Person following and visual relocalization for indoor service robotics

In the last decades the average quality of life improved all over the globe, leading to an increase of elderly people, that often need assistance in their everyday life. Contextually the field of service robotics has been trying to fulfill this social need, providing solutions which can safely coexist in the house. Inside this scenario, PIC4SeR (PoliTO Interdepartmental Centre for Service Robotics) has been putting efforts in a wide project, with the aim of assisting elder people in their daily routines. In particular, the goal of this thesis was to develop a series of software applications to be run on an Unmanned Grounded Vehicle (UGV), designed to roam safely in a domestic environment. Person following is the task of navigating while maintaining the user framed as he walks. To do so, the robot detects the presence of a person in the camera stream and recognizes the main parts of the human body, exploiting an already trained, light and low resource demanding neural network: PoseNet. Adopting SORT (Simple Online and Real time Tracking), the presence of the same person in multiple successive frames is tracked. Finally, the relative distance between the robot and the person is computed. The other main subject of this work was relocalization, correcting the odometry error accumulated while roaming. At first it has been performed via markers. Adopting the April tag system, knowing a priori position and orientation of the marker, it is possible to derive the robot global position and orientation very precisely. Another approach to relocalization was then tried in the last part. Acquiring a database of images when the robot turns on, it can later be compared with a query frame. Finding features matching in two frames, an estimation of the relative pose difference between them can be estimated. This framework, although less precise, has the advantage of working in an unstructured environment, unlike the previous one. It also leaves space for improvements in the way matching couples are selected.