Aerospace Science and Technology ( IF 5.0 ) Pub Date : 2022-10-21 , DOI: 10.1016/j.ast.2022.107961
Francesco Sanfedino , Gabriel Thiébaud , Daniel Alazard , Nicola Guercio , Nicolas Deslaef
The increased need in pointing performance for Earth observation and science Space missions together with the use of lighter and flexible structures directly come with the need of a robust pointing performance budget from the very beginning of the mission design. An extensive understanding of the system physics and its uncertainties is then necessary in order to push control design to the limits of performance and constrains the choice of the set of sensors and actuators. A multi-body framework, the Two Input Two Output Ports approach, is used to build all the elementary flexible bodies and mechanisms involved in a fine pointing mission. This framework allows the authors to easily include all system dynamics with an analytical dependency on varying and uncertain mechanical parameters in a unique Linear Fractional Transformation (LFT) model. This approach opens the doors to modern robust control techniques that robustly guarantee the expected fine pointing requirements. In particular, a novel control architecture is proposed to reduce the microvibrations induced both by reaction wheel imbalances and Solar Array Drive Mechanism driving signal, by letting them work during the imaging phase. Thanks to a set of accelerometers placed at the isolated base of the payload and in correspondence of the mirrors with the largest size in a Space telescope (typically the primary and secondary ones), it is possible to estimate the line-of-sight error at the payload level by hybridizing them with the low-frequency measurements of the camera. While a classical Fast Steering Mirror in front of the camera can compensate for a large amount of microvibration, an innovative architecture with a set of six Proof-Mass Actuators installed at the payload isolator level can further improve the pointing performance. In particular, it is shown how the proposed architecture is able to robustly guarantee an absolute performance error of 10 arcsec in face of system parametric uncertainties at low frequency (≈ 1 rad/s) with a progressive reduction of the jitter down to 40 marcsec for higher frequencies where micro-vibration sources act.
中文翻译:
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大空间柔性结构精细视距控制研究进展
地球观测和科学太空任务对指向性能的需求增加以及使用更轻和灵活的结构直接伴随着从任务设计一开始就需要强大的指向性能预算。为了将控制设计推向性能极限并限制传感器和执行器组的选择,需要对系统物理及其不确定性进行广泛的了解。多体框架,即两输入两输出端口方法,用于构建精细定位任务中涉及的所有基本灵活体和机制。该框架允许作者在独特的线性分数变换 (LFT) 模型中轻松包含所有系统动力学,并分析依赖于变化和不确定的机械参数。这种方法为现代稳健控制技术打开了大门,这些技术稳健地保证了预期的精细定位要求。特别是,提出了一种新颖的控制架构,通过让它们在成像阶段工作,以减少由反作用轮不平衡和太阳能阵列驱动机构驱动信号引起的微振动。由于一组加速度计放置在有效载荷的隔离底座上,并且与空间望远镜中最大尺寸的镜子(通常是主镜和副镜)相对应,因此可以估计视线误差通过将它们与相机的低频测量值混合来达到有效载荷水平。而相机前的经典快速转向镜可以补偿大量的微振动,在有效载荷隔离器级别安装了一组六个质量证明执行器的创新架构可以进一步提高指向性能。特别是,它展示了所提出的架构如何能够在低频(≈1 rad/s),对于微振动源作用的更高频率,抖动逐渐降低到 40 marcsec。