Showing papers on "Control reconfiguration published in 1991"

Stability of the pseudo-inverse method for reconfigurable control systems

Abstract: One of the key reconfigurable control methods, the pseudo-inverse method (PIM), is analysed and new insight is obtained which provides the theoretical basis for this practical approach. The main shortcoming of this method, the lack of stability guarantees, is pointed out and a new approach is proposed in which recent results on the stability robustness of linear systems are used to provide stability constraints for the solutions of the PIM. When the original PIM solution results in an unstable closed-loop system, the control redesign problem is treated as a constraint minimization problem. For single-input systems, a closed-form solution is presented; for multi-input systems, a near-optimal solution is found which maintains the stability of the closed-loop system.

Reconfigurable flight control via multiple model adaptive control methods

Abstract: An aircraft flight control system with reconfigurable capabilities is considered. A multiple model adaptive controller (MMAC) is shown to provide effective reconfigurability when subjected to single and double failures of sensors and/or actuators. A command generator tracker/proportional-plus-integral/Kalman filter (CGT/PI/KF) form of controller was chosen for each of the elemental controllers within the MMAC algorithm and each was designed via LQG synthesis to provide desirable vehicle behavior for a particular failure status of sensors and actuators. The MMAC performance is enhanced by an alternate computation of the MMAC hypothesis probabilities, use of maximum a posteriori probability (MAP) versus Bayesian form of the MAC (or a modified combination of both), and reduction of identification ambiguities through scalar residual monitoring for the case of sensor failures. >

Feeder reconfiguration for loss reduction: an application of distribution automation

Abstract: The authors present a comparison of various methods applied to feeder reconfiguration for loss minimization. A new linear programming method using transportation techniques and a new heuristic search method are proposed for comparison with a previously developed heuristic technique which was based on an optimal load flow analysis. The methods are compared on simulations of both a small feeder distribution system, and a larger system based on a model of a public utility commission 44 kV distribution system. This study indicates that linear programming, in the form of transportation algorithms, is not suitable for real-time application to feeder reconfiguration, whereas heuristic approaches, although not optimal, can provide substantial savings if properly formulated and are suitable for real-time implementation. >

Service restoration in distribution networks via network reconfiguration

Abstract: A description is presented of the principle and the implementation of a heuristic methodology to restore service to the isolated portions of a distribution system via network reconfiguration. The methodology determines a minimum possible number of switching operations needed to restore service to network branches that are isolated due to forced or scheduled outages. Major operating constraints are taken into account in the restoration. A computer program has been developed based on this methodology for use in operations planning of the PG&E distribution system. >

Accommodation of failures in the F-16 aircraft using adaptive control

Abstract: Surface and hardware failure affect the flight control system of the F-16 fighter aircraft. In the absence of failures and unpredictable changes, the controller, based on gain scheduling, performs very well and exhibits a good degree of robustness, even for high angles of attack. In order to accommodate for possible failure and maintain good performance characteristics, the control system is augmented with a hybrid adaptive linear quadratic control scheme. The augmented adaptive flight control system has the online capability for learning and accommodating to drastic changes in the aircraft dynamics due to surface or hardware failure. The proposed flight control system has been tested on the nonlinear model of the F-16 aircraft, and the simulation results demonstrate its ability to accommodate control failures and maintain good performance. >

Reconfigurable arrays by phase-only control

Abstract: Due to space or cost reasons, a single array antenna can be required to radiate more than one pattern, each pattern being selected by an electronic control, in which only the phase can be modified. A synthesis method for such a problem that is able to determine both the common amplitude and the various phases in an integrated way is presented. Moreover, the approach is flexible enough to take into account additional constraints and allows an efficient implementation. Some test cases showing the effectiveness of the method are presented. >

Intelligent failure-tolerant control

Abstract: An overview of failure-tolerant control is presented, focusing on the control of continuous-time dynamic systems (or plants) whose motions can be represented by integrals of nonlinear ordinary differential equations. Failure tolerance may be called upon to improve system reliability, maintainability, and survivability, and the issues attached to achieving these goals are examined. Robustness, which is required in some degree by all failure-tolerant systems, is discussed. The use of parallel redundancy is examined. Analytical redundancy, the principal functions of which are failure detection, failure identification, and control-system reconfiguration, is also considered. The use of expert systems and neural networks is discussed. >

Using distributed topology update and preplanned configurations to achieve trunk network survivability

Abstract: The authors present a new approach for trunk network survivability. This modular approach is intended for a telephone trunk network consisting of high-bandwidth fiber-optic links connected through reconfigurable digital cross-connect nodes. It works for both node and link failures. This approach comprises a distributed protocol with two parts. First, the surviving digital cross-connect nodes are caused to converge to an agreement on the topology (i.e., what is up and what is down). Second, based on the agreed topology and on a precomputed plan for that topology, the digital cross-connect nodes are reconfigured to restore as much call-carrying capacity as possible. The modularity of this approach comes from separating the problem of devising a distributed fault-tolerant protocol to determine what the failure is from the problem of designing a network reconfiguration for that failure. >

Automatic reconfiguration in Autonet

Abstract: Autonet is a switch-based local area network using 100 Mbit/s full-duplex point-to-point links. Crossbar switches are interconnected to other switches and to host controllers in an arbitrary pattern. Switch hardware uses the destination address in each packet to determine the proper outgoing link for the next step in the path from source to destination. Autonet automatically recalculates these forwarding paths in response to failures and additions of network components. This automatic reconfiguration allows the network to continue normal operation without need of human intervention. Reconfiguration occurs quickly enough that higher-level protocols are not disrupted. This paper describes the fault monitoring and topology acquisition mechanisms that are central to automatic reconfiguration in Autonet.

Method and apparatus for remote maintenance and error recovery in distributed data processing networks

Abstract: A method and apparatus for remote maintenance and error recovery for plural stations interconnected in a distributed network. A monitor application is established within selected stations within the network in a terminate and stay resident mode. The monitor application is then automatically invoked in response to error message, reconfiguration messages, or network status messages received at that station by listing the monitor application address within user appendages associated with such error messages or reconfiguration messages within the network interface of the station. An error message may be displayed and any selected application or procedure may then be invoked by the monitor application in an application independent manner. In one embodiment of the present invention, a station may be reset remotely in response to an error message or reconfiguration message by utilizing the monitor application and the station may then be directed to establish communication with a server device in order to update system software. This may be simply accomplished within a computer station utilizing a DOS operating system by merely altering the automatic execution batch file.

The power of reconfiguration

Abstract: This paper concerns the computational aspects of the reconfigurable network model. The computational power of the model is investigated under several network topologies and assuming several variants of the model. In particular, it is shown that there are reconfigurable machines based on simple network topologies, that are capable of solving large classes of problems in constant time. These classes depend on the kinds of switches assumed for the network nodes. Reconfigurable networks are also compared with various other models of parallel computation, like PRAM's and Branching Programs.

Method and apparatus for dynamically changing the configuration of a logically partitioned data processing system

Abstract: A request is made by a system in a first logical partition, within a logically partitioned data processing system, to dynamically change the I/O configuration of the host system in a way that affects a system in a second logical partition. The hypervisor intercepts the request, ensures the serialization of such dynamic I/O requests, and allows dynamic reconfiguration to proceed. Subsequently, the hypervisor determines the effect of the reconfiguration on the second partition, and notifies the second partition of the change.

A fault-tolerant FFT processor

Abstract: A scheme for concurrent fault detection by recomputing and a fault-tolerant FFT processor using the scheme are proposed. An FFT processor with perfect shuffle is considered. The realization of the processor is based on a linear cellular automaton (LCA) model having the constant-weight and equidistance properties. When a fault occurs in the processor, the fault is detected concurrently and the processor is reconfigured by replacing the faulty butterfly unit with a normal one according to the state of the processor. The reconfiguration can be made within a clock period by making a state transition based on the LCA model and by reconnecting the butterfly units according to the new state. The processor can be reconfigured quickly, so that it can be used for highly reliable real-time data processing systems. >

Reconfigurable SIMD massively parallel computers

Abstract: This paper is a brief introduction to a new class of computers, the reconfigurable massively parallel computer. Its most distinguishing feature is the utilization of the reconfigurability of the interconnection network to establish a network topology well mapped to the algorithm communication graph so that higher efficiency can be achieved, and to remove faulty processors from the network so that the system operation can be kept uninterrupted while maintaining the same or slightly degraded efficiency. Several existing reconfigurable single instruction multiple data (SIMD) parallel architectures and their reconfiguration mechanism are described, the effectiveness of algorithm mapping, through reconfiguration, is demonstrated, and fault-tolerant schemes via reconfiguration are discussed. >

Dynamic reconfiguration of distributed programs

Abstract: A general framework is developed for reconfiguring applications dynamically, where developers may alter the application without loss of service. After presenting the overall framework within which reconfiguration is possible, a description is given of the formal approach for programmers to capture the state of a process abstractly. An environment to support experimentation with dynamic reconfiguration is then described. >

Dynamic reconfiguration in distributed hard real-time systems

Abstract: The paper focuses on the problem of dynamic workload reconfiguration in distributed systems_ After the failure of a node, the processes that were allocated to that node must be redistributed among the remaining nodes. The main technique considered is process redundancy. After an overview of design issues and solving techniques, the relevant literature is discussed. Proposals are given for the methods to be used in the DEDOS project, with directions for further research.

New technique for aircraft flight control reconfiguration

Abstract: A particular algorithm is applied to the aircraft flight control reconfiguration problem. The determination of the desired control law, which can adapt in a very short period of time to major damage of a control surface, is obtained by making use of the recent control and response time histories. The estimated model of the damaged aircraft used in this technique is obtained by using a multiple model Kalman filtering approach. The model estimation and the control algorithm have been codified in a computer simulation program for a six degree-of-freedom aircraft model. The simulation results of the reconfiguration are presented.

Reconfigurable Massively Parallel Computers

Abstract: Reconfigurable massively parallel computers polymorphic VLSI arrays with distributed control implementation and application of A gated-connection network in image understanding reconfiguration in the low and intermediate levels of the image understanding architecture reconfigurable arrays using local autonomy embedding pyramid into mesh arrays hypercube - a reconfigurable mesh arrays for digital signal processing functions - fault tolerance and functional reconfiguration fault-tolerant rectangular array processors via reconfiguration.

An adaptive hardware machine architecture and compiler for dynamic processor reconfiguration

Abstract: Substantial gains can be achieved by allowing the configuration and fundamental operations of a processor to adapt to a user's program. A method is presented for improving the performance of many computationally intensive tasks by extracting information at compile-time to synthesize new operations that augment the functionality of a core processor. The newly synthesized operations are targeted to RAM-based reconfigurable logic located within the processor. A proof-of-concept system called PLADO, consisting of a C configuration compiler and a hardware platform, is presented. Computation and performance results confirm the concept viability, and demonstrate significant speed-up. >

Model-based reconfiguration: toward an integration with diagnosis

Abstract: We extend Reiter's general theory of model-based diagnosis [Reiter, 1987] to a theory of reconfiguration. The generality of Reiter's theory readily supports an extension in which the problem of reconfiguration is viewed as a close analogue of the problem of diagnosis. Using a reconfiguration predicate rcfg analogous to the abnormality predicate ab, we formulate a strategy for reconfiguration by transforming that for diagnosis. A benefit of this approach is that algorithms for diagnosis can be exploited as algorithms for reconfiguration, thereby promoting an integrated approach to fault detection, identification, and reconfiguration.

Reconfiguration in a cellular communications network

Abstract: A method and apparatus for performing reconfiguration of a cellular network is provided. Cell parameters of affected mobile switching centers in the network are copied to a database, and the copied parameters are stored. A set of proposed changes to the stored parameters are prepared and the consistency of the prepared set of proposed changes is verified. Any necessary alterations to the set of proposed changes responsive to the verification are made and the verified set of proposed changes are copied to the affected mobile switching centers. The verified set of proposed changes are then introduced into the network. Additionally, at all times, an up-to-date image of all the cell parameters in all the mobile switching centers in the network is maintained in a system parameter database.

Gracefully degradable disk arrays

Abstract: The problem of designing fault-tolerant disk arrays that are not susceptible to 100% load increases on the functional disks when one of the disks in the system fails is addressed. A technique that combines the advantages of parity schemes and the traditional dual copy methods and offers a wide variety of options in providing fault-tolerance is proposed. A theoretical framework for solving the problem is presented and a number of constructive techniques are proposed. By utilizing the same amount of hardware as the earlier methods but with a better data organization and a different reconstruction technique, the system yields better performance during a failure. Merging two parity groups as a reconfiguration strategy is shown to have a number of benefits, such as reduced hardware overhead and improved reliability. A combination of block designs and the proposed reconfiguration strategy results in a highly reliable disk array with the same or less overhead as the earlier approaches and better performance during a failure. >

Fault isolation and bypass reconfiguration unit

Abstract: A multiport access and reconfiguration unit for use in a dual token ring network is provided with three adapters (10,15,16) which in the presence of an internal fault establishes an isolated token ring which includes one of the adapters and the associated ports, to test and bypass the fault and operate the reconfigured ring with the other two adapters.

Adaptable method of managing jets and aerosurfaces for aerospace vehicle control

Abstract: An actuator selection procedure is presented that uses linear programming to optimally specify bounded aerosurface deflections and jet firings in response to differential torque and/or force commands. This method creates a highly adaptable interface to vehicle control logic by automatically providing intrinsic actuator decoupling, dynamic response to actuator reconfiguration, dynamic upper bound and objective specification, and the capability of coordinating hybrid operation with dissimilar actuators. The objective function minimized by the linear programming algorithm is adapted to realize several goals, i.e., discourage large aerosurface deflections, encourage the use of certain aerosurfaces (speedbrake, body flap) as a function of vehicle state, minimize drag, contribute to translational control, and adjust the balance between jet firings and aerosurface activity during hybrid operation. A vehicle model adapted from Space Shuttle aerodynamic data is employed in simulation examples that drive the actuator selection with a six-axis vehicle controller tracking a scheduled re-entry trajectory.

An efficient modular spare allocation scheme and its application to fault tolerant binary hypercubes

Abstract: Consideration is given to fault tolerant systems that are built from modules called fault tolerant basic blocks (FTBBs), where each module contains some primary nodes and some spare nodes Full spare utilization is achieved when each spare within an FTBB can replace any other primary or spare node in that FTBB This, however, may be prohibitively expensive for larger FTBBs Therefore, it is shown that for a given hardware overhead more reliable systems can be designed using bigger FTBBs without full spare utilization than using smaller FTBBs with full spare utilization Sufficient conditions for maximizing the reliability of a spare allocation strategy in an FTBB for a given hardware overhead are presented The proposed spare allocation strategy is applied to two fault tolerant reconfiguration schemes for binary hypercubes One scheme uses hardware switches to replace a faulty node, and the other scheme uses fault tolerant routing to bypass faulty nodes in the system and deliver messages to the destination node >

Method and system for managing an operating system definition of a dynamically modifiable i/o configuration

Abstract: An installation creates a source I/O definition file (IODF), defining a current system I/O configuration, and a target IODF, defining a future I/O configuration When the configuration definition is dynamically changed from the current to the target, a serialization mechanism--comprising a "device pin" technique and a "group serialization" technique to handle changed device group definitions--insures that data integrity is not lost on devices undergoing reconfiguration; and a change detection mechanism insures that changes to control structures affected by the dynamic reconfiguration, are noticed by programs accessing those control structures while the structures are changing

Efficient reconfiguration algorithms for degradable VLSI/WSI arrays

Abstract: A systematic method for reconfiguration in VLSI/WSI (wafer scale integration) arrays using the degradation approach for yield enhancement is presented. Based on the bipartite graph representation of faulty cells in a reconfigurable host array, the problem of finding a maximum fault-free target array is shown to be equivalent to finding a restricted independent set of vertices in the graph models. Three constraints on the row and column reconfigurability are considered. The complexity is analyzed and heuristic algorithms are developed for variations of the problem under the three constraints. These algorithms have been implemented in C and experimental results were collected which demonstrate the efficiency of the proposed approaches. >

Method of updating network reconfiguration information exchanged between a host computer and a communication control processor

Abstract: A method for use in a network having a plurality of host computers, at least one communication control processor (CCP) commonly connected to the host computers, and a plurality of resources connected to the CCP. According to the method, if a resource is to be added to or deleted from the network, an operator designates a reconfiguration directory including at least one reconfiguration designating data for defining a relation between the network and a resource to be changed. Each host computer is assigned a reconfiguration command. In response to this reconfiguration command, each host computer reconfigures its own network configuration definition information in accordance with the defined reconfiguration designating data within the designated reconfiguration directory. If the designated reconfiguration directory contains the reconfiguration designating data related to a resource to be connected to the CCP, a host computer operating as a master, issues a control command to the CCP in conformity with the reconfiguration designating data in order to reconfigure the network configuration definition information of the CCP.