Abstract: According to the requirement of cumulative Mean Time Between Failures(MTBF)and interval estimation precision of reliability for Numerical Control(NC)machine tools,the minimal testing truncated time and sample size of reliability assessment test were given by using Fisher information matrix method for failure process that described by power law process model.Thus the problem of determining sample size and testing time of reliability assessment test for NC machine tools was resolved.The results showed that the log ratio of upper bound to lower bound and confidence level of reliability indices interval were the main factors for truncated time and sample size.The minimal sample size increased significantly with the improvement of required precision of interval estimation and confidence level of reliability indices,but the minimal testing truncated time was less affected by these two factors.

Key words: power law process, sample size, testing time, numerical control machine tool, reliability assessment

摘要： 以数控机床的累积平均无故障工作时间和可靠度的区间估计精度为要求,应用信息矩阵法,对故障过程可用幂律过程模型描述的数控机床,给出了可靠性评估试验的最小试验截止时间和最小样本容量,解决了数控机床可靠性评估试验中确定试验截止时间和样本容量的难题。计算结果显示,可靠性指标区间估计的上、下区间比和置信度是影响可靠性评估试验中最小试验截止时间和最小样本容量的主要因素。其中,最小样本容量随可靠性指标区间估计精度要求的提高和置信度的增加而显著加大,而最小试验截止时间受两者的影响较小。

关键词: 幂律过程, 样本容量, 试验时间, 数控机床, 可靠性评估