Generation of a Robot Program and Determination of an Optimal Workpiece Placement Considering the Manipulability of Industrial Robots

Abstract

Various operations in the production sites of manufacturing industries are being automated using industrial robots instead of operators. In recent years, an offline teaching method for robot motion has been implemented, where programs are generated in a work environment that is reproduced virtually inside a computer. However, the robot program developed using the offline teaching method can pass through singularities or suddenly change the robot’s posture, making the robot incapable of performing safe operations. To achieve optimal operation, the operator must determine the workpiece placement and create a robot program through trial and error. In this study, we proposed a method that uses manipulability to generate a program that commands the robot to move without passing singularities or changing the robot’s posture. Manipulability is quantitatively evaluated as an indicator of a robot’s ability to move its end effector in arbitrary directions. We proposed another method to determine the optimal workpiece placement for robot operations that can maximize the sum of manipulability during the operation. We implemented the aforementioned methods in an offline teaching system. We applied the developed system to a welding operation and verified its effectiveness by conducting motion simulations. The developed system was able to generate a practical robot program that maintained high manipulability and did not cause sudden changes in the posture or pass singularities. The developed system was able to simultaneously determine the optimal workpiece placement for the task, thereby confirming the usefulness of the proposed method.