Vision system for detection of defects in the electrical connector of electric motors: test rig and algorithms

Electric motors are used in a great number of applications. These machines are mainly composed of a rotor and a stator. Regarding induction motors, the rate of defects in the stator manufacturing process is greater than in the rotor one, due to its higher complexity. To identify these faulty situations, the most common scenario is human operators performing inspections, but they are subjected to fatigue and lack of attention. This paper presents three redundant automatic vision systems and a mechanical test rig to inspect the force-induced disconnection of the stator power cables inside the electrical connector, a common defect of electric motor parts in assembly lines. These defects are typically not detected by electric tests, since in many situations the disconnection occurs after these tests, in operation, thus characterizing a field failure of the motor. A detailed description of each software routine for implementing the proposed inspection principles is presented.  The test rig components and its operation to evidence the defects are also herein described. A case study using 20 connectors of real motors was proposed for evaluating the developed system and the achieved results are discussed, showing that the system could correctly identify 100% of the defects.