基于离散小波变换的滑移隔震结构非平稳随机响应计算

将地震地面运动模拟成非平稳随机过程,基于离散小波变换得到地面运动离散小波系数的统计值,并以此作为输入,使用等价线性方法获得了滑移隔震结构在非平稳地震作用下的均方滑动位移和速度反应。通过计算实例与Monte-Carlo法的计算结果进行对比,验证了本文方法的正确性。最后,给出了这种结构的最大滑动位移响应随滑移面摩擦系数的变化曲线,可供设计时参考。     

非线性离散动态系统优化与参数估计集成的多模型方法

在非线性系统分时段线性化多模型基础上,给出了非线性离散动态系统优化与参数估计集成的多模型方法,并论证了算法的最优性和收敛性.在存在模型-实际差异的情况下,从分时段线性化多模型出发通过迭代运算可得到实际非线性离散动态系统的真实最优解.仿真结果表明了算法的有效性和实用性.     

Noise-Tolerant ZNN-Based Data-Driven Iterative Learning Control for Discrete Nonaffine Nonlinear MIMO Repetitive Systems

Aiming at the tracking problem of a class of discrete nonaffine nonlinear multi-input multi-output (MIMO) repetitive systems subjected to separable and nonseparable disturbances, a novel data-driven iterative learning control (ILC) scheme based on the zeroing neural networks (ZNNs) is proposed. First, the equivalent dynamic linearization data model is obtained by means of dynamic linearization technology, which exists theoretically in the iteration domain. Then, the iterative extended state observer (IESO) is developed to estimate the disturbance and the coupling between systems, and the decoupled dynamic linearization model is obtained for the purpose of controller synthesis. To solve the zero-seeking tracking problem with inherent tolerance of noise, an ILC based on noise-tolerant modified ZNN is proposed. The strict assumptions imposed on the initialization conditions of each iteration in the existing ILC methods can be absolutely removed with our method. In addition, theoretical analysis indicates that the modified ZNN can converge to the exact solution of the zero-seeking tracking problem. Finally, a generalized example and an application-oriented example are presented to verify the effectiveness and superiority of the proposed process.

     

State-Based Opacity Verification of Networked Discrete Event Systems Using Labeled Petri Nets

The opaque property plays an important role in the operation of a security-critical system, implying that pre-defined secret information of the system is not able to be inferred through partially observing its behavior. This paper addresses the verification of current-state, initial-state, infinite-step, and K-step opacity of networked discrete event systems modeled by labeled Petri nets, where communication losses and delays are considered. Based on the symbolic technique for the representation of states in Petri nets, an observer and an estimator are designed for the verification of current-state and initial-state opacity, respectively. Then, we propose a structure called an I-observer that is combined with secret states to verify whether a networked discrete event system is infinite-step opaque or K-step opaque. Due to the utilization of symbolic approaches for the state-based opacity verification, the computation of the reachability graphs of labeled Petri nets is avoided, which dramatically reduces the computational overheads stemming from networked discrete event systems.

     

水泥稳定钢渣混合料离散元模型参数反演及断裂损伤研究

钢渣骨料的多孔结构对沥青混合料低温抗裂性能影响的宏细观机制尚不掌握, 不利于钢渣骨料沥青路面长期性能的有效保持。针对此不足, 基于室内低温弯曲试验, 构建了可表征钢渣骨料多孔结构的沥青混合料小梁试样精细化离散元模型, 进而开展了不同的钢渣孔隙率和开口孔隙沥青填充度下的虚拟低温弯曲试验, 量化分析了钢渣多孔结构对试样整体强度和细观断裂性能的影响规律及机制。试验研究结果表明: 多孔钢渣骨料仅可替代粒径大于2.36 mm的粗骨料, 控制钢渣加热温度并延长湿拌时间可确保沥青胶浆充分填充钢渣骨料表面孔隙; 离散元数值模拟结果表明钢渣骨料表面开口孔隙附近出现应力集中, 裂缝贯通钢渣开口孔隙; 钢渣骨料表面孔隙率越高, 则峰值应力越低, 裂缝越易从开口孔隙处发育; 峰值应力随钢渣骨料表面开口孔隙沥青胶浆填充度的降低而显著降低; 钢渣骨料表面孔隙对沥青胶浆的吸收作用会显著影响裂缝萌生路径及混合料的低温抗裂性能, 裂缝易在钢渣孔洞附近萌生, 且开口孔隙无沥青填充时此裂缝扩展特征更明显; 钢渣骨料表面孔隙可增强沥青-钢渣界面的黏结性能, 但开口孔隙过大会导致应力集中且易萌生裂缝。在实际工程中建议控制大孔隙钢渣骨料含量, 并确保沥青砂浆充分填充钢渣骨料表面孔隙, 以提高其低温抗裂性能。

     

SCR-DDC双闭环系统数字仿真

在进行计算机控制系统的设计时,如若系统中有不同的采样周期,那么将很难利用离散系统稳定性判别方法——Z平面上极点的分布来判断系统的稳定性,此时利用数字仿真来研究其稳定性是一种重要的手段。本文主要是以实际的SCR-DDC转速、电流双闭环系统为对象,分析其系统模型,选择数字仿真的方法,最后给出仿真系统的运行结果。     

一种离散时间直接自适应控制算法

应用给出的离散时间直接自适应控制算法改进了离散简单自适应控制的一些缺陷,能够在计算控制律不违反因果律的条件下,使被控对象的输出直接跟踪理想参考模型输出.应用Lyapunov函数和正实引理证明了算法的收敛性,并通过仿真研究说明了算法的有效性和可行性.     

随机离散人口系统建模及稳定性分析

建立了随机人口系统生育、死亡、迁移过程的差分方程模型,对随机离散人口系统按龄均值和二阶中心矩的Lyapunov稳定性进行了研究,给出了根据我国1987年1％人口抽查资料进行仿真的结果.     

间接自适应极点配置控制算法的跟踪能力研究

为了研究现有间接自适应极点配置控制算法的跟踪能力,提出了一般形式的间接自适应极点配置控制算法.分析了这种算法用于已知和未知系统时的跟踪能力,并分别给出了渐近跟踪参考输出的充要条件.利用上述结果,可以对现有间接算法的跟踪能力进行逐一研究.研究表明,现有间接自适应极点配置控制算法的跟踪能力是有限的,它们至多能实现对一类参考输出的渐近跟踪.     

基于SAP5P程序的刚架结构离散变量优化系统

利用优化准则法,结合机械设计的特点,编制了以SAP5P程序为基础的大型复杂刚架结构离散变量优化程序SOP,并对一刚架结构模型进行了优化分析。