How to take into account potential change of the deterioration mode in Condition-Based Maintenance decision rule

Classical results in maintenance optimization are based on the characterization of an average system degradation behaviour. The main reasons of such approaches are the robustness of the decisions with respect to the system state and the time horizon. By cons, the ''smoothing'' effect in existing degradation models and the ``generic'' aspect of the decision affect the decision quality as these models do not take into account potential changes in deterioration modes. Such consideration can be particularly valuable in a safety context. We propose here a condition-based maintenance approach which adapts the maintenance decision according to the degradation behaviour updated using current state observations. First, we propose to extend the system state definition, usually limited to an indicator of observable degradation by adding information related to the speed of deterioration referred hereafter as potential of degradation or deterioration growth rate. Moreover, we propose to take benefit of current observations as well as performed actions to update the degradation laws. More than the model fitness improvement, another advantage of our approach is the proposition of a more realistic modelling of the maintenance impact onto the future behaviour of the system. However, the introduction of the potential of degradation as a new decision parameter does not prejudge an intuitive structure for the decision policy. Moreover, as the classical concept of the failure rate, the potential of degradation is non observable. which implies more efforts in both optimization modelling and solution procedure. We highlight the structural properties of the optimization problem which ensure an optimal control limit policy. We will conclude our communication by the illustration of the results of our maintenance model in a pavement management context.