Active compensation of the movement inaccuracies of feed drives with profiled rail guides based on high dynamic piezo actuators

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So far, hydrodynamic and magnetic linear guidance systems are preferred over linear profiled rail guides at high precision applications, because these guidance systems have a high running accuracy, a high damping capacity, a high rigidity and they are free of stick- slip effects and ware. Whereas profiled rail guides are constructed relatively simple, don’t need expensive and complex additional aggregates and therefore they can be used very cost-efficiently. The deficit of profiled rail guides is, that the nonlinear rigidity is dominated by the conditions in the rolling contact and these conditions change cyclically due to the dynamic rolling element recirculation. The sum of different displacement parts of the profiled rail guides lead to inaccuracies in feed drives. Especially the dynamic rigidity, caused by self- and separate excitation, can be up to 171 times higher than the static rigidity, also because of the low damping capacity with damping factors of d=0.001 to d=0.01. The part of cyclical movement inaccuracies without separate excitation (stroke pulsation) can be up to 1 µm. Profiled rail guides are only used as a custom-built in high precision applications (geometric optimized inlet areas that are adapted to special applications) with ball chains and additional damping guides, in order to reduce vibration stimulation and stroke pulsation. The problem of static and dynamic displacements cannot be solved, especially not for variable process parameters, completely with that. The Reason for this are velocity- and load-dependent effects in the nonlinear rolling contact. For profiled rail guides as a well-researched and versatile applicable standard component in mechanical engineering with its numerous application benefits, there is no active procedure to compensate movement inaccuracies.The proposed research project wants to provide new fundamental insights on how the movement accuracy of feed drives with profiled rail guides can be improved actively, in order to use them in high precision applications with accuracy requirements in the lower micrometer or even nanometer range and make them competitive to hydrostatic and magnetic guidance systems. Therefore the known theoretical insights about the dynamic descriptiveness of profiled rail guides, based on a mathematical equivalent mechanical vibration system, and the static load-displacement-model, based on the Hertzian displacements in the rolling contact and the elastic deformation of the guide carriage and the guide rail, are combined with new investigated insights about the real dynamic behavior of the rolling elements, the guide carriage and additional assemblies. Building on this, a real-time capable system for a model-based compensation of movement inaccuracies, based on piezo actuators, will be developed.