Design Of Vehicle Air Particulate Concentration Detection Device

As a common means of transportation for modern people,people spend more and more time in the car every day.Due to the space inside the car is relatively narrow,closed and the air flow is not smooth,the air inside it is easily turbid.As people’s requirements for the comfort of the ride environment increase,people are paying much more attention to the air quality inside the car than before.Being a main pollutant affecting air quality,suspended particulate matter in the air not only seriously endangers human health,but also adsorbs other pollutants in the vehicle,which in turn causes greater harm to people inside the vehicle.To this end,based on the principle of light scattering method combined with embedded technology,this thesis designs a vehicle airborne particle concentration detection device.The detecting device performs real-time detection and alarm on the total suspended particulate matter(TSP)concentration and temperature and humidity of the vehicle,performs short-range communication with the user mobile terminal,and transmits the collected related data information to the corresponding electronic control unit of the automobile for the automobile electronic.The control unit takes corresponding measures when the concentration of particulate matter exceeds the standard.In addition,the detecting device also provides a function of recording the use time of the particle concentration detecting means in the device to remind the user to replace it in time when it reaches the service life.The main works done in this thesis are as follows.1.The thesis firstly introduces the principle of particle group light scattering detection of particle concentration,which is used as the theoretical basis for detecting particle concentration.Then,it analyzes the function and performance requirements of the detection device and determines the overall design framework of the device.The device is divided into two parts: the particle concentration detection front end and the on-board particle concentration collection system.2.The front end of the particle concentration detection was designed based on the principle of light scattering.The detection front end is used to sense the concentration of particulate matter in the air and output a voltage signal proportional to the concentration.It is divided into two parts: the optical path system and the circuit system during design.The selection of the light source and photo detector and the structural design of the optical cavity are completed in the optical path system part.In the circuit system part,it is fulfilled that the light source driving and modulation circuit and the design of the signal conditioning circuit for converting and amplifying the weak current signal output from the photo detector.3.The hardware design of the vehicle particle concentration collection system was completed.The system takes the main control module as the core,uses the ADC module to collect and convert the voltage output from particle concentration detection front end,and uses the temperature and humidity detection module to collect the temperature and humidity data inside the vehicle.The control alarm module alarms when the concentration exceeds the standard.The TFT-LCD display module displays the working status of the system and the relevant environment information in the vehicle.The data transmission between the device and the mobile terminal is realized by the Bluetooth module,and the data information collected by the system is transmitted to the electronic control unit of the vehicle through the CAN communication module,and the modules are respectively performed for these modules.Design the entire system hardware PCB after design.4.The software design of the vehicle particle concentration collection system was completed.Considering the many functional tasks of the acquisition system,in order to improve the real-time performance of the system,the software design of the collection system is based on the μC/OS-Ⅲ operating system.In the system software design,the μC/OS-Ⅲ operating system is transplanted and the multi-task concurrent program design based on μC/OS-Ⅲ is divided.There are seven tasks catalogued according to the system functions: data acquisition task,particle concentration calculation and alarm task,TFT-LCD display task,communication task,button detection task,independent watchdog task,and initial task.These seven tasks are assigned priorities and are designed for each task.Finally,an experimental test of the vehicle air particulate concentration detecting device was carried out,including an experiment of the particle concentration detecting front end and a functional test of the entire vehicle air particle concentration detecting device.Among them,the calibration experiment and the preliminary analysis of its measurement error were completed in the experiment of detecting the front end;the alarm function,CAN communication function and Bluetooth data transmission function were mainly tested in the functional test of the detection device.The test results show that the front end of the particle concentration detection has a good ability to perceive the change of the particle concentration;the vehicle air particle concentration detection device displays the information normally,the alarm is timely and the data transmission is accurate,and the expected design goal is achieved.