Optimal position and velocity navigation filters for autonomous vehicles

This paper presents the design and performance evaluation of a set of globally asymptotically stable time-varying kinematic filters with application to the estimation of linear motion quantities of mobile platforms (position, linear velocity, and acceleration) in three dimensions. The proposed techniques are based on the Kalman and H_∞ optimal filters for linear time-varying systems and the explicit optimal filtering solutions are obtained through the use of an appropriate coordinate transformation, whereas the design employs frequency weights to achieve adequate disturbance rejection and attenuation of the measurement noise on the state estimates. Two examples of application in the field of ocean robotics are presented that demonstrate the potential and usefulness of the proposed design methodology. In the first the proposed filtering solutions allow for the design of a complementary navigation filter for the estimation of unknown constant ocean currents, while the second addresses the problem of estimation of the velocity of an underwater vehicle, as well as the acceleration of gravity. Simulation results are included that illustrate the filtering achievable performance in the presence of both extreme environmental disturbances and realistic measurement noise.     

基于数据融合模型的网络安全分析评估系统

在借鉴网络性能监控模型的基础上,该文基于数据融合技术提出了一个网络安全分析与评估的分层实现模型,分析了网络系统中存在的脆弱性,采用安全案例表示与贝叶斯推理相结合的方法对网络安全状况进行建模和分析,并阐述了模型的实现要点。     

Three-dimensional optimal path planning for waypoint guidance of an autonomous underwater vehicle

In this paper, optimal three-dimensional paths are generated offline for waypoint guidance of a miniature Autonomous Underwater Vehicle (AUV). Having the starting point, the destination point, and the position and dimension of the obstacles, the AUV is intended to systematically plan an optimal path toward the target. The path is defined as a set of waypoints to be passed by the vehicle. Four criteria are considered for evaluation of an optimal path; they are “total length of path”, “margin of safety”, “smoothness of the planar motion” and “gradient of diving”. A set of Pareto-optimal solutions is found where each solution represents an optimal feasible path that cannot be outrun by any other path considering all four criteria. Then, a proposed three-dimensional guidance system is used for guidance of the AUV through selected optimal paths. This system is inspired from the Line-of-Sight (LOS) guidance strategy; the idea is to select the desired depth, presumed proportional to the horizontal distance of the AUV and the target. To develop this guidance strategy, the dynamic modeling of this novel miniature AUV is also derived. The simulation results show that this guidance system efficiently guides the AUV through the optimal paths.     

Development of a real-time control architecture for a semi-autonomous underwater vehicle for intervention missions

The need for autonomous underwater vehicles (AUVs) for intervention missions becomes greater as they can perform underwater tasks requiring physical contacts with the underwater environment, such as underwater plug-in/plug-out, construction and repair, cable streaming, mine hunting, munitions retrieval, and scientific sampling. This paper describes a semi-autonomous underwater vehicle for intervention missions that has multiple on-board CPUs, redundant sensors and actuators, on-board power source and a robotic manipulator for dextrous underwater performance. Such a complex robotic vehicle system requires advanced control software architecture for on-board intelligence with a wide range of sensors and actuators to carry out required missions. In this paper, AUV control architectures are reviewed and a sensor data bus based control architecture (SDBCA) is presented. SDBCA is a modified hierarchical architecture that offers good controllability and stability while sensor data bus increases flexibility of system design, making it possible to have a prompt response from high-level control with respect to low-level sensor data. The overall sensor input mechanism of SDBCA becomes similar to the sensor input mechanism of subsumption architecture.     

Decentralized estimation and control of graph connectivity for mobile sensor networks

The ability of a robot team to reconfigure itself is useful in many applications: for metamorphic robots to change shape, for swarm motion towards a goal, for biological systems to avoid predators, or for mobile buoys to clean up oil spills. In many situations, auxiliary constraints, such as connectivity between team members or limits on the maximum hop-count, must be satisfied during reconfiguration. In this paper, we show that both the estimation and control of the graph connectivity can be accomplished in a decentralized manner. We describe a decentralized estimation procedure that allows each agent to track the algebraic connectivity of a time-varying graph. Based on this estimator, we further propose a decentralized gradient controller for each agent to maintain global connectivity during motion.     

A new approach to vision-based unsupervised learning of unexplored indoor environment for autonomous land vehicle navigation

A vision-based approach to unsupervised learning of the indoor environment for autonomous land vehicle (ALV) navigation is proposed. The ALV may, without human's involvement, self-navigate systematically in an unexplored closed environment, collect the information of the environment features, and then build a top-view map of the environment for later planned navigation or other applications. The learning system consists of three subsystems: a feature location subsystem, a model management subsystem, and an environment exploration subsystem. The feature location subsystem processes input images, and calculates the locations of the local features and the ALV by model matching techniques. To facilitate feature collection, two laser markers are mounted on the vehicle which project laser light on the corridor walls to form easily detectable line and corner features. The model management subsystem attaches the local model into a global one by merging matched corner pairs as well as line segment pairs. The environment exploration subsystem guides the ALV to explore the entire navigation environment by using the information of the learned model and the current ALV location. The guidance scheme is based on the use of a pushdown transducer derived from automata theory. A prototype learning system was implemented on a real vehicle, and simulations and experimental results in real environments show the feasibility of the proposed approach.     

高校网络系统的安全管理策略

分析了高校网络系统安全的现状，建议必须加强内部的安全管理和提高安全技术水平，以规避高校网络系统应用的风险。还从管理和技术两个方面对高校网络系统的安全体系作了进一步论述，并提出了高校网络系统的安全策略、安全设计的原则和措施。     

浅谈计算机网络安全的具体问题及控制策略

随着我国科技水平的不断提高,计算机技术也逐渐被应用到我们的日常生活当中,极大地丰富了我们的日常生活内容,也带来了更多的信息资源,促进了社会主义精神文明的快速发展,计算机的安全问题也越来越受到人们的重视,在对计算机的网络系统进行设计的时候一定要充分考虑到计算机网络系统设计的稳定性和规范性,保障计算机的运行安全,采用先进的技术手段,制定相应的解决措施,保障我国计算机应用的安全性,促进我国计算机信息安全产业的快速发展。     

ACL技术在网络安全中的应用

访问控制列表(ACL)被广泛应用在路由器和三层交换机上,它是用来过滤和控制数据包的一种访问控制技术。该文主要阐述了访问控制列表的基本概念、主要功能、工作过程及配置,并以H3C路由器为例说明了访问控制列表在网络安全方面的具体应用,同时给出了ACL的关键配置代码。     

Robust online roll dynamics identification of a vehicle using sliding mode concepts

This paper proposes a robust observer concept for joint estimation of system states and model parameters related to the roll dynamics of a vehicle. Using sliding mode concepts introduces robustness to parametric uncertainties and also allows reconstruction of the latter. These model parameters are of interest for vehicle dynamics assessment and estimation of the roll angle. A novel classification concept exploits these parameter estimates for assessing the roll dynamics. An additional benefit of the proposed method is the minimal requirement of measurement equipment as it only relies on cost-efficient angular rate and acceleration sensors. Evaluation of the framework is performed in simulations and real-world using an experimental vehicle.     

OA系统安全防范的几点方法

几年来，OA工作者一直在寻找能够保证OA系统安全的方法，本文从内部办公、远程办公、internet三个方面介绍了OA系统中安全性防范的几点方法。     

Design method for a new control system for an autonomous underwater vehicle using linear matrix inequalities

The independent administrative corporation Japan Agency for Marine–Earth Science and Technology (JAMSTEC) has developed a small light autonomous underwater vehicle (AUV) named marine robot experimental 1 (MR-X1).¹ The motion control of MR-X1 is considered in this article. Since the dynamics of MR-X1 mainly depends on its own speed, the motion control is a nonlinear control system. We propose a new controller design method for this system using linear matrix inequalities (LMIs). This algorithm gives a solution as a linear matrix inequality, and can be adapted to solve many LMIs simultaneously. LMIs can be obtained by substituting several speeds into the dynamics of the MR-X1. The proposed controller, which can be derived from the solution of the LMIs, was adapted to MR-X1 and showed good performance in experiments. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Algorithms for dense graphs and networks on the random access computer

We improve upon the running time of several graph and network algorithms when applied to dense graphs. In particular, we show how to compute on a machine with word size = (logn) a maximal matching in ann-vertex bipartite graph in timeO(n ²+n ^2.5/)=O(n ^2.5/logn), how to compute the transitive closure of a digraph withn vertices andm edges in timeO(n ²+nm/), how to solve the uncapacitated transportation problem with integer costs in the range [O.C] and integer demands in the range [–U.U] in timeO ((n ³ (log log/logn)^1/2+n² logU) lognC), and how to solve the assignment problem with integer costs in the range [O.C] in timeO(n ^2.5 lognC/(logn/loglogn)^1/4).Assuming a suitably compressed input, we also show how to do depth-first and breadth-first search and how to compute strongly connected components and biconnected components in timeO(n+n ²/), and how to solve the single source shortest-path problem with integer costs in the range [O.C] in time0 (n ²(logC)/logn). For the transitive closure algorithm we also report on the experiences with an implementation.Most of this research was carried out while both authors worked at the Fachbereich Informatik, Universität des Saarlandes, Saarbrücken, Germany. The research was supported in part by ESPRIT Project No. 3075 ALCOM. The first author acknowledges support also from NSERC Grant No. OGPIN007.     

Design and analysis of an underwater inductive coupling power transfer system for autonomous underwater vehicle docking applications

We develop a new kind of underwater inductive coupling power transfer （ICPT） system to evaluate wireless power transfer in autonomous underwater vehicle （AUV） docking applications. Parameters that determine the performance of the system are systematically analyzed through mathematical methods. A circuit simulation model and a finite element analysis （FEA） sim- ulation model are developed to study the power losses of the system, including copper loss in coils, semiconductor loss in circuits, and eddy current loss in transmission media. The characteristics of the power losses can provide guidelines to improve the effi- ciency of ICPT systems. Calculation results and simulation results are validated by relevant experiments of the prototype system. The output power of the prototype system is up to 45 W and the efficiency is up to 0.84. The preliminary results indicate that the efficiency will increase as the transmission power is raised by increasing the input voltage. When the output power reaches 500 W, the efficiency is expected to exceed 0.94. The efficiency can be further improved by choosing proper semiconductors and coils. The analysis methods prove effective in predicting the performance of similar ICPT systems and should be useful in designing new systems.     

Design and implementation of an autonomous flight control law for a UAV helicopter

In this paper, we present the design and implementation of an autonomous flight control law for a small-scale unmanned aerial vehicle (UAV) helicopter. The approach is decentralized in nature by incorporating a newly developed nonlinear control technique, namely the composite nonlinear feedback control, together with dynamic inversion. The overall control law consists of three hierarchical layers, namely, the kernel control, command generator and flight scheduling, and is implemented and verified in flight tests on the actual UAV helicopter. The flight test results demonstrate that the UAV helicopter is capable of carrying out complicated flight missions autonomously.     

物联网安全问题及解决方案

本文介绍了物联网的概念,分析了其体系架构并总结了其特点,从物联网的体系架构、信息安全的机密、完整等角度阐述了物联网发展存在的安全问题,并进行了提出了一些相应的安全策略。     

网络安全中网络欺骗的作用初探

网络技术的进步对网络安全带来了一系列的负面影响,网络攻击行为越来越普遍,严重威胁到了网络环境的安全性,成为现代社会备受人们关注的问题。网络欺骗能够提高网络的安全性分析,并对网络安全进行准确的效果评价,有效地减少了网络被入侵和攻击的概率,为维护网络安全具有一定的作用,我们必须不断改进自己的网络技术,更好地维护网络环境的安全性。     

网络欺骗在网络安全中的作用研究

随着近年来网络信息技术的不断发展与进步,网络技术已经给人们的生产生活带来了方便,因此,网络技术在人们的日常生活和工作等多领域中得到广泛运用,然而成也萧何败也萧何,正因为网络技术在人们的生活和工作中的广泛应用,使得一些不法分子有了可乘之机,网络安全问题也随之而来。本文主要对网络欺骗在网络安全中的主要作用进行分析。     

Pattern recognition and control by adaptive methods for an intelligent mobile vehicle

This paper describes adaptive methods for both pattern recognition and control in an experimental mobile vehicle (MV). An adaptive resonance theory (ART) neural network is used as the character recognizer. It can self-organize and self-stabilize in response to complex binary input vectors. New input patterns can be saved in such a fashion that the stored patterns are not forgotten or destroyed. By merging the advantages of the feed-forward neural network, adaptive algorithm, and fuzzy control, a neuro-fuzzy system also is proposed. This can deal with a large amount of training data in the neural network, from these data produce more reasonable fuzzy rules with the adaptive algorithm, and then control the object by fuzzy control. This is not a simple combination of the three methods, but a merger into one intelligent control system. Finally, the experimental results and some conclusions are given. This work was presented in part at the 7th International Symposium on Artificial Life and Robotics, Oita, Japan, January 16–18, 2002     

网络控制系统的安全域研究

基于网络控制系统(networked control system,NCS)的网络空间特性,对NCS信息安全的时空特性和NCS的安全域进行了研究,在此基础上提出了一种具有自律可控性和自律可协调性的NCS安全域的新型体系结构,并对新构建的NCS安全域体系的一些关键问题进行了探讨。