Sliding Mode Control for Diesel Engine Using Extended State Observer

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.