tailieunhanh - The Robot Vision_2

The purpose of robot vision is to enable robots to perceive the external world in order to perform a large range of tasks such as navigation, visual servoing for object tracking and manipulation, object recognition and categorization, surveillance, and higher-level decision-making. Among different perceptual modalities, vision is arguably the most important one. | 22 Direct visual servoing of planar manipulators using moments of planar targets Eusebio Bugarin and Rafael Kelly Centro de Investigation Cientifica y de Education Superior de Ensenada Mexico 1. Introduction Visual servoing is a control strategy that uses a vision system with one or more cameras to establish the movement of a robotic system Hutchinson et al. 1996 and emerges as a good alternative to close the control loop between the robot and its environment. Vision is a noncontact method that can relax the setup on an industrial robot and can give more characteristic of autonomy to advanced robots which operate in adverse ambient or execute service tasks. Depending on the place where the cameras are located visual servoing is classified by the fixed-camera and camera-in-hand configurations. This chapter addresses the regulation of a planar manipulator by the visual servoing strategy in fixed-camera configuration. To simplify the problem it is considered that the camera optical axis is perpendicular to the robot motion plane. The specification of the robot motion by the visual servoing strategy must be established trough image features obtained from target objects in the scene or robot workspace. However most of the developed theory in this area is based on the use of target objects with simple geometry like points lines cylinders or spheres local features or in more complex target objects but simplifying them to simple geometric objects trough image processing techniques Collewet Chaumette 2000 Benhimane Malis 2006 . On the other hand image moments represent global features of an arbitrary target object projected in image plane. The main objective of this chapter is to extend the use of simple target objects toward the use of a more complex target objects in the direct visual servoing of manipulators. Particularly the target object will be a planar object with arbitrary shape and the image features will be computed trough image moments combinations of this planar