Tham khảo tài liệu 'petri net part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Error Recovery in Production Systems A Petri Net Based Intelligent System Approach 321 possible transient trajectories dotted lines to return to the original trajectory. The disrupted state is reached involuntarily. After being generated the recovery subnet is incorporated into the workstation activities net the Petri Net of the multi-agent system environment . In this research we followed the designation of others Zhou and DiCesare 1993 and denoted the incorporation of a recovery subnet into the activities net as net augmentation. Zhou and DiCesare developed a formal description of these three possible trajectories in terms of Petri net constructs namely input conditioning backward error recovery and forward error recovery. This prior work on error recovery strategies was intended to model the specifics of low level control typified by the equipment level of a hierarchical control system. The terms original net or activities net refer to the Petri Net representing the workstation activities within a multi-agent environment during the normal operation of the system. In the work presented here the three recovery trajectories are applied to the workstation level within a hierarchical model. The enormous number of errors and the corresponding ways to recover that can occur at the physical workstation implies unlimited possibilities for constructing recovery subnets. The important issue is that any error and the corresponding recovery steps can be modeled with any of the three strategies mentioned above. Without loss of generality this research limited the types of errors handled by the control agent to errors resulting from physical interactions between parts and resources . machines and material handling devices . The reason for this assumption was to facilitate the simulation of generic recovery subnets. Backward recovery suggests that a faulty state can become a normal state if an early stage in the original trajectory can be reached. The forward recovery .