Design Of Sub-pixel Level High Precision Measuring System For Wire Diameter Based On ARM

In the production process of wire,its diameter is an important indicator for the quality control.It can directly affect the product quality and cost of the wire,and the deviation of wire quality will lead to the waste of resources,the economic loss and other issues.There are many types of methods for measuring the diameter of wire,here the parallel light projection method is the more common one,which is relatively simpler structure and lower cost.But the measuring accuracy is limited by the pixel size of CCD and the degree of parallel light collimation.Although the measuring accuracy can be improved by using smaller pixel size CCD and complex collimating system,but these need to increase production cost and difficulty of the measuring system.Therefore,aiming at the problems of parallel light projection method,this paper designs a non-contact measuring system for wire diameter based on ARM Cortex-M4 microprocessor to improve the measuring accuracy by using sub-pixel edge detection algorithm.In this paper,the designed measuring system for wire diameter is divided into three parts:(1)the optical system design of projection method,(2)the electronics design and(3)the system software design.Firstly,in the optical system design,by comparing a variety of methods for measuring wire diameter,the improved orthogonal structure parallel light projection method is selected as the system’s measuring method.Through the filter,the light beam with the information of the wire is projected onto the linear CCD photosensitive surface.Then,in the hardware circuit design,the ARM M453VG6 AE is used as the main control unit of the system,and the relevant circuit is divided into: CCD driving module,video signal sampling module,data communicating module and LCD displaying module.The driving timing of the linear CCD TCD1103 GFG is controlled by M453VG6 AE.The video sampling is using built in12 bit high-speed ADC to complete the data conversion.PL2303 is used to realize the data exchange between the system and the host computer in the data communicating module.LCD1602 A is used to display the measuring result.Finally,in the system software design,the C language is used to realize the software design of each module linkage work on the hardware circuit.Here the main study is a sub-pixel edge detection algorithm,it can be using measuring wire diameter.The differential operator is discussed for coarse positioning,and the sub-pixel edge detection algorithm based on quintic polynomial fitting is adopted to realize accuracy positioning.Compared with the threshold level method,this method has better accuracy and more stability.After calibrating to the experimental results,study has obtained the result of a higher measuring accuracy,which shows this design scheme has some maneuverability and practicability.