Research On Differential Measuring Method Of Wire Diameter Based On Laser Projection Imaging And Its System

Thin cylinders are widely used in the fields of aviation, astronavigation, military industry and civil industry. The manufacturing accuracy and the assembly accuracy of these matched parts can be increased by precision and high efficiency measurement of their diameters. So do the performance and producing efficiency of instrument or weapon, in which these parts are used. At the same time the defective rate, production costs and resource consumption can be also reduced. So the research on diameter's high-accuracy-separation measurement technique of thin cylinder is very significant.In this dissertation, to improve the sorting accuracy of thin cylinder diameter by using the laser projection imaging method, a large quantity of references is consulted and the current situation of domestic and external research are also studied. The main content and innovative achievements of this dissertation are as follows:At first, the differential measurement method based on laser projection images of thin cylinder diameter has been proposed. V-groove was used for position reference which has a zoom function for the small changes. The signals received from the two-array silicon photocell should be differential to eliminate the noises of background light intensity and the system errors. The system's measurement accuracy and measurement resolution rate will be improved which is good for high-precision sorting.Secondly, proposed a software compensation method using C8051F330 SCM feedback control current which flows through the laser to restrain the drift of the laser beam. The laser intensity's self-regulating behaving can make itself go to the ideal state in a short time, and ensure its stability. Experiments proved that:after adopting this feedback control system, the converted voltage of the laser intensity can be controlled under 25mv±3mv.Thirdly, hardware measurement system has been deeply researched, which contains the part of device selection, the hardware circuit design and optimization, etc. The detailed analysis to AC modulated processing circuits verified the differential for the measured signal would result the laser intensity asymmetry which received by silicon photocell, which had not been found at all the previous study.Fourthly, carried out the feedback control algorithms to against the laser drift and the programmer of A/D, D/A and the liquid crystal display based on KeilC were also be done in detail.Finally, the test results and measurement errors of this diameter measuring instrument were analyzed. Experimental data shows that:for the same standard measured parts, the measurement accuracy can up to±0.2μm, the overall system measurement error is 0.98 percent, the measuring range is lmm-6mm, and this researched apparatus well meet the other basic performance indexes.