Autonomous Mobile Robot Navigation in Sparse LiDAR Feature Environments

In the industrial environment, Autonomous Guided Vehicles (AGVs) generally run on a planned route. Among trajectory-tracking algorithms for unmanned vehicles, the Pure Pursuit (PP) algorithm is prevalent in many real-world applications because of its simple and easy implementation. However, it is challenging to decelerate the AGV’s moving speed when turning on a large curve path. Moreover, this paper addresses the kidnapped-robot problem occurring in spare LiDAR environments. This paper proposes an improved Pure Pursuit algorithm so that the AGV can predict the trajectory and decelerate for turning, thus increasing the accuracy of the path tracking. To solve the kidnapped-robot problem, we use a learning-based classifier to detect the repetitive pattern scenario (e.g., long corridor) regarding 2D LiDAR features for switching the localization system between Simultaneous Localization And Mapping (SLAM) method and Odometer method. As experimental results in practice, the improved Pure Pursuit algorithm can reduce the tracking error while performing more efficiently. Moreover, the learning-based localization selection strategy helps the robot navigation task achieve stable performance, with 36.25% in completion rate more than only using SLAM. The results demonstrate that the proposed method is feasible and reliable in actual conditions.

Three-dimensional evaluation of a rare case with multiple impacted teeth using CT

A 15-year-old patient is presented with 11 impacted teeth including 2 supernumerary teeth, who did not exhibit hereditary or clinical disease. The patient showed the extruded and lingually inclined lower incisors, the anteriorly inclined palatal plane, extremely large curve of Spee, and crowding in the bone. A detailed description of the positional relationship between each impacted tooth and the neighboring tooth was given using the 3D CT-image.