Design Of Piston Displacement Test System For Accumulator

Accumulator,as an important part of hydraulic system of hydraulic press,is the key link to ensure the safe operation of hydraulic press.The measurement of liquid level,hydraulic pressure and other parameters in accumulator is mainly obtained by measuring the position of accumulator piston.Because the traditional liquid level measuring device does not meet the requirements of the testing environment of hydraulic press,and considering the excellent characteristics of radar testing,a 120 GHz LFMCW?Linear Frequency Modulated Continuous Wave?radar displacement testing device is proposed.Based on the analysis of the structure characteristics and basic principles of LFMCW radar measurement,combining the time-frequency domain characteristics and processing methods of differential frequency signals,the design of radar piston displacement measuring device mainly includes five parts: microcontroller unit,modulation signal generating unit,transceiver integrated unit,baseband amplifier unit and power management unit.The microcontroller unit uses STM32 chip as the core for peripheral control and differential frequency signal processing,ADF4169 frequency synthesizer chip is used to generate the required modulation signal,TRX₁20_RFE monolithic millimeter wave integrated circuit based on Silicon Radar is used to complete the radar front-end transceiver and differential frequency signal output.After filtering,amplification and acquisition of weak differential frequency signal,the distance information is transmitted through serial port.The beat frequency signal sampled by ADC is processed by wavelet de-trending with Matlab,which makes FFT close-range processing more stable.In order to improve the testing accuracy,a linear frequency modulation Z transform?CZT?and spectral maximum estimation compensation algorithm based on FFT technology are adopted in the beat signal processing.After the simulation analysis and actual signal processing verification,the best processing scheme of the real-time processing unit is selected.The experimental results show that the ranging accuracy can reach 2cm within the range of 1.5m for a single static target.