Experimental validation of a 3-D vision-based measurement system applied to robot calibration

Abstract

One of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. Robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. A large number of robot measurement systems are now available commercially. Yet, there is a dearth of systems that are portable, accurate and low cost. In this work a measurement system that can fill this gap in local calibration is presented. The measurement system consists of a single CCD camera mounted on the robot tool flange with a wide angle lens, and uses space resection models to measure the end-effector pose relative to a world coordinate system, considering radial distortions. Scale factors and image center are obtained with innovative techniques, making use of a multiview approach. The target plate consists of a grid of white dots impressed on a black photographic paper, and mounted on the sides of a 90-degree angle plate. Results show that the achieved average accuracy varies from 0.2mm to 0.4mm, at distances from the target from 600mm to 1000mm respectively, with different camera orientations

Improving accuracy and flexibility of industrial robots using computer vision

“…The first one is to fix cameras in the robot environment so that the cameras can see a calibration fixture mounted on the robot end-effector while the robot changes its configuration. The second typical setup is to mount a camera or a pair of cameras on the end-effector of the robot manipulator (Albada, et al 1994;Meng & Zhuang, 2007;Motta, et al 2001;Motta & McMaster, 2002).…”

Camera Modelling and Calibration - with Applications

“…Also here, usually only even powers of r r are used. These methods are described in (Brown 1971), (Tsai 1987), (Swaminathan & Nayar 1999), (Heikkila 2000), (Motta & McMaster 2002) and (Nowakowski & Skarbek 2007). If there is a need to calculate from the 2D image to 3D object space an equation for a straight line from the undistorted image coordinate converted to the 3D coordinate system through the pinhole point, P , is made.…”

Metodo de posicionamento e dimensionamento 3D baseado em imagens digitais

“…Os sistemas de visão podem operar com uma ou mais câmeras, e que podem ser móveis ou fixas, como descreve Motta (2002). Embora seja possível se ter uma idéia do mundo 3D usando uma única imagem, por um processo direcionado de segmentação como em Ryoo (2004), procedimentos mais consistentes podem ser obtidos a partir de duas imagens, que podem ser obtidas de uma mesma câmera que muda de posição, como descrevem Jain (1995), Trucco (1998), Forsyth (2003) e Ma (2004).…”