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This paper addresses the visual servoing for regulation of robot manipulators evolving in the 3D Cartesian space. The image-based approach using a single camera but multiple feature points is considered to propose a direct visual servoing to deal with the complete robot nonlinear dynamics. This paper exploits first the well-known fact that in general four coplanar feature points on an object are sufficient to determine its posture form their projection in the image plane, and second, the transpose Jacobian control technique to design the proposed direct visual servoing scheme. Experiments on a nonlinear direct-drive spherical wrist are presented to illustrate the effectiveness of the proposed method.

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This article presents an image processing system that can work in hard real-time. Compared with systems that use the traditional multiprocessor architecture approach, this computer system takes advantage on recent technological advances and it is designed to work with a single processor PC under RTLinux. Its programming environment is similar to C programming language and it offers a friendly graphical user interface. The performance of the system is illustrated by means of experiments applied to visual guidance of mobile robots via velocity fields using a fixed high-speed camera. The experiments were carried out with a strict sampling frequency of 100 Hz. I. INTRODUCTIONToday it is accepted that industrial robots have reached a level of mature technology (Sciavicco and Siciliano, 1996). The current industrial robots can develop operations at high speeds and with a high degree of precision, however most of them do not see the operation that they are doing. To achieve these performances they have required considerable engineering effort to condition their work spaces (specialized part feeders, particular end-effectors, etc.) and at least this increases the operation costs as a consequence. Furthermore, this additional work provokes that the robot versatility and reprogramming properties will not be so simple (Engelberger, 1980).On the other hand, modern robots have a wider range of applications, including applications for the solution of operation problems in adverse environments and applications in which service is the demand. We can note that in most of these applications the robot environment is not structured. A natural strategy that looks for to solve these challenges is the incorporation of visual perception to robots. It has been demonstrated that robots with this capability can relax mechanical accuracy and rigidity increasing accuracy in proposed operations (Jägersand et al., 1996).