A regular scalable fault tolerant interconnection network for distributed processing

Bounded degree networks like deBruijn graphs or wrapped butterfly networks are very important from VLSI implementation point of view as well as for applications where the computing nodes in the interconnection networks can have only a fixed number of I/O ports. One basic drawback of these networks is that they cannot provide a desired level of fault tolerance because of the bounded degree of the nodes. On the other hand, networks like hypercube (where degree of a node grows with the size of a network) can provide the desired fault tolerance but the design of a node becomes problematic for large networks. In their attempt to combine the best of the both worlds, authors in [IEEE Transactions on Parallel and Distributed Systems 4(9) (1993) 962] proposed hyper-deBruijn (HD) networks that have many additional features of logarithmic diameter, partitionability, embedding, etc. But, HD networks are not regular, are not optimally fault tolerant and the optimal routing is relatively complex. Our purpose in the present paper is to extend the concepts used in the above-mentioned reference to propose a new family of scalable network graphs that retain all the good features of HD networks and at the same time are regular and maximally fault tolerant; the optimal point to point routing algorithm is significantly simpler than that of the HD networks. We have developed some new interesting results on wrapped butterfly networks in the process.     

Design and analysis of a fault tolerant hybrid mobile scheme

Mobile computing systems provide users with access to information regardless of their geographical location. In these systems, Mobile Support Stations (MSSs) play the role of providing reliable and uninterrupted communication and computing facilities to mobile hosts. The failure of a MSS can cause interruption of services provided by the mobile system. Two basic schemes for tolerating the failure of MSSs exist in the literature. The first scheme is based on the principle of checkpointing used in distributed systems. The second scheme is based on state information replication of mobile hosts in a number of secondary support stations. Depending on the replication scheme used, the second approach is further classified as a pessimistic or an optimistic technique. In this paper, we propose a hybrid scheme which combines the pessimistic and the optimistic replication schemes. In the proposed scheme, an attempt is made to strike a balance between the long delay caused by the pessimistic and the high memory requirements of the optimistic schemes. In order to find the best ratio between the number of pessimistic to the number of optimistic secondary stations in the proposed scheme, we used fuzzy logic. We also used simulation to compare the performance of the proposed scheme with those of the optimistic and the pessimistic schemes. Simulation results showed that the proposed scheme performs better than either schemes in terms of delay and memory requirements.     

Heavy-traffic analysis of mean response time under Shortest Remaining Processing Time

Shortest Remaining Processing time (SRPT) has long been known to optimize the queue length distribution and the mean response time (a.k.a. flow time, sojourn time). As such, it has been the focus of a wide body of analysis. However, results about the heavy-traffic behavior of SRPT have only recently started to emerge. In this work, we characterize the growth rate of the mean response time under SRPT in the M/GI/1 system under general job size distributions. Our results illustrate the relationship between the job size tail and the heavy traffic growth rate of mean response time. Further, we show that the heavy traffic growth rate can be used to provide an accurate approximation for mean response time outside of heavy traffic regime.     

Scalable network file systems with load balancing and fault tolerance for web services

Because of the rapid growth of the World Wide Web and the popularization of smart phones, tablets and personal computers, the number of web service users is increasing rapidly. As a result, large web services require additional disk space, and the required disk space increases with the number of web service users. Therefore, it is important to design and implement a powerful network file system for large web service providers. In this paper, we present three design issues for scalable network file systems. We use a variable number of objects within a bucket to decrease internal fragmentation in small files. We also propose a free space and access load-balancing mechanism to balance overall loading on the bucket servers. Finally, we propose a mechanism for caching frequently accessed data to lower the total disk I/O. These proposed mechanisms can effectively improve scalable network file system performance for large web services.     

一类时延网络控制系统的骱容错保成本控制

针对具有时延和参数不确定性的网络控制系统的研究。考虑系统的时延小于一个采样周期,传感器是时钟驱动,控制器和执行器是事件驱动。当执行器发生故障时,研究网络控制系统的Hoo容错保成本控制。依据所描述情况建立系统模型,基于Lyapunov稳定性理论、容错控制理论和线性矩阵不等式（LMIs）处理方法,推导出网络控制系统是渐近稳定的,并且得出系统的Hoo容错保成本控制的充分条件和系统的保成本上界。实例仿真证明结论的有效性。     

Model-based diagnosis and fault tolerant control for ensuring torque functional safety of pedal-by-wire systems

This paper presents a model based approach for defining automotive functional safety requirements and provides a solution to ensure functional safety through model-based diagnosis and fault tolerant control. This model-based approach is consistent with ISO 26262 – functional safety standard. In particular, this paper presents the necessary steps for defining and implementing functional safety requirements, including item and function definition, Hazard Analysis and Risk Assessment, as well as the design of a model-based diagnostic and fault tolerant control (FTC) system that can lead to a systematic solution to automotive functional safety problems. The methodology proposed in this paper is applied to the problem of torque functional safety of pedal-by-wire systems.     

Fault tolerant control for networked control systems with packet loss and time delay

In this paper, a fault tolerant control with the consideration of actuator fault for a networked control system (NCS) with packet loss is addressed. The NCS with data packet loss can be described as a switched system model. Packet loss dependent Lyapunov function is used and a fault tolerant controller is proposed respectively for arbitrary packet loss process and Markovian packet loss process. Considering a controlled plant with external energy-bounded disturbance, a robust H _∞ fault tolerant controller is designed for the NCS. These results are also expanded to the NCS with packet loss and networked-induced delay. Numerical examples are given to illustrate the effectiveness of the proposed design method.     

Effect of fault tolerance and communication delay on response time in a multiprocessor system with a bus topology

The effect of interprocessor communication and fault tolerance on the response time of N processors (nodes) interconnected through a bus type communication medium is discussed. Deterministic as well as probabilistic approaches are considered. Four correction methods to handle the unprocessed data by the faulty processor(s) are studied and compared. It is found that the effect of interprocessor communication and fault tolerance on the response time for communication-extensive programs (I/O bound) is more than that for computation-extensive programs (CPU bound). It is also found that the effect of fault tolerance on the response time is significant, and cannot be ignored when evaluating the performance of multiprocessor systems. We have shown that the work presented in this paper for a bus topology can be generalized and readily adopted by other multiprocessor network topologies.     

Sliding mode for detection and accommodation of computation time delay fault

Computation time delay in digital control systems reduces its robustness as well as degrades its performance. In this paper, the computation time delay is assumed to be constant and smaller than the sampling time and is treated as a fault to be detected, using an appropriate controller to minimize its effects. Thus, a discrete-time sliding mode control that improves the systems’ performance when a computation time delay fault is found is proposed herein. A robust sliding mode observer-based is used to generate the residuals. Using the accumulated residual functions, a new scheme for fault detection and for controller adaptation is proposed. The technique is used to control a Rotary Motion Inverted Pendulum System to illustrate the design procedures and the effectiveness of the method.     

毗邻建筑非平稳随机地震响应LQG控制问题的闭合解

研究了毗邻建筑在非平稳随机地震激励下的LQG控制问题,首先建立了主动液压传动装置连接的毗邻建筑在地震激励下的动力方程,然后采用复模态分析得到系统的动力特性,包括模态频率和模态阻尼比;通过引入成形滤波器来描述地震功率谱密度函数,最终利用虚拟激励法和留数定理推导出LQC;控制问题的闭合解,算例结果表明：只要适当选择LQG控制器参数,LQG控制可有效地减小两栋建筑的地震响应,并且其响应达到稳态的速度比无控时要快得多。     

一类交通网络模型下路段行程时间的解析解

针对一类路段输入流量具有时变特性的路段行程时间进行讨论．所讨论的路段行程时间与路段流量具有指数函数关系．因无法直接求出这类方程关于路段行程时间的解析解，故对指数函数按级数进行展开，得出了路段行程时间以及输出流量随输入流量变化的关系．最后用数值试验对所得结论进行了仿真，结论令人满意．     

Sensor fault diagnosis for a class of time delay uncertain nonlinear systems using neural network

In this paper, a sliding mode observer scheme of sensor fault diagnosis is proposed for a class of time delay nonlinear systems with input uncertainty based on neural network. The sensor fault and the system input uncertainty are assumed to be unknown but bounded. The radial basis function (RBF) neural network is used to approximate the sensor fault. Based on the output of the RBF neural network, the sliding mode observer is presented. Using the Lyapunov method, a criterion for stability is given in terms of matrix inequality. Finally, an example is given for illustrating the availability of the fault diagnosis based on the proposed sliding mode observer.     

Modeling and response time analysis of the Level 2 system for a continuous steel casting process

When a process control system (PCS) is designed or improved, it is very desirable to check in advance whether it responds within time constraints because correcting a system after implementation requires time and effort. A PCS processes bursty messages from programmable logic controllers. The response time to each individual message is different from one another, so it must be evaluated. This paper presents a modeling method to set up an analytic model of a PCS for the response time analysis using Colored Generalized Stochastic Petri Net. The model is analyzed using transient queueing analysis and simulation. A test bed system is built that is identical to a part of a PCS in a continuous casting plant, and is used to measure response times. The approach is validated by showing that simulations using the analytic model match the measured values well. The approach is applied to the whole PCS in the same plant to estimate the response times, which are presented and discussed in the paper.     

基于混沌理论的动态系统故障检测研究与发展

混沌理论是一种用于描述确定非线性系统内在随机性的一种数学方法。作为确定论和概率论的桥梁，混沌理论具有对初始条件敏感、短期可预测等特点，近年来在各工程领域得到应用。基于混沌理论的故障检测是混沌理论应用的一个重要方面。本文在简单介绍混沌原理的基础上，分类介绍了基于混沌理论的各种故障检测方法及其研究现状，探讨了这一领域中有待进一步研究的若干问题。     

多处理机容错系统中实时任务的轮转式调度算法

基于多处理机实时系统的“主从备份技术”,文章提出一种采用轮转式调度策略实现容错调度的算法。模拟结果表明,该算法可达到较均衡的任务分布,提高了CPU利用率。