一类多包传输网络控制系统的H∞鲁棒控制

研究了一类不确定时延多包传输网络控制系统的最优H∞控制问题. 针对传感器时钟驱动、控制器和执行器事件驱动的多包传输网络控制系统, 考虑不大于一个采样周期的不确定时延和有限能量的外部扰动, 提出一种基于模型的反馈控制策略, 利用Lyapunov理论推导了H∞控制律存在的充分条件, 通过求解矩阵不等式约束的优化问题得到最优H∞控制律. 数值仿真表明了所用方法的有效性.     

Ka频段卫星通信上行链路自适应功率控制

为提高Ka频段（30GHz／20GHz）卫星通信系统上行链路功率控制的可靠性,提出一种上行链路自适应功率控制算法。该方法基于自回归滑动平均模型,能由测量到的下行链路降雨衰减值预测出上行链路的降雨衰减值,从而提高功率控制精度。仿真结果表明,该方法对降雨衰减具有较好的补偿效果。     

基于克里金空间插值的位置指纹数据库建立算法*

为解决室内定位系统中建立位置指纹数据库工作量庞大的问题,提出了一种融合信号衰减因素的普通克里金空间插值建库算法。该方法首先采用高斯滤波对有限预选参考点的信号强度采样数据进行预处理,并基于球状模型由参考点预处理数据拟合出空间变异函数,然后采用普通克里金插值法对其它位置的信号强度进行估值并生成相应的位置指纹,最后由有限实测数据生成大容量高分辨位置指纹数据库,并通过KNN_Filter算法和对数权重算法完成了定位仿真,验证了该建库方法的有效性。仿真实验结果表明,该算法在保证定位精度的前提下相比传统建库方法可降低40%左右的工作量,提高了室内位置指纹定位方法的工作效率。     

Output feedback control of linear fractional transformation systems subject to actuator saturation

In this paper, the control problem for a class of linear parameter varying (LPV) plant subject to actuator saturation is investigated. For the saturated LPV plant depending on the scheduling parameters in linear fractional transformation (LFT) fashion, a gain-scheduled output feedback controller in the LFT form is designed to guarantee the stability of the closed-loop LPV system and provide optimised disturbance/error attenuation performance. By using the congruent transformation, the synthesis condition is formulated as a convex optimisation problem in terms of a finite number of LMIs for which efficient optimisation techniques are available. The nonlinear inverted pendulum problem is employed to demonstrate the effectiveness of the proposed approach. Moreover, the comparison between our LPV saturated approach with an existing linear saturated method reveals the advantage of the LPV controller when handling nonlinear plants.     

Consensus and disturbance attenuation in multi‐agent chains with nonlinear control and time delays

In this paper, we investigate consensus and disturbance attenuation in a chain of mobile agents, which include non‐autonomous agents, semi‐autonomous agents and autonomous agents. In particular, the nonlinear dynamics of non‐autonomous agents is given and cannot be designed, while the dynamics of semi‐autonomous and autonomous agents can be partially and fully designed, respectively. To improve the robustness of multi‐agent chains against disturbances, we propose a nonlinear control framework for semi‐autonomous and autonomous agents such that they mimic the behavior of non‐autonomous agents for compatibility while also exploiting long‐range connections with distant agents. This framework ensures the existence of a unique consensus equilibrium, which is independent of the network size, connectivity topologies, control gains and information delays. Robustness of multi‐agent chains against disturbances is investigated by evaluating the frequency response at the nonlinear level. For infinitely long multi‐agent chains with recurrent patterns, we also derive a condition that ensures the disturbance attenuation but only requires the analysis of the linearized model. A case study is conducted for a connected vehicle system where numerical simulations are used to validate the analytical results. Copyright © 2016 John Wiley & Sons, Ltd.     

一类非线性系统的H∞鲁棒控制

考虑了在实际中具有工程应用背景的一类非线性不确定系统的H∞鲁棒控制问题.基 于Hamilton-Jacobi不等式,给出了这类非线性系统渐近稳定且L2增益有限的充分条件.在这个 条件下,得到了确保闭环系统满足H∞鲁棒扰动衰减性能准则的状态反馈控制器.     

Limitations of nonlinear discrete periodic control for disturbance attenuation and robust stabilization

This paper presents a performance analysis of nonlinear periodically time-varying discrete controllers acting upon a linear time-invariant discrete plant. Time-invariant controllers are distinguished from strictly periodically time-varying controllers. For a given nonlinear periodic controller, a time-invariant controller is constructed. Necessary and sufficient conditions are given under which the time-invariant controller gives strictly better control performance than the time-invariant controller from which it was obtained, for the attenuation of l_p exogenous disturbances and the robust stabilization of l_p unstructured perturbations, for all p[1,∞].     

桥梁施工安全事故流变-突变规律

结合桥梁施工事故的特点,通过对流变-突变理论的桥梁施工安全事故规律研究,绘制出桥梁施工安全事故流变规律曲线。建立了桥梁施工安全事故流变-突变数学模型,基于该数学模型采用数学软件MATLAB分析了事故致因与流变突变曲线的关系。对该数学模型进行假设性验证分析,得到起始安全度和衰减系数对事故时间的影响。通过支架结构的施工期变形的监测数据和某次支架坍塌事故实例验证流变-突变数学模型是合理的。     

Determination of Linear Attenuation Coefficients of Materials by Using Timing Method

Abstract

In this work, gamma-ray linear attenuation coefficients of aluminum (Al) and lead (Pb) materials were determined by using timing method. The used setup is different from the conventional ones. The goal of the presented setup is the fact that it is used the timing technique. The detection system is composed of a 3″ × 3″ NaI(Tl) inorganic scintillation detector and related equipment together with ¹³⁷Cs and ⁶⁰Co radioactive sources. Obtained results are in good agreement with each other.     

掺气水流声速的研究

采用一维双流体模型,利用小扰动原理研究了压力波在水气两相泡状流中的传播规律。针对水利工程中高速掺气水流的特点,对方程进行合理模化和封闭。详细分析了掺气浓度、压力、扰动频率、相间相互作用力对掺气水流中声波传播速度和衰减的影响。结果表明,适当的掺气浓度会使掺气水流的声速显著降低;压强的减小和相间传热的增强可使声速减小、衰减加快;虚拟质量力主要影响高频声速,并使声波衰减减慢。