Scheduling Of Hybrid Production Systems With Research Of Experimental Systems

With the enlargement of control systems and the enhance of control objectives, hybrid phenomena which arise from many engineering systems, such as manufacturing, communication networks, embedded control systems, traffic control, and chemical processes, etc., are more and more recognized. The research work of hybrid system, that is to consider both continuous dynamics and discrete dynamics which interact with each other in a single system, is rapidly developed recent years. This thesis focuses on hybrid production systems and three-buffer hybrid systems, both of which can be researched independently but somewhat interrelated to each other. The interaction between continuous production processes and discrete events/scheduling as well as hierarchical organization makes hybrid production systems be a special research branch in hybrid systems field. Three-buffer hybrid systems are the classical hybrid models which can model inventory of production systems and buffered operation units in computer and communication systems. Moreover, three-tank systems as one kind of the physical realization of three-buffer systems can be used as a experimental platform for hybrid systems research.This thesis deals with production systems first. Optimal production control for production systems, as the core of the production planning and management, attract more attention from the producer due to the intensive marketing competition environment. Over the past decades, many scholars devoted themselves to the control and scheduling of manufacturing systems. Based on their research outcomes, with the special features of processing production in mind, building hierarchy on the flow rate model with receding horizon optimization from predictive control, some discussion for practical solution for control and scheduling of production systems, especially processing production systems, is made. In order to help verify the results from hybrid production systems, author took part in the work of designing and implementing the classic three-tank hybrid system experimental equipment. Wealthy discussion is set forth for three-buffer hybrid systems as abstract models for the three-tank hybrid system. Given some simple and intuitive feedback control policies, the closed-loop systems are simulated and analyzed. The contents in details are as following:â—† Based on the flow rate model, the optimal control problems for flexible production systems which contain a set of unreliable equipment are formulated. The conditions which optimal control policies and value functions satisfied are described and hedging point control schemes are also covered.â—† Two main hierarchical methodologies, i.e., event frequency based hierarchy and construction of limiting problems, are introduced. Event frequency based method is discussed in more details. And with this kind of idea, morecomplex flexible systems which contain several kinds of equipments and can produce several kinds of products at the same time are formulated. The flow rate control level is focused and the simple engineering approximation of the original problem proposed by other scholars is discussed.â—† Processing industry production systems which involve setup duration and setup cost are abstracted into an inflexible production system. Considering the special features of the processing industry, a hierarchical receding horizon control scheme is proposed. The kind of organization is feasible and capable of handling random and unexpected events like the change of demands rate or system parameters. The aging of the equipment is also considered and handled under this hierarchy by piecewise approximation. Simulation results imply the condition of stable scheduling.â—† The design and implementation of three-tank hybrid control experimental equipment done by author during his master study is described briefly. Then, as abstract inventory models of production systems, the more general three-buffer hybrid systems are introduced. According to the location of the server, two similar kinds of three-buffer systems...