Design and application of mobile automobile exhaust gas analyzer
Mobile automobile exhaust gas analyzer
After the car is started, the mobile car exhaust gas analyzer starts the exhaust pump to sample the exhaust gas from the car exhaust pipe, and enters the gas analysis component IRidium100 through dust removal, oil removal, and water filtration treatment, and performs the internal infrared processing to collect CO, CO2, HC Concentration data, and then the exhaust gas enters the external O2, NOx sensor to collect the corresponding O2, NOx exhaust gas concentration data. These data are digital results after signal detection, amplification and processing, and are transmitted to the microprocessor through the RS-232 serial port of IRidium100. The microprocessor is processed and stored by algorithms such as statistics and averaging, and the data is encapsulated according to a custom-made environmental protection communication protocol, and then transmitted to the designated upper management platform through GSM / GPRS / CDMA data communication or short message communication. There is an operation menu on the LCD of the analyzer. The user can operate the menu through the keyboard to obtain the working status and exhaust gas analysis results. The LCD can display the specific detection data results of CO, CO2, HC, O2 and NOx. The structure of the mobile car exhaust gas analyzer is shown in Figure 1.
Hardware design of the mobile vehicle exhaust gas analyzer
The gas analysis component of the exhaust gas analyzer adopts IRidium100 gas analysis module of British CITY company. It is processed by the internal infrared method to collect the concentration data of CO, CO2, and HC. IRidium100 can obtain O2 and NOx concentration data through the external O2 sensor and NOx sensor.
The single chip microcomputer system uses C8051F020, which has two serial ports, one of which is connected to IRidium100, and the other is connected to GSM / GPRS or CDMA communication module, and uses a custom communication protocol to exchange data with the upper management platform.
The input power is directly connected to the car power DC12V ~ DC24V, converted to DC12V and provided to IRidium100, and at the same time provides a set of DC5V power output for single-chip and communication modules.
The single chip microcomputer controls the operation of the sampling air pump through the relay, and mainly controls the actions of intake and exhaust. The relay controls the suction pump, which is normally off. When the system starts to analyze the exhaust gas, the relay is energized to operate the suction pump for 5 minutes.
The GSM module uses MC37I from Siemens. The module is a complete mobile communication industrial module. The CPU controls and transmits data through the serial port, and can transmit data including SMS, CSD, GPRS, etc. The control of the module by the CPU is the AT command, which complies with the ETSI standards GSM 07.07 and GSM 07.05.
Software design of mobile vehicle exhaust gas analyzer
Working mode of exhaust gas analyzer
The special vehicle exhaust gas analyzer is designed with four working modes:
â‘ Manual working mode, through the keyboard to control the menu in the power-on state, to perform a process of exhaust gas analysis;
â‘¡Automatic working mode, when the time set every day is reached, an exhaust gas analysis process will be executed automatically;
â‘¢ Command work mode, when receiving the command of the upper management platform, execute an exhaust gas analysis process;
â‘£Calibration work mode, enter through the menu selection in the power-on state, and conduct an exhaust gas calibration process.
Among them, the manual work mode and the calibration work mode are triggered by the main menu provided by the LCD, which is triggered by the key value entered on the keyboard at the scene, and then execute the corresponding control commands.
In manual operation mode, when exhaust gas analysis is required immediately, manually enter the main menu to select, and then select an exhaust gas test, or choose to perform n exhaust gas tests (n is entered by the menu setting option), one or more exhaust gas analysis process . The automatic working mode is compared with the real-time clock in the RTC, which can be configured, and triggered after the time is equal to perform an exhaust gas analysis process. The automatic working mode is the default mode.
The command work mode is triggered by commands issued by the upper management platform, and executes a corresponding exhaust gas analysis process. In the command working mode, the instrument receives the remote command "collect exhaust" from the communication module through the serial port. At this time, the instrument automatically performs an exhaust gas analysis process.
In the calibration work mode, in the first start-up state or when there is a need for calibration, the inlet of the suction pump is connected to the standard exhaust gas, and the main menu is manually entered to select the calibration range and a calibration process is performed. The calibrated exhaust gas analyzer calibrates the reference test reference point, which can improve the accuracy of exhaust gas detection.
Selection of key command sequence of exhaust gas analysis module
According to the IRidium100 user manual, the key command sequence for data collection for the CITY IRidium100 exhaust gas analysis module is as follows.
Range calibration of exhaust gas analyzer
â‘ RESET (command number: $ 30), use this command before calibrating the exhaust gas analyzer. After the reset command is issued and the response is received, the reset is successful.
â‘¡ZERO ($ 35), zero calibration before collection, half a minute after starting the suction pump, and then send the zero calibration command, within one minute after receiving the zero calibration completion response, that is, zero calibration is successful, and the suction pump stops working at this time.
â‘¢SPAN SPECIFIED CHANNELS ($ 36), calibrate the range command. After the zero calibration is completed, manually connect the exhaust gas standard gas and perform the calibration operation. At this time, the exhaust pump is started. After 15 seconds of ventilation, the calibration command is sent to the exhaust gas analysis module. The LCD displays the instantaneous value and stops the exhaust pump after receiving the calibration completion response. , And stop the operation of the serial port at the same time.
Exhaust gas data collection, ie an exhaust gas analysis process
â‘ RESET ($ 30), this command is issued before each exhaust gas analysis command is executed. The reset is successful after the reset command is issued and the response is received.
â‘¡ZERO ($ 35), zero calibration before collection, half a minute after starting the suction pump, and then send the zero calibration command, 1 minute to receive a zero calibration completion response that zero calibration is successful. At this time, stop the suction pump.
â‘¢COMPENSATED DATA ($ 31), data can be collected after zero calibration is completed, let the air pump work for half a minute before sending the data collection command, and then collect the data after 10 seconds, and collect a group every 10 seconds. The LCD displays the instantaneous value, and the average value is calculated as the final display after the collection process is completed (five data collection). After collecting 5 times, stop the operation of the serial port, and at the same time stop the work of the suction pump.
Software process design and implementation
The basic logic of the program flow is that the main program is triggered according to the conditions in the four working modes and sends the corresponding command to the CITY IRidium100 exhaust gas analysis module. After the module executes the command, it returns the execution result / status data. The main program displays the result data on the LCD on the one hand and sends it to the communication device on the other hand, which is transmitted to the upper management platform by the communication device.
When the command of the upper management platform is received, or the keyboard triggers manual execution of exhaust gas detection, or when the automatic detection time is reached, the action of performing exhaust gas detection is started. After an exhaust gas analysis process, set a flag that has been tested that day.
The main menu of the LCD is as shown below, and the keyboard menu is operated through the up key, down key, + key,-key and confirm key, and the corresponding command execution is triggered.
"1.Show SetTIngs", // Parameter display
"2.Setup", // Parameter setting
"3.Analysis 1 TIme", // Manually perform an exhaust gas detection
"4.Analysis n TImes", // Manually perform multiple exhaust gas detection
"5.CalibraTIon Zero", // School Zero
"6.Calibration Span", // Calibration Span
"7.Show Date / Time", // Show RTC time
"8.Setup Date & Time", // Set RTC time
"9.Factory Default", // Restore the default detection range
"10.RETURN", // Return the result data measured in the four working modes are sent to the communication module through the serial port. The test result data format is as follows:
"CO = xx.xx%; CO2 = xx.xx%; HC = xxxxxppm; O2 = xx.xx%; NOx = xxxxxppm;". Conclusion
This design uses C8051F020 as the core single-chip microcomputer system to control the work of Iridium 100, and realizes the detection of CO, CO2, HC, O2, NOx concentration in automobile exhaust, and transmits the detected concentration data to the remote upper management platform through SMS data transmission . The prototype designed and implemented was tried in an environmental protection bureau in Xinjiang, and the field test data was approved by the environmental protection department.
Reference materials:
[1] CITY Corporation. Iridium Specification.pdf
[2] CITY IRIDIUM OPERATING INSTRUCTIONS.PDF
[3] Hu Hancai. The principle and interface technology of single chip microcomputer [M]. Beijing: Tsinghua University Press, 1993.
[4] RJ Case. Photodetector and Infrared Detector [M]. Translated by Dong Peizhi et al., Beijing: Science Press, 1984
[5] Xu Aijun. Principle and design of intelligent measurement and control instruments [M] Beijing: Beijing University of Aeronautics and Astronautics Press, 1995
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