Study And Development On Automatic Screw Machine Based On Machine Vision Technology

Automatic screw fastening equipment is used widely in manufacturing industries because of the high assembly efficiency and low cost.But currently the equipments on the market requires high positioning accuracy for the fixture and can't correct the position deviation automatically.The process of inputting information of threaded hole is tedious.When facing with the workpiece that have much irregularly distributed hole,the equipment on the market can not achieve stable and efficient work effect.Hence,in order to improve the accuracy of the screw fastening process,the thesis designed and developed an automatic screw fastening machine based on machine vision and analysed high-precsion locationing method for threaded hole.Main works of the thesis are as follows:First of all,the thesis studies the craft of screws fastening.While on the basis of technical requirements,the thesis has made detail treatments for machine driven system,electric control system and visual imaging system and so on.The thesis also designs and develops the hardware control system of the automatic screw fastening machine.Secondly,according to the actual needs,the thesis sets up the camera model to calculate the internal camera parameters using Zhang's calibration method.Then it proposes an algorithm to locate the center of the holes on the product.Firstly,the thesis uses the Hough transform method to identify the hole area and then analysis the contours in the area to identify the center of the hole.Then it combines the result of the servo-control system to get the accurate position of the hole center.Experiment has proved the praticability of the system and the effectiveness of the detection algorithm.Finally,the thesis develops the software of automatic screw fastening control system based on the modular thought.At first,the thesis introduces the overall structure and operation process of the software,and then introduces the various functional modules of it,the key parts such as the torque controlling in screw locking,the determination of pulse equivalent and the screw hole positioning algorithm,are in detail.The control software is programmed to realize the control of the automatic screw fastening machine.