带有曝光时间自动控制的CCD带钢宽度测量仪

A CCD Strip-steel Widthmeter With Automatic Exposure Timing Control

钢材白热化时的发光强度随其表面温度的变化,是以钢材本身发光为光源的CCD钢材尺寸热测法中一个突出的难点。本文介绍一种基于自适应算法的CCD 曝光时间自动控制器及相应的波形处理电路。该套电路在APPLE 计算机控制之下工作,测量精度达到±0.5mm。本文对于曝光时间自动控制原理、主要电路的结构和具体实现及软件的处理过程作了重点讨论,并简要介绍了软件的其它功能。

A CCD device is applied to measure the width of white-heat strip-steel,using its self-luminescence as the light source.A specialdifficulty exists when such a measurement is carried out,that is,the lu-minous intensity is greatly changed following the change of the steel te-mperature.An adaptive exposure timing controller is designed to deal withthis problem.Under its control,the CCD exposure time can be adjustedfrom 2ms to 20ms,corresponding to the temperature region from 1200℃ to550℃,so as to keep the amplitude of the CCD output waveform withintolerance.Thus,by the help of the waveform processing circuit and some softwaremeasures,the measuring precision can be ensured within the range of ±0.2%.The controller is designed based on the widrow-Hoff LMS self-adaptivealgorithm with the improvement of introducing a variable gain for thepurpose of both keeping track of the intensity of the CCD output signal andsuppressing noise disturbance.A noise mixed CCD output signal X_K is rever- se overlapped with the desire signal D_K to form the error signal E_K,andthe control algorithm is applied on E_K and X_K to produce the exposurecontrol signal T_(K+1).T_(K+1) is then processed by the signal transforming linkto form D_(K+1).At the same time,T_(K+1) is converted,by an A/D converter,into the digital strobe signal of a multiplexor.The input signal of themultiplexor are a series of different exposure timing signal,each is drawnout from different point of a timing circuit.At last,there is a 3 positionswitch K,the first and second positions of which are fixed timing signal,4ms and 10ms respectively,and the third one is the output of the mul-tiplexor.The selected timing signal,variable or static,is connected directlyto the CCD device.The waveform processing circuit involves two parts,thewaveform amplifier with adjus table gain and the differential edge detector.The former amplifies the CCD output waveform to a given amplitude,and thelater checks the edge out,then a square wave is formed and fed to thecomputer to calculate the width of the strip-steel.The main content of thispaper is the principle,algorithm and realization about the timing controllerand the waveform processing circuit,and introduces briefly the other softwarefeatures.