Real-time static deflection compensation of an LCD glass-handling robot

Progress in the LCD industries has been very rapid and the demand for large LCD panel has also been increasing. Therefore, LCD device makers have invested in manufacturing line which uses larger mother glasses than before. As the size of mother glass is larger, LCD glass-handling robots also get larger. The large robot causes unavoidable static deflection of the arm inherently. This static deflection should be compensated to stack maximum mother glasses on the given footprint. This paper presents a novel static deflection compensation algorithm. This algorithm does not need any measurement instrument and additional vertical axis on the robot. It can be realized by robot controller software only. The forward and inverse kinematics considering compensation always guarantee a unique solution, so that the proposed algorithm can be applied to an arbitrary robot position. The proposed algorithm reduces static deflection by 40% in stationary robot state experiment. Furthermore, when the robot arm moves with the maximum speed, static deflection compensation improves vertical path accuracy up to 60%. This algorithm has been commercialized and applied to the 7th generation LCD glass-handling robot.