Gasoline Engine Control Strategy On Idle Working Condition

Idle speed condition which has close relation to the engine emissions and energy consumption. It is one of the important working condition of engine,and engines operate under this condition lots of the time.During the process of idle speed,air-conditioning compressor,power steering gear and automatic transmission changed suddenly,and these disturbance factors make the working-engine speed fluctuating,instability or even flameout. So in order to meet the demand of the auto emission regulations which become more and more strict today,it is especially important to control the idle speed and keep it stable as far as possible.A lot of factors should take into consideration when controlling the idle speed of the engine,such as the uncertain lagging time of the system,the disturbance and the noise of sensors signal measurement,the effect of environment and the parametric variation with aging and frication etc.All these factors increase the instability of engine control.The target of engine idle speed control is composed of:1) keep the Engine speed around a certain value;2)reduce engine fuel consumption;3) avoiding large engine speed deviation even sudden load disturbance emerged;4)required engine air intake within the ability of throttle.Firstly,the dissertation introduce many methods to meet the requirements of engine idle speed control.A lot of researchers had taken efforts to fulfill the requirements of ISC. Then an mean value engine model at idle working condition was developed according to the physical model and engine test map data.And the dissertation analyse the uncertainty of the model.Idle speed regulators are nowadays mainly designed by using the throttle opening and the spark advance as control variables.The throttle governs the amount of air supplied by the engine and provides large control authority,but is relatively slow due to the transportation phenomena inside the intake manifold.On the contrary,the spark advance provides a much faster control action,but must be used only in transient conditions and with limited variations to prevent combustion instabilities and engine stall.So firstly,the constitution and working principles of the automotive electronic throttle control system were introduce.An non-linear electronic throttle model is setup in simulink.The general structure of the controllers consists of a Input shaping subsystem and Baekstepping controller that deal with the nonlinearity of the electronic throttle system.Secondly in order to improve the performance of fuel economy,air-fuel ratio control is introduce by state observer.Thirdly,a robust controller based LMI is formulated.The validation by Matlab/Simulink indicated that the controller would greatly reduce the idle speed's change and fluctuation.Finally,a hardware-in-the-loop(HIL) testing platform based on xPC Target is developed.And the controller that introduced here are tested in this platform.The result of simulation shows that the control strategy has been veried experimentally.The dissertation mainly consists of five parts:Firstly,especially for the four-stroke four-cylinders gasoline engine,the general methods of modeling was discussed.Using the mean value model theory and the basic theory of thermodynamics,an mean-value based gasoline engine model was developed,including dynamic model for intake manifold,static model for throttle body,static model for cylinder air induction,fuel path dynamics,torque production and engine speed dynamics. Using the engine real-time simulation software en-DYNA,some important coefficients in gasoline engine model was determined.The total nonlinear engine model is developed by Matlab/Simulink toolbox.Secondly,the constitution and working principles of the automotive electronic throttle control system are introduced.An non-linear electronic throttle model is setup in simulink. The general structure of the controllers consists of a Input shaping subsystem and Backstepping controller that deal with the nonlinearility of the electronic throttle system.By setting up the communication interface between CANoe and Matlab,the CAN nodes embedded automotive electronic throttle simulation system was used.The result of simulation shows that the Backstepping control strategy has been verified experimentally.Thirdly,in order to improve the performance of fuel economy,the model based control strategy and algorithm is applied to air-fuel ratio control under steady conditions and transient conditions,which not only can reduce the calibrating work,but also can improve the robustness of the control system.Fourthly,basing the developed nonlinear model,a linear engine model was also developed at the engine model's operation point.It was necessary for robust H_∞controller design.For the purpose of controlling idle speed,throttle angle is the only control input that influences engine torque generation,and thus engine speed.The model has two state variables:manifold pressure and engine speed,the disturb input is load torque.It is also necessary to unitary the system's parameters for designing accurate controller.The parameter's uncertainty and hard constraints of the engine model were given after analyzing the system's inputs variables,state variables,output variables.And then an LMI-based robust controller was designed with the limits of the hard constraints such as throttle angle and manifold pressure are actually limited in a certain range.Finally the designed controller was used into both the linear model and nonlinear model,the simulation verified the engine speed could be controlled effectively with disturb load torque,at the same time, the requirements of input constraint and output constraint could be meet.Simulation also shows that model can be controlled well under parameters uncertainty.Finally,a hardware-in-the-loop testing platform based on xPC Target is developed. And the controller that introduced here are tested in this platform.It is a general procedure which can be adopted for all the active engine control systems,not only for their development but also for the verification of their reliability.The steps of the procedure are described in this paper.The specific application on which this paper is focused concerns ISC working condition.Simulation results are presented in order to validate the proposed model and compare it with the 'true' one.The result of simulation shows that the control strategy has been veried experimentally.