2 research outputs found
Accelerated degradation modeling considering long-range dependence and unit-to-unit variability
Accelerated degradation testing (ADT) is an effective way to evaluate the
reliability and lifetime of highly reliable products. Existing studies have
shown that the degradation processes of some products are non-Markovian with
long-range dependence due to the interaction with environments. Besides, the
degradation processes of products from the same population generally vary from
each other due to various uncertainties. These two aspects bring great
difficulty for ADT modeling. In this paper, we propose an improved ADT model
considering both long-range dependence and unit-to-unit variability. To be
specific, fractional Brownian motion (FBM) is utilized to capture the
long-range dependence in the degradation process. The unit-to-unit variability
among multiple products is captured by a random variable in the degradation
rate function. To ensure the accuracy of the parameter estimations, a novel
statistical inference method based on expectation maximization (EM) algorithm
is proposed, in which the maximization of the overall likelihood function is
achieved. The effectiveness of the proposed method is fully verified by a
simulation case and a microwave case. The results show that the proposed model
is more suitable for ADT modeling and analysis than existing ADT models
A Data-Driven Predictive Model of Reliability Estimation Using State-Space Stochastic Degradation Model
The concept of the Industrial Internet of Things (IIoT) provides the foundation to apply data-driven methodologies. The data-driven predictive models of reliability estimation can become a major tool in increasing the life of assets, lowering capital cost, and reducing operating and maintenance costs. Classical models of reliability assessment mainly rely on lifetime data. Failure data may not be easily obtainable for highly reliable assets. Furthermore, the collected historical lifetime data may not be able to accurately describe the behavior of the asset in a unique application or environment. Therefore, it is not an optimal approach anymore to conduct a reliability estimation based on classical models. Fortunately, most of the industrial assets have performance characteristics whose degradation or decay over the operating time can be related to their reliability estimates. The application of the degradation methods has been recently increasing due to their ability to keep track of the dynamic conditions of the system over time. The main purpose of this study is to develop a data-driven predictive model of reliability assessment based on real-time data using a state-space stochastic degradation model to predict the critical time for initiating maintenance actions in order to enhance the value and prolonging the life of assets. The new degradation model developed in this thesis is introducing a new mapping function for the General Path Model based on series of Gamma Processes degradation models in the state-space environment by considering Poisson distributed weights for each of the Gamma processes. The application of the developed algorithm is illustrated for the distributed electrical systems as a generic use case. A data-driven algorithm is developed in order to estimate the parameters of the new degradation model. Once the estimates of the parameters are available, distribution of the failure time, time-dependent distribution of the degradation, and reliability based on the current estimate of the degradation can be obtained