Papers by Keyword: Videogrammetry

Abstract: This paper present the aspects regarding the kinematics analysis of the human lower limb, respectively the angular positions and the angular velocities of the body segment, thigh, leg and foot, during of the direct free kick at football. For the analysis were videotaped the direct free kicks of 10 human subjects, children between 10 and 13 years, after which the images were processed using a specialized software. The method of the direct experimental kinematics analysis it allowed the determination of the amplitudes and the angular speeds segmentation advisable for to obtain accurate kicks in the direct free kicks with the ball. Regarding the performance, the objective pursued was that the ball must to have a trajectory on the space of the gate and also exceed the human wall which it is in front of the gate.

Abstract: Videogrammetric measurement is a research focus for the organizations of wind tunnel test because of its no special requirements on the test model, its key techniques for the vibration environment of the high speed wind tunnel are introduced by this paper, such as the solution of exterior parameters with big-angle large overlap, the algorithm of image processing for extracting marked point, the method of camera calibration and wave-front distortion field measurement. The great requirements and application prospects of videogrammetry in wind tunnel fine testing have been demonstrated by several practice experiments, including to measure test model’s angle of attack, dynamic deformations and wave-front distortion field in high speed wind tunnels whose test section size is 2 meters.

Abstract: Displacement is a good descriptor of the structural behavior and safety status. However, measuring displacement of structures under dynamic excitations is still a challenging task. Videogrammetry shows great potential for dynamic displacement measurement, benefiting from its non-contact and long-distance characteristics. Nevertheless, its all-weather performance has to be fully evaluated before gaining wide applications. This study therefore carried out an investigation into the environmental effects of the all-weather videogrammetry for structural dynamic displacement monitoring. First, long-term outdoor dynamic displacement monitoring tests were carried out. Virtual structural displacement was generated by a motion simulation device and monitored by a commercialized industrial digital camera. The adaptive filter was then employed to filter out noises, which had the primary input of the major displacement component and the reference input of the minor displacement component. The results show that the adaptive filter is well capable of filtering out noises and the measurement accuracy of videogrammetry is significantly enhanced.

Abstract: The videogrammetric measurement is a favorite technology in wind tunnel testing, because it neither destroys the model’s shape, nor changes the stiffness or strength. In this paper, a videogrammetric measurement system(VMS) is introduced, and it is used to measure model’s attack angle. Three engineering videogrammetric experiments of attack angle in 2 meter supersonic wind tunnel testing have demonstrated that the precision of VMS established by this paper is ≤0.0094°, so it is useful and effective.

Abstract: The advanced precision of drag coefficient is 0.0001 for the high speed wind tunnel test of measuring forces, the model’s angle of attack precision is ≤0.01°following errors distribution. A videogrammetric method of model’s attitude is therefore proposed, its uncertainty is investigated, and a compensation method of its systematic error is also presented by this paper. The three engineering videogrammetric experiments of attack angle in 2 meter supersonic wind tunnel testing have demonstrated that measuring standard deviation of videogrammetric measurement system established by this paper is ≤0.0094°, in addition it neither destroys the model’s shape, nor changes the stiffness or strength, so it is useful and effective.