Systems Reliability/Safety Analysis Using System Behavior Model

研究的主要内容是开发一种基于系统行为模型的获取系统故障信息的方法，以防止系统分析员的主观判断和经验造成的分析错误。在项目的第一年，检验键合图的适用性，以从系统设计假设中获得系统行为模型。键合图可以从能流的角度统一表示由机械、电气和液压元件组成的系统。系统的动态行为可以用表示能量储存的系统状态变量、表示能量供应的输入变量和表示元件的特征函数表示为系统状态方程。针对零件特征函数在设计初期只能定性表示的问题，提出了一种基于STEA…的零件失效状态下工艺变量偏差的定性评价方法在第二年，开发了一种方法来提高定性评估的效率。首先，用树形图表示从系统键合图得到的系统状态方程。树形图由节点和分支组成，前者表示键合图元素、输入变量和系统状态变量，后者表示输入输出关系和节点之间的关系，并具有其源节点的输出值。通过沿树形图传播由部件故障假设引起的偏差，可以评估节点处的所有偏差。可以处理多种故障情况。由于节点对应于系统状态，因此可以根据树图的节点值来评估所有系统状态。只要对系统行为的假设是正确的，就可以保证来自树图的评估结果的有效性。进一步考虑了分析结果在系统故障诊断中的应用。然而，由于无法找到一种有效的方法来减少能够解释观察到的系统状况的可能候选者的数量，因此利用树图进行故障识别仍然是近期需要解决的课题。较少

The main of the research is to develop a method of obtaining information on the system failure based on the system behavior model to prevent analysis errors caused by the subjective judgment and experience of system analysts.In the first year of the project, the applicability of bond graphs is examined for obtaining a system behavior model from the system design assumptions. Bond graphs can represent a system composed of mechanical, electrical and hydraulic components in a unified way from the viewpoint of energy flow. The system dynamical behavior can be represented as system state equations in terms of system state variables denoting energy storage, input variables denoting energy supply and characteristic functions denoting elements. Since component characteristic functions can be represented only qualitatively at the early stage of design, a method is developed for the qualitative evaluation of deviation in process variables caused under a component failure condition using the stea … More dy state condition.In the second year, a method is developed for making the qualitative evaluation more efficient. Firstly, system state equations obtained from a system bond graph are represented using the tree graph. A tree graph is composed of nodes and branches : the former represent bond graph elements, input variables and system state variables, while the latter represent input-output relations and between nodes and has the output value of their source node. By propagating a deviation caused by a component failure assumption along the tree graph, all the deviations at nodes can be evaluated. Multiple failure conditions can be dealt with. Since a node corresponds to a system state, all system states can be evaluated from the node values of a tree graph. As long as the assumptions on the system behavior are correct, the validation of the evaluation result from the tree graph is guaranteed. Further, application of the analysis result to the system failure daignosis is considered. However, the failure identification using the tree graph remains a subject to be solved in the near future because an efficient method cannot be obtained to reduce the number of possible candidates which can explain the observed system condition. Less