A discontinuous Galerkin method combined with mixed finite element for seawater intrusion problem

<正> Seawater intrusion problem is considered in this paper.Its mathematical model is anonlinear coupled system of partial differential equations with initial boundary problem.It consistsof the water head equation and the salt concentration equation.A combined method is developedto approximate the water head equation by mixed finite element method and concentration equationby discontinuous Galerkin method.The scheme is continuous in time and optimal order estimates inH~1-norm and L~2-norm are derived for the errors.     

Fixed-Order l_1-Control for Systems with Time-Delay

1. INTRODUCTIONPhysical plaaes are inevitably affected by exogenous disturbance, hence rejecting disturbanceis important. Ffor example, HOO-control systems can reject the LZ disturbance. But in factthere are maily species of disturbances: some are LZ-attenuation; some are stochastic; andsome are Loo(loo) [6]. If the exogenous disturbance is modeled as the energy-bounded signal, and the performance is the output energyt that is Hoo problem. If the performance isoutput energy, that is p…     

PID feedback for mixed H2/H∞ tracking control of robotic manipulators

The design objective of a mixed H2/H∞ control is to find the H2 optimal control law under aprescribed disturbance attenuation level. This paper addresses a optimal PID control law on the basis of the newsolution to mixed H2/H∞optimal control problem that provide much more flexible design compared to the existing works. Then a closed-form PID controller to mixed H2/H∞ robotic tracking problem is simply constructed and hence the design procedure is presented.Finally, numerical simulations illustrate the effectiveness of the optimal PID feedback design proposed in this paper via a two-link robotic manipulator.     

基于T-S模型的非线性系统非脆弱保性能模糊控制

针对一类用T-S模糊模型描述的非线性系统,采用状态反馈的并行分布补偿方法研究其非脆弱保性能模糊控制问题,使得在控制器存在可加性摄动的情况下,其闭环性能指标值低于确定的上界。利用线性矩阵不等式处理方法,导出了非脆弱保性能模糊控制律的存在条件。通过建立和求解一个凸优化问题,给出了最优非脆弱保性能模糊控制律的设计方法,并用此方法设计一级倒立摆的非脆弱模糊控制律。仿真结果表明了方法的有效性。     

Observer-based fault detection scheme for a class of discrete time-delay systems

In this contribution, robust fault detection problems for discrete time-delay systems with l2-norm bounded unknown inputs are studied. The basic idea of our study is first to introduce a state-memoryless observer-based fault detection filter (FDF) as the residual generator and then to formulate such a FDF design problem as an Hen optimization problem in the sense of increasing the sensitivity of residual to the faults, while simultaneously enhancing the robustness of residual to unknown input as well as plant input. The main results consist of the formulation of such a residual generation optimization problem, solvability conditions and the derivation of an analytic solution. The residual evaluation problem is also considered, which includes the determination of residual evaluation function and threshold. A numerical example is used to demonstrate the proposed fault detection scheme.     

Non-fragile decentralized H∞ controller design for uncertain linear systems

Considering the design problem of non-fragile decentralized H∞ controller with gain variations, the dynamic feedback controller by measurement feedback for uncertain linear systems is constructed and studied. The parameter uncertainties are considered to be unknown but norm bounded. The design procedures are investigated in terms of positive definite solutions to modify algebraic Riccati inequalities. Using information exchange among local controllers, the designed non-fragile decentralized H∞ controllers guarantee that the uncertain closed-loop linear systems are stable and with H∞ -norm bound on disturbance attenuation. A sufficient condition that there are such non-fragile H∞ controllers is obtained by algebraic Riccati inequalities. The approaches to solve modified algebraic Riccati inequalities are carried out preliminarily. Finally, a numerical example to show the validity of the proposed approach is given.     

基于l1范数主成分分析的极化SAR图像变化检测

为提高极化合成孔径雷达(synthetic aperture radar, SAR)图像变化检测算法的鲁棒性以及检测精度,提出基于范数主成分分析(linorm principal component analysis,l1-PCA)模型的变化检测算法。首先,采用基于Hotelling-Lawley复矩阵迹变化检测算子构造差异图;其次,采用l1-PCA模型获取差异图的变化信息,使得每个像素以一个特征向量来表示;最后,使用k-means算法对变化信息进行聚类,得到变化检测结果。该方法是一种非监督变化检测方法,相比于基于2范数的PCA检测方法,l1-PCA在特征提取方面具有更高的鲁棒性,并且可以进一步提高变化检测精度。基于RADARSAT-2卫星获取的3幅图像进行的实验结果表明,相较于其他两种典型算法,所提算法更加稳定,精确度更高。     

二次D稳定约束下不确定T-S模糊系统的L∞鲁棒可靠控制

针对一类受持续有界扰动的T-S不确定模糊系统,提出了考虑执行器故障的鲁棒可靠控制器设计方法。引入基于L_∞范数理论的鲁棒性能指标及二次D稳定的概念,给出了鲁棒可靠控制器存在的充分条件。通过求解线性矩阵不等式完成可靠控制器的设计,从而使系统即使在发生执行器故障的情况下仍能满足给定的L_∞性能指标,并且闭环系统二次D稳定。仿真实例表明了本方法的有效性。     

分段线性微分包含系统的最优控制设计

针对分段线性微分包含系统,根据Hamilton-Jacobi-Bellman(H-J-B)不等式将最优控制设计问题转化成最优控制性能上界的优化问题及性能下界的求取问题.其中性能上界的优化是一组以反馈增益为寻优参数的双线性矩阵不等式(bilinear matrix inequalities,BMI)问题,而性能下界是一组基于线性矩阵不等式(linear matrixinequalities,LMI)的半正定规划问题.结合遗传算法和内点法设计了一种混合算法对BMI问题进行求解.算例表明方法的有效性.     

State and Output Feedback Finite-time Guaranteed Cost Control of Linear It Stochastic Systems

The problem of guaranteed cost control based on finite-time stability for stochastic system is first investigated in this paper.The motivation of solving this problem arises from an observation that finite/infinite-horizon guaranteed cost control does not consider the transient performance of the closed-loop system,but guaranteed cost control based on finite-time stability involves this practical requirement.In order to explain this problem explicitly,a concept of the stochastic finite-time guaranteed cost control is introduced,and then some new sufficient conditions for the existence of state and output feedback finite-time guaranteed cost controllers are derived,which guarantee finite-time stochastic stability of closed-loop systems and an upper bound of a quadratic cost function.Furthermore,this problem is reduced to a convex optimization problem with matrix inequality constraints and a new solving algorithm is given.Finally,an example is given to illustrate the effectiveness of the proposed method.     

Robust generalized H2 control:time-delay case

Generalized H2 control problem is considered for a class of linear time-delay systems covering linear timeinvariant (LTI) case and time-varying but norm-bounded linear differential inclusion (NLDI) case. The issues focus on the synthesis of so-called generalized H2 controller, which guarantees internal/robust stability and a certain performance level of generalized H2 norm of resulting closed-loop system. By using Lyapunov functional technique, sufficient conditions for the existence of such a kind of controllers are obtained in terms of two linear matrix inequalities (LMIs).In the state space, for memoryless state feedback case, we treat the controller design in a unified framework for both LTI and NLDI. The presented results are illustrated by numerical examples.     

Receding horizon H∞ control for discrete-time Markovian jump linear systems

Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given quadratic performance criteria. First, a control law is established for jump systems based on pontryagin’s minimum principle and it can be constructed through numerical solution of iterative equations. The aim of this control strategy is to obtain an optimal control which can minimize the cost function under the worst disturbance at every sampling time. Due to the difficulty of the assurance of stability, then the above mentioned approach is improved by determining terminal weighting matrix which satisfies cost monotonicity condition. The control move which is calculated by using this type of terminal weighting matrix as boundary condition naturally guarantees the mean square stability of the closed-loop system. A sufficient condition for the existence of the terminal weighting matrix is presented in linear matrix inequality (LMI) form which can be solved efficiently by available software toolbox. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.     

不确定系统实时保性能控制

研究了一类不确定离散系统在控制约束下的实时控制问题。在SDP凸优化理论的框架下,对这类不确定离散系统实施保性能控制,融合预测控制的优化思想,通过在线求解线性矩阵不等式技术,在满足控制约束的条件下,获得了滚动优化的保性能控制律,并使闭环系统稳定。     

Event-Triggered L1-Gain Control of Nonlinear Positive Switched Systems

This paper is concerned with the event-triggered L_1-gain control of a class of nonlinear positive switched systems. First, an event-triggering condition in the form of 1-norm is presented for the systems. By virtue of the event-triggering strategy, the original system is transformed into an interval uncertain system. An event-triggered L_1-gain controller is designed by decomposing the controller gain matrix into the sum of nonnegative and non-positive components. Under the design controller, the resulting closed-loop systems are positive and L_1-gain stable. The obtained approach is developed for the systems subject to input saturation. All presented conditions are solvable in terms of linear programming. Finally, two examples are provided to verify the effectiveness of the design.     

不确定广义系统的鲁棒H2控制

利用线性矩阵不等式 (LMI)方法 ,研究范数有界的不确定广义系统的鲁棒H2 性能分析与控制问题。对该系统所有容许的不确定参数 ,提出了满足鲁棒H2 次优性能的一个线性矩阵不等式 (LMI)的充分条件。进而设计了一个状态反馈控制律 ,保证了闭环系统是容许的且满足鲁棒H2 次优性能 ,即闭环传递函数的H2 范数小于一个给定的正数。利用Matlab控制工具箱 ,给出了该控制律的LMI实用设计方法。最后的数值例子进一步说明了所取得的主要结果     

Design of Luenberger function observer with disturbance decoupling for matrix second-order linear systems-a parametric approach

1.INTRODUCTIONThere have been many approaches to disturbance de-couplinginlinear multivariable control systemdesign.Linnemann[1]proposed a numerically stable algorithmfor disturbance decoupling by measurement feedback.Van Der Woude[2]considered the combined problemof disturbance decoupling and stabilization by mea-surement feedback.Syrmos[3]proposed a numericallyefficient algorithm based on Sylvester equations forthe problemof disturbance decoupling with arbitrarypole placement usingstat…     

Guaranteed cost control with constructing switching law of uncertain discrete-time switched systems

A guaranteed cost control problem for a class of linear discrete-time switched systems with norm-bounded uncertainties is considered in this article. The purpose is to construct a switching rule and design a state feedback control law, such that, the closed-loop system is asymptotically stable and the closed-loop cost function value is not more than a specified upper bound for all admissible uncertainties under the constructed switching rule. A sufficient condition for the existence of guaranteed cost controllers and switching rules is derived based on the Lyapunov theory together with the linear matrix inequality (LMI) approach. Furthermore, a convex optimization problem with LMI constraints is formulated to select the suboptimal guaranteed cost controller. A numerical example demonstrates the validity of the proposed design approach.     

基于压缩感知的米波雷达低空测角算法

为解决多径环境下米波雷达对低空目标探测问题,本文结合信号空域稀疏性和多径模型下的复合导向矢量提出了一种多径环境下高分辨的低空测角方法,能够有效地克服多径效应问题。该方法首先利用多径模型下的先验信息产生复合导向矢量,然后利用该导向矢量构造压缩感知矩阵,此时的感知矩阵是整合了多径衰减系数和回波角度关系等先验信息,同时通过对多快拍数据矩阵的奇异值分解获得较高信噪比的信号数据矩阵,继而利用感知矩阵和信号数据矩阵建立最优化L1范数约束求解模型,最后利用凸优化工具求解稀疏空间谱,估计直达波和反射波入射角度值。该方法能够增强信息矢量稀疏性,在较低信噪比下可获得高分辨的角度估计性能。仿真实验证明了该方法的优越性。     

#br# 基于伪谱重构的采样反馈近最优制导

利用采样反馈控制和轨迹快速重构技术,设计了固定采样反馈和自适应采样反馈两种有限推力远程变轨近最优闭环制导策略。建立了空间变轨和交会最优制导数学模型。结合变轨运动方程特征,给出了伪谱优化参数缩减方法和实时性提升策略;基于采样反馈和最优控制理论,利用采样数据进行连续轨迹重构,并将开环最优解进行闭环反馈以更新制导指令。仿真结果表明,两种策略在保证任务指标近最优性的同时,可以有效抑制地球扁率J2摄动和计算误差的影响;自适应采样策略自主性好、制导精度误差收敛快,但计算量和燃耗偏大,二者使用时需要根据具体任务要求合理选择。