應用於工具機誤差檢測之多自由度雷射光學尺研製

Development of a Multi-Degrees-of-Freedom Laser Encoder for Error Verification of the Machine Tools

鄭仲翔(Chung-Hsiang Cheng)

指導教授 ： 劉建宏

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2011年)

摘要

本論文研製之多自由度雷射光學尺係利用反射式繞射光柵作為運動平台位移與誤差訊號傳導之媒介。運用光柵繞射原理與都普勒效應，搭配光學干涉技術，並結合四象限光檢測器量測光柵繞射光繞射方向三維空間變化，建立多自由度雷射光學尺。其可同時量測運動平台之橫轉度、偏搖度與俯仰度三個角位移量，以及水平真直度及線性位移量，共計運動平台的五個自由度誤差。
本論文共發展出兩種五自由度雷射光學尺。第一種使用高階繞射光所建立的光學尺，主要利用正負一階繞射光作為線性位移量測，正負二階繞射光的繞射方向變化做為其他自由度的量測。利用正負二階繞射光可提高系統的相對於量測的自由方向的靈敏度。此光學尺經Agilent 55292A雷射干涉儀校正系統驗證，橫轉度誤差為±0.8 arcsec /±50 arcsec，標準差為0.2 arcsec；偏搖度誤差為±0.8 arcsec /±20 arcsec，標準差為0.11 arcsec；俯仰度誤差為±0.8 arcsec/±80 arcsec，標準差為0.5 arcsec；水平真直度誤差為±0.5 μm /±50 μm，標準差為0.06 μm與線性位移誤差為±1.5 μm /±500 μm，標準差為13 nm。
第二種的光學尺設計僅使用正負一階繞射光發展多自由度的光學尺。主要係考量正負一階繞射光具有較強的光強度與較好的訊噪比。此外再加上考量雷射二極體工作穩定與防止零階繞射光返回共振腔的影響，因此再設計光隔離系統與建立波長變化量測模組，對光源波長變化量補償可達0.001 nm。多自由度驗證結果橫轉度誤差為±0.7 arcsec/±60 arcsec，標準差為0.025 arcsec；偏搖度誤差為±0.7 arcsec/±30 arcsec，標準差為0.05 arcsec；俯仰度誤差為±0.8 arcsec/±90 arcsec，標準差為0.18 arcsec、水平真直度誤差為±0.5 μm /±250 μm，標準差為0.05 μm與線性位移誤差為±1 μm/ ±20000 μm，標準差12 nm。故第二種設計之光學尺量測誤差比第一種光學尺較小，標準差亦減小。
本論文之研究將光學尺之應用提供一新的應用發展方向。若將其應用於工具機中將可實現空間幾何誤差自我量測、補償與診斷，並可減少使用雷射干涉儀校正所需花費的大量時間，進一步可發展出可誤差自我補償之智慧型工具機。

關鍵字

多自由度 ； 雷射光學尺 ； 繞射原理 ； 干涉技術 ； 自動視準儀原理 ； 波長補償

並列摘要

The multi-degrees-of-freedom laser encoder developed in this paper uses a reflection diffraction grating as a transformed medium to deliver the motion error signals of a linear stage. Based on the diffraction principle, the Doppler princilple, and the optical interference principle, the multi-degrees-of-freedom laser encoder simultaneously measures linear displacement, roll, yaw, pitch, and horizontal straightness errors of a linear stage.
Two kinds of laser encoders are developed in this paper. The first encoder uses the phase difference of the ±1 order diffraction rays to measure linear displacement and the directional change of ±2 order diffraction rays detected by two quadrant photodiode detectors to measure other motion errors which can improve the measuring sensitivity of the sensing direction. The encoder is vefrified by Agilent 55292A laser calibration system. The measurement errors of roll, yaw and pitch errors are verified as ±0.8 arcsec and the standard deviation are about 0.5 arcsec. The horizontal straightness error is ±1.5 μm/±50 μm and the standard deviation is 0.06 μm. The linear displacement error is ±1.5 μm/± 500 μm and standard deviation is 13 nm.
The second design uses only ±1 order diffraction rays because the diffracted rays has higher light intensity and better signal to noise ratio. In addition, considering the stabiltiy of the laser diode and preventing the zero order diffraction ray back to the cavity, an optical isolation system and a wavelength measuring system are develpoed in the second design of laser encoder. The verification results show the roll, yaw and pitch errors are less than ±0.8 arcsec and the standard deviations are less than 0.18 arcsec. The horizontal straightness error is ±0.5 μm /±250 μm and standard deviation is 0.05 μm. The linear displacement error is ±1 μm/ ±20000 μm and the standard deviaiton is 12 nm. The verification results showed the second laser encoder is superior to the first laser encoder.
The study of this paper provides a new application of the laser encoder to the multi-axes CNC machine tools. The spatial geometric error measurement, error compensation and error diagnosis can be implemented in the CNC machine tools. Using the multi-degrees-of freedom laser encoder, the time of using laser interferometer calibration is decreased. The developement of an error self-compensation intelligent machine tools is possible.

並列關鍵字

multi-degrees-of-freedom ； laser encoder ； diffraction principle ； interference principle ； autocollimation ； wave length compensation

參考文獻

[40] 沈欣懋，2005，”高對位公差之微小化雷射繞射式光學尺系統的研製”，國立台灣大學機械工程學研究所碩士論文。

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