Condition monitoring of an industrial robot

A method for detecting a fault in a robot joint, the method comprising the steps of:

• performing a first torque measurement at the robot joint to obtain a first set of torque values and weighting each individual torque value of the first set of torque values by means of a weighting vector to thereby obtain a first set of weighted torque values, the weighting vector having a set of different weights so that the first set of weighted torque values reflects torque magnitudes in time domain;
• calculating a first distribution characteristic reflecting a distribution of the first set of weighted torque values;
• performing a second torque measurement at the robot joint to obtain a second set of torque values and weighting each individual torque value of the second set of torque values by means of the weighting vector to thereby obtain a second set of weighted torque values reflecting torque magnitudes in time domain;
• calculating a second distribution characteristic reflecting a distribution of the second set of weighted torque values;
• comparing the first and the second distribution characteristics to determine whether a fault is present or not;
• and
• performing maintenance on the robot joint when it is determined that a fault is present;
• wherein the weighting individual torque values amplifies an indicator of whether a fault is present or not.

A method for detecting a fault in a robot joint, the method comprising the steps of:

• performing a first torque measurement at the robot joint to obtain a first set of torque values;
• calculating a first distribution function reflecting a distribution of the first set of torque values using a weighting function;
• performing a second torque measurement at the robot joint to obtain a second set of torque values;
• calculating a second distribution function reflecting a distribution of the second set of torque values using the weighting function;
• calculating a difference between the first and the second distribution functions to determine whether a fault is present or not;
• and
• performing maintenance on the robot joint when it is determined that a fault is present;
• wherein the weighting function has joint speed as an input.