Reconfiguration Tasks Research Articles

Application Research of MRAC in Fault-tolerant Flight Controller

Damage, failure, and other configuration variety of aircraft would make the model parameters changed uncertainly, and lead to unknown deviations of the equilibrium points and unexpected coupling characters. One type of fault-tolerant flight controller which contains model reference adaptive theory is released for dealing with these problems. Design requirement for fault-tolerant flight controller is discussed and one structure of controller is presented. The reconstruction simulation for serious shift of center of gravity which could not detected by FDI system demonstrates this type of controller can complete the reconfiguration task without failure information, and demonstrated the validity of this structure.

Adjusting the Frequency of Automated Phosphorus Measurements to Environmental Conditions

Extreme weather events are likely to increase in the future, and thus damage to the environment and infrastructure will likely increase during this time, too. To adapt to these weather impacts, forecasting, now-casting, and in situ monitoring installations have increased during the last years. Even though monitoring stations deliver frequent measurements in realtime, a dynamic implementation of measurement frequencies, adapted to certain environmental conditions, are rarely implemented. Within this paper we provide a framework where low frequency phosphorus measurements in the Mondsee catchment can be adapted to high frequency measurements during storm events. When heavy rainfall is observed, a threshold event triggers a reconfiguration task for the phosphorus measurement device, using asynchronous, push-based communication. A Sensor Planning Service commits such a request into the wireless sensor network, and updates the measurement frequency of the target nodes to enable nutrient peak flow estimation during storm events. This setup introduces the possibility of measurements in flooded areas without using traditional (manual) sampling methods, and we expect to obtain a better understanding of discharge to phosphorus runoff relations.

Experimental Investigation of the Influence of Burnishing Parameters on Surface Roughness and Hardness of Brass Alloy

Burnishing is a cold working surface finishing process in which peaks and valleys on machined surfaces deformed plastically by the application of hard and finished ball or roller against to it. Recently burnishing is becoming popular among post finishing processes because of its many advantages along its primary role i.e., increasing surface finish. In this paper the effect of burnishing process parameters on surface roughness and hardness of brass alloy is experimentally investigated. A simple roller burnishing tool was used for the experiential work of the present study, surface test and micro hardness test were used to demonstrate the effects of the burnishing force and feed rate on surface roughness and surface hardness of a brass alloy. The smoothing process under consideration can be performed on standard machine tools without additional reconfiguration tasks. Process is very useful for any workshop and can be carried out without coolant. The results proved that all the parameters have significant effect on the above said two surface characteristics. The results revealed that improvements in the surface finish and increase in the surface hardness are obtained by reduce the burnishing feed and increase the burnishing force.

Risk-Constrained Microgrid Reconfiguration Using Group Sparsity

The system reconfiguration task is considered for existing power distribution systems and microgrids, in the presence of renewable-based generation and load foresting errors. The system topology is obtained by solving a chance-constrained optimization problem, where loss-of-load (LOL) constraints and ampacity limits of the distribution lines are enforced. Similar to various distribution system reconfiguration renditions, solving the resultant problem is computationally prohibitive due to the presence of binary line selection variables. Further, lack of closed-form expressions for the joint probability distribution of forecasting errors hinders tractability of LOL constraints. Nevertheless, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">convex</i> problem reformulation is developed here by resorting to a scenario approximation technique, and by leveraging the underlying group-sparsity attribute of currents flowing on distribution lines equipped with tie and sectionalizing switches. The novel convex LOL-constrained reconfiguration scheme can also afford a distributed solution using the alternating direction method of multipliers, to address the case where multifacilities are managed autonomously from the rest of the system.

Neuro-Behavioral Correlates of Post-Deviance Distraction in Middle-Aged and Old Adults

The presentation of a task-irrelevant deviant (novel) stimulus among otherwise repeated standard stimuli usually reduces performance not only for the deviant stimulus, but also for the standard following that deviant. Here, the so-called post-deviance distraction was investigated in 58 middle-aged and 52 old adults, using an auditory duration discrimination task and event-related potential (ERP) measures. After a deviant stimulus, the participants showed a decrease in performance in the subsequent standard stimulus. This effect was more pronounced in the old, than middle-aged, group. Relative to the standard stimuli preceding the deviant, post-deviant standards triggered a chain of mismatch negativity (MMN), P3a, and reorienting negativity (RON). While MMN and P3a did not differ in old and middle-aged adults, older participants showed a delayed RON. Assuming the RON to reflect processes of general task or feature reconfiguration and updating, these results suggest a delay in orienting-reorienting mechanisms as possible source of increased post-deviance distraction in elderly.

Shipboard Power Systems Reconfiguration—A Cyber-Physical Framework For Response Time Analysis

Several applications within a shipboard system involve the integration of physical systems (e.g., power systems) and cyber computing platforms such as command and control, communications, and sensing networks, and require real-time quality of service (QoS) guarantees. In this paper, the distribution of total (end-to-end) delay associated with fault diagnosis and reconfiguration of shipboard power system (SPS) is investigated from a cyber-physical systems (CPS) perspective. Specifically, a cross-layer end-to-end delay analysis framework is introduced for SPS reconfiguration. The proposed framework stochastically models the heterogeneity of actions of various subsystems involved in the reconfiguration tasks viz., generation of fault information by sensor nodes associated to the power system, processing of actions at control center to resolve fault locations and reconfiguration, and flow of information through communication network to perform necessary actions. The proposed framework then combines appropriately the output delay distributions from each subsystem to: 1) analytically predict the distribution of end-to-end delay in SPS reconfiguration after the occurrence of faults and 2) analyze and design real-time reconfiguration solutions for shipboard CPS, that meet total delay requirements. Simulations using various topological scenarios demonstrate that the proposed analytical framework closely predict the total delay associated with SPS reconfiguration.

Functional safety of adaptive embedded control systems: new solutions

This paper deals with the functional safety of embedded control system following component-based technologies. The functional safety in a device of the interconnected control components is handled by an agent that controls and adapts the local behaviour at run-time. The interaction between control agents in devices is ensured via the communication protocol based on a coordination agent. We propose technical solutions to implement the whole agent-based architecture, by defining UML meta-models for both control components and also agents. At the operational level, an OS task is assumed to be a set of components having some properties independently from any real-time operating system. To guarantee safety reconfiguration of OS tasks at run-time, we define service and reconfiguration processes for safety. We apply the priority ceiling protocol as a method to ensure the scheduling between periodic tasks with precedence and mutual exclusion constraints.

Set-based Fault-Tolerant Control of Convex Polytopic LPV Systems using a Bank of Virtual Actuators

We propose a robust actuator fault tolerant control strategy for systems with linear parameter varying (LPV) uncertainty model description. The scheme employs a set-based robust fault detection and identification (FDI) approach and a bank of virtual actuators (VA). An interesting feature is that the virtual actuators are used both for FDI and controller reconfiguration (CR) tasks. The robust FDI method is based on the separation of relevant sets defined for measurable residual signals, which are computed based on the virtual actuator signals and taking into account model uncertainty, noises and process disturbances. For CR, each VA is designed to operate adequately in combination with a nominal controller (designed for the fault-free plant) to achieve correct reconfiguration for a particular fault situation in a considered range of fault scenarios. The resulting robust fault tolerant control scheme ensures boundedness of the closed-loop system trajectories under a wide range of actuator fault scenarios. The performance of the scheme is illustrated through a simulation example.

Influence of sensor and actuator errors on impulsive satellite formation control methods

This paper investigates how sensor and actuator errors are impacting formation control accuracy and propellant consumption of a two-satellite formation in a low Earth orbit. Realistic relative navigation errors are implemented, based on the results from the PRISMA mission, as well as realistic actuator uncertainty and actuator constraints. Two impulsive control methods are investigated. The first method is based on a controller that is implemented onboard PRISMA and the second method uses linear programming to arrive at a model predictive controller. The control methods are tested in a simulation environment and are subjected to orbital perturbations and realistic sensor errors and actuator errors. Both control methods are able to maintain the desired relative geometry of a projected circular orbit in the presence of the errors. The PRISMA control method demonstrates lower propellant consumption, while the model predictive controller shows better control accuracy. The results show that, based on the used scenario, sensor errors dominate both the formation control accuracy and propellant consumption. The versatility of the model predictive controller is demonstrated in a challenging formation control scenario including formation maintenance and formation reconfiguration tasks.

On the monitoring task of solar thermal fluid transfer systems using NN based models and rule based techniques

Supervising thermal fluids transfer systems applied in solar parabolic through fields deals with a typical non linear process which suffers from lack of detectability when analytic model based techniques are applied on fault detection, isolation and reconfiguration tasks. This work describes the implementation of a supervision strategy to be applied in thermal fluids transfer systems used on solar parabolic through based power plants for which massive neural networks based functional approximation techniques associated to recursive rule based techniques on the basis of parity equations has been applied. Experimental results carried out on a test rig show that diagnosis applied to the thermal fluid transfer problems can be carried out under acceptable determinism and reliability.

Integrated sensor and actuator fault-tolerant control

We propose a fault-tolerant control scheme that deals with sensor and actuator faults through the use of a virtual actuator (VA) and a bank of virtual sensors (VSs). A novel feature of the scheme is that the VSs implicitly integrate both fault detection and isolation (FDI) and – in conjunction with the VA – controller reconfiguration tasks. The VA and the bank of VSs operate in closed-loop with an observer-based tracking controller designed for a nominal (fault free) model of the plant. A switching rule that reconfigures the VA and engages the suitable VS from the bank is based on sets defined for measurable residual signals constructed directly from the VS signals. Our method handles abrupt actuator and sensor faults of arbitrary magnitude including complete outage. The overall scheme is shown to guarantee closed-loop boundedness and setpoint tracking under all considered fault situations. Enhancements of the scheme to deal with errors in the fault detection and isolation are also proposed. Applications of the scheme to a winding machine and an interconnected tank system are presented.

Towards formalising installation and reconfiguration tasks of AADL architecture

Software applications are becoming more and more distributed rendering their deployment which consists essentially of the installation and dynamic reconfiguration activities crucial and important phase in software development lifecycle. Although, several approaches for software deployment exist in the literature, most of them deal with specific technologies and offer limited models. In this paper, we focus on the formalisation of the most important deployment tasks of software systems using bigraphical reactive systems BRS. We aim to give a complete semantic framework for AADL specifications, including the installation of software application on execution platform and its dynamic reconfiguration. AADL offers necessary tools to define both software and execution platform characteristics in the same description. For this purpose, our model allows the specification of software architecture configuration by a suitable pair of bigraphs, the first one models software components and their interconnections, and the second one models the execution platform. Thus, software entities installation on hardware ones is achieved by composing the two designed bigraphs. Besides, reconfiguration activity is formalised in terms of BRS reactions rules.

Age differences in voluntary task switching.

Task choice processes in older (60+ years) and younger (18-30 years) adults were compared using a voluntary task switching procedure (Arrington & Logan, 2004). To assess age-related differences in task representation maintenance, preparation times were varied across a large range of response-to-stimulus intervals (100, 500, 1,000, and 5,000 ms) and the environmental influence on task selection was varied by repeating or changing stimuli from trial to trial. Older adults switched less frequently than younger adults and this effect was the same at each RSI. Younger adults were more likely to switch tasks when the stimulus changed than when it repeated suggesting that they used a different process to determine task choices, either endogenous task selection or environmentally supported task repetitions. Older adults' task selection was unaffected by stimulus repetitions indicating that they were less flexible with the processing they used to guide task selection. These findings are consistent with previous observations of age-related increases in goal shielding, but not with age-related deficits in task goal maintenance. Robust age differences in switch costs were observed across RSIs suggesting that task reconfiguration processes are different following endogenous than exogenous task selection.

New Optimal Solutions for Real-Time Reconfigurable Periodic Asynchronous Operating System Tasks with Minimizations of Response Time

Scheduling tasks is an essential requirement in most real-time and embedded systems, but leads to unwanted central processing unit (CPU) overheads. The authors present a real-time schedulability algorithm for preemptable, asynchronous and periodic reconfigurable task systems with arbitrary relative deadlines, scheduled on a uniprocessor by an optimal scheduling algorithm based on the earliest deadline first (EDF) principles and on the dynamic reconfiguration. A reconfiguration scenario is assumed to be a dynamic automatic operation allowing addition, removal or update of operating system’s (OS) functional asynchronous tasks. When such a scenario is applied to save the system at the occurrence of hardware-software faults, or to improve its performance, some real-time properties can be violated. The authors propose an intelligent agent-based architecture where a software agent is used to satisfy the user requirements and to respect time constraints. The agent dynamically provides precious technical solutions for users when these constraints are not verified, by removing tasks according to predefined heuristic, or by modifying the worst case execution times (WCETs), periods, and deadlines of tasks in order to meet deadlines and to minimize their response time. They implement the agent to support these services which are applied to a Blackberry Bold 9700 and to a Volvo system and present and discuss the results of experiments.

A Dynamic Re-Configuration Task Holon Assignment Model and Its Solution with Pareto Ant Colony Optimization Algorithm

A Dynamic Re-Configuration Task Holon Assignment Model and Its Solution with Pareto Ant Colony Optimization Algorithm

WDM network re-optimization avoiding costly traffic disruptions

Network re-optimization is a process that must be triggered periodically in order to improve the inefficient resource allocation of online routing heuristics due to the uncertainty of online lightpath demand arrivals and departures. Network re-optimization involves two tasks: a) finding new lightpaths for a (sub)set of current demands, i.e. rerouting, and b) migrating the current traffic to the new configuration diminishing traffic disruptions, i.e. lightpath reconfiguration. If not controlled, excessive traffic disruptions may be a cause of violations of clients' Service Level Agreement, which should be compensated by the network operator with penalization fees. So far, rerouting and reconfiguration tasks of a re-optimization process have been done separately, hence, efforts in trying to achieve the best network performance (rerouting) yields to solutions incurring on unacceptable traffic disruptions (reconfiguration) and vice-versa. In this paper, given a time-disruption threshold for reconfiguring every demand, we present a novel methodology consisting on two procedures that collaboratively find the best network performance without incurring on penalization fees. Our numerical results are extremely encouraging: in our scenarios, it is always possible to achieve an optimal routing performance without incurring on penalization fees.

ARC: a metacomputing environment for clusters augmented with reconfigurable hardware

The addition of reconfigurable hardware (FPGAs) to the nodes of Beowulf-style clusters has the potential to accelerate a variety of parallel applications through a combination of parallel programming and reconfigurable computing techniques. However, making efficient use of the computational resources available places a significant burden on the application developer due to the lack of support for reconfigurable computing and task heterogeneity in standard message-passing libraries. This paper describes Accessible Reconfigurable Computing (ARC), a metacomputing environment designed to address these issues. The architecture, implementation, and operation of the system are described in detail.

Data Preparation 101: How To Use Query-By-Example To Get Your Research Dataset Ready For Primetime

Researchers are often distressed to discover that the data they wanted to use in their landmark study is not configured in a way that is usable by a Statistical Analysis Software Package (SASP). For example, the data needed may come from two or more sources and it may not be clear to the researcher how to get them combined into one analyzable dataset. Fortunately, there is hope. The query facility within database management software (DBMS), such as Microsoft Access, is particularly well-equipped to do the data reconfigurations necessary to get datasets ready for a SASP. Unfortunately, most researchers have either never been exposed to a DBMS or are unaware of the powerful data-transforming queries that they can perform. The purpose of this paper is to introduce researchers to some very helpful and relatively easy to learn techniques for solving common dataset misconfiguration problems. It is presented in three sets of hands-on examples: (1) how to import a dataset from an electronic spreadsheet into a database table, (2) how to use an easy-to-learn DBMS facility called Query-By-Example (QBE) to perform specific data reconfiguration tasks, and (3) how to import the reconfigured dataset from the DBMS into a SASP. The software used is MS Excel, MS Access, and SPSS (originally called Statistical Package for the Social Sciences). The examples are presented step-by-step so that the reader can follow along using files downloadable from the authors website

A Geometric Approach to Dynamically Feasible, Real-Time Formation Control

Abstract We propose a framework for synthesizing real-time trajectories for a wide class of coordinating multi-agent systems. The class of problems considered is characterized by the ability to decompose a given formation objective into an equivalent set of lower dimensional problems. These include the so called radar deception problem and the formation control problems that fall under formation keeping and/or formation reconfiguration tasks. The decomposition makes the approach scalable, computationally economical, and decentralized. Most importantly, the designed trajectories are dynamically feasible, meaning that they maintain the formation while satisfying the nonholonomic and saturation type velocity and acceleration constraints of each individual agent. The main contributions of this paper are (i) explicit consideration of second order dynamics for agents, (ii) explicit consideration of nonholonomic and saturation type velocity and acceleration constraints, (iii) unification of a wide class of formation control problems, and (iv) development of a real-time, distributed, scalable, computationally economical motion planning algorithm.

Bank of Virtual Actuators for Fault Tolerant Control

AbstractWe propose an actuator fault tolerant control scheme based on a bank of virtual actuators (VA), with the novel feature that the virtual actuators implicitly integrate both fault detection and isolation (FDI) and controller reconfiguration (CR) tasks. The bank of VAs operates in closed-loop with an observer-based tracking controller designed for a nominal (fault free) model of the plant. We consider abrupt actuator faults ranging over a finite cover. Each VA is designed to operate appropriately in combination with the nominal controller to achieve correct CR for a particular fault situation in the considered range. A switching rule that engages the suitable VA from the bank is based on sets defined for measurable residual signals constructed directly from the virtual actuators signals. The overall scheme is shown to guarantee closed-loop boundedness and setpoint tracking under all considered fault situations. The method is applied to an example of aircraft lateral control.