Device Controller Synthesis for Systems of Interacting Discrete-State Components

With complex systems, monolithic models become impractical and it becomes necessary to model them through subsystems and components. Development of control logic for such systems also becomes complex, unless the structure of the subsystems and components can be exploited in a systematic way. In this proposal, we consider the development of methods that use the structure of discrete-state model components for synthesizing control logic and diagnostic information. These methods are automated, generating formal control logic models that can be analyzed, generating control software that can be executed, and generating diagnostic models that can provide fault diagnosis hypotheses. Such automated methods would reduce controller development time, would provide enhanced reliability compared to manually developed controllers, and would be automatically reconfigured as underlying system designs are modified. In this research, we propose to develop such tools and techniques by building upon our prior research. In our previous research, techniques were developed for: modeling common components of manufacturing systems; assembling such components together to represent custom system designs; synthesizing control logic called "taskblocks" for control of those components; and assembling those taskblocks together sequentially and hierarchically in order to achieve given specifications. Software tools were developed for graphical entry of the component models and the specifications, and for automatically converting the synthesized control logic into C++ code. An automatically synthesized software "supervisor" then coordinates the multiple concurrent control activities, steering the system around undesired states. The models we consider are a form of discrete event system, and the synthesis techniques build upon discrete event control methods. There are several unresolved issues with this current approach that will be addressed in the proposed research. One major emphasis of this work is recognizing and exploiting the multiple layers of interaction with components of the system. The modeling frame- work and our current analysis methods are ideally suited for such models of interacting components, but they must be extended in order to compactly represent components with large state spaces. A second issue involves the timed dynamics of the system. Some activities may be time critical, such as turning off an actuator within a certain period of time or immediately upon receipt of a sensing. The synthesized control software should consider such time issues, and should ensure appropriate priorities among various potentially concurrent activities. Finally, we propose to extend our current software tools to become a resource for other researchers and educators. This would allow others to test, develop, and evaluate other techniques using our graphical system editor, our code synthesis tool, and our hardware interface techniques. The automated control synthesis and diagnostic synthesis techniques will be demonstrated using both manufacturing and embedded control applications.