# Three-Dimensional Identification for Unbalanced Mass of Rotor Systems in Operation  
[PERSON]  
1 School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, No. 193 Tunxi Road, Hefei 230009, China; [EMAIL_ADDRESS] (Y.D. ); [PERSON]DDRESS] (J.Z. ); [EMAIL_ADDRESS] (P.Z. ); [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (L.Y.) [PERSON]  
1 School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, No. 193 Tunxi Road, Hefei 230009, China; [EMAIL_ADDRESS] (Y.D. ); [PERSON]DDRESS] (J.Z. ); [EMAIL_ADDRESS] (P.Z. ); [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (L.Y.) [PERSON]  
1 School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, No. 193 Tunxi Road, Hefei 230009, China; [EMAIL_ADDRESS] (Y.D. ); [PERSON]DDRESS] (J.Z. ); [EMAIL_ADDRESS] (P.Z. ); [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (L.Y.) [PERSON]  
1 School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, No. 193 Tunxi Road, Hefei 230009, China; [EMAIL_ADDRESS] (Y.D. ); [PERSON]DDRESS] (J.Z. ); [EMAIL_ADDRESS] (P.Z. ); [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (L.Y.) [PERSON]  
1 School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, No. 193 Tunxi Road, Hefei 230009, China; [EMAIL_ADDRESS] (Y. The actual vibration of rotor-bearing systems is in three-dimensional space, which performs quite different with the analysis based on 2D information [11]. When the rotor operates in low rotating speed, the vibration responses are mainly in a plane and the rotor can be treated as rigid at this condition. If the rotating speed keeps increasing, the flexibility of the rotors cannot be ignored and the dynamic responses are three-dimensional for the flexible rotor systems, which raise a challenge for the measurement technology. The traditional sensor measurement is not adequate for this challenge and new measurement methods are required [12]. Recently, different non-contact vibration-based measurement methods have been developed such as laser vibrometers [13; 14], stator current method, digital image correlation (DIC) and videometric technology. [PERSON] et al. determine the torsional vibration of a rotating shaft system under electrical network impact using laser doppler vibrometer [15]. Stator current-based methods use the current information from the stator of a motor to identify the motor failure even the gearbox perturbations [16]. [PERSON] et al. discuss the advantages and disadvantages of existing non-contact measurements in detail and introduce that DIC techniques which have the potential to provide 3D data at a wealth of points at a time [17]. DIC is a full-field measurement technique for deformation measurement which is developing rapidly over the years [18]. The studies of the photogrammetry make significant progress in the speed of image processing and measurement accuracy [19; 20]. In the meantime, this technique is widely applied to identify the displacement and strain of materials and structures [21]. However, DIC random speckled patterns are usually applied to a structure for the DIC approach, which are difficult to remove after the testing and lead to long duration measurement images in different time series [22]. Moreover, DIC has some limitations for high frequency measurement and requires relatively complex algorithms to obtain initial prediction parameters to converge correctly and rapidly [23]. 3D point tracking (3 DPT) stereovision measurement is a method to obtain surface information of a static structure by three-dimensional reconstruction [24; 25]. Unlike DIC techniques, 3 DPT does not need spraying speckled patterns on the surface of the structure and only requires some discrete points. To apply 3D point stereovision measurement for dynamic test, videometric technology is adopted for the development of 3 DPT technology. [PERSON] et al.