Development Of A Portable Dynamic Parameter Measurement Instrument For The Engine

The automobile engines run under unsteady operating conditions in themost of time, which results in40%~80%of emissions and fuel consumption.Therefore, the dynamic parameters measurement plays a very important rolein studying on transient characteristics of the parameters under differentoperating conditions of the engine and in improving transition processcontrol. However, the measurement of different engine parameters hasdifferent requirements on the measuring instrument. Dynamic parameters foranalyzing working process of the engine, such as in-cylinder pressure, needa dedicated equipment with high sampling frequency and high-speed,high-accuracy. Whereas, there is no needs of a very high sampling rate forelectronic control system of the engine, as it is constrained by the sensordynamic characteristics and the ECU processing capability. Therefore, thedata acquisition equipment with lower sampling rate and lower accuracy canbe used to measure dynamic parameters related to engine control. In thedevelopment or parameter calibration process of the electronic controlsystem of the engine, the acquisition of dynamic parameters only needs to bein agreement with the dynamic characteristics of the sensors in the vehicleand the sampling rate of the ECU or to be slightly higher rate.In general, the engine’s dynamic parameter measurement has two basicrequirements on the measuring instrument: one is the crankshaft-angle (CA）based external trigger sampling, that is, the equal interval sampling in crankangle domain; the other is rotation frequency measurement in synchronismwith analog acquisition to obtain the relationship between the instantaneousspeed and the measured parameters. At present, the most of domestic dataacquisition equipment, no matter what the high-end products or the low-endproducts, are equal-interval sampling, which can hardly meet the dataacquisition requirements of the rotating machinery. Aimed at dynamicparameters acquisition on the development of the electronic control systemof the engine and in vehicle experiments, a low-cost dynamic parametersmeasurement instrument was designed based on the Freescale16-bit dual-core microcontroller, which can achieve multi-channel synchronousacquisition and obtain dynamic information of the measured parameterswithin a long time through performing the sampling, transmission andstorage at the same time. The main research contents are as follows:1) Considering entirely dynamic response of the commonly used sensors,maximum engine speed, angle resolution of the crankshaft-angle basedsampling, the maximum sampling frequency and memory size of themicrocontroller, multi-channel synchronous acquisition requirements,network transmission rate etc. the performance index of the measurementinstrument was determined, and overall structure was designed.2) Hardware design of the dynamic measurement instrument. It includes theselection of the main controller and the core circuit design, the powersupply modules design, the analog signal conditioning modules design,the speed measurement modules design, the communication modulesdesign, the LCD drivers design and key-press detection modules designetc.3) Software design of the dynamic measurement instrument. It includes theFlash memory reading/writing programs design, the analog dataacquisition program design, the speed signal measurement proceduresdesign, the Ethernet communication program design, the LCD display andthe key-press response program design.4) The design of the background managing software. Main task of thebackground managing software is to monitor running status of themeasuring instrument and to manage collected data. The softwarefunctions include parameter setting of the measuring instrument,running-and-stopping control of the meter, receiving the data uploaded bythe measuring instrument and storing them in the database, time-domainwaveform display of the data and playback of the history data etc.5) Simulation verification and real testing. Developed dynamic measuringinstrument is tested by various ways: The measurement instrument isverified using the analog signals in different frequencies deriving fromthe signal generator. The measuring instrument is used to measuretemperature of the wide-range oxygen sensor LSU4.2in the closed-loopheating process. The actual tests under the steady-state operatingconditions and the acceleration/deceleration operating conditions areperformed on the test bench equipped with Xiali376engine and on the combined EFI engine/automatic transmission ABS test-bed equippedwith the Santana2000ARJ gasoline, respectively. The results show thatthe measurement data can truly reflect the dynamic process and cyclevariation of the various parameters of the engine, and the requirements onthe routine engine bench testing and in-vehicle testing can be meet by themeasuring instrument.