Determining Component Reliability and Redundancy for Optimum System Reliability

The usual constrained reliability optimization problem is extended to include determining the optimal level of component reliability and the number of redundancies in each stage. With cost, weight, and volume constraints, the problem is one in which the component reliability is a variable, and the optimal trade-off between adding components and improving individual component reliability is determined. This is a mixed integer nonlinear programming problem in which the system reliability is to be maximized as a function of component reliability level and the number of components used at each stage. The model is illustrated with three general non linear constraints imposed on the system. The Hooke and Jeeves pattern search technique in combination with the heuristic approach by Aggarwal et al, is used to solve the problem. The Hooke and Jeeves pattern search technique is a sequential search routine for maximizing the system reliability, RS (R, X). The argument in the Hooke and Jeeves pattern search is the component reliability, R, which is varied according to exploratory moves and pattern moves until the maximum of RS (R, X) is obtained. The heuristic approach is applied to each value of the component reliability, R, to obtain the optimal number of redundancies, X, which maximizes RS (R, X) for the stated R.     

On Optimal Redundancy of Multivalue-Output Systems

This paper considers improving the reliability of multivalue-output systems by the use of n-redundant systems in which n copies of systems are used redundantly and the output is determined from the outputs of those copies by the voter. A k-out-of-n redundant system minimizes the mean loss caused by the occurrence of output errors under the condition that the voter can be composed of only two kinds of operators, logical sum and logical product. The optimal k depends on the probability and loss matrices, but it can be specified in some special cases. The mean loss of multivalue-output systems with multichannels can be minimized by adopting k-out-of-n redundancy for each channel. The results provide a powerful guide to the improvement of fail-safe characteristics of many systems and the design of fault-tolerant systems.     

Methods for Calculating the Reliability Function for Systems Subjected to Random Stresses

The reliability function is calculated for components and systems which are subjected to stresses arriving randomly in time at a given average rate. The component is assumed to exist in a finite number of states, each of which is affected differently by the applied stress. During normal operation, failure rates are assigned to each of the states of the component; when the stress is applied, the failure rates for each state change to a new value. By defining the transitions among the states as a first order Markov process, the average probability of no failure prior to and including time t is calculated for the cases where the sets of failure rates are either discrete or continuous. The solution for the average probability is given as a matrix equation and several methods for reducing the equation to a useable form are examined. In addition, the theory of failure and repair processes is reviewed and methods for simplifying the calculation of the reliability of a system are presented.     

Optimization Techniques for System Reliability with Redundancy?A Review

This paper is a state-of-art review of the literature related to optimal system reliability with redundancy. The literature is classified as follows. Optimal system reliability models with redundancy Series Parallel Series-parallel Parallel-series Standby Complex (nonseries, nonparallel) Optimization techniques for obtaining optimal system configuration Integer programming Dynamic programming Maximum principle Linear programming Geometric programming Sequential unconstrained minimization technique (SUMT) Modified sequential simplex pattern search Lagrange multipliers and Kuhn-Tucker conditions Generalized Lagrangian function Generalized reduced gradient (GRG) Heuristic approaches Parametric approaches Pseudo-Boolean programming Miscellaneous     

A Built-In Redundancy-Analysis Scheme for Random Access Memories with Two-Level Redundancy

Built-in self-repair (BISR) technique is a popular method for repairing defective embedded memories. To allocate redundancy efficiently, built-in redundancy-analysis (BIRA) component is a core component in a BISR design. This paper presents a BIRA scheme for RAMs with two-level redundancy, i.e., spare rows, spare columns, and spare words. A compressed local bitmap is used to collect faulty information for redundancy allocation. Then an efficient redundancy analysis algorithm based on the compressed local bitmap is proposed to allocate redundancy. Experimental results show that the repair rate (the ratio of the number of repaired memories to the number of defective memories) of the proposed redundancy analysis algorithm approaches to that of the exhaustive search algorithm. Also, area overhead of the proposed BIRA scheme is low. It is only about 2% for an 8K × 64-bit RAM with three spare rows, three spare columns, and two spare words.     

On Product Reliability Under Random Field Loads

This paper presents a simple design problem to illustrate the relationship between product reliability and design strength for the case where product failure is due to a single overload in a sequence of loads applied during the mission of the product.     

The Highest & Lowest Reliability Achievable with Redundancy

Often system reliability can be enhanced through the use of redundancy. Redundancy may, however, have a detrimental effect on the statistical relationship of redundant elements. When the components in a redundant system have more than one failure-mode and when failures are s-dependent, it is difficult to assess the reliability of the system. The paper describes the ?-transformation by which the highest and lowest reliability achievable can be determined for a configuration using components with specified reliabilities. As a by-product we become able to pinpoint the statistical relationships that give rise to highest and lowest system reliabilities.     

Improving Reconfigurable Systems Reliability by Combining Periodical Test and Redundancy Techniques: A Case Study

This paper revises and introduces to the field of reconfigurable computer systems, some traditional techniques used in the fields of fault-tolerance and testing of digital circuits. The target area is that of on-board spacecraft electronics, as this class of application is a good candidate for the use of reconfigurable computing technology. Fault tolerant strategies are used in order for the system to adapt itself to the severe conditions found in space. In addition, the paper describes some problems and possible solutions for the use of reconfigurable components, based on programmable logic, in space applications.     

Reliability of a Repairable Multicomponent System with Redundancy in Parallel

Consider a multicomponent system consisting of two series subsystems. One contains identical components connected in parallel, while the other has nonalike components connected in series. Each component has constant hazard rate, while the subsequent repairs follow some general distributions. The supplementary variable technique developed by Kielson and Kooharian [1] and the phase technique are used to obtain the various time-dependent and steady-state solutions for the system. A numerical illustration compares the effect of two repair policies on the behavior of the system. The optimum number of components connected in parallel is obtained.     

On Standby Redundancy with Delayed Repair

This paper derives a) the Laplace-Stieltjes transform of the time-to-system-failure distribution, and b) the mean time-to-system-failure. The system consists of several elements with one repair facility which remains idle until a queue of failed units is built up.     

Redundancy Allocation for Series-Parallel Systems Using Integer Linear Programming

We consider the problem of maximizing the reliability of a series-parallel system given cost and weight constraints on the system. The number of components in each subsystem, and the choice of components are the decision variables. In this paper, we propose an integer linear programming approach that gives an approximate feasible solution, close to the optimal solution, together with an upper bound on the optimal reliability. We show that integer linear programming is a useful approach for solving this reliability problem. The mathematical programming model is relatively simple. Its implementation is immediate by using a mathematical programming language, and integer linear programming software. And the computational experiments show that the performance of this approach is excellent based on a comparison with previous results.      

面向对象的分布式系统的组件聚合

用预制的组件建立分布式系统需要有效的聚合方法。从组件体系、组件本身和分布式对象的基础结构三方面来分离组件的相关性，使用端口和链接使组件的核心功能从组件通信机制中隔离出来，并且桥接它们之间的间隙。     

On the Stability of Announced Retransmission Random Access Systems

A finite user model for stability analysis of announced retransmission random access (ARRA) systems is presented. It is shown that as in other ALOHA-type random access protocols, bistable behavior and saturation can occur unless a suitably long retransmission delay is used. The higher expected delay associated with an unconditionally stable nonadaptive system can be avoided by adaptively varying retransmission parameters with system backlog. Optimal retransmission control (ORC) policies of this type are derived and evaluated.     

On Determining the Reliability of Protective Relay Systems

This paper lays the ground work for the statistical determination of the reliability of protective relay systems found in electric power systems. The reliability problem has two conflicting requirements: 1) failure to operate in the presence of a fault and 2) unnecessary operation when a fault occurs that the relay or relay system was set to ignore. It is not often treated in reliability literature.     

Reliability Improvement for Simplex Communication Systems with Multiple Channels

The reliability of a communication system can be improved by using channel coding. Complex coding and decoding are often required to achieve high performance. An alternative approach is channel redundancy in which the same information is transmitted over two or more channels at the same time. In this way, the coding complexity required to achieve a given error probability can be appreciably reduced. However, a decoder is required for each channel. This paper describes a method which uses channel redundancy to obtain higher performance compared to similar systems and requires only one channel decoder.     

Kalman Predictive Redundancy System for Fault Tolerance of Safety-Critical Systems

The dependence of intelligent vehicles on electronic devices is rapidly increasing the concern over fault tolerance due to safety issues. For example, an x-by-wire system, such as electromechanical brake system in which rigid mechanical components are replaced with dynamically configurable electronic elements, should be fault-tolerant because a critical failure could arise without warning. Therefore, in order to guarantee the reliability of safety-critical systems, fault-tolerant functions have been studied in detail. This paper presents a Kalman predictive redundancy system with a fault-detection algorithm using the Kalman filter that can remove the effect of faults. This paper also describes the detailed implementation of such a system using an embedded microcontroller to demonstrate that the Kalman predictive redundancy system outperforms well-known average and median voters. The experimental results show that the Kalman predictive redundancy system can ensure the fault-tolerance of safety-critical systems such as x-by-wire systems.      

Multiuser MIMO Systems with Random Transmit Beamforming

This paper considers the wireless downlink transmissions in a single cell environment, for which the base station (BS) is assumed to schedule its transmission to each mobile station (MS) on a time-slot basis. Only one MS is selected for transmission during each time-slot and the selected MS possibly changes from one time-slot to another. This transmission scheme is thus referred to as dynamic time-division multiple-access (D-TDMA). Random transmit beamforming with the feedback of effective signal-to-noise ratio (ESNR) was proposed by Viswanath and Tse [IEEE Transactions on Information Theory, Vol. 48, No. 6, pp. 1277–1294, 2002] for D-TDMA-based systems in which multiple transmit antennas are equipped at the BS but only single receive antenna is equipped at each MS, or the so-called “MISO” systems. It was also shown in [Viswanath and Tse, 2002] that when the number of MSs in the system becomes large, the system throughput achieved by random transmit beamforming converges to that by coherent transmit beamforming which, however, requires the complete channel state information (CSI) of each MS at the BS. This paper extends upon the work in [Viswanath and Tse, 2002] to a more general scenario for which multiple transmit antennas and multiple receive antennas are equipped at the BS and each MS, respectively, or the so-called “MIMO” systems. We also consider several linear and nonlinear receiver structures and propose novel power allocation schemes to further improve the achievable system throughput. The throughput performance of the proposed receivers and power allocations schemes is compared through computer simulations and their fast convergence to the system throughput by coherent transmit beamforming is demonstrated.

三模冗余演化自修复系统设计及可靠性分析

将演化硬件与TMR技术相结合在系统级层面设计并实现了一款ETMR系统,并以马尔可夫过程理论为基础探讨了其可靠性规律.发现在任意区间上,ETMR较之单模和TMR系统具有较高可靠性,同时指出修复率与故障率比值是影响ETMR系统可靠度的主要因素,且比值越大其可靠度接近于1的区间跨度越大.系统构建方法及所得结论对于将ETMR系统应用于具体工程实践具有一定的启发和指导作用.     

Reliability of Systems with Limited Repairs

Reliability is the probability that a system functions according to specifications over a given period of time. During this period, system specifications may allow failures and repairs to occur. This paper considers systems with specifications which limit the repair process. Such systems place a limitation on either the repair duration or the number of repairs. For example, a system controlling a real-time process may go down, be repaired, and continue proper control as long as the repair duration does not exceed a specified bound. Otherwise, the system fails. We model and analyze systems with three different types of limited repairs: 1) Bounded repair time, 2) Bounded cumulative repair time, and 3) Bounded number of repairs. Examples of such models exist in real-time process control, shock models, transaction processing, and maintenance models. For each of the three types of systems with limited repairs, we derive the distributions and the mean values of the system lifetime, the cumulative operational time, and the largest continuous operational time before a complete system failure. We also consider the execution of a task on such systems. The task is preempted upon the occurence of a failure, and is resumed or repeated after repair. The probability of completion of a task with a given work requirement in the three limited downtime scenarios is derived. We study the effect of preemptive-resume versus preemptive-repeat failures on the probability of task completion.     

Reliability of Systems with Standby Components

A method is introduced for approximating the reliability of a large complex system with standby components. It is done by substituting an approximate simple model for the more complex system. Each part of the model has a simple formula for its reliability.