Differential joint device for robot, and method for diagnosing state of differential joint device for robot

A method for diagnosing a state of a differential joint device for a robot, the method comprising:

• identifying an expected output value of a pitch output encoder and an expected output value of a roll output encoder;
• detecting an actual output value of the pitch output encoder and an actual output value of the roll output encoder;
• identifying a difference value between the expected output value and the actual output value of the pitch output encoder and a difference value between the expected output value and the actual output value of the roll output encoder;
• comparing the difference value of the pitch output encoder with a pitch reference error and comparing the difference value of the roll output encoder with a roll reference error;
• outputting an alarm based on the difference value of the pitch output encoder being equal to or greater than the pitch reference error or the difference value of the roll output encoder being equal to or greater than the roll reference error;
• and
• compensating for the difference value of the pitch output encoder based on the difference value of the pitch output encoder being smaller than the pitch reference error and compensating for the difference value of the roll output encoder based on the difference value of the roll output encoder being smaller than the roll reference error.