Study On The Graphical Display Of Time-Frequency Analysis Results Used In Embedded Devices

Most of the embedded fault diagnosis devices can only provide two-dimensional(2D)forms,such as time-domain waves or frequency spectrum waves.Users obtain no information about the appearance of different frequency components varying with time in signals,of which time-frequency spectrogram is an important visual tool to display the information.Mechanical fault signals are usually time-varying signals.The conventional time-domain or frequency-domain analysis cannot fully describe the real-life signal,whose frequency content varies with time.To gain frequency-related,as well as time-related information,of non-stationary and non-periodic signals,it is recommendable to use analysis in time-frequency domain.Short-time Fourier transform(STFT)is not only one of the most commonly used linear time-frequency transforms,but also used in some other time-frequency analysis of its deformation form.It can effectively analyze time-varying signals.Three-dimensional(3D)graphic display enables users to get more abundant fault information intuitively,and can guarantee the accuracy of the analysis results.The main purpose of this paper is to design and implement the time-frequency analysis and 3D graphical display portion of portable fault diagnosis devices based on embedded technique,time-frequency analysis algorithm and computer graphics algorithm.The main research contents are as follows:(1)Aiming at the tradeoff problem of long window and short window used in STFT,an adaptive algorithm of window length selection is proposed,and the simulation signals are analyzed to verify the effectiveness of the method.(2)According to the characteristics of the joint time-frequency distribution matrix and the specific application requirement of embedded device platform,a fast 3D spectrogram mesh surface generation algorithm,also known as SMSG algorithm,is proposed.The experimental results show that the algorithm can save considerable time,and has small memory occupancy.The method can used in real-time and efficient embedded system applications.(3)The ARM and DSP embedded solution is proposed based on analysis of the system function.The algorithms are implemented on embedded devices,in which the signal processing part and the calculation of 3D display parameters are finished by the Digital Signal Processor(DSP),and the display module is realized by a Thin Film Transistor Liquid Crystal Display(TFT-LCD)screen driven by STM32.The communication protocol between two modules is studied and implemented.Considering the storage of intermediate variables,the complexity of algorithm and the efficiency of algorithm implementation,the programs of this system are optimized.(4)Three-phase permanent magnet synchronous motors(PMSM)are taken as the research objects,tests are carried out on the experimental platform.The experimental results obtained in embedded devices are compared with the simulation results generated by MATLAB software,which proves the effectivity of the algorithms and the validity of practical application.