A NOTE ON THE GENERAL STABILIZATION OF DISCRETE FEEDBACK CONTROL FOR NON-AUTONOMOUS HYBRID NEUTRAL STOCHASTIC SYSTEMS WITH A DELAY

Discrete feedback control was designed to stabilize an unstable hybrid neutral stochastic differential delay system(HNSDDS) under a highly nonlinear constraint in the H_∞ and exponential forms.Nevertheless,the existing work just adapted to autonomous cases,and the obtained results were mainly on exponential stabilization.In comparison with autonomous cases,non-autonomous systems are of great interest and represent an important challenge.Accordingly,discrete feedback control has here been adjusted with a time factor to stabilize an unstable non-autonomous HNSDDS,in which new Lyapunov-Krasovskii functionals and some novel technologies are adopted.It should be noted,in particular,that the stabilization can be achieved not only in the routine H_∞ and exponential forms,but also the polynomial form and even a general form.

Restoring force correction based on online discrete tangent stiffness estimation method for real-time hybrid simulation

In real-time hybrid simulation（RTHS）, it is difficult if not impossible to completely erase the error in restoring force due to actuator response delay using existing displacement-based compensation methods. This paper proposes a new force correction method based on online discrete tangent stiffness estimation（online DTSE） to provide accurate online estimation of the instantaneous stiffness of the physical substructure. Following the discrete curve parameter recognition theory, the online DTSE method estimates the instantaneous stiffness mainly through adaptively building a fuzzy segment with the latest measurements, constructing several strict bounding lines of the segment and calculating the slope of the strict bounding lines, which significantly improves the calculation efficiency and accuracy for the instantaneous stiffness estimation. The results of both computational simulation and real-time hybrid simulation show that：（1） the online DTSE method has high calculation efficiency, of which the relatively short computation time will not interrupt RTHS; and（2） the online DTSE method provides better estimation for the instantaneous stiffness, compared with other existing estimation methods. Due to the quick and accurate estimation of instantaneous stiffness, the online DTSE method therefore provides a promising technique to correct restoring forces in RTHS.

A hybrid model for numerical wave forecasting and its implementation-Ⅱ .The discrete part and implementation of the model

In the first part of the present paper we have explained why we manage to formulate another wave prediction model when so many of them, including the so-called third generation model, have already been in use. The wind-wave part of the proposed model has also been given. Now we proceed to discuss the swell part,the implementation of the model as a prediction method,mumerical experiments done with ideal wind fields and hindcasts made in the Bohai Sea,in the neighboring seas adjacent to China and in the Northwest Pacific.

Synchronization of stochastically hybrid coupled neural networks with coupling discrete and distributed time-varying delays

A general model of linearly stochastically coupled identical connected neural networks with hybrid coupling is proposed, which is composed of constant coupling, coupling discrete time-varying delay and coupling distributed timevarying delay. All the coupling terms are subjected to stochastic disturbances described in terms of Brownian motion, which reflects a more realistic dynamical behaviour of coupled systems in practice. Based on a simple adaptive feedback controller and stochastic stability theory, several sufficient criteria are presented to ensure the synchronization of linearly stochastically coupled complex networks with coupling mixed time-varying delays. Finally, numerical simulations illustrated by scale-free complex networks verify the effectiveness of the proposed controllers.

A Geometric Method for Generating Discrete Trace Transition System of a Polyhedral Invariant Hybrid Automaton

Supervisory control and fault diagnosis of hybrid systems need to have complete information about the discrete states transitions of the underling system. From this point of view, the hybrid system should be abstracted to a Discrete Trace Transition System (DTTS) and represented by a discrete mode transition graph. In this paper an effective method is proposed for generating discrete mode transition graph of a hybrid system. This method can be used for a general class of industrial hybrid plants which are defined by Polyhedral Invariant Hybrid Automata (PIHA). In these automata there are no resetting maps, while invariant sets are defined by linear inequalities. Therefore, based on the continuity property of the state trajectories in a PIHA, the problem is reduced to finding possible transitions between all two adjacent discrete modes. In the presented method, the possibility and the direction of such transitions are detected only by computing the angle between the vector field and the normal vector of the switching surfaces. Thus, unlike the most other reachability methods, there is no need to solve differential equations and to do mapping computations. In addition, the proposed method, with some modifications can be applied for extracting Stochastic or Timed Discrete Trace Transition Systems.

Arbitrary full-state hybrid projective synchronization for chaotic discrete-time systems via a scalar signal

In this paper we present a new projective synchronization scheme, where two chaotic （hyperchaotic） discrete-time systems synchronize for any arbitrary scaling matrix. Specifically, each drive system state synchronizes with a linear combination of response system states. The proposed observer-based approach presents some useful features： i） it enables exact synchronization to be achieved in finite time （i.e., dead-beat synchronization）; ii） it exploits a scalar synchronizing signal; iii） it can be applied to a wide class of discrete-time chaotic （hyperchaotic） systems; iv） it includes, as a particular case, most of the synchronization types defined so far. An example is reported, which shows in detail that exact synchronization is effectively achieved in finite time, using a scalar synchronizing signal only, for any arbitrary scaling matrix.

Discrete element modeling and verification of the simulation parameters for chopped hybrid Broussonetia papyrifera stems

In this study,the discrete element software EDEM was applied to establish a simulation model of non-uniform-sized particle units for Broussonetia papyrifera stalks,which aimed to address the low utilization rate of existing Broussonetia papyrifera harvesting machinery,the significant variation between the simulated model of Broussonetia papyrifera stalks and their actual appearance,as well as the absence of contact parameter calibration.Through a combination of the free-fall collision method,inclined plane sliding method,and inclined plane rolling method,numerical simulation was conducted to analyze the pattern of variations in contact parameters between Broussonetia papyrifera stalks and the steel material of the machinery.Accordingly,these parameters were calibrated.The results showed that the coefficient of restitution between Broussonetia papyrifera stalks and steel materials was 0.321,the static friction factor was 0.589,and the rolling friction factor was 0.078.With the parameters of contact between Broussonetia papyrifera stalks as variables and the experimentally measured pile angle as the objective of optimization,the steepest ascent experiment and the three-factor five-level rotation combination experiment were conducted.In this way,a second-order response model was constructed to analyze the relationship between the contact parameters and the pile angle.Through the optimization analysis of experimental data,it was determined that the coefficient of restitution between Broussonetia papyrifera stalks was 0.21,the static friction factor was 0.24,and the rolling friction factor was 0.03.Furthermore,the calibration results were validated through experimentation to show that the relative error between the obtained pile angle under the context of optimal parameter combination and the actual one was 4.11%.In addition,the relative error of mass flow rate in spiral transport was within a reasonable range,this study lays a foundation both theoretically and statistically for the simulation of contact parameters for Broussonetia papyrifera stalk harvesting processing,mechanical harvesting,and so on.

Power Quality Improvement Using ANN Controller For Hybrid Power Distribution Systems

In this work,an Artificial Neural Network(ANN)based technique is suggested for classifying the faults which occur in hybrid power distribution systems.Power,which is generated by the solar and wind energy-based hybrid system,is given to the grid at the Point of Common Coupling(PCC).A boost converter along with perturb and observe(P&O)algorithm is utilized in this system to obtain a constant link voltage.In contrast,the link voltage of the wind energy conversion system(WECS)is retained with the assistance of a Proportional Integral(PI)controller.The grid synchronization is tainted with the assis-tance of the d-q theory.For the analysis of faults like islanding,line-ground,and line-line fault,the ANN is utilized.The voltage signal is observed at the PCC,and the Discrete Wavelet Transform(DWT)is employed to obtain different features.Based on the collected features,the ANN classifies the faults in an effi-cient manner.The simulation is done in MATLAB and the results are also validated through the hardware implementation.Detailed fault analysis is carried out and the results are compared with the existing techniques.Finally,the Total harmonic distortion(THD)is lessened by 4.3%by using the proposed methodology.

Constructing exact solutions to discrete systems with the trial function method

Based on the homogenous balance method and the trial function method, several trial function methods composed of exponential functions are proposed and applied to nonlinear discrete systems. With the.help of symbolic computation system, the new exact solitary wave solutions to discrete nonlinear mKdV lattice equation, discrete nonlinear （2 ＋ 1） dimensional Toda lattice equation, Ablowitz-Ladik-lattice system are constructed.The method is of significance to seek exact solitary wave solutions to other nonlinear discrete systems.

混合白鲸优化算法求解柔性作业车间调度问题

针对柔性作业车间调度问题(flexible job-shop scheduling problem,FJSP),提出一种混合白鲸优化算法(hybrid beluga whale optimization,HBWO)对其求解,旨在最小最大化完工时间。采用既定策略改进标准白鲸优化算法(beluga whale optimization,BWO),加快其收敛速度;基于机器选择和工序排序问题设计双层编码方案,解决FJSP离散化问题;采用主动编码及种群初始化策略,提高求解质量;基于工序的开始和结束时间确定关键路径和关键块,注重各工序时间维度;引入贪心思想至基于关键路径的混合变邻域搜索策略中,加大勘测搜索空间及减少无效搜索;此外,引入遗传算子防止算法陷入局部最优;通过35个标准算例的仿真实验与分析,证明了算法在求解FJSP问题中具有有效性。

含不相关机的多目标混合流水车间调度

考虑不相关机和传送等因素的多阶段混合流水车间问题,以最小化最大完工时间和总能耗为优化目标建立整数规划模型。针对该问题,提出一种多目标离散灰狼优化算法来求解。设计基于机器分配码和速度选择码的编码方式和基于最短处理时间原则的解码方案;采用反向学习策略改进初始灰狼种群质量;将基于多点变异的自走模式和基于均匀两点交叉与多点交叉的跟随模式结合构成搜索模式以协调开发和搜索能力;引入精英保留策略确保优良个体不丢失。通过一系列的仿真实验验证了该算法的有效性。

基于粗-细网络模型分步训练的地震数据重建方法

由于地形等复杂条件的限制,叠前地震数据在空间上存在不完整或不规则分布的情况,导致数据出现缺失或混淆等现象。近年来,基于卷积神经网络的方法已经广泛应用于缺失地震数据重建工作。然而一步训练过程的网络模型不足以重建具有宽振幅范围的缺失地震数据,低振幅缺失部分的重建结果仍需改进。因此本文提出一种具有分步训练过程的粗-细网络模型。该模型由粗网络和细网络组成,分步恢复宽振幅范围内的缺失地震数据。在细网络中引入离散小波变换代替池化操作,其可逆性在上采样阶段有利于保留细节特征。模型采用混合损失函数重建缺失信号的真实细节。粗网络的初步恢复结果经过掩码操作处理后输入到细网络,细网络进一步精确恢复缺失部分的低振幅信号。实验结果表明,与残差网络(ResNet)、U型网络(U-Net)和多级小波卷积神经网络(MWCNN)的重建方法相比,本文方法在合成数据和真实数据上展现出更卓越的重建性能:在缺失75%的合成数据上,信噪比为18.818 5 dB;在缺失50%的真实数据上,信噪比为12.2551 dB。在消融研究中,本文模型重建的均方误差为1.689 3×10^(-4),信噪比为19.284 6 dB,峰值信噪比为43.743 5 dB,结构相似性为0.984 1,均优于其他三组对照实验。

A Stable FE-FD Method for Anisotropic Parabolic PDEs with Moving Interfaces

In this paper,a new finite element and finite difference(FE-FD)method has been developed for anisotropic parabolic interface problems with a known moving interface using Cartesian meshes.In the spatial discretization,the standard P,FE discretization is applied so that the part of the coefficient matrix is symmetric positive definite,while near the interface,the maximum principle preserving immersed interface discretization is applied.In the time discretization,a modified Crank-Nicolson discretization is employed so that the hybrid FE-FD is stable and second order accurate.Correction terms are needed when the interface crosses grid lines.The moving interface is represented by the zero level set of a Lipschitz continuous function.Numerical experiments presented in this paper confirm second orderconvergence.

离散mKdV Lattice和Hybrid Lattice的双曲函数型精确解(英文)

在双曲函数法和试探函数法的基础上,引入两个新的双曲试探函数,构造了离散mKd Vlattice和Hybrid Lattice的双曲函数型精确孤波解.该方法也可以用于其他非线性差分微分方程.

细粒度状态驱动的离散车间动态瓶颈识别方法

针对当前瓶颈识别方法难以动态、及时、准确地响应离散制造过程的问题,结合图式推演建模方法,提出事件-数据混合驱动的资源细粒度状态监测方法(EDH),以实时识别离散制造过程中的动态瓶颈。首先,通过制造物联技术和复杂事件处理技术获取并处理复杂多变的制造过程实时信息,通过信号渐变模型提高实时位置信息的准确性;在此基础上,对制造资源的状态数据进行细粒度聚类,提出改进的数据分析算法(IFGCM)提高聚类的准确性;最后,结合建立的状态时序流图式模型和动态瓶颈识别方法实时感知制造资源瓶颈。通过在某电梯零部件制造车间的实际应用,验证了其有效性。

融合粗糙数据推理的离散麻雀搜索算法求解HFSP问题

针对麻雀搜索算法(SSA)易陷入局部最优、无法求解离散优化问题等不足,提出了一种改进离散麻雀搜索算法(IDSSA)。抽象原始麻雀搜索算法的位置更新公式,针对个体的不同身份设计新的离散化启发式位置更新策略,并针对混合流水车间调度问题(HFSP)设计了编码与解码方式;引入粗糙数据推理理论,通过数学证明解释了引入理论的可行性与合理性,为算法提供理论支撑,提高可解释性;利用上近似的性质扩大搜索空间,提高种群多样性,避免算法早熟,结合划分及粗糙数据推理提出3种策略,促进种群间信息共享,调节种群的开发能力与探索能力,降低算法陷入局部最优的概率;使用改进离散麻雀搜索算法求解混合流水车间调度问题,对3个小规模实例与10个Liao经典测试集进行仿真实验,验证了改进离散麻雀搜索算法求解混合流水车间调度问题的可行性,通过与遗传算法、差分进化算法等经典算法的对比实验,证明了所提算法的优越性与改进策略的有效性。

露天矿场无人驾驶自卸车路径规划方法研究

针对矿用自卸车在露天矿场环境下的路径左行要求以及长距离运输路径的平滑效率问题,提出了基于Clothoid曲线拓展的左行混合A*算法和离散点对角向量模最小化平滑算法相结合的路径规划方法。首先,在混合A*算法节点拓展搜索过程中,采用Clothoid曲线代替传统圆弧进行拓展,以保证混合A*搜索路径的曲率连续性和曲率变化率限制要求。然后,利用左行规则改进混合A*算法累加代价和启发代价,在累加代价中加入左转代价和碰撞吸引代价保证路径向左和沿地图边界左侧进行规划,在启发代价中根据拓展方向与地图边界最近点的左右位置关系调整拓展代价得到利于左行的启发代价图,以生成左行全局粗略路径。最后,结合二次规划技术,以离散点对角向量模最小化为目标函数,坐标轴方向移动量为约束,构建平滑优化模型,对全局路径进行平滑,同时为防止平滑过程中曲率超限超出车辆转向响应能力,利用大曲率点可行域隧道缩减技术,限制大曲率点平滑可移动量。试验结果表明:所提方法可以生成适应矿区左行规则的沿地图左侧边界行驶的全局路径;启发代价的改进有效地减少了混合A*算法拓展的节点数量,有利于更好实现左行;离散点路径平滑方法有效提高了全局路径的平滑度,利于车辆控制跟踪;Clothoid曲线拓展与可行域隧道缩减技术可有效应对装载、卸载等大曲率路径,不存在曲率超限情况;对比不同长度路径规划耗时数据,路径平滑算法有效降低了路径规划的总耗时,4 km路径平滑耗时只需76 ms;左行规划的实现和总耗时的减少提高了路径对于矿区场景的适应性。

A Hybrid Local/Nonlocal Continuum Mechanics Modeling and Simulation of Fracture in Brittle Materials

Classical continuum mechanics which leads to a local continuum model,encounters challenges when the discontinuity appears,while peridynamics that falls into the category of nonlocal continuum mechanics suffers from a high computational cost.A hybrid model coupling classical continuum mechanics with peridynamics can avoid both disadvantages.This paper describes the hybrid model and its adaptive coupling approach which dynamically updates the coupling domains according to crack propagations for brittle materials.Then this hybrid local/nonlocal continuum model is applied to fracture simulation.Some numerical examples like a plate with a hole,Brazilian disk,notched plate and beam,are performed for verification and validation.In addition,a peridynamic software is introduced,which was recently developed for the simulation of the hybrid local/nonlocal continuum model.

Multiscale Hybrid-Mixed Finite Element Method for Flow Simulation in Fractured Porous Media

The multiscale hybrid-mixed(MHM)method is applied to the numerical approximation of two-dimensional matrix fluid flow in porous media with fractures.The two-dimensional fluid flow in the reservoir and the one-dimensional flow in the discrete fractures are approximated using mixed finite elements.The coupling of the two-dimensional matrix flow with the one-dimensional fracture flow is enforced using the pressure of the one-dimensional flow as a Lagrange multiplier to express the conservation of fluid transfer between the fracture flow and the divergence of the one-dimensional fracture flux.A zero-dimensional pressure(point element)is used to express conservation of mass where fractures intersect.The issuing simulation is then reduced using the MHM method leading to accurate results with a very reduced number of global equations.A general system was developed where fracture geometries and conductivities are specified in an input file and meshes are generated using the public domain mesh generator GMsh.Several test cases illustrate the effectiveness of the proposed approach by comparing the multiscale results with direct simulations.

Hybrid Level of Detail Algorithm for Real-Time Rendering of Large-Scale Terrain

Hybrid level of detail （LOD） （HLOD） algorithm based on discrete LOD and continuous LOD is presented for real-time rendering of large-scale terrains. There are n HLOD models created off-line, which form a pyramid with n layers. Each of these models contains countless versions of the model at various levels of detail. When rendering, the corresponding models in some layer will be chosen. As the viewer＇s moves, either the continuous LOD algorithm will be applied to the selected models, or the visible models in another layer will be selected. An experiment on a triangular irregular network（TIN） terrain model was performed respectively using discrete LOD, continuous LOD and HLOD. The experimental results show that the HLOD algorithm exceeds the other two kinds of LOD in frame rate without reduction of terrain＇s fidelity.