Showing papers on "Redundancy (engineering) published in 1993"

Solving Bernstein's problem: a proposal for the development of coordinated movement by selection.

Abstract: In recent years, many established concepts in the theory of human motor development have undergone profound change, and our knowledge has increased greatly. Nevertheless, some outstanding problems remain unsolved. A central problem concerns the redundancy of effective movements, first pointed out by N. A. Bernstein. The human motor system is mechanically complex and can make use of a large number of degrees of freedom. The controlled operation of such a system requires a reduction of mechanical redundancy, effectively by reducing the number of degrees of freedom. More recent work has shown that this problem is hard to solve explicitly by computing solutions to the equations of motion of the system. Equally challenging to traditional computational approaches is the fact the motor systems show remarkable adaptability and flexibility in the presence of changing biomechanical properties of motor organs during development and when faced with different environmental conditions or tasks. Solutions to these problems would have a large impact on a variety of issues in child development. In this article, we stress the importance of the somatic selection of neuronal groups in maps for the progressive transformation of a primary movement repertoire into a set of motor synergies and adaptive action patterns. We present results from computer simulations of a simple motor system that works according to such selectional principles. This approach suggests a provisional solution to Bernstein's problem and provides new parameters to guide experimental approaches to the development of sensorimotor coordination.

Identifying redundancy in source code using fingerprints

Abstract: A prototype implementation of a mechanism that uses fingerprints to identify exact repetitions of text in large program source trees has been built and successfully applied to a legacy source of over 300 megabytes This prototype system has provided useful information as well as establishing the scalability of the technology The approach will form the basis of a suite of tools for the visualization and understanding of programs and will complement other approaches currently under investigation

TTP - A time-triggered protocol for fault-tolerant real-time systems

Abstract: The Time-Triggered Protocol (TTP), which is intended for use in distributed real-time control applications that require a high dependability and guaranteed timeliness, is discussed. It integrates all services that are required in the design of a fault-tolerant real-time system, such as predictable message transmission, message acknowledgment in group communication, clock synchronization, membership, rapid mode changes, redundancy management, and temporary blackout handling. It supports fault-tolerant configurations with replicated nodes and replicated communication channels. TTP provides these services with a small overhead so it can be used efficiently on twisted pair channels as well as on fiber optic networks.

AIRBUS A320/A330/A340 electrical flight controls - A family of fault-tolerant systems

Abstract: The digital electrical flight control system of the Airbus A320/A330/A340 is discussed. The A320 was the first civil aircraft equipped with such a system. It was certified and entered into service in the first quarter of 1988. The A330 and A340 have identical systems, closely related to the A320 system. These systems are built to very stringent dependability requirements both in terms of safety (the systems must not output erroneous signals) and availability. The basic building blocks are fail-safe control and monitoring computers. The control channel performs the function allocated to the computer (control of a control surface for example). The monitoring channel ensures that the control channel operates correctly. A high level of redundancy is built into the system. Special attention has been paid to possible external aggressions. The system is built to tolerate both hardware and software design faults. The A320 system is described together with the significant differences between the A320 and the A330/A340, and A320 in service experience.

Distributed data access system including a plurality of database access processors with one-for-N redundancy

Abstract: In a distributed data access system in which a plurality of computers maintain and provide access to a database of stock exchange information, 1-for-N redundancy is provided by operating one computer in a standby mode, while the other computers operate online. Each on-line computer provides access to the database to a predefined set of a geographically broad plurality of users. The set of users for any on-line computer is defined by user connectivity data structures that define connectivity between the user set and the computer. When a failure is detected in any one of the computers, the user connectivity data structures of that computer are provided to the standby computer, which then assumes all operations of the failed computer. An arbitrator computer facility observes the health and determines the status of each of the computers, including the standby computer, and controls the transfer of online status from a failed computer to the standby computer. The arbitrator computer facility is a pair of redundant computers, one of which executes the arbitration function and the other of which operates as a standby.

Aggregation in Natural Language Generation

Abstract: In this paper we address the problem of redundancy in text generation. Redundancy typically occurs when the material selected for communication contains information that is duplicated in the text, or else is so closely related that the reader can automatically infer one piece when reading another. Such redundant material is invariably removed by people, and ought to be removed by generator systems, to produce better quality text. We call the process of removing redundancy aggregation. In addressing the problem, three questions arise: Why do people object to redundancy? Which redundant portions are best removed? What mechanisms or rules are used to remove redundant information? In this paper we begin to answer the third question by identifying and describing the aggregation processes generators can use. We first survey the studies we have found on aspects of aggregation. We next outline a study we performed with human subjects. Finally, we define and describe eight aggregation strategies we identified, and discuss several associated issues and open questions.

Synthesis of timed asynchronous circuits

Abstract: The authors present a systematic procedure for synthesizing timed asynchronous circuits using timing constraints dictated by system integration, thereby facilitating natural interaction between synchronous and asynchronous circuits. Their timed circuits also tend to be more efficient, in both speed and area, compared with traditional asynchronous circuits. The synthesis procedure begins with a cyclic graph specification to which timing constraints can be added. First, the cyclic graph is unfolded into an infinite acyclic graph. Then, an analysis of two finite subgraphs of the infinite acyclic graph detects and removes redundancy in the original specification based on the given timing constraints. From this reduced specification, an implementation that is guaranteed to function correctly under the timing constraints is systematically synthesized. With practical circuit examples, it is demonstrated that the resulting timed implementation is significantly reduced in complexity compared with implementations previously derived using other methodologies. >

Redundancy identification/removal and test generation for sequential circuits using implicit state enumeration

Abstract: Finite state machine (FSM) verification based on implicit state enumeration can be extended to test generation and redundancy identification. The extended method constructs the product machine of two FSMs to be compared, and reachability analysis is performed by traversing the product machine to find any difference in I/O behavior. When an output difference is detected, the information obtained by reachability analysis is used to generate a test sequence. This method is complete, and it generates one of the shortest possible test sequences for a given fault. However, applying this method indiscriminately for all faults may result in unnecessary waste of computer resources. An efficient method based on reachability analysis of the fault-free machine (three-phase ATPG) in addition to the powerful but more resource-demanding product machine traversal is presented. The application of these algorithms to the problems of generating test sequences, identifying redundancies, and removing redundancies is reported. >

An on-line approach to coordinated mobility and manipulation

Abstract: The author presents simple and computationally efficient approach for online coordinated control of mobile robots consisting of a manipulator arm mounted on a mobile base. The effect of base mobility on the end-effector manipulability index is discussed. The base mobility and arm manipulation degrees of freedom are treated equally as the joints of a kinematically redundant composite robot. The redundancy introduced by the mobile base is exploited to satisfy a set of user-defined additional tasks during the end-effector motion. A simple online control scheme that allows the user to assign weighting factors to individual degrees-of-mobility and degrees-of-manipulation, as well as to each task specification, is proposed. The computational efficiency of the control algorithm makes it particularly suitable for real-time implementations. A computer simulation study for a spatial three-jointed manipulator mounted on a one degree-of-freedom mobile platform, which demonstrates the online coordination of mobility and manipulation, is presented. >

Optimization models for reliability of modular software systems

Abstract: The authors present optimization models for software systems that are developed using a modular design technique. Four different software structures are considered: one program, no redundancy; one program, with redundancy; multiple programs, no redundancy; and multiple programs, with redundancy. The optimization problems are solved by using the authors' version of established optimization methods. The practical usefulness of this study is to draw the attention of software practitioners to an existing methodology that may be used to make an optimal selection out of an available pool of modules with known reliability and cost. All four models maximize software reliability while ensuring that expenditures remain within available resources. The software manager is allowed to select the appropriate model for a given situation. >

Multi-level logic optimization by redundancy addition and removal

Abstract: A multilevel logic optimization technique is presented that is a generalization of redundancy removal and Boolean resubstitution. The network is optimized through iterative addition and deletion of redundant connections. With the use of the connection fault model, the problem of identifying connections that can be made without affecting the network's functionality is converted into the problem of identifying redundant connection faults. Efficient test generation algorithms can thus be applied directly. Techniques that can efficiently locate redundant wires and/or nodes after adding a redundant wire are also proposed. Experiment results on MCNC benchmark circuits show that, on average, a 16% reduction in gate count and a 20% reduction in connection count can be achieved at a low computational cost. The suggested technique can also be applied for timing optimization. >

Introducing redundancy in field programmable gate arrays

Abstract: A redundancy scheme and circuitry for field programmable gate arrays (FPGAs) are proposed. The scheme requires the modification of the wiring resource segmentation and the addition of spare rows and selector circuits. An improved yield gross product is quantitatively studied. The disadvantages caused by this architecture, such as an area overhead and speed degradation, are discussed. It is concluded that, in this redundancy scheme, the sufficient number of spare rows is one or two for practical cases and the gross yield product can be doubled at an early stage of production. The proposed scheme can be applicable to a wide range of FPGA architectures.

Low-power frequency-hopped spread spectrum reverse paging system

Abstract: An acknowledgement paging system is described which fits within the existing infrastructure of a paging network and which provides low cost manufacture and low power operation while still enabling the acknowledgement paging over long distances. The acknowledgement paging system consists of a standard paging transmitter and a plurality of remote paging units which respond to a page using frequency-hopped spread-spectrum differential bi-phase shift keying communications. The plurality of pagers are assigned to groups with each group being assigned a separate starting location in a common, repeating pseudo-random noise code which determines the frequency hops. The grouping of pagers minimizes the collisions of acknowledgment transmissions between groups and the enables a large number of paging units to operate within a single geographic area. The pagers include a special double loop PLL synthesizer to produce an accurate narrow band frequency and to change or hop frequencies in a rapid fashion. The base receiving unit employs special algorithms for retrieving very low power acknowledgement paging messages in a noisy environment by using data redundancy, data interleaving, soft decoding and error correction codes to strip the bi-phase-modulated, frequency-hopped spread-spectrum digital data transmitted from the remote pocket pagers. A history of the frequency and phase drift is used during reception of the acknowledgement messages to predict the phase and frequency drift of the encoded digital information to further reduce decoding error. Signal to noise ratios are determined for each frequency hop and relatively noisy hops are discarded or minimized in a soft decoding process based redundancy of data bits.

The problem of redundancy in movement control: the adaptive model theory approach.

Abstract: The problem of redundancy in movement control is encountered when one attempts to answer the question: How does the central nervous system (CNS) determine the pattern of neural activity required in some 5,000,000 descending motor fibres to control only 100-150 biomechanical degrees of freedom of movement? Mathematically this is equivalent to solving a set of simultaneous equations with many more unknowns than equations. This system of equations is redundant because it has an infinite number of possible solutions. The problem is solved by the neuronal circuitry hypothesized in Adaptive Model Theory (AMT). According to AMT, the CNS includes neuronal circuitry able to compute and maintain adaptively the accuracy of internal models of the reciprocal multivariable relationships between outgoing motor commands and their resulting sensory consequences. To identify these input-output relationships by means of regression analysis, correlations between the input signals have to be taken into account. For example, if the inputs are perfectly correlated, the model reduces to a virtual one-input system. In general, the number of inputs modelled equals the number of degrees of freedom encoded by the signals; that is, the number of independently varying (orthogonal) signals. The adaptive modelling circuitry proposed in AMT automatically tunes itself to extract independently varying sensory and motor signals before computing the dynamic relationships between them. Inverse models are employed during response execution to translate movements pre-planned as desired trajectories of these high-level sensory-feature signals into appropriately co-ordinated motor commands to send to the muscles. Since movement is pre-planned in terms of a number of orthogonalized sensory-feature signals equal to the number of degrees of freedom in the desired response, the problem of redundancy is solved and the correlation or co-ordination between motor-command signals is automatically introduced by the adaptive models.

Sequential logic optimization by redundancy addition and removal

Abstract: This paper presents a method of multi-level logic optimization for combinational and synchronous sequential logic. The circuits are optimized through iterative addition and removal of redundancies. Among the large number of possible connections that can be added, the proposed method can efficiently identify those connections that would create more redundancies and, thus, would result in a smaller network. This is done with the use of combinational and sequential ATPG techniques based up the concept of mandatory assignments. Experiments on ISCAS-85 combinational benchmark circuits show that best results are obtained for most of them. For sequential circuits, experimental results on MCNC FSM benchmarks and ISCAS-89 sequential benchmark circuits show that a significant amount of area reduction can be achieved beyond combinational optimization and sequential redundancy removal.

Investigating the applicability of Petri nets for rule-based system verification

Abstract: It is suggested that as rule-based system (RBS) technology gains wider acceptance, the need to create and maintain large knowledge bases will assume greater importance. Demonstrating a rule base to be free from error remains one of the obstacles to the adoption of this technology. An approach to RBS verification in which the system is modeled as a Petri net on which error detection is performed is presented. A set of propositions is formulated to locate errors of redundancy, conflict, circularity, and gaps in domain knowledge. Rigorous proofs of these propositions are provided. Difficulties in implementing a Petri net-based verifier and the potential restrictions of the applicability of this approach are discussed. >

Compliant motion control of kinematically redundant manipulators

Abstract: Two control schemes, termed extended hybrid control and extended impedance control, respectively, are proposed for compliant motion control of redundant manipulators. In the two control schemes, the basic compliant motion task is accomplished while the redundancy is utilized to realize some additional constraints that optimize any user-defined objective function. Some experimental results on a three-DOF planar redundant manipulator are presented to illustrate the two proposed schemes and demonstrate their capabilities for optimizing various objective functions. >

A heuristic method for solving redundancy optimization problems in complex systems

Abstract: The authors present a heuristic method for solving constrained redundancy optimization problems in complex systems. The proposed method allows excursions over a bounded infeasible region, which can alleviate the risks of being trapped at a local optimum. Computational results show that the method performs consistently better than other heuristic methods in terms of solution quality. If solution quality is of more concern and if one is willing to accept a moderate increase in computing time for better solutions, then the authors believe that this method is an attractive alternative to other heuristic methods. >

Event-based planning and control for multi-robot coordination

Abstract: A planning and control scheme for multi-robot coordination is presented. An event-based motion reference that drives the system to achieve the best possible coordination is introduced. The general task space is combined with the nonlinear feedback technique to design hybrid position/force controllers. To improve the force control performance, the dynamics of joint motors are taken into account. For a given task, a task projection operator can be found for each robot, with consideration of redundancy management. A distributed computing architecture is proposed for parallel implementation of this scheme. The event-based coordination scheme was experimentally implemented and tested for the coordinated control of two six-degree-of-freedom PUMA 560 robots with very good results. >

Motion control of 7-DOF arms: the configuration control approach

Abstract: Graphics simulation and real-time implementation of configuration control schemes for a redundant seven-degree-of-freedom (7-DOF) Robotics Research arm are described. The arm kinematics and motion control schemes are described briefly. This is followed by a description of a graphics simulation environment for 7-DOF arm control on the Silicon Graphics IRIS Workstation. Computer simulation results are presented to demonstrate elbow control, collision avoidance, and optimal joint movement as redundancy resolution goals. The laboratory setup for experimental validation of motion control of the 7-DOF Robotics Research arm is then described. The configuration control approach is implemented on a Motorola-68020/VME-bus-based real-time controller, with elbow positioning for redundancy resolution. Experimental results demonstrate the efficacy of configuration control for real-time control. >

Exploiting nonholonomic redundancy of free-flying space robots

Abstract: Nonholonomic redundancy is an intrinsic property of nonholonomic mechanical systems. A free-flying space robot is a nonholonomic mechanical system, and exhibits the presence of nonholonomic redundancy even in the absence of ordinary kinematic redundancy. Like ordinary kinematic redundancy, nonholonomic redundancy can also be utilized while planning trajectories for the system. In the paper, a trajectory planning scheme for a 6-DOF space robot is developed in which nonholonomic redundancy for avoiding joint limits and obstacles is utilized. >

Method of making a 3-dimensional programmable antifuse for integrated circuits

Abstract: The invention is directed to a concept to use a 3-dimensional DRAM capacitor as a one-time non-volatile programming element (programmable antifuse) to make redundancy repair and/or to select other options on a DRAM. The programmable element of the present invention provides some significant advantages, such as a lower programming voltage, which allows use of the DRAM's existing operating supply, and requiring only half of the operating voltage to test the element once programming is accomplished. The lower programming voltage allows for redundancy repair of defective DRAM cells (or selecting other options) to be made after the DRAM die is packaged including after it is installed at a customer's site.

Functional redundancy in mitotic force generation.

Abstract: HE pushing and pulling forces that characterize the rocess of mitosis have fascinated and frustrated bioloists for over a century. While considerable progress has been made in understanding how these forces are used in mitosis, the nature of the molecules that generate the forces has remained obscure. Several recent papers (Hoyt et al., 1992; Roofet al., 1992; Saunders and Hoyt, 1992), including one in this issue of The Journal of Cell Biology (O'Cormell et al., 1993), have demonstrated that members of the kinesin superfamily of microtubule motors are likely to generate some of these forces. Intriguingly, the functions of some of these molecules are nonessential. Coupled with recent demonstrations that dynein (Pfarr et al., 1990; Steuer et al., 1990) and microtubule depolymerization (Koshland et al., 1988; Coue et al., 1991) could also produce spindle forces, these observations raise the possibility that spindle force generation is a highly redundant process. Three of the most obvious mitotic movements and forces occur during prophase, metaphase, and anaphase (reviewed in McIntosh and Pfarr, 1991). First, during prophase, the newly duplicated spindle poles or centrosomes separate to form the bipolar mitotic spindle. Second, during anaphase, chromosomes move to the spindle poles as a result of pnlling forces generated between the chromosomes and the spindle poles. At metaphase, when chromosomes are aligned at the middle of the spindle, a similar force may also cause poles to be pulled towards one another (see Fig. 1). Third, also during anaphase, spindle poles separate from one another as the spindle elongates. This movement appears to be largely driven by forces intrinsic to the spindle that push the spindle poles apart. This force may also counterbalance the force generated between chromosomes and poles at metaphase, and thus keep the spindle from collapsing. All of these forces may, at least in part, be generated by members of the kinesin superfamily of proteins. The kinesin superfamily was defined by its founding member, the kinesin heavy chain, which is the principal component of the microtubule-dependent motor protein kinesin (Vale et al., 1985). This protein was first found in squid axoplasm but was subsequently found to be virtually ubiquitous, which led to the view that kinesin itself might produce the force driving some of the various mitotic movements (reviewed in Sawin and Scholey, 1991). While this view could still have some validity, the bulk of recent evidence suggests that kinesin itself may not play a role in mitosis. Instead, a group of proteins distantly related to kinesin heavy chain, called kinesin-like proteins or kinesin-related proteins, appear to play key roles in mitosis. These proteins are all related to kinesin heavy chain by virtue of having substantial sequence similarity only to the motor region of kinesin heavy chain. Interestingly, these proteins each have unique \"tail\" domains attached to the putative motor domain. These tail domains may confer functional diversity on this large superfamily of proteins (reviewed in Goldstein, 1991). In Saccharomyces cerevisiae three genes required for norreal mitosis have been found to encode members of the kinesin superfamlly. The first of these, KAR3, was identified by mutations that interfere with the process of nuclear movement during zygote formation in this organism (Polaina and Conde, 1982; Meluh and Rose, 1990). However, in addition to a role in this process, K A ~ was also inferred to have a nonessential (redundant?) role in mitosis, based on its slow growth, production of nonviable cells, and accumulation of large budded cells with short mitotic spindles. The other two genes are called CIN8 and KIP1. CIN8 was first identified by mutations that cause elevated rates of chromosome loss (Hoyt et al., 1990, 1992); C/N8 was also independently found because it caused synthetic lethality in combination with KIP1 deletions, which have no phenotype of their own (Roof et al., 1992). KIP1 was found in a polymerase chain reaction (PCR)-based search for genes encoding members of the kinesin superfamily (Roof et al., 1992). KIP1 was also found as a gene that could rescue the defect in CIN8 mutants when overexpressed (Hoyt et al., 1992). As just mentioned, KIP1 deletions have no phenotype when present as single mutants, while CIN8 deletions have a mild chromosome loss phenotype at 26~ and a severe chromosome loss phenotype and viability defect at 37~ Had KAR3, CINS, and KIP1 only been studied in isolation, one would have concluded that each of these genes encode motor proteins that play an unimportant role in mitosis, since deletions of each gene are viable (at least at 26~ Producing double and triple mutants among these, however, demolished such a view. For example, the consequence of removing both CIN8 and KIP1 function before spindle assembly is to block the separation of spindle poles during mitosis such that a bipolar spindle is not formed (Hoyt et al., 1992; Roof et al., 1992). Removing CIN8 and KIP] function after spindle assembly, but before anaphase starts, leads to spindle collapse (Saunders and Hoyt, 1992). A surprise comes when KAR3 CIN8 KIP1 triple mutants are produced. These triple mutants are healthier than C1N8 KIPI double mutants, at least in part because the removal of A R 3 function partially rescues the spindle collapse phenotype seen in CIN8 KIP1 double mutants (Saunders and Hoyt, 1992). Thus, KAR3 function somehow compensates for the loss of

Joint trajectory generation for redundant robots in an environment with obstacles

Abstract: Collision avoidance is an absolutely essential requirement for a robot to complete a task in an environment with obstacles. For kinematically redundant robots, collision avoidance can be achieved by making full use of the redundancy. In this article, the problem of determining collision-free joint space trajectories for redundant robots in an environment with multiple obstacles is considered, and the “command generator” approach is employed to generate such trajectories. In this approach, a nondifferentiable distance objective function is defined and is guaranteed to increase wherever possible along the trajectory through a vector in N(J), the null space of Jacobian matrix J. Algorithms that implement this nondifferentiable optimization problem are fully developed. It is shown that the proposed collision-free trajectory generation scheme is efficient and practical. Extensive simulation results of a four-link robot example are presented and analyzed.