Fault detection response in a robot arm

Abstract

A method of testing a motor of a robot arm for a fault during a start-up procedure of the robot arm. The robot arm comprises a first link connected to a second link by a joint, the joint permitting the second link to move relative to the first link. The motor is for driving the joint and is a multiple-phase motor, each phase of the motor comprising a motor winding and a motor drive circuit for applying power to the motor winding from a power supply rail and for applying drive signals to the motor winding. The method comprises, in the following order: (i) driving the motor to a known state; (ii) connecting a first phase only of the motor to the power supply rail; (iii) driving a Pulse Width Modulation (PWM) signal through the motor drive circuit of the first phase of the motor; (iv) driving the motor to a known state; (v) with the first phase of the motor disconnected from the power supply rail, driving the PWM signal through the motor drive circuit of the first phase of the motor; and (vi) repeating steps (ii) to (v) for each of the other phases of the motor; the method further comprising, during each of steps (i) to (vi), testing whether the current from the power supply rail to the motor drive circuit exceeds a current limit.

Dependencies are inferred from the claim text.