| Steel tape is widely used in life and engineering.As a commonly used length measuring tool,the accuracy of measurement is widely influenced by all aspects of life and engineering.Therefore,all countries have made clear verification standards for them.The current standard for verification in China is JJG4-2015.The project is based on the enterprise entrustment project of the Anhui Institute of Metrology Science(number: W2014JSKF0454).The main research content is to study the automatic verification of steel tape by using fixed and moving cameras on the testing platform of five meter length.The main contents of the work include:The specifications and types of common steel tape are introduced,and the methods for checking the steel tape at home and abroad and the equipment used are described.At present,the latest verification regulation of China is JJG4-2015.According to the current regulations,a verification platform is designed to meet the requirements.The platform is divided into two parts: Mobile verification and fixed verification.The fixed calibration includes six fixed CCD cameras.The mobile verification part includes a mobile CCD camera,a guide rail system,a stepper motor as a driver,and a grating as the standard quantity.The fixed part transmits image data to the computer with Gigabit Ethernet switch and Gigabit Ethernet card.The mobile part uses USB interface to transmit image directly to the computer,and finally the computer analyzes and processes the image.The grating part must keep the grating stable when it is installed for five meters long grating.It ensures continuity of grating signal and can not generate signal interruption,and ensures enough signal strength to ensure accuracy.Using the magnifying circuit of the subdivision card,the grating signal is magnified enough,and the acquisition card is used to deal with the grating signal.The laser interferometer is used as a standard quantity to calibrate the grating.After calibration,the grating value is corrected to reduce the uncertainty of grating measurement,so that it can meet the measurement uncertainty of less than ± 0.01 mm.The use of feature extraction algorithm to identify the image line,automatically find the steel tape line position,and the number of pixels,calculated the relative position of grain,and the standard error relative to the amount of the value of.The accuracy is compared with the existing algorithms,and the advantages and disadvantages of the processing speed,the identification accuracy and the accuracy are obtained.We should improve the whole program process,develop the man-machine interaction interface,and use the convenient operation mode,so that the staff can efficiently complete the verification work of all types of steel tape,and automatically generate report forms,write the measurement data,and automatically get the verification results. |
