This paper does a research on turbocharged diesel engines both of air-path or speed-path alone, and proposes a cooperative control strategy of air and speed-path two loop TDE system. For modern diesel engines, accurate air/fuel ratio (AFR) and exhaust gas recirculation (EGR) rates design are very important to meet the requirements of emission standards of NOx and PM. For the EGR and AFR rates are controlled by the EGR and the variable geometry turbine (VGT) actuators, we propose a fourth-order simplified nonlinear model which takes into account the crankshaft speed dynamics and the air-path dynamics for the turbocharged diesel engine. The controller for the speed-path we designed which is based on Lyapunov function is used to track the desired engine speed. For the air-path, a sliding mode controller based on exponential reaching law which uses the concept of total disturbances to control the EGR and VGT valve is designed. In order to estimate the disturbances in the system, we proposed a 2nd-order extended space observer (ESO). The simulation results show that the sliding mode controller which utilizes observer and reaching law can alleviate the chattering problem obviously and the proposed two-loop structure dynamic model exhibits excellent performances in tracking desired signals and overcoming the system disturbances. In the presence of disturbances, the system can still observe the total disturbances, including the unmodeled dynamics and actuator faults, accurately and timely.

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In this paper, a nonlinear observer based sliding mode control (NOSMC) approach for air-path and a model-based observer for oxygen concentration in the diesel engine equipped with a variable geometry turbocharger and exhaust gas recirculation is introduced. We propose a less conservative observer design technique for Lipschitz nonlinear systems using Ricatti equations. The observer gains are obtained by solving the linear matrix inequality (LMI). Then a robust nonlinear control method, sliding mode control is applied for the states of intake and exhaust manifold pressure and compressor mass flow rate for the sake of the minimization of emissions. The proposed NOSMC controller is applied on a mean value model of turbocharged diesel engine. Besides this, a model-based observer is developed to estimate the oxygen concentration in the intake and exhaust manifolds owing to its significance in reducing emissions of diesel engines. The validation and efficiency of the proposed method are demonstrated by AMESim and Matlab/Simulink co-simulation results.

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