A method was introduced for control of the detachment frequency in automatic GMAW process to achievemore regularity in drop detaching. The deposition area, heat input and voltage to current ratio were reg-ulated as the performance indicators. This method was designed based on a three-layer cascade controlstrategy. A four-input four-output matrix transfer function was assigned to the system using the exper-imental data. A decoupling MIMO controller was designed for the internal loop. In the middle controlloop, a pattern was introduced to neutralize the angle effects on the drop detachment. In the exter-nal 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 byimplementation on an automatic industrial pipeline GMAW system.

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