Showing papers on "Control reconfiguration published in 2009"

Coordinated and Reconfigurable Vehicle Dynamics Control

Abstract: A coordinated reconfigurable vehicle dynamics control (CRVDC) system is achieved by high-level control of generalized forces/moment, distributed to the slip and slip angle of each tire by an innovative control allocation (CA) scheme. Utilizing control of individual tire slip and slip angles helps resolve the inherent tire force nonlinear constraints that otherwise may make the system more complex and computationally expensive. This in turn enables a real-time adaptable, computationally efficient accelerated fixed-point (AFP) method to improve the CA convergence rate when actuation saturates. Evaluation of the overall system is accomplished by simulation testing with a full-vehicle CarSim model under various adverse driving conditions, including scenarios where vehicle actuator failures occur. Comparison with several other vehicle control system approaches shows how the system operational envelope for CRVDC is significantly expanded in terms of vehicle global trajectory and planar motion responses.

Enhanced Modeling and Solution of Layered Queueing Networks

Abstract: Layered queues are a canonical form of extended queueing network for systems with nested multiple resource possession, in which successive depths of nesting define the layers. The model has been applied to most modern distributed systems, which use different kinds of client-server and master-slave relationships, and scales up well. The layered queueing network (LQN) model is described here in a unified fashion, including its many more extensions to match the semantics of sophisticated practical distributed and parallel systems. These include efficient representation of replicated services, parallel and quorum execution, and dependability analysis under failure and reconfiguration. The full LQN model is defined here and its solver is described. A substantial case study to an air traffic control system shows errors (compared to simulation) of a few percent. The LQN model is compared to other models and solutions, and is shown to cover all their features.

Vicis: a reliable network for unreliable silicon

Abstract: Process scaling has given designers billions of transistors to work with. As feature sizes near the atomic scale, extensive variation and wearout inevitably make margining uneconomical or impossible. The ElastIC project seeks to address this by creating a large-scale chip-multiprocessor that can self-diagnose, adapt, and heal. Creating large, flexible designs in this environment naturally lends itself to the repetitive nature of network-on-chip (NoC), but the loss of a single link or router will result in complete network failure. In this work we present Vicis, an ElastIC-style NoC that can tolerate the loss of many network components due to wearout induced hard faults. Vicis uses the inherent redundancy in the network and its routers in order to maintain correct operation while incurring a much lower area overhead than previously proposed N-modular redundancy (NMR) based solutions. Each router has a built-in-self-test (BIST) that diagnoses the locations of hard fault and runs a number of algorithms to best use ECC, port swapping, and a crossbar bypass bus to mitigate them. The routers work together to run distributed algorithms to solve network-wide problems as well, protecting the networking against critical failures in individual routers. In this work we show that with stuck-at fault rates as high as 1 in 2000 gates, Vicis will continue to operate with approximately half of its routers still functional and communicating.

Scalable and/or reconfigurable beamformer systems

Abstract: A scalable and/or reconfigurable true-time-delay analog beamformer system having a hierarchical distributed control architecture composed of an arbitrary number of reconfigurable and scalable units. The beamformer system may be applied to an antenna array with an arbitrary number of elements in a scalable manner and the configuration of the beamformer system may be implemented so that it is capable of reconfiguration by changing its beam-position mapping, either dynamically or at install-time. The number of beams or beam positions that are desired advantageously do not need to be known prior to the design or selection of the beamformer system.

Distribution Systems Reconfiguration Based on OPF Using Benders Decomposition

Abstract: This paper presents a new and efficient methodology for distribution network reconfiguration integrated with optimal power flow (OPF) based on a Benders decomposition approach. The objective minimizes power losses, load balancing among feeders, and is subject to constraints: capacity limit of branches, minimum and maximum power limits of substations or distributed generators, minimum deviation of bus voltages, and radial optimal operation of networks. A specific approach of the generalized Benders decomposition algorithm is applied to solve the problem. The formulation can be embedded under two stages: the first one is the master problem and is formulated as a mixed integer nonlinear programming problem. This stage determines the radial topology of the distribution network. The second stage is the slave problem and is formulated as a nonlinear programming problem. This stage is used to determine the feasibility of the Master problem solution by means of an OPF and provides information to formulate the linear Benders cuts that connect both problems. The model is programmed in the general algebraic modeling system. The effectiveness of the proposal is demonstrated through three examples extracted from the literature.

Run-time Partial Reconfiguration speed investigation and architectural design space exploration

Abstract: Run-time Partial Reconfiguration (PR) speed is significant in applications especially when fast IP core switching is required. In this paper, we propose to use Direct Memory Access (DMA), Master (MST) burst, and a dedicated Block RAM (BRAM) cache respectively to reduce the reconfiguration time. Based on the Xilinx PR technology and the Internal Configuration Access Port (ICAP) primitive in the FPGA fabric, we discuss multiple design architectures and thoroughly investigate their performance with measurements for different partial bitstream sizes. Compared to the reference OPB HWICAP and XPS HWICAP designs, experimental results showthatDMA HWICAP and MST HWICAP reduce the reconfiguration time by one order of magnitude, with little resource consumption overhead. The BRAM HWICAP design can even approach the reconfiguration speed limit of the ICAP primitive at the cost of large Block RAM utilization.

Terminal Sliding Mode Control for Spacecraft Formation Flying

Abstract: This paper considers the problem of relative motion control for spacecraft formation flying (SFF). Using terminal sliding mode technique, a relative position/velocity tracking control based on the nonlinear model is developed. The presented controller enables rapid formation reconfiguration with feasible fuel cost and strong robustness in the presence of uncertain but bounded disturbances. A nonlinear model with J2 disturbance and bounded uncertainties is used for dynamic simulation.

Current Sensor Fault Detection, Isolation, and Reconfiguration for Doubly Fed Induction Generators

Abstract: Fault tolerance is gaining growing interest to increase the reliability and availability of distributed energy sources. Current sensor fault detection, isolation, and reconfiguration are presented for a voltage-oriented controlled doubly fed induction generator, which is mainly used in wind turbines. The focus of this analysis is on the isolation of the faulty sensor and the actual reconfiguration. During a short period of open-loop operation, the fault is isolated by looking at residuals calculated from observed and measured signals. Then, replacement signals from observers are used to reconfigure the drive and reenter closed-loop control. Laboratory measurement results are included to prove that the proposed concept leads to good results.

Doubly Fed Induction Generator Model-Based Sensor Fault Detection and Control Loop Reconfiguration

Abstract: Fault tolerance is gaining interest as a means to increase the reliability and availability of distributed energy systems. In this paper, a voltage-oriented doubly fed induction generator, which is often used in wind turbines, is examined. Furthermore, current, voltage, and position sensor fault detection, isolation, and reconfiguration are presented. Machine operation is not interrupted. A bank of observers provides residuals for fault detection and replacement signals for the reconfiguration. Control is temporarily switched from closed loop into open-loop to decouple the drive from faulty sensor readings. During a short period of open-loop operation, the fault is isolated using parity equations. Replacement signals from observers are used to reconfigure the drive and reenter closed-loop control. There are no large transients in the current. Measurement results and stability analysis show good results.

Spin transfer torque (STT)-MRAM--based runtime reconfiguration FPGA circuit

Abstract: As the minimum fabrication technology of CMOS transistor shrink down to 90nm or below, the high standby power has become one of the major critical issues for the SRAM-based FPGA circuit due to the increasing leakage currents in the configuration memory. The integration of MRAM in FPGA instead of SRAM is one of the most promising solutions to overcome this issue, because its nonvolatility and high write/read speed allow to power down completely the logic blocks in “idle” states in the FPGA circuit. MRAM-based FPGA promises as well as some advanced reconfiguration methods such as runtime reconfiguration and multicontext configuration. However, the conventional MRAM technology based on field-induced magnetic switching (FIMS) writing approach consumes very high power, large circuit surface and produces high disturbance between memory cells. These drawbacks prevent FIMS-MRAM's further development in memory and logic circuit. Spin transfer torque (STT)-based MRAM is then evaluated to address these issues, some design techniques and novel computing architecture for FPGA logic circuits based on STT-MRAM technology are presented in this article. By using STMicroelectronics CMOS 90nm technology and a STT-MTJ spice model, some chip characteristic results as the programming latency and power have been calculated and simulated to demonstrate the expected performance of STT-MRAM based FPGA logic circuits.

FPGA partial reconfiguration via configuration scrubbing

Abstract: SRAM-based FPGA devices are susceptible to single event effects (SEE) including single event upsets (SEU) within the configuration memory. Configuration scrubbing along with TMR or other hardware redundancy techniques are often used to mitigate the effects of these SEUs. However, the use of traditional configuration scrubbing prevents the ability to reconfigure the FPGA dynamically or to perform partial reconfiguration. This paper presents a novel technique that allows partial reconfiguration to be used with configuration scrubbing. A self scrubber, utilizing a small portion of the FPGA, performs the necessary operations to reconfigure a portion of the design while continuously scrubbing the entire FPGA.

A cost-sensitive adaptation engine for server consolidation of multitier applications

Abstract: Virtualization-based server consolidation requires runtime resource reconfiguration to ensure adequate application isolation and performance, especially for multitier services that have dynamic, rapidly changing workloads and responsiveness requirements. While virtualization makes reconfiguration easy, indiscriminate use of adaptations such as VM replication, VM migration, and capacity controls has performance implications. This paper demonstrates that ignoring these costs can have significant impacts on the ability to satisfy response-time-based SLAs, and proposes a solution in the form of a cost-sensitive adaptation engine that weighs the potential benefits of runtime reconfiguration decisions against their costs. Extensive experimental results based on live workload traces show that the technique is able to maximize SLA fulfillment under typical time-of-day workload variations as well as flash crowds, and that it exhibits significantly improved transient behavior compared to approaches that do not account for adaptation costs.

Microgenetic multiobjective reconfiguration algorithm considering power losses and reliability indices for medium voltage distribution network

Abstract: This study proposes and applies an evolutionary-based approach for multiobjective reconfiguration in electrical power distribution networks. In this model, two types of indicators of power quality are minimised: (i) power system's losses and (ii) reliability indices. Four types of reliability indices are considered. A microgenetic algorithm ('GA) is used to handle the reconfiguration problem as a multiobjective optimisation problem with competing and non-commensurable objectives. In this context, experiments have been conducted on two standard test systems and a real network. Such problems characterise typical distribution systems taking into consideration several factors associated with the practical operation of medium voltage electrical power networks. The results show the ability of the proposed approach to generate well-distributed Pareto optimal solutions to the multiobjective reconfiguration problem. In the systems adopted for assessment purposes, our proposed approach was able to find the entire Pareto front. Furthermore, better performance indexes were found in comparison to the Pareto envelope-based selection algorithm 2 (PESA 2) technique, which is another well-known multiobjective evolutionary algorithm available in the specialised literature. From a practical point of view, the results established, in general, that a compact trade-off region exists between the power losses and the reliability indices. This means that the proposed approach can recommend to the decision maker a small set of possible solutions in order to select from them the most suitable radial topology.

Autonomic Computing through Reuse of Variability Models at Runtime: The Case of Smart Homes

Abstract: Our research shows that autonomic behavior can be achieved by leveraging variability models at runtime. In this way, the modeling effort made at design time is not only useful for producing the system but also provides a richer semantic base for autonomic behavior during execution. The use of variability models at runtime brings new opportunities for autonomic capabilities by reutilizing the efforts invested at design time. Our proposed approach has two aspects: reuse of design knowledge to achieve AC and reuse of existing model-management technologies at runtime. We developed the Model-Based Reconfiguration Engine (MoRE) to implement model-management operations. Our research demonstrates the approach's feasibility for smart homes, especially for self-healing and -configuring capabilities.

A Reinforcement Learning Approach to Online Web Systems Auto-configuration

Abstract: In a web system, configuration is crucial to the performance and service availability. It is a challenge, not only because of the dynamics of Internet traffic, but also the dynamic virtual machine environment the system tends to be run on. In this paper, we propose a reinforcement learning approach for autonomic configuration and reconfiguration of multi-tier web systems. It is able to adapt performance parameter settings not only to the change of workload, but also to the change of virtual machine configurations. The RL approach is enhanced with an efficient initialization policy to reduce the learning time for online decision. The approach is evaluated using TPC-W benchmark on a three-tier website hosted on a Xen-based virtual machine environment. Experiment results demonstrate that the approach can autoconfigure the web system dynamically in response to the change in both workload and VM resource. It can drive the system into a near-optimal configuration setting in less than 25 trial-and-error iterations.

Mechanism for Automated Re-Configuration of an Access Network Element

Abstract: A mechanism for controlling resources and/or settings of an access network element like a base station is provided which allows an autonomous reconfiguration of, for example, the antenna configuration based on a set of performance indicators in a base station. The base station can reconfigure itself without the need of operator control so that during periods with low capacity demands the base station will reconfigure correspondingly, which may comprise a reduction of active cells by turning off the power for a part of the installed equipment.

Dynamic Partial Reconfiguration in FPGAs

Abstract: Dynamic parital reconfigurable FPGAs offer new design space with a variety of benefits: reduce the configuration time and save memory as the partial reconfiguration files (bitstreams) are smaller than full ones. This paper introduces a simple reconfigurable system and focuses on the advantages of the newest dynamic partial reconfiguration design flow.

Experimental Evaluation of Dynamic Redundancy Resolution in a Nonholonomic Wheeled Mobile Manipulator

Abstract: Mobile manipulators derive significant novel capabilities for enhanced interactions with the world by merging mobility with manipulation. However, a careful resolution of the redundancy and active control of the reconfigurability, created by the surplus articulated DOFs and actuation, are the keys to unlocking this potential. Nonholonomic wheeled mobile manipulators, formed by mounting manipulator arms on disc-wheeled mobile bases, are a small but important subclass of mobile manipulators. The primary control challenges arise due to the dynamic-level coupling of the nonholonomy of the wheeled mobile bases with the inherent kinematic and actuation redundancy within the articulated chain. The solution approach in this paper builds upon a dynamically consistent and decoupled partitioning of the articulated system dynamics between the external (task) space and internal (null) space. The independent controllers, developed within each decoupled space, facilitate active internal reconfiguration, in addition to resolving redundancy at the dynamic level. Specifically, two variants of null-space controllers are implemented to improve disturbance rejection and active reconfiguration during performance of end-effector tasks by a primary end-effector impedance mode controller. These algorithms are evaluated within an implementation framework that emphasizes both virtual prototyping and hardware-in-the-loop testing with representative case studies.

Multiple-Model Adaptive Fault-Tolerant Control of a Planetary Lander

Abstract: In this paper we present an approach to fault-tolerant control based on multiple models, switching, and tuning and its implementation to a hardware-in-the-loop simulation of Delta Clipper Experimental dynamics. The Delta Clipper Experimental is characterized by large control input redundancy, which made it an ideal test bed for evaluation of advanced fault-tolerant and adaptive reconfigurable control strategies. The overall failure detection, identification, and accommodation architecture is an upgraded version of our Fast Online Actuator Reconfiguration Enhancement (FLARE) system. The FLARE approach is based on representing different possible fault and failure scenarios using multiple observers, such that the case of nominal (no-failure) operation is covered along with the loss-of-effectiveness, lock-in-place, and hardover failures of the flight control effectors. Based on a suitably chosen performance criterion, the FLARE system quickly detects single or multiple failures and reconfigures the controls, thus achieving either the original desired performance or graceful performance degradation. In the first stage of the project, the FLARE system was tested on a medium-fidelity simulation of Delta Clipper Experimental dynamics, resulting in excellent performance over a large range of single and multiple faults and failures. Following that, in collaboration with Boeing Phantom Works, the FLARE run-time code was installed at their site and tested on a hardware-in-the-loop test bed consisting of an electromechanical actuator actuating a gimballed engine as a part of a simulation of the Delta Clipper Experimental dynamics. A large number of hardware-in-the-loop simulations were run to cover a dense test-case matrix, including cases of up to 10 simultaneous control effector failures. In all cases FLARE was able to quickly and accurately detect the failures and reconfigure the controls, resulting in excellent overall system performance. In this paper we describe the Delta Clipper Experimental and its dynamics model, along with the multiple models, switching, and tuning based modification of our FLARE system. This is followed by a description ofthe experimental test bed and a discussion of the results obtained through hardware-in-the-loop testing.

On Dynamic Reconfiguration of a Large-Scale Battery System

Abstract: Electric vehicles powered with large-scale battery packs are gaining popularity as gasoline price soars. Large-scale battery packs usually consist of an estimated 12,000 battery cells connected in series and parallel, which are susceptible to battery-cell failures. Unfortunately, current battery-management systems are unable to handlethe inevitable battery-cell failures very well. To address this problem, we propose a dynamic reconfiguration framework that monitors, reconfigures, and controls large-scale battery packs online. The framework is built upon a syntactic bypassing mechanism that provides a set of rules for changing the battery-pack configuration, and a semantic bypassing mechanism by which the battery-cell connectivity is reconfigured to recover from a battery-cell failure. In particular, the semantic bypassing mechanism is dictated by constant-voltage-keeping and dynamic-voltage-allowing policies. The former policy is effective in preventing unavoidable voltage drops during the battery discharge, while the latter policy is effective in supplying different amounts of power to meet a wide-range of application requirements. Our experimental evaluation has shown the proposed framework to enable the battery packs to be 9 times as fault-tolerant as a legacy scheme.

Applying genetic algorithms to decision making in autonomic computing systems

Abstract: Increasingly, applications need to be able to self-reconfigure in response to changing requirements and environmental conditions. Autonomic computing has been proposed as a means for automating software maintenance tasks. As the complexity of adaptive and autonomic systems grows, designing and managing the set of reconfiguration rules becomes increasingly challenging and may produce inconsistencies. This paper proposes an approach to leverage genetic algorithms in the decision-making process of an autonomic system. This approach enables a system to dynamically evolve reconfiguration plans at run time in response to changing requirements and environmental conditions. A key feature of this approach is incorporating system and environmental monitoring information into the genetic algorithm such that specific changes in the environment automatically drive the evolutionary process towards new viable solutions. We have applied this genetic-algorithm based approach to the dynamic reconfiguration of a collection of remote data mirrors, with the goal of minimizing costs while maximizing data reliability and network performance, even in the presence of link failures.

Nonlinear Reconfiguring Flight Control Based on Online Physical Model Identification

Abstract: This paper presents a study on fault tolerant flight control of a benchmark aircraft model. Reconfiguring control is implemented by making use of adaptive nonlinear dynamic inversion for manual and autopilot control. The weakness of classical nonlinear dynamic inversion, its sensitivity to modeling errors, is circumvented here by making use of a real-time identified physical model of the damaged aircraft. With help of the Boeing 747 benchmark simulation model, including the realistic component as well as the structural failure modes, it is possible to analyze the damage accommodation capabilities of the considered approach. In failure conditions, the damaged aircraft model is identified by the so-called two-step method in real time and this model is applied subsequently to the model-based adaptive nonlinear dynamic inversion routine in a modular structure, which allows flight control reconfigurations online. After discussing the modular adaptive controller setup, reconfiguration test results are shown for damaged aircraft models using a desktop computer as well as the moving base Simulation, Motion, and Navigation Research Flight Simulator of Delft University. These results indicate satisfactory failure handling capabilities of this fault tolerant control setup, for component as well as structural failures.

FPath and FScript: Language support for navigation and reliable reconfiguration of Fractal architectures

Abstract: Component-based systems must support dynamic reconfigurations to adapt to their execution context, but not at the cost of reliability. Fractal provides intrinsic support for dynamic reconfiguration, but its definition in terms of low-level APIs makes it complex to write reconfigurations and to ensure their reliability. This article presents a language-based approach to solve these issues: direct and focused language support for architecture navigation and reconfiguration make it easier both to write the reconfigurations and to ensure their reliability. Concretely, this article presents two languages: (1) FPath, a domain-specific language that provides a concise yet powerful notation to navigate inside and query Fractal architectures, and (2) FScript, a scripting language that embeds FPath and supports the definition of complex reconfigurations. FScript ensures the reliability of these reconfigurations thanks to sophisticated run-time control, which provides transactional semantics (ACID properties) to the reconfigurations.

Dynamic topological adaptation

Abstract: Apparatus and methods for reconfiguration of a communication environment based on loading requirements. Network operations are monitored and analyzed to determine loading balance across the network or a portion thereof. Where warranted, the network is reconfigured to balance the load across multiple network entities. For example, in a cellular-type of network, traffic loads and throughput requirements are analyzed for the access points and their user equipment. Where loading imbalances occur, the cell coverage areas of one or more access points can be reconfigured to alleviate bottlenecks or improve balancing.

Multimode Control of a DFIG-Based Wind-Power Unit for Remote Applications

Abstract: This paper proposes a multimode control strategy for a doubly fed induction generator-based wind-power unit, which enables operation in the islanded (autonomous) mode as well as the grid-connected mode. The configuration can be an option for electricity generation in remote communities with favorable wind conditions, but limited or unreliable connection to the grid. In the grid-connected mode, the proposed control enables the wind power unit to operate with or without battery energy storage, as desired. In case that the wind-power unit is augmented with battery energy storage, in the islanded mode, the proposed control strategy enables voltage and frequency regulation for the network, and parallel operation with constant-speed wind-power units, induction motor loads, and passive loads. The proposed control strategy employs a unified controller for all of the foregoing modes of operation and, therefore, relieves the need for switching between different controllers or reconfiguration of the hardware. The effectiveness and robustness of the proposed control strategy are demonstrated for faulted as well as normal operating conditions through simulation studies carried out on a detailed switched model of the system in the PSCAD/EMTDC software environment.