Model-Free Unified Tracking and Regulation Visual Servoing of Wheeled Mobile Robots.

In this paper, a unified tracking and regulation visual servoing strategy is proposed for a wheeled mobile robot equipped with an onboard camera, wherein the 2-1/2-D visual servoing scheme helps to keep targets in the camera's field of view. Specifically, a novel composite error vector, including both image signals and rotational angles, is defined and then calculated by comparing the feature points of the unmodeled target object from the current image, the reference image, and the desired sequence of images. After that, an error transformation is designed to construct the chained-form error system, for which a time-varying continuous controller is designed to accomplish both tracking and regulation tasks. As shown by Lyapunov analysis, the proposed unified controller achieves asymptotic stability even in the presence of uncertainties regarding object model and depth information. Both simulation and experimental results are collected to investigate the feasibility of the proposed approach.