Gain Scheduled Controller of EGR and VGT Systems with a Model-Based Gain Scheduling Strategy for Diesel Engines

This study proposed a gain scheduled controller for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems with a model-based gain scheduling strategy to manage strong nonlinearity in diesel engines. The feedback controller uses a gain scheduling strategy to obtain appropriate controller gains of the PI controller under various engine operating conditions. The gain scheduling strategy is designed using the proposed static gain model that predicts varying static gains of EGR and VGT plants. The static gain model uses scheduling variables derived from indirect measurements of the EGR mass flow such as the pressure ratio of the intake and exhaust manifolds and the exhaust air-to-fuel ratio. The scheduling variables are effective to reduce a large static gain dispersion caused by various operating conditions of the EGR and VGT actuators. With the predicted static gains of the plant, a Skogestad internal model control (SIMC) method determines PI gains in runtime. The proposed control algorithm is evaluated through engine experiments. The experimental results proved that the integrated absolute error (IAE) and overshoot of the gain scheduled feedback controller are significantly reduced compared to the fixed gain controller.