User detection, recognition and tracking is at the heart of Human Robot Interaction, and yet, to date, no universal robust method exists for being aware of the people in a robot surroundings. The presented work aims at importing into existing social robotics platforms different techniques, some of them classical, and other novel, for detecting, recognizing and tracking human users. These algorithms are based on a variety of sensors, mainly cameras and depth imaging devices, but also lasers and microphones. The results of these parallel algorithms are then merged so as to obtain a modular, expandable and fast architecture. This results in a local user mapping thanks to multi-modal fusion.

Thanks to this user awareness architecture, user detection, recognition and tracking capabilities can be easily and quickly given to any robot by re-using the modules that match its sensors and its processing performance. The architecture provides all the relevant information about the users around the robot, that can then be used for end-user applications that adapt their behavior to the users around the robot. The variety of social robots in which the architecture has been successfully implemented includes a car-like mobile robot, an articulated flower and a humanoid assistance robot.

Some modules of the architecture are very lightweight but have a low reliability, others need more CPU but the associated confidence is higher. All configurations of modules are possible, and fit the range of possible robotics hardware configurations. All the modules are independent and highly configurable, therefore no code needs to be developed for building a new configuration, the user only writes a ROS launch file. This simple text file contains all wanted modules.

The architecture has been developed with modularity and speed in mind. It is based on the ROS architecture, a de facto software standard in robotics. The different people detectors comply with a common interface called PPLP, while the people recognition algorithms comply with an interface called PPLM. The fusion of all these different modules is based on UKF techniques. Extensive benchmarks of the sub-components and of the whole architecture, using both academic datasets and data acquired in our lab, and end-user application samples demonstrate the validity and interest of all levels of the architecture.