AOCS Fault Detection, Isolation and Recovery : A Model-Based Dynamic Verification and Validation Approach

Current and future space mission are characterised by an increasing level of on-board autonomy to satisfy the need of high availability. Long operational periods can be achieved by monitoring the system's health and actively acting on it to prevent the cessation of system functions when faults occur. The Fault Detection, Isolation and Recovery (FDIR) mechanism is in charge of this and thus it is a key enabling technology to increase spacecraft's availability.The FDIR concept and architecture definition in past and current space missions is only started at late phase B and its consolidation and verification and validation is postponed until late phase C, when inputs to subsystem and software development have already been given. If then the FDIR mechanism is found not to comply with the design specifications, this can require software modifications, which are costly and time-consuming. Therefore, there is the need of an earlier start of the FDIR design process as well as a dynamic, project-long verification and validation process which minimises the risk of late occurrences and enables the creation of more cost-efficient FDIR mechanisms.This thesis presents a softare tool that supports the design of FDIR and establishes a bridge between the FDIR verification and validation phase and the FDIR design phase. It enables an iterative design process from phase A on, by means of open-loop and closed-loop tests of an automatically customised MATLAB® Simulink® module which contains the FDIR mechanism specified by the user.Finally, a H∞ fault detection and isolation method for the generation of monitors is introduced, applied to a spacecraft attitude control system and compared with an observer-based method in order to show the potential of these techniques in the creation of more meaningful monitors and thus in the reduction of the number of monitors needed for the FDIR mechanism.Validerat; 20141017 (global_studentproject_submitter