过驱动轮控卫星的动态控制分配方法

Dynamic Control Allocation for Overactuated Satellite with Redundant Reaction Wheels

反作用飞轮在卫星姿态控制中具有重要作用,配置3个以上飞轮的卫星构成一类过驱动系统,能够提高姿态控制系统的可靠性。针对期望控制力矩到冗余飞轮的指令分配问题,提出了一种基于伪逆法的动态控制分配方法,并针对传统伪逆法难以考虑飞轮最大力矩等物理约束问题,采用零空间方法对传统伪逆法给出的分配结果进行了修正。基于稳定控制模式下姿态变化平稳性假设,在分配问题中增加飞轮输出力矩的最大变化量约束,能够有效抑制姿态控制中敏感器噪声影响,剔除敏感器野值,提高了卫星姿态控制精度。最后对本文提出的修正伪逆法及降低敏感器噪声和野值剔除效果等进行了数学仿真验证,结果表明了上述方法的可行性和有效性。

The reaction wheels play an important role in shaping satellite attitude command. To ensure the reliability of sat- ellite in orbit, the reaction wheels are often overactuated with more than three reaction wheels. Therefore, dynamic control allocation method based on pseudo-inverse method distributing the desired control command among the reaction wheels is proposed. But for controls constrained to operational limits, the pseudo-inverse approach yields admissible control deflec- tions for only a small portion of the set of attainable moments. So a null-space method is used to modify the results. Under the assumption that the attitude changes smoothly when satellite is stabilized, the minimum-torque dynamic control allocation can remove the unexpected signals and reduce noise effect in attitude control by limiting the differences between current val- ue and one-step previous value. In this way, the precision of attitude control system is improved. Finally, the proposed dy- namic control allocation method is tested in removing undesired signals and reducing noise effects. The method is proved to be feasible and effective after simulation.