1. A face detection and tracking method of a robotic device, comprising: obtaining a video frame from a camera of the robotic device; performing a face detection process on the video frame to detect one or more faces in the video frame; after the face detection process, identifying the detected one or more faces in the video frame; performing a vision-based tracking process to track the identified one or more faces using a combination of a feature points tracker and a correlation tracker, comprising: for each identified face, determining whether the identified face has been tracked; when it is determined that the identified face has not been tracked, initializing the feature points tracker and the correlation tracker based on a set of feature points of the identified face; when it is determined that the identified face has been tracked, refining the feature points of the identified face; and using the correlation tracker to provide both translation and scale estimation of the identified face; and after the vision-based tracking process, performing a detection and tracking fusion process and providing desired target prediction of the identified one or more faces.