Abstract
In this article, we present a method to position the tool in a micromachine system based on a camera-LCD screen positioning system that also provides information about angular deviations of the tool axis during its running. Both position and angular deviations are obtained by reducing a matrix of LEDs in the image to a single rectangle in the conical perspective that is treated by a photogrammetry method. This method computes the coordinates and orientation of the camera with respect to the fixed screen coordinate system. The used image consists of 5 × 5 lit LEDs, which are analyzed by the algorithm to determine a rectangle with known dimensions. The coordinates of the vertices of the rectangle in space are obtained by an inverse perspective computation from the image. The method presents a good approximation of the central point of the rectangle and provides the inclination of the workpiece with respect to the LCD screen reference system of coordinates. A test of the method is designed with the assistance of a Coordinate Measurement Machine (CMM) to check the accuracy of the positioning method. The performed test delivers a good accuracy in the position measurement of the designed method. A high dispersion in the angular deviation is detected, although the orientation of the inclination is appropriate in almost every case. This is due to the small values of the angles that makes the trigonometric function approximations very erratic. This method is a good starting point for the compensation of angular deviation in vision based micromachine tools, which is the principal source of errors in these operations and represents the main volume in the cost of machine elements’ parts.
Highlights
Positioning systems are increasingly present in all industrial processes
Camera-screen positioning systems with dedicated artificial vision algorithms [3,4,5] have provided high precision at a very interesting cost compared to other positioning technologies such as encoders or resolvers
A new method was developed to position the tool in a micromachine system based on a camera-LCD screen positioning system that provided information on the angular deviations of the tool axis during operation
Summary
Positioning systems are increasingly present in all industrial processes. Technology requires progressively more precise systems capable of positioning rapidly and robustly. The cost of those is one of the key factors to integrate high precision systems. Thanks to the advances in screen and camera technology, positioning algorithms that analyze a pattern shown in a photographic image have been developed [1,2]. Camera-screen positioning systems with dedicated artificial vision algorithms [3,4,5] have provided high precision at a very interesting cost compared to other positioning technologies such as encoders or resolvers.
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