Abstract: Aiming at the dynamic characteristics of Computer Numerical Control(CNC)machining process, a task-based reliability allocation method based on the research limitations of existing reliability allocation of CNC machine tools was proposed by combining the phased-mission system theory and the task reliability principle. The mission section hierarchical model of CNC machine tools was established according to the actual situation of all the tasks. To analyze and research the meta task level of CNC machine tools, five important impact factors of reliability allocation including run time, importance degree, complexity degree, technical level and working condition were identified. By fully considering the suggestions of many experts and the risks in CNC machine tools research and development process, a function to decide the fuzzy truth value was defined and a way to determine the membership degree was given through fuzzy set theory. The reliability allocation indicator system, weights and fuzzy evaluation matrix of meta task were established. An example of main processing meta-task group was taken to prove the availability of the method.

Key words: CNC machine tools, meta task, fuzzy set, reliability allocation

摘要： 在分析现有数控机床可靠性分配技术局限的基础上，针对数控机床加工零件过程的动态性特征，将多阶段任务系统理论和任务可靠性原理结合起来，提出一种基于任务的可靠性分配方法。根据数控机床加工零件总任务的实际情况，建立数控机床的任务剖面层次模型。通过对数控机床元任务层的分析与研究，确定了运行时间、重要程度、复杂程度、技术水平和工作状况5个影响可靠性分配的重要因素。运用模糊集理论，充分考虑到多领域专家的意见和数控机床研发过程的风险性，定义了一种判定模糊真值的函数，给出一种确定隶属度的方法，并建立起数控机床可靠性分配指标体系和权重，以及元任务的模糊评判矩阵。以一个数控机床主加工元任务组为例，证明了该方法的可用性。

关键词: 数控机床, 元任务, 模糊集, 可靠性分配