Reasoning about dynamically evolving process structures

We develop a Hoare-style proof system for reasoning about the behaviour of processes that interact via a dynamically evolving communication structure.     

Structure evolving systems and control in integrated design

Existing methods in Systems and Control deal predominantly with Fixed Systems, that have been designed in the past, and for which the control design has to be performed. The new paradigm of Structure Evolving Systems (SES), expresses a new form of system complexity where the components, interconnection topology, measurement-actuation schemes may not be fixed, the control scheme also may vary within the system-lifecycle and different views of the system of varying complexity may be required by the designer. Such systems emerge in many application domains and in the engineering context in problems such as integrated system design, integrated operations, re-engineering, lifecycle design issues, networks, etc. The paper focuses on the Integrated Engineering Design (IED), which is revealed as a typical structure evolution process that is strongly linked to Control Theory and Design type problems. It is shown, that the formation of the system, which is finally used for control design evolves during the earlier design stages and that process synthesis and overall instrumentation are critical stages of this evolutionary process that shapes the final system structure and thus the potential for control design. The paper aims at revealing the control theory context of the evolutionary mechanism in overall system design by defining a number of generic clusters of system structure evolution problems and by establishing links with existing areas of control theory. Different aspects of model evolution during the overall design are identified which include cases such as: (i) Time-dependent evolution of system models from “early” to “late” stages of design. (ii) Design stage-dependent evolution from conceptualisation to process synthesis and to overall instrumentation. (iii) Redesign of given systems and constrained system evolution. Within each cluster a number of well defined new Control Theory problems are introduced, which may be studied within the structural methodologies framework of Linear Systems. The problems posed have a general systems character, but the emphasis here is on Linear Systems; an overview of relevant results is given and links with existing research topics are established. The paper defines the Structural Control Theoretic context of an important family of complex systems emerging in engineering design and defines a new research agenda for structural methods of Control Theory. Copyright ©2002 IFAC     

A mathematical model of dynamically evolving economics

Cybernetics and Systems Analysis -     

3-Col problem modelling using simple kernel P systems

This paper presents the newly introduced class of (simple) kernel P systems ((s)kP systems) and investigates through a 3-colouring problem case study the expressive power and efficiency of kernel P systems. It describes two skP systems that model the problem and analyses them in terms of efficiency and complexity. The skP models prove to be more succinct (in terms of number of rules, objects, number of cells and execution steps) than the corresponding tissue P system, available in the literature, that solves the same problem, at the expense of a greater length of the rules.     

Simulation of systems with dynamically varying model structure

Hybrid systems are dynamical systems composed of components with discrete and continuous behavior. Some systems change their structure during simulation, or their components behavior is essentially changing. This “structural dynamics” can be described in some modeling languages but the corresponding hybrid simulators have more or less restrictions in handling models with dynamically varying structure. Some basic approaches for the simulation of such systems are discussed in the context of modeling languages and simulators.     

一种多层次的P2P VoD系统结构

针对VoD系统节目点播的不均匀特性以及P2P系统的动态变化特性,设计了一种多层次的网络拓扑组织结构,包括：链网状结构、基于服务频道的块状分群结构、以及DHT查询存储结构,以保证不同点播频率的节目都能获得较好的QoS保证。仿真结果表明,这种多层次的系统结构可以有效地保证用户的QoS需求。     

Decentralized stabilization of dynamically interconnected systems

A decentralized stabilization design with most evenly distributed complexity of controllers is presented for dynamically interconnected systems.     

DECM,A User Oriented Formalism for High Level Discrete Event Specifications of Real-Time Systems

In this paper, we present DECM (Discrete Event Calculus Model), an original discrete event mathematical model for the specification of control systems at a high level of abstraction. Because the concept of event is more natural for nonspecialists than the concept of state, the proposed model is centered on the latter concept. This in turn permits the expression of asynchronous behavior without relying on the classical concept of state. In addition, DECM-based formalism offers an explicit representation of time that allows the use of timed simulations for the validation of formal specifications. This formalism is illustrated on a real-world industrial example.     

Incremental maintenance of semantic links in dynamically changing hypertext systems

One purported advantage of hypertext systems is the ability to move between semantically related parts of a document (or family of documents). If the document is undergoing frequent modification (for example while an author is writing a book or while a software design stored in the hypertext system is evolving) the question arises as to how to incrementally maintain semantic interconnections in the face of the modifications.

The paper presents an optimal technique for the incremental maintenance of such interconnections as a document evolves. The technique, based on theories of information retrieval based on lexical affinities and theories of incremental computation, updates semantic interconnections as nodes are checked into the hypertext system (either new or as a result of an edit). Because we use the semantic weight of lexical affinities to determine which affinities are meaningful in the global context of the document, introducing a new affinity or changing the weight of an existing affinity can potentially have an effect on any node in the system. The challenge met by our algorithm is to guarantee that despite this potentially arbitrary impact, we still update link information optimally.

Once established the semantic interconnections are used to allow the user to move from node to node based not on rigid connections but instead on dynamically determined semantic interrelationships among the nodes.     

Stochastic affine quadratic regulator with applications to tracking control of quantum systems

This paper deals with the regulator theory of stochastic affine systems. Applying a tensor formal power series method, stochastic bilinear quadratic regulator is solved numerically. An example about tracking control of quantum systems is given to show the usefulness of the developed theory.     

基于动态膜计算系统的自组织网络广播算法

应用仿生学原理设计了一种新型的广播算法——基于动态膜计算系统的广播算法,提出了动态膜计算系统,并给出了解决自组织网络中广播问题的规则集。系统中节点转播信息的优先权通过节点间距离及邻居个数确定,适合不同密度的网络;并根据信息数与门限值的比较,取消部分节点的转播权,从而提高了可达率和转播节省率。仿真测试验证了此系统用于广播是可行的、高效的,为设计无线自组织网络中的广播算法提供了新思路。     

A concept of dynamically reconfigurable real-time vision system for autonomous mobile robotics

This paper describes specific constraints of vision systems that are dedicated to be embedded in mobile robots. If PC-based hardware architecture is convenient in this field because of its versatility, flexibility, performance, and cost, current real-time operating systems are not completely adapted to long processing with varying duration, and it is often necessary to oversize the system to guarantee fail-safe functioning. Also, interactions with other robotic tasks having more priority are difficult to handle. To answer this problem, we have developed a dynamically reconfigurable vision processing system, based on the innovative features of Cleopatre real-time applicative layer concerning scheduling and fault tolerance. This framework allows to define emergency and optional tasks to ensure a minimal quality of service for the other subsystems of the robot, while allowing to adapt dynamically vision processing chain to an exceptional overlasting vision process or processor overload. Thus, it allows a better cohabitation of several subsystems in a single hardware, and to develop less expensive but safe systems, as they will be designed for the regular case and not rare exceptional ones. Finally, it brings a new way to think and develop vision systems, with pairs of complementary operators.     

Bounds on the optimal quantization performance of dynamically quantized linear systems with bounded noise

This paper studies a class of quantized linear control systems with diagonalizable system matrices and perturbed by bounded noise. The quantization performance of such systems is measured with the supremum of the quantization error sequence. Our goal is to improve this performance (reduce the quantization error) through designing appropriate quantization policies. Due to their efficiency, the dynamic quantization policies are considered in this paper. A lower bound on the optimal (minimum) quantization error is provided. We also propose a new quantization policy, whose quantization error is an upper bound on the optimal one. A more tractable upper quantization error bound is derived from the new policy. It is shown through simulations that the new policy's quantization error is very close to the lower bound, which confirms both the tightness of the lower bound and the efficiency of the new policy. The achieved lower and upper quantization error bounds, together with the quantization error of the new quantization policy, may provide a good indication on the optimal quantization performance. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

A formalization of geometric constraint systems and their decomposition

For more than a decade, the trend in geometric constraint systems solving has been to use a geometric decomposition/recombination approach. These methods are generally grounded on the invariance of systems under rigid motions. In order to decompose further, other invariance groups (e.g., scalings) have recently been considered. Geometric decomposition is grounded on the possibility to replace a solved subsystem with a smaller system called boundary. This article shows the central property that justifies decomposition, without assuming specific types of constraints or invariance groups. The exact nature of the boundary system is given. This formalization brings out the elements of a general and modular implementation.     

A formal framework to test soft and hard deadlines in timed systems

This paper introduces a formal framework to specify and test systems presenting both soft and hard deadlines. While hard deadlines must always be met on time, soft deadlines can be sometimes met in a different time, usually greater, from the specified one. It is this characteristic (to formally definetextitsometimes) that produces several reasonable alternatives to define appropriate implementation relations, that is, relations to decide whether an implementation is correct with respect to a specification. In addition to introducing these relations, the paper also presents a formal testing framework to test implementations and provides an algorithm to derive sound and complete test suites with respect to the implementation relations previously defined. That is, an implementation conforms to a specification if and only if the implementation successfully passes all the tests belonging to the suite derived from the specification. Copyright © 2011 John Wiley & Sons, Ltd.     

Robust output feedback stabilization of uncertain dynamic systems with bounded controllers

We propose a new class of infinitely many bounded output feedback controllers for uncertain dynamic systems with bounded uncertainties. No statistical information about the uncertainties is assumed. A variable structure systems approach is employed in the synthesis of the proposed output feedback controllers. The role of the system zeros in the output feedback stabilization using the variable structure approach is discussed. We show that the proposed controllers guarantee the practical stability of the closed-loop system and give estimates of the regions of practical stability.