2250mm带钢热连轧机板形调控性能改善与提高

以2250mm热连轧精轧机为对象,通过有限元仿真,针对末机架在轧制薄带钢时因出现工作辊端部压靠而引起的整机板形控制性能劣化问题,进行了多种工况的定量研究,得出轧件规格和轧制力对工作辊端部压靠的产生及压靠程度的影响,揭示了工作辊端部压靠对轧机板形控制性能的严重负面影响。通过比较研究轧机抵抗工作辊端部压靠的能力,提出了采用基于变接触轧制策略的变接触支承辊初始辊形设计的技术对策,并在投入实际生产使用后取得了明显效果。     

Ku波段LNA仿真优化设计

本文论述了应用Ansoft公司的Serenade8．7微波仿真软件设计Ku波段LNA的过程，通过优化仿真和最后测量的结果比较，采用该软件设计出的产品技术指标较好。     

A 60 GHz Medium Power Amplifier for Radio‐over‐Fiber System

We present the design and fabrication of a 60 GHz medium power amplifier monolithic microwave integrated circuit with excellent gain‐flatness for a 60 GHz radio‐over‐fiber system. The circuit has a 4‐stage structure using microstrip coupled lines instead of metal‐insulator‐metal capacitors for unconditional stability of the amplifier and yield enhancement. The gains of each stage of the amplifier are modified to provide broadband characteristics of input/output matching for the first and fourth stages and to achieve higher gains for the second and third stages to improve the gain‐flatness of the amplifier for wideband.     

Alternative approach to low‐noise amplifier design for ultra‐wideband applications

Conventional ultra‐wideband low‐noise amplifiers require a flat gain over the entire 3.1–10.6 GHz bandwidth, which severely restraints the trade‐off spaces in low noise amplifier design. This article proposes a relaxed gain‐flatness requirement based on system level investigations. Considering the wireless transceiver front‐end with antenna and propagation channel, the unflat‐gain low‐noise amplifier with an incremental gain characteristic does not degrade the performance of overall system. As an alternative to its flat‐gain counterpart, the proposed unflat gain requirement tolerates gain ripple as large as 10 dB, which greatly eases the design challenges to low‐noise amplifier for ultra‐wideband wireless receivers. Two low‐noise amplifier examples are given to demonstrate the feasibility and design flexibility under the proposed gain‐flatness requirement. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

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。     

温度对平晶平面度影响的定性分析及相关问题探讨

在测量平晶工作面的平面度时，温度不仅对平晶平面度的大小有影响，而且直接影响对平晶表面形状（凹凸）的判断。文章给出了温度对平晶平面度影响的实例分析，并提出了两种平晶表面形状判断的辅助方法，且对JJG28—2000《平晶》检定规程中平晶表面形状判断方法进行了必要的补充说明。