采用可用度理论的瓶颈设备前缓冲时间估计

Estimation of feeding time buffer size of bottleneck based on availability theory

针对确定缓冲时间困难的问题,提出了一种基于可用度理论的缓冲时间估算方法,将瓶颈前的每道工序都看成独立的单部件可修系统,根据故障率和维修率由马尔可夫过程方法得到该工序的持续时间估计,从而估计出必需的缓冲时间.分别给出了瓶颈前有单个工序、多个工序串联、并联或混联时的缓冲时间估算公式,还提出了一种改进模糊概率PERT方法,对得到的缓冲时间进行可信度计算.基于在制品存储费用和概率风险损失给出了缓冲时间的最优化模型.仿真试验的结果表明,该方法得到的缓冲时间合理、可信.

Aimed at the difficulty in determining the size of buffer properly, an availability theory based buffer sizing approach is proposed, in which each activity before the bottleneck is considered as a single repairable system, then the availability function infered by Markov process is used to estimate the processing time of the activities, and the proper buffer size can be calculated. The time buffer estimation formulas for different situa- tions are given respectively, in which the activities are in series, parallel or serials-parallel before bottleneck Moreover, an improved fuzzy probability PERT method is proposed to evaluate the credibility of the buffer size obtained. Finally, an optimization model is built to determine the optimal buffer size, taking inventory cost and total risk delay penalty as performance indicators. The results of simulation test indicate that the buffer size calculated by the proposed method is reasonable and believable.