Device and method for detecting abnormality of joint of parallel link robot

A device for detecting an abnormality of a joint part of a parallel link robot, the parallel link robot comprising:

• a base part;
• a movable part positioned away from the base part;
• two or more link parts which connect the base part and the movable part, each link part including one degree-of-freedom relative to the base part;
• and
• a plurality of motors configured to respectively drive the link parts,
• wherein each link part comprises:
• a drive link connected to the base part;
• two passive links which extend parallel to each other and connect the drive link to the movable part;
• a pair of first ball joints which connect the passive links to the drive link;
• a pair of second ball joints which connect the passive links to the movable part;
• and
• a restraining plate positioned between the pair of first ball joints so as to restrict a rotation of the two passive links about each axis of the robot, and
• wherein the device comprises:
• a torque measurement section configured to measure, while the parallel link robot is operated, an amount of change in a drive torque, based on a current value of the motor, before and after the robot represents a specified posture where a sign of a relative angular velocity between a ball and a housing of each of the first and second ball joints is changed;
• a judgment section configured to judge, in response to the amount of change in the drive torque exceeding a predetermined threshold, that a friction state of the ball joint corresponding to the motor is abnormal;
• and
• a display section configured to display a result of judgement that the friction state of the ball joint is abnormal to prompt repair or exchange of the ball joint.