Optimal Boost Control for an Electrical Supercharging Application

Electrical on demand supercharging provides an internal combustion engine with the facility to increase its volumetric efficiency without being subject to the mechanical constraints associated with a conventional pressure charging device. This enables improvement in fuel economy through engine downsizing with the added ability to enhance torque. The Visteon Torque Enhancement System (VTES) is a fully integrated air management system, at the heart of which is an electronically controlled, electrically powered supercharger. Based on the driver demand, the supercharger responds by rotating a compressor at a speed which pressurizes the intake air to the desired level. The control system associated with an electrical boosting device (EBD) considers the engine and electrical motor torque requirements for providing the actuator with an appropriate compressor set-point. Optimal tracking of the set-point requires inclusion of physical limits of the actuator for the supercharger operation. Conditioning of the compressor speed set-point is done such that driver's perception remains unaffected by any such limits. Electrical supercharging provides an opportunity to address the low-end torque deficit in both naturally aspirated and turbocharged applications. The use of the electrical supercharger in series with a turbocharger aids in the reduction of turbo lag. The resultant modifications in the supercharger boost demand are made as a function of the 2-stage pressure charging requirements.