GOALI: Nanoscale Hysteresis Modeling and Control in Precision Equipment

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Heightened performance requirements have driven improvements in precision motion equipment that now boast accuracies in the nanometer range. However, such accuracies require expensive noncontacting bearings, while roller bearings provide the best performance/cost benefit. Despite past research in this area, adequate friction mitigation remains the limiting factor for precision mechanical motion stages. This research will investigate techniques for improving precision motion control using knowledge of friction. Hysteresis models will be used to identify, evaluate and predict friction experimentally, and to design improved motion control systems that mitigate friction's effects. This research will also investigate the ability to reject disturbances caused by roller bearings on precision motion stages by sensing the ball bearing position and relate that to fluctuations in velocity. Finally, control approaches for minimizing the effects of bearing disturbances and bearing friction on the ultra-slow motion of stages will be studied. If successful, this research will increase the accuracy and speed of response of precision motion systems by pushing the accuracy of roller bearing stages to the nanoscale. While noncontact bearings provide the lowest friction and highest precision, manufacturing them to ever tighter tolerances drives up cost. Improved manufacturing techniques for roller bearings have improved their performance, and now stages using roller bearings can realize nanometer performance. Still, the hysteretic characteristics of roller bearings limits their performance. This research will enable precision stages to be operated at lower cost with higher precision and accuracy. This provides considerable impact for end users of precision motion stages, who will be able to achieve improved manufacturing and metrology processes as a result of improved motion control systems. Finally, this research will provide an alignment of university research with industrial needs and the opportunity for students to conduct research in an industrial setting, working on research problems with immediate technological application.