Bachelor and Master Theses

Title: An approach to allow safety requirements to be efficiently decomposed, traced and validated
Subject: Computer Science
Level: Advanced
Description: The integration of systems with other systems has increased the complexity level of the avionic systems to a point where it is troublesome to allocate and to validate the requirements. In particular, this trend of integration and increased complexity is problematic regarding safety requirements. In addition, this complexity level has made harder to assess the independences and fault propagation.
During the development of avionic systems, a number of different standards are taken into account. Some of these are:
- ARP 4754 addresses the development cycle for aircraft and systems that implement aircraft functions [1];
- ARP 4761 provides a guideline for conducting an industry accepted safety assessment consisting of Functional Hazard Assessment (FHA), Preliminary System Safety Assessment (PSSA), and System Safety Assessment (SSA) [2];
- DO-178B/ED-12B and DO-254/ED-80 provide more specific guidelines concerning software and hardware development [3-4].
An example of complex system that is taken into account is the High Lift Control & Monitoring system developed at Saab, where there are several subsystems, e.g. computers, actuators and sensors, with functional and structural dependency [5].
To reduce the complexity of the system architectures, this thesis aims at providing an approach to ease the traceability, the validation and the allocation of safety requirements.

Task included:
1) Getting familiar with the avionic standards ARP 4754 [1] and ARP 4761 [2].
2) Evaluate how safety requirements are captured and managed, in particular how these will flow down into hardware and software requirements.
a. The work includes taking a handful of system level safety requirements, allocating and breaking down the selected requirements for different hardware and software architectures. For example how can required “independence” between control and monitoring be designed (different software and hardware architecture).
b. Particular effort is to understand and capture HW/SW integration in order to validate the fulfillment of the system level safety requirement “e.g. independent”.
c. Compare with developed designs at Saab e. g. High Lift Control and Monitoring System.
3) Establishment of process and methods to provide the framework for the system architecture development, using ARP 4754 [1].

Required outcomes:
a) An analysis about the current state of the art concerning the methods used to trace/validate/allocate the safety requirements from system level to item level. The focus will be on safety requirements related to independence.
b) A process and methods for the system architecture development allowing for efficient traceability/allocation/validation of safety requirements.
c) A case study.
d) A thesis report.

References to start with:
[1] ARP 4754. Certification Considerations for Highly-Integrated or Complex Aircraft Systems.
[2] ARP 4761. Guidelines and methods for conducting the safety assessment process on civil airborne systems and equipment.
[3] DO-178B/ED-12B. Software Considerations in Airborne Systems and Equipment Certification.
[4] DO-254/ED-80. Design Assurance for Airborne Electronic Hardware.
[5] M. Sghairi, A. de Bonneval, Y. Crouzet, J.-J. Aubert, P. Brot. Architecture Optimization based on Incremental Approach for Airplane Digital Distributed Flight Control System. Processing World Congress on Engineering and Computer Science (WCECS). Advances in Electrical and Electronics Engineering - IAENG Special Edition, Oct. 2008.
Company: SAAB AB, Electronic Defence Systems, kontaktperson: Kristina Forsberg
Prel. end date: 2014-03-02
Presentation date: 2014-09-26
Student: Achille Penna
IDT supervisor: Barbara Gallina, 021-101631
Examinator: Kristina Lundqvist
Kristina Lundqvist, +46 (0)21 101428

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