三軸數控工具機阿貝誤差補償器之研製

Abstract

數控工具機的位置回授控制均是採用位移感測器(光學尺或編碼器)的單感測系統，但是其位移感測器所裝置處的量測軸線永遠無法和切削刀具在加工空間的運動軸線同軸。眾所周知，各軸移動時具有基本的六自由度幾何誤差(三線性三角度)，其中偏角誤差更會因阿貝原理而放大，因此阿貝誤差是工具機定位誤差來源中主要的成因。 本研究利用微型自動視準儀偵測運動平台的俯仰度、偏搖度。另外利用兩支準直雷射搭配兩個四象限感測器，製作可量測滾動度誤差之感測器，上述可整合成一套同時量測三角度(pitch、yaw、roll)量測系統。 本研究的阿貝誤差補償系統將結合現有NC控制器的單感測系統以及自製的多角度感測器組成多感測回饋補償系統，即時量測運動平台之偏角誤差與阿貝偏位量，從而可動態補償工具機的阿貝誤差。在本研究中以立式三軸工具機為對象，依此結構配置、位置回授方式(光學尺)、阿貝誤差，推導體積誤差公式，針對PC-based控制器發展阿貝誤差補償器，透過原點漂移的方式補償阿貝誤差。本系統可建立於PC-based控制器內，使得數控工具機具有內藏式阿貝誤差補償系統的功能。 實驗結果可知，以光學尺作位置回授，其定位誤差主要是阿貝誤差造成，經過阿貝誤差補償器的補償後，其定位誤差可有效提升80%以上，工具機的精度可大幅改善。

The position feedback control of current NC machine tool controllers all adopt displacement sensor (optical scale or encoder) as a single sensor system. This displacement sensor is, however, never in line with the motion axis of the cutter. It is known that each axis motion has inherent six degrees of geometrical errors, namely three linear and three angular errors, among which the angular errors being enlarged to cause the positioning error of the axis motion due to the well known Abbé principle. In the measurement system, the micro autocollimator is developed for the detection of pitch and yaw angular errors. Moreover, a sensor that can measure the roll angular error is fabricated by use of two collimated laser and two quadrant detectors. Finally, the micro autocollimator and the roll sensor are integrated into three angle measurement system, which can measure pitch、yaw and roll angular errors. This research aims at the development of three angular sensors and in corporation with the current NC control to develop an Abbé error compensation system, being an innovative multi-sensor feed-back compensation system. This system allows the machine tool to detect the angular error of each axis in real-time and the corresponding Abbé offsets so as to dynamically compensate for the Abbé error. Based on the 3-axis vertical machining center and position feedback type (light scale), the volumetric error for Abbé error is derived. In addition, the Abbé compensator for PC-based controller is also developed. This developed Abbé error compensation system is to be built in the NC controller to enhance the machine tool accuracy. Experiments show that the positioning error of an investigated NC machine tool is mainly affected by Abbé error. With the proposed Abbé error compensation system, the positioning accuracy can be significantly improved to more than 80%