Online Emissivity Estimation of the Hollow Cathode and the Treated Part in the HC Plasma Nitriding Process

摘要

Modeling the thermal process in the Hollow Cathode Anodic Plasma Nitriding (HCAPN) is essential for control. The heat transfer mechanism consists mainly of conduction by gas and radiation. The essential parameter of the heat radiation is the emissivity of the metal surface. It was shown that the emissivity of the commonly used metals (carbon steel, aluminum) is highly temperature dependent and in the case of surface heat-treatment, the modification of the surface structure modify the emissivity also. The goal of the paper is to present an online emissivity estimation method using Extended Kalman Filter, thus a simultaneous state and parameter estimator. For this, an augmented state-space model will be used. The HCAPN setup consist of a hollow cathode and the treated part, in most cases having different materials, thus the algorithm was developed to estimate the emissivity of both materials.