Johannes Kepler University, Linz, Austria
Self-Adaptive Forecast Models in Predictive Maintenance Systems
Predictive maintenance relies on real-time monitoring and diagnosis of system components, and process and production chains. The primary strategy is to take action when items or parts show certain behaviors that usually result in machine failure, reduced performance or a downtrend in product quality.
In the first stage, it is thus of utmost importance to recognize potentially arising problems as early as possible. Therefore, a core component in predictive maintenance systems is the usage of techniques from the fields of forecasting and prognostics, which can either rely on process parameter settings (static case) or process values recorded over time (dynamic case). We will focus on the latter and demonstrate a robust learning procedure of time-series based forecast models, which can deal with very high-dimensional batch process modeling settings. Furthermore, our approach allows the forecast models to be on-line updated over time and on the fly whenever required due to intrinsic system dynamics (such as, e.g. varying product types, charges, settings, environmental influences) => leading to the paradigm of self-adaptive forecast models. This is achieved i) by recursive adaptation of model parameters to permanent changes and to increase model significance and accuracy and ii) by evolution of new model components (rules) on the fly in order to account for variations in the process, which require a change in the model’s ‘non-linearity degree’. We will also present some enhanced methods in model adaptation for increased flexibility to properly compensate system drift and shifts, such as dynamic forgetting, rule merging and splitting as well as an incremental update of the latent variable sub-space as a variant of incremental feature space transformation (accounting for dynamic changes in the influences of input variables on the output).
In the second stage, the forecast models can be used as surrogates in a fully automatized optimization procedure in order to prevent operator’s intervention and time-intensive manual reactions to predicted downtrends. The assumption is that there are some “control wheels”, usually machine parameter settings which are able to change the behavior of the production process in order to meet the quality standards. Such settings may have indeed been optimized before, but may not take into account dynamically changing factors during production. In other cases, such settings could not be optimized before at all (as requiring time-intensive design of experiments cycles) such that often a default parametrization is used which is suboptimal for the final product quality. For both cases, we will define the optimization problem, which typically leads to a many-valued problem with very-high dimensional input parameter space; thus, we also demonstrate possibilities how a reduction to smaller problems can be achieved.
The talk will be concluded with a real-world application scenario from a (micro-fluidic) chip production site, where the time-series based forecast models have been successfully applied; some results will be presented.
Edwin Lughofer received his PhD-degree from the Johannes Kepler University Linz (JKU) in 2005. He is currently Key Researcher with the Fuzzy Logic Laboratorium Linz / Department of Knowledge-Based Mathematical Systems (JKU) in the Softwarepark Hagenberg, see www.flll.jku.at/staff/edwin/.
He has participated in several basic and applied research projects on European and national level, with a specific focus on topics of Industry 4.0 and FoF (Factories of the Future). He has published around 190 publications in the fields of evolving fuzzy systems, machine learning and vision, data stream mining, chemometrics, active learning, classification and clustering, fault detection and diagnosis, quality control, predictive maintenance, including 75 journals papers in SCI-expanded impact journals, a monograph on ’Evolving Fuzzy Systems’ (Springer) and an edited book on ’Learning in Non-stationary Environments’ (Springer). In sum, his publications received 3500 references achieving an h-index of 33. He is associate editor of the international journals IEEE Transactions on Fuzzy Systems, Evolving Systems, Information Sciences, Information Fusion and Soft Computing, the general chair of the IEEE Conference on EAIS 2014 in Linz, the publication chair of IEEE EAIS 2015, 2016, 2017 and 2018, the publication chair of the 3rd INNS Conference on Big Data and Deep Learning 2018, and the Area chair of the FUZZ-IEEE 2015 conference in Istanbul. He co-organized around 10 special issues and more than 20 special sessions in international journals and conferences. In 2006 he received the best paper award at the International Symposium on Evolving Fuzzy Systems, in 2013 the best paper award at the IFAC conference in Manufacturing Modeling, Management and Control (800 participants) and in 2016 the best paper award at the IEEE Intelligent Systems Conference.