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Fault Tolerant Multiphase Electrical Drives: The Impact of Design

Fault Tolerant Multiphase Electrical Drives: The Impact of Design

Received: 28 June 2007 / Accepted: 22 February 2008 Published online (Inserted Later) – c  EDP Sciences Abstract. This paper deals with fault tolerant multiphase electrical drives. The quality of the torque of vector-controlled Permanent Magnet (PM) Synchronous Machine supplied by a multi-leg Voltage Source Inverter (VSI) is examined in normal operation and when one or two phases are open-circuited. It is then deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation. Experimental results confirm the predicted characteristics.
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Fault-Tolerant Consensus in Unknown and Anonymous Networks

Fault-Tolerant Consensus in Unknown and Anonymous Networks

eventually knows forever that it is the leader. In [9], fault- tolerant and obstruction-free 1 consensus is solved if registers are available. There has also been some research on systems where IDs are known but the number of processes is not. In [8], it is assumed that processes may crash, but furthermore that it is possible to detect the participants initially. In [12], a leader election algorithm for a system where infinitely many processes may join the system is presented if the number of processes simultaneously up is bounded.

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DEPENDABILITY MODELING AND EVALUATION OF SOFTWARE-FAULT TOLERANT SYSTEMS

DEPENDABILITY MODELING AND EVALUATION OF SOFTWARE-FAULT TOLERANT SYSTEMS

The main outcome of the evaluation concern the derivation of analytical results enabling (i) to identify the conditions of improvement, when compared to a non fault-tolerant software, that could result from the use of RB (the acceptance test has to be more reliable than the alternates) and NVP (related faults among the versions and the decider have to be minimized) and (ii) to reveal the most critical types of related faults. In particular, for safety, the related faults between the variants have a significant impact for NVP, whereas only related faults between the alternates and the acceptance test, have to be considered for RB.
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Fault-tolerant distributed computing scheme based on erasure codes

Fault-tolerant distributed computing scheme based on erasure codes

tion was introduced and several examples of XOR-able applications were presented. Several classical error correcting codes were proposed to be used in this context. Several problems are opened by this work. The first one is to verify whether it is possible to apply the proposed fault-tolerant scheme to given distributed applications such that, for example, classical matrix operations. Another problem concerns error correcting codes and more precisely the construction of efficient codes for distribu- ted computing. Finally, the implementation of the fault-tolerant scheme in distributed systems opens several problems related to the consensus, the distributed decoding strategy or the dynamic management of redundant computing nodes.
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Fault Diagnosis and Fault-Tolerant Control of an Octorotor UAV using motors speeds measurements

Fault Diagnosis and Fault-Tolerant Control of an Octorotor UAV using motors speeds measurements

Scientifique en Ing´ enierie (CRSI), Liban (e-mail: { cfrancis, hassan.shraim } @ul.edu.lb) Abstract: This paper presents an active fault-tolerant control strategy (AFTCS) for an octorotor unmanned aerial vehicle (UAV) regarding several motors failures or rotors damages. A complete AFTC architecture including error detection, fault isolation and system recovery is presented. The diagnosis system is based on the motors speeds and currents measurements. Once the motor failure or the rotor loss is diagnosed, a recovery algorithm is applied. It uses the pseudo-inverse control allocation approach to redistribute the control efforts among the healthy actuators. This architecture is validated in real flights.
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Design of Minimal Fault Tolerant Networks: Asymptotic Bounds

Design of Minimal Fault Tolerant Networks: Asymptotic Bounds

Fig. 2: A valid (3,1,1)-network. tolerant network. An example of a (3,1,1)-fault tolerant network is given in figure 2. As a matter of fact all the possible configurations for the unused input and the non valid output, the three used inputs can be connected to the valid outputs. Other examples achieving this bounds are presented in Figure 3. Realizing such a network is easy, but it is difficult to optimise it. To decrease launch costs, it is crucial to minimise the network physical weight, i.e. for us, to minimize the number of switches. As launch costs are dramatically high, it is worth saving even one switch. So our aim will be to construst valid (p, λ , k)-networks with the minimum number of switches denoted by N (p, λ , k). On one side we consider asymptotic cases. The networks are large in the sense that p and k go to infinity. For symmetry reasons, we can assume k ≥ λ . We give results for k = O(log p). On the other side we have also studied exact values for small k.
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Optical index of fault tolerant routings in WDM networks

Optical index of fault tolerant routings in WDM networks

Our work is a contribution to a variant of this problem, introduced by Maˇ nuch and Stacho [7], in which we focus on possible breakdowns of nodes in the network. Precisely, for a given fixed integer f , we have to provide, for every request, not just one directed path to satisfy it, but rather a set of f +1 directed paths with the same beginning and end nodes (corresponding to the request) and which are internally disjoint. In this routing, if f nodes break down, every request between the remaining nodes could still be satisfied by a previously selected routing path which contains no failed component. Such a routing set of directed paths is called an f -fault tolerant
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Fault Tolerant Control Strategy Using Two-Layer Multiple Adaptive Models for Plant Fault

Fault Tolerant Control Strategy Using Two-Layer Multiple Adaptive Models for Plant Fault

Index Terms—multiple model, adaptive control, fault tolerant control I. I NTRODUCTION As we all know, automatic facilities are widely used and are also getting advanced and complicated. Security and stability performances are always strong demands for these systems to deteriorate the risks and losses caused by unexpected faults, especially in the domains of industry and traffic. For this reason, researches on Fault Detection and Diagnosis (FDD) [2] and FTC systems have attracted great attentions. FTC, that has the ability to guarantee the control performance in acceptable range in faulty situations [3] [4], is one of the most popular research direction in the domain of automatic control. FTC techniques are generally classified into active and passive ones [5]. Passive FTC strategies behave more like robust control, which are pre-designed and run without the module of neither real-time FDD nor control reconfiguration [6]. Active FTC, on the other hand, would automatically
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LPV -MPC Fault Tolerant Control of Automotive Suspension Dampers

LPV -MPC Fault Tolerant Control of Automotive Suspension Dampers

Considering the given contextualization, the global prob- lem dealt within this work is the following: how to design an efficient Fault Tolerant Control scheme for a vehicle with four Semi-Active suspensions, considering faults on the dampers, while maintaining (sufficient) comfort and handling performances whenever a faulty situation occurs? To tackle this issue, this work proposes to use an MPC controller, as seen in literature, as a Fault Tolerant scheme, with a Linear Parameter-Varying (LPV ) model that is able to describe the vehicle in both faulty and faultless situations. Also, to do so, a separate FDD system is designed to collect information about whether the damper is faulty, following an extended-observer design methodol- ogy, as seen in (Nguyen et al., 2015b). This work can be compared to (Tudon-Martinez et al., 2013), while a new methodology is used, since (LPV ) MPC -FTC hasn’t yet been seen applied to vehicle suspensions in the literature. The efforts herein were done to demonstrate that handling and comfort performances of a vehicle can be enhanced when using controlled Semi-Active suspensions, even if faulty situations occur. Overall good results are obtained and illustrated with the aid of high-fidelity simulations and comparisons to simpler control schemes.
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An LPV Fault Tolerant control for semi-active suspension -scheduled by fault estimation

An LPV Fault Tolerant control for semi-active suspension -scheduled by fault estimation

Fault estimation is a key step in designing a fault tolerant control. In the litterature, there exist many di fferent approaches to estimate a fault which can be either actuator or sensor malfunction. Let us mention the classical methods, based on the parity space theory (see in Gertler (1997)) to generate the residues and approximate the fault or the bank of observers approach (see Varrier (2013)) as well as by sliding mode observers (Edwards et al. (2000)). Recently, a new approach (see in Shi and Patton (2014)) considered the fault element as a state of the augmented system and designed an extended observer to estimation at the same time the state and the fault of system. However, it is limited to constant faults ˙ f (t) = 0. Then, Zhang et al. (2008) presented a method allowing to evaluate the time-varying fault by using a fast adaptive fault estimation (FAFE) methodology based on an adaptive observer. But therein, the authors solved the problem with a regular LTI system without considering the disturbances. Next, Rodrigues et al. (2014) proposed an adaptive polytopic observer for time- varying fault estimation in spite of the disturbances for a class of descriptor LPV systems.
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A Fault Tolerant Control Architecture Based on Fault Trees for an Underwater Robot Executing Transect Missions

A Fault Tolerant Control Architecture Based on Fault Trees for an Underwater Robot Executing Transect Missions

A Fault Tolerant Control Architecture Based on Fault Trees for an Underwater Robot Executing Transect Missions Adrien Hereau 1 , Karen Godary-Dejean 1 , J´er´emie Guiochet 2 , Didier Crestani 1 Abstract— Robotic systems evolving in hazardous and harsh environment are prone to mission failure or system loss in presence of faults. This paper presents a fault tolerant methodology, implemented into a control architecture of an underwater robot that executes biological monitoring missions. High level constraint violations (mission, safety, energy, time and localization) and low level faults (software and hardware faults) are considered using a method based on fault trees. These undesirable events are detected and treated by a fault tolerant module that decides to recover at low level or to give a feedback to the mission manager which selects the high level reaction. This fault tolerant architecture has been tested on real field conditions, and we illustrate our methodology on a set of selected events. We conclude about reliability improvement of low cost underwater robots for complex and long missions.
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Fault Tolerant 7-phase Hybrid Excitation Permanent Magnet Machine

Fault Tolerant 7-phase Hybrid Excitation Permanent Magnet Machine

1 Shandong University, School of Electrical Engineering, Jinan 250061, Shandong, China 2 Univ. Lille, Arts et Metiers ParisTech, Centrale Lille, HEI, EA 2697 - L2EP -Laboratoire d’Electrotechnique et d’Electronique de Puissance, F-59000 Lille, France This paper presents a novel 7-phase hybrid excitation permanent magnet (HEPM) machine with three rotors around one stator. Two rotors with PMs axially magnetized and the third rotor with PMs radially magnetized. Thanks to the addition of the third rotor, the inactive end-windings in the configuration with two rotors are then becoming active with a contribution to the torque with an increase of 30%. The impact of the third rotor on the torque density and on the pulsating torques is presented. The fault-tolerant characteristics of the proposed machine are also presented, which proves the interests of this machine for low speed applications.
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Fault Tolerant Resource Allocation for Query Processing in Grid Environments

Fault Tolerant Resource Allocation for Query Processing in Grid Environments

In this paper, we assume that the node that posts the query and the nodes in which base relations reside are fault-tolerant or stable by default during the execution of the query. We consider a query as consisting of hash join operators which are composed of atomic tasks, namely scan, build and probe. Scan tasks act as providers to both build and probe tasks by reading tuples from their storage units and sending them to their corresponding tasks. Build tasks receive tuples from their scan tasks and create hash tables for that operator. Probe tasks are blocked during the execution of their corresponding build tasks. After build tasks complete, probe tasks start receiving tuples from their corresponding scan tasks and check for matching tuples in the hash table. Probe tasks pipeline matched tuples through their successor tasks in the query tree. More detailed description of distributed hash join operator can be found in the work of Özsu and Valduriez (2011).
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Towards efficient and fault-tolerant optical networks : complexity and algorithms

Towards efficient and fault-tolerant optical networks : complexity and algorithms

world has become very dependent. In this thesis, we tackle mainly optimization problems related to these two desired properties of optical networks: fault-tolerance and efficiency. Fault-tolerant optical networks. Fault-tolerance is an important requirement in optical networks [ RS02 ]. These networks carry significant amounts of data and any failure can result in the loss of considerable traffic and the disruption of numer- ous services. Failures in optical networks can be full or partial, single or multiple, software or hardware caused. They can be triggered by a fiber cut or a power out- age, by a human error or a natural disaster. Service providers have to account for all these types of failures while designing the schemes which ensure the resiliency of their networks. These schemes are generally of two types: protection schemes and restoration schemes [ RM99 ]. In the protection schemes, redundant capacity is reserved in the network and used to reroute the traffic in case of failures. These schemes ensure a fast failure recovery (within 50 ms in general). In the restoration schemes, the resources ensuring the recovery are computed after the detection of a failure and the traffic is restored on a slower time scale [ RS02 ]. We will be concerned in the first part of this thesis with protection schemes and more precisely with the dedicated path protection scheme (DPP).
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FAIL-MPI: How fault-tolerant is fault-tolerant MPI ?

FAIL-MPI: How fault-tolerant is fault-tolerant MPI ?

In order to validate this implementation, a rigorous testing approach can be used. Au- tomatic failure injection is a general technique suitable for evaluating the effectiveness and robustness of the distributed applications against various and complex failure scenarios. After having validated the fault tolerant implementation, it is necessary to evaluate its performance, in order to adapt the best protocol suitable for an actual distributed system. Fault-Tolerant distributed applications are classically evaluated without failures. However, performances under a failure-prone environment is also a significant information to evaluate and tune a fault-tolerant distributed system. Automatic failure injection is desirable to evaluate fairly different heuristics or parameters under the same failure conditions.
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Fault Tolerant Control Strategy applied to PEMFC water management

Fault Tolerant Control Strategy applied to PEMFC water management

manner, the FTCS efficiently prevented important flooding and high performance losses. This strategy improves perfor- mance stability and FC reliability. The presented results are encouraging for recovering from flooding issues, thanks to easy-to-implement Fault Tolerant Control Strategy. However, the FDI tool efficiency is highly dependent of the empirical thresholds selection. In future works, the empirical thresholds optimization according to operating conditions or FC ageing could be a great research challenge. Moreover, the use of empirical models restricts the applicability of the proposed strategy and collecting adequate training data to identified ANN models can be complex and time consuming. To overcome these limitations, further works are currently in progress to substitute the model-based FDI tool by a non-model based one.
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Minimal selectors and fault tolerant networks

Minimal selectors and fault tolerant networks

Keywords: Fault Tolerant Networks, Switching Networks, Network Design, Concentrators, Routing, Connectivity, Disjoint paths, Expanders. 1 Introduction Motivation. In this paper we study a network-design combinatorial optimization problem. Our problem, originally posed by Alcatel Space Industry, comes from the design of efficient on-board networks in satellites (also called Traveling Wave Tube Amplifiers). The satellites under consideration are used for TV and video transmission (like the Eutelsat or Astra series) as well as for private applications. Signals incoming to a telecommunication satellite through ports have to be routed
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A Fault-Tolerant Approach to Distributed Applications

A Fault-Tolerant Approach to Distributed Applications

objective optimization problem. This illustrates the algorithm- based fault-tolerance approach (ABFT) used here. Figure 4. Fault-tolerant algorithm: Part B. As mentioned above, the implementation of the application is distributed, parallel and asynchronous. It is distributed because the tasks are deployed on the various sites where the application codes run. It is parallel because these tasks can run multiple instances simultaneously for the computations of the surrogates and the exact solutions. It is asynchronous because the surrogates and exact solutions are computed in two distinct parallel loops and produce their results whatever the state of the other loop. This paves the way to implement an inherently fault-tolerant algorithm which is described in more details in this section.
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On-Line Optimization for Fault Tolerant Flight Control

On-Line Optimization for Fault Tolerant Flight Control

Abstract: In this communication the case in which an aerodynamic actuator failure occurs to an aircraft while it has to perform some guidance maneuver is considered. This problem is dealt with the reassignment of remaining operational actuators in order to perform the required maneuver while maintaining the structural integrity of the aircraft. Nonlinear Inverse Control technique is used to generate online nominal moments along the three axes of the aircraft. Taking into account all material and structural constraints as well as the redundant effects from other actuators, a mathematical programming problem to be solved on-line which related to control reallocation can be formulated. Solution techniques, based on dynamic neural networks, active set methods and interior point methods are discussed and the respective performances are compared. Keywords: active set, interior point, neural network, on- line optimization, fault tolerant flight control
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Fault-Tolerant Partial Replication in Large-Scale Database Systems

Fault-Tolerant Partial Replication in Large-Scale Database Systems

One solution to this problem, is given a transaction T , (i) to execute T on every replicas of T , (ii) to compute the transitive closure of the precedence constraints linking T to concu[r]

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