Detection System For Scratch On The Wheel Tread Of Train Based On PSD

The condition of wheel scratch has great importance to the safety of trainoperation. This paper introduces a detection system of wheel scratch by theapplication of PSD(Position Sensitive Detector). The system can realize theonline detection of wheel scratch during the train running.The principle of detection for wheel scratch based on PSD has been studied.The system takes advantage of laser displacement measurement technology.According to the force between wheel and trail, when the train comes, theposition of the light on PSD changes because of the deformation of trail, PSDconverts the change of position to electrical signal which is easy to detect. Thesystem can get the scratch information from the detection for the output of PSD.With TMS320F2812as the core, the system consists of the judgement andprocess about the coming signal of train, scratch data acquisition and process, thecommunication with man-machine interaction system.The first part is wheelsensor and corresponding signal conditioning circuits including amplitudelimiting circuit, filter circuit, waveshaping circuit, monostable circuit and levelconversion circuit. The coming signal of train can be processed by wheel sensorsconditioning circuits including amplitude limiting, filtering, signal shaping,denoising and level conversion. The second part is made up of semiconductorlaser source and PSD detector, AD converting circuits and memory circuit. Thesemiconductor laser source has been used as light, the DL16-7PCBA3detectorhas been used to detect the light position. The16-bit AD chip, AD7606, has beenused to gather the signal from PSD. TMS320F2812realizes digital filter and dataprocessing. The third part consists of MAX485serial communication circuits andUT-728PCI multi-serial-port card which realize the communication with man-machine interaction system. The detection data have been stored on PC. Thesystem accomplishes signal condition, photoelectric conversion, analog-to-digitalconversation, data processing, data storage, the communication with man-machine interaction system.Based on the theoretical analysis, the test curve has been simulated byMATLAB, different kinds of bandpass filters have been designed by MATLABincluding filter designed by Kaiser Window, equiripple filter, elliptic filter andChebyshev filter. The simulation test curve can be filtered by the designed filters. The optimal filter has been chosen by comparing the filter effects of differentfilters.The results show that the system can realize acquisition of PSD with highprecision. The effect of designed filter is good which can remove the noise andthe laser curve because of the normal deformation of rail. The scratch depth canbe extracted.