Motion Trajectory Measurement of NC Machine Tools Using Accelerometers
Ryuta Sato* and Kotaro Nagaoka**
*Organization of Advanced Science and Technology, Kobe University, 1-1 Rokko-dai, Nada, Kobe 657-8501, Japan
**Advanced Technology R&D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661, Japan
NC controllers use different types of compensation systems to improve motion accuracy of feed drive systems against pitch error, friction, backlash, and elastic deformation. Compensators for static error, such as pitch and squareness errors, are tuned semiautomatically. However, for dynamic error such as quadrant glitches and vibration, parameter tuning takes too much time. In this study, motion trajectory measurement for parameter tuning using accelerometers has been proposed. In the methods, displacements of each axis can be obtained from measured accelerations along each axis. Although the obtained displacements include some errors, such as setting error, sensitivity error, and integral error in numerical integration, the errors can be compensated for based on the feedback positions measured simultaneously. To confirm the feasibility of the proposed methods, measurement tests using a grid encoder are carried out. Results of the measurements confirm that the circular trajectories and vibrations can be measured by the proposed method. Automatic parameter tuning method for the backlash compensator is also proposed.
-  ISO 230-1, “Test Code for Machine Tools – Part 1: Geometric Accuracy of Machines Operating under No-load or Finishing Conditions,” 1996.
-  ISO 230-4, “Test Code for Machine Tools – Part 4: Circular Tests for Numerically Controlled Machine Tools,” 2005.
-  Website: http://www.renishaw.com/.
-  A. Teimel, “Technology and Applications of Grating Interferometers in High-precision Measurement,” Precision Engineering, 13-3, pp. 147-154, 1992.
-  Y. Suzuki, A. Matsubara, Y. Kakino, S. Ibaraki, and K. Lee, “A Study on the Tuning of CNC Parameters to Improve Contour Precision for NC Machine Tools,” J. of the Japan Society for Precision Engineering, 69-8, pp. 1119-1123, 2003 (in Japanese).
-  Website: http://www.heidenhain.com/.
-  B. Bringmann and P. Maglie, “A Method for Direct Evaluation of the Dynamic 3D Path Accuracy of NC Machine Tools,” CIRP Annals – Manufacturing Technology, 58-1, pp. 343-346, 2009.
-  S. Weikert and W. Knapp, “A New Device for Accuracy Measurements on Five Axis Machine Tools,” Annals of the CIRP, 53-1, pp. 429-432, 2004.
-  M. Cramer, GPS/INS Integration, Proc. of Photogrammetric Week 1997, pp. 1-10, 1997.
-  W. D. Iwan, M. A. Moser, and C. Y. Peng, “Some Observations on Strong-Motion Earthquake Measurement Using a Digital Accelerograph,” Bulletin of the Seismological Society of America, 75-5, pp. 1225-1246, 1985.
-  R. Sato and M. Tsutsumi, “Dynamic Behavior of Feed Drive Systems around Quadrant Changes in Circular Motion,” Proceedings of the 2nd CIRP Int. Conf. on High Performance Cutting (CD-ROM), 2006.
-  Website: http://www.rion.co.jp/english/.
-  H. Sugie, T. Iwasaki, H. Nakagawa, and S. Kohda, “Modeling and Compensation for the Exponential Type Lost Motion to Improve the Contouring Accuracy of NC Machine Tools,” Transaction of the Institute of Systems Control and Information Engineers, 14-3, pp. 117-123, 2001 (in Japanese).
-  M700V Series Specifications Manual, Mitsubishi Electric Corporation, 2009.