Accuracy analysis and optimization of industrial robots for aerospace production

Growing demand for aircrafts, the competitive global market, and customer-focused individualization call for versatile and cost-effective aircraft production systems with high output. Concerning these needs automation with industrial robots is a promising solution as robots have already shown their performance in the automotive industry. Nevertheless, aircraft production automation is a challenge as robots with high absolute accuracy are needed. The main reasons for this requirement are high tolerances of the components resulting from their huge dimensions and part-manufacturing processes making automotive typical teach-in strategies impossible. Especially processes like machining that even need absolute path accuracy of the robot are challenging. Besides a detailed state-of-the-art analysis of robot accuracy and an optimized strategy for application-oriented robot calibration this paper also presents a new approach for advanced accuracy assessment. By simultaneously recording robot controller axes values and actual Tool Center Point poses with a laser tracker, the error chain can be acquired, separated, and thereby indications for different error sources and ways to eliminate them are discovered. To make evaluation and interpretation easier for the operator, the obtained pose-error-results are depicted by 3D-plotsand error-histograms. In addition the impact on part accuracy, which typically cannot be judged from pose-errors, is visualized by material removal simulations considering the real (laser tracker measurements) and virtual (controller data) toolpaths acquired. To take the nonlinear behaviour of industrial robots into account, application-representative trajectories are used. The paper makes clear that especially in the aerospace production a use-case dependent optimization is reasonable and effective.