Robust time-varying thresholds for supervision of valves in a flotation process

Abstract

Abstract-Robust thresholds for observer-based residuals are developed for the purpose of detecting clogging in the valves of a flotation process. The observer in the residual generator is a linear model of the flotation process extended with integrators and corrected with a linear feedback term. The integral states in the observer constitute the residual. Contribution to the residual comes not only from the faults but also from uncertainties in measurements, estimates and working point. To avoid false alarms generated by these uncertainties, robust time-varying thresholds depending on the uncertainties are derived.Experiments on a froth flotation process with four cascade coupled tanks are carried out successfully. The data was provided by Boliden Area Concentrator in Boliden, Sweden.

Linear Optimization of Parameters in Dynamic Threshold Generators

“…The threshold is generated by a linear dynamical system and depends on the upper bounds on the uncertainties, Π which are unknown. So far the thresholds have been designed by manually tuning a set of parameters, π * , see (Johansson and Bask 2005), (Bask and Johansson 2004), such that the threshold is larger than the residual for a set of test data. In this section, an automatic way to determine the parameters π * is suggested.…”

“…Time-domain uncertainty description are utilized in e.g. (Zhang et al 2002), (Ding et al 2003), (Bask and Johansson 2004) and (Johansson and Bask 2005). In the latter, the threshold is generated by a linear system with the uncertainty upper bounds, which are unknown, as parameters.…”

“…In the latter, the threshold is generated by a linear system with the uncertainty upper bounds, which are unknown, as parameters. The upper bounds are substituted by a vector of parameters which, so far, has been tuned manually in (Bask and Johansson 2004) and (Johansson and Bask 2005). The main purpose of this study is thus to provide an algorithm to choose these parameters in an automatic way.…”

An Adaptive Threshold Algorithm Based on Satisfactory Filtering Principle

“…In this paper, Aero-engine parameter perturbation "soft boundary" probability model is established from the idea of "probability robust" control theory [5,6] . With consideration of "satisfactory filtering" principle, linear matrix inequality (LMI) method is used to calculate the upper bound of residual.…”