Quadrant multiscale optical flow approach for markerless phase identification and vibration displacement tracking of bladed disk systems

The traditional optical flow approach for vibration tracking of bladed disk encounters the following two challenges: (1) The rotational motion cannot satisfy the “spatial continuity” assumption of the optical flow approach, which leads to the inability to track the key points stably and accurately, and makes it impossible to realize the displacement tracking problem of rotational motion. (2) The optical flow approach obtains the integrated information of rigid body rotational motion and structural vibration, which cannot effectively realize the vibration tracking of rotating structures. For this reason, this study proposes a non-contact vibration detection quadrant multiscale optical flow approach for bladed disk. The first step establishes a quadrant multiscale optical flow model, which realizes the displacement tracking of rotational motion by the optical flow approach without markers by reducing the average inter-frame rotation angle. The second step introduces virtual reference points on the bladed disk to propose a method for separating the optical flow information of rotational motion, which distinguishes the rigid-body rotational component from the vibrational component when measuring the dynamic vibration of the rotating blade. The separation of the rigid-body rotational and local vibration components of the blade is achieved by introducing a reference region that is not disturbed by local vibration, thus enabling vibration tracking measurements. This method reduces the coupling interference between the rigid-body rotation component and the local vibration component, thereby improving the continuity and stability of optical flow estimation under experimental conditions. It provides a feasible non-contact measurement approach for extracting vibration displacements of rotating structures. Additionally, the method enables the analysis of multi-blade rotating structures. Ultimately, the proposed algorithm achieves phase detection and vibration tracking measurement of multi-blade rotating structures.