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Intelligent software is being developed for closed life support systems with biological components, for human exploration of the moon and Mars. The intelligent software functions include planning/scheduling, reactive discrete control and sequencing, management of continuous control, and fault detection, diagnosis, and management of failures and errors. The CONFIG modeling and simulation tool has been used to model components and systems involved in production and transfer of oxygen and carbon dioxide gas in a plant growth chamber and between that chamber and a habitation chamber with physico-chemical systems for gas processing. CONFIG is a multi-purpose discrete event simulation tool that integrates all four types of models, for use throughout the engineering and operations life cycle. Within CONFIG, continuous algebraic quantitative models are used within an abstract discrete event qualitative modeling framework of component modes and activity phases. Component modes and activity phases are embedded in transition digraphs. Flows and flow reconfigurations are efficiently analyzed during simulations. Modeled systems for the Life Support Testbed have included biological plants and crew members, oxygen concentrators and an oxygen transfer control subsystem, and injectors and flow controllers in a carbon dioxide control subsystem. To test the discrete control software, some elements of the lower level control layer and higher level planning layer of the intelligent software architecture are modeled, using CONFIG activity models. CONFIG simulations show effects of events on a system, including control action or failures, local and remote effects, and behavioral and functional effects, the time course of effects, and how effects may be detected. The CONFIG models are interfaced to the discrete control software layer and used to perform dynamic interactive testing of the software in nominal and off-nominal scenarios. |
