This article describes the development of a one-dimensional extensible ball bar designed to measure the positioning accuracy and repeatability of industrial robots. The ball bar has a linear travel of 5 cm (2 in) that is monitored by a built-in electronic transducer having a resolution of 2.5 pm (0.0o01 in). At each end of the bar is a precision steel sphere, one of which is attached to an universal joint mounted on a robot's wrist. The other steel ball is magnetically attached to a socket which is firmly located within the work zone of the robot. During the measuring process the robot wrist is programmed to move in an arc whose radius is the nominal length of the bar. The variation of the length of the bar is recorded from the linear transducer and used to obtain a one-dimensional measurement of the positioning poerformance of the robot. Linear displacement and sag tests indicate that the ball bar has an accuracy of 32 pm (0.0013 in) and a repcatability of 20 pm (0.0008 in). Test procedures to evaluate a robot's performance are also presented.
A novel, non-touch, screen pointing interface is proposed for the use of intelligent presenter/audience collaborative environment. The underlying methodology for detecting a virtual passive pointer is described. The passive pointer or device does not have any active energy source within it (as opposed to a laser pointer) and thus cannot easily be detected or identified. The modeling and simulation task is carried out by generating high resolution color images of a pointer viewing via two digital cameras with a popular three-dimensional (3D) computer graphics and animation program, Studio 3D Max by Discreet. These images are then retrieved for analysis into a Microsoft’s Visual C++ program developed based on the theory of image triangulation. The program outputs a precise coordinates of the pointer in the 3D space in addition to its projection on a view screen located in a large display/presentation room. The computational results of the pointer projection are compared with known locations specified by Studio 3D Max for different simulated configurations. High pointing accuracy is achieved: a pointer kept 30 feet away correctly hits the target location within a few inches. Thus, this technology is useful in a large setting where presenter-audience collaborative applications are needed.
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