Theoretical improvements in the stability analysis of a new class of model-free visual servoing methods

This paper concerns the stability analysis of a new class of model-free visual servoing methods. These methods are "model-free" since they are based on the estimation of the relative camera orientation between two views of an object without knowing its 3-D model. The visual servoing is decoupled by controlling the rotation of the camera separately from the rest of the system. The way the remaining degrees of freedom are controlled differentiates the methods within the class. For all the methods of the class, the robustness with respect to both camera and hand-eye calibration errors can be analytically studied. In some cases, necessary and sufficient conditions can be found not only for the local asymptotic stability but also for the global asymptotic stability. In the other cases, simple conditions on the calibration errors are sufficient to ensure the global asymptotic stability of the control law. In addition to the theoretical proof of the stability, the experimental results prove the validity of the control strategy proposed in the paper.