基于TLA的事件图模型形式化验证方法*

针对目前没有直接对事件图模型进行形式化验证的方法,提出了一种基于行为时态逻辑(temporal logic of action,TLA)的事件图模型形式化验证方法.该方法利用TLA语言能够同时表达模型行为与逻辑规则的特点及其与事件图的相似性,将事件图模型及性质规约用TLA语言进行形式化描述,从而使该模型能够被TLA模型...     

基于赋时事件图的故障诊断

赋时事件图(TEG)是一类用于描述同步特性的重要的Petri网.本文提出并研究了基于赋时事件图的故障诊断问题.文中定义了两类系统故障类型:变迁失效(Invalidation)故障和变迁时间延迟(Time_lag)故障.基于事件图关联矩阵,通过研究变迁失效故障的可观测传播特性,引入了故障特征向量的概念.基于此,给出了失效故障的可诊断性的充分必要条件.对于时延故障,提出了一种基于变迁触发时间估计进行故障诊断的简单算法.并基于此算法,研究了时延故障的可诊断条件.     

Feedback stabilization using two-hidden-layer nets

The representational capabilities of one-hidden-layer and two-hidden-layer nets consisting of feedforward interconnections of linear threshold units are compared. It is remarked that for certain problems two hidden layers are required, contrary to what might be in principle expected from the known approximation theorems. The differences are not based on numerical accuracy or number of units needed, nor on capabilities for feature extraction, but rather on a much more basic classification into direct and inverse problems. The former correspond to the approximation of continuous functions, while the latter are concerned with approximating one-sided inverses of continuous functions, and are often encountered in the context of inverse kinematics determination or in control questions. A general result is given showing that nonlinear control systems can be stabilized using two hidden layers, but not, in general, using just one.     

Feedback stabilization of single-input nonlinear systems

Nonlinear geometric techniques (partial feedback linearization) and center manifold theory allow to reduce the design of a feedback stabilizing control for single-input nonlinear systems into a lower dimensional stabilization problem. The reduced order control system is explicitly constructed.     

Debugging parallel programs using event graph manipulation

The need for more accurate results and larger problem sizes pushes the users in certain fields towards using supercomputing power. Besides problems with initial program development, another problem arises with debugging this kind of program. Debugging parallel programs is one of the hard tasks that users have to deal with when using parallel architectures. Where memory hot spots and bus contention are problems with shared memory architectures, nondeterminism arising from race conditions and the lack of a global clock are severe problems in using distributed memory architectures. We will discuss a new approach for detecting and/or studying concurrent events in distributed memory machines if race conditions occur in a certain program run. Through event graph manipulation the user can investigate whether wrong results may appear through different ordering of events.     

Feedback stabilization of uniform rigid body rotation

This abstract discusses the stabilization of uniform rigid body rotation about an arbitrary axis by feedback control. The class of feedback control laws considered is linear and is shown to robustly stabilize rotation with respect to inertia uncertainty. The methodology developed in this paper is based on the energy-momentum method of stability analysis and fully exploits the underlying geometry. The methodology is illustrated with several examples.     

Feedback stabilization of discrete-time homogeneous semi-linear systems

For discrete-time semi-linear systems satisfying an accessibility condition asymptotic null controllability is equivalent to exponential feedback stabilizability using a piecewise constant feedback. A constructive procedure that yields such a feedback is presented.     

Feedback stabilization and tracking of constrained robots

Mathematical models for constrained robot dynamics, incorporating the effects of constraint force required to maintain satisfaction of the constraints, are used to develop explicit conditions for stabilization and tracking using feedback. The control structure allows feedback of generalized robot displacements, velocities, and the constraint forces. Global conditions for tracking, based on a modified computed-torque controller and local conditions for feedback stabilization, using a linear controller, are presented. The framework is also used to investigate the closed-loop properties if there are force disturbances, dynamics in the force feedback loops, or uncertainty in the constraint functions     

Feedback stabilization of dissipative impulsive dynamical systems

In this paper, we derive conditions under which a dissipative impulsive dynamical system is asymptotically stabilizable by a feedback controller. Specializing the obtained results to the case of dissipative linear impulsive dynamical systems with the quadratic supply rate, we establish the corresponding sufficient conditions. Finally, simulation results are given to demonstrate the effectiveness of our results.     

离轴式拖车移动机器人的反馈镇定

由于离轴式拖车移动机器人的模型不能转化为非完整链式模型, 因而无法采用针对非完整链式模型的控制方法. 针对有多节离轴式拖车的移动机器人, 给出了一种基于时间–状态能控形的反馈镇定控制算法. 首先推导出系统的线性化时间–状态模型, 并证明了其能控性; 进而设计了一种线性切换反馈镇定控制律, 该控制律可以保证系统的状态在有限时间内收敛到原点的任意小邻域内. 仿真结果证实了所提控制算法的有效性.     

Feedback stabilization of multivariable two-dimensional linear systems

A constructive algorithm is presented for solving a two-dimensional (2-D) polynomial matrix equation that plays an important role in the output feedback stabilization of multivariable 2-D linear systems. It is shown that this algorithm can have some computational advantages over the previous known ones based on the Gröbner-basis approach. As an application of the algorithm, the class of all stabilizing strictly causal 2-D compensators is parametrized for a given stabilizable causal (not necessarily strictly causal) 2-D plant.     

Feedback stabilization via designed planar centre manifold

This paper addresses the problem of local state feedback stabilization of a class of nonlinear systems, which have planar centre manifold. A new technique for designing centre manifold has been developed. Using this approach, a sufficient condition for stabilization of a class of nonlinear system is obtained. The approach has been specified for two particular critical cases: ‘zero centre’ with zero eigenvalue of multiplicity 2 and ‘oscillatory centre’ with a pair of pure imaginary eigenvalues. The control law, which stabilizes the overall system, is also presented. Some examples are presented to indicate how the present theorem may be implemented. Copyright © 2003 John Wiley & Sons, Ltd.     

Diversity of graph models and graph generators in mutation testing

When custom modeling tools are used for designing complex safety-critical systems (e.g., critical cyber-physical systems), the tools themselves need to be validated by systematic testing to prevent tool-specific bugs reaching the system. Testing of such modeling tools relies upon an automatically generated set of models as a test suite. While many software testing practices recommend that this test suite should be diverse, model diversity has not been studied systematically for graph models. In the paper, we propose different diversity metrics for models by generalizing and exploiting neighborhood and predicate shapes as abstraction. We evaluate such shape-based diversity metrics using various distance functions in the context of mutation testing of graph constraints and access policies for two separate industrial DSLs. Furthermore, we evaluate the quality (i.e., bug detection capability) of different (random and consistent) model generation techniques for mutation testing purposes.

     

Feedback stabilization of linear autonomous time lag systems

A stabilization theory which employs well-established finite-dimensional control system tools is developed for the stabilization of linear autonomous time lag systems. The main ideas include 1) a set whose elements are matrices each of which is a left zero of the system characteristic quasi-polynomial matrix, and 2) a linear transformation which reduces the delay system to a delay-free system whose state matrix is a direct sum ofNelements of the matrix set whereNis some positive integer. From the definition of this matrix set, it is shown that each of its elements inherits its spectrum from that of the delay system so that by design, the system unstable poles may be embedded in the spectrum of the delay-free system. Under the assumption of spectral stabilizability, it is then shown how to obtain a stabilizing feedback control law on the basis of the delay-free system. Numerical examples are presented to confirm the theory.     

Feedback stabilization of abstract neutral linear control systems

In this paper, the asymptotic stabilization of linear distributed parameter control systems of neutral type is considered. Specifically, we study control systems described by a special type of abstract neutral functional differential equation with finite delay. Assuming appropriate conditions, and using the spectral properties of quasi-compact semigroups, we show that the usual spectral controllability assumption implies the feedback stabilization of the system. We applied our results to the stabilization of several real systems of first and second order described by partial neutral functional differential equations.     

一类分布参数系统的反馈能稳性

研究了一类分布参数系统在有限维输出反馈下的指数能稳性,用构造有限维观测输出反馈控制器的方法,得到这一类系统反馈指数能稳的充分条件.     

Domain-specific discrete event modelling and simulation using graph transformation

Graph transformation is being increasingly used to express the semantics of domain-specific visual languages since its graphical nature makes rules intuitive. However, many application domains require an explicit handling of time to accurately represent the behaviour of a real system and to obtain useful simulation metrics to measure throughputs, utilization times and average delays. Inspired by the vast knowledge and experience accumulated by the discrete event simulation community, we propose a novel way of adding explicit time to graph transformation rules. In particular, we take the event scheduling discrete simulation world view and provide rules with the ability to schedule the occurrence of other rules in the future. Hence, our work combines standard, efficient techniques for discrete event simulation (based on the handling of a future event set) and the intuitive, visual nature of graph transformation. Moreover, we show how our formalism can be used to give semantics to other timed approaches and provide an implementation on top of the rewriting logic system Maude.     

基于图卷积网络的重大事件趋势预测

针对基于公开新闻数据的重大事件趋势预测研究在文本特征提取上语义理解不足问题,提出基于图卷积网络的重大事件趋势预测方法.利用结构化事件信息构建以事件为中心的语义关联图;按时间片粒度分割出局部事件语义关联图,利用预训练词向量对节点文本初始化特征表示;将带有节点特征的局部事件语义关联图输入图卷积网络,聚合节点邻域信息计算图特征表示并输入到分类器,训练预测模型并输出预测结果.以朝鲜核行为趋势预测问题验证所提出方法的有效性,对测试集(2017年3月～2018年3月)预测准确率达到76.92％,全时间段预测准确率为89.58％.预测结果表明,该方法增强了对文本的语义理解,预测精度优于基于专家知识构建特征的方法.     

Feedback stabilization of rotating Timoshenko beam with adaptive gain

The problem of boundary feedback stabilization of rotating Timoshenko beam, arising from control of flexible robot arms, is studied in this paper. First, under gain adaptive direct strain feedback controls, a counterexample is given to show that the corresponding closed loop system is not asymptotically stable, which is contrary to traditional conjecture. The counterexample given in this paper also exemplifies an interesting result: certain two two-order linear partial differential equations with five homogeneous boundary conditions have non-trivial solutions. Then, with an additional boundary feedback control, the related energy of the closed loop system is proved to be strongly stable, or more precisely, the configuration of the beam can be exponentially stabilized with some suitable non-linear boundary feedback controls with adaptive gain.