Improvement of Reverse Motion of an NC Moving Table Based on Vector Control Method by Friction Force Compensation
Akio Hayashi, Tatsuya Mukai, Yusuke Inomata, and Yoshitaka Morimoto
Kanazawa Institute of Technology
7-1 Ohgigaoka, Nonoichi, Ishikawa 924-8501, Japan
Lost motion is a phenomenon that often occurs during the motion of a moving table, which is used for machine tools to ensure their precise positioning. Lost motion occurs when the direction of the table’s motion reverses as a result of nonlinear friction characteristics between the feed drive mechanisms such as the ball screw and linear guide. Lost motion directly influences the machining accuracy of a machine tool, because the accuracy of machining depends on the relative motion between the tool and the workpiece. A number of studies have dealt with suppressing the occurrence of lost motion using model-based control. However, nonlinear friction has not been addressed to the same extent, as it is difficult to determine the motion characteristics of and therefore develop a model for the nonlinear friction. Thus, to address these problems, we propose a compensation method for revers motion based on vector control, which is used to control the torque and velocity of the alternating current (AC) servomotor in the moving table. In this study, the current applied to the AC servomotor for a vector with force components in the rotational direction (torque component) and in the direction perpendicular to the axis of rotation (field component) was measured to clarify and establish the relationship between the motion and the control current. The compensation current was then derived as a functional value based on the results of the measured torque at the occurrence of lost motion. Further, tests were carried out using the proposed method, which directly applies the drive current of the AC servomotor by using a field-programmable gate array controller to improve the reverse motion of the table. The results reveal that the motion characteristics of a numerical control (NC) table can be determined by measuring the drive current of the AC servomotor. In addition, it is verified that the proposed method can compensate for the torque command smoothly at the time of velocity reversal, resulting in suppression of the lost motion and reduction of reverse motion of the moving table.
-  Z. Jamaludin, H. Van Brussel, and J. Swevers, “Friction Compensation of an XY Feed Table Using Friction-Model-Based Feedforward and an Inverse-Model-Based Disturbance Observer,” IEEE Trans. on Industrial Electronics, Vol.56, No.10, pp. 3848-3853, 2009.
-  L. Mostefai, M. Denaï, and Y. Hori, “Robot Joint Friction Compensation Based on a Local Modeling Technique,” 2008 10th IEEE Int. Workshop on Advanced Motion Control, Trento, Italy, pp. 229-233, 2008.
-  M.-S. Kim and S.-C. Chung, “Friction identification of ball-screw driven servomechanisms through the limit cycle analysis,” Mechatronics, Vol.16, pp. 131-140, 2006.
-  K. Menon and K. Krishnamurthy, “Control of low velocity friction and gear backlash in a machine tool feed drive system,” Mechatronics, Vol.9, pp. 33-52, 1999.
-  Y. Suzuki, A. Matsubara, Y. Kakino, and K. Tsutsui, “A Stick Motion Compensation System with a Dynamic Model,” JSME Int. J. Series C, Mechanical Systems, Machine Elements and Manufacturing, Vol.47, No.1, pp. 168-174, 2006.
-  K. Nagaoka, “Control Method of Motion Error Compensation for NC Machine Tools,” Int. J. Automation Technol., Vol.3, No.3, pp. 292-297, 2009.
-  N. Uchiyama and K. Mori, “Adaptive Control for Feed Drives Considering Coupling Effects Among Multiple Axes,” Int. J. Automation Technol., Vol.4, No.1, pp. 45-52, 2010.
-  R. Sato, “Generation Mechanism of Quadrant Glitches and Compensation for it in Feed Drive Systems of NC Machine Tools,” Int. J. Automation Technol., Vol.6, No.2, pp. 154-162, 2012.
-  H. Sugie, T. Iwasaki, H. Nakagawa, and S. Kohda, “Adaptive Lost Motion Compensation Using Disturbance Observer,” J. of Environment and Engineering, Vol.5, No.2, pp. 264-274, 2012.
-  M. Ruderman, “Tracking Control of Motor Drives Using Feedforward Friction Observer,” IEEE Trans. on Industrial Electronics, Vol.61, No.7, pp. 3727-3735, 2014.
-  A. H. Jafari, R. Dhaouadi, and A. Jhemi, “Nonlinear friction estimation in elastic drive systems using a dynamic neural network-based observer,” J. Adv. Comput. Intell. Intell. Inform., Vol.17, No.4, pp. 637-646, 2013.
-  N. A. Rafana, Z. Jamaludina, T. H. Chiewa, L. Abdullaha, and M. N. Maslana, “Contour error analysis of precise positioning for ball screw driven stage using friction model feedforward,” Procedia CIRP, Vol.26, pp. 712-717, 2015.
-  R. Sato and K. Nagaoka, “Motion Trajectory Measurement of NC Machine Tools Using Accelerometers,” Int. J. Automation Technol., Vol.5, No.3, pp. 387-394, 2011.
-  M. Shiraishi and H. Sumiya, “Sensing and Control of Friction in Positioning,” Int. J. Automation Technol., Vol.7, No.5, pp. 476-481, 2013.
-  R. Sato, “Feed drive simulator,” Int. J. Automation Technol., Vol.5, No.6, pp. 875-882, 2011.
-  A. Matsubara, A. Sayama, T. Sakai, and M. Reuss, “Analysis of measured friction of rolling balls in raceway grooves,” Int. J. Automation Technol., Vol.8, No.6, pp. 811-819, 2014.
-  R. Dhaouadi, “Torque Control in Harmonic Drives with Nonlinear Dynamic Friction Compensation,” J. Robot. Mechatron., Vol.16, No.4, pp. 388-396, 2004.
-  G. Holroyd, C. Pislaru, and D. G. Ford, “Modelling The Dynamic Behaviour of a Ballscrew System Taking into Account the Changing Position of the Ball-Screw Nut,” WIT Trans. on Engineering Sciences, Vol.44, No.6, pp. 337-347, 2003.
-  M. Hikizu, H. Seki, and Y. Kamiya, “Effects and Application of Current Feedback in Servo System with Current Limiter,” Int. J. Automation Technol., Vol.11, No.1, pp. 104-111, 2017.
-  S. Patal, I. Şenol, A. F. Bakan, and K. N. Bekiroğlu, “Online speed control of a brushless AC servomotor based on artificial neural networks,” Turk. J. Elec. Eng. & Comp. Sci., Vol.19, No.3, pp. 373-383, 2010.