In response to the production capacity and functionality variations, a genetic algorithm （GA） embedded with deterministic timed Petri nets（DTPN） for reconfigurable production line（RPL） is proposed to solve its s...In response to the production capacity and functionality variations, a genetic algorithm （GA） embedded with deterministic timed Petri nets（DTPN） for reconfigurable production line（RPL） is proposed to solve its scheduling problem. The basic DTPN modules are presented to model the corresponding variable structures in RPL, and then the scheduling model of the whole RPL is constructed. And in the scheduling algorithm, firing sequences of the Petri nets model are used as chromosomes, thus the selection, crossover, and mutation operator do not deal with the elements in the problem space, but the elements of Petri nets model. Accordingly, all the algorithms for GA operations embedded with Petri nets model are proposed. Moreover, the new weighted single-objective optimization based on reconfiguration cost and E/T is used. The results of a DC motor RPL scheduling suggest that the presented DTPN-GA scheduling algorithm has a significant impact on RPL scheduling, and provide obvious improvements over the conventional scheduling method in practice that meets duedate, minimizes reconfiguration cost, and enhances cost effectivity.展开更多
A new real time control model based on the fundamental Petri net theory is built for a complete close loop welding robot system with time delay. The new Petri net model synchronizes with devices at the primary level b...A new real time control model based on the fundamental Petri net theory is built for a complete close loop welding robot system with time delay. The new Petri net model synchronizes with devices at the primary level by introducing into the basic Petri net expression new parameters which contain the responding real time information. In addition, time delay is taken into account by adding some necessary time related parameters. Usually, in a system without time delay, if the condition is enabled, the transition must be fired, but in a system with time delay, this property is only a necessary but not a sufficient condition.展开更多
延迟时间Petri网(Delay Time Petri Nets,DTPN)是一类重要的时间扩展Petri网系统,解决了其他时间扩展Petri网(如时间Petri网)在保存时间约束时所面临的困难。可调度验证的目的是验证工作流模型时间约束的合理性,对流程实例的时间可达性...延迟时间Petri网(Delay Time Petri Nets,DTPN)是一类重要的时间扩展Petri网系统,解决了其他时间扩展Petri网(如时间Petri网)在保存时间约束时所面临的困难。可调度验证的目的是验证工作流模型时间约束的合理性,对流程实例的时间可达性进行仿真。提出一种基于DTPN的时间约束工作流验证分析方法。给出了DTPN的相关定义,并结合工作流控制结构描述了变迁可触发的时间条件;提出了DTPN触发点的概念以及基于此的验证分析算法;简要分析了DTPN的特性。DTPN的研究丰富完善了现有时间Petri网体系,具有积极的意义。展开更多
基金This project is supported by Key Science-Technology Project of Shanghai City Tenth Five-Year-Plan, China (No.031111002)Specialized Research Fund for the Doctoral Program of Higher Education, China (No.20040247033)Municipal Key Basic Research Program of Shanghai, China (No.05JC14060)
文摘In response to the production capacity and functionality variations, a genetic algorithm （GA） embedded with deterministic timed Petri nets（DTPN） for reconfigurable production line（RPL） is proposed to solve its scheduling problem. The basic DTPN modules are presented to model the corresponding variable structures in RPL, and then the scheduling model of the whole RPL is constructed. And in the scheduling algorithm, firing sequences of the Petri nets model are used as chromosomes, thus the selection, crossover, and mutation operator do not deal with the elements in the problem space, but the elements of Petri nets model. Accordingly, all the algorithms for GA operations embedded with Petri nets model are proposed. Moreover, the new weighted single-objective optimization based on reconfiguration cost and E/T is used. The results of a DC motor RPL scheduling suggest that the presented DTPN-GA scheduling algorithm has a significant impact on RPL scheduling, and provide obvious improvements over the conventional scheduling method in practice that meets duedate, minimizes reconfiguration cost, and enhances cost effectivity.
文摘A new real time control model based on the fundamental Petri net theory is built for a complete close loop welding robot system with time delay. The new Petri net model synchronizes with devices at the primary level by introducing into the basic Petri net expression new parameters which contain the responding real time information. In addition, time delay is taken into account by adding some necessary time related parameters. Usually, in a system without time delay, if the condition is enabled, the transition must be fired, but in a system with time delay, this property is only a necessary but not a sufficient condition.
文摘延迟时间Petri网(Delay Time Petri Nets,DTPN)是一类重要的时间扩展Petri网系统,解决了其他时间扩展Petri网(如时间Petri网)在保存时间约束时所面临的困难。可调度验证的目的是验证工作流模型时间约束的合理性,对流程实例的时间可达性进行仿真。提出一种基于DTPN的时间约束工作流验证分析方法。给出了DTPN的相关定义,并结合工作流控制结构描述了变迁可触发的时间条件;提出了DTPN触发点的概念以及基于此的验证分析算法;简要分析了DTPN的特性。DTPN的研究丰富完善了现有时间Petri网体系,具有积极的意义。
