Abstract: The fault diagnosability evaluation method of the momentum wheel based on the quantitative and qualitative model was proposed to enhance its fault diagnosis performance. Considering the momentum wheel model and its controller model, the momentum wheel system model was obtained and it included the influence of three types of faults, namely measurement related, driven-related and the controller-related faults. By judging whether the transfer function from the fault to the output equals to 0 or whether different faults have different transfer functions, the fault detectability and isolability discriminant conditions were obtained and applied to the momentum wheel. Some problems related to the method based on the quantitative model were concluded. To the unisolable fault sets, the qualitative model based fault diagnosability evaluation method was addressed, including the fault symptom incidence matrix establishment by considering the relationship of the function modules, the FMEA and its data analysis. Finally, the quantitative indexes were proposed as well as the diagnosable degree of the momentum wheel which offered some important information to the fault diagnosability design.

Key words: Momentum wheel, Fault diagnosability evaluation, Fault detectability, Fault isolability, Satellite