High Speed Data Acquisition And Signal Processing Of Short Pulse Discharge Current In Electromagnetic Forming

As a new technology of light alloy material of high speed forming, electromagnetic forming technology has been used widely. It can achieve the forming process of some of kinds of metal with high strength, while having the advantages of non-contact, high speed and improving the material surface quality with the decreasing of metal work piece rebounding, which can overcome the technical bottleneck of traditional forming method., The electromagnetic force between the forming coils and the interaction of metal work piece is formed by rapid changes in the coil current in electromagnetic forming technology. The discharge current in the forming loop is a parameter with great significance, which on the one hand reflects the real time characteristics of electrical parameters of discharge circuit, on the other hand is the basis of calculation of electromagnetic force driving the material deformation. Therefore, it has the vital significance to the accurate measurement of the discharge current in electromagnetic forming device.In the process of electromagnetic forming, the discharge current is a kind of high frequency, large amplitude pulse current measurement, whose measurement has difficulties in traditional current measurement method. According to the actual measurement requirements, this article analyzed the measuring principle of short pulse discharge current in electromagnetic forming and the changing characteristics of the discharge current by means of simulation, put forward to the overall technical scheme which using the hollow coil as the sensor to get the signal differential form of discharge current and the digital integrator with flexible structure to achieve the integral operation.In the aspect of hardware design of measurement system, in consideration of the problem of high output voltage of the sensor, the measurement system sent the data to the hardware with FPGA and DSP as its core to achieve the differential amplification after attenuation in order to eliminate interference factors like the zero drift on the accuracy of the data, and then sent the data to the AD chip to achieve the conversion from the analog signal to the digital form by integral operation. During the realization of software of the measuring system, the article described the software design of each module of the framework of measuring device, introduced the software design scheme of data acquisition and processing, gave some parts of the program code combined with the specific function realization. The key part of signal measurement and processing system adopted the scheme of data acquisition based on FPGA and DSP, the advantage of DSP high speed data processing and high speed FPGA control features has been combined to achieve high-speed data acquisition of 10 MSps discharge current measurement.The article completed the design of the discharge current measurement device, tested the discharge current in the experiment of electromagnetic ring expansion in Huazhong University of Science and Technology National Pulsed High Magnetic Field Center 973 spatiotemporal electromagnetic forming experiment platform. The experimental results show that the consistency of the data and the measurement error can be controlled within 3%, satisfying the need of the measurement of high pulse current, verifying the feasibility of this measurement system. The article calculated and analyzed the measurement error, on the basis of which put forward the improvement scheme in the future according to the actual problems in the design process.Finally, the article summarized the whole work and put forward the prospect in the future.