Distributed Fault-Tolerant Containment Control for Nonlinear Multi-Agent Systems Under Directed Network Topology via Hierarchical Approach

This paper investigates the distributed fault-tolerant containment control(FTCC)problem of nonlinear multi-agent systems(MASs)under a directed network topology.The proposed control framework which is independent on the global information about the communication topology consists of two layers.Different from most existing distributed fault-tolerant control(FTC)protocols where the fault in one agent may propagate over network,the developed control method can eliminate the phenomenon of fault propagation.Based on the hierarchical control strategy,the FTCC problem with a directed graph can be simplified to the distributed containment control of the upper layer and the fault-tolerant tracking control of the lower layer.Finally,simulation results are given to demonstrate the effectiveness of the proposed control protocol.

Task-Oriented Topology System Synthesis of Reconfigurable Legged Mobile Lander Integrating Active and Passive Metamorphoses

To explore hostile extraterrestrial landforms and construct an engineering prototype,this paper presents the task-oriented topology system synthesis of reconfigurable legged mobile lander(ReLML)with three operation modes from adjusting,landing,to roving.Compared with our preceding works,the adjusting mode with three rotations(3R)provides a totally novel exploration approach to geometrically matching and securely arriving at complex terrains dangerous to visit currently;the landing mode is redefined by two rotations one translation(2R1T),identical with the tried-and-tested Apollo and Chang'E landers to enhance survivability via reasonable touchdown buffering motion;roving mode also utilizes 2R1T motion for good motion and force properties.The reconfigurable mechanism theory is first brought into synthesizing legged mobile lander integrating active and passive metamorphoses,composed of two types of metamorphic joints and metamorphic execution and transmission mechanisms.To reveal metamorphic principles with multiple finite motions,the finite screw theory is developed to present the procedure from unified mathematical representation,modes and source phase derivations,metamorphic joint and limb design,to final structure assembly.To identify the prototype topology,the 3D optimal selection matrix method is proposed considering three operation modes,five evaluation criteria,and two topological subsystems.Finally,simulation verifies the whole task implementation process to ensure the reasonability of design.

A high performance fault-tolerant approach based on simultaneous multithreading

To cope with the ever-increasing susceptibility to transient fault in modern processors,a scheme called Tri-modular Redundantly and Simultaneously Threaded processor with Recovery is proposed,which provides transient fault coverage and reconfiguration from partial permanent fault with high performance.Besides two redundant thread contexts,an arbitrator context is introduced to act as either arbitrator or ordinary thread,which can make better use of hardware resources.Its sphere of replication is reconfigurable and flexible in handling changing demands.The simulation with 11 SPEC2000 benchmarks shows that its performance outperforms SMT-Single by 21.5% on average,while maintaining flexibility and fault-tolerant capability.

Flexible path planning-based reconfiguration strategy for maximum capacity utilization of battery pack

Maximizing the utilization of lithium-ion battery capacity is an important means to alleviate the range anxiety of electric vehicles.Battery pack inconsistency is the main limiting factor for improving battery pack capacity utilization,and poses major safety hazards to energy storage systems.To solve this problem,a maximum capacity utilization scheme based on a path planning algorithm is proposed.Specifically,the reconfigurable topology proposed is highly flexible and fault-tolerant,enabling battery pack consistency through alternating cell discharge and reducing the increased risk of short circuits due to relay error.The Dijkstra algorithm is used to find the optimal energy path,which can effectively remove faulty cells and find the current path with the best consistency of the battery pack and the lowest relay loss.Finally,the effectiveness of the scheme is verified by hardware-in-the-loop experiments,and the experimental results show that the state-of-charge SOC consistency of the battery pack at the end of discharge is increased by 34.18%,the relay energy loss is reduced by 0.16%,and the fault unit is effectively isolated.

Decentralized fault-tolerant cooperative control of multiple UAVs with prescribed attitude synchronization tracking performance under directed communication topology

In this paper, a decentralized fault-tolerant cooperative control scheme is developed for multiple unmanned aerial vehicles(UAVs) in the presence of actuator faults and a directed communication network. To counteract in-flight actuator faults and enhance formation flight safety, neural networks(NNs) are used to approximate unknown nonlinear terms due to the inherent nonlinearities in UAV models and the actuator loss of control effectiveness faults. To further compensate for NN approximation errors and actuator bias faults, the disturbance observer(DO) technique is incorporated into the control scheme to increase the composite approximation capability.Moreover, the prediction errors, which represent the approximation qualities of the states induced by NNs and DOs to the measured states, are integrated into the developed fault-tolerant cooperative control scheme. Furthermore,prescribed performance functions are imposed on the attitude synchronization tracking errors, to guarantee the prescribed synchronization tracking performance. One of the key features of the proposed strategy is that unknown terms due to the inherent nonlinearities in UAVs and actuator faults are compensated for by the composite approximators constructed by NNs, DOs, and prediction errors. Another key feature is that the attitude synchronization tracking errors are strictly constrained within the prescribed bounds. Finally, simulation results are provided and have demonstrated the effectiveness of the proposed control scheme.

Topology Control Algorithm Using Fault-Tolerant 1-Spanner for Wireless Ad Hoc Networks

A fault-tolerant 1-spanner is used to preserve all the minimum energy paths after node failures to cope with fault-tolerant topology control problems in wireless ad hoc networks. A fault-tolerant 1-spanner is a graph such that the remaining graph after node failures will not only remain connected, but also have a stretch factor of one. The fault-tolerant 1-spanner is used in a localized and distributed topology control algorithm, named the k-Fault-Tolerant 1-Spanner （k-FT1S）, where each node constructs a minimum energy path tree for every local failed node set. This paper proves that the topology constructed by k-FT1S is a k-fault-tolerant 1-spanner that can tolerate up to k node failures, such that the remaining network after node failures preserves all the minimum energy paths of the remaining network gained from the initial network by removing the same failed nodes. Simulations show that the remaining network after removal of any k nodes still has the optimal energy efficiency and is competitive in terms of average logical degree, average physical degree, and average transmission radius.

Optimal Scheduling of Distribution Network Incorporating Topology Reconfiguration,Battery Energy System and Load Response

Distributed generation(DG)is becoming increasingly important due to the serious environmental pollution caused by conventional fossil-energy-based generation and the depletion of non-renewable energy.As the flexible resources in the active distribution network(ADN),battery energy system(BES)and responsive load(RL)are all able to assist renewable DG integration in day-ahead dispatch.In addition,the security and economic level can be significantly improved by adjusting network topology.Therefore,in this paper,a coordinated day-ahead scheduling method incorporating topology reconfiguration,BES optimization and load response is presented to minimize the total day-ahead operational costs in the ADN.Linearized current injection models are presented for renewable DG,RL and BES based on the linear power flow model,and an extensible linear switching operations calculation(ELSOC)method is proposed to address the network reconfiguration.Thus,a mixed integer linear programming(MILP)model is proposed for optimal coordinated operation of an ADN.The correctness and effectiveness of the proposed method are demonstrated by simulations on a modified test system.In addition,the combined scenario and Monte-Carlo method is used to handle the uncertainties of loads and DGs,and the results of different uncertainties can further verify the feasibility of the proposed model.

Reconfigurability evaluation method for input-constrained control systems

This paper proposes a quantitative reconfigurability evaluation method for control systems with actuator saturation and additive faults from the perspective of system stability.Placing the saturated feedback law in the convex hull of a group of auxiliary linear controls,the sufficient reconfigurability conditions for the system under additive faults are derived using invariant sets.These conditions are then expressed as linear matrix inequalities(LMIs)and applied to quantify the degree of reconfigurability for the fault system.The largest fault magnitude for which the system can be stabilized,the largest initial state domain from which all the trajectories are convergent,and the minimum final state domain to which the trajectories will converge are investigated.The effectiveness of the proposed method is illustrated through an application example.

可重构3-RRR并联机器人的“点对点”路径规划

通过拓扑重构,可以提高并联机器人的静刚度、故障修复等性能,但机器人重构之后能否到达任意指定的位姿且不经过奇异位形,尚无定论。为此,以可重构3-转动副转动副转动副(3-revolute-joint,revolute-joint,revolute-joint,3-RRR)并联机器人为研究对象,提出了一种能够实现“点对点”路径跟踪的规划算法。首先,建立了机构重构之前的反向运动学模型,据此确定了6组重构序列。接着,构建了一种“四步”规划算法,适用于任意自由度的可重构并联机器人的“点对点”路径跟踪,具有直观的几何解释,并且能够消除全部的奇异位形;通过算例验证了规划算法的有效性。然后,基于螺旋理论,计算出各组参量下的输入、输出和局部传递指标值,据此,确定了重构序列下的最优输入参量。最后,将“点对点”路径规划算法推广至连续路径规划的情形。

可重构3-RPR平面并联机构的静刚度研究

以3-RPR平面并联机构为研究对象,通过设计一种在驱动、被动和锁定3种状态之间相互切换的移动副和转动副锁定装置,实现机构的重构。对重构前、后机构的静刚度特性进行理论建模和软件仿真。通过锁定任意两个运动副的方式,实现机构的拓扑重构。根据动平台的运动状态对锁定方式进行分类,并建立机构的反向运动学模型。对机构的雅克比进行推导,并基于虚功原理,推导静刚度矩阵。最后,对重构前、后的机构进行静力学虚拟实验,对比分析实验数据。结果表明:拓扑重构可以提升平面并联机构的静刚度性能。特别地,动平台做定轴转动时,其静刚度的提升效果尤其明显。这为少自由度可重构并联机构的性能评价和参数优化提供了理论依据。

基于分层架构的退役电池可重构均衡控制研究

利用退役电池构建储能系统,充分利用其剩余价值,是解决大量退役电池再利用的重要途径。然而,经过多次充放电影响,退役电池不一致性问题较新电池更为突出。在此背景下,首先,针对退役电池储能系统提出了分层式可重构均衡拓扑。其次,基于该拓扑提出了分层式均衡控制策略。考虑组内部和组间两个层次的均衡控制,组内以SOC和端电压为均衡变量,通过重构实现电池单体状态均衡,组间以SOC为均衡变量,通过重构保证全电池簇均衡。同时考虑多种运行工况:静置过程中通过自均衡提高电池组的均衡效率和可用容量,放电过程中通过拓扑结构变换维持输出电压稳定,充电过程中考虑能量损耗和充电速度合理优化充电电流,缩短充电时间,减少温升,延长电池使用寿命。最后,在Matlab中验证了所提拓扑与均衡策略在不同工况下的有效性。

一种超宽电压增益双LLC谐振变换器及控制方法

为解决传统LLC谐振变换器在宽电压增益应用中所需开关频率范围过宽、总体效率较低等问题,文中提出一种多模式双LLC谐振变换器。该变换器基于半桥、全桥切换以及桥式、倍压整流切换的拓扑重构思路,以增益不同的4种模式实现较窄频率范围内的超宽输出电压,提高变换器效率的同时通过复用开关器件来降低成本。为了实现模式间的平滑过渡,针对所提变换器设计一种脉冲宽度频率调制控制方法,并根据模式切换特性进一步优化,提高模式切换速度。基于SiC开关器件,设计并搭建一台60~450 V输出电压、最大功率为900 W的实验样机,以验证所提拓扑及控制方法的可行性。

计及拓扑相似性的含分散式风电配网双层优化重构方法

高比例风电接入背景下,配网优化重构是缓解弃风、失负荷问题的一种有效手段。多对象优化重构作为非凸非线性优化问题,同时含大量离散变量求解难度较大,为此建立了基于拓扑相似性的含高比例分散式风电配网双层交互式优化重构模型。模型设计了支路复介数相似度评价指标,来衡量所有辐射状拓扑的相似度,再将相似网络进行聚类,形成了重构层的树状解空间。重构层以分段/联络开关状态为决策变量优化网络拓扑结构,并传输至调度层;调度层以分散式风电出力、储能运行状态、无功补偿装置功率及需求响应量为决策变量,进行配电网有功无功协同优化调度,以确定各对象最优运行状态并反馈到重构层,两层不断交互迭代得出最终策略。为适应该模型提出了一种剪枝和声搜索算法,其中和声库从树枝切换到枝内的过程,提高了重构层网络重构的求解效率。采用IEEE 33节点系统仿真测试,验证了所提方法在提升系统电压安全性、降低系统运行成本方面的优越性。

Reconfigurable fault-tolerant control for supersonic missiles with actuator failures under actuation redundancy

Aircraft undergoing actuator failures into under-actuation have been seldom studied in literature.Aiming at addressing actuator failures of Total Loss of Effectiveness(TLOE)as well as Partial Loss of Effectiveness(PLOE)resulting in different system actuations,reconfigurable FaultTolerant Control(FTC)is proposed for supersonic wingless missiles under actuation redundancy.The under-actuated system of TLOE failure patterns is solved by transformation to cascade systems through a’shape variable’.Meanwhile,actuator TLOE faults of different unknown failure patterns from proper actuation to under-actuation are accommodated by a reconfigurable adaptive law on a multiple-model basis.The backstepping technique with the Extended State Observer(ESO)method adopted as a basic strategy is applied to an established symmetric coupled missile system with actuator PLOE faults,modeling errors,and external disturbances.Additionally,the nonlinear saturation characteristics of actuators are settled by an auxiliary system with the Nussbaum function technique.The stability of the control system is analyzed and proven through Lyapunov theory.Numerical simulations are implemented in the presences of aerodynamic uncertainties,gust disturbance,and actuator failures.Results demonstrate the effectiveness of the proposed method with satisfactory tracking performance and actuator fault tolerance capacity.

Reconfiguring the Logical Topology With Performance Guarantees in WDM Networks

To improve the network performance after traffic demand changes, reconfiguring the logical topology is necessary. We present an ILP algorithm to find out the least lightpath changes needed with guaranteed network performance.

Actively Reconfigurable Valley Topological Edge and Corner States in Photonic Crystals Based on Phase Change Material Ge2Sb2Te5

The immunity of topological states against backscattering and structural defects provides them with a unique advantage in the exploration and design of high-precision low-loss optical devices.However,the operating bandwidth of the topological states in certain photonic structures is difficult to actively tune and flexibly reconfigure.In this study,we propose a valley topological photonic crystal(TPC)comprising two inverse honeycomb photonic crystals,consisting of hexagonal silicon and Ge2Sb2Te5(GST)rods.When GST transitions from the amorphous phase to the crystalline phase,the edge band of the TPC appears as a significant redshift and is inversed from a“∪”to an“∩”shape with topological phase transition,which enables active tuning of the operating bandwidth and propagation direction of topological edge states.Both the topological edge and corner states in a triangular structure constructed using TPCs can be simultaneously adjusted and reconfigured via GST phase transition,along with a change in the group number of corner states.Using the adjustability of topological edge states and electromagnetic coupling between two different topological bearded interfaces,we develop a multichannel optical router with a high tuning degree of freedom,where channels can be actively reconfigured and their on/off states can be freely switched.Our study provides a strategy for the active regulation of topological states and may be beneficial for the development of reconfigurable topological optical devices.

Fault-Tolerant Dynamical Consensus of Double-Integrator Multi-Agent Systems in the Presence of Asynchronous Self-Sensing Function Failures

Double-integrator multi-agent systems(MASs)might not achieve dynamical consensus,even if only partial agents suffer from self-sensing function failures(SSFFs).SSFFs might be asynchronous in real engineering application.The existing fault-tolerant dynamical consensus protocol suitable for synchronous SSFFs cannot be directly used to tackle fault-tolerant dynamical consensus of double-integrator MASs with partial agents subject to asynchronous SSFFs.Motivated by these facts,this paper explores a new fault-tolerant dynamical consensus protocol suitable for asynchronous SSFFs.First,multi-hop communication together with the idea of treating asynchronous SSFFs as multiple piecewise synchronous SSFFs is used for recovering the connectivity of network topology among all normal agents.Second,a fault-tolerant dynamical consensus protocol is designed for double-integrator MASs by utilizing the history information of an agent subject to SSFF for computing its own state information at the instants when its minimum-hop normal neighbor set changes.Then,it is theoretically proved that if the strategy of network topology connectivity recovery and the fault-tolerant dynamical consensus protocol with proper time-varying gains are used simultaneously,double-integrator MASs with all normal agents and all agents subject to SSFFs can reach dynamical consensus.Finally,comparison numerical simulations are given to illustrate the effectiveness of the theoretical results.

基于JSON自描述模型的配网拓扑重构技术

在中低压配电网中,配电自动化系统依靠线路拓扑和台区拓扑实施状态监控及故障处理,当前配电网网架结构愈加复杂且变更频繁,尤其是低压配电台区的现场拓扑实施困难,提出一种基于Json自描述模型的配网拓扑重构技术。基于Json格式实现配网终端标准化自描述模型,同时基于该模型提出终端设备注册机制和配网拓扑重构机制,实现中压线路拓扑及低压台区拓扑的自适应拓扑重构。基于动模仿真平台和现场测试,验证所提方法的有效性与实用性。

可重构网络中基于中心度与拓扑势排序的资源分配算法

可重构网络中的一个研究难点是虚拟资源的分配问题。首次将社会网络中心度和拓扑势研究引入到可重构网络虚拟资源分配问题中,在映射虚拟网络时考虑节点在网络中的位置重要性,提出了基于中心度和拓扑势的虚拟网映射算法。实验表明,所提出的新算法在提高资源分配效率,降低物理网络开销方面,与本领域以往算法相比,具有显著的进步。

基于基本树的网络拓扑放射性快速判断方法及配网重构

网络重构是配网运行及优化的重要功能之一,随着智能电网建设的进展,其重要性越发显现。基于随机优化技术(如粒子群方法等)的网络重构算法中,为保证重构解满足拓扑的放射性约束,往往采用图的遍历方法进行确定,当网络规模比较大时,遍历的计算量很大且繁琐。根据配网的结构特点,首先根据配网重构解所需满足放射性约束的必要条件,对配网进行化简,而得到相应的等效简化网络;然后提出基于基本树的拓扑放射性快速判断方法;进而把该快速拓扑判断方法应用于基于粒子群优化方法的配网重构中,以加快其计算速度。算例表明,所提拓扑快速判断方法相对于全网络遍历方法,在计算速度上有明显优势,且随着系统规模的增大,所提方法的优越性更明显。