Epistemic Uncertainty Propagation and Reliability Evaluation of Feedback Control System

When evaluating the reliability of a complex system, epistemic uncertainty exists due to the lack of data and knowledge. The control system's feedback compensation mechanism propagates the uncertainty throughout the system. In addition, the real-time performance compensation causes the system to exhibit implicit degradation, which brings new challenges to reliability evaluation. This article proposes a method to solve the problems of complex feedback control system epistemic uncertainty propagation and reliability evaluation. The arithmetic Liu process is used to model the uncertain performance degradation process of the components in the feedback control system. The feedback behavior of the system and the propagation of uncertainty are described by the uncertain degradation state space model. The Laplace transform is then used to deduce the reliability expression of the system. Afterward, the epistemic uncertainty of the components is transmitted to the uncertainty of the system output. Taking the wind turbine pitch control system as a case, the proposed reliability evaluation method is compared with the method based on probability theory. When there is a lack of degradation data, the results suggest that the proposed strategy is more conservative.