Model-Based Tampering for Improved Process Performance—An Application to Grinding of Shafts

Abstract

This paper presents the model-based tampering (MBT) methodology to address performance degradation in complex nonlinear processes. MBT involves characterizing the dynamics of a process through experiments to derive nonlinear stochastic differential equation (n-SDE) models that can accurately and compactly represent a process, and using these models to dynamically compensate for the effects of process degradation on the performance. This research has yielded a new method to derive n-SDE models of complex processes through a signal-based reconstruction of Fokker-Planck equations. MBT was applied to control surface finish during cylindrical grinding of shafts of air bearings used in aircraft environmental control systems (ECS)—a core competency of Honeywell. It has been shown that n-SDE models help capture patterns in process outputs that cannot be captured using any simpler models, and that MBT reduces the surface finish variation by 62% over the current industry practice.