Abstract
Thin-walled parts (TWPs) have been widely employed in various industry fields and put forward a specific requirement of simultaneous multipoint vibration measurement for their dynamic behaviours understanding. The development of machine vision theory and technology enable the machine vision-based technique to measure the vibration of mechanical equipment. Lucas-Kanade based template tracking (LKBTT) can provide a robust, longer term motion estimation of the interesting object, but lacks spatial resolution and also deeper use of contextual cues. Lucas-Kanade based optical flow tracking (LKBOPT) is usually used for frame-by-frame feature-level motion estimation, and has the potential to satisfy the vibration measurement requirements of TWPs. LKBOPT has not been introduced to vibration measurement yet, and also had the challenge of long-term motion estimation. In order to satisfy the simultaneous multipoint vibration measurement requirements of TWPs, a coarse-to-fine tracking method is developed by introducing LKBOPT to vibration measurement and combining it with LKBTT. A region of interest detection algorithm is investigated to acquire the tracking template according to the measurable object. LKBTT is introduced to realize the coarse tracking and obtain the vibration information of the tracking template. An improved LKBOPT is investigated to realize the fine tracking and acquire the vibration information of multipoint inside the tracking template simultaneously. Finally, the simultaneous measurement system of multipoint mechanical vibration for TWPs is utilized with a high-speed camera system based on both Python and open source computer vision (OpenCV) libraries. The vibration measurement performance of the proposed method has been experimentally verified with two experiments under laboratory conditions by comparing the results with those using accelerometers. The experiment has shown that the proposed method is effective in the remote simultaneous multipoint vibration measurement of TWPs with satisfactory accuracy and efficiency.
Simultaneous Measurement of Multipoint Mechanical Vibration For Thin-Walled Parts Using Monocular Machine Vision Optical Flow Tracking