Design And Implementation Of Embedded Software For Real-time Acquisition And Processing Of Vehicle Exhaust

With the rapid and sustainable development of industrialization and urbanization in China,effective and frequent monitoring of vehicle exhaust is needed to prevent the air pollution caused by vehicle exhaust emission.Vehicle exhaust remote sensing detection technology can detect the concentration of vehicle exhaust in normal running.This technology can carry out long-distance induction measurement of vehicle exhaust using optical principle,which improves the detection speed and efficiency,and gradually becomes the preferred technology of vehicle exhaust pollution detection.The technology mainly use infrared light,ultraviolet light and green light source for the detection of signal source,photoelectric detector calculate different concentrations of gaseous pollutants and particulates opacity.The technology uses multiple light sources,so it needs to collect,store and transmit a large amount of optical data in real time,and meanwhile process a variety of control instructions and obtain optical information in time.Software layered architecture design has the advantages of high cohesion,low coupling,high development efficiency and high readability.According to the functional requirements of vehicle exhaust real-time acquisition and control system in remote sensing detection technology,the software layered architecture for real-time acquisition and control of vehicle exhaust is designed on the MPLAB X IDE software development platform by using the advantages of high cohesion and low coupling,high development efficiency and high readability of layered software design and the embedded software development technology and the information processing technology of PIC microcontroller.The embedded software architecture is divided into hardware layer,hardware driver layer,operating system layer and application task layer,and the Free RTOS real-time operating system is transplanted on PIC microcontroller to implement the priority scheduling based on SPI communication task,USB communication task,smoke signal acquisition task,network communication task and system security task division.The inter task synchronization and communication are realized by using semaphore and event methods of Free RTOS operating system.Finally,the functions of vehicle exhaust data collection,instruction control of microcontroller,signal transmission and processing,and communication with industrial computer are successfully realized.The DOAS technique is studied in depth,and the concentration inversion of exhaust with narrow absorption band(NO)is realized by polynomial fitting and least square method,so as to improve the sensitivity of UV signal detection.The polynomial fitting model is used to realize the nonlinear correction of the measured exhaust concentration and further reduce the measurement error.The static test environment of vehicle exhaust remote sensing detection was set up,and the gas concentrations of CO,CO2,NO and 1,3 butadiene were measured.The error of the test results fully complied with the national measurement standard.The gas concentration test shows that the vehicle exhaust real-time acquisition and control system based on embedded software fully satisfys the functional requirements of the system,and also confirms the real-time and stability of the system achieve the expected requirements.