Design and Realization of Synchronized Motion Controllers for CNC Rigid Tapping Procedures

• Main Authors: Yeh, Chao-Fu, 葉釗甫
• Other Authors: Hsu, Pau-Lo
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/17569346536008516587

碩士 === 國立交通大學 === 電控工程研究所 === 99 === Closed-loop control in both position and velocity loops for induction motors (IM) applying the indirect field oriented control scheme is implemented in this study. For its rotor time constant which is an important parameter but cannot be directly measured, a practical auto-tuning strategy to estimate its value is proposed in this Thesis. Furthermore, limitation of the motor speed due to the back electromagnetic force is overcome by applying the field weakening control to increase its maximum speed from 900 rpm to 4000 rpm as 110 V was provided. In general CNC rigid tapping machines, performance of the spindle axis implemented with an induction motor and the Z axis implemented with a servo motor are not matching well in dynamic responses; thus, significant synchronized motion error exists. Therefore, the tapping tool is broken easily and its machining quality is seriously degraded due to the significant error. In this study, the cross-coupled control (CCC) was applied to coordinate these two axes in tapping machining procedures. When the tapping tool reaches the bottom of the hole, maximum static friction will then deteriorate control performance. A nonlinear friction compensator (NFC) is then proposed to generate a suitable compensated value which is determined according to the nonlinear friction curve. Moreover, as the machine vibration and other undesirable external disturbance and modeling error are significant, a disturbance observer (DOB) is then applied to estimate and compensate for the lumped disturbance. Thus, the taping precision is greatly improved by applying the proposed advanced motion control. Results indicate that the synchronized motion error is thus greatly reduced from 132 um to 4.4 um by applying the proposed motion controller. Finally, the newly proposed positional type CCC (P_type CCC) is developed in this Thesis. This newly developed CCC control structure is easier to be implemented on industrial motor drives with more tolerance in network delays. Consequently, the proposed P_type CCC is more applicable in high-speed-high-precision CNC rigid tapping machines under real network implementation.