Design Of Vehicle Exhaust Gauge Based On Non-dispersive Infrared Method

Vehicle exhaust contains a variety of harmful compounds,such as carbon dioxide,carbon monoxide,hydrocarbons and nitrogen oxides,which can quickly and accurately obtain the concentration information of pollutant gases and become an important part of environmental protection.In order to implement the simultaneous detection of carbon monoxide,carbon dioxide and hydrocarbons in vehicle exhaust,a new type of gas gauge design based on the basic principle of non-dispersive infrared method(NDIR)is proposed.First of all,the theoretical modeling of gas concentration measured by non-dispersive infrared method is carried out based on Lambert Beer's law in this paper.Besides,a multi-channel detection method is introduced and the working mechanism of gas concentration calculation is deduced.It adopts a new wide spectrum thermal radiation infrared light IRL715,a cylindrical air chamber structure and a four-channel thermopile detector TPS4339 to raise the accuracy of the measurement.Secondly,with STM32 as the core processor of the control circuit,the design of peripheral circuits such as light source driving circuit,signal processing circuit and single chip control circuit is realized.Simultaneously,the STM32 MCU is used for software development of the host computer and serial communication with the computer,which reduces the difficulty of data acquisition and the overall complexity of the system.In order to eliminate the interference of error,the support vector machine algorithm is introduced to modify the model,combined with the adaptive particle swarm optimization algorithm to optimize the parameters of the kernel function,which is applied to the multi-component gas quantitative analysis.Finally,calibration test and performance experiment are carried out due to the construction of experiment environment for the vehicle exhaust gas sensor.The ratio of the corresponding gas channel to the reference channel is measured,and both values are applied to PSO-SVM model to obtain the nonlinear function.This function is substituted into the data set of the test sample,so that the concentration of the gas to be tested is reversed by the ratio of the gas channel to the reference channel.The experimental results show that the relative error of the gauge is within the interval of ±1%.Such sensor has achieved similar product levels in terms of sensitivity and stability,which can meet the demands of measurement and analysis of vehicle exhaust.