利用方位角观测的多机器人系统离散分布式最优围陷控制

本文研究了离散时间多机器人系统对静态目标的同步定位与围陷问题。首先,为了引导多机器人系统以任意编队在任意轨道上运动,本文提出了基于虚拟系统法的路径规划方案。其次,为了实现在缺少机器人全局位置信息下的目标定位与跟踪问题,本文设计了基于方位角观测的离散时间估计器与控制器的联合设计方法。估计 器充分利用了正交性质估计实时相对位移,并基于估计值设计控制律。基于离散时域拉塞尔原理与迭代法,本文给出了估计误差与跟踪误差收敛的充分条件与稳定性证明。此外,本文还设计了一种增益调整优化算法以提高收敛速率,使得离散时间多机器人系统可以更快达到理想编队。最后,仿真实验结果证明了整体方案的有效性。     

模糊控制系统的Matlab仿真过程

以一个车辆速度控制系统为例,阐述了使用Matlab仿真模糊控制系统的一般步骤。通过仿真试验,着重介绍了模糊控制环节各个要素对控制系统的影响。     

Perceived beneficial and detrimental postwar responses of Israeli adults: Are they positively or negatively linked to each other?

This study first compares two theoretical perspectives on the links between beneficial and detrimental posttraumatic responses. One group of studies claims that positive posttraumatic responses tend to be positively related with negative stress-related responses. Others posit that, after a severe stress, these responses are negatively correlated with each other. We argue that these contradictory results represent the different theoretical positions on the nature of favorable postwar outcomes. A second issue investigated is the associations of beneficial and detrimental postwar responses with demographic variables as well as with exposure to the stress of war. An Israeli adult sample (n = 870) was administered two different measures of negative posttraumatic outcomes (resource loss and postwar symptoms) and two different measures of positive posttraumatic outcomes (resource gains and posttraumatic recovery) one year after they were badly affected by a war. Resource gains correlated positively with resource loss, whereas PTR correlated negatively with postwar symptoms. There were also positive associations between the two measures of stress as well as the two beneficial posttraumatic outcomes. Older age, being a woman, lower economic status, and higher exposure to traumatic events tended to correlate positively with both measures of detrimental outcomes. These variables correlated negatively with PTR, and three of them (excluding economic status) were not significantly linked with resource gains. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

非线性增益递归滑模动态面自适应NN控制

针对一类严反馈非线性不确定系统的跟踪控制问题,提出一种非线性增益递归滑模动态面 (Dynamic surface control, DSC)自适应控制方法. 通过设计一个新的非线性增益函数,并构造递归滑模动态面的控制策略和新的Lyapunov函数,同时利用神经网络在线逼近系统不确定项, 该方法有效解决了具有输入饱和约束条件下系统控制精度与动态品质间的矛盾,增强了控制器对其自身参数摄动的非脆弱性. 理论证明了闭环系统所有状态是半全局一致最终有界的,且跟踪误差可收敛至任意小.     

Multi‐parametric extremum seeking‐based iterative feedback gains tuning for nonlinear control

We study in this paper the problem of iterative feedback gains auto‐tuning for a class of nonlinear systems. For the class of input–output linearizable nonlinear systems with bounded additive uncertainties, we first design a nominal input–output linearization‐based robust controller that ensures global uniform boundedness of the output tracking error dynamics. Then, we complement the robust controller with a model‐free multi‐parametric extremum seeking control to iteratively auto‐tune the feedback gains. We analyze the stability of the whole controller, that is, the robust nonlinear controller combined with the multi‐parametric extremum seeking model‐free learning algorithm. We use numerical tests to demonstrate the performance of this method on a mechatronics example. Copyright © 2016 John Wiley & Sons, Ltd.     

Carbon footprint of green roof installation on school buildings in Greek Mediterranean climatic region

Green roof installation in contemporary urban centres is increasing due to their numerous benefits, including microclimate improvement. However, the magnitudes of influence of the green roof design to energy savings is not fully clear, as well as the environmental benefit, in terms of reducing greenhouse gases emissions. The aim of this study was to estimate the effect of green roofs design on energy savings and their carbon footprint when installed on school buildings. The cooling and thermal insulation features of green roofs have been studied by using the TRNSYS simulation software. Different types of green roof systems (extensive and semi-intensive) and construction options are studied in four types of school buildings. Results showed that the estimated reduction in annual CO₂ emissions due to energy savings and CO₂ capture by plants was many times greater than the CO₂ emissions that caused from roof construction.     

Fast consensus algorithm of multi-agent systems with double gains regulation

Two novel fast consensus algorithms based on local information of first-order discrete multi-agent systems under a directed network are proposed in this paper. By applying matrix theory and the frequency-domain analysis methods, two sufficient conditions about the convergence rate of the systems are presented, respectively, where the proportional-like gain feedback and incremental proportional–integral–differential gains feedback only with local information are added. Finally, a numerical example is given to show the double gains regulation algorithm proposed in this paper has much faster consensus rate compared with the classical consensus algorithm in the same condition for its two-degree freedom parameters.     

Funnel‐like prescribed tracking control for uncertain nonlinear stochastic switched systems

This paper deals with the funnel‐like prescribed tracking control problem for a class of uncertain nonlinear stochastic switched systems. An improved performance technique is developed to restrain the fluctuation at the moment of switches and a new algorithm is proposed to address the funnel‐like prescribed tracking problem. First, a dynamic gain‐based switched K‐filter is constructed to estimate the unmeasured state information of the switched system. Subsequently, the performance technique is applied to prescribe output tracking error and restrain fluctuations of the system. Thereafter, the dynamic output feedback switched controller is designed by the use of the backstepping method. Moreover, based on the Lyapunov stability theory, it is proved strictly that all signals of the resulting closed‐loop system are bounded in probability if the switching signal satisfies the average dwell time. Finally, a numerical simulation is presented to illustrate the effectiveness of the proposed theoretical results.     

Distributed adaptive output consensus control of second-order systems containing unknown non-linear control gains

In this paper, we address the output consensus problem of tracking a desired trajectory for a group of second-order agents on a directed graph with a fixed topology. Each agent is modelled by a second-order non-linear system with unknown non-linear dynamics and unknown non-linear control gains. Only a subset of the agents is given access to the desired trajectory information directly. A distributed adaptive consensus protocol driving all agents to track the desired trajectory is presented using the backstepping technique and approximation technique of Fourier series (FSs). The FS structure is taken not only for tracking the non-linear dynamics but also the unknown portion in the controller design procedure, which can avoid virtual controllers containing the uncertain terms. Stability analysis and parameter convergence of the proposed algorithm are conducted based on the Lyapunov theory and the algebraic graph theory. It is also demonstrated that arbitrary small tracking errors can be achieved by appropriately choosing design parameters. Though the proposed work is applicable for second-order non-linear systems containing unknown non-linear control gains, the proposed controller design can be easily extended to higher-order non-linear systems containing unknown non-linear control gains. Simulation results show the effectiveness of the proposed schemes.     

一种单位代价收益决策树剪枝算法

目前关于决策树剪枝优化方面的研究主要集中于预剪枝和后剪枝算法。然而,这些剪枝算法通常作用于传统的决策树分类算法,在代价敏感学习与剪枝优化算法相结合方面还没有较好的研究成果。基于经济学中的效益成本分析理论,提出代价收益矩阵及单位代价收益等相关概念,采用单位代价收益最大化原则对决策树叶节点的类标号进行分配,并通过与预剪枝策略相结合,设计一种新型的决策树剪枝算法。通过对生成的决策树进行单位代价收益剪枝,使其具有代价敏感性,能够很好地解决实际问题。实验结果表明,该算法能生成较小规模的决策树,且与REP、EBP算法相比具有较好的分类效果。