Development Of Dual-core Integrated Engine Control System Oriented At In-cycle Combustion Feedback Control

In-cylinder pressure based combustion feedback control is regarded as a keyplatform technology for the development of future advanced internal combustionengines. In terms of control frequency, there are two types of combustion feedbackcontrol: cycle-to-cycle and in-cycle. Research on cycle-to-cycle combustion feedbackcontrol has been done by several research institutes in abroad as well as in China. Theresearch results show that through cycle-to-cycle combustion feedback control, theaverage performance of the engine in steady states can be optimized. However, it cannoteliminate the control deviation of the combustion state caused by high-frequencycycle-to-cycle variation. In order to solve this problem, an in-cycle combustionfeedback control oriented high-performance dual-core engine control unit is developedin this paper. Start of combustion is selected as the feedback signal. A start ofcombustion detection method based on motored cylinder pressure online estimation isdeveloped. At the end of the paper, research is done on the influence of in-cyclecombustion control on the cycle-to-cycle variation of φCA50when the EGR rate of theengine is fluctuated.The dual-core integrated engine control unit contains two micro-chipcomputers. One is used to process the cylinder pressure related information, andthe other is used to perform the normal engine control tasks as well as in-cyclecombustion feedback control algorithm. SPI bus is used to realize high-speeddata exchange between the two micro-chip computers.Through thermodynamic analysis on the motored process of the engine, theconcept of equivalent isentropic exponent is proposed. Experimental research isdone to identify the relationships between equivalent isentropic exponent andcrank angle as well as in-cylinder temperature. According to the research results,a motored in-cylinder pressure estimation model, in which the motored cylinderpressure trace is calculated from one reference point located at the trace, isestablished. For a fixed reference point, only the motored cylinder pressure tracewithin the10°crank angle after the reference point can be accurately estimated.Therefore, a varied reference point estimation method is developed. The experiment results show that, by using this method, the motored cylinderpressure estimation error from50°CA BTDC to40°CA ATDC is below0.15MPa.Taking0.2MPa pressure difference as the criteria for detecting whether thecombustion starts, a crankshaft pulse signal trigged SOC detection algorithm isdesigned. This algorithm is executed periodically from50°CA BTDC until thestart of combustion is detected or the crank angle reaches to40°CA ATDC.Experimental validation show that the detection results of this algorithm isaccurate, reasonable and reliable.Taking injection timing as the control variable, aiming at reduce theinconsistency of main injection phase under different EGR rates, an in-cyclecombustion feedback control algorithm is designed. When the EGR rate isfluctuated manually, the cycle-to-cycle variations of φCA50with and withoutin-cycle combustion feedback control are tested. The experiment results showthat, after using in-cycle combustion feedback control, the cycle-to-cyclevariation of φCA50is significantly improved.