Process control for plasma electrolytic removal of TiN coatings. Part 1: Duration control

The paper addresses problems of creating a feedback control system for plasma electrolytic removal of titanium nitride coating from stainless steel. A study of the subject has been implemented in phenomenological, informative and mathematical models of the process. The models form a background for creating a control system for the process. Within the phenomenological model, the mechanism of the process from the point of view of control theory is presented. Within the informative model, a feedback parameter for the surface state estimation has been established. This parameter is power spectral density of the current in the bandwidth 500-1500 Hz. By the temporal fall of the power spectral density the beginning and the end of the coating removal could be identified. Based on the established regularity, an algorithm for the process duration control is proposed. Application of the control algorithm could increase the efficiency of the plasma electrolytic removal of titanium nitride coating by over 25%.