Abstract: A path correction system of an automatic welding machine has means for differentiating welding current values at respective left and right positions of a torch when weaving is performed, and means for sensing welding current when a value obtained from the differentiating means is zero. The difference is found between welding current values when left and right differentiated values are zero, and the position of the center of the weaving pattern along which the torch advances is corrected based on the difference value.

Abstract: A uniform velocity control method for rotating a first movable element (3) at a uniform velocity in a rectilinear-to-rotational motion converting mechanism, in which a second movable element (2c) is moved along a linear shaft (2a) and the first movable element is rotated in dependence upon rectilinear movement of the second movable element. The uniform velocity control method includes (1) a second step of monitoring a position of the second movable element along the linear shaft; (2) a second step of calculating a traveling velocity of the second movable element, which traveling velocity is for rotating the first movable element at a uniform velocity, in dependence upon the position of the second movable element along the linear shaft; and (3) a third step of moving the second movable element at the calculated traveling velocity to make the rotational velocity of the first movable element uniform.

Abstract: A tool posture control system according to the present invention rotates a tool vector v.sub.1 indicative of a present tool position to a target tool vector v.sup.1 through vector rotation, and generates data for driving robot axes from the data produced by the vector rotation. For a welding robot, for example, the inclination of a torch with respect to an arc starting surface can automatically and appropriately be established, so that an arc starting point can accurately be searched for. Therefore, the operation to search for a desired arc starting point can properly be carried out without human intervention.

Abstract: A method of returning a movable machine element having a flat dog to a zero point includes advancing the movable machine element in the direction of the flat dog, stopping the movable machine element after a changeover signal (S.sub.D) produced by the flat dog is detected, reversing the direction of the movable machine element, moving the movable machine element a first predetermined distance (L) and stopping it after the changeover signal (S.sub.D) is received again, then moving the movable machine element in the opposite direction a second predetermined distance (l) shorter than the first predetermined distance (L) and stopping the movable machine element, thereafter moving the movable machine element at a low velocity and stopping it at an initial one-revolution signal of a servomotor, which operates the movable machine element, after the changeover signal produced by the flat dog is detected.