An Optical System to Measure the End Effector Position for On-line Control Purposes

This article describes an optical system to measure the coordinates of a manipulator's end effector, which can move in a horizontal plane of approximately 1 × 1 m². Two rotatable laser beams track a retroreflector pair, mounted on the end effector. The coordinates are calcu lated from the measured beam rotations. The resolution and reproducibility of the coordinate measurement is 0.05 mm. The maximum tracking speed mounts up to 5 m/s. Using components similar to those applied in CD players, the total cost of all mechanical, optical, and analog elec tronic components can be kept as low as $3000. On an IBM AT-compatible PC, it takes 1 ms to calculate the x and y coordinates from the measured signals.