Parameter identification and design of a robust attitude controller using <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> methodology for the raptor E620 small-scale helicopter

Rigorous control synthesis for an unmanned aerial vehicle necessitates the availability of a good, reasonable model for such a vehicle. The work reported in this paper focuses on the modeling of a rotary unmanned aerial vehicle (RUAV) and the development of a robust controller that can handle parameter uncertainties and disturbances. The parameters of the plant model are obtained through the use of the prediction error method with real flight data. The response of the identified linear model shows a good match with the measured flight data. The H _∞ control scheme is applied to obtain a robustly stable controller using the identified model. The proposed controller is analyzed using frequency-domain analysis and time-domain simulations. The performance of the proposed H _∞ controller is better than that of the conventional proportional derivative controller in that the proposed controller has a shorter settling time and less overshoot. Furthermore, the degradation of the proposed controller performance is negligible and stability is maintained when the input gains to the plant are doubled, which demonstrates the good performance and robustness of the controller.     

A vertical and floor line-based monocular SLAM system for corridor environments

In this paper, we propose a vertical and floor line-based monocular simultaneous localization and mapping (SLAM) system which utilizes vertical lines, floor lines, and vanishing points as sensory input to perform robust SLAM in corridor environments. By combining three map feature types, our design can help a robot to perform accurate pose estimation, repeatable loop closure, and to construct a more expressive environmental map. As a primitive element of a geometric structure, a line segment has one additional dimension compared to a point feature, thereby allowing the use of line segments to easily represent a geometric structure using a smaller number of features. This system presents map features on a 2D ground space: the vertical line as a projection point, the floor line as the original line, and the vanishing point as a directional vector. Although the vertical line, floor line, and vanishing point use different parameterization and initialization methods, their measurement models are integrated into a unified extended Kalman filter (EKF) framework. Experimental results show that our system can be deployed in a structured indoor environment as a suitable SLAM solution.     

An investigation into vehicle rollover prevention by coordinated control of active anti-roll bar and electronic stability program

This paper presents a method for designing a controller that uses an active anti-roll bar (AARB) and an electronic stability program (ESP) for rollover prevention. ESP with longitudinal speed control (LSC) can carry out active braking to reduce vehicle speed and lateral acceleration to prevent a rollover. To enhance the rollover prevention capability of the ESP, an AARB is adopted. The controller for the AARB was designed based on linear quadratic (LQ) static output feedback (SOF) control methodology, which attenuates the effect of lateral acceleration on the roll angle and roll rate by control of the suspension stroke and the tire deflection of the vehicle. Although this AARB significantly increases ride comfort and rollover prevention, it has a drawback — the vehicle loses its maneuverability. Therefore, the ESP with LSC is used to overcome this drawback. Simulations showed that the proposed method was effective in preventing a rollover.     

Deciding bisimilarity is<Emphasis Type="Italic">P</Emphasis>-complete

In finite labelled transition systems the problems of deciding strong bisimilarity, observation equivalence and observation congruence areP-complete under many—oneNC-reducibility. As a consequence, algorithms for automated analysis of finite state systems based on bisimulation seem to be inherently sequential in the following sense: the design of anNC algorithm to solve any of these problems will require an algorithmic breakthrough, which is exceedingly hard to achieve.     

基于OpenCv运动目标识别技术的研究

在智能视频监控系统中,快速、准确、有效地检测出运动目标成为人们研究的主要课题之一。本文根据背景差分与帧间差分各自的特点,提出一种基于高斯模型的背景差分与帧间差分相结合的运动目标检测算法。说明高斯背景建模原理以及算法的背景模型更新方法,最后介绍了算法的实现流程和实验结果。在VisualC++6.0环境下,利用计算机视觉类库OpenCV对算法进行了验证。实验结果表明:该算法能快速、有效地提取目标。     

基于SOA的高校教学管理平台

通过分析高校教学管理目前信息化面临的问题,提出基于SOA体系结构对目前的应用系统进行整合,实现各应用系统之间的协同工作。描述了教学管理平台的需求、体系结构、设计思路,说明了在开发过程中所使用的关键技术。同时在实现了基于SOA体系结构的教学管理平台之后,在移动终端上开发了相应的客户端应用程序,使学生能够实时了解相关教学信息。     

提升细节捕捉能力的非下采样轮廓波变换

针对传统NSCT(非下采样轮廓波变换)算法中NSP(多尺度分解方法)对细节信息捕捉能力较差及利用其进行图像融合得到的融合图像出现细节丢失问题,提出改进的NSCT算法。不同于传统NSCT算法,该算法首先采用细节捕捉能力较强的非下采样形态学小波分解替代NSP分解,实现对源图像的多尺度分解,将源图像分解成水平高频、垂直高频、对角高频和低频4部分;然后利用NDFB(非下采样的方向性滤波器)对高频部分进行多方向分解得到一系列高频信息,实现改进型NSCT分解。实验结果表明,该算法的细节捕捉能力较传统算法好,在相同融合规则下其图像融合效果更好,各项融合指标值均有所提高,其中平均梯度提高了10%,且易于实现,可广泛用于多分辨率图像融合,是一种有效的融合图像算法。     

3DGIS环境下雨雪天气实时仿真

3D GIS最重要的特征之一就是虚拟现实表现,其本质是可视化技术与GIS数据库的整合,以满足各种应用如生态农业、灾害预测等方面的需求。以GIS数据库的环境数据和气象数据为基础,通过对雨雪的效果模拟,将GIS气象数据以实时的可视化形式逼真地表现出来。实验方法采用粒子系统,对单个点元赋予利用Photoshop制作的大面积纹理,这样采用的粒子数减少到普通粒子系统的十分之一,渲染速度为普通粒子系统的十倍以上,以较小的系统资源消耗达到了更加实时逼真的效果,对雪的动态堆积和雨水地面效果采用GPU加速3维渲染,原型系统同时能接受用户对实验环境如粒子纹理、雨雪量的设置。提出根据气象数据进行天气模拟的自适应策略,从而更加适应实际应用需要。     

保持几何特征的自适应弹性二次曲线模型

物体形状特征的准确提取往往受到图像获取、目标分割等过程中各种因素的影响,因而需要构造一种鲁棒的形状表现来保有其本质特征。揭示弹性二次曲线(EQW)模型中能量权重因子和样条重叠度因子与形状几何特性间的关系,提出一种自适应保持几何特征的EQW形状表现模型,并将该模型与交互式Live Wire算法相结合,应用至图像分割中,对于各种模态图像中的目标进行分割实验。直观上,本文方法能够在去除噪声同时较好地保持目标形状的显著特征;量化结果方面,交互式分割误差保持在较小稳定范围内,引入EQW模型带来的时间开销亦在可接受范围内。     

基于特征互补图像的人脸识别仿真研究

研究人脸识别精度问题。由于人脸图像中存在大量干扰信息的缺点,而造成了人脸识别正确率下降,为了解决上述问题,提出了一种基于特征互补图像快速特征融合算法。算法通过对人脸图像的位平面切片图像分析,采用位平面图像分解法,通过各种合成策略构造多幅样本图像。并突出高位平面图像,采用两种加权策略将每一幅人脸图像样本都生成"特征互补图像"。然后,直接用图像的二维典型相关分析(2DCCA)法对两种特征互补图像进行特征抽取。最后通过在ORL国际标准人脸库上进行的实验,结果表明,高位平面图像的典型相关鉴别特征提高了正确识别率,并且因为摒弃了原始人脸图像的大部分干扰信息所以具有更强的鲁棒性。