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小天体着陆抗扰轨迹优化方法

A Desensitized Trajectory Optimization Method for Landing of Small Bodies

  • 摘要: 针对探测器着陆小天体过程中存在动力学参数和状态不确知问题,提出了一种小天体着陆抗扰轨迹优化方法,以提升复杂环境下探测器着陆控制精度。首先,考虑不确知参数影响建立小天体着陆增广随机状态方程,将小天体引力场的不确定性和探测器发动机推力误差作为着陆过程的过程噪声;然后,推导了不确知性沿标称轨迹传播的线性协方差动态方程,将状态变量的协方差矩阵扩展为状态方程的新状态,并构造燃料消耗和状态协方差加权的联合性能指标,继而通过轨迹优化直接法进行最优控制问题解算,以提高轨迹的抗扰能力。最后,以433Eros为例进行仿真分析,结果证明该方法能够克服随机参数对探测器的影响,提高着陆精度。

     

    Abstract: A desensitized trajectory optimization method was proposed to improve the precision of small body landing control in complex environment, under the influence of the uncertainty of dynamic parameters and state during small body landing. Firstly, considering the influence of uncertain parameters, the augmented stochastic state equation of small body landing is established, and the uncertainty of the gravitational field of small body and the thrust error of probe engine are regarded as the process noise of landing process. Then, the linear covariance dynamic equation of uncertainty propagating along the nominal trajectory is derived, the covariance matrix of state variables is extended to a new state of the state equation, and the joint performance index weighted by fuel consumption and state covariance is constructed. Then the optimal control problem is solved by direct trajectory optimization method and the trajectory's desensitization is finally improved. Taking 433Eros as an example, the simulation results show that the proposed method can overcome the influence of random parameters in the process of small body landing and improve the landing accuracy.

     

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