Low-Cost and Energy-Efficient Reduction of Vibrations in Ultra-precision Manufacturing Machines 

Ultra-precision manufacturing (UPM) machines (e.g. micro machine tools, wafer scanners and micro CMMs) are designed to fabricate and measure complex parts having micrometer-level features and nanometer-level tolerances/surface finishes. To achieve the stringent precision requirements of UPM machines, they must be isolated from ground vibrations and residual vibrations stemming from the motion of their axes. In this project, we are carrying out a model-based study of the dynamics of passively isolated UPM machines to determine ways of reducing vibrations via design-level optimization – without resorting to active vibration control – thus reducing costs and energy consumption. Specifically, this research investigates the effects of mode-coupling on improving the performance of passively isolated UPM machines.

Highlights 

• Our analyses have shown that our proposed method (i.e, mode coupling) is almost always better than the widely recommended practice of modal decoupling with regard to reducing transmissibility and residual vibration of UPM machines.
• We have come up with analysis-based guidelines for locating passive vibration isolators (for single-variable planar systems) such that the benefits of mode coupling are realized. Simulations and experiments have demonstrated up to 50% reduction in both transmissibility and residual vibration using mode coupling.
• A control framework has been developed for systematically optimizing the location of passive isolators for a generalized UPM machine consisting of any number of isolators configured in 3D. Our framework also assures that the optimized system is stable. 

Example of drastic reduction of residual vibration of UPM machine due to mode coupling

Project Team and Collaborators

• Jihyun Lee (Ph.D. candidate, U-M)
• Amir H. Ghasemi (Postdoctoral researcher, U-M)

Related Publications/Patents

• Lee, J., Okwudire, C.E., 2015, “Reduction of Vibrations of Passively-Isolated Ultra-Precision Manufacturing Machines using Mode Coupling,” Precision Engineering, In press.
• Okwudire, C.E., Lee, J., 2013, “Minimization of the Residual Vibrations of Ultra-Precision Manufacturing Machines via Optimal Placement of Vibration Isolators,” Precision Engineering, Vol. 37, No.2 pp. 425-432.
• Ghasemi, A.H., Lee, J.,  Okwudire, C.E., 2015, “A Control Theoretic Framework for Optimally Locating Passive Vibration Isolators to Minimize Residual Vibration,” Accepted for presentation at the ASME 2015 Dynamic Systems and Control Conference (DSCC2015), October 28-30, 2015, Columbus, OH
• Lee, J., Okwudire, C.E., 2014, “Effects of Non-Proportional Damping on the Residual Vibrations of Mode-Coupled Ultra-Precision Manufacturing Machines,” ASME 2014 Dynamic Systems and Control Conference (DSCC2014), October 22-24, 2014, San Antonio, TX.
• Lee, J., Okwudire, C.E., 2013, “Optimal Damping for the Reduction of Residual Vibrations in Ultra-Precision Manufacturing Machines,” ASPE 2013 Annual Meeting, October 20-25, 2013, St. Paul, MN.
• Okwudire, C.E., Lee, J., 2013, “Optimal Motor Location for the Reduction of Residual Vibrations in Mode-Coupled Ultra-Precision Manufacturing Machines,” ASME International Manufacturing Science and Engineering Conference (MSEC), June 10-14, 2013, Madison, WI.
• Okwudire, C.E., Kim, C.-J., Kim, J., 2012, “Reduction of the Vibrations of Ultra-precision Manufacturing Machines via Mode Coupling,” ASPE 2012 Annual Meeting, October 21-26, 2012, San Diego, CA.
• Okwudire, C., 2012, “A Study on the Effects of Isolator, Motor and Work Surface Heights on the Vibrations of Ultra-Precision Machine Tools,” 7th International Conference on Micro Manufacturing (ICOMM), March 12-14, 2012, Evanston, IL. 

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