Fault Tolerance Measures Research Articles

The super connectivity of augmented cubes

The augmented cube AQ n , proposed by Choudum and Sunitha [S.A. Choudum, V. Sunitha, Augmented cubes, Networks 40 (2) (2002) 71–84], is a ( 2 n − 1 ) -regular ( 2 n − 1 ) -connected graph ( n ≠ 3 ). This paper determines that the super connectivity of AQ n is 4 n − 8 for n ⩾ 6 and the super edge-connectivity is 4 n − 4 for n ⩾ 5 . That is, for n ⩾ 6 (respectively, n ⩾ 5 ), at least 4 n − 8 vertices (respectively, 4 n − 4 edges) of AQ n are removed to get a disconnected graph that contains no isolated vertices. When the augmented cube is used to model the topological structure of a large-scale parallel processing system, these results can provide more accurate measurements for reliability and fault tolerance of the system.

Robust neuro-identification of nonlinear plants in electric power systems with missing sensor measurements

Fault tolerant measurements are an essential requirement for system identification, control and protection. Measurements can be corrupted or interrupted due to sensor failure, broken or bad connections, bad communication, or malfunction of some hardware or software. This paper proposes a novel robust artificial neural network identifier (RANNI) by combining a sensor evaluation and (missing sensor) restoration scheme (SERS) and an ANN identifier (ANNI) in a cascading structure. This RANNI is able to provide continuous on-line identification of nonlinear plants when some crucial sensor measurements are unavailable. A static synchronous series compensator (SSSC) connected to a power system is used as a test system to examine the validity of the proposed model. Simulation studies are carried out with single and multiple phase current sensors missing; results show that the proposed RANNI continuously tracks the plant dynamics with good precision during the steady state, the small disturbance, the transient state after a large disturbance and the unbalanced three-phase operations. The proposed RANNI is readily applicable to other plant models in power systems.

Fault-Tolerant Design and Testing of USB2.0 Peripheral Devices IP Core System

Universal serial bus 2.0 (USB2.0) is a kind of mainstream interface technology. The traditional USB developing is only to develop USB peripheral devices. For the USB2.0 peripheral devices IP core system that has wide application foreground, some interference inevitably exists in signal transmitting. Some fault-tolerant design and test methods must be adopted in order to correctly transmit and receive data. Combining with a project, this paper introduces in detail about measures, hardware implement, and test methods of fault-tolerant design about USB2.0 peripheral devices IP core system. Fault-tolerant design measures, noise reduction measures of signal processing, fault-tolerant methods about data encode and decode, package identification (ID) field fault-tolerant methods, and cyclic redundancy checks fault-tolerant methods are discussed. The paper also presents some hardware implement methods about fault-tolerant design of data decode and test methods about fault-tolerant design of USB2.0 IP core system. These methods can offer the reference for development of USB2.0 system in all kinds of electronics instrumentations.

Restricted arc-connectivity of digraphs

Since interconnection networks are often modeled by graphs or digraphs, the edge-connectivity of a graph or arc-connectivity of a digraph are important measurements for fault tolerance of networks. The restricted edge-connectivity λ ′ ( G ) of a graph G is the minimum cardinality over all edge-cuts S in a graph G such that there are no isolated vertices in G − S . A connected graph G is called λ ′ -connected, if λ ′ ( G ) exists. In 1988, Esfahanian and Hakimi [A.H. Esfahanian, S.L. Hakimi, On computing a conditional edge-connectivity of a graph, Inform. Process. Lett. 27 (1988), 195–199] have shown that each connected graph G of order n ⩾ 4 , except a star, is λ ′ -connected and satisfies λ ′ ( G ) ⩽ ξ ( G ) , where ξ ( G ) is the minimum edge-degree of G. If D is a strongly connected digraph, then we call in this paper an arc set S a restricted arc-cut of D if D − S has a non-trivial strong component D 1 such that D − V ( D 1 ) contains an arc. The restricted arc-connectivity λ ′ ( D ) is the minimum cardinality over all restricted arc-cuts S. We observe that the recognition problem, whether λ ′ ( D ) exists for a strongly connected digraph D is solvable in polynomial time. Furthermore, we present some analogous results to the above mentioned theorem of Esfahanian and Hakimi for digraphs, and we show that this theorem follows easily from one of our results.

Restricted connectivity for three families of interconnection networks

Vertex connectivity and edge connectivity are two important parameters in interconnection networks. Even though they reflect the fault tolerance correctly, they undervalue the resilience of large networks. By the concept of conditional connectivity and super-connectivity, the concept of restricted vertex connectivity and restricted edge connectivity of graphs was proposed by Esfahanian [A.H. Esfahanian, Generalized measures of fault tolerance with application to N-cube networks, IEEE Transactions on Computers 38 (1989) 1586–1591]. Such measures take the resilience of large networks into consideration. In this paper, we propose three families of interconnection networks and discuss their restricted vertex connectivity and restricted edge connectivity. In particular, the hypercubes, twisted-cubes, crossed-cubes, möbius cubes, star graphs, pancake graphs, recursive circulant graphs, and k-ary n-cubes are special cases of these families.

On reliability of the folded hypercubes

In this paper, we explore the 2-extra connectivity and 2-extra-edge-connectivity of the folded hypercube FQ n . We show that κ 2( FQ n ) = 3 n − 2 for n ⩾ 8; and λ 2( FQ n ) = 3 n − 1 for n ⩾ 5. That is, for n ⩾ 8 (resp. n ⩾ 5), at least 3 n − 2 vertices (resp. 3 n − 1 edges) of FQ n are removed to get a disconnected graph that contains no isolated vertices (resp. edges). When the folded hypercube is used to model the topological structure of a large-scale parallel processing system, these results can provide more accurate measurements for reliability and fault tolerance of the system.

Scalable error correction in distributed ion trap computers

A major challenge for quantum computation in ion trap systems is scalable integration of error correction and fault tolerance. We analyze a distributed architecture with rapid high fidelity local control within nodes and entangled links between nodes alleviating long-distance transport. We demonstrate fault-tolerant operator measurements which are used for error correction and non-local gates. This scheme is readily applied to linear ion traps which cannot be scaled up beyond a few ions per individual trap but which have access to a probabilistic entanglement mechanism. A proof-of-concept system is presented which is within the reach of current experiment.

Fault tolerance of parallel manipulators using task space and kinematic redundancy

When a parallel manipulator suffers from failures, its performance can be significantly affected. Thus, fault tolerance is essential for task-critical applications or applications in which maintenance is hard to implement. In this paper, we consider three types of common strut failures corresponding to stuck joints, unactuated actuators, or the complete loss of struts, respectively. The impacts of different failures on the kinematics of a manipulator are examined, and the task space redundancy and kinematic redundancies are used to help overcome these failures. In addition, local measures of fault tolerance and their properties are analyzed. These measures can be helpful in architecture design and path planning

Optical substrate thickness measurement system using hybrid fiber-freespace optics and selective wavelength interferometry

Proposed and demonstrated is a simple few components non-contact thickness measurement system for optical quality semi-transparent samples such as Silicon (Si) and 6H Silicon Carbide (SiC) optical chips used for designing sensors. The instrument exploits a hybrid fiber-freespace optical design that enables self-calibrating measurements via the use of confocal imaging via single mode fiber-optics and a self-imaging type optical fiber collimating lens. Data acquisition for fault-tolerant measurements is accomplished via a sufficiently broadband optical source and a tunable laser and relevant wavelength discriminating optics. Accurate sample thickness processing is achieved using the known material dispersion data for the sample and the few (e.g., 5) accurately measured optical power null wavelengths produced via the sample etalon effect. Thicknesses of 281.1μm and 296μm are measured for given SiC and Si optical chips, respectively.

Lower bounds on the vertex-connectivity of digraphs and graphs

Since interconnection networks are often modeled by graphs or digraphs, the connectivity of a (di-)graph is an important measurement for fault tolerance of networks. Let G be a graph of order n, minimum degree δ, and vertex-connectivity κ. If G is not the complete graph, then Chartrand and Harary [G. Chartrand, F. Harary, Graphs with prescribed connectivities, in: P. Erdös, G. Katona (Eds.), Theory of Graphs, Academic Press, New York, 1968, pp. 61–63] proved in 1968 that κ ⩾ 2 δ + 2 − n . In 1993, Topp and Volkmann [J. Topp, L. Volkmann, Sufficient conditions for equality of connectivity and minimum degree of a graph, J. Graph Theory 17 (1993) 695–700] proved the following analog bound for bipartite graphs. If G is a bipartite graph with κ < δ , then κ ⩾ 4 δ − n . In this paper we present some generalizations and extensions of these inequalities for digraphs as well as for graphs.

A Dynamic Shadow Approach to Fault-Tolerant Mobile Agents in an Autonomic Environment

Large-scale distributed applications such as online information retrieval and collaboration over computational elements demand an approach to self-managed computing systems with a minimum of human interference. However, large scales and full distribution often lead to poor system dependability and security, and increase the difficulty in managing and controlling redundancy for fault tolerance. In particular, fault tolerance schemes for mobile agents to survive agent server crash failures in an autonomie environment are complex since developers normally have no control over remote agent servers. Some solutions inject a replica into stable storage upon its arrival at an agent server. But in the event of an agent server crash the replica is unavailable until the agent server recovers. In this paper we present a failure model and an exception handling framework for mobile agent systems. An exception handling scheme is developed for mobile agents to survive agent server crash failures. A replica mobile agent operates at the agent server visited prior to its master's current location. If a master crashes its replica is available as a replacement. The proposed scheme is examined in comparison with a simple time-out scheme. Experimental evaluation is performed, and performance results show that the scheme leads to some overhead in the round trip time when fault tolerance measures are exercised. However the scheme offers the advantage that fault tolerance is provided during the mobile agent trip, i.e. in the event of an agent server crash all agent servers are not revisited.

Designing an Archival Satellite Transmitter for Life-Long Deployments on Oceanic Vertebrates: The Life History Transmitter

Despite the widespread use of sophisticated telemetry transmitters in behavioral, physiological and ecological studies, few studies on population dynamics of oceanic vertebrates use such technology, primarily due to the difficulty of obtaining multi-year records from individual animals. We present the first telemetry transmitter specifically designed for collecting vital data from marine vertebrates over extended periods, up to a decade. The implantable Life History Transmitter records data throughout the life of a host animal. After the host animal dies, the tag is extruded, and, while floating on the ocean or lying on a beach, transmits previously stored data to orbiting satellites. For tags relying solely on end-of-deployment transmission, reliability and proper recognition of tag state is crucial. The Life History Transmitter uses heuristic tag state determination, in combination with simple error detection and fault tolerance measures, to increase tag reliability and likelihood of data recovery. We used a computer simulation of tag deployments and various sensor failures on a PC platform, in combination with time-accelerated simulations running on the actual deployment platform, to test the functionality of fault tolerance and error detection protocols

The maximal restricted edge connectivity of Kautz undirected graphs

Abstract The restricted edge connectivity is an accurate measure of fault-tolerance for interconnection networks. In this paper, we obtain the following: for d ≥ 3 , n ≥ 2 , the restricted edge connectivity of Kautz undirected graph U K ( d , n ) is 4 d − 4 , and U K ( d , n ) is a maximal restricted edge connected graph.

Edge fault tolerance analysis of a class of interconnection networks

Fault tolerant measures have played an important role in the reliability of an interconnection network. Edge connectivity, restricted-edge-connectivity, extra-edge-connectivity and super-edge-connectivity of many well-known interconnection networks have been explored. In this paper, we study the 2-extra-edge connectivity of a special class of graphs G(G0, G1; M) proposed by Chen et al. [Appl. Math. Comput. 140 (2003) 245– 254]. Then by showing that several well-known interconnection networks such as hyper

Periodic Linear Programming with applications to real-time scheduling

In this paper we introduce a new mathematical modelling technique called Periodic Linear Programming; the periodic properties of Periodic Linear Programs (PLPs) permit the specification of inter-period constraints in embedded systems, in a straightforward and natural manner. We analyse PLPs in which the relationship between program variables is restricted to the class of difference constraints. Our analysis establishes that such PLPs can be reduced to simple linear programs, and hence decided in polynomial time. The class of difference constraints is extremely important from the perspective of embedded systems design, in that it permits the specification of complex timing constraints in real-time specification languages. A PLP can be thought of as a finite-description tool that represents infinite-state systems; although we use this tool purely for the purpose of modelling real-time scheduling problems, PLPs also find applications in other areas, such as concurrency design. In studying this programming paradigm, we develop novel techniques that, to the best of our knowledge, are not part of the literature. We build on the PLP structure to introduce a generalisation called Periodic Quantified Linear Programming; this programming paradigm permits the specification and analysis of uncertainty in the parameters of a PLP. Consequently, a Periodic Quantified Linear Program (PQLP) is the natural modelling tool to capture the requirements of periodic, embedded systems that are characterised by uncertainty in the execution times of processes, periodicity and relative timing constraints. In this paper, we use the PQLP structure to model and solve the periodic version of the zero-clairvoyant scheduling problem. Modelling uncertainty in the problem description is a typical technique used to incorporate a measure of fault-tolerance in the specification.

Optimal fault-tolerant routings with small routing tables for k-connected graphs

We study the problem of designing fault-tolerant routings with small routing tables for a k-connected network of n processors in the surviving route graph model. The surviving route graph R( G, ρ)/ F for a graph G, a routing ρ and a set of faults F is a directed graph consisting of nonfaulty nodes of G with a directed edge from a node x to a node y iff there are no faults on the route from x to y. The diameter of the surviving route graph could be one of the fault-tolerance measures for the graph G and the routing ρ and it is denoted by D( R( G, ρ)/ F). We want to reduce the total number of routes defined in the routing, and the maximum of the number of routes defined for a node (called route degree) as least as possible. In this paper, we show that we can construct a routing λ for every n-node k-connected graph such that n⩾2 k 2, in which the route degree is O(k n ) , the total number of routes is O( k 2 n) and D( R( G, λ)/ F)⩽3 for any fault set F (|F|<k) . In particular, in the case that k=2 we can construct a routing λ′ for every biconnected graph in which the route degree is O( n ) , the total number of routes is O( n) and D( R( G, λ′)/{ f})⩽3 for any fault f. We also show that we can construct a routing ρ 1 for every n-node biconnected graph, in which the total number of routes is O( n) and D( R( G, ρ 1)/{ f})⩽2 for any fault f, and a routing ρ 2 (using ρ 1) for every n-node biconnected graph, in which the route degree is O( n ) , the total number of routes is O(n n ) and D( R( G, ρ 2)/{ f})⩽2 for any fault f.

SINGLE EVENT EFFECTS IN AVIONICS AND ON THE GROUND

Single event effects in electronics caused by the atmospheric neutrons have been an issue for systems using large blocks of random access memory (RAM) in avionics applications as well as those on the ground. At ground level there are two main sources of single event effects, alpha particles from the packaging materials as well as the neutrons, but at aircraft altitudes, where the neutron flux is about 300 times higher than the ground, the alpha particles make a negligible contribution. We review the trends over the last 5-10 years in the response of COTS computer systems to single event effects, taking into the response of devices as well as fault tolerant measures incorporated into the systems.

A measure of fault tolerance for functional networks

This paper presents a study of the influence of perturbations in the parameters of a functional network. A quantitative measure is introduced, related to the change in the mean squared error when noise is applied to the network parameters. This measure, based on statistical sensitivity, provides a fault tolerance estimate for a functional network and allows the performance degradation of this kind of system to be predicted. It can be used, therefore, to evaluate performance differences between the training process carried out on a computer and its hardware implementation. The experimental results obtained for different functional network architectures and a feedforward multilayer neural network confirm the validity of the proposed model.

A measure of fault tolerance for functional networks

A measure of fault tolerance for functional networks

Design of automatic measurement stations with fault accommodation capabilities

A technique for the systematic design of fault-tolerant automatic measurement systems based on ‘analytical redundancy’ relationships is proposed. Starting from the user requirements in terms of quantities to be monitored and of number and type of faults to be detected, isolated, and accommodated, the proposed technique suggests the number and location of the sensors to be used in the measurement system to be designed or the modifications needed in an existing measurement system for satisfying the user requirements. The peculiarities of this technique were highlighted by applying it to some real measurement stations.