Optimization Design Of Peak Detection Circuit And Energy Spectrum Storage And Control Module For Density LWD Logging Tool

The measurement principle of the Density LWD technology is to obtain the formation characteristics by using the signal generated by the reaction between the ray from the artificial radioactive source and the formation medium.The Density LWD Tool is an instrument that uses Density LWD technology to emit radioactive gamma rays into the formation,collect signals returned from the formation,and then process and calculate the formation density.The current Density LWD Tool has some shortcomings in pulse signal peak detection,data storage,data download and vibration measurement mechanism.Firstly,the maximum pulse signal processing frequency of the peak-detection circuit of Density LWD Tool is lower,only 200 kHz.Secondly,The NAND Flash controller of the energy spectrum storage and control module of Density LWD Tool has insufficient data correction and bad block management.First,the instrument uses an ECC check algorithm based on Hamming code.This check algorithm can only correct 1-bit error for 1024-bits data.Under the conditions of high temperature in underground mines,this error correction capability is insufficient.Second,the bad block management method based on the block jumping strategy is adopted.Although this method is simple to operate,it causes the phenomenon of discontinuous in memory addresses.Thirdly,the data download rate is only 0.78 Mbps,which takes a lot of time to download memory data.Finally,only measuring the vibration intensity once in a logging cycle,so as to characterize the vibration condition of the logging cycle.This thesis first analyzed the functional requirements and the working flow of Density LWD Tool,and determined the tasks and design requirements of the energy spectrum storage and control module and the peak-detection circuit.First,a peak-detection circuit based on analog integration and digital differentiation is designed according to the index requirements of peak-detection circuit,so as to improve the maximum processing frequency of the pulse signal.Then,according to the functions,workflow and deficiencies of the energy spectrum storage and control module,it is determined to use “FPGA + MCU” as the hardware framework to design an optimization version of the energy spectrum storage and control module,including hardware circuit and software logic,so that the optimization version can achieve correcting 32-bits errors for 8192-bits data,the memory address is always continuous.Data download rate up to 5Mbps.Continuously measuring the vibration intensity in a logging cycle,and use the number of times that the measured vibration intensity is greater than the threshold vibration intensity to characterize the vibration intensityFinally,this thesis verifies the performance of the peak-detection circuit through simulation experiments.Through a series of experiments,the energy spectrum draw function,the storage function,the fast download function and the vibration measurement function of the energy spectrum storage and control module are verified.The experimental results show that the energy spectrum storage and control module and the peak-detection circuit of Density LWD Tool basically meet the optimization design requirements.