Composites offer outstanding mechanical properties in combination with a low density. To profit from the full potential of these materials there are still some challenges to meet. Efficient, reproducible, and material appropriate repair is one of them. It requires accurate machining on damaged structures to generate an optimal surface for the following bonded repair. In case of large scale structures, machining has to be done on-work-piece because those structures are not removable. This application requires a flexible, low-weight and cost-efficient machine, but also a system that considers the elasticities of on-work-piece machining setups. Small industrial robots offer high availability and flexibility, low investment costs, and a low weight in combination with a suitable workspace. The general disadvantage of these machines is a low stiffness in addition to the existing elasticities. However, in this application only moderate process forces occur. Furthermore, high system elasticity is expected any way, due to the detachable fixation and the workpiece. Accordingly, in this paper an online, low frequency method for the compensation of tool deviations is proposed to enhance the performance of small robots as on-workpiece milling machines. For a high industrial acceptance, a simple robot model for compensation is chosen, thus the measurement effort is minimal and the method can be integrated into a state of the art robot controller without external hardware. Additionally, a concept for an extended method for deviation compensation is presented which also considers the changing elasticity of fixation and workpiece.
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