A microinstruction based procedure to diagnose hardware failures in industrial robots

Abstract

Modern industrial robots contain substantial amount of electronic hardware, both analog and digital. When an internal hardware fault develops, robot operations will be adversely effected. This paper presents three different diagnostic strategies, to locate hardware faults at the lowest replaceable integrated circuit level. First method is based on enumerating all paths in the circuit and designing test sequences for each path enumerated. Second method is based on identifying sets of test sequences with individual microinstructions of the robot controller and designing microinstruction routines for diagnosis. Third method is based on running software routines, designed exclusively to move the robot arm through pre-defined diagnostic moves. The data during these dummy arm movements are collected and compared with the expected data. Discrepancies between these two data sets will yield another set of diagnostic information. Diagnostic information obtained from each method is refined using the information from the other methods to give the fault location information at the desired level. In the presence of multiple faults, these three methods are applied repeatedly, after replacing the faulty chip located during the previous application.