Abstract: An automatic welding apparatus comprises a welding torch including an electrode and a fixture for fixing a workpiece, and a relative positional relation of the welding torch and the workpiece fixture is controlled such that the electrode of the welding torch is moved to trace the welding line of the workpiece, whereby automatic welding is achieved. The automatic welding apparatus further comprises a switch for selectively connecting the electrode of the welding torch to a welding power supply or a detecting power supply, and a sensor for sensing a current or a voltage between the electrode and the workpiece when the electrode is switched to the detecting power supply, whereby the relative positional relation between the welding torch and the workpiece is detected in response to the output of the sensor, and thus a welding point or a welding line is sensed.

Abstract: An increment type position control apparatus is adapted to evaluate a numerical value concerning a positional point by making subtraction between the data in a position feedback counter for counting a feedback pulse from an incremental encoder and the data in a commanded position buffer from a processor. Upon depression of an origin return command button provided on a control panel, the position feedback counter and the commanded position buffer are each loaded with a predetermined value, whereupon a pitch is given, whereby an object being controlled is controllably moved in the direction toward the origin. If and when the object being controlled exceeds the origin position, the same is stopped and the counter and the buffer are each again loaded with an appropriate numerical value, whereupon a given pitch is provided, whereby the object being controlled is moved in the direction toward the origin and comes to a point to almost exceeding the origin position.