Showing papers on "Control reconfiguration published in 1984"

Replication methods for abstract data types

Abstract: Replication can enhance the availability of data in a distributed system. This thesis introduces a new method for managing replicated data. We propose new techniques to address four problems associated with replication: (i) the representation and manipulation of replicated data, (ii) concurrency control, (iii) on-the-fly reconfiguration, and (iv) enhancing availability in the presence of partitions. Unlike many methods that support replication only for uninterpreted files, our method makes use of type-specific properties of objects (such as sets, queues, or directories) to provide more effective replication. Associated with each operation of the data type is a set of quorums, which are collections of sites whose cooperation suffices to execute the operation. An analysis of the algebraic structure of the data type is used to derive a set of constraints on quorum intersections. Any choice of quorums that satisfies these constraints yields a correct implementation, and it can be shown that no smaller set of constraints guarantees correctness. By taking advantage of type-specific properties in a general and systematic way, our method can realize a wider range of availability properties, more concurrency, more flexible reconfiguration, and better tolerance of partitions than existing replication methods.

Fault diagnostic distributed processing method and system

Abstract: In a distributed processing system having a plurality of interconnected subsystems of equal level, each subsystem operates to diagnose faults in other subsystems and protects its own subsystem based on the diagnosis of the faults of the other subsystems. The subsystems may be network control processors connected to common signal transmission lines, each of which carries major and minor loop check messages used to detect the faults in the other network control processors and constitutes a bypass route to protect its own unit when the fault occurs. If a transient fault occurs in the systems, an indication of the degree of the transient fault is stored and a possibility that the transient fault will change to a permanent fault is determined based on a time variation of the degree of the fault. If it is determined that the transient fault will change to a permanent fault, it is indicated to a man-machine system. In this manner, a loop transmission system which can be readily prediction-diagnosed for a fault is provided. In a second embodiment, means for calculating a feedback rate of a signal sent out to the transmission line and means for calculating the degree of fault on the transmission line based on the feedback rate calculated by the calculation means are provided.

Method for managing redundant resources in a complex avionics communication system

Abstract: A digital computer based system for managing a plurality of redundant sig processing equipment in a complex avionics system provides fast reconfiguration of the signal processing equipment to add, delete, or modify signal processing functions. A single user may thereby control a very large number of signal processing functions for communication, navigation, and identification from a single input/output device. The system utilizes a data base thereby making additions or deletions of equipment easily achievable.

Modular article processing machine and method of article handling therein

Abstract: Automated article processing, particularly semiconductor wafer processing, is accomplished in a modular article processing machine. The design of the machine allows easy reconfiguration between single and multiple processing station systems. Articles are handled according to a method which easily accommodates the various configurations of the machine and which provides efficient throughput. The machine includes a number of electromechanical and pneumatic systems under the control of at least one microprocessor. Machine state knowledge necessary for startup in the midst of operation, such as following a power interruption, is provided by a mechanical counter indexed at the completion of each stage of operation by the microprocessor controller.

Investigation of control law reconfigurations to accommodate a control element failure on a commercial airplane

Abstract: The ability of a pilot to reconfigure the control surfaces on an airplane after a failure, allowing the airplane to recover to a safe condition, becomes more difficult with increasing airplane complexity. Techniques are needed to stabilize and control the airplane immediately after a failure, allowing the pilot more time to make longer range decisions. This paper presents a baseline design of a discrete multivariable control law using four controls for the longitudinal channel of a B-737. Non-reconfigured and reconfigured control laws are then evaluated, both analytically and by means of a digital airplane simulation, for three individual control element failures (stabilizer, elevator, spoilers). The simulation results are used to evaluate the effectiveness of the control reconfiguration on tracking ability during the approach and landing phase of flight with severe windshear and turbulence disturbing the airplane dynamics.

Fault Tolerance in Continuous Process Control

Abstract: Increasing the reliability of continuous process control systems means choosing a fault tolerance technique that matches computer hardware capabilities, as well as applications.

Control system reconfiguration

Abstract: The problem of reconfiguring a control system to accommodate the failure of a sensor or actuator is discussed in the context of several different system configurations. First, some ground rules under which the reconfiguration algorithms are to function are established. A variety of control system configurations is then considered, and it is found that the approach to reconfiguration is obvious in some cases but not clear in others. Several possible strategies for reconfiguration, applicable to different situations, are examined.

Flight Control System Reconfiguration Design Using Quantitative Feedback Theory.

Abstract: : Quantitative theory is used to develop control laws for the AFTI/F-16 with a reconfigurable flight control system. Compensators are synthesized to control pitch rate and roll rate through individually controlled elevators and flaperons. Robust control of these variables is required over a larger portion of the flight envelope despite flight control surface failures. Linearized aerodynamic data are used to develop the aircraft model in state-variable format. The longitudinal and lateral-directional equations are coupled in the control matrix. Individual control of the elevators and flaperons is obtained by dividing the dimensionalized control derivatives for a control surface pair in half and assigning each surface of the pair one-half of the total derivative value. The system with individually controlled surfaces represents a four input-two output system which is transformed into an equivalent two input-two output system for each control surface configuration and flight condition. Quantitative feedback theory is then applied to the equivalent systems. Originator-supplied keywords included: Inherent Reconfiguration; Loop Transmission; Flight control Systems; Quantitative Feedback Theory; Control Systems; Computer Programs; Theses.

Fault Tolerance in Regular Network Architectures

Abstract: Computer systems with large numbers of processors pose serious reliability problems. One solution is to build redundant communication paths and dynamic reconfiguration into network designs.

A new high-speed controller with simple program language for the control of variable-speed converter-fed ac-drives

Abstract: This paper presents a new microprocessor-based high-speed controller with a simple program language for the control of various kinds of converter-fed ac-drives. Its applications as a flexible controller of different drives is described. From the example of the current control loop the striking processing speed of the controller is shown.

Digital feedwater controller for a BWR: a conceptual design study

Abstract: The requirements for the replacement of an existing analog controller with a highly reliable microprocessor based digital controller were developed for the feedwater control system of the Monticello boiling water reactor. Based on an analysis of these requirements, a preliminary hardware and software design is described that uses a fault-tolerant dual-redundant microprocessor architecture with a design mission time of 10 years without loss of controller function. Examination of the system reliability requirements shows that a signal validation capability should be provided in the microprocessor's software to provide automatic controller reconfiguration in the event of a failure of the BWR water level or feedwater instrumentation. The preliminary design was validated by a simulation study of the proposed digital controller. The results of the simulation showed that a significant improvement in BWR water level control can be provided with the digital feedwater controller.

Artificial Intelligence Theory and Reconfigurable Control Systems.

Abstract: : The principal topic of research in this effort was the development of analysis and design methods for fault-tolerant control systems, using artificial intelligence concepts to screen failure hypotheses, and more conventional control theory for reconfiguration and actual control. Methods developed include new graphical presentations of logic trees and signal dependency graphs, procedures for translating expert systems from LISP to Pascal, the definition of performance metrics for real-time expert systems, a Control Equation Parser computer program for computer-aided control system design, and a control- reconfiguration strategy based on proportional-integral implicit model- following. A Rule-Based Flight Control System for a tandem-rotor helicopter, implemented with parallel microprocessors and operating in real time, was developed in the course of this research. This task made use of the Princeton Rule-Based Controller, a unique software architecture for combining procedural and symbolic processing. The knowledge base is developed in the LISP computer language and is translated with the inference engine into the Pascal language. The ease with which Pascal code can be embedded in the knowledge-base structure makes this a highly suitable tool for task and algorithm scheduling.

An uniform approach to the operating system in fault-tolerant distributed computer systems

Abstract: In the paper a formal model of the fault-tolerant distributed computer system with the possibility of reconfiguration is considered. A fault-tolerant distributed computer system model from hardware viewpoint forms a fault-tolerant net, in which concurrent algorithms are performed. Due to uniform criteria of reconfigurations and interactions, an uniform analysis, synthesis and optimization is possible. Next the main idea of the operating system for the above systems has been described.

Fibre-optic local-area network with arbitrary topology

Abstract: The lack of satisfactory passive connectors, of standardisation in fibre-optic devices and the unidirectional light transmission employed in most fibre links prohibits the direct translation of networking techniques from the better developed wire or cable systems. A point-to-point network with nodes connected in an arbitrary fashion can provide an ideal solution to these problems while maintaining high network reliability and permitting easy reconfiguration, but has associated problems in the routing of the data. A possible solution is to use the flood routing technique as proposed by Neff and Senzig in their Anarchy network. Unfortunately, this network exhibits very low channel utilisation and has packet looping problems. In the paper we discuss methods of removing the looping problem and then propose a modified Anarchy flood routing (MAFR) protocol, for which a simplified performance analysis and simulation studies indicate that better network performance can be achieved with little additional hardware. However, we believe that a hybrid flood routing scheme (HFR) involving MAFR and a virtual circuit approach will produce a better system.

VLSI Arrays for Pattern Recognition and Image Processing: I/O Bandwidth Considerations

Abstract: Very Large Scale Integration (VLSI) computing arrays for pattern recognition and image processing have received increasing attention in recent years. The computation speed of an array is often limited by the I/O bandwidth of the host system or the VLSI array. Reconfiguration techniques are used to restructure a computing array, so that successive functional computation steps can be carried out without the data leaving the array. Computation time is reduced, since with reconfiguration the limited I/O bandwidth affects only the first and last phases of the necessary computations.

REPLICA--A reconfigurable partitionable highly parallel computer architecture for active multi-sensory perception of 3-dimensional objects

Abstract: REPLICA is a special-purpose computer architecture for active multi-sensory perception of 3-D objects. Active multisensory perception of 3-D objects means the ability to manipulate and probe objects as well as to see, hear, and touch them, where the objects involved may be static, changing or in motion. It is becoming an important area in robotics research. In order to support active multi-sensory perception efficiently, the system must be highly parallel, reconfigurable, and partitionable. The ability to achieve these functional requirements depends strongly on the capabilities and flexibilities of the underlying interconnection networks. In this paper, the architecture of REPLICA is presented and a set of interconnection networks is proposed. This set consists of a capability-enhanced cross-bar switch for controller-processor communications and a set of bidirectional rings for processor-processor communications. This set of interconnection networks support the required flexibilities in partitioning and reconfiguration. The cost of these networks can also be kept low.

Muteam: a multimicroprocessor architecture with decentralized fault treatment

Abstract: MUTEAM is aimed at experimenting in the field of decentralized control policies for error treatment and resource management. This paper contains a brief discussion of the design philosophy, followed by a description of the hardware, operating system kernel and fault-tolerance mechanisms. The fault-treatment policies are then described. The hardware architecture is composed of a set of clusters: each cluster is a tightly-coupled multiprocessor. Within a cluster, specialized hardware is provided for memory protection and management, and for interprocessor communication. The kernel implements the run-time support for a csp-like, message-based concurrent programming language. The implemented prototype includes an integrated set of fault-tolerance mechanisms, inserted in the system programming language and run-time support, and in the physical architecture. These are used to develop a fault-treatment policy, consisting of separate phases of diagnosis, reconfiguration and recovery. All of these are executed by sets of parallel processes, without a supervisor entity. Diagnosis is provided, in particular by a set of dedicated processes, one of which runs in each computer element, while reconfiguration and recovery are obtained through instrumentation of the application code. 100 references.

Fault tolerant architectures for integrated aircraft electronics systems, task 2

Abstract: The architectural basis for an advanced fault tolerant on-board computer to succeed the current generation of fault tolerant computers is examined. The network error tolerant system architecture is studied with particular attention to intercluster configurations and communication protocols, and to refined reliability estimates. The diagnosis of faults, so that appropriate choices for reconfiguration can be made is discussed. The analysis relates particularly to the recognition of transient faults in a system with tasks at many levels of priority. The demand driven data-flow architecture, which appears to have possible application in fault tolerant systems is described and work investigating the feasibility of automatic generation of aircraft flight control programs from abstract specifications is reported.

A methodology for designing and modeling reconfigurable systems

Abstract: The problem of designing communicating systems with internal state and facilities for reconfiguration is considered. A technique for designing such systems, called dynamically reconfigurable systems, based on a data driven model is proposed. The data driven model uses undirected or partially directed graphs. The nodes of the graphs can represent the components of a concurrent system, modules of an operating system including local and global control elements, and modules of a knowledge-based expert systems. The arcs can represent interconnections between components or data paths for intermodule communication. Each node has a number of attributes including a distinct name, an operation, and a set of specifications describing its input and output arcs. Each arc also has a number of attributes including an arc name, arc type, and the maximum number of tokens the arc can carry. Each node has local memory to store the values of the node and arc attributes and executes in data driven manner. A configuration is an assignment of values to the attributes of the nodes and arcs. Special nodes, called configuration specifying nodes, can assign values to the attributes of nodes and arcs. This process is termed reconfiguration. Reconfiguration is based on the information gathered from the nodes using “snoop arcs.” A formal description of the technique and the execution of a graph are described. The issues related to what, when, and how to reconfigure are identified and resolved. Several reconfiguration strategies are presented using local information, global information, and a combination of the two. Problems arise when local and global requirements are in conflict. A conflict free approach to reconfiguration is presented. Dynamic systems that cannot be accurately modeled using Petri Nets can be modeled using the proposed technique. For example, the Cray-1S computer system has been modeled using the proposed methodology and its architecture analyzed to improve performance. The proposed improvements have been incorporated in the Cray-XMP computer.

Redundant command generator tracker control technique for self-repairing flight control systems

Abstract: The command generator tracker (CGT) technique is used to design an explicit model following scheme in which the stabilizing feedback control law is designed to be a redundant control law. The scheme is applicable to the selfrepairing flight control system concept. The A-7D DIGITAC aircraft linearized data, at one flight condition and one type of impairment, is employed to demonstrate the validity of the approach. The employment of a redundant control law will increase the survivability and operational reliability of the aircraft and will enhance its maintainability during the combat and peace time missions.

Fault Tolerant Computing in Real-Time Control

Abstract: This paper will examine the various strategies used in the design of fault tolerant systems for real-time control. In comparing these systems, we focus our attention on the coverage that they afford and the reliability that the they provide.