Development And Test Of Alternating Current Field Measurement Detection Instrument Based On FPGA

With the rapid development of industrial technology,the research and innovation of non-destructive testing methods and technologies are of great value.Alternating current field measurement detection technology has become a new member of electromagnetic nondestructive testing technology with its advantages of non-contact detection,rapid detection,high detection accuracy and low detection requirement.The electromagnetic transformation in the process of detection can not only be used to detect the surface defects of ferromagnetic materials,but also to detect the surface defects of non-ferromagnetic materials.The technique of Alternating current field measurement technology has high accuracy and detection rate for ferromagnetic materials,but its detection signal is weaker for non-ferromagnetic materials,and the ACFM system for the crack detection of non-ferromagnetic materials is less.And most of the testing instruments have a narrow scope of application,which limits the scope of application of the instrument.In this paper,a set of alternating current field measurement detection system based on FPGA is developed for the current detection technology of ACFM,which has some problems such as complicated detection control,single signal processing and low detection efficiency.This paper summarizes the development situation at home and abroad,discusses the principle of ACFM detection technology and its influencing factors,analyzes the formation reason and the change rule of the detection signal.Based on the existing detection probes,an alternating current field measurement detection probe based on photoelectric encoder is designed and fabricated.In order to deal with the defect detection of different materials,from the perspective of hardware design and digital circuit design,an ACFM detection system based on FPGA was designed and manufactured.A hardware acquisition board with adjustable excitation source and corresponding signal processing circuit is designed.The digital circuit of ACFM detection is realized by Verilog HDL language programming.The test results show that the design instrument can be used to detect the defect length and positioning of ferromagnetic material,aluminum plate and 304 L austenitic stainless steel by testing the 45# steel plate,aluminum plate and austenitic stainless steel containing artificial groove defects.Digital design can not only reduce the design cost of the instrument,but also improve the flexibility and intelligence of the instrument.On the Quartus II platform,this paper uses the hardware description language to design the FPGA logic,makes full use of the language flexibility,and uses the Modelsim SE software to perform the function of the module and the timing simulation,which guarantees the reliability,efficiency and low cost of the design.According to the test of each module,the digital circuit simulation sequence diagram and related program are given.