Research On High Precision Ultrasonic Benchmark And Test Method

Ultrasonic phase method has high requirements on ultrasonic frequency reference and phase reference.Therefore,researching high precision ultrasonic reference is of great significance for improving the accuracy of ultrasonic ranging.In this paper,FPGA is selected as the ultrasonic frequency reference and phase reference generator.The ultrasonic frequency reference generated by FPGA is easy to control and does not affect external factors,but the ultrasonic phase reference generated by FPGA will be affected by external factors such as devices and transducers.In order to achieve accurate measurement and control of the ultrasonic phase reference generated by the FPGA,it is necessary to construct a complete FPGA ultrasonic signal source generation system and an accurate ultrasonic phase detection system.In response to the above research requirements,an FPGA+DDS hardware experimental platform was established as an experimental device for the ultrasonic frequency reference and phase reference.Set the frequency,phase and amplitude of the dual sinusoidal data outputted by the FPGA+DDS experimental platform in the host computer,and continuously output the signal by the AC A/D acquisition card AC6684 at high speed,using the phase difference detection algorithm proposed in this paper.The phase difference measurement obtains the difference between the set phase difference value and the actual phase difference value.Set the two-way sine wave phase difference interval 10 °,from 0 ° to 90 ° a total of ten groups,each group to do five repeated experiments and calculate the standard deviation of five data.In order to improve the accuracy of phase difference detection,this paper proposes a full-period algorithm to cycle the 40 kHz ultrasonic data so that it can be transformed into the frequency domain by FFT(Fast Fourier Transform)without spectral leakage.The data is denoised in the frequency domain and then converted to the time domain for phase difference detection by IFFT(Inverse Fast Fourier Transform).The hardware experiment platform built in this paper generates 39.0625 kHz ultrasonic cycle data for comparison experiments.In order to simulate the interference and attenuation of ultrasonic waves between the hardware platform and the real environment,two-way ultrasonic data of equal amplitude and unequal amplitude are generated for comparison experiments;another set of white noise data is generated,which is scaled down to 3% of the amplitude of the ultrasonic data.And 5% additive interference data and multiplicative interference data.The experiment was divided into 40 kHz and 39.0625 kHz,equal-amplitude and unequal amplitude,interference and interference-free,additive and multiplicative interference,frequency domain denoising and frequency domain denoising,and the experimental data were recorded.Drawing data charts and analyzing the data for reference for further experimental research.