In this paper, a low-cost dynamic measurement system using the RGB-depth camera, Microsoft Kinect® v2, is proposed for measuring time-varying free surface motion of liquid dampers used in building vibration mitigation. Various experimental studies are conducted consecutively: performance evaluation and validation of the Kinect® v2, real-time monitoring using the Kinect® v2 SDK(software development kits), point cloud acquisition of liquid free surface in the 3D space, comparison with the existing video sensing technology. Utilizing the proposed Kinect® v2-based measurement system in this study, dynamic behavior of liquid in a laboratory-scaled small tank under a wide frequency range of input excitation is experimentally analyzed.

Background: The Microsoft Kinect which is a low-cost gaming device has been studied as a promise clinical gait analysis tool having satisfactory reliability and validity. However, its accuracy is only guaranteed when it is properly positioned in front of a subject. Objects: The purpose of this study was to identify the error when the Kinect was positioned at a 45˚ angle to the longitudinal walking plane compare with those when the Kinect was positioned in front of a subject. Methods: Sixteen healthy adults performed two testing sessions consisting of walking toward and 45˚ obliquely the Kinect. Spatiotemporal outcome measures related to stride length, stride time, step length, step time and walking speed were examined. To assess the error between Kinect and 3D motion analysis systems, mean absolute errors (MAE) were determined and compared. Conclusion: Based on our study experience, positioning the Kinect directly in front of the person walking towards it provides the optimal spatiotemporal data. Therefore, we concluded that the Kinect should be placed carefully and adequately in clinical settings.

본 연구에서는 건물 실내 공간 정보 획득을 위해 Microsoft사의 Kinect® v2를 활용한 point cloud 기법을 도입하였다. 카메라로 취득한 2차원의 투영 공간 이미지 픽셀 좌표를 각 카메라의 보정을 거쳐 3차원 이미지 변환하며 이를 토대로 공간 정보를 구현하였다. 기준점을 중심으로 360° 회전하여 취득한 3차원 이미지를 통해 거리 측정이 불가한 기존의 2차원 이미지의 한계를 개선하였으며, 이 과정을 통해 얻은 point cloud를 통해 3차원 map을 형성하였다. 형성된 3차원 map은 기존의 공간정보 융·복합을 위한 센서와 비슷한 수준의 측정 효율을 가지면서 동시에 렌즈 왜곡 현상에 대한 후처리 과정을 통해 공간 정보를 정확하게 측정할 수 있도록 하였다. 측정한 결과를 2D 도면과 실제 공간 및 구조부재의 길이 및 위치 등과 비교하여 검증하였다.