一种面向欠约束几何系统求解的二部图匹配优化处理方法

针对一般几何约束系统欠约束状态下约束分解的多样性 ,对相应的有向图强连通子图提出了进一步分解的二部图匹配优化处理策略 ,并给出了主要算法 ,最终实现了欠约束系统的优化分解 ,有利于一般几何约束系统的快速求解 .     

面向性能仿真的非连续微分代数模型的指标分析

针对物理系统性能仿真形成的非连续高指标微分代数模型,提出一种基于加权二部图的指标转换方法．该方法将微分代数系统表示为加权二部图,基于二部图匹配算法可以判定微分代数系统是否为高指标系统．对于高指标系统,采用文中方法可以找出需要求导的最小结构奇异方程子集,以便将高指标系统转换为低指标形式．最后,针对定结构与变结构的非连续微分代数模型给出了相应的指标分析策略．文中策略与相关算法已在基于Modelica语言的建模仿真平台MWorks上实现．     

模块化模型相容性分析方法研究

对多领域建模与协同模型的相容性分析是系统仿真设计中的一个重要部分.针对陈述式物理建模语言模型的检验方法,都是从整个模型出发,研究模型内所有方程和变量之间的关系.但是当系统所包含的方程和变量比较多时,方法在分析过程中容易出错.现提出了一种以模块为研究对象的模型检验的新方法.它将系统划分为多个子模块,将各个模块内部和模块之间的约束关系表示为二部图的形式,以DM分解为基本算法,来分析模型的约束性,从而确定系统模型的正确性.由于每个分析过程只涉及一小部分方程和变量,因此,大大减小了出错的几率.通过一个分析实例,描述了模块化模型检验方法的具体实现.上述分析方法结合了Modelica建模语言的特性,层次清晰.     

多体系统传递矩阵法不须进行违约修正的验证

对一含有完整约束的多体系统在平面、空间中的运动规律进行了计算机仿真研究,采用通常动力学方法,以卡尔丹角作为位置角建立和求解动力学方程,并对进行和不进行违约修正的仿真结果进行了比较,然后采用多体系统离散时间传递矩阵法进行了计算机仿真,仿真结果表明多体系统传递矩阵法在不进行违约修正的情况下,仍能保证完整约束不被违反与通常动力学方法相比,多体系统传递矩阵法不需进行违约修正。     

一种启发式与/或优先约束任务调度算法

系统描述了与或网模型及与或优先约束任务调度的可行性判定算法.以顶点覆盖问题为基础,证明与或优先约束任务调度最小完成时间问题是NP完全的.提出一种启发式调度算法,解决与或优先约束任务调度最小完成时间问题.仿真结果表明,该算法在降低算法复杂度的同时较其它相关算法具有更好的调度性能,从而证明在实时优先约束任务调度中引入图优化的理论是解决优先约束任务调度问题的一个有效途径.     

陈述式基于方程仿真模型的约简

为解决复杂多领域连续系统的高效仿真问题,研究了陈述式基于方程仿真模型的约简策略.基于符号处理技术,提出了一种模型约简方法.该方法从方程的规范转换入手,通过消除特定形式方程缩减系统规模,将整个方程系统规划分解为一个可顺序求解的子系统序列.给出的实例表明文中约简方法效果显著.文中策略与算法已在多领域物理系统混合建模与仿真平台EMWorks中实现.     

基于二部图的控制系统故障诊断方法

针对连续控制系统,建立了由系统约束集、变量集和边集构成的二部图模型,提出了一种定性描述与定量分析相结合的故障诊断算法。该算法通过分离子系统,求解系统的关联矩阵及最大匹配,定义了描述变量与系统约束之间依赖关系的规则,并设计了关联矩阵分层算法,以此来计算控制系统残差。以一个线性系统为例,探讨了该算法的应用过程,并通过仿真实例验证了该算法的有效性。     

具有奇异位置的多体系统动力学方程的改进算法

多体系统进行数值仿真时,很多选择了微分代数混合方程作为多体系统动力学数学模型.本文在现有的约束稳定化理论基础上,提出了针对具有奇异位置的多体系统动力学方程的改进算法.算法通过修正速度违约和控制稳定项,讨论了具有奇异位置的微分代数混合方程的数值仿真问题并给出了稳定项中相关系数的建议值,从而有效克服了求解混合方程时因为构型奇异给计算造成的困难.算例分别采用改进算法与ADAMS软件进行仿真,计算结果的比较表明了改进算法的有效性.本文给出的基于能量守恒的能量差曲线也证明了改进算法的有效性.     

电机起动暂态的仿真及测试分析

针对电机起动暂态仿真计算时的模型参数时变问题,以小型异步电机为对象,建立二维有限元电磁场模型.通过绕组端部电阻参数场化、端部漏感参数路化修正建立场路结合的模型.经过模型的短路仿真与解析计算对比,进行二次修正模型参数,得到场路结合的起动暂态模型,对电机性能进行仿真计算.对不同负载转动惯量下的起动时间、起动转矩、起动电流曲线、起动转速及角位移曲线等特性进行测试.经测试与仿真计算对比分析,结果表明参数修正的场路结合模型能准确地仿真计算电机起动暂态各性能.     

多模式刚柔结合欠驱动抓取机构的设计、分析与实验测试

结合刚性欠驱动抓取机构与柔顺机构,提出一种多模式刚柔结合欠驱动抓取机构,并对所提出的机构进行分析与实验研究。基于刚体替代法,设计了二指多模式欠驱动抓取机构的刚柔结合方案。运用正运动学分析与载荷平衡方程,对驱动单元进行静力学建模。结合伪刚体模型法、载荷平衡方程与操作对象平衡位置枚举搜索,建立两点抓取与包络抓取模式下抓取力与驱动力矩的关系式。将驱动单元静力学建模与抓取单元静力学建模相结合,可以得到完整的多模式抓取力模型。进一步地,考虑由于接触引起的柔性杆件变形,结合线性插值,对抓取力模型进行修正。基于修正后的抓取力模型,对机构尺寸参数进行优化设计,综合提升机构在两点抓取模式和包络抓取模式下的载荷输出性能。RecurDyn仿真结果显示,在两点抓取模式和包络抓取模式下,修正后完整的抓取力模型与仿真值的最大相对误差为7.62%,并且所提出的优化算法有效提升了机构的两点抓取力与综合包络抓取力。实验结果显示,优化后的抓取机构抓取力有较大的提升,修正后完整的抓取力模型与实验值的最大相对误差为1.87%,验证了抓取力建模、优化设计的有效性。     

Flexible multibody modelling for exact constraint design of compliant mechanisms

In high precision equipment, the use of compliant mechanisms is favourable as elastic joints offer the advantages of low friction and no backlash. If the constraints in a compliant mechanism are not carefully dealt with, even small misalignments can lead to changes in natural frequencies and stiffnesses. Such unwanted behaviour can be avoided by applying exact constraint design, which implies that the mechanism should have exactly the required degrees of freedom and non-redundant constraints so that the system is kinematically and statically determinate. For this purpose, we propose a kinematic analysis using a finite element based multibody modelling approach. In compliant mechanisms, the system’s degrees of freedom are presented clearly from the analysis of a system in which the deformation modes with a low stiffness are free to deform while the deformation modes with a high stiffness are considered rigid. If the Jacobian matrix associated with the dependent coordinates is not full column or row rank, the system is under-constrained or over-constrained. The rank of this matrix is calculated from a singular value decomposition. For an under-constrained system, any motion in the mechanism that is not accounted for by the current set of degrees of freedom is visualised using data from the right singular matrix. For an over-constrained system, a statically indeterminate stress distribution is derived from the left singular matrix and is used to visualise the over-constraints. The analysis is exemplified for the design of a straight guiding mechanism, where under-constrained and over-constrained conditions are visualised clearly.     

Solving Interval Constraints by Linearization in Computer-Aided Design

Current parametric CAD systems require geometric parameters to have fixed values. Specifying fixed parameter values implicitly adds rigid constraints on the geometry, which have the potential to introduce conflicts during the design process. This paper presents a soft constraint representation scheme based on nominal interval. Interval geometric parameters capture inexactness of conceptual and embodiment design, uncertainty in detail design, as well as boundary information for design optimization. To accommodate under-constrained and over-constrained design problems, a double-loop Gauss-Seidel method is developed to solve linear constraints. A symbolic preconditioning procedure transforms nonlinear equations to separable form. Inequalities are also transformed and integrated with equalities. Nonlinear constraints can be bounded by piecewise linear enclosures and solved by linear methods iteratively. A sensitivity analysis method that differentiates active and inactive constraints is presented for design refinement.     

三维几何约束系统的等价性分析

针对过约束、完整约束和欠约束三维几何约束系统的求解问题,提出了等价性分析方法.该方法基于三维几何约束系统的内在等价性,充分挖掘几何领域知识,依据拆解约束闭环、缩减约束闭环和析出约束闭环等原则,采用等价约束替换来处理几何约束闭环问题,优化几何约束图的结构,实现几何约束系统的优化分解.最后用多个实例验证了该方法的正确性和有...     

复杂非线性电路系统的动力学方程模型

Lagrange和Hamilton运动方程是分析力学的基本原理之一和方法论。应用Lagrange和Hamilton原理建立复杂非线性电路保守动力学方程模型是一种形式化可行的方法。对非保守的动力学系统,定义描述电路系统的荷控支路和链控支路的微观结构概念,应用Hamilton结构的方法,可以得到与La-grange结构等价的方程组;考虑大规模电路系统的复杂性,依据电路系统荷控支路和链控支路微观结构的概念,给出具有控制参量的Lagrange和Hamilton函数,以及具有相应关联矩阵和联接矩阵形式的Lagrange和Hamilton的动态方程;分析了保守和非保守复杂系统拓扑结构关系的描述和其动力学系统的建模,其建模过程具有规范性和方程具有对称性。虽然数学推导过程繁琐,但适合于计算机辅助形式化分析;基于Hamilton方法建立的电路模型为一阶微分动态方程组,特别适合进行理论分析和数值仿真计算。     

自治分段线性振荡系统的离散映射数值建模与稳定性分析

为研究自治分段线性振荡系统中出现的分叉及混沌动力学行为，系统建模及稳定性分析是一种必不可少的分析手段. 本文通过构造周期内离散映射解析模型，并结合边界条件的动态数值求解，提出了一种动态离散映射数值建模方法，进而推导了用以判定系统周期闭轨稳定性的Jacobian 矩阵求解模型. 最后，本文以电力电子系统中一种常用的5 维软开关逆变自治振荡电路作为实例，通过模型仿真观察到频率的分叉现象，并根据Jacobian 矩阵的特征乘数对系统的稳定性进行了研究. 基于该模型的仿真分析结果与实验系统中所观察到的现象一致，从而验证了该方法的有效性.     

GM（1，N）和QSIM结合的复杂系统的定性仿真建模方法

针对复杂系统仿真中系统信息缺乏、QSIM建模方法可使用微分方程的特点,在复杂系统仿真方法中,提出了一种GM（1,N）和QSIM相结合的定性建模方法.首先给出了相关研究的现状,然后提出了GM（1,N）和QSIM相结合的仿真建模方法的基本原理和主要过程.最后通过一个系统仿真建模实例验证了该方法的可行性.结果表明,该方法具有充分利用系统较少信息,能将定量和定性信息有效地融合与复杂系统的仿真建模之中的特点.     

A new constructive approach to constraint-based geometric design

In the paper, a new constructive approach to solving geometric constraints in 2-D space is presented. Constraints are employed on lines and points only, but more sophisticated geometric elements like Bézier curves and ellipses can also be constrained by mapping them onto auxiliary lines and points. The algorithm is based on local propagation, but first, the problem is transformed into a form that guarantees success of employing this simple technique. The most important steps are substitution of complex constraints with sets of simpler ones and insertion of redundant constraints by solving triangles and determining sums and differences of adjacent angles. In this way, various well-constrained problems with a few exceptions are solved, over-constrained scenes and input data contradictory to some well-known mathematical theorems are detected, and the algorithm is proved successful in many under-constrained cases as well.     

Defining tools to address over-constrained geometric problems in Computer Aided Design

This paper proposes a new tool for decision support to address geometric over-constrained problems in Computer Aided Design (CAD). It concerns the declarative modeling of geometrical problems. The core of the coordinate free solver used to solve the Geometric Constraint Satisfaction Problem (GCSP) was developed previously by the authors. This research proposes a methodology based on Michelucci’s witness method to determine whether the structure of the problem is over-constrained. In this case, the authors propose a tool for assisting the designer in solving the over-constrained problem by ensuring the consistency of the specifications. An application of the methodology and tool is presented in an academic example.     

基于多Agent的天战系统建模与仿真方法研究

简单介绍了复杂系统理论及其建模方法，分析了天战系统的总体行为特征，指出对天战系统的仿真研究需采用复杂适应系统（CAS）理论的研究方法，即采用基于Agent的建模仿真方法学来开展研究，概述了Agent和多Agent系统的概念及基于多Agent的仿真，并给出了一个基于高层体系结构（HLA）的天战系统的仿真框架，最后展望了将来的研究工作。     

Constraint based approach for the steady-state simulation of complex systems: Application to ship control

When the steady states are largely predominant with respect to transitional phases, steady-state simulation seems sufficient to predict the behavior of a complex system. Over the past 20 years, different modeling languages and dedicated tools have been developed to improve steady state simulation.In this paper, focus is made on steady-state simulation for system control and design. A model combining an emission sub-model with a ship propulsion sub-model was implemented in a constraint programming (CP) approach. It will help to determine the efficiency (i.e. the ability to model and solve the problem) and complexity of implementation (i.e. difficulties encountered during the implementation) of this approach.First, requirements for the steady-state simulation of complex systems are defined. Then, CP approach is shown to be able to answer these issues through experiments. This approach is then compared to one of the main simulation languages: Modelica.Although the two approaches (i.e Modelica and CP) are able to reverse models, the study shows that the use of Modelica principles for steady-state simulation involves some crippling limitations, such as the non-management of under/over-constrained systems, or inequalities.This study also shows that the constraint programming approach permits to meet some needs for steady-state simulation not yet covered by current approaches.