Showing papers on "Redundancy (engineering) published in 1986"

Avoiding obstacles and resolving kinematic redundancy

Abstract: While obstacles in a robot workspace can effectively reduce the number of degrees of freedom, there need not be a corresponding loss of functionality for kinematically redundant mechanisms. In this paper, disk-like obstacles for a planar three-bar mechanism are classified. The extended Jacobian technique is used to implement an obstacle avoidance technique based on optimizing a distance criterion. The feasibility of applying multiple constraints or optimality criteria for resolving redundancy is investigated.

VLASIC: A Catastrophic Fault Yield Simulator for Integrated Circuits

Abstract: This paper describes the yield simulator VLASIC (VLSI Layout Simulation for Integrated Circuits). VLASIC is a Monte Carlo simulator that uses defect models and statistics to place random catastrophic point defects on a chip layout and determine what circuit faults, if any, have occurred. The defect models are described in tables, and so are readily extended to new processes or defect types. The defect statistical model is based on actual fabrication line data, and has not appeared before in the literature. The circuit fault information generated by VLASIC can be used to predict yield, optimize design rules, generate test vectors, evaluate redundancy, etc. A redundancy analysis system which uses these data is described, and an example of its use given.

Quantitative Approaches to Reliability Assessment in Pipe Networks

Abstract: Two quantitative approaches to the incorporation of reliability measures in the least‐cost design of looped water distribution networks are developed and assessed. Both approaches begin by obtaining an “optimal” layout design through linear programming. The first approach, addresses the probability of isolating a node through simultaneous failure of all links connected directly to that node. The second approach attempts to recognize redundancy by minimizing the deviations in the reliabilities of all pipes connected to each node within the network. In both cases, the probability of failure of individual links is modeled using the Poisson probability distribution. Comparison of the techniques suggests that minimizing the differences in the reliabilities of pipes connected to each node seems the most promising.

Standby redundancy in reliability - a review

Abstract: Redundancy is used to improve the reliability of a system beyond that obtained by redesigning the system or selecting better parts. This paper reviews the literature related to standby redundancy over the past ten years.

A closed-form solution for the control of manipulators with kinematic redundancy

Abstract: A closed-form equation for inverse kinematics of manipulators with redundancy is derived, using the Lagrangian multiplier method. The proposed equation is proved to provide the exact equilibrium state for the resolved motion method, and is shown to be a general expression that yields the extended Jacobian method. The repeatability problem in the resolved motion method does not exist in the proposed equation. The equation is demonstrated to give more accurate trajectories than the resolved motion method.

Contribution to control of redundant robotic manipulators in an environment withobstacles

Abstract: The redundancy of robot manipulators plays an important role in increasing their flexibility and versatility, especially in an environment with obstacles. In this paper, the redundancy is utilized for enabling collision-free motion for a given tra jectory of a manipulator hand. The calculation of the corre sponding trajectory in the space of joint coordinates is per formed using several performance criteria that take into account the vicinity of the obstacles. The advantages and shortcomings of the proposed algorithms are discussed. The implementation of the algorithms is real-time due to modest computational complexity.

Yield and performance enhancement through redundancy in VLSI and WSI multiprocessor systems

Abstract: New challenges have been brought to fault-tolerant computing and processor architecture research because of developments in IC technology. One emerging area is development of architectures, built by interconnecting a large number of processing elements on a single chip or wafer. Two important areas, related to such VLSI processor arrays, are the focus of this paper; they are fault-tolerance and yield improvement techniques. Fault tolerance in these VLSI processor arrays is of real practical significance; it provides for much-needed reliability improvement. Therefore, we first describe the underlying concepts of fault tolerance at work in these multiprocessor systems. These precepts are useful to then present certain techniques that will incorporate fault tolerance integrally into the design. In the second part of the paper we discuss models that evaluate how yield enhancement and reliability improvement may be achieved by certain fault-tolerant techniques.

Theoretical Foundation of Algebraic Optimization Utilizing Unnormalized Relations

Abstract: Unnormalized (NF2) relations, not conforming to the first normal form condition (1NF) of the relational model have been proposed recently for a variety of new applications. In this paper we extend NF2 relational theory in a way that it becomes possible to use NF2 relations as storage structures for conventional 1NF relational database interfaces. Physical clustering of precomputed joins can be achieved this way without introducing redundancy. However, applying transformation rules to internal relations straightforwardly, will still yield unnecessary join operations. With the equivalence rules introduced here we prove that efficient algebraic optimization can be performed using standard (1NF) techniques. Particularly, all redundant joins can be properly removed.

A state transition model for distributed query processing

Abstract: A state transition model for the optimization of query processing in a distributed database system is presented. The problem is parameterized by means of a state describing the amount of processing that has been performed at each site where the database is located. A state transition occurs each time a new join or semijoin is executed. Dynamic programming is used to compute recursively the costs of the states and the globally optimal solution, taking into account communication and local processing costs. The state transition model is general enough to account for the possibility of parallel processing among the various sites, as well as for redundancy in the database. The model also permits significant reductions of the necessary computations by taking advantage of simple additivity and site-uniformity properties of a cost model, and of clever strategies that improve on the basic dynamic programming algorithm.

Reliability Optimization Problems with Multiple Constraints

Abstract: This paper presents a class of reliability optimization problems with multiple-choice constraints. We assume that at least one design alternative can be chosen as redundancy for each subsystem. A 2-phase solution method is presented for solving these problems. In phase I, we decompose a problem into n subproblems. These subproblems can be solved by dynamic programming, independently. That is, these subproblems can be solved by parallelism. In phase II, we solve a 0-1 multiple-choice knapsack problem which is generated from phase I. We use a combinatorial tree which always satisfies the multiple-choice constraints. The 2-phase solution method is illustrated with a numerical example.

Redundancy enable/disable circuit

Abstract: A redundancy enable/disable circuit for enabling and disabling subsequently the use of redundant elements includes first through third P-channel MOS transistors, an N-channel MOS transistor, an enable fuse, and a disable fuse. The enable fuse is blown so as to enable the use of the redundant elements, and the disable fuse is blown subsequently to disable use of the redundant elements.

Synchronization of binary source codes (Corresp.)

Abstract: The problem of achieving synchronization for variable-length source codes is addressed through the use of self-synchronizing binary prefix-condition codes. Although our codes are suboptimal in the sense of minimum average codeword length, they have the advantages of being generated by an explicit constructive algorithm, having minimal additional redundancy compared with optimal codes-as little as one additional bit introduced into the least likely codeword for a large class of sources-and having statistical synchronizing performance that improves on that of the optimal code in many cases.

There is more than One Way to be Redundant: A Comparison of Alternatives for the Design and Use of Redundancy in Organizations

Abstract: This article extends Landau's work on redundancy in organizations. Three basic and two hybrid approaches to redundancy are described and compared. The types are explored in the context of redundancy as duplication, and also in the context of redundancy as overlap, with modifications as appropriate. The dynamics of duplication versus overlap are also explored. Issues regarding the "triggering" of redundancy, the difference between redundancy and the `fail-safe" mentality, and redundancy in the special case of secrecy concerns are also discussed.

GPS failure detection by autonomous means within the cockpit

Abstract: In civil aviation, it is desirable to be able to detect navigation system failures quickly and alert the pilot and crew accordingly. Also, while not absolutely necessary, it certainly would be simpler in the GPS case if the detection could be done autonomously within the cockpit rather than via a communication link with a network of monitoring stations on the ground. There is some redundancy in the GPS system, even if only four satellites are in view. This can be further enhanced with the addition of baro-altitude information, and it is the system redundancy that makes autonomous failure detection possible. The scheme used for failure detection in this investigation is the Magill adaptive filter, which is also known as the Multiple Model Estimation Algorithm (MMEA) in control theory. Preliminary results indicate that soft ramp-type satellite clock failures can be detected and identified in a relatively short time for the low dynamic environment that might be encountered in the high-altitude enroute situation. Failure detection is more difficult in the low-altitude nonprecision approach scenario, but preliminary results indicate that this can also be done.

Modular redundancy in a message passing system

Abstract: Modular redundancy in the form of replicated computations in a concurrent programming model consisting of communicating sequential processes is investigated. Some conditions are given which must always be verified to ensure correctness in the presence of nondeterminism. Then some implementations which satisfy the given conditions are proposed. This approach permits redundant systems to be robust with respect to failures in redundant processors, and also permits the use of software fault tolerance techniques such as N-version programming. The concurrent programming model which has been chosen is based on a set of active entities, i.e. processes, each running in a local protected environment. The processes interact using message passing only.

On Measuring the Complexity of Monitoring and Controlling Large-Scale Systems

Abstract: The complexity of monitoring and controlling a large-scale system, such as a communication network, is considered. Relevant literature is reviewed, with emphasis on both behavioral and nonbehavioral approaches to measuring complexity. A simulated large-scale network is described that is used in an experiment to assess the effect of network redundancy and number of systems levels on human fault-diagnosis performance. Experimental data are also used to evaluate two time-varying measures of task complexity (using analysis of variance and time-series analysis). The first measure is dependent on the structure of the system; the second measure is dependent on the strategy of the person controlling the system. Results suggest that this distinction is appropriate. In addition, results emphasize the different implications that complexity can have for normal system operation and human failure diagnosis performance. Although system design characteristics such as redundancy may help to avoid the short-term effects of failures, these same characteristics may have the dual effect of making the human supervisory controller's task more difficult.

Analysis of a Class of Recovery Procedures

Abstract: Recovery procedures involving time redundancy in the form of instruction retries and program rollbacks have proved to be very effective against transient failures in computer systems. A class of such recovery procedures is presented and analyzed here, and the parameters of each procedure are determined so that the system's operation is optimized. These procedures are then compared in order to select the most appropriate one for given system parameters.

Hierarchical burst communication system

Abstract: PURPOSE: To suppress the influence for the deterioration in a quality to a burst deficiency to a minimum by applying a hierarchization according to the contribution of the quality and a precedence according to the contribution of the quality and applying a proper redundancy suppressing technique in the respective hierarchies. CONSTITUTION: Input data 1a from a video data source 11 is divided into three hierarchies 2a∼2c, for instance, different in the contribution for the quality in a hierarchization part 12 and a redundancy suppression encoding proper for the respective hierarchies in view of the repercussion of the deterioration in the quality is applied. The encoded data 3a∼3c of the respective hierarchies 2a∼2c is once decoded in a reverse hierarchization part 14 and the decoded data 19 is compared with the input data 1a in a quality decision part 15. The contribution to all the quality is decided, a signal relating to the precedence is fed to a precedence applying part 16, and a precedence applied packet or burst 21 is outputted. COPYRIGHT: (C)1988,JPO&Japio

Emergency supply system for an aircraft control system

Abstract: An emergency supply system for maintaining the emergency flight control of a high-performance aircraft of aerodynamically unstable design having three energy systems, namely, two identical hydraulic systems, connected in parallel for redundancy, for actuation of the control surfaces of the aircraft required for its ability to fly, and an electric on-board system having at least one generator, a rechargeable battery and a non-rechargeable emergency battery, the three energy systems being interconnectible in terms of energy by a power transmission unit, and wherein the two hydraulic systems are divided into subsystems associated with single or several rudder functions which, if necessary, can be disconnected singly.

Formulations of Structural System Reliability

Abstract: Two formulations are developed for the determination of the reliability of general redundant structural systems. One is the failure mode approach, which is based on ways in which a structure may fail. The other is the stable configuration approach, which is based on the possible configurations in which a structure may carry an applied load. Conceptually, the stable configuration approach has the advantage over the failure mode approach in that neglecting possible configurations will be conservative, whereas neglecting potential failure modes will be unconservative. For a class of structures, in which the load effects on a surviving element never decrease with the failure of other elements (consistent redistribution), simplified formulations are obtained. Such simplifications for this type of structure result from the fact that the exact sequence in which the elements will fail is irrelevant. Results of the simplified formulations are conservative for structures in which the load effect on a member may be ...

On the existence of optimum cyclic burst-correcting codes

Abstract: It is shown that for each integer b \geq 1 infinitely many optimum cyclic b -burst-correcting codes exist, i.e., codes whose length n , redundancy r , and burst-correcting capability b , satisfy n = 2^{r-b+1} - 1 . Some optimum codes for b = 3, 4 , and 5 are also studied in detail.

A Triple Modular Redundancy Technique Providing Multiple-Bit Error Protection Without Using Extra Redundancy

Abstract: A well-known technique for providing tolerance against single hardware component failures is triplication of the component, called triple modular redundancy (TMR). In this paper a component is taken to be a processor-memory configuration where the memory is organized in a bit-sliced way. If voting is performed bitwise in an orthodox TMR configuration consisting of three of these components, failure of a complete component or failure of bit-slices not on corresponding positions in the memories can be tolerated. We present a TMR technique, not using more redundancy than orthodox TMR, that can tolerate the failure of arbitrary bit-slices (including those on corresponding positions) up to a certain amount. Additionally it can tolerate the failure of arbitrary bit-slices up to a certain amount whenever one component is known to be malfunctioning or whenever one component is disabled. This generalized TMR technique is described for processor-memory configurations processing 4-, 8-, and 16-bit words, respectively.

Method to reduce the sign bit extension in a multiplier that uses the modified Booth algorithm

Abstract: A technique that reduces the number of full adders that are used to implement the modified Booth algorithm is described. This technique is based on the need to extend the sign bit of the partial products and on the redundancy that is implicit in this operation.