Model-based feedforward control of the VGT in a diesel engine based on empirical models of compressor and turbine efficiencies

Current diesel engines commonly employ a variable geometry turbocharger (VGT) to improve drivability and fuel efficiency, and this paper addresses model-based feedforward control of the VGT based on empirical models of compressor and turbine efficiencies to improve transient response. Though compressor and turbine efficiencies affect compressor air flow and turbine power, respectively, it is challenging to understand exactly the compressor and turbine efficiencies in real engines. In order to cope with this problem, we propose empirical models of compressor and turbine efficiencies. The input states are proposed based on maps of the compressor and turbine efficiencies, which are provided by turbocharger manufacturers. Parameters of the efficiency models are identified with 225 data of steady-state engine experiments to reflect engine operating conditions. The proposed compressor and turbine efficiency models were applied to the model-based VGT feedforward control algorithm to verify the effectiveness of the efficiency models. The proposed modelbased VGT feedforward control algorithm based on the compressor and turbine efficiency models was experimentally verified with 2.2 L common-rail-direct-injection diesel engines.