基于混杂系统理论的制造系统仿真

根据制造系统连续事件与离散事件并存的特点,提出一种制造系统半实物仿真方法,设计连续事件和离散事件并存时仿真系统的时间推进机制。在Arena环境中实现对离散事件系统的建模,在Labview环境中实现特定连续变量事件的半实物仿真。设计并实现离散事件系统与连续事件的接口连接。仿真实验结果表明,该系统能较好地反映出整个制造系统的混杂特性,为混杂制造系统的仿真提供一种新的思路。     

离散事件系统规范DEVS研究

离散事件系统是一类常见的系统，如何对这类系统进行描述与建模是离散事件系统仿真研究的核心内容。离散事件系统规范DEVS是一种离散事件系统形式化描述方法，它具有层次化和模块化的特点，利用该方法可对复杂的离散事件系统进行建模、设计、分析和仿真。该文详细介绍了DEVS基本模型和耦合模型，给出了DEVS在耦合运算下的封闭性构造证明，并提出了一种具有嵌套层次结构的DEVS耦合模型实现算法，该算法对基于DEVS描述的离散事件系统的仿真实现具有一定参考价值。     

离散事件系统N步稳定性分析

讨论基于自动机/形式语言模型的离散事件系统(DES)稳定性问题,引入了确定性离散事件系统N步稳定性定义,并得到了稳定性的判据定理,推导了具体的算法实现。该算法具有多项式复杂度。     

分布式模糊离散事件系统的故障预测

本文研究分布式模糊离散事件系统的故障预测问题.先根据系统的模糊特性,提出一种分布式模糊离散事件系统的协同可预测性的形式化方法,使分布式模糊离散事件系统的协同可预测度不小于各分站点的局部可预测度.通过构造协同预测验证器,提出一种基于协同预测验证器的协同预测算法,并得到一个关于分布式模糊离散事件系统协同可预测性的充分必要条件.     

判定非确定离散事件系统稳定性的梯度搜索算法

讨论基于非确定自动机/形式语言模型的非确定离散事件系统(NDES)稳定性问题.引入非确定离散事件系统稳定性的定义,并得到了稳定性的判据定理.给出了基于梯度的搜索算法,该算法可有效消除观测器的冗余,从而降低了计算复杂度.     

离散事件系统不透明性监督控制研究综述

离散事件系统不透明性是指外部观察者无法分辨系统的一系列行为是否为系统所发生的.而离散事件不透明性监督控制则是构建监督器控制系统行为,使系统满足不透明性的一种方法.离散事件系统不透明性与信息安全有着紧密的联系,并得到了广泛的应用.首先对离散事件系统做了简要的概述,然后介绍了不透明性监督控制算法的研究现状,最后进行了总结和展望.     

基于混合随机Petri网的一类混合系统的模型及稳定性

混合动态系统是包含离散事件系统（ＤＥＳ）和连续变量系统（ＣＶＳ）的复杂系统。讨论了一类每个离散状态包含一个连续动态系统,且离散事件具有Ｍａｒｋｏｖ链性质的随机混合系统,在提出利用混合随机Ｐｅｔｒｉ网的建模方法的基础上,给出混合均方稳定的概念、稳定性和可镇定条件,最后以一个简单的例子做子说明和仿真。     

基于粗糙集理论的离散事件系统不透明性的验证算法

近年来,离散事件系统的不透明性研究引起了国内外众多学者的广泛关注.本文针对离散事件系统的不透明性,提出了一种将粗糙集理论作为知识提取工具来处理离散事件系统不透明性验证的方法.先对离散事件系统的不透明性进行形式化,再利用粗糙集理论对离散事件系统以信息表及决策表的形式进行表示,得到一个关于离散事件系统不透明性的充分必要条件.在此基础上,给出一个验证离散事件系统不透明性算法.与现有方法相比,该验证算法既适用于对强不透明性的验证,又适用于对弱不透明性的验证,并且在时间复杂度上也有较明显改进.     

离散事件系统的稳定性

讨论离散事件系统（DES）的稳定性问题,给出DES稳定性,可吸收性和渐近稳定性有关结论,证明了关于DES稳定性的某些函数的存在性。     

连续计时离散事件系统监控及其可观性

本文提出了一种带有连续时间变量的离散事件系统(称为计时离散事件系统)结构模型.通过讨论计时语言的性质,如封闭性、可控性以及可观性,研究了计时离散事件系统的监控综合问题,并基于这些性质,分别提出了计时离散事件系统在完全可观与部分可观条件下监控器存在的充要条件.     

Control of Robotic Vehicles with Actively Articulated Suspensions in Rough Terrain

Future robotic vehicles will perform challenging tasks in rough terrain, such as planetary exploration and military missions. Rovers with actively articulated suspensions can improve rough-terrain mobility by repositioning their center of mass. This paper presents a method to control actively articulated suspensions to enhance rover tipover stability. A stability metric is defined using a quasi-static model, and optimized on-line. The method relies on estimation of wheel-terrain contact angles. An algorithm for estimating wheel-terrain contact angles from simple on-board sensors is developed. Simulation and experimental results are presented for the Jet Propulsion Laboratory Sample Return Rover that show the control method yields substantially improved stability in rough-terrain.     

Turbogenerator-system controller design via exact model-following techniques

Exact model-following (matching) techniques using output (or state) feedback are proposed for the design of an excitation controller for a two input-output linear time-invariant multivariable model of a turbogenerator with constant excitation voltage E _FD, supplying power to an infinite grid. The transfer function matrix of the selected model is such that the design by the exact model-matching method closed-loop system attains enhanced dynamic (stability) characteristics. This constitutes a good indication that the designed excitation controller will be suitable for real implementation.     

On the explicit dead-time compensation for robust model predictive control

Computational simplicity is one of the most important aspects to take into account in robust model predictive control (MPC). In dead-time processes, it is common to use an augmented state-space representation in order to apply robust MPC strategies but, this procedure may affect computational aspects. In this paper, explicit dead-time compensation will be used to avoid augmented representation. This technique will be analyzed in terms of robust stability and constraint satisfaction for discrete-time linear systems. The results of this discussion will be applied to a robust tube-based MPC strategy which is able to guarantee robust stability and constraint satisfaction of a dead-time system by considering a prediction model without dead-time. Moreover, taking advantage of the proposed scheme, the robust MPC will be particularized for first-order plus dead-time models which simplifies significantly controller synthesis. The proposed dead-time compensation method will be applied to different robust MPC strategies in two case studies: (i) a simulated quadruple-tank system, and (ii) an experimental scaled laboratory heater process.     

Rotor-resistance estimation for induction machines with indirect-field orientation

This paper presents a detailed study of a method of rotor-resistance estimation for indirect-field-oriented control of induction machines based on the reactive-power reference model. It will show how the estimation procedure can be carried out independently of the stator frequency and the load torque. The stability of the estimation procedure will also be demonstrated. Simulation and experimental results will be presented to validate the main contributions of this work. Finally, the sensitivity of the algorithm to errors in other machine parameters will be investigated.     

Modeling the correlations of crude oil properties based on sensitivity based linear learning method

This paper presented a new prediction model of pressure-volume-temperature (PVT) properties of crude oil systems using sensitivity based linear learning method (SBLLM). PVT properties are very important in the reservoir engineering computations. The accurate determination of these properties, such as bubble-point pressure and oil formation volume factor, is important in the primary and subsequent development of an oil field. Earlier developed models are confronted with several limitations especially their instability and inconsistency during predictions. In this paper, a sensitivity based linear learning method (SBLLM) prediction model for PVT properties is presented using three distinct databases while comparing forecasting performance, using several kinds of evaluation criteria and quality measures, with neural network and the three common empirical correlations. In the formulation used, sensitivity analysis coupled with a linear training algorithm for each of the two layers is employed which ensures that the learning curve stabilizes soon and behaves homogenously throughout the entire process operation. In this way, the model will be able to adequately model PVT properties faster with high stability and consistency. Empirical results from simulations demonstrated that the proposed SBLLM model produced good generalization performance, with high stability and consistency, which are requisites of good prediction models in reservoir characterization and modeling.     

Numerical determination of reduced order linear synchronous machine models

A method is presented for the determination of reduced order linear synchronous machine models for dynamic stability evaluation's and as a basis for excitation and governor controller design. The reduction technique is based on Davisons method and is presented in such a way that enables it to be used in isolation, for general linear model reduction, or to be included in an overall synchronous machine stability procedure.     

Force Reflecting Bilateral Control of Master–Slave Systems in Teleoperation

In this paper, a simple structure design with arbitrary motion/force scaling to control teleoperation systems, with model mismatches is presented. The goal of this paper is to achieve transparency in presence of uncertainties. The master–slave systems are approximated by linear dynamic models with perturbed parameters, which is called the model mismatch. Moreover, the time delay in communication channel with uncertainties is considered. The stability analysis will be considered for two cases: (1) stability under time delay uncertainties and (2) stability under model mismatches. For the first case, two local controllers are designed. The first controller is responsible for tracking the master commands, while the second controller is in charge of force tracking as well as guaranteeing stability of the overall closed-loop system. In the second case, an additional term will be added to the control law to provide robustness to the closed-loop system. Moreover, in this case, the local slave controller guarantees the position tracking and the local master controller guarantees stability of the inner closed-loop system. The advantages of the proposed method are two folds: (1) robust stability of the system against model mismatches is guaranteed and (2) structured system uncertainties are well compensated by applying independent controllers to the master and the slave sites. Simulation results show good performance of the proposed method in motion tracking as well force tracking in presence of model mismatches and time delay uncertainties.     

基于视点评分的三维模型摆正

3D模型摆正方向的确定,有利于模型对齐、功能恢复等应用.但已有方法只关注于人造模型的处理,且不少方法还需人工干预,工作效率不高.提出一种可处理任意模型的方法,具有很好的适应性.这主要是基于以下的观察:无论是人造模型还是自然模型,其底部往往是表面内容很贫乏的区域;而主要能观察到这些区域的视点,其视点评分一般很低.因此,根据视点评分,就能有效地寻找到模型的底部朝向,即,模型的摆正方向.为了提高计算的可靠性,进一步引入了物体摆放稳定性和人们观察物体习惯性的度量.实验结果表明:新方法能够高效地处理不同种类的模型,包括一些已有方法中难以处理的情况,并具有很好的计算效率.     

On the capability of wheeled mobile robots for heavy object manipulation considering dynamic stability constraints

In the current research, the maximum mass that can be transferred by a Wheeled Mobile Robot (WMR) equipped with a manipulator will be found. Once such a multibody system carries a heavy payload, it may turn-over. Thus, a very important problem of how to design the motion of the wheeled robot in order to prevent its turn-over or, in other words, to maintain its dynamical stability appears. The solution of this problem is the main focus of the present study. Toward the solution of the aforementioned problem, a pseudospectral approach, which is based on powerful direct optimization technique, will be utilized. To tackle the loss of postural stability during object manipulation, which may have potentially severe concerns, a proper dynamic stability margin measure will be exploited to superiorly estimate and remove the risk of fall. The stability constraints will appear as inequality constraints that will then be transcribed into an equality constraint to solve the problem. Using the provided direct search method, an algorithm will be suggested to find the maximal mass that can be manipulated by the considered robot. The obtained simulation results reveal the success of the provided novel methodology to assess the manipulation capability of the considered WMR while considering dynamic stability and actuator limitations.     

On the stability radius of a Schur polynomial

The robust Schur stability of a polynomial with uncertain coefficients will be investigated. The stability hypersphere for such polynomials will be determined in terms of Tshebyshev Polynomials.