This assignment studies the development of an automatic imagining system for the inspection of huge curved surfaces. Positioning of the imaging camera is purportedly under numerical control. Without loss in generality, the motion platform depends on a 6-axis PUMA robot. The main objective is on imaging applications which need large magnification. The field of view is normally small in comparison to the combined positioning error because of the repeatability of the robot and the tolerance and positioning of the surface for inspection. This challenge of inadequate positioning accuracy of the primary motion system is alleviated with the introduction of a motion sub-system at the camera mounting. In the present implementation, a linear slider is installed at the end-effector of the robot to make it possible for fine motion of the camera along the normal direction of the surface. The tactic is to take a number of images of the surface as the camera travels in-and-out of the focusing range…
It’s known in Fourier optics that a nicely focused image has higher spatial frequency content than one which is out-of-focus. Depending on this, a fast and simple algorithm was put in place for choosing the perfect focused image. The algorithm demands computing the standard deviation of grey scale values for all pixels of an image. A pair of imaging functions have been implemented: (i) capturing an image at a specific location of the curved surface; and (ii) capturing images along a particular path on the curved surface as the robot is tracking the path. These functions, especially the second, needs coordinated motion of the robot and the linear slider. An application of part surface polishing inspection has additionally been researched that is ideal for the suggested imaging system. Polishing is a multi-stage process. Grooves are produced on the surface during polishing and their direction follow the direction of the rubbing of abrasive particles. Assume polishing is planned so that the direction of rubbing is unique for each location of the surface between the current stage and the prior stage of polishing. The change of direction of the grooves might then be utilized to flag the finish of the current polishing stage. A non-contact strategy for the on-site inspection of moulds and dies polishing is discovered. The strategy depends on analyzing the directions of the grooves from images of the surface being polished…
Source: City University of Hong Kong