Showing papers on "Control reconfiguration published in 2001"

Scheduling of networked control systems

Abstract: The defining characteristic of a networked control system (NCS) is having one or more control loops closed via a serial communication channel Typically, when the words networking and control are used together, the focus is on the control of networks, but in this article our intent is nearly inverse, not control of networks but control through networks NCS design objectives revolve around the performance and stability of a target physical device rather than of the network The problem of stabilizing queue lengths, for example, is of secondary importance Integrating computer networks into control systems to replace the traditional point-to-point wiring has enormous advantages, including lower cost, reduced weight and power, simpler installation and maintenance, and higher reliability In this article, in addition to introducing networked control systems, we demonstrate how dispensing with queues and dynamically scheduling control traffic improves closed-loop performance

A new controller architecture for high performance, robust, and fault-tolerant control

Abstract: We propose a new feedback controller architecture. The distinguished feature of our new controller architecture is that it shows structurally how the controller design for performance and robustness may be done separately which has the potential to overcome the conflict between performance and robustness in the traditional feedback framework. The controller architecture includes two parts: one part for performance and the other part for robustness. The controller architecture works in such a way that the feedback control system can be solely controlled by the performance controller when there is no model uncertainties and external disturbances and the robustification controller can only be active when there are model uncertainties or external disturbances.

Wdm Optical Networks: Concepts, Design and Algorithms

Abstract: (NOTE: Each chapter begins with an Introduction and concludes with Problems.) Preface. 1. WDM Technology and Issues in WDM Optical Networks. Optical Networks. Wavelength Division Multiplexing. WDM Optical Networking Evolution. Enabling Technologies for WDM Optical Networks. WDM Optical Network Architectures. Issues in Wavelength Routed Networks. Next-Generation Optical Internet Networks. Book Overview. 2. Wavelength Routing Algorithms. Classification of RWA Algorithms. RWA Algorithms. Fairness and Admission Control. Distributed Control Protocols. Permutation Routing and Wavelength Requirements. Summary. 3. Wavelength-Convertible Networks. Need for Wavelength Converters. Wavelength-Convertible Switch Architectures. Routing in Convertible Networks. Performance Evaluation of Convertible Networks. Networks with Sparse Wavelength Conversion. Converter Placement Problem. Converter Allocation Problem. Summary. 4. Wavelength Rerouting Algorithms. Benefits of Wavelength Rerouting. Issues in Wavelength Rerouting. Lightpath Migration. Rerouting Schemes. Algorithm AG. Algorithm MWPG. Rerouting in WDM Networks with Sparse Wavelength Conversion. Rerouting in Multifiber Networks. Rerouting in Multifiber Unidirectional Ring Networks. Summary. 5. Virtual Topology Design. Virtual Topology Design Problem. Virtual Topology Design Subproblems. Virtual Topology Problem Formulation. Virtual Topology Design Heuristics. Regular Virtual Topology Design. Predetermined Virtual Topology and Lightpath Routes. Predetermined Virtual Topology. Design of Multifiber Networks. Summary. 6. Virtual Topology Reconfiguration. Need for Virtual Topology Reconfiguration. Reconfiguration Due to Traffic Changes. Reconfiguration for Fault Restoration. Summary. 7. Network Survivability and Provisioning. Failures and Recovery. Restoration Schemes. Multiplexing Techniques. Provisioning Restorable Multifiber Networks. Provisioning Restorable Single-Fiber Networks. Backup Multiplexing-Based Routing. Primary-Backup Multiplexing-Based Routing. Distributed Control Protocols. Survivability in WDM Ring Networks. Summary. 8. Optical Multicast Routing. Multicast Routing Problem. Node Architectures. Multicast Tree Generation. Source-Based Tree Generation. Steiner-Based Tree Generation. Virtual Source-Based Trees. Summary. 9. Next-Generation Optical Internet Networks. Optical Circuit Switching. Optical Burst Switching. Optical Packet Switching. MPLS in WDM Networks. Summary. References. Appendices. AWEB RESOURCES LIST. BATM Technology. CSONET Technology. DMPLS Framework. Acronyms. Index.

Concepts and methods in fault-tolerant control

Abstract: Faults in automated processes will often cause undesired reactions and shut-down of a controlled plant, and the consequences could be damage to technical parts of the plant, to personnel or the environment. Fault-tolerant control combines diagnosis with control methods to handle faults in an intelligent way. The aim is to prevent that simple faults develop into serious failure and hence increase plant availability and reduce the risk of safety hazards. Fault-tolerant control merges several disciplines into a common framework to achieve these goals. The desired features are obtained through online fault diagnosis, automatic condition assessment and calculation of appropriate remedial actions to avoid certain consequences of a fault. The envelope of the possible remedial actions is very wide. Sometimes, simple re-tuning can suffice. In other cases, accommodation of the fault could be achieved by replacing a measurement from a faulty sensor by an estimate. In yet other situations, complex reconfiguration or online controller redesign is required. This paper gives an overview of recent tools to analyze and explore structure and other fundamental properties of an automated system such that any inherent redundancy in the controlled process can be fully utilized to maintain availability, even though faults may occur.

Method for creating circuit redundancy in programmable logic devices

Abstract: In a field programmable gate array (FPGA) allowing dynamic reconfiguration in time multiplexing fashion, duplicate copies are configured in a time multiplexing manner which are functionally identical to a primary circuit specified for a predetermined FPGA's application. The primary and duplicate circuits are interrogated by a voting circuit which determines the existence of a faulted circuit in order to eliminate the faulted circuit from the operation of the FPGA. In this manner, without physical addition of redundant circuits, fault tolerancy for the FPGA is provided to minimize the cost, weight, volume, heat and energy associated issues of conventional redundance techniques.

Distributed Control for 3D Metamorphosis

Abstract: In this paper, we define Proteo as a class of three-dimensional (3D) metamorphic robotic system capable of approximating arbitrary 3D shapes by utilizing repeated modules. Each Proteo module contains embedded sensors, actuators and a controller, and each resides in a 3D grid space. A module can move itself to one of its open neighbor sites under certain motion constraints. Distributed control for the self-reconfiguration of such robots is an interesting and challenging problem. We present a class of distributed control algorithms for the reconfiguration of Proteo robots based on the “goal-ordering” mechanism. Performance results are shown for experiments of these algorithms in a simulation environment, and the properties of these algorithms are analyzed.

Two Reconfigurable Flight-Control Design Methods: Robust Servomechanism and Control Allocation

Abstract: Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method feasible. These methods have been applied to reconfigurable entry flight control design for the X-33 vehicle. Examples presented demonstrate simultaneous tracking of angle-of-attack and roll angle commands during failures of the fight body flap actuator. Although simulations demonstrate success of the first method in most cases, the control-allocation method appears to provide uniformly better performance in all cases.

Pipeline vectorization

Abstract: This paper presents pipeline vectorization, a method for synthesizing hardware pipelines based on software vectorizing compilers. The method improves efficiency and ease of development of hardware designs, particularly for users with little electronics design experience. We propose several loop transformations to customize pipelines to meet hardware resource constraints while maximizing available parallelism. For runtime reconfigurable systems, we apply hardware specialization to increase circuit utilization. Our approach is especially effective for highly repetitive computations in digital signal processor (DSP) and multimedia applications. Case studies using field programmable gate arrays (FPGAs)-based platforms are presented to demonstrate the benefits of our approach and to evaluate tradeoffs between alternative implementations. For instance, the loop-tiling transformation, has been found to improve vectorization performance 30-40 times above a PC-based software implementation, depending on whether runtime reconfiguration (RTR) is used.

A Modular Self-Reconfigurable Bipartite Robotic System: Implementation and Motion Planning

Abstract: In this manuscript, we discuss i>I-Cubes, a class of modular robotic system that is capable of reconfiguring itself in 3-D to adapt to its environment This is a bipartite system, ie, a collection of (i) active elements for actuation, and (ii) passive elements acting as connectors Active elements (i>links) are 3-DOF manipulators that are capable of attaching/detaching from/to the passive elements (i>cubes), which can be positioned and oriented using links Self-reconfiguration capability enables the system to perform locomotion tasks over difficult terrains the shape and size can be changed according to the task This paper describes the design of the system, and 3-D reconfiguration properties Specifics of the hardware implementation, results of the experiments with the current prototypes, our approach to motion planning and problems related to 3-D motion planning are given

A quick safari through the reconfiguration jungle

Abstract: Cost effective systems use specialization to optimize factors such as power consumption, processing throughput, flexibility or combinations thereof. Reconfigurable systems obtain this specialization at run-time. System reconfiguration has a vertical, a horizontal and a time dimension. We organize this design space as the reconfiguration hierarchy, and discuss the design methods that deal with it. Finally, we survey existing commercial platforms that support reconfiguration and situate them in the reconfiguration jungle.

An open platform for reconfigurable control

Abstract: Advances in software technology have the potential to revolutionize control system design. Component-based architectures encourage flexible "plug-and-play" extensibility and evolution of systems. Distributed object computing allows interoperation. Advances are being made to enable dynamic reconfiguration and evolution of systems while they are still running. Technologies are being developed to allow networked, embedded devices to connect to each other and self-organize. This article describes a software infrastructure that gives an open control platform (OCP) for complex systems that coordinates distributed interaction among diverse components and supports dynamic reconfiguration and customization of the components in real time. Its primary goals are to accommodate rapidly changing application requirements, incorporate new technology (such as hardware platforms or sensors), interoperate in heterogeneous environments, and maintain viability in unpredictable and changing environments. The next section describes the current practice in control system implementation and discusses features of a complex control system architecture. It is followed by a description of the desired features a software infrastructure must have to promote new advances in control system design. We then describe an open-control software infrastructure to support these desired features, followed by a brief overview of a first-generation prototype of this infrastructure that has been developed for an autonomous aerial vehicle control.

A graph based architectural (Re)configuration language

Abstract: For several different reasons, such as changes in the business or technological environment, the configuration of a system may need to evolve during execution. Support for such evolution can be conceived in terms of a language for specifying the dynamic reconfiguration of systems. In this paper, continuing our work on the development of a formal platform for architectural design, we present a high-level language to describe architectures and for operating changes over a configuration (i.e., an architecture instance), such as adding, removing or substituting components or interconnectons. The language follows an imperative style and builds on a semantic domain established in previous work. Therein, we model architectures through categorical diagrams and dynamic reconfiguration through algebraic graph rewriting.

Optimal FPGA module placement with temporal precedence constraints

Abstract: We consider the optimal placement of hardware modules in space and time for FPGA architectures with reconfiguration capabilities, where modules are modeled as three-dimensional boxes in space and time. Using a graph-theoretic characterization of feasible packings, we are able to solve the following problems. (a) Find the minimal execution time of the given problem on an FPGA of fixed size, (b) Find the FPGA of minimal size to accomplish the tasks within a fired time limit. Furthermore, our approach is perfectly suited for the treatment of precedence constraints for the sequence of tasks, which are present in virtually all practical instances. Additional mathematical structures are developed that lead to a powerful framework for completing optimal solutions. The usefulness is illustrated by computational results.

Network Reconfiguration for Service Restoration in Shipboard Power Distribution Systems

Abstract: Summary form only given, as follows. The electric power systems of US Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. Circuit breakers (CBs) and fuses are provided at different locations for isolation of faulted loads, generators or distribution system from unfaulted portions of the system. These faults could be due to widespread system faults resulting from battle damage or material casualties of individual loads or cables. After the faults and subsequent isolation of the faults, there will be unfaulted sections that are left without supply. Fast restoration of supply to these unfaulted sections of the shipboard power system is necessary for system survivability. This paper presents a new method to reconfigure the network to restore service to unfaulted sections of the system. The problem is formulated as a variation of the fixed charge network flow problem. The method is illustrated using various case studies on a small power system with a similar topology to a shipboard power system.

Online reconfiguration in replicated databases based on group communication

Abstract: Over the last years, many replica control protocols have been developed that take advantage of the ordering and reliability semantics of group communication primitives to simplify database system design and to improve performance. Although current solutions are able to mask site failures effectively, many of them are unable to cope with recovery of failed sites, merging of partitions, or joining of new sites. This paper addresses this important issue. It proposes efficient solutions for online system reconfiguration providing new sites with a current state of the database without interrupting transaction processing in the rest of the system. Furthermore, the paper analyzes the impact of cascading reconfigurations, and argues that they call be handled in an elegant way by extended forms of group communication.

Transparent dynamic reconfiguration for CORBA

Abstract: Distributed systems with high availability requirements have to support some form of dynamic reconfiguration. This means that they must provide the ability to be maintained or upgraded without being taken off-line. Building a distributed system that allows dynamic reconfiguration is very intrusive to the overall design of the system, and generally requires special skills from both the client and server side application developers. There is an opportunity to provide support for dynamic reconfiguration at the object middleware level of distributed systems, and create a dynamic reconfiguration transparency to application developers. We propose a Dynamic Reconfiguration Service for CORBA that allows the reconfiguration of a running system with maximum transparency for both client and server side developers. We describe the architecture, a prototype implementation, and some preliminary test results.

Configuration Compression for Virtex FPGAs

Abstract: Although run-time reconfigurable systems have been shown to achieve very high performance, the speedups over traditional microprocessor systems are limited by the cost of configuration of the hardware. Current reconfigurable systems suffer from a significant overhead due to the time it takes to reconfigure their hardware. In order to deal with this overhead, and increase the compute power of reconfigurable systems, it is important to develop hardware and software systems to reduce or eliminate this delay. In this paper, we explore the idea of configuration compression and develop algorithms for reconfigurable systems. These algorithms, targeted to Xilinx Virtex series FPGAs with minimum modification of hardware, can significantly reduce the amount of data needed to transfer during configuration. In this work we have extensively researched the current compression techniques, including the Huffman coding, the Arithmetic coding and LZ coding. We have also developed different algorithms targeting different hardware structures. Our readback algorithm allows certain frames to be reused as a dictionary and sufficiently utilize the regularities within the configuration bitstream. In addition, we have developed frame reordering techniques that better uses the regularities by shuffling the sequence of the configuration. We have also developed the wildcard approach that can be used for true partial reconfiguration. The simulation results demonstrate that a factor of 4 compression ratio can be achieved.

PARBIT: A Tool to Transform Bitfiles to Implement Partial Reconfiguration of Field Programmable Gate Arrays (FPGAs)

Abstract: Field Programmable Gate Arrays (FPGAs) can be partially reconfigured to implement Dynamically loadable Hardware Plugin (DHP) modules. A tool called PARBIT has been developed that transforms FPGA configuration bitfiles to enable DHP modules. With this tool it is possible to define a partial reconfigurable area inside the FPGA and download it into a specified region of the FPGA device. One or more DHPs, with different sizes can be implemented using PARBIT.

Modular Robot Motion Planning Using Similarity Metrics

Abstract: In order for a modular self-reconfigurable robotic system to autonomously change from its current state to a desired one, it is critical to have a cost function (or metric) that reflects the effort required to reconfigure. A reconfiguration sequence can consist of single module motions, or the motion of a “branch” of modules. For single module motions, the minimization of metrics on the set of sets of module center locations serves as the driving force for reconfiguration. For branch motions, the question becomes which branches should be moved so as to minimize overall effort. Another way to view this is as a pattern matching problem in which the desired configuration is viewed as a void, and we seek branch motions that best fill the void. A precise definition of goodness of fit is therefore required. In this paper, we address the fundamental question of how closely geometric figures can be made to match under a given group of transformations (e.g., rigid-body motions), and what it means to bisect two shapes. We illustrate these ideas in the context of applications in modular robot motion planning.

Polymorphic Electronics

Abstract: This paper introduces the concept of polymorphic electronics (polytronics) -referring to electronics with superimposed built-in functionality. A function change does not require switches/reconfiguration as in traditional approaches. Instead, the change comes from modifications in the characteristics of devices involved in the circuit, in response to controls such as temperature, power supply voltage (VDD), control signals, light, etc. For example, a temperature-controlled polytronic AND/OR gate behaves as AND at 27°C and as OR at 125°C. The paper illustrates polytronic circuits in which the control is done by temperature, morphing signals, and VDD respectively. Polytronic circuits are obtained by evolutionary design/evolvable hardware techniques. These techniques are ideal for the polytronics design, a new area that lacks design guidelines/know-how,- yet the requirements/objectives are easy to specify and test. The circuits are evolved/synthesized in two different modes. The first mode explores an unstructured space, in which transistors can be interconnected freely in any arrangement (in simulations only). The second mode uses a Field Programmable Transistor Array (FPTA) model, and the circuit topology is sought as a mapping onto a programmable architecture (these experiments are performed both in simulations and on FPTA chips). The experiments demonstrate the polytronics concept and the synthesis of polytronic circuits by evolution.

The effect of reconfigurable units in superscalar processors

Abstract: This paper describes OneChip, a third generation reconfigurable processor architecture that integrates a Reconfigurable Functional Unit (RFU) into a superscalar Reduced Instruction Set Computer (RISC) processor's pipeline. The architecture allows dynamic scheduling and dynamic reconfiguration. It also provides support for pre-loading configurations and for Least Recently Used (LRU) configuration management.To evaluate the performance of the OneChip architecture, several off-the-shelf software applications were compiled and executed on Sim-OneChip, an architecture simulator for OneChip that includes a software environment for programming the system. The architecture is compared to a similar one but without dynamic scheduling and without an RFU. OneChip achieves a performance improvement and shows a speedup range from 2.16 up to 32 for the different applications and data sizes used. The results show that dynamic scheduling helps performance the most on average, and that the RFU will always improve performance the best when most of the execution is in the RFU.

Real-Time Adaptive Control Allocation Applied to a High Performance Aircraft

Abstract: This paper presents the development and application of one approach to the control of aircraft with large numbers of control effectors. This approach, referred to as real-time adaptive control allocation, combines a nonlinear method for control allocation with actuator failure detection and isolation. The control allocator maps moment (or angular acceleration) commands into physical control effector commands as functions of individual control effectiveness and availability. The actuator failure detection and isolation algorithm is a model-based approach that uses models of the actuators to predict actuator behavior and an adaptive decision threshold to achieve acceptable false alarm/missed detection rates. This integrated approach provides control reconfiguration when an aircraft is subjected to actuator failure, thereby improving maneuverability and survivability of the degraded aircraft. This method is demonstrated on a next generation military aircraft Lockheed-Martin Innovative Control Effector) simulation that has been modified to include a novel nonlinear fluid flow control control effector based on passive porosity. Desktop and real-time piloted simulation results demonstrate the performance of this integrated adaptive control allocation approach.

Hormone-controlled metamorphic robots

Abstract: Metamorphic robots with shape-changing capabilities provide a powerful and flexible approach to complex tasks in unstructured environments. However, due to their dynamic topology and decentralized configuration, metamorphic robots demand control mechanisms that go beyond those used by conventional robots. This paper builds on our previous results of hormone-based control, and develops a novel distributed control algorithm called CELL that can select, synchronize, and execute gaits and other reconfiguration actions without assuming any global configuration knowledge. This algorithm is flexible enough to deal with changes of configuration, and can resolve conflicts between locally selected actions and manage multiple active hormones for producing coherent global effects.

Self-reconfigurable modular robot - experiments on reconfiguration and locomotion

Abstract: We have proposed a self-reconfigurable robotic module, which has a very simple structure. The system is capable of not only building a static structure, but also generating a dynamic robotic motion. We have also developed a simulator for the motion planning. In this paper, we present details of the mechanical and electrical designs of the developed module and its control system architecture. Experiments using ten modules demonstrate the robotic configuration change, crawling locomotion and three types of quadruped locomotion.

Architecture and method for partially reconfiguring an FPGA

Abstract: An FPGA architecture and method enables partial reconfiguration of selected configurable logic blocks (CLBs) connected to an address line without affecting other CLBs connected to the same addressl line. Partial reconfigutration at a memory cell resolution is achieved by manipulating the input voltages applied to the address and data lines of the FPGA so that certain memory cells are programmed while other memory cells are not programmed. In addition, partial reconfiguration at at CLB resolution can be achieved by hardwiring the FPGA to enable selection of individual CLBs for reconfiguration.

Compatibility of e -Services in a Cooperative Multi-platform Environment

Abstract: Dynamic composition and reconfiguration of e-Services in cooperative processes involving several organizations requires mechanisms for ensuring that each cooperative process is guaranteed to evolve correctly against its specification The cooperative process is specified and deployed as a set of cooperating e-Services, each with specific interfaces and evolution, and the concept of compatibility between e-Services is defined, based on their external behavior An algorithm for checking compatibility is proposed and a tool provides support both at design-time and at run-time A run-time architecture supporting the execution of e-Services in a multti-platform environment is dicussed, based on a repository storing all e-Services and process specifiication

Distributed services for information dissemination in self-organizing sensor networks

Abstract: Dynamic enterprise systems, such as the battlefield, use self-organizing sensor network infrastructure to gather and disseminate real-time information for controlling the enterprise. Very large number of highly mobile sensor data sources and users may be scattered over a wide area with little or no fixed network support. These large surveillance sensor networks must adapt rapidly to dynamic changes in sensor nodes configuration. Dynamic query processing and target tracking through this unstructured sensor network of surveillance information sources and users must use the appropriate distributed services and network protocols to solve the problems of mobility, dispersion, weak and intermittent disconnection, dynamic reconfiguration and limited power availability. We provide three main distributed services: lookup service, composition service and dynamic adaptation service. Through a distributed implementation of these services, other application-specific network and system services can be defined spontaneously in the sensor network. They also enable dynamic adaptation of these services to incremental addition and removal of sensor nodes, device failure and degradation, migration of sensor nodes, and changing requirements in tasks and networks. When placed together impromptu, sensor nodes should immediately know about the capabilities and functions of other smart nodes and work together as a community system to perform coordinated tasks and networking functionalities.