THE COMPLEXITY OF LIMIT LANGUAGES OF CELLULAR AUTOMATA: AN EXAMPLE

1 IntroductionCellular automata (abbreviated as CA) are typical complex systems that their global behaviors cannot be PrediCted from the Properties of their componellts (i.e. cells or automata)which are identically located on the nodes of a periodic lattice and have the same updatingrules.Historicallys the first cellular automaton was proposed by von Neumann to formalize thereproductivity phenomena in living systems[IJ. Since then cellular automata as mathematicalmodels have been used to si…     

Research on robust fault-tolerant control for networked control system with packet dropout

A kind of networked control system with network-induced delay and packet dropout, modeled on asynchronous dynamical systems was tested, and the integrity design of the networked control system with sensors failures and actuators failures was analyzed using hybrid systems technique based on the robust fault-tolerant control theory. The parametric expression of controller is given based on the feasible solution of linear matrix inequality. The simulation results are provided on the basis of detailed theoretical analysis, which further demonstrate the validity of the proposed schema.     

Trajectory linearization control of an aerospace vehicle based on RBF neural network

An enhanced trajectory linearization control （TLC） structure based on radial basis function neural network （RBFNN） and its application on an aerospace vehicle （ASV） flight control system are presensted. The influence of unknown disturbances and uncertainties is reduced by RBFNN thanks to its approaching ability, and a robustifying itera is used to overcome the approximate error of RBFNN. The parameters adaptive adjusting laws are designed on the Lyapunov theory. The uniform ultimate boundedness of all signals of the composite closed-loop system is proved based on Lyapunov theory. Finally, the flight control system of an ASV is designed based on the proposed method. Simulation results demonstrate the effectiveness and robustness of the designed approach.     

FBFN-based adaptive repetitive control of nonlinearly parameterized systems

An adaptive repetitive control scheme is presented for a class of nonlinearly parameterized systems based on the fuzzy basis function network （FBFN）. The parameters of the fuzzy rules are tuned with adaptive schemes. To attenuate chattering effectively, the discontinuous control term is approximated by an adaptive PI control structure. The bound of the discontinuous control term is assumed to be unknown and estimated by an adaptive mechanism. Based on the Lyapunov stability theory, an adaptive repetitive control law is proposed to guarantee the closed-loop stability and the tracking performance. By means of FBFNs, which avoid the nonlinear parameterization from entering into the adaptive repetitive control, the controller singularity problem is solved. The proposed approach does not require an exact structure of the system dynamics, and the proposed controller is utilized to control a model of permanent-magnet linear synchronous motor subject to significant disturbances and parameter uncertainties. The simulation results demonstrate the effectiveness of the proposed method.     

H 2/H ∞ control problems of backward stochastic systems

This paper is concerned with the mixed H2/H∞ control problem for a new class of stochastic systems with exogenous disturbance signal.The most distinguishing feature,compared with the existing literatures,is that the systems are described by linear backward stochastic differential equations（BSDEs）.The solution to this problem is obtained completely and explicitly by using an approach which is based primarily on the completion-of-squares technique.Two equivalent expressions for the H2/H∞ control are presented.Contrary to forward deterministic and stochastic cases,the solution to the backward stochastic H2/H∞ control is no longer feedback of the current state;rather,it is feedback of the entire history of the state.     

H_ index based fault estimation for micro quad-rotor

Taking the attitude control system of micro quad-rotor as a research object, a design scheme of fault estimator based on generalized Kalman-Yakubovic-Popov （GKYP） lemma is put forward to deal with the problem of estimating multiple actuators malfunctions with couplings. Using an H_index and an appropriate algorithm, the goal of weakening the coupling can be achieved by limiting the fault frequency to a certain range, then different kinds of actuator faults can be estimated correctly. The simulations demonstrate the reliability and validity of the proposed method.     

Periodic performance of the chaotic spreadspectrum sequence on finite precision

It is well known that the periodic performance of spread spectrum sequence heavily affects the correlative and secure characteristics of communication systems. The chaotic binary sequence is paid more and more attention since it is one kind of applicable spread spectrum sequences. However, there are unavoidable short cyclic problems for chaotic binary sequences in finite precision. The chaotic binary sequence generating methods are studied first. Then the short cyclic behavior of the chaotic sequences is analyzed in detail, which are generated by quantification approaches with finite word-length. At the same time, a chaotic similar function is defined for presenting the cyclic characteristics of the sequences. Based on these efforts, an improved method with scrambling control for generating chaotic binary sequences is proposed. To quantitatively describe the improvement of periodic performance of the sequences, an orthogonal estimator is also defined. Some simulating results are provided. From the theoretical deduction and the experimental results, it is concluded that the proposed method can effectively increase the period and raise the complexity of the chaotic sequences to some extent.     

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.     

Introduction to the special issue on mathematics and algorithms in computer-aided manufacturing, engineering, and numerical control

Sixty years have passed since numerical control of machine tools was first demonstrated at MIT. Since then, rapid developments in advanced manufacturing technology have posed new challenges and requirements, among them faster machining （high-speed machining）, higher feed-rates, more accurate parts and better surface finish. Not only are sophisticated computer- enabling technologies needed to cope with these challenges, but also significantly improved and more sophisticated mathematical tools. These emerging challenges and requirements under- score the growing importance of mathematical methods and algorithms. On the other hand, new challenges, optimization functions and constraints, arising in the field of advanced man- ufacturing have also stimulated the development of new branches of industrial and applied mathematics. Mathematics and Algorithms for Computer-Aided Manufacturing, Engineering and Numerical Control （MAMENC） is an annual workshop organized by the National Cen- ter for Mathematics and Interdisciplinary Sciences of China （NCMIS）. The workshop＇s topics focus on how mathematical methods and algorithms interact with computer-aided manufac- turing, computer-aided engineering and computer numerical control. MAMENC 2012 is the second workshop in the series. The first was held in Beijing in 2011, and the proceedings were published in the September 2012 issue （number 3） of the Mathematics in Computer Science journal under the title Special Focus on Mathematics and Algorithms for CAM and CNC.     

改进点格自动机交通网络模型及交通系统自组织现象的研究

基于点格自动机的原理,提出一种比较切合实际的改进点格自动机交通网络模型。该模型把交通网络分为“道路”和“路口”。用队列来模拟“车流”,车辆密度分为三档。在此模型基础上,研究了不同情况下交通系统中的自组织现象。理论上分析了自组织形成的动态过程。并进行计算机仿真     

基于群体智能的森林火灾蔓延仿真模型

针对传统森林火灾蔓延模型的计算复杂度高、仿真精度低等缺点，提出一种基于群体智能的森林火灾蔓延仿真模型。在模型中通过建立可燃物因素影响因子矩阵和地貌因素影响因子矩阵，并结合实时检测的气象信息，降低计算复杂度；将森林火灾的蔓延行为抽象为每一个模块火点的集群行为，考虑模块之间的关联性，提高森林火灾蔓延仿真模型精度。将模型与王正非模型和二维元胞自动机模型进行对比实验，结果表明模型具有较高精度，能够更加准确地仿真出森林火灾蔓延趋势。     

基于元胞自动机的地下矿火灾蔓延仿真方法

提出了基于元胞自动机模型的地下矿火灾发生时火灾在巷道网络系统中蔓延的可视化仿真方法。在该方法中,用元胞自动机模型描述地下矿巷道网络系统,用元胞来描述火焰蔓延能量单元,该单元用火焰温度、蔓延速度、烟雾浓度和有毒气体浓度等状态参数来描述。在仿真过程中,可以获得大量关于火灾蔓延、灾害动态、灾害严重程度及其可行的调控方法。该方法将时间、空间和系统行为有机地结合起来,在形象、直观、真实的条件下完成火灾在巷道系统中蔓延的仿真。     

基于元胞自动机的行业危机扩散博弈分析

元胞自动机(Cellular Automata,CA)模拟仿真实现了行业危机扩散博弈过程的可视化,简化了博弈分析过程。本文首先进行了行业危机扩散的博弈分析,通过纳什均衡解的求解误差发现危机扩散受到很多因素影响,并且具有一定的随机性,增加了博弈分析的难度。基于此,引用元胞自动机结合行业危机扩散博弈的策略组合,构建了行业危机扩散的CA算法,解决了行业危机扩散博弈的有限理性假设问题,并使用仿真效果较好的多主体可视化软件Netlogo进行仿真,结果符合实际情况。     

混入智能网联车队的混合交通流元胞自动机模型

针对现有自动-手动驾驶混合交通流元胞自动机模型未考虑智能网联车队队列行为,提出了考虑智能网联车队的混合交通流元胞自动机模型,研究混入智能网联汽车车队的混合交通流特征。对混合交通流中的跟驰行为进行了分析,基于跟驰行为的特征,分别构建人工驾驶跟驰模式、自适应巡航模式、协同自适应巡航车队模式的元胞自动机规则,基于数值仿真实验对不同智能网联车渗透率下的混合交通流特性及拥堵情况进行了分析。结果表明：智能网联汽车的应用可显著提高道路通行能力和车辆平均速度,进而有效地缓解交通拥堵。     

局部车道缩减的双车道元胞自动机交通流模型研究

针对道路使用过程中可能发生的意外,考虑双车道有一条车道出现局部维护,车辆需要绕行的情况,在一维对称双车道元胞自动机模型的基础上,建立一种有局部车道缩减的双车道元胞自动机模型,结合实际交通情况给出计算机数值仿真的流量-密度图,分析受堵车道上的交通状况,并给出受堵车道的时空斑图。数值仿真结果显示,对于不同的延迟概率,整个路段都有相应的瓶颈流量,对受堵车道上的换道规则的调整有助于增加该车道上的换道车辆数,减少车辆的滞留。     

行人运动仿真研究综述

行人运动仿真是近年来仿真领域研究的热点之一。从行人运动仿真的研究意义和研究内容出发,介绍了国内外行人运动仿真研究发展历程和研究现状,论述了行人运动仿真模型的三种类型,分析了成本效益元胞模型、元胞自动机模型、磁场力学模型、社会力学模型、排队网络模型五种典型的行人运动仿真模型的原理和适用条件。最后探讨了目前行人运动仿真研究中存在的问题及未来的发展前景。     

Distributed intrusion detection for mobile ad hoc networks

Mobile ad hoc networking （MANET） has become an exciting and important technology in recent years, because of the rapid proliferation of wireless devices. Mobile ad hoc networks is highly vulnerable to attacks due to the open medium, dynamically changing network topology, cooperative algorithms, and lack of centralized monitoring and management point. The traditional way of protecting networks with firewalls and encryption software is no longer sufficient and effective for those features. A distributed intrusion detection approach based on timed automata is given. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then the timed automata is constructed by the way of manually abstracting the correct behaviours of the node according to the routing protocol of dynamic source routing （DSR）. The monitor nodes can verify the behaviour of every nodes by timed automata, and validly detect real-time attacks without signatures of intrusion or trained data. Compared with the architecture where each node is its own IDS agent, the approach is much more efficient while maintaining the same level of effectiveness. Finally, the intrusion detection method is evaluated through simulation experiments.     

地下煤矿瓦斯渗出、运移与积聚过程仿真方法

提出了基于元胞自动机模型的地下煤矿生产过程中瓦斯渗出后在巷道网络系统中运移和积聚的可视化仿真方法。在该方法中,用元胞自动机模型描述地下矿巷道网络系统,用瓦斯元胞来描述从工作面煤壁、采落的煤堆、围岩和采空区渗出的瓦斯能量单元;用格子元胞描述巷道格子及其状态,这些格子元胞均用瓦斯运移速度和瓦斯含量等状态参数来描述。在仿真过程中,可以获得大量关于瓦斯渗出、运移、稀释、积聚和排放等动态信息以及瓦斯积聚区域形成及其严重程度的量化指标及其可行的调控方法。该方法将时间、空间和系统行为有机地结合起来,在形象、直观、真实的条件下完成积聚在巷道系统中渗出、运移和积聚的仿真。     

基于元胞自动机的复杂系统脆性仿真

复杂系统研究是当前的热点,脆性是复杂系统的一个基本属性．在一个复杂系统中,当一个子系统遭受足够大的打击而崩溃时,整个系统将会崩溃．元胞自动机是一个离散的动力学系统,它可以用来仿真复杂系统的行为．文章应用元胞自动机对复杂社会系统的脆性进行仿真．仿真结果说明传染病扩散对其它社会子系统具有很大的影响．作为复杂系统的一个子系统,传染病的大规模扩散会使社会混乱,进而得出它具有脆性的结论．