Goal-Function Tree Modeling for Systems Engineering and Fault Management

Johnson, Stephen B.; Breckenridge, Jonathan T.

doi:10.2514/6.2013-4576

Cited by 14 publications

(41 citation statements)

References 5 publications

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“…The linkage between functions, goals, and SHM capabilities are clearly visible in a Goal-Function Tree (GFT) representation, as described in the 2013 Infotech@Aerospace paper, "Goal-Function Tree Modeling for Systems Engineering and Fault Management." 2 The relationship of goals and functions is defined through the simple equation y = f(x), where the function f is a transformation or mapping of a set of input state variables x into the output state variables y. A goal is represented by the system's output state variables y being constrained or controlled to be within some nominal range.…”

Section: Goals and Function Preservationmentioning

confidence: 99%

System Health Management Design Strategies

Day

Johnson

2014

SpaceOps 2014 Conference

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Development of dependable systems relies on the ability of the system to determine and respond to off-nominal system behavior. Specification and development of these fault management capabilities must be done in a structured and principled manner to improve our understanding of these systems, and to make significant gains in dependability (safety, reliability and availability). Prior work has described a fundamental taxonomy and theory of System Health Management (SHM), and of its operational subset, Fault Management (FM). This conceptual foundation provides a basis to develop framework to design and implement FM design strategies that protect mission objectives and account for system design limitations. Selection of an SHM strategy has implications for the functions required to perform the strategy, and it places constraints on the set of possible design solutions. The framework developed in this paper provides a rigorous and principled approach to classifying SHM strategies, as well as methods for determination and implementation of SHM strategies. An illustrative example is used to describe the application of the framework and the resulting benefits to system and FM design and dependability.

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Section: Goals and Function Preservationmentioning

confidence: 99%

System Health Management Design Strategies

Day

Johnson

2014

SpaceOps 2014 Conference

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“…If the function output is below the threshold for success an off nominal function is triggered. Unlike the fault tree's requirement of defining all the possible ways of failure, the GFT failure detection coverage is determined from the bottom up to ensure that each branch has at least one failure detection goal (Johnson 2013).…”

Section: Goal Function Treementioning

confidence: 99%

“…The standard for hierarchical decomposition of system failure scenarios is the fault tree. Fault trees are useful in determining possible points of failure in a system by specifying how a system may fail at its highest point then the failure is decomposed to the lowest level to locate the root cause (Johnson 2013). Vast amounts of decomposition are required for complex engineered systems, and even then fault trees only cover failures that the creator has thought of.…”

Section: Introductionmentioning

confidence: 99%

“…Vast amounts of decomposition are required for complex engineered systems, and even then fault trees only cover failures that the creator has thought of. When the system fails in a manner not addressed by the fault tree, the failure cause is attributed to a "failure of imagination" (Johnson 2013). The Goal Function Tree attempts to remove gaps of possible sources of failure by listing the system's goals that enable mission success instead of failure.…”

Section: Introductionmentioning

confidence: 99%

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Utilization of Goal Function Trees for Robust Requirements Definition

Gethers

Thomas

2018

INCOSE International Symp

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This paper describes the implementation of the Goal Function Tree (GFT) for an Unmanned Aerial Vehicle (UAV) in a Systems Modeling Language (SysML) environment which tracks nominal and off nominal goals for a successful flight of a UAV. The utility of the GFT enables the traceability of the system's goals and requirements to perform a successful mission scenario. Definition of nominal goals reduces ambiguity about mission success and can be followed more easily by the customer. Furthermore, the Goal Function Tree can also track and implement corrections if the measurements for success are deviating through the use of off nominal functions. The GFT's off nominal functions create a new set of functions and goals that attempt to mitigate a failing attribute instead of the other methods that only defined failure. This methodology creates a set of procedures for an operator or system when action is needed, thereby identifying more robust requirements as compared to traditional requirements development based only on nominal mission scenarios. The advantage of the SysML environment enables the legible traceability of the overlapping of goals of various structural and behavioral system objects, the execution of functions, and implementation of stereotypes which classifies the interactions between objects.

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“…The state-based, goal-based system engineering method espoused in this paper specifies that a Goal-Function Tree (GFT) model [16] of the system should be constructed from the beginning of the SE process, and should be elaborated into further depth and detail as design choices are selected. The GFT provides a number of benefits, among which are a rigorous requirements (goal) definition and traceability in functional success space, beginning the development of fault trees by taking the logical complement of the GFT, analysis and definition of the required system health management and fault management to protect system goals, and most intriguingly for this paper, the creation of a physically and logically accurate tree structure that forms the starting point of the autonomous artificial intelligence for the system that can be used in system operations.…”

Section: Spacecraft System State Variablesmentioning

confidence: 99%

System engineering of autonomous space vehicles

Watson

Johnson

Trevino

2014

2014 International Conference on Prognostics and Health Management

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Human exploration of the solar system requires fully autonomous systems when travelling more than 5 light minutes from Earth. This autonomy is necessary to manage a large, complex spacecraft with limited crew members and skills available. The communication latency requires the vehicle to deal with events with only limited crew interaction in most cases. The engineering of these systems requires an extensive knowledge of the spacecraft systems, information theory, and autonomous algorithm characteristics. The characteristics of the spacecraft systems must be matched with the autonomous algorithm characteristics to reliably monitor and control the system. This presents a large system engineering problem. Recent work on product-focused, elegant system engineering will be applied to this application, looking at the full autonomy stack, the matching of autonomous systems to spacecraft systems, and the integration of different types of algorithms. Each of these areas will be outlined and a general approach defined for system engineering to provide the optimal solution to the given application context.

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Goal-Function Tree Modeling for Systems Engineering and Fault Management

Cited by 14 publications

References 5 publications

System Health Management Design Strategies

System Health Management Design Strategies

Utilization of Goal Function Trees for Robust Requirements Definition

System engineering of autonomous space vehicles

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