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It is well known that redundancy is a potentially powerful means of increasing reliability, provided the increased size, weight, maintenance, and cost are acceptable. A simple means of implementing redundancy is to rely on human detection of errors and subsequent switching to a standby unit. However, in control computers and other real-time devices, uninter-rupted operation becomes crucial, and automatic detection of error followed by automatic switching is thus required. Indeed, this requirement would seem to be the heart of the problem of implementing real-time redundancy and is the problem to which this paper is addressed.

By analysing an ideal model of a redundancy scheme, a measure for the reliability improvement produced by a redundancy scheme is found; and it is shown that for real redundancy schemes this measure is effectively independent of the size of system to which the scheme is applied. Other advantages of the measure are that it is relatively easy to evaluate, and has a good sensitivity characteristic. This measure, together with a redundancy "cost" factor, represents the performance of a redundancy scheme more generally than was previously possible. A new high performance redundancy scheme - "radial logic" is described, and its error correcting action explained. It can be applied to combinational and sequential logic circuitry, and in this application appears to have a better performance than other schemes, as well as being simple to design, and offering considerable flexibility in the degree of error correction.

Redundancy is a feature of systems that arises by design or as an accidental byproduct of design, and can be used to detect, diagnose or correct errors that occur in systems operations. While it is usually investigated in the context of fault tolerance, one can argue that it is in fact an intrinsic feature of a system that can be analyzed on its own without reference to any fault tolerance capability. In this paper, we submit three alternative views of redundancy, which we propose to analyze to gain a better understanding of redundancy; we also explore means to use this understanding to enhance the design of fault tolerant systems.

This paper presents the redundancy architecture of the Programmable Logic Controller called the Safety PLC(SPLC) for the safety functions such as reactor protection in a nuclear power plant. The architecture of the SPLC is designed to switch flexibly redundancy model between the Dual Modular Redundancy(DMR) and Triple Modular Redundancy(TMR). Using this flexible redundancy architecture, the controller can be optimally configured to the application area, and the reliability and availability of the overall system can be increased because redundancy model varies as failures occur. The operating system of the SPLC is also specially designed to guarantee the strict real-time operation using the non-preemptive state-based scheduler and the supervisory task that manages timing violation of each task. The data communication of the SPLC uses the deterministic state-based protocol based on the Guaranteed Time Slot(GTS) protocol. The reliability analysis results show that MTTF of SPLC is 41,630 hours, which is about 15% and 50% more reliable than the TMR or DMR architecture, respectively.

This paper describes the methodology used and the implementation of the cyclic redundancy check (CRC) algorithm using C++ programming. The technique gained its popularity because it combines three advantages: extreme error detection capabilities, little overhead, and ease of implementation. The CRC is calculated by performing a modulo 2 division of the data by a generator polynomial and recording the remainder after division. The most commonly used polynomials are implemented. The conclusions and analysis results were shown and suggest that the cyclic redundancy check encoder be used in error detection for digital signals due to its ability to quickly determine if errors are present. The redundancy bits produced by the cyclic encoder enable the receiver to quickly determine if an error was produced. Different types of polynomials are used in the CRC.

T paper addresses the problem of selecting data from redundant processors without introducing vulnerable hardware. An original hardware-software switchover concept ensures correct system operation subsequent to any single failure, including a failure within the switch itself. A distributed output selection switch and voting mechanism are controlled by distributed software. Both hardware and software are fully specified. The concept has been implemented and tested on a microprocessor-based flight

This paper considers r-out-of-n:G and dynamic redundant systems with non-i.i.d. units, and extends two previously published algorithms for calculating fail-safe and fail-danger probabilities of such systems.

A technique for synthesizing reliable systems using parallel redundancy at the subsystem level is described. The specification of a loss function allows the calculation of the average expected loss which can be used to determine the optimum amount of redundancy for a given application. This optimum is statistical and therefore applicable only when the mission is performed many times.

—Triple modular redundancy becomes common when applications place a high premium on the reliability of a digital computer . As the weight, volume, and cost of electronic components decrease, 5-, 7-, or 9-fold redundancies should be considered. This short note presents expressions on the reliabilities of a general n-fold redundant system.

The capability of redundancy method for increasing the reliability of circuit elements of both switch- and nonswitch-type is investigated in this paper. The reliability gain of various ways of circuit connections is derived with regard to open circuit and short circuit failures. The change of loading effects of all redundant elements due to the failure of a few elements among them is also considered. The evaluation of the average life of a redundancy elements shows that the redundancy technique is particularly suitable for short period operation or nonreparable systems. Some design considerations for practical applications are discussed in substantial detial with illustrations.