基于面向对象方法的过程操作评价系统的研究

【作者】 滕利明；

【导师】 吴嘉；

【作者基本信息】 浙江大学 ， 化学工程， 2003， 硕士

【摘要】 本论文研究了专家系统在过程操作领域的应用，设计了符合过程操作领域特点的知识表示方式和推理机策略。在此基础上，采用面向对象技术，建立了一个过程操作评价系统，并且探讨了面向对象专家系统的分析设计方法。 过程操作领域的知识大都具有经验性的特点，难以用简洁统一的理论来概括；问题的求解一般可以表示成一系列相对独立的操作；且知识易于同运用知识的方法分离开来。这些特点都符合产生式系统的前提，因此本系统的知识表示采用基于产生式规则的专家系统的技术。产生式规则采用面向对象技术来实现，规则表示为对象。面向对象的知识表示是一抽象数据类型，是类、对象与属性的三元组合，它能方便地表示对象的静态特征、动态行为以及对象间的相互作用；类的层次关系与组合关系可大大减少知识表示的冗余；对象的封装性和类的继承性方便了知识的更新和扩充，使得知识易于管理。通过分析过程操作领域的特点，本系统建立了符合过程操作领域特点的知识表示的对象模型。 过程操作一般具有比较严格的步骤顺序，规则的前提和结论都可以确定地描述，因此推理机制可采用简单的精确推理方法。本系统的冲突消解主要采用简单冲突消解策略，即将多条知识按照优先级从高到低排序，系统将匹配的第一条知识作为选定知识进行推理。本系统的推理控制主要采用反向推理控制策略，即先假设一个目标，然后在知识库中找出那些其结论部分导致这个目标的知识集，再执行启用知识集，改变求解状态，逐步求解直至问题解决。为了提供良好的通用性和扩展性，在本系统的对象模型中建立一个推理机类，使推理机制独立于知识表示，因此只要通过扩展、派生推理机类即可实现对不同推理策略的选择。 本论文通过分析实验远程教学系统的传热实验和离心泵实验的操作步骤，制定了这两个实验的操作规则，并指定相应的分值，添加到过程操作评价系统中，作为实验远程教学系统的实验评分系统模块，实现了对学生实验操作考核的自动评分。此外，本文也对某甲醇合成塔的操作进行了分析，得到了相应的知识库，表明在甲醇合成等等化工生产领域，本文提出的操作评价专家系统也有用武之地。更多还原

【Abstract】 In this paper, the application of Expert System in Process Operation is investigated. An appraise system of process operation, which consists of knowledge representation and inference engine, is designed according to the characteristics of Process Operation and is implemented using object-oriented technology.The knowledge of process operation possesses experiential property usually and is difficult to describe using compact method. The solutionof question is composed of a series of unattached operations. The knowledge and the method using knowledge are easy to separate. So the knowledge representation of the system can use the technology of production system. The production rule’s are realized by object-oriented technology. The rules are expressed as objects. The object-oriented representation of knowledge is a composite of classes, objects and attributes. It can express static characteristics, dynamic actions and interrelation of objects. The hierarchy and composition of classes decrease greatly the redundancy of knowledge representation. The encapsulation of objects and the inheritance of classes promote updating and extension of knowledge, and make the management of knowledge easier. According to the characteristics of process operation, an object model is established in this paper.The process operation is usually in sequence, and the precondition and the conclusion of rules are described definitely, so the precise inference can be used in this system. The rule of matching the highest priority is a good solution to clear-up the conflicts of operations. The converse ratiocination is adapted also as the inference method of the system. With generality and extensibility, an inference class is build to make inference engine be independent on knowledge representation, sosystem can provide different inference engine by inheriting inference class.The operation rules of the heat transfer experiment and the pump experiment of distance laboratory system are established by analyzing the corresponding experimental operations, and the scores of operation steps are added into the system. As the examination system of experiment operation, the system grades the operations of students in experiments automatically to give the overall scores, which used to be a task of teachers tedious and poor-efficient.In the paper, the operation of an industrial reactor of methanol synthesis is also analyzed to establish a knowledge representation. It showed that the expert system can be used in the field of chemical industrial production.更多还原