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Ball Screw Health Monitoring Using Ball Pass Frequency Spectra



In a precise ball screw feed drive system, the backlash caused either by the manufacturing clearance between ball and ball track or by the deflection backlash induced by the external force can be eliminated by a preload. In practice, the ball screw is deemed as expired and required to be replaced when the preload loss occurs. A technique based on the method of Angular Velocity Vold-Kalman Filtering Order Tracking (AV VKF-OT) for monitoring the change of the ball pass frequency (BPF) in order to determine the onset of preload loss of a ball screw in a feed drive system is proposed. The advantage is that the vibration caused by sources other than the ball screw itself can be excluded in the measurement. Moreover, the signal that correlates directly to the moving ball and thus the preload can be extracted with a better signal to noise ratio. Tests were conducted on ball screw feed drive systems with different temperature for the performance assessment of the proposed method. It concludes that the preload loss detection using AV VKF-OT can be implemented whenever the ball screw feed drive system is warming up or have been operated for some time if the temperature varies less than 10.8ï‚°C.

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