Polarization‐independent and electrically tunable liquid‐crystal Fresnel lenses based on photoalignment in dye‐doped liquid crystals

Abstract— This work demonstrates polarization‐independent and electrically tunable liquid‐crystal (LC) Fresnel lenses based on photoalignment in dye‐doped liquid crystals (DDLCs). The LC alignments in the adjacent odd and even zones of the LC Fresnel lens are orthogonally hybrid alignments. Those are generated by surface treatment of homeotropic and homogeneous alignment layers, and the dye‐adsorption layer onto the UV‐cured surface‐relief Fresnel zone plate. The maximum focusing efficiency (～34.14%) of the fabricated LC Fresnel lens by applying a suitable AC voltage is close to the maximal theoretical focusing efficiency of a binary phase LC Fresnel lens (～40.5%). Additionally, the focusing efficiency is polarization‐independent and electrically tunable.     

Polarisation independent liquid crystal lenses and contact lenses using embossed reactive mesogens

Liquid crystal lenses have promise in optical systems owing to their tunability combined with low electrical power, cost, and weight. A good example of such a system is switchable contact lenses for the correction of age‐related presbyopia. Sufficiently large phase modulation can be done using nematic liquid crystals in a meniscus lens configuration. However, the birefringent materials are inherently polarisation dependent, usually requiring orthogonal polarisations to be focussed separately. A novel method is presented for producing polarisation independent lenses based on reactive mesogens. Results are presented for a 2‐level and 3‐level diffractive Fresnel lenses, and the promise of the technique for use in refractive lenses such as contact lenses is discussed.     

Control design for integrator hybrid systems

The authors define controllability for hybrid systems as the existence of correct control laws that transfer the hybrid plant between predefined subsets of the hybrid state space. A methodology for analyzing controllability and synthesizing control laws for a class of hybrid systems, applicable especially in batch control, is proposed. They use a framework consisting of a hybrid plant and a hybrid controller that interact in a feedback fashion     

基于中红外光谱技术的非接触式气体识别电子鼻系统

为了对混合气体进行非接触式识别,基于可调谐二极管激光吸收光谱与波长调制光谱(TDLAS—WMS)技术,采用激射波长为中红外的可调谐分布反馈式量子级联激光器(DFB—QCL),设计并研制了可对被测混合气体进行实时、非接触识别的电子鼻系统。该系统采用主成分分析(PCA)和反向传播(BP)混合神经网络模式,通过LabVIEW对气体"指纹信息"数据库进行分析。实验结果表明:该系统可以区分成分为一氧化碳(CO)、甲烷(CH4)、二氧化氮(NO2)和乙烯(C2H4)的混合气体,为混合气体非接触式识别提供了一种便利方法。     

Hybrid attitude control in steering maneuver using ARC Hil setup

This paper presents the design of an active roll controller for a vehicle and an experimental study using an electric actuating roll control system. Firstly, based on a three degrees of freedom linear vehicle model, the controller is designed using lateral acceleration and rollrate feedback. In order to investigate the feasibility of an active control system, experimental work is carried out using a hardware-in-the-loop (Hil) setup which has been constructed using the devised electric actuating system and the full vehicle model including tire characteristics. The performance is evaluated by an experiment using the Hil setup in which steering maneuvers are carried out. Finally, in order to enhance the control performance in a transient region, the hybrid control strategy is proposed and evaluated.     

User Activities Outliers Detection; Integration of Statistical and Computational Intelligence Techniques

In this article, a hybrid technique for user activities outliers detection is introduced. The hybrid technique consists of a two‐stage integration of principal component analysis and fuzzy rule‐based systems. In the first stage, the Hamming distance is used to measure the differences between different activities. Principal component analysis is then applied to the distance measures to find two indices of Hotelling's T² and squared prediction error. In the second stage of the process, the calculated indices are provided as inputs to the fuzzy rule‐based systems to model them heuristically. The model is used to identify the outliers and classify them. The proposed system is tested in real home environments, equipped with appropriate sensory devices, to identify outliers in the activities of daily living of the user. Three case studies are reported to demonstrate the effectiveness of the proposed system. The proposed system successfully identifies the outliers in activities distinguishing between the normal and abnormal behavioral patterns.     

多智能体网络系统的能控性代数条件

能控性是多智能体系统研究的核心问题,主要包括结构可控性和精准可控性。对多智能体系统的模型和能控性代数条件进行了总结。在相对协议和绝对协议条件下,运用图论和矩阵论的知识系统分析了多智能体系统能控性的代数条件。按照同质多智能体到异质多智能体的顺序,对现有的多智能体系统模型和代数条件进行了梳理,并在已有结论的基础上对多智能体系统能控性的代数条件进行了改善,进一步提出了新的代数条件。多智能体能控性代数条件的改进大大简化了能控性的计算量。     

Robust roll motion control of a vehicle using integrated control strategy

This paper presents an electrically actuated roll motion control of a vehicle using simulation and experimental analysis. The controller is designed with an H_∞ control scheme based on the 3 DOF vehicle model considering parameter variations, which affect the roll dynamics. To investigate the feasibility of the active roll control system, its performance is evaluated by simulation in a full vehicle model under various conditions. The Hil setup with the electrically actuated roll control system was devised and its performance was investigated through experimental works. Finally, to enhance the performance in a transient region, an integrated control strategy is presented.     

Span-reachability and observability of bilinear hybrid systems

The paper presents an algebraic characterization of observability and span-reachability of bilinear hybrid systems without guards, i.e. hybrid systems whose continuous dynamics are determined by bilinear control systems, and whose discrete transitions are triggered externally. The proposed characterization provides necessary and sufficient conditions for observability and span-reachability in terms of rank conditions for generalized observability and controllability matrices. This characterization is useful for the system theory of bilinear hybrid systems, in particular, it is used in the realization theory of bilinear hybrid systems, (Petreczky, 2006).     

Data-based hybrid modelling of the component placement process in pick-and-place machines

In this paper, an experimental study in the identification of the electronic component placement process in pick-and-place machines is presented. Unilateral contact and saturation phenomena characterize the hybrid dynamics of the system. Furthermore, the mode switch cannot be measured and identification algorithms for hybrid systems, that are capable of reconstructing both the modes and the switching law, must be used. Piece-wise autoregressive exogenous (PWARX) models, which consist of a number of ARX modes together with the partition of the regressor space into regions where each model is valid are identified. Reconstructed models are able to capture the relevant dynamics of the experimental setup. Practical insights on hybrid system identification and comments on possible improvements of the identification algorithm complement the quantitative results.     

An algebraic approach towards the controllability of controlled switching linear hybrid systems

Based on the hybrid controllability concept (IEEE Automat. Control 43(4) (1998) 491), the controllability problem for a class of hybrid control systems referred to as controlled switching linear hybrid systems is discussed. One sufficient condition and one necessary condition are derived by employing algebraic manipulations of related system matrices. The computational test of these conditions and some examples are also discussed.     

DISCRETE OUTPUT FUZZY CONTROLLER DESIGN FOR ACHIEVING COMMON CONTROLLABILITY GRAMIAN

In control theory, the robust properties of linear systems can be related directly to properties of the controllability or observability Gramian. In this paper, a discrete fuzzy controller for a class of nonlinear systems is developed to achieve a common controllability Gramian. We assume that the nonlinear system is represented by the Takagi‐Sugeno fuzzy model. The purpose of this paper is to find the output feedback gains for the T‐S fuzzy controller after assigning a certain common controllability Gramian. Finally, we provide a numerical example to verify the effects of the proposed method.     

基于行为法多智能体系统构形控制研究

为实现多智能体系统的构形控制,针对二阶多智能体系统,采用了一种基于智能体行为的控制算法,这种控制算法考虑到智能体的驶向目标行为和构形维持行为,可以有效实现智能体相对于期望目标的构形控制,由于采用该算法使得多智能体系统中有明确的队形反馈,因而有利于分布式控制和实时控制。智能体的动力学模型采用多智能体问题研究广泛使用的独轮车模型,通过反馈线性化方法,将这种非线性模型转化成了实用的双积分系统模型。通过Matlab仿真验证了算法的有效性,结果表明控制器参数整定简单,具有很好的稳定性和鲁棒性。     

Atomic Spin Polarization Controllability Analysis: A Novel Controllability Determination Method for Spin-Exchange Relaxation-Free Co-Magnetometers

This paper investigates the atomic spin polarization controllability of spin-exchange relaxation-free co-magnetometers(SERFCMs). This is the first work in the field of controllability analysis for the atomic spin ensembles systems, whose dynamic behaviors of spin polarization are described by the Bloch equations. Based on the Bloch equations, a state-space model of the atomic spin polarization for SERFCM is first established,which belongs to a particular class of nonlinear systems. For this clas...     

Input addition and leader selection for the controllability of graph-based systems

In this paper, we consider dynamical graph-based models, which are well fitted for the structural analysis of complex systems. A significant amount of work has been devoted to the controllability of such graph based models, e.g. recently for multi-agent systems or complex networks. We study here the controllability through input addition in this framework. We present several variants of this problem depending on the freedom which is left to the designer on the additional inputs. We use a unified framework, which allows us to encompass the different applications and representations (large scale systems, complex communications networks, multi-agent systems, …) and provide convenient graph tools for their analysis. Our contribution is to characterize the structural modifications of the system resulting from an input addition (or a leader selection) and of the mechanisms which lead to controllability. We provide information on the possible location of additional inputs and on the minimal number of inputs to be added for controllability.     

基于OpenFlow的入侵检测评估模型

针对传统测评方法依赖模拟环境来仿真真实网络流量的现状,提出一种基于OpenFlow的入侵检测评估系统.该系统基于软件定义网络技术（OpenFlow）的入侵检测评估模型,随后对该模型的框架、设置方法、具体工作过程等进行详细阐述,设计了基于该模型的测评系统,该系统利用OpenFlow灵活的网络控制能力为IDS测评搭建真实可控的网络环境,提供入侵检测所需的真实网络流量和攻击数据.最后利用该测评系统对该模型进行试验仿真,实验结果表明传统方法相比,本文提出的基于OpenFlow的入侵检测评估模型在测评效果和准确性上有较好的性能.     

基于自控网系统的混杂控制

混杂控制系统通常是复杂的非线性控制系统,难以用统一的模型进行建模. David和Alla提出的混杂Petri网,虽然可以解决一般混杂系统的建模问题,并得到了广泛的应用,但对于传统的如PID这类控制器,缺乏统一建模的能力.探讨了基于广义自控网系统的混杂控制方法,实现了对混杂控制器中监控器和数字控制器进行统一的Petri网建模.仿真实例设计了基于广义同步自控网系统的电加热炉控制系统,给出了可根据不同温度状态实施多种控制策略的变结构数字控制器模型,并详细分析了控制器的性能,证明了广义自控网系统具有十分强大的建模能力和广泛的应用前景.     

Water Supply Networks as Cyber-physical Systems and Controllability Analysis

Cyber-physical systems (CPS) is a system of systems which consists of many subsystems that can stand alone in an individual manner and can be taken as a typical complex network. CPS can be applied in the critical infrastructures such as water supply networks, energy supply systems, and so on. In this paper, we analyze the structure of modern city water supply networks from the view of CPS theory. we use complex network theory to build an undirected and unweighted complex network model for the water supply networks to investigate the structural properties, and present the structure of the water supply networks and detect communities by a spectral analysis of the Laplacian matrix. Then, we analyze the structure and controllability of water supply networks by the structural controllability method. The results show the feasibility and effectiveness of the proposed complex network model.      

Model-reduced fault detection for multi-rate sensor fusion with unknown inputs

In multi-sensor fusion, it is hard to guarantee that all sensors work at the single sampling rate, especially in the distributive and/or heterogeneous case, and fault detection (FD) in multi-rate sensor fusion may face the existence of unknown inputs (UIs) in complex environment. Meanwhile, model reduction often refers to propose a possible lower-dimensional model to replace the original model without adding significant error in practical applications. By the fact that FD in dynamic systems should only focus on the fault-related controllability and observability characteristics, it is a good idea to obtain the fault-related controllable and observable subsystem via system decomposition (i.e., model reduction) for FD. Such a kind of model reduction not only guarantee the FD performance, but also reduce the system dimensions. To this end, we propose the model-reduced fault detection (MRFD) problem for multi-rate sensor fusion subject to UIs and faults imposed on the actuator and sensors. Our aim is to design a fast and computation-effective FD scheme based on the reduced model. We use the singular decomposition for UI decoupling, and then obtain the fault-related subsystem via controllability and observability decomposition. And then the multi-rate observer (MRO) with causality constraints is designed. Different from the traditional observer used for FD, the proposed MRO outputs the fault-related partial state estimate as soon as any a sensor measurement is received, resulting in fast and computation-effective FD. Furthermore, conditions for the existence of a stable MRO, fault-to-state controllability, and fault detectability are explored. A simulation example for simplified longitudinal flight control system and method comparison with the existing multi-rate FD algorithms show the effectiveness of the proposed MRFD method.     

Controllability and observability of 2D thermal flow in bulk storage facilities using sensitivity fields

To control and observe spatially distributed thermal flow systems, the controllable field and observable field around the actuator and sensor are of interest, respectively. For spatially distributed systems, the classical systems theoretical concepts of controllability and observability are, in general, difficult to apply. In this study, sensitivity fields were used to analyse the behaviour from input to state and from initial state to output. For the analysis of controllability and observability, a large-scale, bulk storage facility with coupled thermal flow of air and agro-products was used. Analysis of this system using the classical systems theory results in controllability and observability results that are dependent on the step size of the spatially discretised system. Due to matrix multiplications, inaccurate results are calculated if the step size is too small. Our findings indicate that input-state and initial-state output sensitivity fields provide sufficient information about the controllability and observability of large coupled spatially distributed systems, using finite-dimensional state space representation with small discretisation steps.