本論文針對進給系統中的雙螺帽式滾珠螺桿(Double-nut Ball Screw)提出一故障診斷(Fault Diagnosis)架構，過去用於滾珠螺桿故障診斷的方式多以加速規(Accelerometer)量測螺帽振動訊號或球通頻率為主，容易受到加工廠內之雜訊或電磁干擾而降低準確度，本研究則參考使用力量感測器(Force Sensor)的方式，利用財團法人工業技術研究院南創園區所研發之預壓感測器(Preload Sensor)搭配訊號處理模組(Signal Processing Module)結合邏輯判斷法則，判斷雙螺帽式滾珠螺桿是否發生故障。
本論文之研究目標在於判斷雙螺帽式滾珠螺桿故障發生時，其預壓訊號之變化以及對進給平台造成之影響。 為了達到上述目標，本論文首先建立進給平台之動態模型，探討進給平台各組件剛性值與預壓之間的關係式，以確定預壓變化會對進給平台造成影響。 接著於全球傳動廠區內的恆溫量測室進行實驗，降低因溫度所造成的熱膨脹對滾珠螺桿導程之影響以使預壓感測器之實驗條件一致並測試加速規於廠區內量測螺帽振動所受到之雜訊干擾，經實驗顯示，原先預期量測到的球通頻率範圍被雜訊覆蓋，無法用於判斷滾珠螺桿是否發生異常。 接著透過更換較小尺寸滾珠的方式等效螺帽磨損之情況以及利用雷射加工與手工具的方式，在迴流道上產生裂痕與變形以等效迴流道故障。
本論文使用LabVIEW軟體介面記錄預壓感測器之預壓訊號，經實驗結果得知，本研究所使用型號之雙螺帽式滾珠螺桿，其預壓閥值約為1981 N，較原先預壓值(3251 N)下降39%。 在迴流道方面，經實驗結果可知，迴流道發生故障會對滾珠螺桿在高預壓段(行程> 300 mm)的預壓造成不等的預壓上升或下降的現象，在迴流道變形的實驗中，預壓訊號在頻域上，其特徵頻率相較正常迴流道的特徵頻率(相等於伺服馬達之轉速頻率)而言，由原先的2 Hz往低頻偏移至1.8~1.9 Hz，且特徵頻率的訊號強度下降約25%~70%。
藉由預壓失效實驗所建立之預壓閥值，於LabVIEW建立一診斷介面，並用於其他同型號之雙螺帽式滾珠螺桿測試後可知，不同的進給平台，其預壓整體變化趨勢符合診斷介面原先記錄之預壓變化，驗證了本論文所提出之預壓診斷架構在實務上之成效。

A novel diagnosis strategy for double-nut ball screw system is proposed. Most traditional diagnosis approaches are based on using accelerometers to measure ball pass frequency from ball screw-nut. Severe signal contamination might occur because of noises from servo motor or other machineries in factories. Therefore, traditional approaches usually suffer from low accuracy. The methodology employed by this thesis is to use a preload sensor developed by Industry Technology Research Institute (ITRI) for double-nut ball screw failure diagnosis. To clarify how variation of preload affects the drive system, this thesis at first builds up a dynamic model and discusses the relationship between preload and stiffness of each component in the test rig. Secondly, a test environment with constant temperature is set up to reduce the impact of heat expansion. Thirdly, different sizes of smaller steel balls are used to imitate the preload loss situation, and the crack of recirculating mechanism is made by laser machinery. The results of preload sensor show that: (i) the threshold of preload is 1981 N; (ii) additional variation of preload can be measured as the failure occurs in recirculating mechanism, compared with normal recirculating mechanism, characteristic frequency moves from 2 Hz to 1.8 Hz, and the signal strength (by volts) of characteristic frequency is dropped by 25%~70%; (iii) more experimental test is undertaken on another test rig without lubrication, and the results shows that the trend of preload variation is as same as the first test rig. From the intensive experimental tests, the diagnosis strategy in this thesis can be potentially applied to the real-world machine tools.

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