Trajectory tracking control for underactuated unmanned surface vehicle subject to uncertain dynamics and input saturation

Neural Computing and Applications - In this paper, one concerns with the problem of trajectory tracking control for an underactuated unmanned surface vehicle subject to uncertain dynamics and input...     

Customer knowledge discovery from online reviews

The explosive growth of Chinese electronic market has made it possible for companies to better understand consumers?? opinion towards their products in a timely fashion through their online reviews. This study proposes a framework for extracting knowledge from online reviews through text mining and econometric analysis. Specifically, we extract product features, detect topics, and identify determinants of customer satisfaction. An experiment on the online reviews from a Chinese leading B2C (Business-to-Customer) website demonstrated the feasibility of the proposed method. We also present some findings about the characteristics of Chinese reviewers.     

Hysteresis Compensation and Adaptive Controller Design for a Piezoceramic Actuator System in Atomic Force Microscopy

This paper presents an indirect adaptive controller combined with hysteresis compensation to achieve high accuracy positioning control of piezoceramic actuators and illustrates the results with an atomic force microscope (AFM) application. A dynamic model of a piezoceramic actuator system in AFM is derived and analyzed. A feedforward controller based on the Preisach model is proposed to compensate for the nonlinear hysteresis effects. Then an indirect adaptive controller is designed to achieve desired tracking performance as well as deal with the uncompensated nonlinearity from hysteresis and the system parameter variation due to creep. Experimental results indicate that the proposed controller can significantly improve the positioning control accuracy of the piezoceramic actuator as well as achieve high image quality of the AFM system. The maximum scanning error was reduced from 2µm to 0.3µm in comparison with a proportional‐integral‐derivative (PID) controller. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

New constructions of OSBE schemes and their applications in oblivious access control

Oblivious signature-based envelope (OSBE) schemes have demonstrated their potential applications in the protection of users privacy and rights. In an OSBE protocol, an encrypted message can only be decrypted by the receiver who holds a valid signature on a public message, while the sender (encrypter) does not know whether the receiver has the signature or not. Our major contributions in this work lie in the following aspects. We improve the notion of OSBE so that a valid credential holder cannot share his/her credential with other users (i.e., all-or-nothing non-transferability). We clarify the relationship between one-round OSBE and identity-based encryption (IBE) and show that one-round OSBE and semantically secure IBE against the adaptively chosen identity attack (IND-ID-CPA) are equivalent, if the signature in the OSBE scheme is existentially unforgeable against adaptively chosen message attacks. We propose an oblivious access control scheme to protect user privacy without the aid of any zero-knowledge proof. Finally, we also highlight some other novel applications of OSBE, such as attributed-based encryption.     

未知环境下机器人障碍物检测技术

未知环境下地面的不平坦性和机器人相对障碍物位姿的不确定性会造成障碍物特征提取困难,为了准确检测障碍物特征,采用3维相机获取机器人周围环境的灰度图像和距离信息。在此基础上,提出基于灰度信息和3维信息的"阈值法"进行障碍物区域的提取,并针对3维信息"阈值法"剔除的地面与障碍物过渡区域过多,以及机器人相对斜坡方位的不确定性引起的障碍物特征检测不准确,提出区域的恢复算法和表面法线坡度计算。实验结果表明,所提出的算法具有简单、有效、准确和鲁棒性强的优点。     

一种基于EPID的安全OA系统

文章对OA系统中存在的安全问题进行了讨论,引人了一种新的基于远程匿名身份认证EPID模式,它能通过保存设备拥有者私密信息的硬件设施进行身份鉴定。一个嵌入EPID私密的硬件设备可以向远程机构证实它的有效性,而不必暴露自己的身份和其他私密信息。可以撤消一个签名的EPID私钥,即使不知道密钥的身份。同时,把EPID和其它的一些方法进行了对比。     

A Brief Introduction on Joint Radar and Communication Systems

Joint radar and communication(JRC) technology is gradually becoming an essential approach to alleviating spectral congestion. Radar and communications systems were designed with common spectral and hardware resources to reduce size, improve performance, reduce cost, and decongest the spectrum. Various approaches have been proposed to achieve the coexistence of radar and communication systems. This paper mainly focuses on the research directions of radar communication coexistence(RCC) and dual-function radar communication systems(DFRC) in JRC technology. We summarize and analyze the existing research problems in the JRC era. According to the characteristics and advantages of JRC technology, we highlight several potentials in military and commercial applications.     

深海带电插拔连接器力学特性分析

以水下7 000 m工况的深海带电插拔连接器为研究对象,旨在获得湿插拔连接器在深海双重高压下的受力特性和插拔过程中的动密封性能。介绍连接器的插头结构与压力补偿技术;推导压力补偿器工作容积的计算公式;运用Ansys Workbench建立插头内壳体组件与插孔组件的动密封有限元模型,对内壳体、压力平衡膜及内胆进行强度计算;分析由连接器插拔引起的平衡膜内外瞬时压差对膜的应力分布及变形情况;讨论密封件径向压缩量、密封接触面摩擦因数、插拔速度对插拔过程中动密封性能的影响。结果表明:插头插合时,平衡膜外表面应力基本不变,其变形减小;拔出时,平衡膜外表面的应力及变形都逐渐增大。密封件之间的接触压力受密封接触面过盈配合量的影响明显,增大过盈配合量可显著提高动密封区域的接触压力及密封性能,同时也会加剧密封件失效的可能性,密封接触面的摩擦因数、插拔速度对接触压力的影响则较小。     

低压光伏集群无功运行模式优化

配电网中存在大量低压接入的分布式小容量光伏电源,其规模庞大且实时通信条件有限,在线调节的经济性和可操作性没有保障,因此难以有效利用这些无功资源进行配电网辅助调节.在此背景下,为发挥低压光伏无功调节潜力,提出一种按集群进行模式预设、在线自律运行的低压光伏参与中压电网无功运行模式优化策略.首先,以配变台区为无功集群单元进行平台化管理,以补偿馈线无功需求为目标进行日前无功匹配优化;其次,设计5种集群无功运行模式,构建日前预测运行场景并依据场景特征建立综合考虑馈线无功平衡度最优和集群间无功流动最小为目标的集群无功运行模式及参数优化模型,运用改进粒子群算法进行优化求解,使集群在各时段的运行模式组合方案能够最佳匹配馈线的无功需求并抑制无功不合理流动.最后,算例验证了该方法的有效性.