| Monofilaments are widely used in production and life.Diameter is an important indicator of the quality and use of monofilaments.Monofilament diameter uniformity will affect its ability to withstand tension.Therefore,it is very necessary to measure the diameter of the monofilament.There are two methods for measuring the diameter of a monofilament,one is a contact measurement based on a mechanical structure,and the other is a non-contact measurement based on sensor conversion.The first method means that the measuring device is in direct contact with the monofilament being tested,which is a low-cost and simple measurement methods,and more used by digital micrometer or traditional micrometer.However,due to the device,the surface of the monofilament is deformed and the error is introduced during measurement.In addition,the conventional micrometer measurement is not convenient for recording data,analyzing the uniformity of the thickness of the entire monofilament,and the on-line measurement cannot be performed.The non-contact measurement method does not directly touch the monofilament under test.At present,the non-contact measurement method adopted in China is based on a digital image sensor.Through the analysis of the image,the value of the diameter of the monofilament is obtained.But this method is used to query the pixel elements,and The calculation of the diameter is limited by the pixel size of the image sensor.At present,the common image sensor pixel size in China is 8 to 10 micrometers.This value is far lower than the accuracy requirement of the monofilament precision to be measured,and has to be increased to achieve high precision measurement.Optical system modules or the use of custom high-precision image sensors,these two methods not only increase the development costs and can not eliminate the digital signal quantization error.In this research,a high-precision single-wire diameter measurement method based on analog image signal acquisition is designed to not only ensure the measurement accuracy and accuracy of the monofilament diameter,but also to reduce costs,and is suitable for industrial applications.The design is mainly divided into two parts.The first part is the photoelectric conversion part.The analog camera photographs the single filament to be measured,so that the diameter of the monofilament is converted into the voltage pulse width.The second part is the measurement part.The pulse width is measured and converted to the actual monofilament diameter.This research also details the hardware structure of the monofilament diameter measuring instrument.The hardware includes the illumination system,photoelectric sensor,signal separation unit,waveform processing unit,FPGA and STM32 microprocessor,and power supply module.The optical device includes LED line light source,the black light-absorbing backplane comprises a driving module,a CCD sensor,a signal processing module,and a timing control module.The specific selection of the equipment unit is discussed,and the design principle and use of each module are explained in detail.Also discussed in detail are the measurement methods and numerical processing calculations.The software for designing measurement algorithms is designed,including hardware description language in FPGA and C language in STM32.In addition to the various modules that describe the completion of the hardware description language,the simulation results of the core module are also given.Introduce the software development environment of STM32,the control flow of the whole system,draw the software flow chart.Finally complete the overall system debugging and data analysis,discuss the final measurement accuracy and error sources of the subject.Through the analysis of experimental data,the expected accuracy of the diameter measuring instrument is reached,and at the same time,a new scheme is proposed on the human-computer interaction and intelligent measurement,which has certain research significance for the development and production of the final equipment. |
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