Design And Experimental Research Of Start And Idle Control In GDI Engine

Good starting and idling performance is a prerequisite for direct injection (GDI) engine subsequent runs. So, starting and idling control is the basis for the entire engine control. Not only to meet the low emissions and low fuel consumption requirements, but also to meet users of stability and reliability, especially start-responsive demand. However, the working condition of start and idle are complex and difficult to control. Therefore,the researching of control strategy of GDI engine start and idle has a vital significance.Based on the GDI engine electronic control unit (ECU) designed before, the paper focus on the start and idle control strategy designing for the GDI engine, and test the research on the1.8TGDI engine test bench. Also, the relevant strategies of sensor fault diagnosis is studied in order to ensure the input signal correctly. In this paper, the main content can be summarized as follow:(1) Researching the diagnosis strategy of sensor which associated with GDI engine start and idle control, involving the coolant temperature sensor, fuel pressure sensors, electronic throttle position sensor, crankshaft and camshaft position sensor. Diagnostic modalities include limit diagnosis and rationality diagnosis. According to the principles of diagnosis and evaluation, it has designed the corresponding failure mode protection strategy. Finally, observing the sensor and actuator corresponding signal in oscilloscope and verifying the sensor diagnosis strategy.(2) The GDI engine could be divide into motor starting, fire starting and after-starting stage according to the characteristics of start, and each stage of the control strategy is designed. Starting performance experiments in the engine bench were controlled on the same ignition timing and different fuel injection timing as well as the same injection timing and different ignition timing. The results show that60°BTDC injection timing and19°TDC ignition timing is starting fast.(3) Designing the electronic throttle control strategy. Using piecewise PID closed-loop control throttle opening, and holding the torque when the actual opening with the target opening deviation is less than±0.4%. Verifying the throttle can quickly stabilize in the target opening when in small opening.(4) Designing the idle control strategy, the idle condition is divided into stages of warming-up open-loop control and idle speed closed-loop control.Warm-up phase using open loop control strategy, namely the throttle opening according to the coolant temperature change to adjust; In idle speed closed-loop control, the output that is throttle opening increment is calculated by PID control. After adjusting the PID parameters in test verify, GDI engine idle speed can be controlled within±20r/min.