Browsing by Author "De Jongh, Wille Carel"
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- ItemSpace debris: pose estimation using stereo vision(Stellenbosch : Stellenbosch University, 2019-04) De Jongh, Wille Carel; Jordaan, H. W.; Van Daalen, C. E.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Tracking the relative attitude and position of uncooperative in-orbit objects is vital for autonomous operations in space. Vision-based solutions have low power consumption and can provide a system with valuable information to perform pose determination. Estimation algorithms are required to extract the system states from visual measurements and many similar approaches have been investigated in mobile robotics. In this thesis, a chaser satellite is fitted with stereo cameras which are used to extract unique features on the surfaces of an uncooperative, unknown target. The scale invariant feature transform (SIFT) feature detector is used to identify and establish correspondence of the target features. A full state kinematic estimator is implemented using an extended Kalman filter (EKF) based on the simultaneous localisation and mapping (SLAM) approach. The filter makes use of the observations from the feature extractor to estimate the position and orientation of the target relative to the chaser along with the angular and linear velocities of the target. Shape and size reconstruction of the target is made possible using the sparsely tracked features. A simulation environment providing ground truth is used to verify the performance of the estimation algorithm. The integration of the estimator with the feature extractor is assessed using real world data. Experimental data is obtained from image sequences of a moving target in a laboratory set-up. Results show that the filter estimates the system states successfully and that the developed feature extractor is capable of detecting robust features with reliable correspondence. It is concluded that the use of a stereo-vision-based estimator is a viable option for autonomous operations such as space debris removal and satellite service missions.