Electric Arc Length Control of Circular Seam in Welding Robot Based on Arc Voltage Sensing

Arc length control plays an important role in improving welding quality, especially for tube-to-tubesheet welding with numerous and dense circular seams. The difficulty of arc length control lies not only in acquisition and processing of arc voltage signal, but also in designing reasonable tracking algorithm and control method. This paper proposes an arc voltage tracking system with a self-developed arc voltage module for orbiting robotic welding. A real-time arc voltage tracking algorithm based on direct current (DC) pulse square-wave is proposed, and a two-dimension and three-section fuzzy controller are also presented. The experimental results show that the maximum peak voltage (PV) decreases from 13.92 V (circular seam A) to 13.44 V (circular seam B). The surface morphology of circular seam B with arc voltage tracking is obviously superior than that of circular seam A without arc voltage tracking. The arc voltage tracking method proposed in this manuscript has an active influence on welding quality.