深空双质量块无拖曳卫星H∞鲁棒控制器设计

H∞ robust controller design for deep space drag-free satellite with two test masses

摘要:

针对执行深空任务的双质量块无拖曳卫星模型复杂、控制自由度多且精度要求高的问题,提出了一种基于频域约束规范的GS/T混合灵敏度H_∞鲁棒控制器快速设计方法,该方法物理意义明确,降低了无拖曳控制系统设计的复杂度.首先,推导了双质量块构型无拖曳卫星的高精度动力学模型,表明了其各回路间的强耦合特性.其次,通过设计选择矩阵以及输入解耦策略,将控制系统划分为单输入单输出的质量块无拖曳控制回路、悬浮控制回路以及航天器姿态控制回路,并建立了各回路的闭环反馈控制策略.然后,在频域结合科学性能要求与外部扰动和传感器测量噪声的频谱模型,构建了各个回路的灵敏度函数与补灵敏度函数设计规范,从而可以快速且准确地设计出符合性能要求的加权函数阵,完成了无拖曳与姿态控制系统的设计.仿真结果表明,提出的控制系统设计方法具有足够的稳定性和抗干扰能力,达到了超稳超静的无拖曳水平要求.最后结合传递函数分析,给出了进一步减小加速度噪声的工程改进思路.

Abstract:

This paper proposes a GS/T mixed-sensitivity H_∞ controller design method based on spectrum specifications to tackle the multiple-degree-of-freedom control problem with high precision requirements of drag-free satellite in deep space mission. The method is explicit in physical meaning and can reduce the complexity in the design of drag-free control system. First, the high precision dynamic model of drag-free satellite with two test masses was derived, which shows the strong coupling characteristics of the loops. Next, selection matrices and input decoupling strategies were designed to divide the control system into single-input single-output (SISO) drag-free control loops, suspension control loops, and spacecraft attitude control loops, and closed loop feedback control strategies for each loop were further established. Then, combined with various scientific requirements and spectrum models of external disturbances and sensor noises, constrains for sensitivity functions and complementary sensitivity function of each loop were derived. With the help of these design criteria, weighting function matrices could be chosen quickly and accurately for the design of the drag-free and attitude control system in frequency domain. Simulation results proved the stability and capabilities of the proposed control system in resisting disturbances, which can achieve the ultra-quiet-stable requirement for drag-free control. Finally, on the basis of transfer function analysis, a method to further reduce acceleration noises was given.