Output feedback control of a class of nonminimum‐phase nonlinear systems

The problem of global stabilization by output feedback is investigated in this paper for a class of nonminimum‐phase nonlinear systems. The system under consideration has a cascade configuration that consists of a driven system known as the inverse dynamics and a driving system. It is proved that although the zero dynamics may be unstable, there is an output feedback controller, globally stabilizing the nonminimum‐phase system if both driven and driving systems have a lower‐triangular form and satisfy a Lipschitz‐like condition, and the inverse dynamics satisfy a stronger version of input‐to‐state stabilizability condition. A design procedure is provided for the construction of an n‐dimensional dynamic output feedback compensator. Examples and simulations are also given to validate the effectiveness of the proposed output feedback controller. Copyright © 2016 John Wiley & Sons, Ltd.     

Generic properties and control of linear structured systems: a survey

In this survey paper, we consider linear structured systems in state space form, where a linear system is structured when each entry of its matrices, like A,B,C and D, is either a fixed zero or a free parameter. The location of the fixed zeros in these matrices constitutes the structure of the system. Indeed a lot of man-made physical systems which admit a linear model are structured. A structured system is representative of a class of linear systems in the usual sense. It is of interest to investigate properties of structured systems which are true for almost any value of the free parameters, therefore also called generic properties. Interestingly, a lot of classical properties of linear systems can be studied in terms of genericity. Moreover, these generic properties can, in general, be checked by means of directed graphs that can be associated to a structured system in a natural way. We review here a number of results concerning generic properties of structured systems expressed in graph theoretic terms. By properties we mean here system-specific properties like controllability, the finite and infinite zero structure, and so on, as well as, solvability issues of certain classical control problems like disturbance rejection, input-output decoupling, and so on. In this paper, we do not try to be exhaustive but instead, by a selection of results, we would like to motivate the reader to appreciate what we consider as a wonderful modelling and analysis tool. We emphasize the fact that this modelling technique allows us to get a number of important results based on poor information on the system only. Moreover, the graph theoretic conditions are intuitive and are easy to check by hand for small systems and by means of well-known polynomially bounded combinatorial techniques for larger systems.     

Building an automated and self‐configurable emulation testbed for grid applications

Distributed systems, such as grids, are composed of geographically distributed computing elements that belong to multiple administrative domains and are controlled by multiple entities. It is unlikely that testers are able to acquire repeatedly the same resources, for the same amount of time, and under the same network conditions, which are paramount requirements for enabling reproducible and controlled tests in software under development. An alternative to experiments in real testbeds is the use of emulation tools, which allow the software to run in an environment that behaves like a distributed system. Although advances in virtualization technology allowed the development of efficient emulators, few efforts were put in making operation of such emulators easier. This paper presents the design and the development of the Automated Emulation Framework that allows automatic mapping of virtual machines to hosts, virtual machine deployment, network configuration, and proactive management and reconfiguration of the virtual infrastructure. Copyright © 2010 John Wiley & Sons, Ltd.     

Uncertainty handling in rule-based mobile context-aware systems

Uncertainty handling is one of the most important aspects of modelling of context-aware systems. It has direct impact on the adaptability, understood as an ability of the system to adjust to changing environmental conditions or hardware configuration (missing data), changing user habits (ambiguous concepts), or imperfect information (low quality sensors). In mobile context-aware systems, data is most often acquired from device’s hardware sensors (like GPS, accelerometer), virtual sensors (like activity recognition sensor provided by the Google API) or directly from the user. Uncertainty of such data is inevitable, and therefore it is obligatory to provide mechanisms for modelling and processing it. In this paper, we propose three complementary methods for dealing with most common uncertainty types present in mobile context-aware systems. We combine modified certainty factors algebra, probabilistic interpretation of rule-based model, and time-parametrised operators into a comprehensive toolkit for modelling and building robust mobile context-aware systems. Presented approach was implemented and evaluated on the practical use-case.     

Membrane Systems with Peripheral Proteins: Transport and Evolution

Transport of substances and communication between compartments are fundamental biological processes, often mediated by the presence of complementary proteins attached to the surfaces of membranes. Within compartments, substances are acted upon by local biochemical rules. Inspired by this behaviour we present a model based on membrane systems, with objects attached to the sides of the membranes and floating objects that can move between the regions of the system. Moreover, in each region there are evolution rules that rewrite the transported objects, mimicking chemical reactions. We first analyse the system, showing that interesting qualitative properties can be decided (like reachability of configurations) and then present a simulator based on a stochastic version of the introduced model and show how it can be used to simulate relevant quantitative biological processes.     

Swing-up and stabilization of a cart–pendulum system under restricted cart track length

This paper describes the swing-up and stabilization of a cart–pendulum system with a restricted cart track length and restricted control force using generalized energy control methods. Starting from a pendant position, the pendulum is swung up to the upright unstable equilibrium configuration using energy control principles. An “energy well” is built within the cart track to prevent the cart from going outside the limited length. When sufficient energy is acquired by the pendulum, it goes into a “cruise” mode when the acquired energy is maintained. Finally, when the pendulum is close to the upright configuration, a stabilizing controller is activated around a linear zone about the upright configuration. The proposed scheme has worked well both in simulation and a practical setup and the conditions for stability have been derived using the multiple Lyapunov functions approach.     

An Efficient Algorithm for Minimizing Real-Time Transition Systems

We address the problem of performing simultaneously reachability analysis and minimization of real-time transition systems represented by timed automata, i.e., automata extended with a finite set of clock variables. The transitions of the automaton may depend on the values of the clocks and may reset some of the clocks. An efficient algorithm is presented for minimizing a system with respect to a given initial partition that respects the enabling conditions of the transitions of the timed automaton. Our algorithm generates the portion of the minimized system that is reachable from a given initial configuration in time polynomial in the input and the size of the minimal reachable system.     

Coordination and communication issues in multi-agent expert system: concurrent configuration design advisor

The model of concurrent configuration design and the architecture of Concurrent Configuration Design Advisor (CCDA) are considered. The CCDA is developed as an open dynamic expert system of interacting agents. In the context of this article a configuration problem is defined as a decision-making procedure performed by concurrent processes (agents). The analysis of concurrent and sequential activities in this system is based on structural transformations (in the form of graph grammars) that permits the definition of correct criteria for data integrity and the consistency of configured project data model, and any dynamic changes in the project to be modeled conveniently. This approach also makes it possible to handle complex hierarchial data structures of real configured objects and to model communication and synchronization of decision making in a distributed expert system in a common formalism. The system to be configured is decomposed into structured objects, called fragments. The proposed model consists of three types of agents. D-agents are those capable of the object configuration design within the constraints on their attributes. To cope with agents' coordination, objects' consistency and data integrity problems, a special type of agent, facilitator or F-agent, is introduced. Finally, project assistants or A-agents are responsible for the user interface at the stage of object model definition. The discussion is illustrated with examples from the application domain of flexible manufacturing systems. Experimental results, current and future work on the expert system implementation are considered.     

Coordinating components in middleware systems

Configuration and coordination are central issues in the design and implementation of middleware systems and are one of the reasons why building such systems is more complex than constructing stand‐alone sequential programs. Through configuration, the structure of the system is established—which elements it contains, where they are located and how they are interconnected. Coordination is concerned with the interaction of the various components—when an interaction takes place, which parties are involved, what protocols are followed. Its purpose is to coordinate the behaviour of the various components to meet the overall system specification. The open and adaptive nature of middleware systems makes the task of configuration and coordination particularly challenging. We propose a model that can operate in such an environment and enables the dynamic integration and coordination of components by observing and coercing their behaviour through the interception of the messages exchanged between them. Copyright © 2003 John Wiley & Sons, Ltd.     

高能物理实验数据传输系统的研究和实现

高能物理主要通过各种实验来研究基本粒子及其相互作用，每个高能物理实验每天都会产生大量的实验数据。由于高能物理实验异地建设的特点，如何把实验数据实时、可靠的从实验现场传输到远程的数据中心进行处理和分析，是各个实验需要研究的重要课题。介绍了一种通用的高能物理数据传输系统，通过接口定义与配置文件相结合的方法，满足各个高能物理实验的需求。该系统的模块包括：多路径源数据扫描模块、数据传输模块、数据共享模块、系统配置模块、日志和监视模块等。目前，该系统已经应用于江门中微子实验光电倍增管测试的数据传输。实际运行结果表明，该系统性能良好，能够满足实验的需求。     

A feature-oriented approach for developing reusable product line assets of service-based systems

Service orientation (SO) is a relevant promising candidate for accommodating rapidly changing user needs and expectations. One of the goals of adopting SO is the improvement of reusability, however, the development of service-based system in practice has uncovered several challenging issues, such as how to identify reusable services, how to determine configurations of services that are relevant to users’ current product configuration and context, and how to maintain service validity after configuration changes. In this paper, we propose a method that addresses these issues by adapting a feature-oriented product line engineering approach. The method is notable in that it guides developers to identify reusable services at the right level of granularity and to map users’ context to relevant service configuration, and it also provides a means to check the validity of services at runtime in terms of invariants and pre/post-conditions of services. Moreover, we propose a heterogeneous style based architecture model for developing such systems.     

Simulation of resource synchronization in a dynamic real‐time distributed computing environment

Today, more and more distributed computer applications are being modeled and constructed using real‐time principles and concepts. In 1989, the Object Management Group (OMG) formed a Real‐Time Special Interest Group (RT SIG) with the goal of extending the Common Object Request Broker Architecture (CORBA) standard to include real‐time specifications. This group's most recent efforts have focused on the requirements of dynamic distributed real‐time systems. One open problem in this area is resource access synchronization for tasks employing dynamic priority scheduling. This paper presents two resource synchronization protocols that the authors have developed which meet the requirements of dynamic distributed real‐time systems as specified by Dynamic Scheduling Real‐Time CORBA (DSRT CORBA). The proposed protocols can be applied to both Earliest Deadline First (EDF) and Least Laxity First (LLF) dynamic scheduling algorithms, allow distributed nested critical sections, and avoid unnecessary runtime overhead. In order to evaluate the performance of the proposed protocols, we analyzed each protocol's schedulability. Since the schedulability of the system is affected by numerous system configuration parameters, we have designed simulation experiments to isolate and illustrate the impact of each individual system parameter. Simulation experiments show the proposed protocols have better performance than one would realize by applying a schema that utilizes dynamic priority ceiling update. Copyright © 2004 John Wiley & Sons, Ltd.     

Multi-Kepler GPU vs. multi-Intel MIC for spin systems simulations

We present and compare the performances of two many-core architectures: the Nvidia Kepler and the Intel MIC both in a single system and in cluster configuration for the simulation of spin systems. As a benchmark we consider the time required to update a single spin of the 3D Heisenberg spin glass model by using the Over-relaxation algorithm. We present data also for a traditional high-end multi-core architecture: the Intel Sandy Bridge. The results show that although on the two Intel architectures it is possible to use basically the same code, the performances of a Intel MIC change dramatically depending on (apparently) minor details. Another issue is that to obtain a reasonable scalability with the Intel Phi coprocessor (Phi is the coprocessor that implements the MIC architecture) in a cluster configuration it is necessary to use the so-called offload mode which reduces the performances of the single system. As to the GPU, the Kepler architecture offers a clear advantage with respect to the previous Fermi architecture maintaining exactly the same source code. Scalability of the multi-GPU implementation remains very good by using the CPU as a communication co-processor of the GPU. All source codes are provided for inspection and for double-checking the results.     

A connection between formation infeasibility and velocity alignment in kinematic multi-agent systems

In this paper, a feedback control strategy that achieves convergence of a multi-agent system to a desired formation configuration is proposed for both the cases of agents with single integrator and nonholonomic unicycle-type kinematics. When inter-agent objectives that specify the desired formation cannot occur simultaneously in the state space the desired formation is infeasible. It is shown that under certain assumptions, formation infeasibility forces the agents’ velocity vectors to a common value at steady state. This provides a connection between formation infeasibility and flocking behavior for the multi-agent system. We finally also obtain an analytic expression of the common velocity vector in the case of formation infeasibility.     

A polynomial alternative to unbounded environment for tissue P systems with cell division

The standard definition of tissue P systems includes a special alphabet whose elements are assumed to appear in the initial configuration of the system in an arbitrarily large number of copies. These objects reside in a distinguished place of the system, called the environment. Such potentially infinite supply of objects seems an unfair tool when designing efficient solutions to computationally hard problems in the framework of membrane computing, by performing a space–time trade-off. This paper deals with computational aspects of tissue P systems with cell division where there is no environment having the property mentioned above. Specifically, we prove that the polynomial complexity classes associated with tissue P systems with cell division and with or without environment are actually identical. As a consequence, we conclude that it is not necessary to have infinitely many copies of some objects in the initial configuration in order to solve NP–complete problems in an efficient way.     

A homogeneity property of discrete‐time systems: Stability and convergence rates

A new definition of homogeneity for discrete‐time systems is introduced. As in the continuous‐time case, the property can be verified algebraically in the transition map of the system, and it implies that a dilation of the initial conditions leads to a scaling of the trajectory. Stability properties and convergence rates of the system's solutions can be established by considering only the homogeneity degree. The existence of homogeneous Lyapunov and Lyapunov‐like functions is proven.     

Real-time control of video surveillance systems with program supervision techniques

In this article, we describe a knowledge-based controlled platform using program supervision techniques. This platform eases the creation and the configuration of video surveillance systems. Several issues need to be addressed to provide a correct system configuration: (1) to choose, among a library of programs, those which are best satisfying a given user request, (2) to assign a correct value for each program parameter, (3) to evaluate performances and to guarantee a performance rate which is satisfactory regarding end-user requirements. This platform is composed of three main components: the library of programs, the knowledge base and the control component. The knowledge is either given by experts or learnt by the system. The control is generic in the sense that it is independent of any application. To validate this platform, we have built and evaluated six video surveillance systems which are featured with three properties: adaptability, reliability and real-time processing.     

Model-based detection of routing events in discrete flow networks

A theoretical framework and its practical implications for formulating and implementing model-based monitoring of discrete flow networks are discussed. Possible flows of items are described as discrete-event (DE) traces. Each trace defines the DE sequence(s) that are triggered when an entity follows a given flow-path, visiting tracking locations within the monitored system. To deal with alternative routing, creation of items, flow bifurcations and convergences are allowed. Given the set of possible discrete flows, a possible-behavior model—an interacting set of automata—is constructed, where each automation models the item discrete flow at each tracking location. In this model, which assumes total observability, event labels or symbols contain all the information required to unambiguously distinguish each discrete movement. Within the possible behavior, there is a special sub-behavior whose occurrence is required to be detected. The special behavior may be specified by the occurrence of routing events, such as faults or route violations, for example. These intermittent or non-persistent events may occur repeatedly. An observation mask is then defined, characterizing the observation configuration available for collecting item tracking data. The verification task is to determine whether this observation configuration is capable of detecting the specified special behavior. The assessment is accomplished by evaluating several observability notions, such as detectability and diagnosibility. If the corresponding property is satisfied, associated formal observers are constructed to perform the monitoring task at hand. The synthesis of observation masks may also be conducted to suggest optimal observation configurations (specifying number, type, and tracking locations of observation devices) guaranteeing the detection of special events and to construct associated monitoring agents. The developed framework, modeling methodology, and supporting techniques for defining and implementing discrete flow monitoring of entity movements are presented and illustrated with examples.     

User-programmable gate arrays: design methodology and development systems

Unlike conventional mask-programmed gate arrays, the logic, I/O functions, 7 and interconnections of Xilinx-programmable gate arrays, logic cell arrays (LCAs), are fully user programmable. The functions implemented in an LCA are determined by a configuration program that is loaded during system initialization, much like a programmable microprocessor peripheral. Powerful development tools allow the designer to progress easily from design conception to the generation of the LCA configuration programs. The basic design methodology involves three main steps: design entry, design implementation, and design verification.