Optimal analysis for cylinder recognition control of electronically controlled diesel engine based on window checking

Abstract: A complaint against the electronic control diesel engine is that it starts "one second slower" than other conventional mechanical pump diesel engines. That is because that on conventional mechanical pump diesel engines, the phase position between the fuel supply sequence of fuel systems and fuel pump cams is fixed in the starting process and there is no need to cylinder recognition. While on the electronic control diesel engine, the controller cannot determine the specific phase of diesel engine until it receives a sufficient number of crank and cam signals, so as to need cylinder recognition. The establishment process of the control timing sequence at the beginning of the starting (cylinder recognition control) is directly determining the duration of the diesel engine starting process. The cylinder recognition control is one of the most basic parts of the electronic control diesel engine management system. In this work, in order to shorten the process of cylinder recognition, a quick and reliable method to determine the precise phase of diesel engine by possibly reducing the crank and cam speed signal is studied. Firstly, according to the firing order of the target diesel engine, speed signal, and the phase of the electronic control system have been designed, using two sets of speed computing devices of cam and crank, not only can shorten the time of cylinder recognition, but also can help to improve the reliability of the control system. And then two methods are proposed in this work, one is judge mode of counting teeth, the other is judge mode of checking window. By analyzing the working principles of the two modes, judge mode of checking window needs less cam and crank signal to cylinder recognition. In the judge mode of counting teeth, at least two cam signals are necessary for cylinder recognition and in the worst case, the cylinder recognition will not succeed until the engine spins two revolutions. While in the judge mode of checking window, the most rapid cylinder recognition only takes 70° crank angle and in the worst situation, the engine only needs to rotate around a little more than that cylinder recognition can succeed. Based on the finite state machine, drive control software of complex driver layer was developed for cylinder recognition control of window observation. Finally, the engine starting test has been done on the engine test bench in order to verify the feasibility of cylinder recognition strategy. By using the cylinder recognition of checking window, the fastest detected two cam teeth can achieve cylinder recognition success in the ideal condition and the cylinder recognition time is 0.3s, in the worse condition the successful cylinder recognition takes 1.3 turn and the time is 0.5s. Besides the starting success rate and time is statistic and compared between the above two modes, by using cylinder recognition of checking window, the success rate of starting has been increased by more than 10%, reaching 100%, and the starting time has been shortened from 1.5s to within 1s. Above experimental results show that the strategy is effective and feasible. The achievement of this strategy not only improves the preferment of electronic control diesel engine in starting condition but also perfects the timing control of electronic control system.