Control-oriented Modeling Based On TGDI And VVT Related Technologies

In order to cope with increasingly strict emission regulations and continuously improve the performance of gasoline engines,variable valve timing(VVT),Gasoline Direct Injection(GDI)technology and turbocharging technology have become the development trend of gasoline engines.The development of gasoline engine performance is greatly affected by the engine electronic control unit(ECU).Therefore,in the actual development process,a large number of verification and testing of the control strategy and control algorithm are needed.In the V-based development process,model-in-the-loop(MIL)simulation is an important part of TGDI engine control strategy development.Therefore,the establishment of control model and closed-loop verification of control strategy are crucial for its development.In this paper,the VVT system and output torque in the TGDI gasoline engine are studied.The hydraulic phase system is modeled by the system identification method on the Matlab/Simulink platform.The model-based idea is used to predict the output torque in real time.The control model is applied to the closed-loop simulation verification of the scavenging control strategy,and compared with the experimental data.The main work is as follows:(1)Identification modeling of hydraulic phase systems.The working principle of the phase system is analyzed,and the modeling idea of closed-loop identification is proposed.According to the physical structure of the phase system,the nonlinear model structure of the phase system is determined.Combined with the experimental data on the engine test bench,the step signal is taken as the input,the phase change is the output,and the identification is performed according to the steps of the system identification.Using different identification algorithms for identification,combined with experimental data to analyze different evaluation indicators,the identification model of the phase system was determined.(2)Model-based torque prediction.The gas exchange process of gasoline engine including scavenging and recirculating is studied in detail.The influence of VVT on the fresh charge in the cylinder and the residual amount of exhaust gas is analyzed.At the same time,in order to improve the calculation accuracy and real-time calculation under different working conditions,the idea of fitting correction and MAP interpolation is proposed.The real-time prediction model of the torque of the TGDI engine is combined with the crankshaft dynamics.The experimental data is collected as the model input on the engine test bench.The actual output torque is compared with the calculated torque of the model to verify the correctness of the established model.(3)Closed loop verification of the scavenging control strategy.Combined with the scavenging control strategy constructed in the previous stage of the research group,a scavenging control strategy was established under the Simulink platform,including the determination of scavenging conditions,the control of the valve timing and the scavenging feedback control.The segmented PID controller and the phase system identification model combine to form a closed-loop phase control model.The scavenging control strategy model is combined with the phase control model and the torque prediction model to form a complete closed-loop simulation model.MIL simulation,by turning the scavenging function on and off,can compare the torque changes under scavenging and non-scavenging conditions.At the same time,when the scavenging is turned on,it can be further explained by comparing with the scavenging output torque on the experimental bench.The correctness of the control strategy and control model.