Shape measurement using a laser range sensor mounted on an articulated robot

A shape measurement system to determine the geometrical structure of a robot work space is presented. A robot is equipped with a range sensor, which can yield both co-ordinates and an illuminance distribution on a projected line produced by the intersection of an object surface with a laser fan-beam light. The measuring robot scans the work space with the holding sensor in its hand. Shape and surface illuminance data for the objects situated in the space, such as workpieces, jigs and tooling machines, are obtained from the sensor output and input to a workstation, where off-line programming of robotic work can be done interactively on a CRT screen using geometrical information on the work space. The principle of measurement is described based on the calibration of positions for the robot hand and transformations between the sensor, the hand, and the robot co-ordinates. Experimental results show a measurement precision of 1 mm which is sufficient for robot off-line teaching and the realistic 3-D representation of industrial products, obtained through the flexible selection of measuring paints in the work space and the addition of illuminance data to position data.