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The demand for higher production rates in aircraft industry requests more flexible manufacturing solutions. A bottleneck in production is the machining of large components by vast portal machines. Time-consuming referencing processes result in non-satisfying cost-effectiveness of these high-invest-machines. Mobile robot-based solutions are able to operate simultaneously which increases the productivity significantly. However, due to the limited workspace of robots, machining tasks have to be divided and long trajectories are separated in single overlapping segments. Thus high-accuracy referencing strategies are required to achieve desired production tolerances. In this publication different advanced optical reference strategies will be discussed taking the inhomogeneous behavior of a mobile robotic machining system into account.

The high demand of efficient large scale machining operations by concurrently decreasing operating time and costs has led to an increasing usage of industrial robots in contrast to large scaled machining centers. The main disadvantage of industrial robots used for machining processes is their poor absolute accuracy, caused by the serial construction, resilience of gearings and sensitivity for temperature changes. Additionally high process forces that occur during machining of CFRP structures in aerospace industry lead to significant path errors due to low structural stiffness of the robot kinematic. These errors cannot be detected by means of motor encoders. That is why calibration processes and internal control laws have no effect on errors caused by elastic deformation. In this research paper an approach for increasing the absolute accuracy of an industrial milling robot with help of a Laser Tracker system during machining tasks will be presented.

The demand for higher production rates of large parts in aircraft industry requests more flexible manufacturing solutions. High-accurate mobile robots show a promising alternative in comparison with high-invest special machines. With mobile robot-based solutions processes can be executed simultaneously which increases the productivity significantly. However, the freedom of mobility results in insufficient positioning accuracy of these machines. Hence fast and accurate referencing processes are required to achieve cost-effectiveness and meet production tolerances. In this publication a Mobile Laser Tracker (MLT) system and a holistic approach for future manufacturing systems with mobile robots will be introduced and discussed.

A mobile robotic system is presented as a new approach for machining applications of large aircraft components. Huge and heavy workshop machines are commonly used for components with large dimensions. The system presented in this paper consists of a standard serial robot kinematics and a mobile platform as well as a stereo camera system for optical measurements. Investigations of the entire system show that the mechanical design of the mobile platform has no significant influence on the machining accuracy. With mobile machines referencing becomes an important issue. This paper introduces an optical method for determining the position of the mobile platform in relation to the component and shows its accuracy limits. Furthermore, a method for increasing the absolute accuracy of the robots end-effector with help of stereo camera vision is presented.