一类分数阶神经网络的自适应H∞同步

针对一类不确定分数阶神经网络系统，研究了其自适应H_∞同步问题和参数辨识问题。提出了一个新的可以使闭环系统实现H_∞同步的自适应控制协议，利用鲁棒控制的方法和Gronwall-Bellma不等式证明了驱动系统和响应系统在该协议下可以实现同步，同时满足H_∞性能。通过仿真实验，验证了所设计控制协议的有效性，并且说明了利用该控制协议可以对未知参数进行辨识。     

弹性飞机自动寻优H∞/PID控制器设计

针对弹性飞机高阶性和鲁棒性要求,研究了自动寻优的H∞/PID控制器设计方法.以国外某大型飞机12阶模型作为研究对象,利用平衡截断法进行降阶,得到在较宽频段内近似于全阶模型的6阶模型.基于降阶模型,利用粒子群优化算法得到合适的加权函数及PID控制器参数,用于控制全阶模型.仿真结果证明,在系统同时存在参数不确定性和非参数不确定性的情况下,与H∞混合灵敏度控制器相比,H∞/PID控制器具有更强的鲁棒性,并能取得更好的时域控制效果.     

H∞ controller design for linear systems with time-invariant uncertainties

This paper considers the problem of designing robust H _∞ state feedback controller for linear continuous-time systems with time-invariant uncertainties. The main result given here concerns H _∞ controller design using the parameter dependent Lyapunov function approach and a new control law. A new condition ensuring the linear systems to be is asymptotically stable with a prescribed H _∞ performance is proposed in terms of a set of linear matrix inequalities (LMIs). Theoretic proof is given to show that the proposed condition is less conservative than existing results in the literature. An example is provided to demonstrate the efficiency of the proposed method.     

H∞ Tracking Control for Switched LPV Systems With an Application to Aero-Engines

This paper focuses on the H_∞ model reference tracking control for a switched linear parameter-varying (LPV) model representing an aero-engine. The switched LPV aero-engine model is built based on a family of linearized models. Multiple parameter-dependent Lyapunov functions technique is used to design a tracking control law for the desirable H_∞ tracking performance. A control synthesis condition is formulated in terms of the solvability of a matrix optimization problem. Simulation result on the aero-engine model shows the feasibility and validity of the switching tracking control scheme.      

Asynchronous H∞ Control for Unmanned Aerial Vehicles: Switched Polytopic System Approach

This study is concerned with the H_∞ control for the full-envelope unmanned aerial vehicles (UAVs) in the presence of missing measurements and external disturbances. With the dramatic parameter variations in large flight envelope and the locally overlapped switching laws in flight, the system dynamics is modeled as a locally overlapped switched polytopic system to reduce designing conservatism and solving complexity. Then, considering updating lags of controller's switching signals and the weighted coefficients of the polytopic subsystems induced by missing measurements, an asynchronous H_∞ control method is proposed such that the system is stable and a desired disturbance attenuation level is satisfied. Furthermore, the sufficient existing conditions of the desired switched parameter-dependent H_∞ controller are derived in the form of linear matrix inequality (LMIs) by combining the switched parameter-dependent Lyapunov function method and average dwell time method. Finally, a numerical example based on a highly maneuverable technology (HiMAT) vehicle is given to verify the validity of the proposed method.      

Non-fragile dynamic output feedback H∞ control for discrete-time systems with FWL consideration

The non-fragile dynamic output feedback H _∞ controller design problem is investigated. The controller to be designed is assumed to be with additive gain variations. A two-step procedure is proposed to develop sufficient conditions for the non-fragile H _∞ controller design by employing the structured vertex separator. A comparison between the proposed and the existing controller design methods is provided, and a numerical example is carried out to support the theoretical findings.     

Finite Frequency Fuzzy H∞ Control for Uncertain Active Suspension Systems With Sensor Failure

This paper investigates the problem of finite frequency fuzzy H_∞ control for uncertain active vehicle suspension systems, in which sensor failure is taken into account. TakagiSugeno (T-S) fuzzy model is established for considered suspension systems. In order to describe the sensor fault effectively, a corresponding model is introduced. A vital performance index, H_∞ performance, is utilized to measure the drive comfort. In the framework of Kalman-Yakubovich-Popov theory, the H_∞ norm from external perturbation to controlled output is optimized effectively in the frequency domain of 4 Hz-8 Hz to enhance ride comfort level. Meanwhile, three suspension constrained requirements, i.e., ride comfort level, manipulation stability, suspension deflection are also guaranteed. Furthermore, sufficient conditions are developed to design a fuzzy controller to guarantee the desired performance of active suspension systems. Finally, the proposed control scheme is applied to a quarter-vehicle active suspension, and simulation results are given to illustrate the effectiveness of the proposed approach.      

Decentralized Resilient H∞ Load Frequency Control for Cyber-Physical Power Systems Under DoS Attacks

This paper designs a decentralized resilient H_∞ load frequency control (LFC) scheme for multi-area cyber-physical power systems (CPPSs). Under the network-based control framework, the sampled measurements are transmitted through the communication networks, which may be attacked by energy-limited denial-of-service (DoS) attacks with a characterization of the maximum count of continuous data losses (resilience index). Each area is controlled in a decentralized mode, and the impacts on one area from other areas via their interconnections are regarded as the additional load disturbance of this area. Then, the closed-loop LFC system of each area under DoS attacks is modeled as an aperiodic sampled-data control system with external disturbances. Under this modeling, a decentralized resilient H_∞ scheme is presented to design the state-feedback controllers with guaranteed H_∞ performance and resilience index based on a novel transmission interval-dependent loop functional method. When given the controllers, the proposed scheme can obtain a less conservative H_∞ performance and resilience index that the LFC system can tolerate. The effectiveness of the proposed LFC scheme is evaluated on a one-area CPPS and two three-area CPPSs under DoS attacks.      

H∞ Output Feedback Control of Linear Time-invariant Fractional-order Systems over Finite Frequency Range

This paper focuses on the H_∞ output feedback control problem of linear time-invariant fractional-order systems over finite frequency range. Based on the generalized Kalman-Yakubovic-Popov (KYP) Lemma and a key projection lemma, a necessary and sufficient condition is established to ensure the existence of the H_∞ output feedback controller over finite frequency range, a desirable property in control engineering practice. By using the matrix congruence transformation, the feedback control gain matrix is decoupled and further parameterized by a scalar matrix. Two iterative linear matrix inequality algorithms are developed to solve this problem. Finally, numerical examples are provided to illustrate the effectiveness of the proposed method.      

随机网络控制系统的量化L2-L∞滤波

考虑到带宽有限网络环境下信号需经过量化处理才能进行发送,研究了一类带宽受限随机网络控制系统的L_2-L_∞滤波问题。采用对数量化器,将量化后的测量信号作为滤波器输入信号。首先将滤波误差系统建模成范数有界不确定随机时滞系统,进一步基于线性矩阵不等式方法推出了该随机网络控制系统的稳定性和滤波器设计的充分条件,并将滤波器的设计转化为一个凸优化的求解问题。所设计的滤波器能够保证相对于所有能量有界的外界扰动信号,随机网络控制系统的L_2-L_∞性能指标小于一定值γ。仿真实例证实了该设计方法的有效性。     

Distributed Sparse Signal Estimation in Sensor Networks Using H∞-Consensus Filtering

This paper is concerned with the sparse signal recovery problem in sensor networks, and the main purpose is to design a filter for each sensor node to estimate a sparse signal sequence using the measurements distributed over the whole network. A so-called l₁-regularized H_∞ filter is established at first by introducing a pseudo-measurement equation, and the necessary and sufficient condition for existence of this filter is derived by means of Krein space Kalman filtering. By embedding a high-pass consensus filter into l₁-regularized H_∞ filter in information form, a distributed filtering algorithm is developed, which ensures that all node filters can reach a consensus on the estimates of sparse signals asymptotically and satisfy the prescribed H_∞ performance constraint. Finally, a numerical example is provided to demonstrate effectiveness and applicability of the proposed method.      

Robust H∞ Load Frequency Control of Multi-area Power System With Time Delay: A Sliding Mode Control Approach

This paper is devoted to investigate the robust H_∞ sliding mode load frequency control (SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of renewable energies, a new sliding surface function is constructed to guarantee the fast response and robust performance, then the sliding mode control law is designed to guarantee the reach ability of the sliding surface in a finite-time interval. The sufficient robust frequency stabilization result for multi-area power system with time delay is presented in terms of linear matrix inequalities (LMIs). Finally, a two-area power system is provided to illustrate the usefulness and effectiveness of the obtained results.      

l1优化在网格去噪中的应用

目的 网格去噪是计算机图形学中的经典问题,而如何在去除噪声的同时保持网格的特征结构是这一研究方向所面临的最大挑战。方法 提出一种具有稀疏性的全局网格去噪方法,该方法源于信号处理理论中稀疏表示的基本思想,通过优化全局能量函数来去除网格模型的噪声,同时能够保持网格模型的特征结构。该方法共分为两个步骤,第1步为网格面法向量的滤波,首先建立全局优化模型,对噪声网格的面法向量进行滤波优化,其中引入l₁范数来保证解的稀疏性,使得优化后新的面法向量能够保持网格的特征结构;第2步为网格曲面的重建,根据第1步得到的新的面法向量,按照面法向量的定义,建立最小二乘意义下的网格顶点的重建模型,求解得到新的网格曲面。结果 由于该模型是全局方法,避免了现有滤波方法可能出现的不收敛等问题,能够取得比较满意的去噪效果。结论 大量实验结果表明,本文方法在去除噪声的同时,能较好地保持网格的特征结构,尤其对于CAD模型有很好的实验效果。     

The Fuzzy Neural Network Control Scheme With H∞ Tracking Characteristic of Space Robot System With Dual-arm After Capturing a Spin Spacecraft

In this paper, the dynamic evolution for a dual-arm space robot capturing a spacecraft is studied, the impact effect and the coordinated stabilization control problem for post-impact closed chain system are discussed. At first, the pre-impact dynamic equations of open chain dual-arm space robot are established by Lagrangian approach, and the dynamic equations of a spacecraft are obtained by Newton-Euler method. Based on the results, with the process of integral and simplify, the response of the dual-arm space robot impacted by the spacecraft is analyzed by momentum conservation law and force transfer law. The closed chain system is formed in the post-impact phase. Closed chain constraint equations are obtained by the constraints of closed-loop geometry and kinematics. With the closed chain constraint equations, the composite system dynamic equations are derived. Secondly, the recurrent fuzzy neural network control scheme is designed for calm motion of unstable closed chain system with uncertain system parameter. In order to overcome the effects of uncertain system inertial parameters, the recurrent fuzzy neural network is used to approximate the unknown part, the control method with $\pmb H_{{\infty }}$ tracking characteristic. According to the Lyapunov theory, the global stability is demonstrated. Meanwhile, the weighted minimum-norm theory is introduced to distribute torques guarantee that cooperative operation between manipulators. At last, numerical examples simulate the response of the collision, and the efficiency of the control scheme is verified by the simulation results.      

结合纹理梯度抑制与L0梯度最小化的纹理滤波

目的 纹理滤波是计算机视觉领域的一个基础应用工具,其目标是抑制图像中不必要的纹理细节和保持图像的主要结构。目前已有的纹理滤波方法多存在强梯度纹理无法被抑制或结构丢失的问题,为此提出一种结合纹理梯度抑制与L₀梯度最小化的纹理滤波算法。方法 首先,提出一种能够区分结构/纹理像素的方向性区间梯度算子,其中采取了局部对比度拉伸和尺度自适应策略,提升了弱梯度结构像素的识别能力。随后,利用区间梯度幅值对原始图像梯度进行抑制,并用抑制后的图像梯度进行图像重建,获得纹理像素梯度小于结构像素梯度的纹理抑制图像。最后,考虑到纹理梯度抑制时会对结构像素的梯度产生一定的衰减作用,本文采用具有梯度提升作用的L₀梯度最小化方法对纹理抑制图像进行滤波,得到纹理抑制结构保持的纹理滤波图像。结果 通过测试马赛克和自然风景等不同类型的图片,并与L₀梯度最小化、滚动引导图像滤波、相对总变分、共现滤波等方法相比较,本文算法能够在抑制强梯度纹理的情况下对图像的主要结构得以保持,并且具有良好的普适性和鲁棒性。同时本文将纹理滤波应用于图像的边缘检测和细节增强,取得了不错的效果提升。结论 本文算法在兼顾强梯度纹理的抑制和结构的保持方面已超越已有的方法,对于图像的目标识别、图像融合、边缘检测等易受强梯度纹理干扰的技术领域,具有较大的应用潜力。     

基于A2范数的加权低秩子空间聚类

子空间聚类在运动分割、人脸聚类上得了广泛的应用,并且取得很好的聚类效果.针对稀疏子空间聚类和最小二乘回归子空间聚类求得的表示系数存在类内过于稀疏和类间过于稠密的问题,本文利用l₂范数,提出一种基于欧氏距离的且具有组效应的加权低秩子空间聚类算法,此算法通过基于欧氏距离的加权方式,使得最终的表示系数在保证同一子空间数据点联系的同时,减小不同子空间数据点之间的联系.利用此表示系数建立相似矩阵J,将J应用到谱聚类得到聚类结果.实验结果表明,与当前流行的算法比较,本算法取得了较好的聚类效果.     

一种基于L2,1范数的PCA维数约简算法

传统PCA存在对异常值和特征噪声敏感等问题,基于L2,1范数的PCA算法改进了这些缺点。现有的基于L2,1范数的PCA算法是通过降低矩阵的秩来实现维数约简,而秩的计算复杂。针对这一问题,提出一种新的维数约简算法。该算法提出利用迹范数代替矩阵的秩来简化L2,1-PCA的计算,提高算法效率;对于算法的求解提出了基于拉格朗日乘子的方法并将算法应用扩展Yale B人脸数据集进行图像去噪。可视化的实验结果表明所提出的算法有效。     

Thermodynamic reassessment of the Y 2O3–Al2O3–SiO2 system and its subsystems

Phase equilibria and thermodynamic properties at 1 bar in the Y ₂O₃–Al₂O₃–SiO₂ ternary system and its constituent binaries Y ₂O₃–Al₂O₃ and Y ₂O₃–SiO₂ have been reevaluated using the CALPHAD approach. The liquid phase is described by the ionic two-sublattice model with the formula (Al⁺³,Y ⁺³)_P(AlO₂⁻¹,O⁻²,SiO₄⁻⁴,SiO₂⁰)_Q. The SiO₂ solubility in the YAM phase was described using a compound energy model. Two datasets of self-consistent model parameters are presented. However, the rather meagre and scattered experimental data imply that the present assessments should be regarded as provisional. Some critical experiments are suggested for this system.     

NOx adsorption behavior of LaFeO3 and LaMnO3+δ and its influence on potentiometric sensor response

NO_x adsorption behavior on LaFeO₃ (LFO) and LaMnO_3+δ (LMO) was characterized using temperature controlled methods and mass spectrometry. Temperature program desorption revealed decomposition of complex surface species formation when NO or NO₂ was adsorbed on LFO and LMO. LFO exhibited higher adsorption capacity for NO_x species than LMO and was shown to be more active for NO_x surface conversion. Both effects were attributed to the different B-site cations, with iron in LFO in the 3+ valence state, and manganese in LMO in the 3+ and 4+ valence states. Results from diffuse reflectance infrared spectroscopy were used to identify specific nitrite and nitrate species that are formed on the surfaces of LFO and LMO at room temperature. Temperature programmed reaction revealed a complex NO₂ decomposition mechanism to NO and O₂ for LFO and LMO in which the formation of nitrite and nitrate species serve as intermediates below ∼600 °C. NO_x sensing mechanisms were considered and predicted based on the types and quantities of surface species formed.     

具有模态词□φ=□1V□2φ且可靠与完备的公理系统

提出具有模态词□φ=□₁V□₂φ的命题模态逻辑,给出其语言、语法与语义,其公理化系统是可靠与完备的,其中,□₁与□₂是给定的模态词.该逻辑的公理化系统具有与公理系统S5相似的语言,但具有不同的语法与语义.对于任意的公式φ,□φ=□₁V□₂φ;框架定义为三元组W,R₁,R₂,模型定义为四元组W,R₁,R₂,I;在完备性定理证明过程中,需要在由所有极大协调集所构成的集合上构造出两个等价关系,其典型模型的构建方法与经典典型模型的构建方法不同.如果□₁的可达关系R₁等于□₂的可达关系R₂,那么该逻辑的公理化系统变成S5.