EGR-VGT Diesel Engine

Recent years,the fast development of industry and highway traffic has caused great pressure on energy and environment.As a major power source,diesel engine has been booming for its good dynamic performance,economic fuel consumption and long service life.However,many cities in China occurred the "Haze" phenomenon in recent years,together with the increasing number of diesel engine vehicles,which make the energy problem more serious.The exhaust emission pollutants mainly include NOx and PM,and they are the major causes of Haze.In order to guarantee the good dynamic and low emission performance simultaneously,one effective approach is to take the speed loop and the air path of the diesel engine into account together.Therefore,for diesel engine with EGR(Exhaust gas recirculation)and VGT(Variable geometry turbocharger),especially for the unmeasured states in real application,an unknown state observer based control strategy is proposed in this paper,considering the speed path and air-path subsystems as objectives at the same time.Specifically:Firstly,in the air path,owing to the precision of diesel engine and accuracy problem of sensors,some states of air path system are difficult to be obtained from the measured output.To reduce its impact on control performance,this paper estimated these states by state observer,and proposed two different observer design approaches—Riccati equations and invariant ellipsoids method respectively,obtaining the observer gain matrices with the Linear Matrix Inequality(LMI).Secondly,an unknown state observer based sliding mode controller for air-path is proposed.The control objectives are to track the intake manifold pressure,exhaust manifold pressure and compressor mass flow rate in face of the existence of the unmeasured states.Besides,the real control inputs of air-path are valve positions of EGR and VGT.For simplicity,this paper firstly regards EGR and VGT gas mass flow rates as control inputs,then inverts the gas mass flow rates into corresponding valves positions by flow-position transformation module.Then for the speed loop,a Lyapunov function controller is proposed.The control objective is to achieve good trajectory tracking of engine speed,in the presence of outer load and friction disturbances.Consequently two control subsystems are combined together to construct the complete two-loop control system of the diesel engine.To demonstrate the performance of the proposed control strategy,this paper also use the emission model(particles)and influence factor(air-fuel ratio and EGR rate)to verify the control results.Finally,a two loop diesel engine model is also built in AMESim platform,and the co-simulation of AMESim&MATLAB/Simulink is realized too.The effectiveness of the proposed unknown state observer based control approach is further demonstrated by the co-simulation results.