基于Petri网的非串行制造系统的可靠性分析

Reliability Analysis of Non-series Manufacturing Systems Based on Petri Nets

对带有中间缓冲区的非串行系统深入研究其可靠性问题,建立基于广义随机Petri网的可靠性模型,着重考虑出现的装配、拆分以及按不同比例进行装配或拆分的加工工序,其中间缓冲区可用度对机器可用度的影响,在此模型基础上,采用缓冲区可用度定理,对中间缓冲区和机器本身的状态转移概率分别分类求解,计算出相应的缓冲区可用度和等效机器可用度;同时通过功能可靠度指标,对整个加工任务车间的可靠性进行总体评价,从时间量和产品量因子出发,来衡量由于生产率的不平衡以及中间缓冲区的库存太小,引起生产流程中传输道的阻塞和缺料,进而造成的相关工件的加工时间延迟等问题。以三台机床和两个待加工工件的加工装配单元为例,验证该模型与分析方法的有效性。

Through in-depth study on the reliability of non-series manufacturing systems with buffers, the reliability model based on generalized stochastic Petri nets is built. The occurring of assembly and disassembly, the working procedures with assembly or disassembly carried out per different proportions, and the influence of buffer availability on the machine availability are considered emphatically. On the basis of this model, the buffer availability theorem is adopted for classification and solution of the state transition probabilities of buffer and machine itself respectively, and the corresponding buffer availability and equivalent machine availability are calculated. Moreover, through the function reliability index, overall evaluation of the reliability of the whole manufacturing workshop is carried out. By starting from factors of time variable and production volume, the delay of processing time of related work pieces caused by the blocking of transmission path and stock shortage due to the unbalance of productivity and too small buffer inventory is measured. A manufacturing assembly cell with three machines and two work pieces is taken as an example to verify the effectiveness of the model and analysis method.