基于自适应模糊滑模控制的机器人轨迹跟踪算法

针对控制参数的不确定性以及存在未知外部扰动情况下移动机器人的轨迹跟踪问题,提出一种基于光滑非线性饱和函数的自适应模糊滑模轨迹跟踪控制算法。通过建立不确定非线性移动机器人运动控制模型,利用自适应模糊逻辑系统构建自适应模糊滑模控制器。为了增强轨迹跟踪控制算法对随机不确定外部扰动适应能力的同时削弱滑模控制算法中的输入抖振现象,利用有界输入有界输出(BIBO)稳定的方法,通过带有自适应调节算法的模糊系统对滑模控制律中非线性函数项进行自适应逼近,并设计了模糊系统中可调参数的自适应控制律,保证了控制系统的稳定与收敛。实验结果表明,所设计的控制器对系统参数不确定性和外界扰动均具有较强的轨迹跟踪性能和鲁棒性。与传统的滑模控制算法相比,该算法不仅能有效减小输入抖振而且轨迹跟踪控制精度提高了18.89%。     

Levy噪声中EMD降噪的随机共振研究

经验模态分解(empirical mode decomposition,EMD)降低噪声的同时也削弱信号能量,并会产生虚假信号,导致信号检测存在缺陷,针对这一问题,提出Levy噪声环境下经验模态分解随机共振检测方法。通过将含噪信号进行EMD分解,对分解后信号进行叠加取平均二次采样等处理方法,使其满足随机共振要求,利用自适应算法优化系统参数,进而使处理后信号能够在双稳系统中产生随机共振,达到精确检测的目的。理论分析及实验证明在Levy噪声下,此方法能实现同一特征指数下单频信号与多频信号检测,实验表明在单频信号信噪比为-28 dB情况下能有14 dB的提高,特征指数为1.8下多频信号5 Hz频谱幅值从311.8增加到724,10 Hz频谱幅值由138.9增加到143.2。此方法对在复杂噪声环境中降低剩余噪声能量同时,提高信号能量,减少虚假信号,相对于仅仅进行EMD分解无法判断信号成分,能更好的达到检测效果。     

Optimal planning of distributed generation from the DisCo and the DGO viewpoints considering the uncertainties in future demand and electricity price

Since electricity demand is increasing continuously, it is necessary to invest in expansion of distribution network capacity. From the asset management point of view, it is necessary to encourage the private sector to invest in distribution network. To do this, distribution network managers must provide important opportunities for private sector to profit from their investments. One of the options for private sector is to invest on distributed generations (DGs). In this regard, distribution company (DisCo) must sign power purchase agreement (PPA) with DG owners (DGOs). So, optimal siting, sizing and PPA rates from economic point of view are important challenges which are considered as the main contribution of this paper. The proposed methodology of this paper applies load and price uncertainties into the planning problem. The proposed scheme involves using non-dominated sorting genetic algorithms II (NSGA II), since it attains non-dominated solutions in which DisCo and the DGO can put their personal preferences into practice. To evaluate the effectiveness of the suggested method, the computer simulations are done on a 33-bus distribution network and the results are discussed.     

航空器轨迹冲突探测方法的改进与仿真

针对传统轨迹冲突探测方法忽略航空器外形轮廓会造成空域浪费的问题,对冲突探测几何近似法进行改进.考虑航空器外形尺寸对轨迹冲突探测结果的影响,提出扩展保护区的概念,给出相应几何近似法的计算步骤,并通过仿真实验对所提出的几何近似法的有效性进行验证.仿真实验表明:所提出的几何近似法的结果能反映轨迹冲突概率的变化趋势,更接近冲突概率的真实情况.     

AN INEXACT TWO-STAGE STOCHASTIC PROGRAMMING MODEL FOR WATER RESOURCES MANAGEMENT UNDER UNCERTAINTY

An inexact two-stage stochastic programming (ITSP) model is proposed for water resources management under uncertainty. The model is a hybrid of inexact optimization and two-stage stochastic programming. It can reflect not only uncertainties expressed as probability distributions but also those being available as intervals. The solution meth od for ITSP is computationally effective, which makes it applicable to practical problems. The ITSP is applied to a hypothetical case study of water resources system operation. The results indicate that reasonable solutions have been obtained. They are further analyzed and interpreted for generating decision alternatives and identifying significant factors that affect the system's performance. The information obtained through these post-optimality analyses can provide useful decision support for water managers.     

A systems theoretic approach to second moment modelling of probabilistic engineering systems∗

A new approach to modelling probabilistic and stochastic engineering systems using graph theory is outlined. This approach emphasizes the introduction of probabilistic and stochastic concepts at the very beginning of the model building process. This is in marked contrast to past tendencies to add probabilistic concepts to the end of an otherwise deterministic model building process. The development of topological models founded on oriented probabilistic measurements is given. which leads to the identification of some useful statistical properties of the’ random interconnection equations’. The development of probabilistic component models is given, where a component can be characterized independently of other components. Methods for automatically building the second moment representation of the Mixed Nodal Tableau are discussed. The application of the above theory to the probabilistic analysis of a pipe network problem is briefly described.     

基于隐式梯度理论的混凝土细观随机断裂模型

根据多尺度力学的基本思想,将隐式梯度非局部化理论与串并联弹簧模型理论相结合,建立了混凝土细观随机断裂模型。通过引入微弹簧断裂应变为服从对数正态分布的随机变量,验证了混凝土材料微观断裂的不可控制性;通过引入非局部化比例,解决了传统串并联弹簧模型的层数敏感性问题。对建立的模型从特征参数、局部应变与损伤的演化发展和层数敏感性几个方面进行了分析。最后,将模型结果与试验结果进行了对比,验证了该模型的正确性。研究结果表明:该模型计算效率高,且更加有利于在计算软件中实现。     

结构可靠度分析中作用的随机过程组合方法

结构可靠度分析应以直接描述作用随机变化的概率模型和随机过程组合方法为基础,但在目前的作用概率组合中,对由频遇值、准永久值参与组合的可变作用实际采用的是以最大值表达的随机变量组合方法,这将导致不合理的分析结果。依据可变作用的等时段平稳二项矩形波过程概率模型,确定与频遇值、准永久值超越比率对应的时段样本,提出可变作用频遇序位值和准永久序位值的概念,据此建立以作用序位值表达的随机过程组合方法和可靠度分析模型。该方法以随机过程理论为基础,具有明确、合理的工程概念,可准确反映作用组合的基本思想,得到合理的可靠度分析结果,从根本上克服了目前随机变量组合方法的缺陷。     

FRP加固局部损伤钢压杆的稳定分析

钢结构中存在大量的轴心受力构件,作为承受永久竖向荷载的主要构件,往往是结构加固的重点.采用能量方法,分析各种杆端约束条件下,纤维增强复合材料（FRP）加固局部损伤的轴心受压钢构件在弹性失稳时的弹性屈曲临界力,并建立普遍适用的近似欧拉公式.利用ANSYS通用有限元分析软件分析FRP的厚度对损伤空心圆管临界力的影响并与该公式解析解进行对比.计算结果表明,该公式计算结果可靠,采用纤维增强复合材料加固修复局部损伤的钢结构可以有效恢复其刚度和稳定性.