Trajectory planning/re-planning for satellite systems in rendezvous mission in the presence of actuator faults based on attainable efforts analysis

The objective of fault-tolerant control (FTC) is to minimise the effect of faults on system performance (stability, trajectory tracking, etc.). However, the majority of the existing FTC methods continue to force the system to follow the pre-fault trajectories without considering the reduction in available control resources caused by actuator faults. Forcing the system to follow the same trajectories as before fault occurrence may result in actuator saturation and system's instability. Thus, pre-fault objectives should be redefined in function of the remaining resources to avoid potential saturation. The main contribution of this paper is a flatness-based trajectory planning/re-planning method that can be combined with any active FTC approach. The work considers the case of over-actuated systems where a new idea is proposed to evaluate the severity of faults occurred. In addition, the trajectory planning/re-planning approach is formulated as an optimisation problem based on the analysis of attainable efforts domain in fault-free and fault cases. The proposed approach is applied to two satellite systems in rendezvous mission.     

Left invertibility,flatness and identifiability of switched linear dynamical systems: a framework for cryptographic applications

The purpose of this article is to illustrate the potential interest of the control theory framework for cryptographic applications. It is shown that under the properties of left invertibility and flatness, dynamical systems are structurally equivalent to some specific cryptographic primitives called self-synchronising stream ciphers. After having motivated the interest of considering hybrid systems for such ciphers, the development is particularised for the special class of switched linear systems. We also show that identifiability is a necessary condition for security, and we describe an identification procedure as a possible attack and assess its complexity.     

Minimum-time trajectory generation for constrained linear systems using flatness and B-splines

In this article, we discuss minimum-time trajectory generation for input-and-state constrained continuous-time LTI systems in the light of the notion of flatness and B-splines parametrisation. Flat systems have the useful property that the input and the state trajectories can be completely characterised by the (so-called) flat output. We propose a splines parametrisation for the flat output, and the corresponding parametrisations for the performance output, the states and the inputs. Using this parametrisation the problem of minimum-time constrained trajectory planning is cast into a feasibility-search problem in the splines control-point space, in which the constraint region is characterised by a polytope. A close approximation of the minimum-time trajectory is obtained by systematically searching the end-time that makes the constraint polytope to be minimally feasible.     

Geometry of the minimum zone flatness functional: planar and spatial case

The zone straightness and flatness functional is constructed from the definition of the measure. The geometry of the straightness functional is illustrated in the plane, and in three dimensions, a novel means to visually represent flatness is described using the zone separation body. The zone separation body is a new construction that is uniquely associated with every measurement dataset and can be used to represent the flatness functional visually.     

恒包络信号识别与快速突发捕获

为了迅速判断恒包络信号的起始点,详细推导了信号平坦度的计算公式,将信号平坦度概念引入到信号捕获和端点检测领域,在快衰落信道下通过计算噪声和信号平坦度不同,快速区分噪声和恒包络信号;并利用搜索窗快速定位信号起始点位置。经过试验表明在信噪比不低于5dB条件下,该参数能够迅速捕获恒包络信号,并能准确得判定信号的起始点位置,该方法适用在实时性要求比较高的领域。     

平板波动量检具的研制

平板波动量是平板局部工作面平面度的判定依据之一。提出依据最小包容原则计算平板波动量并研制一种新型的测量工具,并进行不确定度和可行性分析。     

浅谈DAVY系统Ⅱ板形控制系统

板形控制是铝带轧制过程中重要环节，直接影响产品质量，本文介绍了有关板形控制的有关知识，并结合本公司DAVY轧机系统Ⅱ的板形控制系统进行探讨。     

基于Sigmoid函数参数调整的双隐层BP神经网络的板形预测

提出一种改进的BP神经网络处理板形缺陷数据的方法,建立双隐层BP神经网络模型,并对Sigmoid激活函数的形状进行调节。将其应用到冷轧的板形缺陷识别中,与利用Levenberg-Marquardt规则训练的BP神经网络预测结果作对比,表明该方法不仅有效地减少双隐层BP网络的学习时间,同时改善了网络的泛化能力,有利于板形缺陷在线识别。     

机载大尺寸天线平面度控制与测试研究

从系统的角度研究了天线设计、分析和测试验证的思路和方法,提出了一种机载大尺寸平面相控阵天线动态平面度的控制措施,提出了光电位置传感器和动态位移传感器相融合的实时测量技术,通过对飞行条件下天线动态变形的实时测试,研究了天线的动态平面度变化规律,该结果为动平台条件下大尺寸平面阵天线结构设计和优化提供了技术手段,测试方法为类似研究提供了工程参考.     

板型仪在带钢质量检测控制中的应用

带钢板型优劣是影响产品质量的重要指标,而仪表与TDC相结合能够实现热连轧的精确检测和闭环控制;凸度仪和平直度仪能够提供精确、稳定的钢坯质量反馈数据来源,通过闭环控制,提高了板型质量;采用控制参数的自适应优化保证了控制的精度;对于钢坯板形控制有着良好的借鉴价值。