METHOD AND APPARATUS FOR DETECTING AN ABNORMAL LOAD ON A SERVO GUN SHAFT

摘要

A method and apparatus for detecting an abnormal load on a servo gun shaft by quickly detecting fusion between the welding tip and the work before moving a robot without adversely affecting the work. The load on the servomotor that drives the welding tip of a welding gun is measured with an observer (S8). When the estimated external disturbance load is out of the range defined by the reference value beta ( beta >0), an abnormal load signal is output (S12). The check to see whether or not the estimated external disturbance load exceeds the sum of reference value and beta (S9, S10) is not made during the interval from the moment when the welding gun starts the closing operation (FLG1=1) to the moment when the estimated external disturbance load becomes smaller than a preset value alpha . When the welding tip and the work are fused together, a negative estimated external disturbance load in excess of - beta is found, and an abnormal load signal is output (S12).