Variable geometry turbocharger active control strategies for enhanced energy recovery

Abstract

This paper describes the development of the control system for a new type of mechanical turbocharger, the Active Control Turbocharger (ACT). The main difference of ACT compared to its predecessor, the Variable Geometry Turbocharger (VGT), lies in the inlet area modulation capability which follows an oscillating (sinusoidal) profile in order to match as much as possible the similar profile of the emitted exhaust gases entering the turbine in order to capturing the highly dynamic, energy content existent in exhaust pulses. This paper describes the development of a new controller in an adaptive framework in order to improve the response of the ACT. The system has been modelled using a one-dimensional Ricardo WAVE engine simulation software and the control system which actuates the nozzle (rack) position is modelled in Matlab-Simulink and uses a map-based structure coupled with a PID controller with constant parameters. Steady-state simulations have been carried out for different speeds and a fuel-air ratios in order to determine the optimum settings for highest brake torque for a given operating point, namely the maximum rack position, the amplitude and the phase offset. Finally, an adaptive controller has been developed in Matlab-Simulink. The controller adapts its parameters according to the operating point in order to improve the system response for a wide range of operating conditions. Regarding the control system in a transient regime, the response is significantly more accurate and the discrepancy between the desired boost pressure and the actual one has been decreased by 0.5 bar to a value of less than 0.05 bar difference.