面向不完全维修数控机床的可靠性建模与评估

Reliability modeling and evaluation of CNC machine tools for a general state of repair

数控机床是典型的机电液可修系统,维修活动既不会使机床“修复如新”,亦不会“修复如旧”,而是处于一种不完全维修状态。该文提出双重对数线性比例强度模型(S-LPIM)对不完全维修状态机床的可靠性进行建模,并采用最小二乘法给出该模型的参数估计。基于故障强度模型,求解数控机床可靠性评价指标,采用似然比检验方法对数控机床可靠性的故障趋势及修复功效进行检验。通过对3台数控加工中心可靠性建模,验证了S-LPIM模型可以拟合机床故障率浴盆曲线特性,定量描述维修活动对机床可靠性的影响。

Computer numerical control(CNC) machine tools are typical repairable electro-hydraulic mechanical systems. Repair activities do not return the machine tool to like-new conditions, but to some intermediate state of general repair. A superposed log-linear proportional intensity model(S-LPIM) was used here to model the general repair state of machine tools using a least squares parameter estimation method. A failure intensity model was used to calculate a reliability evaluation index for the CNC machine tool with the failure probability and repair efficiency of the CNC machine tool evaluated based on the likelihood ratio test method. Tests of the reliability of three CNC machining centers verified that the S-LPIM model can fit the failure rate bathtub curve of machine tools and quantitatively describe the effect of maintenance activities on the machine tool reliability.