Evaluation of perpendicularity methods for a robotic end effector from aircraft industry

The use of commercial robots in aircraft industry faces many challenges. Among them, this work approaches the problem of maintaining the robotic end-effector perpendicular to the work surface. The perpendicularity error when performing operations such as drilling and riveting affects can affect the overall aircraft drag and cause fatigue cracks. In this work, we present, compare and analyse two different solutions for the correction of the perpendicularity error of a robot. Both solutions are different from existing ones described in the literature. The first solution uses only a point distance laser sensor fixed in robot end effector. The end effector moves in its X and Y axes sequentially to determine the correct robot angle B, C. It then correct distance Z to normalize the pose and adjust the position between the effector and target. Two different point distance lasers were tested. The second solution normalizes the robot pose through a linear scan sensor and a point sensor that allows us to quickly generate the correction angles and Z distance direct without robot movements. The paper verifies if the methods are able to comply with a perpendicularity requirement of 0.5° of maximum error between the manipulator and the normal of the tested table. The results showed that only the second solution is able to achieve the required perpendicularity.