Device Controller Synthesis for Systems of Interacting Discrete-State Components

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With complex systems, monolithic models become impractical and it becomesnecessary to model them through subsystems and components. Development of controllogic for such systems also becomes complex, unless the structure of the subsystemsand components can be exploited in a systematic way. In this proposal, we consider thedevelopment of methods that use the structure of discrete-state model components forsynthesizing control logic and diagnostic information. These methods are automated,generating formal control logic models that can be analyzed, generating control softwarethat can be executed, and generating diagnostic models that can provide fault diagnosishypotheses. Such automated methods would reduce controller development time, wouldprovide enhanced reliability compared to manually developed controllers, and would beautomatically reconfigured as underlying system designs are modified. In this research,we propose to develop such tools and techniques by building upon our prior research. Inour previous research, techniques were developed for: modeling common componentsof manufacturing systems; assembling such components together to represent customsystem designs; synthesizing control logic called "taskblocks" for control of thosecomponents; and assembling those taskblocks together sequentially and hierarchicallyin order to achieve given specifications. Software tools were developed for graphicalentry of the component models and the specifications, and for automatically convertingthe synthesized control logic into C++ code. An automatically synthesized software"supervisor" then coordinates the multiple concurrent control activities, steering thesystem around undesired states. The models we consider are a form of discrete eventsystem, and the synthesis techniques build upon discrete event control methods.There are several unresolved issues with this current approach that will be addressed inthe proposed research. One major emphasis of this work is recognizing and exploitingthe 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 interactingcomponents, but they must be extended in order to compactly represent componentswith 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 certainperiod of time or immediately upon receipt of a sensing. The synthesized controlsoftware should consider such time issues, and should ensure appropriate prioritiesamong various potentially concurrent activities. Finally, we propose to extend our currentsoftware tools to become a resource for other researchers and educators. This wouldallow others to test, develop, and evaluate other techniques using our graphical systemeditor, our code synthesis tool, and our hardware interface techniques. The automatedcontrol synthesis and diagnostic synthesis techniques will be demonstrated using bothmanufacturing and embedded control applications.