基于状态空间表示法的机械产品概念设计

分析了机械工程系统的功能关系。确立待设计系统的状态变量，利用键合图的基础元件建立状态空间转换矩阵，根据机械系统中能量传递建立系统状态空间模型，采用状态空间变换操作，产生多个设计方案，并结合电动静脉注射器设计说明其应用。     

键合图在火电厂热工对象建模中的应用

针对火电机组这种复杂的多能量转换系统,功率键合图以能量守恒定律为依据,用4种统一的物理变量表达不同的工程系统,在机、电、液、热等多种能量范畴的耦合系统建模中具有独到优势。在研究热工对象汽包的工作过程基础上,利用功率键合图理论,将其分解划分为相关键图子系统,通过连接各子系统键图模型综合得到汽包对象的键合图模型,并推导了该模型对应的数学描述,通过仿真验证了键合图模型的精确性,为热工对象的建模提供了一种崭新方法。     

Development of operation-aided system for chemical processes

This paper presents the development of a knowledge-based operation-aided system for polypropylene process. The important part of this system is the search for the root cause of faults by detecting and analyzing the symptoms which occurred in the process in the case of abnormal situations. In this system, an artificial neural network which is able to handle pattern recognition is used for qualitative interpretation of sensor data and generating symptoms. For effective fault diagnosis, two causal effect models which are based on SDG (Signed Directed Graph) are developed. One model, RCED (Reduced Cause Effect Digraph) uses only the measurable sensor data of the process and is constructed off-line and stored in the knowledge base of the system. The other model, PGTT (Pattern Graph Through Time) is generated in the real-time mode during the diagnosis period. It is generated from symptoms—status and/or tendency change—and can handle dynamic state effectively. By implementing the developed qualitative interpretation method and two causal effect graph models, the operation-aided system for the polypropylene process, FINDS/PP (Fault Isolation aNd Detection System/PolyPropylene) was developed. This system was developed with the expert system tool G2 and showed good results.     

Study of the diagnosability of automated production systems based on functional graphs

Functional graphs are a convenient representation that we have introduced to model automated production systems. They are useful for the monitoring and the supervision of manufacturing processes or other industrial processes, such as chemical processes. An approach based on relational theory and graph theory is presented in this paper. This approach allows to characterize formally structural properties of a functional graph and to map it into a set of relations translating all the complete paths existing in the initial graph. Two kinds of functional graphs are analyzed and algorithms exploiting their structures are presented. We introduce the concept of diagnosability as a system property that reflects the possibility to observe the behavior of a system with respect to faults. The diagnosability is defined and analyzed by means of computable states and mathematical relations. Propositions explaining causality relations between functions of a functional graph are given.     

A model for simulating a lead-acid battery using bond graphs

This paper presents a model of a lead-acid battery developed with bond graphs. The bond graph structure is used to reproduce the behavior of reversible electrochemical cells in charging conditions or in discharging conditions. The work presented here has been applied to the particular case of lead-acid battery, so widely used in the automotive industry as standard 12 V batteries and as traction batteries in electrical or hybrid vehicles.The model considers each half-cell independently. For each half-cell the main electrode reaction and the electrolysis reaction of water are considered, that will be the hydrogen evolution reaction in the negative electrode and the oxygen evolution reaction in the positive.Electrochemical principles are considered in order to consider the main phenomena that appear in the battery, like the equilibrium potential, and the overpotential, modeled by means of the activation or charge transfer and the diffusion mechanisms.Each one of this phenomena are modeled with their corresponding bond graph elements and structures, showing the correspondence between bond graph elements and its physical interpretation in this field.First, an isothermal model has been developed in order to show the behavior of the main phenomena. A more complex model has also been developed including thermal behavior. This model is very useful in the case of traction batteries in electrical and hybrid vehicles where high current intensities appear.Some simulation results are also presented in order to show the accuracy of the proposed models and the differences of behavior if thermal effects are considered.     

基于调控流图的定性仿真系统研究

针对复杂系统定性仿真效率较低的问题,在实体语法系统理论的基础上,为改进定性仿真系统,提出调控流图定性仿真系统,利用以三值量空间为基础的五值量空间,在不增加计算量的前提下解决了调控流图定性仿真中的负反馈问题,利用规则、观测变量的二级约束形式降低了系统多途径调节所产生的不确定性,通过变量与多维空间区域的映射实现利用调控流图对时空复杂性进行定性仿真。通过CSTR系统的定性仿真表明,可用于复杂系统的扰动传播途径预测、复杂系统故障诊断等问题,为复杂系统的建模与定性仿真提供了一种新的技术手段。     

基于功率键合图和Matlab／Simulink的液压激振系统的建模及仿真

液压振动系统是采用激波器控制的机电液一体化系统,具有高动态特性。运用键合图方法建立液压振动系统的键图模型,提出将控制参数加入键图模型,用于控制液压振动系统功率流向的交替变化;根据键合图理论和控制关系建立系统的数学模型;并利用Matlab／Simulink仿真软件建立其仿真模型,可以直观地表达系统的功率流向和控制关系;根据液压振动系统模型易产生病态的特点,利用Matlab提供多种求解方法的优势,设置合理的仿真参数以得到更精确的仿真结果;利用键合图方法的扩展功能和Simulink建模的模块化可以深入研究系统中受关注的任何子系统,为液压振动系统的设计和应用提供理论依据。     

Stability of control systems and graphs of linear systems

New conditions for internal stability of a closed-loop control system are given in terms of the graphs of the multiplication operators induced by the transfer functions of the plant and the controller. These conditions can be given a geometrical interpretation. This relates closed-loop stability to the minimal angle between the graph space associated with the system and the graph space associated with the controller. The maximally stabilizing controller is defined as the controller that maximizes the minimum angle between the graph space associated with the system and the graph space associated with the controller. It is shown that this controller can be calculated as a Nehari extension of the coprime factors of the system.     

Optimal control problem in bond graph formalism

This paper presents a new way to derive an optimal control system for a specific optimisation problem, based on bond graph formalism. The procedure proposed concerns the optimal control of linear time invariant MIMO systems and can deal with both cases of the integral performance index, these correspond to dissipative energy minimization and output error minimization. An augmented bond graph model is obtained starting from the bond graph model of the system associated with the optimal control problem. This augmented bond graph, consisting of the original model representation coupled to an optimizing bond graph, supplies, by its bicausal exploitation, the set of differential-algebraic equations that analytically give the solution to the optimal control problem without the need to develop the analytical steps of Pontryagin’s method. The proof uses the Pontryagin Maximum Principle applied to the port-Hamiltonian formulation of the system.     

Integrating role graphs: a tool for security integration

Role-based access control provides a very flexible set of mechanisms for managing the access control of a complex system with many users, objects and applications. The role graph model of Nyanchama and Osborn is one example of how role administration algorithms can be implemented. In our previous research, we have also shown how the access control information of existing systems can be extracted and represented as a role graph. In this paper, we extend this research by showing how, when two systems are being integrated, their role graphs can also be integrated.