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Study On Pose Relay Videometrics Method With Camera-series And Ship Deformations Measurement

Posted on:2011-06-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:G W JiangFull Text:PDF
GTID:1118360305482724Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Traditional photogrammetry/videometrics methods and techniques are invalid to measure three-dimensional positions and attitudes of nonintervisible objects, for the basis that the camera must capture images of objects to be measured. An innovative prinple of"pose relay videometrics with camera-series"is proposed in this dissertation to resolve the problem of pose measurement between nonintervisible objects. The new method has been applied in ship deformations measurement, which has been one difficulty in navy equipment research and ship building industry. The prototype system for ship deformation measurement based on pose-raly videometrics is developed, and then sea trials are carried on. The main contents and innovations of this dissertation are as follows:1. Pose relay videometrics with camera-series method is proposed for the first time internationally. The method uses a series of cameras and markers to build up camera-series and connect the nonintervisible measuring target and reference, and then the three-dimensional positions, attitudes and their changes are obtained by pose relay. Principles of pose relay videometrics method by camera-series are studied systemicly, and the forms of relay stations are discussed. In succession, precision analysis and validation experiments are carried on. The method can resolve the problem of pose and deformation measurement of two or more nonintervisible objects, and those of objects with a very large angle of view, which cannot be processed by conventional principles and methods of videometrics, so that it can be applied in deformations measurement of ships and other large structures.The pose relay videometrics method with camera-series relays errors while relaying pose. Surrounding how to improve the precison and practicality, several key techniques such as camera calibratioin, marker detection and cameras synchronization are studied in this dissertation.2. A camera calibration method based on controllable rotation is proposed to resolve the problem of overmuch coupled parameters with many commonly used calibration methods. The camera is controlled to rotate a known angle around (or around nearby) the optical center to calculate the accurate efficient focus length departed from other parameters. And then a camera calibration method combined by controllable rotation and traditional two steps calibration is put forward to get all parameters including distortion coefficients.3. A cooperative marker combined by several infrared crosses is designed to suit the all-condition measurement requirements. Aiming at detection of random and irregular cross, a new sub-pixel detection method based on gray projecting integration (GPI, in short) and correlation is put forward. GPI method is applied to get the line width and the angles between each cross'arm and the image horizontal axis, and then digital correlation model is created according to the angles, at last, high-accurate sub-pixel location is obtained by fitting the correlation coefficients. Experiments show that the proposed detection method is robust and can locate cross center with the accuracy prior to 0.05 pixels.4. A synchronous image acquisition and processing system for multiple cameras is designed and implemented. A general digital output module is adopted as the synchronous trigger signal generator and controlled by computer program. On the basis of hardware-level synchronization, a certain software synchronous strategy is designed to ensure the synchronous frames of every camera to be processed synchronously. The method is universal, easy to operate, and able to resolve the synchronous problem of multiple cameras connected in one or more computers.5. On the ground of principle and key techniques research and project demonstration, a prototype videometrics system for ship deformation measurement is developed and applied in ship deformations measurement. Sea trials are carried on, from which long time and continuous data of position and attitude deformations between some point on the deck and the ship reference, and those between the ship head and stern, are achieved. The proposed method therefore has the potential to be applied in deformation measurement of ships and other large structures after more thorough researches and improvements.
Keywords/Search Tags:videometrics, pose relay, camera series, nonintervisible, pose estimation, camera calibration, camera synchronization, ship deformation
PDF Full Text Request
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