Control Reconfiguration Of Discrete Event Systems With Dynamic Control Specifications

At present,there are a large number of artificial systems in human life.Their control requirements are often dynamic,such as reconfigurable manufacturing systems.Such systems can adjust their structure quickly and smoothly to meet different production task demands.According to the change,the system's supervisory controller should also be able to be synthesized quickly,so that the controlled system can operate normally under different control specifications.Typically,people will redesign the controller based on new control specifications,which are wasting time and energy sometimes.Thus,the more efficient controller reconfiguration methods have been studied,through which the controller can adjust its structure online in real time,and continue proper control actions of the DES under the new specifications.This thesis defines a reconfiguration method of the supervisory controller for a class of Discrete Event Systems(DES)that are subject to linear inequality constraints as their control specifications.The main work is stated as follows:First,the control specifications which are enforced on the plant can be represented by linear inequalities constraints.A supervisory controller of Petri nets is designed based on P-invariants.And the change of the control specifications which are enforced on the actual system is reflected by changing the parameters of the linear inequality reasonably.Then,the mechanism of the supervisory control reconfiguration is designed.Secondly,a supervisory control reconfiguration strategy is adjoined to the control structure called a monitor-switcher.With the control of the switcher,the controller can adjust its structure in real time,and response control specifications change quickly.By the monitor-switcher,the control reconfiguration is faster,more efficient and less costing,especially for some artificial systems,such as hospital emergency room system and human resource system,which need to be refactored in case of emergency.When emergent situations occur,the system needs to be reconstructed.Through the reconstruction strategy proposed in this thesis,the system can meet the change requirements quickly.When the emergency situation is over,the reconfiguration strategy proposed in this thesis can be used to restructure the system quickly and meet the original normal control constraints.Finally,this thesis further studies the deadlock problem in the supervision and control reconfiguration.And the reason of the deadlock occurrences during the reconfiguration is exposed.A deadlock control policy is proposed based on the characteristics of the deadlock problem which may arise during reconfiguration.The deadlock control strategy is based on the theory of siphon and reachability graph analysis.Compared with other deadlock control strategies,this method can not only ensure the controlled system to gain more permissive,but also improve the computational efficiency.