Abstract:The paper is concerned with the problem of multi-view three-dimensional (3D) point cloud registration. A novel global registration method is proposed to accurately register two series of scans into an object model underlying 3D imaging digitization by using the proposed oriented bounding box (OBB) regional area-based descriptor. A robot 3D scanning strategy is nowadays employed to generate the complete set of point cloud of physical objects by using 3D robot multi-view scanning and data registration. The automated operation has to successively digitize view-dependent area-scanned point cloud from complex-shaped objects by simultaneous determination of the next best robot pose and multi-view point cloud registration. To achieve this, the OBB regional area-based descriptor is employed to determine an initial transformation matrix and is then refined employing the iterative closest point (ICP) algorithm. The key technical breakthrough can resolve the commonly encountered difficulty in accurately merging two neighboring area-scanned images when no coordinate reference exists. To verify the effectiveness of the strategy, the developed method has been verified through some experimental tests for its registration accuracy. Experimental results have preliminarily demonstrated the feasibility and applicability of the developed method.
Sports robots have become a popular research topic in recent years. For table-tennis robots, ball tracking and trajectory prediction are the most important technologies. Several methods were developed in previous research efforts, and they can be divided into two categories: physical models and machine learning. The former use algorithms that consider gravity, air resistance, the Magnus effect, and elastic collision. However, estimating these external forces require high sampling frequencies that can only be achieved with high-efficiency imaging equipment. This study thus employed machine learning to learn the flight trajectories of ping-pong balls, which consist of two parabolic trajectories: one beginning at the serving point and ending at the landing point on the table, and the other beginning at the landing point and ending at the striking point of the robot. We established two artificial neural networks to learn these two trajectories. We conducted a simulation experiment using 200 real-world trajectories as training data. The mean errors of the proposed dual-network method and a single-network model were 39.6 mm and 42.9 mm, respectively. The results indicate that the prediction performance of the proposed dual-network method is better than that of the single-network approach. We also used the physical model to generate 330 trajectories for training and the simulation test results show that the trained model achieved a success rate of 97% out of 30 attempts, which was higher than the success rate of 70% obtained by the physical model. A physical experiment presented a mean error and standard deviation of 36.6 mm and 18.8 mm, respectively. The results also show that even without the time stamps, the proposed method maintains its prediction performance with the additional advantages of 15% fewer parameters in the overall network and 54% shorter training time.
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