PROPOSITION AND VALIDATION OF A SYSTEM FOR UNDERWATER THREE-DIMENSIONAL KINEMATICS ANALYSIS OF THE HUMAN MOVEMENTS

Abstract

Systems for underwater three-dimensional kinematics analysis have been developed aiming to a better understanding of the physical variable related to the underwater human movements. However, the systems found in literature present some limitations, mainly, the calibration of the cameras, which, traditionally, needs a rigid object, with points known previously, that delimit the size of the acquisition volume. For an analysis in large volumes, as example, of swimming, a large object construction is necessary and this causes a difficult construction and transport. Thus, this project objective to proposition and validation a system for underwater three-dimensional kinematics analysis of human movements in large volumes. For the development of a system for underwater three-dimensional kinematics analysis it is necessary to solve some problems related to the data acquisition, cameras synchronization, data measurement, cameras calibration, three-dimensional reconstruction and the experimental procedures in an accomplishment of data collection.The data acquisition will be made by cameras Basler and for the protection of the cameras we will be used housing, that were especially developed for these cameras and they had been tested in previous research in the Laboratory of Instrumentation for Biomechanics of the FEF/UNICAMP (Silvatti, 2009). The Basler cameras make possible the cameras synchronization made in the hardware for a device (trigger), this procedure will be tested and evaluated in this research. Since, in the water hasdifferent characteristics of a situation in laboratory, (swimming pool colors, water coloration, illumination and etc.) for the data measurement we will test different algorithms in Dvideo software. Since, this research, objective to analyze the influence of large volumes in the cameras calibration we will test and evaluate the non-linear cameras calibration, method proposed by Wang et al. (2008) and Zhang (2000) to correct the distortion caused by the water and we will develop a system of portable object calibration and accurate to use in any swimming pool, that will be facilitating the construction and the transport of this rigid object. The underwater three-dimensional reconstruction will be evaluated by the accuracy of a rigid body motion in a large acquisition volume in the front of the underwater cameras system. In the experimental procedures the problems will be solved: related the fixation and support of the cameras, possibilities of the cameras positioning, markers definition that can be used in this system, which can be retro-reflexives or not, models test of the body segments representation and the necessary illumination underwater will be developed and tested based on LED's to substitute the use of white light.