Patent ID: 7979160

Claim:
A system for sensing and correcting unintended movement of a first joint of a robotic arm, wherein the robotic arm comprises a plurality of sections including an end effector, a plurality of joints at which the plurality of sections interconnect with each other, and a plurality of robot motor encoders, each for actuating physical movement of at least one of the sections of the robotic arm at one of the joints, wherein the first joint is coupled to a first robot motor encoder for actuating physical movement of the first joint, the system comprising: a first external encoder in intimate physical contact with an external portion of the first joint and configured to sense pivotal movement of the first joint and to transmit a first data signal corresponding to an amount of pivotal movement sensed by the first external encoder; a computing device configured for: receiving the first data signal from the first external encoder, determining a first compensation amount corresponding to the amount of pivotal movement sensed by the first external encoder, and communicating the first compensation amount to the first robot motor encoder to actuate the first joint by an amount corresponding to the first compensation amount; and an attachment apparatus configured to hold an intermediate wheel in intimate contact with the first joint on one side of the intermediate wheel and in intimate contact with the first external encoder on another side of the intermediate wheel, creating a gear reduction between the first external encoder and the first robot motor encoder, the attachment apparatus further comprising: a first arm rotatably attached to the intermediate wheel and fixedly attached to one of the plurality of sections of the robotic arm; and a second arm rotatably attached to the first arm and rotatably attached to the first external encoder, the second arm being configured to bias a wheel portion of the first encoder against the intermediate wheel.