<p>Space habitats will involve a complex and tightly coupled
combination of hardware, software, and humans, while operating in challenging
environments that pose many risks, both known and unknown. It will not be
possible to design habitats that are immune to failure, nor will it be possible
to foresee all possible failures. Rather than aiming for designs where “failure
is not an option”, habitats must be resilient to disruptions. We propose a
control-theoretic approach to resilient design for space habitats based on the
concept of safety controls from system safety engineering. We model disruptions
using a state and trigger model, where the space habitat is in one of three
distinct states at each time instance: nominal, hazardous, or accident. The
habitat transitions from a nominal state to hazardous states via disruptions,
and further to hazardous and accident states via triggers. We develop an
approach for identifying safety controls that considers these disruptions,
hazardous states, and identifies control principles and their possible control
flaws. We use safety controls as ways of preventing a system from entering or
remaining in a hazardous or accident state. We develop a safety control option
space for the habitat, from which designers can select the set of safety
controls that best meet resilience, performance, and other system goals. We
show how our approach for identifying safety controls drives our
control-theoretic approach for resilient design, and how that fits into the
larger system safety engineering process. To identify and assess hazards, we
use a database and create a network format that stores the relationships
between different disruptions and hazardous states for an example space
habitat. We use this database in combination with traditional hazard assessment
techniques to prioritize control of possible disruptions and hazardous states.
To mitigate hazards, we develop a safety control option space that contains
safety controls that either prevent transition to hazardous states or return
the habitat to a nominal state. We use generic safety controls, or the
principle of control, to generate new safety controls as our set of disruptions
and hazardous states grows, and store these in the database. Lastly, we evaluate
our mitigation techniques using our control effectiveness metric, a metric
intended to assess how well a safety control addresses the hazardous state or
disruption that it is designed for. Our control-theoretic approach is one way
in which we can complete the system safety engineering process for a space
habitat system and can provide design guidance for the development of resilient
space habitats.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12574067 |
| Date | 29 June 2020 |
| Creators | Robert E Kitching (9029741) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/A_Control_Theoretic_Approach_to_the_Resilient_Design_of_Extra-Terrestrial_Habitats/12574067 |
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