Frequency control of the drop detachment in the automatic GMAW process

Abstract

A method was introduced for control of the detachment frequency in automatic GMAW process to achieve more regularity in drop detaching. The deposition area, heat input and voltage to current ratio were regulated as the performance indicators. This method was designed based on a three-layer cascade control strategy. A four-input four-output matrix transfer function was assigned to the system using the experimental data. A decoupling MIMO controller was designed for the internal loop. In the middle control loop, a pattern was introduced to neutralize the angle effects on the drop detachment. In the external control loop, the detachment frequency was estimated by a Short Time Fourier Transform (STFT) block. A controller was designed to track the desired frequency reference. The results were evaluated by implementation on an automatic industrial pipeline GMAW system.