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A hybrid discrete/continuous simulation tool, CONFIG, has been developed to support evaluation of the operability of life support systems. CONFIG simulates operations scenarios in which continuous change in system flows and pressures interacts with discrete events during system reconfigurations. In simulation, intelligent control software interacts dynamically with a model of the hardware system. CONFIG simulations have been used to evaluate control software and intelligent agents for automating life support systems operations. A CONFIG model of an advanced biological water recovery system has been developed to interact with intelligent control software that is being used in a water system test at NASA Johnson Space Center.

Diverse modeling information is needed for system modeling and simulation for the purposes of developing, testing and supporting intelligent layered software for planning/scheduling, monitoring, control and fault management for test articles in BIO-Plex. A framework of types of system management goals is used to provide perspective for integrated discussion of the diverse modeling and control approaches. This paper discusses model representations in the CONFIG discrete-event modeling and simulation tool, which are used to link diverse modeling styles, to support integrated use and reuse of diverse modeling information.

Gas transfer systems in a closed life support test were controlled by intelligent layered monitoring and control software. Interactive simulation-based testing was used for system-level validation of the discrete sequencer layer of the software. An advanced discrete event simulation tool was used to model diverse components and systems for processing gases in a plant growth chamber, crew chamber and incinerator, and transferring gases between chambers. Models included physico-chemical and biological gas processors, pumps, concentrators, chambers and tanks, and devices for configuring and controlling gas transfer. Several types of control were modeled. This paper describes the models, the testing approach, and some results of the testing.

Future long duration manned space missions will require regenerative Life support subsystems which operate efficiently and reliably with minimum attendance from the crew. An essential prerequisite to achieving this goal is the development of highly reliable controllers to control the various life support processes, to monitor subsystem performance, and to provide automatic shutdown of a process when out of tolerance conditions persist. While life support controller designs have improved dramatically over the years, it is now no Longer good enough to continue a philosophy where the only result of the fault monitoring process is to provide an automatic shutdown of the subsystem.