Each servo contains a potentiometer attached to the output shaft of the gearbox. This potentiometer is used by the internal controller to hold the position you send as a command. In order for the servo to allow the user to move freely when the robot is not in contact with an object we need to be able to counteract the internal controller and to do this we must also be able to read the output from the potentiometer. This is also our only way of measuring the current position of the user's hand.