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基于改进人工势函数的航天器近距离安全控制方法

A COLLISION-AVOIDANCE CONTROL ALGORITHM FOR SPACECRAFT PROXIMITY OPERATIONS BASED ON IMPROVED ARTIFICIAL POTENTIAL FUNCTION

  • 摘要: 针对航天器近距离操作的安全问题,提出了一种基于人工势函数改进的碰撞规避控制算法.根据航天器与目标、障碍物之间的实时状态, 利用人工势函数算法,计算航天器的实时加速度, 规划航天器的轨迹. 为改进人工势函数方法的适用性,提出三个方面的改进措施: 首先, 在人工势函数算法中, 为提高碰撞预警的准确性,减少额外机动, 碰撞预警采用碰撞概率代替相对距离. 其次, 为了提高对接安全,降低接近目标航天器的相对速度, 利用相对速度的安全接近走廊来计算目标排斥力.最后, 针对大多航天器不能提供任意连续变化推力的情况, 设置两种实用的推力形式,如bang-bang控制的推力形式和恒定变化率的推力形式, 代替连续变推力形式.通过对不同算例的比较,成功地揭示了主要任务参数(如碰撞预警方法、速度安全边界和实际加速度形式)对近距离操作安全的影响.结果表明, 该方法可以提高航天器近距离操作的安全性、效率性, 并且结构简单,实时性强.

     

    Abstract: Aiming at the proximity operation of spacecraft, a collision-avoidance control algorithm based on improved Artificial Potential Fields (APF) method is proposed. According to the real-time state between the spacecraft and the target and obstacles, the APF method is used to calculate the real-time acceleration of the spacecraft, and the trajectory of the spacecraft is planned. In order to improve the applicability of the artificial potential function method, three improvement measures are proposed. First, in order to improve the accuracy of collision warning and reduce additional maneuvers, the collision probability combined with the relative distance, instead of only the relative distance, is used to evaluate the collision. Second, in order to increase the docking safety and slow down the approaching relative velocity, the safety boundary and control margin of relative velocity are used to calculate the target repulsion force. Third, in view of the fact that most spacecraft cannot provide any continuously varying thrust, two practical thrust forms, including the thrust with upper limit and constant variation rate and the bang-bang thrust, are used to substitute for the continuously variable thrust form. Numerical simulations are executed to validate the proposed method. The effects of the major mission parameters, such as the collision warning method, the target repulsion acceleration and acceleration forms, are successfully revealed by the comparison between different examples. The results show that the proposed method can improve the safety and efficiency of the spacecraft proximity operations, and has simple structure and strong real-time performance.

     

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