强脉冲噪声环境下的多径衰信道估计

提出一种在强干扰脉冲噪声存在下对无线多径信道进行估计的算法.在无线通信系统中,衰落信道可以采用自回归(AR)模型建模,通过RLS算法和自适应Kalman滤波器分别对AR模型的参数进行估计,但是,这两种算法对噪声干扰非常敏感.为了加快RLS算法的收敛性,并有效抑制大脉冲干扰的影响,在算法的改进中引入了抑制因子,用于对脉冲干扰幅度的抑制.仿真结果显示:相比于传统的算法,改进后的算法在联合估计信道时,提高了抵抗大脉冲干扰的能力,加快了待估参数的收敛速度.     

基于颜色信息和光学增益的阴影消除

运动阴影常被误分为前景对象,会给目标的跟踪和识别带来很大困难,所以阴影消除在许多的监控系统中都是非常重要的。针对阴影检测算法受特定条件约束,不能自动适用于不同场景,为解决上述问题,提出了一种新颖鲁棒且无需复杂的参数调整的运动阴影消除方法。通过自适应高斯混合模型重建背景,采用背景差分法提取出包含阴影的运动区域,综合颜色信息与光学增益,将运动区域分类为运动对象区域和运动阴影区域。实验结果表明:所提方法在多种不同的场景下均能有效可靠的消除运动阴影。     

基于T-S模型的输出反馈滑模控制及应用

为了使系统满足品质要求并对不确定因素具有较强的鲁棒性,采用滑模控制方法。建立被控对象T-S模糊模型。针对系统状态不完全可测特点,采用迭代线性矩阵不等式方法,利用输出信息构造滑模面。根据系统品质要求,采用参数鲁棒设计方法,配置所需极点,确定相应在参数空间的映射关系。应用平行分布补偿算法,根据映射产生的参数样本训练T-S模糊控制器,实现等效控制律。在此基础上应用高增益方法设计切换控制律,保证系统对满足匹配条件的不确定因素具有较理想的自适应性。最后,直升机模型的仿真结果表明,方法具有很好的控制效果。     

ID3算法及其改进

文章对ID3算法的基本概念和原理进行了相应的详细阐述以及解释说明,并针对ID3算法倾向于取值较多的属性的缺点,引进信息增益率对ID3算法作了改进,并通过实验对改进前后的算法进行了比较,实验表明,改进后的算法行之有效。     

Semi-global finite-time observers for nonlinear systems

It is well known that high gain observers exist for single output nonlinear systems that are uniformly observable and globally Lipschitzian. Under the same conditions, we show that these systems admit semi-global and finite-time converging observers. This is achieved with a derivation of a new sufficient condition for local finite-time stability, in conjunction with applications of geometric homogeneity and Lyapunov theories.     

振动式微机械陀螺驱动环路数字AGC研究

对微机械陀螺系统的自激驱动环路进行了分析,并对数字处理电路中自动增益控制（AGC）模块进行了深入研究,给出了一种高控制精度的定点数字AGC算法。通过理论分析和模型仿真,结果表明AGC控制精度得到很大的提高,对陀螺驱动输出信号的幅度具有很好的控制效果,从而可以大大减小陀螺温漂及其他一些因素引起的不稳定性。最后给出了算法的直线逼近近似实现方法,能在的定点DSP当中很方便的实现。     

动态偏置射频宽带功放设计

射频宽带功率放大器是目前功率放大器的主要发展趋势。为了提高射频宽带功率放大器的增益平坦度与效率,采用推挽结构LDmos晶体管,使用ADS软件对动态偏置电路和匹配电路进行仿真设计。详细介绍了动态偏置功率放大器的工作原理及其实现方法。实现了多倍频程带宽、确保带内增益平坦、提高功率附加效率。仿真结果表明该功率放大器对于100MHz~400MHz的信号,在整个输入功率变化范围内,功率附加效率（PAE）与传统的功放相比提高了5~15%左右。     

On the design of multi‐rate tracking controllers: Application to rotorcraft guidance and control

This paper presents a new methodology for the design and implementation of gain‐scheduled controllers for multi‐rate systems. The proposed methodology provides a natural way to address the integrated guidance and control problem for autonomous vehicles when the outputs are sampled at different instants of time. A controller structure is first proposed for the regulation of non‐square multi‐rate systems with more measured outputs than inputs. Based on this structure, an implementation for a gain‐scheduled controller is obtained that satisfies an important property known as the linearization property. The implementation resembles the velocity implementation for single‐rate systems. The method is then applied to the problem of steering an autonomous rotorcraft along a predefined trajectory defined in terms of space and time coordinates. By considering a convenient error vector to describe the vehicle's dynamics, the trajectory tracking problem is reduced to that of regulating the error variables to zero. Because of the periodic multi‐rate nature of the onboard sensor suite, the controller synthesis is dealt with under the scope of linear periodic systems theory. Simulation results obtained with a full non‐linear rotorcraft dynamic model are presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Multiple robust H∞ controller design using the nonsmooth optimization method

This paper proposes a systematic technique to design multiple robust H_∞ controllers. The proposed technique achieves a desired robust performance objective, which is impossible to achieve with a single robust controller, by dividing the uncertainty set into several subsets and by designing a robust controller to each subset. To achieve this goal with a small number of divisions of the uncertainty set, an optimization problem is formulated. Since the cost function of this optimization problem is not a smooth function, a numerical nonsmooth optimization algorithm is proposed to solve this problem. This method avoids the use of Lyapunov variables, and therefore it leads to a moderate size optimization problem. A numerical example shows that the proposed multiple robust control method can improve the closed‐loop performance when a single robust controller cannot achieve satisfactory performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Stabilization of linear systems with input delay and saturation—A parametric Lyapunov equation approach

This paper studies the problem of stabilizing a linear system with delayed and saturating feedback. It is known that the eigenstructure assignment‐based low‐gain feedback law (globally) stabilizes a linear system in the presence of arbitrarily large delay in its input, and semi‐globally stabilizes it when the input is also subject to saturation, as long as all its open‐loop poles are located in the closed left‐half plane. Based on a recently developed parametric Lyapunov equation‐based low‐gain feedback design method, this paper presents alternative, but simpler and more elegant, feedback laws that solve these problems. The advantages of this new approach include its simplicity, the capability of giving explicit conditions to guarantee the stability of the closed‐loop system, and the ease in scheduling the low‐gain parameter on line to achieve global stabilization in the presence of actuator saturation. Copyright © 2009 John Wiley & Sons, Ltd.