Abstract: To control the welding current in a resistance spot welding system, a current measurement sensor is used with a current feedback control to vary the firing angle of power devices in the primary side of the power supply. The closed-loop feedback control assures the desired current is applied independent of variations in the resistance of the welding equipment and primary line voltage variations. In the current feedback control, the commanded current, proportional error, integral error and line voltage offset are summed to derive the firing angle signal, and the power supply is adjusted until actual current equals the desired current.

Abstract: The positioning system of an industrial robot having a vision sensor and structured light pattern projector, such as a welding robot, is centered and vectored along a joint to be tracked. Navigation information derived from the scene is used to compute move microvectors; the next move vector is extracted and computed while the current move vector is executed. To track 90.degree. corners and small radius turns, the parallelism between two lines formed by the intersection of concentric circular arc light stripes and the joint edges is determined. When the parallelism is out of limits the previously calculated microvector is used until parallelism is re-established.

Abstract: A compact gas tungsten arc welding torch, which may have an integral puddle view optical system, utilizes an inert gas supply line and coolant supply and return lines, one carrying current for the weld process. The torch body has passages for flow of cover gas from a connection tube to the gas nozzle. The gas supply hose additionally carries the filler wire for the weld process, which passes into the gas connection tube and out of the torch body to an integral wire feed guide tube that is alternatively inside or outside of the gas nozzle.