Research On Digital Variable Pulse Excitation Ultrasonic Testing System Based On Fpga And DDS

Ultrasonic testing is the main technical means of railway locomotive and vehicle parts and rail non-destructive testing.Many domestic and foreign developed countries have attached great importance to develop ultrasonic testing equipment for railway locomotive and vehicle parts and rail non-destructive.With the development of computer technology and digital electronic technology, ultrasonic testing equipment is developed from traditional analog equipment to digital testing equipment.But the excitation pulse of ultrasonic testing equipment that exist today is relatively single,mostly sharp pulses or square wave pulse, and many parameters of pulse cannot be seted,For most portable devices, the power supply voltage amplitude is low, resulting in detection ability is not enough, did not take any compensation measures.Based on this, this paper aims to research and design a field-programmable gate array (FPGA) as the core,the direct digital synthesis (DDS) technology as technology means,combined with high-speed A/D digital variable pulse excitation ultrasonic detection system,by programmably controlling the ultrasonic excitation signal generation, in order to improve the ultrasonic testing system detection capability and adaptability, to meet the needs of different detection applications.This detection system uses direct digital synthesis (DDS) technology, by programmably controlling an ultrasonic excitation signal generation, for different detection needs the detection system can flexible setting and selecting waveform,frequency, pulse width and pulse number of excitation signal.Meanwhile, the parameters that affect the performance of the excitation signal (pulse type, number of pulses, pulse width) conducted a pilot study, analysis of the influence of various parameters on the excitation signal energy.Put forward at a low voltage condition,to appropriately increase the number of excitation pulses to increase the transmission power, in order to improve the detection system’s detection ability and adaptability.The paper take FPGA component EP2C35F672 as the core control unit, used the modular thought to complete the hardware circuit design of detection system, realize the functions of ultrasonic transmitting and receiving, programmable amplifier, band-pass filter, high-speed data acquisition and human-computer interaction.Components of the hardware system have the characteristics of low noise, high precision,high reliability,while designed take various measures to guarantee and improve the accuracy and anti-jamming capability of detection system.Using FPGA development software Quartusll complete the design and Simulation of the excitation signal generation, sequence control, logic control, data acquisition, cache and other functional modules,the validity of the software design is verified.In the laboratory using standard CSK-IA test block to carry on the function test for digital ultrasonic detection system designed.The results show that the multi-pulse excitation in a manner that at low excitation voltage, to obtain stronger ultrasonic echo signals, to achieve effective detect deeper range defects of the work piece interior.Single pulse excitation method in the condition of low pulse width,for the closer defects have the better detection,strong resolving power, can be very good to distinguish the defect.The detection system to achieve the basic functions of the ultrasonic echo signal conditioning, high-speed data acquisition and storage; variable pulse excitation method to improve the detection system adaptive and intelligent, have the strong practical and research value.