A port-Hamiltonian formulation of physical switching systems with varying constraints

This paper extends a generic method to design a port-Hamiltonian formulation modeling all geometric interconnection structures of a physical switching system with varying constraints. A non-minimal kernel representation of this family of structures (named Dirac structures) is presented. It is derived from the parameterized incidence matrices which are a mathematical representation of the primal and dual dynamic network graphs associated with the system. This representation has the advantage of making it possible to model complex physical switching systems with varying constraints and to fall within the framework of passivity-based control.     

Explicit simplicial discretization of distributed-parameter port-Hamiltonian systems

Simplicial Dirac structures as finite analogues of the canonical Stokes–Dirac structure, capturing the topological laws of the system, are defined on simplicial manifolds in terms of primal and dual cochains related by the coboundary operators. These finite-dimensional Dirac structures offer a framework for the formulation of standard input–output finite-dimensional port-Hamiltonian systems that emulate the behavior of distributed-parameter port-Hamiltonian systems. This paper elaborates on the matrix representations of simplicial Dirac structures and the resulting port-Hamiltonian systems on simplicial manifolds. Employing these representations, we consider the existence of structural invariants and demonstrate how they pertain to the energy shaping of port-Hamiltonian systems on simplicial manifolds.     

Superposition: composition vs refinement of non-deterministic,action-based systems

The traditional notion of superposition has been used for supporting two distinct aspects of parallel program design: composition and refinement. This is because, when trace-based semantics of concurrency are considered, which is typical of most formal methods, these two relationships are modelled as inclusion between sets of behaviours. However, when forms of non-deterministic behaviour have to be considered, which is the case for component and service-based development, these two aspects do not coincide. In this paper, we show how the two roles of superposition can be separated and supported at the language and semantic levels. For this purpose, we use a categorical formalisation of program design in the language CommUnity that we are also using for addressing architectural concerns, another area in which the distinction between composition and refinement is particularly important.Correspondence and offprint request to: Antónia Lopes, orgdivisionDepartment of Informatics, Faculty of Sciences, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal.Received November 2002 Accepted in revised form June 2003 by B.T. Denvir and E. Boiten     

Asymptotic stabilization via control by interconnection of port-Hamiltonian systems

We study the asymptotic properties of control by interconnection, a passivity-based controller design methodology for stabilization of port-Hamiltonian systems. It is well-known that the method, in its basic form, imposes some unnatural controller initialization to yield asymptotic stability of the desired equilibrium. We propose two different ways to overcome this restriction, one based on adaptation ideas, and the other one adding an extra damping injection to the controller. The analysis and design principles are illustrated through an academic example.     

Full-order observer design for a class of port-Hamiltonian systems

We consider a special class of port-Hamiltonian systems for which we propose a design methodology for constructing globally exponentially stable full-order observers using a passivity based approach. The essential idea is to make the augmented system consisting of the plant and the observer dynamics to become strictly passive with respect to an invariant manifold defined on the extended state-space, on which the state estimation error is zero. We first introduce the concept of passivity of a system with respect to a manifold by defining a new input and output on the extended state-space and then perform a partial state feedback passivation which leads to the construction of the observer. We then illustrate this observer design procedure on two physical examples, the magnetic levitation system and the inverted pendulum on the cart system.     

Jet bundle formulation of infinite-dimensional port-Hamiltonian systems using differential operators

We consider infinite-dimensional port-Hamiltonian systems described on jet bundles. Based on a power balance relation we introduce the port-Hamiltonian system representation using differential operators regarding the structural mapping, the dissipation mapping and the input mapping. In contrast to the well-known representation on the basis of the underlying Stokes–Dirac structure our approach is not necessarily based on using energy-variables which leads to a different port-Hamiltonian representation of the analyzed partial differential equations. The presented constructions will be specialized to mechanical systems to which class also the presented examples belong.     

实例讲解七层协议参考模型

对OSI七层协议参考模型的概念,通过用寄信收信的过程,形象的说明了每一层的功能,以QQ信息的发送过程为例,深入探讨了通过七层进行网络互联.     

Energy shaping of distributed parameter port-Hamiltonian systems based on finite element approximation

The main contribution of this paper is a procedure for the control by energy shaping via Casimir generation of infinite dimensional port-Hamiltonian systems based on a particular finite element approximation. The proposed approach is justified by the fact that the adopted spatial discretization technique is able to preserve Casimir functions in the closed-loop system when going from the distributed to the (approximated) lumped parameter system. Besides the intrinsic difficulties related to the large number of state variables, the finite element model is generally given in terms of a Dirac structure and is completely a-causal, which implies that the plant dynamics is not given in standard input-state-output form, but as a set of DAEs. Consequently, the classical energy Casimir method has to be extended in order to deal with dynamical systems with constraints, usually appearing in the form of Lagrangian multipliers. The general methodology is illustrated with the help of an example in which the distributed parameter system is a lossless transmission line.     

Structure preserving model reduction of port-Hamiltonian systems by moment matching at infinity

Model reduction of port-Hamiltonian systems by means of the Krylov methods is considered, aiming at port-Hamiltonian structure preservation. It is shown how to employ the Arnoldi method for model reduction in a particular coordinate system in order to preserve not only a specific number of the Markov parameters but also the port-Hamiltonian structure for the reduced order model. Furthermore it is shown how the Lanczos method can be applied in a structure preserving manner to a subclass of port-Hamiltonian systems which is characterized by an algebraic condition. In fact, for the same subclass of port-Hamiltonian systems the Arnoldi method and the Lanczos method turn out to be equivalent in the sense of producing reduced order port-Hamiltonian models with the same transfer function.     

Discrete-event modeling of multi-agent systems with broadcasting-based parallel composition

Multi-agent systems have been widely used in logistics and manufacturing. In this paper we develop an automaton-based modeling framework for a special type of multi-agent systems, where agents are instantiated from a finite number of finite-state automaton templates, and interactions among agents are characterized via cooperative synchronization and broadcasting. To describe the compositional behavior of all agents, we propose a novel broadcasting-based parallel composition rule and show that it is commutative and associative. The effectiveness of this modeling framework and the parallel composition rule is illustrated in a simple multi-agent system.     

LEO卫星网络的有限互联

随着空间技术的发展,空间飞行器产生越来越多的数据,这些数据需要传输到地面或者其它卫星上。受星载设备性能和其它因素的限制,IP路由技术难以应用LEO卫星网络上。IP路由的负荷之所以高,主要原因是IP网络采用“无限互联”的设计理念。为了降低路由负荷,提出“有限互联”的概念。端节点在网络地址发生变化时只通知有限个友节点,端节点维护与友节点之间的联系,由此将部分路由负荷从路由节点转移到端节点上。     

Novell Netware和WindowsNT互连技术

在对网络协议软件的接口技术和网络体系结构分析的基础上,阐述了Ｎｅｔｗａｒｅ和ＷｉｎｄｏｗｓＮＴ互连的可能性,并以Ｎｅｔｗａｒｅ和ＷｉｎｄｏｗｓＮＴ互连的实现方法为例,说明异种网络操作系统互连的实现具有广泛的实用价值。     

长距离宽带网络互联通道的设计与实现

介绍了一种简单实用的长距离网络互联方案,着重讨沦了其管理和运行模式、设备选择、路由策略和带宽分配等问题。     

一种多平台互连网络设计

本文给出了TGRC计算机组网设计方案，分析和比较了计算机网络技术中的拓扑结构技术、网络操作系统技术以及异种机互连技术．结合TGRC的网络应用特点和将来的网络业务扩展，论述了该网络设计方案的先进性、高可靠性、易维护性和易扩充性．     

A dual relation between port-Hamiltonian systems and the Brayton-Moser equations for nonlinear switched RLC circuits

In the last decades, several researchers have concentrated on the dynamic modeling of nonlinear electrical circuits from an energy-based perspective. A recent perspective is based on the concept of port-Hamiltonian (PH) systems. In this paper, we discuss the relations between the classical Brayton-Moser (BM) equations—stemming from the early sixties—and PH models for topologically complete nonlinear RLC circuits, with and without controllable switches. It will be shown that PH systems precisely dualize the BM equations, leading to possible advantages at the level of controller design. Consequently, useful and important properties of the one framework can be translated to the other. Control designs for the PH model cannot be directly implemented since they require observation of flux and charges, which are not directly available through standard sensors, while the BM models require only observation of currents and voltages. The introduced duality allows to pull back PH designs to the space of currents and voltages. This offers the possibility to exchange several different techniques, available in the literature, for modeling, analysis and controller design for RLC circuits. Illustrative examples are provided to emphasize the duality between both frameworks.     

Interconnection of CAN segments through IEEE 802.16 wireless MAN

The Controller Area Network (CAN) is a high-performance and highly reliable advanced serial communication protocol, which efficiently supports distributed real-time control. CAN-based distributed control systems have generally two main problems that are the size of distributed area and the need for communication with other LANs and with remote CAN segments. A straightforward solution is to use internetworking devices with wireless support to extend CAN segments. In this paper, a new solution to interconnect CAN segments is proposed, which uses a wireless MAN based on the IEEE 802.16 standard as a backbone system. Also, the solution describing a model for internetworking unit integrates the traffic generated by CAN segments into IEEE 802.16 wireless MAN using encapsulation technique.     

Vertex-neighbour-integrity of composition graphs of paths and cycles

A vertex subversion strategy of a graph G is a set of vertices X? V(G) whose closed neighbourhood is deleted from G. The survival subgraph is denoted by G/X. The vertex-neighbour-integrity of G is defined to be VNI(G)=min{|X|+τ(G/X):X? V(G)}, where τ(G/X) is the maximum order of the components of G/X. This graph parameter was introduced by Cozzens and Wu to measure the vulnerability of spy networks. Gambrell proved that the decision problem of computing the vertex-neighbour-integrity of a graph is 𝒩𝒫-complete. In this paper we evaluate the vertex-neighbour-integrity of the composition graphs of paths and cycles.     

Robust integral control of port-Hamiltonian systems: The case of non-passive outputs with unmatched disturbances

Regulation of passive outputs of nonlinear systems can be easily achieved with an integral control (IC). In many applications, however, the signal of interest is not a passive output and ensuring its regulation remains an open problem. Also, IC of passive systems rejects constant input disturbances, but no similar property can be ensured if the disturbance is not matched. In this paper we address the aforementioned problems and propose a procedure to design robust ICs for port-Hamiltonian models, that characterize the behavior of a large class of physical systems. Necessary and sufficient conditions for the solvability of the problem, in terms of some rank and controllability properties of the linearized system, are provided. For a class of fully actuated mechanical systems, a globally asymptotically stabilizing solution is given. Simulations of the classical pendulum system illustrate the good performance of the scheme.     

Cognitive loads and the empowering effect of music composition software

An investigation of music composition software in classrooms was used to study some ways in which open software can support problem solving and thinking. Students of different abilities and ages were observed doing music composition with the software in a variety of teaching contexts. The observations, and the resulting compositions, often showed a level of sophistication in musical structure which could not have been achieved unaided. A number of explanations are considered for this: it is argued that an explanation based on cognitive loads is most convincing in this case. The removal of cognitive loads does nothing positive to help students, but simply gives more space to think by transferring low level cognitive burdens to the software.