Study On Modeling And Nonlinear Control Method For Turbocharged Gasoline Engine Air-path System

To meet the increasing demands of customer for vehicle performance and to satisfy stringent emission standard,the turbocharged gasoline engine emerges at the right moment.The turbocharged technology of engine increases the amount of the intake air via recycling the energy of exhaust gases,so that the output torque of the engine with a certain displacement can be improved effectively.In addition,as the combustion in cylinders can be more fully,this technology enables to generate higher fuel economy and less emissions.Therefore,the turbocharged technology of engine obtains automobile manufacturers' favor.The structure of turbocharged gasoline engine which integrates a suitable turbocharger into traditional gasoline engine,increases the complexity and coupling of gasoline engine,and puts forwards a great challenge to the air-path system modeling and control of turbocharged gasoline engine.In this paper,based on the control framework of torque requirement,the modeling and nonlinear control method is proposed for four-cylinder turbocharged gasoline engine.According to the structural characteristics and working mechanism of the turbocharged gasoline engine,it is divided into several sub-models based on the idea of modular modeling.The several sub-models is built in advanced simulation software AMESim and the mathematical expressions of each module are given.Then,the turbochared gasoline engine model is obtained by the combination of each sub-model and the matching of model parameters.By comparing to the natural aspiration gasoline engine with the same displacement,the functional rationality of the turbocharged gasoline engine is verified.At the same time,a control-oriented mechanism/MAP hybrid description model is summarized from the mathematical model of the air-path system,while the nonlinear factors which are difficultly described in mathematical expression such as the volumetric efficiency,the isentropic efficiency of turbine and the mass flow rate through turbine,are retained in the form of MAP commonly used in engineering.Towards the practical engineering application,on the basis of the decoupling control scheme,aiming at the characteristics of long regulating circuit,strong nonlinearity and large inertia in air-path system,a nonlinear dual closed-loop control scheme is designed for boost pressure control.First,the outer-loop controller including a neural network feedforward controller and a PID controller is built to generate the desired turbine speed for tracking boost pressure.Then,to track the desired turbine speed,a Backstepping controller is designed to adjust wastegate,and the system stability is ensured by constructing the Lyapunov function during the controller derivation.Finally,in the environment of joint-simulation of MATLAB/Simulink and AMESim,the simulation results demonstrate the effectiveness and anti-disturbance performance.Aiming at the problems of the dynamical coupling between intake manifold pressure and boost pressure and the difficulty in mechanism modeling,a coordination controller based on nonlinear neural network predictive control is designed for turocharged gasoline engine air-path system.First,in order to reduce the model complexity and restrain the influence of time-varying parameters,a predictive model of air-path system based on online learning neural network is established.By comparing with the AMESim model,the dynamic behaviour and the predictive precision of the predictive model are verified and analyzed.Then,based on the neural network predictive model,the objective function is extracted from the control requirements,and the coordination control of air-path system is converted to a multi-input and multi-output optimal control with constraints.On the framework of predictive control,the quantum-behaved particle swarm optimization is applied to solve the objective function and then the control input satisfying the system is obtained.Finally,in the environment of joint-simulation of MATLAB/Simulink and AMESim,the simulation results show the advantages of the coordination control method.