- 學位論文
三維雷射追蹤球桿系統之研製與串並聯工具機之誤差分析
Development of a 3D Laser Ball Bar Measurement System and Error Analysis of a Serial-Parallel Type Machine Tool
摘要
CNC工具機精度檢測的方法，在ISO 230規範中已有明確的記載，而採用的量測儀器幾乎都是屬於一維的量測尺度，例如：雷射干涉儀、階規或量表等。對於二維的動態循圓檢測，在ISO 230-4規範中有記載檢測的方法，某些特定儀器因此被發展出來，例如：雙球桿系統以及最近被發展的雷射球桿系統，雖然這些儀器具有CNC工具機二維誤差的檢測能力，但是他們能然只是對單一尺度軸向具敏感性而已。 CNC工具機的精度評估，傳統以來一值都是遵守 ISO 230的規範，不同的誤差種類評估需要不同的量測儀器配合，這些使用到的儀器或感測器包括：雷射干涉儀以及各種光學鏡組、直規、電子水平儀以及雙球桿系統等，所以，當評估 CNC 工具機整體精度時，必須更換不同的量測設備，造成工具機精度評估過程非常耗時。另外，對於多軸運動型態的工具機，因為主軸可以傾擺角度，整個工具機誤差校正的過程更形艱困。 本研究提出一套量測方式新構想，他整合了雷射球桿系統與雷射追蹤系統的優點，可以用來即時量測任何空間中運動機構的三維座標位置，它是以球座標參數量測空間中運動機構位置。系統包括了一組精密的雷射線性量測裝置，被架設在線性滑軌尾端，用來量測滑座的線性位移量，而滑軌機構被架設在具有兩個角度自由旋轉而且互相垂直的基座上，每一個旋轉軸安裝雷射旋轉角度編碼器，所以當工具機主軸端的球窩磁力座被主軸驅動移動時，便可以拖曳追蹤球桿上的標準球，球桿系統上的三個感測器便可以即時記錄標準球球心的座標位置資訊，並且將球座標參數轉換成卡式座標參數。 本系統的主要目的在於量測主軸上刀具相對於工具機工作台的位移量，不論被檢測的工具機屬於卡式座標系統抑或是並聯型多軸工具機型式。在本研究中，對三維雷射追蹤球桿系統的機構設計進行了詳細的探討，並且辨識出所有的機構組裝誤差，分析其誤差量大小與方向，最後進行量測機構運動學分析與誤差補償，因而可以進一步提升整體量測系統的精度。在實際應用的實驗驗證方面，對工具機進行不同種類誤差量測，例如：線性誤差、直線度誤差、動態循圓誤差以及體積誤差等，並與不同的商用量測儀器進行量測結果比較，差異都在2μm以內 。不管被檢測的工具機是屬於卡氏座標系統或是並聯型多軸工具機，都可以簡單省時地使用本研究所提出的三維雷射追蹤球桿系統進行精度檢測。
並列摘要
Techniques for performing accuracy testing of CNC machine tools can be found in many standards, such as the ISO 230. Most of the existing linear measurement instruments are one dimensional, such as the laser interferometer or step gauge. For the circular test of 2D motion, as specified in the ISO 230-4, some instruments have been developed, such as the, double ball bar (DBB), Contisure, and the latest laser ball bar (LBB). Although these instruments are capable of 2-axis error measurements, they are still sensitive to one dimension only. Conventional techniques for assessing machine tool accuracy conforming to ISO-230 specifications should adopt a variety of precision instruments, such as laser interferometer and optics, straightedge, electronic level, double ball bar, etc. It is a time-consuming process when changing different equipment for different accuracies. For multi-axis machines, where the spindle can swing, the error calibration is more difficult. A novel design, which integrates the merits of LBB and LTS (laser tracking system) is proposed in this research for the three dimensional measurements of moving object in real time phase. This system is based on the spherical coordinate principle containing only one precision Laser linear measurement device and two precision Laser rotary encoders in the gimbals base with a precision linear guide for slider motion. Such a system can be dragged by any 3D moving target with a magnetic head and freely moved in the space. Three sensors simultaneously record the ball positions and transform into the Cartesian coordinate in real time. It aims to measure the tool position relative to the worktable at any working point no matter the inspected machine is of 3D Cartesian type or parallel type multi-axis machines. The design of the instrument is discussed and the errors attributes are analyzed to enhance its accuracy. Practical applications will be addressed with respect to different error measurements, such as linear errors, circular errors, volumetric errors, and to different types of machine tools, such as Cartesian type and parallel type. The measuring result is compared to a commercial instrument, the maximum difference is around 2μm. All can be done simply with the developed 3D LBB system.