An immersion and invariance-based speed observer for visual servoing

Abstract

In visual servoing, joint speeds of the robot are required for feedback control. However, most robots are not equipped with the angular velocity sensors. This paper deals with a speed observer for a visual servoing system based on the immersion and invariance (I&I) technique. The visual servoing system, a new binocular stereo visual model (BSVM) is considered, which 3-dimension image information is obtained directly, that we need not to estimate the depth information. We have considered the visual servoing system that contained the non-linear robot dynamics, an image-based controller and a speed observer. It will make the stabilisation analysis of the closed-loop system very difficult. A controller is designed so that the robot visual servoing system is transformed into a port-controlled Hamiltonian (PCH) system. It will simplify the stabilisation analysis. For the PCH system, firstly, a speed observer is designed by the technical of I&I. Secondly, a visual servo controller is designed to satisfy the visual servoing performance. Simulation experiments illustrate the theory and show the effectiveness of the proposed designs.