Simplified Turbocharged Diesel Engine Air Path Modeling and Control Using Sliding Mode Controllers

Recently, the emission of hazardous materials (NOx and PM) in diesel engine is a critical issue. The regulations with respect to the NOx and PM are getting stricter, increasingly. Not only the emission problem but also fuel efficiency is considered as a serious issue to develop new turbocharged diesel engines. Thus, currently diesel engines are equipped with exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT). Basically, the diesel engine with EGR and VGT is a highly nonlinear system as well as a Multi-input and multi-output (MIMO) system. Moreover, since EGR and VGT are powered by exhaust gas, severe coupling effect exists. However, conventional Electric Control Unit (ECU) ignores this severe coupling effect and controls the turbocharged diesel engine by using independent single-input single-output (SISO) control methods. Hence, the model based MIMO control method is required not only to treat the coupling effect of EGR and VGT, but also to improve the performance of the engine operation with high fuel economy and low emission level. In this paper, three different model based sliding mode control approaches are proposed to regulate intake manifold pressure (MAP) and exhaust manifold pressure (EXMAP), simultaneously, by controlling exhaust gas recirculation (EGR) flow rate and turbine flow rate. The first approach is high performance robust controller design using nonlinear sliding surface. The second approach is extended input-output linearization for sliding mode control. The third approach is using proportional integral sliding mode control (PISMC) method into turbocharged diesel engine.