Method and device for monitoring the condition of an industrial robot

1. A method for monitoring a condition of an industrial robot comprising a plurality of links movable relative to each other, and a plurality of actuators controlling movements of the links, the method comprising:

calculating a feed forward torque for at least one of the actuators based on reference values for a position of the actuator and a mathematical model of the robot,

calculating a feedback torque for the actuators based on measured values from the actuators and said reference values for the position of the actuator,

calculating a reference value for a torque of the actuator at least based on said feedback torque,

monitoring a difference between the reference value for the torque of the actuator and the feed forward torque, and

determining whether the difference is normal or non-normal, and based thereon monitoring the condition of the robot.

2. The method according to claim 1 , further comprising:

calculating a difference between the reference value for the torque of the actuator and the calculated feed forward torque, and

monitoring the calculated difference.

3. The method according to claim 1 , further comprising:

monitoring the calculated the feedback torque and

determining whether the feedback torque is normal or non-normal.

4. The method according to claim 1 , wherein said monitored condition of the robot comprises wear of driving components of the robot.

5. The method according to claim 4 , wherein said driving components comprises any of: motors, motor gears, bearings, axes, and brakes.

6. The method according to claim 1 , further comprising:

generating an alarm when said difference exceeds a maximum value.

7. The method according to claim 1 , further comprising:

calculating a deviation parameter based on the difference between the reference value for the torque of the actuator and the feed forward torque, the deviation parameter being a measure of the condition of the performance of the robot.

8. A device for monitoring a condition of an industrial robot, said robot comprising a plurality of links movable relative to each other, actuators controlling movements of the links, a path planner adapted to calculate reference values for a position of the actuators, and at least one drive unit calculating reference values for the torque of the actuators, the drive unit having a feed forward loop calculating a feed forward torque for the actuator based on said reference values for the position of the actuator and a mathematical model of the robot, and a feedback loop calculating a feedback torque for the actuator based on measured values from the actuator and said reference values for the position of the actuator, wherein the device is configured to monitor the difference between the reference value for the torque of the actuator and the feed forward torque, to determine whether said difference is normal or non-normal, and to monitor the condition of the robot based thereon.

9. The device according to claim 8 , wherein the device is configured to calculate the difference between the reference value for the torque of the actuator and the feed forward torque, and to monitor the calculated difference.

10. The device according to claim 8 , wherein the device is configured to monitor the calculated the feedback torque and to determine whether the feedback torque is normal or non-normal.

11. The device according to claim 8 , wherein said device is adapted to generate an alarm if said difference is non-normal.

12. The device according to claim 8 , wherein said device is adapted to calculate a deviation parameter based on the difference between the reference value for the torque of the actuator and the feed forward torque, which parameter is a measure of the condition of the performance of the robot.