Robust control strategies facing disturbances in manufacturing workshops with time constraints

Developments presented in this paper are devoted to the robustness control of manufacturing job-shops with time constraints and without assembling tasks. Such systems have robustness properties which allow them to face time disturbances. Three robust control strategies towards time disturbances are presented. The first one consists of generating by the control a temporal shift similar to the disturbance, in order to avoid the death of marks on the levels of synchronization transitions of the P-time Petri net model. The second one rejects the disturbance as soon as it is observed, using the control. The third strategy represents the main contribution of this paper. It is a combination of the two preceding approaches in order to face time disturbances. Based on this last approach, an algorithm allowing computing the robustness margin at various graph nodes is established, providing a value integrating the constraints of the whole system.