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| Author(s): |
Amanda Piaia Silvatti
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Educação Física |
| Defense date: | 2013-07-02 |
| Examining board members: |
Claudio Alexandre Gobatto;
Marcos Duarte;
Luiz Eduardo Barreto Martins;
Andre Luiz Felix Rodacki
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| Advisor: | Ricardo Machado Leite de Barros |
| Abstract | |
In order to perform a three-dimensional motion analysis in underwater conditions is necessary to calibrate accurately large volumes. Methods based on linear camera models are commonly used in biomechanics and this requires to construct, to transport and to measurement rigid structures, which becomes more difficult when larger volumes are involved. Recently, alternative methods based on nonlinear camera models have been proposed to address this aspect. The aims of this study were 1) to evaluate the accuracy of 3D reconstruction out and underwater using the method proposed by Zhang (2000); 2) to evaluate the accuracy of nonlinear camera calibration methods proposed by Hatze, 1988, Cerveri, et al., 1998 and Zhang, 2000 for underwater applications using submerged cameras and the effects of object position in the acquisition volume on the accuracy of 3D reconstruction methods, highlighting the advantages and disadvantages of each method, and 3) to test the applicability of the nonlinear methods proposed by Cerveri et al., 1998 and Zhang, 2000 for the reconstruction of the swimmers hand trajectory in different swims styles. For data acquisition, we used a kinematic analysis system (DVideo), which was adapted for underwater conditions. The system consists of cameras (Basler) connected in computers for online data acquisition. Waterproof housings were specially designed to protect the cameras and a genlocker trigger was used to synchronize the cameras. Tripods to support and to fix the cameras were adapted with suction cups and were used to fix them on the swimming pool floor. In order to perform the distortion correction the nonlinear camera calibration methods were implemented in Matlab software. A rigid bar test was used to assess the accuracy and precision. The results showed that the methods proposed by Cerveri et al. 1 998 (1.16 mm to 0.96 mm) and Zhang, 2000 (0.73 mm) are promising alternatives for 3D underwater motion analysis. Both methodologies presented results with greater accuracy than those found in the literature. This occurred due to an improvement of the distortion modeling and that was confirmed by the smallest influence of the object position on the error values. Related to the flexibility and portability of the calibration object, both methods use objects easier to build and manipulate than the objects traditionally used. The 3D motion analysis system using submerged cameras showed to be suitable for underwater applications. The results reported here can be immediately appreciated by coaches, because it was possible to identify symmetry or asymmetry between the two sides, the variability within and between subjects in terms of movement patterns and agreement or disagreement with the theoretical model. Important to emphasize that there is the possibility of extending the analysis for different body segments and the system and the camera calibration methods presented in this work can be used for any sport or activity performed in water, such as hydro gymnastic or rehabilitation practices (AU) | |
| FAPESP's process: | 09/09359-6 - PROPOSITION AND VALIDATION OF A SYSTEM FOR UNDERWATER THREE-DIMENSIONAL KINEMATICS ANALYSIS OF THE HUMAN MOVEMENTS |
| Grantee: | Amanda Piaia Silvatti |
| Support Opportunities: | Scholarships in Brazil - Doctorate |