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Behavioural Preservation in Fault Tolerant PatternsDIAS, Diego Machado 02 March 2012 (has links)
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Previous issue date: 2012-03-02 / FACEPE / In the development of critical systems it is common practise to make use of redundancy
in order to achieve higher levels of reliability. There are well established design patterns
that introduce redundancy and that are widely documented in the literature and adopted
by the industry. However there have been few attempts to formally verify them with
respect to behavioural preservation.
In this work, we purpose an approach to specify such design patterns, called here
fault tolerant patterns, using HOL. We use the theorem prover HOL4 to prove the compositionality
and correctness of the fault tolerant patterns. We illustrate our approach
by modelling three classical fault tolerant patterns: homogeneous redundancy, heterogeneous
redundancy and triple modular redundancy. Our model takes into account that the
original system (without redundancy) computes a certain function with some delay and is
amenable to random failures.
In order to prove that a fault tolerant pattern preserves the behaviour of its subsystems,
we defined new notions of refinement. Systems engineers commonly accept the fact that
fault tolerant patterns do not change the functionality of a system. However, this practise
is not compatible with the classical refinement notions. Thus we defined axiomatic
notions of refinement to prove that the formalised fault tolerant patterns preserve the
behaviour of its subsystems.
We also proved that our fault tolerant patterns are compositional in the sense that
we can apply fault tolerant patterns consecutively and for an arbitrary number of times.
The result of that is still a system whose delay, failure model and functionality can be
systematically discovered (by proof) with almost no effort.
In order to illustrate the usage of the patterns we applied the triple modular redundancy
pattern to a simplified avionic Elevator Control System. We showed that once a fault
tolerant pattern is verified, the application of it to a specific system and the proof of the
behavioural preservation of the resulting system becomes trivial. This work has been
done in collaboration with the Brazilian aircraft manufacturer Embraer.
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Failure diagnostic expert systems: a case study in fault diagnosisAdam, Johan D. 20 January 2010 (has links)
<p>Downtime associated with fault isolation impacts the performance of any system to a
significant degree. Few repairmen are well versed in the art of troubleshooting and
experienced repairmen are not always available and/or are very costly. A failure
diagnostic expert system provides an effective method of failure diagnosis.</p>
<p>
Diagnostic reasoning in expert systems is discussed with demonstrating methodologies
by using a 1.6 liter, 1981 model Volkswagen Vanagon as an example. A procedure and
methodology for building a diagnostic case base is demonstrated by building a
Volkswagen Vanagon diagnostic case base. A significant diagnostic case base was
developed in order to demonstrate and evaluate the appropriateness of CBR Express for
failure diagnosis. CBR Express is a case-based matching application from Inference
Corporation.</p> / Master of Science
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Practical and consistent database replicationLin, Yi, 1972- January 2007 (has links)
No description available.
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Proposal of an optimized checkpoint-recovery environment for Windows NT 5.xZounmevo, Judicaël. January 2007 (has links)
No description available.
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A modular approach to fault-tolerant binary tree architectures /Hassan, Abu S.M. (Abu Saleem Mahmudul) January 1984 (has links)
No description available.
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FPGA-based fault tolerant design and deterministic routing-based synthesis for Digital Microfluidic BiochipsTodakar, Onkar January 2015 (has links)
No description available.
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A Single Fault-Tolerant Dual Channel ControllerLowery, Thomas J. 01 January 1984 (has links) (PDF)
The advent of the VLSI technology makes it feasible to offer a once expensive system attribute called fault-tolerance to a wide variety of applications. This can be accomplished by using off-the-shelf single board computers and peripherals as the heart of the system. Custom design boards can then be added to meet the specific requirements of each application.
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Fault-Tolerant Supervisory ControlMulahuwaish, Aos January 2019 (has links)
In this thesis, we investigate the problem of fault tolerance in the framework of discrete-event systems (DES). We introduce our setting, and then provide a set of fault-tolerant definitions designed to capture different types of fault scenarios and to ensure that our system remains controllable and nonblocking in each scenario.
This is a passive approach that relies upon inherent redundancy in the system being controlled, and focuses on the intermittent occurrence of faults.
Our approach provides an easy method for users to add fault events to a system model and is based on user designed supervisors and verification. As synthesis algorithms have higher complexity than verification algorithms, our approach should be applicable to larger systems than existing active fault-recovery methods that are synthesis based. Also, modular supervisors are typically easier to understand and
implement than the results of synthesis.
Finally, our approach does not require expensive (in terms of algorithm complexity) fault diagnosers to work. Diagnosers are, however, required by existing methods to know when to switch to a recovery supervisor. As a result, the response time of diagnosers is not an issue for us. Our supervisors are designed to handle the original and the faulted system.
In this thesis, we next present algorithms to verify these properties followed by complexity analyses and correctness proofs of the algorithms. Finally, examples are provided to illustrate our approach.
In the above framework, permanent faults can be modelled, but the current method was onerous. To address this, we then introduce a new modeling approach for permanent faults that is easy to use, as well as a set of new permanent fault-tolerant definitions. These definitions are designed to capture several types of permanent fault scenarios and to ensure that our system remains controllable and nonblocking in each scenario. New definitions and scenarios were required as the previous ones were incompatible with the new permanent fault modeling approach.
We then present algorithms to verify these properties followed by complexity analyses and correctness proofs of the algorithms. An example is then provided to illustrate our approach.
Finally, we extend the above intermittent and permanent fault-tolerant approach to the timed DES setting. As before, we introduced new fault-tolerant properties and algorithms. We then provide complexity analyses and correctness proofs for the algorithms. An example is then provided to illustrate our approach. / Thesis / Doctor of Philosophy (PhD)
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Modeling reconfiguration algorithms for regular architectureDeBrunner, Linda Sumners 12 October 2005 (has links)
Three models are proposed to evaluate and design distributed reconfigurable systems for fault tolerant, highly reliable applications. These models serve as valuable tools for developing fault tolerant systems. In each model, cells work together in parallel to change the global structure through a series of separate actions. In the Local Supervisor Model (LSM), selected cells guide the reconfiguration process. In the Tessellation Automata Model (TAM), each cell determines its next state based on its state and its neighbors' states, and communicates its state information to its neighbors. In the Interconnected Finite State Machine Model (IFS:MM:), each cell determines its next state and outputs based on its state and its inputs.
The hierarchical nature of the TAM and IFSMM provides advantages in evaluating, comparing, and designing systems. The use of each of these models in describing systems is demonstrated. The IFSMM: is emphasized since it is the most versatile of the three models. The IFSMM: is used to identify algorithm weaknesses and improvements, compare existing algorithms, and develop a novel design for a reconfigurable hypercube. / Ph. D.
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Real time health monitoring and control system methodology for flexible space structuresJayaram, Sanjay 01 January 2004 (has links)
No description available.
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