factor that affects the soft landing at fixed points. From the perspective of transfer ability, the paper studies the optimal energy guidance law of the descent phase of Mars soft landing force, and analyzes the influence of fuel quality coefficient, time weight and different initial height and velocity on the transfer ability. Because the optimal energy guidance law can not guarantee to satisfy the path constraints, the lander transfer ability is not only related to the fuel quality coefficient but also restricted by the guidance law itself for the initial state of the determined lander. When the transfer distance exceeds a certain limit, despite sufficient fuel, the landing trajectory will be below the surface, causing the mission to fail. Time weighting is the key parameter of the optimal energy law, which affects both fuel consumption and the shape of the landing trajectory. In actual engineering tasks, in order to realize the full utilization of fuel, the time weight in the guidance law needs to be adjusted according to the state of the lander. This paper gives the method of determining the optimal time weight, and achieves the maximum transfer ability under a certain fuel quality coefficient.