Multi-Loop Contouring Control of CNC Machines based on Task Space Coordinate Frame

• Main Authors: Huang, Yen-Yeuh, 黃彥岳
• Other Authors: Hsiao, Te-Sheng
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/47un24

碩士 === 國立交通大學 === 電控工程研究所 === 107 === In the traditional CNC control system, no matter how many axes the CNC machine has, the control objective is to increase the quality of the final machined products through the small tracking error of each axis. The premise that the small tracking error guarantees good machining quality relies on independency of each axes; however, the real machine tool is not the case. This motivates the research in this thesis. A new multi-loop control architecture based on the task coordinate frame rule is proposed that can be applied to systems with any order and arbitrary delay, so that better contouring control accuracy can be achieved. Besides, we use a saturation weighting parameter to improve the robustness of this multi-loop contouring controller. Moreover, a velocity estimator is proposed to eliminate feedback quantization noise in the inner velocity loop, which can prevent the controller from generating excessive compensation commands due to quantization interference. The multi-loop contour control method of this study is realized on the XZ-table of Tongtai CNC lathe TC-2000, and the experimental results are compared with those of the common single-axis tracking control method. In the circular trajectory experiment, the multi-loop task coordinate frame controller can improve the contouring control performance by 57% based on the measurments of motor encoders, and improve the roundness by 11.8% based on the measurements of the double ball-bar. Additionally, in the experiment of the low speed and large curvature trajectory, the multi-loop task coordinate frame controller can improve the maxumium contour error by 66%, while in the experiment of the high speed and large curvature trajectory, the improvement is 60%.