Safety Cases for Advanced Control Software: Safety Case Patterns

Abstract

This report results from a contract tasking University of York. The project will undertake one activity: Produce a unified (generic) approach to developing safety cases for adaptive avionics and software and identifying a "way ahead" to develop and validate the approach, based on the outline produced in the preceding NASA project. As with the previous report, the authors' focus in addressing safety cases for "advanced" control systems is to concentrate on the class of adaptive systems. A system can be considered adaptive if its behavior cannot be predicted solely from knowledge of its initial software design and state. The behavior of an adaptive system is the product of its initial state and the adaptations (state changes) that have taken place according to the stimuli it has encountered. Adaptive systems can be introduced to improve safety (e.g., to continue to control an aircraft safely in the event of losing a control surface), or to improve other system characteristics (e.g., to improve the fuel consumption of an aero-engine). The motivation for introducing an adaptive capability has a significant impact on the nature of the required safety argument. Where improved safety is the goal of the adaptation, the safety argument must justify that the adaptive system is capable of reducing some of the risks associated with hazards already present with the equipment under control. At the same, it is necessary to ensure that the introduction of the adaptive capability does not introduce new, or increase existing, risks. Where adaptation is being introduced for reasons other than safety, safety can be viewed as a constraint. The principal concern is that the adaptive capability doesn't introduce new, or increase existing, risks.

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Document Details

Document Type
Technical Report
Publication Date
Oct 15, 2007
Accession Number
ADA491299

Entities

People

  • John A. Mcdermid
  • Robert Alexander
  • Tim P. Kelly
  • Zeshan Kurd

Organizations

  • University of York

Tags

Communities of Interest

  • C4I
  • Materials and Manufacturing Processes
  • Space

DTIC Thesaurus Topics

  • Acceptability
  • Accuracy
  • Adaptive Control Systems
  • Adaptive Systems
  • Application Software
  • Artificial Intelligence
  • Computer Programming
  • Computer Programs
  • Computer Science
  • Control Systems
  • Engineers
  • Failure Mode And Effect Analysis
  • Life Cycles
  • Models
  • Neural Networks
  • Safety
  • Simultaneous Localization And Mapping

Fields of Study

  • Computer science
  • Engineering

Readers

  • Adaptive Control and Estimation with Uncertainty in Dynamic Systems.
  • Software Engineering.
  • Systems Analysis and Design